Tuesday, 26 October 2021

MODERN CARBON CAPTURE TECHNOLOGIES (#carbon)(#chemistry)(#ipumusings)

MODERN CARBON CAPTURE TECHNOLOGIES

MORDERN CARBON CAPTURE TECHNOLOGIES (#carbon)(#chemistry)(#ipumusings)


Author: Harsh Pandey 

INTRODUCTION

The cost factor plays a very important role for a technology to be equipped in an industry. The same is the case with carbon capture technologies. The feasibility of these technologies is still questionable since the cost of capturing the carbon becomes a major issue along with the fact that the energy required for these technologies itself counter produces carbon indirectly.

It has been found that if the carbon dioxide is captured from the source itself the process becomes quite effective for large industries where the carbon production is quite high like the cement industries and some of the other fossil fuel-based industries like the hydrogen-producing plants.

The three basic ways to capture carbon include, Capturing carbon after it is evolved from the process which is also called post-combustion capture, The second way is pre-combustion capture which could be observed in some industries like the chemical industries or pet fertilizers, The third process includes burning of pure oxygen instead of air due to which zero-emission cycles could be observed end up your stream of CO2 is recirculated called oxy-fuel combustion.

Although employment of several capture technologies could be observed in the industries, Still there is a much need for research to be done in terms of cost-effectiveness. All of the technologies including pre-combustion, post-combustion and oxyfuel are much costlier when it comes to carbon capture the other factor which leads to the increased cost of CO2 capture is its transportation. The effective pressure needed for the transportation of carbon dioxide is generally around 7.4 Mpa hence the gas needs to be compressed. Also in these conditions, supercritical properties of CO2 have been observed i.e. it is a liquid with a gas characteristic which further creates difficulties for its transportation.

In stationary CO2 points, sources like in modern-day natural gas processing plants are getting equipped with these technologies. The Sleipnir gas field in Norway and The Salad gas field in Algeria are some examples.

As discussed earlier the carbon capture technologies are still in their initial stages of development, they also face regulatory uncertainty and these uncertainties require a bit of time for being resolved. Modification in the international legislative provisions like the London protocol and the Paris agreement is working towards favouring these technologies.

The basic methods applied in the capture of carbon include passage of the evolved gas from a semipermeable membrane material, oxyfuel combustion, partial absorption of the gas evolved from the chambers which can also take place in multi-step adsorption of the CO2 gas with the use of certain special materials, combustion technologies like chemical looping or calcium looping are some of the processes.


CARBON CAPTURE USING SEMI-PERMEABLE MEMBRANE

The oil and gas industries using the EOR technologies i.e. enhanced oil recovery were the initial ones to show interest in the capture of carbon using membrane technologies as this carbon dioxide could be used in the EOR process for gas injection for improved production. 

The carbon capture technologies using membrane separation are quite feasible for those industries in which the emission is low, as the technology can be used in a continuous process rather than those techniques which use conventional methods such as adsorption and absorption. As in this kind of process, the gas as feed and exiting of purified gas can be present at the same time. CO2 is separated from the exhaust gas streams before the subsequent transportation and storage. The separation includes H2 and CO2 separation for the pre-combustion. CO2 and N2 separation for post-combustion and O2 and N2 separation for oxy-fuel combustion. These technologies possess great potentials to fulfil the need of CCS. 

Different gases show different values of permeability ratios for different kinds of membrane material. this permeability depends upon the selectivity of the gases which further depends upon the factor-like molecular size and the affinity of the material.

For separation to be highly effective, the feed gas is used in pressurized form whereas the pressure for the permeate gas is kept very low close to zero i.e. vacuum condition is used. the mechanical strength of the membrane is weak for this pressure hence additional outer layers are provided to the membrane for its mechanical strength. Thick porous substances are used for the strength of the membrane but the supporting substrate also needs to offer minimum resistance to the flow of the inlet gases as the large flow of the gases through these pores are permeated through the top layer. Also, there is an interlayer with a small pore size which enables an even smoother transition in between these layers.

The modern membrane is operated in such a way in which size sieving pattern could be observed and this popular mechanism is also called size sieving separation. the key factor in this separation is the membrane spot size. the porch size also classifies the membranes into the dense membrane, non-porous membrane and etc.

