RU2029195C1 - Automatic control method for oil/gas combination burner - Google Patents

Abstract

FIELD: automation of thermal power generation process. SUBSTANCE: method involves testing of shut-off valves for tightness of closure (hydrostatic test) while they are all fully closed. Gas is supplied to pipeline between main and working shut-off valves through additional by-pass pining provided with design-section throttle and time within which desired pressure in this pining is attained is determined. This time is used to check system for leakage. In the course of burner preparation for work and in normal service under desired conditions time of execution of process operations is also determined and if it deviates from desired value, stop command is sent. Emergency situations for stopping are ranked according to gravity of probable consequences. Upon execution of command for stop, all process parameters are still under check and in case of one more emergency situation of heavier gravity, process stop operations are executed according to more serious emergency situation. In addition, during all process interruption periods all burner sensors are continuously interrogated. EFFECT: improved reliability of control. 6 dwg

Description

 The invention relates to the automation of heat and power processes, in particular to the automated regulation and control of the operation of gas-oil burners of small capacity, which have found widespread use in the production of heat and energy, metallurgical, thermal and other industries.

 A known method of automated control of a gas-oil burner [1], intended, for example, for boilers of the DKVR type with a productivity of 2.5 - 20 tons of steam per hour. The method is based on an automated sequence of technological operations specified through the automatic process control system of the boiler. These operations include checking the readiness of technological systems and actuators, checking the health of sensors, checking the closure density of the main and operating shutoff valves, turning on the actuators and monitoring their operation, igniting the burner, its normal operation in a given mode, and stopping it in a given sequence of technological operations , including from the onset of emergency situations.

 A disadvantage of the known method for automated control of a gas-oil burner is that the closing density of the shut-off valves is checked by opening them one by one and checking the presence of gas in the furnace, which is a very time-consuming operation carried out almost manually (crimping operation). In addition, although the execution time of technological operations is measured, it is used only as a static value, after which a command is given to perform the next operation, i.e. time is not used as a safety factor. A means of implementing the known method is a hard programming system and control of all processes from a single centralized computer. At the same time, there is no constant monitoring and diagnostics of the state of both actuators and sensors, and any failure of the system leads to an emergency shutdown with the completion of a full technological shutdown cycle, which is not always justified due to the high complexity.

 The purpose of the invention is the development of a method for automated control of a gas-oil burner, which would ensure the versatility and adaptability of the control system to the changing conditions of the burner, would simplify and automate the laborious manual operation of crimping the valves, and also provide a high degree of safety of the burner, and therefore the entire boiler .

 The goal is achieved in that the check of the closure density of the shutoff valves is carried out with their complete simultaneous closure. Gas is supplied to the pipeline between the main and the working shutoff valves through the bypass additional pipeline with a throttle of the calculated cross section and the time to reach the set value of the gas pressure in this pipeline is determined. The magnitude of this time is judged by the presence of leaks. In the process of preparing the burner for operation and in the process of its normal operation in a predetermined mode, the amount of time for performing technological operations is also determined and, when it deviates from the set value, they give a stop command. Emergency situations for shutdown are ranked according to the severity of the possible consequences. After executing the shutdown command, they continue to monitor all the technological parameters of the burner operation and, in the event of an additional emergency, higher in severity of the possible consequences, the technological shutdown operations corresponding to the most severe emergency are performed. In addition, during all technological breaks, all burner sensors are continuously polled. This method is implemented through a flexible freely programmable microprocessor system, which contains microprocessor control devices in the form of a local distributed microcomputer network with block construction of programs.

 In FIG. 1 shows a gas supply circuit for crimping valves; in FIG. 2 - graph "pressure-time" during pressure testing of valves; in FIG. 3-5 - an algorithm for the automatic control of a gas-oil burner; in FIG. 6 is a functional diagram of burner automation levels.

 A method for automated control of a gas-oil burner is as follows.

Before the first start-up of the burner, start-up from a cold reserve or start-up after an emergency stop (after performing all necessary preparatory measures provided for by the instructions for putting the burner into operation), press button 1.1 (Fig. 2) "Reset" on the control system cabinet and set the switch to 1.2 " Fuel oil "to the" Gas "position. At the same time, commands are formed for the complete closure of the guide apparatus of the smoke exhaust, the guide apparatus of the fan, the regulating organ of gas, the “Planned stop” panel is turned on (not shown in the diagram); the countdown of the time t _o necessary for closing the above-listed managed objects begins. At the same time, the execution time of the operation is compared with the specified control time: it should not be less than it and should not exceed it. Step 1.3 begins - checking the readiness of the object for work and diagnosing the health of the sensors. After 1.4 time t _o , if the object is ready and the sensors are operational, go to step 1.5; otherwise, go to step 3.1 to implement the shutdown routine N 1.

