Hydrocarbon pyrolysis with reduced exhaust emissions

Abstract

Methods, systems and apparatus are provided for using a common working fluid for one or more turbines for processing process gases and a furnace for a pyrolysis process for producing process gases. The turbine(s) are operated based on a modified Allam cycle to generate power for operating one or more compressors and / or refrigerators involved in the processing of the process gases while producing reduced or minimal amounts of CO2 released as a low pressure gas phase product. Integrating the pyrolysis furnace with the working fluid loop can provide further benefits.

Description

[0001] priority

[0002] This application claims priority to and the benefit of U.S. Provisional Application No. 62 / 954,783, filed on December 30, 2019, and European Patent Application No. 20168291.1, filed on April 6, 2020, the disclosures of which are incorporated herein by reference in their entireties. Technical Field

[0003] The present invention relates to reducing exhaust emissions from hydrocarbon pyrolysis, to a method for performing hydrocarbon pyrolysis with reduced exhaust emissions, to an integrated system for performing such a method, to certain exhaust products of hydrocarbon pyrolysis, and to certain hydrocarbon pyrolysis products. Background Art

[0004] Hydrocarbon pyrolysis processes, such as steam cracking, produce commercially important quantities of useful products and co-products, such as saturated and unsaturated hydrocarbons. Certain pyrolysis products, such as C 4- Olefins, particularly useful as feedstocks for petrochemical processes such as polymerization processes, pyrolysis processes such as steam cracking use considerable amounts of energy. Because hydrocarbon pyrolysis is highly endothermic, energy is required to "crack" large hydrocarbon molecules to produce a pyrolysis effluent containing molecular hydrogen and desired hydrocarbon products such as light olefins. The pyrolysis effluent is typically compressed and cooled to facilitate separation and recovery of desired products and co-products from the pyrolysis effluent, which requires more energy, such as for turbines and refrigeration equipment. When at least a portion of this energy is generated by hydrocarbon combustion, a considerable amount of waste gas (typically comprising CO2) is emitted, typically as flue gas.

[0005] Difficulties have been encountered in attempts to treat exhaust emissions. For example, it has been found that the high temperatures required for hydrocarbon pyrolysis (typically at least 700°C) limit opportunities for recovering and using heat from combustion exhaust gases. Alternative methods of supplying energy via renewable means (e.g., renewable electricity) do not yet have the capacity to supply the world's needs, let alone the technical solutions to do so.

[0006] Therefore, pyrolysis processes such as steam cracking can produce undesirable amounts of waste gas emissions, particularly waste gas emissions containing CO2. In addition, certain hydrocarbon pyrolysis processes, such as steam cracking, produce pyrolysis effluents that themselves contain considerable amounts of CO2. Attempts have been made to reduce the amount of CO2 and other greenhouse gases ("GHG") emitted by pyrolysis processes and related combustion processes. In addition to careful efficiency steps, the only prior art method for reducing these emissions is to remove CO2 from combustion exhaust gases (e.g., from steam cracking furnace flue gases) and from pyrolysis effluents by using gas treatment techniques such as amine treatment. Although this technology is effective and cost-effective for removing CO2 from pyrolysis effluents, it is impractical for removing CO2 from combustion exhaust gases emitted by pyrolysis facilities such as steam cracking facilities. It has been found that, for example, the dilute nature of exhaust gases (e.g., flue gases) causes amine treatment to account for a considerable portion of the total cost of producing the desired pyrolysis products. Therefore, there is a need for a pyrolysis process with less exhaust gas emissions, particularly less CO2 exhaust gas emissions. There is a particular need for a steam cracking process with reduced CO2 off-gas emissions.

[0007] Light olefins such as ethylene are usually manufactured in olefin devices (e.g., steam cracker devices), which include production (pyrolysis) facilities and recovery facilities. In some conventional olefin devices, olefin production facilities include one or more steam cracking furnaces for steam cracking hydrocarbon-containing feeds. Steam cracking furnaces generally include convection sections and radiant sections. The radiant section includes a plurality of tubular members commonly referred to as "radiant tubes". Conventionally, the radiant tubes are located near one or more combustion heaters (e.g., burners) that heat the outer surface of the furnace tubes in the radiant section. Hot combustion gases leave the radiant section and are introduced into the convection section. The convection section also includes tubular members, commonly referred to as "convection tubes". The hot gas from the radiant section heats the outer surface of the convection tubes and then leaves the convection section.

[0008] Conventional steam cracking methods usually produce light olefins by pyrolysis of hydrocarbons during pyrolysis mode. Coke and other deposits formed during pyrolysis mode are removed from the furnace interior during regeneration (decoking) mode. During pyrolysis mode, hydrocarbon-containing feed is introduced into a convection tube for feed preheating. Feed preheating is carried out in a convection tube section located in the upper region of the convection section. Steam is combined with the preheated feed, and the steam-feed mixture is further heated in a convection tube section located in the lower region of the convection section. The heated feed-steam mixture is introduced into the heated furnace tube in the radiant section, and the heat transferred from the furnace tube to the mixture causes at least a portion of the feed to be pyrolyzed to produce a process gas containing light olefins. During regeneration mode, the hydrocarbon-containing feed is replaced by a stream of a decoking fluid (e.g., a gaseous steam-air mixture) containing oxygenates, and the burner continues to heat the radiant section and the convection section. The decoking fluid is directed through the heated convection tubes, heated radiant tubes and associated furnace piping, internals, etc. to at least partially remove the deposited coke. After sufficient coke removal is achieved, the steam cracking furnace is returned to pyrolysis mode operation.

[0009] Further greenhouse gas emissions may be generated due to the need to process the pyrolysis effluent produced during the pyrolysis mode of operation. For example, multiple compression and / or refrigeration steps may be required to separate the desired light olefin components from the remaining components in the pyrolysis effluent. Each compression and / or refrigeration step represents another processing element that requires power and therefore may represent other locations where fuel can be burned to provide such power. Although some heat exchange and heat integration can be used to reduce the amount of additional fuel used, it may not be feasible to heat integrate all processing elements involved in separating the desired components from the pyrolysis effluent.

[0010] What are needed are systems and methods that can reduce or minimize greenhouse gas emissions when pyrolysis is used to produce light olefins, such as when steam cracking is used as the pyrolysis process for an ethylene plant.

[0011] U.S. Patent Application Publication 2019 / 0169510 describes systems and methods for decoupling the production and recovery facilities of an olefin plant.

[0012] A closed loop cycle, sometimes referred to as the "Allam cycle," for powering a turbine using CO2 as a working fluid is described in U.S. Patent Application Publications 2012 / 0067056 and 2017 / 0058712. The Allam cycle is described as providing electricity via natural gas fuel with reduced CO2 emissions.

[0013] Modern olefin production units consume a large amount of shaft power to drive various compressors and pumps. It is highly desirable to improve energy efficiency in the power production of the device. For example, the process gas compressor discussed in the previous paragraph may be very large, thereby requiring a large amount of shaft power to drive. In addition, the compressor used in the refrigeration unit in the olefin production unit also can consume a large amount of shaft power.

[0014] From the product recovery section of a typical steam cracker olefin production unit, a large amount of "tail gas" containing methane and optionally hydrogen is usually produced. The tail gas is usually burned as a fuel to provide energy, producing CO2 and water in the process. It would be highly desirable that the energy released from the combustion of the tail gas could be used to power process steps in the olefin production unit, that the CO2 produced could be concentrated, captured, stored and / or utilized, and that the water produced could be used in an efficient manner. However, there are significant challenges in achieving one, let alone two or all of these goals.

[0015] The olefin production unit comprising steam cracker is ideally located near the user (for example polyethylene and / or polypropylene production facility) of olefin products, so that the transportation of olefins is minimized.For being positioned near the hydrocarbon feed source and away from the olefin production unit of user, it may be highly desirable that one or more conversions in the olefin products be more easily transported in the conversion unit of the olefin production unit adjacent to the olefin production unit.It will be highly desirable that the operation of the steam cracker and the recovery section in the olefin production unit, conversion unit and power production unit (if any, comprising tail gas combustion) is integrated to provide a high level of energy efficiency.

[0016] The present disclosure satisfies this need and other needs. Summary of the invention

[0017] The present invention is based in part on the integration of an effluent processing equipment group (train) for a pyrolysis reactor with a furnace for a pyrolysis reactor to allow the use of a common working fluid. This can allow both the turbine and the furnace that provide power for the processing equipment group (at least a portion of) to operate based on an improved Allam cycle. The turbine can be used to provide power for other parts of a process gas compressor, a refrigeration compressor and / or an effluent processing equipment group. By using a separate turbine based on Allam cycle operation to provide power for one or more parts of the effluent processing equipment group, the operation of the processing equipment group can be decoupled from the operation of the pyrolysis reactor, while also reducing or minimizing the emission of CO2 and / or other greenhouse gases. By operating the pyrolysis furnace as part of the same working loop, further CO2 reduction benefits can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A Mollier diagram for operating a single turbine and a single combustor based on the Allam cycle is shown.

