Method for high-temperature and high-pressure synergic treatment of red mud and coal or coal gangue

Abstract

The application discloses a method for high-temperature and high-pressure collaborative treatment of red mud, coal or coal gangue, and belongs to the field of resource utilization of red mud, coal or coal gangue. The method comprises the following steps: mixing red mud, coal or coal gangue and water, and then placing the mixture into a high-temperature and high-pressure device; introducing an oxygen-containing gas or adding an oxidant; under the high-temperature and high-pressure conditions, mineral decomposition and reconstruction of the red mud and the coal or coal gangue occur, acidic substances produced by oxidation of sulfide minerals and carbon-based minerals in the coal or coal gangue and alkaline substances in the red mud are subjected to neutralization reaction; and after desalination of reaction products of the red mud and the coal or coal gangue, the reaction products are used as ecological matrix soil. The method disclosed by the application accelerates decomposition of alkaline minerals such as nepheline in the red mud and release of alkali under high-temperature and high-pressure conditions, and accelerates oxidation of carbon-based minerals and sulfide minerals in the coal or coal gangue and transformation of humus and humic acid, neutralizes alkaline substances and acidic substances produced in the reaction, realizes rapid dealkalization of the red mud, controls the degree of oxidation of the carbon-based minerals, and improves the content of organic matter in the reaction products, so that full resource utilization and ecological utilization of the red mud, the coal or the coal gangue are realized.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment and resource utilization technology, specifically relating to a method for the co-treatment of red mud with coal or coal gangue under high temperature and high pressure. Background Technology

[0002] Red mud, a major industrial solid waste generated during alumina production, is highly alkaline due to its high content of alkaline minerals such as nepheline and sodalite. Its storage process results in the slow release of alkaline substances over a long period, causing environmental pollution to surrounding soil and groundwater. Coal and coal gangue contain various mineral components, including carbon-based minerals and sulfide minerals. The utilization of high-sulfur coal is limited by environmental protection regulations; coal gangue, due to its low calorific value and high ash content, is classified as a major industrial solid waste. Currently, there is a lack of effective large-scale disposal methods for both red mud and coal gangue. Coal gangue and red mud can be used in various ways, such as building materials, underground backfilling, extraction of valuable components, and stockpiling and landfilling. The utilization of coal gangue as building materials is limited by the economic transportation radius and the demand of the construction market, resulting in a limited consumption. Backfilling mined-out areas with coal gangue involves large investments and affects the safety of mining production. Extraction of valuable components from coal gangue has problems such as reduced volume and environmental risks from the leaching residue after extraction. All of the above treatments have problems such as limited disposal capacity and high treatment costs.

[0003] Currently, there are four existing technologies for red mud disposal: (1) seabed discharge, (2) wet stockpiling, (3) dry stockpiling, and (4) ecological restoration. Seabed discharge is subject to significant geographical limitations, wet stockpiling poses risks of groundwater pollution and dam failure, dry stockpiling has high dehydration and solidification costs, and ecological restoration currently faces challenges such as immature technology.

[0004] Therefore, it is essential to develop a method for the co-processing of red mud with coal or coal gangue under high temperature and pressure. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the synergistic treatment of red mud with coal or coal gangue under high temperature and high pressure.

[0006] The objective of this invention is achieved by including the following steps:

[0007] S1. Mix red mud, coal or coal gangue, and water and place them into a high-temperature pressure device.

[0008] S2. When oxygen-containing gas is introduced or an oxidant is added, red mud and coal or coal gangue undergo mineral decomposition and reconstruction under high temperature and high pressure conditions. The acidic substances produced by the oxidation of sulfide minerals and carbon-based minerals in coal or coal gangue react with the alkaline substances in red mud.

[0009] S3. The reaction products of red mud and coal or coal gangue are desalinated and used as ecological substrate soil.

[0010] Among them, coal refers to peat, lignite, bituminous coal, anthracite, washed gangue, and tunneling gangue containing coal-like components.

[0011] Preferably, in step S1, the mass ratio of red mud to coal or coal gangue is 1:0.03~50, and the amount of water added is 0.3 to 10 times the total volume of solids.

[0012] Preferably, the amount of oxygen-containing gas or oxidant added in step S2 is 1% to 50% of the carbon content of the solid material.

[0013] Preferably, in step S2, the introduction of oxygen-containing gas or the addition of an oxidant can be done in a single addition, multiple additions, or continuous addition.

