Experimental Study on Resource Utilization of Ferromanganese Furnace Ash

I. Introduction

Manganese Iron is necessary for production of manganese alloy steel materials, in the ferromanganese alloy production process, especially when the lance smelting furnace, a large amount of dust. The ash of many ferromanganese alloy plants in China has been piled up everywhere and become solid waste that pollutes the environment. In addition, the newly released ash powder is very thin and easy to drift with the wind, seriously affecting the quality of the city's atmospheric environment. It is determined that the furnace ash contains 17% manganese, 5% to 6% iron, 20% calcium, and more than 20 kinds of elements, which has extremely high recycling value.

Manganese sulfate solution is the main intermediate product in the production of manganese metal and its compounds. Therefore, this study aims to prepare manganese sulfate solution by sintering method and sulfur dioxide reduction method through laboratory test, using manganese iron furnace ash as raw material, and exploring reasonable manganese recovery process to maximize the utilization of manganese iron furnace ash. use.

Second, the test principle and device

(1) Sulfur dioxide reduction method

The MnO 2 in the reduction furnace ash is contacted with sulphur dioxide gas to be MnSO 4 , and then dissolved in water to form a MnSO 4 solution. In this process, MnO 2 and SO 2 react rapidly to form MnSO 4 and MnS 2 O 6 (manganese disulfate).

In the presence of SO 2 gas, MnS 2 O 6 can also undergo a violent exothermic reaction with MnO 2 to form MnSO 4 . At this time, the SO 2 gas does not directly participate in the reaction, but only plays a catalytic induction role, and the excess SO 2 tail gas can be absorbed by the aqueous solution of manganese sulfate, and no new pollution is caused by the overflow of the SO 2 gas.

While preparing the MnSO 4 solution, other metal ions (Fe 3+ and Fe 2+ ) in the manganese ore are also made into sulfate and mixed in the MnSO 4 solution. To ensure the quality (purity) of the final manganese series, these sulfates must be removed.

This test device is shown in Figure 1. The reaction tank has a volume of 45 L. The tank is equipped with two mixers, a circulation pump, a thermometer and an absorption tower. The absorption tower is filled with a spherical filler. The sulphur dioxide gas is supplied from an outsourced sulphur dioxide storage tank, and the flow rate is controlled by a control valve and a pressure gauge.

Fig.1 Test device for preparing manganese sulfate solution by sulfur dioxide method

(2) Sintering method

Sintering method, after the manganese ore and powdered anthracite powder proportion of 0.2 to 0.3 (mass ratio) mixture and mix well, the reduction in the firing furnace at a high temperature (800 deg.] C) and less amount of air situation Next, the carbon in the pulverized coal is oxidized to carbon monoxide. Carbon monoxide has a very strong reducing ability, and at a high temperature, manganese dioxide can be reduced to manganese monoxide. Also at a high temperature of 800 ° C, manganese dioxide can be reduced to manganese monoxide by carbon in the pulverized coal. Since the ferromanganese ash contains 11% to 13% of carbon, no anthracite is added in the production.

After the formation of manganese monoxide, it is leached with sulfuric acid to obtain a MnSO 4 solution.

This test uses a method in which the furnace ash is placed in a high-temperature precision electric resistance furnace for firing.

Third, the test materials

(1) Sulfur dioxide reduction method

The manganese iron furnace ash used in the test was taken from a ferromanganese alloy factory in Zhejiang. The manganese content in the ash was 17%, the ash of the furnace was 10kg (Mn 1.7kg), 30kg of tap water was added, and the black mixed solution of 1:3 was prepared. The total volume was 27.45L.

(2) Sintering method

The manganese iron furnace ash used in the test was taken from a manganese-iron alloy factory in Zhejiang. The manganese content in the furnace ash was 20%, and the ash of the furnace was 20kg (Mn 4kg).

