Automation of production processes in the chemical industry. Automation of technological processes and production of the chemical industry Operation of automation equipment in the chemical industry
Operation and repair of automation equipment.
The operation of automation equipment in agricultural production has its own characteristics, namely that some of these equipment, such as sensors and actuators, are installed directly in production premises. The environment of such premises is aggressive towards automation elements. In this regard, all automation equipment used in agricultural production must have appropriate protection from the effects of harmful environmental factors in production premises.
Another serious factor that negatively affects the operation of automation equipment in agricultural production is the voltage level, which in rural areas is subject to significant fluctuations. Because of this, the stability of automatic devices is significantly reduced.
Preventative work. During the operation of automation equipment, special attention is paid to preventive maintenance that prevents failure of automation elements and largely eliminates accidents.
The purpose of this work is as follows:
a) achieve guaranteed levels of insulation resistance of all parts of the installations;
b) maintain cables, wires, electromagnetic and motor mechanisms, relays, contacts and other equipment in good condition;
c) achieve compliance of protection parameters with the specified settings;
d) maintain the backup power device in good condition and 100% ready for switching on; e) ensure appropriate reliability of interlocks and interlocked parts of circuits, alarms, etc.
Before putting installation automation equipment into operation, a technical (external) inspection is carried out, as a result of which installation and adjustment errors are identified. The technical inspection is preceded by a preliminary study of automation documentation, acts for hidden work, acts and protocols of audits and equipment passports, etc.
Maintenance. The set of measures for the maintenance of automation equipment includes the following work:
1) preventive, aimed at preventing failures (replacement of elements, lubrication and fastening work, etc.);
2) related to technical condition monitoring, the purpose of which is to check the compliance of the parameters characterizing the operational state of automation devices with the requirements of regulatory and technical documentation (form, passport, etc.);
3) adjustment and tuning, designed to bring the parameters of automation equipment (blocks, sensors, components) to the values established by the regulatory and technical documentation.
Maintenance is aimed at restoring the functionality or serviceability of automation devices by eliminating failures and damage.
Depending Depending on the operating conditions, design features of the equipment and the nature of failures, three principles can be used when organizing maintenance: calendar, operating time and mixed.
Calendar principle is that maintenance is assigned and carried out after a certain calendar period (day, week, month, quarter, etc.), regardless of the intensity of use of automation devices. The scope of each maintenance is determined by the operational documentation (maintenance instructions, operating instructions, etc.).
Operating principle involves setting maintenance dates upon the equipment reaching a certain operating time. In this case, the operating time can be calculated in hours of operation, number of starts. This principle can be used to organize maintenance in cases where failures are caused by wear processes, equipment operates in difficult conditions, significantly different from normal, or for a long time.
Mixed principle maintenance organization is used for automation devices in which failures are caused by both wear and aging processes.
All chemical industry enterprises are already at the modern level; in order to produce competitive products in the required quantities, they must introduce automated systems into the production process, such as automated process control systems for chemical industry enterprises.
That is why at the modern level, automation of technological processes of chemical industry enterprises is an urgent task. Automated systems are designed to ensure higher quality of products, reduce production costs, increase the profitability of the enterprise, as well as neutralize and minimize waste in this industry.
Various automation tools can be used in the chemical industry, and their choice is most often based not only on management preferences, but also on issues of increasing the efficiency and profitability of products.
What automation systems may be in demand? in chemical industry enterprises
Automated traffic management systems;
Automated feeding systems for feeders or conveyors;
Automation and visualization of production processes using special software;
Automation and implementation of automated process control systems for weighing devices and dosing devices for feeding elements;
Automation of cable routes;
Equipping the operator's workplace with computer equipment and automating the production line;
And many other elements of automation and implementation of automated process control systems may be relevant for chemical industry enterprises.
Automated systems created by our company’s specialists are designed to ensure uninterrupted operation of the enterprise, therefore maintenance is carried out by our specialists.
Documentation in automated control systems for technological processes in the chemical industry
To ensure human participation in process control, it is necessary to document information. Subsequent analyzes require the accumulation of statistical initial data by recording the states and values of process parameters over time. Based on this, compliance with the technological process regulations is checked, the formation of product quality is analyzed, the actions of personnel in emergency situations are monitored, directions for improving the process are searched, etc.
When developing that part of the automated process control system information support that is associated with documentation and registration, the following is necessary:
- determine the type of parameters to be registered, the place and form of registration;
- select the time factor of registration (dating, registration intervals, duration of continuous registration);
- minimize the number of recorded parameters for reasons of necessity and sufficiency for operational actions and subsequent analysis.
Minimization in this case means that only those parameters are selected for registration that are sufficient for the operational control of the technological process and its subsequent analysis. This number of parameters cannot be reduced, since the quality of process control decreases; it is also impossible to increase, since the cost of management unreasonably increases.
Choose a method for grouping documented information from the point of view of ease of use by humans and machines.
In this case, the determining factors are the complexity and dynamics of the technological process, the capabilities of technical means and the human operator, the purpose and capabilities of analysis, economic and time factors.
There are no uniform and comprehensive rules for the development of documentation in automated process control systems, however, a significant part of the important formal provisions can be gleaned from a series of GOST standards for ESKD and USD .
Typical documentation is the registration of the date, the single current time in automated process control systems (hour, minute, second), measurement point code, object code (if necessary), parameter name (if necessary), current parameter value (absolute or relative deviation from the standard), unit of measurement, adjustment sign (if necessary). Depending on the conditions of formation and purpose of the document, some of the specified details can be entered in advance into the document form or excluded from it if it is intended only for further machine processing.
When developing a documentation system, document formats are unified
and common details and document structures. Attention is paid to the visibility and clarity of documents, in particular through the use of tabular forms. In documents intended for machine processing, special details are entered: document code in the processing system, analysis type code, columns filled in on programmable controllers, etc. Issues of classification (grouping) of documents and routes of their movement are resolved. The volumes of information in documents and document flows are determined. The place and period of storage of documents is established.
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The purpose of this course project is to acquire practical skills in analyzing the technological process, selecting automatic control means, calculating measuring circuits of instruments and control means, as well as teaching the student independence in solving engineering and technical problems of constructing automatic control circuits for various technological parameters.
Introduction
Automation is the use of a set of tools that allow production processes to be carried out without the direct participation of a person, but under his control. Automation of production processes leads to increased output, reduced costs and improved product quality, reduces the number of service personnel, increases the reliability and durability of machines, saves materials, improves working conditions and safety precautions.
automation and monitoring of their action. If automation facilitates human physical labor, then automation aims to facilitate mental labor as well. The operation of automation equipment requires highly qualified technical personnel.
In this case, the production of thermal and electrical energy at any given time must correspond to consumption (load). Almost all operations at thermal power plants are mechanized, and transient processes in them develop relatively quickly. This explains the high development of automation in thermal energy.
Automating parameters provides significant benefits:
1) ensures a reduction in the number of working personnel, i.e. an increase in their labor productivity,
3) increases the accuracy of maintaining the parameters of the generated steam,
Automation of steam generators includes automatic regulation, remote control, technological protection, thermal control, technological interlocks and alarms.
Automatic regulation ensures the progress of continuously occurring processes in the steam generator (water supply, combustion, steam superheating, etc.)
Remote control allows the personnel on duty to start and stop the steam generator unit, as well as switch and regulate its mechanisms at a distance, from the console where the control devices are located.
flowing in a steam generator installation, or are connected to the measurement object by service personnel or an information computer. Thermal control devices are placed on panels and control panels, as convenient as possible for observation and maintenance.
eliminate incorrect operations when servicing a steam generator installation, ensure shutdown of equipment in the required sequence in the event of an accident.
emergency condition of the steam generator and its equipment. Sound and light alarms are used.
The operation of boilers must ensure reliable and efficient production of steam of the required parameters and safe working conditions for personnel. To meet these requirements, operation must be carried out in strict accordance with laws, rules, norms and guidelines, in particular, in accordance with the “Rules for the design and safe operation of steam boilers” of Gosgortekhnadzor, “Rules for the technical operation of power plants and networks”, “Rules for technical operation of heat-using installations and heating networks".
