| This paper mainly studied the influence of organic acid on original liquor recycling. The first stage cooled waste liquor from Reed Three-stages Counter-current Ethanol-water pulping Process was diluted with 0.8 times and part of lignin was removed, which was called original liquor in this paper. The original liquid adding calcium hydroxide called calcium alkali liquid, while adding sodium hydroxide called sodium alkali liquid. And the optimal reflux liquid was produced by the condition of the optimal reflux ratio of original liquor directly back to the first step pulping. The original liquid, the calcium alkali liquid, the sodium alkali liquid and the optimal reflux liquid were distilled by atmospheric distillation. Fractions were compared to concluded the influence law of organic acids on waste recycling. In addition, the law was verified by the method of artificial simulation. Moreover, The paper also studied the influence of the original liquor directly back to the first step pulping on the quality of pulp. Results could lay a theoretical basis for the liquid waste recycling technology.The original liquid was distilled by atmospheric distillation, results show that the distillate temperature range from 85℃ to 103℃. The pH value of the total fraction is 4.68. And the major components in the fraction are water, ethanol, furfural, formic acid, acetic acid and levulinic acid. The content of ethanol was tested by gas chromatography, the concent of furfural was measured by ultraviolet spectrophotometer, and the content of formic acid, acetic acid and levulinic acid were measured by ion chromatography. They are very reliable methods. Results show that alcoholic strength of the fraction is 17.8%(v/v). And the concentration of furfural, formic acid, acetic acid, levulinic acid are 5.387 g/L, 1.424 g/L,2.298 g/L,0.087 g/L. After the original waste liquor was conducted by atmospheric distillation, the rest of solids was tested by ion chromatography. Results show that in a liter of original waste liquor contain the concentration of arabinose, galactose, glucose, xylose, galacturonic acid and glucuronic acid respectively are 2.365 g,0.382 g, 0.204 g,0.189 g,0.130 g,0.067 g, and the ash content is 1.934 g/L.The water, ethanol, furfural, formic acid, acetic acid, levulinic acid in the original liquor could form complex multivariate azeotropic system when atmospheric distilling. And the compositions of the azeotrope differ as the distillation temperature varies. Ethanol, furfural, organic acid could be tested mainly in the fraction with a temperature of 85 95℃，95～99℃,99～103℃ respectively. And ethanol, furfural, formic acid, acetic acid recycle mass of total respectively are79.9%,70.9%,86.4%,89.8%.Results show that weak alkali (calcium hydroxide), alkali (sodium hydroxide) were added into the original liquor which would destroy the original liquid azeotropic system. At the same time, the ethanol recovery were hardly affected in calcium alkali liquid and sodium alkali liquid, but the levulinic acid recycled had a large improvement. The sodium alkali liquid distillation could hardly tested formic acid and acetic in the fractions, as well as furfural is destructed mostly. In addition, the highest liquid boiling point has grow to 115℃, it is not conducive to energy conservation. Precipitation appeared when calcium hydroxide added into the original liquor, the results showed that the precipitation was lignin calcium salt. It should be good for subsequent degradation of the purification of sugar.On the basis of waste recycling process is not affected, the original liquor directly back to the first step pulping could be not only reduce the load of waste recycling, but also improved the quality of pulp. Results show that the optimal reflux ratio of the original liquid recycling is 25%. Compared with the original pulp, the the fine pulp yield of optimal reflux increase by 8.23%. The value of potassium permanganate decreased by 5%. The beating degree is 32°SR. The paper get the tensile index, burst index and whiteness increased by 26.86%,18.1% and 20.2% respectively. The original liquor directly back to the first step pulping has a certain influence to azeotropic system, but not obvious. Compared with the original liquid atmospheric distillation, the range of the temperature of the obtained distillate is consistent, but the composition in fractions are changed. The content of ethanol and formic acid increased, the content of acetic acid decreased, and the content of furfural and levulinic acid content are almost invariable in liquid after reflux. The decrease of pH results from the increase of formic acid content.In addition, the model liquid be used to verify whether the rule of liquid composition and azeotropic is correct or not. It was mixed with standard content. Compared with the azeotropic rule of model liquid and original liquid. Results show that concentration and mass percentage of ethanol, furfural, formic acid, acetic acid, and the pH variation trend are almost consistent in the model liquid and the original liquid fractions. While, compared the distillate composition of the model with the original liquid, results show that the temperature range appear fraction slightly narrow. That is to say there are something unknown in the original liquid involved in the formation of azeotropic system.The proposal for recovery of waste liquor from Reed Three-stages Counter-current Ethanol-water pulping Process as follows.The waste liquor is diluted with 0.8 times and gather the lignin precipitation at first, then the 25%volume of original liquor directly back to the first step pulping. Residual liquid has two kinds of recovery methods. The first method is that the liquid is distilled by atmospheric distillation. The fraction with a temperature of 85～95℃, which contains a large amount of ethanol, used to make cooking liquor directly. The fraction with a temperature of 95～99℃ used to recycle furfural. And the fraction of 99～103℃ used to extract the organic acid by-product. Distillation residue solid is degradation of sugar that contain a small amount of lignin. The second method is that excess calcium hydroxide is added into the liquid then gather the lignin precipitation, distill the supernatant liquid, the fraction all used to make cooking liquor. The residue solid is degradation of sugar that contain a small amount of formic acid calcium and calcium acetate. |
PDF Full Text Request