Research Of Pulping From Mechanical Straw

Biorefinery is a scientific concept with full and effective use of biomass resources to achieve the sustainable development. The target product cellulose extracted from pulp which made by crop straw with mechanical method are used to make paper. Hemicellulose and lignin removed from this process can be recycled and turned into new biological products, such as biofuels, polymers, etc., which can greatly enhance its value. There is serious pollution, low hemicellulose and lignin removal rate, low recycling rate and much time-consuming issues in the traditional method of dealing with plant fiber. hydroxyl radical actived oxygen has a high oxidation potential, so it is applied to treat wastewater and so on.The main research in this paper is about hydroxyl radical actived oxygen produced by Beijing University of Chemical Technology and applied to treatment of mechanical straw, separation of hemicellulose and lignin, bleaching experiments, effective extraction hemicellulose and lignin from black pulp to provide raw materials for biorefinery. The specific contents are as follows: (1) Based on combination of biorefinery and pulping, the treatment mechanical straw with hydroxyl radical actived oxygen, the separation hemicellulose and lignin, and the discussion of the effect of four factors including reaction temperature (T), reaction time (t), H2O2 mass fraction (w), and solid to liquid ratio(r) are researched in this paper. Finally, the relatively optimized condition is T=160℃, t=2h, w (H2O2)=1.5%, r=5%, removal of hemicellulose and lignin reach to the highest rate, at 91.72%,96.67%, respectively. The mechanical pulp treated by the hydroxyl radical actived oxygen are observed in the microscope. Individual fibers can be seen clearly, indicating that the removal of lignin and hemicellulose are well.(2) The hydroxyl radical actived oxygen are used to bleach mechanical pulp. It works best under the condition of T=160℃,t=2.5 h, w (H2O2)=1.5%, r=5 g/L.(3) Hemicellulose is extracted from black liquor of cellulose pulp. At 60℃, black liquor was concentrated to about 50%. The loss of hemicellulose content is 4.97%. At room temperature, black liquor and 2 times volume 100% methanol are mixed. After stiring the mixture, standing 5h and centrifugating, hemicellulose cake is obtained. The hemicellulose removal rate is 92.31%. Methanol is recycled. The recovery rate of methanol is 84%. Recovery methanol can extract the hemicellulose from black liquor still well. (4) Lignin is extracted from black liquor of cellulose pulp. The pH of black pulp is adjusted to 3.5 with sulfuric acid. Flocculation and sedimentation are carried out at 60℃for 2 h. The crude lignin can be obtained with centrifugation. The lignin removal rate can reach to 91.4% under this condition.