Research On The Hot-air Drying Characteristics And Drying System Of Biomass Fuel

As the energy problem increases prominently today, biomass energy as an important renewable energy, with zero emission of CO2, huge reserves of resources, environmental friendly characteristics, has aroused people’s wide attention. Biomass utilization technologies can be mainly divided into two kinds:biochemistry method and thermochemical conversion. Thermal chemical conversion including direct combustion, gasification and pyrolysis technology. Biomass moisture content will affect the efficiency of thermal chemical conversion, the lower the moisture content of biomass, the more it suitable for thermal chemical conversion.Biomass fuel mainly include all kinds of straw, wood and wastes of agriculture and forestry. Fresh biomass fuel moisture content is higher, sometimes even can reach above 90%. When the fuel moisture content is high, it would do great harm to the fuel storage, the boiler feeding system and combustion system. Thus, the biomass resources should be dried before utilization, but drying is a high energy consumption industry, how to make dried biomass resources economic is an important research field on biomass energy utilization. This paper has researched the drying properties with hot wind of some typical biomass fuel in biomass plant, and has analyzed the drying properties of biomass fuel with drying dynamics.Firstly, this paper analysis the no-dried and dry biomass fuel by the thermogravimetric analyzer. By research the combustion characteristic curve and the combustion characteristics, we discussed the influence of hot air drying to biomass fuel combustion, therefore, it can provide a certain theoretical basis for efficient utilization of biomass fuel.Secondly, this paper has studied the influences of hot-air temperature, speed, relative humidity and the blowing way (parallel and vertical) on the drying characteristics of camphor by self-building hot air drying test system. The results show that the whole drying process includes two phases, one is the constant speed and the other is the declining speed phase, the temperature of the hot air is the main factor that affects the drying process, vertical flow increases the drying rate, this result is confirmed by Fluent simulation. Nonlinearly fitting was also made on four drying model using the test data. After comparing the value of relative correlation R2, residual sum of squares RSS and the root mean square error SD, it is indicated that the Page model is the optimal model for describing camphor hot air drying process at low temperature. The obtained Deff demonstrates that Deff would increase with the hot-air temperature.Than, according to the characteristics of the biomass power plant fuel, this paper has studied the influence of thickness to the biomass fuel, which give necessary basic data for the design of drying machine. Finally, on the basis of these hot air drying characteristics of the biomass fuel and the comprehensive evaluation of dying technology and relevant comparison, this paper has put forward the basic design for the multilayer belt dryer for biomass power plants and mainly designed the structure.