ANALYSIS ON COMPOSITION OF FOULANTS FROM ALKALINE WHEAT STRAW BLACK LIQUOR AND DISCUSSION ON ITS FOR MING MECHANISM

1.INTRODUCTIONWheat straw is the main raw material in northern China, and its black liquor is blamed for contributing serious pollution to the environment. A technical breakthrough has been achieved in the field of chemical recovery for wheat straw pulping after more than twenty years' developments and practices. Wheat straw pulp chemical recovery projects with the pulping capacity of 75-100t/d have been put into 132--production gradually in recent years. Evaporation of wheat straw pulp…

ANALYSIS ON COMPOSITION OF FOULANTS FROM ALKALINE WHEAT STRAW BLACK LIQUOR AND DISCUSSION ON ITS FORMING MECHANISM

Analysis on foulants shows that: the elements(except for C, H and O) in foulants formed during evaporating alkaline wheat straw black liquor are Si,Ca, K, Na, Mg and Al; Si and Ca account for about 36% of the weight of foulants; The organic ingredients amout to about 20% of the foulant;Rhodesite (Ca,K,Na)8Si16O40 @llH2O is the main composition in foulants.The fouling mechanism of wheat black liquor is quite different from that of soft/hard wood black liquor,because the content of Si inside wheat straw black liquor is much more than that of soft/hard wood black liquor. Complex chemical reactions occur when evaporating wheat straw black liquor. The author considers that colloid H2SiO3 plays an important role in the process. The minerals produced by reactions between H2SiO3, with anion charges and positive ions, such as Ca2+, K+, Na+, etc. Further investigation on the process should be done.The fractal theory is used to analyze the fouling geometric texture. The fractal dimension values D of foulants are also calculated.