Development of a full process simulation package for tail gas cleaning from melamine production with ionic liquids

Melamine production is known to produce a tail gas with a significant amount of NH3 and CO2. The most common separation methods applied to melamine tail gas are water scrubbing and urea co-production technology. With good stability, non-volatility and tailored properties, ionic liquids (ILs) are regarded as vital potential solvents for gas separation. Therefore, two new process technologies, one is the ionic liquid-based process (IL-0), and the other is the enhanced ionic liquid process (IL-En) were employed and evaluated for energy and cost efficiency. The IL-En employs stripping on the treatment of melamine tail gas. The protic ionic liquid named 1-butyl imidazolium bis (trifluoromethylsulfonyl) imide ([Bim][NTf2]) was selected for the evaluation of the melamine tail gas cleaning process. Thermodynamic data were fitted to the NRTL equations. Three full process flowsheets were simulated in Aspen Plus V11 TM. A basic and an enhanced ionic liquid process (IL-0 and IL-En), a conventional water scrubbing (WS) technology as a comparison, process sensitivity analysis and energy/economic evaluation were carried out. The results showed that the total separation cost of the IL-En can be reduced by 61% compared to that of the WS process. Moreover, the IL-based flowsheet is simpler than WS and avoids wastewater discharge.In order to give deep analysis of the proposed technology, a detailed multi-objective optimization (MOO) for the NH3/CO2 separation of the tail gas by IL in technical-energy-economic evaluation. According to the optimization results, specific cases with different objective functions were chosen, and the relationship between key parameters was analyzed. The results showed that the ionic liquid-based technology could realize a better performance regarding the technical-energy-economic than the base case. Deeper analyses with the influence of operation parameters with evaluation index were carried out, thus providing support to the industrial application of the new separation technology.On the basis of the process steady-state design and multi-objective optimization work, the dynamic control behavior and evaluation of balanced IL-based NH3/CO2 separation were carried out. In order to analyze the dynamic behavior of this new technology, the two step test were considered: the tail gas flowrate and composition fluctuation were introduced to the process. With the procedure of definition of control problem, conversion from steady-state to dynamic mode and successful inventory control, the simulation results showed that NH3 concentration and NH3 recovery have a positive response with more tail gas and NH3 in the system. With the analysis of the parameter behavior on the different tail gas fluctuations, basic dynamic control could be built to guarantee stabilization with different fluctuations. Based on the detailed investigation about this process’s dynamic behavior, this new technology is fairly easy and simple to operate. Finally, the full-scale simulation package for the IL- based NH3/CO2 separation process will be established and provide strong support to this novel and new technology industrial application

Review of Methods for Sustainability Assessment of Chemical Engineering Processes

Integrating sustainability principles as a design goal in chemical engineering has become a major challenge facing modern society. This review aims to provide a comprehensive investigation regarding available methods that can potentially be used by industries to quantify the sustainability performance of chemical processes. First, the expansion in the definition of sustainable processes is summarized, forcing corresponding methods to broaden the assessment scope. Then, 30 methods are classified into three categories based on their scope to facilitate their analysis: material and energy flow analysis, life cycle assessment, and sustainability assessment. Key attributes of methods in each category are extracted and discussed in detail. In addition, illustrative examples have been introduced to demonstrate the applicability of these methods. Finally, challenges of the present methods and future research directions for sustainability assessment methods are also highlighted, such that the objective of efficient, environmentally friendly, and economic processes can be realized

Technoeconomic Analysis and Process Design for CO2 Electroreduction to CO in Ionic Liquid Electrolyte

Electrochemical reduction of CO2 to chemical feedstocks offers a sustainable way to reduce carbon emissions by shifting the industry away from fossil fuel dependence. However, the lack of understanding of economic feasibility is hindering this technology from large-scale application. We proposed a systematic methodology to evaluate and design the novel route of CO2-to-CO conversion taking ionic liquid as the electrolyte. Not only a comprehensively economic model was developed to offer targets for achieving economically competitive industrialization, but also the Route Selection Index was established to quickly identify the minimum feed concentration for making use of diluted CO2 feed more profitable than using pure CO2 streams. We found that although this route is currently expensive owing to high electrolyzer capitals, it can be economically acceptable if advanced electrocatalytic performance and electrolyzer system could be obtained. The results showed that current densities need to reach at least 200 mA cm(-2) at 99% faradaic efficiency to make this route become competitive with fossil fuel-derived feedstocks. Furthermore, a minimum concentration of 28 mol % is required to make the route of using diluted CO2 feed more economically attractive, providing insights into the feasibility of directly utilizing CO2 from different industry sources

Simulation and energetic assessment of the ammonia synthesis loop with ionic liquid-Based ammonia recovery from recycle gas

Ammonia (NH3) synthesis by Haber-Bosch process is recognized as the most important pathway for NH3 pro-duction. However, NH3 recovery from recycle gas using conventional condensation separation is still an energy-intensive process. Ionic liquids (ILs) have been proved to be effective solvents for NH3 separation and recovery due to their unique properties. In this work, a novel IL-based ammonia synthesis loop (IL-HB) was proposed, taking the protic IL [Bim][NTf2] as the absorbent to separate and recover NH3 from recycle gas, aiming to reduce the energy consumption and increase the NH3 production capacity of the synthesis tower. Then, a systematic methodology that considers reliable thermodynamic models as well as process simulation and assessment was established to evaluate the feasibility of the IL-HB. Furthermore, two entire processes (ILa-HB and ILb-HB) that integrate the optimal sections of IL-based NH3 recovery from recycle gas with the ammonia synthesis loop as a whole were simulated, taking the conventional Haber-Bosch ammonia synthesis loop (HB) as the benchmark. The simulation results prove great techno-economic potentials of the proposed ILa-HB and ILb-HB. Compared with the HB, the energy consumption and CO2 emissions of ILb-HB can be reduced by 16.01% and 29.44%, respec-tively, presenting enormous energy-saving and environment-friendly superiority

