Method for enriching carbon dioxide and hydrogen by water-gas shift coupling of blast furnace gas

Abstract

A method for enriching carbon dioxide and hydrogen by water-gas shift coupling of blast furnace gas is disclosed in the present application, belonging to the technical field of flue gas resource utilization, where the method includes: purifying the blast furnace gas by a dry purification method, followed by heating and mixing with water vapor, allowing for water vapor shift coupling reaction under an action of a catalyst to obtain a mixed gas of carbon dioxide and hydrogen; adsorbing the mixed gas of carbon dioxide and hydrogen with a carbon dioxide adsorbent and desorbing to obtain carbon dioxide; introducing a gas not adsorbed by the carbon dioxide adsorbent into a molecular sieve adsorbent to remove impurities, then obtaining a hydrogen. Blast furnace gas is used as raw material, and hydrogen is provided for subsequent hydrogen smelting while realizing carbon enrichment in the blast furnace process.

Claims

1. A method for enriching carbon dioxide and hydrogen by water-gas shift coupling of blast furnace gas, comprising following steps: purifying the blast furnace gas by a dry purification method, followed by heating and mixing with water gas, allowing for a water-gas shift coupling reaction under an action of a catalyst to obtain a mixed gas of the carbon dioxide and hydrogen; wherein components of the blast furnace gas comprise 15-30 vol. % CO.sub.2, 15-30 vol. % CO, 0.1-5 vol. % H.sub.2, 30-60 vol. % N.sub.2, 0-1.5 vol. % O.sub.2, 20-200 mg/m.sup.3 H.sub.2S, 20-160 mg/m.sup.3 COS, 2-6 vol. % water gas, 5-20 mg/m.sup.3 HCl, and 0.2-0.4 vol. % CH.sub.4; and the dry purification method is performed with a multilayer composite adsorbent that consists of alkali-modified activated carbon, molecular sieve and alumina; wherein the mass ratio of alkali-modified activated carbon:molecular sieve:alumina is (3-5):(3-5):2; wherein the blast furnace gas after purification has a concentration of 20 vol. % CO.sub.2, 25 vol. % CO, and 3 vol. % H.sub.2; a temperature of the blast furnace gas after purification is 160-220 C., a pressure is 0.18-0.3 MPa, and a temperature of the heating is 320-400 C.; the catalyst is an iron-based catalyst; and a space velocity of the water-gas shift coupling reaction is 400-1200 h.sup.1; and after the water-gas shift coupling reaction, the water-gas shift coupling reaction is carried out again; and a temperature for carrying out the water-gas shift coupling reaction again is 200-250 C., with a catalyst of a copper-based catalyst, and a space velocity of 2000-3600 h.sup.1.

2. The method according to claim 1, further comprising separating and purifying the mixed gas of carbon dioxide and hydrogen by adsorbing the mixed gas of carbon dioxide and hydrogen with a carbon dioxide adsorbent and desorbing to obtain carbon dioxide; introducing a gas not adsorbed by the carbon dioxide adsorbent into a molecular sieve adsorbent to remove impurities, then obtaining a hydrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to explain the embodiments of the present application or the technical scheme in the prior art more clearly, the drawings needed in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings may be obtained according to these drawings without creative work for ordinary people in the field.

(2) FIG. 1 is a schematic diagram of the process for enriching and purifying carbon dioxide and hydrogen by CO water-gas shift coupling of blast furnace gas of the present application.

(3) FIG. 2 is a schematic structural diagram of a device for enriching and purifying carbon dioxide and hydrogen by CO water-gas shift coupling of blast furnace gas.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) A number of exemplary embodiments of the present application are now described in detail, and this detailed description should not be considered as a limitation of the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

(5) It should be understood that the terminology described in the present application is only for describing specific embodiments and is not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. The intermediate value within any stated value or stated range and every smaller range between any other stated value or intermediate value within the stated range are also included in the present application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

(6) Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application relates. Although the present application only describes the preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and/or materials related to the documents. In case of conflict with any incorporated document, the contents of this specification shall prevail.

