Evaluation of technological tendencies in the carbon capture process: a review.

This paper evaluates the technological trends in the carbon sequestration process. For this purpose, these systems have been classified into two subsystems: conventional technologies subsystem and emerging technologies subsystem. Each is explored for its suitability for meeting a set of six attributes. A bibliometric analysis process was developed using the Scopus database and VOSviewer Software to present the potential of each subsystem evaluated, through an evaluation matrix. The analysis of the subsystems and attributes was performed through the formal concept analysis methodology (8FCA). To facilitate the processing of the information, the open access software concept Explorer was used. The analysis shows that conventional technologies, despite their cost, will be maintained and advance in their implementation process. The bibliometric analysis integrated with the applied FCA methodology has proven to be useful for the evaluation of technological typologies and serves as an alternative to develop theoretical studies that group and link different options as a model to evaluate a deterministic set of attributes.


Introduction
Industrial development and population growth have generated an increase in world energy demand, directly affecting global warming.Consequently, there has been an interest on the part of various world communities in progressively controlling anthropogenic CO2 emissions [1].Renewable energies and carbon capture technologies are the two alternatives with the greatest short, medium and long term projection to contribute to the reduction of greenhouse gases [2].Currently, carbon capture and storage presents commercial technological developments and research projects, which show the reliability of the process and the potential, with application to various industrial and residential sectors [3].The Intergovernmental Panel on Climate Change (IPCC) will publish its Sixth Assessment Report (AR6) in late 2021-2022, which provides the most accurate estimate of temperature change over the next century, i.e., the data sets contributed approximately 0.1 ° for AR6 and AR5 [4].To avoid a significant temperature increase, the IPCC estimates that global greenhouse gas emissions would need to be reduced by 50 to 80 percent by 2050.
Carbon dioxide emissions originate both naturally and from human activity.Biological processes such as decomposition, ocean release and respiration contribute to carbon dioxide emissions.The sources of air pollution from human activities are major industries such as cement production, electricity generation, food production, etc. [5].Currently, renewable technologies are still under development.Although there are many solar, wind and hydro plants in operation, 80% of the world's energy is generated by fossil fuels.Carbon capture is a promising solution to reduce greenhouse gases as long as we rely on combustion-based power generation [6].
The term Carbon Capture and Storage (CCS) refers to the capture and storage of carbon dioxide (CO2) in stable subway reservoirs [7].As a result of carbon sequestration, enhanced oil recovery (EOR) processes are also possible, involving the injection of CO2 into depleted oil fields to provide the pressure needed to recover more oil.The future availability of energy from fossil fuels, such as natural gas, is likely to be influenced by how effectively the associated CO2 emissions can be mitigated through carbon capture and sequestration (CCS).In turn, understanding how CCS affects the efficient recovery of energy from fossil fuel reserves in different parts of the world requires data on how the performance of each part of a particular CCS scheme is affected by technology-specific parameters and location-specific parameters, such as ambient temperature.This paper presents a study on how the energy consumption of an essential element of all CCS schemes, the CO2 compression process, varies with compressor design, CO2 pipeline pressure and cooling temperature.
Successful application of CCS technology will require overcoming many obstacles, including the need for government and industry to continue to advance the technology [8].Another obstacle to the successful application of CCS technology is public opposition to the technology.Politicians, industry, and other stakeholders need to understand how the public perceives CCS, along with the factors that influence public acceptance or resistance to the technology [9].
For the theoretical development of this document, carbon capture technologies will be evaluated by applying a bibliometric analysis by means of specialized software and the information obtained will be evaluated by means of the method of formal analysis of concepts [10] [11] and the use of concept Explorer software [12], relating attributes and objects, simplifying information processing.With this in mind, the objectives of this work are: i. Define the attributes that each carbon sequestration technology satisfies.ii.
Develop a review of the academic literature through databases and specialized software to evaluate the objects under the established attributes.iii.
Discuss the relationship between the technology and the established attributes through the use of the formal Concept Analysis.This approach, the document is organized as follows.Section 2 presents the methodology, defining the bibliometric search string, as well as the attributes and assigning each technology an object for the development of the formal concept analysis.Section 3 covers the literature review on carbon capture and storage technologies, focusing on the level of compliance with each of the attributes.Section 4 presents the critical review using the Concept Explorer tool and the formal concept analysis method.Finally, Section 5 presents the most relevant conclusions of the paper

