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Coal fly ash (CFA), an industrial by-product of high-temperature combustion of coal in coal-fired power plants, is one of the most complex and largest amounts of industrial solid wastes generated in China. It is widely recognized that CFA should be considered as a potential alumina resource to substitute bauxite. In this review, the features of high-alumina fly ash and aluminum recovery technologies are first described. Later, the merits and drawbacks of alumina extraction technologies in recovering more valuable materials are compared in terms of extraction mechanisms and equipment requirements. It is shown that “predesilicating-sodium carbonate (Na2CO3) activation-acid leaching” is currently a promising method in achieving multimetal synergistic extraction. Finally, the hydrochloric acid and sulfuric acid combination process is proposed as a sustainable development of the predesilicating-Na2CO3 activation-acid leaching process. The findings of this review provide theoretical guidance for novel developments and applications of aluminum extraction technologies.

Coal fly ash is an industrial solid waste generated from coal preparation during the processing and cleaning of coal for electric power generation. Comprehensive investigation on the reutilization of waste heat of activated coal fly ash is of great economic significance. The method of recovering the waste heat, proposed in this study, is the transfer of heat from activated coal fly ash to gas with the movement of air using the packed bed, providing valuable energy sources for preheating the raw coal fly ash to reduce the overall energy consumption. The investigation is carried on the heat transfer characteristics of gas–solid (activated coal fly ash) phases and air temperature fields of the packed bed under some key conditions via computational fluid dynamics. A two dimensional geometry is utilized to represent key parts of packed bed. The distribution mechanism of the temperature field for gas phase is analyzed based on the transient temperature contours at different times. The results show that the obtained rule of gas–solid heat transfer can effectively evaluate the influences of operating parameters on the air temperature in the packed bed. Simultaneously, it is found that no temperature differences exist in the hot air at the outlet of the packed bed. The investigation provides guidance for the design and optimization of other similar energy recovery apparatuses in industries.

The process of synthesizing syngas with the triple CO2 feeds is proposed to achieve an efficient use of CO2 that mitigates climate warming. Also, the amount of CO2 added in three locations as the v...

Steam methane reforming (SMR)-based methanol synthesis plants utilizing a single CO2 feed represent one of the predominant technologies for improving methanol yield and CO2 utilization. However, SMR alone cannot achieve full CO2 utilization, and a high water content accumulates if CO2 is only fed into the methanol reactor. In this study, a process integrating SMR with dry methane reforming to improve the conversion of both methane and CO2 is proposed. We also propose an innovative methanol production approach in which captured CO2 is introduced into both the SMR process and the recycle gas of the methanol synthesis loop. This dual CO2 feed approach aims to optimize the stoichiometric ratio of the reactants. Comparative evaluations are carried out from a techno-economic point of view, and the proposed process is demonstrated to be more efficient in terms of both methanol productivity and CO2 utilization than the existing stand-alone natural gas-based methanol process.

The investigation of dynamic controllability for the double side-streams ternary extractive distillation (DSTED) is necessary due to its advantages in energy-efficient. However, the control strategy of the energy-saving DSTED scheme is unique and complex issues owing to the wobbly of side-stream flow rate. Herein, control strategy of the energy-saving DSTED scheme is explored for separating ternary azeotropic mixtures acetonitrile/methanol/benzene. Inspiring from the control strategy of the ordinary triple-column extractive distillation scheme, the fundamental control structure CS1 is firstly designed. The control scheme CS2 with feed/side-stream (F/SS) ratio and control structure CS3 with feedforward and F/SS are then investigated to achieve higher efficiency of process control. Finally, a robust control strategy CS4 with the ratio of reboiler duty and feed flow rate and without F/SS ratio is proposed to well maintain the product purities. Moreover, additional ±15% feed flow rate and composition disturbances are added in the CS4 to assess the stability and controllability of the energy-saving DSTED. Dynamic performances illustrate that the structure CS4 can handle as well as that of confronted ±10% disturbances when the large disturbances are occurred in the real chemical process.

