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Environmental Benefit Assessment for the Carbonation Process of Petroleum Coke Fly Ash in a Rotating Packed Bed Si-Lu Pei, Shu-Yuan Pan, Ye-Mei Li, and Pen-Chi Chiang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b00708 • Publication Date (Web): 24 Aug 2017 Downloaded from http://pubs.acs.org on August 26, 2017

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Environmental Science & Technology

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Environmental Benefit Assessment for the Carbonation Process

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of Petroleum Coke Fly Ash in a Rotating Packed Bed

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Si-Lu Pei,† Shu-Yuan Pan,‡ Ye-Mei Li,§ and Pen-Chi Chiang*,†,‡

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†

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ABSTRACT

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A high-gravity carbonation process was deployed at a petrochemical plant using petroleum coke

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fly ash and blowdown wastewater to simultaneously mineralized CO2 and remove nitrogen

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oxides and particulate matters from the flue gas. With a high-gravity carbonation process, the

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CO2 removal efficiency was found to be 95.6%, corresponding to a capture capacity of 600 kg

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CO2 per day, at a gas flow rate of 1.47 m3/min under ambient temperature and pressure.

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Moreover, the removal efficiency of nitrogen oxides and particulate matters was 99.1% and

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83.2%, respectively. After carbonation, the reacted fly ash was further utilized as supplementary

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cementitious materials in the blended cement mortar. The results indicated that cement with

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carbonated fly ash exhibited superior compressive strength (38.1 ± 2.5 MPa at 28 d in 5%

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substitution ratio) compared to the cement with fresh fly ash. Furthermore, the environmental

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benefits for the high-gravity carbonation process using fly ash were critically assessed. The

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energy consumption of the entire high-gravity carbonation ranged from 80 to 169 kWh/t-CO2

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(0.29−0.61 GJ/t-CO2). Compared with the scenarios of business-as-usual and conventional

Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Road, Daan District, Taipei City, 10673 Taiwan ‡ Carbon Cycle Research Center, National Taiwan University, 71 Fan-Lan Road, Da-an District, Taipei City, 10672 Taiwan § Department of Environmental Science and Engineering, College of the Environment & Ecology, and Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Xiamen University, Xiamen 361102, China.

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ACS Paragon Plus Environment


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carbon capture and storage plant, the economic benefit from the high-gravity carbonation process

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was approximately 90 and 74 USD per ton of CO2 fixation, respectively.

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1. INTRODUCTION

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Carbon capture and utilization by mineralization (CCUM) offers several advantages over

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conventional CO2 capture technologies such as chemical absorption. For instance, CCUM uses

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industrial alkaline wastes rather than chemical absorbents such as amine solution (toxic to human

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and environmental health).1 By the CCUM, CO2 can be fixed and mineralized as solid

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precipitates that can be directly used, eliminating the need for a pressurized pipeline and tank and

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thereby reducing the operating cost.2 Moreover, the reacted alkaline wastes can be used as

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supplementary cementitious materials (SCM) in the blended cement mortar,3 which can meet the

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concept of circular economy. With respect to CO2 fixation capacity, product durability and

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environmental sustainability, CCUM is superior to other carbon capture and storage (CCS)

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technologies.4,

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transfer rate, especially the slow kinetics of CO2 dissolution.6 To overcome this barrier, Pan et

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al.7, 8 have developed a high-gravity carbonation (HiGCarb) process to enhance the overall mass

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transfer efficiency by using a rotating packed bed reactor for CO2 mineralization.

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However, the efficiency of CCUM is usually restricted by the limited mass

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On the other hand, careful control of air pollutant emissions in the flue gas such as nitrogen

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oxides (NOx)9, 10 and particulate matters (PM)11, 12 is another important challenge for industry, as

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these emissions can lead to severe impacts on human and environmental health.13, 14 However,

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existing air pollutant control technologies, which have been operated for many decades, are not

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efficient and effective in terms of energy and resource usages as well as land footprint. As for

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NOx, the current control technology is selective catalytic reduction (SCR), which has to be

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operated under high temperatures for the catalysts to reductively convert NOx to N2. Thus, the

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operating costs of SCR including heating and catalysts are relatively high.15 In the case of PM,

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the suspended particles are usually separated from the trajectory of the gas stream by external

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forces.16 To enhance the effectiveness of external forces on the particles, the existing collectors

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generate intensified turbulence of the gas stream (e.g., cyclone) or manage to make the particles

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larger (e.g., wet scrubber and venturi scrubber) such that the momentum can be bolstered. Both

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measures would consume a great deal of energy or could lead to a considerable pressure drop.

