CLEANER PROCESS OF NH_4OH-KOH PULPING OF WHEAT STRAW
A cleaner process of wheat straw pulping with aqueous ammonia containing a small amount of caustic potash was studied.The caustic potash as a strong base not only could reduce the needed quantity of NH 3 used and cooking time, but also enriched black liquor with potassium element.The black liquor after recovering excess NH 3 contained nitrogen, potassium and organic substance and could be used as a fertilizer.The black liquor could be applied as liquid fertilizer directly,or the black liquor could be treated by coagulation in alkaline condition and the precipitate could be chemically modified to solid fertilizer.The clear liquid after precipitation could be recycled to cooking by adding NH 4OH and KOH.The environmental pollution of black liquor would be solved and a new pattern of virtuous cycle was set up between paper industry and farming.