Boiler shutdown protection problem?

Before planning to shut down for a long time, the liquid sulfur in each tank and tank must be used up before shutting down. Open the slag discharge port in time to clean the sulfur residue, and finally turn off the heating steam. Remove the stirring and liquid sulfur pumps of each tank for inspection and maintenance. Empty the filter and set aside.

If the boiler is not used for a long time, the boiler must be maintained. Generally speaking, wet maintenance can be used within one month, and dry maintenance should be used if the boiler is shut down for more than one month. 1. Dry maintenance After all the boiler water is discharged, remove scale and soot, close the steam pipes (hot water boilers should close the inlet and outlet circulating water pipes), valves on the water supply pipes and sewage pipes, or block them with partitions to completely isolate them from other operating boilers. Then open the manholes and hand holes to allow the drum and header to dry naturally. If the boiler room is humid, it is best to use firewood to maintain a low fire to dry the boiler body, or send hot air into the pot to dry it. After the furnace supply is completed and the boiler has cooled down for several hours, the desiccant (such as quicklime, silica gel, anhydrous calcium chloride or activated aluminum oxide, etc.) prepared in the open tank is placed into the pot (drum, header box). Then the manholes, hand holes and valves connected to the drum should be closed tightly. For some leaking valves, blocking plates should be installed to completely isolate them from the outside atmosphere. The amount of desiccant put in can be calculated according to the volume of the pot. Generally speaking, if the drum is relatively dry, use quicklime at 2-3kg/m3 ； Press 1kg/m3 with silicone ； Use anhydrous calcium chloride or activated aluminum oxide to calculate at 1.5kg/m3. About a week after placing the desiccant in the pot, the drum should be opened to check whether the desiccant has absorbed moisture and become ineffective. If it has expired, the expired desiccant should be replaced in time, or the desiccant that has expired due to moisture should be taken out, heated to 105-110°C to dry, and then placed in the drum for continued use. In the future, you can check again every 1-2 months. If the boiler is out of service for a long time, the outer wall of the heating surface should be painted with anti-rust paint, and all ventilation gates, gray doors, etc. should be closed. Desiccant can also be placed in appropriate places in the furnace and flue. Before a boiler maintained by dry method is put into operation, the desiccant contained in the pot must be taken out together with the open tank, and the blocking plates of each pipe must be removed. 2. Wet maintenance Wet maintenance is to fill the boiler with a solution with high alkalinity, and use the oxide protective film generated by the action of alkali solution and metal to prevent corrosion of the boiler metal. There are many ways to prepare alkaline anti-corrosion liquid. Domestic industrial boilers are usually prepared by adding 2 kg of sodium carbonate or 1.5 kg of sodium hydroxide and 0.5 kg of trisodium phosphate to each ton of feed water (treated soft water). You can also use a mixed antiseptic solution of three chemicals: sodium hydroxide, phosphate and sodium sulfite. The ratio is 1kg sodium hydroxide, 0.1kg phosphate and 0.5kg sodium sulfite per ton of pot water. No matter which alkaline anti-corrosion solution is used, when the solution is injected into the pot (steam boiler, the water level in the drum reaches the lowest water level ； After the hot water boiler (the drum should be filled), a fire should be lit in the furnace and heated with low heat until the pressure in the pot rises to 2-3kgf/cm3. Keep the pressure for 2-3 hours until the concentration of the alkaline solution in the pot is uniform, then stop the fire and reduce the pressure. Then fill the steam boiler drum with anti-corrosion liquid through the upper part of the drum or the economizer until water comes out of the vent (air valve). Close the vent (air valve) and use a hydraulic pump to maintain the pot at 1.5-4kgf/cm3. This pressure is maintained throughout the maintenance period. In the future, the pot water should be sampled and tested at regular intervals. If the concentration of the alkali solution decreases, it should be replenished. Before the boiler is ready to be ignited and run, all the solution in the pot should be drained out, or half of the solution should be drained out and then diluted with water until it meets the required standards for pot water. The advantage of wet maintenance boiler is that it can shorten the startup time of the boiler. This method is generally suitable for boilers whose shutdown period does not exceed one month. When using this method in winter, antifreeze measures must be taken to avoid freezing the equipment. If there is a liquid nitrogen storage tank in the factory and the pipeline transportation is convenient, nitrogen can also be passed into the boiler for protection, which can be used in conjunction with the above dry maintenance.

The content above is very detailed. I would like to add a question. One of our furnaces is disconnected intermittently. Sometimes it is not turned on for a month, and sometimes it is turned on for half a month. I would like to add that it is the kind of equipment with over-configuration called a backup furnace. How to protect it? Thanks!

Reply to the 4th floor: If this is the case, the main method is to use wet maintenance (but pay attention to anti-freeze in winter) or to shut down the boiler to maintain pressure (which may be more suitable for small-tonnage oil-fired boilers). If the steam pressure in the boiler is too low, turn on the burner and let it automatically stop burning after it reaches high pressure. Keep the pressure in the boiler and strengthen water quality management during the shutdown period. The advantage is that it can be resumed immediately, but the disadvantage is that too much fuel, water, electricity, etc. are consumed. The above is a personal experience and is for reference only.

After a short-term shutdown of the boiler to stop feeding materials, the boiler still has a high pressure, a considerable amount of heat energy is still accumulated in the furnace, and water is still in a small amount of evaporation. Therefore, a dedicated person still needs to pay close attention to the liquid level, replenish water in time, and is not allowed to fall below the indicator. Boiler maintenance for long-term shutdown (more than one week). During the boiler shutdown, the metal surface of the water and steam system will be corroded by dissolved oxygen. If there are sediments and slag on the boiler surface, the corrosion process will be faster. Therefore, the following shutdown protection measures must be taken.: (1) The water side protection adopts alkali solution protection (wet protection). The boiler is filled with water with a pH value of above 10 to form a corrosion-resistant protective film on the metal surface to prevent dissolved oxygen from corroding the metal surface of the boiler. The alkali solution includes industrial NaOH, adding 5~6Kg per cubic meter of furnace water, or industrial Na3PO4, adding 10~12 Kg per cubic meter of furnace water. During the protection period, the alkali concentration should be frequently sampled and analyzed to ensure that there is no significant decrease. When the boiler is put back into use, the boiler water should be released and clean water should be supplied. (2) Gas side protection means that the dirt deposited on the heating surface and refractory lining during boiler operation must be removed.

To deal with leaks and carry out overall maintenance, our system produces nitrogen and will definitely be filled with nitrogen to protect you. You can make your own choice based on the actual situation. It was made very clear above.

Regarding the maintenance of the standby furnace mentioned on the 4th floor, we use wet maintenance and then nitrogen filling. It is also convenient to start the furnace in this way.

Personally think: Stop the furnace for a short time and close all inlet and outlet valves. The alkaline water inside does not need to be discharged. ； If the furnace is shut down for a long time, drain the water and flush with nitrogen for protection.