SEPARATION OF ALKALI FROM SILICA-RICH BLACK LIQUOR

The black liquor produced from the pulping of rice straw with alkaline solution contains much silica which causes trouble during evaporation to obtain energy. The alkali material can be recovered by the use of a dialysis process. In this process, the factors affecting the efficie ncy of separation can be summarized as-volume of water used, time of t he dialysis process, the concentration, and volume of black liquor, te mperature, surface area, and types of membrane, vibration and stirring . The experiments showed that the period of time and the volume of wat er are related to each other, the best results were obtained with a sm all volume of water and a long time period. Half the concentration of the black liquor increased the efficiency of the dialysis. Also doubli ng the volume of black liquor to be dialyzed increased the dialysis ef ficiency. High efficiency can be obtained with less water and shorter time by using the appropriate membrane. The results confirmed that cel lophane membrane dialyzed more grams of alkali than other dialysis mem branes under the same conditions. Vibration of the liquor during the d ialysis process increased the effect of the surface area. Increasing t he temperature to about 50 degrees C increased the dialysis efficiency and decreased both the volume of water and the time required.