Stopping maintenance of hot water boilers and steam boilers

In the operation of steam boilers, hot water boilers, gas boilers, oil-fired boilers, coal-fired boilers, energy-saving and environmentally-friendly boilers, it is often necessary to stop the furnace due to accidents, malfunctions, power outages, and the end of the boiler operation. This involves the operation of the shutdown. Also pay attention to the maintenance work after the shutdown, the following describes the boiler shutdown method and maintenance.
one. Steam boiler hot water boiler gas boiler oil-fired boiler coal-fired boiler, energy-saving and environmentally-friendly boiler shutdown The boiler shutdown can be divided into three situations: pressure ignition, normal shutdown and emergency shutdown. The first two are planned shutdowns, which should be interrupted slowly and the load reduced until the load on the hot water boiler drops to zero. The latter is an accident in the operation of the boiler, which interrupts the combustion and causes the boiler load to drop sharply to zero.
(1) Pressure ignition (hot standby) shutdown When the external load is reduced, the boiler can be fired by one or several boilers, so that when the load increases, the boiler that stops running can be the fastest. The speed returns to normal operation, eliminating the need for ignition preparation and shortening the boost time.
1. Steam boiler operation method:
Before the boiler is pressed, the actual party reduces the boiler load, and then according to the length of the shutdown time, the coal seam is thickened (generally only 200 mm), and the grate speed is appropriately accelerated, when the thickened coal seam is from the old millimeter eagle iron ( When the slag stopper is about 1 mm, stop the grate rotation, stop the drum and the induced draft fan, and adjust the regulating plate block and the flue baffle for the small-section air supply, and rely on natural ventilation to maintain the weak combustion of the coal, and then discharge the sewage. Raise the boiler water level to the highest allowable water level. If the fire burns off the coal sluice, the grate can be activated again to move the coal back a distance. When the boiler needs to resume operation, as long as the pilot and blower are activated, adjust the opening degree of the smoke, wind baffle and sectional wind chamber to adjust the baffle. When the combustion is normal, adjust the thickness of the coal seam and start the grate to resume operation.
2. Hot water boiler hot-press operation method The hot water boiler usually adopts an intermittent operation mode. For the combustion method using the layered equipment, the wet coal can also be used to shut down the fire on the upper part of the grate. After the fire is extinguished, the duct baffle and the ash door should also be closed and the furnace door should be opened (the furnace door can be closed if there is no re-ignition during the fire). However, it should be noted that the operation of the circulating water pump should not be stopped immediately after the ignition is stopped. The circulating water of the network should be continuously circulated in the system for a period of time, and the operation of the circulating water pump can be stopped when the temperature of the outlet water of the boiler drops below 50oC. Because the furnace temperature is still very high at this time, if the pump is stopped, the system water circulation is interrupted immediately. For the forced circulation of the hot water boiler due to the stop of the water circulation, the pot water will vaporize and cause water hammer or high temperature heating surface to overheat and burn out.
Precautions for boiler fire extinguishing (1) There is still steam pressure in the pot during the fire stop, so it is still necessary to pay attention to monitoring and keep the boiler at the highest allowable water level;
(2) When the temperature of the fire is stopped for more than 6 hours, the main steam valve of the boiler should be closed after a period of pressure, and the steam trap of the superheater outlet header is opened to cool the superheater. If the air pressure rises after closing the main steam valve, it can be depressurized by the method of water supply to the boiler and simultaneous discharge. When the boiler resumes operation, it needs to be boosted and protected.
(3) During the process of pressure ignition, the boiler should be properly drained to remove sediment from the furnace;
(4) For boilers equipped with cast iron gas, after the boiler stops supplying water, the provincial gas flue baffle should be closed, the side furnace baffle should be opened or used in the circulation pipeline to stop the water temperature in the gas from exceeding the specified value.
(2) The normal hot water boiler is scheduled to be shut down due to the reduced load, the end of the heating period and the maintenance, etc., called the normal shutdown. Normal shutdown, generally in the following order: stop supplying fuel; stop blasting, then stop the air; stop the water supply, reduce the pressure, close the water supply valve; close the steam valve, open the steam trap; close the flue baffle.
(III) Emergency shutdown When an accident occurs in the operation of the boiler, if the furnace is not immediately shut down, there is a possibility of expanding the accident and the human body and equipment. Therefore, the boiler operation must be stopped immediately. This is an emergency shutdown.
Operation method of emergency shutdown 1. Emergency shutdown of steam boilers (1) First stop the coal supply and supply air, the chain furnace should hang the curved baffle, the coal pulverizer stops the coal throwing, and weakens the induced air and closes the small flue baffle.
(2) Depending on the nature of the accident, some should release coal from the furnace, and some should not let off coal. The method of releasing coal is: the grate should send the coal into the hopper at the highest speed. After burning the coal ash hopper, the water can be used to smear or use sand, and the ash of the wet furnace is pressed on the coal to extinguish the fire, but under no circumstances should the water be cooled in the furnace to cool the boiler.
(3) After the steam boiler is extinguished, the main steam valve should be closed to isolate the main steam pipe from the steam main pipe and close the induced draft fan. To make the nature of the accident, if necessary, open the air valve, safety valve and superheater trap to quickly discharge steam and reduce pressure.
(4) Turn on the provincial gas bypass flue, close the main road flue, and open the large flue baffle, ash door and furnace door to promote air dredging and increase the cooling rate.
(5) In the case of emergency shutdown, there is no shortage of water and full water. Water supply and sewage can be used to accelerate cooling and reduce boiler pressure. When the water temperature drops below 70oC, the pot water can be drained.
