Use of Direct Steam Injection to Control Black Liquor Temperature and Ensure Optimal Drop Size

摘要

This paper presents a review of black liquor heating methods used to optimize recovery boiler feed rates. A review of traditional heating methods, as well as, novel technology will be presented. Each of these methods are compared, presenting benefits and limitations related to energy efficiency, space (footprint) of heating equipment, maintenance, and reliability. Direct steam injection ensures precise and accurate temperature control. A high velocity method of direct steam injection eliminates the common problems associated with sparging such as steam hammer and vibration. The high velocity steam also creates the mixing needed to distribute the heat uniformly in 70% solids black liquor without scaling or fouling. An additional benefit of direct steam injection is the ability to change temperature quickly. If solids change, then temperature can easily be adjusted to compensate for the change in viscosity. Precise and consistent temperature control allows for easy adjustment of liquor viscosity and efficient boiler firing. Black liquor is heated to achieve optimum drop size of the black liquor feed into the recovery boiler. Adding or improving the methods used for black liquor heating can provide recovery boiler operators with another tool for optimizing boiler efficiency.