Methodology
La Carbon sequestration is an alternative to combat climate change.Commercially available technologies are available on the market; however, the high cost of operation and maintenance often generate an inefficient factor for their implementation. .For this reason, this work takes into consideration variables that consider relevant aspects for the implementation of commercial or emerging carbon capture technologies.
Initially, a specialized bibliometric analysis is carried out to recognize the articles with the highest incidence in the subject of study to feed the FCA methodology.The database used was Scopus and the program used to manage the information was the VOSviewer software as shown in Figure 1.For its part, the formal analysis of concepts is based on the fulfillment to a greater or lesser extent of a series of attributes with respect to a series of objects [13].The following are the attributes that each carbon sequestration technology system must meet: A1.Conventional technology A2.Emerging technology A3.Post-combustion A4.Pre-combustion A5.Oxy-combustion A6.Technological Maturity at Industrial Level Considering two technological categories: conventional and emerging, a literature review is carried out considering the attributes.Specifically, each of the characteristics that meet each attribute to a greater or lesser extent.This will result in a matrix that presents the degree to which each object or solar tracking system complies with the attributes, which will allow a qualitative analysis.
In this work, the evaluation of the information is carried out by applying the formal concept analysis (FCA) method, which allows the data to be analyzed by relating them conceptually [11].The data analysis will be performed through the open access tool "Concept Explorer" [12], evaluating all existing relationships, grouping technological typologies and attributes.