The separation of ternary mixtures with homogeneous or heterogeneous multi-azeotropes has received increasing attention. In this work, a systematic design, optimization and control procedure is proposed for extractive distillation of heterogeneous mixtures with four azeotropes. Herein, the ternary system isopropyl alcohol/isopropyl acetate/water is taken as a case study. The suitable entrainer is first obtained through a proposed approach combining the vapor–liquid equilibrium (VLE) curves and infinite dilution activity coefficient ratios. Conceptual design of two alternative separation sequences involving double-column extractive distillation with a pre-concentrator (DEDP) and triple-column extractive distillation (TED) are then investigated based on thermodynamic insights. With the method of sequential iterative optimization and taking total annual cost (TAC) as the objective function, the two processes are optimized. The optimal results indicate that the DEDP process with dimethyl sulfoxide as entrainer can save 6.43% TAC than that of TED. Finally, a new control structure combining reflux flowrate-to-feed (R/F) and adjustable reboiler duty-to-feed (QR/F) with “HiLoSelect” strategy is proposed to better handle three product purities than that of the basic control structure while feed flowrate and composition disturbances are introduced in the studied DEDP process.

Extractive distillation (ED) is one of the most promising approaches for the separation of the azeotropic or close-boiling mixtures in the chemical industry. The purpose of this paper is to provide a broad overview of the recent development of key aspects in the ED process involving conceptual design, solvent selection, and separation strategies. To obtain the minimum entrainer feed flow rate and reflux ratio for the ED process, the conceptual design of azeotropic mixture separation based on a topological analysis via thermodynamic feasibility insights involving residue curve maps, univolatility lines, and unidistribution curves is presented. The method is applicable to arbitrary multicomponent mixtures and allows direct screening of design alternatives. The determination of a suitable solvent is one of the key steps to ensure an effective and economical ED process. Candidate entrainers can be obtained from heuristics or literature studies while computer aided molecular design (CAMD) has superiority in efficiency and reliability. To achieve optimized extractive distillation systems, a brief review of evaluation method for both entrainer design and selection through CAMD is presented. Extractive distillation can be operated either in continuous extractive distillation (CED) or batch extractive distillation (BED), and both modes have been well-studied depending on the advantages in flexibility and low capital costs. To improve the energy efficiency, several configurations and technological alternatives can be used for both CED and BED depending on strategies and main azeotropic feeds. The challenge and chance of the further ED development involving screening the best potential solvents and exploring the energy-intensive separation strategies are discussed aiming at promoting the industrial application of this environmentally friendly separation technique.

The petroleum refining industry is one of the most complex and energy-intensive separation units that produce various petroleum products from crude oil. In this work, an entire crude oil distillation unit (CDU) process is retrofitted and optimized by a proposed theoretical retrofit-optimization framework based on established exergy loss analysis. The purpose of this analysis is to further improve the energy utilization efficiency of the process both qualitatively quantitatively. The theoretical derivation is carried out on exergy loss of key components in CDU including condensers, furnaces, and distillation columns. The locations and magnitudes of the inefficiency in the whole process are detected according to the exergy loss distribution analysis of the basic process. The exergy loss of every studied sub-unit is defined as the objective function to be minimized in the optimization of key operational parameters using the Sequential Quadratic Programming (SQP) methodology. Compared to the basic process, the exergy efficiency of improved process is increased from 28.9% to 41.4%, and the total annual consumption (TAC) is reduced by 28.7% under the same flow rates and qualities of every product. The proposed framework is able to be extended to other similar chemical separation processes to achieve a higher energy and exergy saving.

The design of the diethyl carbonate (DEC) production process has received much attention due to its key role as the oxygenated gasoline additive with much fewer environmental and health issues than methyl tert-butyl ether. In this study, two configurations including vapor recompression heat pump (VRHP)-reactive dividing wall column (RDWC) with or without the splitting top stream are investigated for DEC production to screen out the best VRHP sequence. Furthermore, a novel alternative approach of different pressure thermally coupled-RDWC (DPTC-RDWC) is comparatively proposed to achieve less capital and energy cost. The effects of pressure within stripping section of the RDWC on total annualized cost (TAC) and the temperature difference between the condenser and reboiler are studied. The results illustrate that the proposed optimum process produces DEC production with the purity of 99.8 mol% and significant reduction of TAC is achieved by 20.52% with 10 years payback period. Apart from that, carbon dioxide emission of the process is decreased by 33.74% compared to that through conventional RDWC.

