The oil and air must be mixed for the combustion of the fuel droplets to take place. The combustion speed depends on the evaporation speed of oil droplets and the mixing speed of oil and air. The evaporation speed of oil droplets is related to the diameter and temperature of oil droplets. The smaller the fuel droplets, the higher the temperature and the faster the evaporation. On the other hand, it is conducive to mixing and combustion. The smaller the fuel droplets, the larger the air contract surface. Therefore, the fuel oil must be atomized before combustion. And, the oil can be heated and evaporated rapidly and fully burnt after it is injected to the furnace.
1. The fuel volume is 1 / 30 ~ 40 of the raw material volume after molding;
2. The specific gravity is 10-15 times of the raw material, and the moisture content is between 12% and 18% (the moisture content of coal is below 10-15);
3. The net calorific value can reach 3500-4500 kcal (the net calorific value of class II bituminous coal is 3700-4700 kcal / kg);
4. The ash content is less than 10% (the ash content of coal is more than 20%);
5. Volatile matter ≥ 65.62% (volatile matter of class II bituminous coal≥20%).
6. Biomass fuel belongs to renewable clean energy, which is the same as wind energy and solar energy. The biomass fuel is rich in resources, it can ensure the sustainable use of energy.
7. The sulfur content and nitrogen content of biomass fuel are low, the amount of SOx and NOx generated in the combustion process is low.
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.
A steam boiler plant must operate safely, with maximum combustion and heat transfer efficiency. To help achieve this and a long, low-maintenance life, the boiler water can be chemically treated.
The operating objectives for steam boiler plant include:
Safe operation.
Maximum combustion and heat transfer efficiency.
Minimum maintenance.
Long working life.
The quality of the water used to produce the steam in the boiler will have a profound effect on meeting these objectives.
The term “boiler efficiency” is often substituted for thermal efficiency or fuel-to-steam efficiency. When the term “boiler efficiency” is used, it is important to know which type of efficiency is being represented. Why? Because thermal efficiency, which does not account for radiation and convection losses, is not an indication of the true boiler efficiency. Fuelto-steam efficiency, which does account for radiation and convection losses, is a true indication of overall boiler efficiency. The term “boiler efficiency” should be defined by the boiler manufacturer before it is used in any economic evaluation.
A process load is usually a high-pressure steam load. A process load pertains to manufacturing operations, where heat from steam or hot water is used in the process. A process load is further defined as either continuous or batch. In a continuous load, the demand is fairly constant - such as in a heating load. The batch load is characterized by short-term demands. The batch load is a key issue when selecting equipment, because a batch-type process load can have a very large instantaneous demand that can be several times larger than the rating of the boiler. For example, based on its size, a heating coil can consume a large amount of steam simply to fill and pressurize the coil. When designing a boiler room for a process load with instantaneous demand, a more careful boiler selection process should take place.
The number of passes that the flue gas travels before exiting the boiler has been a good criterion when comparing boilers. As the flue gas travels through the boiler it cools, and therefore changes volume. Multiple pass boilers increase efficiency because the passes are designed to maximize flue gas velocities as the flue gas cools. ZOZEN has developed new design technologies in our WNS series boilers allowing for comparable efficiencies in fewer passes, resulting in smaller boiler systems that will fit in tighter quarters.
System load is measured in either BTUs or tons of steam (at a specific pressure and temperature). It would be nearly impossible to size and select a boiler(s) without knowing the system load requirements. Knowing the requirements leads to the following information:
The boiler(s) capacity, taken from the maximum system load requirement.
The boiler(s) turndown, taken from the minimum system load requirement.
Conditions for maximum efficiency, taken from the average system load requirement.
Determining the total system load requires an understanding of the type(s) of load in the system. There are three types of loads: heating, process, and combination.
