Check coal fired boiler before use
Before burning the brazier, you need to check the condition of the following parts:
– The measuring devices, safety devices have been installed in accordance with the technical requirements:
- Does the barometer indicate the maximum allowable working pressure?
- Did the light tube indicate the intermediate water level (horizontal water level) or the highest and lowest level 50mm from the average water level?
- Has the safety valve been adjusted to operating pressure in accordance with the regulations (working pressure +0.2kg/cm2)?
– Valves, hand/electrical pumps, intermediate water tanks, piping systems, water tanks: all must be assembled and adjusted to the correct specifications.
– Is the water supply for the boiler sufficient?
– Is the pressure part of the boiler damaged?
– Is the fuel for the furnace sufficiently stocked and guaranteed to meet the specifications?
– Prepare tools for operation such as:
- Rake: size 2m
- Shovel type 2 teeth: length 2m
- Crowbar with spear-shaped head: length 2m
- Hammer, wrench, wrench…
Steps to use coal fired boiler
After checking that the boiler is correct and safe, we proceed to group and operate the boiler. The steps are as follows:
Group of coal-fired boilers
Prepare the furnace group:
To group the furnace, you need to do some preparation as follows:
– Close the exhaust valves, steam valves, safety valves and open the air valves to let the gas out. Simultaneously open the water supply valve and the circulation valve with the water pipe, open the three-way valve of the manometer.
– Proceed to pump water up to the specified level (lowest level of the water pipe). Check the tightness of the valves and flanges.
– Then, close the water supply valve to the furnace, open the valve to pump water into the intermediate water supply tank, open until full, then close.
– Carrying out putting fuel into the combustion chamber:
- If burning with firewood, spread a layer of chopped dry firewood below, then large firewood piled on top.
- If burning with coal, you spread a thin layer of coal around the combustion chamber, dry wood in the middle.
– Open the louver, the smoke shield for the oven for about 15 minutes for natural ventilation.
Group of steam boilers:
– Use a dry rag soaked in oil to ignite the fire, then put it into the combustion chamber.
– After the firewood is completely burned, a layer of hot coal is covered on the surface of the furnace, then a thin layer of coal is added, then close the door of the furnace, the louver opens cleverly to catch the weak wind. The furnace grouping time lasts about 40 minutes.
– When you see the pot appear steam, start closing the valves to increase suction and combustion. Remember to check the status of the literature, clear the water pipe. Don’t forget to observe the manometer operation, from 1 – 1.5kG. When the furnace pressure reaches
– 2kG/cm2, you use a short-hand wrench, tighten the nut within the boiler.
– The furnace reaches the maximum working pressure, then check the water supply system for the furnace by opening the steam valve, the water valve connecting the intermediate water supply tank and the furnace. If you see water entering the oven normally, raise the oven pressure, the safety valve and the manometer adjust slightly above the red line.
– When the furnace reaches the limit pressure and the furnace operation is stable, the furnace grouping is completed.
Coal-fired boiler operation
When operating the furnace, you need to pay attention to the following points:
Burning mode of furnace:
During the steam supply process, the furnace must maintain the correct level of combustion to ensure complete combustion of the fuel. Adjust the wind when there is smoke so that it is reasonable. If there is black smoke, you must supply more wind, increase suction power. If the smoke is gray, it is a good combustion mode.
Coal put into the furnace must be spread evenly on the recording surface, add coal in small amounts to maintain even burning. Manipulating coal into the furnace needs to be done quickly and close the coal door.
The best coal thickness rating is at 300mm. When there is slag, it is necessary to scrape it out with the ash door and dust door. This work is done cyclically. Remember to widen the smoke shield to increase the suction power of the furnace.
When you feel the furnace pressure is close to maximum, prepare to supply steam. Note, do not supply steam higher than normal, ensuring stable combustion of the furnace.
When performing saturated steam supply, you need to open the steam valve slowly, the small amount of steam slowly heats up the steam pipeline and drains all the standing water in the steam pipe. Usually it will take about 10-15 minutes. At that time, you must also observe to avoid expansion of the tube and the tube holder.