A steam boiler is a complex of units designed to produce water steam. This complex consists of a number of heat exchange devices interconnected and used to transfer heat from fuel combustion products to water and steam. The initial carrier of energy, the presence of which is necessary for the formation of steam from water, is fuel.
The main elements of the work process carried out in a boiler plant are:
1) fuel combustion process,
2) the process of heat exchange between combustion products or the burning fuel itself with water,
3) the process of vaporization, consisting of heating water, evaporating it and heating the resulting steam.
During operation, two flows interact with each other are formed in boiler units: the flow of the working fluid and the flow of the coolant formed in the furnace.
As a result of this interaction, steam of a given pressure and temperature is obtained at the output of the object.
One of the main tasks that arises during the operation of a boiler unit is to ensure equality between the energy produced and consumed. In turn, the processes of steam formation and energy transfer in a boiler unit are uniquely related to the amount of substance in the flows of the working fluid and coolant.
Fuel combustion is a continuous physical and chemical process. The chemical side of combustion is the process of oxidation of its combustible elements with oxygen. passing at a certain temperature and accompanied by the release of heat. The intensity of combustion, as well as the efficiency and stability of the fuel combustion process, depend on the method of supplying and distributing air between the fuel particles. Conventionally, the fuel combustion process is divided into three stages: ignition, combustion and afterburning. These stages generally occur sequentially in time and partially overlap one another.
Calculation of the combustion process usually comes down to determining the amount of air per m3 required for the combustion of a unit mass or volume of fuel, the amount and composition of the heat balance and determining the combustion temperature.
The meaning of heat transfer is the heat transfer of thermal energy released during fuel combustion to water, from which it is necessary to obtain steam, or steam, if it is necessary to increase its temperature above the saturation temperature. The heat exchange process in the boiler occurs through water-gas-tight heat-conducting walls called the heating surface. Heating surfaces are made in the form of pipes. Inside the pipes there is a continuous circulation of water, and outside they are washed by hot flue gases or receive thermal energy by radiation. Thus, all types of heat transfer take place in the boiler unit: thermal conductivity, convection and radiation. Accordingly, the heating surface is divided into convective and radiation. The amount of heat transferred through a unit heating area per unit time is called the thermal stress of the heating surface. The magnitude of the voltage is limited, firstly, by the properties of the heating surface material, and secondly, by the maximum possible intensity of heat transfer from the hot coolant to the surface, from the heating surface to the cold coolant.
The intensity of the heat transfer coefficient is higher, the higher the temperature difference of the coolants, the speed of their movement relative to the heating surface, and the higher the cleanliness of the surface.
lies in the fact that individual molecules of a liquid located at its surface and possessing high speeds, and therefore greater kinetic energy compared to other molecules, overcoming the force effects of neighboring molecules, creating surface tension, fly out into the surrounding space. With increasing temperature, the intensity of evaporation increases. The reverse process of vaporization is called condensation. The liquid formed during condensation is called condensate. It is used to cool metal surfaces in superheaters.
The steam generated in the boiler unit is divided into saturated and superheated. Saturated steam is in turn divided into dry and wet. Since thermal power plants require superheated steam, a superheater is installed to superheat it, in which the heat obtained from the combustion of fuel and waste gases is used to superheat the steam. The resulting superheated steam at temperature T=540 C and pressure P=100 atm. goes for technological needs.
The operating principle of a boiler plant is to transfer the heat generated during fuel combustion to water and steam. In accordance with this, the main elements of boiler installations are the boiler unit and the combustion device. The combustion device serves the fuel in the most economical way and converts the chemical energy of the fuel into heat. The boiler unit is a heat exchange device in which heat is transferred from the combustion products of the fuel to water and steam. Steam boilers produce saturated steam. However, during transportation over long distances and use for technological needs, as well as at thermal power plants, the steam must be superheated, since in a saturated state, upon cooling, it immediately begins to condense. The boiler includes: a firebox, a superheater, a water economizer, an air heater, lining, a frame with stairs and platforms, as well as fittings and fittings. Auxiliary equipment includes: draft and feed devices, water treatment equipment, fuel supply, as well as instrumentation and automation systems. The boiler installation also includes:
1. Tanks for collecting condensate.
2. Chemical water treatment plants.
3. Deaerators for removing air from chemically purified water.
4. Feed pumps for supplying feed water.
5. Installations for reducing gas pressure.
6. Fans for supplying air to the burners.
Smoke exhausters for removing flue gases from furnaces. Let's consider the process of producing steam with given parameters in a boiler house running on gas fuel. Gas from the gas distribution point enters the boiler furnace, where it burns, releasing an appropriate amount of heat. The air required for fuel combustion is forced by a blower fan into the air heater located in the last gas duct of the boiler. To improve the fuel combustion process and increase the efficiency of the boiler, the air can be preheated by flue gases and an air heater before being supplied to the firebox. The air heater, perceiving the heat of the exhaust gases and transferring it to the air, firstly, reduces heat loss with the exhaust gases, and secondly, improves the conditions of fuel combustion by supplying heated air to the boiler furnace. This increases the combustion temperature and the efficiency of the installation. Part of the heat in the firebox is transferred to the evaporative surface of the boiler - the screen covering the walls of the firebox. The flue gases, having given up part of their heat to the radiation heating surfaces located in the combustion chamber, enter the convective heating surface, are cooled and removed through the chimney into the atmosphere by a smoke exhauster. Water continuously circulating in the screen forms a steam-water mixture, which is discharged into the boiler drum. In the drum, steam is separated from water - the so-called saturated steam is obtained, which enters the main steam line. The flue gases leaving the furnace wash the coil economizer, in which the feed water is heated. Heating water in an economizer is advisable from the point of view of fuel economy. A steam boiler is a device that operates under difficult conditions - at high temperatures in the furnace and significant steam pressure. Violation of the normal operating mode of the boiler installation can cause an accident. Therefore, each boiler installation is equipped with a number of devices that issue a command to stop the supply of fuel to the boiler burners under the following conditions:
1. When the pressure in the boiler increases beyond the permissible limit;
2. When the water level in the boiler decreases;
3. When the pressure in the fuel supply line to the boiler burners decreases or increases;
4. When the air pressure in the burners decreases;
To control the equipment and monitor its operation, the boiler room is equipped with instrumentation and automation devices.
1. Reducing the pressure of gas coming from the hydraulic fracturing;
2. Reducing the vacuum in the boiler furnace;
3. Increasing the steam pressure in the boiler drum;
5. Extinguishing of the torch in the furnace.
3. Selection of means for measuring technological parameters and their comparative characteristics
3. 1 Selection and justification of control parameters
The choice of controlled parameters ensures obtaining the most complete measurement information about the technological process and the operation of the equipment. Temperature and pressure are subject to control.
4. Selection of monitoring and control parameters
The control system must ensure the achievement of the control goal due to the specified accuracy of technological regulations in any production conditions while observing the reliable and trouble-free operation of the equipment, explosion and fire hazard requirements.
The purpose of power consumption management is to: reduce specific electricity costs for production; rational use of electricity by technological services of departments; proper planning of electricity consumption; control of consumption and specific electricity consumption per unit of output in real time.
The main task in developing a control system is the selection of parameters involved in control, that is, those parameters that need to be monitored, regulated and by analyzing the change in values of which it is possible to determine the pre-emergency state of the technological control object (TOU).
The parameters subject to control are those whose values are used to carry out operational control of the technological process (TP), as well as the start and stop of technological units.
4.1 Pressure measurement
pressure and vacuum meters; pressure meters (for measuring small (up to 5000 Pa) excess pressures); draft meters (for measuring small (up to hundreds of Pa) vacuums); thrust gauges; differential pressure gauges (for measuring pressure differences); barometers (for measuring atmospheric pressure). According to the principle of operation, the following instruments for measuring pressure are distinguished: liquid, spring, piston, electric and radioactive.
For measuring gas and air pressure up to 500 mm water. Art. (500 kgf/m2) use a glass U-shaped liquid pressure gauge. The pressure gauge is a glass U-shaped tube attached to a wooden (metal) panel that has a scale marked in millimeters. The most common pressure gauges have scales of 0-100, 0-250 and 0-640 mm. The pressure value is equal to the sum of the heights of the liquid levels lowered below and raised above zero.
