JP2008300047A - Fuel cell power generator - Google Patents

Abstract

The present invention provides a fuel cell power generation apparatus that can reduce the operating cost and the apparatus cost by using coke oven gas as a raw fuel and can be downsized.
A hydrogen purifier that separates and purifies coke oven gas obtained by carbonizing coke into high-purity hydrogen and coke oven off-gas, and a coke oven off-gas discharge side of the hydrogen purifier 20 are connected to a hydrogen purifier. A reformer 31 including a reformer 31 for generating a reformed gas by steam reforming the coke oven off-gas discharged from the reactor 20, a reformer 30 including a combustion device 32 for supplying reaction heat to the reformer 31, and hydrogen purification The high-purity hydrogen discharged from the hydrogen purifier 20 and the reformed gas discharged from the reformer 30 are connected to the high-purity hydrogen discharge side of the apparatus 20 and the reformed gas discharge side of the reformer 30 as fuel gas. A fuel cell power generator comprising a fuel cell main body 10 to be used.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell power generator that uses coke oven gas generated at an ironworks, refinery, or the like as a fuel.

  A fuel cell is a power generation device that directly converts chemical energy of fuel into electrical energy without passing through mechanical energy or thermal energy, and is a power generation device that can realize high energy efficiency.

  As a well-known fuel cell configuration, a pair of electrodes are arranged with an electrolyte layer in between, a fuel gas containing hydrogen is supplied to one electrode (anode side), and the other electrode (cathode side) is supplied. An oxygen-containing oxidizing gas is supplied, and an electromotive force is obtained by utilizing an electrochemical reaction that occurs between both electrodes. Below, an equation representing an electrochemical reaction occurring in the fuel cell is shown. (1) represents the reaction on the anode side, (2) represents the reaction on the cathode side, and the reaction represented by the formula (3) proceeds in the entire fuel cell.

H ₂ → 2H ⁺ + 2e ⁻ (1)
1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + 1 / 2O ₂ → H ₂ O (3)

  In a normal fuel cell, air is used as an oxidizing gas, and a gas containing hydrogen generated by steam reforming a hydrocarbon-based raw fuel such as methanol or natural gas is used as a fuel gas.

  On the other hand, about 50 to 60% of hydrogen is contained in coke oven gas discharged in the process of dry distillation of fossil fuels such as coke at steelworks and refineries. Since the coke oven gas was mainly exhausted as exhaust gas, the fuel gas used in the fuel cell can be obtained at low cost by recovering and using hydrogen from the coke oven off-gas, and the operation of the fuel cell power generator Cost reduction can be expected.

  For recovering hydrogen from coke oven gas with high purity, for example, in Patent Document 1 below, hydrogen is separated from coke oven gas by the pressure swing adsorption (PSA) method and separated coke oven off gas. Is subjected to steam reforming treatment and then mixed with coke oven gas again, and separated by the PSA method to recover hydrogen.

Patent Document 2 below discloses that steam and oxygen are added to coke oven gas to perform steam reforming, and then hydrogen is recovered by the PSA method, and the recovered hydrogen is used as fuel gas for the fuel cell. Yes.
JP-A-4-357101 JP 2004-127757 A

In the above Patent Documents 1 and 2, hydrogen is finally separated and purified using a hydrogen purifier such as a PSA apparatus.
However, when the fuel gas supplied to the fuel cell body is supplemented only with hydrogen purified by the hydrogen purifier, a hydrogen purifier with a large processing volume and other incidental facilities are required, so the entire apparatus is large. As a result, there is a problem that the apparatus cost and the installation space increase. In addition, there is a problem that the power required for hydrogen separation from the coke oven gas (for example, compression power, etc.) is increased and operation cost is required.

  Further, as in Patent Document 1, in the method of returning the coke oven off-gas separated by the PSA apparatus to the PSA apparatus after performing the steam reforming treatment, the amount of the compression power is increased and the PSA is increased by further purifying the reformed gas by the PSA apparatus. The equipment was enlarged.

  Further, as in Patent Document 2, when a reformed gas obtained by directly steam reforming coke oven gas is used in a fuel cell, it is incorporated into a fuel cell power generator using general city gas as a raw fuel. The reformer cannot handle this, and the capacity must be changed in accordance with the composition of the coke oven gas, and the system design of the fuel cell power generator must be changed in accordance with this reformer. There is a problem that the cost increases.