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In the face of climate change, industrial air pollution controls such as NOx and PM should

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be integrated with CO2 reduction and/or capture and utilization to provide an overall green

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solution for achieving a circular economy. The HiGCarb process could be considered as an

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alternative to simultaneously controlling industrial air pollutants and CO2 emissions. An

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alternative NOx control strategy to SCR is oxidizing NOx, especially nitrogen monoxide (NO),

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into nitrogen oxides with higher valences, i.e., N2O5, such that the solubility of NOx could be

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drastically elevated.10 Thereafter, due to the improved mass transfer within the HiGCarb system,

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NOx is expected to dissolve into the slurry and be removed under ambient temperature and

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pressure. In addition, there is a similarity between the HiGCarb system and the wet scrubber,

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with respect to structure design. In other words, the HiGCarb process is expected to be capable

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of dealing with multiple types of air pollutants. Three major mechanisms dominating the motion

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of particles in wet scrubbers including diffusion,17 interception,18 and inertial impaction19 can be

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enhanced by high-speed rotation.

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To the best of our knowledge, this article should be considered a pioneering study

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evaluating the environmental benefits of simultaneous CO2 capture and utilization, and industrial

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air pollutant control via the developed HiGCarb process. Both PCFA and blowdown wastewater

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from a petrochemical plant were introduced to reduce the emissions of CO2 and air pollutants

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(i.e., NOx and PM). The objectives of the study were to (1) evaluate the performance of the

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HiGCarb process for CO2 mineralization using PCFA at a petrochemical plant; (2) investigate

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the removal efficiency of NOx and PM via the HiGCarb process; (3) assess the physico-chemical

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properties of PCFA before and after the HiGCarb process for further utilization as SCM in

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cement mortars; and (4) determine the environmental benefits for simultaneous removal of CO2,

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NOx and PM in terms of removal efficiency, energy consumption, and economic analysis.

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2. MATERIALS AND METHODS

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2.1 Alkaline Wastes and Exhaust Stream in the Petrochemical Industry

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The on-site operation of HiGCarb experiments were conducted at a petrochemical plant in

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Taiwan. Both PCFA and blowdown wastewater were used to purify the flue gas via the HiGCarb

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process. The reactive calcium species in PCFA was about 13.9%, while the Ca2+ concentration in

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the blowdown wastewater was 1239.0 ± 1.4 mg/L. The exhaust stream originated from a hard

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coal-fired power plant and passed on to the HiGCarb system through SCR, an electrical

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precipitator, and an exhaust stream desulfurization system. The concentrations of CO2, NOx and

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PM in the exhaust stream were about 12.81 ± 0.03%, 31.00 ± 0.31 ppm, and 1.44 ± 0.04 mg/m3,

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respectively. The temperature and humidity of the exhaust stream were maintained at 54 oC and

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14.9%, respectively, during the entire operation.

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2.2 HiGCarb Process for CO2 Mineralization and Air Pollutant Removal

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In this study, the HiGCarb process was equipped with a counter-current rotating packed bed

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reactor with a packing size of 25.4 cm in height and 28.0 cm in width. The body of the

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equipment is made up of SS-316 to improve resistance to corrosive gaseous components (e.g., 5



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sulphur) in flue gas. During the HiGCarb process, the exhaust stream from a petrochemical plant

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was introduced by a blower. The fresh PCFA was mixed with blowdown wastewater in a mixture

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tank, where the liquid-to-solid ratio of PCFA slurry was maintained at 10.0 L/kg. After the

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HiGCarb process, the reacted PCFA slurry was discharged into a sediment tank for solid and

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liquid separation. In addition, the gas flow rate of the exhaust stream was designated at

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1.47−1.84 m3/min with a PCFA slurry flow rate of 0.02 m3/min. For NOx removal, ozone gas [O3]

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was generated by a corona ozone generator (LAB2B, Triogen, UK), and then was injected into

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the HiGCarb at a flow rate of 0.1 L/min.