[0020] Figure 2 Mollier diagram showing the integration of a pyrolysis furnace (burner and reactor housing) with a combustor and a turbine.

[0021] Figure 3 An example of a pyrolysis reactor configuration suitable for integration with a combustor and associated turbine is shown.

[0022] Figure 4 Certain aspects of the invention are schematically illustrated wherein a process gas derived from hydrocarbon pyrolysis product production is compressed in a process gas compressor. DETAILED DESCRIPTION OF THE INVENTION

[0024] Overview

[0025] Certain aspects of the present invention relate to methods, systems and apparatus for producing compressed process gases containing light olefins such as ethylene. The method utilizes a pyrolysis reactor, such as a tubular flow-through reactor, to produce process gases. The generator utilizes a turbine based on the Allam cycle (using a working fluid containing CO2) to generate shaft power for operating a compression stage, which is used to compress the process gas while producing a reduced amount or a minimum amount of CO2 that is recovered and taken away as a gas phase product. The compression stage compresses the process gas in at least one process gas compressor powered by the shaft power generated. In addition, at least a portion of the working fluid containing CO2 from the power generation turbine is used as a working fluid for the flow-through reactor environment. By using a working fluid containing CO2 for a pyrolysis reactor and one or more turbines for providing power to a pyrolysis effluent processing equipment group, the production of light olefins can be achieved while reducing, minimizing or even eliminating the emission of low-pressure CO2 to the environment.

[0026] The working fluid containing CO2 may have a significantly increased CO2 content relative to conventional working fluids for turbines. Conventionally, air and / or combustion products formed using air as an oxygen source have been used as working fluids. This results in the following working fluid: wherein half or more of the working fluid volume corresponds to nitrogen. Instead of using air, the working fluid may be formed by combustion products produced using oxygen from an air separator unit. This may produce a working fluid consisting essentially of CO2 and H2O. H2O may be separated from the working fluid relatively efficiently, allowing the production of a working fluid having a large portion of the volume of CO2.

[0027] In order to integrate the pressurized pyrolysis furnace into the same working fluid circuit as the combustor and turbine of the process gas compressor, the working fluid in the reactor shell needs to be at an increased pressure. Because the pyrolysis furnace is usually operated at near ambient pressure (or even under reduced pressure), various structural and process changes are required to accommodate the use of high pressure in the pyrolysis furnace. These structural and process changes can include adding thicker refractory layers and pressure containing boundaries of the furnace reactor wall, including removing visual inspection windows; improving furnace tubes to withstand high pressures and changes in coke detection and removal methods based on structural changes in furnace tubes.

[0028] In certain aspects, the invention relates to a configuration that can provide the above advantages while integrating the operation of the pyrolysis furnace with other power generation turbines. These aspects may include one or more of the following features AF. The invention is not limited to these aspects, and the description of these aspects should not be interpreted as excluding other aspects within the broader scope of the invention.

[0029] A) A set of turbines that do not drive power generation, but rather drive light olefin unit recovery compression (e.g., ethylene unit recovery compression). This may include using a set of turbines to drive process gas compression, refrigeration stages, or a combination thereof.

[0030] B) A low pressure outlet for the turbine unit to discharge the turbine effluent at a temperature of 600°C-700°C and a pressure of 800 kPa-a or higher.

[0031] C) A set of one or more low pressure burners that inject natural gas or tail gas (e.g. obtained from a recovery facility of a steam cracker unit) and oxygen for combustion to heat the turbine effluent from 600°C-700°C to 1100°C. In some aspects, the low pressure burners can use a grid of raw gas burner nozzles and oxygen nozzles to provide combustion heating similar to that demonstrated as duct burners in heat recovery steam generators. This configuration provides a compact heat output for the mixed heat stream used in the reactor vessel.

[0032] D) For each low pressure burner, a close coupled pyrolysis reactor having hot CO2 on a shell lined with refractory material around a furnace tube, a pyrolysis reactor feed containing hydrocarbons is introduced into the furnace tube, and a pyrolysis effluent is extracted from the furnace tube. In some aspects, the reactor may include triangular pitch tubes with a selected pitch to take advantage of the higher radiation efficiency provided by higher pressure operation and by using a working fluid consisting essentially of CO2 and H2O. This may also improve convective heat transfer efficiency. In some aspects, the furnace tube may correspond to a U-shaped tube to help manage thermal expansion with a pressurized reactor vessel. The tube distribution manifold may be insulated to relieve external pressure (by providing a lower design temperature for higher allowable stresses). In some aspects, process control may be based in part on the use of inlet and outlet housing thermowells located within the insulated portion of the vessel.

[0033] E) After heat exchange to cool the furnace working fluid exiting the pyrolysis reactor (corresponding heating of the working fluid after water removal), the CO2 loop undergoes water separation and removal, compression to the high pressure side of the loop, and CO2 removal to the pipeline. The pyrolysis effluent from the reactor is similarly cooled by heat exchange with the pyrolysis feed and by additional dilution steam generation. This approach saves capital and allows more efficient heat transfer.

[0034] F) Decoking of the pyrolysis reactor is performed using steam, with the coke effluent discharged to a decoking facility upstream and / or within the quench tower and primary fractionator facility. The reactor includes an erosion-resistant outlet manifold or channel to manage the erosive effects of decoking. Alternatively, steam and air decoking may be used, thus requiring atmospheric discharge of the decoking effluent and more CO2 emissions. To overcome the loss of visual monitoring, inlet and outlet temperature monitoring and a less rigorous decoking process may be used to manage the decoking exotherm.

[0035] definition

[0036] For purposes of this specification and the following claims, the following terms are defined.

[0037] The term "C n "Hydrocarbon" refers to a hydrocarbon containing n carbon atoms per molecule, where n is a positive integer. The term "C n+ "Hydrocarbon" means a hydrocarbon containing at least n carbon atoms per molecule. The term "C n - "Hydrocarbon" refers to a hydrocarbon containing up to n carbon atoms per molecule. The term "hydrocarbon" refers to a class of compounds containing hydrogen bonded to carbon, and encompasses (i) saturated hydrocarbons, (ii) unsaturated hydrocarbons and (iii) mixtures of hydrocarbons, and includes mixtures of hydrocarbon compounds (saturated and / or unsaturated), such as mixtures of hydrocarbon compounds having different values ​​of n.

[0038] The terms "alkanes" and "paraffins" refer to substantially saturated compounds containing only hydrogen and carbon, such as those containing ≤ 1 mol % unsaturated carbon atoms. The terms "unsaturates" and "unsaturated hydrocarbons" refer to compounds containing one or more C 2+ A hydrocarbon compound containing at least one carbon atom directly bonded to another carbon atom through a double bond or a triple bond. The term "olefin" refers to one or more unsaturated hydrocarbon compounds containing at least one carbon atom directly bonded to another carbon atom through a double bond. In other words, an olefin is a compound containing at least one pair of carbon atoms, wherein the first and second carbon atoms of the pair of carbon atoms are directly connected by a double bond. The terms "aromatic compound" and "aromatic hydrocarbon" refer to a hydrocarbon compound containing at least one aromatic ring.

[0039] The term "pyrolysis" refers to an average endothermic reaction for converting molecules into (i) atoms and / or (ii) smaller molecular weight molecules, and optionally (iii) larger molecular weight molecules, such as the process for converting ethane and / or propane into molecular hydrogen and unsaturates such as ethylene, propylene and acetylene.

[0040] The term "periodic table" refers to the periodic table of the elements appearing on the inside cover of the Merck Index, 12th edition, Merck & Co., Inc., 1996. "Steam tables" can be found in MD Koretsky, "Engineering and Chemical Thermodynamics", John Wiley & Sons, 2004. When indicating temperature, the unit "K" indicates degrees Kelvin, the SI unit of temperature.

[0041] Operating a pyrolysis (steam cracking) furnace at high pressure

[0042] Steam cracking is an example of a pyrolysis process in which heat is indirectly transferred to the pyrolysis environment through the walls of a furnace tube (or another type of vessel). This has the advantage of keeping the desired pyrolysis products separate from the combustion and / or heating environment. However, it also means that any coke formed during pyrolysis is also separated and therefore not consumed or transported away by the process environment. Therefore, it is necessary to monitor the coke accumulation and remove the accumulated coke regularly.

[0043] Conventionally, the holding vessel for the heating environment surrounding the furnace tube is operated at a lower pressure, such as at a pressure of 150kPa-a or less. This is based on various considerations. First, operating the holding vessel / heating environment at a lower pressure avoids the need for a large amount of compression of air, which is a typical oxygen source and working fluid for a conventional steam cracking furnace. It should be noted that the use of air means that the working fluid in a conventional steam cracking furnace contains a considerable amount of nitrogen. Secondly, since coke accumulates in the reactor tube of the steam cracker, visual inspection is usually used to identify coke accumulation in the reactor tube during pyrolysis. Visual identification can also help avoid undesirable hot spots during coke removal. Conventionally, when the heating environment is operated at a pressure of 150kPa-a or higher, such a visual inspection window is structurally unsuitable for inclusion in the reactor tube.

