Study On The Key Technologies Of Energy Saving And Emission Reduction In Alginate Production

This study is to investigate the key technologies of energy saving and emission reduction in alginate production and decarboxylation method for alginate quantification. The process is improved mainly through altering the steps of dilute floatage and flocculation. The influence of the technologies on yield, quality, water consumption, filtration time and costs of alginate production is also conducted, in order to decrease the water consumption and provide reliable references for alginate production and applications.1. The reaction condition of decarboxylation method is studied, and four determinations for alginate quantification are compared. The reaction condition of decarboxylation method is 6mol/L hydrochloric acid solution.The linear correlation of four determinations is discussed. The results show that the linear dependence of decarboxylation method, colorimetry of carbazole and calcium acetate method is perfect. Besides, the study on the stability of four determinations indicates that the stability of decarboxylation method is good, and calcium acetate method gets the best stability.2. The technology of energy saving and emission reduction in dilute floatage process is discussed. Single factor experiment shows that the optimum floating time is 6h, the optimum chitosan addition is 7.5ppm, the optimum dilution multiple is 110 and the optimum pH is original pH. The optimum conditions obtained by the orthogonal test are as follows:floating time is 5h, chitosan addition is 9ppm and the dilution multiple is 100. Under these conditions, the water consumption reduces 25.19% and the time decreases above 50% while the yield of alginate increases 2.58%, which suggests the new technology could save energy and reduce emission.The optimum chitosan addition is 15ppm with the dilution multiple is 80 or 90 through single factor experiment. And the alginate yield and filtration time are compared with the traditional process. If the reduction of water consumption is the first assessment standard and the filtration time is not increased,90 dilution multiple with 15ppm chitosan addition will be the best process conditions. Under these conditions, the water consumption reduces 30.68% while the alginate yield increases 1.39%.3. The technology of energy saving and emission reduction in flocculation process is studied. There are two methods, calcification precipitation and acidulation precipitation, to extract alginate in production. The water content, viscosity, ash content and transparency are measured of alginate collected from the above two methods. The water-insoluble content, gel strength, level of calcium and purity are also detected.The results indicate that there are no significant differences in water content, ash content, transparency, level of calcium and purity between the alginate samples extracted by the two methods. However, the water-insoluble content of the alginate extracted by acidulation precipitation is lower with significant difference, while the viscosity and the gel strength are higher with extremely significant differences. All the above show that the quality of alginate extracted by acidulation precipitation is better than that extracted by calcification precipitation. In addition, the acidulation precipitation consumes much shorter time, fewer water and raw materials than calcification precipitation with no significant difference in alginate yield. So acidulation precipitation was of great significance for energy saving and emission reduction.