Feed Preheating Research Articles

Sustainable process design and multi-objective optimization of efficient and energy-saving separation of xylene isomers via extractive distillation based on double extractants

The focus of the chemical industry on environmental protection and energy conservation has driven the development of green distillation technology. Xylene isomers are extensively utilized industrial raw materials, whose separation is challenging and energy-intensive due to their closely similar boiling points. Therefore, it is urgent to develop energy-saving and environmental protection technology. In this paper, an energy-saving and environmental protection process for separating the xylene isomers by extractive distillation was designed combing the vapor recompression process with feed preheating (VRAPFP). The parameters of extractive distillation processes were synthetically optimized by multi-objective genetic algorithm (MOGA) with total annual cost (TAC), CO2 emission (ECO2) and separation efficiency (Eext) as the objective evaluation indexes. The economical optimal process was used further for VRAPFP design through heat integration to reduce energy consumption, and all the designed candidate processes were synthetically analyzed, compared and evaluated with performance indexes. Results show that the VRAPFP process has superior economic efficiency and ecological sustainability compared with the existing distillation process, wherein the TAC and ECO2 are reduced by 14.2 % and 30.2 %, respectively. This work provides a new reference and idea for separating xylene isomers with the economy and developing new processes for energy conservation and environmental protection.

Effect of Wire Preheat and Feed Rate in X80 Steel Laser Root Welds: Part 1 — Microstructure

Laser welding with cold versus hot wire feed was employed as a root pass to weld X80 pipeline steel. The influences of wire feed rate and preheat on the fusion zone microstructure were investigated. Increasing the wire feed rate helped generate acicular ferrite in the weld metal, and preheating the wire further suppressed the formation of bainite. The acicular ferrite in the upper region of the fusion zone was finer than that in the lower region, which was due to an increase in nucleation sites available. Five fill and cap passes were applied by gas metal arc welding to fill the remaining top part of the groove. Compared to arc welding with a higher heat input, laser welding led to finer prior austenite grains and smaller bainite packet size in the coarse-grained heat-affected zone and limited the formation of martensite-austenite constituents in the intercritically reheated coarse-grained heat-affected zone.

Effect of Wire Preheat and Feed Rate in X80 Steel Laser Root Welds: Part 2 — Mechanical Properties

In Part 1 of this study, the influences of feed rate and preheat of the wire on the fusion zone microstructure of X80 steel laser root welds were investigated. Part 2 of this study reveals the effect of cold versus hot wire feed on mechanical properties. Although strength overmatching with the X80 base metal was maintained, the wire alloying elements reduced the hardness of the upper region of the laser fusion zone but had limited effect on the bottom of the fusion zone due to the incomplete mixing of the filler material with the base metal in the bottom root region of the joint. The addition of ER70S-6 filler wire improved the impact toughness of the weld metal at 0°C, due to the formation of an acicular ferrite microstructure. As the temperature decreased to –20°C (–4°F) and –45°C (–49°F), ductile to brittle transition occurred, leading to lower weld metal toughness.

Performance Evaluation of Single Stage Flash Evaporation Desalination Unit Integrated with a Parabolic Trough Solar Collector for Basrah City Climate, Iraq

Solar energy is the most suitable among all renewable energy options for competing with fossil fuels in desalination due to its ability to utilize both heat and power for the process. In this study, the Parabolic Trough Solar Collector (PTSC) for powering a Single Stage Flash (SSF) desalination unit was proposed for Basrah city climate, Iraq. The desalination system comprises two directly coupled sub-systems: the PTSC and the SSF desalination unit. The preheated feed brine water coming from condenser was used as a Heat Transfer Fluid (HTF) for PTSC, which gets heated to a desired temperature referred to as the Top Brine Temperature (TBT). The numerical simulations were performed via EBSILON professional 16.02 (2022) software. The effects of TBT, mass flowrate of feed brine water to get the desired TBT, solar collector area, and vacuum pressure inside flash chamber on the performance of the desalination system was studied. A major finding of the current study can be summarized as follows: The collector efficiency is enhanced eventually as TBT increases. The maximum values of distillate water in June are around 5.5, 4.56, 3.69, 2.75 and 1.85 kg/h for 12.408, 10.434, 8.3472, 6.26, and 4.1736 m² collector area respectively, when TBT 107 °C and vacuum pressure 40 kPa. For 1.598 m² collector area, the total distillate in the 1st of June amounted to 7.9 kg, with an average production rate of around 0.7 kg/h. The solar SSF system's productivity per solar collector unit area at 20 kPa, 15 kPa, and 10 kPa vacuum pressures was 4.7 kg/day/m², 5.3 kg/day/m², and 6.25 kg/day/m², respectively. The average Performance Ratio (PR) values are determined to be 0.694, 0.577, and 0.491 for 10 kPa, 15 kPa, and 20 kPa, respectively. These results are very acceptable when compared with an existing literature.

