JP2019196414A - Tar reforming apparatus and tar reforming method - Google Patents

Abstract

To provide the tar reforming apparatus and the tar reforming method, that can efficiently reform the tar in one tower without circulating calcium oxide particles in a plurality of towers.SOLUTION: The tar reforming apparatus 10 for steam reforming tar contained in gas comprises: a reforming furnace body 11, a fluidized bed 13 containing calcium oxide (CaO) particles, arranged in the reforming furnace body 11 and not in contact with the gas, and a gas introduction part 12 for introducing the gas containing the tar and steam into the fluidized bed 13 simultaneously or separately, wherein the tar contained in the gas is reformed by steam at a temperature of 750 to 950°C by a catalytic action of the calcium oxide particles in the fluidized bed 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tar reforming apparatus and a tar reforming method for steam reforming a tar contained in a gas without oxygen.

  High-grade gas used in fuel gas for power generation facilities and synthetic gas for chemical products, etc. by pyrolyzing and gasifying various organic materials such as coal, biomass, waste, petroleum residue, heavy oil, etc. Techniques for manufacturing are known. In the gasification step of the organic raw material, tar is often contained in the gas, but tar is known to inhibit the water gasification reaction (carbon + water vapor → carbon monoxide + hydrogen). Furthermore, high-grade gas is generated through a heat exchanger for heat recovery or the like, but tar may cause clogging of the heat exchanger or the like. For this reason, in the process which produces | generates high quality gas, it was necessary to remove a tar part from gas.

  Two methods are mainly used to remove tar. One is a method of partially burning tar using pure oxygen. This has problems such as a large energy loss and a low hydrogen content of the product gas. The other is a catalyst reforming method using an expensive catalyst. This method has problems such as high catalyst costs.

The present inventors have developed a three-column circulating fluidized bed gasifier using calcium oxide (CaO) particles, which is a relatively inexpensive catalyst (for example, Patent Document 1). This three-column circulating fluidized bed gasification apparatus includes a fluidized bed combustion tower, a fluidized bed tar reforming tower, and a fluidized bed gasification tower, and circulates CaO particles in an apparatus connecting the three towers. In the tar reforming tower, the CaO particles heated in the combustion tower are steam reformed (decomposed) while being in contact with the tar, and the gas in which the tar is decomposed is supplied to the gasification tower. Here, the CaO particles function not only as a tar reforming catalyst but also as a desulfurization agent. In the gasification tower, the reaction of CaO + H ₂ S → CaS proceeds, and in the combustion tower, the reaction of CaS + 2O ₂ → CaSO ₄ proceeds. .

JP 2014-240472 A (Claim 6, paragraph 0012, paragraph 0013, etc.)

In the three-column circulating fluidized bed gasification apparatus of Patent Document 1, since the tar reforming tower is incorporated in the tower, the tar reforming tower alone cannot be removed and used alone. Further, in this three-column circulating fluidized bed gasifier, CaO particles circulate through the three towers, and the CaO particles function not only as a tar reforming catalyst but also as a desulfurizing agent. For this reason, CaO that has become CaS or CaSO ₄ has reduced tar reforming performance, and from the viewpoint of pure tar reforming, the reforming efficiency is low in the conventional three-column circulating fluidized bed gasifier. It was.

  An object of the present invention is to provide a tar reforming apparatus and a tar reforming method capable of efficiently reforming tar in one tower without circulating calcium oxide particles in a plurality of towers. And

  As a result of intensive studies to solve the above problems, the present inventor arranges a fluidized bed made of unreacted calcium oxide particles that are not in contact with gas in the reforming furnace main body, thereby allowing tar in one tower. Has been found to be able to be efficiently modified, and the present invention has been completed.

  The present invention relates to a tar reforming apparatus for steam reforming tar contained in a gas, the reforming furnace main body, and an oxidation in a state of being arranged in the reforming furnace main body and not in contact with the gas A fluidized bed containing calcium (CaO) particles, and a gas introduction part that introduces tar-containing gas and water vapor into the fluidized bed simultaneously or individually, and in the fluidized bed, by the catalytic action of the calcium oxide particles The tar contained in the gas is modified by the water vapor at a temperature of 750 to 950 ° C.

