JP4224609B2 - Reducing gas production apparatus and method - Google Patents

Description

  The present invention relates to a reducing gas production apparatus and method for producing a reducing gas containing carbon monoxide and hydrogen.

In general, various methods such as a partial combustion method, a steam reforming method, and a carbon dioxide reforming method have been proposed as methods for obtaining a reducing gas from hydrocarbons. The reaction proceeds according to

  For example, in the partial combustion method, a reducing gas is obtained by incomplete combustion with oxygen in an amount less than that required for complete combustion of the combustion gas stoichiometrically. In the case of complete combustion, hydrocarbons become water vapor and carbon dioxide, whereas combustion up to hydrogen and carbon monoxide is partial combustion as shown in equation (1).

However, in the case where the reducing gas is produced by any of the above methods, soot (C (S)) due to carbon deposition and incomplete combustion reaction are always accompanied. For example, in the partial combustion method, in the actual reaction, the reaction rate dominates the reaction, and the reaction of the formula (1) does not proceed promptly. Further, when the uniform reaction does not proceed, the reaction of the formula (4) proceeds, and soot that is an undesired product is generated.

  If soot is generated in a large amount, it clogs the piping and the combustor, causing not only abnormal combustion but also hindering practical use as a reducing gas.

  One way to prevent soot generation is to bring the amount of oxygen supplied to the combustion system closer to that required for complete combustion. However, as a result, in the composition of the reducing gas, the proportion of hydrogen and carbon monoxide effective for the reduction is reduced, and the proportion of water vapor and carbon dioxide that is undesirable for the reduction is increased.

In the partial combustion method, when the oxygen ratio is increased, the reaction of the formula (5) easily proceeds.

  As a result, surplus water vapor and carbon dioxide not only have no reducing ability, but if they are contained in a reducing gas in a certain ratio or more, the reducing ability of hydrogen or carbon monoxide is undesirably restricted due to equilibrium.

When a reducing gas obtained by burning hydrocarbon-based fuel gas and oxygen at an oxygen ratio of about 0.3 to 0.4 by the partial combustion method is produced by incomplete combustion due to the low oxygen ratio, the combustion reaction It is considered that the enthalpy (thermal energy) generated is reduced and the carbon atom in the decomposed hydrocarbon is not easily bonded to the oxygen atom, so that the reaction of the above formula (4) occurs and soot is generated. The oxygen ratio shown here is the ratio of the amount of oxygen actually supplied to the combustion system with respect to the amount of oxygen necessary to theoretically completely burn the fuel gas. As a device that suppresses the generation of soot by suppressing the loss of enthalpy caused by the combustion reaction due to heat dissipation to the outside of the system and preventing the reaction rate from decaying and non-uniform reaction, it mixes oxidant and fuel gas. Reducing gas generation burner (Patent Document 1) in which an oxidizing agent is supplied to the mixing throat at supersonic speed or subsonic speed, and a reducing gas generation with a small combustion chamber at the tip to increase the volume load with respect to the combustion amount Examples thereof include a device (Patent Document 2).
No. 2-9238 JP-A-62-59502

  In any of the above-described devices, the temperature of the combustion exhaust gas is low, so if the degree of reduction of the combustion exhaust gas is increased, soot is excessive and continuous operation cannot be performed, and if the amount of soot generation is suppressed, the degree of reduction is low. There is a problem of becoming.

Therefore, by using pure oxygen with a concentration of 100% as an oxidant, the relationship between the oxygen ratio when burning propane gas as a fuel gas, the reducing gas component, and the adiabatic flame temperature neglecting heat radiation for convenience is obtained by calculation. In addition, the relationship between the Bacharach index of the reducing gas and the oxygen ratio (R value) when the combustion was performed by the apparatus described in Patent Document 2 was obtained by actual measurement. The former calculation result is shown in FIG. 2, and the latter actual measurement result is shown in FIG. In FIG. 2, C (S) means carbon in a solid state. The Bacharach index is an index that represents the amount of soot and dust in the combustion exhaust gas. Here, the soot generation amount is shown. The R value is an index that represents the degree of reduction of the combustion exhaust gas, and the gas in the combustion exhaust gas. It is calculated from the component by the following equation (6).

From FIG. 2, in order to produce a stoichiometrically strong reducing gas consisting only of hydrogen and carbon monoxide, the oxygen ratio is reduced to 0.30 where the molar fraction of CO ₂ and H ₂ O is minimized. You can see that it needs to be lowered. The reaction formula in that case is shown by (7) Formula.

