Barium sulfate, a compound with diverse industrial applications, undergoes various production processes globally. This article conducts an in-depth study of the current status of the barium sulfate precipitation process. Complex topics are broken down to provide a comprehensive understanding of the approach. Usually, we have the nitrate method, barium carbonate-sulfuric acid method, and barium sulfide-sulfuric acid method.
1. Nitrate Method: Tradition Meets Maturity
We explore the traditional nitrate method, a well-established technique with widespread use. This method involves heavy spar and sodium nitrate as raw materials. But it leads to the production of barium sulfide as a byproduct. The chemical reactions at play are crucial to understanding the efficiency of this process.
1.1 A Closer Look
In this method, barite and coal powder form a precise mixture. These mixtures undergo a journey from the end of the roaster. Here, it encounters a countercurrent of high-temperature air. It triggers a strong reduction reaction. The necessary heat comes from the combustion of pulverized coal or heavy oil. Finally, barium sulfide clinker is formed, commonly known as “black ash”.
1.2 Secondary Processes
Following this, a specific amount of barium sulfate solution is cycled back into the nitration tank. Steam heats the mixture to a designated temperature. Then activate the stirrer to introduce sodium nitrate. Sample purification involves using barium sulfide to eliminate calcium and magnesium impurities. The nitric solution then undergoes warm settling for subsequent stages.
1.3 Reaction Sequences
The clarified solution is transferred proportionally to a mixing tank. Complex decomposition reactions take place here. The reaction continues until the equivalence point is reached, or a slight excess of barium halide. The resulting barium sulfate and sodium sulfide solutions undergo multiple solid-liquid separation cycles in a horizontal spiral centrifuge. The separated sodium sulfide solution enters the recovery system for evaporation and concentration.
1.4 Filtration and Refinement
Filtered barium cakes undergo washing and acid treatment before being discharged into a barium slurry pool. Adjustments to pH occur with dilute sulfuric or phosphoric acid. It follows thorough acidification and optimal pH adjustment. Excess water is removed using a plate-and-frame filter press. The barium cake, after conveyance to a flash steam dryer or a rotary kiln for drying, goes through a Raymond mill for grinding. The final step involves packaging.
1.5 Utilization of Byproducts
This process produces sodium sulfide as a by-product. It is widely used in the pharmaceutical, paper, tanning, and sulfur-dye industries. Industries such as polyphenylene sulfide and other special engineering plastics are growing rapidly. This helps the sodium sulfide industry expand. In the traditional dye industry, China has become the world’s largest producer and consumer of it. Its importance is further highlighted.
1.6 International Practices
Internationally, Germany’s Sachibin Company, Japan’s Sakai Chemical Company, and Switzerland’s Solvay Company mainly use the nitric acid method to produce barium sulfate. Although the process flow is similar. But, international counterparts all use high-purity barite and high-quality coal and oil as raw materials. This approach minimizes overall waste. Repurpose leftovers into building materials. It complies with more environmentally sustainable practices.
1.7 Closed-Loop Production
German practice expanded the use of sodium sulfide by using it in the production of zinc sulfide. This closed-loop industrial strategy enabled automation at the end of the 20th century. It reflects a holistic and environmentally friendly production approach.
Although the nitrate process is deeply rooted in China’s production field. It demonstrates its proven technology. But. Its huge environmental footprint highlights the need to explore alternative approaches. It also faces challenges related to particle size distribution and the limitations of high-end applications. These highlight the need to continue to explore innovative approaches. This exploration can lead to greater efficiency, environmental sustainability, and improved product quality on a global scale.
2 Barium Carbonate-Sulfuric Acid Method
The barium carbonate-sulfuric acid method introduces a unique method of producing barium sulfate. Some manufacturers are limited by space or environmental considerations. They will prefer this method. This method utilizes naturally occurring high-quality barite or industrially purchased barium carbonate. The chemical reaction proceeds as follows:
BaCO3 + H2SO4 → BaSO4 + H2O + CO2 (Equation 4)
In this process, industrial barium carbonate is initially slurried with water. Keep the solids mass fraction around 20%. Slowly add the specified amount of sulfuric acid solution while stirring continuously. Be careful to prevent spillage during feeding. After the addition is complete, continue stirring for 30 minutes. It is important to make sure the reaction is adequate. Then filter, wash, dry, and package. This reaction produces a large amount of carbon dioxide bubbles. It results in fine particle size distribution and high surface area.
The production cost of this method is higher. However, the products are positioned in the mid-to-high-end market. It has the features of high whiteness, low impurities, and extremely low free barium content. It has no hydrogen sulfide odor and excellent dispersibility. Its particle size distribution is narrow and its specific surface area is high. These characteristics contribute to the formation of a glossy coating.
3 Barium Sulfide-Sulfuric Acid Method
The barium sulfide-sulfuric acid process replaces sodium sulfate with sulfuric acid. Similar to the nitrate method, it produces hydrogen sulfide as a by-product. The chemical reaction proceeds as follows:
BaS + H2SO4 → BaSO4 + H2S (Equation 3)
The process begins by mixing a specified proportion of barite and coal powder. It is introduced into the tail of the roasting furnace for high-temperature countercurrent contact. It relies on the combustion of pulverized coal or heavy oil to obtain the required heat. This results in the production of barium sulfide clinker, also known as “black ash”. The next steps include leaching, settling, clarification, and reaching a specific concentration. Sulfuric acid and barium sulfide are added simultaneously to the pump reactor. Finally, nanoprecipitated barium sulfate is produced.
The resulting barium sulfate is desulfurized. Then apply the modified coating. It removes excess water by centrifugation or filtration. The barium sulfate slurry is then transported to a spray dryer for drying. It is then ground and packaged. The produced nanoprecipitated barium sulfate has a variety of applications. Especially it is used in high-end automotive coatings and water-based inks.
Currently, there are very few Chinese companies adopting this approach. Japan’s Sakai Chemical is a notable exception. This flexible process can be easily reverted to the nitrate process. It demonstrates its versatility. This product has the characteristics of high whiteness and strong dispersion. It has no impurities. It also has excellent qualities such as stable performance between batches. So it is suitable for high-end automotive coatings and water-based inks. But, the release of hydrogen sulfide requires strict safety management.
4 Other Processes
Beyond the aforementioned methods, industrial barium sulfate production encompasses alternative techniques. One method involves a combination of barium chloride and sodium sulfate. Mainly used for medicinal barium (barium powder). Additionally, a method for recovering barium sulfate from sludge has gained attention.
In the chlor-alkali industry, some manufacturers use barium chloride for preliminary treatment of brine. This results in the production of large amounts of sludge. They are dominated by barium sulfate and calcium carbonate. A few smaller companies in China also recover barium sulfate from sewage sludge. But, the product is of lower quality and has increased impurities. Moreover, the particle size is uncontrollable and batches are unstable. The whiteness is low (usually less than 94%) and tends towards yellow.
In recent years, the country’s environmental protection efforts have continued to increase. Chlor-alkali companies began to focus on recovering barium sulfate from sludge. They work hard to improve the quality of recycled products.
In the end, it is important to explore these diverse methods of producing barium sulfate. It highlights the industry’s adaptability and pursuit of improved environmental sustainability. Each method has its unique advantages and challenges. It also targets a specific market niche. As technology advances and environmental considerations take center stage. The pursuit of innovative production methods continues. Barium sulfate will provide higher quality and sustainability in a variety of applications in the future
