CO2 Removal Process Research Articles

In-situ biogas upgrading during anaerobic digestion of food waste amended with walnut shell biochar at bench scale.

A modified version of an in-situ CO2 removal process was applied during anaerobic digestion of food waste with two types of walnut shell biochar at bench scale under batch operating mode. Compared with the coarse walnut shell biochar, the fine walnut shell biochar has a higher ash content (43 vs. 36 wt%) and higher concentrations of calcium (31 vs. 19 wt% of ash), magnesium (8.4 vs. 5.6 wt% of ash) and sodium (23.4 vs. 0.3 wt% of ash), but a lower potassium concentration (0.2 vs. 40% wt% of ash). The 0.96-3.83 g biochar (g VSadded)-1 fine walnut shell biochar amended digesters produced biogas with 77.5%-98.1% CH4 content by removing 40%-96% of the CO2 compared with the control digesters at mesophilic and thermophilic temperature conditions. In a direct comparison at 1.83 g biochar (g VSadded)-1, the fine walnut shell biochar amended digesters (85.7% CH4 content and 61% CO2 removal) outperformed the coarse walnut shell biochar amended digesters (78.9% CH4 content and 51% CO2 removal). Biochar addition also increased alkalinity as CaCO3 from 2800 mg L-1 in the control digesters to 4800-6800 mg L-1, providing process stability for food waste anaerobic digestion.

Molecular Dynamic Simulation of Amine-CO2 Absorption Process

Objectives: Modelling and simulation of amine absorption process for CO2 removal at macro-scale is well established. This study used to investigate the amine-CO2 absorption process at molecular level using Molecular Dynamic (MD) simulation. Methods/Statistical Analysis: Analysis on different types of amine and blended amines for absorption process was conducted in this study. COMPASS and Ewald models used for force field and summation method calculation, respectively. Findings: The results shows MEA solvent was the highest tendency (39.70%) to interact with CO2 compared to DEA and MDEA because can directly react with CO2 and easily form carbamate ions. Due to the lack of –HN bond in MDEA, it was determined to be less reactive and suggested to be blended with other reactive amines. Blended MDEA/AMP (33.50%) and MDEA/PZ (23.80%) improved the efficiency of MDEA in CO2 absorption process. The addition of AMP and PZ assisted MDEA to have intermolecular interaction with CO2. Application/Improvements: Research on molecular modelling of amine absorption process for CO2 capture was proposed in this study to give insight about this process at molecular level and to analyse the intermolecular interaction between CO2 and amine solution.

Experimental results of split flow process using AMP/PZ solution for post‐combustion CO2 capture

AbstractThe goal of reducing energy consumption of the CO2 removal process from flue gas may be pursued by developing new solvents as well as by modifying the technological process itself. This paper provides a discussion of the experimental results obtained from a process development unit (PDU) using an aqueous 2‐amino‐2‐methyl‐1‐propanol (AMP) solution activated with piperazine (PZ) for post‐combustion carbon capture located at the Clean Coal Technologies Centre in Poland. The results are compared for two distinct process setups, namely one with the lean amine stream being split – a solution referred to as split flow, and a system with standard configuration. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

Exergy analysis: A CO2 removal plant using a-MDEA as the solvent

An exergy analysis was conducted for CO2 removal process from syngas using methyldiethanolamine activated by piperazine (a-MDEA). The process was simulated with Aspen HYSYS and the validation of the results was performed using the field data of Fanavaran Petrochemical Company. The process was divided into five separate sections. In order to determine the exergy loss, exergy balance equation was established around each section. The results showed that the highest exergy loss amongst five sections returns to the flasher (contributes 31.5% of total exergy loss); followed by the absorber column, stripper column, heat recovery section and the pump. In order to decrease the exergy loss in the process, piperazine concentration in a-MDEA solvent was increased which led to reduction in amine solvent flow rate. According to the results, the total exergy loss is decreased from 3.25 MW to 2.63 MW. When the amine flow rate decreased by 27%, the exergy loss, total energy consumption and the total utilities cost decreased by 19%, 18% and 25%, respectively.