In practice, pressure gauges with a double scale are sometimes used, in which the division value is halved and the numbers from zero up and down go with an interval of 20: 0-20-40-60, etc. in this case, there is no need to indicate the heights of liquid levels , it is enough to measure the pressure gauge readings at the level of one bend of the glass tube. Measurement of small pressures or vacuums up to 25 mm of water. Art. (250 Pa) single-pipe or U-shaped liquid pressure gauges leads to large errors when reading measurement results. To increase the scale of the readings of a single-tube pressure gauge, the tube is tilted. TNZh liquid draft pressure meters operate on this principle, which are filled with alcohol with a density of r = 0.85 g/cm3. in them, liquid is forced out of a glass vessel into an inclined tube along which there is a scale graduated in mm of water. Art. When measuring vacuum, the pulse is connected to a fitting that is connected to an inclined tube, and when measuring pressure, it is connected to a fitting that is connected to a glass vessel. Spring pressure gauges. To measure pressure from 0.6 to 1600 kgf/cm2, spring pressure gauges are used. The working element of the pressure gauge is a curved tube of ellipsoidal or oval cross-section, which is deformed under the influence of pressure. One end of the tube is sealed, and the other is connected to a fitting that is connected to the medium being measured. The closed end of the tube is connected through a rod to the gear sector and the central gear wheel, on the axis of which an arrow is mounted.
The pressure gauge is connected to the boiler through a siphon tube in which steam is condensed or water is cooled and pressure is transmitted through the cooled water, which prevents damage to the mechanism from the thermal action of steam or hot water, and the pressure gauge is also protected from water hammer.
In this process, it is advisable to use a Metran-55 pressure sensor. The selected sensor is ideal for measuring the flow of liquid, gas, steam. This sensor has the required measurement limits - min. 0-0. 06 MPa to max. 0-100 MPa. Provides the required accuracy of 0.25%. It is also very important that this sensor has an explosion-proof design, the output signal is unified - 4 -20 mA, which is convenient when connecting a secondary device since it does not require additional installation of an output signal converter. The sensor has the following advantages: 10:1 reconfiguration range, continuous self-diagnosis, built-in radio interference filter. Microprocessor electronics, the ability to simply and conveniently configure parameters with 2 buttons.
The measured pressure is supplied to the working cavity of the sensor and acts directly on the measuring membrane of the strain gauge transducer, causing it to deflect.
The sensitive element is a single-crystal sapphire plate with silicon film strain gauges. Connected to the metal plate of the strain gauge transducer. The strain gauges are connected in a bridge circuit. Deformation of the measuring membrane leads to a proportional change in the resistance of the strain gauge and imbalance of the bridge circuit. The electrical signal from the output of the sensor bridge circuit enters the electronic unit, where it is converted into a unified current signal.
The sensor has two operating modes:
Pressure measurement mode; - mode for setting and monitoring measurement parameters.
In pressure measurement mode, the sensors provide constant monitoring of their operation and, in the event of a malfunction, generate a message in the form of a decrease in the output signal below the limit.
4.2 Temperature measurement
One of the parameters that must not only be monitored, but also signaled as the maximum permissible value is temperature.
resistance thermometers and radiation pyrometers.
In boiler rooms, instruments are used to measure temperature, the operating principle of which is based on the properties exhibited by substances when heated: Change in volume - expansion thermometers; Pressure change – manometric thermometers; The emergence of thermoEMF - thermoelectric pyrometers;
Changes in electrical resistance - resistance thermometers.
extensions are used for local temperature measurements ranging from -190 to +6000C. The main advantages of these thermometers are simplicity, low cost and accuracy. These instruments are often used as reference instruments. Disadvantages - impossibility of repair, lack of automatic recording and the ability to transmit readings over a distance. The measurement limits of bimetallic and dilatometric thermometers are from – 150 to +700 0С, error 1-2%. Most often they are used as sensors for automatic control systems.
Manometric thermometers. Used for remote temperature measurement. The principle of their operation is based on changing the pressure of liquids, gas or steam in a closed volume depending on temperature.
The type of working substance determines the type of manometric thermometer:
Gas – with inert gas (nitrogen, etc.)
Their advantage is simplicity of design and maintenance, the possibility of remote measurement and automatic recording of readings. Other advantages include their explosion safety and insensitivity to external magnetic and electric fields. Disadvantages are low accuracy, significant inertia and a relatively short distance for remote transmission of readings.
Thermoelectric pyrometer. It is used to measure temperatures up to 16000C, as well as transmitting readings to a heat shield and consists of a thermocouple, connecting wires and a measuring device.
A thermocouple is a connection of two conductors (thermoelectrodes) made of different metals (platinum, copper) or alloys (chromel, copel, platinum-rhodium), insulated from each other by porcelain beads or tubes. Some ends of the thermoelectrodes are soldered together, forming a hot junction, while the others remain free.
For ease of use, the thermocouple is placed in a steel, copper or quartz tube.
When the hot junction is heated, a thermoelectromotive force is generated, the magnitude of which depends on the temperature of the hot junction and the material and material of the thermoelectrodes.
electrical resistance of conductors or semiconductors when temperature changes. Resistance thermal converters: platinum (RTC) are used for long-term measurements in the range from 0 to +650 0C; copper (TCM) for measuring temperatures in the range from –200 to +200 0C. Automatic electronic balanced bridges with an accuracy class of 0.25 to 0.5 are used as secondary devices. Semiconductor resistance thermometers (thermistors) are made from oxides of various metals with additives. The most widely used are cobalt-manganese (CMT) and copper-manganese (MMT) semiconductors, used to measure temperatures in the range from – 90 to +300 0C. Unlike conductors, the resistance of thermistors decreases exponentially with increasing temperature, making them highly sensitive. However, it is almost impossible to produce thermistors with strictly identical characteristics, so they are calibrated individually. Resistance thermal converters, complete with automatic electronic balanced bridges, allow you to measure and record temperature with high accuracy, as well as transmit information over long distances. The most widely used primary measuring converters of such thermometers are currently: platinum-rhodium - platinum (TPP) converters with measurement limits from – 20 to + 1300 0С; chromel-copel (TCA) converters with measurement limits from – 50 to + 600 0С and chromel-alumel (TCA) converters with measurement limits from – 50 to + 1000 0С. For short-term measurements, the upper temperature limit for the TXK converter can be increased by 200 0C, and for the TPP and TXA converters by 300 0C. To measure temperature on pipelines and on boilers, I decided to choose thermoelectric converters of the TXA type - the choice of these particular converters is due to the fact that in the measurement range from –50 to +600 0C it has a higher sensitivity than the TXA converter. The main characteristics of the thermoelectric converter type THK - 251 manufactured by CJSC PG "Metran":
· Purpose: for measuring temperatures of gaseous and liquid media;
· Range of measured temperatures: from – 40 to +600 0С;
· The length of the mounting part of the converter is 320 mm;
· Protective cover material; stainless steel, grade 12Х18Н10Т, and its diameter is 10 mm;
· Average service life of at least 2 years;
· Sensing element: thermocouple cable KTMS-HK TU16-505. 757-75;
4.3 Level measurement
The level is the height of filling of a technological apparatus with a working medium - liquid or granular solid. The level of the working environment is a technological parameter, information about which is necessary to control the operating mode of the technological apparatus, and in some cases to control the production process.
By measuring the level, you can obtain information about the mass of liquid in the tank. Level is measured in units of length. The measuring instruments are called level gauges.
There are level gauges designed to measure the level of the working environment; measuring the mass of liquid in a technological apparatus; signaling limit values of the level of the working environment - level switches.
Based on the measurement range, level gauges are divided into wide and narrow ranges. Wide range level gauges (with measurement limits of 0.5 - 20 m) are designed for inventory accounting operations, and narrow range level gauges (measurement limits of (0÷ ±100) mm or (0÷ ±450) mm) are usually used in automatic control systems.
Currently, level measurement in many industries is carried out by level gauges of various operating principles, of which float, buoy, hydrostatic, electric, ultrasonic and radioisotope are widespread. Visual measuring instruments are also used.