[0044] Operating a steam cracking furnace environment with low pressure air as the oxygen source also means that a considerable amount of low pressure dilute CO2 is produced. Historically, a considerable portion of the low pressure dilute CO2 from the steam cracker has been vented to the atmosphere. One option for capturing this low pressure, dilute CO2 is to treat the furnace effluent with amine scrubbing. However, since the furnace produces a large amount of low pressure gas, this requires a considerable amount of additional cost.

[0045] In contrast to conventional operation, in various aspects, a pressurized steam cracker vessel (or other pressurized vessel for a pyrolysis environment) and one or more associated turbines can be operated so that at least a portion of the working fluid is common. For example, one or more pressurized vessels for pyrolysis and one or more turbines for associated process gas compressors (one or more) can be operated based on an Allam cycle using a CO2-containing feed fluid as a common working fluid. By using a common working fluid, the generation of a large amount of low-pressure diluted CO2 is avoided. On the contrary, high-purity, high-pressure CO2 can be extracted from the system during operation. This high-purity, high-pressure CO2 can be used directly as a reagent or for a chelating agent. Alternatively, the high-purity, high-pressure CO2 may require a reduced amount or a minimum amount of further processing to be suitable for use as a reagent or for a chelating agent.

[0046] In order to integrate the working fluid for the turbine combustor and the pressurized pyrolysis environment, the turbine combustor is operated at a higher pressure, such as 15MPa-a or higher, or 20MPa-a or higher pressure. After providing power to the turbine, the working fluid is at a reduced pressure. The decompressed working fluid is then passed into the low-pressure combustor to reheat the turbine effluent from about 700°C to 1100°C. This combustion can then be closely coupled with the pressurized container to provide high-temperature pyrolysis heat transfer. The pressurized container for the pyrolysis environment can be operated at a pressure of 800kPa-a or higher, or 1000kPa-a or higher. Depending on this aspect, the total concentration of CO2 and H2O can correspond to 80% by volume or more of the fluid in the pressurized container of the pyrolysis environment, or 90% by volume or more, or 95% by volume or more, such as up to substantially only containing CO2 and H2O (less than 1.0% by volume of other components). This is in contrast to conventional steam cracking furnace operation at about 100 kPa-a and a total concentration of CO2 and H2O of about 30% by volume. It should be noted that the use of a working fluid consisting primarily of CO2 and H2O can provide improved radiant efficiency per unit flue gas volume, resulting in significant floor space and capital savings. In some aspects, higher pressures can be used in the pressurized vessel used for the pyrolysis environment, such as 1300 kPa-a or higher, or 1500 kPa-a or higher, or 2000 kPa-a or higher, such as up to 3000 kPa-a or possibly higher pressures. Such higher pressures can be used to improve cycle efficiency and reduce reactor floor space / surface area through appropriate mechanical design.

[0047] In addition to having improved radiative efficiency, increased pressure within the high pressure steam cracking furnace can allow for increased convective heat transfer. This can allow, for example, improved convective heat transfer / available surface area, thereby reducing the amount of high alloy heat transfer area required to provide a desired level of heat transfer to the process gas within the reactor tubes. This also allows for additional capital cost savings.

[0048] The auxiliary low temperature heating step can be provided with waste heat recovery from the quench system or CO2 loop. The auxiliary low temperature cooling step can be provided using dilution steam condensate preheat or air fin heat exchangers. With this approach, furnace stacks, boiler stacks, cooling towers and decoking exhaust ports are not required, and emissions to the atmosphere are virtually eliminated.

[0049] Process cycle overview

[0050] Figure 1 An example of a Mollier diagram (pressure versus enthalpy plot) for a single combustor and turbine operating based on the Allam cycle is shown. Figure 1Also shown are the lines corresponding to the constant temperature curves (temperature in °C is indicated on the upper long axis of the graph), and the regions of phase space where distinct gas and liquid phases of CO2 can exist when CO2 is not in the supercritical state. Figure 1 In the example shown, the working fluid circuit only includes the burner and the associated turbine. In other words, the turbine and the pyrolysis furnace are not integrated in the Figure 1 in the cycle shown.

[0051] exist Figure 1 , the Allam cycle is illustrated based on how various processes within the cycle cause changes in the pressure and / or enthalpy of the working fluid. The cycle can begin by adding a fuel input 610 to the working fluid before the fuel and working fluid are passed into the combustor. The fuel is burned (completed at 620), which results in an increase in enthalpy at a relatively constant pressure. This high pressure, high enthalpy working fluid is then used to provide power to a turbine 630. Providing power to the turbine 630 results in a decrease in both the pressure and enthalpy of the working fluid. The decompressed working fluid is then heat exchanged 640 with the high pressure working fluid 680 combined with the fuel input 610. The heat exchange reduces the enthalpy of the low pressure working fluid while increasing the enthalpy of the high pressure working fluid.

[0052] After the heat exchange, water is removed from the working fluid 650. The water removal is performed by cooling the working fluid to condense the water. However, such cooling may also place the working fluid in a region of the phase space where the CO2 in the working fluid will no longer be in the supercritical region. To avoid this, as Figure 1 As shown, the water removal 150 is performed in a series of alternating cooling steps 152 and compression steps 154. This allows the CO2 in the working fluid to remain in a supercritical state (substantially) during the water removal process so that no phase change occurs in the working fluid. After the water removal 650, the remaining working fluid substantially corresponds to CO2. The CO2 working fluid is then further compressed (e.g., by pumping) 660 to return the working fluid to the pressure required by the burner 620. After pressurization 660, the working fluid is then heated 670 and heat exchanged 680 to prepare for the burner.

[0053] Figure 2 Another example of a Mollier plot (pressure versus enthalpy plot) is shown. Figure 2 In Figure 1, the Mollier diagram shows a process cycle where the burner, turbine and pyrolysis furnace operate based on the Allam cycle. Figure 2 Also shown are the lines corresponding to the constant temperature curves (in °C, according to the upper long axis), as well as the regions of phase space where distinct gas and liquid phases of CO2 can exist since CO2 is not in a supercritical state.

[0054] exist Figure 2In, with Figure 1 Similar cycle parts are represented by similar numbers. The cycle begins with the addition of a fuel input 610 to the working fluid before the fuel and working fluid are passed into the combustor. The fuel burns 620, which results in an increase in enthalpy at a relatively constant pressure. This high pressure, high enthalpy working fluid is then used to power a turbine 630. Powering the turbine 630 results in a decrease in both the pressure and enthalpy of the working fluid.

[0055] and Figure 1 Unlike the cycle shown in , the decompressed working fluid leaving the turbine 630 does not undergo heat exchange. Figure 2 In the cycle shown, additional fuel 712 is added to the turbine effluent. The combined additional fuel and turbine effluent are then combusted 722 in one or more low-pressure combustors to produce a working fluid with increased enthalpy. The increased enthalpy working fluid provides heat 732 to the pyrolysis furnace. After leaving the furnace, the furnace effluent is heat exchanged 742 with the high-pressure working fluid 680 with which the fuel input 610 is combined. The heat exchange reduces the enthalpy of the low-pressure working fluid while increasing the enthalpy of the high-pressure working fluid.

[0056] After the heat exchange, water is removed from the working fluid 750. Due to the additional low pressure combustion 722 and providing heat to the pyrolysis furnace 732, the working fluid is relatively Figure 1 The process in the working fluid is at a lower pressure. Therefore, additional cooling and compression cycles may be required to remove water while maintaining the CO2 in the working fluid in a single (supercritical) phase. After removing water 750, the remaining working fluid substantially corresponds to CO2. The CO2 working fluid is then further compressed 660 to return the working fluid to the desired pressure for the burner 620. After pressurization 660, the working fluid is then heated 670 and heat exchanged 680 in preparation for the burner.

[0057] The composition of the working fluid may vary depending on the location in the cycle where the working fluid is sampled. After combustion and before water is removed, the working fluid may include CO2, CO, H2O, and optionally one or more components that are present due to a fuel containing compounds other than hydrogen and hydrocarbons and / or due to the use of an oxygen-containing stream containing compounds other than oxygen. Optionally but preferably, the oxygen-containing stream may include 90% by volume or more of O2, or 95% by volume or more, or 97% by volume or more, such as an oxygen-containing stream consisting essentially of O2 (less than 0.1% by volume of components other than O2). Optionally, but preferably, the fuel used for combustion may include 90% by volume or more of hydrogen, hydrocarbons, CO, CO2, and H2O, or 95% by volume or more, or 97% by volume or more, such as containing at most 0.1% by volume or less of other components. Suitable fuels include those designated for regeneration in pyrolysis reactors, such as those with a calorific value ≥1×10 6 J / kg of fuel. For example, the fuel may include one or more of natural gas, gaseous hydrocarbons in natural gas, gaseous hydrocarbons separated and / or derived from natural gas, gaseous hydrocarbons separated and / or derived from natural gas condensate, gaseous hydrocarbons separated and / or derived from crude oil, molecular hydrogen, carbon monoxide, and mixtures thereof. Additionally or alternatively, a tail gas stream produced by an ethylene unit may be used as at least a portion of the fuel.