  In the reaction product of combustion at an oxygen ratio of 0.3, the R value is ∞ (infinite) because there are no oxidizing gases such as water vapor and carbon dioxide. Moreover, about reaction products other than oxygen ratio 0.3, water vapor | steam and a carbon dioxide generate | occur | produce, the quantity increases as it leaves | separates from 0.3, and it is not a perfect strong reducing gas. However, the calculated value of the adiabatic flame temperature when the oxygen ratio is 0.3 is as low as 1329K. At this adiabatic flame temperature, as shown in FIG. 3, the temperature is too low and incomplete combustion and a large amount of soot are generated. There are practical problems.

  FIG. 3 shows an oxygen ratio of 0.35 (R value = 13), and the amount of soot generated in the reaction product in the case of partial combustion does not impede practical use as a reducing gas (Bacalac) Index: 3), and the adiabatic flame temperature at this time is 1810K from FIG. That is, when the oxygen ratio and the adiabatic flame temperature are lower than this, incomplete combustion and a large amount of soot are generated, which hinders practical use as a reducing gas of the reaction product. 1810K is the lower limit of the adiabatic flame temperature that does not interfere with practical use.

  In the case where the present inventor combusts a hydrocarbon-based fuel gas with an oxidant having an oxygen ratio of 0.3, and generates only carbon monoxide and hydrogen as reaction products, as described above, In order to solve the problem that the adiabatic flame temperature is as low as 1320K and incomplete combustion and a large amount of soot occur, as described above, the lower limit of the adiabatic flame temperature that does not hinder practical use is 1810K. In view of the above, attention was paid to applying energy corresponding to the size of the double-headed arrow A in FIG. 2 and 3, in order to generate reducing gas without generating incomplete combustion and a large amount of soot, considering the temperature of the reducing gas in the combustion reaction field, considering that FIG. 2 is a calculated value. Therefore, it is necessary to make it approximately 1800K or more. The inventor of the present application paid attention to the practical and efficient use of arc discharge (plasma), for example, as means for this purpose.

  The present invention has been made on the basis of the above-mentioned attention to eliminate such conventional problems, and suppresses the generation of soot, water vapor and carbon dioxide, and is a reducing gas mainly composed of carbon monoxide and hydrogen. It is an object of the present invention to provide a reducing gas production apparatus and method capable of producing the above.

In order to solve the above problems, the first invention is:
In a reducing gas production apparatus for producing carbon monoxide and hydrogen by mixing a hydrocarbon fuel gas with an oxidant and burning it in a combustion system,
When the ratio of the oxygen amount actually supplied to the combustion system to the oxygen amount in the complete combustion state according to the reaction formula (5) is defined as an oxygen ratio,
Partial combustion according to the reaction formula (1) is performed at an oxygen ratio (m / 2) / (m + n / 4),
In order to make the adiabatic flame temperature at the oxygen ratio (m / 2) / (m + n / 4) higher than the adiabatic flame temperature in the incomplete combustion state according to the reaction formula (4),
An energy supply means for supplying energy to the combustion system is provided.

The second invention is a reducing gas production method for producing carbon monoxide and hydrogen by mixing and burning a hydrocarbon fuel gas with an oxidant in a combustion system,
When the ratio of the oxygen amount actually supplied to the combustion system to the oxygen amount in the complete combustion state according to the reaction formula (5) is defined as an oxygen ratio,
Partial combustion according to the reaction formula (1) is performed at an oxygen ratio (m / 2) / (m + n / 4),
In order to make the adiabatic flame temperature at the oxygen ratio (m / 2) / (m + n / 4) higher than the adiabatic flame temperature in the incomplete combustion state according to the reaction formula (4),
The energy is supplied to the combustion system .

  In addition to the configuration of the second invention, the third invention has a configuration in which the energy is energy required to set the temperature of the reducing gas containing carbon monoxide and hydrogen to about 1800 K or higher.

The fourth invention is, in addition to the configuration of the second or third invention, has a configuration in which the error Ne Energy is added by the arc discharge.
In the fifth aspect of the invention, in addition to the second to fourth aspects of the invention, the Bacharach index indicating the amount of soot generated in the combustion exhaust gas is less than 3.