In step 1.5, all fittings are reset. During this technological pause 1.6 - t ₁ , the health of all mechanisms and sensors is re-diagnosed through communication “a”, starting from step 1.3. If all signals are positive, then go to step 1.7 - check the execution of command 1.5 (bringing the valve to its original position), check for the presence of enable signals from the limit switches (SC) in the closed state of all controlled objects (UO).

If, after the time t _{1 has} elapsed and until furthermore, the short circuit of any of the enabling short-circuit signals or any of the sensor signals has an emergency value, then a general alarm signal is generated and a signal decoding the root cause of the accident and issuing recommendations on the sequence of technological shutdown operations; burner 3.1 stops in accordance with stop routine 1.

 In the absence of an emergency, the automated burner enters the standby mode of direct start 1.8, which corresponds to starting the burner from a hot reserve or starting it after a scheduled stop.

 Start-up is carried out by pressing the 1.9 “Start” button on the control system cabinet or upon receipt of the corresponding signal from the control room or from the boiler-house control device.

In the absence of an emergency, a command 1.10 is formed to turn on the smoke exhaust; 1.11 begins - the countdown of time t ₂ ; this technological pause is used to diagnose the health of mechanisms and sensors, starting from step 1.3 (checking the burner is ready for operation). Then go to step 1.12 - checking the execution of the command of step 1.10 to turn on the smoke exhaust. If command 1.10 is not completed, then go to step 7.1 to implement the stop subroutine N 7. If the exhaust fan is on, go to step 1.13 - turn on the fan; 1.14 begins - the countdown of time t ₃ for the execution of this command, during which the actuators and sensors are diagnosed through communication "a", starting from step 1.3.

 In the absence of an emergency, step 1.15 is carried out - verification of the execution of command 1.13 to turn on the fan. If command 1.13 is not executed, then go to step 3.1 to implement the shutdown routine N 1. The same happens if the command is executed with a deviation from the specified time period.

If there are no alarms, go to step 1.16 - transfer of technological mechanisms to the pre-start ventilation mode of the furnace; 1.17 begins - the countdown of time t ₄ required to complete this operation. During this technological pause, the diagnostics of the functioning of mechanisms and sensors is carried out through the connection “a” along the entire technological chain, starting from step 1.3. Then go to step 1.18 - verification of the implementation of 1.16 in accordance with the specified norm. If the program in step 1.16 is not completed or is not fully executed, or is executed with deviations from the set time in one direction or another, then go to step 4.1 to implement the shutdown routine N 2.

In the absence of an emergency, go to step 1.19 - directly ventilate the furnace before starting the burner; 1.20 begins - the countdown of time t ₅ necessary for the implementation of this operation. This technological pause is also used to diagnose the health of mechanisms and sensors through communication “a”, starting from step 1.3.

In the absence of an emergency, they proceed to the implementation of automated crimping cycles, that is, checking for tightness of the closing of the main and working shutoff valves on the gas supply line to the burner and igniter, steps 1.21, 1.24 and 1.27. During the implementation of all three pressure testing cycles during technical pauses 1.22 (t ₆ ), 1.25 (t ₇ ), 1.28 (t ₈ ), actuators and sensors are diagnosed through communication “a”, starting from step 1.3. In the event of a malfunction or abnormality in steps 1.23, 1.26 and 1.29, a transition to step 4.1 is provided for the implementation of the stop routine N 2.

In the absence of an emergency after the crimping operation, go to step 1.30 - preparation for ignition. Commands are formed to close the fan guide apparatus, open the main gas shut-off valve and close the pressure test valve, 1.31 begins - the countdown of t ₉ required to perform the indicated operations. During this technological pause, the diagnosis of all actuators and sensors through the connection “a” is carried out for the last time, starting from step 1.3.

 In the absence of an emergency, they proceed sequentially to steps 1.32 - canceling control signals, 1.33 - checking the ignition conditions. Monitoring of the open state of the main gas shutoff valve is turned on, and the operability of the flame device is removed. If the ignition conditions are not met, go to step 5.1 to implement the shutdown routine N 3.

