Post-Combustion CO2 Capture Using K2CO3 As Solvent

The UNO MK 3 Process

Question:

Discuss about the Post Combustion Carbon Capture by using Chemical Absorption Method.

According to CO2CRC (2014), the researchers have researched the post-combustion capture of CO₂ emissions by using K₂CO₃ as the solvent. The process, named as UNO MK 3 process, is a precipitating K₂ CO₃ process the process is as follow:

The reason K₂CO₃ is chosen in the process over amine-based solvent is that it is less volatile and have less impact to the environment. In addition, K₂CO₃ can capture sulfur oxides and nitrous oxides (SO_X and NO_X). This reduces the needs of equipment for these 2 oxides’ removal and has the potential to produce fertilizer products.

-downside of this reaction is that the reaction is slow, therefore expensive and large equipments are needed. Promoters can be introduced to the reaction to speed it up

- The corrosion that is caused by the solvent during the absorption process. The problem can be eased by using corrosion inhibitors. However some of the solvent will react with the solvent inhibitors, causing erosion and forming of solid suspensions.

- Some processes require additional chemicals to act as an activation agent such as amines.

- It operates at a higher partial pressure. Raising the bulk flue gas to the required pressure will lead to a very high energy cost.

- This process offers reduced regeneration heat and energy recovery.

- This process can withstand a certain amount of percentage of tolerability of impurities (sulfur oxides and nitrous oxides). Useful byproducts, which is fertilizers, can be formed according to the reactions below:

Synthesis gas treating for ammonia plants and direct iron ore reduction plants,  natural gas treating to achieve LNG or pipeline specifications, recycle gas purification for ethylene oxide facility.

Kothandaraman (2010) stated that in the chemical absorption process involving MEA, the CO₂ will dissolve in either carbamate, carbonate or bicarbonate form. The reactions that occur in the system are shown by the equations below:

The unit contains of assimilation vicinity in which CO2 is expelled from a fuel stream via PC dissolvable, and restoration vicinity in which the retention potential of the applied dissolvable is reestablished. In the retention area, the fuel circulation containing CO2 is going via the retention (Jayakumar, Abhimanyu, Arturo Gomez, and Nader Mahinpey, 2015) segment and contacts the fluid dissolvable which enters the section from the top. At this degree, CO2 is exchanged from the gas movement to the fluid dissolvable. This gives a handled gasoline with low CO2 content, going out of the section beat, and also a wealthy dissolvable with high CO2 content material, leaving the base of the section. With a specific give up goal to provide an ok driving compel in the guard for alternate of CO2 from the gaseous petrol move to the lean association, the PC process is labored at high weights.

An excessive running weight is agreeable to a better CO2 fractional weight inside the petroleum gasoline move than the balance weight of CO2 over the carbonate association. The excessive running weight moreover empowers the safeguard to keep walking at temperatures close to the climatic breaking point of potassium arrangement (373.15–413.15 K) without intense dissipation of the arrangement. In this way, the method is worked at an excessive temperature, and CO2 is assimilated at about the same temperature as it is desorbed. This is practicable for the reason that coveted warmth of assimilation of the superior PC association is close or beneath that of water. What's greater, the excessive temperature anticipates hydrocarbon buildup. These realities now not simply wipe out the need to cool the petroleum gasoline move before segment into the safeguard, be that as it can, likewise expel the want to heat the rich association before passage into the stripper. High temperatures of the shield increment the dissolvability of potassium carbonate and potassium bicarbonate which purpose the usage of focused preparations of 20–forty wt% potassium carbonates. This situation complements the corrosive gasoline expulsion from the framework. A solution grouping of 30 wt% potassium carbonate is a reasonable and stated outline an incentive for the most programs. The erosion inhibitors like V2O5 had been utilized for the technique efficaciously. The centralization of inhibitor relies on upon the metal surface condition and the arrangement technological know-how.

Benefits and Drawbacks

Carbon dioxide (CO2) need to be remote from gas circulation, in particular in Petrochemical, oil, and petroleum fuel establishments, considering CO2 is a corrosive gasoline and destructive which can damage the plant application and the funneling framework. CO2 can decrease the warming estimation of flammable gas. In melted petroleum gas refinery, CO2 gasoline ought to be evacuated in light of the fact that CO2 will solidify at low temperature so which could preclude the funneling framework and moreover can damage the tube inside the fundamental warmth exchanger. Rather than that, CO2 is an aspect effect of the smelling salts industry. CO2 is a toxic substance to the smelling salts union impetus, along those traces CO2 have to be isolated from the fuel stream before creating a beeline for the smelling salts combination unit.

