Method for neutralizing carbon dioxide

Abstract

Method for neutralizing carbon dioxide from flue gases generated by the combustion of fossil fuels, characterized in that water vapor at a temperature of 50°C to 372°C and a pressure of 0.01 MPa to 30 MPa and alkali are introduced into the flue gas path, where there is dispersion of water molecules and simultaneously dispersion of alkali molecules, with mixing of steam with alkali and flue gases, and acid-base neutralization of carbon dioxide directly in the flue gas paths, with the products of acid-base neutralization being captured on a filtration or separation device for flue gas discharge.

Description

[0001] Title: Method for neutralizing carbon dioxide

[0002] Technical Field

[0003] The invention relates to method for neutralizing carbon dioxide generated by the combustion of fuels containing carbon, using acid-base neutralization in flue gas paths.

[0004] Background of the Invention

[0005] The combustion of fossil fuels containing carbon is inherently linked to the production of carbon dioxide, which is one of the significant greenhouse gases. Greenhouse gases (including carbon dioxide, methane, nitrous oxide, halogenated hydrocarbons, ozone) are believed to contribute to climate change by trapping heat in the atmosphere, leading to global warming. The concentration of carbon dioxide in the atmosphere was around 290 ppm until the mid-18th century but has since risen to levels around 400 ppm. Carbon capture and storage (CCS) technology is a method aimed at long-term reduction of carbon dioxide emissions. It involves three main steps: capture, transport, and storage of carbon dioxide. Carbon dioxide is stored underground at high pressure in depleted oil and gas reservoirs, which can also increase the yield of oil and gas. It can also be stored in deep saline porous rocks containing salty water, where it is isolated from the atmosphere and can undergo natural exchange between the atmosphere and the ocean surface. Other storage options include the formation of solid carbon dioxide hydrates or liquid lakes on the seabed.

[0006] However, these technical solutions have drawbacks, including the technical and energy-intensive nature of carbon dioxide separation and capture, the complexity of transporting captured carbon dioxide, and the fact that these methods only involve carbon dioxide storage or carbonation with the rock environment, which is a very longterm and difficult-to-predict process. Storage of carbon dioxide in geological layers poses certain risks that cannot be reliably estimated at present. For example, it is assumed that carbon dioxide will partially leak along geological faults. The stored carbon dioxide must be compressed at high pressure or liquefied, which can cause unpredictable movement of deep waters or micro-earthquakes, risking disruption of overlying layers. Changes in pH during carbon dioxide dissolution can lead to the dissolution of some minerals, with further negative consequences. Before CCS technology can be considered a suitable solution for reducing carbon dioxide emissions, thorough evaluation of potential risks, health , and environmental impacts is necessary.

[0007] Another technical solution is high-temperature carbon dioxide sorption, also known as post-oombustion technology, based on the chemical reaction between carbon dioxide and an adsorbent at elevated temperatures. The core of this process is chemisorption, where carbon dioxide is adsorbed onto a solid adsorbent, accompanied by a chemical reaction between carbon dioxide and the adsorbent. Calcium oxide is commonly used as the adsorbent. The carbon dioxide sorption system consists of two key reactors - the carbonator and the calciner, The carbonator is where carbon dioxide capture, known as carbonation, occurs according to the following reaction: CaO + CO2 -> CaCO3. The product of carbon capture - calcium carbonate CaC03 - is then transported from the carbonator to the second reactor, called the calciner. Here, the adsorbent is regenerated through calcination according to the following reaction: CaCO3 -* CaO + CO2. Carbonation is an exothermic reaction, so heat is released in the carbonator, and the temperature typically reaches around 650 °C. Heat is mainly supplied by the regenerated adsorbent from the calciner, which is delivered at a high temperature, in contrast, calcination is an endothermic process that occurs at a high temperature of approximately 900 °C. Therefore, ensuring an adequate heat source is essential for the reactions to proceed. Flue gases containing carbon dioxide to be captured enter the carbonator together with the regenerated adsorbent, where adsorption takes place. The output from the carbonator consists of the original flue gases depleted of captured carbon dioxide and the saturated sorbent heading into the calciner. In the calciner, the adsorbent is regenerated, resulting in the production of regenerated adsorbent that returns to the carbonator and a stream of pure carbon dioxide. Fresh limestone is continuously supplied to the calciner. Continuous limestone addition reduces the declining sorption capacity of the adsorbent with increasing carbonation / calcination cycles and also requires some material to be removed to minimize the accumulation of inactive substances. If untreated flue gases containing sulfur oxides are introduced into the process, sulfur dioxide SO2 reacts with the adsorbent to form calcium sulfate (CaSO4) according to the equation: CaO + SO2 + 0.502 CaSO4. This sulfate cannot be regenerated at temperatures below 1000 °C. The disadvantage of using high-temperature carbon dioxide sorption is that it is a highly thermally intensive process resulting in the decomposition of the resulting limestone back into calcium oxide and carbon dioxide in concentrated form. Another disadvantage is the gradual deactivation of the material - limestone CaC03 - which is part of the process. Additionally, the technology of the carbonate loop causes significant corrosive stress on reactor materials, with even high-quality anti-corrosive steels starting to degrade after several hundred operating hours. US Patent Nos. US009085497B2 and US9133074B2 describe a method for converting carbon dioxide into hydrocarbons in a reactor using carbon monoxide and hydrogen. The main drawback of this technical solution is the necessity of using pure carbon dioxide, carbon monoxide, and hydrogen, which is economically demanding, and subsequent catalytic purification of the obtained hydrocarbons is required.

