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ORGANIC RANKINE CYCLE SULFUR DEWPOINT CONTROL

IP.com Disclosure Number: IPCOM000224574D
Publication Date: 2012-Dec-31
Document File: 3 page(s) / 69K

Publishing Venue

The IP.com Prior Art Database

Abstract

This invention relates to organic Rankine cycles that are useful for extracting work from energy streams whose temperature is too low to generate steam. Typically, the heating source may be a low temperature post-combustion exhaust stream containing sulfur in the form of SOx, that could result in the condensation of acid in the heat exchangers. The system consists of two heat exchangers, with the first one providing organic fluid economization and the second performing vaporization and superheating. The invention works by recirculating some of the heated organic fluid from the superheater back to the inlet of the first heat exchanger. The amount of recirculation is controlled by a temperature controller on the exhaust gas leaving the heat exchanger. The gas temperature is maintained at a specified amount of superheat above the condensation point. The invention creates a more competitive organic Rankine cycle due to the ability to maximize work output without risking corrosion of a key heat exchanger. It also enables extraction of the maximum amount of exhaust stream energy and optimizes power output and improves overall efficiency.

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ORGANIC RANKINE CYCLE SULFUR DEWPOINT CONTROL

BACKGROUND

This invention relates to organic Rankine cycles that are useful for extracting work from energy streams whose temperature is too low to generate steam. One key step of the cycle is to convert an organic component (i.e. propane, butane, hexane) from a liquid to a vapor phase via heat exchange with a heating source. The heating source may be a low temperature post-combustion exhaust stream containing sulfur in the form of SOx. As the exhaust stream is cooled in the presence of water, the SOx can become sulfuric acid as it condenses onto the heat exchanger. Heavy corrosion occurs to the heat exchanger as a result. This invention helps prevent the condensation of acid in the heat exchangers of an organic Rankine cycle.

BRIEF DESCRIPTION OF DRAWINGS

Organic Rankine cycle sulfur dewpoint control is described further with reference to the following drawing in which:

Figure 1 shows a schematic of the organic Rankine cycle sulfur dewpoint control system.

DETAILED DESCRIPTION

This invention is an application of a similar principle that is used in heat recovery steam generators (HRSG) to prevent acid condensation on the cold end of the heat transfer surface. Condensation is prevented by limiting the inlet water temperature to the heat exchanger that is the cause of the condensation by recirculating some of the water heated upstream. Thus, the exhaust gas temperature can drop no lower than the water inlet temperature to the heat exchanger.

A process flow diagram of the proposed design is shown in Fig. 1. As shown in the figure, the system consists of two heat exchangers, with the first one providing organic fluid economization and the second performing vaporization and superheating. The invention works by recirculating some of the heated organic fluid from the superheater back to the inlet of the first heat exchanger. The amount of recirculation is controlled by a temperature controller on the exhaust gas leaving the heat exchanger. The gas...