WO2022237528A1 - Quicklime preparation process and system based on carbon emission reduction - Google Patents

Abstract

The present invention belongs to the field of chemical engineering. Disclosed are a quicklime preparation process and system based on carbon emission reduction. Industrial coal gas or natural gas, etc. is used for providing the energy required for calcination, and the properties of a reaction atmosphere are adjusted by means of adjusting the amount of circulating flue gas. After being dried and preheated, gypsum is reduced and calcined by means of a hydrogen-containing reducing gas, wherein the decomposition rate thereof is close to 100%; and whether the calcination product is subjected to CaO upgrading is determined on the basis of the percentage content of CaO in the calcination product, and the yield of CaO after upgrading is also close to 100%. The content of hydrogen atoms in the reducing gas determines the emission reduction amount of CO2 during the technological process. The process not only provides a new, sustainable and pollution-free treatment means for industrial gypsum that is currently difficult to treat, but can also relieve the current situation of the sulfur resource shortage in China, and reduce the external dependency on sulfur resources; in addition, the calcination product, i.e. quicklime, can replace natural limestone as an agent for desulfurization and denitrification. Moreover, the emission of CO2 during the quicklime production process is greatly reduced, which has great significance in carbon emission reduction and carbon neutrality in the industrial process.

Description

A technology and system for quicklime preparation based on carbon emission reduction technical field

The invention belongs to the field of chemical industry, and in particular relates to a quicklime preparation process and system based on carbon emission reduction.

Background technique

The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and is not necessarily taken as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

my country has abundant reserves of gypsum resources, and the proven reserves are about 57 billion tons. Gypsum is also a by-product of the fertilizer industry and various pollutant control systems. Phosphogypsum is a solid waste discharged during the production of phosphate fertilizer and phosphoric acid. The annual discharge of phosphogypsum in my country is about 55 million tons, the comprehensive utilization rate is only about 10 million tons, and the cumulative stacking volume is about 300 million tons. Desulfurization gypsum is a solid waste produced by industrial flue gas desulfurization systems. The annual output of desulfurization gypsum in my country is about 100 million tons.

At present, the total utilization of industrial by-product gypsum in the world is relatively small, and 90% of it is low-end and low-value-added utilization. The utilization rate of phosphogypsum in the United States and Europe is generally lower than 10%, and most of them are stockpiled. At present, the global stockpile of phosphogypsum is about 6 billion tons, and the average annual increase is 150 million tons. The utilization rate of desulfurized gypsum is much higher than that of phosphogypsum, which is basically maintained at about 50% in Europe and China, and most of it is used for basic building materials such as gypsum board. Although the utilization rate of phosphogypsum and desulfurized gypsum in Japan is over 90% (there is a serious lack of natural gypsum sources in Japan), the amount is relatively small, and it is also in low-end low-tech fields such as building materials.

At present, sulfuric acid, sulfur and liquid SO ₂ can be produced by resource utilization for the pollutant SO ₂ in the flue gas. However, the prerequisite for recovering SO _{2 in the flue gas is that the SO 2 in} the flue gas must reach a certain concentration, and the higher the concentration, the more convenient the recovery and the lower the recovery cost.

Quicklime is widely used in metallurgy, environmental protection, fine chemicals, food and other industries. The annual demand for lime in China is about 250 million tons, of which the demand for high-quality, high-activity high-calcium lime is about 100 million tons. The main source of industrial quicklime is calcined limestone. Although China has abundant limestone reserves, over-exploitation has caused serious damage to surface preparation and ecological environment. In addition, the limestone calcination process to produce quicklime will produce a large amount of CO ₂ , about 1.79 tons of limestone is needed to produce 1 ton of quicklime, and about 0.79 tons of CO ₂ are produced. Such a large CO ₂ emission has greatly hindered the progress of carbon emission reduction and carbon neutrality. Therefore, it is urgent to find a quicklime preparation process with low CO ₂ emission or even zero CO ₂ emission.