Indicator or level glasses are made in the form of one or several chambers with flat glasses connected to the apparatus. The operating principle is based on the property of communicating vessels. Used for local level measurement. The length of the glass does not exceed 1500 mm. The advantages include simplicity, high accuracy: disadvantages - fragility, inability to transmit readings over a distance.
When calculating float level gauges, design parameters of the float are selected that ensure the state of equilibrium of the “float-counterweight” system only at a certain immersion depth of the float. If we neglect the gravity of the cable and the friction in the rollers, the equilibrium state of the float-counterweight system is described by the equation
where Gr, Gп – gravity forces of the counterweight and float; S - float area; h1 – float immersion depth; pl is the density of the liquid.
An increase in the liquid level changes the immersion depth of the float and an additional buoyant force acts on it.
The advantage of these level meters is their simplicity, fairly high measurement accuracy, the ability to transmit over a distance, and the ability to work with aggressive liquids. A significant disadvantage is the sticking of a viscous substance to the float, which affects the measurement error.
The principle of operation of capacitive level meters is based on the change in the capacitance of the converter due to changes in the level of the controlled environment. The measurement limits of these level gauges are from 0 to 5 meters, the error is no more than 2.5%. Information can be transmitted over a distance. The disadvantage of this method is the inability to work with viscous and crystallizing liquids.
The operating principle of hydrostatic level gauges is based on measuring the pressure created by a liquid column. Hydrostatic pressure is measured:
· a pressure gauge connected at a height corresponding to the lower limit value of the level;
· by measuring the pressure of gas pumped through a tube lowered into the liquid filling the tank at a fixed distance.
In our case, the most suitable are water indicator devices with round and flat glass, lowered level indicators and water testing taps. Water indicators with round glass are installed on boilers and tanks with a pressure of up to 0.7 kgf/cm2. glass height can be from 200 to 1500 mm, diameter - 8 -20 mm, glass thickness 2.5-3.5 mm. Flat glass can be smooth or grooved. Klinger glass has vertical prismatic grooves on the inside and is polished on the outside. In such glass, water appears dark and steam appears light. If during operation of the steam boiler the taps of the water indicating device are not dirty, then the water level in it fluctuates slightly.
4.4 Flow measurement
One of the most important parameters of technological processes is the flow rate of substances flowing through pipelines. The means that measure the consumption and quantity of substances during commodity accounting operations are subject to high accuracy requirements.
Let's consider the main types of flowmeters: variable pressure differential flowmeters, constant differential pressure flowmeters, tachometer flowmeters, velocity pressure flowmeters, electromagnetic (induction) flowmeters, ultrasonic.
One of the most common principles for measuring the flow of liquids, gases and steam is the variable pressure principle.
The operating principle of constant differential pressure flowmeters is based on vertical movement of the sensing element depending on the flow rate of the substance, while the flow area changes so that the pressure drop across the sensing element remains constant. The main condition for correct reading is the strictly vertical installation of the rotameter.
Flow meters. Flow meters belong to a large group of flow meters, also called constant differential pressure flow meters. In these flow meters, a streamlined body perceives a force action from the oncoming flow, which, as the flow rate increases, increases and moves the streamlined body, as a result of which the moving force decreases and is again balanced by the opposing force. The counteracting force is the weight of the streamlined body when the flow moves vertically from bottom to top, or the force of the counteracting spring in the case of an arbitrary flow direction. The output signal of the flow transducers under consideration is the movement of the streamlined body. To measure the flow of gases and liquids on process streams, rotameters are used, equipped with converting elements with an electrical or pneumatic output signal.
Liquid flows out of the vessel through a hole in the bottom or side wall. Vessels for receiving liquid are made cylindrical or rectangular.
a thin disk (washer) with a cylindrical hole, the center of which coincides with the center of the cross-section of the pipeline, the device measuring the pressure difference and connecting tubes. The summing device determines the flow rate of the medium based on the rotation speed of the impeller or rotor installed in the housing.
To measure gas and steam flow, I chose a Rosemount 8800DR smart vortex flow meter with built-in conical adapters, which reduces installation costs by 50%. The operating principle of a vortex flow meter is based on determining the frequency of vortices formed in the flow of the measured medium when flowing around a body of a special shape. The vortex frequency is proportional to the volume flow. It is suitable for measuring the flow of liquid, steam and gas. For digital and pulse output, the basic permissible error limit is ±0. 65%, and for current additionally ±0. 025%, output signal 4 - 20 mA. The advantages of this sensor include a non-clogging design, the absence of impulse lines and seals increases reliability, increased resistance to vibration, the ability to replace sensors without stopping the process, and short response time. Possibility of simulating verification; there is no need to narrow the pipeline during operation. A-100 can be used as a secondary device. To measure water flow, we use a correlation water flow sensor DRK-4. The sensor is designed to measure the flow and volume of water in completely filled pipelines. Main advantages:
· lack of flow resistance and pressure loss;
· possibility of mounting primary transducers on the pipeline at any orientation relative to its axis;
· correction of readings taking into account inaccuracy of installation of primary transducers;
· spill-free, simulation verification method;
· intercheck interval – 4 years;
· unified current signal 0-5.4-20 mA;
· self-diagnosis;
temperature of liquid fuel in the common pressure line; steam pressure in the line for spraying liquid fuel; pressure of liquid or gaseous fuel in common pressure lines; consumption of liquid or gaseous fuel in the boiler room as a whole. The boiler room must also provide for recording the following parameters: the temperature of superheated steam intended for technological needs; water temperature in the supply pipelines of the heating network and hot water supply, as well as in each return pipeline; steam pressure in the supply manifold; water pressure in the return pipeline of the heating network; steam flow in the supply manifold; water flow in each supply pipeline of the heating network and hot water supply; water consumption used to recharge the heating network. Deaerator-feeding installations are equipped with indicating instruments for measuring: water temperature in storage and feed tanks or in the corresponding pipelines; steam pressure in deaerators; feed water pressure in each line; water pressure in the suction and pressure pipes of feed pumps; water level in battery and feed tanks.
| Controlled parameter | Availability of indicating devices on boilers | |||
| <0,07 | >0,07 | <115 | >115 | |
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4. Flue gas temperature behind the boiler 6. Steam pressure in the boiler drum 7. Steam (water) pressure after the superheater (after the boiler) 8. Steam pressure supplied to fuel oil spraying 9. Water pressure at the boiler inlet 11. Air pressure after the blower fan 12. Air pressure in front of the burners (after the control dampers) 15. Vacuum in front of the smoke exhaust valve or in the flue 16. Vacuum before and behind the tail heating surfaces 18. Water flow through the boiler (for boilers with a capacity of more than 11.6 MW (10 Gcal/h)) 19. Level in the boiler drum |
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*For boilers with a capacity of less than 0.55 kg/s (2 t/h) – pressure in the common feed line 6. Basic information about fuel.
Fuel refers to combustible substances that are burned to produce heat. According to the physical state, fuel is divided into solid, liquid and gaseous. Gaseous gases include natural gas, as well as various industrial gases: blast furnace, coke oven, generator and others. High-quality fuels include coal, anthracite, liquid fuel and natural gas. All types of fuel consist of combustible and non-combustible parts. The combustible part of the fuel includes: carbon C, hydrogen H2, sulfur S. The non-combustible part includes: oxygen O2, nitrogen N2, moisture W and ash A. The fuel is characterized by working, dry and combustible masses. Gas fuel is most convenient for mixing it with air, which is necessary for combustion, since fuel and air are in the same state of aggregation.
