Method for producing high-purity carbon dioxide with low energy consumption

Abstract

The invention provides a method for producing high-purity carbon dioxide with low energy consumption, and belongs to the technical field of carbon dioxide preparation. The process comprises the following steps: S1, carrying out cleaning pretreatment on limestone, and then sequentially carrying out drying, crushing and microwave treatment to obtain a limestone primary material; s2, mixing the limestone to-be-sintered material, sodium carbonate and sodium silicate, and spraying and wetting to obtain the limestone to-be-sintered material; s3, putting the limestone to-be-sintered material into a calcining furnace, introducing combustion-supporting gas into the calcining furnace until air is exhausted, calcining for 0.8-1.2 hours, and collecting carbon dioxide; continuing to introduce the combustion-supporting gas until air is exhausted, then calcining for 0.8-1.2 hours, and collecting carbon dioxide; s4, the collected carbon dioxide is subjected to heat exchange through a heat exchanger, cooling and dust removal through a sprayer, molecular sieve absorption, membrane filtration and compression storage in sequence, and the high-purity carbon dioxide is obtained. The process method disclosed by the invention is low in energy consumption, short in preparation time and thorough in limestone decomposition, almost does not generate other gases such as NOx and SOx, and the prepared carbon dioxide is high in purity.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon dioxide preparation, and in particular relates to a method for producing high-purity carbon dioxide with low energy consumption. Background Art

[0002] Calcium carbonate is an important inorganic chemical raw material with a history of industrial development of more than a hundred years. As a high-quality filler and white pigment, calcium carbonate is widely used in composite material filling in the fields of chemical industry, metallurgy, building materials, electronics, light industry, medicine, agriculture, etc. The real value of calcium carbonate application is its deep-processed products. The demand for scale, refinement, functionality and diversification of calcium carbonate products has led to the rapid development of calcium carbonate products in the direction of ultra-fine, ultra-purification, surface modification and composite, making it have both filling and reinforcing properties. The calcination of calcium carbonate to obtain products such as carbon dioxide and quicklime is one of its important research directions.

[0003] Regarding the production of food-grade carbon dioxide from calcium carbonate, the calcined limestone method is usually used for large-scale production of industrial-grade carbon dioxide. Through fine control and subsequent purification treatment, carbon dioxide that meets food-grade standards can also be produced. The main step is calcination at high temperature to decompose into calcium oxide and carbon dioxide gas. Subsequently, the generated carbon dioxide gas is cooled, washed, dried, and compressed to remove impurities and meet food-grade standards. In actual production, the calcination temperature should be controlled at around 1050°C to ensure that the limestone can be fully decomposed while avoiding overburning to ensure the quality of the lime. However, the current use of calcium carbonate to produce food-grade carbon dioxide has the disadvantages of high energy consumption, incomplete decomposition of calcium carbonate, and easy generation of impurity gases (such as NO x ), low purity of carbon dioxide and other problems.

[0004] Therefore, there is an urgent need for a method for producing high-purity carbon dioxide with low energy consumption and simple and easy operation. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for producing high-purity carbon dioxide with low energy consumption. The process of the present invention has low energy consumption, short preparation time, complete decomposition of limestone, and almost no production of other gases such as NO x 、SO x The carbon dioxide produced is of high purity.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for producing high-purity carbon dioxide with low energy consumption, comprising the following steps:

[0008] S1. After the limestone is cleaned and pretreated, it is dried, crushed, and microwaved to obtain the limestone raw material;

[0009] S2. The limestone material to be burned, sodium carbonate, sodium silicate was mixed and sprayed to obtain limestone material to be burned;

[0010] S3. The limestone material to be burned is placed in a calciner and then passed through a combustion-supporting gas in the calciner until the air is exhausted for calcination, and then calcined for 0.8-1.2h to collect carbon dioxide; continue to pass through a combustion-supporting gas until the air is exhausted and then calcined for 0.8-1.2h to collect carbon dioxide;

[0011] S4. The collected carbon dioxide is sequentially subjected to heat exchange by a heat exchanger, cooling and dust removal by a sprayer, absorption by a molecular sieve, membrane filtration, and compression and storage to obtain high-purity carbon dioxide;

[0012] The combustion-supporting gas is a mixture of oxygen and an inert gas in a volume ratio of 3:1-3; the inert gas is helium and / or argon.

[0013] The present invention uses combustion-supporting gas to exhaust air, which can reduce the impurity gas NO x The production of carbon dioxide is reduced during the production process. Collecting carbon dioxide to reduce the concentration of carbon dioxide helps the reaction proceed in the forward direction, improves the reaction efficiency, and reduces the calcination time; Helium and argon mixed with oxygen as limestone calcination gas can reduce the generation of pollutant gases. This mixed gas can improve the combustion efficiency. At the same time, due to the chemical inertness of helium and argon, it can reduce the generation of harmful substances such as nitrogen oxides that may be produced when the fuel is burned. In addition, the high thermal conductivity of helium and argon helps to increase the calcination temperature, thereby accelerating the decomposition process of limestone and improving production efficiency.

