Experimental And Simulation Study On Decomposition Characteristics Of Cement Raw Meal In High Altitude Area

The decomposition process of cement raw meal in the furnace is very important in the cement production,which involves the combustion of fuel and the decomposition reaction of cement raw meal.The infrastructure needs of the “Belt and Road” and the regional characteristics of cement production make the construction of cement plants in high-altitude areas particularly urgent.But the atmospheric conditions of low pressure and low oxygen in high-altitude areas will affect the operation of the precalciner,causing problems such as low decomposition rate,high heat consumption,and unstable quality of the product.Therefore,it is imminent to master the decomposition characteristics of the raw meal in the furnace at high altitude,and to propose suggestions for optimizing the operation of the calciner under highaltitude conditions.Based on the research on the physicochemical characteristics of materials,a low-pressure suspension furnace experiment system was built to explore the effects of pressure,temperature and oxygen concentration on the decomposition characteristics of the raw meal.Then the cement production process model was constructed to explore the influence of tertiary air and kiln gas on the decomposition process of cement raw meal.And based on the genetic algorithm,the optimization suggestion for the operation of cement precalciner at high altitude was obtained.The physicochemical properties of raw materials were studied.Firstly,the industrial and elemental analysis of fuel and the component analysis of cement raw meal based on loss-onignition method was carried out,obtained the composition of materials.Also the particle size and pore structure of the cement raw meal were analyzed and obtained.Finally,the thermogravimetric analysis of cement raw meal,coal and their mixtures under unconventional hypoxic conditions was carried out,the reaction kinetic parameters of cement raw meal and coal under low oxygen concentration were obtained,and the interaction between cement raw meal and coal was explored.A low-pressure suspension furnace experiment system was constructed for the atmospheric conditions of low pressure and low oxygen in high altitude areas.Based on this system,the low-pressure experiments of coal,cement raw meal and their mixtures were carried out,obtained the effect of the pressure,temperature and oxygen concentration on the reaction characteristics of cement raw meal.The results show that the decomposition of cement raw meal in the low-pressure suspension state conforms to the random nucleation and growth model,and the reaction activation energy is 36.11 k J/mol,which is significantly lower than the 185.03 k J/mol obtained by the thermogravimetric experiment in the stacking state.With the decrease of the reaction pressure,the decomposition rate of cement raw meal increases,and the specific surface area and specific pore volume of the product also increase but the decomposition ratio of raw meal will decrease.The reaction rates of coal and cement raw meal will gradually increase with the increase of reaction temperature,and the burnout ratio of coal varies little with temperature under high temperature conditions,the decomposition ratio of cement raw meal is affected by the decomposition rate and residence time will first increase and then decrease.The burnout ratio and reaction rate of coal increases with the increase of oxygen concentration under low pressure conditions,which increases the temperature of the reaction zone and the reaction rate of the reactants.Based on the analysis of the decomposition process of cement raw meal,a 5800 t/d cement raw meal decomposition process model in high-altitude area was constructed with a cement production plant at an altitude of 2000 m as a prototype,and the model was verified based on the actual operating parameters of the plant.Then,based on the process model,the influence of tertiary air and kiln gas on the decomposition process of cement raw meal was investigated.The results show that increasing the tertiary air volume increases the amount of oxygen and the heat carried by the high temperature gas into the furnace,which can effectively improve the temperature of the furnace and decomposition rate of the raw meal.When adjusting the operation of the calciner in high-altitude areas,priority should be given to increasing the air supply volume and increasing the oxygen concentration of the tertiary air.The temperature of the supply air can be increased to increase the heat entering the calciner under the condition that the amount of oxygen fed into the furnace is sufficient.