  Accordingly, an object of the present invention is to provide a fuel cell power generator that can use coke oven gas as raw fuel, reduce operating costs and equipment costs, and can be downsized.

In order to achieve the above object, a fuel cell power generator of the present invention comprises:
A hydrogen purification apparatus for separating and purifying coke oven gas obtained by carbonizing coke into high-purity hydrogen and coke oven off-gas,
A reformer that is connected to the coke oven off-gas discharge side of the hydrogen purifier and steam reforms the coke oven off-gas discharged from the hydrogen purifier to generate a reformed gas, and heat of reaction to the reformer. A reformer comprising a combustion device to supply;
The high purity hydrogen discharged from the hydrogen purifier and the reformed gas discharged from the reformer are fueled by being connected to the high purity hydrogen discharge side of the hydrogen purifier and the reformed gas discharge side of the reformer. And a fuel cell main body used as gas.

  According to the fuel cell power generator of the present invention, the high purity hydrogen separated and purified from the coke oven gas by the hydrogen purifier and the reformed gas obtained by steam reforming the coke oven off-gas discharged from the hydrogen purifier Are combined and used as fuel gas to be supplied to the fuel cell body, so a small amount of coke oven gas is required for processing in the hydrogen purifier, and the hydrogen purifier and reformer can be miniaturized. The operating cost can be reduced.

  In the fuel cell power generator of the present invention, a coke oven gas flow meter for measuring the flow rate of the coke oven gas is disposed in a path on the inlet side of the hydrogen purifier, and based on the measured value of the coke oven gas flow meter, It is preferable that the coke oven off-gas of the hydrogen purifier is steam reformed by adjusting the amount of steam supplied to the reformer. Since the hydrocarbons in the coke oven gas are hardly mixed in the high purity hydrogen separated in the hydrogen purifier, the amount of hydrocarbons in the coke oven off-gas discharged from the hydrogen purifier is the same as the inlet of the hydrogen purifier. There is no change at the exit. For this reason, the ratio of water vapor to hydrocarbons is maintained within a predetermined range by adjusting the amount of steam mixed with the coke oven off-gas based on the amount of coke oven gas supplied to the hydrogen purifier. The coke oven off-gas can be efficiently steam reformed.

  In the fuel cell power generator according to the present invention, at least a part of the fuel off-gas discharged from the anode electrode of the fuel cell main body and combustion air are supplied to the combustion device and combusted, and the fuel to the combustion device It is preferable that the temperature of the reformer is adjusted by adjusting the supply amount of the fuel off gas. Since the fuel off-gas usually contains about 20 vol% of hydrogen, it can be effectively used as a heat source for heating the reformer by supplying the fuel off-gas to the combustion device. However, if the entire amount of the fuel off-gas is burned by the combustion device, the thermal balance is lost, the reformer is excessively heated, and the operation of the reformer may be difficult. Since the temperature of the reformer is adjusted by adjusting the amount of fuel off-gas supplied to the combustion device, overheating of the reformer can be prevented.

  According to the fuel cell power generator of the present invention, in the hydrogen purifier, the high purity hydrogen separated and purified from the coke oven gas and the reformed gas obtained by steam reforming the coke oven off gas discharged from the hydrogen purifier Is used as the fuel gas supplied to the fuel cell body, so that the hydrogen purifier and the reformer can be downsized.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a fuel cell power generator according to the present invention.

  The fuel cell body 10 includes an electrolyte 11, an anode electrode 12 and a cathode electrode 13 disposed on both sides of the electrolyte 11, and a cooling water system 14 having a cooling pipe disposed each time a plurality of unit cells made of these are stacked. It is mainly composed.

  The cooling water system 14 is connected to a cooling water supply pipe L 9 extending from the steam separator 15, and operates the cooling water circulation pump 16 to supply cooling water to the cooling water system 14 and cool the fuel cell main body 10. The cooling water can be stored in the steam separator 15 again.