  According to the present invention, since the fluidized bed of calcium oxide particles is provided in the reforming furnace body, the reforming reaction of tar can be performed by the reforming furnace alone. Further, since the calcium oxide in the fluidized bed is unreacted that is not in contact with gas, tar can be reformed with high reforming efficiency.

  In said case, it is preferable to provide the heating means which heats the said calcium oxide particle to 750-950 degreeC.

  With such a configuration, the calcium oxide particles can be heated under strict temperature control. For this reason, the reforming efficiency of tar can be controlled more strictly.

  Alternatively, in the above case, a combustion device that generates a high-temperature gas of 750 ° C. or higher as the gas may be further provided, and the calcium oxide particles may be heated to 750 to 950 ° C. in the fluidized bed by the heat of the high-temperature gas. preferable.

  With such a configuration, it is not necessary to separately provide a means for heating the calcium oxide particles, and the apparatus configuration can be simplified.

In the above case, the particle diameter adjusting means for adjusting the particle diameter so that the particle diameter of the calcium oxide particles is within a range of 0.1 to 1 mm, and the mole (C) of carbon contained in the gas. The molar ratio adjusting means for adjusting the molar ratio so that the ratio (S / C) of the mole (S) of water vapor to the water is 1.5 or more, and the gas flow rate relative to the minimum fluidization speed (u _mf ) in the fluidized bed ( u 0 ratio _{of) (u} 0 _/ u _mf) that that and a gas flow rate adjusting means for adjusting the gas flow rate at 2 or more is preferable.

  With such a configuration, tar reforming can be performed under optimum conditions.

  The present invention is a tar reforming method for steam reforming tar contained in a gas, wherein a fluidized bed containing calcium oxide (CaO) particles not in contact with the gas is disposed in the reformer main body. In the fluidized bed, the gas introduction step in which the gas containing the tar and the water vapor are introduced into the fluidized bed simultaneously or individually, and the fluidized bed in the gas by the catalytic action of the calcium oxide particles. A reforming step of reforming the tar with the water vapor at a temperature of 750 to 950 ° C.

  According to the present invention, since the fluidized bed of calcium oxide particles is provided in the reforming furnace body, the reforming reaction of tar can be performed by the reforming furnace alone. Further, since the calcium oxide in the fluidized bed is unreacted that is not in contact with gas, tar can be reformed with high reforming efficiency.

  In said case, it is preferable to provide the heating process which heats the said calcium oxide particle to 750-950 degreeC.

  With such a configuration, the calcium oxide particles can be heated under strict temperature control. For this reason, the reforming efficiency of tar can be controlled more strictly.

  Or in said case, it is preferable to produce | generate high temperature gas of 750 degreeC or more as said gas, and to heat the said calcium oxide particle to 750-950 degreeC in the said fluidized bed with the heat | fever of this high temperature gas.

  With such a configuration, it is not necessary to separately provide a means for heating the calcium oxide particles, and the apparatus configuration can be simplified.

Moreover, in said case, the particle diameter of the said calcium oxide particle exists in the range of 0.1-1 mm, and the ratio (S / of the mole (S) of water vapor | steam with respect to the mole (C) of carbon contained in the said gas. Preferably, C) is 1.5 or more, and the ratio (u ₀ / u _mf ) of the gas flow rate (u ₀ ) to the minimum fluidization rate (u _mf ) in the fluidized bed is 2 or more.

  With such a configuration, tar reforming can be performed under optimum conditions.

  According to the present invention, there is provided a tar reforming apparatus and a tar reforming method capable of efficiently reforming tar in one tower without circulating calcium oxide particles in a plurality of towers. Can do.

