Black Liquor Testing
Several properties of black liquor – including residual alkali, temperature, and solids content – are regularly monitored in order to monitor pulping, washing, and evaporation processes at kraft pulp mills. Residual alkali is monitored during cooking to ensure that sufficient residual alkali is present and prevent lignin redeposition. Weak black liquor, strong black liquor, and heavy black liquor solids are observed to monitor washer, evaporator, and concentrator performance, and ensure consistent solids contents to the evaporators and recovery boiler. Other analyses, including heating value, elemental, inorganic, and organic analyses, are used for research, design, and troubleshooting purposes.
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Course Details
Learning Objectives
Describe the basic stages and flow path of black liquor in the kraft pulping liquor cycle List the typical components of black liquor Describe what happens to the inorganic compounds, organic compounds, and water in heavy black liquor in a recovery boiler Define “viscosity,” “density,” “specific heat,” “thermal conductivity” and “boiling point rise” List the properties of black liquor that are regularly monitored at kraft pulp mills Describe the importance of black liquor solids testing and monitoring Recognize how more advanced analyses – including heating value, elemental, inorganic, and organic analyses – are used for research, design, and troubleshooting purposes
Specs
Frequently Asked Questions
What is in black liquor at a kraft pulp mill?
Why are concentrators often positioned downstream of multiple effect evaporators?
Why is the residual alkali content of the black liquor monitored after cooking?
Why would someone bother to measure the solids content of the weak black liquor coming off the brown stock washers?
Why is it mandatory to monitor the black liquor solids of the liquor being burned at the recovery boiler?
Sample Video Transcript
It is important to always sample from the same locations and to follow a standardized sampling, and testing procedure. Weak black liquor should be sampled on the line from the washers that goes to the evaporators. Strong black liquor should be sampled on the line exiting the last evaporator effect. Heavy black liquor should be sampled on the line exiting the concentrator. And at the recovery boiler, the heavy black liquor should be sampled either on the liquor line to the recovery boiler or on the liquor header itself.
