Although the frequency of accidents in the ceramic industry is lower than that in the construction industry, the water and gas used in the ceramic industry are dangerous sources and can cause great harm to people and property. If an accident occurs at a water and gas station, exceptgas generatorIn addition to its own risks, the gas stored inside is also a gas that can easily cause poisoning and is also flammable. Once leaked, it can easily cause an explosion. In addition, water and gas maintenance operations are completed in a confined space, so it is easy to cause chain poisoning of maintenance personnel. Explosion accidents mainly occur under the following conditions.

 

Gas generator hot operation

 

In the actual operation of the gas generator, if the outlet gas temperature reaches 600°C, it has exceeded the auto-ignition temperature of the generator gas (530°C). This abnormal situation is called the thermal operation of the gas generator. The main characteristic of this situation is that if the fire detection hole on the stove top is opened, the gas coming out will naturally ignite and burn. At this time, if air enters the furnace or the emerging gas mixes with the surrounding air, it will cause an explosion accident in the gas generator, so the hot operation of the gas generator is not allowed.

 

After this situation occurs, the following measures should be taken immediately: speed up the ash removal, speed up the coal feeding, and thicken the dry layer fuel coverage. The position of the oxide layer moves downward, and the amount of steam entering the furnace bottom needs to increase to cool down the oxide layer until the furnace conditions are adjusted and the temperature of the gas coming out of the furnace drops to normal temperature.

 

Steam drum is short of water

 

The steam drum is a pressure vessel connected to the water jacket of the gas generator and is part of the gas generator. The principles of explosion accidents caused by lack of water in the steam drum are different from those caused by the mixing of gas and air. When the water jacket is short of water for a long time, the furnace body and water jacket of the gas generator have been baked to 500°C or even higher. If water is added to the water jacket at this time, the water will vaporize into water vapor in an instant, and the volume will expand rapidly. The water jacket is a closed space, which is far smaller than the volume required for the rapid expansion of water vapor. When the pressure in the water jacket exceeds the pressure that the material can withstand, an explosion will occur.

 

When the steam drum is short of water, it is forbidden to add water until the cause is identified. The treatment measures for water shortage in the steam drum are: first open the water level gauge cock to drain the water. If water flows out, it indicates that the water shortage time is not long. At this time, water can be added to the water jacket. When the water level gauge cock is opened, no water flows out, indicating that the water shortage time is long. The pressure change of the steam drum should be observed through the pressure gauge. If the pressure is the same as the normal operating pressure at this time, it means that the water shortage is not serious; if the steam pressure has exceeded the working pressure, it means that the water jacket is seriously short of water. In this case, the furnace should be shut down urgently, and it is strictly forbidden to add water to the water jacket to prevent explosion accidents.

 

Gas reverse flow in air duct

 

When the air duct connected to the gas generator body is operating normally, gas will not flow back into the air duct. However, if a sudden power outage causes the blower to stop working and the check valve does not work, the gas may return from the bottom of the furnace to the blast box. Since the temperature of the returned gas is high (above 600°C), it will explode when mixed with air in the air pipe and reaches the explosion limit.

 

The main preventive measures include: ensuring that the check valve seal is reliable; after a power outage, increase the amount of steam delivered to the furnace to maintain positive pressure in the furnace; after a power outage, close the air valve as quickly as possible to cut off the air entering the furnace bottom to prevent air from entering the furnace and causing an accident; depending on the gas outlet pressure, open the release valve to reduce the pressure at the furnace bottom and prevent the gas from flowing back to the blast box; after a power outage, the gas in the air main pipe must be purged with steam before it can be transferred to normal operation.

 

Operation status changes

 

Among users who use generator gas, the gas demand is not fixed, but changes continuously with the production situation. When the change is small, the gasification intensity of a single generator can be adjusted by increasing or decreasing the gasification intensity of a single generator; when the change is large, a certain number of hot backup generators must be configured to meet the needs of adjusting the load. Hot standby generator. There are two situations in which an explosion may occur when switching to normal production:

 

An explosion occurred as soon as air was supplied to the furnace. The cause of the explosion was that when the hot standby furnace was converted to normal production, part of the gas returned to the blast box. As it was converted to normal operation, this part of the gas entered the furnace along with the air. When the gas and air were mixed and reached the explosion limit, an explosion occurred when it encountered the flame of the oxide layer. To avoid accidents, the gas in the air pipe must be purged with steam before starting the fan.

 

An explosion occurred during normal air supply. The cause of the explosion was that the temperature of the oxide layer in the furnace was low when the hot standby furnace was converted to normal production, and some oxide layer fires had even been extinguished. At this time, if the wind pressure changes greatly and air enters the furnace, part of the air will support combustion in the oxide layer, while the other part of the air will not support combustion, but will be mixed in the gas, causing an explosion. The way to eliminate this explosion phenomenon is to gradually reduce the air inlet volume, and then slowly increase the air inlet volume after the oxide layer is evenly established in the furnace. Also pay attention to adding less coal. It is forbidden to add a large amount of coal when starting the furnace. You should wait until the oxide layer is normal before adding more coal according to the situation in the furnace.

 

Overhaul

 

When the furnace is shut down for maintenance, the entire set of equipment of the gas generator is often cleaned, inspected and repaired. The manhole covers of purification equipment such as the double vertical pipes of the cold gas generator, electric tar traps and scrubbers need to be opened, and some need to be welded and repaired. At this time, great attention should be paid to the preparation work before maintenance. Before maintenance, the entire equipment of the gas generator must be purged with steam to ensure that no gas remains in the equipment. After the purging is completed, the gas in it must be sampled and tested, and maintenance work can only be carried out after passing the test. Otherwise, the gas remaining in the equipment will mix with air and explode when encountering sparks generated by welding.

 

There are many factors that affect gas explosions during the production, operation and shutdown of gas generating stations for maintenance. During operation, if the operating experience is insufficient and the signs of many explosions are unclear, the situation will develop and eventually lead to an explosion accident. If we can clearly understand the abnormal phenomena in operation and take timely measures, explosion accidents will be avoided. First of all, gas station managers must be familiar with the gas business of the entire station and the safety and technical performance of the gas equipment of the entire station. Then regularly organize personnel in each process to conduct on-the-job practical training, so that the operators at each position must be familiar with the various safe operation techniques of their positions. The operating procedures, safety procedures, power outage and gas outage operating procedures for each position in the gas station should be complete. The gas station production dispatch room, fan room, power supply room, laboratory, and boiler room should have communication facilities. Finally, we must strictly follow the regulations. If each process parameter is carefully controlled, the oxygen content of the outbound gas will be less than 0.2% to 0.3%. The water seals of gas equipment and gas pipelines should be checked regularly, drained, and operated under overflow conditions.