It is a mimetic diagram showing tar reforming device 1 concerning one embodiment of the present invention. It is a schematic diagram which shows the mechanism of the tar modification | reformation by CaO. It is a schematic diagram which shows the heating method which concerns on other embodiment. It is a schematic diagram which shows the tar reforming apparatus used in the Example. In an Example, it is a photograph which shows the tar improvement effect in case CaO particle | grain fluidized bed temperature 900 degreeC, 850 degreeC, and 800 degreeC. In an Example, it is a photograph which shows the modification | reformation effect in the case of different CaO particle diameter. In an Example, it is a photograph which shows the tar reforming effect in the case of different water vapor | steam density | concentrations. It is a graph which shows the relationship between a gas flow rate and a fluidized bed differential pressure (fluid state). In an Example, it is a photograph which shows the tar reforming effect (reforming temperature 900 degreeC, S / C = 1.5, particle diameter 0.1-1 mm) in the case of a different gas flow velocity (superficial velocity). In an Example, it is a graph which shows the tar reforming production | generation gas composition on optimal conditions.

1. First Embodiment Hereinafter, a tar reforming apparatus and a tar reforming method according to a first embodiment of the present invention will be described. The tar reforming device is a device for reforming tar contained in a gas generated by pyrolysis and gasification of coal or biomass to generate fuel gas or synthesis gas.

  FIG. 1 is a schematic diagram showing a tar reforming apparatus according to a first embodiment of the present invention. The tar reforming apparatus 10 is an apparatus for steam reforming tar contained in a gas. The tar reforming apparatus 10 of the present embodiment includes a reforming furnace main body 11, a gas introduction unit 12, a fluidized bed 13, a particle introduction unit 14, and a gas discharge unit 15.

  The reforming furnace body 11 is a tower having a space inside. The reformer main body 11 of the present embodiment has a cylindrical shape with a rectangular side surface, but is not limited to this, and various forms can be adopted.

  The gas introduction unit 12 communicates the fluidized bed 13 with the outside, and can introduce a gas containing tar and water vapor into the fluidized bed 13 simultaneously or individually. The gas introduction part 12 is formed on the lower side of the reforming furnace main body 11 and introduces gas and water vapor from the lower side of the fluidized bed 13. A gas flow rate adjusting means 17 and a molar ratio adjusting means 18 are provided on the upstream side of the gas introduction unit 12 from the downstream side.

  The gas flow rate adjusting means 17 is a means for controlling the flow rate of the mixed gas of gas and water vapor, and is constituted by a control valve in this embodiment. The gas flow rate adjusting means 17 adjusts the flow rate of the mixed gas introduced into the fluidized bed 13 based on a gas flow meter (not shown) or the like. The gas flow rate adjusting means 17 is not limited to the control valve, and other means having a gas flow rate adjusting function can be used.

  The molar ratio adjusting means 18 is a means for adjusting the mixing ratio of gas and water vapor, and is constituted by a gas mixer in this embodiment. Two pipes, a gas introduction pipe and a water vapor introduction pipe, are connected to the molar ratio adjusting means 18, and the mixing ratio of the gas and the water vapor can be adjusted by adjusting the throttle of each introduction pipe. it can. The molar ratio adjusting means 18 is not limited to a gas mixer, and other means having a molar ratio adjusting function can be used.

  The fluidized bed 13 is a layer that is disposed in the reforming furnace body 11 and contains calcium oxide (CaO) particles. The CaO particles used in the present embodiment are quick lime particles obtained by calcination (thermal decomposition) of natural limestone or dolomite. The CaO particles of the fluidized bed 13 in the present invention are unreacted particles that are not in contact with the gas. The upper side of the fluidized bed 13 is a free board 11a.

CaO particles used for tar modification can be made by calcination of CaCO ₃ -containing natural minerals such as limestone and dolomite, and CaO particles may be prepared by calcination of these natural minerals in advance. A commercially available product may be purchased and used. Furthermore, when the temperature of the fluidized bed 13 is 850 ° C. or higher, limestone or dolomite particles can be directly charged into the fluidized bed 13 to decompose CaCO ₃ in the fluidized bed 13 to generate CaO particles.

  The particle introduction unit 14 communicates the free board 11 a with the outside, and can introduce CaO particles into the fluidized bed 13. In the present embodiment, a control valve and a particle diameter adjusting unit 16 are connected to the upper side of the particle introduction unit 14. The particle diameter adjusting means 16 is a means for adjusting the particle diameter of the CaO particles. In this embodiment, a filter that passes particles having a predetermined particle size range is used. The particle diameter adjusting means 16 is not limited to a filter, and other means having a particle diameter adjusting function such as a cyclone can be used.