If there are no alarms, go to step 1.34 — turn on the ignition transformer and supply a spark. Begins 1.35 - the countdown of time t ₁₀ for the implementation of this operation. If the command fails, the operation is repeated. After t ₁₀ seconds, go to step 1.36 - a command is formed to open the pilot valve, 1.37 starts - t ₁₁ countdown. In case of failure, the operation to turn on the igniter is repeated. After t ₁₁ seconds go to step 1.38 - polling sensors. If the readings of the sensors do not match the settings, go to step 5.1 to implement the shutdown routine N 3.

In the absence of an emergency, they go to 1.40 - a command is formed to open the working gas shut-off valve, step 1.41 starts - countdown t ₁₂ , the ignition transformer is turned off, the vacuum regulator is turned off, the closed state control of the gas cut-off valve is turned off, and the torch control is turned on. During this technological pause, mechanisms and sensors are diagnosed through communication “b”, starting from step 1.38, i.e. those that serve the burner directly. If malfunctions occur, then go to step 5.1 to implement the shutdown routine N 3.

If there are no alarms, go to step 1.43 - the igniter valve is turned off, the vacuum regulator is turned on, step 1.44 starts, the countdown is t ₁₃ , during which the mechanisms and sensors are diagnosed through communication "b", starting from step 1.38.

If there are no alarms, go to step 1.45 - the gas regulator moves (stepwise) to the position corresponding to 5% of its full opening, the closed state control of the gas regulator, the fan guide is turned off, the fuel-air ratio regulator is turned on, step 1.46 starts time t ₁₄ . During this technological pause, mechanisms and sensors are diagnosed through communication “b”, starting from step 1.38.

If there are no alarms, after t ₁₄ seconds go to steps 1.47 and 1.48 - the load fan turns on and the “Normal operation” display starts, the minimum gas pressure and air pressure are monitored, the time t ₁₅ = ∞, corresponding to the normal operation of the burner, starts.

 During normal operation, the burners work: smoke exhaust, fan, regulators: load, fuel-air ratio, vacuum; “Normal operation” display and current information display; open: main gas shutoff valve, working gas shutoff valve; monitored: burner readiness, air pressure, discharge in the firebox, torch extinction, fire in the chimneys, smoke exhaust, fan operation, gas pressure, minimum gas pressure in front of the burner, opening of the main gas shut-off valve, opening of the working gas shut-off valve, opening (from the button) electric shutter.

 The proposed method for automated control of a gas-oil burner includes an automatic operation of crimping the shutoff valves. The crimping operation is a very critical technological operation in the process of preparing the burner for operation, since it is aimed at preventing an explosive situation in connection with possible gas leaks and is provided as mandatory by the Gosgortekhnadzor Rules. It is carried out in accordance with the proposed scheme for supplying gas to the burner (Fig. 1), which includes a gas pipeline 1 for supplying gas to the burner with a shut-off device 2 and a flow meter 3. On the gas pipeline 1, a main gas shut-off valve 4 and a working gas shut-off valve 5 are installed . Between valves 4 and 5 at point 6 of gas pipeline 1, an additional bypass pipe 7 of small cross section with a throttle 8 and a pressure test valve 9 is installed, the second end of which is connected at point 10 to the main gas pipeline 1 in front of the main gas shutoff valve 4. Manometers 11 are installed on both sides of point 6 on the gas line 1. The bypass line 7 also serves to ignite the igniter, to which gas enters through the ignitor gas line 12, on which the ignition valve 13 and the safety valve 14 are installed.

The crimping operation is carried out automatically through the automatic process control system of the burner as follows. Close the main gas shut-off valve 4, the working gas shut-off valve 5 and valves 13 and 14 on the igniter gas line 12. Open the disconnecting device 2 on the gas pipeline 1 and the crimping valve 9 on the additional bypass pipe 7. Gas begins to flow through the bypass pipe 7 and throttle 8 to the point 6 of the pipe connection, from where through manometers 11 to the closed valves 4 and 5. Knowing the exact calculated cross section of the throttle and gas flow through it, set the nominal time t _n , after which the pressure gauges 11 show the nominal gas pressure in the pipeline R _n . If during the set time t _n is reached the pressure P ₁ <P _n, it follows that in valves 4 and 5 are a gas leak. In this case, an emergency shutdown command will be issued. If the pressure P _n is reached within a time t ₁ <t _n , an emergency shutdown of the burner will also be given, since the presence of excess pressure in the gas pipeline 1 can also cause a future accident.

