Novel PAU zeolite with enhanced working capacity for waste-heat-driven temperature swing adsorption CO₂ capture

The growing concerns over CO2 emissions have led to the development of various methods for CO2 capture. CO2 capture by amine-based sorbents has been achieved by temperature (thermal) swing adsorption (TSA) process, pressure swing adsorption (PSA) process, and temperature pressure or vacuuming swing adsorption (TPSA or TVSA) process for CO2 capture. Amine sorbents for energy-efficient TSA, PSA, VSA, TPSA or TVSA CO2 capture should possess a capability which allow adsorbed CO2 to desorb and amine sorbent to be regenerated at low temperatures or low vacuums. Development of such amine sorbents would significantly decrease energy consumption and sorbent degradation during the regeneration step. The objective of this project is to develop a low vacuum swing adsorption (VSA) process for the capture of CO2 from air. The focus is on the development of amine sorbent which allows CO2 to adsorb in the form of weakly adsorbed CO2. The weakly adsorbed CO2 species can be collected from the sorbent by applying a low vacuum at ambient temperature. Specifically, no heating (i.e., thermal energy) is needed for regeneration of amine sorbents. This novel sorbent allows VSA to be operated at ambient temperature without a significant energy demand. This process eliminates the energy-intensive heating and cooling process in temperature swing adsorption (TSA) process. Ambient temperature operation could prolong the lifetime of sorbent and minimize the maintenance cost. Extensive sorbent studies with in-situ infrared spectroscopy have revealed the modifications of conventional amine sorbents with additives can increase the fraction of weakly adsorbed CO2. The amine sorbents with loaded CO2 can be regenerated in part by the following approaches: (i) mild heating to temperatures below 70 oC, (ii) flowing purging gas over modified amine sorbents at temperatures below 40 oC , (iii) vacuuming at pressure below 0.2 atm and temperatures below 40 oC. The performance of these modified amine sorbents has been tested in a 60 grams VSA unit at ambient temperatures. The results show that weakly adsorbed CO2 which can be desorbed from modified amine sorbents with purging gas at 100 cc/min can also be evacuated at a vacuum of 1 psia at room temperature. A preliminary techno- economic analysis indicates the major cost of the VSA process with modified amine sorbents stems from the operation of vacuum pumps. Thus, developing an excellent sealing with minimum leakage for the VSA unit is the most critical task for further the development of this VSA technology.

Carbon capture and storage (CCS) offers one of the most promising ways for reducing the accumulation of greenhouse gases in the atmosphere. Currently available post-combustion CO2 capture technologies lack the desired energy efficiency, we have developed a CO2 capture technology which converts CO2 to a hydrate under substantially atmospheric temperature and pressure conditions. Being cooled to a low temperature of 5 degree Celsius and a pressure of 2.2 MPa, CO2 containing water can separate out the only CO2 component as a solid called a hydrate. This technology has long been known to enable separate CO2 from a mixed gaseous stream. However, practical application had been considered difficult due to the high operating cost of high pressure and low temperature conditions. We have discovered a phenomenon in which formation of the hydrate of CO2 is produced under significantly eased conditions of pressure and temperature by using a semi-clathrate hydrate such as tetra-n-butyl ammonium bromide and other quaternary ammonium compounds. These quaternary ammonium compounds form a semiclathrate hydrate crystal with water molecules under atmospheric pressure. Our preliminary result of X-ray diffraction shows that there are empty dodecahedral cages. Therefore, semi-clathrate hydrates can be used to separate small gas molecules that fit in these dodecahedral cages. We have found that they could encage CO2 molecules at higher selectivity than nitrogen and oxygen. We have performed a bench scale experiment to encage CO2 under substantially atmospheric pressure and temperature conditions such that pressure of 0.12 MPa and temperature of 18 degree Celsius, confirming the possibility of CO2 capture under those conditions. Our feasibility study has revealed that the operating costs of carbon capture will be half compared to a conventional chemical absorption process. We expect to conduct larger scale tests in the future, preconditioned on a CCS plant for CO2 capture of flue gas from thermal power plants and steel works assumed CCS scale from 0.3 million to 1 million tons per year. The improved CO2 capture process with minimized energy demand will play a significant role for the reduction of CO2 emissions. 1. Introduction Atmosphere carbon dioxide is a focus of attention as one of the greenhouse gases (GHG) which cause global warming. Early implementation of effective measures to prevent global warming is strongly desired. One conceivable measure for preventing global-scale warming is separation and capture of the CO2 contained in flue gas discharged into the atmosphere from thermal power plants, steel works, factories, and other facilities in the course of industrial activity, followed by fixation and effective utilization. This approach, if possible, would make an important contribution to prevention of global warming. Various methods for separation and capture of CO2 from flue gas have been proposed, including chemical absorption using an amine solution, physical adsorption using an adsorbent, and membrane separation methods, among others. However, in order to realize practical application of these technologies, the cost of CO2 separation and capture must be substantially reduced, as this accounts for a large part of the total cost of carbon dioxide capture and storage (CCS). This paper presents a hydrate-based CO2 separation and capture method which has the potential for large cost reduction in comparison with conventional techniques in CO2 separation and capture technology.

