RU2560883C1 - Method of operating solid-polymer water electrolyser - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of operating a solid-polymer water electrolyser, which includes applying dc supply voltage and feeding reaction water into the electrolyser, heating the solid-polymer electrolyser and the reaction water to operating temperature which corresponds to a given electrolysis current while monitoring the present electrolysis current and temperature values, measuring the operating temperature of the solid-polymer water electrolyser which provides the given electrolysis current value, and breaking down water at said temperature and electrolysis current into hydrogen and oxygen. The method is characterised by that measurement of the operating temperature of the solid-polymer water electrolyser is carried out once the electrolysis current during heating reaches its maximum value and begins to fall, having reached the given value.

EFFECT: use of the present invention provides high-speed thermal stabilisation of the electrolysis cell.

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Description

The invention relates to electrochemistry and can be used in the operation of solid polymer (TP) electrolyzers of water (EV), as well as electrochemical generators (ECG) made on the basis of proton-conducting membranes of the Nafion type (domestic version - MF-4SK).

The generally accepted method of operating electrochemical plants with EV or ECG is known, when these units together with the working fluid (reaction water or hydrogen and oxygen) are first heated, and then they are already operating in stationary mode. In some cases, heat accumulators are used to start the heating of the electrochemical generator, and in the ECG + EV regenerative system, the electrolyzer is heated with the heat generated by ECG (application No. 2008123214, 01/10/2010, IPC: C25B 1/04 (2006.01)).

As a prototype chosen technical solution proposed in «DEVELOPMENT OF A HIGH PRESSURE PEM ELECTROLYZER: ENABLING SEASONAL STORAGE OF RENEWABLE ENERGY , RA Engel, GS Chapman, CE Chamberlin and PA Lehman, 15 ^{th Annual US Hydrogen Conference, Los Angeles} , CA, April 26-30, 2004 ”for solid polymer water electrolyzer. Here, to start the TP EV with the Nafion membrane, a procedure is used that includes:

- turning on the power supply of the EV (constant voltage);

- inclusion of water circulation through the electrolyzer, its heating to the working temperature (36-50 ° C) and the corresponding value of the electrolysis current;

- control of current values of electrolysis current and temperature;

- fixing the operating temperature of the solid polymer electrolyzer of water, ensuring its predetermined performance, and the corresponding value of the electrolysis current;

- generation of gases - hydrogen and oxygen - in stationary mode at operating temperature and electrolysis current.

The disadvantage of the prototype is its thermal inertia - to regulate in this way can only be quite slow thermal processes. Pulse temperature fluctuations in individual electrolysis cells (EJ), especially the overheating of individual zones on their membranes, is not able to fend off such a device. Meanwhile, it is precisely in these cases that burnout of the EE most often occurs, which leads to the occurrence of an explosive situation. It should be noted at the same time that the membrane burns out in those parts of it that do not come into contact with liquid water, since in the gas cavities near the membrane surface the heat sink is several orders of magnitude worse than in water.

The objective of the invention is the provision of high-speed thermal stabilization of EJ by damping possible pulse and local overheating of the membrane.

The technical result of the invention is to increase the reliability of the electrolysis cells, reduce the likelihood of burnout of their proton-conducting polymer membranes and prevent an explosive situation.

The technical result is achieved due to the fact that in the method of operation of the solid polymer electrolyzer of water, which includes supplying a constant supply voltage and reaction water to it, heating the solid polymer electrolyzer and reaction water to a working temperature corresponding to a predetermined value of the electrolysis current with monitoring of the current values of the electrolysis current and temperature, fixing the working temperature of the solid polymer electrolyzer of water, providing a given value of the electrolysis current, and the subsequent decomposition of water and a given temperature and current electrolysis into hydrogen and oxygen, operating temperature fixing a solid polymer water electrolyzer is performed after the electrolysis current in the heating process reaches its maximum value and begins to fall, having reached a predetermined value.

