JPS63162504A - Reaction furnace for producing city gas - Google Patents

Abstract

PURPOSE:To obtain city gas while reducing the effort of operators and facilitating the countermeasure in case of emergency, by providing a radial tube burner on the upstream side of the reforming catalyst in the title reaction furnace to remarkably reduce the temp. increasing time and to efficiently increase the temp. CONSTITUTION:The reforming catalyst bed 2 is supported by a perforated plate part 3 for uniformly diffusing a gas stream, and a combustion chamber 4 consisting of a furnace wall 6 provided with a combustion burner 5 is furnished under the part 3 to form the low-pressure continuous partial combustion type reaction furnace 1 for producing city gas. The radiant tube burner 7 obtained by inserting an inner cylinder 9 into an outer cylinder 8 and wherein combustion is carried out at the tip of the inner cylinder 9 is provided in the combustion chamber 4 on the upstream side of the reforming catalyst bed 2. The burner 7 is ignited when the operation is stopped at night and combustion is continued until the next morning to heat the combustion chamber 4, the furnace wall 6, and perforated plate part 3 from the operation temp. (400 deg.C) to about 800 deg.C by the radiant heat, hence the cooling of the catalyst bed 2 is prevented, the temp. increasing time can be reduced to several tens min from several hours in the conventional process at the start in the next morning, and the gas is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (11) Industrial Application Field The present invention relates to a reactor for producing city gas.

BACKGROUND ART A low-pressure continuous partial combustion production device (hereinafter referred to as a continuous partial combustion device), which is an IT part of city gas production equipment, is a facility employed in small and medium-sized city gas business establishments.

City gas production involves decomposing petroleum-based hydrocarbon raw materials with steam to produce a mixture of hydrogen, carbon oxide, carbon dioxide, and the like. This steam decomposition reaction is endothermic, so heat must be applied to continue production. A continuous partial combustion system is a system that continuously provides this heat by partially combusting the raw material. Therefore, there is no need to heat the reactor from the outside, and there is no problem of intermittent gas production.

In addition, the demand for city gas is extremely high (and fluctuates) throughout the day.It can be said that there is almost no demand late at night.For this reason, unless the gas holder is very large, manufacturing equipment should not be operated at night. Most of the equipment is stopped, so the equipment must be started every morning.

Because operations are stopped overnight, the temperature of the reactor's catalyst layer has dropped in the morning. If the catalyst layer has not reached a predetermined temperature, operation cannot be performed and a heating step is required, in which fuel is combusted in the combustion chamber to raise the temperature of the catalyst layer.

As shown in the example in Figure 1, a partial combustion type reactor has a catalyst layer (2) in the middle of the reactor (1), and supports the catalyst at the bottom to uniformly disperse the gas flow. A combustion chamber (4) is provided further below the perforated plate portion (3). Of course, there are various structures other than this, such as those in which the raw material is introduced at an upper side or sideways, but such differences in structure are not directly relevant to the present invention, and there is no problem as long as the principle is the same.

Raw materials LPG, steam and air are introduced from the bottom,
When the air moves up the reactor (1) and reaches the catalyst layer (2), part of the air and the raw material are combusted, and a reforming reaction occurs between the raw material and the steam. Gas is produced by the reforming reaction, and the heat required for the reforming reaction is supplied by combustion. At this time, the catalyst layer (
The temperature of 2) is required to be 750 to 800°C, and if this temperature is low, troubles such as carbon precipitation and gum formation occur. The temperature of the combustion chamber is about 400'C, and if it is too high, a thermal decomposition reaction will occur, causing the generation of unnecessary substances.

At the start of each morning, the temperature of the catalyst layer (2) decreases (7
00°C), the burner (5) is ignited in the combustion chamber to begin heating up. At this time, the furnace wall of the combustion chamber (4) (
6) and the perforated plate part (3), the temperature of the combustion exhaust gas decreases, and when it reaches the catalyst layer (2), it reaches 60°C.
The temperature will be around 0℃. For this reason, the catalyst layer (2) will be cooled conversely, and the temperature of the catalyst layer (2) will decrease when the temperature starts to rise. Eventually, the temperature of the furnace wall (6) and perforated plate (3) of the combustion chamber (4) rises, and the temperature of the exhaust gas rises (in other words, the heat is not absorbed and reaches the catalyst layer at a high temperature). ) and the catalyst layer (2) are also heated. and,
When the catalyst layer (2) reaches a predetermined temperature, gas production begins.

(C) Problems to be Solved by the Invention In such conventional methods, the temperature raising step every morning takes a very long time, often 2 to 3 hours. This requires the operators to work from early in the morning, which requires a lot of effort. Furthermore, even if gas has to be produced hastily for some reason, it is impossible to do so and it is impossible to deal with an emergency.

Therefore, there has been a desire in the industry to shorten the temperature raising process every morning as much as possible.

(dl Means to Solve the Problems In view of the above-mentioned current situation, the inventors have completed the present invention as a result of intensive research, and its characteristics are: In a reactor for producing gas, a radiant tube burner is provided upstream of a reforming catalyst in the reactor.

Here, the reactor refers to a device in which raw materials and steam react to produce gas. The reforming catalyst refers to a catalyst for steam reforming.

A radiant tube burner provides heat by radiant heat from the outer surface of the burner, and its major feature is that the combustion exhaust gas does not come into contact with the object to be heated. The structure is such that a mixture of air and fuel is burned inside the outer cylinder, the resulting heat heats the outer cylinder, and the heat is radiated from the outer surface of the outer cylinder. Therefore, the amount of heat that can be provided is determined by the burner capacity and the effective surface area of the outer cylinder.

