JP2003321205A - Method for operating heat exchanging type steam reformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a heat exchanging type steam reformer which can eliminate or reduce as quickly as possibly reforming temperature turbulence even if an operation after load change or a start up work is in an excessive state. <P>SOLUTION: The method for operating the heat exchanging type steam reformer having a combustion chamber with a burner is characterized by correcting a combustion chamber temperature by a temperature difference between a target reforming temperature and an actually measured reforming temperature and controlling its correction value to be in the upper and lower definite restricted widths of the temperature difference to a target reforming temperature when the reforming temperature is controlled by the combustion chamber temperature. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a heat exchange type steam reformer, and more particularly to an operation method for a heat exchange type steam reformer having a combustion chamber by a burner.

[0002]

2. Description of the Related Art The steam reforming method for hydrocarbons, which is one of the industrial hydrogen production methods, is used for methane, ethane, propane, butane, city gas, LP gas, natural gas, and other hydrocarbons (two or more kinds). (Including a mixture of hydrocarbons of 1) is reformed with steam to produce a hydrogen-rich reformed gas. In the steam reforming method, those hydrocarbons are converted into hydrogen-rich reformed gas by a catalytic reaction in the steam reforming apparatus.

FIG. 1 is a view showing the principle of a steam reforming apparatus. In general, it is composed of a combustion section in which a burner is arranged and a reforming section in which a reforming catalyst is arranged. In the reforming section, the hydrocarbon reacts with steam to produce a hydrogen-rich reformed gas. Since this reforming reaction is an endothermic reaction, it is necessary to supply heat, and a temperature of about 750 ° C. to 800 ° C. or higher is necessary. Therefore, the combustion heat (ΔH) generated by the combustion of the fuel gas in the combustion section by the air (combustion air) is supplied to the reforming section.

FIG. 2 is a diagram for explaining a reforming system using a steam reforming apparatus from the supply of hydrocarbons (hereinafter, also referred to as raw material gas or hydrocarbon gas as appropriate) to the CO shift converter. Since the reforming catalyst is poisoned by the sulfur compounds in the raw material gas and deteriorates in performance, it is introduced into the desulfurizer to remove the sulfur compounds. Water is added to and mixed with the desulfurized raw material gas and introduced into the reforming section of the steam reforming apparatus.

When the source gas is methane, the reforming reaction is
Generally, "CH_Four+ 2H₂O → CO ₂+ 4H₂Indicated by
It Unreacted methane and unreacted methane in the reformed gas produced
In addition to steam and generated carbon dioxide, carbon monoxide (CO)
Around 8 to 15% (volume%) is included. others
For the reformed gas, the by-product CO is converted into carbon dioxide (CO₂) And hydrogen
To a CO transformer to remove it. CO
Shift reaction in a transformer "CO + H₂O → CO₂+ H₂"
Unreacted residual water in the reforming section
Steam is used.

[0006]

The steam reforming system as described above is normally operated continuously, but the reformer is caused by seasonal factors such as the required reformed gas production amount and the outside air temperature. It is necessary to operate so that a reformed gas of a constant quality is generated according to the operating load. Therefore, in the conventional technique, the correlation between the temperature of the combustion chamber for each load (combustion chamber temperature) and the reforming temperature in the reforming section is checked in advance with an actual machine to ensure that the reforming temperature is optimal for the reforming reaction. , The combustion chamber temperature is controlled.

In addition, the reforming temperature is an important factor in the operation of the reformer, and when the reforming temperature is high, it causes fatal mechanical damage to the constituent material of the reformer, and conversely, When the reforming temperature is low, it has a great influence on the capacity of the gas purifying section such as the PSA unit following the CO shift converter. For this reason, conventionally, the reforming temperature in the reformer has been taken into consideration as an emergency stop factor for the safety of the reforming system.

By the way, in the heat exchange type steam reforming apparatus, there is a large time delay in directly controlling the reforming temperature by the normal PID control due to the characteristics of this apparatus. Therefore, in consideration of a case where the driving situation changes such as a load change or a case where the driving situation is not stable such as after the start-up operation, it is quite difficult to directly control the PID control.

