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Abstract: This paper introduces the successful application of the variable-layer multi-coal coal feeding device in our company, analyzes the characteristics of the device and the characteristics of the ordinary coal feeding device and the pre-layered coal hopper to achieve combustion and save coal. purpose.
Key words: transformation level, segmented coal, multiple coal-shaped coal feeding devices, energy saving
1 Overview
Ningbo Haolong Electric Co., Ltd. is a cogeneration enterprise with an installed capacity of 27Mw, equipped with four 35t/h and one 45t/h forward chain boiler. In order to conscientiously implement the "Decision of the State Council on Strengthening Energy Conservation Work", to achieve the goal of reducing the energy consumption per 10,000 yuan of GDP by 20% from the end of the "11th Five-Year Plan" period, this year we will supply coal to the boiler. The device was technically modified, and the BC-FDDX type variable-layer multi-coal coal feeding device manufactured by Qinhuangdao Mingxin Environmental Protection and Energy Saving Equipment Development Co., Ltd. was selected. After installation and trial operation, the expected target was achieved. , saving more than 8% of coal, the blower and induced draft fan are reduced in frequency due to the required air volume, and the average power saving is 20%.
2. Problems and deficiencies in conventional coal feeding devices and stratified coal feeding devices in the early stage
2.1 The traditional coal feeding device is only controlled from the coal hopper above the boiler front, by adjusting the height of the coal gate, controlling the thickness of the coal seam entering the furnace to control the amount of coal entering the furnace, but it can not distribute the particle distribution into the coal. For any adjustment, the coal is free to fall on the surface of the grate in the coal hopper. After the coal seam passes through the gimbal plate, the coal bed is mixed and compacted, resulting in large ventilation resistance, and the coal granules are uneven. Coal seams are not evenly burned, and some coals cannot be fully burned.
2.2 Problems and shortcomings of stratified coal feeding technology in the early stage:
2.2.1 Layered coal into a single fixed layered coal form. Due to the difference between the thickness of the coal seam and the ignition time of the ignition point due to the lateral wind chamber of the grate, the distribution of the air is uneven, and local fire and air outlets appear. Under the action of excess wind at the end of the coal and ash, it is easy to produce ridges and piles. The coal seam in the ridge portion is burned due to lack of oxygen. Due to the uneven distribution of the cloth, the coal seams are burnt in the coal seam, resulting in high carbon content in the ash.
2.2.2 Since the combustion mode is layer burning, the upper coal seam is burned to form a ash covering layer. Covered in the upper part of the coal that is not fully burned, thickened with the accumulated ash accumulated in the combustion. The bottom coal seam radiant heat and the supply air are blocked and the combustion is insufficient. This is a problem and shortcoming of the chain boiler burning mode.
2.2.3 When burning low calorific value and low volatile coal, the coal in the form of stratified coal is the bottom of the lump coal, the coal in the upper part is in the upper part, and the bottom lump coal is under the influence of the low temperature combustion air, which can not reach the lump coal. The optimum ignition temperature causes incomplete and insufficient combustion of lump coal, which produces a layer of unburned or inexhaustible coal seam on the grate, resulting in waste of energy.
3. Characteristics analysis of coal feeding technology of BC-FDDX variable layer multi-coal coal feeding device:
BC-FDDX variable-layer multi-coal coal feeding device, transforming layers, sectioning coal, various coal shapes, coal feeding devices, energy saving, its combustion mode and combustion concept, different from traditional forward chain The concept of combustion of boilers and stratified coal. It changes the top-down layer burning method from the bottom up. Solved the problems and deficiencies of the stratified coal feeding technology, and its burning method is realized as follows:
3.1 In order to improve the uneven distribution of coal to the stratified coal, there are many problems of burning and strip burning. The BC-FDDX variable-layer multi-coal coal feeding device uses reverse thinking. The coal feeding device evenly arranges the wave-like wave-wave-type coal seam on the full furnace surface to balance the lateral air distribution of the wind chamber. After the coal enters the pre-combustion zone of the furnace, it ignites in a straight line. The phenomenon of uneven coal fires is eliminated. The co-combustion wind resistance at the trough is first burned. In the combustion process, the entire grate surface forms a uniform and multi-channel fire mouth. Since the full furnace surface is burned by the fire, there is no local fire phenomenon. The coal seam at the trough is fully burned and the lump coal in the lower part of the crest is ignited. As a result, the lump coal at the bottom of the coal seam at the peak gradually extends to the upper part to burn. Due to the burning of the bottom of the coal seam, the coal in the upper part of the coal seam collapses, so that the secondary agitation phenomenon occurs, so that the unburned coal seam is fully exposed. Under the action of the upper radiant heat and the bottom combustion heat, a flame is formed from the bottom of the coal seam to the upper part. The coal seam is semi-boiling. In addition, due to the fire breakage in the flameout zone, the blast air chamber at the rear of the flameout point can be closed, which effectively controls the amount of cold air entering the furnace, which not only improves the furnace temperature, but also achieves the purpose of full combustion and reduces the ash content. The amount of carbon. According to the operating conditions of the boiler, the spacing of the peaks and valleys of the wavy coal seam can be adjusted accordingly, and the density of the burning interval of the crater can be adjusted. This combustion mode makes the ventilation of the grate cross-section uniform. Reduces the air volume of the blower fan by 20%. Under the air volume that fully guarantees combustion, the peroxygen combustion is effectively controlled. The surface area of ​​the wavy coal seam is expanded by 20% compared with the limited combustion area of ​​the original grate, which can increase the output of the boiler by up to 20%, achieving the goal of energy saving and consumption reduction. This is a brand-new combustion concept and method of chain boiler, which completely overcomes and solves the inherent shortage of the positive-chain boiler and the pre-layered coal-feeding technology.
