Seawater Distillation Research Articles

Preliminary design and cost analysis of a solar distillation system

In this paper different solar systems of seawater distillation are proposed and economically analyzed. The solar collectors are parabolic trough ones in which brine circulates as thermal fluid. Steam is directly obtained from circulating brine. The solar collector field could be connected to condenser/preheater heat exchangers; nevertheless, the system would have a low performance ratio. In addition, the solar collectors could be coupled to multi-stage flash or multi-effect distillation systems to continue the evaporation of the remaining brine. The steam generated by the solar field would drive the distillation plant. The above systems are analyzed in comparison with other solar distillation ones as follows: a multi-effect distillation plant connected to a solar field in which steam is directly generated from fresh water, and a multi-stage flash plant that uses parabolic trough collectors as the brine heater. The specific cost of the product is evaluated for different climatic conditions, plant capacities, cost of the solar collectors, and costs of a conventional energy supply. Results obtained are useful in preliminary cost evaluation of the proposed solar distillation systems.

Seawater distillation from low-temperature streams: a case history

The paper describes the objectives and the operational results of an experimental project aimed for the exploitation of very low temperature differences (associated with many waste streams commonly available in industrial environments) for the distillation of seawater. The case described is relevant to the engineering, construction and operation of a seawater desalination plant, called LTF, able to utilize as prime energy source the cooling seawater discharged by a turbine condenser, at only 8°C above ambient seawater temperature. The project was developed in the early 1990s by the Italian company Sowit, with a grant from the European Community. The desalination plant is presently in operation at the Piombino power station (owned by ENEL, the Italian Electricity Board) for the production of high-purity distillate for boiler make-up. Plant operational results confirmed the feasibility and the technical-economical convenience of this process. From the design point of view, the most critical aspect is related to the vent system of non-condensible gases released in the evaporator, while plant operation showed various advantages, such as a good reliability, a very high purity of produced distillate, reduced environmental impact and a competitive operation cost.

海水淡水化への原子力エネルギーの利用とＩＡＥＡの活動

海水淡水化への原子力エネルギーの利用とＩＡＥＡの活動

Thermodynamics and Thermoeconomics

Raising the efficiency of an energy system is within the domain of thermodynamics. Raising the efficiency cost-effectively (Thermoeconomics) is a multi-disciplinary problem in which thermodynamics interfaces other disciplines of knowledge which in this particular case are design, manufacture and economics. This paper deals with a communication/optimization strategy, via the concept of costing equations, whereby the system can be analyzed and optimized for minimum cost within the domain of thermodynamics. The communication/optimization strategy is explained. The generation of costing equations is demonstrated. A gas turbine power system and seawater distillation process system are used as examples for improved design point and improved configuration. The results of their optimized design points for configurations in order of increasing complexity are displayed on cost-efficiency coordinates.

Operation processes affecting corrosion in MSF distillers

Multi-stage flash (MSF) distillation of seawater is an established technique for desalinating seawater in coastal arid countries. Although MSF distillers differ in design, size and capacity, their operation encompasses a number of standard processes which aim to overcome a performance difficulty or improve production efficiency. These processes affect the corrodability of certain elements of the distiller, either beneficially or detrimentally. The successful running of the distiller depends, therefore, on the proper execution of these operations and the understanding of their mutual interaction. In the following we describe in short six various operations commonly carried out during seawater desalination by MSF distillation. The impact of each of these processes on the corrosion of members of the distiller and the precautions recommended to annihilate or minimize the adverse effects are briefly outlined.

Environmental impacts of seawater distillation and reverse osmosis processes

The paper presents and compares the marine and atmospheric discharges of typical large MSF and RO plants. Distillation plants require an inlet seawater flow around 8 to 10 times the fresh water production rate, for cooling and feed make-up. The discharge is raised in salinity and in temperature, due to heat rejection from the process. A seawater RO plant generally requires a lower feedwater flow rate of around 2.5 to 3 times the production. Salinity of the discharge is correspondingly greater than in distillation, but temperature rise is small. Chemical discharges are compared for the different processes. A comparison is made of atmospheric emissions from generating the power to drive RO process pumps and the emissions resulting from generation of steam and auxiliary power for distillation (in dual purpose desalination/power plants). The factors affecting site selection and requirements for seawater intakes and outfalls are briefly discussed, with examples. The land area needed for a desalination plant is compared with the catchment and reservoir areas needed for a typical surface water collection scheme to illustrate the much lower impact of desalination on land resources. Factors such as noise and aesthetics are also briefly discussed.