Contents of the invention

In order to overcome the above problems, the present invention proposes a quicklime preparation process based on carbon reduction by combining the reduction and decomposition process of gypsum, the preparation of CaO by CaS, and the preparation of sulfur by coupling reducing gas with high concentration of SO ₂ . Use industrial gas or natural gas to provide the required energy for calcination, and adjust the nature of the reaction atmosphere by adjusting the amount of circulating flue gas. Gypsum (natural gypsum or industrial by-product gypsum), the main component is CaSO ₄ 2H ₂ O, after drying and preheating to obtain CaSO ₄ or CaSO ₄ 0.5H ₂ O, after reducing and calcining with hydrogen-containing reducing gas, its decomposition The yield of the calcined product is close to 100%, and the calcined product determines whether to perform CaO upgrading according to the percentage content of CaO in it. The yield of CaO after upgrading is also close to 100%. The hydrogen atom content in the reducing gas determines the _CO2 emission reduction in the process. _The high _- concentration SO2 produced in the process can continue to react with the reducing gas under the action of the catalyst to produce sulfur, and the sulfur obtained by reducing SO2 with the gas reducing agent has higher purity and better quality.

In order to realize the above-mentioned technical purpose, the present invention adopts following technical scheme:

The first aspect of the present invention provides a kind of quicklime preparation process based on carbon emission reduction, comprising:

Contact the preheated gypsum with hydrogen-containing reducing gas at 700-1200°C to generate CaO, CaS and SO ₂ flue gas; then, separate the SO ₂ flue gas from gas to solid, and collect solid materials and SO ₂ flue gas Ⅰ; if CaO%<95% in the calcined solid material, carry out CaO upgrading to the solid material so that CaO%≥95% in the solid material, then carry out gas-solid separation, collect solid CaO, cool, store, and Collect SO ₂ flue gas II;

Or contact the preheated gypsum with hydrogen-containing reducing gas at 700-1200°C, so that the concentration of reducing agent M is controlled below 10%, and at the same time, the concentration of _CO2 is controlled to be more than 8 times the concentration of reducing agent M, so that CaSO ₄ is completely decomposed into CaO, after cooling, store;

Use SO ₂ flue gas I for preheating gypsum first, then mix it with SO ₂ flue gas II, and reduce it to elemental sulfur vapor in the presence of a catalyst, recover sulfur and store it;

The exhausted gas after recovering sulfur is divided into three parts, one part returns to the reduction calciner to adjust the reaction atmosphere, one part goes to the upgrader for CaO upgrading, and the last part enters the system boiler for combustion, purification and removal.

The invention provides a quicklime preparation process based on carbon emission reduction, which uses hydrogen-containing reducing gas to reduce and decompose gypsum (natural gypsum or industrial by-product gypsum), which can not only alleviate the problem of difficult treatment of industrial gypsum (mainly calcium sulfate dihydrate) in my country At the same time, it can also make resource utilization, recycle sulfur resources and quicklime, alleviate the current situation of shortage of sulfur resources in my country, and reduce the foreign dependence of sulfur resources. Quicklime can replace natural limestone as a desulfurization agent for wet desulfurization and an additive for blast furnace ironmaking sintering materials, reducing the exploitation of natural limestone resources. In addition, it can greatly reduce the CO ₂ emissions in the quicklime production process, which is of great significance to carbon emission reduction and carbon neutrality in industrial processes.

Studies have shown that the main component of gypsum is calcium sulfate dihydrate. After calcium sulfate is in contact with hydrogen-containing reducing gases such as hydrogen, methane, and coal gas, the decomposition path of calcium sulfate will change. In the temperature range of 700°C-1200°C, gypsum undergoes two reactions at the same time, the first is at a lower reduction potential

