Steel slag-turned soil conditioner changes saline-alkali land into fertile farmland
By Dou Hanyang, Zhang Jinke Source: People’s Daily
With the help of a drone, a herdsman driving a harvester followed navigation system to an alfalfa grassland that covers an area of over 300 mu (20 hectares) on a vast expanse of saline-alkali land in Xianfeng township, Urad Front Banner, Bayannur city, north China’s Inner Mongolia autonomous region.
The grassland, which used to be barren saline-alkali land, is a pilot and demonstration project for saline-alkali wasteland transformation. It has been turned into fertile farmland by soil conditioner made from an iron and steel plant’s desulfurization byproducts.
Baogang Group, an iron and steel enterprise headquartered in Inner Mongolia, produces over two million tons of steel slag every year. The steel debris it has accumulated over the years has piled up like a mountain, not only occupying land resources, but polluting the air.
To dispose of steel slag, a subsidiary of Baogang Group introduced a desulfurization project developed by Taiji Environmental Protection Equipment Co., Ltd., a private technology enterprise based in Cixi city, east China’s Zhejiang province, which removes sulfur dioxide from flue gases with steel slag.
The project can consume 7,000 tons of steel slag every year, and the nearly 10,000 tons of byproducts from flue gas desulfurization (FGD) can be used to produce soil amendments.
At the factory of the subsidiary of Baogang Group, the chimneys of three 75-ton circulating fluidized bed (CFB) boilers equipped with desulfurization devices soar into the sky.
According to an executive of the company, steel slag is ground first, and the powder is added with water and then sent into the desulfurization tower. After a series of chemical reactions, the desulfurization byproducts become sources of soil amendments.
Unlike waste generated by iron and steel plants, which are hard and rough large particles, FGD byproducts are fine powder and feel like wet soil. Based on the properties of different patches of land, technicians then add suitable microelements into these FGD byproducts, eventually creating soil conditioners.
“Saline-alkali soil is formed as salts are kept within. After soil conditioners made from FGD byproducts are added into saline-alkali soil, they replace ions in the soil, including potassium, sodium, magnesium ions, with their own chemical elements such as calcium and iron, which makes it possible to take the salts away from the soil with water later,” said Shi Yuezhan, general manager of Taiji Environmental Protection Equipment Co., Ltd.
The company has also taken measures to ensure that the desalted soil will not be affected again by the salts contained underground and in the surrounding land, according to Shi.
“After the salinity in the soil is reduced, crops can grow on the land,” Shi explained.
Stressing that solid waste disposal shouldn’t risk generating new waste, Shi believes it important to form a green chain to truly realize circular economy.
Replacing traditional desulfurizer such as limestone and lime with steel slag in desulfurization can not only save limestone resources, but avoid carbon dioxide emissions during the production of lime, according to Shi.
If a project that produces 21,500 tons of sulfur dioxide per year uses steel slag as desulfurizer, it can save 26,000 tons of lime and reduce carbon dioxide emissions by 11,400 tons a year. Its exhaust will also be able to meet China’s ultra-low emission standards.
Taiji Environmental Protection Equipment Co., Ltd., one of China’s national-level “little giant” enterprises that focus on specialization, refinement, uniqueness and innovation, has reaped the rewards of innovation through continuous input into research and development (R&D).
The company spends over four percent of its annual revenue on R&D every year. Last year, the proportion was raised to 6.6 percent. Research personnel in the enterprise has always accounted for more than 30 percent of its employees; and 12 R&D achievements of the company were put into commercial use in the past two years.
Technological accumulation has enabled the company to expand its self-developed technologies from the desulfurization technology using steel slag to energy recycle system, and helped draft the technical specifications for the adoption of steel slag in FGD.
The number of national-level “little giant” enterprises has reached 30 in Cixi. While making independent innovation the driving force for their development, these companies have endeavored to increase the commercialization rate of scientific and technological innovations and translate advances in science and technology into practical productivity.
“In the coming years, we will continue increasing R&D investment and enhancing support for our fund for R&D of eco-friendly technologies so as to encourage research personnel to carry out technological innovation and new product development and further accelerate the commercialization of scientific and technological achievements,” Shi said.