Zhang Huajun
Abstract: In recent years, with the improvement of national energy conservation and environmental protection requirements, high-pollution and high-energy consuming equipment in various places are being gradually phased out, including coal-fired boilers.In the boiler equipment (including biomass boilers, fuel gas boilers, etc.) , Especially for biomass-fired boilers, have obvious economic cost advantage and are adopted by most small, medium and large-sized micro-enterprises. A brief analysis.
0 Preface
The use of traditional coal-fired boilers, the transformation of biomass-fired boilers, compared with the traditional coal-fired boilers, with higher energy saving and environmental protection benefits, in line with national policy requirements; compared with the oil gas boiler, the investment cost and operating costs are outstanding Of the advantages, more close to the needs of small and medium micro-enterprises.From the overall analysis, the current stratified combustion boiler to burn biomass biomass pellet fuel, because of its different characteristics with the traditional coal-fired, often lead to boiler operation defects, energy saving The effect is not obvious and so on.Aiming at improving the combustion efficiency of biomass pellet fuel and ensuring boiler efficiency, it is necessary to make technical analysis based on the status quo, to take measures to optimize and reduce potential safety hazards, to further improve the energy efficiency indicators of the boiler after transformation, to reduce pollution emission.
1 biomass pellet fuel overview
Biomass pellet fuel is mainly produced from lumps, peanut shells, rice husks, straw, cottonseed husks and other specialized technologies. It is a new type of energy-saving energy source and has a great development prospect in the combustion of boilers Biomass pellet fuel has the characteristics of a large amount of combustion, the general calorific value can reach 3900 ~ 4800 kcal / kg, after carbonization the calorific value can reach 7000 ~ 8000 kcal / kg. Compared with coal-fired materials, biomass pellet fuel Better purity control, generally does not contain other non-heat debris, and will not contain carbon waste, stones and other impurities, with high combustion efficiency. In addition, it also has the advantages of clean, safe and simple process, and Compared with coal, coal is cleaner and the boiler is convenient for feeding when it burns, which can liberate manpower and improve work efficiency, and the quality of ash produced after biomass pellet fuel is burned is also relatively high, which can be used as potash recovery.Compared with traditional fuel, With economic and environmental advantages, to meet the concept of sustainable development.
Analysis of 2 - Layer Burning Boiler Combustion to Combustion Biomass Pellet Fuel Accident
Although biomass pellet fuel is a new type of clean energy and has a relatively high combustion efficiency, because of differences with coal-fired properties, it can easily cause boiler operation defects during the combustion process, and serious cases can occur For example, in order to reduce the production cost, the coal-fired boiler will be cascaded to burn biomass fuel without reforming and improving the boiler hearth structure and the air supply system. After application, it is easy to appear bulge on the high temperature side of the boiler tube plate Pipe leakage problems, cracks in the ends of the welded pipe, and even tube sheet cracking.
Common safety accidents occur mainly because biomass fuel density is low, and the structure of the high degree of looseness, there is high volatility in the combustion process, usually 250 ~ 350 ℃ conditions, most of the volatile analysis will be 0. Such After the volatilization of loose coke will be trapped by the airflow into the flue gas inside the In response to this, if the stratified combustion boiler from burning coal to biomass burning particulate fuel, the need to transform the boiler system and control the ventilation intensity in the design The combustion system should follow the characteristics of biomass fuels, appropriately increase the volume of the furnace, and to fully perturbation, to ensure adequate heating surface in the furnace.In addition, to improve the overall efficiency of biomass fuel combustion, but also need to do all the parameters Control, such as boiler body shape, location and size, as well as temperature, flow rate, pressure and other parameters to improve the combustion safety of the boiler.
Optimization of 3 - Layer Combustion Boiler Coal Combustion to Biomass Granulated Fuel Technology
3.1 A reasonable choice of combustion equipment
The combustion equipment should be selected according to the characteristics of biomass pellet fuel to improve the fuel combustion efficiency.Circulating fluidized bed can generally be selected.For the relatively small combustion system, you can choose to use the coal pulverizer to rewind the grate, using its layer Combustion and suspension fuel combustion characteristics to reduce the probability of safety accidents.At the time of system design, an adjustable mechanical pulverizer is formed from the point of view of several fuel imports in front of the furnace and coal pushing, and the prepared biomass fuel is thrown into the interior of the furnace.
The larger part of the particles will fall to the rear of the grate, while the smaller particles fall on the front of the grate. When the grate is in operation, it will be propelled from the rear to the front, combusted under the action of a wind, and the burned slag will enter To the front of the slag bucket.And the front of the smaller fuel particles, when thrown into the furnace will appear in suspension, through the secondary air to full combustion.With the front wall secondary air care and influence of the combustion process To strengthen, to ensure that all the fuel thrown into full combustion, improve boiler thermal efficiency.
3.2 additional combustion equipment
The main purpose of the design of the structural system of coal-fired boiler-fired boilers is to meet the demand of coal combustion, and it is impossible to exactly match the combustion requirements of biomass fuels even when the biomass is burned, therefore, the allowable space for the boiler system , And the economic conditions to meet the requirements, you can take to increase the combustion equipment or combustion chamber method, the occurrence of combustible gas and the initial combustion, while the system's existing combustion chamber is used as the burnout chamber.This design can be the largest To improve the fuel combustion efficiency, can be applied to the small boiler transformation.While the boiler furnace volume is large enough, when the system is modified, you can use the mobile grate to replace the fixed grate.If you need to choose to use a small grate , Should try to choose inclined reciprocating grate to reduce the amount of slagging combustion and improve biomass pellet fuel combustion.
3.3 additional secondary air system
In general, for a small and medium-sized boiler system, a primary air system can meet the fuel combustion needs, but because of the high volatility of biomass fuels and the shorter deposition time compared to coal combustion, To complete the combustion, and more occurred in the furnace space.In order to improve the combustion efficiency, the need for additional combustion of coal-fired boilers secondary air system to avoid primary air system can not meet the combustion needs, through reasonable transformation to provide for the furnace Sufficient air for fuel suspension combustion to provide sufficient oxygen.Among them, before the addition of secondary air system, need to make the system required for the combustion pressure and air volume, and configure the frequency control fan.In addition, the secondary air inlet Set in the furnace wall at different locations, from different angles to facilitate the provision of adequate disturbance to the furnace airflow to ensure that the combustion zone has a suitable temperature, and extend fuel and high temperature flue gas stay in the furnace time and improve fuel combustion efficiency .
4 Conclusion
Compared with coal-fired boilers, biomass-fired biomass pellets boast a great environmental protection advantage. Compared with fuel gas boilers, they have significant economic advantages and are therefore adopted by most small and medium-sized micro-enterprises. In order to improve its application efficiency, it is necessary to reform the structure of the coal-fired boilers and revamp their systems so as to avoid the operational defects and the reduction of energy consumption index due to the difference in performance among the fuels, so as to improve the overall efficiency of biomass fuel combustion .
references:
'1' BI Hui-jie, WU Ying-wei, HUANG Zhi.Study on Combustion of Coal to Biomass Particulate Fuel in a Stoker-fired Boiler [J]. Energy Saving, 2009, 01: 27-29.
'2' Meng Fengping, Lou Jinjie. Accident Analysis Caused by Burning Coal-fired Boiler to Burn Biomass Fuel 'J'. Industrial Boiler, 2009, 01: 51-53.
'3' BI Hui-jie, WU Ying-wei, HUANG Zhi.Technique Revamp of Coal-fired Biomass Pellet Fuel for District Heating Boiler House 'J'. Regional Heating, 2010, 0t: 35-39.