  The gas discharge unit 15 communicates the free board 11a with the outside, and can discharge the gas modified by the fluidized bed 13 to the outside.

  Next, peripheral equipment of the tar reforming apparatus 10 of the present invention will be described. A pyrolysis furnace, a gasification furnace, etc. (not shown) are connected to the upstream side of the gas introduction unit 12, and pyrolysis of coal, biomass, etc., and the gasification gas passes through the molar ratio adjusting means 18 and the gas flow rate adjusting means 17. It is introduced into the free board 11 a of the reforming furnace body 11.

A CaO particle storage unit (not shown) is provided above the particle introduction unit 14 and stores unreacted CaO particles and calcium carbonate (CaCO ₃ ) particles (limestone, dolomite, etc.). CaO particles and CaCO ₃ particles are introduced into the reforming furnace main body 11 through the particle diameter adjusting means 16.

  The reformed gas discharged from the gas discharge unit 15 is used for various applications as necessary through a heat exchanger (not shown).

Next, a tar reforming method using the tar reforming apparatus 10 will be described. From the particle introduction unit 14, CaO particles or CaCO ₃ particles are introduced into the fluidized bed 13 of the reforming furnace main body 11 in advance to form the fluidized bed 13 made of CaO particles (fluidized bed arranging step). The CaCO ₃ particles release carbon dioxide at approximately 825 ° C. or more to become CaO particles.

  On the other hand, pyrolysis and gasification gas generated by pyrolysis and gasification of coal, biomass, etc. in a pyrolysis and gasification apparatus (not shown) passes through the molar ratio adjusting means 18 and the gas flow rate adjusting means 17, and is supplied to the gas introduction unit 12 is introduced into the fluidized bed 13 of the reforming furnace body 11 (gas introduction step). Pyrolysis and gasification gas is mixed with water vapor by the molar ratio adjusting means 18 and introduced into the fluidized bed 13 with the gas flow rate adjusting means 17 adjusting the flow rate of the mixed gas.

  In the fluidized bed 13, pyrolysis, gasification gas and calcium oxide particles are in contact. Since pyrolysis and gasification gas are high temperature, CaO particle | grains are also heated at 750-950 degreeC. The tar contained in the combustion gas is reformed (decomposed) by the catalytic action of the CaO particles (reforming step). In the present embodiment, the tar reforming is performed by heating the CaO particles by high-temperature pyrolysis and gasification gas, but the CaO particles of the fluidized bed 13 may be heated by a heating means described later (heating step). .

FIG. 2 is a schematic diagram showing the mechanism of tar decomposition by CaO particles. The main raw material for tar is hydrocarbon (C _m H _n ). In the first stage, tar cracks on the surface of CaO particles, and carbon (carbon) and gas are generated. In the subsequent second stage, carbon and water vapor react with the catalytic action of CaO particles to produce carbon monoxide (CO), carbon dioxide (CO ₂ ), and hydrogen (H ₂ ). Due to the catalytic action of CaO, carbon deposited on the surface of the CaO particles is gasified, tar cracking is accelerated, and the reforming reaction proceeds. The reaction at each stage is shown below.
First stage: C _m H _n → (high temperature CaO particle surface) → C + H ₂
Second stage: C + H ₂ O → (CaO catalysis) → CO + H ₂
C + 2H ₂ O → (CaO catalytic action) → CO ₂ + 2H ₂

  The pyrolysis and gasification gas reformed in the fluidized bed 13 is discharged to the outside through the free board 11a and the gas discharge unit 15. Similarly, gases such as carbon monoxide, carbon dioxide, and hydrogen generated by reforming tar in the fluidized bed 13 are discharged to the outside through the gas discharge unit 15. These gases are appropriately separated or liquefied and used for various purposes.

  The CaO particles pulverized or deteriorated in the fluidized bed 13 may be discharged to the outside through a cyclone through a particle discharge unit (not shown), or may be discharged to the outside through a gas discharge unit 15.