  A fuel gas supply pipe L1 is connected to the reformed gas introduction port of the anode electrode 12. The fuel gas supply pipe L1 includes a hydrogen supply pipe L2 extending from the hydrogen purifier 20 and a reformer 30. The extended reformed gas supply pipe L3 is connected. And the flow meter F1 is arrange | positioned at the hydrogen supply pipe | tube L2, and it is comprised so that the measurement value can be transmitted to the control apparatus 40 by measuring the hydrogen flow volume which distribute | circulates the hydrogen supply pipe | tube L2.

  A fuel off-gas discharge pipe L4 extends from the fuel off-gas discharge port of the anode electrode 12 and is connected to a combustion source introduction part 32a provided in the combustion device 32 of the reformer 30. The fuel off-gas discharge pipe L4 is branched and extended in the middle, and the branched pipe L5 is provided with a valve V1 configured so that the opening degree can be adjusted by the output from the control device 40.

  An oxidant gas supply pipe L6 extending from the air supply device 17 is connected to the oxidant gas inlet of the cathode electrode 13.

  An oxidant off-gas discharge pipe L7 extends from the oxidant off-gas discharge port of the cathode electrode 13 and is connected to the condensing device 18 to condense water in the off-gas and collect condensed water, and the gas component is sent to the outside. It is configured to be able to exhaust. A condensate discharge pipe L8 in which a condensate discharge pump 19 is arranged extends from the condensing device 18 and is connected to the cooling water supply pipe L9.

  The hydrogen purification device 20 is not particularly limited as long as it is a device that can selectively separate and purify hydrogen from coke oven gas as a fuel. For example, a pressure swing adsorption device (PSA device) that adsorbs and separates specific gas species by filling a plurality of containers with an adsorbent such as activated carbon or zeolite, and changing the pressure, or a membrane separator with selective permeability Etc. are preferred.

  The fuel input side of the hydrogen purifier 20 is connected to a flow meter F3 extending from a coke oven gas supply source and a pipe L11 where the compressor 21 is arranged, and the flow rate of the coke oven gas flowing through the pipe L11 is determined. The measurement value can be measured and transmitted to the control device 40.

  A coke oven off-gas discharge pipe L10 extends from the coke oven off-gas discharge side of the hydrogen purifier 20 and is connected to the desulfurizer 23.

  The coke oven off-gas discharge pipe L10 is provided with an off-gas tank 22, a flow meter F2, and a valve V2. The measured value is transmitted to the control unit 40, and the opening degree of the valve V2 can be adjusted by the output from the control device 40.

  The pipe L15 extending from the desulfurizer 23 is connected to the reformer 31 of the reformer 30, and the reformed steam supply pipe provided with the reformed steam flow meter F4 and the valve V3 is extended from the steam separator 15. L13 is connected on the way. The valve V <b> 3 is configured to adjust the opening degree by the output from the control device 40 and adjust the supply amount of reformed steam to the reformer 31.

  The reformer 30 is mainly composed of a reformer 31, a combustion device 32, and a CO converter 33.

  The reformer 31 is a reactor that generates a reformed gas mainly composed of hydrogen from a hydrocarbon by a steam reforming reaction. The reformer 31 is provided with a thermometer T <b> 1 that measures the temperature of the catalyst layer, and is configured to output the measurement result to the control device 40. The reformer 31 is connected with a combustion device 32 that heats the reforming catalyst layer filled with the reforming catalyst and supplies reaction heat for performing the reforming reaction.

  A combustion air supply pipe L12 extending from the combustion air blower 35 and a fuel offgas discharge pipe L4 extending from the fuel offgas discharge port of the anode electrode 12 are connected to the combustion source introduction portion 32a of the combustion device 32.

  A combustion exhaust gas exhaust pipe L14 for exhausting the combustion exhaust gas extends from the combustion exhaust gas discharge port of the combustion device 32 and is connected to the condensing device 18.

  A piping L15 is connected to the reforming raw material input side of the reformer 31.

A CO converter 33 is disposed on the reformed gas discharge side of the reformer 31. The CO converter 33 is a device that reacts CO in the reformed gas with water vapor to convert it into hydrogen and CO ₂ (water gas shift reaction; exothermic reaction). Depending on the type of fuel cell main body 10 to be applied, the type of raw fuel, the type of catalyst charged in the reformer 31, etc., a CO remover and other reactors may be combined. It may be used.

