Multiple Effect Evaporator Research Articles

Investigation of Performance Improvement of the Evaporation Process in Raw Sugar Manufacturing by Increasing Heat Transfer Surfaces

A multiple-effect evaporator is used to evaporate water from sugar juice in a series of pressure vessels. Steam is used for evaporation in the first vessel, and vapor from all vessels, except the last one is used for evaporation in subsequent vessels. In order for evaporator surfaces to be used efficiently, juice entering the evaporator should be at the saturation temperature. Therefore, incoming juice with a low temperature must be heated in a juice heater. The heating medium in the juice heater is vapor bled from the evaporator. It is apparent that the multiple-effect evaporator and the juice heater interact through mass and energy balances. Previous investigations have focused on only the multiple-effect evaporator, and paid little attention to the juice heater. This paper presents the model of the interaction between the multiple-effect evaporator and the juice heater. The model is used to investigate how variations of surfaces in the evaporator and the juice heater affect the two performance parameters of the system, which are the amount of sugar juice processed by the system and the ratio of the amount of water evaporated from sugar juice in the evaporator to the amount of high-pressure steam required by the evaporator.

Potential energy improvements in a multiple-effect evaporation system: case studies of heat recovery

The primary objective of this study was to quantify the amount of excess energy that is present in the evaporation system of an integrated pulp and paper-board mill and to analyze a number of energ ...

Energy analysis of a solar driven cogeneration system using supercritical CO2 power cycle and MEE-TVC desalination system

Performance analysis is conducted for a solar driven supercritical CO2 Brayton cycle combined with a multiple effect evaporation with thermal vapor compression (MEE-TVC) for power and desalinated water production. The study proposes two new different supercritical Brayton cycles, namely, the regeneration and recompression sCO2 cycles. A new efficiency equation for the combined power and water production is derived. The findings show that a 6.25% of efficiency increase results from utilizing the recompression cycle compared to the regeneration cycle. The effect of the fraction (f) of the heat entering the sCO2 cycle, turbine inlet temperature (TIT), and turbine inlet pressure (TIP) on the power to water ratio (PWR) and effective efficiency are also investigated. It is found that the PWR increases exponentially with respect to the increase in fraction reaching 2.8 and 3 kW/m3day for the regeneration and recompression cycle, respectively at a fraction of 0.8. To assess the variation of solar radiation at different locations, the study is performed for different regions of Saudi Arabia; and it is found that the highest productivity is that for the region of Yanbu, followed by Khabt Al-Ghusn, and the rest in a descending order are Jabal Al-Rughamah, Jizan, Al-Khafji, and Dhahran.

Shale gas flowback water desalination: Single vs multiple-effect evaporation with vapor recompression cycle and thermal integration

This paper introduces a new optimization model for the single and multiple-effect evaporation (SEE/MEE) systems design, including vapor recompression cycle and thermal integration. The SEE/MEE model is specially developed for shale gas flowback water desalination. A superstructure is proposed to solve the problem, comprising several evaporation effects coupled with intermediate flashing tanks that are used to enhance thermal integration by recovering condensate vapor. Multistage equipment with intercooling is used to compress the vapor formed by flashing and evaporation. The compression cycle is driven by electricity to operate on the vapor originating from the SEE/MEE system, providing all the energy needed in the process. The mathematical model is formulated as a nonlinear programming (NLP) problem optimized under GAMS software by minimizing the total annualized cost. The SEE/MEE system application for zero liquid discharge (ZLD) is investigated by allowing brine salinity discharge near to salt saturation conditions. Additionally, sensitivity analysis is carried out to evaluate the optimal process configuration and performance under distinct feed water salinity conditions. The results highlight the potential of the proposed model to cost-effectively optimize SEE/MEE systems by producing fresh water and reducing brine discharges and associated environmental impacts.

Assessment of desalination technologies for treatment of a highly saline brine from a potential CO2 storage site

Brine extraction is a promising strategy for the management of increased reservoir pressure, resulting from carbon dioxide (CO2) injection in deep saline reservoirs. The extracted brines usually have high concentrations of total dissolved solids (TDS) and various contaminants, and require proper disposal or treatment. In this article, first by conducting a critical review, we evaluate the applicability, limits, and advantages or challenges of various commercially available and emerging desalination technologies that can potentially be employed to treat the highly saline brine (with TDS values >70.000ppm) and those that are applicable to a ~200,000ppm TDS brine extracted from the Mt. Simon Sandstone, a potential CO2 storage site in Illinois, USA. Based on the side-by-side comparison of technologies, evaporators are selected as the most suitable existing technology for treating Mt. Simon brine. Process simulations are then conducted for a conceptual design for desalination of 454m3/h (2000gpm) pretreated brine for near-zero liquid discharge by multi-effect evaporators. The thermal energy demand is estimated at 246kWh per m3 of recovered water, of which 212kWh/m3 is required for multiple-effect evaporation and the remainder for salt drying. The process also requires additional electrical power of ~2kWh/m3.

