Water electrolysis hydrogen production process and control system
The process of water electrolysis hydrogen production equipment is divided into hydrogen, oxygen, electrolyte, raw material pure water and cooling water. The equipment is equipped with the following control points to monitor various process parameters, which are described as follows:
Hydrogen system
The product hydrogen is drawn from the hydrogen ports of the pressure plates at both ends of the electrolyzer, and enters the hydrogen separator together with the entrained electrolyte for separation. The rising hydrogen passes through the hydrogen cooler, while the electrolyte stays in the hydrogen separator. The hydrogen cooler is a shell-and-tube heat exchanger. The hydrogen goes on the tube side and the cooling water goes on the shell side. At the hydrogen outlet of the cooler, a wire mesh catcher is arranged to capture the mist droplets in the hydrogen and remove them. Return to the hydrogen separator. After the hydrogen leaves the trap, it enters the hydrogen steam-water separator, and its condensate is discharged by the blowdown valve. The product hydrogen is output through a pneumatic membrane control valve.
Detection points of this system:
①Detection of hydrogen tank temperature: The detection point is set on the outlet pipe of the hydrogen separator. After the measured signal is sent to the PLC, the hydrogen tank temperature can be displayed on the touch screen.
② Detection of the liquid level difference between the two separators: Differential pressure transmitters are installed on the fuze ports of the hydrogen and oxygen separators to measure the liquid level of the two separators respectively. After the signal is sent to the PLC, after calculation, the corresponding signal is output, and the air pressure signal converted by the electrical converter is sent to the hydrogen side pneumatic control valve to adjust the valve position of the valve, so that the liquid of the two separators can be adjusted. bits remain within the set range.
③ Detection of hydrogen temperature: a bimetal thermometer is installed to display the temperature of hydrogen on site.
④ Detection of hydrogen purity: The dried hydrogen is passed through the instrument of the hydrogen purity analyzer. The measured signal is sent to the PLC, and the hydrogen purity and alarm signal can be displayed on the touch screen.
⑤ Detection of hydrogen back pressure: An electric contact pressure gauge is installed on the pipeline behind the valve of the hydrogen membrane control valve to indicate the hydrogen back pressure on site, and output an electrical signal to the PLC. When the pressure exceeds the set value, an alarm will be issued Signal.
oxygen system
The process of this system is exactly the same as that of the hydrogen system, and the detection points are also five, with slightly different functions.
①The detection, display, alarm and other functions of the bath temperature.
② Detection of system pressure: A pressure transmitter is installed on the gas phase fuze port of the oxygen separator. The measured signal is converted into a pneumatic signal, and then sent to the oxygen side pneumatic regulating valve to give a suitable valve position.
⑧ Detection of oxygen temperature: equipped with a bimetal thermometer, the oxygen temperature is displayed on site.
④ Detection of oxygen purity: After drying, oxygen is sent to the PLC through the oxygen purity analyzer, and the measured signal is sent to the PLC, and the oxygen purity and alarm signal are displayed on the touch screen.
⑤ Detection of system pressure: An explosion-proof electric contact pressure gauge is installed on the pipeline in front of the oxygen film control valve. In addition to the pressure displayed on site, it also outputs an electrical signal to the PLC. When the pressure exceeds the standard, the output interlock signal can be used. stop the system.
Electrolyte system
In the process of hydrogen production by water electrolysis, the electrolyte is entrained into the hydrogen and oxygen separator along with the product gas, and then returned to the electrolyzer through the forced circulation of the lye pump. The inlet of the lye pump is connected with the communication pipes of the hydrogen and oxygen separators. After the pump is started, the electrolyte in the separator flows through the lye cooler, and the lye goes through the filter, and finally returns to the electrolyzer.
The generated heat of the electrolysis reaction is taken away in the lye cooler by means of lye circulation. The replenishment of raw material water also enters the electrolytic cell with the circulation of the electrolyte.
On this system, there are two detection points:
①Alkali temperature detection: Platinum resistance is installed on the outlet line of the lye filter to detect the temperature of the lye entering the electrolytic cell. The measured signal is converted into a pneumatic signal and sent to the cooling water pneumatic valve to adjust the valve opening of the valve, control the flow of cooling water, and maintain the temperature of the lye.
②Detection of lye circulating volume: There is a flow meter on the lye pipeline. The flow meter indicates the lye circulating volume on site and outputs the measured signal. If the circulating volume is lower than a certain set value, the PLC will output an alarm. And the interlock signal, and finally make the system stop automatically.
Raw water system
In the process of water electrolysis, the raw water is continuously consumed by being decomposed into hydrogen and oxygen. In order to continue the production, the raw water is replenished into the system.
The replenishment of raw water is completed by the replenishment pump. The plunger pump is used to replenish the water. The start and stop of the pump are controlled by the signals measured by the two differential pressure transmitters. When the value is lower than the set value, the PLC will output to start the pump. Otherwise, stop the pump.
The inlet pipe of the make-up pump is connected with the outlet pipeline of the water tank and the alkali tank, and the make-up pump is activated by starting. It is added to the water electrolysis hydrogen production system, and enters the lye of the separator through the check valve.
Cooling water system
The cooling water is introduced from the outer pipe, and the water pressure should be above 0.2MPa. After the cooling water enters the system, it enters the gas alkali cooler all the way, and then enters the alkali liquid cooler through the cooling water pneumatic control valve. The valve of the control valve The position is controlled by the alkali temperature measured by the platinum resistance, and the cooling water and the alkali liquid flow in the opposite direction. After the cooling water exits the alkali liquid cooler, it enters the return water main pipe. This pipe is directly connected to the external cooling water circulation device.
① Detection of cooling water pressure: On the inlet pipe of cooling water, a spring pressure gauge is installed to detect the inlet pressure of cooling water.