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苛化是指硫酸盐法制浆厂中将绿液转化为白液的过程,这一过程会产生副产物沉淀碳酸钙,这种苛化沉淀碳酸钙(CCC)可以用作造纸填料和涂布颜料。如果CCC提取出来作为造纸原料,可以减少或取消石灰窑的操作,进而减少重油的消耗和CO2气体的排放。传统的CCC作为造纸填料存在白度低、磨耗值高、成纸光学性能差等一系列问题。因此希望能够像商品沉淀碳酸钙(PCC)一样可以控制CCC的形态。实验中将消化与苛化分开进行,且精确控制反应条件,制备了具有良好光学性能、低磨耗值、不同形态的CCC。研究结果表明,在适宜的温度下,以低浓CO23?溶液作为消化剂可以制得文石型晶体,此外,消化剂中存在的NaOH会加速文石型晶体的沉淀,这些有利于合成文石型CaCO3的条件在苛化工段很容易实现。
Causticization refers to the conversion of green liquor to white liquor in a kraft pulping plant. This process produces by-product precipitated calcium carbonate, which can be used as papermaking filler and coating pigment. If CCC is extracted as a raw material for papermaking, operation of the lime kiln can be reduced or eliminated, thereby reducing heavy oil consumption and CO2 gas emissions. The traditional CCC has a series of problems such as low whiteness, high abrasion value, poor paper optical properties and so on. Therefore, it is hoped that the form of CCC can be controlled just like PCC. In the experiment, digestion and causticization were carried out separately, and the reaction conditions were precisely controlled to prepare CCCs with good optical properties, low abrasion values and different morphologies. The results show that at a suitable temperature, aragonite crystals can be obtained by using low concentration CO23? Solution as the digestive agent. In addition, the presence of NaOH in the digestion agent accelerates the precipitation of aragonite crystals, which is good for the synthesis of aragonite Type CaCO3 conditions in the caustic section is very easy to achieve.