Reducing Energy Consumption for Seawater Desalination through the Application of Reflux-Recycle Concepts from Oil Refining

2013 ◽  
Vol 295-298 ◽  
pp. 1456-1462 ◽  
Author(s):  
K. E. Ting ◽  
H.T. Ng ◽  
H.C. Li
Keyword(s):  
High Pressure ◽  
Energy Consumption ◽  
Specific Energy Consumption ◽  
Low Pressure ◽  
Hybrid Membrane ◽  
Oil Refining ◽  
Pressure Side ◽  
Seawater Desalination ◽  
Feed Concentration ◽  
Membrane Processes

The application of the concepts in oil and gas distillation to membrane desalination process to lower the energy cost for seawater desalination was studied in this paper. Drawing on the close analogy between multistage RO and conventional distillation separation processes, a hybrid membrane processes employing reflux and recycle concepts was developed. Reflux in membrane processes involves taking a portion of the effluent stream on the high pressure side and sending it to the low pressure side of the membrane, while recycle involves taking a portion of the permeate stream on the low pressure side and sending it to the high pressure side of the membrane. A predictive model was developed to study the effect of reflux and recycle on the specific energy consumption (SEC) and permeate quality when compared to conventional systems. In this study, the water permeability coefficients of membranes and brine recycle ratios were investigated. The results show that the SEC for a hybrid membrane processes comprising of RO and NF membrane was lower than conventional methods with the same recovery and feed concentration, suggesting that it is feasible to apply reflux and recycle concepts of distillation on desalination. Through the careful selection of RO membranes and NF membranes, benefits of reflux and recycle can be enjoyed for seawater desalination.

scholarly journals Batch Reverse Osmosis Desalination Modeling under a Time-Dependent Pressure Profile

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 173
Author(s):  
Abdeljalil Chougradi ◽  
François Zaviska ◽  
Ahmed Abed ◽  
Jérôme Harmand ◽  
Jamal-Eddine Jellal ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Reverse Osmosis ◽  
Specific Energy ◽  
Energy Demand ◽  
Specific Energy Consumption ◽  
Pressure Profile ◽  
Recovery Ratio ◽  
Feed Concentration ◽  
Energetic Performance ◽  
Feed Volume

As world demand for clean water increases, reverse osmosis (RO) desalination has emerged as an attractive solution. Continuous RO is the most used desalination technology today. However, a new generation of configurations, working in unsteady-state feed concentration and pressure, have gained more attention recently, including the batch RO process. Our work presents a mathematical modeling for batch RO that offers the possibility of monitoring all variables of the process, including specific energy consumption, as a function of time and the recovery ratio. Validation is achieved by comparison with data from the experimental set-up and an existing model in the literature. Energetic comparison with continuous RO processes confirms that batch RO can be more energy efficient than can continuous RO, especially at a higher recovery ratio. It used, at recovery, 31% less energy for seawater and 19% less energy for brackish water. Modeling also proves that the batch RO process does not have to function under constant flux to deliver good energetic performance. In fact, under a linear pressure profile, batch RO can still deliver better energetic performance than can a continuous configuration. The parameters analysis shows that salinity, pump and energy recovery devices efficiencies are directly linked to the energy demand. While increasing feed volume has a limited effect after a certain volume due to dilution, it also shows, interestingly, a recovery ratio interval in which feed volume does not affect specific energy consumption.

Practical Considerations When Conducting a Transient Analysis of a Heat Exchanger Tube Rupture

2012 ◽  
Author(s):  
David R. Thornton ◽  
Robert A. Sadowski ◽  
Philip A. Henry
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Transient Analysis ◽  
Low Pressure ◽  
Lower Pressure ◽  
Pressure Side ◽  
Analysis Methodology ◽  
Large Pressure ◽  
Process Plants ◽  
Shell And Tube

