RU2780167C2 - Gas recycling method including oxidation process with dissipated heat generation, and corresponding device - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: group of inventions relates to a gas recycling method including an oxidation process with dissipated heat generation, and to a corresponding device. The gas recycling method includes an oxidation process with dissipated heat generation, in which the first gas mixture containing an oxidized component is provided. The first gas mixture and oxygen are introduced into an oxidizing plant. Moreover, at least part of the oxidized component in the first gas mixture is oxidized in the oxidizing plant. The first gas mixture and/or the second gas mixture used to provide the first gas mixture, and/or the third gas mixture obtained from at least part of the first gas mixture, using the oxidizing plant, is recycled in one or more gas recycling plants operating using the first amount of steam, characterized by the first operation mode and the second operation mode. The second operation mode is a start mode, and the first operation mode is a normal operation mode implemented in a time period after the second operation mode. The oxidation process with dissipated heat generation is involved in the operation and provides dissipated heat in amount equal to the first amount of dissipated heat in the first operation mode, and it is not involved in the operation or is involved in the operation and provides dissipated heat in amount equal to the second amount of dissipated heat, which is less than the first amount of dissipated heat, in the second operation mode. In the first operation mode, oxygen introduced into the oxidizing plant is at least partially provided by an air separation unit in the form of oxygen contained in an air separation product. The air separation product is pure oxygen or a mixture of components, enriched with oxygen compared to atmospheric air. In the first operation mode, the air separation unit produces the first amount of the air separation product, and, in the second operation mode, the air separation unit produces the second amount of the air separation product, which is less than the first amount of the air separation product, or does not produce the air separation product at all. The air separation unit contains a compressor operating using the second amount of steam expandable in a steam turbine mechanically connected to the compressor. In the first operation mode, the first amount of steam is provided by the first steam generator operating using at least part of dissipated heat, and, in the first operation mode, the second amount of steam is provided by the second steam generator made with the possibility of operation independently of dissipated heat, and, in the second operation mode, at least part of the first amount of steam provided by the first steam generator in the first operation mode, is instead provided by the second steam generator. A corresponding device for implementation of the method is also described.

EFFECT: group of inventions provides for the improvement of a gas recycling method, in particular, in order to reduce capital and operating costs.

7 cl, 3 dwg

Description

The present invention relates to a process for gas processing, including an oxidation process with generation of waste heat, and to a corresponding device in accordance with the preamble of the independent claims.

Prior Art

Methods and apparatus for processing acid gas mixtures based on the Claus process are known from the prior art. See, for example, the reference to the Natural Gas article in Ullmann's Encyclopaedia of Industrial Chemistry, Internet publication July 15, 2006, DOI: 10.1002/14356007.a17_073.pub2, especially chapter 2.4 Removal of Carbon Dioxide and Sulfur Components.

US 4,684,514 A describes a process for recovering sulfur from a gas stream containing hydrogen sulfide, in which water is removed simultaneously with the condensation of sulfur and which can be carried out at high pressure.

US 2013/0071308 A1 relates to a method and plant for the recovery of sulfur from acid gas containing hydrogen sulfide and carbon dioxide, including the oxidation of acid gas, and part of the hydrogen sulfide is oxidized to sulfur dioxide and water, the reaction of the resulting sulfur dioxide with residual hydrogen sulfide to form elemental sulfur and removal of elemental sulfur. The carbon dioxide and/or carbon dioxide resulting from the acid gas oxidation is compressed and at least a portion of the carbon dioxide is injected into the oil well.

US 5,635,541 discloses that natural gas can be partially oxidized to produce synthesis gas containing carbon monoxide and hydrogen, whereby the synthesis gas is catalytically reacted to produce higher molecular weight hydrocarbon products, where excess steam is generated during the conversion, and the oxygen used for the partial oxidation of natural gas is obtained in the process of air separation.

Initially, only hydrogen sulfide or an appropriate mixture of acid gases and oxygen was mixed in the Claus process and the mixture was passed through a preheated catalyst bed. It was later modified by incorporating flame oxidation upstream of the catalyst bed in the so-called Claus furnace. Most of the Sulfur Recovery Units (SPUs) currently in use operate on the basis of a suitably modified process. Thus, if the text below refers to a "Claus process" or a corresponding apparatus for brevity, it is the flame oxidation-modified Claus process described above.

So-called oxygen enrichment is a well-known economical and reliable way to debottleneck existing Claus sulfur plants with minimal capital investment. However, oxygen enrichment, as detailed below, is not limited to retrofitting existing Claus sulfur plants, but can be usefully applied to the design of new plants. In the following, the term "oxygen enrichment" will refer to any process in which, in a Claus sulfur recovery plant or a related process, at least a portion of the air supplied to the Claus furnace is replaced with oxygen or a gas mixture that is enriched compared to ambient air. oxygen or, more generally, has a higher oxygen content than ambient air.

Oxygen or oxygen-enriched gas mixtures for Claus sulfur recovery units can generally be provided by cryogenic air separation processes and associated air separation units (ASUs), as is known in the art, see for example Haering, H.-W ., "Industrial Gases Processing", Wiley-VCH, 2008, especially chapter 2.2.5 "Cryogenic Rectification". Cryogenic air separation plants usually comprise a so-called warm section capable of compressing, pre-cooling, drying and pre-cleaning the feed air, and a so-called cold section capable of heat exchange and rectification.

While the present invention is described below with emphasis on cryogenic air separation, it can also be successfully used in combination with non-cryogenic air separation methods and plants, such as those based on pressure swing adsorption (PSA), especially with desorption pressure levels. below atmospheric pressure (vacuum APD, VAPD). This applies if such methods or installations use rotary equipment driven or capable of being driven by steam, in particular a steam turbine.

The present invention is also not limited to the Claus process, but can equally be used in other gas processing processes, including an oxidation process with waste heat generation, provided that oxygen, such as pure oxygen or oxygen contained in an oxygen-enriched mixture of components, at least temporarily, an air separation plant of the specified type is provided, in particular when, during the start-up of such a process, less or no heat is generated.

The purpose of the present invention is to provide improved methods of this type, in particular for the purpose of reducing capital and operating costs.