Dynamic modelling of cross-flow printed circuit heat exchangers for multistage reactor intercooling

A reduced-order dynamic model of a cross-flow printed circuit heat exchanger was developed to study both steady-state and transient performance under conditions that would be encountered in multistage catalytic combustion reactors to better understand how they can be used to minimize fluctuations in heat-integrated reactors and intensified processes. Previous transient models for cross-flow heat exchangers rely on an initial steady state and apply only for changes in inlet temperature, but this work presents a model that can be applied to intermediate states or multiple concurrent upstream process changes. Steady-state simulations showed that larger channels reduce volumetric heat transfer performance and effectiveness due to convective resistance. Furthermore, larger channel spacing increases effectiveness but also reduces compactness. Operating temperature was found to have a minimal effect on the overall heat transfer coefficient and effectiveness within the range of conditions studied, and operating pressure was found to have no effect on heat transfer. Transient analyses showed that the response to a unit step in temperature matches closely with an analytical infinite gas velocity model, both for time constants and the overall thermal response, with initial variations in outlet temperatures from ideal-case models below 3.8 % of unit step magnitudes, and average differences below 0.75 %. Transient analyses also show the effects of a finite fluid velocity which is critical in the transient response of large heat exchangers. The presented numerical model can also be more easily extended to complex configurations and can be applied to other changes in inlet conditions such as changing composition and flow rates as are found in combustion applications. A three-fluid thermal management system for a multistage packed-bed microreactor using printed circuit heat exchangers is proposed and modelled to provide a method for temperature regulation and pre-heating of fresh reactor feed.

Energy optimization and neural-based dynamic analysis of integrated multiple stage evaporator

Abstract Minimizing energy consumption is often a grave challenge in many industrial energy-intensive process units such as Multiple Stage Evaporator (MSE). Integration of Energy Reduction Schemes (ERSs) is a common technique to resume a countable amount of energy. Hence, the present work proposes a hybrid (h-) ERSs integrated MSE placed in the paper industry, used to increase the solid content of the black liquor. The h-ERSs Integrated MSE comprises several ERSs such as Thermo-Vapor Compressor, Steam-, Feed-split, and Feed Preheater to improve the energy efficiency significantly, and its energy performance is compared with base (b-) MSE. For this purpose, nonlinear mathematical models have been developed and transformed into a constrained optimization problem to search for the optimum energy efficiency obtained as Steam Economy (SE). A state-of-art metaheuristic approach, Equilibrium Optimizer (EO), along with some well-acquainted solution approaches (Interior Point OPTimizer, Interior Point Method, and Particle Swarm Optimization) has been simulated in different platforms to estimate the maximum SE to check their competitiveness for this industrial optimization problem. It is observed that EO outperformed all the algorithms with a 66 % higher SE for h-MSE than b-MSE. Eventually, the steady state parameters are applied as the initial conditions to analyze the nonlinear enthalpy dynamics of the b-and h-MSE. A neural base solution has been adopted to rigorously study the open-loop process dynamics that meet the desired product quality.

Integration of a cryogenic ASU within an IGCC process with simultaneous optimization and energy targeting

The effect of oxygen purity on the thermal efficiency of an enriched-oxygen-fed integrated gasification carbon cycle (IGCC) was studied. A simultaneous process optimization with heat integration framework is proposed and used for the study. Rigorous models were used to represent the cryogenic air separation unit (ASU), gasifier and combined cycle. It was found that the thermal efficiency was highest (41.3–42.3%) within a range of 35–85 mol% O2, with the optimum at 45.5 mol% O2. Furthermore, injection of the nitrogen-rich vapor distillate from the high-pressure column of the ASU to the gas turbine was found to be the optimal nitrogen integration scheme compared to no nitrogen integration or using vapor distillate from the low-pressure column. In the optimized solution, heat integration results showed that pre-heating of the gasifier's oxygen feed occurs at the pinch and steam turbine inlet pressure values were 165, 28.6 and 4.9 bar.

