KR101026566B1 - A method of capturing carbon dioxide - Google Patents

Abstract

The method for capturing carbon dioxide disclosed in the present invention comprises the steps of: (1) electrolyzing a saturated salt solution to obtain sodium hydroxide; (2) adding sodium hydroxide to the seawater solution to convert the magnesium chloride and calcium chloride in the seawater into magnesium hydroxide and calcium hydroxide; And (3) adding carbon dioxide to the solution comprising magnesium hydroxide and calcium hydroxide to convert it to magnesium carbonate and calcium carbonate.

The method makes it possible to capture carbon dioxide in an effective, fast and safe manner, to reduce the amount of carbon dioxide in the atmosphere and consequently to reduce the emission of carbon dioxide.

CO2 capture, electrolysis, salt solution

Description

A method of capturing carbon dioxide

The present invention relates to a capture method for reducing carbon dioxide (CO ₂ ) emissions, and more particularly to a method for capturing carbon dioxide (CO ₂ ) released in the industry using chemical reactions.

Typically, various chemicals exist in the atmospheric environment, and under normal conditions and concentrations, they do not pose a problem for the ecological environment. However, as industrialization continues, the use of all sorts of industrial machinery and transport equipment is releasing more and more chemicals. More importantly, excessive emissions of all kinds of chemicals eventually lead to air pollution.

Many types of air pollutants currently exist, the most common and observed air pollutants include: carbon dioxide (CO ₂ ), carbon monoxide (CO), sulfur dioxide (SO ₂ ), nitrogen oxides (NOx), suspended particles Suspended particulates, ozone (O ₃ ), and volatile organic compounds (VOC).

The air pollutants have a direct and indirect effect on both humans and the environment, including direct damage to the health of humans, animals, and plants living in the biosphere; Indirect impacts, on the other hand, include environmental problems caused by acid rain and global warming.

In the Earth's atmosphere, the main “greenhouse gases” include carbon dioxide (CO ₂ ), methane (CH ₄ ), and nitrogen dioxide (NO ₂ ). So-called “greenhouse gases” refer to these atmospheric gases that contribute to increasing the temperature of the Earth, which is currently the most important environmental issue, where carbon dioxide (CO ₂ ) has the greatest impact on global warming, The first factor contributing to the problem of global warming is the increase in atmospheric greenhouse gases. So How does that will have the most pressing issues currently facing environmental researchers reduced the amount of carbon dioxide in the atmosphere, many countries are now reducing carbon dioxide (CO ₂₎ emissions and party diligently.

In the present situation where the use of fossil fuels cannot be restrained, there is a need to increase the efficiency of fossil fuels and supplement them with techniques to capture, store and reuse carbon dioxide, which is considered to be the most effective way to slow global warming. Thus, people can continue to use low-cost fuels and gradually transition to using new fuel sources in the future.

In addition, "carbon dioxide storage" is the clear storage of carbon dioxide in natural or artificial "vessels", the main purpose of which is to seal and store carbon dioxide for more than a century using physical, chemical and biochemical machinery. Forests, oceans, geological strata, artificial storage tanks, and chemical reactors can all be used as “vessels” for carbon dioxide storage.

Internationally proposed “large-scale production” carbon dioxide storage methods can be further divided into geological storage, sub-surface storage, and ocean storage. The operating costs of capturing, transporting and storing one metric ton of carbon dioxide are currently at US $ 5-115, USD $ 0.4-3.2 per 100km, and US $ 0.5-100, respectively. In addition, in power plants operating the latest technology in the Integrated Gasification Combined Cycle (IGCC), the cost of capturing carbon dioxide is approximately USD $ 13-37 per metric ton, while the cost of geological storage of carbon dioxide is measured in meters. It costs approximately US $ 0.5-8 per ton, the cost of storing carbon dioxide in the ocean is approximately USD $ 5-30 per metric ton, and the cost of storing carbon dioxide below the surface is approximately USD $ 50-100 per metric ton. May 2007, 413, pp. 28-33), “The Storage of Carbon Dioxide” by Cheng-Guo Lin in the journal.

The technique of storing carbon dioxide still faces the problem of determining whether there are suitable storage “containers” currently available, and the technique is not practically used because the problems with stability and subsequent monitoring have not been completely solved. Not well developed below.

Regarding the above problems present in the prior art for storing carbon dioxide, the inventors of the present invention recognize their insufficiency and capture a large amount of carbon dioxide in a fast and safe manner, thereby increasing the concentration of carbon dioxide globally. For the purpose of solving the problem, a method of capturing carbon dioxide by continuous research and personal experience in the industry has been presented.