  According to the present invention, it is possible to suppress the generation of soot, water vapor, and carbon dioxide and to produce a reducing gas mainly composed of carbon monoxide and hydrogen.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a reducing gas production apparatus 1 according to the present invention, and this reducing gas production apparatus 1 includes a combustion system 11 and a discharge heating system 12.

  The combustion system 11 has an oxidant introduction pipe 22 made of, for example, polyfluorinated ethylene, which is an electrical insulator, in which an oxidant supply hole 21 is formed in a side wall portion. Is attached with a tapered anode member 24 made of, for example, copper and having a funnel-shaped through hole 23 formed in the center thereof. The outside of the anode member 24 is surrounded by a cooling jacket 27 that leads to a cooling water inlet 25 and a cooling water outlet 26. A cathode fixing member 28 that closes the other end of the oxidant introduction tube 22 is screwed into the inside of the other end of the oxidant introduction tube 22, and a cathode connecting member 29 is projected from the cathode fixing member 28. The tip of the cathode connection member 29 is provided with a rectifying member 31 having a circular shape and a large number of fluid flow holes inserted into the oxidant introduction tube 22, and further, for example, from copper. The cathode member 32 is extended. In the present embodiment, the cathode member 32 is formed in a shape having a large diameter portion on the proximal end side and a small diameter portion on the distal end side, and a refractory metal such as hafnium is silver brazing at the distal end of the small diameter portion. It is attached. The cathode connecting member 29 and the cathode member 32 extending beyond the cathode connecting member 29 are held at the center of the oxidant introduction tube 22 by the rectifying member 31. An oxidant introduction space 33 having a circular cross section is formed in the oxidant introduction pipe 22 from the opening of the oxidant supply hole 21 into the oxidant introduction pipe 22 to the tip of the small diameter portion. The through-hole 23, the anode member 24, the cathode member 32, and the oxidant introduction space 33 are coaxially positioned. In addition, an appropriate distance is maintained between the tip of the small diameter portion and the bottom of the mortar-like space inside the anode member 24 to form a discharge space 34. A terminal member 35 protrudes from the cathode fixing member 28 outside the oxidant introduction tube 22.

  Further, the combustion system 11 has a combustion pipe 41 made of a refractory provided so as to press the anode member 24 against the oxidant introduction pipe 22, and the combustion pipe 41 has a nozzle 42 extending following the through hole 23. And an open flame holding chamber 43 that extends beyond the nozzle 42 is formed. Furthermore, fuel gas supply ports 44 that lead to the nozzles 42 are provided at a plurality of locations around the combustion pipe 41, for example, four locations, and the flame holding chamber 43 is made of metal cooling that leads to the cooling water inlet 45 and the cooling water outlet 46. Surrounded by a jacket 47. The nozzle 42 and the flame holding chamber 43 are located coaxially together with the above-described through hole 23 and the like.

  The discharge heating system 12 includes a DC power supply 51, an ammeter 52, a switch 53, and a voltmeter 54 arranged in parallel to the DC power supply 51, the negative side being connected to the terminal member 35, and the positive side being an anode. It is connected to the member 24.

Next, the reducing gas production apparatus 1 having the above configuration will be described together with the reducing gas production method according to the present invention applied to this apparatus.
Under the condition that water is passed through the cooling jackets 27 and 47, the supply of the oxidant containing oxygen from the oxidant supply hole 21 is started, and the switch 53 is turned on so that the tip of the cathode member 32 and the anode member 24 are turned on. Arc discharge is caused in the discharge space 34 between and the oxidant, and a high-temperature plasma state is generated. According to the calculated value, the temperature of the oxidant in the discharge space 34 is 6000 to 10000 K. However, the anode member 24 is cooled by the cooling water in the cooling jacket 27, and the oxidant and fuel gas flow paths are melted. Is prevented. In the state where the arc discharge is maintained, the oxidant that has become a high temperature state due to the arc discharge goes from the through hole 23 to the nozzle 42 and is supplied with hydrocarbon-based fuel gas from the fuel gas supply port 44. . The fuel gas is mixed with the oxidant and causes a combustion reaction while facing the flame holding chamber 43. As a result, a reducing gas is generated and sent out from the opening of the flame holding chamber 43. Note that the enthalpy (thermal energy) of the reducing gas in the flame holding chamber 43 is the sum of the enthalpy applied by the arc discharge and the enthalpy generated by the combustion reaction.

