COMBUSTOR

TECHNICAL FIELD

The present invention relates to sulphur combustion and, in particular, to techniques for extracting energy from sulphur combustion.

BACKGROUND

FIG. 1 depicts a sulphur combustion and energy recovery system having an ejector, as disclosed in co-owned US Patent 7,543,438 and in co-owned US Patent Application Publication 2009/0235669, which are fully incorporated herein by reference to the maximum extent permissible by national law. Disclosed are improved systems and methods for employing a gas turbine expander as the major energy extraction device for the recovery of energy from the combustion of sulphur with dry air and/or oxygen, as a gas turbine topping device preceding a steam-raising system at a sulphuric acid plant and/or power plant respectively.

FIG. 2 shows another sulphur combustion system and energy recovery system having an ejector, as disclosed in co-owned US Patent Application Publication 2010/0242478, which is also fully incorporated herein by reference to the maximum extent permissible by national law. Disclosed are a system and method for generating energy from sulphur combustion which involve evaporating liquid sulphur to generate sulphur dioxide gas and sulphur vapor, combusting the sulphur vapor with oxygen containing gas to generate heat, and reducing (either at high temperature or catalytically) the sulphur dioxide to carbon dioxide and sulphur vapor by reacting the sulphur dioxide with carbonyl sulfide. The carbonyl sulphide can be generated by reacting hydrogen sulfide with recycled carbon dioxide that is recycled by condensing sulphur vapor, carbon dioxide, and water to yield liquid sulphur, elemental sulphur, steam, and carbon dioxide. Furthermore, this process can be used for the transshipment by pipeline of sulphur by transporting it as carbonyl sulphide. It is noted that these systems include an ejector that works with the combustor as a mixing, cooling and pressure-exchanging device that ensures that the hot combustion gases remain below the metallurgical limit of the turbine blades. Although an ejector- based system works well, improvements on these foregoing technologies would be highly desirable to further improve efficiencies and/or to reduce the overall system complexity.

SUMMARY

An inventive aspect of the present disclosure is a system for recovering energy from sulphur combustion. The system includes a bubbling chamber for vaporizing sulphur to produce sulphur vapor, a multi-stage combustor for combusting the sulphur vapor, and a turbine for recovering energy from combustion gases emitted from the multi-stage combustor. The bubbling chamber may be connected directly to an inlet of the multi-stage combustor and an outlet of the multi-stage combustor may be connected directly to the turbine.

Another inventive aspect of the present disclosure is a method for recovering energy from sulphur combustion. The method entails vaporizing sulphur to produce sulphur vapor, combusting the sulphur vapor in multiple successive stages in a multistage combustor and recovering energy from combustion gases emitted from the combustor. The bubbling chamber may be connected directly to the combustor and the combustor may be connected directly to the turbine.

By employing a multi-stage combustor, there is no need for an ejector or other mixing, cooling or pressure-exchanging device connected between the outlet of the combustor and the inlet of the turbine in this innovative system and method.

The details and particulars of these aspects of the invention will now be described below, by way of example, with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

Further features and advantages of the present technology will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

FIG. 1 depicts a sulphur combustion and energy recovery system having an ejector as disclosed in US Patent 7,543,438 and US Patent Application Publication 2009/0235669;

FIG. 2 depicts another sulphur combustion and energy recovery system having an ejector as disclosed in US Patent Application Publication 2010/0242478;

FIG. 3 depicts a system in accordance with an embodiment of the invention having a multi-stage combustor and a membrane for enriching pressurized air from a compressor;

FIG. 4 depicts a system in accordance with another embodiment of the invention in which the system employs an oxygen-extracting compressor apparatus for enriching the oxygen content and a membrane for further enriching the pressurized air for supplying to a bubbling chamber;

FIG. 5 depicts a system in accordance with one embodiment of the invention in which uncombusted sulphur vapor is combusted in a sulphur furnace; and

FIG. 6 depicts a system in accordance with one embodiment of the invention.