5. Physico-chemical properties of natural gases
Natural gases are colorless, odorless and tasteless. The main indicators of combustible gases that are used in boiler houses: composition, calorific value, density, combustion and ignition temperature, explosion limits and flame propagation speed. Natural gases from pure gas fields consist mainly of methane (82-98%) and other heavier hydrocarbons. The composition of any gaseous fuel includes flammable and non-flammable substances. Combustibles include: hydrogen (H2), hydrocarbons (CmHn), hydrogen sulfide (H2S), carbon monoxide (CO2), non-flammable ones include carbon dioxide (CO2), oxygen (O2), nitrogen (N2) and water vapor (H2O). Heat of combustion - the amount of heat that is released during the complete combustion of 1 m3 of gas, measured in kcal/m3 or kJ/m3. There is a distinction between the highest calorific value Qвc, when the heat released during the condensation of water vapor that is in the flue gases is taken into account, and the lowest calorific value Qнc, when this heat is not taken into account. When performing calculations, Qwc is usually used, since the temperature of the flue gases is such that condensation of water vapor from combustion products does not occur. The density of a gaseous substance is determined by the ratio of the mass of the substance to its volume. Density unit kg/m3. The ratio of the density of a gaseous substance to the density of air under the same conditions (pressure and temperature) is called the relative gas density pо. Gas density pr= 0.73 - 0.85 kg/m3 (pо = 0.57-0.66) The combustion temperature is the maximum temperature that can be achieved during complete combustion of the gas, if the amount of air required for combustion exactly corresponds chemical combustion formulas, and the initial temperature of gas and air is 0 °C, and this temperature is called the heat output of the fuel. The combustion temperature of individual gases is 2000-2100 o C. The actual combustion temperature in boiler furnaces is much lower, 1100-1600 o C and depends on the combustion conditions. The ignition temperature is the temperature at which fuel combustion begins without the influence of an ignition source; for natural gas it is 645-700 o C. Explosive limits. A gas-air mixture containing up to 5% gas does not burn; from 5 to 15% - explodes; more than 15% - burns when air is supplied. Flame propagation speed for natural gas is 0.67 m/s (methane CH4). The use of natural gas requires special precautions, since it can leak through leaks at the junction of the gas pipeline with gas fittings. The presence of more than 20% of the gas in a room causes suffocation; its accumulation in a closed volume of 5 to 15% can lead to an explosion of the gas-air mixture; with incomplete combustion, carbon monoxide CO is released, which, even at low concentrations, has a poisonous effect on the human body.
6. Description of the automatic control scheme for process parameters
6. 1 Functional diagram of automatic control of process parameters
The principle of constructing a control system for this process is two-level. The first level consists of devices located locally, the second level consists of devices located on the operator’s panel.
Table 2.
Name and technical characteristics of equipment and materials. Manufacturer |
Type, brand of equipment. Designation Document and questionnaire number | Unit measurements |
Quantity |
|
| Pipeline temperature monitoring | ||||
| 1a | Gas temperature in the pipeline Thermoelectric converter |
TKhK-251-02-320-2-I-1-N10-TB-T6-U1. 1-PG |
PC. | 1 |
| 1b | Secondary indicating recording device, speed 5s, time of one revolution 8h | DISK250-4131 | PC. | 1 |
| 2a |
PG "Metran", Chelyabinsk |
TSM254-02-500-V-4-1- |
PC. | 1 |
| 2b | PC. | 1 | ||
| 2v | PRB-2M | PC. | 1 | |
| 2g | Actuator, power supply 220V, frequency 50Hz | MEO-40/25-0.25 | 1 | |
| 3a | Copper resistance thermocouple nominal static characteristic 100M |
TSM254-02-500-V-4-1- TU 422700-001-54904815-01 |
1 | |
| 3b | Electromagnetic converter, flow rate 5 l/min, output signal 20-100 kPa | EPP | 1 | |
| 3v | 1 | |||
| 3g | PR 3. 31-M1 | 1 | ||
| 3D | Actuator, nominal pressure 1.6 MPa | 25h30nzh | 1 | |
| Pipeline flow control | ||||
| 4a | Chamber diaphragm, nominal pressure 1.6 MPa | DK 16-200 | 1 | |
| 4b | Differential transducer, error 0.5%, measurement limit 0.25 MPa | Sapphire 22DD-2450 | 1 | |
| 4v | Secondary indicating recording device. Speed 5s, time of one revolution 8h. | DISC 250-4131 | 1 | |
| Flow control | ||||
| 5a | IR-61 | 1 | ||
| 5 B |
PG "Metran", Chelyabinsk Recorder, 2-channel, scale in Percents. Cl. t. 0. 5, speed 1s. |
Rosemount 8800DR A100-BBD,04. 2, TU 311--00226253. 033-93 |
1 | |
| 5v | Contactless reversible starter, discrete input signal 24V, power supply 220V, 50Hz | PBR-2M | 1 | |
| 5g | Actuator, power supply 220V, frequency 50Hz | 1 | ||
| Level regulation | ||||
| 6a | Level gauge, upper limit of measurement 6m, maximum permissible overpressure 4 MPa, supply pressure 0.14 MPa, output pneumatic signal 0.08 MPa | UB-PV | 1 | |
| 6b | Pressure gauge, power supply 220V, power 10 W | EKM-1U | 1 | |
| 6v | Secondary pneumatic indicating and recording instrument, with control station. Air consumption 600 l/h | PV 10. 1E | 1 | |
| 6g | 25h30nzh | 1 | ||
| Pressure measurement |
7. Basic principles of automation of boiler plants
The scope of boiler plant automation systems depends on the type of boilers installed in the boiler room, as well as the presence of specific auxiliary equipment in its composition. Boiler installations are equipped with the following systems: automatic control, safety automation, thermal control, alarm and electric drive control. Automatic control systems. The main types of ACP of boiler installations: for boilers - regulation of combustion and power processes; for deaerators – regulation of water level and steam pressure. Automatic control of combustion processes should be provided for all boilers operating on liquid or gaseous fuel. When using solid fuel, ACP of combustion processes is provided in cases of installation of mechanized combustion devices.
ASR fuel is not provided.
Power regulators are recommended to be installed on all steam boilers. For boiler installations operating on liquid fuel, it is necessary to provide an ACS for fuel temperature and pressure. Boilers with a steam superheat temperature of 400 0C and above must be equipped with an ASD for superheated steam temperature. Security automation. Automatic safety systems for gaseous and liquid fuel boilers should be provided. These systems ensure that the fuel supply is stopped in emergency situations.
Table3.
| Parameter deviation | Stopping the fuel supply to boilers | |||
| Steam with steam pressure piz, MPa | Hot water with water temperature, 0C | |||
| <0,07 | >0,07 | <115 | >115 | |
1. Increasing the steam pressure in the boiler drum 2. Increasing the water temperature behind the boiler 3. Reducing air pressure 4. Reducing gas pressure 5. Increasing gas pressure 6. Reducing water pressure behind the boiler 7. Reducing the vacuum in the furnace 8. Lowering or raising the level in the boiler drum 9. Reducing water consumption through the boiler 10. Extinguishing of the torch in the boiler furnace 11. Malfunction of automatic safety equipment |
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Conclusion
During the course project, practical skills were acquired in analyzing the technological process, selecting automatic control means according to the assigned tasks, calculating measuring circuits of instruments and control means. We also acquired skills in designing an automatic control system for process parameters.
Literature
1. A. S. Boronikhin Yu. S. Grizak “Fundamentals of production automation and instrumentation at enterprises of the building materials industry” M. Stroyizdat 1974 312s.
2. V. M. Tarasyuk “Operation of boilers”, a practical guide for boiler room operators; edited by B. A. Sokolov. – M.: ENAS, 2010. – 272 p.
3. V. V. Shuvalov, V. A. Golubyatnikov “Automation of production processes in the chemical industry: Textbook. For technical schools. – 2nd ed. reworked and additional - M.: Chemistry, 1985. - 352 s. ill.
4. Makarenko V. G., Dolgov K. V. Technical measurements and instruments: Guidelines for course design. South -Rus. state tech. univ. Novocherkassk: SRSTU, 2002. – 27 p.
Automation is the use of a set of tools that allow production processes to be carried out without direct human participation, but under his control. Automation of production processes leads to increased output, reduced costs and improved product quality, reduces the number of service personnel, increases the reliability and durability of machines, saves materials, improves working conditions and safety precautions.
Automation frees people from the need to directly control mechanisms. In an automated production process, the role of a person is reduced to setting up, adjusting, servicing automation equipment and monitoring their operation. If automation facilitates human physical labor, then automation aims to facilitate mental labor as well. The operation of automation equipment requires highly qualified technical personnel.
