| With the development of urbanization in China,more and more municipal sludge is produced.The reasonable disposal of municipal sludge has aroused widespread concern of the society,which is one of the environmental problems to be solved.As a large thermal equipment,cement precalciner has the advantages of stable combustion and no waste residue discharge when co-combustion municipal sludge,and it is not easy to cause secondary pollution to the environment.In this paper,the three-spout TTF precalciner of a cement plant in He Bei Province are studied.The stability of flow field,temperature field and concentration field of the precalciner were analyzed by changing the mixing proportion,location and particle size of municipal sludge,and the influence of municipal sludge on combustion and cement raw meal decomposition in cement precalciner was studied.1)The main range of urban sludge weight loss is 200-600°C,which has good combustion characteristics and similar combustion behavior to coal.It is reasonable to use it as a substitute for some fuels in cement production.2)The numerical results are in good agreement with the actual operation conditions.The numerical results show that there are three times of spouting effect in the precalciner,and the characteristics of gas flow field are consistent with the structural characteristics.Most of the decomposition reaction takes place in the lower and middle columns of the precalciner.The average temperature at the outlet of the precalciner is about 1250 K,the decomposition rate of calcium carbonate is 84.69%,and the total no concentration at the outlet of precalciner before denitration is 548 ppm.3)In this precalciner,the ratio of municipal sludge to pulverized coal is 10 %,and the inlet is between 8.5 m and 14.5 m,which can obtain better combustion effect,raw meal decomposition rate and lower no emission;If the particle size of municipal sludge is too large,the temperature of the lower and middle columns of the precalciner will decrease and the outlet temperature will increase.However,the decomposition rate of raw meal will not be greatly affected.The larger municipal sludge particles will cause higher no emission. |
