Recovery Section Research Articles

Solar Thermal-Based ORC Power Plant for Micro Cogeneration – Performance Analysis and Control Strategy

The paper deals with the performance assessment of a small scale cogeneration system for building applications, featuring an Organic Rankine Cycle-based plant bottoming a solar collector array for combined heat and electricity generation. A sliding vanes rotary expander and a water cooled condenser are employed in the recovery section. A comprehensive MATLAB® model accounts for the dynamic of each component, as both a stand-alone device and a plant-integrated unit: a parametric study is presented and an off-design analysis is performed to properly assess the performances of both the heat exchanger and the expander. Heat availability to the ORC heat exchanger is evaluated, based on solar availability, thermal losses in the pipes and plant requirements, in terms of operating temperature and pressures, having the collection area, the mass flowrate for the fluid in the solar collector branch and the fluid type in the recovery section as main variables. Due to the need for DHW production, a storage unit for hot water is present, upstream the recovery branch: dependently on the ability the fluid at the collector outlet has to meet the ORC requirements for proper operation (about 110°C), the ORC evaporator is fed and the recovery section enabled. Both continuous and unsteady operation underwent an in-depth analysis, as well as the benefits associated with different discharge times for the storage unit: dependently on whether the electrical output or the thermal one need to be maximized, a different control logic for the whole system comes out (e.g. either a flash or a progressive tank discharge). The virtual platform allowed the setting-up of a pilot plant, for direct performance assessment and model validation.

Phase Equilibrium on Extraction Methylphenols from Aqueous Solution with 3,3-Dimethyl-2-butanone at 333.2 K and 353.2 K

The phenols recovery process is a significant part of treating coal chemical wastewater with highly concentrated phenols and ammonia. Solvent extraction is an important unit for phenol recovery section. The accurate measurement of liquid–liquid equilibrium (LLE) data is essential for realizing partitioning. In this paper, the LLE data for the ternary system water + 2-, 3-, 4-methylphenol +3,3-dimethyl-2-butanone (also known as methyl tert-butyl ketone, MTBK) were studied at the temperatures of 333.2 K and 353.2 K under 101.3 kPa. The extraction performance of MTBK was estimated by partition coefficients and separation factors. The extraction efficiencies of MTBK were compared with those of MIBK, mesityl oxide, and those results of MTBK at five different temperatures from 298.2 K to 353.2 K were also contrasted with each other. In addition, the nonrandom two-liquid (NRTL) and universal quasi chemical (UNIQUAC) models were applied to fit the measured LLE data. The results indicate that the calculated data b...

Performance evaluation of material separation in a material recovery facility using a network flow model

In this paper, we model the recycling process for solid waste as performed in a material recovery facility. The intent is to inform the design and evaluation of a material recovery facility (MRF) in order to increase its profit, efficiency and recovery rate. We model the MRF as a multi-stage material separation process and develop a network flow model that evaluates the performance of the MRF through a system of linear equations. We estimate the parameters of the network flow model from historical data to find the best fit. We validate the model using a case-study of a light-packaging recovery section of an MRF in Spain. Additionally, we examine how uncertainty in the input material composition propagates through the system, and conduct a sensitivity analysis on the model parameters.

COSMO-based/Aspen Plus process simulation of the aromatic extraction from pyrolysis gasoline using the {[4empy][NTf 2 ] + [emim][DCA]} ionic liquid mixture

