The utilization of various conventional and emerging solid adsorbents is an attractive carbon capture method for post-combustion and direct air capture (DAC). This review aims to identify adsorbents with the highest CO 2 adsorption performance at various CO 2 capture conditions inclusive of pre-combustion, post-combustion, and DAC to aid the selection of adsorbents. It presents the various adsorbents' physical and chemical properties, their synthesis methods, CO 2 adsorption performance, and their advantages as CO 2 adsorbents. Findings of the review show that NaX@NaA core-shell microspheres possess the highest CO 2 adsorption capacity at 5.60 mmol g −1 for adsorption at DAC conditions. MOF-177-TEPA exhibited the highest post-combustion condition CO 2 adsorption capacity at 4.60 mmol g −1 given tetraethylenepentamine properties leading to low diffusion resistance for CO 2 and easy access to active sites. Approximation of these adsorbents' adsorption capacity within pre-combustion capture temperature at 1 bar for oxy-combustion process was 0.0000026-48.71 mmol g −1 . It is crucial to understand and evaluate these adsorbents' characteristics for application in the appropriate adsorption conditions. This considers their usage limitations on pilot-scale CO 2 capture because of low productivity, poor durability, and stability for prolonged cyclic adsorption-desorption, expensive adsorption system, high gas flow rate, high adsorbate accommodation requirement, longer flow switching time, and low tolerance towards water and impurities present in flue gas. This paper hence presents future enhancements in overcoming their limitations to accommodate pilot scale carbon capture. These are beneficial in providing insights for capturing CO 2 from flue gases emitted in industries.
Oil palm waste has been widely used in activated carbon (AC) by applying various activation methods and degrees of processing. The aim of this paper was to conduct technoeconomic assessment for pilot-scale oil palm based AC (OPbAC) production to evaluate cost of these methods using different activation and post-activation surface modification processes. Based on the assumptions in earlier publications, the pilot-scale evaluation was estimated by summation of fixed capital investment with total annual operating costs according to the percentages of total equipment cost reported in the literature. The proposed investment in constructing and operating three different types of AC manufacturing facility is investigated by the net present value (NPV) method. The evaluation revealed that the physical activation process required lower fixed capital investment ($2.12 million) and annual operating cost ($1.53 million) compared to chemical and physiochemical processes with respective total fixed capital investment ($6.32 million) and total annual operating cost ($2.57 million). The NPV results reported that positive NPVs are evaluated for all three manufacturing facilities and the proposed investments associated with these facilities are acceptable. The highest production cost related to chemical activation with ZnCl 2 in the presence or absence of an oxidizing gas was estimated to be $3.24 per kg AC, whereas the lowest production cost of $2.72 per kg AC was found for steam activation that required no additional purchase of commodity chemicals. On the other hand, a modification by impregnation using magnesium oxide estimates the highest additional modified AC product cost at $8.60 per kg AC given its high purchased chemical price. These findings are beneficial in providing preliminary insights in terms of economic aspects for OPbAC production.
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