증기 이젝터 위치에 따른 다중효용증발시스템의 설계 및 성능분석

The evaporation of water from an aqueous solution is widely used in the food, desalination, pulp, and chemical industries. Usually, a large amount of energy is consumed in the evaporation process to boil off water due to atmospheric pressure. As a way of improving the energy efficiency of the evaporation process, the combination of multiple effect evaporation and thermal vapor recompression has been proposed and has become a successful technique. In this study, 4 multiple-effect falling film type evaporators for sugar solution are designed and the energy efficiency of the system is analyzed in response to the selection of the steam ejector position. Energy efficiency is increased and vapor is more compressed in the steam ejector as the Thermal Vapor Recompression (TVR) is arranged in the rear part of the evaporator system. A simplified 0-dimensional evaporator model is developed using non-linear equations derived from mass balances, energy balances, and heat transfer equations. Steam economy is calculated to compare the evaporation performance of the 4 proposed evaporators. The entrainment ratio, compression ratio, and expansion ratio are computed to check the ejector performance.

Solar assisted multiple-effect evaporator

Multiple-effect evaporator (MEE) is used for concentrating the liquor. A substantial energy saving can be achieved by integrating MEE with a thermo-vapor compressor (TVC). TVC is a device in which the low-pressure vapor produced from MEE is compressed with the help of the high-pressure motive steam supplied externally, to produce a medium pressure vapor. This medium pressure vapor acts as a heat source for MEE. The high-pressure motive steam can be produced from concentrating solar thermal system, which is a renewable and non-polluting source of energy. The present study deals with the integration of linear Fresnel reflector (LFR) with MEE-TVC system. The objective of the present work is to minimize the total annual cost for the integrated MEE-TVC and LFR system. The important parameters affecting the annual cost for the integrated system are solar design radiation and temperature of the motive steam. A methodology is developed to determine the optimal solar radiation and steam temperature. The proposed methodology is demonstrated through a case study for manufacturing of corn glucose. The annual cost for the system is 87,106 $/y, with optimal steam temperature 250 °C and optimal design radiation 600 W/m2. Sensitivity analysis is also carried out for the selection of the optimal operating parameters. The cost of the auxiliary heating source plays a dominating factor on the economic feasibility of the integrated system.

Integration of thermo-vapor compressor with multiple-effect evaporator

Thermo-vapor compressor (TVC) is used for compressing the low-pressure vapor with the help of the high-pressure motive steam, to produce the medium pressure vapor. A substantial portion of energy may be conserved by integrating TVC with the multiple-effect evaporator (MEE). The common practice in desalination industry is to compress the vapor produced in the last effect of a MEE using TVC to reduce the overall motive steam requirement. Such integration does not necessarily guarantee energy optimality. The objective of the present work is to optimally integrate TVC with a MEE system to maximize the gain output ratio (GOR). GOR is defined as the ratio of the mass flow rate of vapor produced in MEE to the mass flow rate of the motive steam supplied to TVC. GOR is the measure of the energy efficiency of MEE system. Using the principles of Pinch Analysis and techniques of mathematical optimization, a new methodology for integration of TVC with MEE is proposed in this paper. This is the first analytical methodology to optimally integrate TVC with MEE, avoiding multiple simulations of the overall system. A Theorem is proposed to directly calculate the optimal location of TVC suction position. The proposed methodology gives the designer the freedom to design an MEE-TVC with minimum energy consumption and without carrying out the detailed simulation of the entire system. The methodology is demonstrated through the illustrative case studies for concentrating corn glucose, and freshwater production through thermal desalination. In the case of corn glucose, the optimal integration of TVC with 2-effect MEE resulted in the increase in GOR by 10.1% with a decrease in the specific area requirement by 4.1%. For a desalination system with 11-effect MEE, the optimal integration of TVC improves the GOR by 1.5% and reduces the specific area by 4.3%. Furthermore, sensitivity analysis is carried out to determine the optimal operating parameters for both case studies.