As part of operations, petrochemical and process plants sometimes require the exchange of heat between a high pressure fluid and a lower pressure fluid in shell-and-tube heat exchangers. In most cases, the high pressure fluid exists on the tubeside and the lower pressure is on the shellside. While rare, it is possible for a tube inside the exchanger shell to rupture suddenly, releasing the high pressure fluid into the shellside. If the pressure of the high pressure fluid exceeds the design pressure of the low pressure shell or its attached piping, it might be possible for the resulting pressure in the low pressure side to exceed permitted values. In such cases, API 521 provides guidance on assuring that sufficient pressure relief is available to limit the pressures on the heat exchanger(s)’ low pressure side. An overpressure analysis per API 521 can include both steady-state and transient analysis methods for determining that the pressures remain within acceptable levels. In situations where a large pressure differential exists between the high and low pressure sides of the exchanger, the transient, hydraulic analysis of the tube rupture event can be used as a tool to help mitigate over pressure. After briefly discussing the analysis methodology, this paper discusses some of the practical considerations and decisions that normally go into conducting the analysis.

scholarly journals Performance of a small solar-powered hybrid membrane system for remote communities under varying feedwater salinities

2004 ◽  
Vol 4 (5-6) ◽  
pp. 233-243 ◽  
Author(s):  
A.I. Schäfer ◽  
C. Remy ◽  
B.S. Richards
Keyword(s):  
Salt Concentration ◽  
System Performance ◽  
Specific Energy Consumption ◽  
Membrane System ◽  
Hybrid Membrane ◽  
Operating Pressure ◽  
Feed Concentration ◽  
Remote Communities ◽  
Pre Treatment ◽  
Solar Powered

An estimated 1 billion people are living both without access to clean drinking water or electricity. The small photovoltaic (PV)-powered hybrid membrane system described here is designed to address the plight of some of these people. PV and membrane technologies are chosen due to suitability for operation in remote and often harsh conditions. An ultrafiltration (UF) pre-treatment is included to remove bacteria and most pathogens, while a reverse osmosis (RO) or nanofiltration (NF) membrane desalinates the brackish feedwater. Several parameters were examined in order to optimise the system performance, including (i) feed salt concentration, (ii) operating pressure, (iii) system recovery, (iv) specific energy consumption (SEC, kWh/m3), and (v) salt retention. In addition, experiments were performed over a whole day to determine system performance under varying levels of solar radiation. The minimum SEC (relatively high due to the current single-pass mode of operation) varies from 5.5 kWh/m3 at a feed concentration of 1 g/L salt to 26 kWh/m3 at a feed concentration of 7.5 g/L salt, which is the upper limit of the system in terms of salt concentration.

scholarly journals Evaluation of environmental indicators of RO seawater desalination: case study coastal strip of Hormozgan province, Iran

2020 ◽  
Vol 69 (7) ◽  
pp. 694-703
Author(s):  
Somayeh Mohammadi Jouzdani ◽  
Mohammad Mahdi Zerafat ◽  
Peyman Daneshkar Arasteh ◽  
Hassan Vagharfard
Keyword(s):  
Energy Consumption ◽  
Water Supply ◽  
Environmental Sustainability ◽  
Supply And Demand ◽  
Specific Energy Consumption ◽  
Water Shortage ◽  
Environmental Indicators ◽  
Water Withdrawal ◽  
Feed Water ◽  
Seawater Desalination

Abstract In recent years, desalination has been turned into a fresh water supply as a solution in some areas which suffer from water shortage. Desalinated water as an industrial product causes environmental problems. The objectives of this study are investigating environmental sustainability indicators related to seawater desalination via reverse osmosis (SWRO) on the coastline of Hormozgan province to provide a better insight for current and future water and energy demands related to this alternative. The selected indicators are specific energy consumption, seawater withdrawal, and brine volume in desalination, fuel consumption, carbon emission and water withdrawal in electric power generation. Using a solution-diffusion model, the direct indicator of energy consumption was obtained as used to calculate indirect indicators from the energy generation sector. Analysis of results indicates that desalination can lead to out-of-area side effects resulting from fuel type consumed and the practical power of the power plant, in addition to the regional environmental effects that are mostly affected by total dissolved solids of feed water. Based on the results, the environmental issues should be considered for the regions where desalination was planned as the most feasible alternative for water supply. This result can help policymakers to manage water supply and demand for sustainable development appropriately.

