my country's natural gas and coal-based gas (raw material is coal) are rich in resources and are clean energy sources, which have good social and economic benefits. The gas burner conforms to my country's industrial policy, and has a good market prospect and great development prospects. However, in the development and design of gas burners, the characteristics of gas - flammable, explosive and toxic, are the primary issues of safety control. The following introduces the safety control requirements of gas burners:
According to the combustion characteristics of the gas in the furnace, the safety control requirements mainly include pre-blowing, automatic ignition, combustion state monitoring, protection for ignition failure, protection for flameout, protection for high and low gas pressure, protection for insufficient air pressure, and power failure. Measures to protect and prevent gas leakage accidents, etc.
1. Pre-blowing
Before the burner is ignited, there must be a period of pre-blowing to blow off or dilute the residual gas in the furnace and flue. Because there is inevitably residual gas in the working furnace of the burner, if it is ignited without pre-blowing, there is a danger of explosion. The residual gas must be blown off or diluted to ensure that the gas concentration is not within the explosion limit.
The pre-blowing time is related to the structure of the furnace and the blowing volume, generally set to 15-60 seconds
2. Automatic ignition
The gas burner should be ignited by electric spark, which is convenient for automatic control. A high-voltage ignition transformer can be used to generate arc ignition, and its output energy is required to be: voltage ≥ 3.5K V, current ≥ 15mA, and the ignition time is generally 2 to 5 seconds.
3. Combustion status monitoring
The combustion state must be dynamically monitored. Once the flame detector detects the flameout signal, it must be fed back to the burner in a very short time, and the burner will enter the protection state immediately, and the gas supply will be cut off at the same time.
The flame detector should be able to sense the flame signal normally, neither sensitive nor dull. Because it is sensitive, if the combustion state fluctuates, it will easily cause malfunction and become slow, and the feedback flame signal will lag behind, which is not conducive to safe operation.
It is generally required that the response time from the flameout to the flame detector sending out the flameout signal should not exceed 0.2 seconds.
4. Protection against ignition failure
When the burner is ignited, gas is passed in, and the gas ignites and burns. The ignition action is required to occur before the gas is introduced, and the ignition temperature field is formed first, which is convenient for ignition and combustion. If the ignition fails, the flame detector cannot detect the flame signal, and the burner enters the protection state.
The time from ignition to entering the protection state should be appropriate, neither too short nor too long. If it is too short, there will be no time to form a stable flame; if it is too long, a large amount of gas will enter the furnace when the ignition fails. It is generally required that the burner judges the flame signal sensed by the flame detector within 2-3 seconds after the gas is turned on. If it is not on fire, it will enter the protection state, and if it is on fire, it will maintain combustion.
5. Flame protection
During the combustion process of the burner, if the flame is accidentally turned off, the burner will enter the protection state. Because the furnace is hot. Gas entering is prone to deflagration, so it is necessary to enter the protection state in a very short time and cut off the gas supply.
From the flameout to the burner entering the protection state, the response time of the process is required to be no more than 1 second.
6. Gas pressure high and low limit protection
The gas burner has a certain range for stable combustion, and only the gas pressure is allowed to fluctuate within a certain range. The purpose of limiting the high and low pressure of gas is to ensure the stability of the flame: no flameout, no flameout and no tempering, and at the same time limit the output heat power of the burner to ensure the safe and economical operation of the equipment. When the gas pressure exceeds this range, the burner should be locked to work.
The design of the burner generally uses a gas pressure switch to sense the pressure signal and output a switch signal to control the corresponding work of the burner.
7. Insufficient air pressure protection
The gas burner is designed with high heat intensity, and its combustion method adopts forced air blast. If the fan fails and causes air interruption or insufficient air, cut off the gas immediately, otherwise the furnace will deflagrate or flash back to the fan. Therefore, while improving the quality of the fan, the gas control must be interlocked with the air pressure. When the air pressure is insufficient, the gas supply should be cut off immediately.
Generally, a gas pressure switch is used to sense the air pressure signal and output a switch signal to control the corresponding work of the gas solenoid valve.
8. Power failure protection
If the burner suddenly loses power during operation, the natural gas supply must be cut off immediately to protect the safety of the equipment. The gas control solenoid valve must be a normally closed type, once the power is cut off, it will automatically close and cut off the gas supply. Solenoid valve closing response time ≤5s.
9. Measures to prevent gas leakage accidents
Gas leakage includes two aspects, one refers to the leakage of gas to the environment through the pipeline, and the other refers to the leakage of gas through the end of the solenoid valve spool facing the furnace.
Environmental leakage may cause personnel poisoning and explosion accidents at the work site, so we must attach great importance to it. First of all, ensure that the pipeline is sealed, and regularly check the pipeline for leaks. If the pipeline leaks, it must be eliminated before continuing to use; secondly, to avoid the gas concentration that causes poisoning and explosion, the work site is required to be well ventilated: configure permanent ventilation holes and forced ventilation In addition, it is required to prohibit fireworks and explosion-proof electrical parts at the work site.
Leakage in the furnace may cause an explosion in the furnace. There are three ways to solve the leakage problem in the furnace: one is to strengthen the pre-blowing time and blowing volume to blow off or dilute the gas in the furnace; the other is to use two solenoid valves in series in the gas pipeline to improve system safety; the third is to use pipeline The leakage detection device detects the gas pipeline before ignition, and if the gas leakage reaches a certain amount, the burner will be locked to work.
