KR101526945B1 - Cylindrical Steam reformer using multi-tube - Google Patents

Abstract

The present invention relates to a multi-tube cylindrical steam reformer, comprising: a heating furnace; A plurality of reaction tubes installed inside the heating furnace, in which a reforming reaction takes place in which natural gas and steam are converted to reformed gas containing hydrogen; A central burner installed at the center of the heating furnace to heat the reaction tube while burning the fuel to generate the exhaust gas; And at least one side burner installed on a side surface of the heating furnace and heating the reaction tube while burning the fuel to generate an exhaust gas, the present invention provides a multi-cylinder cylindrical steam reformer.

Description

[0001] Cylindrical steam reformer using multi-tube [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam reformer, and more particularly, to a multi-cylinder cylindrical steam reformer capable of designing a compact heating furnace and improving convection heat exchange.

A steam methane reformer (hereinafter referred to as SMR) is a reactor for producing hydrogen from natural gas, which is a main component of methane.

Raw materials Natural gas and water vapor are converted to reformed gas mixed with hydrogen, carbon monoxide and carbon dioxide on the catalyst, and a strong endothermic reaction is required. Therefore, a general steam reforming reactor includes a catalyst layer on which the reaction proceeds and an external heating device for heating the catalyst layer.

Generally, the reformed gas production process using SMR is combined with the steam generator and the reactant preheater, which produce the water vapor required for the reaction, and the whole process is constituted. The steam production and the reactant preheating are employed to heat the SMR catalyst layer and recover the waste heat from the combustion exhaust gas or the produced reformed gas. Therefore, it is necessary to optimize the design of the main body of the SMR and optimization of the waste heat recovery process for the optimum design of the reformed gas production process including the SMR.

The steam reforming reactor used in the existing use process mainly adopts the single tube type tube system. In order to achieve the maximum production capacity in relation to the footprint, a tube of 10 m or more is placed inside the combustion furnace And a plurality of burners are used for heating.

At this time, the heat exchange method mainly uses a radiation heat transfer method. A feature of this approach is that the heat flux from the combustion zone to the reaction zone is very large and, in general, an average heat flux of more than 65,000 kcal / h m2 can be achieved with a top fired reformer. It is possible to design the steam reforming reactor by minimizing the number of reaction tubes according to the high heat flux, and it becomes advantageous for the enlargement.

On the other hand, since direct heat exchange with the flame of the burner occurs, a region where the surface temperature is maintained at a high temperature depending on the position of the reaction tube is generated. Generally, the utilization rate of the burner supplied heat of the steam reforming reactor of the radiant heating type is known to be about 50%.

Haldo Topsoe of Denmark developed the Haldor Topsoe convection reformer (HTCR), which uses a convection heat transfer method in a steam reforming reactor with a capacity of 1,000 N㎥ / h. Generally, the heat flux of the convection heating system is 1/10 of that of the radiating heat transfer system. Therefore, the heat transfer area of the reaction tube is greatly increased in order to transfer the same amount of heat. However, since the local high- .

In the convection heat transfer, the higher the flow rate of the high-temperature gas, the more heat flux increases. Therefore, the space of the furnace can be minimized and the burner and the reforming tube space can be designed separately. Therefore, There is an advantage in designing. In the case of the convection heating system, the burner supply calorie utilization can be increased up to 80%.

Most of the reactors mainly used in the commercial process can be classified into a single-tube reactor and a Bayonet-Tube reactor. The single tube type tube is a type in which a single tube is filled with a catalyst, and a bayonet tube is a kind of double tube tube in which the catalyst is filled in the space between the inner tube and the outer tube, the lower end of the outer tube is closed, and the lower end of the inner tube is opened. For example, Japanese Laid-Open Patent JP2001-302209 exemplifies the structure of a bayonet tube reactor applied by Osaka Gas of Japan, and a similar structure is adopted by Haldor Topsoe's HTCR.

A brief description of how the Bayonet tube is applied to the SMR is given below. The combustion gas is contacted to the outside of the tube and the heat exchange proceeds. The raw material supplied from the top of the reaction tube passes through the catalyst layer packed between the inner tube and the outer tube of the reaction tube, and the reforming reaction proceeds. The reformed gas that escapes to the bottom of the reaction tube becomes higher than the top of the catalyst layer. The reformed gas at a high temperature is discharged through the inner pipe of the furnace to the product gas outlet at the upper end. At this time, the heat is transferred to the catalyst layer while passing through the inner pipe of the Beyonet.