In terms of automation level, thermal power engineering occupies one of the leading positions among other industries. Thermal power plants are characterized by the continuity of the processes occurring in them. At the same time, the production of thermal and electrical energy at any given time must correspond to consumption (load). Almost all operations at thermal power plants are mechanized, and transient processes in them develop relatively quickly. This explains the high development of automation in thermal energy.
Automating parameters provides significant benefits:
1) ensures a reduction in the number of working personnel, i.e. increasing his labor productivity,
2) leads to a change in the nature of work of service personnel,
3) increases the accuracy of maintaining the parameters of the generated steam,
4) increases labor safety and equipment reliability,
5) increases the efficiency of the steam generator.
Automation of steam generators includes automatic regulation, remote control, technological protection, thermal control, technological interlocks and alarms.
Automatic regulation ensures the progress of continuously occurring processes in the steam generator (water supply, combustion, steam superheating, etc.)
Remote control allows the personnel on duty to start and stop the steam generator unit, as well as switch and regulate its mechanisms at a distance, from the console where the control devices are located.
Thermal control over the operation of the steam generator and equipment is carried out using indicating and recording instruments that operate automatically. The devices continuously monitor the processes occurring in the steam generator plant, or are connected to the measurement object by service personnel or an information computer. Thermal control devices are placed on panels and control panels, as convenient as possible for observation and maintenance.
Technological interlocks perform a number of operations in a given sequence when starting and stopping the mechanisms of a steam generator plant, as well as in cases where technological protection is triggered. Interlocks eliminate incorrect operations when servicing a steam generator unit and ensure that equipment is switched off in the required sequence in the event of an emergency.
Process alarm devices inform the personnel on duty about the state of the equipment (in operation, stopped, etc.), warn that a parameter is approaching a dangerous value, and report the occurrence of an emergency condition of the steam generator and its equipment. Sound and light alarms are used.
The operation of boilers must ensure reliable and efficient production of steam of the required parameters and safe working conditions for personnel. To meet these requirements, operation must be carried out in strict accordance with laws, rules, norms and guidelines, in particular, in accordance with the “Rules for the design and safe operation of steam boilers” of Gosgortekhnadzor, “Rules for the technical operation of power plants and networks”, “Rules for technical operation of heat-using installations and heating networks".
Introduction
Introduction
The development of automation in the chemical industry is associated with the increasing intensification of technological processes and the growth of production, the use of units of large unit capacity, the complication of technological schemes, and the imposition of increased demands on the resulting products.
A technological process is understood as a set of technological operations carried out on raw materials in one or more apparatuses, the purpose of which is to obtain a product with specified properties; They are carried out in distillation columns, reactors, extractors, absorbers, dryers and other apparatus. Usually, in order to process chemicals and obtain target products from these devices, complex technological schemes are assembled.
The technological process implemented on the appropriate technological equipment is called technological control object. TOU is a separate apparatus, unit, installation, department, workshop, production, enterprise. Various external disturbing influences (changes in the consumption or composition of feedstock, the state and characteristics of process equipment, etc.) disrupt the operation of the TOU. Therefore, in order to maintain its normal functioning, as well as if it is necessary to change its operating conditions, for example, in order to conduct a technological process according to a certain program or to obtain a target product of a different quality or composition, the technical equipment must be managed. Control- this is a targeted impact on an object, which ensures its optimal functioning and is quantitatively assessed by the value of the quality criterion (indicator). The criteria can be of a technological or economic nature (productivity of a process plant, cost of production, etc.). With automatic control, the impact on the object is carried out by a special automatic device in a closed loop; This combination of elements forms an automatic control system. A special case of management is regulation. Regulationcalled maintaining the output values of an object near the required constant or variable values in order to ensure the normal mode of its operation by applying control actions to the object. An automatic device that ensures that the output values of an object are maintained near the required values is called automatic regulator.
automatic control hydrocracking chemical 1. Process research
1.1 General characteristics of the production facility
Installations for hydrocracking, catalyst regeneration and hydrodearomatization of diesel fuel (RK and GDA) are designed to produce: 1.2 Description of the technological control object
The technological control object is the 10-DA-201 fractionation column, in which the liquid reaction products are separated into target fractions. The main raw material of the 10-DA-201 column is liquid from GSND 10-FA-201 (hydrogenate), heated in a 10-VA-201 furnace to 370-394°C. From the 10-VA-201 furnace, the raw material goes to the 6th tray of the 10-DA-201 column. Light raw materials from the 10-FA-202 separator after heat exchangers 10-EA-201, 10-EA-202, 10-EA-203 and 10-EA-204 with a temperature of 205-237 ° C are supplied to the 19th or 16th fractionation tray columns 10-DA-201 depending on the production of summer or winter type of diesel fuel. To strip and reduce the partial pressure of light hydrocarbon fractions, superheated medium-pressure steam with a temperature of no more than 390°C is supplied to the bottom of the fractionation column 10-DA-201 through a separator 10-FA-206. The steam flow into the column is regulated by a flow regulator 10-FICA-0067 with an alarm for low 2.5 t/h steam flow into the column 10-DA-201. Condensate from separator 10-FA-206 is discharged through a condensate trap into the condensate collector. The condensate level in the 10-FA-206 separator is controlled by the 10-LISA-0033 device with an alarm of 71% and blocking at an emergency high level of 79% for closing the valve 10-FV-0067 on the steam supply line to the column 10-DA-201. From the top of the fractionation column 10-DA-201 vapors of hydrocarbons, hydrogen sulfide, ammonia and water vapor with a temperature of 120-150°C and a pressure of 1.5-1.95 kgf/cm 2enter the air-cooled condenser 10-EC-202A I F. The temperature at the top of the column is controlled using a 10-TIСA-0143 device with an alarm for low temperatures of 120°C and high temperatures of 150°C. The vapor pressure at the top of the column is controlled using devices 10-PISA-0170, 10-PISA-0423A/B with a low alarm of 1 kgf/cm 2and high pressure 3 kgf/cm 2.
When an emergency high pressure of 3.5 kgf/cm is reached at the top of column 10-DA-201 2from two devices out of three 10-PISA-0170, 10-PISA-0423A/B, the blocking to stop the furnace 10-VA-201 is triggered: shutters 10-XV-0023, 10-XV-0024, valve 10-FV-0145 on the fuel gas supply line and shut-off valve 10-XV-0007 on the regeneration gas supply line to the furnace are closed, shutters 10-XV-0025, 10- are opened XV-0006 into the atmosphere; the flow regulator 10-FICA-0142A on the air supply line to the furnace is automatically reset from automatic to manual regulation and the valve 10-FV-0067 on the steam supply line to the fractionation column 10-DA-201 is closed. The temperature of the cube, feed zone, diesel fuel and kerosene extraction zones and the top of the 10-DA-201 column is controlled using devices 10-TI-0149, 10-TI-0148, 10-TI-0147, 10-TI-0146, 10-TI -0145, 10-TI-0144. The pressure difference between trays from 1 to 21 and from 21 to 32 in the height of column 10-DA-201 is monitored using devices 10-PDIA-0176, 10-PDIA-0173 with an alarm for a high difference of 0.3 kgf/cm 2.