[0058] After water separation and before adding more fuel, the working fluid may include less than 1.0 vol% water, or less than 0.1 vol% water. Additionally or alternatively, the working fluid after water separation and before adding more fuel may include 90 vol% or more CO2, or 95 vol% or more, or 97 vol% or more, such as consisting essentially of CO2 (less than 1.0 vol% components other than CO2, or less than 0.1 vol%).

[0059] The tail gas recovered from the process gas can be substantially composed of methane and optionally hydrogen in various concentrations. The tail gas stream from a large industrial steam cracking furnace receiving feed such as ethane may be quite large. In one embodiment of the method of the present disclosure, a portion, preferably most of, preferably all of the tail gas is burned in the Allam cycle to generate power, including shaft power and optionally the electricity of a coupled generator (one or more). Shaft power can be advantageously used to drive one or more devices in an olefin production unit, such as: a) delivered to a process gas compressor to compress the process gas, b) delivered to a refrigeration compressor to cool the compressed process gas, c) delivered to a refrigeration compressor to cool the decompressed working fluid in a cooling step from the series of cooling and compression steps, or d) a), b) and c) in a combination of two or more. Compared with the use of power derived from an external fuel such as a natural gas stream or the electricity transmitted from the outside of the olefin production unit, the use of the shaft power generated by the combustion of tail gas in the Allam cycle can significantly improve the energy efficiency of the olefin production unit. Electricity can be co-generated in an olefin production unit by coupling a portion of the shaft power to one or more generators to accommodate the power demand in the olefin unit and transmitting it to the outside of the unit where appropriate and economical. When consumed on site, the electricity generated in situ does not involve transmission losses, which are otherwise inevitable if it is transmitted from a remote power device. Olefin production units consume a lot of shaft power, which may be met by using a large-scale Allam cycle that achieves a very high level of economies of scale. In contrast, the power generation unit disclosed in U.S. Patent Application Publication No. 2017 / 0058712A1 is much smaller in scale and therefore less efficient.

[0060] In a conventional Brayton cycle (e.g., the cycle disclosed in U.S. Patent Application Publication No. 2019 / 0169510A1), the exhaust gas containing CO2 and water produced by the combustion of the fuel is generally discharged into the atmosphere, resulting in a large amount of CO2 emissions and water vapor losses. In contrast, any water produced in the Allam cycle of the method of the present disclosure can be advantageously reused. For example, at least a portion of the water stream (i) can be fed into the pyrolysis step to mix with the hydrocarbon-containing feed; (ii) heated to produce steam; (iii) used as an indirect cooling medium; (iv) used as a quenching medium; and (iv) fed into the hydrocarbon-containing stream as a diluent. Olefin production units utilize a large amount of water for cooling and as a process diluent. Due to the amount of fuel burned, the Allam cycle used in the method of the present disclosure in an olefin production unit can produce a very large amount of water (e.g., 1500 kilotons per year for an olefin production unit of the prior art). By reusing the water stream generated by the Allam cycle, the need for water from external sources in the plant is reduced, further increasing plant efficiency, reducing the plant carbon footprint, and improving its environmental friendliness.

[0061] The olefin product produced by the olefin production unit can be an ethylene stream. The ethylene product can have many industrial uses. For example, the ethylene stream can be supplied to a nearby polyethylene production unit via a pipeline, where it is converted into polyethylene. In another embodiment, a portion of the ethylene product can be converted into a diol product, including but not limited to monoethylene glycol ("MEG"), which can be used in vehicle antifreeze and in a method for preparing polyester polymers. In a particularly advantageous method, ethylene can first be oxidized by oxygen to produce an oxidized mixture comprising ethylene oxide, which can then be hydrolyzed to produce MEG, or contact CO2 to produce ethylene carbonate, which is then hydrolyzed to produce MEG:

[0062] Ethylene + O22 Ethylene Oxide (1)

[0063] Ethylene oxide + H2O → MEG (2)

[0064] Ethylene oxide + CO22 Ethylene carbonate (C3H4O3) (3)

[0065] Ethylene carbonate + H2O → MEG + CO2 (4)

[0066] The oxygen consumed in the above reaction (1) can be supplied by an air separation facility which also supplies the oxygen-containing stream required for burning fuels such as tail gas in the Allam cycle. By using a common air separation facility for both processes (which is expensive), economies of scale that would not otherwise be possible can be achieved, resulting in high energy efficiency and cost effectiveness in all the units involved.

[0067] In the method of the present invention, the CO2-containing stream produced by the Allam cycle and / or the compressed CO2 stream can be advantageously used in various embodiments. For example, a portion of the CO2 produced in the Allam cycle can be supplied to the reaction (4) in the previous paragraph, so that MEG can be effectively produced from the ethylene produced by the ethylene production unit. In another example, a portion of the compressed CO2 stream can be used to extract hydrocarbon source materials, which can be used to obtain at least a portion of the hydrocarbon-containing feed subjected to pyrolysis to prepare olefin products. This hydrocarbon source material can be, for example, crude oil, shale oil, shale gas, natural gas, etc. stored in underground geological formations. From the extracted crude oil, shale oil, shale gas and / or natural gas, suitable feeds, such as natural gas streams, ethane streams, etc., can be obtained as feeds for steam crackers in olefin production units. In this way, integrating the Allam cycle, olefin production and hydrocarbon extraction can greatly promote the entire production process and significantly improve overall energy efficiency. Any remaining CO2 produced from the Allam cycle can be suitably injected into underground storage for storage, which is generally available at hydrocarbon extraction sites. Alternatively or additionally, a portion of the compressed CO2 stream can be conveniently supplied to other locations via a pipeline for sale, storage or use. In summary, the disclosed olefin production process can leave a very small CO2 footprint, in stark contrast to conventional processes that can produce large amounts of CO2.

[0068] By burning large amounts of tail gas produced in an olefin production unit in an Allam cycle in the process of the present disclosure, it is thus possible to conveniently process relatively low value fuel streams, generate large and flexible amounts of shaft power and / or electricity required by the olefin production unit, supply large amounts of process water otherwise required from external sources to the olefin production unit, supply oxygen to adjacent processes, such as the MEG production process, with greater economies of scale, and facilitate hydrocarbon extraction using a CO2 stream, all with minimized CO2 emissions and water emissions. The overall benefits of the process of the present disclosure may be enormous.

[0069] Configuration Example

[0070] Figure 3 An example of a configuration for integrating the working fluid of a pyrolysis furnace with the working fluid of a gas turbine is shown. Figure 3 , a pyrolysis reactor housing 1411 is shown, which defines a reactor volume 1410 and corresponding reactor tubes or furnace tubes 1420 within the reactor volume 1410. Figure 3The furnace tubes 1420 in the figure correspond to U-shaped tubes, but other suitable furnace tube shapes can be used. Several internal baffles 1430 are also shown. The internal baffles 1430 can extend the path of the working fluid within the reactor volume 1410 while keeping the working fluid substantially in contact with the furnace tubes 1420. During operation, a heated working fluid 1442 heated to the desired temperature of the pyrolysis environment by combustion in the low pressure burner 1440 is delivered to the reactor volume 1410. The heated working fluid 1442 flows through the reactor volume 1410 along the path defined by the baffles 1430. The extended path length created by the baffles 1430 helps transfer heat from the heated working fluid 1442 to the reactor tubes 1420. The pyrolysis feed (and any optional diluent steam) 1405 is delivered to the inlet manifold 1450, which distributes the pyrolysis feed 1405 to the various furnace tubes 1420. The pyrolysis feed 1405 reaches pyrolysis temperature within the reactor tubes to form pyrolysis effluent 1425. The pyrolysis effluent 1425 exits the furnace tubes 1420 via the outlet manifold 1460. The pyrolysis feed 1405 is heated by heat exchanging 370 with the pyrolysis effluent 1425 before entering the furnace tubes 1420. The heat exchanged pyrolysis effluent 1435 can then be further heat exchanged 373 to form steam, which can be used as a diluent for the pyrolysis feed 1405. The cooled pyrolysis effluent can then be passed to the beginning of a recovery system 377 to process the pyrolysis effluent to recover the desired product.

