Record Types
Records with Type: Preprint
Side Stream Control in Semicontinuous Distillation
Pranav Bhaswanth Madabhushi, Thomas Adams II
October 18, 2018 (v1)
Keywords: dynamic optimization, dynamical system analysis, Semicontinuous Distillation, side stream control
The idea to reduce cycle time (𝑇), by controlling the side stream flow rate using a feedforward control model -- the ideal side draw recovery arrangement (ISR) -- was standard in most semicontinuous distillation studies. However, its effect, particularly on ‘𝑇’ and more broadly on the system dynamics, was not clearly understood. In the current study, we compare the performance of using a modified form of ISR model with the status quo, based on the criteria, 𝑇 and separating cost (SC) on different case studies. Results show that the modified control model performed better with a 10-20% reduction in SC while maintaining product purities. Furthermore, the side stream flow rate trajectory that minimizes SC was found by using dynamic optimization and it did not differ a lot from the trajectory generated by the modified control model. The improvement in SC was at most 2%.
Optimization of Coke Oven Gas Desulphurization and Combined Cycle Power Plant Electricity Generation
LINGYAN DENG, Thomas A. Adams II
September 12, 2018 (v3)
Subject: Optimization
Keywords: carbon tax, coke oven gas valorization, combined cycle power plant, desulphurization, net present value, Optimization, steel refinery
Many steel refineries generate significant quantities of coke oven gas (COG), which is in some cases used only to generate low pressure steam and small amounts of electric power. In order to improve energy efficiency and reduce net greenhouse gas emissions, a combined cycle power plant (CCPP) where COG is used as fuel is proposed. However, desulphurization is necessary before the COG can be used as a fuel input for CCPP. Using a local steel refinery as a case study, a proposed desulphurization process is designed to limit the H2S content in COG to less than 1 ppmv, and simulated using ProMax. In addition, the proposed CCPP plant is simulated in Aspen Plus and is optimized using GAMS to global optimality with net present value as the objective function. Furthermore, carbon tax is considered in this study. The optimized CCPP plant was observed to generate more than twice the electrical efficiency when compared to the status quo for the existing steel refinery. Thus, by generating more e... [more]
很多炼钢厂排放大量焦炉煤气。大部分焦炉煤气被用于燃烧来生产低压蒸汽以及通过汽轮机生产少量的电。为了提高发电效率并减少温室效应,本文提出运用联合循环发电来替代蒸汽发电。不同于现有的蒸汽发电的是,在联合循环发电过程中,焦炉煤气必须经过脱硫处理。基于当地炼钢厂的情况,本文提出并设计了焦炉煤气脱硫方案,使得焦炉煤气中H2S含量低于1 ppmv。该脱硫过程采用ProMax模拟。联合循环发电采用Aspen Plus模拟。并且整个联合循环发电过程又用GAMS软件模拟,以最大化纯现价为目标来优化整个联合循环发电过程。本文还考虑了二氧化碳排放税对纯现价的影响。优化后的联合循环发电效率是现有的低压蒸汽发电的两倍多。因此,通过提高发电效率,钢铁厂所需购买电量降低,也因而从生命周期的角度来说大大减少了二氧化碳的排放量。
Combining Petroleum Coke and Natural Gas for Efficient Liquid Fuels Production
Ikenna J Okeke, Thomas A Adams II
August 28, 2018 (v1)
This work explores the technical feasibility and economic profitability of converting petroleum coke (petcoke) and natural gas to liquid fuels via Fischer-Tropsch synthesis. Different petcoke conversion strategies were examined to determine the conversion pathway which can be competitive with current market prices with little or no adverse environmental impacts. Three main design approaches were considered: petcoke gasification only, combined petcoke gasification and natural gas reforming through traditional processing steps, and combined petcoke gasification and natural gas reforming by directly integrating the gasifier’s radiant cooler with the gas reformer. The designs investigated included scenarios with and without carbon capture and sequestration, and with and without CO2 emission tax penalties. The performance metrics considered included net present value, life cycle greenhouse gas emissions, and the cost of CO2 avoided. The design configuration that integrated natural gas refor... [more]
Biomass-Gas-and-Nuclear-To-Liquids (BGNTL) Processes Part I: Model Development and Simulation
James Alexander Scott, Thomas Alan Adams II
August 7, 2018 (v1)
New polygeneration processes for the co-production of liquid fuels (Fischer-Tropsch liquids, methanol, and dimethyl ether) and electricity are presented. The processes use a combination of biomass, natural gas, and nuclear energy as primary energy feeds. Chemical process models were created and used to simulate candidate versions of the process, using combinations of models ranging from complex multi- scale models to standard process flowsheet models. The simulation results are presented for an Ontario, Canada case study to obtain key metrics such as efficiency and product conversions. Sample Aspen Plus files are provided in the supplementary material to be used by others.
Deterministic Global Optimization with Artificial Neural Networks Embedded
Global deterministische Optimierung von Optimierungsproblemen mit künstlichen neuronalen Netzwerken
Artur M Schweidtmann, Alexander Mitsos
October 15, 2018 (v2)
Subject: Optimization
Artificial neural networks (ANNs) are used in various applications for data-driven black-box modeling and subsequent optimization. Herein, we present an efficient method for deterministic global optimization of ANN embedded optimization problems. The proposed method is based on relaxations of algorithms using McCormick relaxations in a reduced-space [\textit{SIOPT}, 20 (2009), pp. 573-601] including the convex and concave envelopes of the nonlinear activation function of ANNs. The optimization problem is solved using our in-house global deterministic solver MAiNGO. The performance of the proposed method is shown in four optimization examples: an illustrative function, a fermentation process, a compressor plant and a chemical process optimization. The results show that computational solution time is favorable compared to the global general-purpose optimization solver BARON.