(6) If the boiler is urgently shut down due to lack of water in the boiler, it is strictly forbidden to supply water to the boiler, nor can it be adjusted to strengthen the exhaust valve such as the air valve or the lift safety valve to prevent the boiler from being subjected to sudden temperature or pressure changes. expand.
(7) When it is determined that the boiler is full of water accidents, stop the water supply immediately, turn off the small ventilation and flue baffles, reduce the combustion, and open the drain valve to release the water, so that the water level is properly lowered; at the same time, open the main steam pipe, superheater The steam main pipe and the hydrophobic door on the sub-cylinder prevent the steam from being heavily watered and the water impact in the pipe.
2. Emergency shutdown of hot water boilers When emergency shutdown, the fuel should be stopped immediately. If necessary, the coal is burned out of the furnace or the ash is used to extinguish the fire. If the circulating water pump is normal, the pump should not be stopped immediately. When the water temperature at the outlet of the boiler drops below 50oC, the operation of the circulating water pump can be stopped.
two. After the boiler is shut down and the boiler is shut down, the humidity in the pot is very high and the ventilation is poor. The metal surface of the boiler is in a damp state for a long time. Under the action of oxygen and carbon dioxide, the boiler metal is corroded and rusted. The rust will continue to undergo strong electrochemical corrosion in the high temperature pot water, resulting in deepening of the corrosion and enlargement of the area. The thinning of the metal wall of the boiler will inevitably reduce the strength of the pressure component of the boiler, which will threaten the safe operation of the boiler and shorten the service life of the boiler. . Therefore, in order to ensure the safe and economic operation of the boiler, it is necessary to do the anti-corrosion maintenance work after the boiler is shut down. According to the length of the shutdown time, the boiler's anti-corrosion maintenance usually has three kinds of heat maintenance, wet maintenance and dry maintenance. Thermal maintenance is suitable for hot standby; wet maintenance is suitable for short-term (generally no more than one month) decommissioning; long-term shutdown for more than one month of shutdown is dry maintenance.
(1) Thermal maintenance Maintain a certain pressure in the hot water boiler, about 0.05-0.1Mpa, so that the boiler water temperature is higher than 100oC and there is no nutrient condition, and the pressure inside the pot can prevent outside air from entering the drum. In order to maintain the temperature of the boiler water, the steam of other boilers can be used to heat the boiler water. When a single boiler has no steam source during maintenance, it can be maintained in the furnace. This method is generally used for hot standby boilers or boilers that have been shut down for less than one week.
(2) Wet maintenance The maintenance of the method is to use a certain concentration of alkaline solution to contact the metal on the inner surface of the boiler to form an alkali protective film on the metal surface to prevent corrosion of the metal. After the boiler is shut down, the pot water is drained, the scale and soot are clear, all the holes, hand holes, valves, etc. are closed, and they are completely isolated from other operating boilers. Then, the softened water is poured into the boiler to the lowest water level, and the configured alkaline anticorrosive liquid is injected into the boiler by a special pump. The composition of the antiseptic solution is: sodium hydroxide, adding 5-6kg per ton of pot water. Or carbonated sodium is added 5-10kg per ton of pot water. When the corrosive liquid is completely injected, the feed water valve is opened to fill the boiler with softened water (including the superheater and the boiler economizer) until the pot water emerges from the air valve. At this time, the air valve and the water supply valve are closed, and then the special pump is turned on for water circulation, so that the concentration of the alkaline antiseptic liquid in the boiler is evenly mixed. During the maintenance period, external inspection should be carried out frequently, and the water alkalinity of the pot should be checked regularly. If the liquid level or alkalinity is found to decrease, the cause should be ascertained in time, and the lye should be added; the pump should be periodically pumped to make the water circulation, so that the alkali is everywhere. The liquid concentration is the same; in winter, the pot water should be prevented from freezing, and the open-air boiler cannot be maintained by wet method. When the wet maintenance boiler is resumed, the pot water should be completely discharged and the softened water should be re-applied.
(3) Dry maintenance Dry maintenance is to use the dryer to absorb moisture to keep the metal inside the boiler dry to prevent corrosion of the boiler. Usually, quicklime or anhydrous calcium chloride is used as a desiccant. After the boiler is shut down, the pot water is drained, the scale and soot are removed, the steam pipe is closed, the valves on the water supply pipe and the sewage pipe are completely isolated from the other operating boilers. Then open the hole to make the drum dry naturally. If the boiler room is wet, it is best to use a slight fire to dry the boiler body, as well as the furnace wall and the flue. The tray (or wooden box) containing the quicklime or anhydrous calcium chloride is then placed on the hob, as well as in the drum header and the flue, and if necessary, hoisted in the drum with a bag to absorb moisture. The amount of desiccant is determined according to the volume of the boiler: massive quicklime, 2-3 kg per cubic meter of boiler volume; if anhydrous calcium chloride is used, 1-2 kg is used. Finally, all the valves of the boiler, such as holes, hand holes, smoke to the windshield and damper, are tightly closed to prevent the boiler from being invaded by the outside world. During maintenance, check the desiccant every 1-2 months. If the lime is changed from block to powder, replace the new quicklime. Check the service at the beginning of the maintenance. The failed calcium chloride can be heated to 105-110oC for drying. Practice has proved that the effect of dry maintenance and anti-corrosion is satisfactory, and the cost is very low, and the operation is simple. Therefore, it is suitable for long-term shutdown maintenance of any type of boiler, especially the heating and hot water boiler which is deactivated in summer.
The above is the aspects of the shutdown and maintenance process of the hot water boiler. In addition, we must pay attention to the maintenance work of auxiliary equipment, accessories and furnace walls, and regularly carry out maintenance work in a planned manner to ensure boiler safety. An important part of reliable, economic operation.