Simulation and energetic assessment of the ammonia synthesis loop with ionic liquid-Based ammonia recovery from recycle gas

Ammonia (NH3) synthesis by Haber-Bosch process is recognized as the most important pathway for NH3 pro-duction. However, NH3 recovery from recycle gas using conventional condensation separation is still an energy-intensive process. Ionic liquids (ILs) have been proved to be effective solvents for NH3 separation and recovery due to their unique properties. In this work, a novel IL-based ammonia synthesis loop (IL-HB) was proposed, taking the protic IL [Bim][NTf2] as the absorbent to separate and recover NH3 from recycle gas, aiming to reduce the energy consumption and increase the NH3 production capacity of the synthesis tower. Then, a systematic methodology that considers reliable thermodynamic models as well as process simulation and assessment was established to evaluate the feasibility of the IL-HB. Furthermore, two entire processes (ILa-HB and ILb-HB) that integrate the optimal sections of IL-based NH3 recovery from recycle gas with the ammonia synthesis loop as a whole were simulated, taking the conventional Haber-Bosch ammonia synthesis loop (HB) as the benchmark. The simulation results prove great techno-economic potentials of the proposed ILa-HB and ILb-HB. Compared with the HB, the energy consumption and CO2 emissions of ILb-HB can be reduced by 16.01% and 29.44%, respec-tively, presenting enormous energy-saving and environment-friendly superiority

Process simulation and evaluation for NH3/CO2 separation from melamine tail gas with protic ionic liquids

Melamine production is known to produce a tail gas with a significant amount of NH3 and CO2. The most common separation methods applied to melamine tail gas are water scrubbing and urea co-production technology. With good stability, non-volatility and tailored properties, ionic liquids (ILs) are regarded as vital potential solvents for gas separation. Therefore, two new process technologies, one is the ionic liquid-based process (IL-0), and the other is the enhanced ionic liquid process (IL-En) was employed and evaluated for energy and cost efficiency. The IL-En employs stripping on the treatment of melamine tail gas. The protic ionic liquid named 1-butyl imidazolium bis (trifluoromethylsulfonyl) imide ([Bim][NTf2]) was selected for the evaluation of the melamine tail gas cleaning process. Thermodynamic data were fitted to the NRTL equations. Three full process flowsheets were simulated in Aspen Plus V11 (TM). A basic and an enhanced ionic liquid process (IL-0 and IL-En), a conventional water scrubbing (WS) technology as a comparison, process sensitivity analysis and energy/economic evaluation were carried out. The results showed that the total separation cost of the IL-En can be reduced by 61% compared to that of the WS process. Moreover, the IL-based flowsheet is simpler than WS and avoids wastewater discharge

Process Simulation and Optimization of Ammonia-Containing Gas Separation and Ammonia Recovery with Ionic Liquids

Ionic liquids (ILs) have been experimenta ly proved to be effective for ammonia-containing gas separation and recovery. A systematic strategy including thermodynamic models, process simulation, multiobjective genetic algorithm, and assessment for novel IL-based separation of ammonia-containing tail gas and ammonia recovery process was proposed. The conventional IL ([C(4)Mim][NTf2]) and the functional IL ([C(4)im][NTf2]) were selected, and their NH3 removal performance was investigated. Physical properties of models of IL systems were established with temperature-dependent equations, and gas-liquid phase equilibria of the NH3-IL system were molded with the nonrandom two liquid model equation. Total purification cost (TPC), total process CO2 emission (TPCOE), and thermodynamic efficiency (eta(eff)) were selected as the objective functions to be optimized. Process simulation results indicated that under same operational parameters, using functional ILs results in lower NH3 concentration in purified gas and higher removal efficiency than that of conventional ILs. After optimization, a series of solutions satisfying the constraints was provided by the Pareto front. The lowest objective functions can achieve 0.0211 $/N m(3) (TPC), 265.67 kg CO2/h (TPCOE), and 48.05% (eta(eff)). Moreover, using functional ILs could greatly decrease purification cost and energy consumption and avoid wastewater discharge, which is an inevitable environmental problem in the water scrubbing process

Dynamic process simulation and optimization of CO2 removal from confined space with pressure and temperature swing adsorption

Pressure and Temperature Swing Adsorption (PTSA) is an appealing purification technology for removing low CO2 concentration from confined space potentially. In this work, a systematic method integrating dynamic process simulation, sensitivity analysis, process optimization, and energy consumption assessment was established to investigate a PTSA process of low CO2 concentration separation in the confined space using two adsorbents (Zeolite 13X and NaUSY). The dual site Langmuir adsorption isothermal models of N-2 and CO2 were established, and calculated results showed good agreement with the experimental data. After parametric sensitivity analysis, key operational parameters (i.e. adsorption pressure, desorption pressure, regeneration temperature and P/F ratio) were optimized to achieve minimum process energy consumption. Those results indicated that Zeolite 13X was a good candidate for separating low concentration CO2 from confined space with lower energy consumption (55.03 kJ.Nm(-3) N-2). The simulation result can provide a novel strategy for removing low CO2 concentration from confined space