Description of the invention

In light of the foregoing, the present invention provides a gas processing method comprising an oxidation process with waste heat generation, and a corresponding apparatus comprising the features described in the independent claims, respectively. Preferred embodiments are the subject of the dependent claims and the description below.

Before specifically considering the features and advantages of the present invention, some of the terms used in this document will be defined and briefly explained. In addition, a further explanation of the operation of the Claus desulphurization unit will be given. Although the present invention and its technical background are described below with reference to the Claus process, the present invention can be equally applied to other gas processing processes, including an oxidation process with waste heat generation.

As used herein, a mixture of components, such as a gas mixture, may be rich or lean in one or more components, where the term "rich" may mean more than 75%, 80%, 85%, 90%, 95%, 99% , 99.5 or 99.9%, and the term "poor" is the content of less than 25%, 20%, 15%, 10%, 5%, 1%, 0.5% or 0.1% in molar, mass or volume measurement. In the acid gas processing industry, an acid gas mixture with more than 80% hydrogen sulfide is commonly referred to as "rich" and an acid gas mixture with less hydrogen sulfide is generally referred to as "lean". As used herein, a mixture may also be enriched or lean in relation to one or more components, especially when compared to another mixture, while "enriched" may mean a content of at least 1.5 times, 2 times, 3 times, 5 times, 10 times or 100 times the content in another mixture, and "depleted" - no more than 0.75 times, 0.5 times, 0.25 times, 0.1 times or 0.01 times less content in another mixture.

As used herein, the term "acid gas mixture" refers to a gas mixture containing hydrogen sulfide and carbon dioxide in a total amount of at least 50%, 75%, 80%, or 90% by volume. Other components may also be present in the acid gas mixture, in particular water, hydrocarbons, benzene, toluene and xylenes (BTX), carbon monoxide, hydrogen, ammonia and mercaptans.

The terms "pressure level" and "temperature level" are used herein to express that exact pressures cannot be used to practice the invention and its preferred embodiments, but pressure ranges can be used. The different levels of pressure and temperature may be in different ranges, or in overlapping ranges with each other. They also cover expected and unexpected, especially unintentional changes in pressure or temperature, such as unavoidable pressure or temperature losses. Pressure levels expressed in bar are absolute pressures.

Compressors for use in air separation plants, whether of cryogenic or non-cryogenic type, can be made in the form of turbomachines or positive displacement hydraulic machines, which differ in their performance. With turbomachines, the amount of compressed gas decreases with increasing pressure, and in positive displacement hydraulic machines, a nearly constant mass flow can be achieved regardless of the compressor discharge pressure. The most commonly used machines for cryogenic air separation are multi-stage turbochargers. Turbochargers can be of radial or axial type. They differ from each other in the direction in which the compressed gas exits the impeller. A radial turbocharger consists of several stages, which are located on one or more shafts. These shafts are driven through a drive by either an electric motor or a steam turbine. The air compressed in the main air compressor (MAC), such as a turbocharger type, of an air separation unit is usually heated by compression to about 100°C, and therefore, before being cooled by heat exchange with air separation products, it is usually pre-cooled with water.

If the term “master air compressor” is used below, this term is intended to refer to that compressor or compressors of a cryogenic or non-cryogenic air separation plant which compresses all the air to be separated to a certain pressure level. The main air compressor may be followed by a booster air compressor (BAC) or multiple booster compressors driven by turbines. However, the latter type of machine is used only for the air portions pre-compressed by the main air compressor. In this document, the main air compressor and the booster air compressor should be understood as machines that are fully or at least partially driven by external energy, while the term "external energy" refers to energy that is not obtained by expanding the process streams arising in the air separation plant, for example, using turbo-expanders.

In classical cryogenic air separation plants, as shown in FIG. 2.3A at Haering, all the air supplied to the distillation column system is compressed to a pressure equal to or slightly higher than the operating pressure of the high pressure column in the main air compressor, and only a part of the air thus compressed is further compressed to a higher pressure in the so-called booster air compressor . Such classic configurations are often also referred to as "GVK/DVK" configurations. At the same time, in more recent configurations, the so-called "high air pressure" (HPA) configurations, all the supply air is compressed in the main air compressor to a pressure significantly higher than the operating pressure in the high pressure column, i.e. at least 2, 3, 4, 5 or 10 bar and up to 20 bar or more. However, this does not exclude the possibility that parts of the air compressed in this way are further compressed in booster air compressors or other additional machines. High air pressure configurations are known from EP 2 466 236 A1, EP 2 458 311 A1 and US 5,329,776 A.

The source of the acid gas mixture used as feedstock for a Claus sulfur recovery plant is typically an acid gas treatment plant, such as natural gas or gas from a petrochemical or refinery. An acid gas mixture containing various amounts of hydrogen sulfide and carbon dioxide is saturated with water and often also contains small amounts of hydrocarbons and other impurities in addition to the main components. In a typical Claus sulfur plant, the acid gas mixture is supplied at a pressure of approximately 0.5 bar(g) or approximately 0.8 bar(g) and at a temperature of 50°C. In classical Claus sulfur recovery plants, the combustion air is compressed to an equivalent pressure by centrifugal blowers. Both inlet streams then enter the burner, which ignites in the Claus furnace, with additional fuel supplied to the burner.

The gas mixture from the Claus furnace, typically up to 1400°C, is typically cooled during steam production in the waste heat recovery boiler and further cooled during low pressure steam production in a separate heat exchanger. In this case, the hot gases are cooled to a temperature of approximately 160°C, condensing most of the sulfur that has already been formed at this point. The resulting liquid sulfur is removed in the separator section of the condenser and flows by gravity into the sulfur storage tank. Here it is kept in a molten state by means of steam coils at a temperature of approximately 140°C. The sulfur accumulated in this tank is pumped to trucks or rail cars for transportation.

