Chapter 7:Mineral Scale Management

Abstract

Mineral scale problems are not new to pulp mills and bleach plants. The liquor recovery system ensures that white liquor is saturated in calcium carbonate, and this mineral will precipitate when heated to cooking temperatures in the digester [1,2]. The original single-vessel continuous digesters sold by Kamyr had an extra liquor heater as standard equipment to enable the mill to take one heater out of service for acid cleaning without impacting production [3]. Although lime scale in the digester is generally the most routine scaling problem in pulp mills, various other scales are common in the chemical recovery area [4,5], and several types of mineral scale can turn up in bleach plants or on the paper machines. Efforts to reduce wastewater discharge using countercurrent filtrate recycle schemes in the bleach plant [6,7] certainly increased problems with mineral scale, but except with direct countercurrent filtrate management [8], scale problems were usually not severe. Mechanical pulping operations can also have problems with scale, partially because these processes are less efficient at removing.

Citation

Rudie, Alan W.; Hart, Peter W. 2012. Mineral scale management. In: Hart, Peter W.; Rudie, Alan W., eds. The Bleaching of Pulp, 5th Edition. Peachtree Corners, GA: Tappi Press. 175-215, Chapter 7.