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2.3 Techniques of PM Sampling and Air Pollutant Measurement

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PM samples were collected by micro-orifice uniform deposit impactors (Model 110,

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MOUDI, MSP, US) consisting of 11 cascades of impactors with 47-mm aluminum foil filters.

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The pressure from the 1st to 7th cascade was 20 inches of water while the one from 8th to 11th was

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70 inches of water, leading to a decrease in the cut size of each impactor with the increment of

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sequences. Therefore, the velocity of PM increases gradually at each cascade, and the particles

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that cannot maintain the trajectory with gas flow hit the impactor. To ensure that the amount of

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the PM sample is sufficient for analysis, the time span of PM sampling was set as two hours at a

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sampling flow rate of 30 L/min. Moreover, the sampling of PM was performed at 50 oC to

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prevent condensation of water vapor. Before and after collection of PM samples, the impactors

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were conditioned under 120 oC for 24 hours and weighed by an electronic balance (AUW220D,

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Shimadzu, Japan) with an appreciable precision of 10-5 gram. The size distribution of PM was

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analyzed by calculating the median diameter and geometric standard deviation via a log-

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probability plot.20

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A portable gas analyzer (PG-350, Horiba, Japan) was used to on-line measure the gaseous

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compositions including CO2, SO2, NO/NOx and O2 in the flue gas of the petrochemical plant.

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The resolutions of both O2 and CO2 were 0.01 vol.%, and 0.01 ppm for both SO2 and NO/NOx.

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The concentration of O2 in the flue gas was maintained below 6% to prevent the malfunction of

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airtight components caused by faulty operation.

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2.4 Potency of Carbonated PCFA Utilization as SCM

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In this study, the carbonated PCFA products were used as SCM to partially substitute for

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clinker in cement mortar. Various characterization techniques including thermogravimetric (TG),

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derivative thermogravimetric (DTG), Fourier transform infrared spectroscopy (FTIR) and

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compressive strength analyses were applied to evaluate the feasibility of carbonated PCFA as

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SCM in cement mortars. The TG analysis (STA6000, PerkinElmer, USA) was carried out in the

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range of 50 to 950oC with a heating rate of 10 oC/min under nitrogen gas atmosphere. To verify

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the released gas after decomposition, FTIR (Frontier, PerkinElmer, USA) analysis was carried

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out with a scanning range of 4000 to 600 cm-1 and a resolution of 4 cm-1. Furthermore, the

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compressive strength of blended cement with different substitution ratios (i.e., 5%, 10%, 15%)

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was evaluated by following the guidance from ASTM C109.21

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2.5 Environmental Benefit Assessment of Carbonation Process

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In this study, three scenarios including business-as-usual (BAU), implementation of

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commercial CCS technology, and deployment of HiGCarb process were established for

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environmental benefit assessment. The HiGCarb process with the optimal performance (i.e.,

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capturing one ton of CO2 accompanied by 0.152 kg of NOx removal with the energy

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consumption of 83.6 kWh) was set as the baseline scenario. In the environmental benefit

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assessment, the total social costs include (i) direct expenditure due to pollution tax incurred by

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the industry (so-called private cost), and (ii) external cost (so-called social cost) from pollutant

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emissions to impose a negative effect on an unrelated third party.

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3. RESULTS AND DISCUSSION

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3.1 Efficiency and Capacity of CO2 Mineralization

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Figure 1 shows CO2 removal efficiency and capture capacity under various operating

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conditions. The highest capture efficiency was 95.6% with a gas flow rate of 1.47 m3/min under

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a rotating speed of 600 rpm. It is noted that the preferable rotating speed of the RPB reactor for

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achieving the highest removal efficiency should range between 550 and 600 rpm. Beyond the

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rotating speed of 600 rpm, the CO2 removal efficiency began to decrease. This was ascribed to

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the broken liquid seal at higher rotating speed such that the exhaust stream might pass through

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the packing area without reaction.22 On the other hand, as gas flow went up, the removal

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efficiency was sacrificed to some extent. However, satisfactory performance was still achievable

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when the gas flow rate was 1.47 m3/min, equivalent to a gas-to-liquid (G/L) ratio of 58.8.

