GB2161596A

GB2161596A - Reactor for exothermic gas reactions

Info

Publication number: GB2161596A
Application number: GB08417687A
Authority: GB
Inventors: Anthony Horton
Original assignee: Humphreys and Glasgow Ltd
Current assignee: Humphreys and Glasgow Ltd
Priority date: 1983-06-13
Filing date: 1984-07-11
Publication date: 1986-01-15
Also published as: GB8417687D0

Abstract

A device for the removal or addition of heat to a catalyst bed which device comprises a tube sealed at one end, finned on its exterior side and containing an internal tube; such tube being inserted into a catalyst bed such that the top of the tube protrudes from the top of the bed and is attached to inlet and outlet headers preferably by pigtail loops or piping containing means to allow differential expansion between the tube and the headers. <IMAGE>

Description

SPECIFICATION Reactor for exothermic gas reactions Many exothermic gas reactions such as those for the synthesis of methanol, ammonia and ethylene oxide are limited in conversions per pass in the synthesis loops by the need to remove the heat of formation.

An advantage of removing the heat from the reacting gases is in many cases, and certainly in the cases of methanol and ammonia synthesis, that the amount of product at equilibrium is greater the lower the temperature of the gases. The further the reacting gases are from equilibrium the larger is the driving force for the reaction to take place, although this may to some extent be offset by the lower activity of the catalyst at the lower temperature.

Normally the heat of formation is either removed by means of heat transfer surfaces or is taken up by the temperature rise of the gaseous mixture.

This invention seeks to provide a means for removal of heat of formation by indirect heat exchange with a secondary cooling fluid such as water, which means comprise a tube, sealed at one end, finned on its exterior side, and containing an internal tube, which is coaxial or with an axis parallel to it. Such tube or multiples of such a tube being inserted into the catalyst bed such that the top of the tube or tubes protrudes from the top of the bed and is attached to inlet and outlet headers preferably by pigtail loops or piping containing expansion bellows to allow for differential expansion between the finned tube and the headers.

Typically the outer finned tube might be 5cm diameter with eight 1 Ocm fins 5mm wide with inner piping of, say, 1.0-3.5cm diameter, the inner tube being small if the secondary fluid changes phase in the device, and larger if it does not.

Although the tubes may be inserted vertically they may also be inserted in planes other than the horiozontal or vertical.

The main advantage of the means provided by the invention is that it allows a reactor to be designed to contain a bed of catalyst rather than catalyst contained in tubes, whilst retaining the advantages of a tube-cooled reactor.

The means provided allow counter-current flow to be obtained within the reactor without the need for piping connected to both ends of the tube.

The tube according to the invention may be mechanically supported on the grid supporting the catalyst bed or directly on the base of the reactor shell.

A further advantage is that the large expensive tube sheets conventionally used in tubecooled reactors are rendered unnecessary by the invention, allowing a cheaper design. It also facilitates easy catalyst loading and unloading.

An additional advantage is that the invention obviates the need to rely on baffles to ensure good distribution of the reacting gas for a reactor with catalyst on the shell side of the tubes.

Fig. 1 shows the arrangement. The gases are shown entering the reactor through a pipe going into a horizontal header and from there via a pigtail into the central tube of the device. The gases flow down the central tube and into the annulus in which it rises and leave the annulus space by means of another pigtailed tube whence it goes into the outlet header and outlet pipe.

The bottom of Fig. 1 shows two different means whereby the tube may be supported.

The left hand tube is supported by an internal structure whereas the right hand tube is supported on the bottom head. The nozzles for gas flow are not shown on this figure. Gas would normally enter at the top and come out at the bottom so as to give counter-current flow, however, co-current flow could also be used.

Whilst this description has described removal of heat from a catalyst bed the device can also be used for adding heat to a bed, e.g. if one should wish to supply heat for the reaction of carbon dioxide + hydrogen to form carbon monoxide and water. Similarly the device may be used for liquid reactions which are either exothermic or endothermic and which take place in a catalyst bed.