To the best of our knowledge, very few efforts have been investigated for separating heterogeneous mixtures methanol/toluene/water with multiazeotropes using extractive dividing-wall column (EDWC)....

The energy analysis and optimization of process system aiming to solve the problems of high consumption, low efficiency and unreasonable use of energy in the process of energy utilization has been widely researched and developed in recent decades. In this work, advanced exergy analysis was carried out for the triple-column extractive distillation (TCED) process separating ternary azeotropic mixture of ACN/EtOH/H2O. The total exergy destruction is 1097.69 KW. The avoidable exergy destruction, is 29.20%, mainly caused by the cooler and three condensers. Based on the thermodynamic analysis results, a superstructure TCED with four-parallel evaporator organic Rankine cycles (FPE-ORC) system is proposed, four working fluids were selected. An improved genetic algorithm is used to obtain the optimal operating parameters of the ORC system by using the exergy efficiency and annual net profit (ANP) of the ORC as two conflict objective functions. Compare with existing process, the FPE-ORC system with working fluid R600 provides the highest exergy efficiency of 12.27%, with working fluid R600a leads to the best economic benefit of 6.43 E + 4 dollar/year.

Surfactants were used for the hydrolysis of bamboo biomass to enhance lignocellulose hydrolysis. Tween 80, polyethylene glycol 4000 (PEG 4000), and sodium dodecyl sulfate (SDS) were tested as surfactants for improving the bamboo hydrolysis with a novel sulfonated cross-linked chitosan solid acid catalyst (SCCAC) in ionic liquid (IL). Compared to the use of only SCCAC in 1-Butyl-3-methylimidazolium chloride ([BMIM]Cl), the surfactants facilitated hydrolysis and improved the yield of total reducing sugar (TRS) under the same conditions. Tween 80 was the most effective surfactant, with a TRS yield of 68.01% achieved at 120°C after 24h. Surfactants broke the lignocellulose structure, promoted lignin removal, and increased positive interactions between cellulose and the catalyst, which were favorable for hydrolysis. This novel surfactant-assisted hydrolysis strategy with SCCAC and IL as the solvent demonstrated a promise for the large-scale transformation of biomass into biofuels and bioproducts.

The contribution of this work is proposing a systematic approach to design an efficient extractive distillation (ED) process for separating binary azeotropic mixture, which including the study of σ-profiles, the analysis of thermodynamic topology, and the investigation of economic validation. The separation of methanol-acetone azeotrope serves as the case study to demonstrate the effectiveness of the proposed method. Firstly, the σ-profiles is employed to select appropriate candidates of ILs via the analysis of interaction between five cations and eight anions. Then, the feasibilities of two candidates ILs (i.e., 1-Methylimidazolium acetate ([MIM][OAc]) and 1-methylimidazolium 2-hydroxypropionate ([MIM][Hpr])) and DMSO are further studied by the thermodynamic topological analysis with residue curve maps and univolatility lines. Finally, the design and optimization of ED with the three potential entrainers are conducted to prove the validity of the proposed method. The results demonstrated that the ED process with [MIM][Hpr] is the most economical process compared with [MIM][OAc] and DMSO indicating that the proposed approach is appropriate for screening entrainer to separate such mixture. Moreover, the proposed comprehensive methodology in this work is a valuable protocol, which could be extended to separate other azeotropic systems by using an energy-saving ED process.

Plasma-assisted catalytic conversion of CH 4 and CO 2 into synthesis gas was performed in a dielectric barrier discharge reactor coupled with perovskite La–Ni nanoparticles (LaNiO 3 NPs). Compared to supported catalysts such as Ni/γ-Al 2 O 3 , La–Ni/γ-Al 2 O 3 and Ni/La 2 O 3 , LaNiO 3 NPs showed better catalytic performance. The results show that the low flow rate of feed gases and high input power were favorable for the conversions of CH 4 and CO 2 as well as the selectivities of desired products, but led to lower energy efficiency. A global kinetic model according to argon dilution in plasma-catalytic system was proposed and employed to foresee the CH 4 and CO 2 conversion assisted by plasma-catalysts hybrid effect. The kinetic model indicates that the reactant conversion rate was an exponential function of the discharge energy.