Abstract The ionic liquids (ILs) have been widely studied as potential replacements of conventional solvents in the extraction of aromatic hydrocarbons from alkanes. However, most of the literature is focused in obtaining liquid-liquid equilibria experimental data without studying the complete extraction and IL regeneration process. In this paper, a computer-aided methodology combining COSMO-based molecular simulations and Aspen Plus process simulations has been used to study the extraction process of aromatic hydrocarbons from pyrolysis gasoline employing a binary mixture of 1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][NTf 2 ]) and the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) ILs as solvent. An extensive comparison (more than 600 points) between experimental data and the predictions obtained by the COSMO-based thermodynamic model of liquid–liquid and vapor–liquid equilibria and ILs physical properties was made for validation purposes. Process simulations were performed in three system configurations: with one, two, or three flash distillations in the IL recovery section. The potential advantage of using binary IL-IL mixture as extracting solvent was studied in the whole range of composition. The configuration with three flash distillations and the binary IL-IL mixture with a 75% of [4empy][NTf 2 ] were selected as the optimal conditions to increase aromatic recovery and purity, improving the separation performance respect to the neat ILs.

Process development and exergy cost sensitivity analysis of a hybrid molten carbonate fuel cell power plant and carbon dioxide capturing process

An integrated power plant with a net electrical power output of 3.71 × 105 kW is developed and investigated. The electrical efficiency of the process is found to be 60.1%. The process includes three main sub-systems: molten carbonate fuel cell system, heat recovery section and cryogenic carbon dioxide capturing process. Conventional and advanced exergoeconomic methods are used for analyzing the process. Advanced exergoeconomic analysis is a comprehensive evaluation tool which combines an exergetic approach with economic analysis procedures. With this method, investment and exergy destruction costs of the process components are divided into endogenous/exogenous and avoidable/unavoidable parts. Results of the conventional exergoeconomic analyses demonstrate that the combustion chamber has the largest exergy destruction rate (182 MW) and cost rate (13,100 $/h). Also, the total process cost rate can be decreased by reducing the cost rate of the fuel cell and improving the efficiency of the combustion chamber and heat recovery steam generator. Based on the total avoidable endogenous cost rate, the priority for modification is the heat recovery steam generator, a compressor and a turbine of the power plant, in rank order. A sensitivity analysis is done to investigate the exergoeconomic factor parameters through changing the effective parameter variations.

Performance optimization of a multi stage flash desalination unit with thermal vapor compression using genetic algorithm

In the present study, a multi stage flash desalination system with brine recirculation and thermal vapor compression (MSF-BR-TVC) is analyzed. From four different configurations of MSF-BR-TVC systems, the one with two ejectors the receives secondary vapor from two successive middle stages of the heat recovery section is studied in more detail due to its higher performance ratio which is 9.90. In this configuration, the compression ratio for the first and second ejectors are 4.55 and 4.06, respectively. Also, the mixing number for these two ejectors are 2.62 and 2.33. Then, an optimization process based on genetic algorithm is carried out to evaluate the effect of most important parameters on the performance ratio. It is observed that optimum performance ratio of 12.80 is achieved for the heat steam, last stage and top brine temperatures of 90.18°C, 39.75°C and 89.97°C, respectively. Although such performance ratio is the highest value in the range of decision variables, it leads to a large, uneconomical specific heat transfer area. To resolve this issue, two-objective optimization is performed using NSGA II method. The two objectives are selected as performance ratio and specific heat transfer area with the latter considered as cost function due to its direct connection with cost. Two-objective optimization using NSGA II leads to a Pareto front curve. Selection of each point on this curve depends on the designer’s decision, namely priority of the performance ratio or the specific heat transfer area. Moreover, the effect of the number of total stages on the optimum performance ratio for the selected MSF-BR-TVC is investigated. Results show that increasing the total number of stages from 20 to 30 increases the optimum performance ratio from 9.97 to 15.27.

