Pulping and Bleaching PSE 476/Chem E 471. Lecture #15 The Kraft Recovery Process. Agenda. Overview of process Black Liquor Evaporation Recovery Furnace Smelt Causticizing Lime Kiln. Pulp. Chips. Cooking & Washing. BLACK LIQUOR Alkali Lignin Hydrolysis Salts Sulfonation Products.
The Kraft Recovery Process
CaOBasics of the Kraft Recovery System
This diagram (taken from “Kraft Pulping: A Compilation of Notes” shows what will be covered in this lecture. The object of this system is to regenerate the cooking chemicals and to generate heat = steam & power.
Black LiquorBlack Liquor
Concentrated black liquor is burned in a recovery furnace. The functions of the recovery furnace are:
Remove remaining water from black liquor.
Burn the black liquor organic compounds
Solves disposal issues.
Produces steam (for heating and energy).
Reduce sulfur species to sulfide.
Generate Na2CO3 which will later be converted to NaOHRecovery Furnace
Air The functions of the recovery furnace are:
AirRecovery Furnace III
System for recovery
of heat to generate power
Gasses from Pyrolysis
Smelt (molten Na2CO3, Na2S, etc)