A method for preparing calcium carbonate by using calcium carbide slag-lignite chemical chain gasification slag

Abstract

The application discloses a method for preparing calcium carbonate by using calcium carbide slag-lignite chemical chain gasification slag, belongs to the field of waste slag resource utilization, and has the following steps: uniformly mixing crushed calcium carbide slag and lignite at a mass ratio of 5-20:1, performing lignite chemical chain gasification reaction under anaerobic condition at 500-800 DEG C, obtaining synthesis gas containing hydrogen and carbon monoxide and chemical chain gasification slag after the reaction, introducing CO2 gas into the chemical chain gasification slag, capturing the CO2 gas under the CO2 atmosphere at 500-800 DEG C, and obtaining calcium carbonate products.

Description

Technical Field

[0001] This invention relates to a method for preparing calcium carbonate using carbide slag-lignite chemical loop gasification slag, belonging to the field of waste residue resource utilization. Background Technology

[0002] Lignite, also known as coking coal, is the lowest grade of coal. It is a brownish-black, dull, low-grade coal, falling between peat and bituminous coal. It has high moisture and volatile matter content (mass fraction > 40%), low calorific value, low ash fusion point, and low grindability index, making it a low-rank, inferior coal. Its industrial applications present many problems, such as low calorific value and low energy utilization rate. Therefore, better energy utilization of lignite is imperative. Calcium carbide slag is the waste residue mainly composed of calcium hydroxide after acetylene gas is obtained through electrolytic hydrolysis. With the continuous development of the chlor-alkali industry, the discharge and stockpiling of calcium carbide slag are increasing, causing serious environmental pollution and waste of land and calcium resources. Therefore, the resource utilization of calcium carbide slag is essential.

[0003] In 1983, Richter and Knoche first proposed the concept of chemical looping combustion (CLC) at the American Chemical Society (ACS) meeting. CLC offers advantages such as flameless combustion, low-energy CO2 capture, and the ability to utilize chemical energy in a cascade manner. In recent years, researchers have developed chemical looping gasification (CLG) technology based on CLC. Both CLG and CLC utilize an oxygen carrier to provide lattice oxygen to the fuel for conversion. However, CLG involves incomplete fuel conversion, with its product being syngas, primarily composed of CO and H2. The main reaction principle of CLG is as follows: in a reduction furnace, the fuel undergoes a redox reaction with the oxygen carrier, causing the oxygen carrier to lose oxygen and produce Me. x O y-1 The fuel is oxidized into gases such as H2 and CO; in the oxidation furnace, the reduced Me x O y-1 The oxygen carrier is regenerated through reaction with air. Since chemical looping gasification technology mainly relies on the interaction between the oxygen carrier and the fuel, the oxygen carrier is an essential participant in the chemical looping gasification process.

[0004] There are currently no reports on the resource utilization of carbide slag-lignite chemical chain gasification slag. The preparation of calcium carbonate from the chain gasification slag obtained after carbide slag-lignite chemical chain gasification provides a new approach for CO2 capture and the resource utilization of chain gasification slag. Summary of the Invention

[0005] To address the resource utilization issues of lignite and carbide slag in existing technologies, this invention provides a method for preparing calcium carbonate using carbide slag-lignite chemical looping gasification slag. This invention uses lignite as fuel and carbide slag as oxygen carrier, obtaining gas slag through chemical looping gasification, and then using the gasification slag to prepare calcium carbonate, thus realizing the resource utilization of the looping gasification slag. Specifically, it utilizes carbide slag to promote the lignite gasification reaction under anaerobic conditions to generate gasification slag, which is then purged with CO2 gas to prepare CaCO3, and the CO2 is captured.

[0006] This invention relates to a method for preparing calcium carbonate using carbide slag-lignite chemical looping gasification slag, the specific steps of which are as follows:

[0007] (1) Crush and sieve the carbide slag and lignite separately. Mix the carbide slag and lignite evenly according to the mass ratio of carbide slag to lignite of 5~20:1. Then keep it at 500~800℃ under oxygen-free conditions for 2~4 hours to obtain syngas containing hydrogen and carbon monoxide and chemical looping gasification slag.

[0008] (2) CO2 gas is introduced into the chemical loop gasification slag and kept at 500~800℃ for 1~4 hours to obtain CaCO3 solid and achieve CO2 gas capture.

[0009] The beneficial effects of this invention are as follows:

[0010] (1) Since carbide slag contains Al2O3, Fe2O3 and SiO2, Fe2O3 / Al2O3 and Fe2O3 / Al2O3 can be used as excellent oxygen carriers in the chemical chain gasification process of lignite. This invention uses carbide slag oxygen carrier and lignite to calcine under anaerobic conditions to achieve efficient chemical chain gasification of lignite, co-produce gasification slag containing Ca, and realize the cascade utilization of lignite chemical gasification energy.

[0011] (2) This invention uses chemical chain gasification slag as raw material to achieve the generation of CaCO3 and the efficient capture of CO2 gas. The solid CaCO3 can be used as an additive in the food industry, and can also be used in the construction and paper industries to realize the resource utilization of waste.

[0012] (3) This invention simultaneously realizes the resource utilization of lignite and the full-scale deep resource utilization of carbide slag. Attached Figure Description

[0013] Figure 1 The XRD pattern of chemical looping gasification slag in this embodiment of the invention;

[0014] Figure 2 The image shows the XRD pattern of the CaCO3 solid obtained in Example 1 of this invention. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described. In the embodiments, the calcium carbide slag comes from a chemical plant in Yunnan Province, and the lignite comes from a coal mine in Yunnan Province.