[0014] Preferably, the high temperature and high pressure conditions in step S2 are specifically controlled at a temperature of 100℃~380℃ and a pressure of 0.1Mpa~20Mpa.

[0015] Preferably, the oxygen-containing gas is air, oxygen-enriched gas, or ozone, and the oxidant is sodium oxide, potassium oxide, calcium oxide, hydrogen peroxide, or persulfate.

[0016] Preferably, the red mud is one or more of the Bayer process red mud, sintering process red mud, and combined process red mud.

[0017] The principle of this invention is as follows: (1) In a supercritical / subcritical environment, minerals such as nepheline in red mud undergo mineral decomposition, releasing a large amount of alkaline substances; (2) In a high-temperature, high-pressure, and aerobic environment, carbon-based minerals (containing carbon components) in coal or coal gangue undergo oxidative decomposition, transforming into humic acid substances such as humin, humic acid, and fulvic acid, which have certain acidic functional groups; (3) In a high-temperature, high-pressure, and aerobic environment, sulfide minerals in coal or coal gangue undergo oxidative decomposition, transforming into acidic substances such as sulfuric acid and sulfurous acid; (4) Red mud and coal or coal gangue are separately or mixed, and mineral decomposition and reconstruction and acid-base neutralization are carried out under high-temperature and high-pressure conditions to achieve rapid dealkalization of red mud and humic transformation of coal or coal gangue. The reaction products have good soil properties.

[0018] The beneficial effects of this invention are as follows: This invention accelerates the decomposition and alkali release of alkaline minerals such as nepheline in red mud through high temperature and high pressure, and accelerates the oxidation of carbon-based minerals and sulfide minerals in coal or coal gangue, as well as the transformation of humic substances / humic acids, etc., by neutralizing the alkaline and acidic substances (including humic acids, small molecule organic acids, sulfuric acid, etc.) produced in the reaction. This achieves rapid dealkalization of red mud and controls the degree of oxidation of carbon-based minerals to increase the organic matter content in the reaction products. Through desalination, organic components such as sodium salts are recovered, and the soil properties of the reaction products are improved. The reaction products can be used as ecological restoration substrate soil, thereby realizing the full resource utilization and ecological utilization of red mud and coal or coal gangue. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0020] Example 1

[0021] The method for high-temperature and high-pressure co-processing of red mud with coal or coal gangue in this embodiment includes the following steps:

[0022] S1. Bayer red mud, anthracite, and water are mixed and placed into a high-temperature pressure device. The mass ratio of Bayer red mud to anthracite is 1:0.03, and the amount of water added is 0.3 times the total volume of solids.

[0023] S2. Air is introduced continuously, with the amount of air being 1% of the carbon content of the solid material. Bayer red mud and anthracite undergo mineral decomposition and reconstruction under high temperature and high pressure conditions. The acidic substances produced by the oxidation of sulfide minerals and carbon-based minerals in the anthracite react with the alkaline substances in the red mud. The temperature is controlled at 100℃ and the pressure is controlled at 0.1 MPa.

[0024] S3. After desalination of the reaction products of red mud and coal or coal gangue, the pH of the reaction products is between 5 and 9, and the organic matter content is between 1% and 8%, which meets the standard of sandy soil and can be used as soil for ecological restoration.

[0025] Example 2

[0026] The method for high-temperature and high-pressure co-processing of red mud with coal or coal gangue in this embodiment is based on Example 1, but differs from Example 1 in the following ways: In step S1, the red mud is sintered red mud, bituminous coal is selected, the mass ratio of sintered red mud to bituminous coal is 1:5, and the amount of water added is equal to the total volume of solids; In step S2, oxygen-enriched gas is introduced in a one-time addition manner, the gas volume is 10% of the carbon content of the solid material, the temperature is controlled at 200℃, and the pressure is controlled at 5 MPa; The pH of the reaction product is between 5 and 9, and the organic matter content is between 1% and 8%.

[0027] Example 3

[0028] The method for high-temperature and high-pressure co-processing of red mud with coal or coal gangue in this embodiment is based on Example 1, but differs from Example 1 in the following ways: In step S1, the red mud is combined red mud, and coal gangue is selected. The mass ratio of combined red mud to coal gangue is 1:20, and the amount of water added is twice the total volume of solids. In step S2, sodium oxide is added in multiple additions. The sodium oxide contains 20% of the carbon content of the solid matter. The temperature is controlled at 300℃, and the pressure is controlled at 10 MPa. The pH of the reaction product is between 5 and 9, and the organic matter content is between 1% and 8%, meeting the clay standard and suitable for use as landscaping soil.