  Next, an operation method using the fuel cell power generator of the present invention will be described.

  Coke oven gas supplied from a coke oven gas source such as a coke oven gas tank is compressed by the compressor 21 to about 0.7 to 0.9 MPa. And it supplies to the hydrogen refiner | purifier 20 and isolate | separates and refine | purifies into hydrogen and coke oven off gas, and obtains high purity hydrogen from coke oven off gas.

  The method for separating and purifying hydrogen in the hydrogen purifier 20 is not particularly limited, and a conventionally known method can be used. For example, when a PSA apparatus (pressure swing adsorption apparatus) is used as the hydrogen purification apparatus 20, hydrogen and adsorption gas (coke oven off-gas) can be obtained by repeatedly performing an adsorption operation and a desorption operation (regeneration operation) according to a conventional method. Can be separated. At this time, by reducing the desorption pressure, more impurities can be adsorbed to the adsorbent, so that the hydrogen recovery rate is improved.

  The high purity hydrogen obtained by separating and refining the coke oven gas in the hydrogen purifier 20 is supplied to the anode electrode 12 of the fuel cell main body 10 through the fuel gas supply pipe L1.

  The flow rate of the coke oven gas supplied to the hydrogen purifier 20 is adjusted so that the flow rate of hydrogen supplied to the anode electrode 12 falls within a predetermined range. That is, reforming in which the flow rate of hydrogen generated by the reformer 30 is calculated from the flow rate of hydrogen flowing through the hydrogen supply pipe L2 measured by the flow meter F1 and the flow rate of coke oven off gas measured by the flow meter F2. The total of the flow rate of hydrogen flowing through the gas supply pipe L3 is adjusted to be within a predetermined range.

  Further, the coke oven off-gas discharged from the hydrogen purifier 20 is supplied to the desulfurizer 23 through the off-gas tank 22 and desulfurized, and mixed with the reformed steam supplied from the reformed steam supply pipe L13 for reforming. Is supplied to the container 31.

  Here, when a PSA device is used as the hydrogen purification device 20, the coke oven off-gas is discharged at intervals of several hundred seconds from the operation pattern of the PSA device. However, since a fuel cell requires hydrogen continuously, when a PSA device is used as the hydrogen purification device 20, the coke oven off-gas discharged from the hydrogen purification device 20 is temporarily stored in the off-gas tank 22. It is preferable to store the coke oven off gas from the off gas tank 22 to the desulfurizer 23. In addition, it is preferable that the offgas tank 22 is designed to be smaller from the viewpoint of apparatus cost, installation space, and the like, and to reduce the pressure fluctuation of the coke oven offgas. For example, the volume of the offgas tank 22 is preferably designed by correcting the coke oven offgas pressure fluctuation by multiplying the required flow rate of the coke oven offgas by the coke oven offgas discharge time.

  The flow rate of the reformed steam supplied from the reformed steam supply pipe L13 is based on the flow rate of the coke oven off-gas supplied to the hydrogen purifier 20, that is, the measured value by the flow meter F3, of the reformed steam flow meter F4 and the valve V3. The supply amount of reformed steam is adjusted by adjusting the opening. Since the hydrocarbons contained in the coke oven gas are hardly mixed in the high purity hydrogen separated by the hydrogen purifier 20, the amount of hydrocarbons in the coke oven off-gas discharged from the hydrogen purifier 20 is There is no change at the 20 entrances and exits. For this reason, the ratio of the reformed steam to the hydrocarbons is controlled within a predetermined range by adjusting the supply amount by adjusting the openings of the reformed steam flow meter F4 and the valve V3 based on the measured value by the flow meter F3. The coke oven off-gas can be efficiently steam reformed.

  In the reformer 31, the coke oven off-gas undergoes a steam reforming reaction to generate a reformed gas rich in hydrogen. Since the steam reforming reaction is an endothermic reaction, the combustion air is supplied to the combustion device 32 from the combustion air supply pipe L12 and the fuel offgas is supplied from the fuel offgas discharge pipe L4. Although the catalyst layer 31 is heated, if the entire amount of the fuel off-gas is burned by the combustion device 32, the thermal balance may be lost and the reformer 31 may be heated excessively. For this reason, while supplying the temperature of the catalyst layer of the reformer 31 with the thermometer T1, the opening amount of the valve V1 is adjusted based on the measured value by the thermometer T1, and the supply amount of the fuel off gas to the combustion device 32 Is preferably adjusted. Excess fuel off-gas is discharged to the outside after performing the required treatment through the pipe L5.

