Research On The Mechanism Of Improving Straw Briquetting Properties By Anaerobic Fermentation Pretreatment

The straw resource is very rich in our country, but it can’t be used popularly because it is scattered and its energy density is very low. It is an efficient way to compress the straw into the densified biomass fuel (DBF). Due to the inherent character of the straw, the briquetting facilities wear quickly during the densification and the densification energy is very high, which are the obstacles of developing the DBF. Considering this problem, our team found started some research on improving straw briquetting properties obviously by anaerobic fermentation. Through the research, we can conclude that anaerobic fermentation can improve straw briquetting properties, which lays the foundation of reducing energy consumption and alleviating the abrasion. Besides, we also find the water resistance of the anaerobic fermentation straw increases evidently. We should study the mechanism of lowering the energy consumption and increasing the water resistance by anaerobic fermentation furtherly to promote the application of the DBF technology. So this paper carries out research from two aspects:First, analyzes the elasticity modulus, the viscidity modulus of the straw and the stress relaxation during the whole densification process to explore the reasons of lowering energy consumption. The second content of this paper is to explore the reason of water resistance increasement based on the change of the straw structure and the viscous material after the anaerobic fermentation.Research on the mechanism of lowering the energy consumption of the briquetting by anaerobic fermentation Different proportions straw is put in the briquetting material compared to the straw dealed with the NaOH solution. Then we can contrast the energy consumption among different groups quantificationally and find the changing rules of the two indexes-elasticity modulus and viscidity modulus-in the straw according to the compressing time. And the reasons of the energy consumption changing will be explained. Meanwhile the stress relaxation after compressing is studied primarily.Research on the mechanism of increasing the briquetting water resistance by anaerobic fermentation Use the method of BET to test the raw straw and the anaerobic fermentation straw. Study the change of specific surface area of the briquetting material. Then the lignin is regarded as the variable to study the effect of adding the lignin to the material on the intensity and density of DBF in different moisture content. Then we can affirm the factors of increasing the DBF’s water resistance.From the above studies, we can draw conclusions as follows:(1) Using the anaerobic fermentation straw as the material can lower the energy consumption markedly, and the decrease range is in direct proportion to the anaerobic fermentation straw content. When there is no anaerobic fermentation straw, the energy consumption is 2.65J/g. And the energy consumption can reach 1.32J/g when there is no raw straw. The decrease range is 50.19%.(2) Anaerobic fermentation lower the elasticity modulus and increase the viscidity modulus of straw, the elasticity modulus changes from 6.50MPa to 4.16MPa and the viscidity modulus changes from 5.08MPa·s to 11.06MPa·s, so the briquetting pressure is lower and the energy consumption is lower during the densification.(3) Anaerobic fermentation increases the specific surface area of straw, then the dispersity is increased, so it can improve the properties of the DBF. Anaerobic fermentation increases viscous material proportion of straw. The experiment indicates that the higher content of lignin can increase the intensity of the DBF briquetted in the higher moisture content. And the two above factors increase the water resistance of densification.