Fresh Water Generating Plants I

Distillation

HP and LP Evaporators

Submerged Tube Types

Flash Evaporators

Distilling Plants

vapor

HEAT SOURCE

HEAT SINK

CONDENSEREVAPORATOR

FEED PUMP

DIST. PUMP

brine

BRINE PUMP

distillate

DIST. COOLER

Saturation Pressures & TemperaturesP (abs) P (rel) oF oC

615 psia≈600 psi 489 254

165 psia≈150 psi 366 186

20 psia ≈5 psi 228 109

14.7 psia 0 psi (0 “Hg) 212 100

10 psia 9.6 “Hg 193 89

6.8 psia 16.1 “Hg 174 79

3.2 psia 23.4 “Hg 143 62

1.9 psia 26.1 “Hg 128 53

1.7 psia 26.5 “Hg 119 48

“LP”

Evaporation under vacuum

“HP”

Evaporation under pressure

1 atm.

“CONTAMINATED” EVAPORATOR

HP Evap example –

40 psi vapor

(285oF)

FEED PUMP

CONTAMINATED DRAIN (Inspection)

TANK

Fuel Oil heating,Lube Oil heating,Galley steam, etc.

150 psi AUX STM

Return to DC HTR

DRAINCOOLER

FS

LP Evap example #1 –

142oF vapor

CONDENSER

“SUBMERRGED TUBE”

EVAPORATOR

FEED PUMP

DIST. PUMP

brine

BRINE PUMP

DIST. COOLER

feedwater

A/E

Air drag line

150 psiAux Steam

A/E Drain

130oF

3 psia≈ 24’Hg

5 psiAux Steam

tube nest

T.nestDrain

65-85oF

LP Evap example #2 –

CONDENSER

“FLASH TYPE”

EVAPORATOR

FEED PUMP

DIST. PUMP

brine

BRINE PUMP

DIST. COOLER

feedwater

A/E

Air drag line

150 psiAux Steam

A/E Drain

130oF

5 psiAux Steam

tube nest

T.nestDrain

65-85oF

3 psia≈ 24’Hg

LP Evap example #2 –

CONDENSER

“FLASH TYPE”

EVAPORATOR

FEED PUMP

DIST. PUMP

BRINE PUMP

DIST. COOLER

feedwater

A/E

Air drag line

150 psiAux Steam

A/E Drain

130oF

65-85oF

FD.W HTR172oF

5 psiAux Steam

Fd.HtrDrain

142oF vapor

Brine: 142oF

3 psia≈ 24’Hg

142oF

Why is the liquid-vapor mix inside the evaporator cooler than the feedwater entering?

172oF172oF

Under Evap feed pump pressure (15-20 psig) water boils at > 225oF so feedwater stays liquid at 172o

In evaporator shell (3 psia) water boils at > 142oF but each lb requires 1000 BTU of latent heat to change phase

In cooling to 142o each lb can “donate” 30 BTU of sensible heat to the process

Therefore it takes 33 lbs of feed cooling to 142o in order to create 1 lb of vapor

Multistage (Subm.Tube) EvapFeed

Pump

Distillate Cooler Distiller

Condenser

Air Ejector

80% O/B

Brine O/B Pump

2nd Effect:1.9 psia (26”Hg)

1st Effect:6.8 psia (16”Hg)

5 psiAux Steam

T.nestDrain

174oF vapor

128oF vapor

Flash Chamber

Distillate Pump

To:POTABLE & RES. FEED Tanks

3-way solenoid Dump Valve

Salinity Cell

Vapor Feed Htr

85o88o

121o

131o

164o

126o

90o

2 134

Multistage (Subm.Tube) Evap 3 or more “Effects:”

1st Effect Heat SourceLOWER PRESS & TEMP

Multistage FLASH EvapFeed

Pump

Distillate Cooler Distiller

Condenser

Air Ejector

Brine O/B Pump

2nd Stage:1.7 psia (27”Hg)

Distillate Pump

To:POTABLE & RES. FEED Tanks

3-way solenoid Dump Vavle

Salinity Cell

FEEDHTR

1st Stage:3.2 psia (23”Hg)

5 psiAux Steam

Fd.HtrDrain

142oF vapor

119oF vapor

to bilge

85o88o

133o138o

172o

105o

90o110o

The SALINITY CELL

Distillate

ammeterTRANSFORMER

SALINITY CELL

“AC” source

“Pure” (0 ppm of dissolved solids) distillate is a very poor conductor of electricity

As the salinity increases the conductivity of the distillate increases (seawater is a very good conductor)

A salinity meter measures current although the meter scale is in ppm

Boiler feedwater requires very pure distillate

The three-way valve is set to dump distillate to the bilge if the salinity cell detects impurities greater than 3 ppm

U.S. maximums for drinking water are in excess of 500 ppm!

current

3-way valve “trips”

Fresh Water Generating Plants II

No Steam RequiredFlat-plate Types (e.g., NYREX)

Vapor Compression Types

Reverse Osmosis (RO) Types

The Flat Plate Heat ExchangerFLAT PLATE: many, small

passages carrying hot fluid

FLAT PLATE: many, small

passages carrying cold fluid

Adjacent, alternate plates: heat transferred from warmer to cooler fluid

The Flat Plate Heat ExchangerEnd view …

Actual construction

Flat Plate Distiller

FPHX #2:CONDENSER

MAIN ENGINE

FPHX #1:EVAPORATOR

FEED PUMP

J.W. PUMP

F.W. PUMP

AIR EJECTOR / BRINE EDUCTOR

1.1 psia

104oF VAPOR

≈180oF

… TSES VI

… TSES VI

TSES VI Flat Plate Distiller (NYREX)

FPHX #2:CONDENSER

FPHX #1:EVAPORATOR

FEED PUMP

J.W. PUMP

F.W. PUMP

AIR EJECTOR / BRINE EDUCTOR

1.1 psia

104oF VAPOR

≈180oF

FPHX #3GLYCOL

HTR

150 psi Aux Stm

Drain

Glycol Circ Pump

Flat Plate Distiller (NYREX)

Vapor-Compression Distiller

219oF vapor

2 psig

S.W. Feed

F.W.

Brine

Compressor

Compressed Vapor:

3.2 psig223oF

Electric Heater (start-up only)

Osmosis

Dilute Concentrated

Semi-permeable Membrabe (cellulose fiber or polyamide)

Osmotic pressure

Diffusion

Reverse Osmosis (RO)

Dilute Concentrated

P

ConcentratedDiffusion

Filtration

Osmotic pressure

P>>

Brine

Typical RO membrane canister

HPPump

M

2-stage RO Fresh Water Generator

Brine

1/s HPPump

M

Pre-filter

2/s HPPump

MBooster Pump

F.W.S.W.

UV

Charcoal Filter

recirculating

200 ppm5-20 ppm

Commercial (1-stage) RO Unit

Commercial (1-stage) RO Unit

AMS ER

FW Storage (TSES VI)

STBD IB23 Tons

PORT IB23 Tons

PORT OB28 Tons

CENTER261 Tons

PORT305 Tons

STBD301 Tons

FWD PEAK TANK

105 Tons

AFT PEAK TANK

109 Tons

Reserve Feed Water (MUF)

POTABLE WATER

Distill Tanks