Fuel freezing point is the temperature at which the fuel loses fluidity. It is an important index that indicates the fuel flows at low temperatures. It often refers to the maximum temperature at which the oil surface remains stationary within 1 minute. The higher the fuel freezing point, the lower the low-temperature fluidity. When the oil temperature is below the freezing point, it cannot be transported in the pipeline.
The selection of a burner of the gas-fired thermal oil heater should be determined according to the boiler proper structure and fuel characteristics and in combination with the actual conditions and requirements. In addition, this kind of boiler can adopt a waste heat recovery device to improve thermal efficiency and reduce heat energy loss.
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.
Although biomass-fired boilers are environment-friendly boiler products, there are also some situations that biomass-fired boilers can’t be used. Main reasons as follows:
Fuel restrictions: The fuels that contain synthetic compounds can’t be used as the fuel of a biomass-fired boiler, such as waste wood furniture, waste paper, production and domestic waste.
Firstly, the combustion of biomass fuel is easy to control. The fuel is easy to ignite. Besides, the combustion speed is faster than that of coal.
Secondly, the biomass-fired boiler can be ignited and extinguished at any time while the coal-fired boiler cannot. The biomass-fired boiler can also be ignited automatically.
Thirdly, the biomass-fired boiler can achieve zero emission of sulfur dioxide, which belongs to environment-friendly boilers.
The economizer is a heat exchanger equipment which utilizes heat recovery of flue gases to heat feedwater. It can increase boiler efficiency, reduce the temperature of flue gas and save the fuel by absorbing recovery of flue gases. Besides, the feedwater is heated through the economizer before it is supplied into steam drum to decrease the thermal stress of the steam drum wall caused by temperature difference, which can improve the operating conditions of steam drum and prolong the service life of the steam drum.
Fuel-to-steam efficiency is a measure of the overall efficiency of the boiler. It accounts for the effectiveness of the heat exchanger as well as the radiation and convection losses. It is an indication of the true boiler efficiency and should be the efficiency used in economic evaluations. As prescribed by the ASME Power Test Code, PTC 4.1, the fuel-to-steam efficiency of a boiler can be determined by two methods: the InputOutput Method and the Heat Loss Method.
Combustion efficiency is an indication of the burner’s ability to burn fuel. The amount of unburned fuel and excess air in the exhaust are used to assess a burner’s combustion efficiency. Burners resulting in low levels of unburned fuel while operating at low excess air levels are considered efficient. Well designed conventional burners firing gaseous and liquid fuels operate at excess air levels of 15% and result in negligible unburned fuel. Well designed ultra low emissions burners operate at a higher excess air level of 25% in order to reduce emissions to very low levels. By operating at the minimum excess air requirement, less heat from the combustion process is being used to heat excess combustion air, which increases the energy available for the load. Combustion efficiency is not the same for all fuels and, generally, gaseous and liquid fuels burn more efficiently than solid fuels.
