High-temperature Reaction Vessel

Abstract

A high-temperature, high-pressure vapor phase reactor for chemical conversions requiring a quench to maintain the reaction temperature substantially isothermal, which is capable of easy field assembly and additionally allows for differential of expansion.

Description

BACKGROUND OF THE INVENTION

The thermal hydrodealkylation of alkylated aromatics such as toluene to produce benzene is well known as described in the King et al. U.S. Pat. No. 3,291,849. It is also recognized that in a hydrogenation reaction, the temperature rise in the reaction zone is on the order of 70.degree. F. per mol of hydrogen consumed and in view of the fact that it is necessary to keep the operating pressures in the range of 500 to 800 p.s.i.g., the reaction time within the period of 10 to 50 seconds and with a temperature range in the order of 1,100.degree.-1,500.degree. F., it is of critical circumstances that the reactor be effectively designed. Quench streams are used for control of the reactor conditions.

It is also known that high-temperature reactors, particularly in the chemical field, must not only provide for maintaining desired temperature conditions but also must permit an effective physical assembly of the parts. With the large variations in a temperature from the normally cold to the normally hot reactor environment, suitable provision must be made for expansion and contraction of the parts. Furthermore, corrosion of the structural materials must be avoided or minimized; protecting the insulation through temperature changes is also critical.

In addition to providing in the reactor for temperature changes, it also becomes necessary to provide a structurally sound quench system. The invention contemplates a unique arrangement of parts whereby operating limits can be observed with an economical construction.

Emphasis is placed on the economic factor inasmuch as reactors of this type, which will operate in the temperature and pressure ranges indicated, and frequently with a hydrogen atmosphere, are necessarily constructed in sizes of 4 feet and more internal diameter with an internal height of from 25 to 100 feet. For the hydrodealkylation of toluene to make benzene, this requires wall thickness in excess of 4 inches. The unit is preferably freestanding and hence must be inherently rigid.

SUMMARY OF THE INVENTION

The invention applies particularly to a high-pressure hydroconversion reactor, substantially free of catalyst or catalytic surface which will permit the control of hydrogenation reactions and will provide for the necessary differential of expansion and permit the effective quench of the reaction to establish for the reaction, a shallow saw tooth temperature profile.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic substantially central vertical section through a reactor with parts shown in elevation.

FIG. 2 is a part elevation, part section of the upper part of a feed distributor unit.

FIG. 3 is a top plan view with parts in section of one of the distributor units as shown in FIG. 2.

FIG. 4 is a horizontal section substantially on the line 4--4 of FIG. 2.

FIG. 5 is a horizontal section substantially on the line 5--5 of FIG. 1.

FIG. 6 is a partial elevation, partial section of a part of the quench unit substantially on the line 6--6 of FIG. 5.

FIG. 7 is an enlarged vertical section approximately on the line 7--7 at the upper part of the reactor showing the details of construction.

FIG. 8 is a partial horizontal cross section through the reactor at line 8--8 of FIG. 9.

FIG. 9 is a vertical section at the lower part of the reactor at right angles to FIG. 8.

FIG. 10 is a diagrammatic top plan view of the quench inlets to the reactor .

DESCRIPTION OF THE PREFERRED EMBODIMENT

The reactor generally shown at 10 is a vertical cylindrical vessel appropriately supported from the ground by a skirt or legs or similar support indicated at 12. A removable head 14 is appropriately secured at the upper part by the typical gaskets and bolting devices, not shown in FIG. 1.

Reactant inlets are indicated at 16 and in a reactor of typical commercial size it is appropriate to have at least two or more which are equally spaced around the perimeter.

Each of the reactant inlets 16 is interconnected to internal vertically extending distributions conduit 18 which are surmounted by a distributor head 20 as shown in FIGS. 2 and 3. By this means, the reactants are introduced at the lower part of the reactor and are distributed at the upper part of the reactor through outlets 21 from which they pass downwardly and out at the bottom thereby minimizing external piping. As indicated in FIG. 2, a suitable slip joint 24 permits a predetermined expansion and contraction of the elements. This becomes critical as hereinafter described.

In a similar manner the discharge outlet of outlets are mounted at the bottom of the reactor which also simplifies piping and assures adequate travel of the reactants through the reactor. A hollow cone q uench spray nozzle 32 adjacent to outlet 30 serves to reduce the temperature of the discharging product effluent so that any further reaction is terminated. The quenching medium fed through nozzle 32 is preferably recycled cooled product and it is at a temperature sufficiently different from that of the product to reduce the effluent temperature to below about 1,200.degree. F.