It will be noted that throughout the appended drawings, like features are identified by like reference numerals. DETAILED DESCRIPTION

In general, as depicted in FIGS. 3-6, a system 1000 for recovering energy from sulphur combustion includes a bubbling chamber 900 for vaporizing sulphur to produce sulphur vapor, a multi-stage combustor 300 for combusting the sulphur vapor, and a turbine 400 for recovering energy from combustion gases emitted from the combustor. The bubbling chamber may be connected directly to the combustor and the combustor may be connected directly to the turbine. This arrangement eliminates the need for an ejector coupled to the combustor. For the purpose of this specification, direct connection of the bubbling chamber to the combustor means that the bubbling chamber is connected via a pipe, duct, tube, feed, line, etc. to the combustor without any ejector, mixing device, cooling device or pressure-exchanging device in between. Likewise, direct connection of the multi-stage combustor to the turbine means that the combustion gases from the combustor flow through a pipe, duct, tube, feed, line, etc. from the outlet of the combustor to the inlet of the turbine without passing through any ejector or ejector-like mixing, cooling device and pressure-exchanging device.

The multi-stage combustor may also be referred to as a multiple-stage combustion system or axially-staged combustor. The multi-stage combustor is characterized by a sequence of at least two combustion chambers or combustion zones for staged combustion of the sulphur vapor. The multi-staged combustor may implement, or be adapted from, the axially staged combustion technologies disclosed in U.S. Patent 7,886,539, U.S. Patent 7,836,677, U.S. Patent 7,631 ,499 and U.S. Patent 6,047,550 which are all incorporated by reference to the maximum extent permitted by national law. The multi-stage combustor 300 may include a primary combustion stage followed by a plurality of secondary combustion stages disposed successively or sequentially downstream of each other. Optionally, the multi-stage combustor may or may not include air/oxygen injectors, fuel injectors, heat exchangers and/or energy- extracting devices between successive combustion stages.

The sulphur vapor may be entirely combusted by the multi-stage combustor such that substantially no sulphur vapor (S ₂ ) is emitted from the combustor or, alternatively, the sulphur vapor may be only partially combusted such that a substantial volume of uncombusted sulphur vapor (S ₂ ) is emitted from the combustor.

FIG. 3 depicts a system 1000 for combusting sulphur vapor and for recovering (extracting) energy from the sulphur combustion. The system 1000 includes a multiple- stage combustion system 300 (multi-stage combustor) that eliminates the need for the ejector shown in FIG. 1 as a mixing and cooling device. Additionally, the system 1000 shown in FIG. 3 may include an optional membrane 800 for enriching pressurized air supplied to the bubbling chamber 900 from the compressor 100. In other words, the compressor receives ambient air via an air intake of the compressor. The intake air is denoted by reference numeral 1. This air is compressed by the compressor 100 which is driven by the turbine 400. Exiting the compressor is pressurized air. The pressurized air is enriched or purified in terms of oxygen content by a membrane 800. Exiting the membrane is enriched pressurized air which is delivered by air duct 4 to the bubbling chamber 900 and also concurrently via air duct 3 to an inlet of the multi-stage combustor 300. Note that the system 1000 of FIG. 3 disposes the membrane between the compressor and the bubbling chamber.

The system 1000 depicted in FIG. 4 represents an improvement over the system of FIG. 3. The system 1000 of FIG. 4 includes a compressor 100, i.e. a combined compressor-separation apparatus for separating a portion of the oxygen from the compressed air as disclosed in U.S. Patent 8,127,558 and in U.S. Patent 5,657,624.

U.S. Patent 5,657,624, which is incorporated by reference to the maximum extent permissible by national law, teaches using an ion transport membrane system in combination with a combustion turbine system to remove a portion of oxygen from compressed air supplied by a compressor apparatus forming part of the combustion turbine system.

U.S. Patent 8,127,558, which is incorporated by reference to the maximum extent permissible by national law, describes an oxygen-extracting compressor apparatus for extracting between 20-60% by weight of oxygen from the air flowing through the oxygen-extracting compressor apparatus.

As stated in U.S. Patent 8,127,558, it is known that up to about 19% of airflow passing through a compressor apparatus of the gas turbine engine may be extracted. A piping system is provided for extracting the compressed air from the compressor apparatus. The air may be extracted for any of several reasons, such as to remove a portion of the compressed air during start-up to avoid compressor apparatus surge; provide cooling air for hotter sections of the gas turbine engine during normal operation; provide oxidizing air for an air-blown gasifier in an air-blown Integrated Gasification Combined Cycle (IGCC) plant; provide compressed air to a cryogenic air separation plant to produce oxygen for an oxygen-blown gasifier in an oxygen-blown IGCC plant.