[0014] Preferably, the cleaning pretreatment in S1 is water washing followed by impurity removal.

[0015] Preferably, the crushed particle size in S1 is 90-110 mm.

[0016] Preferably, the microwave power of the microwave treatment in S1 is 5-10 kW and the time is 2-5 min.

[0017] The present invention reduces impurities, polluted gases and dust by washing limestone raw materials; crushes the limestone to a certain particle size so that it is evenly heated and decomposed quickly; and microwave treatment increases and enlarges limestone cracks to facilitate subsequent mixing of sintering aids and control of moisture.

[0018] Preferably, the weight ratio of limestone to be burned, sodium carbonate and sodium silicate in S2 is 100:0.5-3:0.5-3. The present invention has found through experiments that sodium carbonate and sodium silicate in this ratio can act as catalysts and sintering aids to reduce calcination temperature and improve reaction effect, which helps to increase reaction progress and reduce calcination temperature.

[0019] Preferably, the spray wetted in S2 is to a moisture content of 0.5-2% in the limestone. In the calcination process of limestone, the presence of water (H2O) has a significant promoting effect on the calcination process. The present invention finds that H2O can promote the decomposition of limestone, which is mainly because water can accelerate the intrinsic speed of the calcination reaction and promote the sintering of CaO, thereby further affecting the calcination process of limestone.

[0020] Preferably, the calcination temperature in S3 is 820-920°C.

[0021] Preferably, the membrane material used in the membrane filtration is cellulose acetate, polysulfone, polyethersulfone, polyacrylate, polyamide or polyimide. The present invention uses membrane filtration technology to separate carbon dioxide and inert gas so that the inert gas can be reused and high-purity carbon dioxide can be obtained.

[0022] Contains at least the following beneficial technical effects:

[0023] 1) The present invention has low energy consumption, short preparation time and complete decomposition of limestone.

[0024] 2) The present invention hardly produces other gases such as NO x 、SO x The carbon dioxide produced is of high purity. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below by specific examples. These examples are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. The test methods in the following examples, unless otherwise specified, are conventional methods. Unless otherwise specified, the reagents and materials used can all be obtained through commercial channels.

[0026] Example 1

[0027] A method for producing high-purity carbon dioxide with low energy consumption comprises the following steps:

[0028] S1. The limestone was washed and dried after impurities removal and then crushed to a particle size of 100 mm by a jaw crusher, and then treated with a microwave at a power of 8 kW for 3 min to obtain a limestone primary material;

[0029] S2. The limestone material to be burned, sodium carbonate, sodium silicate in a weight ratio of 100:0.5:0.5 was mixed and sprayed to wet the water content to reach 1% to obtain limestone material to be burned;

[0030] S3. The limestone material to be burned is placed in a calciner and then a combustion-supporting gas is introduced into the calciner until the air is exhausted and calcined at 820 ° C, and then calcined for 1h to collect carbon dioxide; continue to introduce a combustion-supporting gas until the air is exhausted and then continue to calcine for 1h to collect carbon dioxide;

[0031] S4. The collected carbon dioxide is sequentially subjected to heat exchange by a heat exchanger, cooling and dust removal by a sprayer, absorption by a molecular sieve, filtration by a cellulose acetate membrane, and compression and storage to obtain high-purity carbon dioxide;

[0032] The combustion-supporting gas is a mixture of oxygen and inert gas in a volume ratio of 3:1; the inert gas is argon.

[0033] Example 2

[0034] A method for producing high-purity carbon dioxide with low energy consumption comprises the following steps:

[0035] S1. The limestone was washed and dried after impurities removal and then crushed to a particle size of 90 mm by a jaw crusher, and then treated with a microwave at a power of 5 kW for 2 min to obtain a limestone primary material;

[0036] S2. The limestone material to be burned, sodium carbonate, sodium silicate in a weight ratio of 100:3:3 was mixed and sprayed to wet the water content to reach 2% to obtain the limestone material to be burned;

[0037] S3. The limestone material to be burned is placed in a calciner and then a combustion-supporting gas is introduced into the calciner until the air is exhausted and calcined at 850 ° C, and then calcined for 0.8h to collect carbon dioxide; continue to introduce a combustion-supporting gas until the air is exhausted and then continue to calcine for 0.8h to collect carbon dioxide;

[0038] S4. The collected carbon dioxide is sequentially subjected to heat exchange in a heat exchanger, cooling and dust removal by a sprayer, absorption by a molecular sieve, filtration by a polyethersulfone membrane, and compression and storage to obtain high-purity carbon dioxide;

[0039] The combustion-supporting gas is a mixture of oxygen and inert gas in a volume ratio of 3:2; the inert gas is helium.