1,2,3-Trimethoxypropane: A Glycerol-Derived Physical Solvent for CO2 Absorption

1,2,3-Trimethoxypropane (1,2,3-TMP) is the trimethyl ether of propane-1,2,3-triol, better known as glycerol, which can be derived from triglycerides originating from either plant or animal sources. Despite its simple structure and the ubiquity of its glycerol precursor, successful synthesis of 1,2,3-TMP was only recently reported in the literature, with studies suggesting it may be a “green” and nontoxic alternative to solvents such as diglyme, a constitutional isomer. However, no thermophysical properties of 1,2,3-TMP have yet been reported. Furthermore, the structure of 1,2,3-TMP is also analogous to polyether solvents used in the Selexol process for removal of CO2 and other “acid” gases from CH4, H2, etc. As such, examining the solubility of CO2 in 1,2,3-TMP is also of interest. This work details our initial studies and characterization of 1,2,3-TMP as a physical solvent for CO2 absorption, as well as the characterization of its density, viscosity, and vapor pressure with respect to temperature. 1,2,3-...

New process for simultaneous removal of CO2, SOX and NOX

A method for simultaneous removal of CO2, SOX and NOX from industrial flue gases through the injection of ozone diluted in nitrogen, oxygen or nitrogen/oxygen mixtures, as an oxidizing agent and with the addition of specific sequestrants, that induce the precipitation of nitrates and sulphates, is presented. This new process is related with the conventional CO2 removal method using chemical absorption, but presents as main innovation the possibility to remove also simultaneously SOX and NOX.

Solubility of carbon dioxide in aqueous solution of 1,5-diamino-2-methylpentane: Absorption and desorption property

This research focuses on carbon dioxide absorption using aqueous solution of 1,5-diamino-2-methylpentane (DAMP) in an isothermal batch reactor. Equilibrium CO2 loading by the proposed aqueous solution is measured at the temperature range 30–50°C, CO2 partial pressure range 5–150kPa, and different solvent concentrations. To prove the performance of the proposed diamine to capture CO2, absorption and desorption capacity, absorption rate and cyclic capacity of 1,5-diamino-2-methylpentan is measured and compared with MEA and MDEA. The experimental results show that the equilibrium CO2 loading of 1,5-diamino-2-methylpentane, MDEA and MEA are 0.86, 0.43 and 0.54 at 30°C, respectively. Lower volatility of 1,5-diamino-2-methylpentane compared to MEA results in a lower solvent loss through CO2 removal process. Applying the proposed amine in the absorption towers can decrease solvent circulating rate and required equilibrium stages.

Life cycle assessment of heat production from underground coal gasification

In Poland, coal is the main fuel used for heat production. Innovative clean coal technologies, which include underground coal gasification (UCG), are widely developed. This paper presents the analysis results of life cycle assessment (LCA) and material flow analysis (MFA) of using synthesis gas from UCG for heat production. The paper presents the results of a comparative analysis of MFA and LCA for four variants of heat production, which differed in the choice of gasifying agent and heat production installations. Environmental analysis was made based on LCA with ReCiPe Midpoint and ReCiPe Endpoint H/A method, which allowed to analyse of different categories of the environmental impact. LCA was performed based on the ISO 14040 standard using SimaPro 8.0 software with Ecoinvent 3.1 database (Ecoinvent 2014). Umberto NXT Universal software was used to develop MFA for heat production. LCA analyses included hard coal from a Polish mine and synthesis gas obtained in the experimental installations in the Central Mining Institute in Poland. MFA performed for technology of utilizing gases from UCG have made it possible to visualize materials and energy flow between different unit processes in the whole technological chain. Moreover, the analyses enabled identification of unit processes with the largest consumption of raw materials, energy and the biggest emissions into the environment. It has been shown that the lowest environmental burden is attributed to the technology, which uses high-pressure chamber with gas turbine in which the synthesis gas from UCG is burned and oxygen was a gasifying agent. Analysis of LCA results showed that the major environmental burden includes greenhouse gas (GHG) emission and the fossil fuels depletion. GHG emission results primarily from the direct emission of CO2 from gas combustion for heat production and electricity consumption used in gasifying agents preparation phase. In order to increase the environmental efficiency of heat production technology using UCG, the most important activity to be considered is limitation of dust-gas emissions, including primarily CO2 removal process and efficiency increase of the installation, which is reflected in the reduction of coal consumption. It is important to highlight that this is the first attempt of MFA and LCA of heat production from UCG gas. Since no LCA has ever been conducted on the heat production from underground coal gasification, this study is the first work about LCA of the heat production from UCG technology. This is the first approach which contains a whole chain of unconventional heat production including preparation stages of gasifying agents, underground coal gasification, gas purification and heat production.

