State of the Art Evaporation System

摘要

Energy efficiency, high availability and low emissions are the main requirements for a modern recovery island. An evaporation system is a key part of a complete recovery island. This paper describes Andritz's concept for a state-of-the art evaporation system:1. Reliable process design for uninterrupted liquor flow to the recovery boiler 2. High dry solids concentration with falling film crystallization technology 3. Liquor Heat Treatment to decrease liquor viscosity 4. Secondary condensate fractionating and handling to recover clean process water for the mill 5. Maximized steam economy for minimized operating costs 6. Handling or treatment of mill by-product process streams (CNCG, DNCG and foul condensate) One way to improve energy efficiency is to increase the firing liquor dry solids concentration. Increasing the firing liquor dry solids content from 75% to 80% in the recovery boiler provides numerous benefits: 1. Steam flow is increased over 2% 2. Dry solids throughput is increased 3. SO_2 emissions are practically eliminated.