By Yougen Kong
Dry injection of sodium bicarbonate or trona offers a cost-effective application for acid gas mitigation, with both able to remove over 99% of the acid gases - although a plant’s operating conditions will ultimately affect the performance of the dry sorbents in acid gas removal. The most important variables for high removal efficiency are: sorbent particle size, mixing or dispersion of the sorbent into the gas stream, retention time, injection temperature, and concentration.
Often the question is whether or not to mill product. While it is optional to mill trona, milling trona can reduce the particle sizes and thus improve the dispersion of trona particles inside the flue gas. Better mixing between the particles and flue gas, in combination with higher surface areas of finer trona particles, can result in better mitigation performance of HCl and SO2. Sodium bicarbonate out of production is too coarse to be injected directly into the flue gas and should be milled in order to provide good mitigation performance of HCl and SO2.
This document describes the technologies of milling trona and sodium bicarbonate, the pros and cons of each technology, capital and maintenance costs of mill systems, and good system design principles.