Upgrading biogas by a low-temperature CO2 removal technique

Biogas, a renewable energy source, is primarily composed of methane and carbon dioxide and other gaseous species. Biogas upgrading for removing CO2 from raw biogas is a necessary step before the biogas to be used as vehicle fuel or injected into the natural gas grid. Therefore, the present work aimed to propose a low-temperature CO2 removal process as an alternative to the conventional biogas upgrading technologies (water scrubbing, chemical and physical scrubbing, membranes and Pressure swing adsorption). A typical model biogas mixture of 60mol.% CH4 and 40mol.% CO2 is considered. The present process showed that a product purity of 94.5mol.% CH4 is obtained from compressed biogas by combining distillation, flash separation, auxiliary refrigeration and internal heat recovery with a potential specific energy consumption of 0.26kWh/Nm3 raw biogas. The process has been simulated in Aspen HYSYS with avoiding the occurrence of CO2 freeze-out. The process delivers the captured CO2 in liquid form with a purity of 99.7mol.% as a by-product for transport at 110bar. It is concluded that the proposed upgrading process can serve as a new environmentally friendly approach to CO2 removal with an interesting energy-efficient alternative to the conventional upgrading techniques.

Citrate Sol–Gel Method for the Preparation of Sodium Zirconate for High-Temperature CO2 Sorption

The use of sorbents capable of capturing high-temperature CO2 increases the overall efficiency of CO2 removal processes, without the need for cooling the flue gases. In this study, Na2ZrO3 for high-temperature CO2 sorption was newly prepared using a citrate sol–gel method. The characteristics and CO2 sorption behavior of the prepared Na2ZrO3 were examined by field-emission scanning electron microscopy, N2 adsorption analysis, X-ray diffraction, and thermogravimetric analysis, and compared with those of Na2ZrO3 synthesized using a conventional solid-state method. Na2ZrO3 could be synthesized at lower temperature by using the citrate sol–gel method compared to the case of solid-state method. Na2ZrO3 prepared using the citrate sol–gel method showed excellent CO2 sorption performance: high sorption capacity (17.5–21.0 wt % at 823 K and 1 bar), fast sorption kinetics, and good cycling stability. Kinetic analysis was also conducted by fitting the CO2 sorption behavior to the double exponential model.

Laboratory Studies of Post-combustion CO2 Capture by Absorption with MEA and AMP Solvents

With regard to the climate policy that has been adopted, the implementation of the carbon capture and storage and carbon capture and utilization technologies seems to be the unavoidable solution to reduce emissions from the energy sector. As most Polish energy is derived from coal, the government has taken steps to reduce CO2 emissions by initiating a strategic research program—“Advanced technologies for energy generation: Development of a technology for highly efficient zero-emission coal-fired power units integrated with CO2 capture.” This paper presents the results of an investigation of a process for continuous removal of CO2 from the gas stream on a laboratory unit. This study was conducted at the Institute for Chemical Processing of Coal in Zabrze, Poland. The purpose of the tests that were conducted was to establish the effect of the sorption column load on CO2 recovery and on the process regeneration heat duty. In the second part of the paper, a simple comparison of three amine solvents is presented as a part of the solvent selection process for further pilot plant tests.

