High-temperature and high-pressure synergistic treatment method for red mud and coal or coal gangue

Abstract

The invention discloses a high-temperature and high-pressure synergistic treatment method for red mud and coal or coal gangue. The method comprises the following steps: mixing red mud, coal or coal gangue and water, and putting the mixture into a high-temperature pressure device; oxygen-containing gas is introduced or an oxidizing agent is added, the red mud and the coal or the coal gangue are subjected to mineral decomposition and reconstruction under the high-temperature and high-pressure conditions, and acidic substances generated by oxidation of sulfide minerals and carbon-based minerals in the coal or the coal gangue and alkaline substances in the red mud are subjected to a neutralization reaction; a reaction product of red mud and coal or coal gangue is desalted to serve as ecological matrix soil. According to the method, decomposition and alkali release of alkaline minerals such as nepheline in the red mud are accelerated through high temperature and high pressure, oxidation of carbon-based minerals and sulfide minerals in coal or coal gangue and conversion of humus / humic acid and the like are accelerated, alkaline substances produced through reaction are neutralized with acidic substances, and rapid dealkalization of the red mud is achieved; and the oxidation degree of the carbon-based minerals is controlled to increase the content of organic matters in a reaction product, so that full-amount resource and ecological utilization of the red mud and the coal or the coal gangue is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste treatment, disposal and resource utilization, and specifically relates to a method for high-temperature and high-pressure coordinated treatment of red mud and coal or coal gangue. Background Art

[0002] Red mud is a major industrial solid waste produced in the production of alumina. It is highly alkaline because it contains a large amount of alkaline minerals such as nepheline and sodalite. Its storage process will slowly release alkaline substances for a long time, causing environmental pollution to the surrounding soil and groundwater. Coal and coal gangue contain many types of mineral components such as carbon-based minerals and sulfide minerals. High-sulfur coal is restricted in its utilization due to environmental protection; coal gangue is classified as a major industrial solid waste due to its low calorific value and high ash content. At present, there is a lack of effective large-scale disposal methods for red mud and coal gangue. There are currently many ways to use gangue and red mud, including building materials, underground filling, extraction of valuable components, storage and landfill, etc. The utilization of gangue as building materials is limited by the economic transportation radius and the demand of the construction market. Filling goaf with gangue requires large investment and affects mining production safety. The extraction of valuable components from gangue has problems such as volume reduction and environmental risks of leached slag after extraction. The above treatments all have problems such as limited absorption capacity and high treatment costs.

[0003] There are four existing red mud disposal methods: (1) submarine discharge, (2) wet storage, (3) dry storage, and (4) ecological restoration. Submarine discharge is greatly restricted by the geographical environment, wet storage has the risk of groundwater pollution and dam failure, dry storage has high dehydration and solidification costs, and ecological restoration currently has problems such as immature technology.

[0004] Therefore, it is very necessary to develop a method for the coordinated treatment of red mud with coal or coal gangue under high temperature and high pressure. Summary of the invention

[0005] The object of the present invention is to provide a method for the coordinated treatment of red mud and coal or coal gangue under high temperature and high pressure.

[0006] The object of the present invention is achieved by comprising the following steps: S1. Mix red mud, coal or coal gangue and water and place them into a high temperature pressure device; S2. Passing oxygen-containing gas or adding oxidant, red mud and coal or coal gangue undergo mineral decomposition and reconstruction under high temperature and high pressure conditions, and acidic substances produced by oxidation of sulfide minerals and carbon-based minerals in coal or coal gangue react with alkaline substances in red mud to neutralize; S3. The reaction products of red mud and coal or coal gangue are desalinated and used as ecological matrix soil.

[0007] Among them, coal refers to peat, lignite, bituminous coal, anthracite, washed gangue, tunneling gangue, etc. containing coal components.

[0008] Preferably, the mass ratio of red mud to coal or coal gangue in step S1 is 1:0.03-50, and the amount of water added is 0.3 to 10 times the total volume of the solids.

