KR102162987B1 - Method for Capturing, Storaging and Using Carbon Dioxide in Waste Gas of Cement Produciton Comprising the Using of Waste Heat of Cement Calcination Process - Google Patents

Abstract

The present invention comprises a first step of cooling an exhaust gas containing carbon dioxide discharged from a cement kiln and sending it to an absorption tower filled with a carbon dioxide absorbent to absorb the carbon dioxide contained in the exhaust gas by an absorbent; A second step of separating carbon dioxide from the absorbent by sending the absorbent absorbing the carbon dioxide to the regeneration tower, supplying the waste heat discharged and recovered from the cement sintering process to a reheater to heat the absorbent absorbing the carbon dioxide; And a third step of preparing liquefied carbonic acid by compressing and cooling the separated carbon dioxide, or preparing precipitated calcium carbonate by mixing the separated carbon dioxide, powdered quicklime (Lime, CaO), and water. According to the present invention, it is possible to reduce greenhouse gases by directly collecting (CCUS) CO ₂ before being discharged to the atmosphere, and to use the collected CO ₂ to provide high purity PCC. And liquefied carbonic acid can be manufactured and utilized in related industries, and further carbon credits can be obtained.

Description

Method for Capturing, Storaging and Using Carbon Dioxide in Waste Gas of Cement Produciton Comprising the Using of Waste Heat of Cement Calcination Process}

The present invention relates to a method of collecting, storing and using carbon dioxide from exhaust gas of a cement sintering process, and more particularly, absorbing carbon dioxide contained in exhaust gas discharged from a cement calcination furnace with an absorbent and using waste heat of the cement sintering process. After separation, it relates to a method of storing and using precipitated calcium carbonate (PCC) and liquefied carbon dioxide gas.

The global village is experiencing difficulties due to the recent climate change problems caused by global warming, and governments are also making efforts to reduce greenhouse gas emissions. Korea is also reinforcing its GHG reduction policy by announcing targets of 30% reduction compared to BAU (natural increase) by 2020 (November 2009) and 37% reduction compared to BAU by 2030 (2015.6). In particular, by 2020, with only two years remaining, 30% of the estimated CO ₂ emissions of about 600 million tons, or 180 million tons, will be reduced, of which 55%, or 100 million tons, will be reduced by CCUS technology (Kyungho Kim, CO2 capture Reduction by storage technology: Large-scale integrated demonstration technology and securing economic feasibility are key to use, KISTI Market Report, 2011).

In particular, in the case of Korea, the amount of CO ₂ emitted from 1 ton cement production is estimated to be about 0.93 tons. Since 2010, Korea's annual cement production is about 55 million tons, so the total amount of CO ₂ emitted from cement production can be estimated to be about 50 million tons or more. This corresponds to about 7% of Korea's total CO2 emissions. For reference, the average value of the world cement's CO ₂ source is 0.81 tons, and the annual cement production is about 3.3 billion tons. Therefore, CO ₂ emissions from the world's cement production amount can be estimated as approximately more than 24 million tons.

Specifically, the cement manufacturing process can be largely divided into a limestone quarrying process, a raw material crushing and firing process, and a product process. In the raw material crushing and sintering process, clay raw materials including silicate are mixed with lime raw materials, pulverized, and then heated to a high temperature of about 1,450°C. Under such high temperature heating, the calcium carbonate component of limestone is separated into calcium oxide and CO ₂ . The amount of CO ₂ emitted by the decarboxylation of limestone during the firing process is estimated to be about 0.4 to 0.5 tons.

With this CO ₂ capture process, CO ₂ contained in combustion exhaust gas is cooled in a cooling tower, and then CO ₂ is absorbed in an aqueous solution of alkanolamine such as monoethanolamine in the absorption tower, and the remaining combustion exhaust gas Is discharged to the atmosphere, and the aqueous alkanolamine solution absorbing CO ₂ is sent to the regeneration tower, and the alkanolamine aqueous solution is regenerated by heating in a reboiler and returned to the absorption tower, while desorbing CO ₂ . The recovery process is known. However, the alkanolamine has a high heat of CO ₂ absorption reaction and a high heat of decomposition in the regeneration process, so there is a problem in that the economy is poor due to a large amount of energy consumption.

In addition, as the technology for capturing CO ₂ is recently developed, CO ₂ traps are generated, but most of the generated CO ₂ traps are buried or neglected. Therefore, there is a demand for technology development that can utilize or store the generated CO ₂ traps.