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Aside from CO2 removal efficiency, the actual CO2 capture capacity should be critically

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considered since the actual capture capacity reflects the removal efficiency and treatment

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capacity per unit equipment. As shown in Figure 1, the maximum CO2 capture capacity of the

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HiGCarb process using PCFA was approximately 600 kg per day at a gas flow of 1.47 m3/min

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(i.e., inflow CO2 concentration: 12.81 ± 0.03%). From the viewpoint of economics, considering a 8


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carbon price of 6.25 USD/ton-CO2,6 an additional carbon credit of about 3722 USD/day can be

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obtained using the current HiGCarb process. Not only can the captured CO2 exempt the emission

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source from a carbon tax, but also industry could gain profits from the trading of surplus CO2

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emission permits.

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3.2 Enhanced NOx Reduction from Exhaust Stream

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To achieve enhanced NOx reduction from the exhaust stream, the O3 gas was applied in the

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HiGCarb process as an oxidizing agent to convert NO to higher oxidation state components such

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as NO2 and NO3, as shown in eq 1. Since NO3 is a highly reactive radical, it can oxidize NO2 to

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N2O5,23 as shown in eq 2. The solubility of N2O5 in water is much greater than that of NO and

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NO2. NO() + O( ) → NO () + O( ) ,

= 1 2

NO( ) + NO ∙ → N O( )

(1)

(2)

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In the HiGCarb process, the NO was first oxidized by O3 to form NO2, followed by further

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oxidation to N2O5. Therefore, the solubility of NOx can be improved and the NOx can be easily

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removed from the exhaust stream by absorption of nitric acid (HNO3) form into solution, as

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shown in eq 3.10 On the other hand, the catalytic reaction can be initiated and sustained by the

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radicals (OH·) due to the presence of O3. Due to the high reactivity of radicals, the catalytic

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reaction was much faster than the NOx oxidation. H O() + N O( ) → 2HNO()

(3)

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Figure 2 shows the NOx removal efficiency by the HiGCarb process under various rotating

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speeds and gas flow rates (e.g., G/L ratio). The results indicated that, without the PFCA slurry,

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the NOx removal efficiency varied between 28.1% and 91.7% as the gas flow increased from

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1.47 m3/min to 1.84 m3/min, equivalent to a G/L ratio of 73.5 to 92.0. The decrease in efficiency

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could be attributed to the decreased O3/NOx ratio and shortened retention time, resulting in poor

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performance in oxidation. In addition, when nitrogen oxides dissolve, the solution continuously

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acidifies. As a result, the concentration gradient at the gaseous-aqueous interface keeps

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decreasing, with the dissolution proceeding, resulting in a reduction of solubility.

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On the other hand, with the PFCA slurry, NOx removal efficiency can significantly increase

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to 95.7−99.1%, corresponding to capture capacities of 0.08−0.09 kg NOx per day. The rotating

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speed should be operated at 550−600 rpm to maintain a sufficient mass transfer rate for NOx

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dissolution. It was noted that the dissolution of NOx did not exert considerable negative influence

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on the performance of carbonation (CO2 removal). In other words, enhanced NOx reduction from

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flue gas could be successfully incorporated into the HiGCarb process without sacrificing the CO2

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removal efficiency by carbonation. Compared with conventional NOx removal processes such as

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SCR, this process required less energy and material inputs, thus reducing the cost.