(7) It is obvious to those skilled in the art that many improvements and changes may be made to the specific embodiments of the present application without departing from the scope or spirit of the present application. Other embodiments will be apparent to the skilled person from the description of the application. The specification and embodiments of this application are only exemplary.

(8) The terms including, comprising, having and containing used in this specification are all open terms, which means including but not limited to.

(9) The blast furnace gas treated in the following embodiments of the present application consists of 15-30 vol. % CO.sub.2, 15-30 vol. % Co, 0.1-5 vol. % H.sub.2, 30-60 vol. % N.sub.2, 0-1.5 vol. % O.sub.2, 20-200 mg/m.sup.3 H.sub.2S and 20-160 mg/m.sup.3 COS, 2-6 vol. % water vapor, 5-20 mg/m.sup.3 HCl, and 0.2-0.4 vol. % CH.sub.4.

(10) FIG. 1 is a schematic diagram illustrating the process of CO water-gas shift coupling enrichment and purification of carbon dioxide and hydrogen in blast furnace gas of the present application.

(11) The structural schematic diagram of the device for enriching and purifying carbon dioxide and hydrogen by CO water-gas shift coupling of blast furnace gas is shown in FIG. 2. The device for enriching and purifying carbon dioxide and hydrogen by CO water-gas shift coupling of blast furnace gas includes a gas compressor 1, a gas-water separator 2, a gas pretreatment tower 3, a first-stage adiabatic shift furnace 4, a water vapor generator 5, a second-stage adiabatic shift furnace 6, a residual heat and pressure turbine generator 7, a gas-water separator 8, a CO.sub.2 adsorption tower 9, a vacuum pump 10, a compressor 11, a CO.sub.2 storage tank 12, a hydrogen extraction tower 13, and a H.sub.2 storage tank 14.

Embodiment 1

(12) A method for enriching and purifying carbon dioxide and hydrogen by CO water-gas shift coupling of blast furnace gas: the compositions of blast furnace gas are: 20 vol. % CO.sub.2, 25 vol. % CO, 3% H.sub.2, 45 vol. % N.sub.2, 0.2 vol. % O.sub.2, 150 mg/m.sup.3 H.sub.2S, 100 mg/m.sup.3 COS, 6 vol. % water vapor, 10 mg/m.sup.3 HCl and 0.3 vol. % CH.sub.4.

(13) (1) Purification of the blast furnace gas by a blast furnace gas purification unit: after being discharged from the top of the blast furnace, the blast furnace gas is dedusted and cooled by gravity dust removal and bag dust removal, the pressure after dedusting and cooling is 0.18 MPa, and the pressure is increased to 2.5 MPa by the gas compressor 1, then the gas enters the gas pretreatment tower 3 for purification after passing through the gas-water separator 2, and the gas pretreatment tower 3 adopts a dry purification method and is filled with multilayer composite adsorbents (the components of multilayer composite adsorbents are alkali-modified activated carbon, molecular sieve and alumina with a mass ratio of 4:4:2), HCl, COS and H.sub.2S in the gas components are removed (fine desulfurization) to obtain purified blast furnace gas (with temperature of 180 C. and pressure of 2.5 MPa), where the pretreatment tower is equipped with oxygen-containing gas purging.

(14) The concentrations of COS, H.sub.2S and HCl at the inlet of gas pretreatment tower 3 are 150 mg/Nm.sup.3, 100 mg/Nm.sup.3 and 10 mg/Nm.sup.3, respectively. After purification, the concentrations of COS, H.sub.2S and HCl at the outlet are reduced to below 5 mg/Nm.sup.3, 5 mg/Nm.sup.3 and 1 mg/Nm.sup.3, respectively, and the concentrations of CO.sub.2, CO and H.sub.2 in the purified gas are 20 vol. %, 25 vol. % and 3 vol. %, respectively.

