Brief Introduction on H2 generating system I. Description on H2 generating unit 1. flows chart for H2 generator by water electrolysis 1.1 Description on the processing; 1) H2 gas loop and O2 gas loop ; 2) Lye cycling loop; 3) DM water supplementary loop; 4) Cooling water loop; 1.2 Description on the automatic control loops 1) control loop for operating pressure; 2) control loop for balance of H2-lye level and O2-lye level; 3) control loop for operating temperature; 4) Monitoring the H2 purity, O2 purity, lye flows and H2 concentration.
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Brief Introduction on H2 generating system
I. Description on H2 generating unit
1. flows chart for H2 generator by water electrolysis
1.1 Description on the processing;
1) H2 gas loop and O2 gas loop ;
2) Lye cycling loop;
3) DM water supplementary loop;
4) Cooling water loop;
1.2 Description on the automatic control loops
1) control loop for operating pressure;
2) control loop for balance of H2-lye level and O2-lye level;
3) control loop for operating temperature;
4) Monitoring the H2 purity, O2 purity, lye flows and H2concentration.
1. typical flow chart for H2 generating unit by water electrolysis
H2-lyeseparator
O2-lyeseparator
Lye filter
Heatexchanger
electrolyzer
Heatexchanger
To H2 purifier To O2 purifier
or vent
DP
P
CW supply
CW return
T
DM water
DM watersupply
transformer rectifierHV power
supply, 6kV,10kV or 33kV
PLC control HMI monitor
H2 washer O2 washerH2 demister O2 demister
To O2 in H2analyzer
To H2 in O2analyzer
Electrolyser:
Bipolarplate
cathodeanode
diaphragm gasket
Electro-chemical reaction:
Anode : 4OH- -4e=2H2O+O2↑
Cathode : 4H2O +4e=4OH-+2H2↑
General : 2H2O= 2H2↑+ O2↑
Lye solution
Skid of gas-lye treater
H2 –lyeseparator
H2 washer
Explosive-proofjunction box
Cables trench
Frame
H2 in O2analyser
O2 in H2analyser
H2-lyeheat exchanger
H2demister
O2demister
O2 washer
H2-lyeheat exchanger
H2 –lyeseparator
Lyecycling pump
Description on the process of H2 generation unit1. H2 gas loop and O2 gas loop:
H2-lyeseparator
O2-lyeseparator
Heatexchanger
electrolyzer
Heatexchanger
To H2 purifier To O2 purifier
or vent
To O2 in H2analyzer
To H2 in O2analyzer
H2-lyemixture
O2-lyemixture
H2-lyemixture
O2-lyemixture
O2 gasH2 gas
H2 washer O2 washerH2 demister O2 demister
H2 gas loop:
1) H2-lye mixture to enterthe heat exchanger forcooling:
2) The cooled H2-lyemixture entering intoH2-lye separator forseparation of H2 frommixture;
3) The separated H2 gas iswashed in H2 washer toremove the lye drop;
O2 gas loop:
1) O2-lye mixture to enterthe heat exchanger forcooling:
2) The cooled O2-lyemixture entering intoO2-lye separator forseparation of O2 frommixture;
3) The separated O2 gas iswashed in O2 washer toremove the lye drop;
2. Lye cycling loop:
H2-lyeseparator
O2-lyeseparator
Lye filter
Heatexchanger
electrolyzer
Heatexchanger
P
H2 washer O2 washerH2 demister O2 demister
Lye cyclingpump
Lye cycling loop:
The separated lye in the H2-lye separator and O2-lye separator is combined together and flowsinto the lye filter, then is pumped into the electrolyser by lye cycling pump for further waterelectrolysis. The accumulated lye in the H2 washer and O2 washer is overflowed from the washerto the corresponding separator.
H2-lyeseparator
O2-lyeseparator
DM water
H2 washer O2 washerH2 demister O2 demister
3. DM water supplementary loop
Feed-water pump
DM waterDM water
DM water supplementary loop:
After the operation of H2 generator for a period, the DM wateris consumed and the level of H2-lye separator will be lower andlower. The DM water stored in the DM water tank is pumpedinto the H2 washer or O2 washer by Feed-water pump (plungetype) when the H2 generator running and the level of H2separator lower than a certain set-point value. The operation ofthe feed-water pump is fully controlled automatically as per PLCcontrol logic.
4. Cooling water loop:
H2-lyeseparator
O2-lyeseparator
Heatexchanger
electrolyzer
Heatexchanger
CW supply
CW return
H2 washer O2 washerH2 demister O2 demister
Cooling water loop:
With the operation of H2 generator, the heat by water electrolysis shall be brought and thetemperature shall be controlled. The heat is exchanged via lye cycling loop in the heat exchangerwith the cooling water. The cooling water enters into the exchanger to cool the lye fromelectrolyser, the cooled lye flows back to electrolyser via lye cycling loop. The flows of coolingwater is controlled to decide the heat exchanging.
