Impurity removal in hydrocarbon product production processes

Abstract

A process for producing a hydrocarbon product, the process comprising: i) passing a feedstock derived from renewable and / or fossil sources through a hydrotreating step to produce a primary hydrotreated stream; the hydrotreating step comprises: passing the feedstock through one or more catalytic hydrotreating units with the addition of hydrogen to produce a first hydrotreated stream; passing the first hydrotreated stream to a first separation step, said first separation step comprising the use of a separation unit, in particular, to remove impurities H2S, CO, CO2 and H2O; removing an overhead stream from the first separation step and separating an overhead hydrocarbon liquid stream thereof, the overhead hydrocarbon liquid stream being sent to the first separation unit as a reflux stream; withdrawing a bottoms stream from the first separation step and passing at least a portion of the bottoms stream to a dewaxing step comprising using one or more catalytic hydrotreating units with the addition of hydrogen to produce the main hydrotreated stream; and ii) passing the main hydrotreated stream to a second separation step to produce the hydrocarbon product.

Description

[0001] This application is a divisional application of Chinese invention patent application filed on August 13, 2021, with application number 202180055087.0 and invention title "Impurity Removal in Hydrocarbon Product Production Method". Technical Field

[0002] This invention relates to a method for producing hydrocarbons from feedstocks derived from renewable and / or fossil sources, particularly hydrocarbons boiling above 30°C, such as jet fuels, suitably wherein fossil sources constitute a small fraction of the feedstock, totaling at most 30 wt% or less, for example, at most 10 wt%. The method includes feeding the feedstock to a hydrotreating step comprising one or more catalytic hydrotreating units and a dewaxing step, thereby significantly reducing the content of impurities such as H2S, H2O, CO, and CO2 that may be detrimental to the catalyst used in the dewaxing step in a separation step prior to the dewaxing step. Background Technology

[0003] There is growing interest in producing jet fuel or jet fuel and diesel fuel using renewable feedstocks or by co-processing with conventional fossil fuel feedstocks. In particular, when processing renewable feedstocks, oxygen is primarily removed as H₂O during hydrotreating, yielding alkane fuels composed of alkanes with the same number of carbon atoms as the triglyceride backbone. This is known as the hydrodeoxygenation (HDO) pathway. Oxygen can also be removed via a decarboxylation pathway, which produces CO₂ instead of H₂O. HDO pathway: C 17 H 34 COOH + 3.5 H2 C 18 H 38 + 2 H2O Decarboxylation pathway: C 17 H 34 COOH + 0.5 H2 C 17 H 36 + CO2

[0004] Some renewable energy sources also contain nitrogen. Removing nitrogen also requires hydrogen, a process known as hydronitrogen removal (HDN).

[0005] When producing hydrocarbon products, particularly jet fuel or jet fuel and diesel, the feedstock undergoes a hydrotreating step in the hydrotreating section. This step typically involves HDO to obtain a hydrotreated stream, which is then fed to a first separation step, which typically involves using a separation unit, such as a high-pressure stripper (HP stripper), from which the overhead stream is removed. This overhead stream is partially condensed, and the resulting liquid hydrocarbon fraction is fed directly to a downstream dewaxing step, which is included in the hydrotreating step or dewaxing section, where hydroisomerization and possible hydrocracking side reactions occur. After the dewaxing step, the hydrotreated stream is typically fed to another separation step to produce the hydrocarbon product.

[0006] In the dewaxing step, precious metal catalysts are used, which are easily contaminated and thus compromised by impurities carried in the hydrocarbon liquid, particularly H2S. Other impurities, such as H2O, NH3, CO, and CO2, may also be present. When operating with feedstocks from fossil fuel sources, the sulfur content is high, so hydrotreating in the form of hydrodesulfurization (HDS) or hydronitrogen removal (HDN) is typically performed. When operating with feedstocks from renewable sources, the sulfur content is significantly lower, so hydrotreating includes HDO and optionally HDN treatment. As a result, the hydrotreating stream contains not only H2S but also H2O, NH3, CO, and CO2 as impurities, which need to be removed before the downstream dewaxing step.