The method for capturing carbon dioxide disclosed in the present invention includes the following steps:

(1) obtaining sodium hydroxide by electrolyzing the saturated salt solution according to the following chemical scheme:

2NaCl + 2H ₂ 0-> 2NaOH + Cl ₂ + H ₂ ;

(2) adding sodium hydroxide to the seawater solution to convert the magnesium chloride and calcium chloride in the seawater into magnesium hydroxide and calcium hydroxide according to the following chemical reaction scheme:

MgCl ₂ + 2NaOH-> Mg (OH) ₂ + 2NaCl

CaCl ₂ + 2NaOH-> Ca (OH) ₂ + 2NaCl;

(3) converting carbon dioxide to magnesium carbonate and calcium carbonate by adding carbon dioxide to the solution containing magnesium hydroxide and calcium hydroxide according to the following chemical scheme:

Mg (OH) ₂ + CO _2- > MgCO ₃ + H ₂ O

Ca (OH) ₂ + CO _2- > CaCO ₃ + H ₂ O.

In the above method of capturing carbon dioxide, the saturated salt solution used in step (1) is brine with a high concentration of salt, and waste obtained as a result of seawater desalination is preferred.

In addition, the sodium hydroxide of step (1) may be a by-product of chlorine gas obtained by electrolysis of a saturated salt solution.

The carbon dioxide capture method of the present invention employs a chemical reaction for carbon dioxide storage, which is faster, more stable and safer than the physical storage, has less environmental impact, and adds additional cost for future monitoring activities as required by physical methods. It does not require this, and when it is done on a large scale, the cost can be further reduced and additional valuable end products can be obtained.

The above objects, features and advantages of the present invention will become more clearly understood when considered in conjunction with the accompanying embodiments and drawings, wherein:

Another method for capturing carbon dioxide is disclosed in the present invention, comprising mainly three steps: (1) electrolysis of saturated salt solution to obtain sodium hydroxide; (2) adding sodium hydroxide to the seawater solution to convert magnesium chloride and calcium chloride in the seawater into magnesium hydroxide and calcium hydroxide; (3) adding carbon dioxide to an aqueous solution having magnesium hydroxide and calcium hydroxide to convert it to magnesium carbonate and calcium carbonate.

Wherein in the manufacture of sodium hydroxide (NaOH), the sodium hydroxide may be a by-product obtained from an industrial process for the production of chlorine gas, the most common way of obtaining this, in which all of the chlorine atoms are converted to chlorine gas and then dissolved in solution The only material is the electrolysis of the saturated salt solution until it is blown away leaving only sodium hydroxide; The reaction described above has the following chemical scheme:

2NaCl + 2H ₂ O-> 2NaOH + Cl ₂ + H ₂

After electrolysis of the saturated salt solution, the reactants, sodium hydroxide, which are necessary for carrying out the carbon dioxide capture method according to the present invention, can be obtained continuously; Wherein the saturated salt solution can be obtained from the waste resulting from the seawater desalination process.

Previously, the seawater desalination process was employed primarily in the dry Middle East, but as industrialization and commercial activity develop faster, and worsened by factors of global population growth, demand for freshwater is strengthening worldwide. As many countries around the world recognize that they are increasingly struggling to obtain enough fresh water from water sources, the search for new water sources has been intensified, and seawater desalination techniques are the most common used in developed countries to obtain fresh water. Way.

The oceans have the largest surface area on earth, which makes them the largest reservoir and the most stable source of water available on the planet. In addition, the total amount of water in the ocean does not vary significantly or evaporate under all weather conditions during all seasons. Combining the recently developed seawater desalination technology with the above-mentioned elements, it can be suggested that seawater can be used as a high quality water source for humans.

Seawater desalination is a water processing technique, and its important principle is to use energy to separate the brine into two different parts; One of them is fresh water containing a low concentration of salt, the other is saline containing a high concentration of salt, and the brine is further desalted.

Currently, several techniques of desalination are still being experimented with, and the two most commonly used desalination methods are reverse osmosis desalination (47.2% of global desalination capacity) and multi-stage flash desalination (global desalination). Occupies 36.5% of the capacity).

The carbon dioxide capture method of the present invention, for the production of sodium hydroxide, can use brine which is a waste obtained by seawater desalination; This allows for effective use of wastes, resulting in the best use of global resources.

During the sodium hydroxide production, chlorine gas is produced simultaneously, which can be used extensively in the production of polyvinyl chloride (-(CH ₂ CHCl) n-). Since polyvinyl chloride is made from ethylene, chlorine, and a catalyst, and has fire-resistance and heat resistance, this means that polyvinyl chloride can be widely used in various products related to other industries; For example, wiring and cables, fiber optic cables, shoes, handbags, bags, ornaments, signs and billboards, home remodeling, furniture, ornaments, rollers, tubes, toys, curtains, roller doors, auxiliary medical devices, It can be used in gloves, food packaging, and fashion clothing.

