The operation of biomass boiler must keep the normal water level. When the water level is lower than the minimum safe water level, it is called water shortage accident. Water shortage accidents can be divided into two types: slight water shortage and serious water shortage. For example, if the water level is below the minimum safe water level, but it can be seen, or even though the water level is invisible, the water level of biomass boiler that is allowed to use the “water calling method” will appear soon after “water calling”, which belongs to slight water shortage. If the water level cannot be seen and the “water method” cannot be used, it is a serious water shortage.
If the water shortage accident of biomass boiler is handled improperly, it will cause serious damage to the equipment. If the water in biomass boiler is seriously short of water, it will lead to explosion of biomass boiler. This is because after the biomass boiler is short of water, on the one hand, the steel plate is dry burned and overheated, or even burned red, which greatly reduces the strength; on the other hand, because the temperature of the steel plate after overheating is very different from the temperature of the water supply, the part of the steel plate contacting the water first cracks because of the sharp contraction when it is cold, and under the action of the steam pressure, the cracks are immediately torn into large cracks. Steam and water ejected from the breach, which resulted in an explosion accident.
Here are the details:
Lack of water in biomass boilers
1) the water level in the boiler is lower than the minimum safe water level or the water level is invisible in the water level gauge, and the color of the water level gauge is white or bright. Low water level signal alarm, signal light on.
2) for biomass boiler with superheater, the temperature of superheated steam rises abnormally, and an over temperature alarm signal is sent out.
3) the discharge temperature of biomass boiler rises abnormally.
4) the feed water break and steam flow site are abnormal. Generally, the feed water flow is less than the steam flow. In case of leakage of pipes or economizers, the normal water level cannot be maintained even though the feed water level increases, and the feed water surplus will be greater than the steam flow.
5) when the biomass boiler is in severe condition of water shortage, it can smell burnt smell.
Causes of water shortage in biomass boilers
1) the driller violates labor discipline, withdraws from duty or neglects to monitor the water level enough. When the load of biomass boiler increases, the adjustment is not timely or the operation is wrong. Water level alarm and interlock protection device have failed to detect in time.
2) the operator’s operation skill level is low, and the judgment of water level is wrong. For example, the false water level caused by the sudden change of biomass boiler load is not recognized, the false water level caused by the unreasonable installation of water level gauge or the blockage of steam water path, the inadequate switch of steam water cock and other reasons will not be distinguished, and the water shortage or full water will not be distinguished. All of these factors will lead to the misjudgment of water level by the stokers and lead to the lack of water in biomass boilers.
3) failure of water supply equipment or pipeline; failure to feed water into the boiler in time, resulting in water shortage of biomass boiler, such as damage of feed pump, etc.
Biomass boiler water shortage treatment method
1) first check the water level indicated by each water level gauge; correctly judge whether there is water shortage. When it is impossible to determine whether the water is short of water or full of water, open the drain cock of water level gauge. If there is no boiler water flowing out, it indicates a water shortage accident, otherwise it will be a full water accident.
2) for the small biomass boiler that is allowed to call water, call water first to judge whether the biomass boiler is slightly or seriously short of water. This case is only applicable to biomass boilers with higher water capacity and higher fire boundary than the heating surface. Otherwise, the biomass boiler can not be called water, because it will delay the treatment time of the biomass boiler water shortage accident and make the situation worse.
3) when the biomass boiler is slightly short of water, fuel and air supply shall be reduced, combustion shall be weakened, and water shall be slowly fed to the biomass boiler to the normal water level. Generally, by adjusting the opening and size of the water supply valve, the inlet flow rate and water supply quantity are controlled, and attention shall be paid not to excessive inflow. In the process of water inflow, the cause of water shortage (such as water leakage of water supply pipe, boiler pipe and economizer pipe or wrong opening of valve) shall be quickly found out: it shall be eliminated in time, and then the biomass boiler shall be checked to see if there is any abnormal condition, and the operation of biomass boiler can be resumed only after it is confirmed to be normal.
4) in case of serious water shortage of biomass boiler, emergency fire extinguishing and boiler shutdown must be carried out. The operation procedure of fire-fighting and boiler shutdown shall be implemented according to the method of emergency boiler shutdown. In case of serious water shortage, it is forbidden to feed water into the boiler. Some stokers, after finding that the biomass boiler is short of water, adopt the method of multiple intermittent water inflow and a small amount of water supplement each time to cover up the water shortage accident of the biomass boiler. This is very dangerous. If the water shortage of biomass boiler is not serious, it will cause water leakage of biomass boiler. If the water shortage of biomass boiler is serious, it will cause explosion accident of biomass boiler. Because the steel plate is dry burned without water cooling, the temperature of the wall is quite high. At this time, the water will cause the overheated steel plate to cool rapidly and crack or explode. Only when the biomass boiler is naturally ventilated and cooled and the water temperature in the boiler drops below 70 ℃, can the water be slowly fed. After the water level reaches the normal level, the biomass boiler shall be comprehensively inspected. If there is no abnormal condition, the ignition can be restarted and the operation of the biomass boiler can be resumed.