and higher reaction temperature to generate CaO and high concentration SO ₂ (

M in the gas is a reducing agent), at a higher reduction potential

react with lower reaction temperature to form CaS

In most cases, the two reactions exist at the same time and there is a competitive relationship. According to the difference in the reduction potential, the product distribution is different; CaS reacts with CO ₂ at 500°C-1200°C to generate CaO, high-concentration SO ₂ and high-concentration CO ( CaS+3CO ₂ →CaO+SO ₂ +3CO), CaS reacts with water vapor at 500°C-1200°C to generate CaO, high-concentration SO ₂ and high-concentration H ₂ (CaS+3H ₂ O→CaO+SO ₂ + 3H ₂ ); when the reaction temperature is in the range of 700°C-1200°C, regardless of whether the reaction atmosphere is CO, H ₂ , CH ₄ , natural gas or coal gas, it is only necessary to control the concentration of reducing agent M below 10%, and add 8 times more than CO ₂ , CaSO ₄ can be completely decomposed and decomposed into CaO, and the yield of CaO exceeds 99.5%; SO ₂ and CO/H ₂ in the calcined flue gas are generated in the temperature range of 400-1000°C under the action of a catalyst The oxidation-reduction reaction generates elemental sulfur vapor, and the elemental sulfur vapor is recovered to obtain sulfur after dust removal and cooling.

The _second aspect of the present invention provides a quicklime preparation system based on carbon emission reduction, including: reduction calciner, CaO upgrader, quicklime storage bin, SO2 reduction tower, sulfur recovery device, sulfur storage tank, boiler , flue gas purification system; the reduction calciner is provided with a gypsum inlet and a hydrogen-containing reducing gas inlet; the material outlet of the reduction calciner is connected to a CaO upgrader and a lime storage bin respectively, and the gas of the reduction calciner _The outlet is connected to the _SO2 reduction tower, and the material outlet of the SO2 reduction tower is connected to the sulfur recovery device and the sulfur storage tank in sequence, and the _SO2 reduction tower is also connected to the boiler and the flue gas purification system in sequence.

The third aspect of the present invention provides the application of the above quicklime preparation system in carbon emission reduction and carbon neutralization.

The beneficial effects of the present invention are:

The invention proposes a quicklime preparation process based on carbon emission reduction. For gypsum reacting with hydrogen-containing reducing gas at high temperature to generate CaO and CaS at the same time, or control the _CO2 concentration to be more than 8 times the reducing agent M concentration, and directly decompose gypsum into quicklime. CaS reacts with _CO2 or water vapor at high temperature to generate CaO. By using calciner, CaO _upgrader , high temperature separator, SO2 gas phase reduction technology, sulfur recovery device and various heat exchangers, through precise control of the reaction conditions, The solid waste industrial gypsum that is difficult to handle is used to prepare quicklime and sulfur is produced by-product. Quicklime can replace natural limestone as a desulfurization and denitrification agent. Sulfur, as an important industrial raw material, has a very high market value. In addition, the present invention uses hydrogen-containing reducing gas to reduce and decompose gypsum to prepare quicklime, which can reduce _CO2 emissions in the quicklime production process, and the _CO2 emission reduction is related to the hydrogen atom content in the reducing gas. If quicklime is prepared by reducing calcined gypsum with pure _H2 , zero _CO2 emission in the quicklime preparation process can be realized. The invention has great significance for carbon emission reduction and carbon neutralization in the chemical industry.

The beneficial effect of this process is:

1. The use of hydrogen-containing reducing gas to reduce and decompose gypsum to prepare quicklime and sulfur-containing products provides a new quicklime preparation process, which can reduce _CO2 emissions in the production process of quicklime, which is of great significance to carbon emission reduction and carbon neutrality ;

2. The preparation of quicklime and sulfur-containing products through industrial by-product gypsum not only solves the problem that industrial by-product gypsum is difficult to handle, but also realizes high-value resource utilization of industrial solid waste, making the process more valuable and economical better;

3. Using hydrogen-containing reducing agent to reduce and decompose gypsum not only greatly reduces the decomposition temperature of gypsum, but also greatly shortens the reaction time and greatly reduces the energy consumption of the process;

