Research On Combustion Characteristics For Cofiring Of Rubbish, Stalks And Coal

Rubbish incineration power-generation technology is the most effective means for realizing rubbish harmlessness, reutilization and reduction, which has great benefit to environment and economy. But the rubbish incineration power generation have two major problems:One is the rubbish of low heating value,complex component, high moisture and auxiliary fuel added.The relevant departments of the state stipulate its blending conventional fuel cannot be more than 20% in the circulating fluidized bed incinerator, which lead to the rubbish incineration power factory is high investment, high operating costs,which hinders the development of rubbish incineration technology.The other is rubbish incineration if mishandled, solid contaminants will turn into gas or other forms of pollution, which is harm to human health. Aiming at these problems, this topic to do the following research works:1) Analysis the main factors of influencing the pollutant discharge.In view of the situation of rubbish in our country did not implement classified collection, incineration pretreatment is one of the most effective way;Combustion temperature is the most significant influencing factors of affecting the pollutants from the view point of control the main pollution emissions, and furnace temperature should be controlled in 850 to 900 ℃.2) This topic analyzes the combustion characteristic,coke characteristic, pyrolysis characteristic and reaction dynamics analysis of coal, stalks and rubbish as well as different cofiring ratios through experiments, the conclusions as follows:Straw mixed burning contributes to coal fire and burning, and helps to improve the combustion characteristics of coal;But straw mixing ratio is not the greater,the better.When the blending ratio in 10% to 90%, the coke average burning rate is in parabola shape change;Straw mixed burning to improve the performance of the mixed fuel combustion is mainly manifested in pyrolysis stage, no obvious effects on coke burning stage.Components of rubbish are complex and big change, rubbish burning is a variety of complex process of combustion mode by synthesizing evaporation, melting, thermal decomposition and chemical reaction and so on,and can’t simply determine the combustion characteristic through the experiment.3) By using one power plant of Chengde circulating fluidized bed boiler as equipment,taking the mixture of rubbish, corn stalks and coal as fuel through industrial experiments of different cofiring ratios so as to work out the change rules of the circulating fluidized bed boiler operating parameters.Mixed burning rubbish can make the bed temperature is reduced, affect the combustion efficiency of boiler,and the largest proportion of blending should be depending on the bed temperature of the low limit.With the increase of rubbish of blending ratio, the wind chamber air pressure and return air pressure rises, the primary air rate and returned to the coal bed temperature decreases;The addition of straw could increase the bed temperature, improve the waste of blending proportion, but it will reduce circulating ash content, blending ratio will affect the boiler combustion and heat transfer.In order to improve the stability of the waste incineration power generation technology and economy, according to the change of operation parameters, with the increase of rubbish of blending ratio, the following operation adjustment measures are put forward: In order to maintain high bed temperature,higher calorific value of coal which can be used, or increase the straw of blending ratio;Improve the drum slag machine speed to increase rate of slag discharge, maintain a reasonable bed pressure drop, lower fan energy at a time;In the case of the total air volume unchanged, reduce the primary air rate, increase the rate of secondary air, so as to meet the needs of the upper chamber of a stove or furnace combustion share increase; In order to meet the needs of the returns in the bed combustion, the return product air is expected to provide sufficient and proper return,the bypass damper to adjust the size of the return product air volume.