Any further conversion of the sulphurous gases still contained in the Claus furnace gas mixture must be carried out by a catalytic reaction, so the gas mixture is reheated by one of several means and then fed into the catalyst bed. The catalytic Claus reaction releases additional energy and converts more than half of the remaining sulfurous gases into sulfur vapours. These vapors condense during the production of low pressure steam and are removed from the gas mixture. The remaining gas mixture is reheated and fed into the next catalyst bed. This cycle of reheating, catalytic conversion and sulfur condensation is repeated in two to four catalytic stages. A typical Claus sulfur plant contains a single open flame reaction stage, i.e. one furnace, and three stages of catalytic reaction. At each stage of the reaction, an ever smaller proportion of the remaining sulfur gases is converted into sulfur vapor.

If a three-stage or four-stage sulfur recovery unit cannot provide the required emission levels in the gas mixture obtained after the last stage of the catalytic reaction, i.e. in the so-called tail gas, additional processing is necessary. It includes a so-called tail gas cleaning plant (TAG), which can usually be configured to carry out dry bed and wet gas cleaning processes. Wet scrubbing processes, such as the BSR (Bevon Sulfur Removal)/amine process from WorleyParsons, include a pre-treatment section to convert back to hydrogen sulfide any sulfur compounds still present in the tail gas. After cooling, the hydrogen sulfide-containing tail gas is contacted with a solvent to remove the hydrogen sulfide, which is very similar to a conventional gas scrubber. The solvent is then regenerated to remove hydrogen sulfide, which is then recycled to an upstream Claus sulfur removal unit for subsequent conversion and recovery.

The so-called oxygen enrichment, as mentioned, is a well-known economical and reliable way to eliminate the bottlenecks of existing Claus sulfur plants, requiring minimal capital investment. It can also eliminate the need for co-firing a fuel gas in a reaction furnace, which is required to maintain the correct temperature for the destruction of contaminants, such as the destruction of benzene, toluene and xylenes in an acid gas mixture. Generally, higher temperatures (above about 1000° C.) are needed to maintain a stable flame, even higher temperatures are needed to break down the BTX and/or ammonia (present in refinery sour water stripper gas). Whether appropriate co-firing is required depends primarily on the hydrogen sulfide content of the treated acid gas mixture and whether sufficient temperature and stable flame can be obtained by burning the acid gas mixture alone.

The oxygen enrichment concept involves replacing part or all of the air supplied to the Claus furnace with enriched air or pure oxygen. Accordingly, the volume flow through the Claus sulfur recovery unit is reduced, allowing more of the acid gas mixture to be fed into the system. This results in an increase in sulfur recovery capacity without the need for significant modification of existing equipment or a significant change in the pressure dynamics of the process unit.

The use of oxygen enrichment is not limited to retrofitting existing Claus sulfur plants or debottlenecking them, but can also provide benefits in the design of new plants where the resulting acid gas mixtures are lean and contain benzene, toluene and xylenes. Such plants have traditionally required preheating of the feed gas and/or combustion air, as well as co-firing of the fuel gas, and have traditionally not been considered for enriched oxygen operations. However, even for such installations, the use of oxygen enrichment technology results in a reduction in the physical size of all major pieces of equipment and a significant reduction in capital costs associated with this. In particular, significant reductions in fuel requirements can be achieved when co-firing in the Claus furnace and other plants, so that more fuel, such as natural gas, can be used for other purposes or supplied as a product of the entire plant.

In addition, a particular benefit of oxygen enrichment is that the tail gas downstream of the tail gas scrubber is less "diluted" with nitrogen from the combustion air used in the conventional scheme. If little or no additional nitrogen enters the process, then the main component of the acid gas mixture after desulfurization, i.e. carbon dioxide, and other components such as hydrogen, can be obtained in a simpler and more economical way, for example using only cryogenic technology and without energy-intensive wet technology.

Whether air separation plants are based on cryogenic processes or adsorption processes, they require compressors to treat the air used as feedstock. Claus desulphurization plants have traditionally operated by introducing ambient air into the Claus furnace via blowers to introduce oxygen contained in the ambient air as a reaction component. An improved method, as mentioned, is the use of oxygen enrichment, where at least part of the ambient air is replaced with pure oxygen or a gas mixture with a higher oxygen content than the ambient air. For example, pure oxygen or an oxygen-enriched gas mixture can be mixed with the air flow supplied to the Claus furnace by a blower, the amount of air being reduced accordingly to maintain a set mass flow rate. Alternatively, the blower is no longer used to supply air to the Claus furnace, but only oxygen or an oxygen-enriched gas mixture can be used to provide oxygen for combustion. In this case, there is no need for a blower to supply the main air to the Claus oven. The significantly smaller blowers for the reducing gas generator and tail gas afterburner (if present, respectively) can be further reduced.

In particular, in the latter case, no blower is required at all during normal operation of the Claus furnace. However, even in the first case, during normal operation, less air must be supplied to the Claus furnace, which reduces the required blower power. However, the blower requirement may still be present during the start-up phase of the process as the process is started with ambient air and then gradually ramped up by oxygen enrichment to the desired level, such as 100% or at least 100% oxygen. In particular, the respective installation must be preheated before ignition of the main burner in order to avoid thermal shock, etc. To do this, at start-up, the Claus furnace will burn fuel gas with air (supplied by a blower). Feed air, fuel gas and/or acid gas can be further preheated using heat exchangers using steam.

In other words, during the Claus desulphurization process with oxygen enrichment (“oxygen enrichment”, as mentioned, also applies to operation using pure oxygen), the blower power could be significantly reduced or the blower could be dispensed with altogether. However, the Claus desulphurization unit still requires ambient air to run, so a blower can be installed.

The air separation plant used in the present invention is designed to supply oxygen to the Claus desulphurization plant in order to operate the Claus desulfurization plant with oxygen enriched air or 100% oxygen. However, no oxygen is required during the start-up of the Claus desulphurization plant because, as mentioned, the oxygen content of the feedstock fed to the Claus desulfurization plant will gradually increase. In accordance with the present invention, the main air compressor required for the air separation unit can be used during this period to supply the air flow to the Claus unit. The required air pressure level to supply the Claus desulphurization plant, referred to here as the supply pressure level, is 0.5 to 3.5 barg (barg).

