JP5340765B2 - Desulfurization system - Google Patents

Description

  The present invention relates to a desulfurization system that removes sulfur from raw fuel to produce liquid fuel.

  A desulfurization system is used in a fuel cell system. As a fuel cell system to which the desulfurization system is applied, for example, one described in Japanese Patent Application Laid-Open No. 2004-213941 is known. In this fuel cell system, power is generated by reforming liquid fuel or the like to produce a reformed gas containing hydrogen and reacting the reformed gas with a gas containing oxygen. In the case where a raw material fuel containing a sulfur content such as kerosene is used as a raw fuel to be introduced into the fuel cell system, the reforming catalyst is exposed to the sulfur content in the raw fuel, so that sulfur is poisoned and the reforming performance is deteriorated. For this reason, the sulfur content is removed from the raw fuel before the reforming reaction by the desulfurization system.

JP 2004-213941 A

  By the way, when the concentration of sulfur contained in the raw fuel is relatively high, in order to sufficiently remove the sulfur content, it may be possible to promote the sulfur reaction by setting the pressure in the sulfur unit higher than atmospheric pressure. Can be considered. However, when the pressure inside the desulfurizer is increased, the high-pressure liquid fuel flows into the reformer downstream from the desulfurizer. In this case, it is difficult to control the flow rate of the high-pressure liquid fuel, the reforming performance is lowered, and the performance as the fuel cell system is lowered. Further, when the inside of the desulfurizer is set to a high pressure, it is necessary to make equipment such as piping, response vessel, pump and the like in the subsequent stage compatible with the high pressure, which increases the cost. Therefore, it is conceivable that the liquid fuel that has become high temperature and high pressure by providing an oil storage tank on the downstream side of the desulfurizer is brought to normal temperature and normal pressure, but in this case, the amount of oil stored in the oil storage tank must be controlled. The control load of the entire system increases and the cost increases.

  Accordingly, an object of the present invention is to provide a desulfurization system capable of preventing a reduction in reforming performance of a fuel cell system and suppressing an increase in control load and cost of the entire system.

  The desulfurization system according to the present invention includes a desulfurizer that generates liquid fuel by removing sulfur from a liquid raw fuel under a pressure higher than atmospheric pressure, and a desulfurizer that stores and depressurizes the liquid fuel desulfurized by the desulfurizer. A first storage tank, an overflow line having one end connected to a predetermined height of the first storage tank, and a second end connected to the other end of the overflow line to store liquid fuel overflowed from the first storage tank And an oil storage tank.

  In this desulfurization system, the liquid fuel desulfurized in the desulfurizer is stored in the first oil storage tank and decompressed, so that the flow rate of the liquid fuel flowing into the reformer can be controlled reliably, so the reforming performance of the fuel cell system Can be prevented. Here, when applying an oil storage tank in the system, a sensor for detecting the lower limit position of the liquid level of the oil storage tank and a sensor for detecting the upper limit position are attached. However, in the desulfurization system according to the present invention, an overflow line having one end connected to a predetermined height position of the first oil storage tank and a liquid fuel overflowed from the first oil storage tank by connecting the other end of the overflow line. And a second oil storage tank. Therefore, even if the flow rate is not controlled by attaching a sensor to the upper limit position and detecting the liquid level, the liquid fuel that has overflowed via the overflow line when the liquid level in the first oil storage tank reaches a certain level or more is stored in the second oil storage tank. It is possible to accumulate. As a result, by adopting a simple configuration in which only the overflow line and the second oil storage tank are provided, the sensor at the upper limit position is not required, and the load of flow control associated with the liquid level monitoring on the upper limit side can be reduced. . As described above, it is possible to prevent a reduction in reforming performance of the fuel cell system and to suppress an increase in control load and cost of the entire system.

  Moreover, in the desulfurization system, it is preferable that the second oil storage tank is disposed below a predetermined height position of the first oil storage tank. By disposing the second oil storage tank below the predetermined height position of the first oil storage tank, the overflowed liquid fuel can be supplied to the second oil storage tank by gravity without providing a pump or the like separately. . Further, by disposing the entire second oil storage tank below the first oil storage tank, the entire volume of the second oil storage tank can be used as an overflow tank for the first oil storage tank.

  In the desulfurization system, the second oil storage tank is preferably provided on the upstream side of the desulfurizer. This makes it possible to use the liquid fuel storage tank of the desulfurizer as an overflow tank for the first oil storage tank, thereby reducing the cost of the entire system by eliminating the need for a new second oil storage tank. be able to.

  According to the present invention, it is possible to prevent a reduction in reforming performance of a fuel cell system and to suppress an increase in control load and cost of the entire system.

It is a block block diagram which shows the structure of the fuel cell system to which the desulfurization system which concerns on embodiment of this invention is applied. It is a figure which shows the positional relationship of the oil storage tank and liquid fuel storage tank in the desulfurization system which concerns on the modification of this invention.

  Hereinafter, a preferred embodiment of a desulfurization system according to the present invention will be described in detail with reference to the drawings.