In the Bayonet tube reactor, the heat transfer is increased by the uprising tube in which the heat exchange occurs. Since the lower end of the outer tube is sealed, only the upper end of the tube reactor is fixed. Therefore, unlike the single tube type tube, There is no need for a device. On the other hand, since the tube has a complex inlet / outlet structure as compared with a single tube tube, there is a possibility that the tube processing and assembly cost may increase in a large process requiring a plurality of tubes. If the length of the reaction tube is long, the space between the inner tube and the outer tube can be kept constant in the circumferential direction, so that the temperature deviation of the catalyst layer at the same height can be reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-cylinder cylindrical steam reformer capable of reducing the diameter of a center line where reaction tubes are arranged than a conventional one of a top-down type burner, and accordingly,

Another object of the present invention is to provide a multi-cylinder cylindrical steam reformer capable of improving convective heat exchange.

In order to achieve the above object, the present invention provides a heating furnace comprising: a heating furnace; A plurality of reaction tubes installed in the heating furnace, in which a reforming reaction takes place in which raw material natural gas and steam are converted into reformed gas containing hydrogen; A central burner installed at the center of the heating furnace to heat the reaction tube while burning fuel natural gas to generate exhaust gas; And at least one side burner installed on a side of the heating furnace and heating the reaction tube while burning fuel natural gas to generate an exhaust gas.

In the present invention, the side burner is disposed in a tangential direction on the side surface of the heating furnace, at least two side burners are provided symmetrically, and the fuel supply amount of the central burner and the side burner is distributed from 3: 7 to 7: 3 desirable.

The reformer according to the present invention may further include an exhaust gas discharge inducing pipe installed to surround the reaction tube at an interval from the reaction tube, wherein the flow rate of the exhaust gas passing through the flow path formed between the reaction tube and the exhaust gas discharge inducing pipe is 20 m / s, and the length of the exhaust gas discharge pipe is preferably 30 to 70% of the length of the reaction tube.

Since the burner capacity at the inlet of the reforming reactor requiring a large amount of heat exchange can be adjusted and distributed to the central burner and the side burner according to the present invention, the diameter of the center line where the reaction tubes are arranged can be reduced, As a result, a compact heating furnace design is possible.

In addition, by providing a flue gas discharge induction pipe having a narrow clearance at the outer wall surface of the tube at the lower end portion of the heating furnace corresponding to the outlet side of the reaction tube, convection heat exchange can be improved by increasing the flux of the flue gas passing through the outside of the reaction tube .

1 is a perspective view of a multi-pipe cylindrical steam reformer according to the present invention.
2 is a longitudinal sectional view of a multi-pipe cylindrical steam reformer according to the present invention.
3 is a cross-sectional view of a multi-pipe cylindrical steam reformer according to the present invention.
4 is a partially enlarged vertical sectional view of a multi-pipe cylindrical steam reformer according to the present invention.
FIG. 5 shows changes in the longitudinal temperature distribution and methane conversion rate distribution of the catalyst layer according to the installation of the exhaust gas discharge pipe (sleeve).
FIG. 6 shows changes in temperature distribution and methane conversion rate distribution in the longitudinal direction of the reactor with respect to the burner load distribution.
Fig. 7 shows that when the fuel is distributed to the upper burner at 40%, the side burner at 60%, the upper burner at 50%, and the side burner at 50%, respectively, The temperature distribution of the outer wall of the reaction tube is compared.
8 compares the temperature distribution of the outer wall of the reaction tube with respect to the longitudinal direction when the fuel is distributed to the upper burner 60% and the side burner 40%, respectively, and only the upper burner is operated.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

FIG. 1 is a perspective view of a multi-pipe cylindrical steam reformer according to the present invention, FIG. 2 is a longitudinal sectional view, FIG. 3 is a transverse sectional view, and FIG. 4 is a partially enlarged vertical sectional view.

1 to 4, a multi-tube cylindrical steam reformer according to the present invention includes a heating furnace 10, a central burner 20, side burners 30 and 40, a reaction tube 50, (60), an exhaust gas discharge pipe (70), and the like.

The heating furnace 10 is made of a refractory material and can be divided into an outer wall and an inner wall.

The central burner 20 is a top-down burner installed at the upper center of the furnace 10 and facing downward.

The side burners 30 and 40 are provided in a tangential direction on the side surface of the heating furnace 10, and at least two side burners are provided symmetrically.

The central burner 20 and the side burners 30 and 40 heat the reaction tube 50 while burning fuel to generate a flame and an exhaust gas.

