Hydrogen filter for small portable fuel cell suitable for low temperature operation

Abstract

A hydrogen filtering device for small portable fuel cell suitable for low temperature work, comprising a shell, a first pressure adjusting cavity, a coarse pore filtering structure, an impurity removing filtering structure, a fine pore filtering structure and a second pressure adjusting cavity arranged in the shell in sequence, the coarse pore filtering structure comprising a first filter sheet, a plurality of transverse channels being arranged in the first filter sheet, the impurity removing filtering structure comprising a perfluorosulfonic acid membrane, the perfluorosulfonic acid membrane being brushed with platinum carbon catalyst, the fine pore filtering structure comprising a second filter sheet, a plurality of micropores being arranged in the second filter sheet. Brushing platinum carbon catalyst onto the perfluorosulfonic acid membrane can fix the catalyst and ensure the contact surface area of activated carbon and Pt. The activated carbon can remove ammonia and organic solvents. Platinum can remove carbon monoxide. The carrier of platinum particles is activated carbon, and the size of platinum particles is 5-30 nm, which can achieve super large specific surface area in a small space and better absorb toxic and harmful gases and impurities.

Description

Technical Field

[0001] This utility model relates to the field of physics, and more particularly to fuel cells, especially a hydrogen filtration device for a small, portable fuel cell suitable for low-temperature operation. Background Technology

[0002] Hydrogen filters need to ensure the cleanliness and quality of hydrogen, prevent filter material from entering downstream components with the hydrogen, and meet hydrogen flow requirements. Hydrogen filters vary depending on flow requirements, design, and application scenarios. Current technologies use mechanical filtration, chemical adsorption, or composite filters for ultrapure hydrogen in fuel cell vehicle systems, cleanrooms in semiconductor manufacturing, or industrial hydrogen production systems. These filters are large and heavy, unsuitable for small (less than 100W) portable fuel cell systems. Furthermore, the adsorption materials inside these filters are not suitable for magnesium hydride hydrogen purification. For example, the PALL HH series hydrogen filters from Pall are suitable for high-pressure hydrogen refueling stations and can operate at pressures up to 96.3 MPa, but their diameter is 15 cm, far exceeding the weight tolerance of small portable fuel cell systems.

[0003] Due to current limitations in the development of chemistry and chemical materials, the purity of magnesium hydride, the main raw material for hydrogen production, and some auxiliary hydrogen storage compounds cannot reach 100%. Impurities may include other metals, organic solvents, or plastics introduced during the manufacturing process. During hydrogen production, harmful impurity gases or organic solvents released with the hydrogen must be purified to protect the fuel cell stack. Furthermore, because water participates in the hydrolysis of magnesium hydride, some of this water may be released from the reaction vessel along with the hydrogen. Excessive water entering the fuel cell stack could cause flooding.

[0004] Research has identified gases that significantly damage fuel cell stacks, including various organic solvents, ammonia, and CO. Because the hydrolysis of magnesium hydride is an exothermic reaction, the temperature rises as the hydrogen production process progresses. Consequently, various plastics undergo pyrolysis to produce CO, and residual organic solvents also volatilize. CO can adsorb onto the surface of the fuel cell stack, occupying the catalyst surface and preventing hydrogen from undergoing electrochemical reactions within the catalyst, thus greatly affecting the stack's performance.

[0005] The hydrogen produced by impure magnesium hydride contains impurities such as organic solvents and carbon monoxide. Additionally, some water vapor from the magnesium hydride hydrolysis process enters the filter along with the hydrogen. To improve the overall energy density of the fuel cell stack system, the filter's weight and volume must be as small as possible. However, existing filter technologies cannot achieve these functions. Utility Model Content

[0006] The purpose of this invention is to provide a hydrogen filtration device for a small, portable fuel cell suitable for low-temperature operation, which solves the technical problems of existing hydrogen filters, such as poor removal of impurities and organic solvents, unsuitable size and weight for small portable fuel cell systems, and difficulty in operating in low-temperature environments.

[0007] This utility model provides a hydrogen filtration device for a small, portable fuel cell suitable for low-temperature operation, comprising a housing with an inlet and an outlet at both ends. Within the housing, between the inlet and outlet, along the length of the housing, are sequentially arranged a first pressure adjustment chamber, a coarse-pore filter structure, a decontamination filter structure, a fine-pore filter structure, and a second pressure adjustment chamber. The coarse-pore filter structure includes a first filter element with several transverse channels parallel to the length of the housing. The decontamination filter structure includes a perfluorosulfonic acid membrane coated with a platinum-carbon catalyst. The fine-pore filter structure includes a second filter element with several micropores.

[0008] Furthermore, the second filter element is a titanium sintered filter element.

[0009] Furthermore, a heating element and a temperature sensor are provided on the outer side of the housing, and the control end of the heating element and the signal end of the temperature sensor are both connected to a controller.