  First, the structure of the desulfurization system 1 of embodiment of this invention is demonstrated. FIG. 1 is a block configuration diagram showing a configuration of a fuel cell system to which a desulfurization system 1 according to an embodiment of the present invention is applied. As shown in FIG. 1, the fuel cell system 100 includes a desulfurization system 1 that removes sulfur from supplied liquid fuel, and a reformed gas by reforming the liquid fuel from which sulfur is removed by the desulfurization system 1. And a fuel cell stack 3 that generates electric power using the reformed gas generated by the reformer 2. The fuel cell system 100 is used as, for example, a household power supply source, and kerosene is used as a raw fuel from the viewpoint that it can be easily obtained and can be stored independently. Yes.

  The reformer 2 includes a reformer that generates a hydrogen-rich reformed gas by steam reforming a liquid fuel, and a burner that heats a reforming catalyst accommodated in the reformer. The burner heats the reforming catalyst that promotes the steam reforming reaction, thereby supplying the reforming catalyst with heat necessary to effectively exhibit the catalytic reaction. The burner fuel is mainly raw fuel and oxygen. In the reformer, the liquid fuel desulfurized by the desulfurization system 1 is vaporized to become a raw material gas, and the reforming catalyst promotes the steam reforming reaction between the raw material gas and steam (water), thereby reforming the hydrogen rich. Gas is generated.

  The fuel cell stack 3 is a polymer electrolyte fuel cell stack configured by stacking a plurality of battery cells, and generates power using the reformed gas obtained by the reformer 2. Each battery cell has an anode, a cathode, and a polymer ion exchange membrane that is an electrolyte disposed between the anode and the cathode. In each battery cell, the reformed gas is introduced into the anode and air is introduced into the cathode, and an electrochemical power generation reaction is performed.

  The desulfurization system 1 includes a liquid fuel storage tank (second oil storage tank) 11 that stores liquid fuel, a desulfurizer 13 that removes sulfur from the liquid fuel introduced from the liquid fuel storage tank 11 by a constant pressure pump 12, and a desulfurization system. An oil storage tank (first oil storage tank) 14 that stores and depressurizes the liquid fuel discharged from the vessel 13, and an overflow line 16 that connects the oil storage tank 14 and the liquid fuel oil storage tank 11. The raw fuel contains about 80 ppm or less of sulfur such as sulfur and sulfur compounds. The desulfurizer 13 removes sulfur from the raw fuel to produce liquid fuel having a sulfur concentration of about 50 ppb or less. The inside of the desulfurizer 13 is kept in a high pressure state, and the desulfurization reaction proceeds in the high pressure state.

  The oil storage tank 14 has a function of bringing the liquid fuel of high temperature and pressure desulfurized by the desulfurizer 13 to normal temperature and normal pressure. The oil storage tank 14 is formed with a gas vent hole (not shown) on the top plate side and opened to the atmosphere, whereby the pressure in the oil storage tank 14 is maintained at atmospheric pressure. Therefore, the gas contained in the liquid fuel is separated in the oil storage tank 14, and the separated gas is supplied as combustion fuel to the burner of the reformer 2 through the gas vent hole. The liquid fuel stored in the oil storage tank 14 and brought to room temperature and normal pressure is supplied to the reformer 2 by the pump 17.

  A liquid level detection sensor 21 is provided at a lower limit position of the liquid level FL1 of the liquid fuel at a position on the bottom side of the side surface in the oil storage tank 14. On the other hand, an opening 14a is provided at the upper limit position FT of the liquid level FL1 at the position on the upper surface side of the side surface in the oil storage tank 14, and an overflow is made in the opening 14a. One end of the line 16 is connected. The overflow line 16 is constituted by a pipe connecting the oil storage tank 14 and the liquid fuel oil storage tank 11, and the liquid fuel overflowed from the opening 14 a at the upper limit position FT in the oil storage tank 14 is supplied to the liquid fuel oil storage tank 11. It has a function to supply. When the liquid level detection sensor 21 at the lower limit position of the oil storage tank 14 detects a decrease in the liquid level as the liquid level FL1 passes, the liquid level detection sensor 21 outputs an electrical signal to a control device (not shown). The liquid fuel in the oil storage tank 14 is increased by suppressing the supply amount of the oil and increasing the supply amount by the constant pressure pump 12.

  The liquid fuel oil storage tank 11 is disposed at a position lower than the oil storage tank 14, and an opening is provided on the upper surface thereof, and the other end of the overflow line 16 is connected to the opening. The liquid fuel storage tank 11 has a function of storing liquid fuel to be supplied to the desulfurizer 13 and storing liquid fuel overflowed from the oil storage tank 14 via an overflow line 16. On the side surface in the liquid fuel storage tank 11, a liquid level detection sensor 22 is provided at the lower limit position of the liquid level FL2 on the bottom side, and a liquid level detection sensor 23 is provided at the upper limit position of the liquid level FL2 on the upper side. . When the liquid level detection sensor 22 at the lower limit position detects a decrease in the liquid level as the liquid level FL2 passes, the liquid level detection sensor 22 outputs an electrical signal to a control device (not shown), and thereby the control device suppresses the supply amount of the constant pressure pump 12. At the same time, the supply amount of the liquid fuel as the raw fuel is increased to increase the liquid fuel in the liquid fuel storage tank 11. Further, when the liquid level detection sensor 23 at the upper limit position detects an increase in the liquid level due to the passage of the liquid level FL2, it outputs an electric signal to a control device (not shown), whereby the control device supplies the supply amount of the constant pressure pump 12. And the supply amount of the liquid fuel as the raw fuel is suppressed, and the liquid fuel in the liquid fuel storage tank 11 is decreased.