[0029] Example 4

[0030] The method for high-temperature and high-pressure co-processing of red mud with coal or coal gangue in this embodiment is based on Example 1, but differs from Example 1 in the following ways: In step S1, the red mud is a mixture of Bayer process red mud, sintered process red mud, and combined process red mud in a mass ratio of 1:1:1. The coal is a mixture of peat and lignite in a mass ratio of 1:1. The mass ratio of red mud to coal is 1:35. The amount of water added is 5 times the total volume of solids. In step S2, hydrogen peroxide is introduced in a one-time addition manner. The amount of hydrogen peroxide is 40% of the carbon content of the solid matter. The temperature is controlled at 350℃ and the pressure is controlled at 15 MPa. The pH of the reaction product is between 5 and 9, and the organic matter content is between 1% and 8%, meeting the loam standard and suitable for use as soil for economic crops.

[0031] Example 5

[0032] The method for high-temperature and high-pressure co-processing of red mud with coal or coal gangue in this embodiment is based on Example 1, but differs from Example 1 in the following ways: In step S1, the red mud is a mixture of Bayer process red mud, sintered process red mud, and combined process red mud in a mass ratio of 1:1:1. The selected coal mixture is a mixture of peat, lignite, bituminous coal, anthracite, washed gangue, and tunneling gangue in a mass ratio of 1:1:1:1:1:1. The mass ratio of red mud to the coal mixture is 1:50, and the amount of water added is 10 times the total volume of solids. In step S2, persulfate is introduced in a one-time addition manner. The persulfate contains 50% of the carbon content of the solid matter. The temperature is controlled at 380℃, and the pressure is controlled at 20 MPa. The pH of the reaction product is between 5 and 9, and the organic matter content is between 1% and 8%, meeting the requirements for sandy soil, which can be used as landscaping soil.

[0033] Example 6

[0034] The method for high-temperature and high-pressure co-processing of red mud with coal or coal gangue in this embodiment is based on Example 1, but differs from Example 1 in the following ways: In step S1, the mass ratio of Bayer process red mud to anthracite is 1:25.015, and the amount of water added is 5.15 times the total volume of solids; in step S2, the air volume is 25.5% of the carbon content of the solid material, the temperature is controlled at 240℃, and the pressure is controlled at 10 MPa; the pH of the reaction product is between 5 and 9, and the organic matter content is between 1% and 8%, meeting the requirements for loam and can be used as soil for ecological restoration.

Claims

1. A method for the high-temperature and high-pressure synergistic treatment of red mud and coal or coal gangue, characterized in that... Includes the following steps: S1. Mix red mud, coal or coal gangue, and water and place them into a high-temperature pressure device; the mass ratio of red mud to coal or coal gangue is 1:0.03~50, and the amount of water added is 0.3 times to 10 times the total volume of solids. S2. Introduce oxygen-containing gas or add an oxidant, the amount of which is 1% to 50% of the carbon content of the solid material. Under high temperature and high pressure conditions, red mud and coal or coal gangue undergo mineral decomposition and reconstruction. The acidic substances produced by the oxidation of sulfide minerals and carbon-based minerals in coal or coal gangue react with the alkaline substances in red mud. The amount of which is added is 1% to 50% of the carbon content of the solid material. The specific high temperature and high pressure conditions are: temperature controlled at 100℃ to 380℃, and pressure controlled at 0.1 MPa to 20 MPa. S3. After desalination of the reaction products of red mud and coal or coal gangue, the pH of the reaction products is between 5 and 9, and the organic matter content is between 1% and 8%, which can be used as ecological matrix soil.

2. The method for high-temperature and high-pressure synergistic treatment of red mud and coal or coal gangue according to claim 1, characterized in that... In step S2, oxygen-containing gas or oxidant can be introduced in a single, multiple, or continuous manner.

3. The method for high-temperature and high-pressure synergistic treatment of red mud and coal or coal gangue according to claim 1, characterized in that... The oxygen-containing gas is air, oxygen-enriched gas, or ozone, and the oxidant is sodium oxide, potassium oxide, calcium oxide, hydrogen peroxide, or persulfate.

4. The method for high-temperature and high-pressure synergistic treatment of red mud and coal or coal gangue according to claim 1, characterized in that... The red mud is one or more of the Bayer process red mud, sintering process red mud, and combined process red mud.