[0010] Compared with existing technologies, this invention offers significant and positive advantages. By brushing the platinum-carbon catalyst onto a perfluorosulfonic acid membrane, this invention both fixes the catalyst and ensures sufficient contact surface area between the activated carbon and Pt. Activated carbon removes ammonia and organic solvents, while platinum removes carbon monoxide. The platinum particles are supported by activated carbon at the hundreds of nanometer scale, and the platinum particles themselves are 5-30 nm in size, achieving a super-large specific surface area within a small space, enabling better absorption of toxic and harmful gases and impurities. Hydrogen gas, after passing through the first filter with transverse channels, can cover the entire cross-section of the filter. Nanoscale titanium sheets encapsulate the impurity removal filtration structure, preventing detached activated carbon from entering the downstream with the hydrogen gas, while simultaneously filtering out excess liquid moisture, thus better protecting the fuel cell stack. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a hydrogen filtration device for a small, portable fuel cell suitable for low-temperature operation according to the present invention. Detailed Implementation

[0012] The present invention will be further described below with reference to embodiments, but the present invention is not limited to these embodiments. Any similar variations using the present invention should be included in the protection scope of the present invention. The use of directional terms such as up, down, front, back, left, right, middle, inside, and outside in the present invention is only for the convenience of clear description and is not intended to limit the technical solution of the present invention.

[0013] like Figure 1 As shown, this utility model provides a hydrogen filtration device for a small portable fuel cell suitable for low-temperature operation, including a housing. An inlet port 1 and an outlet port 7 are respectively provided at both ends of the housing. Between the inlet port 1 and the outlet port 7, along the length of the housing, a first pressure adjustment chamber 2, a coarse-pore filter structure 3, an impurity removal filter structure 4, a fine-pore filter structure 5, and a second pressure adjustment chamber 6 are sequentially arranged. The coarse-pore filter structure 3 includes a first filter element 8, which has several transverse channels 9. The length direction of the transverse channels 9 is parallel to the length direction of the housing. The impurity removal filter structure 4 includes a perfluorosulfonic acid membrane coated with a platinum-carbon catalyst. The fine-pore filter structure 5 includes a second filter element 10, which has several micropores.

[0014] Furthermore, the second filter element 10 is a titanium sintered filter element.

[0015] Furthermore, a heating element (not shown in the figure) and a temperature sensor (not shown in the figure) are provided on the outer side of the housing. The control terminal of the heating element and the signal terminal of the temperature sensor are both connected to a controller (not shown in the figure).

[0016] Specifically, the specific structure and principle of the perfluorosulfonic acid membrane, platinum-carbon catalyst, titanium sintered filter, heating element, temperature sensor, and controller in this utility model, as well as other aspects not described in detail, all adopt well-known solutions in the prior art, which are understood and implemented by those skilled in the art, and will not be elaborated here.

[0017] Activated carbon can remove ammonia and organic solvents. Due to its well-developed pore structure and large specific surface area, activated carbon is effective in removing ammonia and various organic solvents, and it is also economical. Adding an appropriate amount of platinum (Pt) can remove carbon monoxide.

[0018] In industry, platinum-carbon catalysts, which are platinum supported on activated carbon, are a type of supported catalyst primarily used in fuel cells for chemical reactions such as hydrogen oxidation, methanol oxidation, formic acid oxidation, and oxygen reduction. They are a common type of precious metal catalyst. In platinum-carbon catalysts, the support for the platinum particles is activated carbon at the hundreds of nanometer scale, while the platinum particles themselves are only 5-30 nm in size. This allows for a very large specific surface area within a small space, enabling better absorption of toxic and harmful gases and impurities. This invention coats the platinum-carbon catalyst onto a proton exchange membrane (perfluorosulfonic acid membrane), which both fixes the catalyst and ensures sufficient contact surface area between the activated carbon and the platinum (Pt).

[0019] Platinum-carbon catalysts are used as filter materials to adsorb impurity gases. Nanoscale carbon provides a matrix to support nano-Pt, significantly reducing the amount of Pt required. It also provides a large adsorption surface area, maximizing surface area within a minimal volume. However, nanoscale catalysts present a significant challenge for subsequent packaging; otherwise, carbon particles would enter the fuel cell stack along with hydrogen, disrupting the flow field. This invention coats the surface of a membrane electrode with nanocatalysts, thus effectively locking in a large amount of platinum-carbon catalyst while simultaneously providing a large specific surface area.

[0020] Nanoscale activated carbon can provide a large surface area for CO adsorption, but as the number of hydrogen fuel tanks increases, even this large surface area may be completely occupied and consumed by CO. When the fuel cell system is not operating, oxygen from the air can enter the filter, and nano-Pt and oxygen can desorb CO from the activated carbon surface, allowing the filter to be cleaned again.

[0021] The perfluorosulfonic acid membrane is hygroscopic, allowing it to retain moisture in hydrogen gas when there is a high moisture content, and to humidify the hydrogen gas when there is a low moisture content. This results in more stable humidity levels in the gas entering the fuel cell stack, facilitating performance control. This solves the problem of adsorption surface area requirements, allows for flow control, and prevents the outflow of micro-carbon particles.

