Fly Ash to Trigger Revolution in 4A Zeolite Production

By Wang Zhiping, Inner Mongolia Risheng Recycling Co., Ltd.,
Yan Xueliang, An Aiwen,  Inner Mongolia Datang International Recycling Development Co., Ltd.

In the global movement forbidding and restricting phosphorus in detergents, as 4A zeolite has outstanding functional and economic advantages in replacing sodium tripolyphosphate (STPP), the production of 4A zeolite used in detergents has bloomed throughout the world. As an ideal phosphorus-replacing assistant, 4A zeolite has already gained considerable scale in China today. Problems such as environmental protection and production costs have appeared. The production of 4A zeolite using fly ash has displayed a sound prospect.

Development of 4A zeolite

In the detergent sector, 4A zeolite is used mainly in the production of washing powders with no or low phosphorus. The addition amount is usually 20-25% and can also be 30% or even as high as 40%, such as in WL-B washing powder.
The widespread use of phosphorus-free washing powders and liquid detergents has promoted a rapid growth of 4A zeolite sales. In the early 1990s, 4A zeolite became a leading detergent assistant to replace STPP in the United States. In recent years the detergent industry in Europe has made constant efforts in upgrading product varieties and improving production processes, and 4A zeolite has also gained extensive applications there. In the next few years, with the growing awareness of environmental protection and the issuance of relevant policies in Southeast Asian countries and other developing countries, as well as the spread of the movement forbidding and restricting phosphorus, washing powders with no or low phosphorus will hold a leading position in the washing powder market. The market demand for 4A zeolite as an excellent assistant will also have a major breakthrough.
The consumption of 4A zeolite in detergents was only 54 kt in the world in 1977, but it increased sharply to 1.50 million tons in 1995. Consumption has now exceeded 3.00 million tons. 4A zeolite also has an extensive market in Southeast Asia. PQ, a detergent assistant supplier of the United States, expanded its Thailand-based zeolite capacity to 66 kt/a in 1996 and has also closely followed markets in China and the Asia-Pacific region. By conservative estimate, the market volume of zeolite in East Asia and Southeast Asia is around 200 kt today.

Market in China

The market supply/demand of 4A zeolite in China is basically stable. Major producers include China Aluminum Corporation Shandong Co., Ltd., with a capacity of 300 kt/a, Fujian Risheng Chemical Co., Ltd., with a capacity of 150 kt/a and some producers with individual capacities below 100 kt/a such as Quanzhou Huiying Chemicals Industrial Co., Ltd. (60 kt/a) and Guangzhou Hengbang Fine Chemical Co., Ltd. (60 kt/a). The total capacity to make 4A zeolite in China is around 800 kt/a today.
With the rapid growth, the total output of phosphorus-free washing powders will reach around 3.00 million tons in 2015. The total demand for 4A zeolite will be around 800 kt at that time.
Major target markets of phosphorus-free washing powders are advanced regions in the east of China such as Tai Lake reaches, Chao Lake reaches, Shandong, Hebei and Shanghai. China Aluminum Corporation Shandong Co., Ltd. holds a lion’s share of the 4A market in the north of China such as in Shandong and Hebei. Markets for 4A zeolite produced in Fujian Risheng Chemical Co., Ltd., Quanzhou Huiying Chemicals Industrial Co., Ltd. and Guangzhou Hengbang Fine Chemical Co., Ltd. are mainly concentrated in the south of China. There are more than a dozen major producers of phosphorus-free washing powders in China including Shanghai Unilever Co., Ltd., P&G China Co., Ltd., Henkel China Detergent Co., Ltd., Shanghai White Cat Co., Ltd., Shanxi Nanfeng Chemical Group Co, Ltd., Zhejiang Nice Group Co., Ltd., Huoli Meijie Detergent Products Co., Ltd., Zhejiang Transfer Chemical Group Co., Ltd., Jinling Petrochemical Co., Ltd. Nanjing Alkylbenzene Plant and Weifang Synthetic Detergent Plant.
China Aluminum Corporation Shandong Co., Ltd. exports much of its output. Fujian Risheng Chemical Co., Ltd., Quanzhou Huiying Chemicals Industrial Co., Ltd. and Guangzhou Hengbang Fine Chemical Co., Ltd. mainly export to Southeast Asia and the Americas.

Search for development orientation under pressures of environmental protection and production cost

The commercial production of 4A zeolite mainly uses one of three processes. The first is the kaolin process. The second is the acid clay process, also called the bentonite process. These two processes have not yet reached the stage of large-scale commercial production in China. The third is the hydrothermal process, also called the chemical synthesis process. The production of 4A zeolite in China generally uses this process.
China Aluminum Corporation Shandong Co., Ltd. uses raw slurry from its own alumina production and sodium silicate purchased from outside sources as raw materials to produce 4A zeolite. Fujian Risheng Chemical Co., Ltd., Quanzhou Huiying Chemicals Industrial Co., Ltd. and Guangzhou Hengbang Fine Chemical Co., Ltd. use bauxite and caustic soda as raw materials to produce sodium aluminate solution and use sodium silicate solution dissolved from purchased sodium silicate as raw material to produce 4A zeolite. Slag generated from bauxite in the extraction of sodium aluminate solution cannot be recycled and therefore causes extremely serious harm to environment. Guangzhou Hengbang Fine Chemical Co., Ltd. took the lead in 2013 to use aluminum hydroxide to replace bauxite in 4A zeolite production. The problem of slag generation was thoroughly solved, but the production cost was much higher. As Indonesia stopped exporting bauxite in 2014, Fujian Risheng Chemical Co., Ltd. and Quanzhou Huiying Chemicals Industrial Co., Ltd. are faced with problems in environmental protection and raw material availability. Due to more stringent requirements defined by state policies on energy conservation, emission reduction and environmental protection, quite a few sodium silicate producers in Tangshan, the biggest sodium silicate production base in China, have risks of production reduction and closure. With export restrictions imposed in foreign countries, the import price of bauxite will surely go up. The resultant price rise of aluminum hydroxide will lead to a drastic cost increase of 4A zeolite.
China has rich fly ash resources, and the process for using fly ash in extraction is well developed. Inner Mongolia Datang International Recycling Development Co., Ltd. has already constructed a 150 kt/a alumina production line. As the aluminum/silicon ratio of fly ash is not suitable for the direct production of alumina, however, fly ash cannot be used directly. Silicon must be removed first to increase the aluminum/silicon ratio, and alumina is then produced through sintering. A great deal of sodium silicate with low concentration is generated in silicon removal. To recycle sodium oxide in the solution, lime is usually added to generate calcium silicate through reaction, and filtration is then conducted to attain the recycling. In so using sodium silicate to produce 4A zeolite, sodium oxide and sodium silicate can both be recycled.
With greater attention paid by national governments to natural resources, the import of minerals will be more difficult and the price of minerals will also grow. The use of fly ash as raw material will therefore become a major trend in alumina production. Using sodium silicate generated in fly ash production to produce 4A zeolite will be the only way we can take. Making 4A zeolite from fly ash guarantees the availability of raw materials and stabilizes the prices of products. The inclusion of 4A zeolite production lines in the alumina industrial chain based on fly ash is therefore a development orientation in the 4A zeolite sector.