[0071] After transferring heat to the furnace tubes 1420, the furnace exhaust gas 301 can exit from the reactor volume 1410. The furnace exhaust gas is conveyed to a heat exchanger 310 to further cool the furnace exhaust gas. The cooled furnace exhaust gas 315 is then cooled and compressed in a series of steps 320 to remove water 322 from the remaining working fluid 325. After removing the water 322, a portion of the working fluid, now essentially consisting of CO2, can also be extracted 328. The working fluid 325 is then optionally heated 326 before entering the heat exchanger 310 to further increase the temperature of the working fluid 325. The heated working fluid 325 is then combined with a fuel 331 and oxygen 332 before entering the combustor 340. The fuel 331 and oxygen 332 are burned in the presence of the working fluid 325 to form a heated working fluid 345. The heated working fluid 345 is used to drive one or more turbines 350 to generate shaft power and / or electricity for use by various compressors and / or refrigeration units 353. The depressurized working fluid 355 is combined with additional fuel 361 and oxygen 362 for combustion in the low pressure combustor 1440 .

[0072] Figure 4 An example is shown of how the shaft power provided by a turbine can be used to power a process gas compressor. Figure 4An example of a suitable power device is schematically shown in FIG. Figure 4 In the process, the process gas (e.g. Figure 1 and 2 The process gas is directed to a cooling stage 380 (typically a quench tower or a combined quench tower-primary fractionator) via line 49 to produce a cooled process gas which is carried away via line 61. Water is a typical quench medium which may be recovered via line 39, pressurized in pump 390, directed to a cooler 400 via line 40, and sent back to the cooling stage via line 41. The cooled process gas is initially pressurized in a compressor stage 410 which typically includes at least three stages of increasing compression and inter-stage cooling. The pressurized process gas from the compression stage 410 is directed via line 42 to a process gas upgrading device, typically a caustic and / or amine treatment, schematically shown as tower 420. Spent process media (e.g., spent caustic) is carried away via line 60. The upgraded process gas is directed to a second compression stage 430 via line 62 for further pressurization. Typically, stages 410 and 430 are connected by a rotating shaft 402, which can be connected to a rotating shaft 401 for providing power to these stages. Shaft 402 obtains at least a portion of its shaft power from turbine 520 (as shown in FIG. 5 ). This can be achieved by: (i) direct transfer of rotational energy, for example, via rotational power transmission; (ii) indirect transfer, for example, by powering a generator with power 599 from turbine 520, driving an electric motor with at least a portion of the electricity generated by the generator, and using the electric motor to power shaft 401; and (iii) a combination of direct and indirect power transmission. The compressed process gas is taken away via pipeline 63 for storage and / or further processing, for example, drying, acetylene conversion and recovery of products such as ethylene.

[0073] exist Figure 3 and Figure 4 In the present invention, the processing elements can be described as being in fluid communication, which means that fluid can be transferred from one processing element to another processing element. Fluid communication includes direct fluid communication and indirect fluid communication. For example, in Figure 4 In FIG. 4 , the cooling stage 380 is in direct fluid communication with the compressor stage 410 because the fluid can flow between the cooling stage 380 and the compressor stage 410 without passing through intermediate processing elements. The cooling stage 380 is in indirect fluid communication with the tower 420 via the compressor stage 410. It should be noted that in FIG. Figure 3 In the embodiment, furnace tube 1420 is not in fluid communication with reactor volume 1410.

[0074] Additional improvements to furnace tubes and pressurized pyrolysis vessels

[0075] Operating a pyrolysis environment at high pressure (e.g., 800 kPa-a or higher) presents various additional challenges. These challenges may include providing a suitable pressurized vessel to contain the pyrolysis environment and exposing the furnace tubes to elevated external pressures at high temperatures. Additionally, the pyrolysis reaction within the tubes may be managed to reduce coking, but the tube mechanical design and external pressure are also balanced to mitigate the effects of tube creep under external pressure.

[0076] About providing suitable pressurized container for accommodating pyrolysis environment, refractory material of sufficient thickness can be added to pressure holding shell to allow furnace to maintain structural stability.Having enough pressure to hold can correspond to providing enough holding for fluid at pressure of 800kPa-a to 3000kPa-a and 1000 ℃ or higher, or 1100 ℃ or higher, for example, up to 1400 ℃ or possibly higher temperature.These conditions have proposed mechanical design challenge to both reactor shell and furnace tube.In order to provide enough pressure to hold with actual material and thickness, the inner wall of pressurized container can include the internal refractory material of about 300mm (or thicker) that meets pyrolysis furnace.Such internal refractory material can fully isolate wall, to allow the wall mechanical design close to ambient temperature.This can allow for example carbon steel or low Cr steel wall construction.

[0077] It should be noted that the working fluid in the pressurized vessel contains both H2O and CO2, because the water removal in the process cycle does not occur until the working fluid leaves the pyrolysis environment. Although CO2 remains in a supercritical state, water may potentially be in a gas phase or a liquid phase. Therefore, if the pyrolysis environment is allowed to drop to a sufficiently low temperature, there will be a possibility of forming corrosive CO2-rich water condensation on the back of the refractory. To offset this, a higher design temperature (and a higher minimum operating temperature) can be used for the reactor inner wall, such as a temperature between 160°C and 400°C. In short, this results in a shell mechanical design that is completely within the capacity range of commercially available materials and thicknesses.

[0078] The capacity of each pyrolysis reactor is selected to provide the part of the careful size of the actual shell diameter and steam cracking unit flow, to allow to maintain a reactor (as used in cracking tube replacement) without affecting the total steam cracker flux. Based on the typical configuration of pyrolysis furnace, for the world scale (world scale) 1800kTA unit based on ethane, this leads to about 7-8 reactors, each reactor has the ethylene capacity of 250-300kTA (several thousands of tons). The example of the reactor with this capacity can be a reactor comprising about 160 U-shaped tubes. Based on the average beam length calculation required tube spacing, this causes the diameter of each reactor to be 3-4.5m, as measured outside the refractory material.

[0079] In addition to maintaining structural stability, using a pressurized vessel for a pyrolysis environment presents various other challenges. For example, thermal expansion and contraction need to be considered at any point where the furnace tubes penetrate the pressurized vessel. An example of a suitable tube configuration that can account for thermal expansion and contraction is a "U-tube" type arrangement.

[0080] More generally, it may be desirable to reduce or minimize the number of different locations of the flow path of the pyrolysis feed and / or product in and out of the pressurized vessel. One option for reducing or minimizing the number of interfaces between the pyrolysis feed / product flow path and the pressurized vessel is based on the use of a manifold. The manifold for dividing the pyrolysis feed into separate reactor tubes can be located in the pressurized vessel. In order to manage the external pressure on these larger manifolds using readily available materials and actual thickness, the manifold can be located in the internal insulation portion of the pressurized hot side container. Alternatively, the refractory lined tube sheet can divide the pyrolysis feed from the inlet channel into separate reactor tubes and / or can rejoin the pyrolysis effluent in one or a reduced number of conduits at the reactor outlet. When using this option, each tube inlet can be equipped with a nozzle, a throttle or a venturi tube to improve the flow distribution among the tubes from a given manifold or distributor. These nozzles, orifices or venturi tubes provide a pressure difference for generating a temperature difference to facilitate monitoring coke accumulation.

[0081] Tube size and thickness can be selected to accommodate heat transfer and hydraulic barriers to internal coking. In one embodiment, alumina formation tubes can be used to reduce coking and allow for less coking with lower temperature tubes or smaller diameter tubes, or both. This approach can facilitate higher external mechanical design pressures to improve cycle efficiency and reduce heat transfer / floor area. Similarly, the inner diameter of the tube can be selected to reduce or minimize the pressure drop as coke accumulates in the furnace tube. If desired, small fins can be added to the tubes for enhancement (or for slightly improved heat transfer) to allow for slightly higher hot side operating pressures.

[0082] The increased pressure in the pyrolysis reactor vessel also creates some processing challenges. For example, high temperature operation in steam cracking leads to internal coking, which must be regularly monitored and decoked. For pressurized vessels operating at pressures of 800 kPa-a or higher, it is necessary to provide adequate monitoring devices without relying on visual inspection. U.S. Provisional Patent Application 62 / 611,863 details measurement techniques for monitoring coke accumulation among adjacent radiant tubes. The technique is based on the relationship between pressure and temperature along an adiabatic transition (e.g., a nozzle). This inlet temperature monitoring combined with outlet temperature monitoring and inlet pressure monitoring can provide the required monitoring of radiant tube coking (and decoking) as described in U.S. Provisional Patent Application 62 / 611,863. This temperature monitoring also enables coil leak detection, as high temperatures will indicate leakage of high pressure hot CO2 into the reactor tubes.

[0083] In addition, typical industrial use of decoking with steam and air results in an exotherm that is monitored via visual inspection of the exterior of the tubes to avoid damage due to hot spots within the tubes. In the absence of visual inspection capabilities to monitor hot spots, coke removal methods that remove coke in the absence of these exotherms can be used. U.S. Patents 3,365,387 and 8,864,977 provide examples of endothermic coke removal methods in the absence of air. For example, U.S. Patent 8.864,977 describes a method for removing coke by stopping the flow of process gases in the furnace tubes, introducing steam (or another removal fluid) into the furnace tubes, and maintaining the furnace tubes below 780°C while removing the coke. As another example, U.S. Provisional Patent Application 62 / 821,133 details methods and controls for endothermic removal of coke from a steam cracking furnace using steam at sufficiently high pressures without atmospheric discharge of the decoking effluent. As yet another example, US Provisional Patent Application 62 / 806,274 details a decoking facility that can be used to remove coke and tar from pyrolysis effluent to facilitate decoking without atmospheric emission of the decoked effluent.