[0009] Preferably, the amount of oxygen-containing gas or oxidant added in step S2 is 1% to 50% of the carbon content of the solid matter.

[0010] Preferably, the oxygen-containing gas or oxidant added in step S2 is added once, multiple times or continuously.

[0011] Preferably, the high temperature and high pressure conditions in step S2 are that the temperature is controlled at 100° C. to 380° C., and the pressure is controlled at 0.1 MPa to 20 MPa.

[0012] Preferably, the oxygen-containing gas is air, oxygen-rich gas or ozone, and the oxidant is sodium oxide, potassium oxide, calcium oxide, hydrogen peroxide or persulfate.

[0013] Preferably, the red mud is one or more of Bayer process red mud, sintering process red mud and combined process red mud.

[0014] The principle of the present 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, aerobic environment, carbon-based minerals (carbon-containing components) in coal or coal gangue undergo oxidative decomposition and are converted 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, aerobic environment, sulfide minerals in coal or coal gangue undergo oxidative decomposition and are converted into acidic substances such as sulfuric acid and sulfurous acid; (4) Red mud and coal or coal gangue are separated or mixed, and mineral decomposition, reconstruction and acid-base neutralization are carried out under high-temperature and high-pressure conditions to achieve rapid dealkalization of red mud and humus conversion of coal or coal gangue, and the reaction product has good soil properties.

[0015] Beneficial effects of the present invention: The present invention accelerates the decomposition and alkali release of alkaline minerals such as nepheline in red mud through high temperature and high pressure, accelerates the oxidation of carbon-based minerals and sulfide minerals in coal or coal gangue and the conversion of humus / humic acid, etc. through high temperature and high pressure, neutralizes the alkaline substances and acidic substances (including humic acids, small molecule organic acids, sulfuric acid, etc.) produced by the reaction, realizes the rapid dealkalization of red mud, and controls the oxidation degree of carbon-based minerals to increase the organic matter content in the reaction product; through desalination, organic components such as sodium salt are recovered, and the soil properties of the reaction product are improved, and the reaction product is used as an ecological restoration matrix soil, thereby realizing the full resource and ecological utilization of red mud and coal or coal gangue. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0017] Example 1 The method for co-processing red mud and coal or coal gangue at high temperature and high pressure in this embodiment comprises the following steps: S1. Mixing Bayer process red mud, anthracite and water and placing them into a high temperature pressure device, wherein the mass ratio of Bayer process red mud to anthracite is 1:0.03, and the amount of water added is 0.3 times the total volume of the solids; S2. Air is continuously added, and the amount of air is 1% of the carbon content of the solid matter. The Bayer process 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 to neutralize. The temperature is controlled at 100°C and the pressure is controlled at 0.1Mpa. S3. After desalting the reaction products of red mud and coal or coal gangue, the pH value of the reaction products is between 5-9 and the organic matter content is between 1% and 8%, reaching the sandy soil standard and can be used as soil for ecological restoration.

[0018] Example 2 The method for high temperature and high pressure coordinated treatment of red mud and coal or coal gangue in this embodiment is based on Example 1, and the difference from Example 1 is that: the red mud in step S1 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-rich gas is introduced in a one-time addition manner, the gas amount is 10% of the carbon content of the solid matter, the temperature is controlled at 200°C, and the pressure is controlled at 5Mpa; the pH of the reaction product is between 5-9, and the organic matter content is between 1%-8%.

[0019] Example 3 The method for high-temperature and high-pressure coordinated treatment of red mud and coal or coal gangue in this embodiment is based on Example 1, and the difference from Example 1 is that the red mud in step S1 is combined process red mud, and coal gangue is selected, the mass ratio of combined process red mud to coal gangue is 1:20, and the amount of water added is twice the total volume of the solid; in step S2, sodium oxide is added in a multiple addition manner, and the sodium oxide is 20% of the carbon content of the solid matter, the temperature is controlled at 300°C, and the pressure is controlled at 10Mpa; the pH of the reaction product is between 5-9, and the organic matter content is 1%-8%, which meets the clay standard and can be used as soil for landscaping.

