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New patented technology for treating white clay – Author: Beijing Watermad Environmental Protection Technology Co., Ltd. Through long-term research and practical application, our company has developed a new technology involving the use of refined calcium carbonate as a filler made from white clay (a **patent has been applied for and obtained**). This patented technology requires low investment, is easy to modify, has simple operation and control, and boasts internationally leading technical standards. Through this technological process, white clay can be processed into refined calcium carbonate of filler grade or even coating grade, which can be directly used in the papermaking filling process. This technology effectively resolves the conflict between the requirements of the causticization process and those regarding the quality of calcium carbonate filler (namely, the particle size of the slaked lime produced in the causticization process cannot be too small, otherwise solid-liquid separation becomes difficult, which severely affects the quality of the alkali solution; whereas the quality standards for light calcium carbonate require that the particle size be very small). It is fully capable of meeting the needs of large-scale industrial production. The application of this new patented technology has opened up a new path for the comprehensive utilization of white clay, turning waste into a valuable resource. It not only completely eliminates the environmental pollution caused by white clay but also replaces imported refined calcium carbonate used as a filler, allowing it to be used directly in paper manufacturing. This approach can generate direct economic benefits of 3–4.5 million per year for users, offering significant economic and social advantages. Watermad Group Investment Company can carry out BOT-style investment and process upgrades for paper mills using the patented technology for refining calcium carbonate from white clay, thereby helping these mills to completely eliminate the problem of white clay pollution. Current status of white clay treatment: With the advancement of industrialization, environmental pollution has become increasingly severe. In recent years, regulations and laws related to environmental management have been introduced, and there is an increasing emphasis on environmental protection. As a major source of pollution in this regard, the paper industry is forced to invest heavily in addressing pollution issues. At present, through alkali recovery processes and wastewater treatment systems, paper mill wastewater is generally discharged up to the required standards. However, the problem of waste residue pollution, especially the secondary pollution caused by the white sludge generated during the alkali recovery process, has become a real challenge for paper mills in terms of pollution control. The challenge of treating white sludge: The treatment of white sludge generated from alkali solution recovery is difficult, creating new environmental pollution problems. Traditional white clay treatment methods: 1. Regenerating lime – suitable only for the alkali recovery process in wood pulping ； Consequences: High processing costs, and after multiple cycles it directly affects the causticization process as well as the quality of the recovered alkali ； 2. Direct landfilling – suitable for the white sludge generated from alkali recovery in non-wood pulping ； Consequence: It leads to new secondary pollution. With increasingly strict environmental regulations, this method will eventually be banned ； 3. Other methods—due to high processing costs, they are not suitable for industrial production; or they cannot be practically applied as they affect the normal operation of causticization and alkali recovery. The basic process of the new patented technology for white clay treatment involves adding a reactive flocculating and precipitating agent to the leachate that has been subjected to caustic treatment, thereby removing the colloidal impurities present in the leachate and purifying it ； The white clay is subjected to ash removal treatment to eliminate the excess ash remaining in it from the causticization process ； Wash the white clay to remove residual alkali from it and improve its quality ； Weak acid treatment of the white clay converts the excess lime from the causticization process into calcium salts, while also adjusting the pH value of the white clay emulsion ； Through processes such as homogenization and screening, the whiteness and purity of the white clay are improved, its homogeneity is enhanced, and the quality issues associated with this clay are resolved. Operating costs of the new patented technology for treating white sludge; Benefit analysis of the new patented technology for treating white sludge. The extent of additional economic benefits resulting from the adoption of this technology varies depending on the manufacturer’s current scale of alkali recovery – the larger the scale, the greater the benefits. The additional benefits refer to the benefits added after the technical upgrade, based on the alkali recovery benefits prior to the upgrade. The additional benefits stem mainly from the gains resulting from improved alkali recovery efficiency, the cost savings associated with using refined calcium carbonate instead of purchased commercial calcium carbonate as a filler in papermaking, and the reductions in expenses related to dealing with white clay pollution (such as purchasing land, digging pits, and carrying out landfilling). The additional benefits of adopting this technology for pulp mills of different scales are shown in the table (for other scales, the increases and decreases are roughly proportional). The patented technology for refining calcium carbonate from white clay not only resolves the pollution problems caused by this clay, but also involves process modifications to the green liquor and white clay during implementation. This approach **significantly reduces the loss of sodium salts resulting from the discharge of green liquor, as well as the loss of alkali caused by white clay, thereby improving the recovery rate of chemical alkalis and bringing indirect economic benefits, as well as notable environmental and social benefits. The uniformity of white clay is achieved through a unique control system and specialized programming modes, which enable precise and meticulous control over the clay’s properties. This results in a significant improvement in the particle size, uniformity, and strength of the white clay particles. After homogenization, the quality of the calcium carbonate filler obtained from refined white clay is close to, or even exceeds, the quality standards of commercial light calcium