M.P.S. Ramani

Relative technoeconomics of multistage flash distillation and reverse osmosis for seawater desalination - a case study

Abstract A case study has been carried out for putting up a 225,000 cubic meter/day desalination plant in the city of Madras on south east coast of India and relative techno-economics of single purpose and dual purpose Multistage Flash (MSF) and Reverse Osmosis (RO) has been presented.

Effect of surface roughness & polymeric additive on nucleate pool boiling at subatmospheric pressures

Abstract This investigation pertains to boiling heat transfer from a submerged flat surface at subatmospheric and atmospheric pressures in the presence of hydroxy ethyl cellulose (HEC) as a polymeric additive in small doses. Boiling was carried out in presence of the additive on smooth and rough aluminium surfaces having effective cavity size within the range as predicted by Hsu model and the pressure was kept in the range of 8 – 100 KN/sq.m (abs). Effects of surface roughness, saturation pressure and polymer concentration on boiling heat transfer were studied and the results were compared with Rohsenows correlation.

Nucleate boiling in a thin film on a horizontal tube at atmospheric and subatmospheric pressures

Abstract This investigation pertains to nucleate boiling in a thin film on a horizontal tube at atmospheric and subatmospheric pressures. The experiments are carried out with distilled water and sodium chloride solutions (35 000 and 50 000 p.p.m.) in the pressure range 60–100 kN m −2 . An enhancement in the nucleate boiling heat transfer coefficient is noted for boiling in the horizontal tube falling film. A correlation is proposed to predict the boiling heat transfer coefficient for distilled water and sodium chloride solution in a thin film on a horizontal stainless steel tube at atmospheric and subatmospheric pressures.

Evaluation of thermal desalination and reverse osmosis for the production of boiler feed water from sea water for coastal thermal power stations in India

Abstract A case study was carried out for the production of 150 m3/hr boiler feed water from sea water at a coastal thermal power station in southeastern India. Three alternatives, viz. multistage-flash (MSF), thermocompression (TC), and reverse osmosis (RO) were considered. The first two are thermal desalination processes and the last one is an ambient temperature membrane process. In the case of the thermal desalination processes, extraction steam at appropriate temperature and pressure drawn from the power plant was considered. Since the water from thermal desalination plants will be very pure, only mixed bed downstream polishing units will be required to reach boiler feed water quality, but for the RO process, a full fledged demineraliser (DM) plant will be necessary. It was found that a system with a locally manufactured MSF unit will be the most economical for the purpose. Emphasis is placed on local capability to manufacture and install desalination plants.

Studies on nucleate boiling of sodium chloride solutions at atmospheric and sub-atmospheric pressures

Abstract This investigation pertains to the nucleate pool boiling heat transfer studies on submerged horizontal flat copper surfaces of different roughness at atmospheric and sub-atmospheric pressures. The experiments were carried out for distilled water and sodium chloride solutions (35,000 and 50,000 ppm) in the pressure range 10–100 kN/m2. The experimental results were compared with Rohsenows correlation. The experimental boiling curve slope was lower than the Rohsenows correlation.

Synthesis and study of RO performance of aromatic polyamide hydrazide membranes

Aromatic polyamide hydrazide polymeric membranes were synthesized by dissolving freshly prepared polymer in dimethyl acetamide using lithium salt as additive. The effect of various casting parameters like polymer to solvent ratio, additive to polymer ratio, time and temperature of solvent evaporation, etc., on the RO membrane performance was studied. The membrane performance under various operational parameters like applied pressure, feed molarity and temperature are presented. The membranes prepared from the polymer samples were characterised in terms of pure water permeability constant (A) and solute transport parameter (DAM/Kδ).

Management and feasibility of reverse osmosis schemes for rural water supply in India

Abstract The adoption of reverse osmosis process as a desalination system for meeting the demand for fresh water in rural India has been critically examined with respect to the technical, economic, social and logistic aspects. Apart from the development, the introduction of new technology in the country poses many problems related to capability of manufacturing and operating personnel. The performance of 10 M3/8 hrs. day demonstration reverse osmosis plants installed and maintained in the remote villages have provided besides data, experience for analysis of such problems. Optimum capacities and specifications of the reverse osmosis systems have been worked out taking into account competitiveness with conventional water supply systems currently in vogue. Management problems likely to be encountered in operating a large number of small plants spread over a wide area have also been analysed.

Water & effluent water treatment using reverse osmosis

Abstract Reverse osmosis modules in tubular and plate configurations have been developed by the Bhabha Atomic Research Centre, Bombay, India for desalination of brackish ground waters, containing dissolved salts up to a maximum of 10,000 ppm. The modules use cellulose acetate membranes, developed and prepared in our laboratory. Based on a few field trials, the membranes have been found useful for treatment of low level radioactive liquid waste, effluent water treatment from selected process industries and production of boiler feed quality water in combination with conventional demineralisers. This paper discusses the results obtained from the above studies alongwith the salient design features and technoeconomics.

Role of evaporative and membrane desalination technology in solving drinking water problems in India

Abstract This paper deals with the technoeconomic evaluation of both MSF and RO plants developed locally to augment the water supply in the urban as well as rural areas of the country. The operational experience of a 425 m 3 /d MSF plant for seawater desalination and a 50 m 3 /d RO plant designed and manufactured using indigenous know-how at BARC for treatment of effluent from a fertilizer plant are discussed. The performance of small RO plants installed in a number of villages for providing safe drinking water has been evaluated. Projected estimates for large-size MSF and RO plants have been made based on these studies.

Studies on MSF desalination ― process design, construction and startup of a prototype MSF plant in India

Abstract A Desalination Experimental Facility (DEF) comprising multistage flash (MSF) unit of capacity 15 cubic meter/day with three stages had earlier been commissioned and operated for about two years to study the basic parameters of the MSF process. On the basis of operational experience and the data collected from experiments and the information available in literature a 33 stage 425 cubic meter/day MSF plant was designed, fabricated, installed and the same is under commissioning. This prototype plant was first such unit in India. This paper gives the considerations for the design of 425 cubic meter/day prototype MSF plant and the factors to be considered for scale-up to commercial size plants. The problems experienced during the module fabrication, erection and initial startup of the plant are highlighted.