Lime Mud Filtering

SKU: C-657Duration: 14 Minutes

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Course Details


Training Time: 14 minutes

Compatibility: Desktop, Tablet, Phone

Based on: Industry Standards and Best Practices

Languages: English, Portuguese, French, Polish

During the conversion of green liquor to white liquor in the slaker and causticizers, lime mud is formed. The mud is separated from the white liquor and sent to mud storage. Before the lime mud can be fed into the kiln, it must be washed to remove residual chemicals, and dewatered to remove as much water as possible. This module describes the most common method of lime mud filtering and the components and operation of the lime mud filter.

Learning Objectives

  • Describe the most common method of lime mud filtering
  • Identify and describe the major components of a lime mud filter
  • Describe the purpose and operation of a lime mud filter
  • Describe strategies for achieving high mud solids
  • Identify and describe the safety hazards associated with a lime mud filter

Key Questions

The following key questions are answered in this module:

What is the purpose of the lime mud filter?
The purpose of the lime mud filter is wash residual cooking chemicals from the lime mud and to dewater it as much as possible.

What is recausticizing?
Recausticizing is the process of converting the chemicals in the spent cooking liquor back to their original form so that they can be re-used in the kraft pulping process.

What is the purpose of the precoat layer on a lime mud filter?
The precoat layer provides a layer of filtration media which allow the fresh mud to be washed and dewatered while minimizing plugging of the filter screen by the finest particles in the mud.

What are two methods for renewing the precoat layer on a lime mud filter?
The precoat layer can be continuously renewed through the use of continuous precoat renewal, where a moving strip of precoat is continously removed and rebuilt, or by a traveling doctor blade which removes a thin layer across the entire drum.

How is calcium buildup on a lime mud filter dealt with?
In order to combat calcium buildup on the wire of a lime mud filter, the cake is dropped off the drum, the vat is drained, and an acid wash is applied to the wire.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

The last method to remove small particles is to use a continuous precoat renewal or CPR process. A CPR is a high-pressure nozzle that travels across the face of the drum on the side where mud is lifted out of the vat. The CPR operates in medium and high-pressure modes. In the medium mode, the CPR removes about one-quarter inch of the precoat mud. In the high-pressure mode, the shower removes all of the line mud all the way down to the wire and cleans the wire's surface. It takes about an hour to travel across the drum. Multiple medium pressure cycles can be performed before performing a high-pressure cycle. Cleaning the wire this way reduces the need to drop the sheet off the wire for cleaning, offering consistent delivery of lime mud to the kiln.
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