The vapors leaving the top of the column enter the air-cooled condensers 10-EC-202A I F. Cooled and partially condensed vapor-gas mixture from air-cooled condensers 10-EC-202A I F with a temperature of 48-52°C, which is controlled by the 10-TI-0181 device, enters the annulus of water coolers 10-EA-205A/B, where it is cooled with circulating water, and with a temperature of 30-45°C, which is controlled carried out using devices 10-TIА-0183А/В, enters the separator 10-FA-203. From separator 10-FA-203 hydrocarbon gas with a temperature of 30-45°C and a pressure of 1.2-1.45 kgf/cm 2enters the 10-DA-207 low-pressure scrubber for hydrogen sulfide removal. The unstable gasoline that has condensed and separated from the water from the separator 10-FA-203 through the cut-off valve 10-HV-0119 enters the suction of the pump 10-GA-204A/S. The main part of unstable gasoline with a temperature of 35-45 ° C is returned as irrigation to the column 10-DA-201 on the 32nd plate by the pump 10-GA-204A/S through the flow regulator 10-FICA-0066 with an alarm at a low value of 32 t/h columns 10-DA-201. The balance amount of unstable gasoline is pumped through the 10-FIC-0095 flow regulator with correction according to the 10-LICSA-0037C level in the 10-FA-203 separator into the debutanizer 10-DA-204. Fractionation column 10-DA-201 has two blind trays 17 and 25 for selecting diesel and kerosene fractions. From the 25th blind plate of column 10-DA-201, the kerosene fraction with a temperature of 170-195°C is fed through the flow regulator 10-FIC-0072 into the stripper 10-DA-203 to the upper 6th plate for stripping light hydrocarbons. The temperature of the kerosene fraction before stripping 10-DA-203 is controlled using the 10-TI-0152 device. Light hydrocarbon vapors from the top of stripping 10-DA-203 with a pressure of 1.97 kgf/cm 2and a temperature of 165-210°C, which is controlled using the 10-TI-0158 device, are returned to 10-DA-201 under the 30th plate in 10-DA-201. The 10-DA-203 stripping cube is divided by a partition that ensures a constant level of kerosene fraction in the inter-tube space of the 10-EA-207 thermosyphon reboiler. The kerosene fraction from the lower plate enters the bottom part of the stripper on the side of the flow outlet into the reboiler 10-EA-207. The steam-condensate mixture of 10-EA-207 with a temperature of 203-220°C is returned to the bottom part of the stripper. The temperature of the kerosene fraction streams before and after 10-EA-207 is controlled using devices 10-TI-0154, 10-TI-0155. The clarity of separation of the kerosene and unstable gasoline fractions is ensured by maintaining a set temperature between the 2nd and 3rd stripping plates 10-DA-203, adjusted by pressure from the 10-PI-0428 device. The diesel fraction from the 17th blind plate of column 10-DA-201 with a temperature of 244-295°C, which is monitored using the 10-TI-0151 device, is divided into two streams: the diesel circulation stream and the stream supplied to stripping. 10-DA-202. The circulating irrigation flow by the 10-GA-206A/S pump is supplied to the tube space of the 10-EA-202 heat exchanger, where, giving off heat to the light raw material of the fractionation column entering through the intertubular space, it is cooled and, at a temperature of 170-225°C, is supplied as circulating irrigation to the 21st plate in column 10-DA-201. The flow rate of circulation irrigation into the 10-DA-201 column in the amount of 110-130 t/h is regulated by the flow regulator 10-FIC-0057, the valve 10-FV-0057 of which is installed at the outlet of circulation irrigation from 10-EA-202. The temperature of the circulation irrigation into the column 10-DA-201 at the outlet of 10-EA-202 is regulated by the temperature controller 10-TIC-0125, the valve 10-TV-0125 of which is installed on the bypass of the heat exchanger 10-EA-202. The presence of liquid at the suction of 10-GA-206A/S pumps is monitored by a level switch 10-LS-0068 with a block to stop the 10-GA-206A/S pump due to lack of liquid. The main flow of the diesel fraction removed from column 10-DA-201 with a constant flow rate from 10-FIC-0076 through valve 10-FV-0076 is supplied for stripping light hydrocarbons to the upper 6th plate in stripping 10-DA-202. Light fraction vapors from the top of stripping 10-DA-202 with pressure up to 2.04 kgf/cm 2and a temperature of 246-252°C, which is monitored using the 10-TI-0160 device, and the GDA units from 10-DA-501 are returned under the blind 25th plate in 10-DA-201. The 10-DA-202 stripping cube is divided by a partition that ensures a constant level of diesel fraction and the creation of a driving force in the inter-tube space of the 10-EA-206 reboiler. The steam-condensate mixture of 10-EA-206 with a temperature of 250-293°C is returned to the bottom part of the stripper. From cube 10-DA-201 there is a gravity line for emergency release of the column through shut-off valve 10-HV-0157 into emergency discharge tank 10-FA-412. The level in the bottom of the 10-DA-201 column is regulated by the 10-LICА-0032 level regulator, valves 10-FV-0109, 10-FV-0112 of which are installed on the hot and cold gas oil output lines from the installation after the 10-EA-214A/B heat exchangers and 10-EC-203. The choice of level control in the cube of column 10-DA-201 from devices 10-LICSA-0032A and 10-LICSA-0032B is carried out using the selector 10-HS-0309, with signaling at a low level of 25% and a high level of 80% level. When an emergency low level of 7% is reached from devices 10-LICSA-0032A/B, a block to stop the pump 10-GA-202A/S is triggered, and when an emergency high level of 93% is reached, a block to close the valve 10-FV-0067 on the supply line is triggered pair in column 10-DA-201. Commercial gas oil from the bottom of column 10-DA-201 with a temperature of 342-370°C is supplied through a cut-off valve 10-HV-0075 by a pump 10-GA-202A/S to reboilers 10-EA-206, 10-EA-207, 10-EA -506, from where the combined gas oil flow with a temperature of 328-358°C enters in two parallel flows into the annulus of heat exchangers 10-EA-217C/V/A and 10-EA-217F/E/D, where it heats the hydrocracking raw material. 2. Identification of the control object
To synthesize an ACP, it is necessary to know the mathematical model of the control object. The mathematical model of the control object was obtained by the method of active experiment. It consists of taking transient characteristics and determining the transfer function coefficients from them. The transient response is the solution of the differential equation of the system with a step input action and zero initial conditions. This characteristic, as a differential equation, characterizes the dynamic properties of a linear system (stationarity of object properties, linearity of the control object, concentration of object parameters). 2.1 Identification by reference channel
The transient response along the reference channel was removed after changing the position of the 10FV0076 valve from 40.4% to 42% opening. The object's response to disturbance was measured by a sensor at position 10TI0147 and recorded on the SCADA system. To identify the object, the Shimoyu integral area method will be used. To increase the accuracy of this method, the acceleration curve will be smoothed using the moving average method. Delay time: τз=25 min. 2.2 Identification of an object by disturbance channel
A sharp change in irrigation flow into column 10DA201, measured by the device at position 10FI0066, was chosen as a stepwise impact on the object through the disturbance channel. Such an impact can be considered stepwise with sufficient accuracy. Similar to identifying an object using a reference channel, to improve accuracy it is necessary to smooth out the transient response. Calculation of the object's transmission coefficient: Lag time: Object identification was performed in the LinReg program. As a result, the object model looks like: 3. Synthesis of the regulatory system
3.1 Synthesis of a single-loop temperature control system on the 17th tray of the 10DA201 fractionation column
The temperature in the column is controlled by changing the flow rate of diesel fuel discharge from the 17th plate. In this system, the irrigation flow into the column will be an external disturbance. A system with a PI regulator was considered as a single-circuit level control system. The calculation of the optimal settings of the PI regulator was carried out using the Rotach method V.Ya. using the LinReg program. PI controller settings: Ti=13.6.res=0.046 3.2 Synthesis of a single-circuit temperature control system on the 17th plate of the 10DA201 fractionation column with compensation for disturbance through the irrigation channel
One of the disturbances affecting the operation of the column is a change in the irrigation flow rate supplied under the 31 trays of the column. This disturbance is measurable, which makes it possible to create a system that compensates for this disturbance. The block diagram of such a system will take the form shown in Fig. 8. To ensure the condition of absolute invariance of the controlled quantity relative to the disturbance, the condition must be satisfied After substituting the real values of the transfer functions Wυ (s), Wµ (s) and Wp (s) we obtain This function cannot be implemented due to the presence of the e20s lead. It is impossible to achieve absolute invariance in such a system, so the problem should be solved with invariance up to ε. Let us determine the vector of this function at the most dangerous resonant frequency: WK (jwres) =-2.9+3.2i The CFC vector at the resonant frequency falls into the 2nd quadrant of the complex plane, so it makes sense to use a real second-order differentiating link as a device for inputting the influence of a disturbance, because its CFC is also partially in the 2nd quadrant. In general, the second order differentiating link has the form Neglecting the lead in the transfer function of the ideal compensating element, we obtain the transfer function of the compensator After analyzing the function in Matlab, we can conclude that the coefficient of the first power in the numerator is insignificant. Also neglecting the coefficients at the third degree (since they do not have a significant effect on the properties of the transfer function), we reduce the transfer function to the form of a real second-order differentiating link Fig.9 Adjustment of compensator coefficients. As a result, the transfer function of the compensator was obtained 4. Simulation of an automatic control system in the Simulink application of the MatLab package