The present invention is to provide a method for capturing, storing, and using carbon dioxide generated in a cement kiln.

The present invention is a carbon dioxide absorbent using waste heat generated during the cement sintering process in order to solve the problem that a lot of energy is required for regeneration of the absorbent during the operation of the carbon dioxide capture process, and high purity carbon dioxide is required for producing calcium carbonate and liquefied carbon dioxide gas. It is to provide a method of collecting, storing, and using carbon dioxide in a process consistent with the cement firing process by regenerating high purity carbon dioxide and storing and using it in the form of liquefied carbonic acid or precipitated calcium carbonate.

The present invention comprises a first step of cooling an exhaust gas containing carbon dioxide discharged from a cement kiln and sending it to an absorption tower filled with a carbon dioxide absorbent to absorb the carbon dioxide contained in the exhaust gas by an absorbent;

A second step of separating carbon dioxide from the absorbent by sending the absorbent absorbing the carbon dioxide to the regeneration tower, supplying the waste heat discharged and recovered from the cement sintering process to a reheater to heat the absorbent absorbing the carbon dioxide; And

The waste heat of the cement sintering process including the third step of producing liquefied carbonic acid by compressing and cooling the separated carbon dioxide, or preparing precipitated calcium carbonate by mixing the separated carbon dioxide, powdered quicklime (Lime, CaO) and water Provides methods of capturing, storing and using carbon dioxide used.

The present invention absorbs carbon dioxide discharged from the cement kiln by a carbon dioxide absorbent, separates carbon dioxide using high-temperature waste heat discharged from the cement sintering process and stores it in the form of liquefied carbonic acid or precipitated calcium carbonate. Implement an economical and economical method of capturing, storing and using carbon dioxide.

According to the present invention, it is possible to preoccupy a new field of the environmental market by developing CCUS technology applicable to the cement industry, which is a large CO ₂ generation industry.

According to the present invention, it is not only possible to reduce greenhouse gases by directly capturing (CCUS) CO2 before being discharged to the atmosphere, but also to manufacture high-purity PCC and liquefied carbonic acid using the collected CO2 and utilize it in related industries. You can get credits.

1 illustrates a process of collecting CO ₂ generated from a cement sintering process and converting it to precipitated calcium carbonate or liquefied carbonic acid according to an embodiment of the present invention.

Hereinafter, with reference to the drawings of the present invention will be described in detail. The following embodiments are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Therefore, the present invention is not limited to the embodiments described below and may be embodied in other forms. In addition, in the drawings, the width, length, and thickness of the component may be exaggerated for convenience. The same reference numbers throughout the specification denote the same elements.

In the method of collecting, storing, and using carbon dioxide using waste heat in the cement sintering process of the present invention, the exhaust gas containing carbon dioxide discharged from the cement calcination furnace is cooled and sent to an absorption tower filled with a carbon dioxide absorbent to absorb the carbon dioxide contained in the exhaust gas. A first step of absorbing into;

A second step of separating carbon dioxide from the absorbent by sending the absorbent absorbing the carbon dioxide to the regeneration tower, supplying the waste heat discharged and recovered from the cement sintering process to a reheater to heat the absorbent absorbing the carbon dioxide; And

Compressing and cooling the separated carbon dioxide to prepare liquefied carbonic acid, or mixing the separated carbon dioxide, powdered quicklime and water to prepare precipitated calcium carbonate.

The most expensive place in the operation of the liquid CO ₂ capture process is the process of regenerating the absorbent saturated with CO ₂ , which consumes energy of 3.7 GJ/tCO ₂ or more. The cement sintering process is the most important process in the cement manufacturing process. The raw material supplied from the raw material pulverizer is preheated in a preheater to about 850~900℃, and this raw material is calcined at a high temperature to about 1,450℃ in a rotary kiln. It is the process of manufacturing phosphorus clinker. The present inventors have found that high-temperature waste heat generated in the cement sintering process can be used to regenerate the absorbent saturated with CO ₂ in the CO ₂ capture process, thereby trapping and separating CO ₂ with high purity in an economical manner. The present invention is based on this.

In the present invention, the carbon dioxide absorbent may be a primary or secondary alkanolamine such as monoethanolamine (MEA) or diethanolamine.