At this point in the start-up of the Claus desulphurization plant, air separation can be disabled or can be run at the minimum allowable rate. As the level of oxygen enrichment in the Claus desulfurization plant gradually increases, the volume of air required for the Claus desulphurization plant can gradually decrease accordingly. Thus, the main air compressor can provide an incremental amount of air for the air separation process, which in turn can provide incremental amounts of air separation products. As a rule, "air separation product" refers to any fluid that can be obtained by cryogenic or non-cryogenic air separation and which contains one or more components of ambient air with a higher or lower content than ambient air, i.e. . being enriched or depleted in the above sense. In particular, the air separation product in the context of the present invention is an oxygen-rich or enriched air separation product or (essentially) pure oxygen.

Benefits of the Invention

As stated above, the present invention is of particular advantage in connection with acid gas processing including the Claus process, but is equally applicable to other processes of the type mentioned.

Gas processing plants and processing methods, in particular for the processing of sour natural gas, are quite complex and usually include various process units, such as, for example, acid gas removal plants (for example, the so-called amine treatment plants, in which amine treatment, as described below), natural gas processing plants (for example, for so-called dew point control or dehydration), sulfur removal plants, and tail gas removal plants, as described above. In such plants and methods, air separation units can be used to provide both oxygen (eg, for Claus processes with oxygen enrichment, as also described above) and nitrogen for purge and blanket gas. A more detailed description can be found in the professional literature links at the beginning.

The processes used in such integrated processing plants and methods include successive starts of various process units. In particular, if waste heat is generated in one or more of these plants, such as the heat contained in the gas mixture processed in the Claus furnace in the Claus process, then steam can be generated as a by-product and this steam can be used in other integrated plants. , i.e. in steam consumers. In this context, problems arise when waste heat generating plants are or can only be started after the steam consumers have already been started and they already need steam to operate. In related integrated processes, a sulfur removal plant operating on the basis of the Claus process can be considered as a steam exporter (eg in a refinery or gas processing plant) that provides other process units with steam during normal operation. However, during the launch, such steam is not yet available.

The steam generated using the waste heat from the Claus process can, for example, be sent to an amine scrubber to regenerate the amine solvent. A typical amine gas treatment process includes an absorption and recovery plant, as well as ancillary equipment. In an absorption plant, a top-down amine solution absorbs hydrogen sulfide and carbon dioxide from an upstream gas mixture, such as sour natural gas, to produce a "sweet" gas stream (i.e., a gas stream free of hydrogen sulfide and carbon dioxide) as a product and an amine solution rich in absorbed acid gases. The resulting "rich" amine is then sent to a recovery unit, which is a stripper with a reboiler, to obtain a reduced, or "poor" amine, which is sent back to the absorption plant for reuse. The distilled gas mixture from the reduction unit is enriched or rich in hydrogen sulfide and carbon dioxide. It is a mixture of acid gases that can be processed in the Claus process. In particular, the reboiler of the recovery plant in the amine treatment plant can be operated with steam produced using waste heat from the Claus process.

However, it should be understood that the amine treatment plant producing acid gas for the Claus process and thereby supplying gas for the Claus process must be started prior to the Claus process. However, at the time of the start-up of the amine treatment plant, no heat removed from it has yet been received. The same problem also arises if other plants in the respective integrated plant or process require steam, for example for heating purposes, which is not yet available at the time of start-up.

The tail gas cleaning plant can generally be a steam consumer that needs steam, especially during preheating and during start-up. Typically, using the waste heat of the Claus process produces high and low pressure steam. The tail gas cleaning plant usually consumes low pressure steam. Thus, additional steam can be generated and used for other purposes. In the above BSR/amine tail gas scrubbing process, the primary use of steam is to reboil the amine solvent in the solvent regenerator as mentioned. In addition, steam can be used to heat the tail gases to reaction temperature before they are fed into the hydrogenation reactor. (The latter can also be achieved by burning the fuel gas in a "reducing gas generator" (RGG)).

Therefore, in integrated plants and methods of the type described, a separate steam plant is routinely used, including a steam boiler, which is usually heated by gas or oil and temporarily generates steam to serve the steam consumers at the start-up stage of the plant, when there is no waste heat yet. After the complete start-up of the complex, including the sulfur recovery unit, the steam balance is established, so the steam boiler can be turned off when it becomes possible to generate enough steam using the waste heat from the sulfur recovery unit. Therefore, a separate steam plant or boiler is used only temporarily, and therefore with a very low utilization rate.

In the present invention, at the start-up stage, instead of steam from a separate steam plant or boiler, it is proposed to use steam that generates an additional steam plant or boiler used to drive one or more compressors, in particular the main air compressor, in an air separation unit, which is also included as part of an integrated plant or method. An air separation plant, as noted at the outset, may be a cryogenic or non-cryogenic air separation plant containing an appropriate compressor. According to the invention, the steam plant or boiler associated with the air separation plant is started up first to temporarily supply steam to other gas treatment plants, such as an amine treatment plant, during their start-up, while there is still no waste heat, for example, from the Claus process. After starting the latter and with the start of steam production, the steam boiler switches to steam supply to start and then continuously operate the air separation unit instead. These inventive concepts can obviously also be transferred to other oxidation processes.

The present invention is of particular advantage in connection with oxygen-enriched Claus processes, since such processes, as mentioned, are typically started with ambient air, and then oxygen enrichment is gradually brought to the desired level, for example up to 250%, by oxygen enrichment up to 100 - percent oxygen. Such a gradual start-up can be performed, for example, to warm up the process equipment and to avoid thermal shock, therefore, when starting the Claus process, oxygen or oxygen-enriched air from the air separation unit in the Claus process is not yet required, and the compressor (s) of the air separation unit is not yet involved(s). As mentioned, the steam plant or boiler for supplying steam to the compressor(s) of the air separation plant can instead be used to supply steam to additional gas processing units. However, immediately after starting the Claus process, and also in the case of continued supply of ambient air into it, heat is removed. As mentioned, in order to avoid thermal shock, the fuel gas in the Claus furnace will be combusted with air at start-up.