Polyamidoamine-facilitated poly(ethylene glycol)/ionic liquid based pressure swing membrane absorption process for CO2 removal from shifted syngas

Pre-combustion capture of CO2 from shifted syngas is a major route for carbon capture and sequestration from integrated gasification combined cycle for coal as the fuel. Conventional Selexol absorption-based processes involve cooling the gas to near-ambient temperature. A novel cyclic 5-valve pressure swing membrane absorption (PSMAB) process is being developed for CO2 removal from lower-temperature shifted syngas at ∼100°C in hollow-fiber membrane contactors using ionic liquid (IL) absorbent, 1-butyl-3-methyl-imidazolium dicyanamide ([bmim][DCA]). Separation performance is considerably enhanced by adding nonvolatile polyamidoamine (PAMAM) dendrimer Generation 0 to the IL at higher temperatures for a 40% CO2, 60% He (surrogate for H2) feed. Absorption performance in the cyclic process depends on selective sorption and other absorbent properties especially viscosity and hollow-fiber membrane contactor module design employing microporous hydrophobized polyether ether ketone (PEEK) hollow fiber-based membranes. Equilibrium CO2 solubility and CO2–He selectivity for IL, [bmim][DCA], has been compared with those for poly(ethylene glycol) (PEG) 400 which yields improved equilibrium CO2–He selectivity and CO2 absorption with/without 20wt% PAMAM dendrimer over the temperature range 50–100°C. The PSMAB process separation performance has been explored using PEG 400-based absorbent in two hollow-fiber membrane contactor modules with improved designs in series at temperatures up to 100°C and feed-gas pressures up to 1720kPag. This performance has been compared with that of the system using IL, [bmim][DCA]. The dendrimer-IL system performance for two modules-in-series with reduced dead volume considerably enhanced separation yielding >95% CO2 in the CO2-enriched product; further this performance exceeded easily that of the PEG 400-based system.

Assessment of CO2 capture using potassium-based sorbents in circulating fluidized bed reactor by multiscale modeling

Potassium-based carbonate looping in a circulating fluidized bed system including an absorber and a regenerator is a potential CO2 capture technology, which has attracted great focus in recent years. In the current work, the simulation of CO2 capture process is carried out by considering the influence of clusters on the hydrodynamic and reaction, where the multiscale reaction model is employed to reflect the change of CO2 absorption rate caused by clusters. The non-uniform flow structure in the absorber can be predicted very well. The distributions of solid sorbents and temperature field are also predicted. The results reveal that there exists heterogeneous feature for temperature and solid sorbents owing to the cluster formation. The prediction considering the cluster effect is more consistent with experimental data. Meanwhile, the impact of gas inlet velocities on the hydrodynamic and CO2 removal process is evaluated.

CFD–PBE numerical simulation of CO2 capture using MgO-based sorbent

In this work a novel regenerative sorption enhanced water gas shift (SEWGS) process for high temperature and high pressure CO2 removal from Syngas in a circulating fluidized bed has been proposed. The process is based on an MgO-based solid sorbent. The major advantages of this sorbent include reducing the amount of WGS catalyst required to fully shift the Syngas to CO2 and H2 and eliminating Syngas cooling/reheating that is necessary for current CO2 separation systems. Another goal of this study was to improve the existing mono-disperse continuum models, i.e., Eulerian-Granular models that describe multiphase systems such as fluidized bed reactors, by considering the effect of poly-dispersity through a novel mathematical approach. As a result, a two-way coupled Computational Fluid Dynamics–Population Balance Model (CFD–PBM) along with an efficient numerical solution for the population balance equation has been proposed. The coupled CFD–PBM model along with the two-zone variable diffusivity shrinking core reaction model was utilized in baseline design of a bench scale high temperature, high pressure regenerative carbon capture process in the riser section of a circulation fluidized bed.