That is, the reforming temperature is a function of the combustion chamber temperature, the raw material gas inlet temperature, the raw material gas amount and the combustion exhaust gas amount, and has a strong correlation with the combustion chamber temperature.
Therefore, as described above, in the conventional technique, the reforming temperature is controlled only by the combustion chamber temperature. However, in this way, if the reforming temperature is controlled only by the combustion chamber temperature, it will be understood that the reforming temperature will be disturbed under an excessive operating condition such as after load fluctuation or start operation (that is, start-up operation). It was If the reforming temperature is disturbed, the desired quality reformed gas cannot be obtained.

Therefore, the present invention has been made in order to solve the above problems that occur in the conventional operation method of the heat exchange type steam reforming apparatus, and the heat exchange type steam reforming having a combustion chamber by a burner is provided. In the equipment, by correcting the combustion chamber temperature by the temperature difference between the target reforming temperature and the actual reforming temperature measured in the reforming section during operation, load fluctuations and operating conditions such as after start-up operation are excessive. It is an object of the present invention to provide a method for operating a heat exchange type steam reforming device which eliminates or minimizes the disturbance of the reforming temperature even under the conventional conditions.

[0011]

The present invention is a method for operating a heat exchange type steam reforming apparatus having a combustion chamber by a burner, wherein the reforming temperature in the reforming section is controlled by the combustion chamber temperature. The combustion chamber temperature is corrected by the temperature difference between the target reforming temperature and the actual reforming temperature measured at the reforming section, and the correction amount is a fixed upper and lower limit with respect to the temperature difference with respect to the target reforming temperature. There is provided a method for operating a heat exchange type steam reformer characterized by being controlled by

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The operating method of the present invention is intended for a heat exchange type steam reforming apparatus having a combustion chamber by a burner. Then, when controlling the reforming temperature in the reforming section by the combustion chamber temperature, the combustion chamber temperature is corrected by the temperature difference between the target reforming temperature and the actual reforming temperature measured in the reforming section, and
The correction amount is controlled with a constant limit width with respect to the temperature difference with respect to the target reforming temperature.

That is, although the reforming temperature is controlled by the combustion chamber temperature as in the conventional case, in the present invention, the combustion chamber temperature is changed to a target reforming temperature of the actual reforming temperature measured in the reforming section during operation. The temperature difference is corrected by the temperature difference with respect to the quality temperature, and the correction amount is controlled with a constant limit width with respect to the temperature difference with respect to the target reforming temperature. As a result, it is possible to perform a safe correction such that the excessive deviation is corrected once, and then the deviation from the actual reforming temperature is checked and then the deviation is corrected again.

In this heat exchange type steam reformer, the reforming temperature is operated in the range of about 750 to 850 ° C. Therefore, the target reforming temperature is set to a certain temperature within the range of about 810 to 830 ° C, for example, 814 ° C. Then, the actual reforming temperature is measured in the reforming section during operation, and the temperature of the combustion chamber is corrected based on the temperature difference between this measured value and the target reforming temperature. The combustion chamber temperature is corrected, for example, by controlling the amount of fuel gas supplied to the burner. At that time, the correction amount is controlled with a constant limit width with respect to the temperature difference with respect to the target reforming temperature.

In the vicinity of the target reforming temperature, that is, the control target value thereof, the correlation between the actual reforming temperature and the combustion chamber temperature has a high first-order linearity, and the relationship between them is as shown in FIG. The present invention takes advantage of this fact and applies the temperature difference directly to the control. The combustion chamber temperature is corrected by the temperature difference between the target reforming temperature and the actual reforming temperature measured in the reforming section, but the correction is 5 to
It is preferable to carry out periodically at intervals of 10 minutes. As a result, it is possible to perform a gradual adjustment such that after the correction, the change in the actual reforming temperature is first seen and then the correction is performed again.