In other words, in accordance with the present invention, the waste heat generating oxidation process is integrated with a steam-driven air separation unit and a steam generator, with the steam generator temporarily generating steam for other units when the sulfur removal unit is not operating or is not yet running (and therefore does not generate steam). When the sulfur removal unit and associated steam generator are then started and delivering steam, the separate steam generator is switched to start and operate the air separation unit, the air separation unit generating oxygen which is used in the sulfur removal unit to produce an oxygen-enriched or oxygen-fueled Claus process.

In light of the above aspects, the present invention provides a process for processing a gas comprising an oxidation process with generation of waste heat, wherein a first gas mixture containing an oxidizable component is provided, wherein the first gas mixture and oxygen are introduced into the oxidizer, wherein at least a portion of the oxidizable component in the first gas mixture is oxidized in the oxidizer, wherein the first gas mixture and/or the second gas mixture used to obtain the first gas mixture and/or the third gas mixture obtained from at least part of the first gas mixture using the oxidizer is processed in one or more gas processing units operating using the first amount of steam. According to the invention, a first mode of operation and a second mode of operation are provided, wherein the second mode of operation is a startup mode, and the first mode of operation is a normal mode of operation implemented in a period of time after the second mode of operation. The waste heat generating oxidation process is in operation and provides heat removal in an amount equal to the first heat removal amount in the first mode of operation, and is not in operation or is in operation and provides heat removal in an amount equal to the second heat removal amount, which less than the first amount of heat removed, in the second mode of operation. In the first mode of operation, the oxygen introduced into the oxidizer is at least partly provided by the air separation plant in the form of oxygen contained in the air separation product. The air separation product is pure oxygen or a mixture of components enriched in oxygen compared to atmospheric air. In the first mode of operation, the air separation unit produces the first amount of air separation product and in the second operation mode, the air separation unit produces a second amount of air separation product, which is less than the first amount of air separation product, or does not produce any air separation product. The air separation unit is characterized in that it contains a compressor operating with a second amount of steam. In the first mode of operation, the first amount of steam is provided by the first steam generator operating using at least a portion of the rejected heat, and while in the first mode of operation, the second amount of steam is provided by the second steam generator configured to operate independently of the rejected heat.

The second gas mixture may in particular be a lean mixture of acid gases, i. e. an acid gas mixture containing less than 80%, less than 60% or less than 50% and more than 10%, more than 20%, more than 30% or more than 40% hydrogen sulfide. The present invention is of particular advantage in this context because lean acid gas mixtures contain fewer oxidizable components and therefore less heat is generated than in the case of rich acid gas mixtures. Therefore, it is important to carefully manage the heat dissipation.

In accordance with the present invention, said operation of the compressor using the second amount of steam comprises expanding the second amount of steam in a steam turbine that is mechanically connected to the compressor. This means that in accordance with the present invention there is a direct transfer of rotational energy from the steam turbine to the compressor. In accordance with the present invention, the mechanical connection used may include a connection using equal speeds of the drive shaft of the steam turbine and the driven shaft of the compressor, or a connection through a transmission or gearbox, providing a fixed or variable speed difference. The mechanical connection according to the present invention does not include an indirect connection, in which, for example, the rotational energy of a steam turbine is converted into another form of energy, such as electrical energy, and in which said other form of energy is converted into rotational energy to drive a compressor. The mechanical connection provided in accordance with the present invention eliminates the power conversion losses that otherwise exist.

As mentioned, operating the compressor using the second amount of steam involves expanding the second amount of steam in a steam turbine that is mechanically coupled to the compressor. However, this does not rule out the possibility that the operation of the compressor may also use additional energy that is not provided in the form of steam being expanded in the steam turbine.

In accordance with the present invention, in the second mode of operation, at least a portion of the first amount of steam provided by the first steam generator in the first mode of operation is instead provided by the second steam generator, and in particular, the first steam generator provides a total amount of steam that is less than the second amount steam, or it does not provide steam at all. In other words, the second steam generator, which in the first mode of operation is used to drive the compressor of the air separation unit, in the second mode of operation is used to operate said at least one gas processing unit.

Specific advantages and additional features of the method in accordance with the present invention have already been discussed previously. In particular, by integrating an oxidation process, such as the Claus process, capital costs (CAPEX) as well as operating costs (OPEX, especially repair and maintenance costs) for the entire process can be reduced, since an additional (only temporarily used) steam boiler becomes unnecessary. Moreover, the start-up procedure of the corresponding method is simplified, since less equipment allows for a reduced start-up schedule. In addition, in accordance with the present invention, a smaller area for equipment is required. In addition, steam driven air separation units are generally more efficient in terms of total cost of ownership. Thus, the overall economics of the Claus process with oxygen enrichment are improved.

In accordance with the present invention, the first mode of operation is a normal mode of operation implemented in a period of time after the second mode of operation. The second mode of operation is the start mode.

In general, the possibility of generating waste heat also in the second mode of operation is not ruled out, however, as noted, the amount of heat removed in the second mode of operation is at least less.

In other words, the oxidation process to generate waste heat is preferably in operation and provides heat removal in an amount equal to the first amount of heat removal in the first mode of operation, and is preferably not in operation or is in operation and provides heat removal in an amount equal to the second a heat rejection amount that is less than the first heat rejection amount in the second mode of operation.

As also discussed earlier, the present invention has a particular advantage in connection with the Claus process and associated gas processing. Thus, it is advantageous that the first gas mixture is an acid gas mixture, the oxidizable component is hydrogen sulfide, the oxidation process is a Claus process, the oxidizer is a Claus furnace, and part of the hydrogen sulfide in the acid gas mixture is oxidized by flame oxidation in a Claus furnace . A summary of specific advantages, including for this preferred embodiment, can be found in the above explanations.

The air separation unit may, as also mentioned, supply oxygen or oxygen-enriched air to a Claus process, or a Claus furnace, or other oxidation process. Thus, the method according to the present invention assumes, as noted, that the oxygen provided by the air separation plant is the oxygen contained in the air separation product, the air separation product being pure oxygen or a mixture of components enriched in oxygen compared to atmospheric air.

