Title of Invention : A process for recovery of hydrogen during hydroprocessing of a feedstock comprising oxygenates

Technical Field

[0001] The present invention relates to the field of upgrading liquids originating from thermal decomposition of solid feedstocks.

Technical Problem

[0002] Oxygenates originating from biological materials or from thermal decomposition of solid feedstocks, such as mixed municipal waste, mixed or sorted plastic waste and forestry waste provides a liquid product (for simplicity pyrolysis oil or raw pyrolysis oil) which may be upgraded to quality hydrocarbons and be used as transportation fuels or petrochemical raw materials. The product may also be richer in oxygenates content than commonly required for hydrocarbon transportation fuels, either in the expectation of subsequent hydrotreatment at a different site or in the intention of using such an oxygenate rich product.

[0003] When the final product is rich in oxygenates, the processing conditions and intermediate products will differ from other hydrotreatment where intermediate and final products of quantitatively converted to hydrocarbons. This also means that intermediate processes for purifying intermediate products will differ, and specifically, the presence of oxygenates in the product will mean that a higher amount of product is soluble in wash water, which may result in a yield loss.

[0004] We have identified that this yield loss may be reduced by full or partial recycle of the wash water, such that washing is made with a stream with no capacity for withdrawal of oxygenates, as it is already saturated in oxygenates.

Definitions

[0005] It would be understood that the unit “MPag” denotes MPa gauge, i.e. pressure above surroundings.

[0006] It would be understood, that the unit Nm ³ means “normal” m ³ , i.e. the amount of gas taken up this volume at 0°C and 1 atmosphere. [0007] As used herein, the term “hydrogen to liquid oil ratio” or “H2:oil ratio” means the volume ratio of hydrogen gas stream to the liquid oil stream, and is reported as Nm ³ /m ³ , where the gas phase is reported at normal conditions (0°C and 1 atmosphere) and the liquid phase is reported at standard conditions (25°C and 1 atmosphere) in accordance with practice of the field.

[0008] Where concentrations are stated in wt% this shall be understood as weight/weight %.

[0009] Where concentrations of oxygenates or other groups of molecules are referred to they shall signify the concentration of all the molecules of such a group, and not to the functional group.

[0010] As used herein, the terms “thermal decomposition” and “thermochemical decomposition” shall for convenience be used broadly for any decomposition process, in which a solid material is partially decomposed at elevated temperature (typically 250°C to 800°C or even 1000°C), in the presence of substoichiometric amount of O2 (including no added oxygen). The product will typically be a combined liquid and gaseous stream, as well as an amount of solid char. The term shall be construed to include processes known as pyrolysis and hydrothermal liquefaction, both in the presence and absence of a catalyst. For convenience the product of such a thermal decomposition process may be called pyrolysis oil, but shall be understood to cover any thermal decomposition process.

[0011] In the following a hydrocarbonaceous feedstock shall be used to signify a feedstock rich in molecules comprising hydrogen and carbon, but possibly also heteroatoms, i.e. other elements, such as oxygen, sulfur and nitrogen.

[0012] As used herein, the term “section” means a physical section comprising a unit or combination of units for conducting one or more steps and/or sub-steps.

[0013] The term a feedstock of plastic or polymeric origin or waste plastic or polymer may be understood as including a mixed or sorted waste comprising at least 50 wt%, 80 wt% or 90 wt% plastic and other synthetic polymers. [0014] A feedstock of biological origin may be defined by tracing the origin, but it may also be defined by the ¹⁴ C content being above 0.5 parts per trillion of the total carbon content.

[0015] Where hydrogen and hydrogen concentration is mentioned this shall in general be understood as molecular elemental hydrogen, unless it is implied that hydrogen is part of other molecules.

[0016] Where oxygen content is mentioned this shall in general be understood as atomic oxygen is part of other molecules, unless it is implied that is relates to molecular elemental oxygen.

Solution to Problem

[0017] Conversion of pyrolysis oil to a stabilized product comprising a moderate amount of oxygenates may be carried out in a cost effective manner, with partial hydrotreatment and thus reduced consumption of hydrogen.

[0018] The conversion of oxygenates to transportation fuel by partial hydrotreatment will provide a product, which is partially soluble in water. To minimize the yield loss, it is proposed to use wash water containing oxygenates, such as recycled wash water, even if it comprises other impurities. Thereby additional oxygenate product is not withdrawn to the wash water.

[0019] A hydrocarbonaceous feedstock according to the present disclosure may be provided by a thermochemical decomposition process plant section which may be one of many variants, including rotary oven, fluidized bed, transported bed, or circulating fluid bed, as is well known in the art. This decomposition converts a pyrolysis feedstock into a solid (char), a high boiling liquid (tar) and fraction being gaseous at elevated temperatures. The gaseous fraction comprises a fraction condensable at standard temperature (pyrolysis oil or condensate, C5+ compounds) and a non-condensable fraction (pyrolysis gas, including pyrolysis off-gas). For instance, the thermochemical decomposition process plant section (the pyrolysis section) may comprise a pyrolizer unit (pyrolysis reactor), cyclone(s) and/or filters to remove particulate solids such as char, and a cooling unit for thereby producing pyrolysis off-gas stream and said pyrolysis oil stream, i.e. condensed pyrolysis oil. The pyrolysis gas stream comprises light hydrocarbons e.g. C1-C4 hydrocarbons, and commonly also H2O, CO and CO2. Typically, the term pyrolysis oil comprises condensate and tar, and the pyrolysis oil stream from pyrolysis of biomass may also be referred to as bio-oil or biocrude. The pyrolysis oil is a liquid substance rich in blends of molecules, usually consisting of more than two hundred different compounds, mainly oxygenates such as acids, sugars, alcohols, phenols, guaiacols, syringols, aldehydes, ketones, furans, and other mixed oxygenates, resulting from the depolymerization of the solids treated in pyrolysis. Thermochemical decomposition of non- biological waste comprising suitable compositions, such as plastic fractions or rubber, including end of life tires will in general only provide products which have low contents of oxygen, unless O2 is added to the decomposition process and will commonly provide a hydrocarbonaceous feedstock which has a structure reflecting the solid pyrolysis feedstock.

[0020] For the purposes of the present invention, the pyrolysis section may be fast pyrolysis, also referred to in the art as flash pyrolysis. Fast pyrolysis means the thermochemical decomposition of a solid feedstock typically in the absence of O2, at temperatures typically in the range 350-650°C e.g. about 500°C and reaction times of 10 seconds or less, such as 5 seconds or less, e.g. about 2 sec. Fast pyrolysis may for instance be conducted by autothermal operation e.g. in a fluidized bed reactor. The latter is also referred to as autothermal pyrolysis and is characterized by employing air, optionally with an inert gas or recycle gas, as the fluidizing gas. Thereby, the partial oxidation of pyrolysis compounds being produced in the pyrolysis reactor (autothermal reactor) provides the energy for pyrolysis while at the same time improving heat transfer. In so-called catalytic fast pyrolysis, a catalyst may be used. An acid catalyst, commonly comprising a zeolite, without active metals, may be used to upgrade the pyrolysis vapors, and it can both be operated in an in-situ mode (the catalyst is located in the pyrolysis reactor) and an ex-situ mode (the catalyst is placed in a separate reactor). The use of a catalyst conveys the advantage of helping to stabilize the pyrolysis oil and thereby making it easier to hydroprocess. In addition, increased selectivity towards desired pyrolysis oil compounds may be achieved.

[0021] In some cases, hydrogen is added to the catalytic pyrolysis which is then called reactive catalytic fast pyrolysis. If the catalytic pyrolysis is conducted at a high hydrogen pressure, such as above 0.5 MPa, it is often called catalytic hydropyrolysis. The catalyst for upgrading in the presence of hydrogen, will typically comprise one or more metals active in hydrogenation, such as a metal from Group 6 or Group 8,9 or 10.

[0022] The pyrolysis stage may be fast pyrolysis which is conducted without the presence of a catalyst and hydrogen, i.e. the fast pyrolysis stage is not catalytic fast pyrolysis, hydropyrolysis or catalytic hydropyrolysis. This enables a much simpler and inexpensive process.

[0023] In an embodiment, the thermal decomposition is hydrothermal liquefaction. Hydrothermal liquefaction means the thermochemical conversion of solid feedstocks, such as plastic waste, biomass, municipal solid waste or sewer sludge into liquid fuels by processing in a hot, pressurized water environment for sufficient time to break down the solid biopolymeric structure to mainly liquid components. Typical hydrothermal processing conditions are temperatures in the range of 200-500°C, especially 300-450°C and operating pressures in the range of 4-40 MPag, especially 25-35 MPag. This technology offers the advantage of operation of a lower temperature, higher energy efficiency and lower yield of high boiling product compared to pyrolysis, e.g. fast pyrolysis.

[0024] In an embodiment, the thermal decomposition further comprises passing said solid feedstock through a solid feedstock preparation section comprising for instance drying for removing water and/or comminution for reduction of particle size. Any water/moisture in the solid feedstock which vaporizes in for instance the pyrolysis section condenses in the pyrolysis oil stream and is thereby carried out in the process, which may be undesirable. Furthermore, the heat used for the vaporization of water withdraws heat which otherwise is necessary for the pyrolysis. By removing water and also providing a smaller particle size in the solid feedstock the thermal efficiency of the pyrolysis section is increased.

[0025] Finally, other relevant thermochemical decomposition methods are intermediate or slow pyrolysis, in which the conditions involve a lower temperature and commonly higher residence times - these methods may also be known as carbonization or torrefaction. The major benefit of these thermochemical decomposition methods is a lower investment, but they may also have specific benefits for specific feedstocks or for specific product requirements, such as a desire for bio-char as an associated product.

[0026] When high amounts of solid product are produced, such as processes producing bio-char or when retrieval of unconverted carbon black particles from thermochemical conversion of end-of-life tires is desired, it may be beneficial to filter the liquid product as part of the thermochemical conversion process, which will also have the benefit of minimizing deactivation of downstream catalyst.

[0027] The liquid feedstocks resulting from thermochemical decomposition are not of sufficient quality for use as e g. transportation fuels. They may suffer from a too elevated boiling point, poor stability and presence of undesired heteroatoms, and therefore they require hydrotreatment to be upgraded to feedstocks of practical and economical value.

[0028] Accordingly, we propose a process for hydrotreating a liquid oil stream by reacting the liquid oil stream with hydrogen in the presence of a hydrotreatment catalyst having resistance to sulfur poisoning. This catalyst may be a sulfided catalyst comprising one or more of nickel, cobalt, molybdenum and tungsten typically operating at an inlet temperature of 130-200°C or it may be a metallic catalyst comprising one or more of nickel, palladium and platinum typically operating at an inlet temperature of 80-130°C. In most cases the pressure may be 0.5-2 MPa, but it may be up to 15 MPa, and the liquid hourly space velocity (LHSV) of 0.1-5 IT ¹ , which conditions enable forming a stabilized liquid oil stream.

[0029] In an embodiment, the hydrotreatment catalyst is in sulfided form, e.g. NiMoS or CoMoS. The catalyst may be pre-sulfided by exposure of to a sulfur containing stream or it may be sulfided in-situ i.e. during or immediately prior to operation, for instance by sulfur present in the pyrolysis oil, such that the sulfided catalyst remains sulfided and thus active due to the presence of sulfur.

[0030] The material catalytically active in initial hydrotreating especially of conjugated double bonds, e.g. hydrogenation, typically comprises an active metal (sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum, but possibly also either elemental metals both nickel and noble metals such as platinum and/or palladium) and a refractory support (such as alumina, silica or titania, or combinations thereof). Initial hydrotreating conditions may involve a moderate temperature in the interval 120-200°C, a moderate pressure in the interval 0.5-5 MPa, and a liquid hourly space velocity (LHSV) in the interval 0.1-5. For certain conditions an elevated pressure up to 15 MPa may be required.

[0031] Final hydrotreating e.g. hydrogenation conditions commonly involve a higher temperature in the interval 250-400°C, a higher pressure in the interval 3-15 MPa, and a liquid hourly space velocity (LHSV) in the interval 0.1-4, optionally together with intermediate cooling by quenching with cold hydrogen, feed or product. In general, low severity, and thus limited conversion of oxygenates to hydrocarbon may be obtained by one or more of lowered temperature, increased space velocity, limited catalyst activity and reduced hydrogen availability, which will result in reduced hydrogen consumption. The skilled person will be aware of selecting appropriate conditions for the desired severity in this multi-dimensional space by routine experiments.

[0032] In general, the process is moderately exothermic thus a raise in temperature of 5-20°C typically occurs, but depending on the extent of hydrogenation and hydrodeoxygenation it may be highly exothermic, with a raise of temperature up to 100°C.

[0033] In addition to hydrotreatment to remove heteroatoms, additional steps may be desired to obtain a product of appropriate quality. These steps may especially involve isomerization, hydrocracking and hydrodearomatization, depending on feedstock properties and product requirements.

[0034] The material catalytically active in isomerization typically comprises an active metal (either elemental noble metals such as platinum and/or palladium or sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum), an acidic support (typically a molecular sieve showing high shape selectivity, and having a topology such as MOR, FER, MRE, MWW, AEL, TON and MTT) and a refractory support (such as alumina, silica or titania, or combinations thereof).

[0035] Isomerization conditions involve a temperature in the interval 250-400°C, a pressure in the interval 2-10 MPa, and a liquid hourly space velocity (LHSV) in the interval 0.5-8.

[0036] The material catalytically active in hydrocracking is of similar nature to the material catalytically active in isomerization, and it typically comprises an active metal (either elemental noble metals such as platinum and/or palladium or sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum), an acidic support (typically a molecular sieve showing high cracking activity, and having a topology such as MFI, BEA and FAU) and a refractory support (such as alumina, silica or titania, or combinations thereof). The difference over materials catalytically active in isomerization is typically the nature of the acidic support, which may be of a different structure (even amorphous silica-alumina may be used for hydrocracking) or have a different acidity e.g. due to silica:alumina ratio.

[0037] Hydrocracking conditions may involve a temperature in the interval 250- 400°C, a pressure in the interval 3-20MPa, and a liquid hourly space velocity (LHSV) in the interval 0.5-8, optionally together with intermediate cooling by quenching with cold hydrogen, feed or product.

[0038] Other types of hydroprocessing are also envisaged, for instance hydrodearomatization (HDA). The material catalytically active in hydrodearomatization typically comprises an active metal (typically elemental noble metals such as platinum and/or palladium but possibly also sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum) and a refractory support (such as amorphous silica-alumina, alumina, silica or titania, or combinations thereof).

[0039] Hydrodearomatization conditions involve a temperature in the interval 200 - 350°C, a pressure in the interval 2-10 MPa, and a liquid hourly space velocity (LHSV) in the interval 0.5-8.

[0040] The provision of hydrogen for hydroprocessing is a significant cost, and the reduction of the requirements for hydrogen may be a driver for cost reduction. In hydroprocessing, an amount of hydrogen is consumed per volume of oil, which is termed the H2:oil consumption ratio. Depending on the nature of the raw product, for complete hydroprocessing the H2:oil consumption ratio may be from 50 Nm ³ /m ³ to 1000 Nm ³ /m ³ . However, to minimize the risk of coke deposits on the catalyst due to hydrogen deprivation, it is common to operate with a safety factor of 2, 4 or even 8, such that an H2:oi I consumption ratio of 200 Nm ³ /m ³ results in operation with up to 1000 Nm ³ /m ³ H2:oil [0041] Hydrotreatment in general and especially in processing of oxygenate feedstocks is carried out in excess of hydrogen to increase reaction rate and to minimize the risk of coke deposition on the catalyst. The excess hydrogen is typically recycled, to minimize the hydrogen consumption and the related cost. However, as the reaction rate and process equilibrium depend on the partial pressure of hydrogen, presence of other compounds such as methane and carbon dioxide in the recycle gas will lower this effect of hydrogen or require an increased total pressure, at the cost of more expensive equipment. As an example, an H2:oil consumption ratio of 200 Nm ³ /m ³ will, if the purity of the H2 rich gas in the process is only 80 vol%, result in a gas:oil ratio of 500 Nm ³ /m ³ if a safety factor of 2 was employed.

[0042] The product stream from hydroprocessing will be a two phase gas/l iquid stream. The liquid phase will be a product which has appropriate qualities for use in a final product or for downstream processing and may comprise a high amount of high boiling hydrocarbons and oxygenates, whereas the hot gas phase will comprise unreacted hydrogen and gaseous products. The gaseous products will mainly be released heteroatoms, including oxygen (as H2O or CO and CO2), nitrogen (as NH3), sulfur (as H2S) as well as halides such as chloride (as HCI or NH4CI). In addition, light hydrocarbons and oxygenates may also be present in the hot gas phase, especially if hydrogenation is not complete. Due to the excess amount of hydrogen and the related cost, recycling of hydrogen is desirable.

[0043] Typically, the liquid phase will be separated from the gas phase in a hot high pressure separator (operating at close to process conditions) e.g. at 11 MPa and 240°C. If all catalysts are sulfided and the process operates in the presence of sulfur, this separation may be carried out downstream the full hydroprocessing process, but commonly only the initial step of hydrotreatment employs a sulfided catalyst, and in this case a first step of separation is carried out downstream hydrodeoxygenation and upstream noble metal isomerization or hydrocracking catalysts. If additional (or all) catalysts are sulfided, the separation is commonly made after all sulfided catalysts.

[0044] The gas phase will comprise excess H2, small heteroatomic molecules such as H2O, CO, CO2, NH3, H2S and HCI as well as C1 -C5 hydrocarbons and oxygenates. To separate excess H2from the remainder of the gas phase, the gas phase may be cooled to e.g. 50°C, and separated in a high pressure cold separator.

[0045] If the hot gas phase comprises water and light hydrocarbons, the condensation in the cold separator will result in three phases; a gas phase, a liquid non-polar phase, rich in hydrocarbons, and a liquid polar phase rich in water. Most non-polar gases, such as CO2, CO and paraffins, will have a high solubility in the liquid non-polar phase and salts such as NH4CI will have a high solubility in the polar phase, and thereby these compounds may be withdrawn with the liquid condensates from the high pressure cold separator, whereas H2 will mainly remain in the gas phase as the solubility of H2 is low.

[0046] The salts, such as ammonium chloride, are undesired in the product and may solidify on equipment. To remove such impurities an amount of wash water is commonly added after the hot separator, since salts are highly soluble in liquid water, and easily separable from the gas sterams by lowering the temperature. Thereby salts may be removed from the liquid product. However, when the product is only partially hydrotreated, it contains an amount of oxygenates, which are partially soluble in water. This means that the step of product purification by addition of wash water will not only withdraw salts, but also an amount of oxygenates, which would be viable product.

[0047] The practical addition of wash water involves mixing liquid water with a hot stream, preferably under conditions (pressure, temperature, relative amounts of water) resulting in only partial evaporation of the water, since an amount of liquid water is highly preferable for the washing process, especially if the product is in its liquid phase. The combined stream is then subsequently cooled, to allow formation of a liquid product phase, a liquid aqueous phase and a gas phase. Hydrocarbons are non-polar and have a very low solubility in water, so only ppmwt concentrations of hydrocarbons would enter the aqueous phase. Oxygenates on the other hand are more polar and will have some solubility in water, depending on the specific nature of the oxygenate. As a result, an amount of oxygenates, intended as product, are withdrawn with the wash water. [0048] To minimize the amount of product withdrawn with wash water, we propose using wash water at least partially saturated with oxygenates. This may be obtained cost-effectively by recycling the wash water, but contrary to the common practice of purifying wash water prior to recycling, in this case it is desirable to recycle the wash water with dissolved oxygenates. In this manner additional oxygenates will not be withdrawn, and a higher overall process yield may be obtained.

[0049] An amount of the liquid aqueous phase must be withdrawn to ensure salts are not accumulated in the wash water. This may either be done as a purge to general waste water treatment, or a closed circuit may purify the water, e.g. by evaporative concentration and recycle of purified water. When determining the amount of purge, the production of water by hydrodeoxygenation must also be considered. Often this water produced will be a significant contributor to the wash water consumption in the process.

[0050] However, if the product is only partially hydrotreated, the amount of condensed non-polar hydrocarbons is low. This is especially true it the feedstock is high boiling, since in this case the majority of product liquid at ambient conditions will have been withdrawn in the high pressure high temperature separator. Furthermore, if the moderate amount of condensed non-polar hydrocarbons, is dominated by a high amount of slightly polar compounds, such as light oxygenates, the solubility of non-polar gases in the small volume will be low. As a result, the withdrawal of CO2 and CO from the cold gas phase will be low, and therefore the purity of recycle gas will also be low.

[0051] A common method for purification of gas streams in hydroprocessing plants is the use of amine scrubbers, in which especially CO2 and H2S are reversibly captured in an aqueous amine solution. However, if the gas to be purified also comprises water soluble compounds such as methanol, ethanol and formic acid, these compounds will also be captured in an amine scrubber, but not reversibly.

[0052] The use of an amine scrubber for gas purification involves a very low pressure drop, and therefore a scrubber may be positioned in line with a recycle gas compressor, which is tasked with pressurizing high pressure gas to match process pressure, compensating for the reactor pressure drop of perhaps 1 MPa.

Brief Description of Drawings

[0053] Fig.1 shows a process layout with recycle of wash water without purification.

[0054] Fig.2 shows a process layout with addition of fresh wash water.

Fig.1

[0055] In Fig.1 a feedstock comprising oxygenates (2) is pressurized in a feedstock pump (FP) and is, after heating with the reactor effluent (10) in a heat exchanger (HX), combined with a make up hydrogen gas (4) pressurized in make up gas compressor (MUGC) and a recycle gas (6) pressurized in recycle gas compressor (COMP). This feedstock stream (8) is directed to a hydrodeoxygenation reactor (HDO) comprising one or more catalysts configured, by control of conditions including composition, temperature, pressure and space velocity, to provide a desired hydrodeoxygenation conversion of the reactor feed stream (8). The conditions may be chosen to only support a limited extent of reaction, e.g. by limiting the temperature, the residence time or the availability of hydrogen. The reactor effluent (10) is cooled and the cooled reactor effluent (12) is directed to a hot high pressure separator (HHPS) providing a first product stream (14) and a vapor stream (16). The vapor stream (16) is combined with a stream of wash water (18), and the combined stream (20) is cooled in cooler (C) and directed as cold combined stream (22) to a three phase separator (TPS) from which condensed sour water (28) and light product (24) is separated from light gases (32), which are directed to the recycle compressor (COMP). An amount of the condensed sour water (28) is pressurized in recycle pump (RP) and directed as wash water, while another amount (30) may be withdrawn from the system. The first product stream (14) and light product (24) may be withdrawn as combined product stream (26).

[0056] In other embodiments additional water may be added to the recycled wash water and the process may include further steps, including purification of the recycled light gases (32) and hydroprocessing other than hydrodeoxygenation (HDO), such as hydrogenation of olefins, hydrodearomatization, isomerization. These process steps may be in series with the hydrodeoxygenation step or positioned either upstream or downstream the process illustrated in Fig.1 .

[0057] In further embodiments, the product stream (26) may be directed to a fractionation process to provide products for specific applications according to boiling point, such as naphtha for gasoline, naphtha for use in steam cracking, aviation fuel, automotive diesel or marine fuel. The product stream (26) or a fraction thereof may also be directed to further hydroprocessing steps, including isomerization, hydrocracking and hydrodearomatization.

[0058] In further embodiments, the hydrogen rich gas phase (32) may also be purified to increase the effective hydrogen pressure in the process.

