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INDUSTRIAL PROGRAM Control of Soluble Scale in High- solids Black Liquor Concentrators Study Will Increase Knowledge of the of Sodium Salts in High Solids Black Liquor Benefits for Our Industry and Our Two salts, sodium carbonate ( Na CO) and The pulp and paper industry and its suppliers 2 3 Nation sodium sulfate ( Na2 SO 4) , present a maj or will use the information derived from this fouling problem in falling film concentrators, research to make improvements in the design • Develops fundamental information on the most common for producing and operation of present and future high characteristics of Na2CO3 and Na2SO4 in black liquor with a high solids content. These solids concentrators. These changes will help black liquor solids

salts readily form soluble scales and may minimize fouling from Na2CO3 and Na2SO4 require a shut down of for a boil-out and improve the performance of black liquor • Minimizes fouling of concentrators every four to six days. Before this fouling . This will ultimately improve the • Improves design and operation of existing can be controlled, operators need a better efficiency of the chemical recovery process and future high solids concentrators understanding of the complex in in pulp mills. • Offers a model for evaluating design and which these salts occur and the variables that operational changes affect the process in black liquor concentrators. • Provides a monograph to guide improvements in black liquor evaporators

Applications in Our Nation’s Industry

The entire pulp and paper industry will benefit from information on controlling soluble scale fouling in black liquor concentrators.

Boosting the productivity and competitiveness of U.S. industry through improvements and environmental performance INDUSTRIAL TECHNOLOGIES PROGRAM

Project Description Results Project Partners

Goal: To acquire fundamental data on the • Identified a new double with Institute of Paper Science and Technology chemical and physical behavior of Na2CO3 and an approximate composition of Atlanta, GA Na2SO4 in Kraft black liquor concentrators, and 2Na2CO3·Na2SO4. on the causes and control of soluble scale in high • Discovered that high levels of Georgia Institute of Technology solids falling film concentrators. of sodium sulfate and Atlanta, GA The project consisted of both experimental sodium carbonate, up to 10% of their and modeling efforts to clarify the process of solubility, can be achieved during Oak Ridge National Laboratory Oak Ridge, TN soluble scale fouling. The solubility of sodium evaporation. salts in high solids black liquor were measured • Found that calcium ions control the onset at various temperatures. Researchers collected of nucleation of both burkeite and the For additional information, please solubility data for Kraft black liquor by dicarbonate species. equilibrating Kraft black liquor and mixtures of contact • Carried out solubility studies for Na SO black liquor with Na2CO3, Na2SO4, and NaOH, 2 4 Drew Ronneberg, Ph.D. at a dry-solid content of 50 percent to 80 percent. and Na2CO3 with aqueous solutions of Industrial Technologies Program They also measured the rate of crystallization, inorganic salts and with kraft black liquor. Phone: (202) 586-0205 particle size distribution, and factors that Fax: (202) 586-9234 • Developed a new experimental technique E-mail: [email protected] control deposition rate. Crystallization studies for sampling equilibrated black liquor were conducted using aqueous solutions of through a 2 μm filter Dr. William James Frederick sodium carbonate and sodium sulfate in a batch Institute of Paper Science and -crystallizer, progressing to solutions • Compared solubility data from aqueous and Technology of selected organic constituents, and finally, to black liquor tests to predicted Atlanta, GA 30318 black liquor. obtained from computer simulations Tel: 404-894-5303 Fax: 404-894-5752 • Conducted evaporation studies and found E-mail: [email protected] that two types of fouling can occur at the conditions where black liquor is concentrated to high solids.

• Evaporator modeling results confirmed long-held experimental and theoretical A Strong Energy Portfolio for a positions and experience-based operational guidelines Strong America Energy efficiency and clean, renewable energy

• Results show that black liquor solids will mean a stronger economy, a cleaner

content at which Na2CO3 and Na2SO4 begin environment, and greater energy independence to foul concentrators depends upon both for America. Working with a wide array of state, the amounts of Na CO and Na SO in the community, industry, and university partners, the 2 3 2 4 U.S. Department of Energy’s Office of Energy liquor and their ratio. Efficiency and Renewable Energy invests in a diverse portfolio of energy technologies.

October 2006 Project completed in December 2002 Full award # DE-FC36-99-GO10387, A003

For more information, visit www.eere.energy.gov/industry or call 1-877-337-3463