The absorption reaction of primary and secondary alkanolamines and carbon dioxide is a reaction in which the alkanolamine and carbon dioxide react to produce carbamate, and occurs as shown in the following reaction formula.

_{2R-NH 2 + CO 2 ⇔} R-NH 3 + + R-NH-COO -

The primary and secondary alkanolamines have characteristics of high absorption efficiency due to a low partial pressure of CO ₂ , but the heat of reaction is somewhat different depending on the type of amine, but in the case of monoethanol, the heat of reaction is 1,919 KJ/CO ₂ kg, and diethanol Since amine (DEA) is as high as 1,519 KJ/CO ₂ kg, there is a problem that a lot of energy is consumed for decomposition of carbon dioxide. The present invention solves this problem by using high-temperature waste heat generated in the cement firing process for regeneration of the absorbent.

In one embodiment of the present invention, the absorbent is heated by a heat source of 110 to 120° C. and 1 to 2 atmospheres supplied from the reheater to be separated from carbon dioxide and regenerated. The heat source may be steam, waste heat, exhaust gas, or the like.

In the present invention, the absorption tower is for introducing and discharging a carbon dioxide-containing raw material gas supplied from the outside, and by introducing the raw material gas and supplying an absorbent such as alkanolamine, the absorbent absorbing carbon dioxide from the raw material gas is regenerated. To discharge.

In the present invention, the regeneration tower is for regenerating and recycling the absorbent absorbing carbon dioxide by removing and removing carbon dioxide from the absorbent absorbing carbon dioxide from the raw material gas in the absorption tower. In the regeneration tower, the absorbent and carbon dioxide are separated, so that a high concentration of gaseous carbon dioxide is present at the upper end of the regeneration tower. A supply unit for supplying regeneration heat recovered from waste heat from the cement sintering process is provided at a predetermined position on one side of the regeneration tower.

In one embodiment of the present invention, the CO ₂ capture process was performed at 1000 Nm ³ /h, the C0 ₂ recovery rate was 90% or more, the reheater heat capacity was 2.4 GJ/tCO ₂ or less, and the amount of CO ₂ collected was 10 tons CO _It was ₂ /day.

In the present invention, powdered quicklime and water are mixed with the separated carbon dioxide for storage and use of the captured and separated carbon dioxide, and converted into precipitated calcium carbonate (Precipitated Calcium Carbonate).

In the present invention, the high purity precipitated calcium carbonate of 99.0% or more can be prepared by using the separated high purity carbon dioxide.

Precipitated calcium carbonate is the Lime Slaking process and carbon dioxide capture process in Lime Slurry (18%) to make 18% lime slurry (Ca(OH) ₂ ) by mixing powdered quicklime (Cao) with industrial water. It is produced according to the main process of producing precipitated calcium carbonate (PCC) by injecting and reacting the obtained gaseous carbon dioxide.

In one embodiment of the present invention, the amount of quicklime required for one batch Lime Slaking process is about 1 tonbag (about 800-1260kg), and produces about 4.2m ³ Lime Slurry (18%) and up to twice a day It is designed with a capacity that can be operated.

In an embodiment of the present invention, carbon dioxide is supplied at about 1.03 barg in the carbon dioxide capture process, and after being reduced to about 0.5 barg through a pressure control valve, it is injected into the PCC reaction tank. Excess carbon dioxide that is not reacted is discharged to the outside through the tank vent line, and the vent outlet is extended and installed to a safe external place with a sufficient distance from the operator and the work space.

When quicklime reacts with water, heat is generated, so the temperature varies from 70 to 90°C depending on the state of the CaO raw material or the ratio of water and CaO input, so it is preferable to bubble CO ₂ at 45 to 55°C after completion of the hydration reaction.

The pH of the lime slurry is about 12.4, but when it is converted to PCC while reacting with carbon dioxide, the pH starts to decrease, and when the pH reaches 6-8, the lime slurry reacts with carbon dioxide and the reaction is considered to be in a state that the entire amount is converted to PCC.

In an embodiment of the present invention, a pH meter and a conductivity meter are installed in the PCC reaction tank, and the reaction is completed when the pH meter reaches the set value of pH 6-8 by measuring the pH of the reactant. Preferably, when the pH is 7, the reaction is complete.

In the present invention, the precipitated calcium carbonate (hard calcium carbonate) obtained has an average particle size of 5 μm or less.