Carbon Sequestration: Methods and Technologies
Combustion power plants produce 85% of the world's electricity [13].Fuel is burned with air in a furnace or boiler, producing high-pressure gas or steam that drives the turbine generator [14].The exhaust gases leaving these power plants consist mainly of nitrogen, CO2 and water vapor.Some SO2 and NOx are also produced, depending on the fuel type.CO2 and other pollutants must be removed before the flue gas enters the atmosphere.In general, there are 3 methods to capture CO2 [15]; postcombustion, pre-combustion and oxy-combustion.These methods produce a high density pure CO2 stream that can be stored or used for other industrial purposes.
Post-Combustion: This method is used on flue gas after combustion and before release to the atmosphere in fossil fuel-based power plants.This method is often implicit in industry due to its simplicity and flexibility [15] [16].In a coal-fired power plant, the exhaust gases leaving the boiler are first treated to control air pollution and remove sulfur content.Then a chemical reaction (absorption) with a solvent such as monoethanolamine (MEA) is used to capture CO2 [14] [17].This process has two main pieces of equipment, namely absorber and stripper.About 90% of the CO2 is captured in the absorber.The CO2-loaded solvent then goes to the stripper, where heat is applied to release a highconcentration CO2 stream.The CO2 stream must be compressed for transport to the storage site.The MEA lean solvent is returned to the absorber [14] [18].
Pre-combustion: this method captures CO2 prior to combustion.In a coal-fired power plant, coal first reacts with steam and oxygen at high temperature and pressure in a process called gasification, which produces synthetic gas or synthesis gas (CO and H2) [19].Then, the syngas is reacted with steam (H2O) in a two-state change reactor that is converted to CO2 and H2.The CO2 is captured by Selexol (a glycolbased solvent) using the physical absorption method.The H2 is used for electricity production in a combined cycle as NGCC [14] [20].Pre-combustion can also be used for natural gas power plants.Natural gas is converted to synthesis gas in a reaction with O2 and H2O called reforming.The synthesis gas then goes to a displacement reactor and produces CO2 and H2.This is the method used to manufacture H2 [13] which can be used as a fuel for automobiles or as an energy source for industrial purposes.
Oxy-combustion: is an alternative to post-combustion for coal-fired power plants [21] [13].In this method, coal is burned with pure oxygen instead of air, which eliminates nitrogen.The flue gases consist mainly of CO2 and water vapor and a small amount of other pollutants such as SO2 and NOx.The water vapor is removed by the cooling and compression process, followed by the removal of other pollutants.The result is a pure CO2 stream that is ready for storage.This method does not require an expensive post-combustion carbon capture system, but it does require an air separation unit (ASU) for oxygen production [13] [22].
CO2 capture is a global problem, however, there is no simple generalized solution that can be applied worldwide.It is essential to analyze the origin of the CO2 and which technology fits the specific needs before developing a project at any scale [23].Currently, there are Conventional [24] and emerging technologies, which are adapted to various agricultural and industrial processes [25] [26].
Additionally, Table 1 presents the technologies applied in the carbon sequestration process and their relationship with each method.Source: Own elaboration, information taken from [26] [27] 3.1.Conventional Technologies 3.1.1.Absorption (Ab).Absorption is the only well-used technology and the only commercial technology used in different industries due to costs.Absorption technology for CO2 capture (ACC) has been around since the 1930s and is considered a mature technology.The technology has been used commercially to capture CO2 from oil, coal, natural gas, thermal plants and industrial processes for more than five decades [28].In the process of CO2 capture by absorption, the separation of CO2 from the flue gas is performed by a liquid sorbent through extraction or regeneration by a heating or depressurization process [29].Figure 2 represents a basic technology implementation scheme for a Carbon Capture by absorption, according to Henrys' Law.The absorbing liquid interacts with the gas and performs the absorption process in gas-liquid phase.Generally, the most widely applied sorbent is monoethanolamine (MEA) with an absorption efficiency of more than 90% [31] [32] [33].However, there are other sorbents such as: diglycoamine (DGA), di-2propanolamine (DIPA), methyl diethanolamine (MDEA), diethanolamine (DEA), triethanolamine (TEA), triethylenetetraamine (TETA), sodium carbonate (Na2CO3), ammonia (nH3), potassium hydroxide (K2CO3), glucosamine (GEA) [26].Eventually, modified ionic liquids were used for the CO2 capture process as liquid adsorbent, presenting lower efficiencies than systems using MEA [26] [34].
The liquid solvents used for the absorption process have individual limitations and are not suitable for centralized systems.Consequently, some researchers emphasize that the mixture of two or more liquid solvents improves the energetic conditions and Absorption characteristics [35] [36] [37].Recientemente, el solvente no acuoso Amina mejoró el consumo de energía del proceso de regeneración del solvente [38].Recently, the non-aqueous solvent Amine improved the energy consumption of the solvent regeneration process [38].On the other hand, Guo et al. carried out a novel experimental process, varying the traditional amine-water adsorbent by MEA-glycol, presenting reductions of up to 55% in the energy required by the adsorbent in the regeneration cycle [39].This same year, Hwang et al, performed an experimental analysis, comparing the performance of a water-poor solvent K2Sol and MEA, highlighting that K2Sol requires 35% less energy than MEA for the regeneration process [40].
In general, two requirements should be considered when selecting the sorbent: (i) Reactivity of the gas and liquid, (ii) Solubility of the gas in the liquid.ACC technology has advantages such as [41] process reliability, high absorption efficiency, modularity when integrated into processes compared to other technologies [42], system without human operation [43], and purity levels exceeding 95% [41].However, it still has limitations to be applied in power plants, as well as low process performance, high energy demand, and high investment, operation and maintenance costs [33], limiting its application at the commercial level [41].
Finally, it is of vital importance to highlight the need to continue improving the degradation process of the liquid amine solvent, due to the presence of HCL, HF, SO2 and NO2 in the composition of the combustion gases, incurring in: loss of liquid, generation of volatile gases, high energy demand, corrosion and low performance of the system, as well as the generation of Nitramines and Nitrosamines, affecting the environment and the health of living beings [44].Kozak et al, presented the application of cooled ammonia that uses the ammonium base to separate CO2, reducing the degradation of amines [45].However, research studies and technological developments are still required to improve the current absorption process and the aforementioned problems.
Adsorption (Ad).It is considered one of the most promising technologies in the CO2 capture process [46].The process consists of separating CO2 from flue gases by means of a solid adsorbent [47].The adsorbent material must have a high surface area, high selectivity and high regeneration capacity.They generally include solid adsorbent amines based on carbon, graphite, zeolite and polymer [48].The adsorbent material should have high surface area, high selectivity and high regeneration capacity.They generally include carbon-based solid adsorbent amines, organometallic structures, silica, solid ionic adsorbents, magnesium oxide, calcium oxide and LDH-derived mixed oxides [49].
Structurally, the absorption technology consists of a packed column filled with spherical absorber material.The flue gas flows through the column and CO2 are attracted to the adsorbent material.The process can be performed in several ways [29]: (i) pressure swing adsorption (PSA), (ii) electrical swing adsorption (ESA), (iii) temperature swing adsorption (TSA), (iv) Hybrid Process (PTSA).On the other hand, the adsorption process is divided into two main categories: physisorption and chemisorption, i.e., the relationship of the physical or chemical bond of the gas to the adsorbent surface [50].Finally, the process can be energetically profitable, but it depends on the proper selection of the adsorbent [51].

