JPH07309602A - Tubular cracking furnace for catalytic cracking of hydrocarbon with steam - Google Patents

Abstract

PURPOSE: To provide the cracking furnace capable of performing catalytic steam cracking of a hydrocarbon(s) with high heat efficiency and in a high cracking conversion ratio by providing a tubular cracking furnace with a catalyst chamber contg. the bulk material bed, introducing a process gas consisting of methane and steam into the bulk material bed and concurrently, heating the process gas with heated gas tubes.

CONSTITUTION: In this cracking furnace, a catalyst chamber 3 contains a bulk material bed 5 consisting of catalyst elements 4 and the catalyst elements 4 are downwardly moved in the catalyst chamber 3 by gravity and refluxed with a process gas, transferred through a take-off conduit 15, an excess flow control device 16, a reactivation unit 21, a flow rate control device 12 and a feed conduit 11. Also, one or many heating gas tubes 6 are placed in the snaky or helical shape, so as to pierce the bulk material bed 5 and then, hot helium heated to 950°C is passed through the inside of each of the heating gas tubes 6, to heat the process gas. At this time, the process gas comprises methane and steam in a steam/methane volumetric ratio of 3/1 to 7/1 and is fed into the bulk material bed 5 from a process gas inflow port 19 and in the bed 5, catalytically cracked in a ≥80% cracking conversion ratio and then, the resulting cracked gas is taken off from a cracked gas outflow port 20.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a tubular cracking furnace for the catalytic cracking of gaseous hydrocarbons, in particular methane which forms a process gas mixed with steam, by means of steam.

This tubular cracking furnace is equipped with a catalyst chamber containing a layer of material consisting of catalytic elements through which the process gas flows in order to decompose it. The process gas is heated with a heating gas, especially helium.

[0003]

2. Description of the Prior Art Tubular cracking furnaces of this type are known. That is, the magazine "Nuclear Engineering and Design",
Vol. 78, No.2,1984, “The nuclear heated steam ref
ormer-design and semitechnical operating experienc
In e "P.179-194, a tubular cracking furnace is described, in which the Raschig ring type catalyst elements are present in the cracking tube forming the catalyst chamber.
The cracking tube provided with the catalytic element is heated with heated helium to provide the heat of reaction required for catalytic cracking. In order to increase the heat transfer from the helium side, internals for increasing the heat transfer are provided with the cracking tube in the region where the helium flows, thereby improving the efficiency of catalytic cracking. However, the catalytic properties of the catalytic element change during the continuous operation of the tubular cracking furnace, and depending on the type of catalyst, the catalytic element must be replaced after a certain operating time. The catalytic element is reactivated outside the tubular cracking furnace and subsequently reused.

[0004]

The problem underlying the present invention is to provide a tubular cracking furnace for the catalytic cracking of hydrocarbons with steam in the manner described at the outset, while its construction is easy. , So that its high decomposition efficiency is reached.

[0005]

This object is achieved according to the invention by a tubular cracking furnace of the type described at the outset comprising a catalyst chamber,
The catalytic chamber is provided with a bulk material layer of catalytic elements, which moves under the action of gravity in the catalytic chamber and contains one or more hydrocarbons mixed with steam. It is possible to recirculate with the process gas, in which case the catalyst chamber is connected to at least one feed conduit and withdrawal conduit, each with a flow-through controller for the catalytic element, for transferring the catalytic element. A process gas inlet is provided in the lower region of the bulk material layer and a decomposition gas outlet in the upper region of the bulk material layer, and through the bulk material layer to heat the process gas. One or many heated gas pipes are laid in a meandering or helix shape in the bulk material layer,
This is solved by the fact that the heating gas pipe is designed so that the heating gas, in particular heating helium, flows from the top to the bottom in the region of the bulk material layer.

In order to transfer the catalyst element to the catalyst chamber,
Connected to the supply and withdrawal conduits, these conduits are each equipped with a flow-through regulator for controlling the flow-through of the catalytic element through the feed and withdrawal parts. The catalytic element flows under the action of gravity through the catalytic chamber as a bulk material layer. In this case, the flow-through amount is adjusted so that the time unit-the catalyst element moves in the catalyst chamber within this unit time-is a time unit in which the desired contact action is achieved. The catalytic element leaves the catalytic chamber only when its contact properties are below a certain quality.
The flow-through is carried out continuously or in a manner similar to continuous with a corresponding preselected time period.

In another arrangement according to the invention, the withdrawal conduit of the catalytic element leads to a reactivation unit, from which the reactivated catalytic element is returned to the feed conduit of the catalytic chamber. (See claim 2 in the claims).

In order to achieve a high contact effect, the catalytic element is formed in a spherical shape and is provided with recesses for enlarging the surface on which its catalytic reaction takes place (Claim 3).
reference).