In this study, an integrated vector-based three-dimensional (3D) methodology for the life cycle sustainability assessment (LCSA) of chemical process alternatives is proposed. In the methodology, a 3D criteria assessment system is first established by using the life cycle assessment, the life cycle costing, and the social life cycle assessment to determine the criteria from the environmental, economic, and social pillars, respectively. The methodology incorporates the analytic hierarchy process (AHP) method to convert experts' judgments on the soft criteria into quantitative data and realize a unitary scale for both quantified soft criteria and normalized hard criteria. After assigning appropriate weights to each pillar and criterion by using the AHP method, the sustainability of the alternative processes can be prioritized by employing a novel vector-based algorithm, which combines the absolute sustainability performance and the relative sustainability deviation of the investigated processes. A case study on the sustainability assessment of three alternative ammonia production processes demonstrates that the proposed methodology is able to serve as a comprehensive and rigorous tool for the stakeholders to rank and identify the most sustainable chemical process alternatives.

This chapter proposed a multicriteria decision-making methodology for the sustainability prioritization of industrial systems. The methodology incorporates a fuzzy analytic hierarchy process method that allows the users to assess the soft criteria by using linguistic terms. A fuzzy analytic network process method is used to calculate the weights of each criterion, which can tackle the interdependencies and interactions among the criteria. The preference ranking organization method for enrichment evaluation approach is used to prioritize the sustainability sequence of the alternative systems. Moreover, a sensitivity analysis method was developed to investigate the most critical and sensitive criteria. The developed methodology was illustrated by a case study to rank the sustainability of five alternative hydrogen production technologies. The advantages of the developed methodology over the previous approaches were demonstrated by comparing the results determined by the proposed framework with those determined by using the pervious approaches.

Chromium salts are a group of important chemical raw materials with many applications. While the conventional manufacturing process, i.e. calcium roasting of chromite, has many disadvantages; the novel processes of liquid-phase oxidation, whose main reaction is the oxidation of chromite by oxygen (air) in highly concentrated alkaline solutions, are promising to achieve clean manufacturing. For the oxidation reaction of chromite in NaOH solutions, a significant amount of multicomponent systems consisting NaOH, Na2CrO4, Na2SiO3, and NaAlO2 are generated. It is a prerequisite to clarify the solubility equilibrium of the multicomponent systems for exploring highly efficient separation methods of Na2CrO4 with Na2SiO3 and NaAlO2. In this paper, Na2CrO4 solubility in the ternary system of NaOH–H2O–Na2CrO4 was first measured using the equilibrium analysis method and varying the NaOH concentrations from 100 to 800 g·L–1 and the temperatures from 353.15 to 403.15 K. Aferwards, the solubility of Na2CrO4, NaAlO2, and...

An intensified scheme for the separation of ternary azeotropic system is explored to reduce the energy consumption and recycle important organic solvents. Herein, a novel double-thermally coupled ternary extractive distillation (DTCTED) for separating azeotropic system benzene/toluene/cyclohexane (denoted as B/T/CH) is proposed to achieve energy-saving and emissions reduction. Thermodynamic feasible insights of the B/T/CH using dimethyl formamide as entrainer are firstly analyzed via residue curve maps to find separation constraints. Following that, the proposed intensified scheme is optimized via the in-house multi-objective genetic algorithm software while using total annual cost and CO2 emissions as objective functions. The results show that the total annual cost and CO2 emissions of the proposed intensified DTCTED scheme are significantly reduced by 18.60% and 20.22% compared with the existing single-thermally coupled ternary extractive distillation process. Furthermore, exergy loss and relative volatility are introduced to explore the essence of energy-saving in the proposed DTCTED scheme.

