Background and overview【1】
Yellow phosphorus is an important raw material for industrial production. Products made from yellow phosphorus are widely used in pesticides, medicines, detergents, food additives, flame retardants and other fields. Yellow phosphorus is also an important raw material for the national defense industry. At present, the industrial production of yellow phosphorus in the world basically uses the electric furnace method. Every 1 ton of yellow phosphorus produced by the electric furnace method will produce about 8 to 10 tons of phosphorus slag as a by-product. my country currently produces nearly 1,000 kt of yellow phosphorus and produces nearly 9,000 kt of phosphorus slag every year. The disposal and stacking of huge amounts of phosphorus slag not only pollutes the environment and becomes a burden for enterprises, but it is also a waste of resources. Reasonably solving the outlet of phosphorus residue, turning it into resources, turning waste into treasure, and turning harm into benefit is an important issue and development direction that needs to be solved for yellow phosphorus enterprises.
Application【1】
1. Application in phosphate slag cement production
The application of yellow phosphorus slag in the cement industry mainly includes the following aspects: as cement raw material, phosphate slag cement admixture, making low clinker phosphorus slag cement and clinker-free cement. Yellow phosphorus slag is used as cement raw material, mainly replacing fluorite as a mineralizer for calcining cement clinker, which can improve the burnability of raw materials and reduce cement costs. Relevant research reports believe that when the amount of phosphorus slag added to cement raw materials is within the range of 3% to 5%, there is almost no difference between the cement produced and the cement produced without the addition of phosphorus slag. As an admixture of phosphorus slag cement, research by Zhang Lihua et al. believes that the strength of phosphorus slag cement is related to the specific surface area and dosage of phosphorus slag. When the specific surface area of phosphorus slag is 476 m2/kg dosage The strength of 30% phosphorus slag cement even exceeds that of pure cement; research by Fang Rongli et al. confirmed that with the addition of the FL-stimulated early strength agent developed by them, the amount of phosphorus slag added can reach 40%; at the same time, they also Research has been conducted on using phosphorus slag as a cementing material with the addition of a small amount of initiators such as alkali, alkali metal salts and sulfates. The cementing material does not incorporate high calcium materials and the hydration product is mainly low alkaline. It is made of hydrated calcium silicate, so it has good corrosion resistance. The production process of this cementing material is simple, with low investment and low cost. It has significant economic and social benefits. It is a cheap, energy-saving and high-quality cementing material. Chen Dan’s research used phosphorus slag in cement raw meal, together with fly ash, sulfuric acid slag, etc. It was found that since the phosphorus slag ingredient can significantly improve the burnability of the raw meal, adding phosphorus slag into the raw meal When 18% phosphorus slag is added, the raw material appears 56°C earlier than the batch liquid phase without phosphorus slag during the firing process, which is conducive to promoting the formation of clinker minerals; at the same time, the fired clinker is mixed with gypsum to prepare All physical properties of the Portland cement are in line with national standards. The strength of fired clinker at 3 d and 28 d is significantly better than that of general cement clinker, and the early strength is higher. Research by Liu Zhanxinhui and others also confirmed that low-cost composite admixtures can be developed to produce high-content phosphorus slag cement. When the phosphorus slag content is 50% to 70% (mass percentage), the use of admixture technology can produce 425 # and 525# phosphate slag cement.
2. Use phosphorus slag to produce concrete
Zhang Lihua et al. and Yao Zhiquan studied the use of phosphorus slag as a concrete admixture, which can significantly reduce the hydration heat and adiabatic temperature rise of concrete, reduce the elastic modulus of concrete, and increase the ultimate tensile value of concrete. This kind of concrete has high strength and large strength growth rate in the later stage, and the retarding effect of phosphorus slag can meet the needs of large-volume concrete construction. Phosphorus slag concrete also has excellent resistance to seawater and sulfate erosion, improves the impermeability of concrete, and inhibits the alkali aggregate reaction of concrete. Since the addition of phosphorus slag can effectively improve the ability of large-volume concrete to resist temperature cracks, phosphorus slag has been well used in hydraulic large-volume concrete projects.
3. Use phosphorus slag to prepare unfired bricks
Guizhou Kailin Group Co., Ltd. cooperated with Chongqing University to use phosphogypsum and phosphorus slag to develop phosphorus slag-phosphogypsum bricks. After several years of research, in November 2009, an annual production line using press molding and high-pressure steam curing was built. The phosphorus slag-phosphogypsum brick production line produces 1 billion standard bricks, and the product quality can meet or exceed the relevant national standards.
4. Use phosphorus slag to prepare roadbed materials
The diameter of phosphorus slag particles is mostly concentrated between 1 and 5 mm, and its particles and ratio are close to the stone chips produced by crushing natural stone. It can be used to prepare roadbed materials instead of stone chips. Cha Jin of Wuhan University of Technology studied the use of phosphorus slag or manganese slag as pavement base material, using lime fly ash or cement fly ash to stabilize the phosphorus slag and manganese slag, and the phosphorus in lime-fly ash-phosphorus slag (manganese slag) The suitable dosage of slag (manganese slag) is 60%-70%, the suitable dosage of phosphorus slag (manganese slag) in cement-fly ash-phosphorus slag (manganese slag) is 75%-80%, lime fly ash The strength of (cement)-phosphorus slag (manganese slag) composite aggregate is higher than that of lime fly ash (cement) stabilized gravel. When the phosphorus slag (manganese slag) replacement rate of stone chips is 1/2-2/3, the strength is the highest.
5. Preparation of ceramic materials using phosphorus slag
Zhou Liangliang and others from Kunming University of Science and Technology studied the potential activity of yellow phosphorus slag using physical and chemical activation methods, compounded the activated phosphorus slag and the original phosphorus slag, and through strengthening methods, prepared a compressive strength value of Chemically bonded ceramic composite materials above 80 MPa can replace traditional concrete and stone. Wu Min from Guizhou University used phosphorus slag as the main raw material, and the proportion was 70% phosphorus slag (120~140 mesh), 30% clay (100-120 mesh), and 5% coal powder as a foaming agent. Lightweight ceramic pellets were produced. The product’s�Specific surface area The large pores and ultra-micro pores in the activated carbon structure uniformly adsorb organic impurities, iron, sulfur, and insoluble residues. After sedimentation and filtration, they are washed twice with 75-80°C hot water. It is reported that this method can prepare low arsenic yellow phosphorus, the arsenic mass fraction of Tosoh matte powder is less than 0.2×10-6, and the mass fraction of other impurities is less than 300×10 -6, the phosphorus purity is 5N~6N level. This method has low energy consumption and is more suitable for the preparation of low arsenic yellow phosphorus. However, it is difficult for 6N to 7N grade high-purity phosphorus to reduce the nitrate and other metal impurities contained in it to the specified level. Secondly, the process is long and the number of washings is high. The large amount of waste liquid discharge treatment is also a shortcoming of this method.
Main references
[1] Ran Longwen, Zhu Hong, Lou Yang. Uses and application prospects of yellow phosphorus slag [J]. Guangzhou Chemical Industry, 2014, 42(18):51-53.
[2] YIN Xian-guo- “Phosphate Fertilizer and Compound Fertilizer” 2011 Issue 4