Technical challenges in operating an SOFC in fuel flexible gas turbine hybrid systems: Coupling effects of cathode air mass flow
Nor Farida Harun, David Tucker, Thomas A. Adams II
June 19, 2018 (v1)
Keywords: Cathode air mass flow, Cyber-physical simulations, Fuel cell gas turbine hybrid, Fuel composition changes, Open loop characterization, Solid Oxide Fuel Cells
Considering the limited turndown potential of gasification technologies, supplementing a fuel cell turbine hybrid power system with natural gas provides flexibility that could improve economic viability. The dynamic characterization of fuel composition transients is an essential first step in completing the system identification required for controls development. In this work, both open loop and closed loop transient responses of the fuel cell in a solid oxide fuel cell (SOFC) gas turbine (GT) hybrid system to fuel composition changes were experimentally investigated using a cyber-physical fuel cell system. A transition from methane lean syngas to methane rich gases with no turbine speed control was studied. The distributed performance of the fuel cell was analyzed in detail with temporal and spatial resolution across the cell.

Dramatic changes in fuel cell system post combustor thermal output or “thermal effluent” resulting from anode composition changes drove turbine transients th... [more]
Space-constrained purification of dimethyl ether through process intensification using semicontinuous dividing wall columns
Sarah E. Ballinger, Thomas A. Adams II
June 12, 2018 (v1)
Keywords: Aspen Plus, Dimethyl Ether, Dividing wall column, Mobile Plant, Plant-on-a-truck, Process Intensification, Semicontinuous Distillation, Simulation
In this work, a distillation system is designed to purify dimethyl ether (DME) from its reaction by-products in the conversion of flare gas into a useful energy product. The distillation equipment has a size constraint for easy transportation, making process intensification the best strategy to efficiently separate the mixture. The process intensification distillation techniques explored include the dividing wall column (DWC) and a novel semicontinuous dividing wall column (S-DWC). The DWC and the S-DWC both purify DME to fuel grade purity along with producing high purity waste streams. An economic comparison is made between the two systems. The DWC is a cheaper method of producing DME however the purity of methanol, a reaction intermediate, is not as high as the S-DWC. Overall, this research shows that it is possible to purify DME and its reaction by-products in a 40-foot distillation column at a cost that is competitive with Diesel.
Modeling and simulation of an integrated steam reforming and nuclear heat system
Leila Hoseinzade, Thomas A. Adams II
June 12, 2018 (v1)
Keywords: Dynamic Modelling, Integrated Systems, Methane Reforming, Nuclear Heat, Simulation, Syngas
In this study, a dynamic and two-dimensional model for a steam methane reforming process integrated with nuclear heat production is developed. The model is based on first principles and considers the conservation of mass, momentum and energy within the system. The model is multi-scale, considering both bulk gas effects as well as spatial differences within the catalyst particles. Very few model parameters need to be fit based on the design specifications reported in the literature. The resulting model fits the reported design conditions of two separate pilot-scale studies (ranging from 0.4 to 10 MW heat transfer duty). A sensitivity analysis indicated that disturbances in the helium feed conditions significantly affect the system, but the overall system performance only changes slightly even for the large changes in the value of the most uncertain parameters.
Techno-economic comparison of Acetone-Butanol-Ethanol fermentation using various extractants
Giancarlo Dalle Ave, Thomas A. Adams II
June 12, 2018 (v1)
Keywords: Acetone, Butanol, Cost of CO2 Emissions Avoided, Ethanol, Extraction, Fermentation, Technoeconomic Analysis
This work compares various chemicals for use as extractants in second-generation Acetone-Butanol-Ethanol fermentation on economic and environmental bases. Both non-toxic and toxic extractants are considered in this study. The combinative extractive-distillation separation process was modelled using a combination of Microsoft Excel 2013, MATLAB 2015 and Aspen Plus v8.8. Separation trains were designed and optimized for each extractant to best take advantage of extractant properties. Upstream units considered in this analysis include: biomass (switchgrass) solids processing, biomass pre-treatment and saccharification, and fermentation. Downstream processes considered include utility generation and wastewater treatment. The cost of CO2 equivalent emissions avoided (CCA) was used as the metric to compare the environmental impact of each process as compared to conventional petroleum-based gasoline. The economic and environmental best extractant is shown to be 2-ethyl-hexanol with a minimum... [more]
Direct Steam Generation Concentrated Solar Power Plant with a Decalin/Naphthalene Thermochemical Storage System
Haoxiang Lai, Thomas A. Adams II
June 12, 2018 (v1)
This study presents the design and analysis of a new integrated direct steam generation (DSG) concentrated solar power (CSP) plant with a decalin/naphthalene thermochemical storage system. Model simulations were performed in accordance to historical hourly solar radiation data over a year, using a combination of Aspen Plus v10, MATLAB 2016b, and Microsoft Excel VBA. It was found that the proposed plant feasibly stored and discharged energy, based on the solar radiation and chemical storage availability, to maintain base-load power productions (250 MW or 120 MW) with an overall efficiency of 14.6%. The effectiveness of the designed storage system was found to be comparable to a molten salt storage system which is currently used in existing CSP plants. The proposed integrated DSG CSP plant with a decalin/naphthalene thermochemical storage system shows promise for being an alternative to existing CSP plants.
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