How to safely control a gas burner:
my country's natural gas and coal-based gas resources are abundant, and they are clean energy sources. Gu has good social and economic benefits. Gas burners are in line with my country's industrial policies, and the market prospects are very good, with great development prospects. However, in the development and design of gas burners, the characteristics of gas—flammable, explosive and toxic—are the primary issues for safety control. The following describes 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 status monitoring, non-ignition protection, flameout protection, gas pressure High and low limit protection, insufficient air pressure protection, power failure protection, measures to prevent gas leakage accidents, etc.
1. Before the pre-blowing burner is ignited, there must be a period of pre-blowing to blow away or dilute the remaining air in the furnace and flue. Because there is inevitably remaining gas in the working chamber of the burner, if it is ignited without pre-blowing, there is a danger of explosion. 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 the blowing volume, generally set to 15-60 seconds
2. The automatic ignition gas burner should adopt electric spark ignition to facilitate automatic control. The high-voltage ignition transformer can be used to generate arc ignition, and its output energy is required to be: voltage ≥ 3.5K V, current ≥ 15 mA, and the ignition time is generally 2 to 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 very short time, and the burner will enter the protection 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. Because of its sensitivity, if the combustion state fluctuates, it is easy to cause malfunction and sluggishness, and the feedback flame signal is lagging, which is not conducive to safe operation. It is generally required that the response time from flameout to flameout signal sent out by the flame detector should not exceed 0.2 seconds.
4. Protection against ignition. When the burner is ignited, gas is introduced and the gas ignites and burns. The ignition action requires that the ignition temperature field be formed 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 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, it will not have time to form a stable flame; if it is too long, a large amount of gas will enter the furnace when it fails to ignite. Generally, it is 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. Flameout protection The burner will enter the protection state if the flame is accidentally extinguished during the combustion process. Because the furnace is hot. Gas entering is prone to deflagration, so it must enter the protection state in a very short time and cut off the gas supply. From the occurrence of flameout to the protection state of the burner, the response time of this process requires no more than 1 second.
6. The gas pressure upper and lower limits protect the stable combustion of the gas burner within a certain range, and only allow the gas pressure to fluctuate within a certain range. The purpose of limiting the high and low pressure of the gas is to ensure flame stability: no flameout, no flameout or backfire, and at the same time limit the output heat 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 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 blasting. If the fan fails and the air is interrupted or the air is insufficient, immediately cut off the gas, 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 quantity signal to control the corresponding operation of the gas solenoid valve. 8. Power-off protection When the burner suddenly loses power during the working process, the gas supply must be cut off immediately to protect the safety of the equipment. The gas control solenoid valve must be normally closed. 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 gas leakage to the environment through the pipeline, and the other refers to gas leakage through the solenoid valve core end facing the furnace. Environmental leakage may cause personnel poisoning and explosion accidents at the work site, which must be taken seriously. First, ensure that the pipeline is sealed, and regularly check the pipeline for leaks. If the pipeline leaks must be eliminated, it can be used. Secondly, to avoid the gas concentration that may cause poisoning and explosion, the work site is required to be well ventilated: permanent ventilation holes and forced ventilation are required. Installation; In addition, it is required to prohibit fireworks and explosion-proof electrical parts at the work site. Leaks in the furnace may cause an explosion in the furnace.
There are three ways to solve the leakage problem in the furnace:
One: Strengthen the pre-blowing time and blowing volume, blow off or dilute the gas in the furnace;
Two: The gas pipeline adopts two solenoid valves in series to improve the safety of the system;
Three: 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.