In the embodiment shown by way of example in FIG. 4, the system 1000 further includes either an air separation unit (ASU) or a membrane 800 to provide further enriched pressurized air or oxygen to the bubbling chamber 900. In other words, the oxygen-extracting compressor apparatus 100 enriches or purifies the oxygen content of the air to a first level (while pressurizing the air). The ASU or membrane 800 further enriches or purifies the oxygen content to a second level higher than the first level so that the gas supplied to the bubbling chamber 900 is either highly enriched air (high oxygen content) or substantially pure oxygen. Thus, the system of FIG. 4 provides two oxygen-enrichment stages, the first stage provided by the oxygen-extracting compressor apparatus and the second stage provided by the membrane or ASU. The oxygen-extracting compressor apparatus 100 in FIG. 4 may be an ion transport membrane system. The ion transport membrane system may be made of a ceramic membrane that is permeable to only oxygen. In one embodiment, the ion transport membrane is heated as the membrane only becomes permeable to oxygen at a high temperature, e.g. above 500-700°C (973 K). The ceramic membrane may be perovskite, fluorite or mixed. Specifically, a composite membrane as disclosed in U.S. Patent 5,240,480 (which is hereby incorporated by reference to the maximum extent permissible by national law) may be used. This composite membrane operates at temperatures above 500°C (773 K). Some of the heat for heating the membrane may be taken from the waste heat from the compressor. Heat energy may also be drawn from the hot combustion gases or bubbling chamber to heat the membrane. One or more heat exchangers may be provided to extract heat from hot combustion gases, bubbling chamber or the compressor to transfer heat to the membrane.

The system 1000 of FIG. 4 may also include a heat recovery steam generator (HRSG) 500 connected downstream to the gas turbine 400, a steam turbine 600 connected downstream of the HRSG 500. A sulphuric acid plant may also be downstream of the HRSG 500. As such, the system 1000 may be a gas turbine topping device for use in the manufacturing of sulphuric acid. This system may also be an energy recovery system or power generation system that is independent or unrelated to any sulphuric acid manufacturing plant.

FIG. 5 depicts another system 1000 in accordance with another embodiment of the present invention. The system 1000 depicted in FIG. 5 represents an improvement over the prior art in that the ejector can be eliminated because not all of the sulphur vapor is oxidized in the combustor, resulting in substantially reduced gas temperature exiting from the combustor. The cooling provided by the ejector is thus no longer required. As shown in FIG. 5, the system 1000 includes a bubbling chamber 900 connected directly to the multi-stage combustor 300 which is, in turn, connected directly to the gas turbine 400. The multi-stage combustor 300 emits hot combustion gases that comprise sulphur dioxide, uncombusted sulphur vapor and nitrogen gas. In other words, the combustor 300 may only partially combust the volume of sulphur vapor that enters the combustor with the result that a volume of uncombusted sulphur vapor is emitted from the combustor along with the sulphur dioxide and nitrogen gas. The mixture of sulphur dioxide, uncombusted sulphur vapor and nitrogen gas drives a gas turbine 400 and an optionally also a heat recovery steam generator (HRSG) 500 downstream of the gas turbine 400. The system 1000 may optionally include a steam turbine 600 downstream of the HRSG 500 which may produce additional power. The steam turbine 600 may also be driven by steam produced by a superheater as shown by way of example in FIG. 5. In this illustrated embodiment, the superheater is fed by a furnace, boiler, and converter which may be disposed as shown in FIG. 5. The superheater may also be connected to an economizer and absorber as shown in this figure. The economizer may receive boiler feed water (BFW) as shown.

In the embodiment of the system shown by way of example in FIG. 5, molten sulphur is fed to the bubbling chamber 900 (sulphur bubbler). Dry air is introduced to the bubbling chamber 900 under pressure in this embodiment (for example 10 barg, i.e. 10 bar over atmospheric pressure). The oxygen oxidizes only a small portion of the available sulphur, but creates enough energy to vaporize the required quantity of sulphur. In this embodiment, approximately 3 - 4% is oxidized. In this embodiment, the bubbling chamber 900 operates between 550-650°C, preferably at about 600°C.