[0040] Example 3

[0041] A method for producing high-purity carbon dioxide with low energy consumption comprises the following steps:

[0042] S1. The limestone was washed and dried after impurities removal and then crushed to a particle size of 110 mm by a jaw crusher, and then treated with a microwave at a power of 10 kW for 5 min to obtain a limestone initial material;

[0043] S2. The limestone material to be burned, sodium carbonate, sodium silicate in a weight ratio of 100:2:1 was mixed and sprayed to wet the water content to reach 0.5% to obtain the limestone material to be burned;

[0044] S3. The limestone material to be burned is placed in a calciner and then a combustion-supporting gas is introduced into the calciner until the air is exhausted and calcined at 920 ° C, and then calcined for 1.2h to collect carbon dioxide; continue to introduce a combustion-supporting gas until the air is exhausted and then continue to calcine for 1.2h to collect carbon dioxide;

[0045] S4. The collected carbon dioxide is sequentially subjected to heat exchange by a heat exchanger, cooling and dust removal by a sprayer, absorption by a molecular sieve, filtration by a polyacrylate membrane, and compression and storage to obtain high-purity carbon dioxide;

[0046] The combustion-supporting gas is a mixture of oxygen and an inert gas in a volume ratio of 3:1; the inert gas is helium.

[0047] Comparative Example 1

[0048] The preparation method of this comparative example is the same as that of the embodiment, except that microwave treatment is not performed in step S1.

[0049] Comparative Example 2

[0050] The preparation method of this comparative example is the same as that of the embodiment, except that sodium carbonate and sodium silicate are not added in step S2.

[0051] Comparative Example 3

[0052] The preparation method of this comparative example is the same as that of the embodiment, except that no water is added in step S2.

[0053] Comparative Example 4

[0054] The preparation method of this comparative example is the same as that of the embodiment, except that a one-step calcination method is used in step S3, and the calcination time is 2.4 h.

[0055] Comparative Example 5

[0056] Carbon dioxide was prepared by conventional calcining of limestone: the limestone was calcined in a rotary kiln at 1050°C for 2h, 4h and 8h respectively, and the carbon dioxide was separated and collected.

[0057] Comparative Example 6

[0058] Carbon dioxide is prepared by conventional calcining of limestone: the limestone is calcined in a rotary kiln at 850°C, 950°C and 1050°C for 8 hours, and the carbon dioxide is separated and collected.

[0059] Experimental Example 1

[0060] Carbon dioxide production detection

[0061] The theoretical output of carbon dioxide is calculated based on the mass of limestone and the content of calcium carbonate, and the yield is calculated based on the theoretical output: (actual output / theoretical output)*100%=yield. The test results are shown in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] It can be seen from Table 1 that the process method of the present invention has a short calcination time and a low calcination temperature, CO2 has a high yield, and has the advantages of energy saving and environmental protection.

[0066] Experimental Example 2

[0067] Example 1 and Comparative Example 5, 8h calcination time; after the initial collection of carbon dioxide, the NO in it was directly detected without purification and separation treatment. x and SO x content;

[0068] After testing the NO in Example 1 x and SO x The content is 1.1mg / m 3 , 0.4mg / m 3 ; Comparative Example 5, 8h calcination time NO x and SO x The content is 107mg / m 3 , 12mg / m 3 .

[0069] The process of the present invention significantly reduces NO x and SO x The production of carbon dioxide indirectly indicates that the subsequent separation is simple and easy to obtain high-purity carbon dioxide.

[0070] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing high-purity carbon dioxide with low energy consumption, characterized in that: The following steps are involved: S1. After the limestone is cleaned and pretreated, it is dried, crushed, and microwaved to obtain the limestone raw material; S2. The limestone material to be burned, sodium carbonate, sodium silicate was mixed and sprayed to obtain limestone material to be burned; S3. The limestone material to be burned is placed in a calciner and then passed through a combustion-supporting gas in the calciner until the air is exhausted for calcination, and then calcined for 0.8-1.2h to collect carbon dioxide; continue to pass through a combustion-supporting gas until the air is exhausted and then calcined for 0.8-1.2h to collect carbon dioxide; S4. The collected carbon dioxide is sequentially subjected to heat exchange by a heat exchanger, cooling and dust removal by a sprayer, absorption by a molecular sieve, membrane filtration, and compression and storage to obtain high-purity carbon dioxide; The combustion-supporting gas is a mixture of oxygen and an inert gas in a volume ratio of 3:1-3; the inert gas is helium and / or argon.

2. The method according to claim 1, characterized in that The cleaning pretreatment in S1 is water washing after impurity removal.

3. The method according to claim 1, characterized in that The crushed particle size in S1 is 90-110 mm.

4. The method according to claim 1, characterized in that The microwave power of the microwave treatment in S1 is 5-10 kW and the time is 2-5 min.

5. The method according to claim 1, characterized in that The weight ratio of the limestone to be burned, sodium carbonate and sodium silicate in S2 is 100:0.5-3:0.5-3.

6. The method according to claim 1, characterized in that The S2 is sprayed and moistened until the moisture content of the limestone reaches 0.5-2%.

7. The method according to claim 1, characterized in that The calcination temperature in S3 is 820-920°C.

8. The method according to claim 1, characterized in that The membrane material used in the membrane filtration is cellulose acetate, polysulfone, polyethersulfone, polyacrylate, polyamide or polyimide.

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