carbonate. The results of the particle size distribution analysis of calcium carbonate show that, through a homogenization process, white clay can ultimately be transformed into a series of high-value calcium carbonate products with different particle sizes. Features of new technologies for the refinement of white clay · Solves the problems of low whiteness and poor purity of white clay ； ·Solved the problem of loose particle structure in white mud calcium carbonate, which leads to powder loss when added as a filler ； ·It can improve the uniformity of calcium carbonate particles in white clay ； ·It enables the deep processing of white clay to produce activated calcium carbonate products ； ·Reduce sodium salts and loss of alkali ； ·Low investment required, low operating costs; the investment can be recouped within one to two years ； ·It effectively improved the quality of white clay, bringing it up to the quality standards of light calcium ； ·It effectively solves the problem of difficult treatment of white clay, turning waste into treasure, and brings significant economic and social benefits ； ·The process control features a high degree of automation, is easy to operate, requires minimal maintenance, and has a long service life. The impact of new white clay purification technologies on the causticization process · This technology is highly compatible with traditional alkali recovery processes, and it does not cause any operational difficulties in causticization production ； ·The key technical upgrades implemented in the original causticization section not only increase the degree of causticization of sodium carbonate but also prevent calcium carbonate precipitation particles from becoming too fine, which could cause difficulties in precipitation and filtration and thus affect the normal operation of the causticization process ； ·It ensures that the precipitate separated from this causticization reaction system contains neither impurities introduced by the green liquor or lime, nor excess lime that did not participate in the reaction. Meanwhile, the technical modifications have no impact on traditional alkali recovery causticization processes, effectively resolving the conflict between white mud recovery and causticization production. The application of this technology allows for better optimization of traditional causticization processes ； ·The quality of the recovered alkali has been improved, along with a reduction in alkali loss; moreover, the yield of recovered alkali is higher than that of traditional processes. Application of a new patented technology for processing refined calcium carbonate obtained from white clay recycling – it can be directly used to create calcium carbonate emulsions for addition to paper sheets in neutral papermaking processes. A range of commercial lightweight calcium carbonate products can also be produced. Quality tests and practical application results of the calcium carbonate obtained from alkali recovery in black liquors from different pulping methods show that 1) when this technology is applied to alkali recovery from black liquors in wood pulp and bagasse pulp, the resulting calcium carbonate fully meets the specified standards ； 2. The calcium carbonate produced by the alkaline recovery of wheat straw pulp and reed pulp black liquor has a high content of hydrochloric acid-insoluble substances, as well as a low CaCO3 content. The high content of hydrochloric acid insolubles is due to the silicon content in the black liquor. Experiments and practical applications have shown that a high silicon content makes calcium carbonate particles less prone to agglomeration, resulting in better dispersibility; consequently, calcium carbonate produced from white clay performs even better when used as a filler in paper. Application scope of new white mud refining technologies: It is suitable for the treatment of white mud generated from alkali pulping processes in all types of raw materials, and is particularly effective for dealing with the white mud produced as a result of alkali recovery in non-wood pulping processes. An application example from a factory: The technological modification involves the following steps: 1. Adding a green liquor purification process to the existing causticization section, in order to remove carbon and other impurities from the green liquor ； 2. Add an ash removal process to eliminate components such as active CaO ； 3. Wash and screen the white clay to remove some of the residual alkali ； 4. Add additives to adjust the pH value and concentration ； 5. Uniformity treatment ； 6. Screen to remove the separated SiO2 and carbon particles. The plant’s production capacity is 4–5 T/D (24 hours per day); the filler is prepared at a ratio of 1:1 with talc, and it is used in the two 1760 paper machines in the plant’s papermaking department. The refined calcium carbonate filler, as well as the entire production process, are monitored and tested. While the physical properties of the paper products are measured using standard methods, the more than 270 tons of paper produced in this pilot trial were sent to printing companies for testing, and comparisons were made with paper made using imported commercial calcium carbonate filler. The results are as follows: The total investment for the project is approximately 1.2 million yuan for the green liquor purification process ； The cost of caustic treatment and modification is approximately 800,000 yuan ； Approximately 4.5 million yuan was invested in the refining of white clay. Analysis of test results: 1) White clay before treatment: Solid content: 16.8–17.0%; Brightness: 83.5% (the green liquor was not purified); Free alkali: 0.084%; Residue on a 125-mesh sieve: 0.47%; Settling volume: 3.0 ml/g after 3 hours, and 2.95 ml/g after complete settling. 2) White clay after treatment: Solid content: 16.8–17.0%; Brightness: 86%; Free alkali: 0.084%; Residue on a 325-mesh sieve: 0.014%; Settling volume: 6.0 ml/g after 3 hours, and 4.25 ml/g after complete settling. 3) Commercial lightweight CaCO3: Brightness: 90%; Free alkali: 0.15%; Residue on a 125-mesh sieve: 0.015%; Settling volume: 2.8 ml/g after 3 hours, and 2.2 ml/g after complete settling. Particle size analysis results: 1) For the untreated white clay, the particle size distribution is as follows: 0–10 μm accounts for 25%, 10–25 μm accounts for 35%, 25–45 μm accounts for 31%, and 45–65 μm accounts for 9%; the average particle size is 23.68 μm. 2) For the white clay after purification, the particle size distribution is: 0–4 μm accounts for 92%, and 4–11 μm accounts for 8%; the average particle size is 1.56 μm. 3) For commercial calcium carbonate, the particle size distribution is: 0–4 μm accounts for 89%, and 4–13 μm accounts for 11%; the average particle size is 1.88 μm