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Author: Omkar Ashok Namjoshi Publisher: ISBN: Category : Languages : en Pages : 548
Book Description
The thermal degradation of piperazine (PZ)-promoted tertiary amine solvents for CO2-capture has been investigated and quantified in this study, which takes place in the high temperature (>100 °C) section of the capture plant. PZ-promoted tertiary amine solvents possess comparable energy performance to concentrated PZ, considered a benchmark solvent for CO2 capture from flue gas without its solid solubility limits that hinder operational performance. PZ-promoted aliphatic tertiary amine solvents with at least one methyl group, such as methyldiethanolamine (MDEA), were found to be the least stable solvents and can be regenerated in the desorber between 120 and 130 °C. PZ-promoted tertiary amine solvents with no methyl groups, such as ethyldiethanolamine (EDEA), were found to have an intermediate stability and can be regenerated in the desorber between 130 and 140 °C. PZ-promoted tertiary morpholines, such as hydroxyethylmorpholine (HEM), were found to be stable above 150 °C. Tertiary amines with at least one hydroxyethyl or hydroxyisopropyl functional group form intermediate byproducts that can accelerate the degradation rate of the promoter by a factor from 1.5 to 2.3. Tertiary amines with 3-carbon and 5-carbon functional groups, such as dimethylaminopropanol or dimethylaminoethoxyethanol, form stable intermediate byproducts that do not readily react with the promoter. A degradation model for PZ-promoted MDEA that can be used for process design calculations using acidified solvent degradation to model the initial degradation rate over a range of CO2 loading and initial amine concentration was developed. Thermal degradation was modeled using second-order kinetics as a function of free amine and protonated amine. The degradation kinetics, along with the observed degradation products, suggest that the dominant pathway is by free PZ attack on a methyl substituent group of protonated MDEA to form diethanolamine (DEA) and 1-methylpiperazine (1-MPZ). The model predicts total amine loss from experimental CO2 degradation rate measurements within 20%. The modeling work was extended to other PZ-promoted tertiary amine solvents with bulkier substituent groups. PZ attack on ethyl or hydroxyethyl groups was 17% and 4% as fast, respectively, as attack on methyl groups.
Author: Omkar Ashok Namjoshi Publisher: ISBN: Category : Languages : en Pages : 548
Book Description
The thermal degradation of piperazine (PZ)-promoted tertiary amine solvents for CO2-capture has been investigated and quantified in this study, which takes place in the high temperature (>100 °C) section of the capture plant. PZ-promoted tertiary amine solvents possess comparable energy performance to concentrated PZ, considered a benchmark solvent for CO2 capture from flue gas without its solid solubility limits that hinder operational performance. PZ-promoted aliphatic tertiary amine solvents with at least one methyl group, such as methyldiethanolamine (MDEA), were found to be the least stable solvents and can be regenerated in the desorber between 120 and 130 °C. PZ-promoted tertiary amine solvents with no methyl groups, such as ethyldiethanolamine (EDEA), were found to have an intermediate stability and can be regenerated in the desorber between 130 and 140 °C. PZ-promoted tertiary morpholines, such as hydroxyethylmorpholine (HEM), were found to be stable above 150 °C. Tertiary amines with at least one hydroxyethyl or hydroxyisopropyl functional group form intermediate byproducts that can accelerate the degradation rate of the promoter by a factor from 1.5 to 2.3. Tertiary amines with 3-carbon and 5-carbon functional groups, such as dimethylaminopropanol or dimethylaminoethoxyethanol, form stable intermediate byproducts that do not readily react with the promoter. A degradation model for PZ-promoted MDEA that can be used for process design calculations using acidified solvent degradation to model the initial degradation rate over a range of CO2 loading and initial amine concentration was developed. Thermal degradation was modeled using second-order kinetics as a function of free amine and protonated amine. The degradation kinetics, along with the observed degradation products, suggest that the dominant pathway is by free PZ attack on a methyl substituent group of protonated MDEA to form diethanolamine (DEA) and 1-methylpiperazine (1-MPZ). The model predicts total amine loss from experimental CO2 degradation rate measurements within 20%. The modeling work was extended to other PZ-promoted tertiary amine solvents with bulkier substituent groups. PZ attack on ethyl or hydroxyethyl groups was 17% and 4% as fast, respectively, as attack on methyl groups.
