Post on 01-Nov-2014
description
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