The fuel supplied to the central burner 20 and the side burners 30 and 40 can be used as the fuel for the central burner 20 and the side burners 30 and 40, It is preferable to distribute from 3: 7 to 7: 3 for suppressing thermal deformation.

The reaction tube 50 is installed inside the heating furnace 10 and is a place where the reforming reaction in which the natural gas and the steam are converted into the reformed gas containing hydrogen takes place and may be in the form of a bayonet tube as described above.

A plurality of reaction tubes 50 are formed on imaginary circles having a certain radius with respect to the center of the heating furnace 10 and 12 reaction tubes 50 may be formed as shown in FIG. However, the number and arrangement of the reaction tubes 50 are not limited thereto.

The reaction tube 50 may have a double pipe structure composed of an inner pipe 52 and an outer pipe 54 as shown in Fig. 4, wherein a catalyst layer 52 filled with a catalyst is provided between the inner pipe 52 and the outer pipe 54, (56) is formed.

The reaction tube 50 may be fixed to the heating furnace 10 only at the upper end thereof and may have a shape in which the lower end of the outer tube 54 is closed and the lower end of the inner tube 52 is opened.

The combustion exhaust gas of the burners 20, 30 and 40 is brought into contact with the outside of the reaction tube 50 so that the heat exchange proceeds and the raw material supplied to the upper end of the reaction tube 50 is filled between the inner tube 52 and the outer tube 54 The reforming reaction proceeds while passing through the catalyst layer 56. The reformed gas that has escaped to the lower end of the reaction tube 50 becomes higher in temperature than the upper end of the catalyst layer 56. The reformed gas of a higher temperature rises through the inner tube 52 as a rising tube and is discharged to the product gas outlet at the upper end, And passes through the catalyst layer 56 and exits.

In the horizontal direction, the heat insulating material may be filled in a virtual circular space formed by the plurality of reaction tubes 50, and in the vertical direction, the lower space of the exhaust gas discharge pipe 60. In this case, The heat supplied from the heat sources 20, 30, and 40 can be efficiently utilized.

The exhaust gas discharge induction pipe 60 is installed so as to surround the reaction tube 50 at regular intervals with the reaction tube 50. The flow rate of the exhaust gas passing through the flow path formed at narrow intervals between the exhaust gas discharge induction pipe 60 and the reaction tube 50 is increased to not less than 20 m / s, thereby maximizing heat transfer by convection heat transfer. The length of the exhaust gas discharge pipe 60 is preferably 30 to 70% of the length of the reaction tube 50.

2, the combustion exhaust gas generated from the burners 20, 30, and 40 heats the reaction tube 50 while flowing outside the reaction tube 50, passes through the exhaust gas discharge induction pipe 60, And is exhausted through the exhaust gas discharge pipe 70 after merging in the chamber below the furnace 10.

The present invention relates to a multi-tubular steam reforming reactor and a new heating furnace constituting the reactor, characterized in that one top-down burner is provided at the center of the heating furnace corresponding to the inlet side of the reaction tube, And two or more burners are provided in the tangential direction on the sidewall of the sidewall.

In the prior art, one type of top-down type burner is usually provided at the center of the top plate by heating. However, as the burner capacity increases, flames may directly contact the reaction tube to cause tube damage. Therefore, The diameter of the center line becomes larger.

In the present invention, since the burner capacity at the inlet of the reactor, which requires a large amount of heat exchange, can be adjusted by distributing the burner to the central installation burner and the sidewall surface installation burner, the diameter of the center line where the reaction tubes are arranged is reduced And thus a compact heating furnace design is possible. At this time, the sum of the fuel supply amounts of one burner installed in the center of the heating furnace corresponding to the inlet side of the reaction tube and two or more tangential burners provided on the sidewall of the upper end of the heating furnace can be distributed to 30 to 70% .

The exhaust gas discharge pipe having a narrow gap on the outer wall surface of the tube may be installed at the lower end of the heating furnace corresponding to the outlet side of the reaction tube to increase the flux of the exhaust gas passing through the outside of the reaction tube to improve convective heat exchange. That is, an exhaust gas discharge passage between the outer wall surface of the reaction tube and the wall surface of the exhaust gas discharge induction pipe is formed at the lower end of the heating furnace, and the linear velocity of the exhaust gas passing through the discharge passage is 20 m / s or more to maximize the convection heat exchange . Further, the length of the flue gas discharge induction pipe can be adjusted to 30 to 70% of the reaction tube to improve the heat exchange amount.