Fourth, the detection method

(I) Determination of Fe 2+ : potassium ferricyanide solution K 3 [Fe(CN) 6 ], the solution is blue, indicating that there is Fe 2+ ; it is brown, indicating no Fe 2+ .

(B) Fe 3+ determination: potassium ferrocyanide solution K 2 [Fe(CN) 6 ], the solution is blue, indicating Fe 3+ ; yellow, indicating no Fe 3+ .

(III) Mn measurement: density specific gravity meter. After the MnSO 4 aqueous solution was filtered, the weight ratio of the MnSO 4 solution was measured by a hydrometer to check the MnSO 4 aqueous solution gravity meter, and the manganese content was obtained by calculation.

(4) pH measurement: measured by precision test paper.

(5) Temperature measurement: The temperature of the solution is measured online using a thermometer.

V. Test methods

(1) Sulfur dioxide reduction method

Firstly, turn on circulating water pump, mixer and SO 2 control valve; record pH value, temperature, MnSO 4 aqueous solution concentration, SO 2 output pressure and SO 2 consumption on time; periodically detect Fe 3+ and Fe 2+ in MnSO 4 aqueous solution; When Fe 2+ is present in the aqueous solution, the supply of gas (SO 2 ) is stopped. Then add ammonia water, adjust the pH value to 5.5, precipitate Fe 3+ precipitate, filter to obtain MnSO 4 aqueous solution; add Na 2 S solution in MnSO 4 aqueous solution, stir, gray floc is precipitated, heated to 90 At °C, the yellow mud was filtered to obtain a pale pink MnSO 4 aqueous solution, and the manganese sulfate content was measured.

(2) Sintering method

The ferromanganese furnace ash is placed in a high-temperature gas-type electric resistance furnace and calcined at a temperature of 800 ° C; during the roasting process, it is sautéed once every 1 h to sufficiently roast the lower layer powder. After 4h, turn off the power. When the manganese ore powder is cooled to normal temperature in an electric resistance furnace (the powder is dark brown), take 300 mL of 15% dilute sulfuric acid, pour into the powder which has been cooled to normal temperature, stir well, boil for 10 min, and check that there is no Fe 3+ , Fe in the solution. 2+ ; take 96mL of 96% sulfuric acid, pour into 300mL of the above manganese sulfate solution, stir and boil for more than 10min, the supernatant is brownish yellow. After filtration, the pH was measured to be 1 to 2, and the detection solution contained Fe 3+ and no Fe 2+ . Ammonia was used to neutralize to pH 5.5, and a total of 800 mL of manganese sulfate filtrate was obtained. There was no Fe 3+ and Fe 2+ in the test solution, and the manganese sulfate content was measured.

VI. Results and discussion

(1) Sulfur dioxide reduction method

The final volume of the reaction solution was 30 L, which was calculated by looking up the table and was equivalent to 4118 g of MnSO 4 ·H 2 O.

Manganese recovery Mn = 4118 x 55 / 169 = 1.34 kg.

In ferromanganese ash as a raw material, SO 2 reduction gas production routes ash 4 aqueous MnSO production of MnO 2 is feasible, its recovery rate 78.82% manganese; sludge results from checking to see, there are part of the particles The larger ash was deposited at the bottom of the reaction tank and was not completely reacted, and MnO 2 was not precipitated.

After the above pure MnSO 4 solution is obtained, a metathesis reaction is carried out by adding an ammonium hydrogencarbonate solution to form a manganese carbonate precipitate, which is thermally decomposed at 450 ° C and dried to obtain manganese dioxide.

The obtained solid powder of manganese dioxide product was sampled by the relevant department, and its content was 85.3%. The detailed component analysis is shown in Table 1.

Table 1 Composition of manganese dioxide powder

Taking into account the laboratory conditions and equipment, in order to demonstrate the feasibility of the production process of manganese-manganese ash as a raw material for the production of manganese series products, the production equipment of a metallurgical products company in Ningxia was used for the production test (the plant originally used manganese ore as raw material). ), taking manganese iron furnace ash from a manganese-iron alloy plant in Zhejiang as raw material, after many tests, the extraction rate of manganese is 84%, which is more than 10% higher than the manganese extraction rate of the original production process of the plant.