Generally, the air separation product has an oxygen content higher than the ambient air. It may contain at least 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% oxygen by volume. In other words, various levels of oxygen enrichment are possible. It is also possible to use substantially pure oxygen. The air separation plant can also provide partially oxygenated products, depending on the particular needs of the Claus desulphurization plant, and thus the energy consumption of the air separation plant can be optimized accordingly. In particular, a cryogenic air separation plant including a mixing column can be used for this purpose, as for example described in EP 3 179 187 A1 and references therein.

As noted earlier, in the first mode of operation, the air separation unit provides a first amount of air separation product, and in the second mode of operation, the air separation unit provides a second amount of air separation product, which is less than the first amount of air separation product, or does not provide any air separation product. In other words, during the start of the method having the characteristics of the invention, the operation of the air separation unit can be completely or partially suspended.

In accordance with the most preferred embodiment, in the first mode of operation, a third amount of air separation product is introduced into the Claus furnace, which is less than the first amount of air separation product, and in the first mode of operation, the fourth amount of air separation product is stored and introduced at least partially into the Claus furnace in the second mode of operation. In other words, also during the start-up mode, oxygen or oxygen-enriched air can be supplied to the oxidation process from oxygen or oxygen-enriched air provided during normal operation and, for example, stored in a reserve tank. In this case, in particular, liquid oxygen can be used. This has the advantage of being able to carry out at least partial oxygen enrichment already during start-up.

In accordance with the present invention, for example, the temperature in the Claus furnace of a sulfur recovery plant can generally be further increased using additional oxygen, and as a result, more steam can be supplied. In this way, the overall steam balance can be optimized. In the event that this additional steam, generated by the difference between the standard air-based Claus process and the oxygen-enriched process, is not used by other process units, this excess steam can be at least partially used to drive the steam drives of the air separation unit. From a technological perspective, this means that during the start-up phase of the sulfur recovery plant, air separation can initially be operated on less steam (generated from or independent of heat rejection) in partial mode. With increased steam from the sulfur recovery plant (due to oxygen enrichment), the air separation plant can operate at 100%. In this way, the size of the steam boiler can be optimized.

As mentioned, the first amount of steam can be used to operate one or more gas processing units processing a first gas mixture and/or a second gas mixture used to provide the first gas mixture and/or a third gas mixture derived from at least a portion of the first gas mixture using an oxidizing unit. As mentioned, the third gas mixture can be processed in a tail gas scrubber. As discussed in more detail above, a tail gas cleaning plant typically consumes steam, so the tail gas cleaning plant may be operated using some or part of the steam; in particular, the heat from the first amount of steam or part thereof can be used to heat the tail gases to reaction temperature before they are fed to the hydrogenation reactor in the tail gas scrubber, or the loaded amine solution can be recovered using the heat from the first amount of steam or part thereof. More details can be found in the above explanations.

As mentioned, the present invention can also be used with an amine treatment plant, as explained above, to process the second gas mixture used to produce the first gas mixture. As also mentioned, a tail gas scrubber capable of treating a third gas mixture or a portion thereof may comprise an amine scrubber. In other words, the advantage lies in the fact that the second gas mixture used to provide the first gas mixture and/or the third gas mixture obtained from at least part of the first gas mixture is processed in or one of the gas processing units, the second and/or or the third gas mixture is a gas mixture containing hydrogen sulfide and carbon dioxide, wherein the gas processing unit or one of the gas processing units comprises an amine treatment unit (or an amine scrubbing unit), wherein hydrogen sulfide and carbon dioxide are at least partially removed in the amine treatment unit from the second and/or third gas mixture using an amine solution and obtain an amine solution loaded with hydrogen sulfide and carbon dioxide, and at the same time hydrogen sulfide and carbon dioxide are at least partially separated from the loaded amine solution using heat from the first amount of steam or part thereof. In particular, two gas processing units can be provided, each including an amine treatment unit, to treat the second or third gas mixture, respectively.

The present invention also relates to a device for implementing a gas processing method, including an oxidation process with the generation of waste heat, containing means configured to provide a first gas mixture containing an oxidizable component, an oxidizing unit configured to oxidize at least a portion of the oxidizable component in the first gas mixture, means configured to introduce the first gas mixture and oxygen into the oxidizer, one or more gas processing units configured to process using the first amount of steam of the first gas mixture and/or the second gas mixture used to obtain the first gas mixture , and/or a third gas mixture obtained from at least a portion of the first gas mixture using an oxidizer.

The device is configured to perform the first mode of operation and the second mode of operation, while the second mode of operation is the start mode, and the first mode of operation is the normal mode of operation, implemented in the period of time after the second mode of operation, the oxidation process with the generation of waste heat is involved in operation and provides heat rejection in an amount equal to the first heat rejection amount, in the first mode of operation, and is not involved in operation or is engaged in operation and provides heat rejection in an amount equal to the second heat rejection amount, which is less than the first heat rejection amount, in the second mode of operation. In addition, according to the present invention, an air separation plant is provided which is configured to provide, in a first mode of operation, at least a portion of the oxygen introduced into the oxidizer plant in the form of oxygen contained in the air separation product, the air separation product being pure oxygen. or a mixture of components enriched in oxygen compared to atmospheric air. The air separation unit is configured to produce in the first operation mode the first amount of the air separation product and in the second operation mode the second amount of the air separation product, which is less than the first amount of the air separation product, or not to produce the air separation product at all. In addition, the air separation unit contains a compressor configured to operate using a second amount of steam expanded in a steam turbine mechanically connected to the compressor, a first steam generator is provided, which is configured to operate using at least a portion of the heat removed and generate the first amount of steam in the second mode of operation, and a second steam generator that is configured to operate independently of the heat removed and provide the second amount of steam in the first mode of operation. In accordance with the present invention, in the second mode of operation, at least a portion of the first amount of steam provided by the first steam generator in the first mode of operation is instead provided by the second steam generator, and in particular, the first steam generator provides a total amount of steam that is less than the second amount of steam, or it does not provide steam at all.

Specifically, the first gas mixture is an acid gas mixture, the oxidizable component is hydrogen sulfide, the oxidation process is a Claus process, the oxidizer is a Claus furnace, and part of the hydrogen sulfide in the acid gas mixture is oxidized by flame oxidation in a Claus furnace.

