Straw Formic Acid Pulping And Formic Acid Recovery Process

The straw, a rich raw materials with low cost, is an important renewable biologicalresources, as well as play a very important position in China’s pulp and paper industry.However, due to small recycling radius and serious pollution problems of alkaline pulping, itsapplication is restricted greatly. The topic is to solve the wastewater pollution problem ofstraw pulping mill, make a preliminary study of wheat straw formic acid pulping, and exploreformic acid pulping technology for wheat straw production, at the same time recycle formicacid in a more economical and feasible route.This paper study straw about its fiber morphology and chemical composition, exploreformic acid concentration、cooking temperature、cooking time and liquid ration on pulpquality, range and variance analysis show that: the main factors for pulp yields is acidconcentration, the Kappa number is mainly affected by liquid ratio; optimize a better cookingprocess:acid concentration85percent, cooking temperature100℃, cooking time180min,liquor ratio15:1. This provide theoretical support for the formic acid pulping process, hasgreat significance for optimizing the pulping process, strengthening delignification efficiencyas well as improving product quality.Residual lignin is isolated by two-step methods including enzyme hydrolysis and weakacid hydrolysis, black liquor lignin is isolated by two-step methods including acid hydrolysisand weak acid hydrolysis respectively. Lignin structure transformation during cooking processis compared by the IR spectra, due to α-ether linkages or β-ether bond broke produce moreconjugated and non-conjugated C=O groups, it is much easier to removal the lignin, blackliquor lignin contain more primary alcohol-OH and secondary alcohols-OH, provide atheoretical basis for wheat straw lignin extrusion mechanism.Recovery and the economy of formic acid is a key issue for formic acid pulpingtechnology industrializing, recycling and increasing concentration formic acid in the wasteliquor, not only reduce environmental pollution, but also can create substantial economicvalue. This article innovative adopt vacuum distillation and azeotropic distillation, two-steprecycling formic acid, more in line with the factory production process. First step: vacuum distillation separate waste lignin and formic acid-water binary mixtures, tower-top pressure,reflux ratio, tower-top temperature and other operating parameters on the formic acid purityand yields, and optimize parameters; second step with1,2-dichloroethane as entrainer,heterogeneous azeotropic distillation purify formic acid, final get mass concentration of80.2%formic acid, and recovery yield is above90%. The entire distillation process,1,2-dichloroethane is almost no loss. Costs estimate that1t wheat straw pulp productionconsume around8t steam， if achieve formic acid pulping technology industrializationsuccessfully, it must also strive to reduce the recovery cost.