(2) Sintering method

The final volume of the reaction solution was 800 mL, which was calculated by look-up table and was equivalent to 120 g of MnSO 4 ·H 2 O solid.

Recovered manganese Mn content = 120 × 55 / 169 = 38.4g

Recovery rate η = recovered manganese / total input = 96%

It is feasible to use the ferromanganese ash of a certain enterprise in Zhejiang as raw material to make the production route of the MnSO4 solution by sintering method; the cost of producing raw materials is lower than the traditional method. Because of its small particle size, large specific surface area and easy calcination, it does not require large-scale milling process, which can save the fixed assets investment and daily production and operation cost of the enterprise; the production process of manganese iron furnace ash sintering method In the process, the existing coke in the ash can be fully utilized, and no nearly 12% of the white coal powder is added, which saves the production cost; in addition to iron, most of the iron ions are precipitated in the sludge as iron precipitate. Neutralizers can be used less. However, the manganese iron furnace ash sintering process has high labor intensity, and the ash powder pollution is still serious (compared with the sulfur dioxide reduction method).

(3) Economic analysis

The manganese content of ore in Hanzhong and Xiangfan, the main producing areas of domestic manganese ore, is between 18% and 25%, and the mining price is around 220 yuan/t. The ferromanganese ash used in the test was solid waste, and the current treatment (sold to the cement plant) yielded 20 yuan/t. It can be seen from the price and manganese content ratio of the two, the manganese iron furnace ash has great development and utilization value.

Table 2 shows the main raw material costs required to produce 1t of electrolytic manganese metal. From Table 2, Method 1 and Method 2 use the sintering method to produce manganese series products. Since the manganese iron furnace ash contains 11% to 13% carbon, no anthracite is added in the production, and the production cost is higher than the conventional sintering method. low. From the cost analysis of the two, the use of ferromanganese ash as raw material has a very large promotion significance.

Table 2 Main raw material costs required to produce 1t electrolytic manganese metal

Labor, electricity consumption, and sales expenses are not calculated in the economic costs in Table 2.

Method 3 and Method 4 are to produce a manganese series product by using a sulfur dioxide reduction method (industrial sulfur combustion produces sulfur dioxide, sulfur dioxide as a reducing agent to reduce manganese dioxide to manganese sulfate, and sulfuric acid produced by reduction reaction to form sulfuric acid to acidify The effect of manganese ore), it can be seen that the same method using sulfur dioxide reduction, the production of electrolytic manganese metal using manganese iron furnace ash as the raw material is the lowest, the main part of the cost reduction is that the production process does not require the addition of sulfuric acid and The price of ferromanganese ash is lower.

Seven, conclusion

(1) The process of preparing MnSO 4 solution by roasting method and sulfur dioxide method is feasible in the laboratory with manganese iron ash as a raw material in a certain enterprise in Zhejiang. The extraction rate of manganese is 96% and 78.82%, respectively, but the roasting process is used. The high strength will cause secondary pollution; the remaining SO 2 tail gas by the sulfur dioxide method can be absorbed by the aqueous solution of manganese sulfate, and no new pollution will be caused by the overflow of SO 2 gas. The remaining MnSO 4 mother liquor can be reused without causing new pollution.

(2) Using manganese iron furnace ash as raw material and using sulfur dioxide method, the manganese extraction rate in manganese ore can reach 84%.

(3) The production process of producing manganese series products by using manganese iron furnace ash as raw material and using sulfur dioxide can be extended to the production process of other manganese-poor ore as raw materials. At present, due to institutional reasons, the domestic manganese ore production bases basically only mine manganese ore with a manganese content of more than 20%. For the manganese-poor ore mines, the method of landfilling abandoned ore or abandoning the mine is adopted, and the short-term economic benefits are obvious. .

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