Precipitated calcium carbonate (hard calcium carbonate) is an expensive product used for high-end applications in various industrial fields such as paper, paint, medical, and food because it can be applied to various products depending on the shape and size of the particles.

In the present invention, the separated carbon dioxide is compressed and cooled for storage and use of the captured and separated carbon dioxide and converted into liquid carbonic acid.

In the present invention, by using the separated high-purity carbon dioxide, liquefied carbonic acid having a high purity of 99.95% or more can be prepared.

Liquefied carbonic acid production is a technology that is possible by combining cooling and compression technologies that liquefy gaseous CO ₂ at 1 atmosphere of 20°C. Therefore, we seek the most suitable temperature and pressure for facilities that liquefy CO ₂ captured in cement production technology. the high purity the purity of the collected CO _2, which can be produced more than 99.95% of the liquefied carbon dioxide, so it is useful for the storage of the collected CO _2, and used method.

In an embodiment of the present invention, by supplying 99% CO _{2 and} 1% H ₂ 0 to the liquefaction device under the conditions of 25° C., 1.02 kg/cm ² ·g, 5 Nm ³ /h, moisture is removed, and -30 After cooling to a temperature of °C and pressurizing to 19 kg/cm ² ·g, liquefied carbon dioxide gas containing 99.9% or more of CO ₂ and less than 0.1% of H ₂ 0 was obtained.

The existing production of liquefied carbonic acid uses natural gas, fermentation gas, petroleum refining by-product gas, and by-product gas of the ammonia synthesis process, and these raw material gases are of high purity, but impurities of inorganic and organic sulfur, hydrogen, methane, oxygen, and nitrogen. , And impurity gases such as water vapor are contained. However, according to the present invention, high-purity liquid carbonic acid having a purity of 99,95% or more can be prepared.

In the above, preferred embodiments of the present invention have been illustrated and described, but the present invention is not limited to the specific embodiments described above, and is generally used in the technical field to which the present invention belongs without departing from the gist of the present invention claimed in the claims. Various modifications can be implemented by a person having knowledge of, of course, these modifications should not be individually understood from the technical idea or perspective of the present invention.

Claims (6)

A first step of cooling exhaust gas containing carbon dioxide discharged from the cement kiln and sending it to an absorption tower filled with a carbon dioxide absorbent to absorb the carbon dioxide contained in the exhaust gas by the absorbent;
A second step of separating carbon dioxide from the absorbent by sending the absorbent absorbing the carbon dioxide to the regeneration tower, supplying the waste heat discharged and recovered from the cement sintering process to a reheater to heat the absorbent absorbing the carbon dioxide; And
The waste heat of the cement sintering process including the third step of producing liquefied carbonic acid by compressing and cooling the separated carbon dioxide, or preparing precipitated calcium carbonate by mixing the separated carbon dioxide, powdered quicklime (Lime, CaO) and water How to capture, store and use carbon dioxide used. The method of claim 1,
The carbon dioxide absorbent is monoethanolamine (MEA) or diethanolamine (Diethanolamine), characterized in that the carbon dioxide capture, storage and use method using waste heat of the cement firing process. The method of claim 1,
The absorbent absorbing the carbon dioxide is heated by a heat source of 110 ~ 120 ℃, 1 ~ 2 atm, separated from the carbon dioxide and regenerated carbon dioxide capture, storage and use method using waste heat of a cement sintering process. The method of claim 1,
The precipitated calcium carbonate is a gaseous state obtained by a lime slaking process and a carbon dioxide capture process in lime slurry to make lime slurry (Ca(OH) ₂ ) by mixing powdered quicklime (Cao) with industrial water. A method of collecting, storing and using carbon dioxide using waste heat from a cement sintering process, characterized in that produced by injecting and reacting carbon dioxide. The method of claim 1,
The waste heat of a cement calcination step for because the sedimentation variable by 70 ~ 90 ℃ the temperature depending on the calcium carbonate produced when CaO raw state and water and CaO tuipbi, in 45 ~ 55 ℃ after completion of the hydration reaction characterized by ring CO ₂ bubbles How to capture, store and use carbon dioxide used. The method of claim 1,
A method of collecting, storing and using carbon dioxide using waste heat of a cement sintering process, characterized in that the reaction is completed when the pH reaches 6 to 8 during the production of the precipitated calcium carbonate.

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