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3.3 Enhanced PM Removal from Exhaust Stream

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Figure 3 shows the outlet mass proportions and removal efficiency of PM by the HiGCarb

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process at various rotating speeds. The results indicated that the PM removal efficiencies varied

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with particle size. The highest PM removal efficiency was about 84.9% at 700 rpm with a G/L

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ratio of 73.5. In particular, the removal efficiencies of PM2.5 and PM10 were higher than 70.8%

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and 74.2%, respectively. According to the segmented removal efficiency analysis, the HiGCarb

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process was effective at removing particles ranging in size from 0.25 µm to 1.0 µm, for the mass

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partition falling from 74.0% to as low as 15.0% at 700 rpm. The enhanced removal of PM by the

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HiGCarb system could be attributed to the intensive interaction between PM and fine droplets

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via diffusion, interception and impaction.

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In this study, a modified mathematical model based on Licht equation24 was developed to

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describe the effectiveness of a specific collector in removing PM of various particle sizes using

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the HiGCarb process. Similar to conventional wet scrubbers, fine and tiny liquid droplets in

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HiGCarb are responsible for the PM collection. As the rotating speed shifts, the droplet diameter

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changes accordingly, thereby resulting in varying chances and mechanism of PM collection. As a

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result, rather than being the only independent parameter in the Licht equation, a

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dimensionless factor, i.e., the ratio of particle diameter (dp) to droplet diameter (D), was used for

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modeling, as described by eq 4:

208

=1−"

'( +

#$×&

)

*

(4)

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where a and b were the constants used to describe fractional removal efficiency. Figure S1 (see

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SI) depicts the fitness of the developed mathematical model with the measured experimental

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values. The results showed satisfying correlations between the calculated and measured values,

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indicating the applicability of the modified model.

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Table 1 presents the calculated parameters determined by the developed model and

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experimental data. The droplet diameter decreased with an increase in rotating speeds, resulting

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in an increase of / , ratio. The decreased droplet diameter means that the liquid was scattered

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into many tiny droplets, thereafter raising the chance of collision between droplets and particles.

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The results indicated that the minimum cut size of PM (i.e., at a removal efficiency of 50%) in

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the HiGCarb process was about 0.066−0.120 µm, which was greater than that in conventional

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cyclone.20 It was also observed that the cut size of PM varied as the rotating speed changed in the

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HiGCarb process. This could be ascribed to the dominant mechanisms of PM removal, including

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Brownian diffusion, interception and inertial impaction,25 associated with the variation of droplet

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diameter and velocity under different rotating speeds. As the rotating speed increased, the droplet

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diameter decreased while the velocity of droplet increased. In this case, the removal mechanism

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by Brownian diffusion would decrease and ultimately the inertial impaction would become the

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dominant mechanism. In addition, the results indicated that the PM cut size in the HiGCarb

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process was smaller than 0.25 µm, which was agreed with the observation shown in Figure 3

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where the remained mass portion of PM0.25 at outlet stream (i.e., blue bar) was relatively higher

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than that of other PM particle sizes.

229 230

3.4 Utilization of Carbonated PCFA in Cement Mortars

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In this study, the carbonated PCFA was utilized as SCM in cement mortar at different

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substitution ratios of 5%, 10% and 15%. Figure 4 shows the mechanical strength of blended

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cement mortar with various substitution ratios of PCFA. The compressive strength decreased

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gradually as the substitution ratio of PCFA increased. It was observed that the compressive 12


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strength of blended cement with a substitution ratio of 5% of carbonated PCFA (i.e., C-PCFA)

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was 126.5% higher than that of original Portland cement. The compressive strength of 5% C-

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PCFA substituted cement at 3, 7 and 28 days reached 22.6 ± 3.1, 24.7 ± 2.3 and 38.1 ± 2.5 MPa,

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respectively, meeting the ASTM standard. The results also indicated that blended cement with

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carbonated PCFA in 5−15% substitution ratio exhibited superior compressive strength to cement

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with fresh PCFA.

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This phenomenon could be ascribed to the fact that the produced calcium carbonate behaved

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as fillers, taking possession of void space between aggregates.26 In addition, the added PCFA

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plays an important role in nucleation, facilitating the formation of a compact structure.27-29

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Minerals of hydration products such as C3A (eq 5−6) could be activated by the calcite product,

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thereby resulting in an accelerated hydration process.30, 31 However, this effect of enhancement

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on strength development might be neutralized by the lack of silica (e.g., C3S [3CaO ∙ SiO ] and

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C2S [2CaO ∙ SiO ]) at high substitution ratios of carbonated PCFA.

