Last week we discussed using wood pulp to produce paper products and its byproduct, black liquor. Just like coffee fuels us up on a Monday morning, black liquor fuels the paper-making process.
If you remember from last week, black liquor is created when cellulose fiber and lignin is separated from the wood chips. Wood pulp mills have used black liquor as an energy source since the 1930s.
Black liquor as an energy source
Did you know black liquor can also be used in a boiler? When the black liquor is only 18% solid, it is boiled down using steam heat until it is reduced by about 60%. Then, it is transferred into a recovery boiler to generate steam and recover the chemicals from the wood pulp for re-use.
As a renewable energy source, the steam can be transferred into many different uses, such as:
1. Papermaking Process
2. Turn Electric Generators
3. Electric Sold to Power Grid
Burning a waste product, like black liquor, to produce steam that generates electricity is called cogeneration. After the black liquor is burned off, a substance called green liquor remains. Plant employees then add lime to the substance to create white liquor. Watch the video to see how we've come full circle in this process.
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