Various partition innovations could be applied for CO2 seize. These contain adsorption, bodily ingestion, compound assimilation, cryogenic partition and movies. Concoction assimilation is the most beneficial additionally, compelling technique and is broadly applied as part of concoction and petrochemical enterprise. Concoction assimilation includes the response of CO2 with a concoction dissolvable to form a feebly strengthened center of the street compound which might be get better with the use of warmth growing the primary dissolvable and a CO2 movement. The selectivity of this kind of division is typically high. What's extra, a normally immaculate CO2 circulation may be created. These additives make substance assimilation suitable for CO2 capture for mechanical applications.

The greatest price calculates for CO2 seize is the power usage for dissolvable recuperation, which can attain forty nine% of the aggregate value of CO2 catch. Another variable is restriction of the dissolvable which could decide the measure of CO2 ingested according to unit of dissolvable. Numerous solvents are applied as a part of the gas making ready, yet alkanolamine what's extra, "hot" K2CO3 solvents are the exceptional solvents that may be applied. The upside of alkanolamine is the short retention rate and high dissolvable restrict. While the challenge of alkanolamine, for the most component in important and auxiliary gatherings, is the development of a consistent carbonate mixes and it calls for high energy for healing. Also, it cannot separate the mercaptan mixes, the departure of an expansive vapor reasons a high vapor weight, corrupted at overheating, what's extra, happen in addition response which create repercussions that can't be corrupted.

Potassium carbonate (K2CO3) fluid association has been applied broadly, especially for the partition of CO2 from fuel mixture and flammable gasoline. Since it has a high dependability, low fee, and energy usage for dissolvable recovery is low, but the reaction fee is mild contrasted with alkanolamine. The enlargement of promoter inside the K2CO3 watery arrangement (Fosbøl, Philip, Nicolas von Solms, Arne Gladis, Kaj Thomsen, and Georgios M. Kontogeorgis, 2017) can amplify the CO2 retention manages. Potassium carbonate association with alkanolamine as a promoter exhibits a effective method to progress the general execution of solvents, in particular at important and auxiliary gatherings of alkanolamine.

In organizations, the manner of CO2 ingestion occurs at excessive weight. A few segments close to CO2 can be fed on and connection among the segments may be befallen in the fuel film and fluid movie that impact the mass exchange manner (Kothandaraman and Anusha, 2010) and synthetic responses. Receptive ingestion consists of exceptional segments of the fuel blends and fluid blends that communicate to multi-component framework. The homes of mass flow in the multi-component framework are greater elaborate than the paired mass change.

Potential for Fertilizer Products

Moreover, it is a modern-day practice to utilize stages section every with various breadth to meet sure hydrodynamic trademark necessity. The more a part of beyond fashions receive only a unmarried component which actions through the interface or single component retention what is more, utilize one segment. The intention of this review is to accumulate a medical version of CO2 assimilation in cutting-edge scale pressed phase, comprising of two levels, with diverse width of every, utilizing superior K2CO3 fluid association via considering the assimilation of conveying gasses and the multi-component dissemination version changed into conceived. To rearrange the version, the grouping of species becomes characterized in mild of the influent molar flow price.

This evaluation was driven with the speculative approach (side interest) with the guide of becoming numerical uncover for warmth and mass interchange ponders joined by utilizing invention reaction in CO2 removal manage at non-isothermal condition using progressed K2CO3 watery affiliation. The form depends upon at the going with assumptions: resolute kingdom and adiabatic operations, plug-flow design for gas and liquid, overlooked measure of dissolvable dissemination and customary weight amid the column.

Figure: Absorption system

The reaction in the liquid stage is sufficiently short for a major measure of the gas acclimatized to answer in the liquid film, rather than be transferred un-reacted to the mass. Numerical model advancement was coordinated by methods for creating differential mass changes inside the squeezed segment.

References

Cooperative Research Centre for Greenhouse Gas Technologies. 2014. CO2CRC CCS Cost Reduction

Project: Solvent Precipitation System : Final Report.

https://anlecrd.com.au/wp-content/uploads/2016/08/CO2CRCCCSCostReductionProject-FinalReport.pdf

Kothandaraman, Anusha. 2010. “Carbon Dioxide Capture by Chemical Absorption:

A Solvent Comparison Study.” PhD diss., Massachesetts Institute of Technology.

https://sequestration.mit.edu/pdf/Anusha_Kothandaraman_thesis_June2010.pdf

Jayakumar, Abhimanyu, Arturo Gomez, and Nader Mahinpey. "Study of the kinetic behavior of solid K2CO3 under post-combustion CO2 capture conditions." Industrial & Engineering Chemistry Research (2017).

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