4. This process solves the situation that a small amount of CaS cannot be avoided in the traditional gypsum calcination process. The existence of CaS is an unfavorable factor for the products of quicklime prepared by gypsum calcination. In the process of quicklime utilization, if there is CaS, it will have a great impact on the activity and quality of quicklime, and it may also produce sulfur-containing pollutants such as H ₂ S; ) content is higher, the purity is higher, the activity is higher, the corresponding utilization value is higher, and the way of utilization is wider;

5. Control the concentration of reducing agent M below 10%, and control the concentration of _CO2 at ₈ times the concentration of reducing agent M at the same time, CaSO4 can be completely decomposed and decomposed into CaO, and the yield of CaO exceeds 99.5%. This discovery can expand the scope of reducing gas types, no longer limited to CO as a reducing agent. It can directly reduce and decompose gypsum into quicklime (CaO%≥95%), and use other reducing agents, such as: H ₂ , CH ₄ , C Hydrogen-containing reducing agents such as ₂ H ₄ , H ₂ S, natural gas, and coal gas can reduce and decompose gypsum into quicklime (CaO%≥95%). This finding provides a theoretical basis for quicklime preparation processes with low or zero _{CO emissions} .

This process not only provides a new, sustainable and non-polluting treatment method for industrial gypsum, which is difficult to handle at present, but also realizes the resource utilization of gypsum. Quicklime can replace natural limestone as a desulfurization and denitrification agent, which reduces the mining of limestone and protects the ecological environment. In addition, it can greatly reduce the CO ₂ emissions in the quicklime production process, which is of great significance to carbon emission reduction and carbon neutrality in industrial processes. Therefore, the process has broad market prospects.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

Fig. 1 is a schematic diagram of the quicklime preparation process and system based on carbon emission reduction in Example 1 of the present invention.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, 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 invention belongs.

It should be noted that the terminology used here is only for describing specific embodiments, and is not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, it only means that they are consistent with the directions of up, down, left and right in the drawings themselves, and do not limit the structure. It is for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element needs to have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

Terminology Explanation Part: Terms such as "installation", "connection", "connection" and "fixation" in the present invention should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection, or an integral body; It can be a mechanical connection, an electrical connection, a direct connection, or an indirect connection through an intermediary, or an internal connection between two components, or an interaction relationship between two components. For those of ordinary skill in the art, , the specific meanings of the above terms in the present invention can be understood according to specific situations.

The present invention will be described in further detail below in conjunction with specific examples. It should be pointed out that the specific examples are to explain rather than limit the present invention.

Example 1:

A quicklime preparation process based on carbon emission reduction mainly includes:

The gypsum is stored in the gypsum storage bin, and is transported to the gypsum preheating dryer for preheating and drying through the precise control of the feeding amount by the feeder. The high-temperature heat source comes from the high-temperature flue gas discharged from the calcination section; the temperature of the gypsum after preheating and drying is 600 -1000°C, first enter the calciner, and control the reaction temperature 700-1200°C and the amount of hydrogen-containing reducing gas and circulating flue gas in the reduction calciner to obtain relatively high temperature and low reduction potential