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C A + 3CC3 + 30H → C A ∙ 3CC3 ∙ 30H

(5)

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C A + CC3 + 11H → C A ∙ CC3 ∙ 11H

(6)

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where C3A, CC3, and H were tricalcium aluminate [3CaO ∙ Al O ], calcium carbonate [CaCO3],

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and H2O, respectively.

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According to the chemical composition analysis, the content of free-CaO in PCFA was

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3.24%, which may cause potential concerns in stability for fresh PCFA. After carbonation, the

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content of free CaO in PCFA decreased significantly to 0.21%. This was confirmed by the peak

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of Ca(OH)2 at 415oC in the DTG curve as shown in Figure S2 (see SI), which is ascribed to the

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mass loss of water combined with CaO. After carbonation, the peak nearly disappeared.

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Furthermore, in the TG/DTG curve (Figure S2), the peak of CaCO3 product at 650−850oC

259

increased after carbonation, indicating that the CaCO3 precipitates were formed in the course of

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carbonation. On the other hand, a distinct intensification of the peak located in 2300 cm-1 at

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650−850 oC was observed, indicating a substantial increase in the content of CaCO3 in the

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carbonated PCFA. It was noted that the captured CO2 may not be released back into the

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atmosphere, unless exposed in a critical environment such as acid precipitation. Based on the

264

above observations, it suggests that the carbonated PCFA should be suitable to serve as SCM in

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cement mortar, up to a substitution ratio of 5% without significantly decrease in compressive

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strength.

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3.5 Assessment of Environmental Benefits for HiGCarb Process

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Figure 5 shows the effects of the key operating factors of HiGCarb process on the removal

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of CO2, NOx and PM in the flue gas. To balance engineering performance and energy

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1 ), consumption, the maximum capture capacity, i.e., 570 kg CO2 per day (following the arrow ○

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2 ). In this case, was determined at an optimum centrifugal force of 61 m/s2 (following the Arrow ○

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the energy consumptions of RPB reactor and auxiliaries were expected to be 15 and 65 kWh/t-

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3 ). Under this favorable operating conditions, arrows ○ 4 CO2, respectively (following the arrow ○

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5 also illustrate the capture capacity of NOx (i.e., 0.087 kg per day) and removal efficiency and ○

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of PM (i.e., 83%), respectively.

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In addition to the aforementioned engineering performance, the overall energy consumption

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is an important consideration for CO2 mineralization process. The experimental data indicated

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that the energy consumption of the entire HiGCarb process varied from 80 to 169 kWh/t-CO2

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(i.e., 0.29−0.61 GJ/t-CO2), which meets the requirement (i.e., less than 420 kWh/t-CO2)

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suggested by the USEPA.32 It is also noted that the energy consumption of HiGCarb process is

282

quite attractive as energy acquired from burning coal and methane is about 34 and 55 GJ/ton,

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respectively. In addition, the energy intensity was inversely proportional to the carbon capture

284

scale; that is, for scenarios with the greatest amount of CO2 being fixed, the energy consumption

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for capturing one unit of CO2 would be diluted. On the other hand, the pump and the blower

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consumed more energy than the reactor did. In the future, it is expected that the tank would be

287

elevated such that the height difference between the reactor and the tank could be reduced,

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resulting in less power needed for delivering the slurry. Moreover, it is hoped that waste heat can

289

be used to improve the momentum of the exhaust stream. Combined with the modification in the

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design of the reactor, it would be more energy efficient to maintain the gas flow rate.

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Figure 6 illustrates the economic benefits of the HiGCarb process comparable to the BAU

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and CCS scenarios based on a function unit of one ton of CO2 fixation. In the BAU scenario (no

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CCS technology or HiGCarb process was applied), each ton of emitted CO2 would lead to a tax

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of 31.06 USD.33 Thus, the corresponding environmental impact (direct expenditure) was

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estimated to be 12.0 USD. Similarly, the tax and environmental impact from NOx emission

296

would cost 0.54

34-36

and 8.91 USD,37 respectively. Therefore, the total social cost in the BAU

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scenario, including 31.6 USD paid by enterprise and 20.9 USD of external cost, is about 52.5

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USD/t-CO2 equivalent.