[0020] Example 4 The method for high-temperature and high-pressure coordinated treatment of red mud and coal or coal gangue in this embodiment is based on Example 1, and the difference from Example 1 is that: in step S1, the red mud is a mixture of Bayer process red mud, sintering process red mud, and combined process red mud in a mass ratio of 1:1:1, the coal is peat and lignite mixed in a mass ratio of 1:1, the mass ratio of red mud to coal is 1:35, and the amount of water added is 5 times the total volume of the solid; 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°C, and the pressure is controlled at 15Mpa; the pH of the reaction product is between 5-9, and the organic matter content is 1%-8%, which meets the loam standard and can be used as soil for economic crop planting.

[0021] Example 5 The method for high-temperature and high-pressure coordinated treatment of red mud and coal or coal gangue in this embodiment is based on Example 1, and is different from Example 1 in that: in step S1, the red mud is a mixture of Bayer process red mud, sintering process red mud, and combined process red mud in a mass ratio of 1:1:1, and a mixed coal is selected, specifically peat, lignite, bituminous coal, anthracite, washed gangue, and tunneling gangue are mixed in a mass ratio of 1:1:1:1:1:1, the mass ratio of red mud to the mixed coal is 1:50, and the amount of water added is 10 times the total volume of the solid; in step S2, persulfate is introduced in a one-time addition manner, the persulfate is 50% of the carbon content of the solid matter, the temperature is controlled at 380°C, and the pressure is controlled at 20Mpa; the pH of the reaction product is between 5-9, and the organic matter content is 1%-8%, which meets the requirements of sandy soil and can be used as soil for landscaping.

[0022] Example 6 The method for high temperature and high pressure coordinated treatment of red mud and coal or coal gangue in this embodiment is based on Example 1, and the difference from Example 1 is that: 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 the solid; in step S2, the amount of air is 25.5% of the carbon content of the solid matter, the temperature is controlled at 240°C, and the pressure is controlled at 10Mpa; the pH of the reaction product is between 5-9, and the organic matter content is 1%-8%, which meets the requirements of loam and can be used as soil for ecological restoration.

Claims

1. A method for the coordinated treatment of red mud and coal or coal gangue at high temperature and high pressure, characterized in that The following steps are involved: S1. Mix red mud, coal or coal gangue and water and place them into a high temperature pressure device; S2. Passing oxygen-containing gas or adding oxidant, red mud and coal or coal gangue undergo mineral decomposition and reconstruction under high temperature and high pressure conditions, and acidic substances produced by oxidation of sulfide minerals and carbon-based minerals in coal or coal gangue react with alkaline substances in red mud to neutralize; S3. The reaction products of red mud and coal or coal gangue are desalinated and used as ecological matrix soil.

2. The method for high temperature and high pressure coordinated treatment of red mud and coal or coal gangue according to claim 1, characterized in that 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 0.3-10 times the total volume of the solid.

3. The method for high temperature and high pressure coordinated treatment of red mud and coal or coal gangue according to claim 1, characterized in that The amount of oxygen-containing gas or oxidant added in step S2 is 1% to 50% of the carbon content of the solid matter.

4. The method for high temperature and high pressure coordinated treatment of red mud and coal or coal gangue according to claim 1, characterized in that In step S2, the oxygen-containing gas is introduced or the oxidant is added by one-time addition, multiple additions or continuous addition.

5. The method for high temperature and high pressure coordinated treatment of red mud and coal or coal gangue according to claim 1, characterized in that The high temperature and high pressure conditions in step S2 are specifically that the temperature is controlled at 100°C~380°C, and the pressure is controlled at 0.1Mpa~20Mpa.

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

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