[0008] Another known technical solution is described in US Patent Application No. US2014316016A1, which involves the conversion of carban dioxide into hydrocarbons by hydrogenation. However, this is merely another technical implementation of the above-mentioned patents, with the technical disadvantage of requiring the use of pure carbon dioxide, carbon monoxide, and hydrogen again.

[0009] Another known technical solution is the carbonation of construction debris, cement kiln dust during cement and lime production, accelerated carbonation technology CCU at elevated temperatures. The disadvantage of this technical solution is that it uses significantly heterogeneous hydration products for carbonation - waste - in substantial volumes that need to be crushed and mixed with flue gases, representing a highly energy-intensive process.

[0010] Furthermore, a solution according to Chinese Patent Application No. CN114797361A utilizes comprehensive gas cleaning technology for both sulfur oxides and carbon oxides using acid-base neutralization with sodium hydroxide or calcium hydroxide. Part of the flue gas containing sulfur oxides is treated in a concentrated sulfuric acid bath, while part of the flue gas containing carbon oxides is neutralized with sodium hydroxide and / or calcium hydroxide. The significant disadvantage of this technical solution is that simple gas washing achieves very low process efficiency, as the gas to be neutralized rapidly forms bubbles in the neutralization bath at high flow rates, which quickly rise to the surface and exit the bath without being neutralized. Effective neutralization of carbon dioxide requires the gas to be dissolved in an alkaline solution. Another drawback of this technical solution is that if sulfur oxides react with sodium hydroxide or calcium hydroxide, sodium sulfate is produced, which contaminates the alkaline bath. The technical solution described in Chinese Patent Application No. CN109603490A is merely an arrangement of apparatus for acid-base neutralization, essentially a modification of the carbon dioxide dissolution system in an alkaline bath. Another technical solution according to US Patent No. US7255842B1 is similar to ths previous one but specifies the use of ammonia dissolved in water for acid-base neutralization.

[0011] Technical solutions described in Korean Patent No. KR10140671181 and Chinese Utility Models CN213725730U, CN214765330U, CN210410018U are again merely descriptions of device arrangements for acid-base neutralization. The technical solution according to US Patent Application No. US2020391157A1 describes carbon dioxide neutralization with a basic solution composed of sodium hydroxide, where the neutralization efficiency is increased by multiple flushes of carbon dioxide dissolved in water. The disadvantage of this technical solution, as well as in the case of US Patent Application No. US2009320683A1 , is the requirement for carbon dioxide gas to be dissolved in water, with the solubility of carbon dioxide in water decreasing with increasing temperature, while the solubility of sodium hydroxide and thus the efficiency increase with rising temperature.

[0012] Summary of the Invention

[0013] The disclosed disadvantages are addressed by a method for neutralizing carbon dioxide from the flue gases generated by the combustion of fossil fuels according to this invention, which consists of introducing water vapor at a temperature of 50°C to 372°C and a pressure of 0.01 MPa to 30 MPa, along with a base, into the flue gas path. This results in the dispersion of water molecule and base molecules within the flue gas path. During this dispersion of water vapor and base molecules in the flue gas path, mixing of water vapor, base, and flue gas occurs, leading to the acid-base neutralization of carbon dioxide. Utilizing higher temperature and pressure of water vapor enables rapid and efficient neutralization of carbon dioxide directly in the flue gas paths without the need for its dissolution in water. The de-carbonized flue gases are then discharged from the chimney structure into the external environment along with water vapor, while the products of acid-base neutralization are captured on filtration or separation devices for flue gas discharge. It is advantageous for the water vapor to be either saturated or preheated within the temperature range of 50X to 372°C and pressure range of 0.01 MPa to 30 MPa. It is expedient for the base to be selected from the group of hydroxides, and / or sodium carbonate, and / or potassium carbonate, and / or ammonia, and / or carbanions, and / or amides, and / or amidines, and / or sodium, potassium, or calcium hydrides, and / or aikoxides.