Combining game theory and evolutionary algorithms for optimizing hybrid RDWC–pervaporation–vapor permeation process equipped with solar heating system

A new hybrid RDWC–pervaporation (PV)–vapor permeation (VP) process equipped with a solar heating system was designed and optimized to produce ETBE. Steam is required for feed preheating and RDWC reboiler, and PV heaters. A parabolic trough collector (PTC), one of the most conventionally used commercial solar collectors, was used to produce steam. Tehran, the Capital of Iran, was selected for solar energy analysis, but the results can be generalized to other places with different weather conditions. PV and VP processes can be placed besides RDWC in five zones. The game theory selected the PV and VP processes as two competitors in the hybrid process with RDWC. The combination of PV and PV processes in the hybrid process with RDWC was studied with the help of the hybrid GA–PSO optimizer algorithm. According to the optimization results, the proposed process reduced TAC and CO2 emissions by 72% and 94% compared to the conventional ETBE process. The main reason for the high efficiency of the proposed method is the use of solar energy and eliminating over 70% of the need for hot utility. The PV–VP combination reduced the number of RDWC trays and PV modules, decreasing the total annual cost (TAC).

Comparative optimal design and effective control of different pressure extractive distillation for separating acetone - Methanol

Acetone and methanol are critical industrial feedstocks as well as organic solvents. Previous studies on the separation of the minimum-boiling azeotrope acetone-methanol by pressure-swing extractive distillation have shown superiority in terms of energy and cost savings. However, the pressure-varying configuration inevitably requires high-grade heat steam. To surpass the limitation, a novel different pressure extractive distillation strategy is proposed in this paper. The conceptual design of the different pressure extractive distillation configuration is carried out from thermodynamic insights, and the feasible ranges of entrainer/feed flow rate ratio and reflux ratio are determined. The design parameters are optimized by an improved non-dominated sorting genetic algorithm. Compared with the conventional extractive distillation process, the total annual cost (TAC) and CO2 emissions of the proposed process are reduced by 22.17% and 48.14%, respectively. An alternative different pressure extractive distillation process with feed preheating is then obtained by changing feed thermal condition, which has a 24.08% reduction in TAC and a 48.33% reduction in CO2 emissions in comparison with the conventional extractive distillation process. Compared with the existing heat-integrated pressure-swing extractive distillation process, the new process has a 2.90% and 22.36% reduction in TAC and CO2 emissions, respectively. Subsequently, two control schemes are presented by calculating controllability indicators in the steady-state design stage. The results illustrate that the improved control scheme with multiple feedforward control loops performs the best robustness.

Laser-induced graphene Janus membrane for electrothermal membrane distillation

To improve the energy efficiency of membrane distillation (MD), localized heating of the feed-membrane interface is advantageous relative to heating of the bulk feed. This motivated the current study, which targeted at developing a simple two-step way of fabricating Laser-Induced Graphene (LIG) Janus membrane for electrothermal membrane distillation. Specifically, the Janus membrane had an electrically conductive graphene side and a polydimethylsiloxane (PDMS) coated polyethersulfone (PES) side. The PES membrane was first coated with PDMS in limonene (a green solvent) and the active layer exposed to low-powered laser. Joule heating was carried out on the LIG surface by connecting two electrodes to the opposite ends of the LIG surface and providing power with an alternating current power supply at regular household frequency. This Janus membrane can be heated on the LIG surface while insulated from heat loss on the PDMS-coated PES surface, resulting in a marked improvement in the MD performance. Relative to pre-heated feed at the same power input, Joule heating of the Janus membranes gave a flux increase of up to 119.5%, specific heating energy decrease of up to 53.9% and single-pass heat utilization efficiency increase of up to 119.5%, while maintaining excellent material stability.