[Example]

An SMR reactor as shown in Fig. 1 was prepared. Specifically, a central burner 20 of a top firing type is installed in the heating furnace 10 at the center of the combustion section, and on a concentric circle having a radius where the flame of the central burner 20 is not in direct contact, (50). Two side burners 30 and 40 of a side firing type are installed in the tangential direction on the upper side of the heating furnace 10. Therefore, the upper end of the Beyonet reaction tube 50 is irradiated by the flame of the central burner 20 injected in the vertical direction from the inner and outer sides and the side burners 30 and 40 pivoted on the side wall of the heating furnace 10 from the side . The exhaust gas discharge conduit 60 is installed at the bottom half of the longitudinal direction of the entire Beyonet reaction tube 50 to provide a narrow gap between the outer wall of the outer tube 54 of the Beyonett reaction tube 50 and the outer wall of the outer tube 54, So that heat transfer by convection heat can be maximized. Only the portion of the exhaust gas discharge pipe 70 through which the exhaust gas passing through the exhaust gas discharge induction pipe 60 and merged in the chamber at the lower end of the heating furnace 10 is discharged outside the heating furnace 10 is an asymmetric structure, Respectively. Table 1 summarizes the basic setting conditions.

division Setting condition Remarks Reaction pressure [MPaG] 0.9 Feed amount of raw material NG [Nm 3 / h] 42.6 Water vapor supply [Nm 3 / h] 145.6 117 kg / h S / C ratio [-] 3.0 Burner excess air ratio [-] 1.1 Air preheating temperature for burner [℃] 250 Feed temperature [℃] 500 Reforming temperature [캜] 750 Goal Conversion Rate 71% or more Target Hydrogen Production [Nm3 / h] 150 or more

[Test Example]

The effect of the operating parameters on the main operating parameters of the SMR reactor prepared according to the examples was tested. CFD (Computational Fluid Dynamics) analysis for the structural design of the SMR reactor was carried out and used to determine the detailed dimensions of the test reactor. The performance of the SMR reactor under actual operating conditions was evaluated using the fabricated test reactor.

The main performance requirements for SMR reactors are hydrogen production and reforming efficiency. The double reforming efficiency can be calculated from the energy balance of the entire process of the hydrogen generator and can be defined as the ratio of the calorific value of the produced hydrogen to the total calorific value of the raw natural gas and the fuel natural gas supplied. In the CFD analysis, only the main body of the SMR reactor is analyzed. Therefore, the performance is indirectly compared using two parameters directly affecting the reforming efficiency.

The first indicator is methane conversion. The methane conversion rate is a measure of the rate at which the feedstock natural gas is converted to a gas containing hydrogen. The greater the conversion rate of methane, the greater the amount of hydrogen produced for the same feedstock. Since the steam reforming reaction is an equilibrium reaction, once the reaction temperature and pressure conditions are determined, the operating conditions of the SMR reactor can be determined by calculating the equilibrium methane conversion.

The second indicator is the fuel utilization rate, which is the ratio of the calorific value used in the SMR reactor to the fuel natural gas calorific value required to operate the SMR reactor based on the desired equilibrium methane conversion rate. However, in actual hydrogen production equipment, since the production of steam, which is a reaction raw material, and the preheating of raw materials are performed using combustion exhaust gas which supplies heat to the catalyst layer, it is necessary to optimize the fuel utilization rate The value may vary depending on the process configuration. In general, R / B is used as a simple indicator of fuel utilization. R / B is defined as the ratio of the natural gas feed to the burner fuel natural gas feed.

For the convenience of CFD analysis, the amount of natural gas supplied was determined to achieve a hydrogen production rate of 150 Nm 3 / h or higher when achieving a methane conversion of 70% or more. The main reaction condition of steam reforming, water vapor mixing ratio, And the S / C was set to 3.0. The burner was set in a manner using preheated air and the burner preheating air temperature was set at 250 ° C. The reason why the preheating air temperature is set at 250 ° C is that the use of preheated air at the same fuel amount as in the case of using normal temperature air usually results in a methane conversion improvement of 5% or more. Normally, when the preheating air temperature is 350 ° C or less, the preheating air temperature is set to 250 ° C because a burner can be used in a preheating air mode without using a special burner. Since the temperature of the preheated air actually available is related to the overall reaction system configuration and usually the combustion exhaust gas is used as the heat source of the steam generator, it is necessary to supply the waste heat to the steam generator and determine the upper limit of the air preheating temperature do.

