Recovery BLOX System Overview and Principles
Some recovery boilers use waste heat from the combustion gases to evaporate water from incoming black liquor. This increases the efficiency in the amount of steam produced by the boiler. In direct contact evaporators, hot combustion gases directly contact black liquor. This concentrates the black liquor using waste heat, but it also adds unwanted emissions of malodorous sulfur gases to the flue gas. The black liquor oxidation (BLOX) system is designed to pre-treat the black liquor to minimize these emissions. This module covers direct contact evaporators and the theory and operation of the BLOX system.
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Course Details
Learning Objectives
• Define the term TRS
• Define the term BLOX
• Explain where TRS comes from
• Identify and describe a cascade direct contact evaporator
• Identify and describe a cyclone direct contact evaporator
• Describe where direct contact evaporators fit into the kraft recovery process
• Explain the principle behind a black liquor oxidizer
• Describe where black liquor oxidizers fit into the kraft recovery process
Specs
Frequently Asked Questions
What does BLOX stand for?
Why are BLOX systems used?
What is the primary compound that BLOX systems are trying to eliminate?
What is a direct contact evaporator?
What is the principle of operation of a BLOX system?
Sample Video Transcript
Cascade evaporators are typically positioned between the boiler economizer, and the electrostatic precipitator. A cascade evaporator is a large vat that holds the black liquor, and is connected to the boiler by large duct work. A cascade evaporator is usually located near the economizer to minimize the duct work. A cascade evaporator contains one or more large drums made of horizontally aligned tubes attached on the ends to round metal plates that create a cylindrical drum. There are spaces between the tubes that allow gases to pass through. The drum sits in the vat of black liquor and slowly rotates, picking up the black liquor on the tube surfaces. The combustion gases flow through and around the tubes, heating and evaporating water from the black liquor.