Evaluation of CO2 removal from a CO2 + CH4 gas mixture using gas hydrate formation in liquid water and THF solutions

In this work, the performance of hydrate formation for CO2 removal from a simulated recovered shale gas (40mol% CO2 and 60mol% CH4) was evaluated in liquid water, and THF and THF/SDS solutions. Experiments were carried out at a fixed temperature of 277.15K and in the pressure range of (2.8–6.7) MPa. The impact of driving force (overpressure) on hydrate growth and CO2 selectivity was studied both in liquid water and in THF solutions. It was found that higher driving force resulted in a reduction of the final gas uptake as well as a significant decrease of the CO2 recovery and separation factor. The results indicated that mass transfer for hydrate growth was greatly hindered at high driving force, and the competition between CH4 and CO2 molecules for the occupancy of hydrate cavities became stronger with the increase of driving force. Although the kinetics of hydrate formation with the CO2/CH4 gas mixture was improved by adding THF and SDS into liquid water, the selectivity for CO2 removal from the CO2/CH4 gas mixture was compromised as compared to that in liquid water. The highest CO2 recovery (52%) and separation factor (8.8) were obtained at a low driving force (2.5MPa) in liquid water, which were much higher than those obtained in THF and THF/SDS solutions. As a result, enhancing the kinetics of hydrate formation without reducing CO2 selectivity is the key factor to improve the hydrate based gas separation process for CO2 removal from the CO2/CH4 gas mixture.

Characterisation of Vibration Causing a Two-phase Flow in CO2-removal Process

:Activated-methyldiethanolamine (a-MDEA)-based CO2 removal is a well-established process for deep removal of CO2 from synthesis gas preparation for ammonia synthesis. The process utilises a two-step regeneration of solvent via depressurisation and heating. During depressurisation step, CO2 is released from amine solvent forms a separate vapour phase thus leading to a two-phase flow. The pressure drop in piping network and thermo-kinetic of desorption are highly interlinked phenomena. Accurate estimation of the pressure profile is therefore essential for designing piping network. A methodology has been described in this paper which takes into consideration simultaneous solution of mass, energy and momentum balance equations coupled with thermo-kinetic interaction of CO2 and a-MDEA solvent. This has been applied to two industrial cases to find flow pattern and location in piping network and verified with commercial software available. In one case, a segment of piping network was found in the slug flow and in other case fluid velocity is exceeding the erosion velocity.

Design optimization of a pre-combustion CO 2 capture plant embedding experimental knowledge

Abstract This work is focused on the design optimization of a pre-combustion CO2 capture plant comprising a sweet high-temperature water–gas shift process and an integrated H2S and CO2 removal process using a mixture of dimethylethers of polyethylene glycol as physical solvent. The steady-state model of the commercial-scale plant has been derived from pilot plant models, which have been extensively validated against experimental data obtained from the pre-combustion CO2 capture facility realized at the Buggenum IGCC power station in the Netherlands. A two-phase optimization-based design approach suited to the use of process simulator environments has been adopted. In the first phase, global design decisions at plant level are evaluated, targeting the minimization of the energy consumption due to CO2 capture. These are the extent of CO conversion in the water–gas shift unit and the percentage of CO2 capture in the removal unit. An optimization of both global design variables is presented considering (i) a wide range of carbon capture targets, (ii) deactivation of catalyst activity throughout the catalyst life and (iii) different operational limits of the steam/CO ratio in the water–gas shift unit. Experimental data from the pilot plant has been used to determine the rate of catalyst deactivation and the operational limits of steam/CO ratio. The second phase of the design procedure targets the local decision variables at unit level. Two studies are presented focusing on: (1) the design of the solvent regeneration and CO2 compression section, and (2) the impact of the solvent temperature on the energy consumption and equipment cost of the removal unit. The design optimization revealed that the specific energy consumption of the pre-combustion capture unit can be reduced by 10% when operating at a minimum molar steam/CO ratio of 1.5 in comparison to the current vendor suggestion of 2.65. These energy savings come at the cost of a lower optimal carbon capture rate, namely 78% instead of 87.5% as reported in the preliminary design.

