Boiler efficiency is mainly depended on the amount of losses in the system. In high capacity pulverized coal fired boilers the total losses account to about 12 to 14%. Roughly 50% of the losses are governed by fuel properties like hydrogen in fuel, moisture in fuel and ambient air conditions. The other 50% losses are carbon loss and dry gas loss. The best efficiency in the boiler can be achieved if the losses are kept to the minimum. Since 50% of the losses are dependent on the fuel and ambient condition, the best efficiency can be achieved by properly tuning the other 50%, i.e. mainly carbon loss and dry gas loss.
In the work of transforming a coal-fired boiler into a gas-fired boiler, the principle of changing the original boiler should be reduced without changing the pressure component of the boiler body. The transformation process should focus on the choice of gas burners, the determination of the number of burners, the layout of the burners, the matching design of the furnace layout, and the selection of explosion-proof measures. Step by step, both economic benefits and practicality should be considered.
The proximate analysis of coal is to dry, heat and burn coal samples as required to get the percentage of moisture, volatiles, fixed carbon and ash in the coal and learn about the characteristics of coal combustion.
The dry bottom hopper is formed by bending the lower part of the water wall of the front and rear walls inward. The main function is to gather, cool and automatically discharge ash. It is also convenient for the connection and sealing of the lower header and the ash well.
Volatile matter in coal refers to the components of coal, except for moisture, which are liberated at high temperature in the absence of air. This is usually a mixture of short- and long-chain hydrocarbons, aromatic hydrocarbons and some sulfur. Volatile matter also evaluate the adsorption application of an activated carbon. The volatile matter of coal is determined under rigidly controlled standards. In Australian and British laboratories this involves heating the coal sample to 900 ± 5 °C (1650 ±10 °F) for 7 min. Also as the rank of coal increases the volatile matter decreases (AMK).
The fineness of pulverized coal is an important indicator to measure the pulverized coal quality.
In terms of combustion, the particle size of pulverized coal is expected to be as small as possible to facilitate the ignition and combustion, reduce the heat loss of incomplete combustion, the amount of air supply and heat loss of exhaust smoke.
In terms of pulverized coal milling, the particle size of pulverized coal is expected to be as coarse as possible to reduce the power consumption and steel consumption. Therefore, when selecting the fineness of pulverized coal, a compromise of the two aspects is taken as the economic fineness.
It shall be determined through combustion adjustment tests according to the fuel properties and the type of pulverizing equipment.
The selection of dust collector for coal-fired boilers is determined by the purpose and requirements of dust collecting. If the requirement is just dust collecting, the impulse bag filter is a good choice, the efficiency can reach up to 99%. If both dust collecting and desulfurization are required, you should choose bag filter plus spray desulfurization. Bag filter plus double alkali desulfurization is suggested for higher requirements.
Question details (Performance):1. High temperature of motor, fast temperature rise.2. Overload, high outlet pressure and frequent safety valve open often.3. The vibration is intensified, the side vibration of the fan motor coupling is large, and the fan body never vibrates to vibration.4. No obvious vibration was found in no-load test of fan motor. Answer: Fault reason:Fan bearing vibration is common fault in the operation, the vibration of the fan will cause damage of bearing and blade, bolt looseness, chassis and wind damage, fan vibration rises abruptly in the operation. this is because when the gas enter impeller and the rotating blade working face has certain angle, according to the principle of fluid mechanics, gas from non-working face must be a spiral blade, so the dust particles in the gas will slowly sedimentation due to vortex. Airfoil blades are very easy to accumulate dust. When the accumulated ash reaches a certain weight, a part of the large amount of accumulated ash wi