2. Detailed conditions for oxygen-free tar modification Since tar gas cracks on the CaO surface, carbon gasification proceeds. From the viewpoint of reforming efficiency, the specific surface area of the CaO particles is large and the contact time with the gas is long. Better. The tar reforming conversion rate can be expressed by the following formula.
Tar reforming conversion rate = k · (4π (dp / 2) ² / (4/3 · π (dp / 2) ³ ) · (layer height / gas flow rate)
= K · 6 / dp · (layer height / gas flow rate)
(Here, the bed height represents the height of the fluidized bed 13, the gas flow velocity represents the flow velocity of the gas introduced into the fluidized bed 13 through the gas introduction part 12, dp represents the average diameter of the CaO particles, and k represents the proportional coefficient. Means.)

  From this equation, the tar reforming rate is inversely proportional to the CaO particle diameter dp, and inversely proportional to the gas flow rate when the bed height is constant. However, if the CaO particle diameter is too small, CaO particles are likely to jump out of the fluidized bed 13, and if the gas flow rate is too small, the fluidized state of the fluidized bed 13 is likely to deteriorate, and in any case, the reaction efficiency tends to be low. . Hereinafter, detailed conditions such as CaO particle diameter and gas flow rate will be described.

(1) CaO particle diameter The particle diameter of CaO particles and limestone is usually within a range of 0.01 to 10 mm. From the viewpoint of fluidity of CaO particles in the fluidized bed 13 and tar reforming efficiency, 0.05. The range of ˜2 mm is preferable, and the range of 0.1 to 1 mm is particularly preferable. When the CaO particle diameter is less than 0.1 mm, the CaO particles easily jump out of the fluidized bed 13 and it is difficult to maintain the fluidized bed 13. When the CaO particle diameter exceeds 1 mm, the particles become too large, the specific surface area becomes small, and the tar reforming efficiency tends to decrease. In the present specification, the particle diameter means an average particle diameter and means an average value of the particle diameters of a plurality of particles. The particle diameter can be determined by a method of confirming and calculating the particle diameter with an observation means such as SEM, a method of measuring with a particle size analyzer, or the like. In the tar reforming apparatus 10 of this embodiment, the CaO particles can be adjusted by the particle diameter adjusting means 16.

(2) Temperature of fluidized bed 13 The process of tar reforming with CaO is the first stage, in which tar cracks on the surface of CaO particles to generate carbon and H ₂ , and in the second stage, carbon is a catalyst of CaO particles. Since it reacts with H ₂ O and gasifies into CO and H _{2 due} to its action, a high temperature is required for tar cracking. The temperature of the fluidized bed 13 needs to be a temperature at which tar cracking occurs on the surface of the CaO particles, and is usually 800 ° C. or higher, preferably 850 ° C. or higher. When the temperature of the fluidized bed 13 is lower than 800 ° C., cracking hardly occurs and tar reforming efficiency tends to be low. In the tar reforming apparatus 10 of the present embodiment, the temperature of the fluidized bed 13 is not controlled because it is heated by the combustion gas, but in other embodiments described later, the fluidized bed 13 and CaO particles are directly heated by a heating means. By adjusting the temperature.

(3) Gas carbon / steam molar ratio The second stage of tar reforming is gasification of carbon by steam with CaO catalytic action. This is greatly influenced by the concentration ratio of carbon and water vapor (carbon mole / water vapor mole). The ratio (molar ratio = S / C) of the water vapor mole (S) to the carbon mole (C) in the gas (including tar) in the gas introduction part 12 is preferably 1.5 or more, and more preferably 2.0 or more. When S / C is less than 1.5, tar reforming efficiency tends to be low. In the tar reforming apparatus 10 of the present embodiment, the carbon / steam molar ratio of the gas can be adjusted by the molar ratio adjusting means 18.

(4) Gas flow rate and gas residence time The gas flow rate u ₀ of the fluidized bed 13 is preferably at least twice the minimum fluidization rate u _mf , particularly preferably 2 to 3 times. Here, the minimum fluidization speed u _mf means a minimum gas flow rate necessary for forming the fluidized bed 13, and below this means a gas flow rate at which the fluidized bed 13 stops flowing. Here, the gas flow rate is a superficial gas flow rate of the reforming furnace main body. Although depending on conditions such as the CaO particle diameter, the minimum fluidization speed u _mf is usually 0.05 m / s or more, and generally about 0.1 m / s.