[0084] When the pyrolysis effluent leaves the reactor vessel, the rapid quenching of the reaction requires the close coupling of the cooling medium and the effluent outlet. Conventionally, super high pressure (SHP) steam generators are used to cool the effluent and recover heat to drive the compression equipment. However, using a common CO2 loop to drive the compression equipment eliminates the need for the SHP steam system. On the contrary, in various aspects, the effluent is cooled by the pyrolysis reactor feed effluent heat exchange. By eliminating the atmospheric pressure heat exchange and preheating the feed with the pressurized effluent, the required amount of heat exchange can be carried out with a reduced area and volume, thereby further reducing the investment cost. After separating water from the working fluid, the working fluid leaving the combustion furnace is cooled by heat exchange with a cold working fluid, and additional heat integration can be achieved. By producing dilution steam for cracking, additional cooling required for the whole process can be carried out. Depending on economic optimization, further additional heating can be provided at medium temperatures via integration with hot CO2 loop or potential medium pressure steam condensation.

[0085] Although the power cycle based on the Allam cycle can be provided with a single loop and a generator, the steam cracking unit generally includes multiple compressors for cracked gas compression (CGC) and refrigeration compression and multiple parallel furnaces for supplying cracked gas. In various aspects, the working fluid loop for the olefin production device may include multiple burner / turbine paths and multiple burner / pyrolysis reactor paths for compression drives. As an example, in one configuration, up to 3 parallel high-pressure burner / turbine paths for 3 compression drives can be included in the working fluid loop together with 5 to 8 parallel low-pressure burner / pyrolysis reactor paths. This can provide, for example, the benefit of allowing a single reactor to be maintained while the rest of the device remains online.

[0086] The entire system and method can provide steam cracking of feeds for olefin production with an overall efficiency similar to that of prior art steam crackers (>90%). In addition, the additional facilities of the compressors are similar to those of the cracked gas compressors, with sizes and loads familiar to ethylene plant operations. The capital cost increase of these additional facilities is less than the cost of an amine unit for removing CO2 from the dilute flue gas.

[0087] General Steam Cracker Operation

[0088] In a steam cracking process using a hydrocarbon feed (e.g., a feed consisting essentially of ethane), the hydrocarbon feed is preheated, mixed with dilution steam, and then further preheated to a temperature at which significant thermal cracking is about to begin. For an ethane steam cracker, a feed comprising 50% by volume or more, or 70% by volume or more, or 90% by volume or more ethane may be used, for example, up to a feed consisting essentially of ethane (i.e., greater than 99% by volume ethane and up to 100%). In other aspects, any suitable type of feed may be used, including a vapor phase feed (consisting primarily of C4- hydrocarbons), a liquid phase feed, or a combination thereof. Examples of suitable feeds may include whole crude oil and partial crude oil, naphtha boiling feed, distillate boiling range feed, residual oil boiling range feed (atmospheric pressure or vacuum), or a combination thereof. Additionally or alternatively, a suitable feed may have a T10 distillation point of 100°C or more, or 200°C or more, or 300°C or more, or 400°C or more, and / or a suitable feed may have a T95 distillation point of 450°C or less, or 400°C or less, or 300°C or less, or 200°C or less. It should be noted that the feed for pyrolysis (e.g., steam cracking) may be fractionated to remove a bottom stream portion prior to pyrolysis so that the feed entering the pyrolysis reactor has a T95 distillation point of 450°C or less. The distillation boiling range of the feed may be determined, for example, according to ASTM D2887. If ASTM D2887 is not suitable for some reason, ASTM D7169 may be used instead.

[0089] The preheated feed and dilution steam may be conveyed to the radiant coils of the reactor, where thermal cracking occurs to produce olefins. In the radiant zone or cracking zone of a steam cracking furnace having a conventional coil outlet pressure of ˜150 kPa-g or less, the feed and dilution steam mixture is rapidly heated to a high temperature, e.g., about 1100° F.-1500° F. (˜590° C. to ˜815° C.), to produce the desired product range. During such conventional operation, the residence time of the feed in the radiant zone or cracking zone may be quite low, e.g., about 0.1 to 0.3 seconds.

[0090] Immediately after the radiant zone, the mixture is rapidly cooled to quench the thermal cracking reactions. In various aspects, cooling to quench the thermal cracking reactions can be performed in part by heat exchange with the input feed to the furnace tubes.

[0091] Representative process gas compressors

[0092] In the compressor stage, the process gas is typically compressed to a pressure of 20 bar (2000 kPa) to 40 bar (4000 kPa) in a centrifugal compressor powered by shaft power. Typically, the process gas compressor comprises at least four stages, each stage sequentially providing a pressure increase over its previous stage. Cooling is typically employed between the stages, for example to prevent compressor damage, to prevent fouling caused by diene polymerization, and to facilitate separation of process gas components. The present invention is compatible with conventional process gas compressors, but the invention is not limited thereto. Example

[0093] This prophetic example is provided to illustrate the operation of a commercial scale steam cracker process train in which one or more pressurized pyrolysis environments and one or more turbines share a working fluid containing CO2.

[0094] The capacity of each pyrolysis reactor is selected to provide a practical shell diameter and a prudently sized portion of the steam cracking unit flow, to allow maintenance of one reactor (as used in cracking tube replacement) without affecting the total steam cracker flux. Based on the typical configuration of a pyrolysis furnace, for a world-scale 1800kTA unit based on ethane, this results in about 7-8 reactors, each with an ethylene capacity of 250-300kTA. A reactor with about 160 U-tubes can provide this capacity. Based on the average beam length calculation required tube spacing, this results in a diameter of about 3m-4.5m for each reactor outside the refractory material. In order to manage the corresponding processing equipment group for compressing and separating process gas, up to three turbines can be used.

[0095] The furnace tubes may correspond to U-tubes with an outer diameter of about 115 mm. Based on the elevated operating pressure, the triangular tube spacing may be set to 1.7-3.0 times the outer diameter to give the same radiation efficiency as a much larger firebox operating at a conventional 1.0 bar total pressure (0.3 bar total partial pressure of CO2 and H2O), while greatly reducing the land space and investment costs.

[0096] In this embodiment, the pressurized pyrolysis environment can be operated at an operating pressure of 13 bar (-1300 kPa-a). By using a working fluid containing essentially only CO2 and H2O (thus, essentially no non-radiative N2 in the working fluid), the radiative efficiency per unit volume is 40-45 times the radiative efficiency per unit volume of a conventional pyrolysis environment. Therefore, the average beam length can be reduced to ~1 / 40 or 1 / 45 of the state of conventional systems, thereby reducing land space requirements.

[0097] As an example, the furnace calculation formula from Process Heat Transfer, DQ Kern, Tata McGraw-Hill, 1997, page 691 can be used to calculate the appropriate beam length. The beam length for radiant heat transfer is defined as:

[0098] For a firebox with a size ratio of 1×2×3, L (ft) = 2 / 3×(length×width×height) 0.333 Based on this formula, L (ft) = 0.4 x (tube CL-CL distance in inches) - 0.567 x (tube OD in inches) for tightly packed tube bundles, such as in a convection section or in a pressurized radiant / convective heat transfer zone, such as those proposed herein.

[0099] Using the increased pressure and concentration of the radiant flue gases, beam lengths can be reduced to an unexpected degree, thereby greatly reducing floor space and capital equipment costs.

[0100] Furthermore, by closely coupling the tubes and providing moderate flue gas velocities powered by internal pressure, additional heat transfer efficiency can be provided via convection to further save investment.

[0101] As an example of using this type of configuration, you could use something like Figure 2The process cycle of the cycle shown in . The fuel and oxygen input 610 can correspond to 90 tons per hour. This fuel is added to the substantially pure CO2 working fluid from the previous process cycle, about 3300 tons per hour. The combined fuel and working fluid can be at a pressure of about 20,000 kPa-a (~20 MPa-a). About 3400 tons of working fluid and fuel per hour are distributed between three burners for three turbines to provide power for process gas compressors and refrigeration units for treating pyrolysis effluents. After providing power to the turbines, the pressure of 3400 tons of working fluid per hour is reduced to about 3000 kPa-a. Another 90 tons of fuel and oxygen per hour are added to the low-pressure working fluid of 3400 tons per hour. This fuel and low-pressure working fluid of about 3500 tons per hour are passed into seven burners, each of which is tightly coupled with a corresponding pressurized pyrolysis reactor. After providing heat for the pyrolysis environment, the pressure of 3500 tons of working fluid per hour can be further reduced to about 1300 kPa-a. The decompressed working fluid can then be heat exchanged with the substantially pure CO2 working fluid used at the beginning of the process cycle. After the heat exchange, in a series of cooling and compression steps, about 100 tons of water can be removed from the working fluid per hour. It should be noted that if tail gas from a steam cracking process is used as a fuel instead of natural gas, the amount of water removed at this time can be greater. After dehydration, the substantially pure CO2 working fluid can be at a pressure of about 8000kPa-a. At this point, about 90 tons of CO2 can be removed per hour to maintain a constant level of working fluid in the loop. It should be noted that if tail gas from a steam cracking process is used as a fuel instead of natural gas, the amount of CO2 removed can be less. The remaining working fluid can then be compressed to a desired pressure of about 20MPa-a for the burner associated with the turbine.