Water-chemical regimes of distillation plants operating beyond the calcium sulfate dehydrate scale threshold

Investigations were carried out to evaluate the influence of solution composition, hydrodynamic and heat engineering parameters upon intensity of calcium sulfate dehydrate scale formation in distillation plants and on the restrictive stage of the process. The effect of inhibitors upon mass transfer coefficients during the calcium sulfate dehydrate scale formation was investigated. The calcium sulfate dehydrate scale restriction by means of inhibitors and seed crystals was estimated. Data obtained were used for development of the calcium sulfate dehyrate scaling limiting system in the Aral Sea water distillation plant with horizontal tube film evaporators.

Simulation of the steady-state operation of a multi-effect stack seawater distillation plant

A mathematical simulation of the steady-state operation of a multi-effect stack (MES) distiller was carried out using a number of simplifying assumptions. The distiller consists of a two-tier arrangement in which feed water is pumped to the top effect via a number of preheaters. The computer program which was prepared based on the simulation models of the different plant components was applied to an MES distiller having the same design and operational characteristics as the distiller currently in operation at Abu Dhabi, UAE. The results of the simulation program were then compared with the actual test results from the operating plant. Agreement between the theoretical and test results was found to be good.

A new water and power combination: vacuum vapor compression seawater distillation and natural gas fuel cells

Conventional desalination systems dependent on abundant oil for inexpensive energy are no longer an option for those communities looking for a sustainable solution to the problem of water scarcity. Environmental and political imperatives around the world highlight the increasingly urgent need for a new, affordable, and efficient source of drinking water. To meet this demand, Advanced Distillation Technology (ADTech) has designed an ultra-efficient vacuum vapor compression distillation (VVCD) system for the production of fresh water from seawater. The energy demand of ADTech's all-electric VVCD system is less than half that of competing technologies and is ideal for coupling with the full array of alternative energy sources, including fuel cells, nuclear, sea wave, solar, and wind. Fuel cells offer unique synergy when combined with desalination because the output is not only electricity, but also hot water and air which can be captured to increase the efficiency of the integrated system. Recent technological triumphs made by H Power Corporation of New Jersey eliminate the historical problem of hydrogen storage and make fuel cells a particularly well suited power source for desalination. H Power's total energy module (TEM) implements their proprietary hydrogen storage technology. By integrating the VVCO with TEM, a robust, silent, and autonomous water-power system that produces negligible emissions is possible. A demonstration model of the VVCD system will begin a 6-month tour in early 1995, with operation planned in Monterey, California; Darnmam, Saudi Arabia; and Rarat, Morocco to verify performance and energy efficiency. The dramatic results are expected to create opportunities for new installations as well as replacements around the world for customers seeking to meet growing demand for water with maximum efficiency and minimum environmental degradation. If there is substantial international interest in a system integrating VVCD and fuel cell technology, ADTech and H Power are interested in developing a project to demonstrate this new water-power combination.

Evaluation of Belgard EV 2000 as antiscalant control additive in MSF plants

Scale formation on heat transfer surfaces, which is one of the basic problems in the distillation of seawater, can be effectively controlled or minimized by the addition of chemical additives. The most popular additives polyphosphate and Belgard EVN have extensively been used as scale control additives in Multi Stage Flash (MSF) plants in Kuwait. In 1988, a new product was introduced by Ciba-Geigy known as Belgard EV 2000. Belgard EV 2000 is an aqueous solution of an organic acid which acts either as threshold inhibitor or increases the adsorption of scale so as to reduce adhesion to metal surface. Ciba-Geigy collaborated with MEW in conducting a trial which is designed to show whether Belgard EV 2000 is a more cost-effective alternative than the currently used products Belgard EVN and polyphosphate. The present paper speculates the evaluation of Belgard EV 2000 as antiscaling agent in MSF plants. This additive was tested by the Ministry of Electricity and Water (ME&W) on unit A4 of Doha East Power & Water Production Station. The duration of the trial was from 18th April to 28th August, 1988, on a 130-day trial using low brine temperature (90°C), with a unit capacity of 6.0 migd. This additive exhibited satisfactory performance during the test period and successfully controlled the deposition of alkaline scale. No significant changes were observed in heater fouling when the dose level of Belgard EV 2000 was reduced from 2.5 ppm and maintained at 1.5 ppm. The brine heater and heat gain sections were inspected at the end of the trial period and the condenser tubes were found to be clean, which confirmed the capability of Belgard EV 2000 in controlling alkaline scale formation, in spite of the fact that the evaporator was not fitted with a sponge ball cleaning system.