Membrane separation (MD). Membrane technology has a low removal efficiency and low
CO2 purity [52].Its application is limited because it does not achieve a high degree of gas separation and the working volume is small [53].Therefore, it requires multiple stages to carry out an adequate process.The drawbacks of membrane separation are [54]: i. Membrane moisture: Moisture directly affects the efficiency of the process, it generates an increase of resistance in the mass transfer process.ii.
Solvent volatility: It affects the technology environmentally and economically.Therefore, the use of non-volatile solvents such as ionic liquids is required.iii.
Long-term stability: It directly affects the integrity of the membrane, due to the chemical reaction that may exist between the membrane material, the solvent and temperature changes.iv.
Dirty gas stream: the presence of other gas particles reduces the mass transfer ratio between the membrane and the CO2.Finally, further studies should be conducted to develop composite membranes [55], which are a combination of two or more materials.that generate a better ratio by removing gases, decreasing manufacturing and implementation costs [56], combination with other existing processes to increase the overall efficiency of the process [57].

Chemical Buckle Combustion (CLC). Chemical looping combustion (CLC) was first implemented in 1993 by
Richter and Knoche to capture CO2, under the idea of diluting CO2 in the flue gas to avoid its direct interaction with air [58].Generally, in a CLC system, the combustion air and fuel never interact with each other, creating a CO2 exhaust stream that is not diluted with N2, which facilitates CO2 separation [59] The process reaches temperatures between 800-1200 °C and pressures of 1-69 atm depending on the size of the CLC system [60].In turn, it generally uses transition metal oxides such as Iron, Nickel, Cobalt, Copper, Calcium [29].The main limitation of CLC technology is the variation of reactor pressure, incurring air leakage [61].Additionally, there is a continuous interaction between the metal oxides with the unburned carbon, decreasing the yield [62].However, the energy loss during CO2 separation is low, CO2 separation is easy and its application can be in liquid, solid and gaseous fuels [63].
Finally, it is important to highlight that CLC technology is currently under research and technological development, hoping to overcome the shortcomings of commercial plants and the need to desulfurize the fuel before exposing it to the reactor [60] [64].

Emerging Technologies
3.2.1.Hydrate-based gas separation.Hydrate-based gas separation (HBGS) is a relatively new and promising technology for capturing CO2 from flue gases.The process exposes exhaust gases composed of CO2 to water at high pressures, producing hidrates [65] [66].
The main disadvantage of this technology is the additional cost of equipment to treat large volumes of flue gas with low CO2 content.In large-scale systems, energy consumption can sometimes be high, which reduces the profit margin [29].However, the process has a high CO2 storage capacity, energetically and environmentally sustainable, and is capable of capturing H2S and CO simultaneously.[29].

Direct CO2 air mineralization
It is a promising alternative for carbon capture.The process consists of accelerating the natural reaction of CO2 from the air and minerals rich in magnesium or calcium in order to obtain a solidified and processable carbonate, to regenerate minerals, and be reused, in turn generating a stream of captured CO2 [67].The technology is under development and involves improvements in engineering processes to reduce the cost of permanent removal of high quality carbon and the resulting CO2 could be stored for later application [67].
Finally, Table 2 presents the matrix of attributes for the analysis of the different carbon sequestration technologies.The attributes that meet each attribute are identified with an X in the matrix.Table 1.Selection matrix of attributes with respect to objects At Obj