Desalination of shale gas produced water: A rigorous design approach for zero-liquid discharge evaporation systems

Shale gas has recently emerged as a promising energy source to face the increasing global demand. This paper introduces a new rigorous optimization model for the simultaneous synthesis of single and multiple-effect evaporation (SEE/MEE) systems, considering mechanical vapor recompression (MVR) and energy recovery. The proposed model has been especially developed for the desalination of high-salinity produced water from shale gas hydraulic fracturing (“fracking”). Its main objective is to enhance the system energy efficiency through the reduction of brine discharges. Therefore, the outflow brine salinity should be near to salt saturation conditions to achieve zero liquid discharge (ZLD). The multiple-effect superstructure is comprised by several effects of horizontal-tube falling film evaporation. Due to the inclusion of the electric-driven mechanical compressor, no other external energy source is needed in the SEE/MEE system. A more accurate process design is attained through the calculation of the overall heat transfer coefficients in function of the individual coefficients for the falling boiling film and vapor condensation. Additionally, the SEE/MEE-MVR model allows the estimation of the major geometrical characteristics of the evaporation system. The non-linear programming (NLP)-based model is optimized using the CONOPT solver under GAMS by the minimization of the process total annualized cost. Thermal analysis is carried out to evaluate the effects of the feed salinity and geometrical parameters on system heat transfer performance. The results highlight the ability of the developed model to rigorously design SEE/MEE-MVR systems by improving their cost-effectively and reaching ZLD conditions.

Solution of SNLAE model of backward feed multiple effect evaporator system using genetic algorithm approach

This paper presents the genetic algorithm approach to solve the highly complex set of fourteen simultaneous nonlinear algebraic benchmark problem for the backward feed seven effect evaporator. Generally, Newton’s method may be considered a better numerical technique to solve such nonlinear problems. However, a higher number of effects (seven in this case) complicates the evaluation of a 14 × 14 Jacobian matrix that involves determining the analytical derivative of all system variables. Also, such a simultaneous nonlinear algebraic equations model exhibits the problem of divergence and instability when initial values have not been chosen appropriately. In this work, genetic algorithm approach has been demonstrated to be very efficient to solve such complex nonlinear models for a large number of effects in evaporative system without any complications. To make the model more realistic and representative of physico-thermal properties of liquor, boiling point elevation of the liquor during evaporation has been incorporated. Finally, the developed models are solved using genetic algorithm to determine the process variables, namely liquor and steam flow rates, which yield process performance parameters of energy efficiency (steam economy and consumption). The results indicate that a maximum steam efficiency may be achieved for a 50 % steam split in the first two effects.

Distribution of juice heater surface for optimum performance of evaporation process in raw sugar manufacturing

The evaporation process in raw sugar manufacturing turns diluted juice into granulated sugar. It consists of three main components: juice heater, multiple-effect evaporator, and crystallizer. Previous studies are concerned mostly with multiple-effect evaporator with the assumption that sugar juice entering the evaporator is at the saturation temperature. In fact, juice temperature must be raised to the saturation temperature in juice heater using vapor bled from the evaporator. This study investigates a model of the evaporation process with the objective of determining the distribution of juice heater surface that results in the optimum performance. The model takes into account mass and energy balances in the three components of the evaporation process. If the total juice heater surface is fixed, it is shown that there is a unique distribution of juice heater surface when vapor is bled from the first and second effects of the multiple-effect evaporator. However, if vapor is bled from the first, second, and third effects, many surface distributions are possible, and one of which is the optimum distribution that maximizes either the amount of granulated sugar produced from the process or the ratio of the amount of water evaporated from the process to the amount of high-pressure steam required for the process. Increasing the total juice heater surface increases both performance parameters. Results for two specific systems using different quadruple-effect evaporators are shown to demonstrate the application of the proposed model.