Such a recess is obtained, for example, by slightly cutting off the catalytic element. The formation of bridges between catalytic elements in the bulk material layer can be avoided by providing suitable inclusions.

In order to heat the process gas in the catalyst chamber, a heating gas pipe is drawn through the bulk material layer in a meandering or helix manner (see claim 4 of the claims). Helium is used as the heating gas, and this helium is heated to the gas temperature necessary for the catalytic reaction, for example, in a high temperature reaction vessel. In order to maintain a completely undisturbed passage of the catalytic element, the heating gas pipe is arranged inside the bulk material layer, between the individual curved sections of the tube, the diameter D of the respective catalytic element being spherical.
Is provided so as to maintain an interval a (a ≦ 5D) corresponding to 5 times (see claim 5 of the claims).
In the region of the bulk material layer, the heating gas flows through the heating gas pipe from top to bottom (see claim 6).

The process gas is guided against the flow direction of the catalytic element in the bulk material layer in the catalytic chamber. The catalyst chamber has a process gas inlet in the lower region of the bulk material layer and a cracking gas outlet above the bulk material layer (see claim 6).

Hereinafter, the present invention will be described in detail with reference to the embodiments illustrated in the accompanying drawings.

[0013]

1 is a longitudinal sectional view of a cylindrical tubular cracking furnace with an axis of symmetry 1 and an outer wall 2. At the center of the tubular cracking furnace, there is a catalyst chamber 3 filled with spherical catalyst elements 4 forming a bulk material layer 5. In the present embodiment, the bulk material layer 5 is penetrated by a heating gas pipe 6 oriented in a helix shape, and passes through this heating gas pipe, and in this embodiment, as a heating gas. The heated helium flows. Instead of a heating gas tube oriented in a helix, a meandering arrangement of this heating gas tube is also possible.

In FIG. 1, only two heating gas pipes 6 are shown. Between the individual curve sections of the heating gas pipe, this heating gas pipe 6 has a minimum distance a corresponding to five times the diameter D of the catalytic element (this diameter D is shown in FIG. 2). When a large number of heating gas pipes 6 are used, this minimum interval a ≦ 5
D is maintained between all heated gas lines. As a result, the flow-through of the spherical catalytic element 4 in the bulk material layer 5 caused by the gravity is not impeded.

The heated gas pipe 6 is connected to the heated gas inlet 8 at the head 7 of the tubular cracking furnace. A heating gas line 6 is guided through the bulk material layer 5 and is connected in the outer region of the catalyst chamber 3 with a return flow conduit 9 which runs inside the outer wall 2. This return conduit guides the heating gas to the heating gas outlet 10 after it has released its heat to the process gas flowing through the bulk material layer 5. The heating gas outlet 10 is located in the head portion 7 of the tubular cracking furnace, like the heating gas inlet 8.

The catalytic element 4 comprises one feed conduit 11 or-
As in this embodiment-introduced into the catalyst chamber 3 via a number of feed conduits 11. These supply conduits 11 are
In this embodiment, it is provided annularly inside the head 7 of the tubular cracking furnace. The catalytic element 4 is adjusted from these supply conduits 11—in this supply conduit 11 by a flow-through adjustment mechanism 12 to a predetermined flow-through amount—to the bulk material layer 5 on its surface 1.
Drop on 3.

The spherical catalytic element 4 is provided with a recess 14 in this embodiment which is formed by slightly cutting out the catalytic element in order to enlarge its catalytically active surface (FIG. 2 shows this recess).

From the catalyst chamber 3 the catalyst element 4 is loaded with the bulk material layer 5
From the lower region of the pipe through the take-out pipe 15-the flow-through amount in the take-out pipe is adjusted by another flow-through amount adjusting mechanism 16. The catalyst element exits the tubular cracking furnace at the catalyst element outlet 17.

In the flow-through amount adjusting mechanisms 12 and 16, the catalyst element 4 which flows through the bulk material layer 5 under the action of gravity is disposed in the catalyst chamber 3
After a predetermined residence time in the inside, adjustment is performed so that the gas is removed again from the tubular cracking furnace through the catalyst element outlet 17.
The residence time for the catalytic element is about 6 in this example.
It is the moon. Aluminum oxide, calcium oxide and / or nickel oxide are used as catalyst substances.

A process gas, which is in direct contact with the surface of the catalytic element 4 in a direction opposite to the heating gas flowing in the heating gas pipe 6 in the flow direction 18, flows through the bulk material layer 5. In this embodiment, the process gas, water vapor and methane to be decomposed are in a 3: 1 volume ratio, in particular a 7: 1 volume ratio. In the lower region of the bulk material layer 5, the process gas is
In this embodiment, via the process gas inlet 19
It enters the bulk material layer and flows through this bulk material layer from below to above. The process gas inlet is an inflowing catalyst element 4
Protected against. In the catalyst chamber 3, the process gas is decomposed into decomposition gas containing H ₂ , CO, CO ₂ , CH ₄ and H ₂ O, and after passing through the bulk material layer 5,
It flows out through the cracked gas outlet 20 in the head 7 of the tubular cracking furnace.