Dearomatization of pyrolysis gasoline with an ionic liquid mixture: Experimental study and process simulation

The pyrolysis gasoline is the main source of benzene, toluene, and xylenes. The dearomatization of this stream is currently performed by liquid–liquid extraction using sulfolane. However, the sulfolane process has high operating costs that could be minimized by employing ionic liquids as solvents because of their non‐volatile character. In this work, we proposed a novel process to perform the dearomatization of pyrolysis gasoline using a binary mixture of 1‐ethyl‐3‐methylimidazolium tricyanomethanide ([emim][TCM]) and 1‐ethyl‐4‐methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][Tf2N]) ILs. The composition in the IL mixture was optimized considering their extractive and thermophysical properties. The Kremser method was applied using the experimental data to determine the number of equilibrium stages in the liquid–liquid extractor which provides the same extraction yields of aromatics using the IL mixture that those of the sulfolane process. The recovery section was designed and simulated from the experimental vapor–liquid equilibrium between the hydrocarbons and the IL mixture. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4054–4065, 2017

Design of the recovery section of the extracted aromatics in the separation of BTEX from naphtha feed to ethylene crackers using [4empy][Tf2N] and [emim][DCA] mixed ionic liquids as solvent

Abstract Aromatic hydrocarbons are mainly obtained from reformer and pyrolysis gasolines by liquid-liquid extraction. In these streams, the content of aromatics is between 40 wt.% and 70 wt.%. However, several streams as the naphtha feed to ethylene crackers, in which the aromatics are between 10 wt.% and 25 wt.%, have not available technology to obtain a commercial stream of BTEX. In our previous contribution, the BTEX removing from a naphtha model with the minimum aromatic content, 10 wt.%, was studied using ionic liquids (ILs) as solvents. The high aromatic purity in the extract stream and the good extraction yields obtained suggested liquid-liquid extraction using ILs as a good technological election. To confirm this, in this work the vapor-liquid separation of all hydrocarbons from the solvent in the extract stream have been determined at several temperatures by using a headspace – gas chromatography (HS-GC) technique. After that, the operating conditions were simulated to maximize the purity and recovery of the aromatics. The proposed recovery section to selectively separate the aromatics from the extract stream consists in three flash distillation units that operate at low temperatures and high vacuum conditions, achieving an aromatic-rich stream with a purity of 98.5 wt.%.

Extraction of aromatic hydrocarbons from pyrolysis gasoline using tetrathiocyanatocobaltate-based ionic liquids: Experimental study and simulation

The pyrolysis gasoline is one of the main sources of aromatic hydrocarbons as a result of their high content in these compounds. Organic solvents such as sulfolane are currently employed in the extraction of aromatic but the ionic liquids (ILs) have been recently proposed as potential replacement. In this work, we have studied the use of the bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate ([emim]2[Co(SCN)4]) and bis(1-butyl-3-methylimidazolium) tetrathiocyanatocobaltate ([bmim]2[Co(SCN)4]) ILs in the extraction of aromatic hydrocarbons from pyrolysis gasoline. The extractive properties of both tetrathiocyanatocobaltate-based ILs were compared to those of other promising ILs and sulfolane, showing the highest values. To perform the simulation of the whole process, we have experimentally studied the liquid-liquid extraction of aromatics from pyrolysis gasoline and the recovery of the extracted hydrocarbons from the ILs. In addition, a thermophysical characterization of the ionic solvents was performed measuring their densities, viscosities, thermal stabilities, maximum operation temperatures, and specific heats. Employing the experimental data, the extractor was simulated using the Kremser equation whereas the recovery section formed by flash distillation units was simulated using a new algorithm specifically design to the case of a high concentration of non-volatile compounds.

Dynamic modelling of Heat Exchanger fouling in multistage flash (MSF) desalination

Fouling on heat transfer surfaces due to scale formation is the most concerned item in thermal desalination industry. Here, a dynamic fouling model is developed and incorporated into the MSF dynamic process model to predict fouling at high temperature and high velocity. The proposed dynamic model considers the attachment and removal mechanisms in the fouling phenomena with more relaxation of the assumptions such as the density of the fouling layer and salinity of the recycle brine. While calcium sulphate might precipitate at very high temperature, only the crystallization of calcium carbonate and magnesium hydroxide are considered in this work. Though the model is applied in a 24 stages brine recycle MSF plant, only the heat recovery section (21 stages) is considered under this study. The effect of flow velocity and surface temperature are investigated. By including both diffusion and reaction mechanism in the fouling model, the results of the fouling prediction model are in good agreement with most recent studies in the literature. The deposition of magnesium hydroxide increases with the increase in surface temperature and flow velocity while calcium carbonate deposition increases with the increase in the surface temperature and decreases with the increase in the flow velocity.