Sodium hydroxide is then added to the seawater solution to convert magnesium chloride and calcium chloride in the seawater to magnesium hydroxide and calcium hydroxide, the reaction having the following chemical formula:

MgCl ₂ + 2NaOH-> Mg (OH) ₂ + 2NaCl

CaCl ₂ + 2NaON-> Ca (OH) ₂ + 2NaCl

The elemental composition of seawater on Earth is shown in Table 1 below.

Elemental composition of the earth's seawater Element Name Percent (mass percent) Oxygen 85.7 Hydrogen 10.8 Goat 1.9 salt 1.05 magnesium 0.1350 sulfur 0.0885 calcium 0.04 potassium 0.0380 bromine 0.0065 carbon 0.0026

Elements, including calcium and magnesium, can be found naturally in seawater, mainly in the form of magnesium chloride and calcium chloride in seawater. By reacting magnesium chloride and calcium chloride with sodium hydroxide, it is possible to obtain reactants containing magnesium hydroxide and calcium hydroxide required in the next step, thereby effectively reducing the cost of obtaining the raw material for capturing carbon dioxide according to the present invention. In this way, the use of natural resources available on the planet will be efficient.

After obtaining magnesium hydroxide and calcium hydroxide from the reaction, the industrially discharged carbon dioxide is injected into an aqueous solution containing magnesium hydroxide and calcium hydroxide, and converted to magnesium carbonate and calcium carbonate; The reaction has the following chemical scheme:

Mg (OH) ₂ + CO _2- > MgCO ₃ + H ₂ O

Ca (OH) ₂ + CO _2- > CaCO ₃ + H ₂ O

The above mentioned reaction not only captures carbon dioxide, but also converts it to magnesium carbonate and calcium carbonate. That is, the method can utilize industrially generated waste (salt obtained from seawater desalination) or by-products (sodium hydroxide obtained from chlorine production) to capture carbon dioxide, and the entire chemical reaction is rapid (compared to current physical or biological methods). ), Effectively reducing the overall cost of the method.

According to the invention, the final product obtained by the method of capturing carbon dioxide is: calcium carbonate (which can be used for the production of fire resistant building materials and paints as well as for the manufacture and papermaking of steel and polymer materials); Magnesium carbonate (flooring, fire- and fire-fighting products, cosmetics, cosmetics and toothpaste, fillers, plastic products for suppressing smoke generation, neoprene rubber used as desiccant, as an intestinal emollient And food coloring preservatives).

Experiments according to the invention are described below, which are not used to limit the scope of the invention; Any reasonable modification can be made by one skilled in the art without departing from the scope of the present invention.

Example :

Example 1

(1) Preparation of Sodium Hydroxide (NaOH):

Saturated salt solution or brine is continuously placed in an electrolytic tank as shown in FIG. 1 so that the electrical reaction continues, and a continuous sodium hydroxide (NaOH) solution is obtained; Here, a stable current of 40 amps (A) was set in the electrolytic tank 10, and its voltage was set to 1.5 volts (V) or more. In addition, the ion exchange membrane 16 was installed at the center of the electrolytic tank 10, and the brine was injected into the inlet 12 so that the brine flowed through the electrolytic tank 10; The electrolytic anode in the tank (10) (anode, 17) is 2Cl ^- is the reaction ^{- ->} Cl ₂ + 2e. Here, while the chlorine gas obtained by electrolysis is discharged from the anode, the electrolytic anode in the tank (10) (cathode, 18) is ^{_{2H 2 O + 2e - ->}} 2OH - the reaction of a + H _2, where the electrolysis As a result, hydrogen gas was discharged from the cathode. In addition, sodium ions (Na +) and hydroxide ions (OH −) in the solution are continuously combined to form sodium hydroxide (NaOH _{( aq )} ) therein, which is then discharged to the outlet 14. If the electrolysis reaction is continued for 24 hours, an average of 58 g of sodium hydroxide can be obtained per hour.