In order to catalytically decompose methane with steam, in the present embodiment, the gas composition, temperature and pressure are adjusted as follows in the tubular cracking furnace. - Process Gas Gas composition: water vapor: Methane = 4: 1 inlet temperature: about 500 ° C. - decomposition gas Gas composition :( volume%) _{about: H 2 = 37, CO =} 5, CO
_{2 = 6, CH 4 = 6} , H 2 O = 46 outlet temperature: about 800 ° C. - heating gas helium inlet temperature: about 950 ° C. outflow temperature of about 680 ° C. Pressure: 40 bar - catalyst elemental materials: aluminum oxide, Mixture of calcium and nickel oxide Residence time: Approximately 6 months-Amount of process gas vs. decomposition gas:> 80% -Reaction zone in bulk material layer: Approximately 1111 m at a process gas flow velocity of approximately 1 m / sec. In the example, the catalyst element taken out from the catalyst element outlet 17 is supplied to the reactivating unit 21. The transfer conduit 22 for the catalytic element is the reactivation unit 2
It leads to 1. Within this reactivation unit 21, the catalytic element is brought to its original catalytic quality. Subsequently, the reactivated catalyst element is led to the feed conduit 11 via the transfer conduit 23, where it is again introduced into the tubular cracking furnace. In FIG. 1, the transfer conduits 22 and 23 as well as the reactivating unit 21 are shown only in a schematic view.

[0022]

With the tubular cracking furnace according to the present invention, despite the simple structure, the high thermal efficiency and the reuse due to the reactivation of the catalyst element allow the high cracking efficiency and economically advantageous hydrocarbon steam. Catalytic decomposition is achieved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a tubular cracking furnace according to the present invention.

FIG. 2 is a cross-sectional view of a catalytic element according to the present invention.

[Explanation of symbols]

 1 symmetry axis 2 outer wall 3 catalyst chamber 4 catalyst element 5 bulk material layer 6 heating gas pipe 7 head 8 heating gas inlet 9 backflow conduit 10 heating gas outlet 11 supply conduit 12 flow excess adjustment mechanism 13 surface of bulk material layer 14 recess 16 flow rate adjusting mechanism 17 catalyst element outlet 18 flow direction 19 process gas outlet 20 cracked gas outlet 21 reactivation unit 22 transfer conduit 23 transfer conduit

Claims (5)

[Claims] 1. A tubular cracking furnace for catalytically cracking gaseous hydrocarbons, in particular methane with steam, comprising a catalyst chamber (3), the catalyst chamber comprising a catalytic element (4). (5), the catalyst element moves under the action of gravity in the catalyst chamber (3) and can be refluxed with a process gas containing one or more kinds of hydrocarbons mixed with steam. And in this case the catalyst chamber (3)
To transfer the catalytic element (4) to the catalytic element (4)
One overflow controller for each (12, 16)
Is connected to at least one supply conduit (11) with a withdrawal conduit (15), the process gas inlet (1
9) in the lower region of the bulk material layer (5) and in the upper region of the bulk material layer (5) in the cracked gas outlet (20).
And that one or more heating gas pipes (6) penetrating the bulk material layer (5) for heating the process gas are meandered in the bulk material layer (5). Alternatively, it is laid in a helix shape, in which case the heating gas pipe (6) is constructed so that the heating gas, in particular heating helium, flows from the upper side to the lower side in the region of the bulk material layer (5). , A tubular cracking furnace for catalytically cracking hydrocarbons with hydrogen. 2. A heating gas pipe (6) is combined with a return flow conduit (9) for the heating gas which runs inside the bulk material layer (5) inside and along the outer wall (2) of the catalyst chamber (3). A tubular cracking furnace according to claim 1, characterized in that the return conduit leads to a heated gas outlet (10) in the head (7) of the tubular cracking furnace. 3. The withdrawal conduit (15) opens into a reactivation unit (21) for the catalytic element (4) so that the reactivated catalytic element is transferred to the feed conduit (11). The tubular decomposition furnace according to claim 1, wherein the tubular decomposition furnace is configured. 4. The catalytic element (4) is spherically shaped and is provided with recesses for enlarging its catalytically reactive surface. The tubular decomposition furnace according to one. 5. The heating gas pipe (6) has, in the bulk material layer (5), five times the diameter (D) of the spherical catalytic element (4) (a ≦ 5).
5. The tubular cracking furnace according to claim 1, having a minimum distance (a) between them corresponding to D).