Transient Modeling and Simulation of a Multiple‐Stage Evaporator in the Paper Industry

AbstractThe present work investigates the energy performance analysis of a heptad‐based multiple‐stage evaporator (MSE) under steady and transient conditions, integrated with different energy reduction schemes (such as steam split, feed split, and feed preheater). The steady‐state analysis was performed to optimize the steam economy subjected to the developed steady‐state energy models as the equality constraints. The simulated optimization is a maximization problem and is solved by Interior‐Point Optimizer and Gray Wolf Optimizer on two different platforms, GAMS and MATLAB, respectively. Further, transient and stability analyses were performed by developing and representing the nonlinear dynamic energy models to the state‐space representation using linearization.

Design and multi-objective optimization of reactive-extractive dividing wall column with organic Rankine cycles considering safety

It is challenging and inevitable for the separation of ternary azeotropic mixture with multiple azeotropes in wastewater. Previous research proposed a hybrid double column reactive-extractive distillation (DCRED) process to separate ternary azeotropes in wastewater, which inspires the investigation into the reactive-extractive dividing wall column (REDWC) in this study. However, the design and waste heat recovery of REDWC have not been fully studied. To this end, two hybrid distillation processes, the REDWC process and the REDWC with feed preheating (REDWC-FP) process, are developed to separate ethyl acetate/ethanol/water ternary azeotropic mixture. The design parameters of the two hybrid distillation processes are optimized based upon the maximum total annual cost (TAC), CO2 emissions and minimum process route index (PRI) through the multi-objective genetic algorithm (MOGA) considering safety. In view of massive waste heat in the REDWC process, several new configurations combining the REDWC and Organic Rankine cycles (ORCs) are further proposed. The optimal ORC system is determined via MOGA with the annual net profit, ORC thermodynamic efficiency and PRI as objective functions. Compared with the existing DCRED process, the TAC and CO2 emissions of the REDWC process are reduced by 8.15% and 4.49%, respectively. The TACs of the ORC1-REDWC process with working fluid cyclohexane and the ORC2-REDWC process with working fluid benzene are reduced by 27.50% and 26.32%, respectively.

Inherent safer, eco-friendly and energy saving vapor recompression assisted extractive dividing-wall column process for the separation of minimum-boiling azeotrope

The vapor recompression (VRC) also called heat pump is widely used in the distillation to achieve energy saving. However, considering economic performance, high compression ratio impedes the application of VRC in the wide-boiling mixtures system such as extractive dividing-wall column (EDWC). In addition, the flammability of hydrocarbons as working fluids in VRC causes serious potential hazard especially for wide-boiling mixtures system. Hence, in this article, a systematic method is proposed to investigate vapor recompression assisted extractive dividing-wall column (EDWC-VRC) with multi-criteria assessment for the separation of dimethyl carbonate-methanol with heavy entrainer aniline as a case. Process preliminary analysis shows feed heater/vaporizer (feed preheating strategy) and intermediate reboiler can improve economic and inherent safety performance of VRC simultaneously. Especially for feed heater/vaporizer, the definition of minimum boiling azeotrope demonstrates that the application of vapor recompression between feed heater/vaporizer and condenser in EDWC is inherently attractive. Then, two novel configurations called EDWC-VRC integrating all feed preheating and heat integration (EDWC-VRC-AFPH-HI) and EDWC-VRC integrating two-feed preheating and intermediate reboiler (EDWC-VRC-TFPH-IR) are proposed and optimized to get optimal flowsheet. The economic and environmental results show that EDWC-VRC-AFPH-HI and EDWC-VRC-TFPH-IR are superior to original EDWC process in the open literature and EDWC-VRC with high compression ratio. Especially for EDWC-VRC-AFPH-HI with best performance, there are 12.42% TAC (five-year payback period) and 18.71% CO2 emission reduction and 20.78% energy saving than original EDWC process, respectively. Quantitative consequence assessment shows that EDWC-VRC-AFPH-HI and EDWC-VRC-TFPH-IR is inherent safer than EDWC-VRC with high compression ratio. We believe that integration of feed preheating strategy/intermediate reboiler with VRC can promote the application of VRC in the wide-boiling mixtures system.

