What is the kraft recovery process?
The kraft chemical recovery process is a mature, effective technology that provides for recycling of the pulping chemicals, efficient generation of steam and electrical power from the fuel value of the black liquor, and effective disposal of dissolved wood substances.
How long does kraft process take?
In a continuous digester, the materials are fed at a rate that allows the pulping reaction to be completed by the time the materials exit the reactor. Typically, delignification requires around two hours at 170 to 176 °C (338 to 349 °F).
How does a kraft pulp mill work?
The kraft pulping process (see Figure 10.2-1) involves the digesting of wood chips at elevated temperature and pressure in “white liquor”, which is a water solution of sodium sulfide and sodium hydroxide. The white liquor chemically dissolves the lignin that binds the cellulose fibers together.
How is black liquor recovered?
The spent mixture of white liquor and lignin is known as “black liquor”. The black liquor is concentrated in several stages through evaporation, by heating with steam, until it consists of approximately 66% solids. The concentrated black liquor is then burned in the recovery boiler.
Do all paper mills smell?
Not all pulp and paper mills have an odor. Some paper mills use pulp from other mills to make paper and will have a less noticeable odor.
What is black liquor in kraft pulp process?
Black liquor is the spent liquor from the Kraft process in which pulpwood is converted into paper pulp by removing lignin and hemicellulose constituents and other extractable materials from wood to free the cellulose fibers.
What is kraft material?
Kraft paper or kraft is paper or paperboard (cardboard) produced from chemical pulp produced in the kraft process.
Is kraft process chemical pulping?
Kraft pulping is the most common form of chemical pulping, at 80% of the total chemical pulping industry. Kraft pulping involves the digesting of wood chips at elevated temperature and pressure in “white liquor”.
What is the pH of black liquor?
The black liquor produced in this pulping process has pH 13.8, density 1.03 (g/ml), and dry matter 73.0 (g/l).
What chemicals are in black liquor?
Black liquor contains about 30% to 35% inorganic, and the main components are sodium hydroxide, sodium carbonate, sodium sulfide, sodium sulfate and other sodium salts combined with organic matter. There are 65%~70% organic substances, and the main components are lignin, resin, starch, and low molecular compounds.