CA-3163986-C - DEVICE FOR RECIRCULATING AN AT LEAST PARTIALLY GASEOUS COMPOSITION CONTAINING HYDROGEN AND FUEL CELL SYSTEM

CA3163986CCA 3163986 CCA3163986 CCA 3163986CCA-3163986-C

Abstract

The present invention relates to a device (1, 30) for recirculating an at least partially gaseous composition containing hydrogen, wherein the device (1, 30) is a dry rotary pump comprising a first rotary shaft (13) and a second rotary shaft (14) respectively driving a first piston with jaws (8) and a second piston with jaws (9) rotating in a pumping chamber (2) comprising an inlet orifice (11) and an outlet orifice (10) for the gaseous composition, the first rotary shaft (13) and the second rotary shaft (14) being configured to be rotated by a drive system (17, 18) located in a gear chamber (4), wherein the device (1, 30) comprises a first pair of seals (19) and a second pair of seals (20), each comprising a first seal (19a, 20a) and a second shaft seal (19b, 20b), the first pair of seals (19) being provided around the first rotary shaft (13) and the second pair of seals (20) being provided around the second rotary shaft (14) between the pumping chamber (2) and the gear chamber (4), wherein the device (1, 30) comprises a pressure equalising chamber (25) that is fluidly connected to a gap (24) present between the first shaft seal (19a, 20a) and the second shaft seal (19b, 20b) of the first and the second pair of shaft seals (19, 20) to regulate the pressure in the gap (24), wherein the gear chamber (4) is fluidly connected to the gap (24), and wherein the pumping chamber (2) is fluidly connected to the first shaft seal (19a) of the first pair of shaft seals (19) and to the first shaft seal (20a) of the second pair of shaft seals (20) by means of a pulse attenuation chamber (22). The present invention also relates to a fuel cell system (40, 50, 60, 70, 80, 90) comprising a recirculation device according to the present invention.

Inventors

Theo Bilger
Boris Kossek
Matthias Benz
Yohann Perrot

Assignees

BUSCH PRODUKTIONS GMBH

Dates

Publication Date: 20260505
Application Date: 20200217

Claims (1)

23 Claims 1. A device for recirculating a composition that is at least partially gaseous and contains hydrogen, wherein the device is a dry rotary pump comprising a first rotary shaft and a second rotary shaft driving, respectively, a first claw piston and a second claw piston rotating in a pumping chamber comprising an inlet and an outlet for the gaseous composition, the first rotary shaft and the second rotary shaft being configured to be driven in rotation by a drive system located in a gear chamber, the device comprising: a first pair of seals and a second pair of seals, each comprising a first shaft seal and a second shaft seal, the first pair of seals being provided around the first rotary shaft and the second pair of seals being provided around the second rotary shaft between the pumping chamber and the gear chamber, a pressure equalization chamber which is in fluidic connection with a gap present between the first shaft seal and the second shaft seal. The first and second pairs of shaft seals regulate the pressure in the gap, the gear chamber being in fluidic connection with the gap, and the pumping chamber being in fluidic connection with the first shaft seal of the first pair of shaft seals and with the first shaft seal of the second pair of shaft seals via a pulsation damping chamber. The device according to claim 1, wherein at least one of the shaft seals among the first shaft seal of the first pair of shaft seals, the second shaft seal of the first pair of shaft seals, the first shaft seal of the second pair of shaft seals, and the second shaft seal of the second pair of shaft seals is a lip seal. 3. The device according to claim 1 or 2, wherein the fluidic connection between the gap and the gear chamber is made via a pressure equalization channel provided in the first rotating shaft and/or in the second rotating shaft. 4. The device according to claim 3, comprising a lubricant filter between the pressure equalization channel and the gear chamber. 5. The device according to any one of claims 1 to 4, wherein a regulating inlet is provided for regulating the pressure in the pressure equalization chamber from outside the device. 6. The device according to any one of claims 1 to 5, wherein the pulsation dampening chamber is in fluidic connection with the pressure equalization chamber via a membrane permeable to hydrogen gas but impermeable at least to water molecules in liquid and gaseous form. 7. The device according to any one of claims 1 to 6, wherein the fluidic connection between the pulsation dampening chamber and the pumping chamber is at least partially labyrinthine. 8. The device according to any one of claims 1 to 7, wherein the pulsation dampening chamber is in fluidic connection with a discharge outlet 25. 9. The device according to any one of claims 1 to 8, wherein the inlet orifice of the pumping chamber is oriented to allow discharge of a liquid under the effect of gravity. 10. The device according to any one of claims 1 to 9, configured to raise the pressure of the at least partially gaseous hydrogen-containing composition 5 at the inlet of a fuel cell to a pressure range of up to 15 bar. 11. A fuel cell system comprising a gaseous composition reservoir comprising at least partially hydrogen, the reservoir being connected to an inlet of a fuel cell, the system comprising a device according to any one of claims 1 to 10, an outlet of the fuel cell being connected to the inlet port of the recirculation device and the outlet port of the recirculation device being connected to the inlet of the fuel cell. 12. The fuel cell system according to claim 11, comprising a water separator in fluidic connection with the outlet of the fuel cell and with the inlet port of the recirculation device. 13. The fuel cell system according to claim 12, comprising a relief valve in fluidic connection with the relief outlet of the water separator. 14. The fuel cell system according to any one of claims 11 to 13, wherein the control inlet of the recirculation device is in fluidic connection with the tank. 15. The fuel cell system according to any one of claims 11 to 14, wherein the discharge outlet of the recirculation device is in fluidic connection with the discharge outlet of the water separator.