[0014] Further, it is preferabie for nozzles to be used for conveying water vapor with the base into the flue gas path, with the mixture being directed in any direction relative to the flue gas flow. It is beneficial for water vapor with the base to be introduced into the flue gas path either separately or for water vapor to be pre-enriched with the base before being introduced into the flue gas path, with mixing accomplished using a mixing device. The advantage of this invention for neutralizing carbon dioxide is that the acidbase neutralization reaction mechanism occurs within a timeframe of just a few seconds. Another significant advantage is that if the water vapor has a higher temperature than the flue gas, condensation of water vapor into water does not occur within the flue gas paths, allowing the de-carbonized flue gases to exit the flue gas paths in gaseous form. The vapor-based neutralization process Is highly efficient in terms of precise control over the acid-base neutralization process, and it is characterized by savings in the use of chemicals and flexibility in application.

[0015] Example of an Embodiment of an Invention

[0016] Example 1:

[0017] Method for neutralizing carbon dioxide according to the presented invention involves introducing flue gases from the combustion of natural gas at a temperature of 120°C with a dynamic flue gas pressure of 200 Pa. A solution of sodium hydroxide in water with a mass concentration of 20% and a temperature of 150°C, along with preheated water vapor at a temperature of 200°C and a pressure of 20 kPa, is introduced into the flue gas path. Before entering the flue gas path, the preheated vapor and sodium hydroxide are mixed using a Venturi injector and then directed into the flue gas path through a system of nozzles arranged in a circular patern against the direction of flue gas flow. This results in mixing of carbon dioxide, water vapor, and sodium hydroxide at operational temperature and pressure, ensuring stable flow of flue gases through the flue gas path. The mixing leads to acid-base neutralization of carbon dioxide, and the de-carbonized flue gases are discharged from the chimney structure into the external environment without condensed water vapor. The product of acid-base neutralization, sodium carbonate according to the equation CO2 + NaOH — > H2O + Na2CO3, is captured on the filtration device for flue gas discharge. Example 2:

[0018] Method for neutralizing carbon dioxide according to the presented invention involves introducing flue gases at a temperature of 160°C with a dynamic flue gas pressure of 100 Pa into the flue gas duct, which has already been treated with wet lime slurry (for flue gas desulfurization) and after flue gas denitrification. Using a system of steel nozzles, saturated water vapor at a temperature of 19O °C and a pressure of 1255 kPa enriched with potassium hydroxide at a mass concentration of 10% is introduced in the direction of flue gas flow. Due to the pressure of saturated water vapor enriched with potassium hydroxide, mixing of carbon dioxide and water vapor enriched with potassium hydroxide occurs throughout the length of the flue gas duct. This mixing results in acid-base neutralization of carbon dioxide, and the de-carbonized flue gases are discharged from the flue gas paths into the chimney without condensed water vapor. The product of acid-base neutralization, potassium carbonate according to the equation CO2 + KOH -» H2O + K2CO3, is captured on the filtration or separation device for flue gas discharge.

[0019] Industrial Applicability

[0020] Method for neutralizing carbon dioxide according to this invention can be applied in all processes involving the combustion of fossil fuels, such as heat, electricity, fuel, or other commodity production, with consideration for environmental preservation by reducing its release into the atmosphere.

Claims

CLAIMS1. Method for neutralizing carbon dioxide from flue gases produced by burning fossil fuels, characterized in that water vapor at a temperature of 50 - 372 °C and a pressure of 0.01 MPa to 30 MPa, along with an alkali, are introduced into the flue gas ducts, where water molecules and alkali molecules are dispersed, followed by mixing of steam with alkali and flue gases, resulting in acid-base neutralization of carbon dioxide directly in the flue gas ducts, with the resulting products of acidbase neutralization being captured on filtration or separation devices for flue gas discharge.

2. The method for neutralizing carbon dioxide according to claim 1, characterized in that the water vapor is treated as superheated steam or saturated steam.

3. The method for neutralizing carbon dioxide according to claim 1 , characterized in that the alkali is selected from the group of hydroxides and / or sodium carbonate and / or potassium carbonate and / or ammonia and / or carbanions and / or amides and / or amidines and / or sodium-potassium-calcium hydrides and / or alkoxides.

4. The method for neutralizing carbon dioxide according to any one of claims 1 and 3, characterized in that nozzles are used for conducting steam with alkali into the flue gas ducts.

5. The method for neutralizing carbon dioxide according to any one of claims 1 to 4, characterized in that water vapor with alkali is conducted into the flue gas ducts in any direction relative to the flow direction of the flue gases.

6. The method for neutralizing carbon dioxide according to any one of claims 1 to 5, characterized in that water vapor with alkali is introduced into the flue gas ducts separately.

7. The method for neutralizing carbon dioxide according to any one of claims 1 to 5, characterized in that water vapor is enriched with alkali before being introduced into the flue gas ducts, with a mixing device being used for mixing.

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