MARINE AUXILIARIES

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Distillation Process Basic example of distillation process • Distillation is the production of pure water from sea water by evaporation and re-condensing. Marine Auxiliaries / WAS / Jan 2021 • Distilled water is produced as a result of evaporating sea water either by a boiling or a flash process. • This evaporation enables the reduction of the 32,000 parts per million of dissolved solids in sea water (32,000PPM) down to one or two present in distilled water. (32gm/1 liter of SW) • The machine used is called an 'evaporator', although the word 'distiller' is also used. Malaysian Institute of Marine Engineering Technology (MIMET)

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Example of tube type FWG Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

The single effect vertical evaporator shown in Fig. 3.24 is still Marine Auxiliaries / WAS / Jan 2021 in common use. It operates with a vapour pressure between 1.34 to 1.48 bar and steam for the heating coils is supplied direct from the boiler. The initial cost for such an evaporator is relatively low, it is also compact and thereby space saving. The shell and dome of the evaporator is made of good quality close grained cast iron and the heating coils are made of solid drawn copper. Mountings provided are: vapour outlet valve, steam inlet, coil drain valve, feed check valve, blow down valve, brine ejector, safety valve, gauge glass with fittings, salinometer cock and a compound pressure gauge. In the diagram, a reducing orifice fitting is shown on the steam inlet. Its purpose is to reduce the pressure of steam entering an evaporator shell in the event of failure of a heating coil. Malaysian Institute of Marine Engineering Technology (MIMET)

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

1. Boiling process (The distillation Marine Auxiliaries / WAS / Jan 2021 equipment works) Sea water is boiled by using a heating coil, and by reducing the pressure to vacuum stage by using ejector in the evaporator shell, boiling can take place at about 60°C. The sea water from the ship's services is first circulated through the condenser and then part of the outlet is provided as feed to the evaporation chamber (Figure 7.6). Hot diesel engine jacket water outlet or steam is passed through the heater nest and, because of the reduced vacuum pressure in the chamber, the sea water will boil. Malaysian Institute of Marine Engineering Technology (MIMET)

The steam produced rises and passes Marine Auxiliaries / WAS / Jan 2021 through a water separator or demister which prevents water droplets passing through. In the condensing section the steam becomes pure water, which is drawn off by a distillate pump. The sea water feed is regulated by a flow controller and about half the feed is evaporated. The remainder of brine /sea water constantly overflows a weir and carries away the extra salty water or brine. A combined brine and air ejector draws out the air and brine from the evaporator. Malaysian Institute of Marine Engineering Technology (MIMET)

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

PPM- Part Per Million. Marine Auxiliaries / WAS / Jan 2021 This is a way of expressing very dilute concentrations of substances. Just as per cent means out of a hundred, so parts per million or ppm means out of a million. Usually describes the concentration of something in water or soil. One ppm is equivalent to 1 milligram of something per liter of water (mg/l) or 1 milligram of something per kilogram soil (mg/kg). In the metric system ppm can be expressed in terms of milligram versus kg where 1 mg/kg = 1 part per million (1 PPM) Malaysian Institute of Marine Engineering Technology (MIMET)

Example of fresh water generator Marine Auxiliaries / WAS / Jan 2021 Malaysian Institute of Marine Engineering Technology (MIMET)



2.Flash Process A. Flash evaporation is the result of a liquid containing a reasonable amount of sensible heat at a particular pressure being admitted to a chamber at a lower pressure. B. The liquid immediately changes into steam, i.e. it flashes, without boiling taking place. C. The sensible heat content, water pressure and chamber pressure are designed to provide a desired rate of vaporisation. D. More than one stage of evaporation can take place by admitting the liquid into chambers with progressively lower pressures. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Saturation temperature means boiling point. The saturation temperature is the temperature for a corresponding saturation p ressure at which a liquid boils into its vapor phase

Single stage flash type FWG Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Figure 7.7 Marine Auxiliaries / WAS / Jan 2021 Malaysian Institute of Marine Engineering Technology (MIMET)

A two-stage flash (multiple effect) evaporator is shown in Figure 7.7. The feed pump circulates sea water through the vapour condensers and the preheater. The heated sea water then passes to the first-stage flash chamber where some of it flashes off. A demister removes any water droplets from the steam as it rises and is then condensed in the first-stage condenser. The heated sea water passes to the second-stage flash chamber, which is at a lower pressure, and more water flashes off. This steam is demisted and condensed and, together with the distilled water from the first-stage, is drawn off by the distillate pump. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

The concentrated sea water or brine remaining in the second-stage flash chamber is drawn off by the brine pump. The pre-heater uses steam to heat the sea water and most of the latent heat from the flash steam is returned to the sea water passing through the condensers. An air ejector is used to maintain the low pressure in the chambers and to remove any gases released from the sea water. Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021



Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

THE ORIFICE Example showing the orifice function The small hole on orifice plates restricts flow which causes the pressure to drop. The pressurecan be measured using pressure gauges before and after the orifice plates whichallows you to determine the flow rate using the Bernoulli’s Equation. Anorifice plate is installed between orifice flanges or a metering unit. Vena contracta is the point in a fluid stream where the diameter of the stream is the least, and fluid velocity is at its maximum, such as in the case of a stream issuing out of a nozzle (orifice). (Evangelista Torricelli, 1643). It is a place where the cross section area is minimum.

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021

Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2021