[0016] Example 1: The method for preparing calcium carbonate using carbide slag-lignite chemical looping gasification slag is as follows:

[0017] (1) The calcium carbide slag and lignite were crushed, ground, and passed through an 80-mesh sieve. The calcium carbide slag and lignite were mixed evenly at a mass ratio of 20:1. After deoxygenation, the mixture was calcined at 650℃ under anaerobic conditions for 2 hours to obtain syngas containing hydrogen and carbon monoxide and solid chemical looping gasification slag. The calcium hydroxide content in the chemical looping gasification slag was detected according to the method in "GB 25572-2010 National Food Safety Standard for Food Additives Calcium Hydroxide". The decomposition rate of the calcium carbide slag was calculated by the following formula, and the result was that the decomposition rate of the calcium carbide slag was 100%. The XRD pattern of the chemical looping gasification slag is shown in [reference needed]. Figure 1 ,from Figure 1 It can be seen that the main component of the reaction product is CaO, and no diffraction peak of Ca(OH)2 was found;

[0018] ;

[0019] (2) The chemical loop gasification slag was purged with CO2 gas at a flow rate of 100 mL / min and calcined at 500 °C under a CO2 atmosphere for 3 h to obtain CaCO3. The concentration of carbonate ions in the reaction slag was determined according to the method in GB / T19281-2014, thus obtaining CaCO3 with a purity of 95.10% in the product; The XRD pattern of the product in step (2) is shown in [reference needed]. Figure 2 ,from Figure 2 It can be seen that the reaction product is entirely CaCO3, and no diffraction peaks of CaO were found.

[0020] Example 2: The method for preparing calcium carbonate using carbide slag-lignite chemical looping gasification slag is as follows:

[0021] (1) The calcium carbide slag and lignite were crushed and ground separately and passed through an 80-mesh sieve. The calcium carbide slag and lignite were mixed evenly at a mass ratio of 10:1. After deoxygenation, the mixture was calcined at 550℃ under anaerobic conditions for 4 hours to obtain syngas containing hydrogen and carbon monoxide and solid chemical looping gasification slag. The decomposition rate of calcium carbide slag was 100%.

[0022] (2) The chemical loop gasification slag was purged with CO2 gas at a flow rate of 100 mL / min and calcined at 650 °C under CO2 atmosphere for 2 h to obtain CaCO3 product with a purity of 90.09%.

[0023] Example 3: The method for preparing calcium carbonate using carbide slag-lignite chemical looping gasification slag is as follows:

[0024] (1) The calcium carbide slag and lignite were crushed and ground separately and passed through an 80-mesh sieve. The calcium carbide slag and lignite were mixed evenly at a mass ratio of 15:1. After deoxygenation, the mixture was calcined at 600℃ under anaerobic conditions for 4 hours to obtain syngas containing hydrogen and carbon monoxide and solid chemical looping gasification slag. The decomposition rate of calcium carbide slag was 100%.

[0025] (2) The chemical loop gasification slag was purged with CO2 gas at a flow rate of 100 mL / min and calcined at 800 °C under CO2 atmosphere for 1 h to obtain CaCO3 product with a purity of 95.43%.

[0026] Example 4: The method for preparing calcium carbonate using carbide slag-lignite chemical looping gasification slag is as follows:

[0027] (1) The calcium carbide slag and lignite were crushed and ground separately and passed through an 80-mesh sieve. The calcium carbide slag and lignite were mixed evenly at a mass ratio of 10:1. After deoxygenation, the mixture was calcined at 750℃ under anaerobic conditions for 2.5 hours to obtain syngas containing hydrogen and carbon monoxide and solid chemical looping gasification slag. The decomposition rate of calcium carbide slag was 100%.

[0028] (2) The chemical loop gasification slag was purged with CO2 gas at a flow rate of 100 mL / min and calcined at 750 °C under CO2 atmosphere for 2 h to obtain CaCO3 product with a purity of 93.43%.

[0029] Example 5: The method for preparing calcium carbonate using carbide slag-lignite chemical looping gasification slag is as follows:

[0030] (1) The calcium carbide slag and lignite were crushed and ground separately and passed through an 80-mesh sieve. The calcium carbide slag and lignite were mixed evenly at a mass ratio of 5:1. After deoxygenation, the mixture was calcined at 650℃ under anaerobic conditions for 3 hours to obtain syngas containing hydrogen and carbon monoxide and solid chemical looping gasification slag. The decomposition rate of calcium carbide slag was 100%.

[0031] (2) The chemical loop gasification slag was purged with CO2 gas at a flow rate of 100 mL / min and calcined at 500 °C under CO2 atmosphere for 3 h to obtain CaCO3 product with a purity of 90.42%.

Claims

1. A method for producing calcium carbonate from carbide slag-brown coal chemical looping gasification slag, characterized by: The pulverized carbide slag and the lignite are mixed uniformly, and the lignite chemical chain gasification reaction is carried out under the condition of no oxygen and at 500-800 DEG C; after the reaction, synthesis gas containing hydrogen and carbon monoxide and chemical chain gasification slag are obtained; CO2 gas is introduced into the chemical chain gasification slag, and the CO2 gas is captured under the condition of 500-800 DEG C and CO2 atmosphere, and calcium carbonate product is obtained; wherein the carbide slag and the lignite are mixed at a mass ratio of 5-20:1.

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