Practical Experience With a Mobile Methanol Synthesis Device

2014 ◽  
Author(s):  
Eric R. Morgan ◽  
Tom Acker
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Methanol Synthesis ◽  
Low Pressure ◽  
Practical Experience ◽  
Gaseous Hydrogen ◽  
Water Mixture ◽  
Pressure Side ◽  
Northern Arizona ◽  
Northern Arizona University

Northern Arizona University has developed a methanol synthesis unit that directly converts carbon dioxide and hydrogen into methanol and water. The methanol synthesis unit consists of: a high pressure side that includes a compressor, a reactor, and a throttling valve; and a low pressure side that includes a knockout drum, and a mixer where fresh gas enters the system. Methanol and water are produced at high pressure in the reactor and then exit the system under low pressure and temperature in the knockout drum. The remaining, unreacted recycle gas that leaves the knockout drum is mixed with fresh synthesis gas before being sent back through the synthesis loop. The unit operates entirely on electricity and includes a high-pressure electrolyzer to obtain gaseous hydrogen and oxygen directly from purified water. Thus, the sole inputs to the trailer are water, carbon dioxide and electricity, while the sole outputs are methanol, oxygen, and water. A distillation unit separates the methanol and water mixture on site so that the synthesized water can be reused in the electrolyzer. Here, we describe and characterize the operation of the methanol synthesis unit and offer some possible design improvements for future iterations of the device, based on experience.

Pressure Variation in Low Pressure Side of Shell and Tube Heat Exchanger After Tube Rupture

2014 ◽  
Author(s):  
Ganesh S. Katke ◽  
M. Venkatesh ◽  
N. P. Gulhane
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Low Pressure ◽  
Pressure Variation ◽  
Operating Pressure ◽  
Pressure Side ◽  
Tube Heat Exchanger ◽  
Analytical Algorithm ◽  
Shell And Tube ◽  
Design Pressure

This paper presents an analytical algorithm to determine the pressure variation on the Low Pressure side of a Shell and Tube Heat Exchanger (STHE) after a tube rupture and its validation using CFD simulation. STHEs are often used for exchanging heat between high-pressure (HP) and low-pressure (LP) fluids in the chemical process industry. In case tube rupture occurs in a STHE having a large pressure difference between HP and LP side, there is a risk of release of significant quantity of fluid from the HP side to the LP side. The consequent pressure build-up can lead to the failure of LP side pressure envelope. Generally, design pressure of the LP side is about 10–20% higher than the operating pressure of the LP side fluid, but well below the operating pressure on the HP side. There is no well-established methodology to design the LP side to withstand sudden release of high pressure fluid following a tube rupture. Three dimensional analyses were carried out using Computational Fluid Dynamics to study the pressure variation in LP side (shell side) of a Gas Cooler and to validate the results obtained from the analytical algorithm. It has been observed that the pressure on the LP side exceeds the design pressure instantaneously due to generation of a pressure pulse after tube rupture. This may lead to damage of LP envelope (shell) and internal structure of STHE.

Design and Test Plan of the Supercritical CO2 Compressor Test Loop

2008 ◽  
Author(s):  
Takao Ishizuka ◽  
Yasushi Muto ◽  
Masanori Aritomi
Keyword(s):  
High Pressure ◽  
Critical Point ◽  
Thermal Efficiency ◽  
Supercritical Co2 ◽  
Thermal Power ◽  
Low Pressure ◽  
Fiscal Year ◽  
Pressure Side ◽  
Test Loop ◽  
Pressure Compressor