The reaction atmosphere, the reaction conditions make most of the CaSO ₄ react

Decomposes into CaO, a small amount of CaSO ₄ reacts

Generate CaS. Alternatively, the concentration of the reducing agent M is controlled below 10%, while the concentration of _CO2 is controlled to be more than ₈ times the concentration of the reducing agent M, CaSO4 can be completely decomposed and decomposed into CaO, and the yield of CaO exceeds 99.5%. The high-concentration SO ₂ flue gas produced in the reducing calcination furnace carries the calcined material into the high-temperature separator 1, and the separated solid material determines whether to perform CaO upgrading according to the percentage of CaO in it. If the CaO% in the calcined solid material is ≥ 95%, it can be directly cooled and stored in the quicklime storage bin; if the CaO% in the calcined solid material is < 95%, it needs to enter the CaO upgrader for upgrading; In the upgrader, the CaS in the calcined solid material reacts with the water vapor in the circulating flue gas at 500°C-1200°C to generate CaO, high-concentration SO ₂ and high-concentration H ₂ (CaS+3H ₂ O→CaO+ SO ₂ +3H ₂ ) or react with CO ₂ in the circulating flue gas to generate CaO, high-concentration SO ₂ and high-concentration CO (CaS+3CO ₂ →CaO+SO ₂ +3CO), CaO in the upgraded solid material % ≥ 95%, after being separated from gas and solid by high temperature separator 2 and cooled, it is sent to the quicklime storage bin; the high concentration SO ₂ flue gas separated by high temperature separator 1 is a reducing atmosphere, firstly enters the gypsum preheating and drying system, and uses The residual heat of the flue gas preheats and dries the gypsum, and the flue gas after utilizing the residual heat enters the _SO2 reduction tower. The high-concentration SO2 gas separated by the high-temperature separator ₂ is also a reducing atmosphere, which is mixed with the flue gas separated by the high-temperature separator ₁ and then sent to the SO2 reduction tower _; in the SO2 reduction tower, the temperature range of 400-1000 ° C , under the action of the catalyst, the SO ₂ in the flue gas will be reduced to elemental sulfur vapor by the reducing gas, and the elemental sulfur vapor will be recovered by the sulfur recovery device to obtain sulfur and stored in the sulfur storage tank. The exhausted gas after the sulfur recovery is divided into three parts, Part of it returns to the calciner to adjust the reaction atmosphere, part of it returns to the CaO upgrader to participate in the reaction, and the last part passes into the boiler to burn off the unreacted CO or hydrogen generated during the reaction process, and then enters the flue gas purification system with the boiler flue gas after purification emptying.

The gypsum has a particle size of 60 μm-3mm and a moisture content of 5%-20%, which can be calcium sulfate products such as wet desulfurization gypsum, semi-dry desulfurization ash, phosphogypsum, and natural gypsum;

The high-concentration SO ₂ flue gas produced by the calciner, SO ₂ % = 2-10%, CO% 4-20%, temperature 700°C-1200°C, the main components are SO ₂ , CO, N ₂ , CO ₂ , etc. ;

The high-concentration SO ₂ gas produced by the CaO upgrader, SO ₂ %=2-10%, O ₂ %=4-10%, temperature 500°C-1200°C, the main components are SO ₂ , CO, N ₂ , _CO2 , etc.;

The hydrogen-containing reducing gas mainly consists of H ₂ , CH ₄ , C ₂ H ₄ , H ₂ S, natural gas, coal gas, etc., and the content can be a combination of several or all of the above components according to the source of the reducing gas;

The main components of the deflated gas are N ₂ , CO, CO ₂ , etc., CO ₂ %=10%-80%, H ₂ O%=10%-80%;

The gypsum preheater can be a gas-solid heat exchanger in various forms such as a multi-stage cyclone separator, a shell-and-tube heat exchanger, a plate-shell heat exchanger, and a plate heat exchanger;

The feeder can be a variety of feeding forms such as a screw feeder and an air-lock feeder;

The fuel of the external heat source can be a burner in the form of various fuels such as coal, natural gas, diesel oil, gas, etc., or a microwave reactor or an electric heating reactor;

The high-temperature separator can be a separator in various forms such as a high-temperature cyclone separator, a high-temperature axial flow separator, etc.;

The calciner and CaO upgrader can be in various forms such as moving bed, rotary kiln, fixed bed, turbulent bed, bubbling bed, microfluidized bed, spouted bed, etc.;

The reduction calciner and the CaO upgrader can be two independent reactors, or different positions of the same reactor, as long as different reaction atmospheres can be distinguished;

The above-mentioned gas transportation process is powered by induced draft fan or blower;

The reducing high-concentration SO ₂ flue gas discharged from the reducing calcination furnace is separated by a high-temperature separator and subjected to secondary dust removal by a high-temperature filter, and then condensed by a sulfur condenser to recover sulfur. The purity of recovered sulfur reaches over 99.7%, which meets the standard of first-class industrial sulfur.