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Most CCS plants operate via chemical sorption and geological storage, resulting in

301

difficulty in utilization of the captured CO2, and no other profit return can be expected. The

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minimum operating costs of existing CCS plants were approximately 50.00 USD/t-CO2.38 On the

303

other hand, for each ton of CO2 captured, a carbon credit of about 6.25 USD can be acquired.6 In

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addition, when geologic storage with enhanced oil recovery was implemented, about 27.5

305

USD/t-CO2 could be acquired,39 resulting in an expense of 16.6 USD/t-CO2. Therefore, the total

306

social expenditure on existing CCS was estimated to be 25.7 USD/t-CO2. Furthermore, an

307

enhanced pollution control technology might be required in case the sorbent is poisoned by the

308

acidic pollutant. The results indicate that the existing taxation regime is not powerful enough to

309

offer a reasonable incentive to deploy a CCS plant. Therefore, the emphasis should be placed on

310

technology evolution and regulation reformation.

311

As for the HiGCarb process, the capital cost of the HiGCarb equipment with a designed

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capture scale of 3 tons CO2 per day was 56,000 USD. The life span of the HiGCarb equipment

313

was estimated to be 10 years. Therefore, the capital cost is diluted by the long service time and

314

could be neglected. Under the optimal operating condition, the electricity as well as ozone

315

generation, lead to a total operating cost of 8.4 USD/t-CO2. On the other hand, the profits

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including carbon credits and product sales were 61.3 USD/t-CO2. Therefore, the net economic

317

benefit for the HiGCarb process was 57.9 USD/t-CO2. Compared with the scenarios of BAU and

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conventional CCS technology, the economic benefit from HiGCarb process was about 89.5 (as

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indicated by C→A) and 74.2 (as indicated by C→B) USD per ton of CO2 fixation, respectively.

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ASSOCIATED CONTENT

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Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website at

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DOI:

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ASSOCIATED CONTENT

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Supporting Information

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Relationship between experimental and calculated removal efficiencies for PM with

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different diameters, and thermal analysis spectra (i.e., TG-FTIR and TG-DTG) for fresh and

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carbonated PFCA.

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AUTHOR INFORMATION

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Corresponding Author

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* Phone: +886-2-23622510; fax: +886-2-23661642; e-mail: [email protected] . Notes The authors declare no competing financial interest.

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ACKNOWLEDGMENTS

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High appreciation goes to the Ministry of Science and Technology (MOST) of Taiwan

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(R.O.C.) under Grant Number MOST 106-3113-E-007-002 and 103-2911-I-002-596 for the

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financial support.

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Table 1. Model parameters for determining cut size of PM removal under different rotating

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speeds

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6( model parameters rotating Range of values 7 speed (rpm) a b #: # 55 0.53 550 2.5 × 10 ~7.3 × 10 118 0.68 600 2.3 × 10#: ~7.9 × 10# 650 23900 1.35 2.7 × 10#: ~8.6× 10# #: # 248000 1.71 700 2.9 × 10 ~9.2× 10 a : with a confidence interval of 95% (p PM10 were 11.4%, 74.0%, 3.6%, 6.4% and 4.6%,

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respectively.

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Figure 4. Compressive strength of blended cement with different substitution ratios of fresh and

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carbonated PCFA at curing ages of (a) 3rd, (b) 7th, (c) 28th, and (d) 56th days.

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Figure 5. Systematic approach to determination of optimal operating conditions for HiGCarb

446

Process. The accessories include blower and slurry pump. Acronym: RPB (rotating

447

packed bed)

448

Figure 6. Environmental benefit assessment for the implementation of HiGCarb process. The

449

functional unit is set as one ton of CO2 fixation. Acronym: BAU (bussiness-as-usual),

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CCS (carbon capture and storage), EOR (enhanced oil recovery).

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Figure 1.

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Figure 2.

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Figure 3.

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Figure 4.

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Figure 5.

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Figure 6.

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Graphical Abstract


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