Description on control loops of H2 generation unit1. Control loop for operating pressure
O2-lyeseparator
P
PressureTransmitter
SafetyBarrier
PIDalogrithm
E/Pconverter
PneumaticRegulating valve
+
-PLCSP
OP
t (s)
P (kPa)
SP
PID regulating Curve of operating pressure
Control loop for operating pressure
Regulating valve
PV-1
Operating pressure
O2 washer
SP: Set-point value of operating pressure
2. Control loop for balance between H2-lye level and O2-lye level
O2-lye levelTransmitter
SafetyBarrier
PIDalogrithm
E/Pconverter
PneumaticRegulating valve
+
-PLCH2-level
O2-level
t (s)
SP1
SP2
PID regulating Curve of balance of levels
Control loop for balance
of H2-lye level and O2-lye level
H2-lye levelTransmitter
SafetyBarrier
H2-lyeseparator
O2-lyeseparator
Regulatingvalve LV-1
DP
H2 washer O2 washer
O2-lyelevel
H2-lyelevel
T1 T2
T
T1: period of H2 generator operating;
T2: period of DM water supplementary;
T: One period ; T = T1 + T2 ;
SP1: low limit of DM water supplementary;
SP2: high limit of DM water supplementary;
3. Control loop for operating temperature
Heatexchanger
electrolyzer
Heatexchanger
CWS
CWR
T
H2 washer O2 washer
t (s)
OT (C)
SP
PID regulating Curve of operating temperature
Operating temperature
TemperatureTransmitter
SafetyBarrier
PIDalogrithm
E/Pconverter
PneumaticRegulating valve
+
-PLCSP
OT
Control loop for operating temperature
SP: Set-point value of operating temperature
4. Monitoring for H2 purity, O2 purity, lye flows and H2 concentration
H2-lyeseparator
O2-lyeseparator
Lye filter
Heatexchanger
electrolyzer
Heatexchanger
H2 washer O2 washer
To O2 in H2analyzer
To H2 in O2analyzer
Lye flows
Lye pump
Note:
Action of alarm and / or interlock will be taken, in case the monitored parameters exceeds to their alarm /interlock set point values, to protect the operation of H2 generator. One more, the secondary protection bypressure switch is designed in case the automatic control becomes out of order and the signal from the pressureswitch is transmitted to rectifier to cut off the power to electrolyser directly.
II. Description on the process of H2 purification unit
1. flows chart for H2 purification unit
1.1 Description on the processing:
1) Structure of De-oxy tower;
2) Structure of H2 dryer;
1.2 Description on the automatic control loops
1) gas flows for the H2 purification units
Dryer A : Full service
Dryer B : Regeneration
Dryer C : Half service
Dryer A : Half service
Dryer B : Full service
Dryer C : Regeneration
Dryer A : Regeneration
Dryer B : Half service
Dryer C : Full service
0 hours 8 hours 16 hours 24 hoursZ1 state Z2 state Z3 state
1. typical flow chart for H2 purifying system by catalyst
Raw H2
Gas-filter
Gas cooler
Pneumatic T-way valve
Gas cooler Gas cooler Gas cooler
H2 purifier
H2 dryer A H2 dryer B H2 dryer C
Needle valve
1.1 Description on the process1) Structure of de-oxy tower
Raw H2 gas
H2 gas
Power Supply
380VAC Electricalheater
Catalyst
(Palladium )
Explanation on the structure:
(1) There are two cylinders combinedtogether; the small cylinder is in themiddle of big cylinder;
(2) Inside of the small cylinder, electricalheater is installed and its power isdepended on the gas capacity.
(3) At the bottom of small cylinder, there istemperature sensor to detect the gastemperature;
(4) At the outlet of big cylinder, there isanother temperature sensor to detectthe gas temperature;
(5) The catalyst is filled fully in the spacebetween small cylinder and big cylinder;
Pt100resistor
Pt100resistorPrinciple :
(6) Mini oxygen is reacted with H2 gas with catalyst andmoisture is generated; the moisture is brought by the H2gas flows;
(7) The working of heater is depended on the monitored temps.
Upper port
Under port
2) Structure of H2 dryer
Upper port
Under port
Power Supply
380VAC Electricalheater
Molecularsieve
Explanation on the structure:
(1) There are two cylinders combinedtogether; the small cylinder is in themiddle of big cylinder;
(2) Inside of the small cylinder, electricalheater is installed and its power isdepended on the gas capacity.
(3) At the bottom of small cylinder, there istemperature sensor to detect the gastemperature;
(4) At the outlet of big cylinder, there isanother temperature sensor to detectthe gas temperature;
(5) The desiccant is filled fully in the spacebetween small cylinder and big cylinder;
Pt100resistor
Pt100resistorPrinciple :
(6) When the dryer in service, gas enters via under port andflow out from upper port;
(7) When the dryer in regeneration, gas enters via upper portand flows out from under port.
Service flows
Service flows
Regene service
Regene service
1.2 Gas flows in the hydrogen purification unit1) When the purification unit is in Z1 state
Raw H2
H2 purifierDryer A Dryer B Dryer C
Cooler
Cooler Cooler Cooler
Product H2
T-way pneumaticvalve
Gas-moistureseparator
2) When the purification unit is in Z2 state
Raw H2
H2 purifierDryer A Dryer B Dryer C
Cooler
Cooler Cooler Cooler
Product H2
T-way pneumaticvalve
Gas-moistureseparator
3) When the purification unit is in Z3 state
Raw H2
H2 purifierDryer A Dryer B Dryer C
Cooler
Cooler Cooler Cooler
Product H2
T-way pneumaticvalve
Gas-moistureseparator
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