3.2 For the chain type boiler, the air distribution on the cross section of the grate is not uniform. The BC-FDDX variable-layer multi-coal coal feeding device is equipped with a gate coal plate that can control the coal intake in multiple stages. According to the wind pressure and air volume in the uneven section of the grate, the coal seams with different thicknesses are arranged in the cross section of the grate by adjusting the controllable multi-segment slab. According to the size of the air volume, the thickness of the coal seam is arranged, which effectively solves the problem of uneven distribution and achieves the purpose of uniform combustion.
3.3 In order to effectively solve the problem of stratified coal feeding technology, when burning low-calorie and low-volatility coal, there is a burning coal seam at the bottom of the coal seam. The BC-FDDX variable-layer multi-coal coal feeding device is solved by the variable layer coal feeding method. The variable layer coal feeding method can arrange a layer of coal at the bottom of the coal block at the bottom of the coal seam. The thickness of the final coal can be controlled and adjusted according to the operation of the boiler, so that the coal seam forms the end-block-end form. In the pre-combustion zone, the coal at the bottom of the coal seam is easy to burn and ignite, and the lump coal is ignited. Under the action of the combustion air, the ignited lump coal enters the combustion-supporting zone and fully burns. The variable layer coal feeding technology completely solves the problem that the lump coal at the bottom of the coal seam does not burn and burns when burning low calorific value and low volatile coal.
4, application examples
At the beginning of November 2006, our company replaced the ordinary coal hopper of 1# boiler with BC-FDDX type variable layer multi-coal coal feeding device. After more than two months of operation, it achieved obvious results. In view of the successful transformation of the 1# boiler coal hopper, the coal hopper of the 3# and 5# boilers was rebuilt in December 2006. The 5# boiler was installed after the original stratified coal feeding device was disassembled and BC-FDDX was installed. The variable layer multi-coal coal feeding device has achieved good results after the coal feeding devices of the two furnaces are put into production.
See Table 1 for details.
Table 11# Data comparison stage before and after furnace coal reform
After the project transformation
Furnace temperature
780 ° C
880 ° C
Slag carbon content
10 to 12%
7 to 8%
Boiler output under normal conditions
35~36t/h
38~39t/h
Induced draft fan frequency Hz
45~47
39～41
Blower frequency Hz
40～44
33～35
Raw coal to steam ratio
6.21
6.72
Coal saving rate (estimated, benchmark before transformation)
0
8%
4.1 After applying the new coal feeding device, from the combustion situation in the furnace, under the condition of burning the same coal type, the temperature inside the furnace has been obviously improved, the output of the boiler has increased correspondingly, and the carbon content of the slag has been increased. Dropped significantly. Run according to
The two-month data shows that the raw coal to steam ratio is 6.72 on average, which has a large increase from the previous raw coal to steam ratio of 6.21. It is estimated that the coal saving rate can reach 8%, and at the same time, due to the decrease of the operating frequency of the pilot fan, The power saving rate can reach 15-20%.
4.2 Analyze and compare from the perspective of equipment. Before the transformation, the local fire mouth in the combustion chamber is quite serious. The bareness of the grate is often burned by the radiant heat. After the transformation, the combustion chamber is burned in the form of a fire mouth. However, because the required air supply head is small, the grate part will not be blown out. Exposed, there will be no burning phenomenon of the grate; the front part of the combustion chamber often has a red fire phenomenon, even if the surface layer does not run red, the bottom layer of the ash residue is not completely burned, the temperature of the ash is high, and the slag stopper is extremely It is easy to overheat and burn. After the transformation, the surface and bottom layer of the ash are completely burned, and the temperature of the ash is not high, which can avoid the burning of the slag stopper, thereby prolonging the service life of the equipment.
4.3 From the labor intensity of the workers to analyze and compare, the coal hopper before the transformation is easier to "shed coal", the operation workers often need to clear the coal hopper, labor intensity. After the transformation, the coal is smooth, and the labor intensity of the operating operators is greatly reduced.
4.4 Analysis of the adaptability of coal types: Before the transformation, the adaptation range of coal is narrow, requiring more granularity, higher calorific value and volatile matter, otherwise there will be a red fire, a significant reduction in load, and transformation. After that, the coal with the lowest coal, low volatile matter and low calorific value can be completely burned, and the type of coal can be adapted to a wide surface.
5 Conclusion
Our actual use proves that the BC-FDDX type variable-layer multi-coal coal feeding device is applied on the chain furnace, which has the advantages of simple operation, low labor intensity of the furnace, and increased boiler output. After using the device, the grate is no longer overheated, prolonging the service life of the grate and reducing maintenance costs. Renovate a 35t/h industrial steam boiler coal feeding device, with an input of 100,000 yuan, an average of 8% of coal, and 20% of electricity saving. The investment can be recovered in less than one month. Obviously this is a successful energy-saving technology. Transformation.
Ningbo Xiaolong successfully developed a coal-to-coal energy-saving retrofit technology
——Application of variable layer multi-coal coal feeding device in our company