Further, the combustion chamber temperature is corrected by the temperature difference between the target reforming temperature and the actual reforming temperature measured in the reforming section, and the correction amount is constant with respect to the temperature difference with respect to the target reforming temperature. In addition to the control with the limit width of, it is desirable to control with different limit values on the + side (that is, temperature increase control) and the − side (that is, temperature decrease control) with respect to the target reforming temperature. By controlling separately as described above, more accurate control can be performed.

Further, the combustion chamber temperature is corrected by the temperature difference between the target reforming temperature and the actual reforming temperature measured in the reforming section, and the correction amount is constant with respect to the temperature difference with respect to the target reforming temperature. Of the target reforming temperature with respect to the target reforming temperature, and the + side and the − side are controlled with separate limit values. Is desirable. By this means, that is, by making the upper limit of the reforming temperature more strict, it is possible to solve the problem of mechanical damage to the device due to high temperature with respect to a normal control value.

FIG. 4 is a diagram showing a structural example of a heat exchange type steam reforming apparatus having a combustion chamber by a burner, which is a target of the present invention. Although FIG. 4 shows a mode in which the present reformer is arranged vertically, it can also be used in a mode in which it is installed horizontally. As shown in FIG. 4, it is composed of a combustion chamber by a burner arranged in the lower part and a reforming section connected to the combustion chamber. In the combustion chamber, fuel such as city gas is burned with air (combustion air). The reforming section is composed of a double tube consisting of an inner tube and an outer tube surrounding the inner tube.

A raw material gas, for example, desulfurized city gas to which water is added is supplied from the upper part into the outer pipe (between the outer pipe and the inner pipe) and reformed while descending. The reformed gas returns at its lower end and rises in the inner tube to exchange heat via the inner tube wall, and a part of reaction heat is recovered in the reforming section. FIG.4 (b) is a figure which shows the state of the lower end part. Meanwhile, the double pipe is indirectly heated by circulating the combustion gas generated in the combustion chamber to the outer circumference of the outer pipe.

Temperature sensors are arranged in the combustion chamber and the reforming section, respectively. FIG. 4 shows the arrangement of these temperature sensors. When the heat exchange steam reformer is operated, control is performed based on the combustion chamber temperature and the reformer temperature (= actual reforming temperature) measured by these temperature sensors. The control is basically based on controlling the reforming temperature by the combustion chamber temperature, but in the present invention, at that time, the combustion chamber temperature is set to the target reforming temperature and the actual reforming temperature measured in the reforming unit. The difference is corrected by the temperature difference.

FIG. 5 is a diagram showing a structural example of a reforming system incorporating the present heat exchange type reforming apparatus. A desulfurizer, a water preheater, a heater, a reformer (a heat exchange type steam reforming device having a combustion chamber by a burner), and a CO shift converter are sequentially installed in accordance with the flow of raw material gas such as city gas. The water is preheated by the water preheater, added to the raw material gas, further heated by the heater, and then introduced into the reformer. The reformed gas (hydrogen-rich gas) produced in the reformer is supplied to the CO shift converter after preheating the air introduced into the burner, and is taken out through the gas cooler.

[0022]

The present invention will be described in more detail based on the following examples, but it goes without saying that the present invention is not limited to these examples.

In this embodiment (an example of the present invention), the structure shown in FIG.
A heat exchange type steam reformer was used and assembled as shown in Fig. 5.
A modified reforming system was constructed. As shown in Figure 4, burning
Temperature sensors are installed in the chamber and reforming section, respectively.
It Ni / Al as reforming catalyst ₂O₃(Nickel on alumina
Gas as a raw material gas
(13A) was used.

The present reforming system, which produces 500 Nm ³ / h of hydrogen gas in a steady operation, was started, and thereafter, the temperature of the combustion chamber and the reforming section were measured by a temperature sensor, and the reforming system was continuously operated for a long time. Here, the target reforming temperature is 81
The temperature was set at 4 ° C., and the combustion chamber temperature was corrected by the temperature difference between the target reforming temperature and the measured actual reforming temperature. The correction amount
The limit width on the + side of the temperature difference from the target reforming temperature is 2
The limit width on the − side of 5 ° C. was controlled at a constant limit width of 50 ° C.
In FIG. 5, the flow rate and temperature at each location during steady operation are also shown.