  The reformed gas produced by the reformer 31 is mixed with high-purity hydrogen supplied from the hydrogen purifier 20 through the pipes L3 and L1 after the CO concentration is reduced by the CO converter 33. The fuel gas is supplied to the anode electrode 12.

  In the fuel cell main body 10, an oxidant gas mainly composed of high-purity hydrogen and reformed gas supplied from the fuel gas supply pipe L1 to the anode electrode 12 and oxygen supplied from the oxidant gas supply pipe L6 to the cathode electrode 13. Are reacted at both interfaces of the electrolyte 11 to generate electric power, and this generated output is converted into AC power of a predetermined voltage by an inverter (not shown) or the like and supplied to the electric power system.

  The fuel off-gas discharged from the anode electrode 12 is supplied to the combustion device 32 and used as a combustion source, and the oxidant off-gas discharged from the cathode electrode 13 uses moisture contained in the oxidant off-gas in the condenser 18. The condensed water is recovered and used as cooling water to be supplied to the cooling water system 14.

  Thus, in the present invention, the high-purity hydrogen obtained by separating and purifying from the coke oven gas in the hydrogen purifier 20 and the coke oven off-gas discharged from the hydrogen purifier 20 are obtained by steam reforming. Since the reformed gas is combined and used as the fuel gas supplied to the anode electrode 12 of the fuel cell main body 10, the load on the hydrogen purifier 20, the compressor 21, the reformer 30 and the like can be reduced. As a result, these devices can be miniaturized, and the entire device can be miniaturized and the device cost can be reduced.

  Hereinafter, the effect of the present invention will be specifically described with reference to examples.

Example 1
Power generation of 100 kW was performed using the fuel cell power generator shown in FIG. The fuel cell body 10 was a phosphoric acid fuel cell that required hydrogen at a flow rate of 85 to 100 Nm ³ / h when generating power of 100 kW. Further, a PSA apparatus was used as the hydrogen purification apparatus 20.
Coke oven gas having a flow rate of 45.2 Nm ³ / h was compressed to 0.7 to 0.9 MPa (G) by the compressor 21. The power required by the compressor 21 at this time was about 4.6 kW.
The compressed coke oven gas was supplied to a hydrogen purifier (PSA device) 20 and separated into hydrogen and coke oven off gas.
The flow rate of hydrogen discharged from the hydrogen purifier 20 was 17.7 Nm ³ / h (indicated value of the flow meter F1). Further, the flow rate of the coke oven off-gas discharged from the hydrogen purification apparatus 20 was 27.5 Nm ³ / h (indicated value of the flow meter F2). In addition, when the coke oven off gas discharged | emitted from the hydrogen purification apparatus 20 was analyzed, it was the composition shown in Table 1 below.

Hydrogen obtained by separating the coke oven gas from the hydrogen purifier 20 was supplied to the anode electrode 12 of the fuel cell main body 10.
The coke oven off-gas obtained by separating from the coke oven gas is desulfurized by the desulfurizer 23, then steam reformed by the reformer 31, and CO is converted to CO ₂ by the CO converter 33. A reformed gas having a CO content of less than 1% was obtained and supplied to the anode electrode 12 of the fuel cell body 10. The hydrogen flow rate by the reformed gas was 71.5 Nm ³ / h (the flow rate as the reformed gas was 96.0 Nm ³ / h).
Since the hydrogen discharged from the hydrogen purifier 20 and the reformed gas discharged from the reformer 30 are supplied to the anode electrode 12 of the fuel cell main body 10 together, the hydrogen supplied to the anode electrode 12 is supplied. The flow rate was 89.2 Nm ³ / h.
Therefore, by treating the coke oven gas having a flow rate of 45.2 Nm ³ / h with the hydrogen purifier 20, it was possible to obtain a fuel gas capable of generating 100 kW of power.

