Study On A Fixed Bed Straw Carbonizing Furnace With Two Chambers By Indirect Heating Of Flue Gas

The contradiction between energy,environment and development is becoming more and more obvious in the new era.Biomass energy is favored as a renewable and clean energy source.Based on the problem of difficult treatment of crop straw in smal-scale agricultural production,this paper designs a fixed bed straw carbonizing furnace with two chambers by indirect heating of flue gas that can bundle bundled carbonized crop straws according to the working environment and the specific situation of the population.The combustion chamber is used for indirect heating by heat radiation and conduction through wal s.High-temperature flue gas generated in the combustion chamber is introduced to the two carbonizing chambers with pipelines to act as auxiliary heating in the low temperature zone away from the wall of the combustion chamber,thereby improving the overall thermal efficiency of the equipment and also making the heat distribution of the carbonizat io n chamber more uniform.The equipment has obvious advantages such as convenie nt movement,simple operation,and large amount of raw materials for single carbonization.The main research contents of the thesis include the following aspects:（1）Based on the process requirements of bundled carbonization,the overall design of the equipment is a square box structure.The main components such as the combustio n chamber with large furnace door,the carbonization chamber arranged on both sides,and the tobacco pipe system with high temperature flue gas were designed to complete the overall structural design of the fixed bed carbonization equipment.The ANSYS software was used to simulate the temperature distribution of the carbonization chamber,and the stress and deformation analysis of the wall of the furnace body were carried out to further optimize the design of the fixed bed carbonization furnace.Finally,complete the drawing of the fixed bed equipment with two-box by indirect heating of flue gas,and complete the processing and manufacturing of the equipment according to the design drawings.（2）Through consulting the literature and equipment test run,it is found that the fan speed,heating time and raw material status are important factors affecting the equipment carbonization test.Through the orthogonal test L₂₇(3¹³)of corn straw,it was found that the carbonization effect of the equipment was excellent,and the interaction between the experimental factors was less than the influence of the factors themselves,and the interaction between the determined factors had no significant effect.（3）The carbonization chamber temperature rise has a significant correlation with the fan speed in the corn straw test.When the fan speed is 1000r/min,the temperature of the carbonization chamber increases slowly after heating for 180min;when the fan speed is1900r/min,the temperature increase of carbonization chamber is gentle after heating for120min;when the fan speed is 2800r/min,the temperature of the carbonization chamber does not change much after heating for 210min.The high fan speed can supply enough oxygen in the combustion chamber,the combustion chamber can supply more heat,and the heating rate of the carbonization chamber is higher.However,the excessive fan speed causes excessive air supply and increases the heat loss of the flue gas.（4）A series of carbonization experiments were carried out with corn straw and rape straw as raw materials.It was found that the fixed carbon content in the three indicator s was positively correlated with the final carbonization temperature,and the two were negatively correlated with the carbon yield change.When the equipment is working stably,the temperature change range is mainly between 400°C and 500°C.When the carbonizat io n temperature rises,the carbon content of the charcoal increases and the carbon yield decreases.The industrial analysis shows that the main component of the carbon reduction is volatilization.The secondary pyrolysis occurs at high temperatures for the raw materials.（5）Fan speed,heating time,raw material status have a significant impact on the char forming quality of equipment carbonized raw materials.The fan speed directly controls the inlet air of the combustion chamber of the equipment,which affects the heating of the combustion chamber to the carbonization chamber.The low fan speed makes the combustion chamber heat supply low,resulting in poor charcoal quality.Prolonged heating time can improve the carbon quality.However,if the heating time is too long,the carbonization effect of the biomass will not be significantly improved,but the burning energy consumption will be wasted;the bundle diameter and the accumulation amount affect the heat transfer between the raw materials in the carbonization chamber,and the bulk density of the bundled raw materials is much higher than the natural accumulatio n.The amount of straw in a single bundle of carbonized treatment is large,but the excessive bundle diameter hinders the transfer of heat to the raw materials inside the bundle.