Composition of Water Electrolysis Hydrogen Production System

Hydrogen production by water electrolysis is a technology that decomposes water to produce hydrogen and oxygen under the action of direct current. It follows Faraday's law of electrolysis. Under the action of direct current, water is decomposed into one part hydrogen and 1/2 part oxygen.
 
Water Charging System
The raw water first enters the demineralized water preparation device, and after the process of ultrafiltration and secondary reverse osmosis, it then enters the lye tank, alkali distribution water tank and cooling device water tank.  The water in the lye tank and the alkali distribution tank will be prepared into lye, which will be sent to the air-liquid separator by the alkali distribution pump and enter the lye circulation system to supplement lye for the lye circulation system. The water in the water tank of the demineralized water cooler flows through the water-water heat exchanger under the output of the circulating water pump, and then enters the multiple coolers in the gas-liquid separator and hydrogen purification device, and finally returns to the water tank of the cooler.
 
Lye Circulation System
The electrolyte coming out of the electrolytic cell will enter two channels: One is rich in hydrogen, the other rich in oxygen. The electrolyte in both channels will enter respectively in  hydrogen separator and oxygen separator in the gas-liquid separation device where hydrogen and oxygen will be separated. After the separation, the lye in the two channels will meet, and after the process of alkali filter and lye cooler, it will enter the lye circulation pump, under whose pressure the lye will finally return to the electrolyzer, so as to realize the lye recycling in the hydrogen production system.
 
Electrolyzer
The lye from the lye circulation system enters the electrolytic cell, and the water begins to decompose under the action of direct current. Hydrogen and oxygen are produced respectively on the cathode plate and the anode plate of the electrolyzer. These hydrogen and oxygen along with the electrolyte flow from both ends of the electrolyzer into the gas-liquid separation unit.
 
Gas-liquid Separation Unit
Gas-liquid Separation Unit is equipped with hydrogen separation scrubber, oxygen separator, hydrogen cooler, gas-water separator, lye circulation pump and other equipment. The electrolyte containing hydrogen and oxygen pass through hydrogen separator and oxygen separator respectively, and the gas will be separated from electrolyte under the action of gravity. The separated oxygen will be discharged outdoors, while hydrogen will be further washed, cooled, separated and removed from droplets in the separator, and then enter the hydrogen purification unit.
 
Hydrogen Purification Dvice
Catalyzed by the catalyst, a chemical reaction between the hydrogen in the purification device and the residual oxygen in the hydrogen will happen as follow: 2H2+O2=2H2O
After cooling, adsorption and separation, the 99.999% high purity hydrogen will be available.
 
Hydrogen Storage Device
After the pressure is balanced by the hydrogen bus rack, the high purity hydrogen will be distributed to hydrogen storage tank.
 
Hydrogen Supply System
The main process of hydrogen supply system is as follows:
 
 
Hydrogen storage tank → Hydrogen bus → Hydrogen buffer tank → Hydrogen compressor → Hydrogen charging bus (or filling device) → Hydrogen tank group (or long tube trailer).
 
Auxiliary System
The auxiliary system for hydrogen production mainly includes: demineralized water preparation system, refrigeration and heat exchange system, compressed air supply system, lye storage system and nitrogen purging system. The description of each system is as follows:
 
Demineralized Water Preparation System
The demineralized water preparation system adopts conventional filtration, ultrafiltration and secondary reverse osmosis processes to meet the water quality requirement of hydrogen production system.
 
Process of Demineralization System:
Deep well water (with pressure) → disc filter → ultrafiltration device → ultrafiltration water tank → primary reverse osmosis high pressure pump → primary reverse osmosis device → secondary reverse osmosis high pressure pump → secondary reverse osmosis device → demineralized water tank → demineralized water pump → water points in hydrogen production system.
 
Refrigeration and Heat Exchange System
The equipment of refrigeration and heat exchange system  mainly includes buffer water tank, circulation pump, and compression refrigerator.
 
Compressed Air Supply System
The equipment of compressed air supply system mainly includes air compressor, filter, dryer and compressed air storage tank. This project is equipped with a set of instrument air supply device to meet air supply demand of the instrument of the whole hydrogen station. The equipment includes air compressor, air storage tank etc., to meet the gas requirement of instrument in hydrogen production system.
 
Nitrogen Purging System
The equipment of nitrogen purging system equipment mainly includes nitrogen cylinder assembly rack and nitrogen bus rack, which provides inert gas replacement and purging function for hydrogen production system equipment to ensure the safe operation.