On the other hand, when only hydrogen separated and purified by the hydrogen purifier 20 is used, pure hydrogen is required to be 85 to 100 Nm ³ / h for power generation of 100 kw, and thus the hydrogen purifier 20 has a flow rate of 217 to 255 Nm ^3. / H coke oven gas needs to be separated and purified.
On the other hand, according to the fuel cell power generator of the present invention, the hydrogen purifier 20 has only to have a capacity capable of treating coke oven gas of about 45.2 Nm ³ / h. Compared to a conventional fuel cell power generator that uses only hydrogen, the capacity of the hydrogen purifier 20 could be reduced to 1/4 to 1/5.

(Comparative Example 1)
After the coke oven off-gas discharged from the hydrogen purifier 20 is steam reformed by the reformer 30 based on the method described in Patent Document 1 (Japanese Patent Laid-Open No. 4-357101), the hydrogen purifier 20 again generates hydrogen. Separately, fuel gas to be supplied to the fuel cell main body 10 was generated, and electric power was generated.
That supply to the compressor 21, and the coke oven gas flow rate 45.2Nm ³ / h, the coke oven off-gas discharged from the hydrogen purifier 20 and the reformed gas flow rate 96.0Nm ³ / h was steam reforming (Total flow rate 141.2 Nm ^{3 /} h), compressed to 0.7 to 0.9 MPa (G). At this time, the power of the compressor 21 was about 15.8 kW, which required 3.4 times the power of the first embodiment.
Then, when the coke oven gas subjected to the compression treatment is supplied to the hydrogen purifier 20 and separated into hydrogen and coke oven off-gas, the flow rate of hydrogen discharged from the hydrogen purifier 20 is 67.8 Nm ³ / h. In order to generate power of 100 kW, the flow rate of hydrogen was insufficient, and power generation of 100 kW could not be performed.
Also, when to do the power generation of 100 kW, with an increasing flow rate of the coke oven gas, it was necessary to 56.7 nm ³ / h, in which the flow rate of the coke oven gas and 56.7 nm ³ / h, The power of the compressor 21 was about 19.8 kW, which was about 4.3 times that of Example 1. Further, the hydrogen purifier 20 required a processing volume of 152.7 Nm ³ / h, which was 3.4 times that of Example 1.

It is a schematic block diagram of the fuel cell power generator of the present invention.

Explanation of symbols

10: Fuel cell body 11: Electrolyte 12: Anode electrode 13: Cathode electrode 14: Cooling water system 15: Steam separator 16: Cooling water circulation pump 17: Air supply device 18: Condensing device 19: Condensed water discharge pump 20: Hydrogen purifying device 21 : Compressor 22: off gas tank 23: desulfurizer 30: reformer 31: reformer 32: combustion device 33: CO converter 35: combustion air blower 36: reforming water supply pump 40: controllers F1 to F4: Flow meter T1: Thermometer V1 to V3: Valve

Claims (3)

A hydrogen purification apparatus for separating and purifying coke oven gas obtained by carbonizing coke into high-purity hydrogen and coke oven off-gas,
A coke oven off-gas discharge side of the hydrogen purification device is connected to the coke oven off-gas discharged from the hydrogen purification device by steam reforming to produce a reformed gas, and reaction heat is supplied to the reformer. A reformer comprising a combustion device to supply;
The high purity hydrogen discharged from the hydrogen purifier and the reformed gas discharged from the reformer are connected to the high purity hydrogen discharge side of the hydrogen purifier and the reformed gas discharge side of the reformer. A fuel cell power generator comprising: a fuel cell main body used as gas.   A coke oven gas flow meter for measuring the flow rate of the coke oven gas is disposed in a path on the inlet side of the hydrogen purifier, and the supply of steam to be supplied to the reformer based on the measured value of the coke oven gas flow meter The fuel cell power generator according to claim 1, wherein the fuel cell power generator is configured to steam reform the coke oven off-gas of the hydrogen purifier by adjusting the amount.   At least a part of the fuel off-gas discharged from the anode electrode of the fuel cell main body and combustion air are supplied to the combustion device and burned, and the supply amount of the fuel off-gas to the combustion device is adjusted. The fuel cell power generator according to claim 1, wherein the fuel cell power generator is configured to adjust a temperature of the reformer.