(15) (2) Shift reaction between gas CO and water vapor using a CO water-gas shift (WGS) reaction unit: the purified blast furnace gas is heated to 350 C. through a heat exchanger, and the purified blast furnace gas and the water vapor generated by the water vapor generator 5 are subjected to a water vapor shift reaction in the first-stage adiabatic shift furnace 4 to generate CO.sub.2 and H.sub.2, and the reaction space velocity is 600 h.sup.1; the iron-based catalyst is adopted, and the components of the outlet gas are converted into CO.sub.2 with a concentration of 30 vol. %, CO with a concentration of 15 vol. %, and H.sub.2 with a concentration of 13 vol. %; after the reaction, the temperature of the gas is reduced to 200-250 C. by heat exchange, and the gas enters the second-stage adiabatic shift furnace 6, where CO in the gas is continuously converted into H.sub.2 and CO.sub.2, and the space velocity is 3000 h.sup.1 by using a copper-based catalyst; the compositions of the outlet gas are adjusted to CO.sub.2 with a concentration of 44 vol. %, CO with a concentration of 0.2 vol. % and H.sub.2 with a concentration of 27 vol. %.

(16) The catalyst beds in the first-stage adiabatic shift furnace 4 and the second-stage adiabatic shift furnace 6 are adiabatic beds, and segmented baffles are arranged in the furnaces to support the catalyst, and a heat exchanger is arranged between the two adiabatic shift furnaces to recover excess reaction latent heat.

(17) (3) Enrichment of CO.sub.2 by using a pressure swing adsorption separation unit of CO.sub.2: the temperature of the converted gas is reduced to 40 C. and the pressure is reduced to 0.3 MPa through the residual heat and pressure turbine generator 7 (with a turbine power of above 85%), then the gas passes through the gas-water separator 8, and enters the CO.sub.2 adsorption tower 9, where a CO.sub.2 adsorbent (molecular sieve) is filled in the CO.sub.2 adsorption tower 9, and the bottom of the CO.sub.2 adsorption tower 9 is provided with an alumina layer to adsorb low-concentration water vapor in the gas. After the adsorption tower is saturated, CO.sub.2 is desorbed from the bottom by the vacuum pump 10 (with a pressure of 20 kPa), and the desorbed CO.sub.2 enters the CO.sub.2 storage tank 12 for temporary storing, and the desorbed CO.sub.2 concentration is 95 vol. %.

(18) The CO.sub.2 adsorption tower 9 is an adsorption device composed of four adsorption towers connected in parallel, and CO.sub.2 enrichment is completed according to the operation steps of boosting, adsorption, pressure equalization, desorption, purging, etc. The pressure equalizing times of the adsorption tower may be set to two times.

(19) (4) Enrichment of H.sub.2 by using H.sub.2 pressure swing adsorption purification unit: the gas not adsorbed at the top of CO.sub.2 adsorption tower is mainly composed of H.sub.2 with a concentration of 48 vol. %, and the rest is N.sub.2 and a small amount of CO and CH.sub.4. The gas is pressurized to 4 MPa by compressor 11, and enters into hydrogen extraction tower 13, which is filled with deoxidizer, CO and CH.sub.4 adsorbent (copper modified molecular sieve), and the gas discharged from the top of the tower after adsorption cycle is high concentration H.sub.2 (with a concentration increased to 99 vol. %), which enters the H.sub.2 storage tank 14 for temporary storing, and may be used as a raw material for high-purity hydrogen purification.

(20) The hydrogen extraction tower 13 is provided with three towers connected in parallel, and the number of pressure equalizing is set to three times.

(21) According to the method of this embodiment, the concentrations of CO.sub.2 and H.sub.2 at the inlet of the pressure swing adsorption device are improved through water-gas conversion, and the power consumption required for subsequent gas separation is reduced. Compared with the existing process, the overall energy consumption is reduced by 20%, the purity of CO.sub.2 product gas is 95 vol. %, and the concentration of H.sub.2 reaches 99 vol. %, thus realizing carbon reduction and hydrogen extraction at the same time of gas, with good economic benefits.

(22) The above-mentioned embodiments only describe the preferred mode of the present application, and do not limit the scope of the application. Under the premise of not departing from the design spirit of the application, various modifications and improvements made by ordinary technicians in the field to the technical scheme of the application shall fall within the protection scope determined by the claims of the application.