Slaking and Causticizing

SKU: C-661Duration: 15 Minutes





Recaust Series (Details)
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Course Details


Training Time: 15 minutes

Compatibility: Desktop, Tablet, Phone

Based on: Industry Standards and Best Practices

Languages: English, Portuguese, Russian

The slakers and causticizers are where the liquid-based chemical reactions of the recaust area occur. The purpose of slaking and causticizing is to convert clarified green liquor to white liquor for use in the digesters. This module will discuss the role of slaking and causticizing in the recaust system as well as identify and describe the major equipment and process flows.

Learning Objectives

  • Describe the role of slaking and causticizing in the recaust system
  • Describe the slaking and causticizing chemical reactions
  • Identify and describe the major equipment and process flows
  • Describe operating considerations for slaking and causticizing
  • Identify key safety considerations when working around a slaker and causticizers

Key Questions

The following key questions are answered in this module:

What is slaking?
Slaking is the reaction that occurs when solid lime, or calcium oxide is added to water, creating calcium hydroxide.

What is causticizing?
Causticizing is a reaction in which sodium carbonate in green liquor reacts with calcium hydroxide from the slaker to form sodium hydroxide and calcium carbonate.

How is the slaker temperature controlled?
Slaker temperature is controlled by changing the temperature of green liquor flowing into the slaker.

At what temperature does a slaker operate?
Slaking is a reaction which gives off heat, so the slaker operates near the boiling point of water.

What is causticizing efficiency?
Causticizing efficiency is how much sodium carbonate is converted to sodium hydroxide, or how effective the recausticizing process is.

Sample Video Transcript


The slaker is a combination vessel that consists of a large tank called, the slaker bowl and an incline classifer. Its purpose is to mix lime and green liquor and settle out the grits produced this reaction. The slaker bowl has an inlet for both lime and green liquor, an agitator, and a side discharge to the classifier. The classifier has an inlet from the slaker bowl and a conveyor to discharge the grits. It also has an outlet that sends the slurry to the causticizers.
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