Author: Paul Feron Publisher: Woodhead Publishing ISBN: 0081005156 Category : Technology & Engineering Languages : en Pages : 816
Book Description
Absorption-Based Post-Combustion Capture of Carbon Dioxide provides a comprehensive and authoritative review of the use of absorbents for post-combustion capture of carbon dioxide. As fossil fuel-based power generation technologies are likely to remain key in the future, at least in the short- and medium-term, carbon capture and storage will be a critical greenhouse gas reduction technique. Post-combustion capture involves the removal of carbon dioxide from flue gases after fuel combustion, meaning that carbon dioxide can then be compressed and cooled to form a safely transportable liquid that can be stored underground. - Provides researchers in academia and industry with an authoritative overview of the amine-based methods for carbon dioxide capture from flue gases and related processes - Editors and contributors are well known experts in the field - Presents the first book on this specific topic
Author: Mandana Ashouripashaki Publisher: ISBN: Category : Languages : en Pages : 214
Book Description
Piperazine (PZ) is a cyclic diamine, which means it can absorb two moles of CO2 per mole of amine and potentially has a higher capacity for CO2 capture than monoethanolamine, the current solvent of choice for flue gas treatment. Nitrosamines are formed from the reaction between secondary or tertiary amines and nitrites or nitrogen oxides. Over 80% of nitrosamines are carcinogenic. The reaction of PZ and nitrite can form 1-nitrosopiperazine (also mononitrosopiperazine, MNPZ) and N-N, dinitrosopiperazine (DNPZ). Carcinogenicity of DNPZ is almost 20 times as that of MNPZ. There is also a possibility of nitrosamine formation of PZ in the CO2 capture process because of NO[subscript x] in input flue gas, with the oxidative and thermal degradation products of PZ. Analytical methods were developed in order to perform kinetic studies of the reaction between a nitrite solution and PZ over a range of temperature from 20 to 150 °C at two different PZ concentrations, 8 and 2 mol/kg of solution, and three levels of CO2 loading, 0.3, 0.2, and 0.1 mole CO2/mole of alkalinity. At less than 75 °C, nitrite reacts with PZ and disappears during the reaction to an equilibrium concentration while at the higher temperature; the concentration of nitrite quickly decreases to a very low value. There is no evidence of DNPZ as a reaction product in all reaction conditions, but MNPZ is formed at the temperature greater than 75 °C. The MNPZ concentration approaches a maximum value consistent with the material balance and nitrite disappearance. By developing the time of reaction at the higher temperature a decomposition of MNPZ has been observed, by either the reverse of the formation reaction or decomposition to other compounds. By increasing the temperature, the maximum value of MNPZ concentration is achieved more quickly and the rate of MNPZ decomposition increases. Reactions follow the same trend at both PZ concentration and at the three different degrees of CO2 loading. A model has been established considering temperature, PZ concentration, and CO2 loading. The calculated activation energies of MNPZ production and decomposition were determined. MNPZ decomposition is more rapid than PZ degradation.
Author: Iyad Karamé Publisher: BoD – Books on Demand ISBN: 178923574X Category : Science Languages : en Pages : 268
Book Description
Fossil fuels still need to meet the growing demand of global economic development, yet they are often considered as one of the main sources of the CO2 release in the atmosphere. CO2, which is the primary greenhouse gas (GHG), is periodically exchanged among the land surface, ocean, and atmosphere where various creatures absorb and produce it daily. However, the balanced processes of producing and consuming the CO2 by nature are unfortunately faced by the anthropogenic release of CO2. Decreasing the emissions of these greenhouse gases is becoming more urgent. Therefore, carbon sequestration and storage (CSS) of CO2, its utilization in oil recovery, as well as its conversion into fuels and chemicals emerge as active options and potential strategies to mitigate CO2 emissions and climate change, energy crises, and challenges in the storage of energy.