Optimization for energy consumption in drying section of fluting paper machine

Non-linear programming optimization method was used to optimize total steam and air consumption in the dryer section of multi-cylinder fluting paper machine. Equality constraints of the optimization model were obtained from specified process blocks considering mass and energy balance relationships in drying and heat recovery sections. Inequality constraints correspond to process parameters such as production capacity, operating conditions, and other limitations. Using the simulation, the process parameters can be optimized to improve the energy efficiency and heat recovery performance. For a corrugating machine, optimized parameters show the total steam use can be reduced by about 11% due to improvement of the heat recovery performance and optimization of the operating conditions such as inlet web dryness, evaporation rate, and exhaust air humidity, accordingly total steam consumption can be decreased from about 1.71 to 1.53 tonnes steam per tonne paper production. The humidity of the exhaust air should be kept as high as possible to optimize the energy performance and avoid condensation in the pocket dryers and hood exhaust air. So the simulation shows the supply air should be increased by about 10% to achieve optimal humidity level which was determined about 0.152 kgH2O/(kg dry air).

Removal of silicon from green liquor with low-temperature precausticizing

Nonwood materials contain a high percentage of silicon, which causes numerous problems in the chemical recovery section. Researchers previously proposed the method of silicon removal by two-stage causticizing at temperatures of 90ºC to 95ºC, finding that the desilication rate was about 72.9% and the causticizing efficiency was 22.7% when 30% of the causticizing quicklime (calcium oxide; CaO) was added. The present paper deals with the desilication of green liquor recovered from wheat straw black liquor by a low-temperature precausticization method. The results showed that about 89.3% silicon removal and 10.3% causticizing efficiency were achieved under the following precausticizing conditions: added lime amount of 20%, temperature of 20ºC, and reaction time of 60 min. While precausticizing at 90ºC with the same lime amount, only about 63.5% silicon removal and 13.0% causticizing efficiency were gained. Therefore, precausticizing with low temperature was beneficial for silicon removal and retention of carbonate (CO3 2-).

Techno-economic analysis of an absorption based methanol to olefins recovery section

Two grass-roots light olefins recovery sections for a methanol to olefins reactor effluent are compared in terms of energy efficiency, robustness, capital expenditure and operational expenditure. As the methanol to olefins process is characterized by a higher propene to ethene ratio and a lower light ends content compared to the steam cracking process, a novel absorption based separation section for the methanol to olefins process was proposed by Wison Engineering, replacing the traditional cryogenic demethanizer column by the combination of a precutting column and an absorption column.Pinch analysis showed that the heat integration potential for both separation sections is nearly identical, but the absorption configuration operates at a higher thermodynamic efficiency. The cryogenic separation section has a higher robustness when the amount of light ends in the reactor effluent varies. The capital expenditure of the absorption configuration is up to 14% lower and the operational expenditure is up to 9% lower compared to the cryogenic configuration, depending on the light ends content in the reactor effluent, leading to more favorable economic key performance indicators. The novel absorption configuration is an interesting alternative to the traditional cryogenic configuration for a methanol to olefins separation section.