Nutrient removal and biogas upgrading by integrating freshwater algae cultivation with piggery anaerobic digestate liquid treatment.

An integrated approach that combined freshwater microalgae Scenedesmus obliquus (FACHB-31) cultivation with piggery anaerobic digestate liquid treatment was investigated in this study. The characteristics of algal growth, biogas production, and nutrient removal were examined using photobioreactor bags (PBRbs) to cultivate S. obliquus (FACHB-31) in digestate with various digestate dilutions (the concentration levels of 3200, 2200, 1600, 1200, 800, and 400mgL(-1) chemical oxygen demand (COD)) during 7-day period. The effects of the level of pollutants on nutrient removal efficiency and CO2 removal process were investigated to select the optimum system for effectively upgrade biogas and simultaneously reduce the nutrient content in digestate. The treatment performance displayed that average removal rates of COD, total nitrogen (TN), total phosphorous (TP), and CO2 were 61.58-75.29, 58.39-74.63, 70.09-88.79, and 54.26-73.81%, respectively. All the strains grew well under any the dilution treatments. With increased initial nutrient concentration to a certain range, the CO4 content (v/v) of raw biogas increased. Differences in the biogas enrichment of S. obliquus (FACHB-31) in all treatments mainly resulted from variations in biomass productivity and CO2 uptake. Notably, the diluted digestate sample of 1600mgL(-1) COD provided an optimal nutrient concentration for S. obliquus (FACHB-31) cultivation, where the advantageous nutrient and CO2 removals, as well as the highest productivities of biomass and biogas upgrading, were revealed. Results showed that microalgal biomass production offered real opportunities to address issues such as CO2 sequestration, wastewater treatment, and biogas production.

Modeling and simulation of membrane separation process using computational fluid dynamics

Separation of CO2 from air was simulated in this work. The considered process for removal of CO2 was a hollow-fiber membrane contactor and an aqueous solution of 2-amino-2-metyl-1-propanol (AMP) as absorbent. The model was developed based on mass transfer as well as chemical reaction for CO2 and solvent in the contactor. The equations of model were solved using finite element method. Simulation results were compared with experimental data, and good agreement was observed. The results revealed that increasing solvent velocity enhances removal of CO2 in the hollow-fiber membrane contactor. Moreover, it was found that counter-current process mode is more favorable to achieve the highest separation efficiency.

Simulation of Loading Capacity of MDEA and DEA for Amine-Based CO2 Removal Using Hysys

Besides meeting international stringent LNG product specification, this work will address the problem of off-spec product, high operational cost of acid gas (CO2) removal and pollution-free product, which is currently a huge global challenge. This work studied other ways by which amine unit can best be optimized to produce LNG gas with low CO2-content and high cost of acid gas removal. MDEA instead of DEA solvent-absorption method was chosen for the optimization using HYSYS 3.1 process simulator to predict the CO2 removal through the establishment of process operating conditions. A base case of amine-based CO2 removal process was used to create a steady-state and dynamic simulation using HYSYS 3.1 simulator. The differences between the values of acid gas loading capacity and CO2 content of the existing DEA operational value and HYSYS simulations were 0.00005 and 4.98 respectively. This established the advantage and accuracy of the HYSYS simulator and the developed models. The simulation results showed that the proposed MDEA had higher CO2 removal capacity of 89% to 55.02% for DEA and lower CO2 content of 0.0012 mole of CO2 in sweet gas to 0.014 mole of CO2 in DEA. MDEA had higher solvent recovery of 83% to 60% recovery for DEA. The pump size required to recycle MDEA with molar flow rate of 1877 Kg mol/hr. was smaller and less expensive than that required for DEA at 2371 Kg mol./hr. resulting in lower production cost.