Research On PM Generation Characteristics During Zhundong Pulverized Coal Combustion

The accumulative total proven reserve of ZhunDong coalfield is 213.6 billion tons, which makes the coalfield Chinses biggest integrated coalfield. The biggest coalfield can alleviate the tight coal supply, which has important significance to our country. ZhunDong coal is a typical high alkali metal coal.This characteristic makes it can generarte a large number of submicron particle matters（PM） in combustion. General dust removal equipments has a low efficiency when they be usd to removal the submicron particles. What is more, heavy metals can easily enrich the particles, that makes the particles have serious harm to the environment and human health. In view of this, this paper will study the characteristics of PM formation during the ZhunDong pulverized coal combustion. On this basis, several mineral elements be added in the coal, and the effect of the mineral matters on PM reducing be studied.In order to complete the research content of this paper, the author builded a drop tube furnace experimental system. And the temperature field, cooling system,powder feeding system and other aspects of the experimental system are debugged. The results showed that the experimental system is stable and reliable. The PM were collected by ELPI, and then they were analyzed by the XRF, SEM-EDS and so on. Several information about the characteristics of particle number concentration, morphology, chemical composition and so on was got and studied.The basic law of particles matter formed in the combustion process of Zhundong pulverized coal had been studied. The author discussed the influence of temperature, particle size and other factors on the PM formation. The results showed that particulate matter（PM10） showed a bimodal distribution, peaked at around 0.2 μm and 2 μm during Zhundong pulverized coal combustion. The smaller coal particle size, the more submicron PM and supermicro PM generated during coal combustion. The high combustion temperature, the more PM₁₀ generated in general.The pulverized coal was employed to fractionate by deionized water, ammonium acetate and hydrochloric acid, and then the coal was combustion. The treatment pulverized coal was then under combustion experiments. Then the paper analyzed the impact of water soluble metal elements, ion exchangeable state elements, hydrochloric acid soluble and acid insoluble metals on the PM formation characteristics. The results showed that: water soluble salts played an important role during the ultrafine particles matter(PM_0.2) generated. Elements exist in organic form such as Fe, Ca ect can evaporated into the flue gas during the pulverized coal combustion process, and then the vapor condensated and distributed on the PM1 when the temperature of flue gas decreased. Different fractionation methods had not a significant impact on the distribution of Si and Al in PM1-10 in the combustion process.The Zhundong coal genetated more submicron PM than other coals. In this paper, different mineral elements were added in the raw coal by impregnation. Then the experiments were carried out to reduce the generation of PM. The effects of different mineral elements（Mg, Ca, Fe） on the formation of PM were studied. Mineral elements had an obvious effect on PM number concentration, morphology, and chemical composition. The results showed the overall effect is Ca>Fe>Mg for the control of sub micron generation. And that mineral elements supported reducing the generated of submicron particles through accumulation and coagulation and then they were transformed in larger size PM, thereby reducing the submicron PM formation.