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Method of Heat Recovery from the separation of ethylbenzene from styrene

IP.com Disclosure Number: IPCOM000246286D
Publication Date: 2016-May-24
Document File: 9 page(s) / 192K

Publishing Venue

The IP.com Prior Art Database

Related People

TECHNIP: OWNER

Abstract

The present invention relates to the production of styrene by dehydrogenation of ethylbenzene where a crude styrene stream comprised of mostly styrene and ethylbenzene from the dehydrogenation reaction is sent to distillation system where the ethylbenzene is separated from styrene, wherein heat is recovered from the separation process and/or the heat input to the separation is greatly reduced.

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This is the abbreviated version, containing approximately 20% of the total text.

Page 01 of 9

Memorandum

Method of Heat Recovery from the separation of ethylbenzene from styrene

The present invention relates to the production of styrene by dehydrogenation of ethylbenzene where a crude styrene stream comprised of mostly styrene and ethylbenzene from the dehydrogenation reaction is sent to distillation system where the ethylbenzene is separated from styrene, wherein heat is recovered from the separation process and/or the heat input to the separation is greatly reduced. Such processes are described in US6171449, US7642390, and US4628136.

Description of invention and problem solved

In the conventional process for separating ethylbenzene from styrene, a minimum of about
0.90 tons of steam per ton of styrene produced is required to achieve an effective separation of ethylbenzene from styrene. The ability to reduce this steam consumption or recover some of the heat input to this separation is highly desirable.

The use of the apparatus and process in US6171449 allows the steam consumption for this separation to be reduced by at least 45%. This is accomplished by feeding the crude styrene to two distillation columns with one column operated at a higher pressure than the other, where the overheads from the high pressure column is used to reboil the low pressure column.

The processes described in US7642390 and US4628136 recover much of the useful heat from the separation of ethylbenzene from styrene by condensing the overheads of the distillation column against the azeotropic mixture of the ethylbenzene dehydrogenation feed and water.

The present invention benefits from reduction in steam consumption by using the high and low pressure column approach in combination with azeotropic heat recovery from the overheads of the low pressure column.

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Page 02 of 9

Memorandum

The attached figures illustrate the differences between the conventional process (Figure
1), the current state of the art (Figures 2 and 3), and the improved method of this invention (Figure 4).

Referring to Figure 1, one example of the conventional process is as follows. The crude styrene stream 11 enters the EB/SM Splitter 1 where ethylbenzene is separated from styrene. Ethylbenzene is concentrated at in the overheads of the EB/SM Splitter in stream 21 and is condensed against cooling water in the EB/SM Splitter Condenser 2. A portion of the condensed column overheads stream 22 is taken off as the distillate product in stream 12, while the remainder is sent back to the EB/SM Splitter as reflux via stream 23. Styrene is concentrated in the bottoms of the EB/SM Splitter in stream 41. A portion of stream 41 is taken off as the bottoms product in stream 14 while the remainder is sent to the EB/SM Splitter Reboiler 4 via stream 42. The EB/SM Splitter Reboiler heats and partially vaporizers the bottoms against low pressure steam and is returned to the EB/SM Splitter via stream 43.

Using this process for separation of ethylbenzene from styrene consumes large quantities of stea...