[0102] This type of configuration can be used to steam crack a feed containing 100 tons / hour of ethane and 30 tons / hour of diluent steam. This feed can be passed into a furnace tube for pyrolysis. The resulting pyrolysis effluent can include a mixture of hydrocarbons and hydrogen, including more than 50% by weight of ethylene.

[0103] Additional Configuration Examples - Integration with Security Mitigation Devices

[0104] Cracking furnaces are often equipped with emergency shutdown systems (trip systems) that automatically place the furnace in a safe condition when a potentially unsafe condition is detected on the furnace. Historically, these trip systems shut down at least a portion of the incoming feed to the steam cracker furnace tubes, using supplemental steam as needed to maintain sufficient temperatures to prevent cracking on the coke layer inside the tubes.

[0105] Ethylene plants are always equipped with a flare system to safely burn excess gas that may be generated, for example, by shutting down the process gas compressor. With the process gas compressor shut down, gas continues to enter the quench tower from the furnace and the quench tower pressure increases. At a preset pressure, the pressure relief valve on the quench tower will open to the flare system to prevent excessive pressure from damaging the quench tower.

[0106] Historically, ethylene plants have used elevated flares, where a large amount of gas is burned in a single large flare tip. The flare tip is designed to promote mixing of air with the flare gas, but the volume and composition of the gas burned after a process gas compressor trip typically results in significant smoke at the flare tip. Adding steam to the flare gas has proven to be effective in suppressing flare tip smoke, but it has been found that the cooling / dilution effect of the steam reduces hydrocarbon combustion efficiency. Therefore, rather than completely burning the flare gas into CO2 and H2O, some incompletely burned hydrocarbons are released into the atmosphere. These compounds are believed to be air pollutants and may contribute to the formation of photochemical smog.

[0107] In order to achieve smokeless combustion while also achieving high hydrocarbon destruction efficiency, modern ethylene plants are often equipped with so-called "ground flares". A ground flare consists of a large number of small burner tips, each designed to draw in enough air to burn without smoke. A ground flare covers a fairly large area of ​​real estate and is often equipped with a radiant barrier wall around its perimeter.

[0108] Ground flares rely on a flare gas with a sufficiently high heating value (usually measured in BTU / SCF (British thermal units [energy] per standard cubic foot [volume])) to ensure complete combustion of the contained hydrocarbons and also to allow each individual burner tip to ignite from the flame on an adjacent burner tip (so-called "cross-firing"). A common requirement is to have a flare gas with a heating value of no less than 800 BTU / SCF (~30 MJ / m 3 ) of the flare gas. Unfortunately, during a steam partial trip when the process gas compressor is also shut down, steam used to protect the furnace tubes is added to the flare gas. This additional steam from the process gas compressor can significantly reduce the calorific value of the flare gas. In order to maintain the target calorific value of the flare gas, a large amount of additional feed and / or fuel must be added to the flare gas, resulting in a large amount of additional CO2 emissions.

[0109] In some aspects, various amounts and pressures of CO2 used as a working fluid in the Allam cycle can allow large amounts of flare gas to be recycled back into the loop for the Allam cycle, rather than just uneconomically burned. In addition to reducing costs, this can also reduce, minimize or avoid environmental emissions.

[0110] As mentioned above, Figure 2An example of an Allam cycle using a common CO2-containing working fluid is shown, which is used for a) a turbine for providing shaft power to a pyrolysis effluent treatment train and b) a low-pressure burner for providing heat to a pyrolysis furnace. When a "trip" event occurs, the feed to the pyrolysis tube is usually reduced or minimized so that the pyrolysis effluent does not need to be treated. This means that the need for shaft power for the process gas compressor (and / or other compressors and / or cooling stages for treating pyrolysis effluent) is reduced or minimized. Therefore, during a trip event, the CO2 working fluid loop can potentially be used for other purposes.

[0111] In some aspects, during a trip event, rather than exhausting gas from the process gas compressor and / or quench tower and / or other locations as flare gas, the exhaust gas can be redirected into the CO2 working fluid loop. Figure 2 As shown, the CO2 working fluid in the working fluid circuit has a pressure of about 30MPa-a before being used to drive the turbine to provide shaft power. Instead of driving the turbine, this pressurized CO2 can be used to separate a large amount of flare gas to form a combined working fluid and flare gas stream having a pressure suitable for delivery to a low-pressure burner. This can be achieved by combining the pressurized CO2 working fluid and the flare gas so that the mass flow rate of the pressurized CO2 working fluid is about 4 to 10 times (or 5 to 7 times) the mass flow rate of the flare gas. This can produce a combined working fluid and flare gas stream having a pressure of about 1.0MPa-a to 4.0MPa-a, which is suitable for introduction into a low-pressure burner.

[0112] In this type of configuration, the limit of flare gas consumed corresponds to the amount of combustion that can be tolerated in the reactor, which is similar to the amount of burnt effluent produced during a conventional process gas compressor trip situation. Therefore, the flare gas output can be valuably controlled by the reactor feed rate, which is heated by the circulating flare gas. Typically, in these cases, in order to park the furnace or reactor in a safe state and minimize combustion, the hydrocarbon feed is replaced with steam, minimizing hydrocarbons in the unit and keeping the reactor warm. However, major flare scenarios like these in conventional or ground flare systems are controlled by challenging standards for maintaining combustion efficiency in the flare. These standards are necessary to prevent the release of hydrocarbons to the environment, but also limit operating flexibility and upset response by limiting the steam in the furnace effluent from entering the flare. By injecting the flare material into a low-pressure burner, and keeping the flare material within the loop, the emissions can be burned more efficiently at higher pressures, even at higher steam rates. Furthermore, the destruction efficiency is not as important as in direct atmospheric emissions, since the remaining unburned material will circulate in the loop until completely burned or emitted as a trace component of the CO2 stream.

[0113] All patents, test procedures and other documents cited herein, including priority documents, are fully incorporated by reference to the extent that they are not inconsistent with such disclosure. Therefore, the scope of the claims attached to this specification is not considered to be limited to the embodiments and descriptions given here, but the claims are considered to include all features of novelty that can obtain patent rights in this article, including all other features that are considered to be equivalent to these features by a person skilled in the art of the relevant technology of the present invention. When a lower limit and an upper limit are specified, the range from any lower limit to any upper limit is clearly within the scope of the present invention. The term "comprising" and the term "including" are synonymous. When a composition, element or group of components is preceded by the transitional phrase "comprising", the same composition or group of components is preceded by the transitional phrase "essentially composed of", "consisting of", "selected from" or "is" before the description of the composition, component or multiple components, and vice versa. Unless explicitly indicated as a gauge pressure (barg, kPag, psig), the pressure value is absolute (bar, kPa, psi or psia).

Claims

1. A method for pyrolysis, comprising: separating at least an oxygen-containing stream from air, the oxygen-containing stream comprising 90% by volume or more O2; combusting a first fuel with a first portion of the oxygen-containing stream at a pressure of 10 MPa-a or more in the presence of at least a portion of a circulating stream, the circulating stream comprising 80% by volume or more CO2 to produce a heated working fluid; operating a turbine using the heated working fluid to generate power and an intermediate working fluid, the intermediate working fluid comprising at least CO2 and H2O; combusting a second fuel with a second portion of the oxygen-containing stream in the presence of the intermediate working fluid to form a heated intermediate working fluid; exposing the heated intermediate working fluid to a plurality of furnace tubes in a pressurized pyrolysis environment to transfer heat to the plurality of furnace tubes and produce a depressurized working fluid having a pressure of 800 kPa-a to 3000 kPa-a, wherein the depressurized working fluid comprises 90% by volume or more of CO2 and H2O; pyrolyzing at least a portion of a hydrocarbon-containing feed in the plurality of furnace tubes to form a pyrolysis effluent, the pyrolysis effluent comprising at least a process gas comprising ethylene; transferring at least a portion of the generated power a) to a process gas compressor to compress the process gas, b) to a refrigeration compressor to cool the process gas, c) to a refrigeration compressor to cool the decompressed working fluid in a cooling step from a series of cooling and compressing steps, or d) a combination of two or more of a), b) and c); subjecting the depressurized working fluid to a series of cooling and compression steps to form a water stream and a CO2-containing stream, the CO2 in the depressurized working fluid and the CO2-containing stream being in a single phase during the series of cooling and compression steps; and At least a portion of the CO 2 -containing stream is compressed to form a compressed CO 2 -containing stream, and the recycle stream comprises at least a first portion of the compressed CO 2 -containing stream.

