China’s thermal power plant wet FGD (flue gas desulphurization) produces more than 80 million tons of gypsum each year. The factors affecting the quality of wet desulphurization gypsum are limestone quality, flue gas dust, gypsum slurry pH, slurry quality, gypsum water content, desulphurization system design features, and operating conditions, etc. There are many reasons for high gypsum moisture content, and the analysis and solution are particularly complex. Through a case analysis of a power plant with high moisture content of desulphurization gypsum, the main reasons are that the unit has been operating under low load conditions for a long time with low sulphur coal, limestone supply slurry is high, slurry pH is high, and the volume of gypsum crystals generated is small, resulting in gypsum dehydration difficulty and high moisture content. The measures were to add the crystal seeds into the slurry and to lower the operation pH. The slurry quality is improved, and the gypsum dehydration returns to normal. The design margin of the desulphurization system is large, even in a long-term low sulphur and low load operation. There are no similar cases, and this situation generally does not attract attention. It is worth further analysis and reference.
The boiler flame contains a lot of information,among which the pulsation frequen-cy is closely related to the combustion efficiency and thermal efficiency of the boiler,which has a practical guiding significance for the economic operation of the boiler.In this paper,the boiler flame during stable combustion was taken as the research object.With the help of im-age processing and spectrum analysis technology,the average pulse frequency of the boiler flame during stable combustion was obtained from the perspective of the change of flame are-a.Combined with the working condition data of the boiler,the relationship between the aver-age pulsation frequency and the boiler load,thermal efficiency and carbon content of fly ash is established.Within a certain range,the larger the average pulsation frequency,the greater the load corresponding to the operating conditions,the higher the thermal efficiency,and the less carbon content in fly ash.
Cyclone separator is one of the important equipment in the combustion system of circulating fluidized bed boiler.The falling off of central cylinder is a common problem affecting the safe operation of cyclone separator.In this paper,taking the cyclone separator of a 350 MW circulating fluidized bed boiler as the research object,the Reynolds Stress Model is used to simulate and analyze the gas flow characteristics in the cyclone separator before and after the center cylinder falling off.The calculation results show that the air flow structure in the cyclone separator does not change before and after the central cylinder falls off,including external swirling flow and internal swirling flow.When the central cylinder falls off,the longitudinal circulation and short-circuit flow in the upper part of the outer cylinder disappear,and part of the air flow flows directly from the central cylinder;The axial velocity and tangential velocity distribution of the air flow are similar,but the local velocity distribution and magnitude are different;The pressure distribution is similar,and the pressure difference between inlet and outlet decreases.
Due to the nonlinearity,large inertia and large delay of selective catalytic reduction(SCR)flue gas denitration system in coal-fired power plants,the traditional identification methods have the problems of slow convergence speed and low identification accuracy.In this paper,the ideas of adaptive dynamic inertia weight,adaptive variation of particles and natural selection are introduced on the basis of fundamental particle swarm algorithm.The improved particle swarm algorithm is applied to model identification of SCR flue gas denitration system of an ultra-supercritical 660 MW unit.Based on the field operation data of the unit,the transfer function models between the position opening of the regulating valve and the mass flow of ammonia,between the mass flow of ammonia and the concentration of NOx in the outlet,and between the concentration of NOx in the inlet and that in the outlet were established.The results of the study show that the particle swarm algorithm optimization improves the model identification accuracy,and effectively improves the defects of basic particle swarm algorithm which is easy to fall into the local optimum and the loss of population diversity in the later stage.Meanwhile,the simulation results demonstrate the effectiveness of the proposed method.
The serious fouling and blocking problems of several rows at first layer catalysts near the front wall were investigated in this paper,which are common in the selective catalyt-ic reduction(SCR)de-NOx device of coal-fired boilers.Taking a 350 MW coal-fired unit as an example,CFD numerical simulation and field test were used to carry out diagnostic analysis,and the catalyst anti blocking modification was carried out using fly ash interception and uni-form layout.Studies have shown that bias flow of coarse ash leads to a significantly higher fly ash concentration in the area near the front wall upstream of the top catalyst,and the accu-mulation of coarse fly ash in this area aggravates the wear of the catalyst.After adopting the plan of intercepting large particles at the economizer outlet and evenly distributing fly ash in the ascending flue gas duct,the serious fouling and blocking problems at several rows of top layer catalysts has been solved effectively.