(2) Preparation of magnesium hydroxide and calcium hydroxide, and capture of carbon dioxide:

As shown in FIG. 2, the reaction tank 20 includes a seawater inlet 22 which allows seawater to flow therein, and a sodium hydroxide inlet 24 which allows the sodium hydroxide obtained in the previous step to flow; And a carbon dioxide inlet 26 which allows carbon dioxide to flow therein to cause reactants including seawater, sodium hydroxide, and carbon dioxide to react in the reaction tank 20. As a result of the reaction, a precipitate 29 of magnesium carbonate / calcium carbonate precipitated at the bottom of the reaction tank 20 is produced, and the seawater having reacted is discharged from the reaction waste outlet 28; The reaction can be represented by the following chemical schemes:

MgCl ₂ + 2NaOH-> Mg (OH) ₂ + 2NaCl

Mg (OH) ₂ + CO _2- > MgCO ₃ + H ₂ O

CaCl ₂ + 2NaOH-> Ca (OH) ₂ + 2NaCl

Ca (OH) ₂ + CO _2- > CaCO ₃ + H ₂ O

In the above-mentioned reactions, magnesium chloride reacts with sodium hydroxide to form magnesium hydroxide, and the magnesium hydroxide is further reacted with carbon dioxide which flowed into the tank to form magnesium carbonate, so that at the bottom of the reaction tank 20 To precipitate; Calcium chloride also reacted with sodium hydroxide to form calcium hydroxide, which was further reacted with carbon dioxide flowed into the tank to form calcium carbonate, which precipitated at the bottom of the reaction tank 20.

In the apparatus, an average of 445.9 g of magnesium carbonate and 92.3 g of calcium carbonate could be obtained by supplying 90 g of sodium hydroxide and sufficiently exposed to 1 kg of seawater. This indicated that, after conversion, an average of 277 g of carbon dioxide can be captured by adding 90 g of sodium hydroxide to 1 kg of seawater.

(3) Estimated Costs of CO2 Capture Methods:

Due to the conversion rate, it is possible to capture 277 g of carbon dioxide on average by adding 90 g of sodium hydroxide to 1 kg of seawater, so the cost of capturing 1 metric ton of carbon dioxide is as shown in Table 2 below.

Estimated Cost of Processing 1 Metric Ton of Carbon Dioxide Item cost Electricity
Device
driving
material
Etc About USD $ 31.511
About USD $ 5.351
About USD $ 1.338
About USD $ 23.438
About USD $ 1.000 Total amount About USD $ 62.638

The total cost to capture one metric ton of carbon dioxide is expected to be USD $ 62.638, which is close to the cost of USD $ 50-100 to capture one metric ton of carbon dioxide by geological storage. However, the carbon dioxide capture method of the present invention has the following advantages: A. Adopt chemical reactions for carbon dioxide storage, which is faster than physical storage; B. Adopt chemical reactions for carbon dioxide storage, making it more stable and safe than physical storage; C. Storage using this method has less impact on the environment; D. Does not require additional costs for future monitoring activities such as those required by physical methods; E. Material costs can be further reduced at large scale of the present invention; F. Use of the present invention results in additional valuable end products.

The present invention has been described in accordance with preferred embodiments, and those skilled in the art should recognize that the above embodiments are only used for the description of the present invention and do not limit the scope of the present invention. Equivalent changes and substitutions to the above-described embodiments can be performed without departing from the scope of the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

1 is a schematic diagram showing the electrolysis of a saturated salt solution (brine) according to the present invention.

Figure 2 is a schematic diagram showing the production of magnesium hydroxide and calcium hydroxide, capture of carbon dioxide according to the present invention.

Claims (4)

In the carbon dioxide capture method, (1) obtaining sodium hydroxide by electrolyzing the saturated salt solution according to the following chemical scheme: 2NaCl + 2H ₂ 0-> 2NaOH + Cl ₂ + H ₂ ; (2) adding sodium hydroxide to the seawater solution to convert the magnesium chloride and calcium chloride in the seawater into magnesium hydroxide and calcium hydroxide according to the following chemical reaction scheme: MgCl ₂ + 2NaOH-> Mg (OH) ₂ + 2NaCl CaCl ₂ + 2NaOH-> Ca (OH) ₂ + 2NaCl; And (3) converting carbon dioxide to magnesium carbonate and calcium carbonate by adding carbon dioxide to the solution containing magnesium hydroxide and calcium hydroxide according to the following chemical scheme: Mg (OH) ₂ + CO _2- > MgCO ₃ + H ₂ O Ca (OH) ₂ + CO ₂ -> CaCO ₃ + H ₂ O Carbon dioxide capture method comprising a. The method of claim 1, The saturated salt solution used in the step (1) is a carbon dioxide capture method of brine containing a high concentration of salt. The method of claim 2, CO2 capture method wherein the brine is a waste obtained from seawater desalination. The method of claim 1, Sodium hydroxide of step (1) is a carbon dioxide capture method is a by-product of chlorine gas obtained by electrolysis of the saturated salt solution.

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