A tiny drop of water brings "acceleration" to hydrogen energy

Hydrogen energy is a secondary energy source with abundant sources, green and low carbon, and wide applications. It is of great significance to reduce carbon dioxide and other greenhouse gas emissions and achieve carbon peak and carbon neutrality goals. In the future national energy system, hydrogen energy will become an important component and an important carrier for the terminal to achieve green and low-carbon transformation. The hydrogen energy industry is a strategic emerging industry and a key development direction for future industries. With technological progress and application promotion, hydrogen energy is expected to play an increasingly important role in the energy field and contribute to sustainable development.

Hydrogen production by water electrolysis is green, environmentally friendly, flexible in production, and high in purity. It is one of the ideal green production technologies. Hydrogen production by water electrolysis is a technology that uses electrical energy to decompose water into hydrogen and oxygen. An electrolytic cell is composed of a pair of electrodes immersed in an electrolyte, separated by a diaphragm to prevent gas penetration. Under the action of direct current, water is electrolyzed, hydrogen is released at the cathode, and oxygen is released at the anode.

The alkaline water electrolysis hydrogen production system mainly includes five parts: electrolyzer, gas-liquid separation, water replenishment and alkali preparation, DC power supply and control system. Consider whether to configure the hydrogen purification device according to the gas purity requirements. The hydrogen production system pumps the prepared alkali solution into the hydrogen production system through the alkali preparation pump, and supplies direct current to the electrolyzer. When the electrolysis current rises to a certain value, the water in the electrolyzer is electrolyzed into hydrogen and oxygen. With the help of the head of the circulation pump and the gas lift, it enters the hydrogen separator and oxygen separator respectively. Under the action of gravity, the hydrogen and alkali solution are separated, and the electrolyte flows back to the alkaline water electrolyzer. The gas enters the gas cooling system. The cooled gas enters the gas droplet collector to further remove the droplets in the gas. The droplets return to the alkali solution. After the gas is tested for purity, it is emptied or collected for treatment.

On September 27, 2023, the 8MW-class alkaline water electrolysis hydrogen production steady-state transient test and detection platform was officially completed. The test platform is designed to be suitable for hydrogen production system processes of different types of alkaline electrolyzers. It adopts innovative process flows and a full range of detection and monitoring systems. Through the alkaline water electrolysis hydrogen production process control technology that adapts to wide load regulation control, the gas-liquid separation back-end circulation and the electrolyzer alkali liquid supply are decoupled, reducing the impact of the auxiliary machine operation status on the electrolyzer performance test; design a fluctuating operation flow buffer device, and perform multi-process separation and nonlinear regulation of alkali liquid and hydrogen/oxygen under pressure conditions; study new pressure difference control strategies, increase the control dimension of hydrogen and oxygen impurities, and expand the minimum operating limit of the electrolyzer; and observe the gas-liquid separation two-phase flow state in real time. The test platform can achieve stable control and wide-range adjustment of the electrolyzer alkali liquid flow, inlet temperature, and outlet pressure difference, accurately measure the technical indicators of core components such as rectifiers, electrolyzers, and gas-liquid separation, and evaluate the steady-state transient performance of the water electrolysis hydrogen production system.

Under the background of "dual carbon", my country's hydrogen energy industry is booming. As a specification, the technical standards of this test platform provide equipment selection, type testing and operation verification for large-scale grid-connected or off-grid hydrogen production demonstration projects; and provide actual data support for the quality evaluation and standard formulation and revision of water electrolysis hydrogen production systems. It will make the development of the hydrogen energy industry more regular, ensure the safety and reliability of hydrogen energy equipment, and promote the development of hydrogen energy technology.

This article is compiled based on the expert interview "8MW-class alkaline water electrolysis hydrogen production steady transient test platform"

China Association for Science and Technology Department of Science Popularization

Xinhuanet

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