Author: Stephanie Anne Freeman Publisher: ISBN: Category : Languages : en Pages : 1468
Book Description
Absorption-stripping with aqueous, concentrated piperazine (PZ) is a viable retrofit technology for post-combustion CO2 capture from coal-fired power plants. The rate of thermal degradation and oxidation of PZ was investigated over a range of temperature, CO2 loading, and PZ concentration. At 135 to 175 °C, degradation is first order in PZ with an activation energy of 183.5 kJ/mole. At 150 °C, the first order rate constant, k1, for thermal degradation of 8 m PZ with 0.3 mol CO2/mol alkalinity is 6.12 x 10−9 s−1. After 20 weeks of degradation at 165 °C, 74% and 63%, respectively, of the nitrogen and carbon lost in the form of PZ and CO2 was recovered in quantifiable degradation products. N-formylpiperazine, ammonium, and N-(2-aminoethyl) piperazine account for 57% and 45% of nitrogen and carbon lost, respectively. Thermal degradation of PZ likely proceeds through SN2 substitution reactions. In the suspected first step of the mechanism, 1-[2-[(2-aminoethyl) amino]ethyl] PZ is formed from a ring opening SN2 reaction of PZ with HPZ. Formate was found to be generated during thermal degradation from CO2 or CO2-containing molecules. An analysis of k1 values was applied to a variety of amines screened for thermal stability in order to predict a maximum recommended stripper temperature. Morpholine, piperidine, PZ, and PZ derivatives were found to be the most stable with an allowable stripper temperature above 160 °C. Long-chain alkyl amines or alkanolamines such as N-(2-hydroxyethyl)ethylenediamine and diethanolamine were found to be the most unstable with an allowable stripper temperature below 120 °C. Iron (Fe2) and stainless steel metals (Fe2+, Ni2+, and Cr3+) were found to be only weak catalysts for oxidation of PZ, while oxidation was rapidly catalyzed by copper (Cu2+). In a system with Fe2+ or SSM, 5 kPa O2 in the inlet flue gas, a 55 °C absorber, and one-third residence time with O2, the maximum loss rate of PZ is expected to 0.23 mol PZ/kg solvent in one year of operation. Under the same conditions but with Cu2+ present, the loss rate of PZ is predicted to be 1.23 mole PZ/kg solvent in one year of operation. Inhibitor A was found to be effective at decreasing PZ loss catalyzed by Cu2+. Ethylenediamine, carboxylate ions, and amides were the only identified oxidation products. Total organic carbon analysis and overall mass balances indicate a large concentration of unidentified oxidation products.
Author: Abtin Vafadari Publisher: ISBN: Category : Adsorption Languages : en Pages : 149
Book Description
Global warming has become one of the major concerns of the industrial world. Among the pollutants, CO2 has the highest impact on the climate change. Many techniques have been proposed to capture carbon dioxide from exhaust gas of the plants and factories. Temperature swing adsorption (TSA) is the most promising technique for CO2 capture due to low capital cost, heat of regeneration, toxicity and corrosive properties. Amine based sorbents can be applied for low temperature carbon dioxide separation from plant exhaust gases. Gas stream after passing through a packed adsorption bed will go to other separation units depending on requirements of the plant or it will be released into atmosphere. After the adsorption bed reaches into saturation point, control system will bypass that process unit and redirect the gas stream to another packed bed with fresh sorbents while the saturated bed is heating for regeneration. Thermal cycling in presence of exhaust gases can cause thermal and oxidative degradation of the sorbents over a long time frame. Also the high temperature of heating during the regeneration can cause some of the species to evaporate. For our in-house built sorbent, Tetraethylenepentamine (TEPA) is the amine source and EPON 826 is used to initiate the long chain polymers for holding the amine groups on the surface of the sorbents and inhibit them from evaporation. After exposure to a certain number of thermal cycles which causes sorbent degradation, they must be replaced with fresh sorbents but unit overhauls are costly and plant owners prefer to avoid that. There are two suggestions for reduction of overhaul costs due to sorbent deformation: One suggestion is to regenerate the sorbents in their original location by washing them with a cheap solution to improve the performance of the sorbents and the other was, to optimize the sorbents so they can resist to more number of thermal cycles. In this study, the amine degradation due to thermal cycling was studied and it was proved that irreversible reactions between CO2 and amine groups or chemisorbed species are the reasons for degradation of sorbents. The other issue in CO2 adsorption by amine based sorbents is the evaporation of amines which can cause environmental issues. By making a porous polymer to replace solid sorbents evaporation of amines to atmosphere can be avoided. After concentration optimization and rapid heating the liquid phase polymers, porous polymer with high porosity was achieved. Although this polymer had a good number of macro pores but it did not have enough capture capacity, further investigation is required to address this issue.