Evaporator Fouling Tendencies of Thin Stillage and Concentrates From the Dry Grind Process

ABSTRACTIn the United States, more than 200 maize processing plants use multiple-effect evaporators to remove water from thin stillage and steepwater during dry grind and wet milling processes, respectively. During the dry grind process, unfermentables are centrifuged and the liquid fraction, thin stillage, is concentrated in multiple effect evaporators. Evaporator fouling occurs during thin stillage concentration and may be from deposition of proteins, fat, fiber, and/or carbohydrates on evaporator surfaces. Studies on evaporator fouling from maize processing streams are limited and fundamental causes are not well understood. Therefore, the overall objective was to investigate effects of compositional variation on evaporator fouling during thin stillage concentration. Effects of total solids during evaporator concentration, removal of post fermentation oil, corn oil and glycerol addition, and overall plant operation were studied. Thin stillage had lower fouling rates compared to evaporator concentrates. Addition of postfermentation corn oil (0.5 to 1.0% added) increased thin stillage fouling rates, but at higher oil concentration (1.5% added), rates decreased. At 10% solids content in evaporator concentrates, oil recovery had no influence on fouling rates. Glycerol addition (1%) to thin stillage increased fouling rates. Simultaneous plant shutdown and evaporator cleaning decreased subsequent fouling rates.

Comprehensive exergy analysis of a commercial tomato paste plant with a double-effect evaporator

In this study, a detailed exergy evaluation of a commercial tomato paste plant with a double-effect evaporator was conducted in order to provide information on the system thermodynamic inefficiencies. Using energy and exergy balance equations, all components of the plant were analyzed individually and their exergetic parameters were calculated on the basis of actual operational data. The required data were obtained from Nazchin tomato paste factory located in Tehran, Iran. In addition, it was attempted to quantify the exergy utilized for processing a given amount of the tomato paste. The results showed that over 82% of the total destroyed exergy in the plant occurred in the boiler combination as the main component wasting exergy. Furthermore, exergy analysis introduced this combination as the main equipment rejecting exergy to the ambient where 4.79% of its total exergy input was lost. The rational exergy efficiency of the first- and second-effect evaporative units was found to be 65.33% and 56.60%, respectively. The specific exergy consumption of the tomato paste production was also determined as 16.83 MJ/kg. Generally, exergy concept and its extensions could be served as a powerful assessment technique to optimize the design and performance of multiple-effect evaporation systems employed in food industry.

Energy optimization in parallel/cross feed multiple-effect evaporator based desalination system

Desalination of sea water involving multiple-effect evaporator (MEE) is commonly used in industry, especially with the introduction of the low temperature MEE. Parallel/cross feed flow sequence is one of the most commonly used configurations on account of its high gain output ratio (GOR). GOR is defined as the ratio of the distillate produced to the mass of the steam supplied and it measures the energy intensity of a desalination process. Generally, for parallel/cross flow MEE the feed flow rate is same for all the effects. However, the equal feed flow rate may not guarantee an energy optimal solution. A new methodology, based on the principle of process integration combined with mathematical optimization, is developed in this paper to determine the optimal feed flow rate to each effect. MEE is represented as a Grand Composite Curve (GCC) for understanding energy integration and providing better insight of the overall problem. Through an illustrative example, it is shown that the GOR for 12-effect MEE can be increased by 11% with optimized feed flow rate. Sensitivity analysis is carried out for calculating the optimal operating parameters. Finally, it is proposed to design MEE with high temperature driving force for reduction in capital cost as well as specific energy consumption.

Modeling and energy reduction of multiple effect evaporator system with thermal vapor compression

Abstract A general and rigorous mathematical model is developed for a multiple effect evaporator system which includes various energy reduction schemes (ERSs). These ERSs are thermal vapor compression, vapor bleeding, condensate flashing and solution flashing. The model can achieve the function of pumping steam at any effect and can work as an effective screening tool for the selection of optimal feed flow sequence (OFFS). In order to solve the model, the iteration method combining with matrix methods is proposed. To study effect of different ERSs on steam consumption (SC), an example of the co-current quadruple effect evaporator system is considered. These schemes can reduce the SC up to 46.56% if the feed is heated up to 88 °C and ejection coefficient at 3rd effect is set to 0.3. The OFFS is forward sequence as long as preheating temperature is high enough when constraints of heat transfer driving force can be satisfied.

Entropy, exergy, and cost analyses of solar driven cogeneration systems using supercritical CO2 Brayton cycles and MEE-TVC desalination system