Design and operating comparison of MSF and MED systems

This paper compares the technical and cost aspects of Multistage Flash (MSF) and Multiple Effect (MED) of evaporators for the distillation of seawater. Comparisons of heat transfer surface, energy requirements, and process requirements are made. Capital and operating costs are presented. Process optimization are carried out for an assumed dual purpose installation at performance ratios (PR) of 8, 10 and 12 lbs distillate per 1,000 Btu heat input. Capital and operating costs for the optimized processes were: Unit capital cost/pgd: MSF, $8.70 (PR at 10/1); MED, $7.01 (PR at 8/1) Operating and maintenance cost/kgal: MSF, $4.20; MED, $3.35 Total cost of water/kgal: MSF, $7.05; MED, $5.65 Proposed advances in the state-of-the-art for MED systems are presented, as well as capital and operating cost savings for these advanced designs.

Recent achievements of low temperature multiple effect desalination in the western areas of Abu Dhabi. UAE

The multiple effect (ME) process allows optimised desalination at an attractive cost while conserving the proven reliability of seawater distillation. ME has already superseded the more classic MSF in the range of unit productions up to about 10,000 TPD and tends to increase its leading position further to larger unit capacities.

Large-scale sea-water distillation for Southern California

Large-scale sea-water distillation for Southern California

Parabolic type solar still

A complete design and fabrication for a distilled water apparatus using a line concentrator of parabolic reflector type, which can be used for sea water distillation, is given. A steady state theoretical model based on energy balance is presented. The experimental results are compared with the theoretical ones as well as with the available data, and a satisfactory agreement is shown. The maximum fraction that can be evaporated from water flow rates is investigated. Further recommendations are given.

Belgard® EV — 15 years' experience in scale control

Since its introduction in 1973, BELGARD has almost become synonymous with scale control additive for multistage flash plants and other processes involving the distillation of seawater. The initial impetus has been maintained over the last fifteen years by continued research and development. On-site trials and evaluation with the co-operation and assistance of plant manufacturers and end users, has resulted in improved plant performance and chemical dosing and better monitoring techniques. This paper, reviews the early history of BELGARD EV and subsequent work leading to the introduction of BELGARD EV2000. Up-to-date experience with BELGARD products is presented, including use with sponge ball cleaning, optimisation of additive dose levels, advances in dosing techniques, development of analytical methods for polymers, and advances in on-site plant monitoring.

Production of Heavy Water and Concentration of Heavy Water in Seawater Distillation Process

Production of Heavy Water and Concentration of Heavy Water in Seawater Distillation Process

Trihalomethanes (THMs) formation in a distillation process

In this study, the fate of THMs formation in seawater distillation process and the rates of THMs formation in the chlorinated blended distillate were examined under various experimental conditions. The following general equation was obtained empirically: Log (THM) = A * Log (Cl 2) + B * Log (TOC) + C (THM) is the concentration of total THMs in μg/l, (Cl 2) and (TOC) are the concentration of chlorine doese and total organic carton in mg/l, A,B, and C are estimated parameters. The results showed that THMs level increases with the increase of both chlorine and initial humic substances concentrations. Increase in temperature and contact time also increased THMs concentrations. On the other hand, pre-chlorination and aeration step of the seawater resulted in a reduction of THMs concentrations in the blended distillate.

Seawater Distillation by Solar Energy

This paper presents the results obtained from a solar desalination plant during one year of operation (1985). The experimental results are compared with that of a computer simulation developed for the purpose of predicting the performance of the plant. Data for the monthly average daily insolation on the absorber surface and daily collected heat per square meter of collector area are presented. The experimental and calculated values of the heat collecting system efficiency were compared. The results of the monthly average daily distillate production were presented and show that it varies in a manner similar to that of the solar insolation. The distillate production figures were found to generally exceed what was expected using the simulation program.

Sea Water Desalination in Kuwait — A Report on 33 Years Experience

Kuwait has been fully dependent for its fresh water supplies on sea water Distillation Plants for the last 33 years. Multi-Stage Flash Distillation Plants (MSF) have been successfully used in Kuwait for about 30 years, during which period Kuwait has gained wide experience in the design, commissioning, operation and maintenance of MSF Distillation Plants. This paper attempts to cover this long and unparalleled experience. Survey of all existing Power & Distillation Stations is presented and the reasons behind the development of the Dual-Purpose Plants are explained. The historical development of MSF Distillation is also charted. Main design features which characterize Kuwait's Plants are outlined. A summary of the experience gathered over the years concerning Plants Operation & Maintenance is given. Finally, investigations and research into the viability of other desalination methods are summarized.

Desalination: The Solution to Oman's Thirst

The Sultanate of Oman, a country in the Middle East with limited oil and water resources, is coping with the twin problems of rapid modernization and severely limited freshwater supplies by using multiflash distillation of seawater in conjunction with electrical power generation. Limited supplies of fresh well water are blended with the desalinated water before distribution. A series of five‐year development plans, the latest of which takes advantage of a new computer modeling capability, ensures an orderly expansion of the water system for the next several years.