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Inorganic salt industry technical transformation project highlights
**Energy-Saving Reforms in Low-Temperature Pyrolysis**
Currently, the pyrolysis process is a significant energy-intensive step in producing light magnesium carbonate and magnesium oxide from dolomite. This year, the Calcium and Magnesium Salt Branch of the China Inorganic Salt Industry Association initiated an energy-saving transformation by shifting from high-temperature to low-temperature pyrolysis. Several companies have already adopted this approach, achieving remarkable energy savings.
In April, Hebei Qiuqi County Magnesium Products Co., Ltd. conducted internal meetings focused on energy conservation and emission reduction. The company decided to invest 200,000 yuan into the low-temperature pyrolysis energy-saving project promoted by the branch. With technical support from Prof. Hu Qingfu and Shijiazhuang Sayed Machinery Manufacturing Co., Ltd., and financial backing from the county credit union, the project was successfully implemented. After the upgrade, the pyrolysis temperature dropped from 95–105°C to 45–60°C, reducing coal consumption from 12 tons per day to 6 tons. This results in an annual coal saving of 1,800 tons, a reduction of over 600 tons of CO₂ emissions, and cost savings of 2 million yuan. Additionally, industrial waste was utilized, lowering pollution sources and increasing annual profits by 3.7 million yuan.
**Rotary Kiln Calcination Technology**
Traditionally, box furnaces are used for calcining inorganic salts in China, which are highly energy-consuming. For magnesium oxide production, coal consumption per ton is about 3 tons. Yuncheng Yaxing Environmental Protection Technology Co., Ltd. developed rotary kiln calcination technology, reducing coal use to 1.2 tons per ton of magnesium oxide. The rotary kiln uses environment-friendly coal with secondary combustion, offering high thermal efficiency.
The exhaust gas is recycled in three stages: first to heat a waste heat steam boiler for production, then to provide hot water for domestic use, and finally for winter heating. As a result, all steam, hot water, and heating needs are met through waste heat recovery. The thermal efficiency of the rotary kiln exceeds 80%, making it a highly energy-efficient solution.
**Titanium-Molybdenum-Nickel Tube Evaporator**
Most magnesium salt companies use copper tubes in evaporators for magnesium chloride production. However, bromine waste liquid containing free bromine and chlorine corrodes copper tubes, limiting their lifespan to just 2–3 years. Lianyungang Yinhua Magnesium Production Company replaced copper tubes with titanium-molybdenum-nickel alloy tubes, which offer superior corrosion resistance and strength.
These tubes have a light specific gravity, high strength, and excellent resistance to seawater and chloride corrosion. After testing, Yinhua Magnesium successfully implemented these tubes, extending the service life to 15 years—five times longer than copper. Although more expensive initially, the material usage is reduced by 70%, and total costs only increase by about 75%. This innovation improves equipment longevity, reduces environmental impact, and enhances production efficiency.
**Rotary Flash Dryer**
Nanfeng Chemical Group Co., Ltd. replaced fluidized bed dryers with rotary flash dryers in the production of magnesium sulfate monohydrate. Previous attempts with laminar air drying, tower drying, and drum drying were unsuccessful. Fluidized bed drying achieved stable production but at high energy costs.
By switching to a rotary flash dryer, the company improved energy efficiency, simplified operations, and increased production capacity. Using hot air from a hot blast stove as a heat source reduced heat loss. Cyclone and bag dust collectors ensured effective dust removal, meeting environmental standards. Compared to the previous system, coal consumption dropped by 20% and electricity use by 19%.
**Production of Nano-Magnesium Hydroxide via Bubble Liquid Membrane**
Guangdong Zhongshan Institute of Applied Chemistry developed a new method for producing nano-magnesium hydroxide using bubble liquid membrane technology. This process features low energy consumption and easy product separation.
The key equipment is a bubble liquid film reactor, which uses a bubbler-type disc stirrer to generate fine bubbles, creating a thin liquid film for nanoparticle formation. Reactions such as precipitation, nucleation, and growth occur within the bubble liquid film, enabling rapid and energy-efficient production. The resulting product is easy to filter, wash, and dry, solving common issues in nanoparticle processing.
This technology supports continuous production of 600 tons annually, with low investment, simple operation, and low maintenance costs, making it ideal for industrial-scale implementation.
**Using Light Powder as Raw Material**
Traditional methods for producing light magnesium oxide and active magnesium oxide involve the dolomite carbonization or ammonium bicarbonate brine process. Yuncheng Yaxing Environmental Protection Technology Co., Ltd. introduced a new energy-saving process using light-fired powder as raw material.
This method fully hydrates the light-burned powder, removes calcium and impurities, and produces magnesium hydroxide before calcination. The process significantly reduces coal consumption by about 3 tons per unit and lowers power consumption by 250 kWh. As a result, the cost per ton of magnesium oxide decreases by approximately 3,000 yuan.