4.1 Modeling an ideal ATS
Fig. 11 Testing the task of a single-circuit ACS and an ACS with disturbance compensation. Fig. 12 Testing the disturbance of a single-circuit ACS and an ACS with disturbance compensation. 4.2 Comparison of the operation of a single-circuit ACS and an ACS with disturbance compensation
Parameter Single-circuit ACS Single-circuit ACS with disturbance compensation By reference By disturbance By reference By disturbance Maximum surge 1,313,11,313,1 Regulation time, min 16924016995 Degree of attenuation 0,870,870,870,99 4.3 Simulation of a real ATS
The operation of a real system differs from the ideal one by some nonlinearities, such as insensitivity of sensors, limited stroke and backlash of the actuator. The following elements are used to model them: Deadzone - the block generates a zero output within the specified area, called the dead zone (measurement range*accuracy class*0.05=0.06; measurement range*accuracy class*0.05= - 0.06); Backlash - models the backlash present in the actuator ( Δy *0,05=0,5);
Saturate - nonlinear limiter element models the limitation of the actuator stroke (70; - 30); Fig. 13 Model of a real single-circuit ACS and a real ACS with disturbance compensation. 4.4 comparison of characteristics of ideal and real ATS
Fig. 14 Working out the task with an ideal and real system. Fig. 15 Perturbation testing of real and ideal single-circuit ACS Fig. 16 Testing of disturbance of ideal and real ACS with disturbance compensation. Parameter Processing the task Processing the disturbance of a single-circuit automatic control system without disturbance compensation Processing the disturbance of a single-circuit automatic control system with disturbance compensation ideal real ideal real ideal real Maximum overshoot 13,112,831313131 Regulation time, min 16937024047995327 Degree of attenuation 0,870,920,890,910,990,9 9 The ideal and real systems practically do not differ in maximum emission and degree of attenuation, but the real system has a significantly lower performance. It was experimentally found that the main influence on the performance is the backlash of the actuator. Therefore, when choosing automation equipment, special attention should be paid to the choice of actuator. 5. Calculation of the regulatory body and selection of automation equipment
5.1 Regulatory body calculation
P1=P2=2kgf/cm2 Fmax=115000kg/hour = 160 m3/hour Din=0.3m Determination of the total pressure drop in the network: Let's calculate the value of the Reynolds criterion at maximum flow: Condition for hydraulic smoothness of pipes: the condition is met, therefore the pipe is not hydraulically smooth. We determine the friction coefficient λ=0.0185 based on the value of the Re criterion and the ratio of the internal diameter of the pipe to the height of the pipeline roughness protrusions according to the nomogram. Find the total length of straight sections of the pipeline: Determination of the average speed in the pipeline at maximum flow: Let's calculate the pressure loss in straight sections of the pipeline: Let us determine the total coefficient of local resistance of the pipeline: Let's calculate the pressure loss in the local resistance of the pipeline: Total line pressure loss: Pressure drop in the regulator at maximum flow: Let's find the maximum capacity of the regulatory body: Table of conditional capacity of regulatory authorities We select a regulatory body with a conditional throughput and a nominal diameter. Let's check the effect of viscosity on the throughput of the regulator; to do this, we will recalculate the value of the Reynolds criterion in accordance with the diameter of the nominal diameter of the regulator: We select this regulatory body without determining the correction factor for liquid viscosity. Let us determine the adjusted value of the maximum flow rate: Let's determine the relative values of expenses: Determination of the range of movement for n=0 with linear characteristic We determine the range of movements for: a) With linear characteristic: b) With equal percentage characteristic: 0.23< S < 0,57 We determine the maximum and minimum values of the transmission coefficient for the operating load range: a) For linear throughput characteristic: b) For equal percentage throughput: The value of the ratio of the minimum and maximum values of the transmission coefficient with a linear throughput characteristic is greater than with an equal percentage. Therefore, we choose a linear flow characteristic. Static imbalance of the shutter: Maximum possible pressure on the valve; Difference in area of the upper lower body; Medium pressure force on the rod: Rod diameter; Maximum pressure behind the valve 5.2 Selection of technical automation equipment
Small-sized control valve manufactured by LG Avtomatika. The pneumatic actuator is supplied complete with the valve. Nominal pressure Ru, MPa1.6 Nominal bore, mm200 Flow characteristics linear Temperature range of the controlled medium - 40. +500 Ambient temperature range -50…+70 Initial positions of the valve plunger NZ - normally closed Housing material 12Х18Н10ТThrottle pair material 12Х18Н10ТLeakage class for control valves according to GOST 23866-87 (according to DIN) VLeakage class according to GOST 9544-93В Isolating barrier spark-proof meter 631 isobar Basic barrier error when transmitting an analog signal: 0.05% Power input current limitation: 200mA Sensor side input current limitation: 23.30mA Supply voltage, V: 20.30 Explosion protection marking: ExiaIIC Response time, ms: 50 MTBF, hours: 50000 Thermal converter with a unified output signal THAU Metran 271 Output signal: 4.20mA Temperature range: - 40…800 O WITH Basic error limit: 0.25% Signal dependence on temperature: linear Vibration resistance: V1 Explosion protection marking: ExiaIICT5 Supply voltage, V: 14.34 Rosemount 8800D Vortex Flowmeter Output signal: 4.20mA with digital signal based on HART protocol, frequency pulse 0.10kHz, digital FF Medium temperature range: - 40…427 O WITH Volume flow measurement limit m 3/h: 27…885 Limit of permissible basic error: 0.65% Degree of protection against dust and water: IP65 Vibration resistance: V1 Explosion protection marking: ExiaIICT6 Maximum input supply voltage: 30V Maximum input current: 300mA 6. Metrological calculation of measuring channels
The block diagram of the temperature and flow measurement channels is as follows: Fig. 17 Block diagram of measuring channels. The error of this measuring system consists of the errors introduced by the sensitive element of the temperature sensor, the normalizing converter, the spark protection barrier, the communication line, and the input board of the microprocessor complex. At the moment, manufacturers of cables and data transfer interfaces have practically reduced the error introduced by the communication line to zero, therefore, it is not taken into account in calculations. In turn, the errors of the normalizing converter, the sensitive element, as well as the input/output board of the microprocessor complex are determined by the manufacturer, then the permissible error limit of the measuring channel will be determined as: γ dt=0.25% - thermal converter error; γ business=0.05% - error introduced by the spark protection barrier; γ PM=0% - error introduced by the communication line; γ IV γ dt=0.65% - thermal converter error; γ business=0.05% - error introduced by the spark protection barrier; γ PM=0% - error introduced by the communication line; γ IV=0.1% - I/O board error. This error will ensure the required channel measurement accuracy. 7. Calculation of the reliability of the automatic control system
The reliability of a control system is understood as the ability of the system to fulfill the requirements placed on it within a given time within the limits specified by its technical characteristics. It is impossible to completely eliminate equipment failure; therefore, the reliability of the control system cannot be 100%. Let's calculate the probability of sudden failures of the measuring channel if it is known that: for ExperionC300 controllers the mean time between failures tWed n =
150,000 hours; for thermal converter THAU Metran 271 MTBF tWed n=20000 hours; for Rosemount 8800D flowmeter MTBF tWed n=50000 hours; for spark protection barriers Metran 631 MTBF tWed n=50000 hours; for connecting wires, the probability of failure in 2000 hours is 0.004. Let us conditionally assume that the failure distribution law is exponential, then the probability of failure-free operation is determined by the formula: , where λ
=1/tWed n. Probability of failure-free operation of the ExperionC300 controller: Probability of failure-free operation of the thermal converter THAU Metran 271: Probability of failure-free operation of the Metran 631 spark protection barrier: Rosemount 8800D Flow Meter Probability: Probability of failure-free operation of communication lines:
