This picture shows fumes from the combustion of black liquor passing through the test section of the Multifuel Combustor. The deposit is growing on a temperature-regulated probe that simulates a superheated probe in a commercial plant. The red line above the deposit measures particles' size and velocity as they approach the tube.
Black liquor is a recycled byproduct formed during the pulping of wood in the papermaking industry. In this process, lignin is separated from cellulose, with the latter forming the paper fibers. Black liquor is the combination of the lignin residue with water and the chemicals used for the extraction. Black liquor represents the fifth largest source of energy in the country and is burned in a recovery boiler. The boiler produces steam and electricity and recovers the inorganic chemicals for recycling throughout the process.
The primary chemicals are sodium salts, which tend to form deposits on the boiler surface that can become quite troublesome. The combustion of black liquor results in the formation of aerosols that create a fouling problem in the pulp mill recovery boilers. Ash deposition also occurs. This can lead to a reduction in heat transfer effectiveness, corrosion of the boiler, and a plugging of the gas passages. The MFC is studying the mechanisms and rates of ash deposition in order to minimize their impact in boiler operations.
Department of Energy: Office of Energy Efficiency and Renewable Energy
Office of Industrial Technologies