[Objective] To explore the flocculation and sedimentation laws of several flocculants and coagulants under different dosage conditions and optimize the chemical system for treating coal slime water. [Method] In this article, the effects of flocculants only and the composite reagents on the settling performance of slime water in the Liangzhuang coal washing plant were studied. The particle number and the average chord length of slime floc were measured at the different reagent conditions by focused beam reflectance meter (FBRM). [Result] Adding flocculants only had no obvious effect on the settlement of slime water whereas the composite reagents made of flocculant and coagulant promoted the settlement of coal slime water effectively. The best results were obtained when 200 g/t flocculant with 20 million molecular weight was combined with 1 000 g/t CaCl2 coagulant. [Conclusion] The average chord length results showed that the number of flocs obtained with the composite reagent was obviously higher than that observed with flocculant only, indicating that the composite reagent had a better agglomeration effect.
[Objective&Method] In order to promote the utilization of vanadium tailings, a vanadium tailing with high silicon content and low activity in Shangluo County was taken as the research object. By adding cement clinker and smelting slags to vanadium tailings, and through the new compound activator to effectively stimulate the chemical activity of raw materials, a vanadium tailing based cementing material with good performance was prepared. The cementation characteristics of the cementing material were analyzed by X-ray diffraction and scanning electron microscopy. [Result] The suitable mass ratio of vanadium tailings, smelting slags and cement clinker is 60∶15∶25, and the optimum dosage of compound activator XJJ01 is 5%. When the prepared cementing material and the whole tailings of vanadium tailings are used at the cement-sand ratio of 1∶8, the 3, 28 d compressive strengths of the prepared filling body test blocks are 0.42, 2.11 MPa, respectively, which meets the requirements of Z03 and H20 grades of cementing materials. At the action of XJJ01 activator, SiO2, Al2O3 and CaO in vanadium tailings and smelting slags cooperate with water glass, calcium salt and reinforcing agent to form hydrated calcium silicate and ettringite, which is helpful to improve the overall chemical activity of cementing materials. [Conclusion] When the tailings are filled, the tailings particles are closely packed and cross-linked at the action of cementing materials to form a dense structure, which can ensure the strength of the filling body.
[Objective] Coal gasification slag is a bulk solid waste produced by the coal gasification process, which has become a prominent bottleneck restricting the high-quality development of the modern coal chemical industry. Flotation of coal gasification slag is a prerequisite for its resource utilization. [Method] Grinding and flotation tests were conducted on coal gasification fine slag from a coal chemical enterprise in Inner Mongolia to analyze the effects of raw material physical properties, grinding method, and grinding time on the grinding-flotation de-ash effect of the samples. [Result&Conclusion] The ash fraction of coarse and fine particles of the sample was demarcated, so the classification was carried out with 0.125 mm as the boundary before selection, and the coarse particle carbon fraction was recovered in advance. In addition, it was found through the grinding test that the grinding efficiency of wet ball milling was significantly higher than that of rod milling, and it could obtain higher carbon and ash dissociation and lower grinding fineness under the same grinding time. Still, it was also prone to the phenomenon of over-grinding. The flotation test proved that grinding can significantly improve the effect of flotation de-ashification of gasification fine slag, in the best condition ball milling 4 min, flotation refinement, and combustible body recovery was 60.58% and 78.26%, respectively, and can get a low ash concentrate product with ash content of 39.15%, to achieve the flotation de-ashification of gasification fine slag.
[Objective] As a solid waste produced by steelmaking, steel slag has the characteristics of large quantity, high alkalinity and diverse composition. At present, the utilization capacity of steel slag in China is poor, and the utilization rate is only about 10%. The imbalance between the production of steel slag and the consumption of steel slag causes serious environmental pollution and waste of resources. [Method] Based on the physical and chemical properties of steel slag, this article first briefly summarizes the current mainstream utilization methods of steel slag, such as steel slag waste heat recovery, road construction, and wastewater treatment. [Result&Conclusion] Based on the problems of low consumption of steel slag and poor consumption capacity of steel slag by existing mainstream technologies, this paper focuses on the application of steel slag in soil improvement, describes the four aspects of soil pH value adjustment, fertility improvement, heavy metal capture and agricultural emission reduction, and looks forward to the future development direction of steel slag.
[Objective] To achieve the enrichment of nutrients in tailings and further reduce heavy metal elements, and to realize the large-scale utilization of tailings. Taking a certain molybdenum tailings in Hebei Province as the object, the process research for preparing high-quality silicon-calcium-potassium-magnesium fertilizer was carried out. [Method] Firstly, the molybdenum tailings were subjected to two rounds of flotation to eliminate heavy metal minerals and quartz, resulting in high-potassium molybdenum tailings. Subsequently, the high-potassium molybdenum tailing slag was mixed with limestone, dolomite, and gypsum at a mass ratio of 1∶0.6∶1∶0.2 and calcined at 1 200 ℃ for 120 min. During this process, mineral phase reconstruction occurred in potassium feldspar to activate insoluble potassium into soluble effective potassium, thereby producing Si-Ca-K-Mg fertilizer. Simultaneously, some heavy metals and potassium would escape with the high-temperature flue gas. Subsequently, the flue gas was absorbed using a dilute acid absorption solution, and the heavy metals present in the flue gas were precipitated and separated through coprecipitation with calcium hydroxide and potassium phosphate as co-precipitating agents. The resulting high-purity potassium salt was obtained via evaporation and crystallization. Finally, a superior quality silica-calcium-potassium-magnesium fertilizer was prepared by blending calcined fertilizer with potassium salt extracted from the flue gas followed by grinding. [Result] All parameters of the fertilizer comply with Type I standards outlined in the national standard 'silicon calcium potassium magnesium Fertilizer' (GB/T 36207-2018), wherein the effective K2O content surpasses 70.3% of type I specifications while heavy metal content remains significantly below regulatory limits. [Conclusion] This innovative technology presents a novel approach for large-scale utilization of molybdenum tailings while also contributing to advancements in the composite potash fertilizer industry.