Integration of solar field with multiple stage evaporator to sustain eco-energy in pulp and paper plant

Deploying renewable energy to unit design energy-efficient technologies may fulfill the additional demand of various energy-intensive industries for their sustainability and resiliency. Multiple Stage Evaporator (MSE) is one of the most energy-intensive units used to extract the water content of the weak liquor in various industries, including the paper industry. This energy intensiveness may be reduced by integrating various Energy Reduction Schemes (ERSs). Hence, this work proposes a ERSs integrated MSE model to analyze its energy efficiency. These ERSs includes Thermo-Vapor Compressor, Steam-, Feed- Split, Feed Preheater, and Flash Tanks. Further, the performance of the proposed model is investigated under two important real-time plant complexities: Boiling Point Elevation and Fouling to achieve more realistic results. The performance analysis is initiated with the formulation of a nonlinear constrained optimization problem to increase the steam economy (SE). Also, the simulation is extended to validate at two different product concentrations (52% and 65%) by employing state-of-art optimization algorithms: CONOPT, and SCA in GAMS and MATLAB respectively. The simulated results shows an increment 1.64% and 1.37% of SE for both 52% and 65% concentration of weak liquor respectively in case of CONOPT than SCA. Also, the waste heat of the condensate, feed, and product may be further utilized for the heat recovery by incorporating the flash tanks which leads to a countable energy saving. Eventually, integrating the solar fields: PTC and LFR ensures a notable reduction in conventional heat utilization by 85.96% and 92.85%, respectively and hence, enhance the energy efficiency.

Investigation and optimization for multi-effect evaporation with thermal vapor compression (MEE-TVC) desalination system with various feed preheater arrangements

Multi-effect evaporation with thermal vapor compression (MEE-TVC) is still very effective for dealing with the poor quality of seawater or utilizing the waste heat. The arrangement of feed preheaters plays an important role in the optimization design of MEE-TVC. In this work, the mathematical model for MEE-TVC with various feed preheater arrangements is established. The effects of temperature rise and interactions between the positions of TVC and preheater on the performances are investigated, and optimization is further conducted as well. Results indicate that there is an imperceptible interaction of the positions of preheater and TVC. When the allocation of temperature rise for multiple preheaters increases with the increasing serial number of preheater, the maximum improvement for the energy consumption regarding gained output ratio (GOR) and specific cooling seawater (SCS) can be made. The optimal number of preheaters increases with the number of effects n, and varies with the levels of unit price of steam and material. The optimal allocation of temperature rise is increasing with the serial number of preheater for n ≤ 5, while it becomes more complex and shows irregular fluctuation with n more than 5. This work illuminates the logic of feed preheater arrangements in MEE-TVC system.

Energy integration of solar assisted Multiple Stage Evaporator and optimum parameter selection

To reduce the conventional energy utilization in the pulp and paper mill, exploitation of renewable energy may provide a significant energy saving mostly in energy intensive subunits such as Multiple Stage Evaporator (MSE). MSE is used to concentrate the weak black liquor, a reach source of bio energy. Hence, this work explores the performance analysis of MSE with various proposed Energy Reduction Schemes (ERSs): Thermo-Vapor Compressor, Steam Split, Feed Split, Feed Preheater, and Flash Tanks. This analysis has been intended to develop the steady-state nonlinear energy models for proposed ERSs integrated MSE that translated it into a single objective unconstraint nonlinear optimization problem. Further, different optimization approaches (nonlinear programing and metaheuristics) have been employed to search the optimum process parameters and hence, maximize the energy efficiency. Moreover, to utilize the waste heat of condensate, feed, and product, flash tanks have been integrated with MSE which further improves the energy efficiency by 3.9% and 83% than that of base case model. Finally, the LFR solar field has been integrated to reduce the load of conventional energy utilization and ensures the self-sustainability of the paper mill by supplying the required amount of heat (3,399 kW) for the proposed hybrid MSE configuration.