  Further, the gas flow rate is 0.2 m / s or more, preferably in the range of 0.2 to 0.3 m / s. Moreover, the gas residence time in the fluidized bed 13 is usually 1 s or longer, and preferably 1.5 s or longer. In the tar reforming apparatus 10 of the present embodiment, the gas flow rate and residence time can be adjusted by the gas flow rate adjusting means 17.

As described above, by using the tar reforming apparatus and the tar reforming method of the present invention, an inexpensive CaO absorbent (obtained from limestone calcining) is used, and an oxygen separation plant and an expensive catalyst are not required, and low Tar reforming can be realized with a costly and high H ₂ -containing gas.

2. Other Embodiments As a method of heating the fluidized bed 13, in addition to the form in which high-temperature pyrolysis and gasification gas are directly used for heating the fluidized bed 13 as in the above embodiment, means for heating the fluidized bed 13 is used. It may be a form provided separately. FIG. 3 is a schematic view showing an embodiment provided with a heating means.

  In the embodiment shown in FIG. 3A, the fluidized bed 13 is heated by providing the heating means 21 on the outer periphery of the reforming furnace body 11. As the heating means 21, a known means such as a heater can be adopted. It is preferable that the heating means 21 can control temperature. With such a configuration, the temperature of the fluidized bed 13 can be strictly controlled, and the tar reforming efficiency can be improved.

  In the embodiment shown in FIG. 3B, the heating means 22 is provided outside the reforming furnace body 11, and CaO particles are circulated from the reforming furnace body 11 and heated. The heating means 22 is provided with a hollow cylinder, a blower, a heater, etc., and uses a means for heating the CaO particles with a heater provided outside the cylinder while allowing the wind of the blower to pass the CaO particles into the cylinder. Can do. By setting it as such a structure, it becomes possible to heat CaO particle | grains uniformly and tar improvement efficiency can be improved.

3. In the above embodiment, the CaO particle diameter, the temperature of the fluidized bed 13, the gas carbon / water vapor molar ratio, the gas flow rate and the gas residence time are the particle diameter adjusting means 16, the heating means 21, 22, and the molar ratio. The adjusting means 18 and the gas flow rate adjusting means 17 are respectively automatically controlled. However, the tar reforming apparatus and the tar reforming method of the present invention are not limited to this. These means are unnecessary, and it is also possible to adjust manually rather than automatically by the apparatus. That is, it is also possible to implement the tar reforming method using a tar reformer using a device obtained by removing at least one of these means from the device of the above embodiment.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, these do not limit the objective of this invention. The present invention is not limited to these examples.

1. Experimental apparatus and experimental method Using a small two-stage fluidized bed reactor, steam and coal, biomass, and other tar-generating substances such as biomass are continuously supplied to the lower gasifier (approximately 800 ° C) for thermal decomposition. Other gases (including steam) were introduced into the upper reforming furnace. The upper reforming furnace was provided with a CaO particle fluidized bed to perform steam reforming of tar. A tar trap device and a gas composition analyzer were installed in the exhaust gas line, and the exhaust gas composition was continuously measured. Moreover, the carbon content (TOC) in the collected liquid was analyzed.

  Hereinafter, the experimental apparatus and experimental method used in this example will be described in detail. FIG. 4 shows a schematic diagram of the two-stage fluidized bed reactor used in this example. A fluidized bed reactor made of quartz glass was used as the upper reforming reactor, and a fluidized bed gasification reactor made of quartz glass was further provided in the lower stage. The inner diameters of the upper and lower reactors are both about 30 mm, and the lengths are about 1500 mm and 1000 mm, respectively. The heating zone by the electric furnace is about 1000 mm and 500 mm respectively for the upper and lower stage reaction tubes.