Some typical membranes are:

Polymer membranes

It has been observed that polymer membranes show good separation performance they are mechanically stable and cheaper when compared to other ones. these membranes use glass polymers which are highly selective and have good strength. some rubbery polymers are also used for a specific vapour gas separation process.


Microporous organic polymers

These membranes have pore sizes of about 0.4 to 0.9 nanometers they present a molecular sieving transport mechanism for gas permeation. they are also excellent gas separation performance for CO2 and related separation processes like the co2 and methane separation in the high-pressure natural gas sweetening process. 


Fixed site carrier membranes

The fixed side carrier membrane or the FSC membrane for CO2 separation have high CO2 permeance and selectivity over the other gases’ species they also present higher stability when compared to the liquid membranes like the SLM for the emulsion liquid membrane. 


Mixed matrix membranes

This type of membrane is rigid and impermeable particles are dispersed in the continuous polymer phase. these are also called MMMs. these membranes have interesting material for improving the separation performance of common polymer membranes in this kind of matrix membrane system different types of inorganic fillers can be added into the polymer Matrix such as a microporous filter etc. MMS is made by adding non-porous nanoparticles which improve gas permeability by increasing the free volume size.


Carbon molecular sieve membranes

The carbon molecular sieve membranes are usually called CMS EMS are prepared by the polymer by the polymeric precursor which is carbonized to produce polyamide polyacrylonitrile. it involves the Kinetic diameter difference of the gas molecules. the co2 has a smaller Kinetic diameter when compared to oxygen nitrogen and methane hollow fibre present in the membrane helps to delete the high precursor cost and low gas permeance also the cellulose acetate-based hollow fibre carbon membrane.


ADVANTAGES OF MEMBRANE SEPARATION

The advantages of using the membrane separation for the process of carbon capture includes its low capital cost as the membrane requires very little material to cloth. it does not even require any additional facilities like the pre-treatment vessels for the solvent storage operations.

The low operating cost for the membrane is because the membrane does not require much maintenance. the only thing for the operation cost is its replacement. also due to the smaller size and the weight of the membrane, the membranes are very simple in design compared to the traditional solvents.

Solvent techniques during these operations are intended for a long period. the membrane also does not stay or react with the other substances so the membrane has no saturation and also avoids the frequent shutdown and start-up for the process.

In the membrane separation, the percentage of co2 removal is observed rather than the quantity of co2 which means that we only deal with the absolute quantity of co2 removal, therefore, the co2 varies from gas to gas since the concentration of the co2 is different for different gas. 

The membrane separation is not much affected by the gas type and product quality consistency is observed. also, it could be observed that traditional CO2 removal technologies have to operate differently for these steps and they used to have separate units for these steps.

The membrane technology is also advantageous  for the remote areas because they can be packed into one module which helps in reducing the size and weight of the equipment makes it easier for transportation even to  remote locations also that installation is quite simpler and feasible different permeability through a certain membrane The processes involved in a membrane separation includes


Other techniques

The most widely accepted CCS technologies in various treatment types are as follows –

MORDERN CARBON CAPTURE TECHNOLOGIES (#carbon)(#chemistry)(#ipumusings)


MORDERN CARBON CAPTURE TECHNOLOGIES (#carbon)(#chemistry)(#ipumusings)

 

MORDERN CARBON CAPTURE TECHNOLOGIES (#carbon)(#chemistry)(#ipumusings)

References

📌 Membrane-based carbon capture from flue gas: a review (Weblink)

📌 Membrane Separation Technology in Carbon Capture - By Guozhao Ji and Ming Zhao (Weblink)

📌 The Guardian: What are the main types of carbon capture and storage technology? (Weblink)

📌 CO2 Capture Technologies (Weblink)

📌 A review of material development in the field of carbon capture and the application of membrane-based processes in power plants and energy-intensive industries (Weblink)


About the Author:

Harsh Pandey is pursuing his Chemical Engineering at the University School of Chemical Technology(USCT), GGSIP University, Dwarka, Delhi. His main interests are in Carbon Footprinting, Environmental Chemistry and Industrial chemistry. 



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