Manganese is widely used and is an important trace element in agriculture. In the livestock and breeding industries, an appropriate amount of manganese sulfate is often added to the feed. Manganese sulfate is also widely used in medicine, food, pesticide, papermaking, and catalyst industries. With the continuous advancement of science and technology, its dosage and application fields will continue to expand. Manganese sulfate is the basic manganese salt, and only manganese sulfate containing one crystal water is relatively stable. Except for reagent grades and products with 4 to 5 crystal waters with special requirements, almost all factories produce products containing one crystal water. With the depletion of high-grade manganese resources, the traditional evaporation and concentration production process has been difficult to meet the production needs of manganese sulfate products. Therefore, it is especially necessary to research, develop and apply new processes for the production of manganese sulfate.
First, the test part
(1) Raw materials
Pyrolusite, tetrahedrite ore, chemical analysis and rhodochrosite and pyrite ore size are shown in Table 1 and Table 2. Titanium White Industrial Waste: Ï (H 2 SO 4) = 168gL, Ï (FeSO 4) = 118gL. Concentrated sulfuric acid: w(H 2 SO 4 ) = 96%.
Table 1 Chemical analysis results of pyrolusite, strontium manganese ore, rhodochrosite 
Note: 1) Analysis results of soft-manganese mineral phase in Guiping, Guangxi: w(MnO 2 )=30.02%, w(Mn 2 O 3 )=2.25%, w(MnCO 3 )=0.88%; 2) Guangxi Lingshan Taipingé» manganese mineral Phase analysis
Results: w(MnO 2 )=29.5%, w(Mn 2 O 3 )=3.01%, w(MnCO 3 )=0.5%; 3) Guangxi Daxin Ling manganese ore: w(MnCO 3 )=39.58%.
Table 2 Chemical analysis results of Guangxi Debao Pyrite Mine
(2) Major equipment
Immersion manganese tank φ1000mm×1200mm; BMS6/450-U filter press; BAS6/400-N stainless steel filter press (filtration pressure 1MPa, filtration temperature -5～200°C); YS-100L autoclave; 202-4 electric heating thermostat Drying box.
(three) process
The schematic diagram of the process for preparing manganese sulfate from pyrolusite or strontium manganese ore is shown in Figure 1. The process flow for preparing manganese sulfate from rhodochrosite is shown in Figure 2.
Fig.1 Schematic diagram of process flow for preparing manganese sulfate from pyrolusite or strontium manganese ore
Fig. 2 Schematic diagram of the process of preparing manganese sulfate from rhodochrosite
(4) Principle
According to the principle that the solubility of manganese sulfate exceeds 100 ° C sharply, the manganese sulfate product is produced by pre-concentration and depurification purification by autoclave crystallization. The manganese sulfate solubility curve is shown in Figure 3.
Figure 3 MnSO 4 solubility curve
Second, the results and discussion
(1) Pressure vessel crystallization preconcentration
The qualified neutral liquid prepared by the above three kinds of manganese ore was pre-concentrated and purified by an autoclave, and the neutral liquid quality is shown in Table 3. 100 L of the neutral solution was injected into the autoclave and heated indirectly with steam at a pressure of 1.5 MPa. When the temperature in the autoclave is raised to 190-195 ° C, the pressure in the autoclave reaches 1.3 to 1.4 MPa, and the pressure is allowed to stand for 10 to 15 min. The supernatant of the outer part of the sewage trap is sampled to achieve the purpose of preconcentration and one purification. The results are shown in Table 4. Subsequently, the pressure is released by a pressure reducing valve, and the pre-concentrated material is discharged into a cooling dissolution tank through a discharge valve, cooled and dissolved, and allowed to stand for aging, and the secondary purification purpose is achieved. The results are shown in Table 5. It can be seen from the results of Table 4 and Table 5 that pre-concentration by crystallization of the autoclave has an ideal effect. The key is the choice of process flow and the control of the endpoint temperature.
Table 3 Neutral liquid quality analysis results g/L
Table 4 Analysis results of the supernatant of the autoclave
Note: The rest time is 12min.
Table 5 Results of cooling and dissolution of the autoclave pre-concentrated solution
(2) Pressure tank crystallization manganese sulfate products
The purified pre-concentrated liquid is injected into the autoclave. When the temperature in the autoclave is raised to 190-195 ° C, the pressure in the autoclave can reach 1.3-1.4 MPa. In this state, it is allowed to stand for 8-10 min, and is discharged through the sampling drain valve. The clear liquid is discharged into the plate and frame filter press through the discharge valve for solid-liquid separation. The results are shown in Table 6. The product was analyzed after drying and the results are shown in Table 7. It can be seen from Table 6 and Table 7 that the manganese sulfate in the autoclave has high crystallization rate and stable and reliable quality. The key to the control of this process is the production time of each kettle. The time is too long, the iron content of the product increases, and the appearance color of the product turns yellow.
Table 6 Results of research on crystallization of manganese sulfate in autoclave
Note: 1 # , 2 # is the second ore plus acid pre-dope; 3 # , 4 # is the manganese ore pre-dope.
Table 7 Test results of manganese sulfate products %
Note: 1) The appearance color is light rose color; 2) Manganese sulfate refers to MnSO 4 ·H 2 O.
Third, the conclusion
1) The production of manganese sulfate by autoclave crystallization has the advantages of high production efficiency, low energy consumption and high recovery rate. 2) Advanced technology, reliable technology, stable operation and high quality, which is a new way to exploit the comprehensive utilization of China's rich low-grade manganese ore resources and has extremely high social and economic benefits. 3) Based on the production process, high-purity synthetic manganese carbonate with w(Mn) ≥ 45.5%, high-purity manganese monoxide with w(MnO) ≥ 98%, w(MnO 2 ) ≥ 93. 5% can be further developed. High-purity electrolytic manganese dioxide series products. 4) The production of manganese sulfate by autoclave crystallization method is the physical and chemical reaction process of the slightly acidic solution of manganese sulfate in the pressure system. The material requirements and quality requirements of the equipment system are strict, and the equipment pipeline configuration in the system should be scientific and reasonable. Otherwise, It will affect the normal and safe operation of the system. 5) The physical and chemical properties of the raw materials determine the production process and process parameters.
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