The sulphur vapor, S0 ₂ and N ₂ flow directly to the combustor 300 through line/duct 5. In one embodiment, the combustor 300 is operated at less than 1300°C, e.g. about 1260°C. In another embodiment, the combustor may be operated at 1200- 1300°C. Dry air is introduced under pressure resulting in the oxidization of an additional 18 - 20% of the sulphur vapor. In the embodiment illustrated in FIG. 5, the hot combustion gases emitted by the multi-stage combustor 300 include a mixture of S ₂ (sulphur vapor), S0 ₂ , and N _2.

As illustrated in FIG. 5, the hot combustion gases that contain S ₂ sulphur vapor, S0 ₂ , N ₂ flow into the gas turbine 400 (expander) to generate electric power and to drive the compressor 100. The exhaust gas is at approximately 900-950° C. The gas is then cooled in a Heat Recovery Steam Generator (HRSG) 500 to approximately 480° C. The HRSG is connected to a duct that is downstream of the gas turbine 400.

Subsequently, the gas containing sulphur vapor, S0 ₂ , N ₂ flows via line/duct 9 to a sulphur furnace where sulphur vapour is introduced to the furnace as a fuel. The existing air flow from the main air blower supports combustion air for the sulphur vapor and provides the required oxygen needed in the converter. The furnace may be co- located with the turbine at the same plant, facility or installation or it may be located at a remote location.

The system of FIG. 5 may be used for power generation or as a topping device in a sulphuric acid plant.

FIG. 6 depicts another system 1000 in accordance with another embodiment of the present invention. The system 1000 represents an improvement over the prior art disclosed in US 2010/0242478. The system 1000 includes a multiple-stage combustion system (multi-stage combustor) 300 that eliminates the need for the ejector as a mixing and cooling device. The system includes an optional membrane 800 for enriching pressurized air or an air separation unit (ASU), also denoted by 800, for providing pressurized oxygen supplied to the bubbling chamber 90 via line/duct 11 and/or to the combustor 300 via line/duct 12. Pressurized air is supplied from the compressor 10 to the bubbling chamber. The sulphur vapor and sulphur dioxide is supplied from the bubbling chamber 90 directly to the multi-stage combustor 300 via line/duct 91. The multi-stage combustor 300 produces hot sulphur dioxide gas that drives the gas turbine 40 to which the multi-stage combustor 300 is directly connected. The gas turbine 40 is connected to the HRSG 50 which is connected to the steam turbine 55 as shown in FIG. 6.

Additionally, as shown in this figure, COS may be generated in a COS generator 70. COS may be generated not only by CO ₂ reaction with H ₂ S but also by reaction with CS ₂ which are fed to the COS generator via line/duct 72. The COS generator 70 produces COS and water which is drawn off from the COS generator via outlet duct 73. A SO ₂ catalytic reduction reactor 100, which is connected to the COS generator 70, receives the COS directly from the COS generator 70. A condenser 60 as shown in FIG. 6 receives the carbon dioxide and sulphur vapor (which are the reduction products) directly from the SO ₂ catalytic reduction reactor 100 to produce Ss, part of which is fed back (recycled) to the bubbling chamber 90 via line/duct 66. The carbon dioxide from the condenser 60 is fed back to the COS generator 70 via line/duct 64. The system depicted by way of example in FIG. 6 may be used for power generation or as a topping device in a sulphuric acid plant.

The use of a multi-stage combustor in these illustrated embodiments obviates the need for an ejector or other ejector-like fluid-mixing, fluid-cooling or pressure- exchanging device. The sulphur combustion and energy recovery system depicted in the illustrated embodiments thus operates without an ejector since the hot combustion gases exiting from the combustor and entering the turbine are at a temperature lower than the metallurgical limit of the blades of the turbine. In the illustrated embodiments, the multi-stage combustor reduces the temperature of the hot combustion gases by axially combusting the sulphur vapor in sequential stages. In the illustrated embodiments, the multi-stage combustor may be connected directly and without any intervening or intermediary device to the upstream bubbling chamber and to the downstream turbine.

The embodiments of the present invention are intended to be exemplary only. Modifications, variations and refinements to these embodiments may be made without departing from the inventive concept(s) disclosed herein.