A supply pipe that is bent at an angle of about 30 ° C. with respect to the longitudinal direction of the lower reactor was provided below the lower reactor in order to supply coal, biomass, and the like into the lower reactor.
The upper reactor was provided with a transparent air-cooling zone at the outlet of the upper reactor, so that the presence or absence or the state of tar adhesion (generation) to the inner wall surface of the quartz reaction tube could be visually confirmed.
The generated gas (gasification and tar reforming gas) discharged from the upper stage was first cooled to about 150 ° C. through the air cooling zone of quartz glass, and the presence or absence of tar on the inner wall surface of the air cooling zone was confirmed. Furthermore, the product gas after cooling was gas-liquid separated in a condensing bottle and introduced into a gas analyzer through a filter.

2. Experimental results (appropriate conditions for tar reforming)
2.1 Appropriate fluidized bed temperature (800 ° C or higher)
FIG. 5 is a photograph showing the state of tar generation (whether or not tar is generated in the visual range) when the CaO particle fluidized bed temperature is adjusted to 900 ° C., 850 ° C., and 800 ° C. When the CaO particle fluidized bed temperature was 900 ° C. (FIG. (A)) and 850 ° C. (FIG. (B)), almost no deposits were observed and the glass tube remained transparent. When lowered to (figure (c)), there are many deposits on the tar viewing part. Therefore, from the viewpoint of tar reforming efficiency, it was found that the higher the temperature of the fluidized bed 13, the better, 800 ° C or higher, preferably 850 ° C or higher.

2.2 Appropriate particle size (0.1-1mm)
FIG. 6 is a photograph showing the tar reforming effect (presence / absence of tar generation) of CaO particle fluidized beds having different particle sizes. From this result, when the CaO particle diameter is 1 to 2 mm ((a) in the figure), it can be seen that tar adheres to the tar visual observation area. This is thought to be because the specific surface area of the particles decreased because the particles became larger, and the tar reforming effect deteriorated. On the other hand, when the CaO particle diameter is in the range of 0.1 to 1 mm ((b) in the figure), it can be seen that there is almost no tar adhesion in the visual observation area, and the tar has been completely modified by the CaO particles. Therefore, it was found that the CaO particle diameter is preferably 0.1 to 1 mm from the viewpoint of tar reforming efficiency.

2.3 Appropriate carbon / water vapor molar ratio (S / C> 1.5)
FIG. 7 is a photograph showing the tar reforming effect (whether or not tar is produced) when the carbon / water vapor molar ratio is changed in the fluidized bed 13 of CaO particles (particle diameter 0.1 to 1 mm). “S / C” in the figure indicates “water vapor mole / carbon mole”. As shown in this figure, in the case of S / C = 1.5 ((a) in the figure), the glass tube was almost transparent, and tar adhesion was hardly seen. On the other hand, in the case of S / C = 1 ((b) in the figure), the reaction tube was not transparent, and a state where tar adhered was observed. Therefore, it was found that the carbon / steam molar ratio is preferably 1.5 or more from the viewpoint of tar reforming efficiency.

2.4 Appropriate gas flow rate (superficial velocity) ratio (2 to 3 times u _mf )
FIG. 8 is a graph showing experimental results of the fluidized bed differential pressure (fluid state) together with the gas flow rate when the CaO particle diameter is 0.1 to 1 mm. The minimum fluidization speed u _mf is about 0.1 m / s, and when the superficial velocity becomes twice or more than u _mf , bubbles are uniformly generated and the fluidized bed 13 is maintained. Therefore, from the viewpoint of maintaining the fluidized bed, the ratio (u ₀ / u _mf ) of the gas flow rate (u ₀ ) to the minimum fluidization speed (u _mf ) in the fluidized bed is 2 times or more, particularly within a range of 2 to 3 times. It turned out to be preferable.

2.5 Gas residence time in fluidized bed (> 1s)
FIG. 9 shows the tar reforming effect of the fluidized bed 13 at different gas flow rates (superficial velocity) when the reforming temperature is 900 ° C., the CaO particle diameter is 0.1 to 1 mm, and S / C = 1.5. It is a photograph. When the residence time is 1.5 s (gas flow rate is 0.27 m / s) ((a) in the figure) and when the residence time is 1 s (gas flow rate is 0.36 m / s) ((b) in the figure) In both cases, the glass tube was almost transparent, and tar adhesion was hardly observed. Therefore, it was found that the residence time of the gas in the fluidized bed 13 is preferably 1 s or more (gas flow rate is 0.36 m / s or less) from the viewpoint of tar reforming efficiency.