On the other hand, as a comparative example (prior art), the same reforming system as described above was used, and the relationship between the combustion chamber temperature and the target reforming temperature for each production amount (for each load) was taken by an actual machine and the correlation was obtained. Only the program was performed and the combustion chamber temperature was determined and implemented. Table 1 shows the fluctuations of the reforming temperature after the start-up in Examples and Comparative Examples. As shown in Table 1, the effect of the present invention is clear.

[0026]

[Table 1]

[0027]

According to the operation method of the heat exchange type steam reforming apparatus of the present invention, it is possible to eliminate the disturbance of the reforming temperature even under an excessive operating condition such as load fluctuation or after start-up operation. It can be minimized. In addition, the operator can shorten the reforming temperature monitoring period immediately after start-up, which not only saves manpower, but also optimizes the combustion chamber temperature automatically, thus stabilizing the reformer with many load fluctuations. Various useful effects such as driving can be obtained.
The operating method of the present invention is particularly effective and useful for operating a reformer in which the operating conditions are constantly changing and the steady operation is unmanned.

[Brief description of drawings]

FIG. 1 is a diagram showing a steam reformer in principle.

FIG. 2 is a flow chart showing a process of supplying a raw material gas to C by using a steam reformer.
Diagram illustrating the reforming system up to the O-transformer

FIG. 3 is a diagram showing a correlation between an actual reforming temperature and a combustion chamber temperature near a target reforming temperature.

FIG. 4 is a diagram showing a configuration example of a heat exchange type steam reforming apparatus which is a target of the present invention.

FIG. 5 is a diagram showing a configuration example of a reforming system incorporating the heat exchange reforming device.

Continued front page    (72) Inventor Haruhiko Nakamura             2-1 Okawa-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Mitsubishi             Kakoki Co., Ltd. (72) Inventor Yukihiro Kamakura             2-1 Okawa-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Mitsubishi             Kakoki Co., Ltd. F-term (reference) 4G140 EA03 EA06 EB14 EB43                 5H027 AA02 BA01

Claims (4)

[Claims] 1. A method of operating a heat exchange type steam reforming apparatus having a combustion chamber by a burner, wherein the combustion chamber temperature is controlled to a target reforming temperature when the reforming temperature in the reforming section is controlled by the combustion chamber temperature. Is corrected by the temperature difference between the actual reforming temperature measured by the reforming section and the actual reforming temperature, and the correction amount is controlled within a fixed upper and lower limit with respect to the temperature difference with respect to the target reforming temperature. Operation method of heat exchange type steam reformer. 2. The correction amount for correcting the combustion chamber temperature by the temperature difference between the target reforming temperature and the actual reforming temperature measured in the reforming section is fixedly limited with respect to the temperature difference with respect to the target reforming temperature. The method for operating a heat exchange type steam reforming apparatus according to claim 1, wherein the method is controlled by the width and is controlled by separate limit values on the + side and the-side with respect to the target reforming temperature. 3. A correction amount for correcting the combustion chamber temperature by a temperature difference between a target reforming temperature and an actual reforming temperature measured in a reforming section, which is a constant limit with respect to a temperature difference with respect to the target reforming temperature. The width is controlled, and the + and-sides are controlled with different limit values with respect to the target reforming temperature. At that time, the + side adjustment width is made stricter than the − side adjustment width. The method for operating the heat exchange type steam reforming apparatus according to claim 1, wherein 4. The correction for correcting the combustion chamber temperature by the temperature difference between the target reforming temperature and the actual reforming temperature measured in the reforming section is periodically performed at intervals of 5 to 10 minutes. The method for operating the heat exchange type steam reformer according to any one of claims 1 to 3.