Supercritical carbon dioxide (CO2) gas turbine systems can generate power at a high cycle thermal efficiency, even at modest temperatures of 500–550°C. That high thermal efficiency is attributed to a markedly reduced compressor work in the vicinity of critical point. In addition, the reaction between sodium (Na) and CO2 is milder than that between H2O and Na. Consequently, a more reliable and economically advantageous power generation system can be created by coupling with a Na-cooled fast breeder reactor. In a supercritical CO2 turbine system, a partial cooling cycle is employed to compensate a difference in heat capacity for the high-temperature — low-pressure side and low-temperature — high-pressure side of the recuperators to achieve high cycle thermal efficiency. In our previous work, a conceptual design of the system was produced for conditions of reactor thermal power of 600 MW, turbine inlet condition of 20 MPa/527°C, recuperators 1 and 2 effectiveness of 98%/95%, Intermediate Heat Exchanger (IHX) pressure loss of 8.65%, a turbine adiabatic efficiency of 93%, and a compressor adiabatic efficiency of 88%. Results revealed that high cycle thermal efficiency of 43% can be achieved. In this cycle, three different compressors, i.e., a low-pressure compressor, a high-pressure compressor, and a bypass compressor are included. In the compressor regime, the values of properties such as specific heat and density vary sharply and nonlinearly, dependent upon the pressure and temperature. Therefore, the influences of such property changes on compressor design should be clarified. To obtain experimental data for the compressor performance in the field near the critical point, a supercritical CO2 compressor test project was started at the Tokyo Institute of Technology on June 2007 with funding from MEXT, Japan. In this project, a small centrifugal CO2 compressor will be fabricated and tested. During fiscal year (FY) 2007, test loop components will be fabricated. During FY 2008, the test compressor will be fabricated and installed into the test loop. In FY 2009, tests will be conducted. This paper introduces the concept of a test loop and component designs for the cooler, heater, and control valves. A computer simulation program of static operation was developed based on detailed designs of components and a preliminary design of the compressor. The test operation regime is drawn for the test parameters.

Practical Experience With a Mobile Methanol Synthesis Device

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Eric R. Morgan ◽  
Thomas L. Acker
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Synthesis Gas ◽  
Methanol Synthesis ◽  
Low Pressure ◽  
Practical Experience ◽  
Gaseous Hydrogen ◽  
Distillation Unit ◽  
Water Mixture ◽  
Pressure Side

A methanol synthesis unit (MSU) that directly converts carbon dioxide and hydrogen into methanol and water was developed and tested. The MSU consists of: a high-pressure side that includes a compressor, a reactor, and a throttling valve; and a low-pressure side that includes a knockout drum, and a mixer where fresh gas enters the system. Methanol and water are produced at high pressure in the reactor and then exit the system under low pressure and temperature in the knockout drum. The remaining, unreacted recycle gas that leaves the knockout drum is mixed with fresh synthesis gas before being sent back through the synthesis loop. The unit operates entirely on electricity and includes a high-pressure electrolyzer to obtain gaseous hydrogen and oxygen directly from purified water. Thus, the sole inputs to the trailer are water, carbon dioxide, and electricity, while the sole outputs are methanol, oxygen, and water. A distillation unit separates the methanol and water mixture on site so that the synthesized water can be reused in the electrolyzer. Here, we describe and characterize the operation of the MSU and offer some possible design improvements for future iterations of the device, based on experience.

scholarly journals Design and Energy Consumption Analysis of Small Reverse Osmosis Seawater Desalination Equipment

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2275
Author(s):  
Zhuo Wang ◽  
Yanjie Zhang ◽  
Tao Wang ◽  
Bo Zhang ◽  
Hongwen Ma
Keyword(s):  
Energy Consumption ◽  
Water Resources ◽  
Reverse Osmosis ◽  
Specific Energy Consumption ◽  
Membrane System ◽  
Energy Utilization ◽  
Utilization Efficiency ◽  
Small Scale ◽  
Reverse Osmosis Membrane ◽  
Seawater Desalination

The reverse osmosis method has developed extremely rapidly in recent years and has become the most competitive seawater desalination technology in the world, and it has been widely used in all aspects. Large-scale reverse osmosis desalination plants cannot provide fresh water resources in areas with insufficient water resources and limited space. Therefore, this paper proposes a research plan for a small seawater desalination device based on reverse osmosis, which is mainly suitable for handling emergencies, disaster relief, desert areas and outdoor activities and other needs for timely freshwater resources. It mainly includes pretreatment modules, a reaction infiltration module, a post-processing module and an energy supply module. Detailed design calculations are carried out for the small-scale reverse osmosis membrane system, including the selection and quantity and arrangement of membranes. Subsequently, the one-stage two-stage small-scale reverse osmosis membrane system was modeled, and its energy consumption was analyzed theoretically from the perspectives of specific energy consumption and energy utilization efficiency; the main influencing factors were clarified, and the optimal recovery rate for system operation was determined to be 20%–30%. Finally, an experimental prototype was built to conduct relevant experiments to determine the influence trend of pressure, temperature, concentration, and flow rate on the operating performance of the reverse osmosis system.

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