Experimental study of the adsorber performance in a multi-stage fluidized bed system for continuous CO2 capture by means of temperature swing adsorption

Computational simulation study of the influence of faujasite Si/Al ratio on CO2 capture by temperature swing adsorption

ConspectusCarbon dioxide (CO2) capture and storage (CCS) is a means to enable the continued use of fossil fuels in the short term. In particular, postcombustion CO2 capture has attracted considerable attention because it can be retrofitted into existing power plants and industrial plants. Among various CO2 capture technologies, the absorption of CO2 using aqueous amines has been industrially employed for decades. However, such amine scrubbing technologies have inherent limitations of environmental and health concerns due to volatile amine loss, corrosion, and high energy demands for regeneration. To overcome these limitations, CO2 adsorption using solid adsorbents has emerged as a promising alternative due to its noncorrosiveness and low energy demand. Various amine-containing adsorbents have been synthesized and investigated for postcombustion CO2 capture. These materials are prepared by physically impregnating low-vapor-pressure amine polymers or by chemically grafting amines onto nanoporous materials. A wide variety of amine guests and nanoporous hosts (e.g., SiO2, Al2O3, zeolites, MOFs, and polymers) have been combined to develop advanced CO2 adsorbents.The design of CO2 adsorbents is a multifaceted puzzle that must ultimately consider integration with large-scale CO2 capture processes. Various engineering aspects need to be carefully considered. Unfortunately, a significant proportion of previous studies has primarily focused on the use of novel materials for improving the CO2 adsorption capacity. In this Account, we describe key challenges and solutions to develop energy-efficient and stable amine-containing adsorbents for postcombustion CO2 capture via temperature swing adsorption (TSA). We found that a high CO2 working capacity, often overemphasized in the literature, does not necessarily guarantee a low energy demand for CO2 capture. Suppressing coadsorption of H2O during the CO2 adsorption in humid flue gas is also a significant factor. Amine-containing adsorbents can be degraded through various pathways, including hydrothermal degradation of nanoporous hosts and chemical degradation of amine guests via urea formation and oxidation. To inhibit such degradation pathways, it is extremely important to properly design the nanoporous structures of the hosts and the molecular structures of the amine guests. By combining macroporous silica hosts, poly(ethylenimine) (PEI) functionalized with various alkyl epoxides, and phosphate-based oxidative stabilizers, we could synthesize adsorbents exhibiting low energy demands for CO2 capture and unprecedentedly high thermochemical stability under TSA conditions. The macroporous silica host synthesized by assembling fumed silica particles via spray-drying exhibited high hydrothermal stability and enabled uniform distribution of bulky amine polymers within its pores. The functionalization of PEI with alkyl epoxides converted its primary amines into hindered secondary amines, leading to a significant reduction in energy demand for TSA cycles and a remarkable improvement in long-term stabilities. The oxidative stability of amines could be drastically improved by adding phosphate metal-binding reagents, which can poison ppm-level metal impurities that catalyze amine oxidation. The present discussions will provide important insights into designing practical adsorbents for CO2 capture from engineering perspectives.

CO2 Capture and Development of an Advanced Pilot-Scale Cryogenic Separation and Compression Unit

CO2 capture from dry flue gas by means of VPSA, TSA and TVSA

There are numerous types of CO2 capture, utilization and storage technologies, with significant disparities in maturity and applicability, posing challenges to regional CCUS system planning. This article first reviews the technologies and typical CCUS project cases worldwide and concluded that the involved CO2 sources are mainly present in natural gas processing and chemical industries where CO2 capture costs are offset by end-product sales. CO2 utilization and storage primarily henge on the economically viable CO2-EOR activities. By analyzing the development trends of global CCUS projects, it is proposed that matching of source and sink elements and phased implementation are the two fundamental principles in regional CCUS system planning. The elements on both sides of the source and sink are summarized, elucidating the characteristics of source elements including CO2 concentration, capture cost and capture scale on the source side, and sink elements including CO2 concentration, product revenue and storage capacity. The phased regional CCUS system planning methodology is proposed as: individual CCUS opportunities can be established by matching elements of CO2 concentration, cost-revenue, scale and geographical location of the source and sink sides; these CCUS opportunities can be divided into different priority tiers based on their technical feasibility and benefit; and the phased regional CCUS system is suggested to be implemented according to the order of priority tiers. Capacity calculation for each priority tier is also proposed. Finally, using Guizhou Province, China as a case study, a phased regional CCUS system planning is discussed.

