Measurements of the effective mass transfer areas for the gas–liquid rotating packed bed

Rotating packed bed(RPB) is one of the most effective gas–liquid mass transfer enhancement reactors, its effective specific mass transfer area(ae) is critical to understand the mass transfer process. By using the NaOH–CO_(2) chemical absorption method, the aevalues of three RPB reactors with different rotor sizes were measured under different operation conditions. The results showed that the high gravity factor and liquid flow rate were major affecting factors, while the gas flow rate exhibited minor influence.The radius of packing is the dominant equipment factor to affect aevalue. The results indicated that the contact area depends on the dispersion of the liquid phase, thus the centrifugal force of rotating packed bed greatly influenced the aevalue. Moreover, the measured ae/ap(effective specific mass transfer area/specific surface area of packing) values were fitted with dimensionless correlation formulas. The unified correlation formula with dimensionless bed size parameter can well predict the experimental data and the prediction errors were within 15%.

Technical Perspective of Carbon Capture,Utilization,and Storage

Carbon dioxide(CO_(2))is the primary greenhouse gas contributing to anthropogenic climate change which is associated with human activities.The majority of CO_(2) emissions are results of the burning of fossil fuels for energy,as well as industrial processes such as steel and cement production.Carbon capture,utilization,and storage(CCUS)is a sustainable technology promising in terms of reducing CO_(2) emissions that would otherwise contribute to climate change.From this perspective,the discussion on carbon capture focuses on chemical absorption technology,primarily due to its commercialization potential.The CO_(2) absorptive capacity and absorption rate of various chemical solvents have been summarized.The carbon utilization focuses on electrochemical conversion routes converting CO_(2) into potentially valuable chemicals which have received particular attention in recent years.The Faradaic conversion efficiencies for various CO_(2) reduction products are used to describe efficiency improvements.For carbon storage,successful deployment relies on a better understanding of fluid mechanics,geomechanics,and reactive transport,which are discussed in details.

Hydrate-based carbon dioxide capture from simulated integrated gasification combined cycle gas

The equilibrium hydrate formation conditions for CO2/H2 gas mixtures with different CO2 concentrations in 0.29 mol% TBAB aqueous solution are firstly measured.The results illustrate that the equilibrium hydrate formation pressure increases remarkably with the decrease of CO2 concentration in the gas mixture.Based on the phase equilibrium data,a three stages hydrate CO2 separation from integrated gasification combined cycle （IGCC） synthesis gas is investigated.Because the separation efficiency is quite low for the third hydrate separation,a hybrid CO2 separation process of two hydrate stages in conjunction with one chemical absorption process （absorption with MEA） is proposed and studied.The experimental results show H2 concentration in the final residual gas released from the three stages hydrate CO2 separation process was approximately 95.0 mol% while that released from the hybrid CO2 separation process was approximately 99.4 mol%.Thus,the hybrid process is possible to be a promising technology for the industrial application in the future.

Thermodynamic modelling of unloaded and loaded N,N-diethylethanolamine solutions

Chemical absorption is a crucial step for several chemical processes such as ammonia production, coal gasification, methane reforming,ethylene oxide manufacturing and treatment of associated gas streams [1]. It is considered one of the main processes to eliminate CO_2 emissions from power plants by post-combustion.Use of new solvents are of high interest in chemical absorption for carbon capture. For the design of the absorption and desorption columns it is essential to know the vapour-liquid equilibrium(VLE), heat of absorption and densities. N,N-diethylethanolamine(DEEA) appeared as one of the amines with the lowest amount of energy needed for its regeneration [2], which would directly decrease the operation costs. DEEA has a high CO_2 loading of 1 mol/mol of amine compared to the traditional MEA solvent(0.5 mol/mol amine) and is obtained from renewable sources[1]. The main weakness is its low absorption rate and consequently the use of promoters is desirable.In this work, a thermodynamic model based on the electrolyte non-random two-liquid theory(eNRTL) was created and fitted to correlate and predict the partial and total pressures of the unloaded and loaded aqueous DEEA solutions. New interaction parameters were obtained for the binary and tertiary system. This model represents the vapour pressures of the pure components, DEEA and H_2 O, with AARD of 1.9% and 1.73%respectively. Furthermore, the fitted model predicts the total pressure above the binary system, H_2O-DEEA, with AARD of 0.05%. The excess of enthalpy and densities are predicted with AARD of 5.63% and 1.38% respectively. The tertiary system, H_2O-DEEA-CO_2, is fitted for 2 M and5 M DEEA solutions with loading between 0.042 and 0.9 mol CO_2/mol amine up to 80 ℃. Results of CO_2 partial pressures and total pressures are reproduced, with AARD of 19.45% and 16.18% respectively. Densities are predicted with an AARD of 1.52%.

A convenient method for measuring gas-liquid volumetric mass transfer coefficient in micro reactors

The research on gas-liquid multiphase reactions using micro reactors is becoming increasingly widespread, given their excellent mass transfer performance. Establishing an accurate and reliable method to measure the gas-liquid mass transfer performance of micro reactors is crucial for evaluating and optimizing the design of micro reactor structure. In this paper, the physical absorption method of aqueous solution-CO_(2) and the chemical absorption method of sodium carbonate solution-CO_(2) were proposed. By analyzing the chemical reaction equilibrium during the absorption process, the relationship between the mass transfer of CO_(2) and the solubility of hydroxide ions in the solution was established, and the total gas-liquid mass transfer coefficient was immediately obtained by measuring the p H value. The corresponding testing platform and process have been established based on the characteristics of the proposed method to ensure fast and accurate measurement. In addition, the chemical absorption method takes into account temperature factors that were not previously considered. The volumetric mass transfer coefficient measured by these two methods is in the same range as those measured by other methods using the same microchannel structure in previous literature. The methods have the advantages of low equipment cost, faster measurement speed, and simpler procedures, which can facilitate its wide application to the evaluation of the mass transfer performance and hence can guide the structure optimization of microchannel reactors.

Recent Advances in Study on Thermodynamic Models for Real Systems Including Electrolytes

A comprehensive review of recent advances in study on thermodynamic models for real electrolyte solutions is presented. The differences between primitive and non-primitive electrolyte models are demonstrated. Some new thermodynamic models for electrolyte solutions based on the mean spherical approximation and perturbation theory are introduced. An extended scaled-particle theory and modified CleggPitzer equation are presented for physical and chemical absorption processes with mixed solvents, respectively. A pseudo one-component two-Yukawa equation of state is used for the aqueous two-phase extraction process in charged colloidal systems.

Research progress of siloxane removal from biogas

Siloxanes in biogas are detrimental to engine,turbine,fuel cell,etc.,thus it is necessary to remove siloxanes from biogas before biogas high-value utilization.At present,there are few domestic researches and related reports in view of siloxanes removal from biogas.This paper introduces the property of siloxanes as well as sampling and analysis method,and then presents the research progress of siloxanes removal from biogas.Three commercial technologies overseas are adsorption,absorption and cryogenic condensation.Among them,adsorption on activated carbon is the most widely used method.Other technologies,such as biological removal,catalytic processes,membranes,source controlling,etc.are under exploration and development.At last,this paper summarizes the advantages and disadvantages of siloxanes removal technologies as well as the applicability and analyzes the future research trend and emphasis.This paper could provide a reference in the field of biogas high-value utilization.