[0022] Typically, to maximize the surface area of ​​activated carbon for airflow, filters are designed with more tortuous flow fields. However, this increases the filter's volume and the gas pressure drop. This invention uses nano-sized activated carbon, where a flow field of only about 2-3 cm provides sufficient surface area for gas to purify the gas.

[0023] Low-Temperature Operation: To meet the low-temperature operation requirements of fuel cells, the filter also needs to operate at -40℃. Since this filter is used in a hydrogen system, and fuel cells require purging during startup, the design incorporates the utilization of the purging hydrogen initially released from the system. Upon startup, air is present in the filter. When hydrogen passes through, the platinum-depleted carbon catalyst (Pt) catalyzes the reaction, causing the hydrogen and residual oxygen from the air to react rapidly on the Pt surface, generating heat. This heat raises the internal temperature of the filter to above 0℃, melting the ice and ensuring smooth hydrogen flow. This maximizes the utilization of the purged hydrogen and improves the overall system efficiency. The filter is equipped with a temperature sensor and heating elements. When the temperature sensor detects an internal temperature below 0℃, the heating elements are activated under the control of the controller. Heating stops when the temperature rises above 0℃. This design effectively utilizes the residual hydrogen for heat generation while ensuring stable filter operation under various conditions.

[0024] Mechanical Filtration Design: Due to the small size of the filter, it is crucial to fully utilize the internal filter material. This invention places a coarse-pore filter structure 3 and a fine-pore filter structure 5 at both ends of the impurity removal filter structure 4. At the inlet, after the hydrogen pipe with the small interface is connected to the inlet port 1, the hydrogen gas, after passing through the first filter sheet 8 with the transverse channel 9, can cover the entire cross-section of the filter. The hydrogen gas can flow through the activated carbon at any point on the cross-section, thus fully utilizing the active material of the impurity removal filter structure 4 and maximizing the effective contact area within a volume of approximately 15 mL. At the outlet, a nano-sized porous titanium sintered filter sheet is placed, with its pore size controlled to a few micrometers. The nano-sized titanium sheet encapsulates the impurity removal filter structure 4, preventing detached activated carbon from entering downstream with the hydrogen gas. It also filters excess liquid moisture, better protecting the fuel cell stack and providing appropriate resistance, allowing the hydrogen gas to flow back to the entire cross-section at the outlet.

[0025] In one embodiment of this invention, the filter has a diameter of 25mm and a length of 70mm, is filled with 5g of filter material, weighs approximately 22g, and has a volume of approximately 15ml. It can start at -20℃ and operate continuously with smooth gas flow. The hydrogen flow rate is 1-3L / min. The hydrogen passing through the filter continuously powers the fuel cell for 200 hours with stable operation. The hydrogen is derived from on-site hydrogen production using hydrides.

[0026] After the fuel tank is used up, and the system is left to stand in the air for a period of time, the oxygen in the air reacts with the CO adsorbed on the surface of the activated carbon under the action of the platinum-carbon catalyst, producing CO2 gas that escapes from the system. Simultaneously, the heat generated by the reaction raises the temperature inside the filter, helping the organic matter adsorbed on the activated carbon surface to desorb and leave the system. Depending on the actual usage requirements, as long as there is enough filter material in the filter to remove impurities from 1-2 fuel tanks, the filter is cleaned after the fuel cell system has been out of use for a period of time and is ready for the next cycle of use.

[0027] This invention is specifically developed to address the purification needs of hydrogen produced from magnesium hydride and some metal hydrides. It is suitable for low-power portable fuel cell systems, is small in size and light in weight, has good purification effect, and can appropriately adjust the humidity of hydrogen, making it suitable for low-temperature operation and ensuring stable output of the fuel cell stack.

Claims

1. A hydrogen filtration device for a small, portable fuel cell suitable for low-temperature operation, characterized in that, The device includes a housing, with an air inlet and an air outlet at each end. Between the air inlet and outlet, along the length of the housing, are sequentially arranged a first pressure adjustment chamber, a coarse-pore filter structure, a decontamination filter structure, a fine-pore filter structure, and a second pressure adjustment chamber. The coarse-pore filter structure includes a first filter element with several transverse channels parallel to the length of the housing. The decontamination filter structure includes a perfluorosulfonic acid membrane coated with a platinum-carbon catalyst. The fine-pore filter structure includes a second filter element with several micropores.

2. The hydrogen filtration device for a small, portable fuel cell suitable for low-temperature operation according to claim 1, characterized in that, The second filter element is a titanium sintered filter element.

3. The hydrogen filtration device for a small, portable fuel cell suitable for low-temperature operation according to claim 1, characterized in that, A heating element and a temperature sensor are provided on the outside of the housing. The control terminal of the heating element and the signal terminal of the temperature sensor are both connected to a controller.

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