  The front portion of the nozzle 42 is formed in a shape suitable for a combustion cylinder that holds a flame formed by the combustion reaction between the oxidant that has been converted to plasma and the fuel gas, and the periphery of the flame holding portion 43 is illustrated as shown. In addition to the metal cooling jacket 47, it may be made of a material with high fire resistance such as sirconia. When producing a higher temperature reducing gas, it is suitable to use this material with high fire resistance. Yes.

Then, fuel, oxygen ratio, the results generated various modifications to reducing gas energy applied to the combustion system shown in Table 1. In Comparative Examples 1 and 2 , the reducing gas generating burner described in Patent Document 1 is used and, as described in Patent Document 2, the enthalpy loss caused by the combustion reaction is suppressed by reducing the combustion chamber. Means a reducing gas generation method.

For fuel gas, the ratio Comparative Examples 1 and 2, using propane, the actual施例1-3, using propane in Examples 4 and 5 were used methane. As for the oxidizing agent, pure oxygen was used in both the examples and the comparative examples . In addition, a commercially available plasma cutting power source capable of continuous operation was used as the DC power source 51 in order to add enthalpy to the combustion system 11, particularly the discharge space 34. The reason for adopting arc discharge is that the apparatus is cheaper and more compact than, for example, RF discharge that generates an AC plasma state. Further, the enthalpy (thermal energy) given to the combustion system 11 during arc discharge was calculated from the discharge current and discharge voltage measured by the ammeter 52 and the voltmeter 53. Concerning the component analysis of the generated reducing gas, regarding moisture (H ₂ O), the moisture content is calculated from the measured dew point using a specular dew point meter, and other components (CO, CO ₂ , H, etc.) Gas chromatographic analysis was performed. Table 1 lists the R value calculated by Equation 6 based on the measurement result of the component composition obtained as a result of the analysis, that is, an index of the reduction degree of the reducing gas. However, regarding the amount of water, when it was 0.005% (dew point temperature 248K) or less, it was regarded as 0% for convenience in calculating the R value.

When Example 1 and Comparative Example 1 are compared , the Bacharach index is 3 in Comparative Example 1 , whereas it is 0 in Example 1. Energy is applied to the combustion system 11 from outside this system by arc discharge. It turns out that generation | occurrence | production of soot in reducing gas is suppressed by adding. Further, when the combustion reaction is caused at an oxygen ratio of 0.3, there has been a practical problem due to the incomplete combustion and the generation of a large amount of soot as described above according to the conventional method. On the other hand, in the present invention, as shown in Example 3, by applying energy to the combustion system 11 by arc discharge from outside this system so that the reducing gas temperature in the reaction field becomes 1800 K or more. The value is ∞, the Bacharach index is 2, and it can be seen that a reducing gas having excellent reducing ability and a small amount of soot can be obtained. In addition, it is not beneficial from the standpoint of energy cost and considering the heat resistance of the apparatus to set the reducing gas temperature in the reaction field to 2500 K or higher. In Examples 1 to 5, the reducing gas temperature in the reaction field is not useful. It has been shown that by setting 1 to 1800K or more, the generation of soot can be suppressed to an extent that does not impede practically.

  As described above, when the present invention is applied to, for example, the production of a reducing gas by the partial combustion method and energy is supplied from the outside, it is not necessary to increase the oxygen ratio. Incomplete combustion reaction and soot generation can be suppressed without increasing carbon. In addition, according to the present invention, it becomes possible to operate at an oxygen ratio for producing a reducing gas consisting only of carbon monoxide and hydrogen, which has been impossible with a flame in the past, and a gas having a very high reducing ability can be obtained. . Furthermore, in the conventional apparatus, after partial combustion, it is necessary to lower the combustion exhaust gas to the dew point to separate and remove water vapor, and reheating by indirect heating in an atmospheric furnace is necessary. The process becomes unnecessary, and the combustion exhaust gas can be directly fed into the atmosphere furnace at a high temperature.

  In the present invention, the fuel gas type is not particularly limited as long as it is a hydrocarbon-based fuel gas, and the oxygen concentration of the oxidant is not limited. However, when the oxygen concentration in the oxidant is low, the enthalpy generated in the combustion reaction is reduced by the heat release to the gas that does not contribute to the combustion other than oxygen contained in the oxidant. When the enthalpy generated by the combustion reaction is reduced, it is necessary to increase the enthalpy given from the outside of the combustion system 11 in order not to generate soot, and considering the energy intensity, it is not beneficial to reduce the enthalpy. Therefore, it is desirable to use pure oxygen as the oxidant from the viewpoint of preventing heat dissipation to the gas that does not contribute to combustion in the oxidant.