The process for producing Fischer-Tropsch syngas (FTS) with the combination of steam and dry methane reforming (operating in parallel) is demonstrated with the most favorable economics. Conventional exergy analysis (CEA) is firstly used to diagnose the part and degree of inefficiency in the process. The energy-saving potential of each equipment and thermodynamic interactions are further evaluated and classified by advanced exergy analysis (AEA). The Organic Rankine Cycle (ORC) with (or without) recuperators is introduced to recover the waste heat according to the obtained exergy analysis results. The thermodynamic efficiency and total exergy destruction of the ORC are defined as the objective function to determine best working fluids and optimal operation conditions. The performance assessment of proposed three different ORC schemes indicates the dual-pressure ORC system has the best performance with highest thermal efficiency accounting to 15.39%, annual net profit (ANP) accounting to 1.55 E+07dollar/year and 4.6 years payback period. The exergy loss of the novel system integrating with the dual-pressure ORC scheme is reduced to 13.21 MW compare to that of existing process accounts to 34.92 MW, and 88.21% of avoidable endogenous exergy destructions are recovered from waste heat sources. The proposed energy conservation approach in this study can be extended to some other similar chemical processes to achieve the maximum energy and exergy savings.

2-methoxy-2-methyl-heptane (MMH) plays a key role in reformulated gasoline industry due to fewer environmental impacts than methyl tert-butyl ether. Thus, the design of MMH production process has received substantial attention. In this work, we propose a different pressure thermally coupled reactive distillation (DPTCRD) process for the synthesis of MMH aiming at reducing in energy requirements and improvement in environmental benefits. The key design variables are optimized to evaluate the economic feasibility of designed process. Furthermore, the heat integration strategy has been further explored by the application of heat exchanger network based on the observation of the temperature-enthalpy diagram to fully utilize the redundant duty in DPTCRD system. The results demonstrate that the total annual cost of the heat integration-DPTCRD (HI-DPTCRD) is reduced by 29.17% than that of conventional reactive distillation process. In addition, CO2 emission of the proposed HI-DPTCRD is decreased by 75.04% compared with that through the existing process.

International audience; A method is proposed to study the separation of minimum-, maximum-boiling azeotropic, and low volatility mixtures with a light entrainer, to investigate feasible regions of the key operating parameters reboil ratio (S) and entrainer - feed flowrate ratio (FE/F) for continuous processes. The thermodynamic topological predictions are carried out for 1.0–2, 1.0–1a, and 0.0–1 Serafimov’s class diagrams. It relies upon the knowledge of residue curve maps, along with the univolatility line, and it enables the prediction of possible products at the bottom of the column and limiting values of FE/F. The profiles of the stripping, extractive, and rectifying sections are calculated by equations considering S and FE/F, and they bring information about the location of singular points and possible composition profile separatrices that could impair process feasibility. Providing specified product composition and recovery, the approximate calculations are compared with rigorous simulations of extractive distillation processes. Separating non-ideal mixtures using a light entrainer provides more opportunities for the case when it is not easy to find an appropriate heavy or intermediate entrainer

A multicriteria decision-making methodology for the sustainability prioritization of industrial systems is proposed. The methodology incorporates a fuzzy Analytic Hierarchy Process method that allows the users to assess the soft criteria using linguistic terms. A fuzzy Analytic Network Process method is used to calculate the weights of each criterion, which can tackle the interdependencies and interactions among the criteria. The Preference Ranking Organization Method for Enrichment Evaluation approach is used to prioritize the sustainability sequence of the alternative systems. Moreover, a sensitivity analysis method was developed to investigate the most critical and sensitive criteria. The developed methodology was illustrated by a case study to rank the sustainability of five alternative hydrogen production technologies. The advantages of the developed methodology over the previous approaches were demonstrated by comparing the results determined by the proposed framework with those determined using the pervious approaches. © 2015 American Institute of Chemical Engineers AIChE J, 2015

The Martin-Hou (MH) equation is a widely used equation of state in chemical engineering, mechanical engineering, and refrigeration technology design. It has pronounced advantages in calculations of liquid volume and enthalpy-entropy of high pressure gases and polar liquids. However, the determination of parameter B4 of the MH equation by using the conventional method is very time- and computation-consuming, which significantly restricts the application of the MH equation in engineering calculations. This article proposes an empirical equation to conveniently calculate B4 at different temperatures according to B4(0.7) (B4 at reduced temperature = 0.7). The accuracy of the MH equation to calculate volume of pure liquids by using the proposed equation was verified by comparing tcalculated data with literature data. The proposed equation can remarkably decrease the time to determine parameter B4, which would boost the application of the MH equation in engineering calculations.