Design of the Hydrocarbon Recovery Section from the Extract Stream of the Aromatic Separation from Reformer and Pyrolysis Gasolines Using a Binary Mixture of [4empy][Tf2N] + [emim][DCA] Ionic Liquids

Reformer and pyrolysis gasolines are the main benzene, toluene, ethylbenzene, and xylenes (BTEX) sources. In our previous works, the aromatic extraction from reformer and pyrolysis gasoline models formed by three n-alkanes, benzene, toluene, and xylenes were studied using a binary mixture of ionic liquids (ILs). The results showed that the {[4empy][Tf2N] + [emim][DCA]} IL mixture with [4empy][Tf2N] mole fraction of 0.3 required a comparable countercurrent extraction column to that of the Sulfolane process, and extracted BTEX had quite a higher purity using the IL mixture in the three gasoline models analyzed. Here, we have studied the hydrocarbon recovery from the extract stream obtained in these works. For that purpose, the vapor–liquid equilibria (VLE) data involving the extracted hydrocarbons and the IL mixed solvent have been determined by the headspace–gas chromatography (HS–GC) technique for several temperatures. Afterward, the simulation of two new process configurations based on adiabatic flash di...

Preventing roof fall fatalities during pillar recovery: A ground control success story

For decades, pillar recovery accounted for a quarter of all roof fall fatalities in underground coal mines. Studies showed that a miner on a pillar recovery section was at least three times more likely to be killed by a roof fall than other coal miners. Since 2007, however, there has been just one fatal roof fall on a pillar line. This paper describes the process that resulted in this historic achievement. It covers both the key research findings and the ways in which those insights, beginning in the early 2000s, were implemented in mining practice. One key finding was that safe pillar recovery requires both global and local stability. Global stability is addressed primarily through proper pillar design, and became a major focus after the 2007 Crandall Canyon mine disaster. But the most significant improvements resulted from detailed studies that showed that local stability, defined as roof control in the immediate work area, could be achieved with three interventions: (1) leaving an engineered final stump, rather than extracting the entire pillar, (2) enhancing roof bolt support, particularly in intersections, and (3) increasing the use of mobile roof supports (MRS). A final component was an emphasis on better management of pillar recovery operations. This included a focus on worker positioning, as well as on the pillar and lift sequences, MRS operations, and hazard identification. As retreat mines have incorporated these elements into their roof control plans, it has become clear that pillar recovery is not “inherently unsafe.” The paper concludes with a discussion of the challenges that remain, including the problems of rib falls and coal bursts.

Exergy analysis: A CO2 removal plant using a-MDEA as the solvent

An exergy analysis was conducted for CO2 removal process from syngas using methyldiethanolamine activated by piperazine (a-MDEA). The process was simulated with Aspen HYSYS and the validation of the results was performed using the field data of Fanavaran Petrochemical Company. The process was divided into five separate sections. In order to determine the exergy loss, exergy balance equation was established around each section. The results showed that the highest exergy loss amongst five sections returns to the flasher (contributes 31.5% of total exergy loss); followed by the absorber column, stripper column, heat recovery section and the pump. In order to decrease the exergy loss in the process, piperazine concentration in a-MDEA solvent was increased which led to reduction in amine solvent flow rate. According to the results, the total exergy loss is decreased from 3.25 MW to 2.63 MW. When the amine flow rate decreased by 27%, the exergy loss, total energy consumption and the total utilities cost decreased by 19%, 18% and 25%, respectively.

A technical and economic assessment of fuel oil hydrotreating technology for steam power plant SO2 and NOx emissions control

This work presents a simulation approach to the design and economic evaluation of fuel oil hydrotreating processes for the control of SO2 and NOx emission in an Iranian steam power plant. The percent of fuel oil desulphurization was estimated from the SO2 emissions standards for power plants. Based on two different scenarios according to (I) European and (II) Iranian standards, the design and simulation of hydrodesulphurization reactors, separation, heat recovery, and amine gas sweetening sections were performed and an economic assessment of the plant was investigated for each scenario. The results indicated the following: the cost price of each barrel of low sulfur fuel oil produced in such plants was estimated at 4.24 US$ for scenario (I) and 3.17 US$ for scenario (II); the levelized cost of desulfurization in power production was estimated at 0.618 c/kWh for (I) and 0.463 c/kWh for (II); and the social cost savings of replacing every barrel of low sulfur fuel oil instead of one barrel of high sulfur fuel oil were estimated at 26.7 US$ for (I) and 13.6 US$ (II).