The measures to prevent gas leakage belong to peripheral control and are generally not included in the control of the burner itself.
my country's natural gas and coal-based gas (raw material is coal) are rich in resources and are clean energy sources, which have good social and economic benefits. The gas burner conforms to my country's industrial policy, and has a good market prospect and great development prospects. However, in the development and design of gas burners, the characteristics of gas - flammable, explosive and toxic, are the primary issues of safety control. The following introduces the safety control requirements of gas burners:
According to the combustion characteristics of the gas in the furnace, the safety control requirements mainly include pre-blowing, automatic ignition, combustion state monitoring, protection for ignition failure, protection for flameout, protection for high and low gas pressure, protection for insufficient air pressure, and power failure. Measures to protect and prevent gas leakage accidents, etc.
1. Pre-blowing
Before the burner is ignited, there must be a period of pre-blowing to blow off or dilute the residual gas in the furnace and flue. Because there is inevitably residual gas in the working furnace of the burner, if it is ignited without pre-blowing, there is a danger of explosion. The residual gas must be blown off or diluted to ensure that the gas concentration is not within the explosion limit.
The pre-blowing time is related to the structure of the furnace and the blowing volume, generally set to 15-60 seconds
2. Automatic ignition
The gas burner should be ignited by electric spark, which is convenient for automatic control. A high-voltage ignition transformer can be used to generate arc ignition, and its output energy is required to be: voltage ≥ 3.5K V, current ≥ 15mA, and the ignition time is generally 2 to 5 seconds.
3. Combustion status monitoring
The combustion state must be dynamically monitored. Once the flame detector detects the flameout signal, it must be fed back to the burner in a very short time, and the burner will enter the protection state immediately, and the gas supply will be cut off at the same time.
The flame detector should be able to sense the flame signal normally, neither sensitive nor dull. Because it is sensitive, if the combustion state fluctuates, it will easily cause malfunction and become slow, and the feedback flame signal will lag behind, which is not conducive to safe operation.
It is generally required that the response time from the flameout to the flame detector sending out the flameout signal should not exceed 0.2 seconds.
4. Protection against ignition failure
When the burner is ignited, gas is passed in, and the gas ignites and burns. The ignition action is required to occur before the gas is introduced, and the ignition temperature field is formed first, which is convenient for ignition and combustion. If the ignition fails, the flame detector cannot detect the flame signal, and the burner enters the protection state.
The time from ignition to entering the protection state should be appropriate, neither too short nor too long. If it is too short, there will be no time to form a stable flame; if it is too long, a large amount of gas will enter the furnace when the ignition fails. It is generally required that the burner judges the flame signal sensed by the flame detector within 2-3 seconds after the gas is turned on. If it is not on fire, it will enter the protection state, and if it is on fire, it will maintain combustion.
5. Flame protection
During the combustion process of the burner, if the flame is accidentally turned off, the burner will enter the protection state. Because the furnace is hot. Gas entering is prone to deflagration, so it is necessary to enter the protection state in a very short time and cut off the gas supply.
From the flameout to the burner entering the protection state, the response time of the process is required to be no more than 1 second.
6. Gas pressure high and low limit protection
The gas burner has a certain range for stable combustion, and only the gas pressure is allowed to fluctuate within a certain range. The purpose of limiting the high and low pressure of gas is to ensure the stability of the flame: no flameout, no flameout and no tempering, and at the same time limit the output heat power of the burner to ensure the safe and economical operation of the equipment. When the gas pressure exceeds this range, the burner should be locked to work.
The design of the burner generally uses a gas pressure switch to sense the pressure signal and output a switch signal to control the corresponding work of the burner.
7. Insufficient air pressure protection
The gas burner is designed with high heat intensity, and its combustion method adopts forced air blast. If the fan fails and causes air interruption or insufficient air, cut off the gas immediately, otherwise the furnace will deflagrate or flash back to the fan. Therefore, while improving the quality of the fan, the gas control must be interlocked with the air pressure. When the air pressure is insufficient, the gas supply should be cut off immediately.
Generally, a gas pressure switch is used to sense the air pressure signal and output a switch signal to control the corresponding work of the gas solenoid valve.
8. Power failure protection
If the burner suddenly loses power during operation, the natural gas supply must be cut off immediately to protect the safety of the equipment. The gas control solenoid valve must be a normally closed type, once the power is cut off, it will automatically close and cut off the gas supply. Solenoid valve closing response time ≤5s.
9. Measures to prevent gas leakage accidents
Gas leakage includes two aspects, one refers to the leakage of gas to the environment through the pipeline, and the other refers to the leakage of gas through the end of the solenoid valve spool facing the furnace.
Environmental leakage may cause personnel poisoning and explosion accidents at the work site, so we must attach great importance to it. First of all, ensure that the pipeline is sealed, and regularly check the pipeline for leaks. If the pipeline leaks, it must be eliminated before continuing to use; secondly, to avoid the gas concentration that causes poisoning and explosion, the work site is required to be well ventilated: configure permanent ventilation holes and forced ventilation In addition, it is required to prohibit fireworks and explosion-proof electrical parts at the work site.
Leakage in the furnace may cause an explosion in the furnace. There are three ways to solve the leakage problem in the furnace: one is to strengthen the pre-blowing time and blowing volume to blow off or dilute the gas in the furnace; the other is to use two solenoid valves in series in the gas pipeline to improve system safety; the third is to use pipeline The leakage detection device detects the gas pipeline before ignition, and if the gas leakage reaches a certain amount, the burner will be locked to work.
The measures to prevent gas leakage belong to peripheral control and are generally not included in the control of the burner itself.