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JP-7855163-B2 - Fuel cell system

JP7855163B2JP 7855163 B2JP7855163 B2JP 7855163B2JP-7855163-B2

Inventors

  • 正生 明宏

Assignees

  • 三浦工業株式会社

Dates

Publication Date
20260508
Application Date
20220328

Claims (4)

  1. A solid oxide fuel cell system that includes an off-gas burner for burning anode off-gas discharged from the fuel electrode of a cell stack, and utilizes the combustion exhaust gas for thermal purposes, An air preheater that preheats the air supplied to the air electrode of the cell stack by the combustion exhaust gas, The system includes an evaporator that heats the reformed water with the combustion exhaust gas to generate steam for use in steam reforming, A fuel cell system characterized in that the combustion exhaust gas, after heat utilization in the air preheater and the evaporator , is mixed with heated air generated using the waste heat within the system and discharged outside the system.
  2. A condenser that cools and condenses the water vapor contained in the anode off-gas, The system includes a water tank for recovering the condensed water separated from the anode off-gas after cooling as the reformed water, The fuel cell system according to claim 1, characterized in that the off-gas burner burns the anode off-gas after gas-water separation .
  3. The condenser exchanges heat between the water vapor contained in the anode off-gas and the cooling air. The fuel cell system according to claim 2 , characterized in that the cooling air that has passed through the condenser is used as the heated air .
  4. The temperature of the heated air is equal to or greater than the temperature of the combustion exhaust gas after heat utilization. A fuel cell system according to any one of claims 1 to 3, characterized in that the mixing ratio of the combustion exhaust gas and the heated air is within the range of 1:2 to 1:30 .

Description

This invention relates to a fuel cell system using a solid oxide fuel cell. Traditionally, various types of fuel cells have been developed as energy sources that offer high power generation efficiency and are environmentally friendly. In particular, solid oxide fuel cells (SOFCs) achieve high power generation efficiencies of over 50%, and are therefore used in fuel cell systems with a wide range of output levels, from household to industrial applications. In externally reformed fuel cell systems that use hydrocarbon fuels such as city gas as raw fuel, as disclosed in Patent Document 1, for example, the raw fuel is reformed in a reformer, and the resulting reformed gas is used by the cell stack to generate electricity. Furthermore, it is common practice to include an off-gas burner within the system to burn off-gas discharged from the fuel electrode of the cell stack, thereby supplying heat from the off-gas burner to the reformer and other components. Special Publication No. 2016-524303 This is a schematic diagram of the fuel cell system according to this embodiment. One embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a schematic diagram of the fuel cell system 1 according to this embodiment. In Figure 1, the fluid pathways are shown as follows: solid arrows indicate pathways related to fuel gas (gas pathways), dashed arrows indicate pathways related to reformed water (water pathways), dotted arrows indicate pathways related to air (air pathways), and dashed-dotted arrows indicate other pathways. The white arrows shown in Figure 1 indicate the fluid flowing through each pathway. As shown in Figure 1, the fuel cell system 1 comprises a reformer 11, an evaporator 12, a cell stack 13, a water recovery device 14, an air preheater 15, an off-gas burner 16, and a mixing unit 17 (a space for mixing the combustion exhaust gas Gf and cooling air Ad, which will be described later). The cell stack 13 is a solid oxide fuel cell (SOFC), and its operating temperature is, for example, around 700°C. A solid oxide fuel cell can generate electricity by generating an electrochemical reaction when a fuel gas containing hydrogen is supplied to the fuel electrode (anode) and air containing oxygen is supplied to the air electrode (cathode). In this embodiment, as an example, only one cell stack 13 is provided, but multiple cell stacks 13 may be provided in parallel. Most of the elements of the fuel cell system 1, excluding the water recovery device 14 and the mixing unit 17, are located within the thermal insulation region TA shown in Figure 1. The thermal insulation region TA is covered with thermal insulation material, and care has been taken to minimize heat release to the outside. This gives the fuel cell system 1 an advantageous configuration in terms of thermal self-sufficiency. The fuel cell system 1 is equipped with a raw material gas receiving section Pg for receiving raw material gas (in this embodiment, for example, city gas containing methane), and an air receiving section Pa for receiving air. The raw material gas and air are basically supplied from outside the fuel cell system 1. The raw material gas receiving section Pg is connected to the reformer 11 via the first gas path Lg1, and a first blower B1 is provided along the first gas path Lg1. At least a portion of the first gas path Lg1 downstream of the first blower B1 is arranged to pass through the evaporator 12. The reformer 11 is connected to the fuel electrode 13a of the cell stack 13 via the second gas path Lg2. The fuel electrode 13a is connected to the water recovery device 14 via the third gas path Lg3. The water recovery device 14 includes a water tank 14a, a condenser 14b, a cooling air path 14c, and a cooling air (outside air) inlet 14d, and is connected to the off-gas burner 16 via the fourth gas path Lg4. The cooling air path 14c extends from the inlet 14d and is connected to the mixing unit 17 via the condenser 14b. An exhaust pipe Ly extends from the mixing unit 17 to exhaust the gas to the outside. An exhaust pipe for exhausting the gas from a high position is located downstream of the exhaust pipe Ly. The water tank 14a is connected to the evaporator 12 via a water path Lw. A water pump W1 is provided in the water path Lw, enabling the continuous supply of water from the water tank 14a to the evaporator 12 as reformed water Wa. This allows the fuel cell system 1 to achieve water independence. The water pump W1 can adjust the amount of reformed water Wa supplied from the water tank 14a to the evaporator 12. A first air path La1 extends from the air intake section Pa, and a second blower B2 is provided along the first air path La1. The first air path La1 is connected to the air electrode 13b of the cell stack 13. The air electrode 13b is connected to the off-gas burner 16 via the second air path La2. The off-gas burner 16 is connected to the mixing section 17 via the combustion exhaust gas path