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or part of them may be equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention. Although the specific implementation of the present invention has been described above, it is not a limitation to the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art can do it without creative work. Various modifications or deformations are still within the protection scope of the present invention.

Claims (6)

1. A kind of quicklime preparation technology based on carbon emission reduction, it is characterized in that, comprises:

   Contact the preheated gypsum with hydrogen-containing reducing gas at 700-1200°C to generate CaO, CaS and SO ₂ flue gas; then, separate the SO ₂ flue gas from gas to solid, and collect solid materials and SO ₂ flue gas Ⅰ; if CaO%<95% in the calcined solid material, carry out CaO upgrading to the solid material so that CaO%≥95% in the solid material, then carry out gas-solid separation, collect solid CaO, cool, store, and Collect SO ₂ flue gas II; CaO upgrading method is as follows: CaS reacts with water vapor in exhaust gas at 500°C-1200°C to generate CaO, SO ₂ and H ₂ or reacts with CO ₂ in exhaust gas Generate CaO, SO ₂ and CO;

   Use SO ₂ flue gas I for preheating gypsum first, then mix it with SO ₂ flue gas II, and reduce it to elemental sulfur vapor in the presence of a catalyst, recover sulfur and store it;

   The exhaust gas recovered from sulfur is divided into three parts, one part is returned to the reduction calciner to adjust the reaction atmosphere, the other part is sent to the upgrader for CaO upgrading, and the last part enters the system boiler for combustion and purification, and the exhaust gas is mainly composed of Including: N ₂ , CO, CO ₂ , H ₂ O, wherein CO ₂ % is 10%-80%, and H ₂ O% is 10%-80%.
2. The quicklime preparation process based on carbon emission reduction according to claim 1, characterized in that, the particle size of the gypsum is 60 μm-3mm, and the moisture content is 5%-20%; preferably, the gypsum is wet-process desulfurization gypsum, At least one of semi-dry desulfurization ash, phosphogypsum or natural gypsum.
3. The quicklime preparation process based on carbon emission reduction according to claim 1, characterized in that, in the SO ₂ flue gas, SO ₂ % is 2-10%, CO% is 4-20%, and the temperature is 700°C-1200°C ℃, the main components include: SO ₂ , CO, N ₂ , CO ₂ .
4. The quicklime preparation process based on carbon emission reduction according to claim 1, characterized in that, in SO ₂ flue gas II, SO ₂ % is 2-10%, O ₂ % is 4-10%, and the temperature is 500°C-1200 ℃, the main components include: SO ₂ , CO, N ₂ , CO ₂ .
5. The quicklime preparation process based on carbon emission reduction according to claim 1, characterized in that the main components of the hydrogen-containing reducing gas are H ₂ , CH ₄ , C ₂ H ₄ , H ₂ S, natural gas, and coal gas. or a combination of all ingredients.
6. The quicklime preparation process based on carbon emission reduction as claimed in claim 1, wherein the preparation process uses a gypsum preheater, a feeder, an external heat source, a high temperature separator, a calciner, a CaO upgrader, reduction calciner;

   The gypsum preheater is one of a multi-stage cyclone separator, a shell-and-tube heat exchanger, a plate-and-shell heat exchanger, and a plate heat exchanger;

   The feeder is a screw feeder or an air lock feeder;

   The external heat source is: a burner whose fuel is coal, natural gas, diesel oil, or gas, a microwave reactor or an electric heating reactor;

   The high temperature separator is a high temperature cyclone separator or a high temperature axial flow separator;

   The calciner and CaO quality upgrader are one of moving bed, rotary kiln, fixed bed, turbulent bed, bubbling bed, microfluidized bed and spouted bed;

   The reducing calciner and the CaO upgrader are two independent reactors, or are different positions of the same reactor, and the reaction atmospheres are different at the different positions;

   The gas transportation process is powered by an induced draft fan or a blower fan; the reducing high-concentration SO ₂ flue gas discharged from the reducing calciner is separated by a high-temperature separator and subjected to secondary dust removal by a high-temperature filter, and then condensed by a sulfur condenser to recover sulfur.

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