Experimental Validation of a Solar Powered Multistage Flash Desalination Unit with Alternate Storage Tanks

The fossil fuels that power conventional desalination systems cause substantial environmental impact. Solar desalination can satisfy critical water needs with only a minimal contribution to global warming. The current work presents an attractive new design suitable for regions with limited water resources and high solar radiation rates. This work is an experimental study of a newly designed, solar-powered, multi-stage flash (MSF) desalination plant. The design could address the need to increase the limited water resources in solar energy-rich areas. The prototype consists of a solar collector, an MSF unit, and a novel dual thermal storage tank design. In this prototype, preheated brine is directly heated by circulation through the solar collector. Two tanks serve the MSF unit; one tank feeds the MSF unit while the other receives the preheated feed water. The two tanks alternate roles every 24 h. The study was conducted in Taif, Saudi Arabia, throughout the month of September 2020. The results of the experiment showed that 1.92 square meters of solar collector area is needed for an average daily production of 19.7 kg of fresh water, at a cost of approximately $0.015 per liter.

Adaptive MPC Controller based Cascade Control of Distillation Column Parameters Estimation and Optimization

One of the key element of many industrial process plants is a crude oil distillation system. This system requires heat for the vaporization of a mixture of feed to the distillation column in vapor form. In the existing process of distillation, an abnormal change of heat is exhibited due to improper control and monitoring of disturbances affecting the plant. This would result for undesired loss of product and product purity to be reduced. The parameters that are expected to be considered in the analysis, model and control of a distillation system described under the proposed study are inlet feed temperature, distillation column temperature, feed composition, internal liquid and vapor composition, feed flow rate, reboiler temperature and an external reflux temperature to the distillation tower. Controlling distillation column parameters with Adaptive model predictive control allows for the determination of the predicted future instant values of the plant outputs. Using such control technique, the controlled plant outputs such as the temperature of distillation column, feed preheater, re boiler and the upper reflux is properly controlled and their parameters are estimated using recursive least squares approach in the entire process adaptation mechanism. From the analysis and optimization work made on the proposed system, the efficiency of the plant outputs in tracking their corresponding set point has improved based on the value of the transient system parameters as well as the value of relative volatility of feed mixture to the column. As per the finding in the analysis of the process, 95.4% and 93.5% improvement on the set point tracking and to amount of evaporation liquid feed has been obtained respectively. On the other hand an improvement on transient parameters has been achieved to all plant outputs. As per the result obtained from the analysis, the peak overshoot, settling time and peak time of the system response has found to be less than 40% including the effect of measured disturbance to the plant. Hence, entire process variable optimization has been performed using the parameters of the model predictive controller to provide the proper degree of stability. Finally the proposed method of study has compared with with other control strategies through which the performance the proposed design has been ensured.

Pretreatment of Manganese Ore for Improved Energy Efficiency and Smelting Furnace Stability

Preheating of feed for smelting in submerged arc furnace (SAF), has shown to have numerous advantages in the ferroalloy industry. In ferrochrome smelting industry for example, preheating the feed before smelting in SAF has shown excellent results in stabilizing SAF smelting operation by removing moisture and volatiles. More importantly, preheating has shown to reduce smelting energy consumption and to increase the smelting furnace capacity. Furthermore, reducing SAF energy consumption has significant benefits in reducing CO2 emissions. However, preheating technology is currently not widely used in ferromanganese production. In ferromanganese production, smelting is mostly done using a mixture of lump and sintered ore as feed to SAF. The behaviour of feed during preheating in separate shaft kiln is still poorly known in smelting. This research is aimed at understanding optimal operating conditions/steps that could be suitable for using preheating technology when lump ore is used in the feed mix. This is also one of the goals of the EU- funded PreMa project.

Thermochemical Conversion of Biomass and Municipal Waste into Useful Energy Using Advanced HiTAG/HiTSG Technology

An advanced thermal conversion system involving high-temperature gasification of biomass and municipal waste into biofuel, syngas or hydrogen-rich gas is presented in this paper. The decomposition of solid biomass and wastes by gasification is carried out experimentally with a modern and innovative regenerator and updraft continuous gasifier, among others. A ceramic high-cycle regenerator provides extra energy for the thermal conversion of biomass or any other solids waste. Highly preheated air and steam gas (heated up to 1600 °C) was used as an oxidizing or gasification agent (feed gas). Preheated feed gas also enhances the thermal decomposition of the gasification solids for fuel gas. However, the main objective of this work is to promote new and advanced technology for the thermochemical conversion of biomass for alternative energy production. Selected results from experimental and numerical studies are also presented.