In this study, performance and cost analyses are conducted for a solar power tower integrated with supercritical CO2 (sCO2) Brayton cycles for power production and a multiple effect evaporation with a thermal vapor compression (MEE-TVC) desalination system for water production. The study is performed for two configurations based on two different supercritical cycles: the regeneration and recompression sCO2 Brayton cycles. A two-tank molten salt storage is utilized to ensure a uniform operation throughout the day. From the entropy analysis, it was shown that the solar tower is the largest contributor to entropy generation in both configurations, reaching almost 80% from the total entropy generation, followed by the MEE-TVC desalination system, and the sCO2 power cycle. The entropy generation in the two-tank thermal storage is negligible, around 0.3% from the total generation. In the MEE-TVC system the highest contributing component is the steam jet ejector, which is varying between 50% and 60% for different number of effects. The specific entropy generation in the MEE-TVC decreases as the fraction of the input heat to the desalination system decreases; while the specific entropy generation of the sCO2 cycle remains constant. The cost analysis performed for different regions in Saudi Arabia and the findings reveal that the regions characterized by the highest average solar irradiation throughout the year have the lowest LCOE and LCOW values. The region achieving the lowest cost is Yanbu, followed by Khabt Al-Ghusn in the second place, and the rest are as follows, Jabal Al-Rughamah, Jizan, Al-Khafji, and Dhahran. The LCOE of Yanbu at a fraction of 0.5 for the regeneration and recompression solar cogeneration cycles are 0.0915$/kWh and 0.0826$/kWh, respectively.

Energy Integration of Multiple Effect Evaporators with Background Process and Appropriate Temperature Selection

Multiple effect evaporators (MEEs) are energy intensive equipment. Often the focus is on minimizing the energy consumption of MEEs as a standalone system, rather than that of the entire plant. In this paper, process integration techniques are applied to integrate various stages of a MEE with the background process. To identify various energy conservation opportunities, the MEE is represented as a Grand Composite Curve (GCC) and integrated with the GCC of the background process. Change in utility consumption in the first effect, due to energy shift (in the GCC) between various effects, is determined in this paper. It is proved that for the minimum energy requirement all effects should be pinched. Using these mathematical results, a methodology for optimally integrating the MEE with the background process is developed. Furthermore, additional energy may be conserved by appropriately selecting effect temperatures. A methodology for appropriate selection of effect temperatures is also proposed in this paper. ...

DEVELOPMENT OF IMPROVED PID CONTROLLER FOR SINGLE-EFFECT EVAPORATOR

Kraft pulping is the pulping process that is mostly used in paper mills. This is because the chemicals used in cooking are being recovered, and environmental pollution is minimized, as the chemicals are not discarded into the environment, but rather recycled. These chemicals are recovered by burning the black liquor that leaves the digester in a reactor called a recovery boiler. Feeding the black liquor directly from the digester to the recovery boiler will cause a water/smelt explosion. This explosion happens if the percentage of water in the liquor is high, the solid content of the black liquor leaving the digester is usually between 13-18%. To avoid such disaster the concentration of the black liquor has to be increased, which should in the range of 60-70%, this is done in a single or multiple effect evaporator. In this paper, a single effect evaporator control has been designed using a Proportional Integral Derivative (PID) controller. During the first design a simple PID controller with a feedback control was used. Then taking into consideration the load disturbance in the process, a feed forward control has then been introduced into the controller design. Subsequently the concept of boiling point rise (BPR) to measure concentration has then been used in the controller design of a single effect evaporator.

Characterization of evaporator scale of Indian sugar industry

Fouling in Multiple Effect Evaporator (MEE) systems is the major unresolved problem encountered in most of the chemical process industries. In order to mitigate fouling from MEE system used in the cane sugar industry, it is necessary to understand the type and nature of foulant present in it. In the current paper, the authors have tried to present the detailed analysis of deposits present in each effect of a quadruple effect MEE system used in Indian sugar industry. For this purpose, various instrumental analyses were performed and different organic and inorganic compounds and elements present in the deposits were identified. Further, it has also been observed that some elements show a particular trend of deposition from first effect to last effect. This analysis will help industry to select particular mitigation techniques to clean deposits.

Innovative concepts of regeneration of decolorization ion exchange resins in sugar refineries

Regeneration of resins used for decolorization of sugar solutions is done with concentrated salt solutions. Nanofiltration membranes have been proven effective, in terms of industrial efficiency in decreasing salt consumption. More than 90% of the salt that is necessary for regeneration can be recycled through a combination of direct recycling of intermediate eluates, the separation of colored compounds by use of very selective nanofiltration membranes and a system to concentrate salty permeates. According to specific local conditions on energy supply and cost, the concentration of salty permeates can be either a multiple effect evaporator or a combination of electrodialysis and reverse osmosis. The desalted color compound solution is sent to the molasses, limiting considerably the effluent to be treated. Starting from a liquor of 800 IU, the water requirement is limited to less than 100 L/t of sugar and the amount of wastewater can be reduced to less than 40 L/t of sugar.