If you find him at a normal level, open the steam valve all the way to let the air out. When the valve is fully open, turn the valve back half a turn. In order to avoid the phenomenon of water and steam, the water supplied to the furnace must be slowly, not higher than the normal level of the water pipe.
During operation, the coal-fired boiler needs to maintain the water level in the pot. The oven should not be operated for longer than the lowest or highest setting.
The boiler feed water will be periodically taken from the intermediate water supply tank or the main water supply pump for the furnace. The process works as follows:
– Water supplied from the overhead tank flows into the intermediate water supply tank, opening valve 1.4 and closing valve 2,3,5. When the water tank is full, close valve 1.4 and open the steam to supply steam to the intermediate water supply tank.
– Wait 1-2 minutes for the tank to warm up, then open valve 2 again so that the water in the intermediate water supply tank is supplied to the oven.
– When the water is completely supplied to the furnace, close valves 2, 3.
Note, besides, when using a coal-fired boiler, you should be equipped with an electric pump or an inflatable pump with a flow greater than 0.3m3/h and a working pressure greater than or equal to 1kG/cm2.
Dirty discharge operation is carried out at 2 valves 6 and 7. Depending on the water supply mode, each unit using the furnace will determine the number of times of dirty discharge according to the shifts. Normally, the number of discharges is at least 2 times/shift, about 2-3 times per shift, 10-15 seconds each. Hard feed water, the higher the alkalinity, the higher the number of flushes.
Before discharging dirt, you should raise the water level in the oven to about 25 – 30mm according to the water pipe. Water pipes also need to be washed at least twice per shift and the safety valve is checked once per shift.
Supply water with total hardness should not exceed 0.5mg/liter: PH=7.10
Coal-fired boiler decommissioning
Depending on each case, you perform different shutdown operations:
Normal oven shutdown:
– Close the steam supply valve, release steam to the atmosphere by the safety valve. At the same time when the oven frequency is down, raise the oven water level to the highest by adding water to the oven.
– Stop the coal supply, close the ash and coal doors, close the smoke shield.
– Let the oven cool down slowly.
– Remove the water from the boiler when the steam pressure is 0kg/cm and the furnace water temperature is at 70,800C. At the same time, you make safe channels slowly.
Stop the oven when there is a problem:
– Stop the fuel, air supply, the shield is almost closed.
– Quickly scrape burning coal from the steam chamber.
– Stop the fire, close the valve door and smoke shield.
– Close the steam supply valve, let the steam escape by the safety valve.
– Supply water to the furnace. In case of water shortage, do not supply water to the furnace.
– Allow the oven to cool slowly under operator supervision. Do not use water to put out the fire in the boiler.
Depending on the quality of the feed water, you have different boiler cleaning cycles. But normally clean the oven every 3 – 6 months.
The inside of the oven should be cleaned with chemicals, combined with manual and mechanical cleaning in the plumbing and under the furnace. The most suitable residue treatment chemical is 2% NaOH. When cleaning, you fill the boiler with NaOH solution, bring to a boil, the pressure is about 0.3 – 0.4, the working time is about 12 – 24h or longer if the residue is thick and clingy.
After removing the NaOH solution from the oven, you supply the oven wash water and perform mechanical cleaning.
Note: Cleaning the oven with chemicals requires someone who understands chemicals to ensure safety.
There are 2 methods of boiler maintenance:
Dry maintenance for coal-fired boilers that have been out of service for more than 1 month:
– Remove all the water in the oven, open the valve and use water to clean the oven, dry the oven with moderate heat.
– Clean the tube on the furnace body with 10 – 30mm granular quicklime placed on the aluminum tray and put into the boiler. Close the valve.
– Periodically check the furnace every 3 months. If you see quicklime broken into powder, replace it with a new one.
Wet maintenance with coal fired boilers out of service for less than 1 month:
– After stopping operation, drain all the water in the oven, rinse the oven with water. Ignite the oven with the temperature gradually increasing to 100 degrees Celsius. The safety valve opens to let out the air. Then close and put out the fire.
KS – Boiler specializes in manufacturing, installing and maintaining industrial boilers:
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