With regard to specific additional features and embodiments of such a device, reference is made to the above explanations relating to the method in accordance with the invention and its preferred embodiments. This applies equally to the respective device capable of implementing the respective method, or one of its embodiments.

The present invention will be further described with reference to the accompanying drawings, which relate to a preferred embodiment of the present invention.

Brief description of the drawings

In FIG. 1 is a generally schematic representation of a gas processing process including an oxidation process with waste heat generation.

In FIG. 2A is a schematic diagram showing a gas processing method including a waste heat generation oxidation process according to an embodiment of the present invention in a first mode of operation.

In FIG. 2B schematically shows the gas treatment process according to FIG. 2A in the first mode of operation.

Detailed description of the drawings

In the drawings, functionally or technically identical or equivalent components are identified by the same reference numerals and are not re-explained for the sake of brevity. If explanations are given regarding the methods, they apply equally to the corresponding device.

In FIG. 1 generally schematically shows a gas processing process including an oxidation process 4 with waste heat generation. The process is shown as including the Claus process as oxidation process 4. However, as has been repeatedly mentioned, other oxidation processes 4 can also be used in the context of the present invention.

The sour natural gas stream from gas field 1 is introduced into an acid gas removal unit 2, in this particular case including an amine treatment unit 21 as mentioned above. The amine treatment unit 21 operates as is widely known to those skilled in the art; in the present example, it is operated using steam stream b, which is used to heat the reboiler in the amine treatment unit 21 (not shown). In this case, a lower temperature steam stream c or a condensate stream c can be formed.

The sweet gas stream is withdrawn from the acid gas removal unit 2 and optionally subjected to further treatment 3, which results in an additional processed gas stream e, which, for example, can be fed into the gas pipeline. The acid gas stream f is also withdrawn from the acid gas removal unit 2 and introduced into the oxidation process 4, which is carried out as a Claus process 4, or, more specifically, into the Claus furnace 41 in a Claus process 4. A portion of the acid gas stream f can also be re-injected into the gas field 1 as shown by the dotted arrow in FIG. 1. Sulfur stream g is withdrawn from the Claus process 4 and treated 5 with a sulfur product. From here, the sulfur product stream h is withdrawn or otherwise obtained.

In the tail gas cleaning unit 6, the tail gas stream i, also removed from the Claus process 4, is treated in a known manner. The tail gas cleaning plant 6 makes it possible to obtain a purified exhaust gas stream k, which contains small amounts of sulfur compounds or does not contain them at all. Components from the tail gas scrubber 6 may also be recycled to the Claus process 4 or the Claus furnace 41 as indicated by the dotted arrow. The tail gas scrubbing plant 6 may also comprise a heat-operated plant, such as an amine scrubber 61, where the heat is supplied in the form of steam. However, it is also possible to use units other than the amine treatment unit, such as preheating units that heat the tail gas stream i to the reaction temperature, etc. Steam stream b' is supplied to this plant and a lower temperature steam stream c' or a condensate stream c can be formed. One or both of the amine treatment unit 21 in the acid gas removal unit 2 and the unit 61 in the tail gas treatment unit 6 may be provided and/or one or both of these may be steam powered.

Process 4 Claus is carried out with oxygen enrichment. Thus, using the air separation unit 7, an oxygen stream or an oxygen-enriched stream l is generated, which is also introduced into the Claus process 4 or the Claus furnace 41. The air separation plant 7, which can also generate a nitrogen stream or a nitrogen-enriched stream and other products, and which is supplied with air (not shown), includes a compressor 71 operating on a steam-driven turbine 72, which receives a steam stream m. The turbine 72 is mechanically connected to the compressor 71. This may result in a lower temperature steam stream n or a condensate stream n. The steam or condensate streams c, n can be reused to generate steam.

In FIG. 2A schematically shows a gas processing method 100 including an oxidation process 4 with waste heat generation according to an embodiment of the present invention in a first mode of operation.

In addition to FIG. 1 in FIG. 2A and 2B also show a first steam generator 10 and a second steam generator 20. The first steam generator 10 is shown in the vicinity of the Claus process 4 (but need not necessarily be located in the vicinity of the Claus process 4). It operates using at least a portion of the waste heat from the 4 Claus process. The second steam generator 20 is shown in the vicinity of the air separation unit 7 (but need not necessarily be located in the vicinity of the air separation unit 7). It operates independently of the heat removed from the 4 Claus process.

In the shown in FIG. 2A in the first mode of operation, the gas processing unit 2, or more specifically the amine treatment plant 21, and/or the tail gas treatment plant 6, or more specifically the plant 61, is operated using a first amount of steam, the first amount of steam being provided by the first generator. 10 steam operating using at least a portion of the waste heat from the Claus process 4. As shown in FIG. 2A, the first steam generator 10 respectively provides a steam flow b.

In the shown in FIG. 2A in the first mode of operation, the compressor 71 of the air separation unit 7 operates using a second amount of steam in a steam turbine 72 mechanically connected to the compressor 72, the second amount of steam being provided by the second steam generator 20. As shown in FIG. 2A, the second steam generator 20 respectively provides a steam flow m.

In the shown in FIG. 2B in the second mode of operation, at least a portion of the first amount of steam provided by the first steam generator 10 in the first mode of operation, as shown in FIG. 2B is instead generated by the second steam generator 20 (see steam flow b, this is also possible for steam flow b', but not shown for purposes of clarity). From the second generator 10 steam pairs are not supplied. In addition, no steam enters the steam turbine 72 mechanically connected to the compressor 71 of the air separation unit 7, and the air separation unit 7 does not operate.

The heat obtained from the 4 Claus process usually comes from two different sources. The heat received from the Claus furnace 41 may be high pressure steam (HP steam). It can be pressured up to 45 bar(g) and is suitable for reheating acid gas before it is introduced into catalytic reactors and for driving turbines (it can also be superheated in the combustion furnace shaft). Low pressure steam (LP steam) is generated in sulfur condensers; it can be used to reboil the solvent in the amine treatment plant(s), but is not suitable for driving turbines.