The invention is illustrated in the drawing (figure 1), which shows a General view of the temperature characteristics of the proton conducting membrane Nafion.

The essence of the invention lies in the fact that high-speed thermal stabilization of electrolysis cells is provided due to the specific temperature characteristics (TX) of the Nafion membrane, that is, the dependence of its conductivity on temperature (Yu.A. Dobrovolsky et al. “Proton-exchange membranes for hydrogen-air fuel cells” , “Russian Chemical Journal”, 2006, vol. L, No. 6, p. 97). The conductivity of the membrane and, accordingly, the electrolysis current increases in proportion to the temperature, and having reached its maximum i _max (point C), it drops sharply. In the area of growth of TX, an arbitrary operating point A is unstable (Fig. 1). Indeed, any random short-term temperature change in one direction or another leads to a change in current in a direction that stimulates a further change in temperature ("more-more", "less-less"). As a result, heating or cooling is increasing, and the stability of the operating mode at point A is ensured only by the thermal control system (CTP) of the electrolysis unit.

In this case, the STR, which determines the operating temperature (T ₁ ), due to its inertia, cannot damp short-term temperature deviations, especially the formation of local overheating zones on the surface of the EH membranes (the cause of burnout of the membrane).

If you work on the decreasing section of TX at point B at the same electrolysis current (i ₀ ), but a higher temperature (T ₂ ), then the thermal state of the membrane and individual sections of its surface will be stable. In this case, temperature and current deviations will cancel each other out (“more-less”, “less-more”). Thus, the presence of negative feedback between these operating characteristics of the electromagnet provides “thermal auto-stabilization” of the cell. Moreover, the small thickness of the membrane ensures its low thermal inertia and, as a consequence, the synchronism of current and temperature fluctuations.

The method is implemented as follows.

A constant voltage supply voltage from the power source and reaction water are supplied to the solid polymer water electrolyzer. Just as with the well-known method of starting an electrolysis unit, the solid-polymer water electrolyzer and reaction water are heated with the help of a CTP electrolysis unit to a temperature T ₁ , which provides a given EV output and an electrolysis current i ₀ . In this case, the thermal regime of the EV is not stabilized, but the further heating of the solid polymer electrolyzer and reaction water is continued. The increase in the electrolysis current and temperature, which occurs due to the operation of the STR and the heat generation of the electrolyzer itself, continues. After reaching the maximum value of i _max (at a temperature of ≈80 ° C), the electrolysis current begins to fall, despite the fact that the temperature is still growing. The fixation of the operating temperature of the solid polymer water electrolyzer is carried out using the STR at the previous value of the electrolysis current i ₀ , but at a higher temperature T ₂ (T ₂ > T ₁ ). In the future, the operation of the EV occurs in a stationary mode with a given performance and current i ₀ , but at a temperature of T ₂ . At the same time, despite the higher temperature level, the thermal regime of the EH membranes is more stable with respect to short-term temperature fluctuations of the membrane itself and local zones on its surface.

Monitoring the current values of the electrolysis current and temperature, fixing the operating temperature, providing a given performance and the corresponding value of the electrolysis current, is carried out using the STR electrolyzer and a control system for monitoring and parameters of the electrolysis unit.

Thus, the proposed invention improves the reliability of the solid polymer cell, reducing the likelihood of burnout of its membranes.

Claims (1)

A method of operating a solid polymer water electrolyzer, including supplying a constant supply voltage and reaction water to it, heating the solid polymer electrolyzer and reaction water to a working temperature corresponding to a predetermined value of the electrolysis current with monitoring the current values of the electrolysis current and temperature, fixing the operating temperature of the solid polymer water electrolyzer, providing a predetermined the value of the electrolysis current, and the subsequent decomposition of water at a given temperature and electrolysis current into hydrogen and oxygens, characterized in that the fixation of the working temperature is carried out a solid polymer electrolytic water after electrolysis current in the heating process reaches its maximum value and begins to fall, having reached a predetermined value.