2. The method of claim 1, wherein compressing at least a portion of the process gas using the generated power comprises direct power transfer of the generated power, indirect power transfer of the generated power, or a combination thereof.

3. The method of claim 1, wherein at least one of the first fuel and the second fuel comprises a tail gas formed from a compressed process gas.

4. The method of claim 1, wherein at least one of the first fuel and the second fuel comprises one or more of: (i) natural gas, (ii) hydrocarbons in the natural gas, (iii) hydrocarbons separated from and / or derived from the natural gas, (iv) natural gas condensate, (v) hydrocarbons in the natural gas condensate, (vi) hydrocarbons separated from and / or derived from the natural gas condensate, (vii) crude oil, (viii) hydrocarbons in the crude oil, (viii) hydrocarbons separated from and / or derived from the crude oil, and (ix) molecular hydrogen.

5. The process of claim 1, wherein the feed comprises >10 wt% C 2+ hydrocarbon.

6. The process of claim 1, wherein the compressed CO2-containing stream comprises a pressure of 10 MPa-a or higher.

7. The method of claim 1, wherein the intermediate working fluid comprises a pressure of 3000 kPa-a to 6000 kPa-a.

8. The method of claim 1, further comprising transferring at least a second portion of the generated power to a compressor for i) compression in the series of cooling and compression steps, ii) compression of the CO2-containing stream, or iii) a combination of i) and ii).

9. The method of claim 1, wherein pyrolyzing the feed comprises pyrolyzing the feed under steam cracking conditions.

10. The process of claim 1, wherein the recycle stream comprises 95% by volume or more CO2.

11. The method of claim 1, further comprising exchanging heat between at least a portion of the depressurized working fluid and at least a portion of the circulating stream.

12. The method of claim 1, further comprising exchanging heat between at least a portion of the pyrolysis effluent and at least a portion of the feed.

13. The process of claim 1, wherein at least a portion of the water stream is (i) fed to the pyrolysis step to mix with the hydrocarbon-containing feed; (ii) heated to generate steam; (iii) used as an indirect cooling medium; (iv) used as a quenching medium; and (iv) fed to the hydrocarbon-containing stream as a diluent.

14. The method of claim 1, further comprising: recovering an ethylene stream from the process gas; contacting at least a portion of the ethylene stream with at least a portion of the oxygenated stream to produce an oxygenated stream; and A monoethylene glycol product is produced from the oxidized stream.

15. The process of claim 14, wherein the oxidized stream comprises ethylene oxide, and the step of producing the monoethylene glycol product comprises contacting the ethylene oxide with CO2 derived from the compressed CO2 stream and / or the CO2-containing stream.

16. The method of claim 1, further comprising at least one of the following steps: supplying a portion of the compressed CO2 stream to a storage device; carrying away a portion of the compressed CO2 stream in a pipeline; A portion of the compressed CO 2 stream is used to extract a hydrocarbon source material, and at least a portion of the hydrocarbon-containing feed is derived from the hydrocarbon source material.

17. A system for performing the method of any one of claims 1 to 16, comprising: First compression stage; a first burner including a high pressure burner inlet and a high pressure burner outlet, the high pressure burner inlet being in fluid communication with a first fuel source and the first compression stage; a turbine in fluid communication with the high pressure combustor outlet; a second combustor including a low pressure combustor inlet and a low pressure combustor outlet, the low pressure combustor inlet being in fluid communication with the turbine and a second fuel source; a pyrolysis reactor housing comprising a reactor volume containing a plurality of furnace tubes, the reactor volume being in fluid communication with the low pressure burner outlet, the plurality of furnace tubes being in fluid communication with a feed source; a water separation stage in fluid communication with the reactor volume, the water separation stage comprising a working fluid outlet in fluid communication with the first compression stage; and A pyrolysis effluent processing stage is in fluid communication with the plurality of furnace tubes, the pyrolysis effluent processing stage comprising a process gas compressor and one or more refrigeration compressors, at least one of the process gas compressor and the refrigeration compressor of the one or more refrigeration compressors being coupled to the turbine to provide power.

18. The system of claim 17, further comprising a first heat exchanger stage, the reactor volume being in fluid communication with the water separation stage via the first heat exchanger stage, and the first compression stage being in fluid communication with the first combustor via the first heat exchanger stage.

19. The system of claim 17 or claim 18, further comprising a second heat exchanger stage, the process gas compressor being in fluid communication with the plurality of furnace tubes via the second heat exchanger stage, and the plurality of furnace tubes being in fluid communication with the feed source via the second heat exchanger stage.

20. The system of claim 17 or claim 18, wherein the water separation stage comprises a plurality of cooling stages and a plurality of second compression stages.

21. The system of claim 17 or claim 18, wherein the process gas compressor is coupled to the turbine.

22. The system of claim 17 or claim 18, wherein the system further comprises a glycol production stage in fluid communication with an oxygen source and the pyrolysis effluent processing stage.

23. The system of claim 17 or claim 18, wherein the system further comprises a water conduit establishing fluid communication between the plurality of cooling and compression stages and at least one of the pyrolysis reactor and the pyrolysis effluent processing stage.

24. A method of operating a steam cracker during a trip event, comprising: separating air to form at least an oxygen-containing stream, the oxygen-containing stream comprising 90% by volume or more O2; Withdrawing a flare gas stream with a recycle stream to form an intermediate working fluid, the recycle stream comprising 80% by volume or more CO2 and a pressure of 10 MPa-a or more; combusting the intermediate working fluid with a portion of the oxygen-containing stream to form a heated intermediate working fluid; exposing the heated intermediate working fluid to a plurality of furnace tubes in a pressurized pyrolysis environment to transfer heat to the plurality of furnace tubes and produce a depressurized working fluid having a pressure of 800 kPa-a to 3000 kPa-a, wherein the depressurized working fluid comprises 90% by volume or more of CO2 and H2O; subjecting the depressurized working fluid to a series of cooling and compression steps to form water and a CO2-containing stream, the CO2 in the depressurized working fluid and the CO2-containing stream being in a single phase during the series of cooling and compression steps; and At least a portion of the CO 2 -containing stream is compressed to form a compressed CO 2 -containing stream, and the recycle stream comprises at least a first portion of the compressed CO 2 -containing stream.

25. The method of claim 24, wherein combusting the intermediate working fluid further comprises combusting a second fuel.

26. A steam cracking process comprising: separating at least an oxygen-containing stream from air, the oxygen-containing stream comprising 90% by volume or more O2; combusting a first fuel with a first portion of the oxygen-containing stream in the presence of at least a portion of a circulating stream comprising CO2 to produce a heated working fluid; operating a turbine using the heated working fluid to generate power and an intermediate working fluid, the intermediate working fluid comprising at least CO2 and H2O; combusting a second fuel with a second portion of the oxygen-containing stream in the presence of the intermediate working fluid to form a heated intermediate working fluid; exposing the heated intermediate working fluid to a plurality of furnace tubes in a pressurized pyrolysis environment to transfer heat to the plurality of furnace tubes and produce a depressurized working fluid having a pressure of 800 kPa-a to 3000 kPa-a, wherein the depressurized working fluid comprises 90% by volume or more of CO2 and H2O; in an olefin production unit, pyrolyzing at least a portion of a hydrocarbon-containing feed in the plurality of furnace tubes in the presence of steam to form a pyrolysis effluent comprising ethylene; transferring at least a portion of the generated power to at least one process gas compressor and / or at least one refrigeration compressor; cooling and separating the depressurized working fluid to form a CO2-containing stream; and At least a portion of the CO 2 -containing stream is compressed to form a compressed CO 2 -containing stream, and the recycle stream comprises at least a first portion of the compressed CO 2 -containing stream.

27. The method of claim 26, further comprising: recovering ethylene from the pyrolysis effluent; contacting at least a portion of the recovered ethylene with oxygen in a portion of the oxygenated stream to produce an oxidized stream; and Monoethylene glycol is produced from the oxidized stream.

28. The process of claim 27, wherein the oxidized stream comprises ethylene oxide, and the step of producing monoethylene glycol from the oxidized stream comprises contacting the ethylene oxide with CO2 in a portion of the compressed CO2 stream and / or a portion of the CO2-containing stream.

29. The process of claim 26 or claim 27, further comprising cooling and separating the depressurized working fluid to form a water stream, wherein at least a portion of the water stream (i) is fed to the pyrolysis step to mix with the hydrocarbon-containing feed; (ii) heating to generate steam; (iii) use as an indirect cooling medium in an olefin production unit; (iv) used as a quench medium in an olefin production unit; and (iv) fed as a diluent to a hydrocarbon-containing stream.

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