Claims (10)

1. A gas processing method (100) comprising an oxidation process (4) with generation of waste heat, in which a first gas mixture containing an oxidizable component is provided, wherein the first gas mixture and oxygen are introduced into the oxidizer (41), wherein at least a portion oxidizable component in the first gas mixture is oxidized in the oxidizer (41), wherein the first gas mixture and/or the second gas mixture used to provide the first gas mixture and/or the third gas mixture obtained from at least part of the first gas mixture using oxidizing unit (41) is processed in one or more gas processing units (2) operating using a first amount of steam, characterized by a first mode of operation and a second mode of operation, the second mode of operation is the start mode, and the first mode of operation is the normal mode operation, implemented in the period of time after the second mode of operation, the process (4) of oxidation from the generator ion of the removed heat is involved in the operation and provides the removed heat in the amount equal to the first amount of the removed heat in the first mode of operation, and is not involved in the operation or is involved in the operation and provides the removed heat in the amount equal to the second amount of the removed heat, which is less than the first amount of the heat removed, in the second mode of operation, in the first mode of operation, the oxygen introduced into the oxidizing unit (41) is at least partially provided by the air separation unit (7) in the form of oxygen contained in the air separation product, the air separation product being pure oxygen or a mixture of components enriched with oxygen compared to atmospheric air, in the first mode of operation, the air separation unit (7) produces the first amount of air separation product and in the second mode of operation, the air separation unit (7) produces a second amount of air separation product, which is less than the first amount of air separation product, or does not produce an air separation product at all, while the air separation plant (7) contains a compressor (71) operating using a second amount of steam expanded in a steam turbine (72) mechanically connected to the compressor (71), in in the first mode of operation, the first amount of steam is provided by the first steam generator (10) operating using at least a portion of the heat removed, and in the first mode of operation, the second amount of steam is provided by the second steam generator (20) configured to operate independently of the heat removed, and in the second mode of operation, at least a portion of the first amount of steam provided by the first steam generator (10) in the first mode of operation is provided by the second steam generator (20) instead. 2. The gas processing method (100) according to claim 1, wherein the first gas mixture is a mixture of acid gases, wherein the oxidizable component is hydrogen sulfide, while the oxidation process (4) is a Claus process, wherein the oxidizing unit (41) is a Claus furnace, and at the same time, part of the hydrogen sulfide in the acid gas mixture is oxidized by combustion in the Claus furnace. 3. The method (100) according to claim 1, wherein in the first mode of operation, a third amount of air separation product is introduced into the Claus furnace (41), which is less than the first amount of air separation product, and in which a fourth amount of air separation product is stored in the first mode of operation air and introduce it at least partially into the oven (41) Claus in the second mode of operation. 4. Method (100) according to any one of the preceding claims, wherein the third gas mixture obtained from at least a portion of the first gas mixture using the oxidizer (41) is processed in one or one of the gas processing plants, the gas processing plant being is a tail gas cleaning plant (6), and the tail gas cleaning plant (6) operates using some or part of the steam. 5. Method (100) according to any one of the preceding claims, wherein the second gas mixture used to provide the first gas mixture and/or the third gas mixture obtained from at least a portion of the first gas mixture is processed in or in one of the plants ( 2, 6) gas processing, wherein the second and/or third gas mixture is a gas mixture containing hydrogen sulfide and carbon dioxide, and the gas processing unit or one of the gas processing units (2, 6) contains an amine treatment unit (21, 61) , and in the installation (21, 62) amine purification, hydrogen sulfide and carbon dioxide are at least partially removed from the second and/or third gas mixture using an amine solution and an amine solution loaded with hydrogen sulfide and carbon dioxide is obtained, and at the same time hydrogen sulfide and carbon dioxide at least partially separated from the loaded amine solution using heat from the first amount of steam or part thereof. 6. A device for implementing a method (100) for processing gas, including an oxidation process (4) with generation of waste heat, including means configured to provide a first gas mixture containing an oxidizable component, an oxidizing unit (41) configured to oxidize at least as part of the oxidizable component in the first gas mixture, means configured to introduce the first gas mixture and oxygen into the oxidizer (41), one or more gas processing plants (2), configured to process using the first amount of steam of the first gas mixture and /or the second gas mixture used to obtain the first gas mixture, and/or the third gas mixture obtained from at least part of the first gas mixture using an oxidizing unit (41), characterized in that the device is configured to perform the first mode of operation and the second mode of operation, while the second mode of operation is is the start-up mode, and the first mode of operation is the normal mode of operation implemented in the period of time after the second mode of operation, the oxidation process (4) with the generation of waste heat is in operation and provides heat to be removed in an amount equal to the first amount of heat to be removed, in the first mode of operation, and is not involved in operation or is engaged in operation and provides heat removal in an amount equal to the second amount of heat removed, which is less than the first amount of heat removed, in the second mode of operation, an air separation unit (7), which is part of the device and is configured to provide in the first mode of operation at least part of the oxygen introduced into the oxidizing unit (41) in the form of oxygen contained in the air separation product, the air separation product being pure oxygen or a mixture of components enriched with oxygen compared to atmospheric air, the air separation unit (7) is configured to produce in the first operating mode the first amount of the air separation product and in the second operating mode the second amount of the air separation product, which is less than the first amount of the air separation product , or not to produce an air separation product at all, the air separation plant comprises a compressor (71) configured to operate using a second amount of steam expanded in a steam turbine (72) mechanically connected to the compressor (71), the first steam generator (10) configured to operate using at least a portion of the heat removed and generate the first amount of steam in the second mode of operation, and the second steam generator (20) configured to operate independently of the heat removed and provide the second amount of steam in the first mode of operation, and in the second mode of operation, at least a portion of the first amount of steam provided by the first steam generator (10) in the first mode of operation is provided by the second steam generator (20) instead. 7. Apparatus according to claim 6, wherein the first gas mixture is a mixture of acid gases, the oxidizable component is hydrogen sulfide, the oxidation process (4) is a Claus process, the oxidizer (41) is a Claus oven, and at In this part of the hydrogen sulfide in the acid gas mixture is oxidized by combustion in a Claus furnace.

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