Results
Figure 3 represents the graphical diagram of the formal concept analysis performed in the concept Explorer tool for the analysis of carbon capture and storage technologies, based on the information contained in the attribute's matrix in Table 1.This diagram relates the small scale plants; classified in low and micro scale with those 6 attributes proposed to identify their advantages and disadvantages.
The different nodes shown in Figure 3 are identified as follows: i. Blue-white: contains only attributes ii.
Blue-black: they are containers of solar tracking technologies related to attributes iii.
White: connector node Considering the above, the analysis of the diagram is simple.The carbon capture and storage technologies analyzed are related to all the attributes that connect them from top to bottom, up to the source node.Specifically, Attribute A1 is directly related to CLC, MD, CP, Ad and Ab technologies.DAM and HGBS technologies do not meet attribute 1, and do not share characteristics with the other technologies.In general, Ad and Ab technologies have the highest number of attributes fulfilled (3).
From this analysis, it is evident that the two types of carbon capture and storage technologies with greater maturity, development and application at present are Adsorption and Absorption.There are other 8 commercial technologies and applicable to processes, but they lack maturity at a centralized and commercial level, in some specific cases.Figure 4 shows the FCA diagram that relates the carbon capture and storage technologies under a connecting line, i.e., under the compliance or relationship of attributes with each other or individual compliance.The Ad and Ab technologies lead in compliance with attributes A1, A3 and A6, while the MD and Cp technologies do not comply with attribute A6.However, both are commercial technologies at centralized and centralized level, only that Ad and Ab technologies have higher maturity at centralized implementations level.
On the other hand, Figure 5 presents the FCA diagram for CLC technology, which shares attribute A1 with MD, CP, Ad and Ab technologies; however, it is the only technology that complies with attribute A4.CLC is a commercial technology with low and medium scale applications.

Conclusions
Carbon capture and storage technologies are currently presented as a promising technique to reduce and prevent greenhouse gas emissions at industrial and residential levels, through the implementation of various technologies at small, medium and large scales.This review summarizes the progress and technological changes.Relevant conclusions from the theoretical analysis are presented below. i.
It is important to highlight the efforts made by several researchers to evaluate the energy efficiency of sorbents based on the performance of the chemical reaction; however, it would be necessary to thermodynamically evaluate the consumption in order to obtain more conclusive data. ii.
The application of a single solvent generally shows a low absorption capacity for carbon sequestration, presenting shortcomings due to high levels of toxicity, flammability, decomposition, corrosivity, among others.However, the use of additives or mixtures with other solvents considerably improves its performance. iii.
It is important to mention that liquid and solid solvents are a highly efficient alternative in the absorption process.However, it is necessary to continue improving the degradation processes of liquids and solids in order to reduce the environmental impact generated by the process.However, the benefit they offer for the carbon capture process far outweighs the environmental drawbacks of solvents.iv.
Emerging technologies show potential in the medium and long term, but require significant efforts in the area of research and technological development, to solve the drawbacks derived from the few experimental results documented in an academic manner to date.Finally, the academic and scientific information analyzed lends credibility to the quantitative analysis developed, although this type of analysis should not replace qualitative analysis, it is presented as an alternative to conventional studies.

Figure 3 .
Figure 3. Formal Concept Analysis General Diagram Source: own elaboration, image generated with concept Explorer software.

Figure 4
Figure4shows the FCA diagram that relates the carbon capture and storage technologies under a connecting line, i.e., under the compliance or relationship of attributes with each other or individual compliance.The Ad and Ab technologies lead in compliance with attributes A1, A3 and A6, while the MD and Cp technologies do not comply with attribute A6.However, both are commercial technologies at centralized and centralized level, only that Ad and Ab technologies have higher maturity at centralized implementations level.

Figure 4 .
Figure 4. Diagram 01 Formal Analysis of Concepts Source: own elaboration, image generated with concept Explorer software.

Figure 5 .
Figure 5. Diagram 02 Formal Analysis of Concepts Source: own elaboration, image generated with concept Explorer software.Finally, Figure6shows the FCA diagram for the DAM and HGBS technologies, highlighting the lack of sharing of any attribute with another technology.The DAM and HGBS technologies lack maturity at the commercial level; their developments are limited to experimentation in laboratories and low-scale systems under development.

Figure 6 .
Figure 6.Diagram 03 Formal Analysis of Concepts Source: own elaboration, image generated with concept Explorer software.