The recovery of butyl acetate (BA) from lovastatin wastewater was studied by using the method of solvent extraction with liquid paraffin (LP) as the extractant. The effect of several key factors on the extraction efficiency including lysozyme content, initial BA concentration, equilibration time, and phase ratio was investigated. The results showed that the extraction efficiency of BA can reach 98% in 15 min at room temperature when the initial concentration of BA is 7000 mg/L. The loading capability of LP was demonstrated to be high by reusing the loaded LP to extract the fresh wastewater. Moreover, BA in the LP phase can be effectively recovered by vacuum evaporation and the regenerated LP has a very good reusability.

Isobaric vapor–liquid equilibrium (VLE) data for water + n-propanol + n-butanol ternary system have been extensively measured at 99.2 kPa using a recirculating still. The experimental data were then correlated using the extended UNIQUAC model, in which the binary interaction energy parameters between the three components were obtained through a simplex fitting method. The results showed that the calculated data by the extended UNIQUAC model using the same interaction energy parameters agree well with both the experimental data and the literature data. It demonstrated that the experimental data are very consistent with the literature data; and the extended UNIQUAC model is reliable to predict the VLE of the ternary system using the obtained interaction energy parameters.

A large portion of world’s natural gas reserves are “stranded” resources, the drive to monetize these resources leads to the development of gas-to-liquids (GTL) and liquefied natural gas (LNG) technologies. LNG has the advantage of having been developed for the past 40 years and having an excellent safety record. GTL on the other hand is another option with substantial benefits, but its development stage and commercial viability are far behind LNG. This paper presents a techno-economic comparison of GTL with LNG, including technical development, plant efficiency, market potential for the products, and capital cost for the infrastructure. The aim is to give an overall view on both LNG and GTL and provide a perspective on the profitability of these two technologies.

International audience; Extractive distillation is one of the most attractive approaches for separating azeotropic mixtures. Few contributions have been reported to design an extractive distillation for separating maximum-boiling azeotropes and no systematic approaches for entrainer screening have been presented. A systematic approach to design of two-column extractive distillation for separating azeotropes with heavy entrainers has been proposed. A thermodynamic feasibility analysis for azeotropes with potential heavy entrainers was first conducted. Then, five important properties are selected for entrainer evaluation. Fuzzy logic and develop membership functions to calculate attribute values of selected properties have been used. An overall indicator for entrainer evaluation is proposed and a ranking list is generated. Finally, the top five entrainers from the ranking list have been selected and use process optimization techniques to further evaluate selected entrainers and generate an optimal design. The capability of the proposed method is illustrated using the separation of acetone–chloroform azeotropes with five potential entrainers.

International audience; Dividing wall columns (DWCs), as a subset of fully thermally coupled distillation systems (FTCDS), is considered as one of most appealing distillation technologies to the chemical industry, because it can bring about substantial reduction in the capital investment, as well as savings in the operating costs. This study targets on how to improve the energy efficiency of DWCs by achieving their well-designed feasible parameters. Two methods are applied to study the effect of liquid and vapor split ratios including a shortcut method and a method of systematic calculations by using differential equation profiles. In the latter approach, differential composition profiles in each column section are obtained by considering feasible key design parameters. The finding of pinch points for each section profiles allowed determining the limiting values of the operating parameters. The intersections of these profiles are used to get well-designed feasible parameters of the liquid and vapor split ratios in an attempt to obtain the desired purities of the top, bottom, and side-stream products. The obtained parameters are validated by rigorous simulations. Three types of case studies involve the separation of hydrocarbons (n-pentane, n-hexane, n-heptane), aromatics (benzene, toluene, p-xylene), and alcohols (ethanol, propanol, butanol).