[0007] EP 2362892 A1 (WO 2010 / 053468 A1) discloses the hydrotreating of fuel feedstocks derived from bio-components, and the hydrotreating of blends of bio-components and fossil fuel feedstocks. More specifically, this citation discloses a method for producing diesel fuel from a bio-component feedstock, comprising hydrotreating the feedstock followed by catalytic dewaxing. The hydrotreated feedstock can be directly cascaded to the dewaxing step, or the hydrotreated feedstock can be intermediately separated in a separation unit such as a fractionating column. The use of reflux in the separation unit is not explicitly or implicitly disclosed: the use of a fractionating column does not necessarily imply that it has reflux, and it is clearly not the focus of this citation. A reboiler with feed to the first stage and no recirculation can easily be considered a fractionating column.

[0008] US 2002 / 112990 A1 discloses a method for hydrotreating fossil fuels in two or more hydrotreating stages, wherein liquid and vapor products from a first stage are fed to a separation zone (S), where a liquid phase fraction is separated from a vapor phase fraction containing evaporated heavy hydrocarbon components. In the presence of an adsorbent (STA), the vapor phase fraction is fed to an adsorption zone (ST), where at least a portion of the heavy hydrocarbon components is removed. Both the liquid phase fraction and the adsorbed heavy hydrocarbon components are fed to at least one additional hydrotreating stage. Optionally, partial condensation and reflux are present in the adsorption zone (ST) to remove high-boiling hydrocarbon components (heavy tail fractions) from the vapor fraction. No stripping or reflux occurs in the separation zone (S), therefore impurities H₂S, H₂O, NH₃, CO, and CO₂ in the bottom stream are directly sent to the second hydrotreating stage.

[0009] US 2005 / 167334 A1 discloses hydrotreating of fossil fuels, wherein the hydrotreating includes hydrodesulfurization, hydrodenitrogenation, hydrodemetallization (to remove one or more metals, such as vanadium, nickel, iron, sodium, titanium, silicon, and copper), and hydrodearomatization. The hydrotreating includes at least two reaction steps, with intermediate stripping of the effluent from the first step and reflux, each step being carried out using a dedicated hydrogen recirculation loop to remove a portion of the H2S formed. The hydrotreating in the first reaction step does not include HDO, therefore its effluent does not contain additional impurities in the form of CO or CO2 besides H2O. Summary of the Invention

[0010] The purpose of this invention is to significantly reduce the content of impurities H2S, H2O, NH3, CO and CO2, which may come into contact with the noble metal catalyst used in the dewaxing process.

[0011] This invention solves this objective and other objectives.

[0012] Therefore, the present invention provides a method for producing hydrocarbon products, the method comprising: i) Passing feedstocks derived from renewable and / or fossil sources through a hydrotreating step to produce a main hydrotreating stream; said hydrotreating step includes: - In the presence of hydrogen, the feedstock is passed through one or more catalytic hydrotreating units to produce a first hydrotreating stream, for example, a stream containing C1-C30+ hydrocarbons, the hydrotreating stream (i.e. the first hydrotreating stream) containing the following impurities: H2S, NH3, CO, CO2 and H2O; - The first hydrogenation process stream is fed to a first separation step, the first separation step including the use of a separation unit to remove impurities; - From the first separation step, for example from the separation unit, the overhead stream is taken out and its overhead hydrocarbon liquid stream is separated, and at least a portion of the overhead hydrocarbon liquid stream is sent back to the first separation unit as a reflux stream; - From the first separation step, for example from the separation unit, the bottom flow is extracted; - At least a portion of the bottom stream is sent to a dewaxing step, which includes using one or more catalytic hydrotreating units with the addition of hydrogen to produce the main hydrotreating stream; ii) The main hydrotreating stream is fed to a second separation step to produce the hydrocarbon product; One or more catalytic hydrotreating units used to produce the first hydrotreating stream include hydrodeoxygenation (HDO) and optional hydrodenitrification (HDN); One or more catalytic hydrotreating units in the dewaxing step for producing the main hydrotreating stream include hydrodewaxing (HDW) in the presence of a noble metal catalyst and optional hydrocracking (HCR); and The entire overhead hydrocarbon liquid stream (i.e., at least a portion of the overhead hydrocarbon liquid stream is the entire overhead hydrocarbon liquid stream) is sent to the separation unit as a reflux stream.

[0013] It should be understood that impurities are H2S, NH3, CO, CO2, and H2O, or combinations thereof. For example, impurities can be CO and CO2.

[0014] The first hydrotreating stream from the catalytic hydrotreating unit typically contains such impurities that can be detrimental to the catalyst used in subsequent dewaxing steps. When operating in so-called sweet mode, as in this invention, the catalyst in the catalytic hydrotreating unit (hydrodewaxing unit, HDW) used for the dewaxing step is a precious metal catalyst that is sensitive to impurities, thus requiring a first separation step, such as using a high-pressure separator or a separation unit in the form of a tower, to reduce the impurity content.

[0015] By means of this invention, instead of feeding the overhead hydrocarbon liquid stream from, for example, the separation unit as part of the feed to the dewaxing step, the overhead hydrocarbon liquid stream is used as reflux from the separation unit. It has been found, as shown in the examples below, that impurities in the feed entering the dewaxing step, particularly H2O and H2S, are significantly reduced, for example, by an order of magnitude, thereby avoiding the degradation of the precious metal catalyst used therein.

[0016] This invention is particularly useful in the production of jet fuel or a combination of jet fuel and diesel. When producing only diesel, the overhead stream from the separation unit (e.g., an HP stripper) in the first separation step typically bypasses the catalytic hydrotreating unit in the dewaxing step entirely, thus requiring no protection. Ultimately, it becomes a small portion of the overall diesel product stream, so it is acceptable if it does not pass through the catalytic hydrotreating unit in the dewaxing step, as this does not affect the overall properties of the diesel.

[0017] However, the overhead stream from the separation unit in the first separation step contains some jet fuel boiling range components. Therefore, these components need to be dewaxed during jet fuel production to isomerize them. Failure to do so risks failing to meet jet fuel product specifications, particularly the jet fuel freezing point specifications. Here, according to the invention, the overhead stream from the separation unit, such as the overhead stream from an HP stripper, is extracted, partially condensed in, for example, an air cooler, and sent to another (cold) separator to extract the condensed hydrocarbon liquid stream, i.e., the overhead hydrocarbon liquid stream. While this stream is typically fed directly to the dewaxing step as feed, the invention uses it as reflux to the column, resulting in surprisingly better overall impurity removal and thus better protection of the catalytic hydrotreating unit used in the dewaxing step.

[0018] In step ii), the main hydrotreating stream obtained from the dewaxing step is fed to a second separation step, which suitably includes the use of separators, such as cold separators and stripping sections, including product strippers and fractionators, such as distillation columns, to produce hydrocarbon products, particularly jet fuel, diesel and naphtha.

[0019] In one embodiment, step ii) includes feeding the main hydrotreating stream to a separator, preferably a cold separator, to produce an aqueous stream (acidic water stream), a hydrogen-rich stream, and a hydrocarbon stream, the hydrocarbon stream being further separated into the hydrocarbon products in a subsequent stripping section; and wherein the hydrogen-rich stream is supplied as a single recycle loop in the method by adding it to one or more catalytic hydrotreating units for producing the first hydrotreating stream.

[0020] Therefore, a single (common) recirculation loop for hydrogen recirculation is provided, allowing hydrogen-rich gas from the cold separator to be added not only to the HDO step, for example, before the first separation step, but also optionally to the dewaxing step after the first separation step. A single hydrogen recirculation compressor is required, rather than a separate recirculation compressor and additional piping, to independently add hydrogen to either the HDO or dewaxing step.

[0021] In one embodiment, the method further includes adding the hydrogen-rich stream to a dewaxing step, which includes using one or more catalytic hydrotreating units to produce the main hydrotreating stream.

[0022] In another embodiment, the hydrogen-rich stream is not added to the dewaxing step. Instead, supplemental hydrogen, for example from an external source, is added to the dewaxing step. Suitably, the supplemental hydrogen is mixed with the hydrogen-rich stream (recycled gas) after passing through the dewaxing step and then directed back to the HDO step as a single recycle gas loop. In other words, according to this embodiment, the method further includes: not adding a hydrogen-rich stream to the dewaxing step, adding supplemental hydrogen, such as supplemental hydrogen from an external source, to the dewaxing step, and mixing it with the hydrogen-rich stream after passing through the dewaxing step to generate a mixed hydrogen stream, which is then supplied as the single recycle loop. Using only supplemental hydrogen is advantageous because, unlike the hydrogen-rich stream, supplemental hydrogen is essentially pure H2 and therefore free of contaminants.

[0023] In one embodiment, the method further includes: separating an overhead gas stream containing impurities from the overhead stream from the first separation step, and sending the overhead gas stream to the separator in step ii) after suitably mixing it with the main hydrogenation process stream and suitably cooling it subsequently in, for example, an air cooler.

[0024] Therefore, impurities such as H2S and NH3 are carried away and discharged along with the acidic water stream from the separator (e.g., a cold separator), while providing the single (common) recirculation loop for hydrogen recirculation. This enables further integration, simplification, and flexibility of the method.

[0025] In one embodiment, the hydrocarbon product boils at above 30°C and comprises one or more of the following: jet fuel, diesel oil, naphtha, and optionally a lubricating oil base oil (for lubricating oils). In a particular embodiment, the hydrocarbon is jet fuel or jet fuel and diesel oil.

[0026] According to the present invention, for example, the entire overhead hydrocarbon liquid stream from the first separation step of the separation unit is fed to the separation unit as a reflux stream.

[0027] Therefore, complete reflux is provided, i.e., using the entire overhead hydrocarbon liquid stream. As used herein, the term "entire" refers to 95 wt% or more of the overhead hydrocarbon liquid stream, suitably 100 wt%. Thus, complete reflux of the overhead hydrocarbon liquid stream is provided, and the only feed to the dewaxing step is the feed from the bottom of the first separation step, such as the feed from the separation unit. This further increases the removal of impurities, for example, by an order of magnitude or more for some impurities (more specifically, for H₂O and H₂S).

[0028] It should be understood that when full reflux is present, the bottom stream from the first separation step, especially the bottom stream from the separation unit, is the stream destined for the dewaxing step.

[0029] It should also be understood that, if reflux is partial rather than complete, the purified first hydrogenation process stream is optionally formed by combining the bottom stream from the first separation step, particularly the bottom stream from the separation unit, with a portion of the non-refluxed overhead liquid stream. The purified first hydrogenation process stream is then sent to the dewaxing step. At least a portion of the bottom stream from the first separation step, particularly at least a portion of the bottom stream from the separation unit, and a portion of the non-refluxed overhead liquid stream may be sent separately (i.e., without combining these streams) to the dewaxing step.

[0030] In one embodiment of the invention, the hydrocarbon product boils at a temperature above 30°C and comprises one or more of the following: jet fuel, diesel oil, naphtha, and optionally a lubricating oil base oil. Suitably, the hydrocarbon product is jet fuel or a mixture of jet fuel and diesel oil.

[0031] In one embodiment of the invention, in the first separation step, the separation unit is a high-pressure stripper (HP stripper). An HP stripper is also called an HP stripping tower.

[0032] HP strippers are well known in the art. HP strippers offer optimal impurity removal. The stripping medium for HP strippers can be makeup hydrogen (i.e., hydrogen-rich makeup gas), separator tail gas (e.g., thermal separator tail gas), or nitrogen. For example, HP strippers can operate in a pressure range of 40-70 bar and a temperature range of 150-250°C.

[0033] In one embodiment, the first separation step further includes using a thermal separator upstream of the separation unit.

[0034] The liquid from the thermal separator is sent to a downstream separation unit (e.g., an HP stripper), thereby increasing the flexibility and precision of the stripping step in the process.

[0035] As is well known in the art, a thermal separator is a two-phase or three-phase vertical or horizontal separator, most commonly a two-phase separator, in which a gas stream is separated from the top and a liquid stream from the bottom, operating at temperatures above 100°C, thereby removing water as vapor in the gas stream. Thermal separators can operate at high, medium, or low pressures, for example, in the range of 1-70 bar.

[0036] It is understandable that the term "thermal separator" refers to the removal of water as steam, while the term "cold separator" refers to the removal of water as a liquid.

[0037] According to the invention, at least a portion of the bottom stream is sent to the dewaxing step. In one embodiment, in step i), the recirculated oil stream is separated from the bottom stream (e.g., the bottom stream from the first separation step (from the high-pressure stripper)) and sent to one or more upstream catalytic hydrotreating units, i.e., catalytic hydrotreating units for producing the first hydrotreating stream.

[0038] Recycled oil is used as a diluent to reduce the exothermic nature of hydrotreatment, particularly due to the use of feedstocks from renewable sources. Renewable feedstocks are more reactive than typical fossil fuel-based hydrocarbon feedstocks. They contain sulfur, and especially more oxygen, which reacts to form H₂O and H₂S, respectively, with greater exothermic activity. Therefore, this method achieves greater integration, flexibility, efficiency, and especially safety.

[0039] In one embodiment, one or more catalytic hydrotreating units for producing the first hydrotreating stream are hydrodeoxygenation (HDO) and hydrodenitrification (HDN).

[0040] As used in this article, HDO also includes decarboxylation.

[0041] Materials with catalytic activity in hydrotreating typically include active metals (sulfided base metals such as nickel, cobalt, tungsten and / or molybdenum, but may also be elemental noble metals such as platinum and / or palladium) and refractory supports (such as alumina, silica or titanium dioxide, or combinations thereof).

[0042] Hydrotreating conditions include a temperature in the range of 250–400 °C, a pressure in the range of 30–150 bar, and a liquid hourly space velocity (LHSV) in the range of 0.1–2, optionally accompanied by intercooling by quenching with cold hydrogen, feed, or product.

[0043] In one embodiment, the dewaxing step includes hydrodewaxing (HDW) in the presence of a noble metal catalyst, and optionally also hydrocracking (HCR).

[0044] In the dewaxing step, the wax content is reduced by isomerization under isomerization conditions and optionally by cracking in the presence of hydrogen. Therefore, as used herein, the terms hydrodewaxing (HDW) and hydroisomerization (HDI) are used interchangeably.

[0045] Materials with catalytic activity in hydrodewaxing typically include active metals (elemental noble metals such as platinum and / or palladium), acidic supports (usually exhibiting high shape selectivity and possessing properties such as MOR, FER, MRE (more specifically MRE)). Molecular sieves with MWW, AEL, TON and MTT topologies and refractory carriers (e.g. alumina, silica or titanium dioxide, or combinations thereof).

[0046] Isomerization (HDI) conditions include a temperature in the range of 250–400 °C, a pressure in the range of 20–100 bar, and a liquid hourly space velocity (LHSV) in the range of 0.5–8, optionally accompanied by intercooling by quenching with cold hydrogen, feed, or product.

[0047] Materials exhibiting catalytic activity in hydrocracking share similar properties with those exhibiting catalytic activity in isomerization, and typically comprise an active metal (elemental noble metals such as platinum and / or palladium or sulfide base metals such as nickel, cobalt, tungsten, and / or molybdenum), an acidic support (typically a molecular sieve exhibiting high cracking activity and possessing topologies such as MFI, BEA, and FAU), and a refractory support (e.g., alumina, silica, or titanium dioxide, or combinations thereof). The difference from materials exhibiting catalytic activity in isomerization is often the nature of the acidic support, which may have a different structure (even amorphous silica-alumina) or different acidity, for example, due to the silica:alumina ratio. It should be understood that, in the context of this invention, the properties of the metal may also differ; for example, the metal used for HDW may comprise a noble metal catalyst such as platinum, while the metal used for hydrocracking may comprise a base metal such as nickel and / or molybdenum.

[0048] Hydrocracking conditions include a temperature in the range of 250–400 °C, a pressure in the range of 30–150 bar, and a liquid hourly space velocity (LHSV) in the range of 0.5–8, optionally accompanied by intercooling by quenching with cold hydrogen, feed, or product.

[0049] In one embodiment, the feedstock derived from a renewable source is obtained from renewable raw materials, such as those derived from plants, algae, animals, fish, vegetable oil refining, municipal solid waste, plastic-rich waste, industrial organic waste (such as tal oil or black liquor), or from feedstocks derived from one or more oxygenated compounds, wherein the oxygenated compounds are derived from the group consisting of triglycerides, fatty acids, resin acids, ketones, aldehydes, or alcohols, wherein the oxygenated compounds are derived from one or more of biological sources, gasification processes, pyrolysis processes, Fischer-Tropsch synthesis, or methanol-based synthesis.

[0050] In one implementation, the feedstock derived from fossil fuel sources is diesel, kerosene, naphtha, and vacuum gas oil (VGO).

[0051] Optionally, the hydrocarbon products generated in the method are provided as a feedstock, such as the recycle oil stream from step i).

[0052] This invention provides the use of feedstocks derived from renewable sources or feedstocks derived from fossil fuel sources, or combinations thereof (i.e., co-processing). In one embodiment, the feedstocks are derived from both renewable and fossil sources, wherein the fossil source constitutes a small fraction of the feedstock, totaling at most 30 wt% or less, for example, at most 10 wt%.

[0053] 100% renewable feedstock, i.e. feedstock derived from renewable sources, such as co-feeds that do not contain feedstocks from fossil fuel sources, or where the latter constitute only a small fraction as described above, has a significantly lower sulfur content than purified fossil fuel feedstocks and requires hydrotreating with HDO to remove oxygen from the renewable feedstock, thereby yielding not only H2S but also significantly higher concentrations of other impurities such as H2O, NH3, CO, and CO2. Attached Figure Description

[0054] Figure 1 This diagram illustrates a schematic process and equipment layout for producing naphtha, jet fuel, and diesel from feedstock using existing technology. The diagram includes an enlarged view of the separation unit used in the first separation step.

[0055] Figure 2 A schematic process and equipment layout for producing naphtha, jet fuel, and diesel from feedstock is shown according to one embodiment of the invention. The figure includes an enlarged view of the separation unit used in the first separation step. Detailed Implementation

[0056] For details, please refer to the following: Figure 1 The diagram shows a block flow chart of the entire method / equipment 10. Feedstock 12, such as feedstock from a renewable source, is fed into a hydrotreating step or hydrotreating section 110. This step or hydrotreating section includes an optional feed step or feed section 112 and a reactor section, which includes a catalytic hydrotreating unit 114 (e.g., HDO), a dewaxing step or dewaxing section 118, and a first separation step 116, illustrated here using a separation unit 116 in the form of an HP stripper. From the hydrotreating step 110, particularly from the dewaxing step 118, a main hydrotreating stream 14 is generated, which is then fed to a second separation step 120, producing: a water-containing stream 16; a tail stream 20 containing hydrocarbons such as light hydrocarbon streams, and also containing NH3, CO, CO2, and H2S; and hydrocarbon products in the form of diesel 22, jet fuel 24, and naphtha 26.

[0057] After optionally passing feedstock 12 through optional feed step 112, feedstock 12' passes through catalytic hydrotreating unit 114 (e.g., HDO), from which a first hydrotreating stream 12'' is extracted. This stream is then fed to HP stripper 116, generating a vapor stream 46 (i.e., a top gas stream containing the majority of impurities), a bottom stream 44, from which a recirculated oil stream 44' and stream 44'' are separated. Stream 44'' is combined with the top liquid stream from HP stripper 116 to form a purified first hydrotreating stream 12'''. The latter proceeds to dewaxing step 118, which includes using a catalytic hydrotreating unit, i.e., HDW unit 118, to produce a main hydrotreating stream 14. Additional catalytic hydrotreating units in the form of hydrocracking units (HCR units) may also be located downstream or upstream of, for example, the HDO or HDW unit, for producing the first hydrotreating stream 12'' or the main hydrotreating stream 14, respectively.

[0058] The second separation step 120 includes the use of a separator 122 (preferably a cold separator) and a stripping section 124, which includes a product stripper and a fractionator, such as a distillation column (not shown). The overhead gas stream 46 generated in the previous HP stripper 116 can be mixed, for example, with the main hydrotreating stream 14 for the operation of the separator 122. A hydrogen-rich stream 18 is drawn from the separator 122, which can be used for hydrogen recirculation, for example by mixing with streams 12' and 44' entering the catalytic hydrotreating unit 114, and the separator 122 also produces the aforementioned water stream 16. Impurities are thus carried into the water stream 16 (acidic water stream). A hydrocarbon stream 14' is generated from the separator 122 and then fed into the stripping section 124, producing a tail gas stream 20 containing hydrocarbons and hydrocarbon products diesel 22, jet fuel 24, and naphtha 26. Supplemental hydrogen 40, for example, from outside the battery limits, is added to the HP stripper 116, and optionally also to the catalytic units 114, 118 of the hydrotreating step 110.

[0059] Figure 1 An enlarged schematic diagram of the HP stripper 116 is also provided. Stream 12'' is fed, for example, into the first tray of the HP stripper 116. As shown, the overhead stream of the HP stripper is drawn off and partially condensed in, for example, an air cooler 116', and sent to a separator 116'' to extract the condensed hydrocarbon liquid stream, i.e., the overhead hydrocarbon liquid stream 28, along with the acidic water stream 30 and the steam stream 46. The overhead hydrocarbon liquid stream 28 is optionally combined with the bottom stream 44'' drawn off from the HP stripper 116 and fed as feed to the dewaxing step 118. Supplemental hydrogen 40 is used for stripping, and the recirculated oil stream 44' is separated from the bottom stream 44 of the HP stripper 116 and sent to one or more upstream catalytic hydrotreating units 114.

[0060] Now for reference Figure 2 It shows a flowchart of the entire method / apparatus 10 according to one embodiment of the present invention. Figure 1 The process flow diagram is the same, except that the stream 44'', which is separated from the bottom stream 44 from the HP stripper 116, is the only hydrocarbon feed to the dewaxing step 118.

[0061] An enlarged schematic diagram of the HP stripper 116 now shows the use of the overhead liquid stream 28 as reflux to the HP stripper. As shown herein, the entire overhead hydrocarbon liquid stream 28 is fed as reflux, thereby surprisingly achieving a significant improvement in overall impurity removal and thus better protecting the catalytic hydrogenation treatment unit in the dewaxing step 118.

[0062] A hydrogen-rich stream 18 is drawn from separator 122 (preferably a cold separator), which can be used for hydrogen recirculation and is suitably supplied as a single recirculation loop in the process, i.e., the hydrogen-rich stream is added to one or more catalytic hydrotreating units 114 to produce a first hydrotreating stream 12''.

[0063] Example

[0064] Existing technology: according to Figure 1 Prior to any heating, the impurity levels in the liquid phase heading to the dewaxing step or dewaxing section 18 are as follows: H2O: 1589 wppb, NH3: 14 wppb, H2S: 1528 wppb, CO+CO2: 3798 wppb.

[0065] This invention: according to Figure 2 The entire overhead hydrocarbon liquid stream 28 is sent as reflux to the HP stripper 116, i.e., total reflux. Used in conjunction with... Figure 1 Under the same operating conditions (pressure, temperature, stripping gas flow) in the same HP stripper. Prior to any heating, the impurity levels in the liquid phase heading to the dewaxing step or dewaxing section 18 are now as follows: H2O: 136 wppb, NH3: 9 wppb, H2S: 124 wppb, CO+CO2: 1197 wppb This resulted in a surprisingly high reduction in impurity levels (especially H2S, H2O, and / or CO + CO2). The reduction in H2S and H2O was approximately an order of magnitude.

Claims

1. A method for producing hydrocarbon products, the method comprising: i) Process feedstocks derived from renewable and / or fossil sources through a hydrotreating step to produce a main hydrotreating stream; The hydrogenation process includes: - In the presence of hydrogen, the feedstock is passed through one or more catalytic hydrotreating units to produce a first hydrotreating stream, the hydrotreating stream containing the following impurities: H2S, NH3, CO, CO2 and H2O; - The first hydrogenation process stream is fed to a first separation step, the first separation step including the use of a separation unit to remove impurities; - Take out the overhead stream from the first separation step, and separate the overhead hydrocarbon liquid stream therefrom, and send at least a portion of the overhead hydrocarbon liquid stream as a reflux stream to the separation unit; - Extract the bottom flow from the first separation step; - At least a portion of the bottom stream is sent to a dewaxing step, which includes using one or more catalytic hydrotreating units with the addition of hydrogen to produce the main hydrotreating stream; ii) The main hydrotreating stream is fed to a second separation step to produce the hydrocarbon product; One or more catalytic hydrotreating units used to produce the first hydrotreating stream include hydrodeoxygenation (HDO) and optional hydrodenitrification (HDN); One or more catalytic hydrotreatment units in the dewaxing step for producing the main hydrotreatment stream include hydrodewaxing (HDW) in the presence of a noble metal catalyst and optional hydrocracking (HCR). The entire overhead hydrocarbon liquid stream is sent as a reflux stream to the separation unit. Step ii) includes feeding the main hydrotreating stream to a cold separator to produce an aqueous stream (acidic water stream), a hydrogen-rich stream, and a hydrocarbon stream, the hydrocarbon stream being further separated into the hydrocarbon products in a subsequent stripping section; and wherein the hydrogen-rich stream is supplied as a single recycle loop in the method by adding it to one or more catalytic hydrotreating units used to produce the first hydrotreating stream. The method further includes: separating an overhead gas stream containing impurities from the overhead stream from the first separation step, and feeding the overhead gas stream to the cold separator in step ii) after mixing it with the main hydrogenation process stream and subsequently cooling it in, for example, an air cooler.

2. The method according to claim 1, further comprising: Do not add the hydrogen-rich stream to the dewaxing step; Supplemental hydrogen, for example, from an external source, is added to the dewaxing step.

3. The method according to claim 1 or 2, wherein the hydrocarbon product boils at a temperature above 30°C and comprises one or more of the following: jet fuel, diesel oil, naphtha, and optionally lubricating oil base oil.

4. The method according to claim 1 or 2, wherein in the first separation step, the separation unit is a high-pressure stripper, preferably in the form of a stripping tower using supplemental hydrogen as the stripping medium, and operates in a pressure range of 40-70 bar and a temperature range of 150-250°C.

5. The method according to claim 1 or 2, wherein the first separation step further comprises using a thermal separator upstream of the separation unit, the thermal separator being suitably in the form of a two-phase or three-phase vertical or horizontal separator, preferably a two-phase separator, wherein the gas stream is separated from the top and the liquid stream is separated from the bottom, operating at a temperature above 100°C, thereby removing water as vapor in the gas stream.

6. The method according to claim 1 or 2, wherein in step i), the recirculated oil stream is separated from the bottom stream and sent to one or more upstream catalytic hydrotreating units.

7. The method according to claim 1 or 2, wherein the raw material derived from a renewable source is obtained from a renewable source of raw materials, such as those derived from plants, algae, animals, fish, vegetable oil refining, municipal solid waste, plastic-rich waste, industrial organic waste such as tal oil or black liquor, or a raw material derived from one or more oxygenated compounds, wherein the oxygenated compound is derived from the group consisting of triglycerides, fatty acids, resin acids, ketones, aldehydes or alcohols, wherein the oxygenated compound is derived from one or more of biological sources, gasification processes, pyrolysis processes, Fischer-Tropsch synthesis or methanol-based synthesis.

8. The method according to claim 1 or 2, wherein the feedstock derived from fossil fuel sources is selected from diesel, kerosene, naphtha and vacuum gas oil (VGO).

9. The method of claim 1 or 2, wherein the raw material is derived from both renewable and fossil sources, and wherein the fossil source constitutes a small fraction of the raw material, totaling at most 30 wt% or less, for example at most 10 wt%.

Images