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The objective of this work is to improve the process for CO2 capture by alkanolamine absorption/stripping by developing an alternative solvent, aqueous K2CO3 promoted by piperazine (PZ). Pilot plant testing was performed in a 16.8-inch ID absorber and stripper with recirculation of air and CO2. Three solvents (7 m MEA, 5 m K/2.5 m PZ, and 6.4 m K/1.6 m PZ) were tested in four campaigns with three different absorber packings. Pilot plant testing established that 5 m K+/2.5 m PZ requires two times less packing than 7 m MEA and three times less packing than 6.4 m K+/1.6 m PZ. A rigorous model of the thermodynamics and mass transfer was developed in the RateSep{trademark} block of AspenPlus{reg_sign}. The double matrix stripper reduces energy consumption by 5 to 15%. The best K+/PZ solvent, 4 m K+/4 m PZ, and the best process configuration, double matrix stripper with a double intercooled absorber, requires equivalent work of 40 kJ/mole CO2 to produce CO2 at 10 MPa. Inhibitor A is effective at reducing oxidative degradation over a wide range of metal concentrations and solvent types. Piperazine is resistant to oxidative degradation catalyzed by dissolved iron, but it oxidizes at rates comparable to monoethanolamine (MEA) in the presence of dissolved copper. The thermal degradation of MEA becomes significant at 120 C, but loaded piperazine solutions appear to be resistant to thermal degradation up to 135 C. The vapor pressure of PZ over typical lean solution at 40 C will be less than 25 ppm, which is less than the 40 ppm expected for MEA. Significant problems with foaming were encountered and alleviated by antifoamants in the pilot plant campaigns with K+/PZ. Potassium sulfate is not very soluble in 4 m K+/4 m PZ, so SO2 absorption and oxidation to sulfate in the bottom of the absorber may require operation with a slurry of potassium sulfate solids.
Author: Humbul Suleman Publisher: CRC Press ISBN: 1000537412 Category : Science Languages : en Pages : 383
Book Description
A comprehensive resource on different aspects of sustainable carbon capture technologies including recent process developments, environmentally friendly methods, and roadmaps for implementations. It discusses also the socio-economic and policy aspects of carbon capture and the challenges, opportunities, and incentives for change with a focus on industry, policy, and governmental sector. Through applications in various fields of environmental health, and four selected case studies from four different practical regimes of carbon capture, the book provides guidelines for sustainable and responsible carbon capture and addresses current and future global energy, environment, and climate concerns.
Author: Yuying Wu (Ph. D.) Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Piperazine is a promising second-generation solvent for amine scrubbing in post-combustion CO2 capture. However, the oxidative degradation of PZ can cause environmental problems and economic loss. This work presents the effects of two mitigation methods: carbon treating and N2 sparging, on the PZ oxidation in long-term operations. The species and their respective quantities adsorbed by the activated carbon were tested in a bench-scale device. The carbon was then tested in the High Temperature Oxidation Reactor (HTOR), where the solvent oxidizes at a reasonably fast rate. Pilot plant campaigns were also performed at the UT Austin SRP and the National Carbon Capture Center (NCCC) and the effects were verified. When dissolved Fe is removed by carbon treating or other methods, available soluble Fe in the system dissolves and replaces the dissolved Fe. Therefore, all available Fe and ligands need to be removed for the mitigation to be effective. The sources of soluble Fe include fly ash and the corrosion of stainless steel, and the ligands are degradation products. All PZ degraded solvents have two absorbance peaks at 320 nm and 538 nm. The 320 nm peak is caused by dissolved metals, especially Fe, complexed by degradation products. The 320 nm peak is related to the amine degradation level and can be used as a simple and efficient method to estimate the amine degradation rate. The pilot plant data suggest that NO2 can oxidize PZ significantly, possibly through radical reactions. 0.01 mmol/kg-hr absorption of NO2 increased the PZ oxidation rate from 1.2 mmol/kg-hr to 2.5 mmol/kg-hr
Author: Omkar Ashok Namjoshi
Author: Omkar Ashok Namjoshi
Author: Quanzhen Huang
Author: Paul Feron
Author: Mandana Ashouripashaki
Author: Iyad Karamé
Author: Stephanie Anne Freeman
Author: Abtin Vafadari
Author: 
Author: Humbul Suleman
Author: Yuying Wu (Ph. D.)