In a reactor for a hydrodealkylation process which is normally carried out at elevated temperatures and pressures, it is necessary to have insulation. This is generally shown in detail in FIG. 7 at 36 and is supplemented by reinforcing openwork steel filled with plastic at 38. We also find it desirable to provide a shroud or liner 40 conveniently of stainless steel. This is preferably hung at 40a from the plate 40d at the upper part of the reactor and is sealed when the top 14 is added.

It is not necessary that the space 40 c between the liner 40 and the wall 10 or the insulation 38 be pressuretight except that normal flow of vapors is to be prevented. This is accomplished by a suitable overlap of the lower edge of the liner 40 on the shroud 40b provided at the lower part of the reactor as indicated in FIGS. 8 and 9. Spacers 41 serve to center the shroud 40 in the shroud 40b thus forming a slip joint.

The need for the various slip joints will be appreciated when it is recognized that there may be as much as 11 inches of expansion between the cold and the hot condition of the reactor.

As described in the patent hereinbefore indicated, it has been found especially desirable with exothermic reactions such as the hydrodealkylation of toluene, that the reaction be partially quenched throughout the length of the reaction zone. As described herein, we have found it preferable to quench the reactor by a quench unit generally indicated at 42 which contains separate vertical conduits 43.

As indicated more particularly in FIG. 5 and FIG. 6, each of the vertical conduits 43 is blanked off as at 48 at an appropriate horizontal location and is then in communication with a quench distributor 45. As shown in FIG. 6, the quench distributor is annular and has a series of holes 50 for distributing the quench material which may be either liquid or gas at the horizontal elevation. Cooled hydrogen gas is a preferable quench medium in a hydrodealkylation reaction.

In a similar manner, the other vertical conduits 43 are in communication with other quench units 44 so that an accurate control of temperature, which is recorded by the usual temperature reading means, can be accomplished by the control of the quench material entering the upper part of the reactor chamber.

As shown in FIG. 10, a valve 52 is mounted on each quench line 43. These valves are, in turn, actuated by usual controls from the thermocouple assembly 60 shown in FIG. 1 which has a series of stations 62 at vertical locations.

These individual quench valves 52 as controlled by the thermocouples thus will give a shallow saw tooth temperature profile with about a maximum 20.degree. F. temperature difference.

While we have shown and described a preferred form of embodiment of our invention, we are aware that modifications may be made thereto within the scope and spirit of our description herein and only such limitations should be made thereto as come within the terms of the claims appended hereinafter.

Claims

We claim:

1. An elongated substantially cylindrical reactor to be operated under conditions of elevated temperatures and pressures while maintaining a highly exothermic reaction under substantially isothermal conditions with the continuous addition of reactants thereto and withdrawal of effluent therefrom which comprises:

a. a rigid outer cylindrical shell having a closed fixed lower end and a removable upper end closure;

b. a first inner cylindrical shroud concentric with said shell and extending upwardly from the fixed lower end to which it is affixed;

c. a second inner cylindrical shroud concentric with said shell extending downwardly from the upper end of the shell to which it is affixed and telescopically joined to said first shroud;

d. a reactant inlet extending through the lower portion of the rigid shell and the first shroud;

e. a reactant distributor conduit connected to said inlet and extending vertically upward within the shell;

f. a distributor head telescopically joined to the upper portion of the reactant distributor conduit for introducing reactant in the top portion of the reactor;

g. means for mounting the distributor head on the second cylindrical shroud;

h. multioutlet heat-quenching means extending centrally downwardly from and supported by the removable upper closure, said heat-quenching means having a plurality of vertically spaced discharge outlets;

i. means within the shell for controlling flow of quenching medium from the multioutlet heat-quenching means, and

j. a discharge outlet extending through the lower portion of the shell and the first shroud.

2. The reactor of claim 1 wherein said first and second inner shrouds are corrosion resistant.

3. The reactor of claim 1 wherein said heat-quenching means comprises a nest of interdependently supported quench tubes said tubes extending substantially throughout the reactor height with different tubes having outlets at different levels within the reactor for quench distribution at the respective level.

4. The reactor of claim 3 and wherein the nest of quench tubes is provided with valve means for controlling flow in each of said tubes.

5. The reactor of claim 4 and wherein the means within the shell for controlling flow of quenching medium from the multioutlet heat-quenching means comprises thermocouple devices extending throughout the height of the reactor for separately controlling the quench tube valve means.

6. The reactor of claim 1 and wherein the distributor head comprises a vertical conduit telescopically joined to the upper portion of the reactant distributor conduit and horizontally disposed distributing outlet tubes connected to said vertical conduit.

7. The reactor of claim 6 and wherein the outlets for the heat-quenching means are annular members with openings in the outer peripheral portion to introduce quenching medium evenly into the reactor.