Exergy analysis of a MSF desalination plant in Yanbu, Saudi Arabia

This study focuses on determining exergy destruction in a MSF Desalination plant located in Yanbu Saudi Arabia. A non-iterative code in MATLAB is developed to perform mass, energy, and exergy balances around the plant at normal load of distillate production (~159kg/s) at 22.9°C in the winter and at peak load (~200kg/s) at 35.2°C in the summer. Exergy flowrates are calculated and exergy destruction around each of the equipment is estimated. An exergy diagram is prepared to indicate equipment with highest exergy destruction. As expected the major exergy destruction occurs at the Heat Recovery Section (74.9%). The simulation results indicate that as the number of stages increase from 25 to 31 the percent exergy destruction drops from 74.9% to 69.2%. The second law efficiency of the plant is 3.22% and 2.84% at normal and peak load respectively. This efficiency is quite low and several measures can be done to improve it by decreasing inlet exergy to the plant and controlling exergy losses during process operation. Two variations in MSF designs i.e., Once Through (MSF-OT) and Brine Mixing (MSF-M) are considered. It is found that the design of MSF-M is a viable option to minimize exergy losses.

Process Assessment of Heterogeneous Azeotropic Dividing-Wall Column for Ethanol Dehydration with Cyclohexane as an Entrainer: Design and Control

The heterogeneous azeotropic dividing-wall column (ADWC) features significant reduction of capital investment and energy consumption. Conventional azeotropic distillation sequences can be thermally coupled into two types of configurations of ADWCs, namely, the original ADWC with simple azeotropic–recovery section and the other with recovery section also serving as preconcentrator. The ADWC with a combined recovery–preconcentrator section has been investigated in both steady-state design and dynamic controllability. However, the original ADWC has only been proven to be more energy efficient than the conventional azeotropic–recovery column sequence, not compared with the conventional azeotropic–stripper column sequence. Furthermore, the dynamic performance of this ADWC are still unclear. Note that all the benefits of the ADWC are reasonable only under good dynamic controllability. Thus, in this work, we develop a comparative study of optimal design and dynamic performance of the ADWC with two conventional s...

Metronidazole-Induced Encephalopathy in Alcoholic Liver Disease: A Diagnostic and Therapeutic Challenge

BackgroundAcute encephalopathy in a patient with alcoholic liver disease (ALD) is a commonly encountered emergency situation occurring most frequently due to liver failure precipitated by varying etiologies. Acute reversible cerebellar ataxia with confusion secondary to prolonged metronidazole use has been reported rarely as a cause of encephalopathy in patients with ALD. Case ReportWe describe a decompensated ALD patient with recurrent pyogenic cholangitis associated with hepatolithiasis who presented to the emergency department with sudden-onset cerebellar ataxia with dysarthria and mental confusion after prolonged use of metronidazole. Magnetic resonance imaging (MRI) of the brain was suggestive of bilateral dentate nuclei hyper intensities on T2 and fluid-attenuated inversion recovery sections seen classically in metronidazole-induced encephalopathy (MIE). Decompensated liver cirrhosis resulted in decreased hepatic clearance and increased cerebrospinal fluid concentration of metronidazole leading to toxicity at a relatively low total cumulative dose of 22 g. Both the clinical symptoms and MRI brain changes were reversed at 7 days and 6 weeks, respectively, after discontinuation of metronidazole. Why Should an Emergency Physician Be Aware of This?A patient with ALD presenting with encephalopathy creates a diagnostic dilemma for the emergency physician regarding whether to continue metronidazole and treat for hepatic encephalopathy or to suspect for MIE and withhold the drug. Failure to timely discontinue metronidazole may worsen the associated hepatic encephalopathy in these patients. Liver cirrhosis patients have higher mean concentration of metronidazole and its metabolite in the blood, making it necessary to keep the cumulative dose of metronidazole to < 20 g in them.