Performance of TSA and VSA post-combustion CO2 capture processes with a biomass waste-based adsorbent

On the potential of phase-change adsorbents for CO2 capture by temperature swing adsorption.

CO2 capture feasibility by Temperature Swing Adsorption in heavy-duty engines from an energy perspective

This report summarizes scientific/technical progress made for bench-scale membrane contactor technology for post-combustion CO2 capture from DOE Contract No. DE-FE-0004787. Budget Period 1 (BP1) membrane absorber, Budget Period 2 (BP2) membrane desorber and Budget Period 3 (BP3) integrated system and field testing studies have been completed successfully and met or exceeded the technical targets (≥ 90% CO2 removal and CO2 purity of 97% in one membrane stage). Significant breakthroughs are summarized below: BP1 research: The feasibility of utilizing the poly (ether ether ketone), PEEK, based hollow fiber contractor (HFC) in combination with chemical solvents to separate and capture at least 90% of the CO2 from simulated flue gases has been successfully established. Excellent progress has been made as we have achieved the BP1 goal: ≥ 1,000 membrane intrinsic CO2 permeance, ≥ 90% CO2 removal in one stage, ≤ 2 psi gas side pressure drop, and ≥ 1 (sec)-1 mass transfer coefficient. Initial test results also show that the CO2 capture performance, using activated Methyl Diethanol Amine (aMDEA) solvent, was not affected by flue gas contaminants O2 (~3%), NO2 (66 ppmv), and SO2 (145 ppmv). BP2 research: The feasibility of utilizing the PEEK HFC for CO2-loaded solvent regeneration has been successfully established High CO2 stripping flux, one order of magnitude higher than CO2 absorption flux, have been achieved. Refined economic evaluation based on BP1 membrane absorber and BP2 membrane desorber laboratory test data indicate that the CO2 capture costs are 36% lower than DOE’s benchmark amine absorption technology. BP3 research: A bench-scale system utilizing a membrane absorber and desorber was integrated into a continuous CO2 capture process using contactors containing 10 to 20 ft2 of membrane area. The integrated process operation was stable through a 100-hour laboratory test, utilizing a simulated flue gas stream. Greater than 90% CO2 capture combined with 97% CO2 product purity was achieved throughout the test. Membrane contactor modules have been scaled from bench scale 2-inch diameter by 12-inch long (20 ft2 membrane surface area) modules to 4-inch diameter by 60-inch long pilot scale modules (165 ft2 membrane surface area). Pilot scale modules were tested in an integrated absorption/regeneration system for CO2 capture field tests at a coal-fired power plant (Midwest Generation’s Will County Station located in Romeoville, IL). Absorption and regeneration contactors were constructed utilizing high performance super-hydrophobic, nano-porous PEEK membranes with CO2 gas permeance of 2,000 GPU and a 1,000 GPU, respectively. Field tests using aMDEA solvent achieved greater than 90% CO2 removal in a single stage. The absorption mass transfer coefficient was 1.2 (sec)-1, exceeding the initial target of 1.0 (sec)-1. This mass transfer coefficient is over one order of magnitude greater than that of conventional gas/liquid contacting equipment. The economic evaluation based on field tests data indicates that the CO2 capture cost associated with membrane contactor technology is $54.69 (Yr 2011$)/tonne of CO2 captured when using aMDEA as a solvent. It is projected that the DOE’s 2025 cost goal of $40 (Yr 2011$)/tonne of CO2 captured can be met by decreasing membrane module cost and by utilizing advanced CO2 capture solvents. In the second stage of the field test, an advanced solvent, Hitachi’s H3-1 was utilized. The use of H3-1 solvent increased mass transfer coefficient by 17% as compared to aMDEA solvent. The high mass transfer coefficient of H3-1 solvent combined with much more favorable solvent regeneration requirements, indicate that the projected savings achievable with membrane contactor process can be further improved. H3-1 solvent will be used in the next pilot-scale development phase. The integrated absorption/regeneration process design and high performance membrane contactors developed in the current bench-scale program will be used as the base technology for future pilot-scale development.

Adsorbents for the post-combustion capture of CO2 using rapid temperature swing or vacuum swing adsorption

Parametric analysis of thermal-pulse regeneration of activated alumina in temperature swing adsorption process used for gas dehydration

Development of carbon-based vacuum, temperature and concentration swing adsorption post-combustion CO2 capture processes