RU2290725C2 - Method for servicing flow-type alkali fuel cell battery - Google Patents

Abstract

FIELD: direct-current power supplies using oxygen, hydrogen, and alkali electrolyte.

SUBSTANCE: proposed method includes heating of fuel cell battery and its working alkali solution followed by working gas supply. Fuel cell battery is heated by pumping through it working alkali solution preheated under adiabatic conditions by dissolving crystal alkali in water or by diluting more concentrated alkali solution with water; working gases are supplied upon their heating with working alkali solution. Such design of fuel cell battery provides for its high-speed starting with reduced power requirement for its heating and dispenses with external power supplies for its heating to minimal operating temperature.

EFFECT: ability of starting alkali fuel cell battery at low ambient temperatures.

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Description

The invention relates to DC power sources, and more specifically to power plants (EU) on fuel cells (FC), operating on oxygen and hydrogen. In this case, flow-type fuel cells (or with "pumping electrolyte") that operate with a constant circulation of alkaline solution are considered.

It is known that the start-up of power plants on fuel cells is usually carried out by self-heating: they simply start supplying working gases to the fuel cell (BFC) battery and pumping an alkali solution through it. It also uses heating from an external source of electricity. Such methods, taken as analogues [1], take a lot of time, or require significant energy consumption from an external source, and before that, the BFC must be stored at a sufficiently high ambient temperature. It is impossible to start such a BFC at negative temperatures - crystallization begins in an alkaline solution, its viscosity increases by two orders of magnitude, etc. For example, a 30% KOH solution already at a temperature of + 5 ° C becomes cloudy and becomes jelly-like.

From the disadvantages of this method of starting the BFC free technical solution [2], adopted as a prototype. In this case, before starting, the EC (engine) is heated by hot liquid circulating in the heating circuit. In this case, the heating of the liquid is carried out using a gas burner.

The disadvantages of the prototype are the following features:

1. The heating fluid is not the working fluid of the EA (engine), it is only an intermediate coolant. Therefore, if you apply this starting method to a BFC containing a lot of heat-intensive alkaline solution, the process of heat transfer from the intermediate coolant to the working alkaline solution will be greatly delayed.

2. This method does not work if the gas burner does not work (for example, there is no gas).

The objective of the proposed solution is, therefore, to reduce the heating time of the BFC containing a significant amount of heat-consuming alkaline solution, as well as providing the possibility of starting such a BFC in the case when external sources are absent (for example, in an emergency).

The problem is solved by the fact that during operation of an alkaline battery of flow-type fuel cells, including heating it and its working alkaline solution, as well as the subsequent supply of working gases, heating the battery of fuel cells is performed by pumping through it a working alkaline solution, previously heated under adiabatic conditions, and the supply of working gases is carried out after they are heated with a working alkaline solution, while the working alkaline solution is heated by dissolving crystalline alkali in water or by dilution with water of a more concentrated solution of this alkali.

The essence of the proposed method is as follows. Alkaline BTE flow type contains a lot of aqueous alkali solution. For example, a BFC with a dry weight of ~ 60 kg requires ~ 25 l of solution for its operation. Since the heat capacity of water (~ 4 kJ / kg) is noticeably greater than the heat capacity of the materials of which the battery is made (~ 1 kJ / kg), when heating such a BFC, most of the heat is spent on heating the solution. In this regard, it is advisable to heat the solution separately from the battery, and then warm the battery itself with a circulating solution already heated. You can also heat the working gases with the same solution before they are fed to the fuel cell.

In addition, the proposal uses the opportunity to obtain a hot alkaline solution not by heating cold, but using the heat of hydration (dissolution) of crystalline alkali, that is, in the process of preparing the solution itself. As practice has shown, in the preparation of 30% NaOH, the temperature of the finished solution rises to almost 100 ° C.

For BFCs with the weight characteristics mentioned above (dry weight - 60 kg, alkaline solution weight ~ 30 kg), the heat generated during hydration is sufficient to heat the BFC (with alkali) to 50 ÷ 60 ° C at an initial battery temperature of 0 ÷ 20 ° C. Thus, it is possible to warm up even the “cold” BFC to operating temperature without using external energy sources.

This can be useful when starting EC on alkaline fuel cells in an emergency (for example, during an emergency in cold conditions).

The proposed method is implemented as follows. The cold alkaline solution outside the BFC is heated to the calculated temperature (exceeding the BFC operating temperature) and pumped through the battery until it reaches the minimum operating temperature. After that, working gases are supplied to the BTE, and the battery begins to self-heat to its optimum operating temperature. In order not to cool the BFC with working gases (for example, at negative air temperatures), they can be preliminarily passed through the same alkaline solution and heated to the same temperature as the BFC (for this, gas-liquid heat exchangers placed in an alkaline solution can be used).

In some situations (for example, when the alkali heater does not work), a hot alkaline solution is obtained by dissolving the calculated amount of crystalline alkali in water and preventing cooling of the resulting solution (for example, in a thermally insulated container), after which all steps are repeated. Instead of crystalline alkali, you can also use its more concentrated solution, but the heating will be less.

A positive effect in this technical solution is:

- the possibility of accelerated start of BTE with reduced energy consumption for warming up the battery;

- the possibility of heating the BFC to the minimum operating temperature without the use of external energy sources;

- the ability to run alkaline BTE flow type at low ambient temperatures.

These circumstances make it possible to use this technical solution in the operation of autonomous power plants with alkaline fuel cells, including at low ambient temperatures.

Literature

1. N.V. Korovin. Electrochemical generators, M., (p. 93), 1974

2. Pre-heater for gas fuel, RU Pat. 2138676, 1997

Claims (1)

A method of operating an alkaline battery of flow-type fuel cells, including heating it and its working alkaline solution, as well as the subsequent supply of working gases, characterized in that the heating of the battery of fuel cells is carried out by pumping through it a working alkaline solution, previously heated under adiabatic conditions by dissolving in water of crystalline alkali or by diluting with water a more concentrated solution of this alkali, and the supply of working gases is carried out after they are heated with a working alkaline solution Oromo.