How to Control Gas Burners Safely

How to Control Gas Burners Safely
China has abundant natural gas and gas resources, which are clean energy. It has good social and economic benefits. The gas burner is in line with China's industrial policies, with good market prospects and broad development prospects. However, in the development and design of gas burners, the characteristics of gases - flammable, explosive, and toxic - are the primary issues of safety control. The following describes the safety control requirements for gas burners: Based on the combustion characteristics of the gas in the furnace, the safety control requirements mainly include pre blowing, automatic ignition, combustion status monitoring, non ignition protection, flameout protection, gas pressure high and low limit protection, insufficient pressure protection, power outage protection, measures to prevent gas leakage accidents, etc. Etc.
1. Before igniting the pre blown burner, there must be a period of pre blowing to blow away or dilute the remaining air in the furnace and flue. Due to the inevitable presence of residual gas in the working chamber of the burner, there is a risk of explosion if it is ignited without pre blowing. The remaining gas must be blown out or diluted to ensure that the gas concentration is not within the explosion limit. The pre blowing time is related to the furnace structure and blowing volume, and is generally set at 15-60 seconds
2. Automatic ignition gas burner shall adopt electric Spark-ignition engine ignition to facilitate automatic control. High voltage ignition transformers can be used to generate arc ignition, with output energy requirements of voltage ≥ 3.5KV, current ≥ 15mA, and ignition time generally 2-5 seconds.
3. Combustion status monitoring: The combustion status must be dynamically monitored. Once the flame detector senses the flameout signal, it must be fed back to the burner in a short period of time, and the burner will enter a protective state and cut off the gas supply at the same time. The flame detector must be able to sense the flame signal normally, neither sensitive nor dull. Due to its high sensitivity, if the combustion state fluctuates, it is easy to cause faults and dullness, and the feedback flame signal lags, which is not conducive to safe operation. It is generally required that the response time from the flameout signal to the flameout signal emitted by the flame detector should not exceed 0.2 seconds.
4. Flame protection. When the burner is ignited, gas is introduced, ignited, and burned. The ignition action requires the formation of an ignition temperature field before the introduction of gas, in order to facilitate ignition and combustion. If the ignition fails, the flame detector cannot sense the flame signal and the burner enters a protective state. The time from ignition to entering the protective 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 the time is too long, a large amount of gas will enter the furnace when it cannot be ignited. Usually, it is required that the burner judge the flame signal detected by the flame detector within 2-3 seconds after the gas is turned on. If it does not catch fire, it will enter a protected state, and if it catches fire, it will remain burning.
5. Flame out protection: If the flame is accidentally extinguished during combustion, the burner will enter a protective state. Because the stove is very hot. Entering the gas is prone to detonation, so it is necessary to enter a protective state and cut off the gas supply in a short period of time. The response time for this process from the occurrence of flameout to the protection state of the burner should not exceed 1 second.
6. The upper and lower limits of gas pressure protect the gas burner from stable combustion within a certain range, and only allow gas pressure 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, or backfire, while limiting the output thermal power of the burner to ensure safe and economical operation of the equipment. When the gas pressure exceeds this range, the burner should be locked in operation. The design of a burner generally uses a gas pressure switch to sense the pressure signal, and outputs the switch signal to control the corresponding operation of the burner. 7. Insufficient air pressure protection. The gas burner is designed with high thermal intensity, and its combustion method adopts forced air blasting. If the fan malfunctions, the air is interrupted or insufficient, immediately cut off the gas, otherwise the furnace will explode or flash back to the fan.
Therefore, while improving the quality of the fan, gas control must be interlocked with air pressure. When the air pressure is insufficient, the gas supply should be immediately cut off. Usually, gas pressure switches are used to sense gas pressure signals and output switch signals to control the corresponding operation of gas solenoid valves. 8. Power outage protection: When the burner suddenly loses power during operation, the gas supply must be immediately cut off to protect the safety of the equipment. The gas control solenoid valve must always be closed. Once the power is cut off, it will automatically shut down and cut off the gas supply.
The response time for closing the solenoid valve is ≤ 5s. 9. Measures to prevent gas leakage accidents: Gas leakage includes two aspects: one refers to the leakage of gas into the environment through pipelines, and the other refers to the leakage of gas through the electromagnetic valve core end facing the furnace. Environmental leaks may lead to poisoning and explosion accidents among construction personnel, and must be taken seriously. Firstly, ensure that the pipeline is sealed and regularly check for leaks. If pipeline leakage must be eliminated, it can be used. Secondly, in order to avoid gas concentrations that may cause poisoning and explosion, it is required that the work site be well ventilated: permanent ventilation holes and forced ventilation are required. Installation; In addition, it is required to prohibit the use of fireworks and explosion-proof electrical components at the workplace. Leaks in the furnace may cause the furnace to explode.
There are three methods to solve the leakage problem in the furnace:
1： Strengthen the pre blowing time and blowing volume, blow off or dilute the gas in the furnace;
2： The gas pipeline adopts two series electromagnetic valves to improve system safety;
3： Use a pipeline leak detection device to detect natural gas pipelines before ignition. If the gas leakage reaches a certain amount, the burner will be locked.