 In the process of preparing the burner for operation and in the process of its normal operation in a predetermined mode, the process execution time (starting and stopping the units, opening and closing valves, gate valves, etc.) is also determined and compared with the specified nominal values. If the run-time deviates from the set value, a command is sent to either side to stop the burner.

 Thus, for all operations that control the operation of the burner in the automatic mode, not only technological parameters are controlled, but also exact calculation of the execution time of technological operations is carried out, the value of which is constantly compared with the specified nominal (control) time set for this operation. Deviation in any direction is considered the basis for an emergency shutdown of the burner (boiler). This method of controlling a gas-oil burner allows you to judge the state of the executive body on the eve of the event, and not to state its onset, as is done in known methods. Runtime is used as a safety factor for burner operation.

 An essential point in the proposed method for automated control of a gas-oil burner is that all emergency events that cause the boiler unit to stop, which can occur during its start-up, operation and scheduled shutdown, are ranked according to the severity of the possible consequences of such an accident and for each of them apply their set of technological operations. This is done in order to shutdown with the least loss and destruction for the quickest start-up of it after eliminating the cause of the accident.

 In the above example of the method for controlling a gas-oil burner, the following types of automated shutdown (subprograms) are implemented, which are referenced in the text of the description: scheduled shutdown when starting the burner; scheduled stop before ignition of the burner; scheduled stop after ignition of the burner; scheduled shutdown from normal operation; N 1, emergency stop when starting the burner; N 2, emergency stop before ignition of the burner; N 3, emergency stop after ignition of the burner; N 4, emergency stop from normal operation; N 5, emergency stop in case of fire in gas ducts; N 6, emergency stop in violation of vacuum; N 7, emergency stop when the smoke exhaust is stopped.

 For example, consider the emergency shutdown algorithm when starting the boiler according to subroutine N 1. This type of shutdown occurs from the beginning of the control and monitoring program to the start of ventilation and pressure testing. The stop starts if: the "Emergency stop" button is pressed; a corresponding command was received from the top level of management; according to the alarm signals received from any of the emergency sensors; from limit switches of executive bodies, signaling about non-fulfillment of a command at burner start-up; from the time control unit in case of deviation from the specified nominal in one direction or another.

 The stop occurs as follows: the “Emergency stop” panel is turned on; the smoke exhauster and fan are turned off; a team is being formed to close the electric shutter on the descent of the gas pipeline; an audible alarm is turned on and a description of the reason for the violation of start-up operations and recommendations for their elimination appear on the display.

 After a stop command is received and during the shutdown process, they continue to monitor all the technological parameters of the switched-on units. In the event of an additional emergency, the higher-ranking ones in terms of the severity of possible consequences carry out technological shutdown operations corresponding to the most severe emergency.

 A feature of the proposed method for automated control of a gas-oil burner is a continuous interrogation of the burner sensors in order to establish their serviceability and readiness for work. Such a survey is carried out during all technological breaks necessary for the execution of a team by the executive bodies.

 The proposed method a combination of new features provides increased reliability and a fully automated process for controlling a gas-oil burner.

 The method is implemented through a flexible freely programmable microprocessor system in the form of a local distributed software and hardware to discrete levels of a microcomputer network with block-based program design.

Claims (1)

 METHOD FOR AUTOMATED CONTROL OF A GAS-OIL BURNER by checking the readiness of technological systems and actuators and the serviceability of sensors, checking the density of the main and working shutoff valves, turning on the actuators and monitoring their operation, igniting the burner, normal operation in a given mode and stopping in a given sequence, as well as shutdown in the event of an emergency, characterized in that the check of the closing density of the shut-off valves is carried out with their complete simultaneous close the gas by supplying gas to the pipeline between the main and the working shutoff valves through the bypass additional pipeline with a design-throttle throttle, determine the time to reach the set gas pressure in this pipeline and judging by the magnitude of this time about the presence of leaks, and during the preparation of the burner for operation and in the process of its normal operation in a given mode, they also determine the value of the execution time of technological operations and, when it deviates from a given value, give a command to stop, at ohm emergency situations for stopping are ranked according to the severity of the possible consequences, continue to monitor all the technological parameters of the burner after the stop command is executed and in the event of an additional emergency, higher than the severity of the possible consequences, perform technological stop operations corresponding to the most severe emergency, except Moreover, during all technological breaks, all burner sensors are continuously interrogated.

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