Description

1 Device for the recirculation of a composition at least partially gaseous containing hydrogen and fuel cell system Technical field of the invention The present invention relates in a first aspect to the field of devices for the recirculation of a composition at least partially gaseous, in particular a composition at least partially gaseous containing hydrogen. The present invention relates more specifically to the field of devices for the recirculation of a partially gaseous composition containing hydrogen in a fuel cell, in particular a fuel cell for motor vehicles. In a second aspect, the present invention relates to a fuel cell system allowing the recirculation of a partially gaseous composition containing hydrogen. State of the art In a fuel cell system, hydrogen and gaseous oxygen are necessary for the production of electricity. To help remove the water generated by the hydrogen and oxygen reaction in the fuel cell, the cell is supplied with gas at a higher flow rate than can be converted. Thus, a fuel cell discharges a composition that is mostly partially gaseous and contains unreacted hydrogen gas (called hydrogen exhaust gas) that has not been used in the fuel cell. In order to be able to use this hydrogen exhaust gas, the fuel cell system is equipped with a 25-cycle hydrogen recirculation circuit to replenish the fuel cell with the hydrogen exhaust gas. To achieve this, the hydrogen recirculation circuit is normally equipped with a hydrogen recirculation device. CA 03163986 2022-7-6 WO 2021/164843 PCT /EP2020/054026 2 II It is known from the prior art to use as a hydrogen recirculation device, an ejector or a Roots-type pump. The latter consists of the pump part and the motor part including an electric drive motor. A rotating shaft extends from the electric motor of the drive unit to the pumping unit and a pair of rotors is housed in the pumping chamber. When the two rotors are set in motion by the rotation of the rotating shaft driven by the engine, the hydrogen exhaust gas is drawn into the pumping chamber, then discharged from the latter and reintroduced into the fuel cell. It is important that a pump dedicated to hydrogen recirculation be configured in such a way as to prevent the hydrogen exhaust gas drawn into the pumping chamber from entering the engine unit or the hydrogen concentration in the engine unit from reaching a value at which there is a risk of explosion. To do this, the 15 devices known from the prior art use a shaft seal which is normally provided between the gear chamber and the motor around the rotating shaft(s). The shaft seal is designed to prevent leaks of gaseous hydrogen from the pump chamber along the rotating shaft to the engine, thus preventing the hydrogen concentration in the engine unit from becoming an explosive 20 atmosphere. However, hydrogen gas can pass through shaft seals. Hydrogen thus diffuses from the pumping chamber to the engine unit, producing a potentially dangerous increase in the concentration of hydrogen in the engine. To remedy this problem, hydrogen pumps have been proposed in which a flow of gas is actively introduced into the engine unit to pass through it and to carry with it the hydrogen that has potentially passed through the shaft seal. Unfortunately, although these pumps help to limit the danger of explosion due to an increase in the concentration of hydrogen 30 in the motor unit, these pumps do not guarantee that the water molecules which are contained in the at least partially gaseous composition to be recirculated cannot enter the pump drive chamber and/or CA 03163986 2022-7-6 WO 2021/164843 PCT /EP2020/054026 3 in the motor unit. Such contamination of the inside of the pump is problematic because it usually causes the pump to malfunction. Hydrogen pump line, in particular a pump for the recirculation of hydrogen in fuel cells in the automotive field, must also meet a number of additional requirements, namely (the list is not exhaustive): - meet the maximum external hydrogen leakage standard of 10 Ncm3/h; - be able to operate over a wide adjustment range which can extend over a ratio of up to 1:20 and, in particular, reach a maximum speed of 12,000 rpm; - must be able to operate over a wide range of ambient and gas inlet temperatures, in particular from -40°C to 100°C; 15 - must be able to operate, due to the supply voltages of the fuel cell, at nominal voltages of 12 to 800 VDC, particularly 24 VDC, 48 VDC, 200 VDC, 400 VDC or 750 VDC and must have a high efficiency; and - must, due to the sensitivity of the bipolar plates of the fuel cell or the membranes with substances such as lubricants, use suitable substances in the pumping chamber and in the motor unit. The main challenge therefore lies in the different behavior of the fuel cell, such as the different functional cycles and operating pressures, temperatures in the automotive sector, the quantity of water, etc. CA 03163986 2022-7-6 4 There is therefore a need for a robust and flexi