Experimental study of the wet method for removing chlorine and potassium elements by using the straw black liquor raw material

To solve the problem that it is easy for the straw black liquor to agglomerate when burning in a circulating fluidized bed, the wet-method pretreatment procedure was used to reduce the chlorine and potassium content in the black liquor. The deionized water in a range of temperature from 25℃ to 100℃ and sodium hydroxide and citric acid solution at a temperature of 25℃ at a concentration of 0.25 mol/L were chosen respectively to conduct a marination test of rice and wheat straw. In this connection, a liquid chromatograph mass spectrometer (LC-MS) and an inductively coupled plasma optical emission spectrometer (ICP-OES) were employed to measure the chlorine and potassium ion concentration in the marination solution and a scanning electronic microscope was applied to observe the microscopic structure of the rice and wheat straw on the surface having been marinated under various conditions. The influence of the marination time, temperature and acids and alkalis on the lixiviation rate of chlorine and potassium element in the biomass observed.It has been found that to raise the marination temperature can destroy the cell wall of the biomass, thus promoting the lixiviation of chlorine and potassium in the rice and wheat straw. The sodium hydroxide solution at a concentration of 0.25 mol/L will have almost no influence on the lixiviation of chlorine and potassium in the rice and wheat straw. The citric acid solution at a concentration of 0.25 mol/L will restrain the lixiviation of chlorine in the wheat straw, however, will have almost no influence on the lixiviation of chlorine in the rice straw. In addition, the citric acid solution at a concentration of 0.25 mol/L will effectively enhance the lixiviation rate of potassium element in the rice and wheat straw. The water lixiviation method will have a very good result to remove chlorine and potassium element. After three hour lixiviation at 100℃, the lixiviation rate of chlorine and potassium element will exceed 95.18% and 85.12% respectively.