Of course, the shape of this radiant tube burner and the type of fuel may be of any kind and are not limited in any way.

This radiant tube burner may be provided within the combustion chamber or may be provided at an intermediate position between the combustion chamber and the catalyst layer. Of course, any other position may be used as long as it is within the reactor and upstream of the catalyst layer.

The combustion chamber is a space provided with a burner that is ignited when the catalyst layer is heated or scarfed. Scarfing refers to the process of igniting a burner and burning excess air to remove carbon, etc., accumulated in the catalyst layer. For this reason, continuous operation for 50 to 100 hours or more is usually difficult, but in city gas production, there is no problem because the burner is used to raise the temperature at the start of each day, and scarfing is also performed at the same time.

In other words, it is a combustion space where the flame does not come into direct contact with the furnace wall or catalyst. Some reactors have a combustion chamber located directly below the catalyst layer, and others have a structure in which the combustion chamber is placed horizontally so that raw materials and the like do not pass through it during gas production.

First, a method of installing a radiant tube burner in a combustion chamber will be explained.

After installing a radiant tube burner in the combustion chamber and stopping operation during the night, ignite this burner and let it burn until the next morning's scoot. The temperature is raised from about 400°C by the radiant heat, and reaches about 800"C at the start of operation. In other words, the capacity of the radiant tube burner is adjusted so that the temperature can be raised to this extent.

In this way, when the heating burner is ignited and burned at the start of operation, the temperature of the combustion exhaust gas does not drop because the furnace walls and the like are at a high temperature, and the temperature of the catalyst layer can be immediately raised. That is, the above-mentioned drawback that the temperature of the catalyst layer once drops is eliminated.

Furthermore, since heating is indirect and combustion does not occur directly in the combustion chamber, there is no risk of oxidizing the catalyst and there are fewer problems in the event of a misfire. In particular, this example requires simple equipment and can be implemented relatively easily in an existing reactor.

Next, if a radiant tube burner is installed directly below the catalyst layer instead of in the combustion chamber, the radiant (However, it will be ignited and heat the burner outer cylinder before the temperature rises.)
. In this way, as mentioned above, the temperature of the combustion exhaust gas is lowered by absorbing heat in the combustion chamber and the furnace wall, but the temperature is raised by the radiant tube burner and the temperature is not raised in the catalyst layer. As a result, the temperature of the catalyst layer can be raised immediately as in the previous example.

In this case, there is no need for the wasteful process of once raising the temperature of the combustion chamber, furnace walls, etc., which should not be at a high temperature during operation, and then cooling them again at the start of operation. Furthermore, there is no need to keep burning at night.

tel Example FIG. 2 is a schematic cross-sectional view showing one example of the reactor of the present invention. This is an example in which a radiant tube burner (7) is provided in the combustion chamber (4) of the conventional reactor (1) shown in FIG. 1. This is made by opening a cavity in the refractory bricks and heat insulating bricks around the combustion chamber (4) and inserting a burner (7) therein. Although the drawing does not show piping other than the reactor,
The inlet pipe for raw materials, piping to the two types of burners, etc. are normal.

FIG. 3 is a schematic sectional view of the burner used in the example of FIG. 2. The inner cylinder (9) is inserted into the outer cylinder (8) and the inner cylinder (
9) has a structure in which combustion occurs at the tip. Fuel and air for this burner are mixed at the base and introduced into the inner cylinder. This air and fuel control may be of any type, such as a commonly known gas burner type.

FIG. 4 is a schematic sectional view showing another embodiment of the reactor of the present invention. In this example the radiant tube burner (7)
is provided between the catalyst layer (2) and the perforated plate portion (3). In order to support the catalyst, a support stand (lO) similar to the perforated plate part (3) and having a small heat capacity is provided. For this reason, the conventional perforated plate portion (3) serves only as a distributor. In this case, when the temperature rises, the combustion exhaust gas coming from below is heated here to prevent the exhaust gas below the temperature of the catalyst layer from reaching the catalyst layer (2).

fg+ Effects of the Invention By utilizing the present invention described in detail above, the conventional heating time can be significantly shortened. This means that the time required can be reduced from the conventional several hours to several tens of minutes.

Furthermore, if a burner is provided directly under the catalyst, unnecessary temperature rise will not occur, making it extremely advantageous and useful in terms of calorific value.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a conventional reactor, FIG. 2 is a schematic sectional view showing an embodiment of the reactor of the present invention, FIG. 3 is a schematic sectional view of the burner used in the example of FIG. The figure is a schematic sectional view showing another embodiment of the reactor of the present invention. l... Reaction furnace 2... Catalyst layer 3... Perforated plate 4... Combustion 4
Chamber 5... Combustion burner 6... Combustion chamber furnace wall 7... Radiant tube burner 8.
...Outer cylinder 9...Inner cylinder 10...Support stand Fig. 4

Claims (1)

[Claims] 1. A low-pressure continuous partial combustion reactor for producing town gas, characterized in that a radiant tube burner is provided upstream of a reforming catalyst in the reactor. . 2. The reactor for city gas production according to claim 1, wherein the upstream side of the reforming catalyst is inside the combustion chamber. 3. The reactor for city gas production according to claim 1, wherein the upstream side of the reforming catalyst is an intermediate portion between the reforming catalyst and the combustion chamber.