The main operating variables are the first R / B, the second top burner (top) and the side burner (side) fuel distribution ratio.

In order to check the efficacy of the sleeve type flue gas exhaust line, which is installed at the lower part of the bayonet tube and through which the flue gas is passed at high line speed, the case with and without the sleeve is compared under the same operating conditions, The temperature of the outer wall surface was analyzed to confirm whether or not the local high temperature portion was formed, and some of the device durability was also confirmed.

In order to compare the influence of the operating variables, we selected the reference condition as the first R / B = 2.0, the second preheating air temperature = 250 ℃ and the third burner load distribution as Top: Side = 50:50. The results of this study are as follows.

First, the influence of the sleeve for improving the heat exchange is shown in comparison with FIG. 5 in the case where there is no sleeve to compare the influence of the sleeve under the reference condition. The temperature of the outlet of the catalyst layer was high in the case of the sleeve having the same R / B ratio (FIG. 5, first drawing), and thus the methane conversion rate also showed a high value ). Indicating that the heat of the combustion gas is more effectively transferred to the reforming catalyst layer by the installation of the sleeve.

Next, we examined the effect of top (center) and side (side) burner load distribution. In the present invention, a first burner 1 which is sprayed from the upper end to the lower end and a second side spray burner which is sprayed in the tangential direction of the inner wall of the cylindrical furnish are used. The operating characteristics of the SMR reactor were investigated by adjusting the ratio of the amount of fuel supplied to these two types of burners at the same R / B and preheating air temperature. The first diagram of FIG. 6 shows the change of the catalyst bed outlet temperature and the methane conversion rate according to the fuel amount fraction supplied to the upper burner per total fuel. In the case of using only the side burner in the upper burner, even if the ratio of the total fuel amount to the upper burner is increased to 40%, 50%, and 60%, there is no significant difference in the catalyst bed outlet temperature and methane conversion rate. The exit temperature and methane conversion rate increased significantly. This can be seen in the upper right-hand side of FIG. 6 showing the change of the catalyst bed temperature distribution along the length of the reactor and the lower left-hand side of FIG. 6 showing the change of the methane conversion distribution along the reactor longitudinal direction.

According to the first diagram of FIG. 7, when 100% fuel is supplied to the side burner without supplying the burner fuel to the upper burner, the temperature of the tube outer wall without the exhaust gas discharge sleeve is kept high, The tube outer wall temperature at the half portion of the reaction tube outlet side shows an average low temperature distribution, and the tube durability at the upper end of the reaction tube may deteriorate.

8, when the burner fuel is supplied to the upper burner 100% and the fuel is not supplied to the side burner, the temperature of the tube outer wall without the exhaust gas discharge sleeve is kept low and the exhaust gas discharge sleeve is installed The temperature of the tube outer wall at the half portion of one reaction tube outlet side shows an average high temperature distribution, and the tube durability at the lower end of the reaction tube may be deteriorated.

Therefore, it is preferable to control the ratio of the upper burner to the side burner at a ratio of 30: 70 or 70: 30 in view of the durability of the reaction tube.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and changes may be made in the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

10: heating furnace
20: central burner
30, 40: side burner
50: reaction tube
52: Inner pipe
54: Appearance
56: catalyst layer
60: exhaust gas discharge pipe
70: exhaust gas discharge pipe

Claims (7)

Heating furnace;
A plurality of reaction tubes installed in the heating furnace, in which a reforming reaction takes place in which raw material natural gas and steam are converted into reformed gas containing hydrogen;
A central burner installed at the center of the heating furnace to heat the reaction tube while burning fuel natural gas to generate exhaust gas; And
And at least one side burner installed on a side surface of the heating furnace and heating the reaction tube while burning fuel natural gas to generate an exhaust gas.
The method according to claim 1,
And the side burner is installed in a tangential direction on a side surface of the heating furnace.
3. The method of claim 2,
Wherein at least two side burners are provided symmetrically.
The method according to claim 1,
And the fuel supply amount of the central burner and the side burner is distributed from 3: 7 to 7: 3.
The method according to claim 1,
And a flue gas discharge induction pipe installed to surround the reaction tube at an interval from the reaction tube.
6. The method of claim 5,
Wherein the flow velocity of the exhaust gas passing through the flow path formed between the reaction tube and the exhaust gas discharge inducing pipe is 20 m / s or more.
6. The method of claim 5,
Wherein the length of the flue gas discharge induction pipe is 30 to 70% of the length of the reaction tube.

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