2.6 Tar reforming and reformed gas composition under optimum conditions FIG. 10 shows a CaO particle diameter of 0.1 to 1 mm, a reforming temperature of 900 ° C., a water vapor concentration S / C = 1.5, and a gas flow rate u ₀ of u. It is a graph which shows the result of the product gas composition from tar reforming when optimal conditions, such as 2.7 times _{mf and} the gas residence time in a CaO fluidized bed 1.5s, are prepared. Under these conditions, tar is completely reformed, and the gas composition after reforming has a lot of H ₂ , and it is understood that the rest are CO, CO ₂ and CH ₄ . That is, it can be seen that tar (C _m H _n ) is decomposed into H ₂ , CO, and CO ₂ .

DESCRIPTION OF SYMBOLS 10 Tar reformer, 11 Reforming furnace main body, 11a Free board, 12 Gas introduction part, 13 Fluidized bed, 14 Particle introduction part 15 Gas discharge part, 16 Particle diameter adjustment means, 17 Gas flow rate adjustment means, 18 Molar ratio adjustment Means, 21 heating means, 22 heating means

Claims (8)

A tar reforming device for steam reforming tar contained in a gas,
A reformer body,
A fluidized bed containing calcium oxide (CaO) particles arranged in the reformer body and not in contact with the gas;
A gas introduction section for introducing the tar-containing gas and water vapor into the fluidized bed simultaneously or separately,
In the fluidized bed, the tar reforming apparatus characterized in that the tar contained in the gas is reformed by the steam at a temperature of 750 to 950 ° C. by the catalytic action of the calcium oxide particles.   The tar reforming apparatus according to claim 1, further comprising heating means for heating the calcium oxide particles to 750 to 950 ° C. The gas further includes a combustion device that generates a high temperature gas of 750 ° C. or higher,
The tar reforming apparatus according to claim 1, wherein the calcium oxide particles are heated to 750 to 950 ° C in the fluidized bed by the heat of the high-temperature gas. Particle diameter adjusting means for adjusting the particle diameter so that the particle diameter of the calcium oxide particles is within a range of 0.1 to 1 mm;
A molar ratio adjusting means for adjusting a molar ratio so that a ratio (S / C) of a mole (S) of water vapor to a mole (C) of carbon contained in the gas is 1.5 or more;
In that it comprises a gas flow rate adjusting means for adjusting the gas flow rate so that the ratio of gas flow velocity _{(u 0) (u 0 /} u mf) is 2 or more with respect to the minimum fluidization velocity (u _mf) in the fluidized bed The tar reformer according to claim 1, wherein A tar reforming method for steam reforming tar contained in a gas,
A fluidized bed disposing step of disposing a fluidized bed containing calcium oxide (CaO) particles not in contact with the gas in the reformer body;
A gas introduction step of introducing a gas containing tar and water vapor into the fluidized bed simultaneously or separately;
A reforming step of reforming the tar contained in the gas with the steam at a temperature of 750 to 950 ° C. by the catalytic action of the calcium oxide particles in the fluidized bed. .   The tar reforming method according to claim 5, further comprising a heating step of heating the calcium oxide particles to 750 to 950 ° C. As the gas, a high temperature gas of 750 ° C. or higher is generated,
The tar reforming method according to claim 5, wherein the calcium oxide particles are heated to 750 to 950 ° C. in the fluidized bed by the heat of the high-temperature gas. The particle diameter of the calcium oxide particles is in the range of 0.1 to 1 mm,
The ratio (S / C) of the mole (S) of water vapor to the mole (C) of carbon contained in the gas is 1.5 or more,
Tar reforming method according to claim 5, wherein the ratio of gas flow rate to the minimum fluidization velocity _{(u mf)} in the fluidized bed _{(u 0) (u 0 /} u mf) is 2 or more.