A method for preparing sodium chromate by low-nitrogen roasting of chromite ore and continuous leaching of clinker

Abstract

The invention discloses a method for preparing sodium chromate by low-nitrogen roasting of chromite ore and continuous leaching of clinker, comprising the following steps: (1) selecting chromite ore powder, soda ash and returned slag; (2) mixing the selected raw materials After uniformity, it is sent to the rotary kiln, and the oxy-fuel system is used for oxy-fuel combustion, and the temperature of the material is controlled at 850°C-1150°C; (3) The pure oxygen gas is directly and evenly injected into the rotary kiln under the raw material bed , the raw material is roasted with pure oxygen in the rotary kiln; (4) The roasted clinker is poured into the wet vertical mill, and the sodium chromate light solution or pure water is added through the metering pump. After stirring evenly, it is passed through the transfer tank Sodium chromate is obtained after being sent to a belt filter for continuous leaching and filtering. The invention has low energy consumption, high output of sodium chromate, low consumption of chromium ore, low content of nitrogen oxides in flue gas, low consumption of chromium ore, low content of nitrogen oxides in flue gas, and can realize continuous production, improve Increased productivity and clean emissions.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for preparing sodium chromate by low-nitrogen roasting of chromite ore and continuous leaching of clinker. Background technique [0002] At present, chromite and soda ash are reacted at 900-1150°C to prepare sodium chromate, which is usually directly heated and reacted by burning hot flame gas in a rotary kiln. Due to the direct heating of flame gas, the oxygen in the high temperature section of the kiln tail If the content is 8%-12%, it will peroxidize the freshly added raw material and form a molten state, which is easy to form rings or form larger particles, which affects the oxidation efficiency. In the patent CN1109026A, the segmented technology in the furnace is adopted. The injected oxygen content is 70% for roasting, and the oxygen content in the high-temperature section of the kiln tail is controlled below 2%, which can improve the partial ...

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Problems solved by technology

[0002] At present, chromite and soda ash are reacted at 900-1150°C to prepare sodium chromate, which is usually directly heated and reacted by burning hot flame gas in a rotary kiln. Due to the direct heating of flame gas, the oxygen in the high temperature section of the kiln tail If the content is 8%-12%, it will peroxidize the freshly added raw material and form a molten state, which is easy to form rings or form larger particles, which affects the oxidation efficiency. In the patent CN1109026A, the segmented technology in the furnace is adopted. The oxygen content is injected into 70% for roasting, and the oxygen content in the high-temperature section of the kiln tail is controlled below 2%, which can improve the partial oxidation efficiency, but there will still be some rings and sticking phenomena

At the same time, at present, the combustion systems used by all chromium salt enterprises are air-fuel combustion systems, and the nitrogen content brought in through the air is as high as 70%. In the kiln gas at high temperature, nitrogen will be oxidized into nitrogen oxides and discharged into In the atmosphere, it cannot meet the requirements below 200mg / m 3 Emission requirements, in order to reduce the nitrogen oxide content to meet the emission standards, it is necessary to install a denitrification device at the flue mouth or add other reducing substances for treatment. In the patent CN108910950A, the nitrogen oxide gas generated after the reaction is reduced by introducing a reducing agent. However, whether it is to install a denitrification device or add a reducing agent for treatment, it will increase the production cost

After the roasted clinker is generally cooled, it is pulverized with a mill, added with a leaching solution for leaching, and then separated by filtration to prepare a sodium chromate solution. In this method, cooling and milling will consume a large amount of energy, and for Intermittent production, low production efficiency

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