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Dehumidification of Reformate Recycle for the HDS Process

IP.com Disclosure Number: IPCOM000206076D
Publication Date: 2011-Apr-13
Document File: 2 page(s) / 28K

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Abstract

A conventional way of dehumidification is water condensation by cooling and it is an energy intensive process. An alternative approach is using membranes such as those made from zeolite and Nafion-like materials.

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Title:

Dehumidification of Reformate Recycle for the HDS Process

Abstract:

A conventional way of dehumidification is water condensation by cooling and it is an energy intensive process. An alternative approach is using membranes such as those made from zeolite and Nafion-like materials.

 

Disclosure:

The HDS reactor is designed to capture organic sulfur from feed fuel like natural gas, because that sulfur can poison the catalysts in the subsequent fuel processing reactors. Organic sulfur, e.g. thiophane, is first reduced to hydrogen sulfide (H2S) using hydrogen-rich gas recycled from PROX, and the resulting H2S is then captured by zinc oxide (ZnO) sorbent by the following chemical reaction H2S + ZnO --- ZnS + H2O.

This sulphidation is a reversible reaction and its thermodynamic completion depends on the temperature and humidity (moisture concentration). For instance the equilibrium constant of sulfidation is 4.5x10^6 at 316°C (600°F). The humidity needs to be lower than 11% by volume in order to maintain the sulfur level below 25 ppbv, which is the target level. On the other hand, the recycled reformate contains high concentration moisture (~35%). To maintain the sulfur level well below the target over the life span of an HDS reactor, the recycled reformate needs to be dehumidified before it enters the HDS reactor.

A conventional way of dehumidification is water condensation by cooling and it’s an energy intensive process. An alternative approach is using membranes such as those made from zeolite and Nafion-like materials. Zeolite membranes are hydrophilic and nonporous. The dehumidification mechanism can be simply described as adsorption or...