  According to the desulfurization system 1 configured as described above, the liquid fuel desulfurized by the desulfurizer 13 is stored in the oil storage tank 14 and decompressed to reliably control the flow rate of the liquid fuel that flows into the reformer 2. Therefore, the deterioration of the reforming performance of the fuel cell system 100 can be prevented. Here, when the oil storage tank 14 is applied in the system, a liquid level detection sensor 21 for detecting the lower limit position of the liquid level of the oil storage tank 14 and a liquid level detection sensor for detecting the upper limit position FT are attached. . However, in the desulfurization system 1 according to the present embodiment, the overflow line 16 having one end connected to the upper limit position FT of the oil storage tank 14 and the liquid fuel overflowed from the oil storage tank 14 are connected to the other end of the overflow line 16. And a liquid fuel storage tank 11 for storing the fuel. Therefore, even if the flow rate is not controlled by attaching a sensor to the upper limit position FT and detecting the liquid level, if the liquid level in the oil storage tank 14 reaches a certain level or more, the liquid fuel that has overflowed via the overflow line 16 is stored in the liquid fuel oil storage. It can be stored in the tank 11. As a result, by adopting a simple configuration in which only the overflow line 16 and the oil storage tank are provided, the liquid level detection sensor at the upper limit position FT is not required, and the load of flow control associated with the upper liquid level monitoring is reduced. be able to. As described above, it is possible to prevent a reduction in reforming performance of the fuel cell system 100 and to suppress an increase in control load and cost of the entire system.

  Further, in the desulfurization system 1 according to the present embodiment, an oil storage tank that stores liquid fuel that has overflowed from the oil storage tank 14 is provided upstream of the desulfurizer 13. As a result, the liquid fuel oil storage tank 11 of the desulfurizer 13 can be used as an overflow tank for the oil storage tank 14, and the cost of the entire system can be reduced by eliminating the need for a new oil storage tank. Can do.

  Further, in the desulfurization system 1 according to the present embodiment, since the liquid fuel storage tank 11 is disposed below the upper limit position FT of the oil storage tank 14, the overflowed liquid fuel can be supplied without providing a pump or the like separately. The liquid fuel storage tank 11 can be supplied by gravity.

  The present invention is not limited to the embodiment described above.

  For example, in the above-described embodiment, the liquid fuel storage tank 11 is disposed below the oil storage tank 14 as a whole, but instead of this, as shown in FIG. The oil storage tank 11 may be arranged at the same height as the oil storage tank 14. Even in this case, if even a part of the volume of the liquid fuel storage tank 11 is disposed at a position lower than the upper limit position FT of the liquid level FL1, the liquid that has overflowed the oil storage tank 14 via the overflow line 16 Fuel can be stored. However, as shown in FIG. 2B, even if the liquid fuel storage tank 11 is not completely disposed below the oil storage tank 14 as in this embodiment, at least the entire tank is at the upper limit position of the liquid level FL1. More preferably, it is arranged below the FT. Thus, by disposing the liquid fuel storage tank 11 below the upper limit position FT of the oil storage tank 14, the entire volume of the liquid fuel oil storage tank 11 can be used as an overflow tank of the oil storage tank 14. (However, since the function as the liquid fuel storage tank 11 must also be fulfilled, the volume of the raw fuel before desulfurization is not actually used for overflow).

  Further, in the above-described embodiment, the liquid fuel storage tank 11 is also used as the second oil storage tank for overflow, but the oil storage tank having only the function for overflow independent of the liquid fuel storage tank 11. May be provided separately.

  DESCRIPTION OF SYMBOLS 1 ... Desulfurization system, 11 ... Liquid fuel oil storage tank (2nd oil storage tank), 13 ... Desulfurizer, 14 ... Oil storage tank (1st oil storage tank), 16 ... Overflow line, FT ... Upper limit position (predetermined height position) .

Claims (2)

A desulfurizer that generates liquid fuel by removing sulfur from liquid raw fuel under a pressure higher than atmospheric pressure;
A first oil storage tank for storing and depressurizing the liquid fuel desulfurized by the desulfurizer;
An overflow line having one end connected to a predetermined height position of the first oil storage tank;
A second oil storage tank connected to the other end of the overflow line and storing the liquid fuel overflowed from the first oil storage tank, and a desulfurization system for a fuel cell system,
The desulfurization system, wherein the second oil storage tank is provided upstream of the desulfurizer.   The desulfurization system according to claim 1, wherein the second oil storage tank is disposed below the predetermined height position of the first oil storage tank.

Images