CLAIM

1. A device for removing or adding heat to a catalyst bed which device comprises a tube sealed at one end, finned on its exterior side and containing an internal tube; such tube or multiples of such a tube being inserted into the catalyst bed such that the top of the tube or tubes protrude and is attached to inlet and outlet headers by pigtail loops or piping containing expansion bellows to allow for differential expansion between the finned tube and the headers.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

SPECIFICATION Reactor for exothermic gas reactions Many exothermic gas reactions such as those for the synthesis of methanol, ammonia and ethylene oxide are limited in conversions per pass in the synthesis loops by the need to remove the heat of formation.

An advantage of removing the heat from the reacting gases is in many cases, and certainly in the cases of methanol and ammonia synthesis, that the amount of product at equilibrium is greater the lower the temperature of the gases. The further the reacting gases are from equilibrium the larger is the driving force for the reaction to take place, although this may to some extent be offset by the lower activity of the catalyst at the lower temperature.

Normally the heat of formation is either removed by means of heat transfer surfaces or is taken up by the temperature rise of the gaseous mixture.

This invention seeks to provide a means for removal of heat of formation by indirect heat exchange with a secondary cooling fluid such as water, which means comprise a tube, sealed at one end, finned on its exterior side, and containing an internal tube, which is coaxial or with an axis parallel to it. Such tube or multiples of such a tube being inserted into the catalyst bed such that the top of the tube or tubes protrudes from the top of the bed and is attached to inlet and outlet headers preferably by pigtail loops or piping containing expansion bellows to allow for differential expansion between the finned tube and the headers.

Typically the outer finned tube might be 5cm diameter with eight 1 Ocm fins 5mm wide with inner piping of, say, 1.0-3.5cm diameter, the inner tube being small if the secondary fluid changes phase in the device, and larger if it does not.

Although the tubes may be inserted vertically they may also be inserted in planes other than the horiozontal or vertical.

The main advantage of the means provided by the invention is that it allows a reactor to be designed to contain a bed of catalyst rather than catalyst contained in tubes, whilst retaining the advantages of a tube-cooled reactor.

The means provided allow counter-current flow to be obtained within the reactor without the need for piping connected to both ends of the tube.

The tube according to the invention may be mechanically supported on the grid supporting the catalyst bed or directly on the base of the reactor shell.

A further advantage is that the large expensive tube sheets conventionally used in tubecooled reactors are rendered unnecessary by the invention, allowing a cheaper design. It also facilitates easy catalyst loading and unloading.

An additional advantage is that the invention obviates the need to rely on baffles to ensure good distribution of the reacting gas for a reactor with catalyst on the shell side of the tubes.

Fig. 1 shows the arrangement. The gases are shown entering the reactor through a pipe going into a horizontal header and from there via a pigtail into the central tube of the device. The gases flow down the central tube and into the annulus in which it rises and leave the annulus space by means of another pigtailed tube whence it goes into the outlet header and outlet pipe.

The bottom of Fig. 1 shows two different means whereby the tube may be supported.

The left hand tube is supported by an internal structure whereas the right hand tube is supported on the bottom head. The nozzles for gas flow are not shown on this figure. Gas would normally enter at the top and come out at the bottom so as to give counter-current flow, however, co-current flow could also be used.

Whilst this description has described removal of heat from a catalyst bed the device can also be used for adding heat to a bed, e.g. if one should wish to supply heat for the reaction of carbon dioxide + hydrogen to form carbon monoxide and water. Similarly the device may be used for liquid reactions which are either exothermic or endothermic and which take place in a catalyst bed.

CLAIM

1. A device for removing or adding heat to a catalyst bed which device comprises a tube sealed at one end, finned on its exterior side and containing an internal tube; such tube or multiples of such a tube being inserted into the catalyst bed such that the top of the tube or tubes protrude and is attached to inlet and outlet headers by pigtail loops or piping containing expansion bellows to allow for differential expansion between the finned tube and the headers.