??Natural gas burner control system and safety issues

As far as the current situation of the world is concerned, natural gas and coal are relatively abundant as raw materials, which are clean energy and have good social and economic benefits. The proportion of natural gas burners is more in line with the current industrial policy, so the market prospects are very good.

However, in the development process of natural gas burner, the natural gas characteristics of "flammable, explosive, toxic" three hazards are the primary problem of safety control. Today, EBICO burner will explain the control system and safety issues of natural gas burner.

Safety control requirements of natural gas burner: according to the combustion characteristics of the gas in the furnace, safety control requirements mainly include pre-blowing, automatic ignition, combustion condition monitoring, non-ignition protection, flameout protection, high and low pressure limit protection, pressure insufficiency protection, power outage protection, measures to prevent gas leakage accidents, etc.

1. Preblow the natural gas burner??

Before the burner is operational, there must be a period of preblowing to blow away or dilute the remaining gas in the chamber and flue. Due to the inevitable presence of residual gas in the working chamber of the natural gas burner, there is a danger of explosion if it is ignited without pre-blowing. The remaining gas must be blown off or diluted to ensure that the gas concentration is not within the explosion limit.

The preblowing time is related to the furnace structure and the blowing volume, which is generally set to 15-60 seconds

2. Automatic ignition??

The natural gas burner should be ignited by electric spark to facilitate automatic control. High voltage ignition transformer can be used to generate arc ignition, its output energy requirements are: voltage ≥ 3.5kV, current ≥15mA, ignition time is generally 2~5 seconds.

3. Combustion status monitoring??

The burning state must be dynamically monitored. Once the flame detector detects the flameout signal, it must be fed back to the natural gas burner in a short time, and then enter the protected state and cut off the gas supply.

The flame detector must be able to sense the flame signal normally, neither sensitive nor dull. Due to its sensitivity, it is easy to cause failure and slowness if the combustion state fluctuates. The feedback flame signal is delayed, which is not conducive to safe operation. Generally, the response time from flameout to flameout signal issued by the flame detector is not more than 0.2 seconds.

4. Fire prevention measures??

When a natural gas burner is ignited, gas is introduced, and the gas ignites and burns. The ignition action requires the formation of an ignition temperature field before the gas is introduced to facilitate ignition and combustion. If the ignition fails, the flame detector cannot sense the flame signal, and the burner enters the protected state.

The time from ignition to protection should be appropriate, neither too short nor too long. If it's too short, there won't be time to form a steady flame; If the time is too long, a large amount of gas will enter the furnace when it cannot be ignited. Usually, the burner is required to determine the flame signal detected by the flame detector within 2-3 seconds after the gas supply. If it doesn't catch fire, it will go into a protected state, and if it catches fire, it will stay burning.

5. Protection measures for flameout??

In the burner combustion process, if accidentally extinguished, the burner will enter a protected state. Because the stove is very hot. Gas is easy to deignite, so it is necessary to enter the protective state and cut off the gas supply in a very short time. The response time for this process should not exceed 1 second from the time of flameout to the time of the burner entering the protected state.

6. Gas pressure limit protection??

The gas burner has a certain range of stable combustion and only allows the gas pressure to fluctuate within a certain range. The purpose of limiting gas high and low pressure is to ensure the stability of the flame: no flameout, no flameout or backfire, and limit the output thermal power of the burner to ensure the safe and economic operation of the equipment. When the gas pressure exceeds this range, the burner should be locked.

The design of the burner generally uses the gas pressure switch to sense the pressure signal, and the output switch signal to control the corresponding operation of the burner.

7. Insufficient pressure protection??

The gas burner is designed with high thermal strength and the combustion mode is forced air explosion. If the fan fails, the air is interrupted or insufficient, cut off the gas immediately, otherwise the furnace will deignite 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 pressure is insufficient, the air supply should be cut off immediately.

Usually, gas pressure switches are used to sense pressure signals and output switching quantity signals to control the corresponding operation of gas solenoid valves.

8. Power off protection??

When the burner is suddenly cut off in the operation process, the gas supply must be cut off immediately to protect the safety of the equipment. Gas control solenoid valve must be normally closed. In the event of a power failure, it will automatically shut down and cut off the gas supply. The closing response time of the solenoid valve is less than 5S.

9. Measures to prevent gas leakage accidents??

Gas leakage includes two aspects, one refers to the gas leakage into the environment through the pipeline, the other refers to the gas leakage into the furnace through the solenoid spool end.

Environmental leakage may lead to poisoning and explosion accidents in construction sites, which must be taken seriously. First, make sure the pipes are sealed and check them regularly for leaks. Can be used if pipe leaks must be eliminated. Secondly, in order to avoid the gas concentration may cause poisoning and explosion, the work site is required to be well ventilated: permanent ventilation hole and forced ventilation installation; In addition, the requirement prohibits the use of fireworks and explosion-proof electrical components at the work site.

A leak in the furnace may cause it to explode. There are three ways to solve the problem of air leakage in the furnace: one is to strengthen the preblowing time and blowing volume, blowing or diluting the gas in the furnace; Two is the use of two solenoid valve series, improve the safety of the system; The third is to use the pipeline leakage detection device to detect the gas pipeline before ignition. If the gas leakage reaches a certain amount, the burner will be locked. Measures to prevent gas leakage belong to external control and are generally not included in burner control.

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