  For the purpose of giving energy to the combustion system 11, the method is not necessarily limited to the above-described arc discharge method, and energy supply means other than arc discharge may be used, but the configuration of the apparatus is simple and stable. The arc discharge described above is preferably used in that the purpose is surely achieved. In the arc discharge in the combustion system 11, the oxidizing agent, that is, the reactive gas becomes high temperature, and a part thereof becomes a plasma state and becomes ions and radicals, so that the reaction activity is greatly increased, and soot, carbon dioxide, etc. A substance due to a heterogeneous reaction is not generated, and a rapid and uniform combustion reaction proceeds and only carbon monoxide and hydrogen are generated. In the combustion system 11, arc discharge can be generated at three locations, that is, a location where the fuel gas and the oxidant are introduced separately, and a location where both are mixed. However, it is particularly preferable to generate an arc discharge with an oxidizing agent. This is because, with respect to oxygen and nitrogen, it is easy to obtain a stable plasma state, and reducing nitrogen can be used for the nitriding reaction by making nitrogen into a plasma state.

It is a figure showing the whole reducing gas manufacturing device composition concerning the present invention to which the reducing gas manufacturing method concerning the present invention is applied. It is a figure which shows the relationship between the oxygen ratio, reducing gas component, and the calculated value of adiabatic flame temperature at the time of burning propane gas which is fuel gas by using 100% concentration pure oxygen as an oxidant. It is a figure which shows the relationship between the Bacharach index and oxygen ratio (R value) based on the actual value at the time of burning the propane gas which is fuel gas by making into 100% density | concentration pure oxygen with the conventional apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reducing gas manufacturing apparatus 11 Combustion system 12 Discharge heating system 21 Oxidant supply hole 22 Oxidant introduction pipe 23 Through hole 24 Anode member 25 Cooling water inlet 26 Cooling water outlet 27 Cooling jacket 28 Cathode fixing member 29 Cathode connection member 31 Rectification Member 32 Cathode member 33 Oxidant introduction space 34 Discharge space 35 Terminal member 41 Combustion tube 42 Nozzle 43 Flame holding chamber 44 Fuel gas supply port 45 Cooling water inlet 46 Cooling water outlet 47 Cooling jacket 51 DC power supply 52 Ammeter 53 Switch 54 Voltage Total

Claims (5)

In a reducing gas production apparatus for producing carbon monoxide and hydrogen by mixing a hydrocarbon fuel gas with an oxidant and burning it in a combustion system,
When the ratio of the oxygen amount actually supplied to the combustion system to the oxygen amount in the complete combustion state according to the reaction formula (5) is defined as an oxygen ratio,

Partial combustion according to the reaction formula (1) is performed at an oxygen ratio (m / 2) / (m + n / 4),

In order to make the adiabatic flame temperature at the oxygen ratio (m / 2) / (m + n / 4) higher than the adiabatic flame temperature in the incomplete combustion state according to the reaction formula (4),

An apparatus for producing a reducing gas, comprising energy supply means for supplying energy to the combustion system . In a reducing gas production method for producing carbon monoxide and hydrogen by mixing a hydrocarbon fuel gas with an oxidant in a combustion system and burning it,
When the ratio of the oxygen amount actually supplied to the combustion system to the oxygen amount in the complete combustion state according to the reaction formula (5) is defined as an oxygen ratio,

Partial combustion according to the reaction formula (1) is performed at an oxygen ratio (m / 2) / (m + n / 4),

In order to make the adiabatic flame temperature at the oxygen ratio (m / 2) / (m + n / 4) higher than the adiabatic flame temperature in the incomplete combustion state according to the reaction formula (4),

A method for producing a reducing gas, wherein energy is supplied to the combustion system .   3. The reducing gas production method according to claim 2, wherein the energy is energy required to set the temperature of the reducing gas containing carbon monoxide and hydrogen to about 1800 K or more.   The reducing gas production method according to claim 2 or 3, wherein the energy is applied by arc discharge.   The method for producing a reducing gas according to any one of claims 2 to 4, wherein the Bacharach index indicating the amount of generated soot in the combustion exhaust gas is less than 3.

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