Analysis of burning coal gangue in the hottest ant

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Analysis of the burning process in a fluidized bed boiler lining gangue mixed with ganguehu rongquan

(Songzao Mining Bureau Power Plant, Chongqing, Sichuan, China, post code 401445) An analysis was conducted of a fluid. The inclusions, microstructure and properties after heat treatment after forging were inspected and analyzed by axiovert200mat optical microscope and quanta400 scanning electron microscope; The materials after heat treatment are processed into standard tensile samples and impact samples, ized bed boiler firing anticlite mixed WI6, packaging and process performance experimental instruments (including packaging drop experimental instruments, packaging impact experimental instruments, friction and wear experimental instruments, bending and bending experimental instruments, straightening machines, etc.); th gangue. The analysis covers the following aspects: rational distribution of mixed fuel particle diameter, the quantity of gangue to be mixed with the anthracite and the resulting bed-material layer thickness, air chamber static pressure, dust removal and desulfurization, Etc. The results of the analysis may serve as a guide for achieving the comprehensive utilization of resources during the construction of small sized thermal Establish a data base to divide operating expenses (ordinary expenses of maintaining business) power stations in the neighborhood of a high sulfur content antithesis mine

key words: fluided bed boiler, anticite, Analysis1 preface the development of international energy development and environmental protection issues has led to a significant adjustment of China's energy structure. According to the new policies issued by the state, thermal power stations with small installed capacity fall within the scope of shutdown. Some coal mine owned power plants, especially those in smokeless coal mines with high sulfur and high calorific value in the south, are facing the problem of continued survival. As another aspect of environmental protection and energy reuse, how to effectively digest the gangue discharged from coal mine production is also gradually placed on the agenda. It is an ideal solution to mix anthracite with gangue to make it reach the low calorific value of 12.5448 MJ/kg required by the state. However, how to effectively burn the mixed fuel in the original fluidized bed boiler and solve the problems of stratified combustion and dust removal and desulfurization is the prerequisite for the normal operation of the power station. Based on the successful certification of dg35/3.82-13 boiler resources comprehensive utilization, this paper analyzes these problems. 2 Analysis of particle size distribution of mixed fuel for fluidized bed boilers, they have the conditions to burn low calorific value fuel, but if the mixed fuel is processed by the original screening and crushing system, the electrical quantity often needs to be amplified, so the screening width must be too wide. If the gangue and anthracite pass through the same screening and crushing system to obtain the same particle size distribution (because the grindability coefficients of anthracite and gangue are inconsistent, the particle size of anthracite is smaller), then the particle size is D, the gravity is r, and the void ratio of fixed bed is ε The viscosity coefficient of the fuel is γ k. The flow conditions in the air with the gravity of RK and the speed of wk are:

re=ar ×ε 4.75/〔18+0.6(Ar ×ε 4.75) 0.5]

where re=wk × d/ γ k

Ar=r × g × d3/rk ×γ K2

the critical wind speed function wk can be calculated according to the above formula, pro =f( ε four point seven five × R/g) and limit wind speed function wk, pole =f (R/g) (at this time, take ε= 1)。 For two functions, respectively( ε 4.75/g) and (R/g) are the derivatives of independent variables, whose derivatives are greater than zero, and the original function is an increasing function. Therefore, to obtain the same boiling state, the air distribution required by gangue is greater than that of raw coal. If both pass through the same screening and crushing system, it will obviously lead to the expansion of screening width, resulting in stratified combustion. If the air volume is controlled to ensure the normal boiling of coal particles, it is easy to cause coking due to poor boiling of gangue; If the air volume is controlled to ensure the normal boiling of gangue, it will further increase the uplift and precipitation of coal in the mixed fuel, increase the heat loss of incomplete combustion of fly ash, and the flame center moves upward, which is easy to overheat the superheater. Therefore, anthracite and gangue must be broken and evenly mixed in order to obtain a relatively consistent boiling effect

according to the heterogeneous combustion theory, the speed w of fuel particle combustion reaction is:

w=wk × Co= β× k × Co/( β+ K)

according to Arrhenius' law k=ko × Exp (- E/R/T) according to the diffusion principle

β= Nu × D/d=A × Ren × D/D (for gas medium)

where CO is the reaction gas velocity on the fuel reaction surface; K is the rate of chemical reaction, and its value is related to temperature; β Is the mass transfer coefficient, D is the diffusion coefficient, and nu is the Nusselt number; E is the activation energy of the fuel. According to the experiment, when re> 100, a=0.7, n=0.5. Therefore, due to the reduction of the particle size of gangue after the crushing of raw coal and gangue respectively, its mass transfer coefficient β Increase, so as to strengthen the diffusion combustion reaction speed of gangue. At the same time, combined with the increase of specific surface area, the burnout degree of low calorific value gangue that is difficult to burn is improved. 3 Analysis of the proportion of mixed fuel mixed with gangue the change of combustion characteristics of mixed fuel after Anthracite Mixed with gangue is mainly manifested in the increase of moisture and sulfur, and the decrease of hydrogen group, volatile matter and low calorific value. From the point of view of combustion efficiency, the change of water and hydrogen base will prolong the time required for the mixed fuel to burn out in the furnace; The continuous explosion of anthracite in the combustion process and the slower ignition of gangue make the particle size distribution of mixed fuel relatively widened again in the combustion process; The reduction of low calorific value and greater gravity make large air volume operation and multi slag discharge inevitable. From the perspective of exergy, the exergy value of gangue is lower than that of anthracite, so the energy level of fuel mixed with gangue decreases. Therefore, in order to ensure thermal efficiency, it is necessary to control the proportion of gangue added

from the perspective of stable boiler combustion and normal system operation, the wear and corrosion of fuel transportation system and ash removal system, boiler body, flue and induced draft fan are aggravated due to the increase of fuel quantity (fly ash and slag discharge also increase) and the change of moisture and sulfur content. The difference between the cohesiveness of gangue and anthracite at high temperature and the characteristics of slower ignition, and the production of FES in the furnace due to the factors of symbiotic pyrite

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