| China is the second-largest energy consumer, energy energy gap and environmental pressure has been becoming more and more big with the economic and social development of society. Although there was plenty of straw resources, a big part of it has been wasted, which has produced great pollusion.As for the heating energy demand is increasing, using agricultural waste straw as raw materials for the heating energy will be an inevitable trend Howrer, there are some difficulties to be solved when straw is fired in the boiler, including slaggin, agglomeration, and higer NOx emission, for the high alkali and alkaline earth metal elements,Cl and N elements exists in the straw. Meahwhile, biomass straw boiler study is still in the initial stage, which can be embodied in the boiler sturctre and air distribustion optimization by numerical calculation. Therfore, the main research contents are as follows:(1) A new DTG-DTA dealy time method for ignition temperature determination has been estabilished.Based on thermal balance theory, five classic biomass materials were selected to inspect the advantages of the new and tradition using method. Through the error analysis, the results showed that new method has the clear physical significance and higher stability. It was showd that when the heating rate is lower than (or equal to) lOK/min, DTG fixed weight loss ratio method is the first choice, or else is the new method. Especially in multi-samples test, differert ignition temperature determination methods should be selected classified by fuel types, in order to compute results accurately.(2) Based on the perspective of clean combustion, the feasibility study on sweet sorghum stalks after fermentation residue as elding was carried out, including fermentated residue of sorghum stalks’ multi-phase combustion characteristics experiments and NOx emission test has been carried out. Test confirmed that the strict measures was needed to ensure NOx emissions meet the requirements of relevant standards, when the fermentated residue was burned. As to the more nitrogen content fuel, water pretreatment denitrification and other fuel performance improvement research was continued done. It was testified that water pretreatment is beneficial in ash removal, calorific value increasing, Cl and other harmful elements removal (including N, K, Si, etc), slagging reduce. In normal temperature case, to ensure the fuel performance and economic benefits improved, washing solid-liquid ratio1:30was recommended.(3) Based on biomass fuel characteristics,1ton biomass chain boiler design., fuel supply system and dust removal system were desiged., including the selection of grate combustion products, heat balance and furnace structure calculation, the hopper, fuel position detection and relevant logic control system were built.(4) Combined the basic equation of fluid with biomass combustion sub-processes, the material bed combustion model was established. Then coupled with the furnace chamber combustion model, the whole umerical model of biomass boilers was constructed. Then, based on the model, the chame construction was determined with cold air simulation, and the air distribution was settle down too which aim at the lowert NOx emission,116.93mg/Nm3The best real arch coveage is60%, and the best air distribustion is4:3:3.(5) To verify the numerical calculation and design work, biomass boiler thermal performance and pollutant emission tests were carried out. The results showed that the biomass boiler’s average thermal efficiency reaches more than80%, and the pollutant emission is father lower than the national standard requirements.this proves the accuracy of the numerical model and desin work... |
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