Method and equipment for treatment of black liquor at pulp mill

摘要

The invention relates to a method and equipment for treatment of black liquor at a pulp mill in order to recover chemicals and energy contained therein. In the invention, the black liquor is pyrolyzed in a pyrolysis reactor (4), the formed gaseous components are forwarded for utilization and the solids are mixed with water, whereby the formed solids are returned to a lime burning kiln (1) and the sodium-hydroxide-containing liquid is returned to the pulp cooking process.

主权项

1. A method for treating black liquor at a pulp mill in order to recover chemicals and energy contained therein by,
introducing black liquor into a pyrolysis reactor introducing calcium oxide from a lime burning kiln into the reactor to produce gaseous components and a solid mixture of carbon, sodium carbonate and calcium oxide separating from one another gaseous components and solid matter produced in the reactor conveying the separated gaseous components for further utilization and wherein gaseous components are condensed in a condenser, the product being oil, and at least part of the gases uncondensed in the condenser are conveyed for recycling in the lime burning kiln and adding water to the separated solid matter, whereby is formed an aqueous solution of sodium hydroxide and a solid mixture of carbon and calcium carbonate, said sodium hydroxide solution being reintroduced into the pulping process and the residual solid matter is returned to the lime burning kiln, which comprises heating the reactor and the black liquor with heat introduced into the pyrolysis reactor with the calcium oxide from the lime kiln, wherein the calcium oxide at a temperature of 200 to 1000° C. is introduced into the pyrolysis reactor and heating the pyrolysis reactor by providing heat from an outside generated source around the pyrolysis reactor with flue gases from the lime burning kiln, and conveying calcium carbonate and carbon from the reactor back to the lime-burning kiln.