Fig.2

[0059] In Fig.2 a comparative process is illustrated. Here a feedstock comprising oxygenates (2) is pressurized in a feedstock pump (FP) and is, after heating with the reactor effluent (10) in a heat exchanger (HX), combined with a make up hydrogen gas (4) pressurized in make up gas compressor (MLIGC) and a recycle gas (6) pressurized in recycle gas compressor (COMP). This feedstock stream (8) is directed to a hydrodeoxygenation reactor (HDO) comprising one or more catalysts configured, by control of conditions including composition, temperature, pressure and space velocity, to provide a desired hydrodeoxygenation conversion of the reactor feed stream (8). The conditions may be chosen to only support a limited extent of reaction, e.g. by limiting the temperature, the residence time or the availability of hydrogen. The reactor effluent (10) is cooled and the cooled reactor effluent (12) is directed to a hot high pressure separator (HHPS) providing a first product stream (1 ) and a vapor stream (16). The vapor stream (16) is combined with a stream of fresh wash water (18), and the combined stream (20) is cooled in cooler (COOL) and directed as cold combined stream (22) to a three phase separator (TPS) from which condensed sour water (30) and light product (24) is separated from light gases (32), which are directed to the recycle compressor (COMP). In this process all of the condensed sour water (28) is withdrawn to the water treatment of the plant. The first product stream (14) and light product (24) may be withdrawn as combined product stream (26). Description of Embodiments

[0060] A first broad aspect of the present relates to a process for partial hydroprocessing of a feedstock comprising oxygenates, comprising the steps of directing said feedstock, an amount of make-up hydrogen and a recycle gas to a catalytic hydrotreatment process under conditions converting 30-95% of oxygenates to hydrocarbons, to provide a partially hydroprocessed product stream, adding an amount of recycled wash water comprising at least 0.1 wt% oxygenates, to at least an amount of said hydroprocessed product stream, such as a stream comprising at least 50 wt% of said partially hydroprocessed product stream, optionally in combination with a further amount of wash water, to provide a combined hydroprocessed product stream, cooling the combined hydroprocessed product stream and separating it in a vapor product fraction, a liquid aqueous fraction and a liquid product fraction, withdrawing as a waste stream a first amount of said liquid aqueous fraction, directing as said amount of recycled wash water, at least a second amount of said liquid aqueous fraction.

[0061] This is related to the benefit of minimizing the withdrawal of oxygenates in the wash water, since the wash water is at least partially saturated with oxygenates. The withdrawing of the first amount of said liquid aqueous fraction may either be as a purge or by a purification process.

[0062] A second aspect relates to a process according to the first aspect wherein the liquid aqueous fraction comprises at least 0.1 wt% 0.2 wt% or 0.5 wt% of oxygenates.

[0063] This has the associated benefit of providing a liquid aqueous fraction which will withdraw a minimum of oxygenates from the process.

[0064] One aspect relates to a process according to the first aspect wherein the liquid aqueous fraction comprises less than 20 wt%, 10 wt% or 5 wt% of oxygenates, such that the amount of oxygenates bound in the liquid aqueous fraction is moderate.

[0065] A third aspect relates to a process according to the first or second aspect wherein the liquid aqueous fraction comprises at least 50 ppmwt or 100 ppmwt inorganic salts and less than 15 wt% or 10 wt% inorganic salts. [0066] This has the associated benefit of such a process being able to hydroprocess a feedstock comprising inorganic salts, and recycling wash water having a capacity for recuperation of salts.

[0067] A fourth aspect relates to a process according to the first three aspects wherein the ratio of the mass of the wash water to the mass of the amount of said hydroprocessed product stream combined with wash water is more than 1 : 50, 1 :20 or 1 :10 and less than 1 :1 , 1 :2 or 1 :5.

[0068] This has the associated benefit of balancing the process convenience of a low amount of water relative the partially hydroprocessed product stream against the increased level of removal of water soluble impurities such as salts.

[0069] A fifth aspect relates to a process according to the first four aspects wherein an amount of liquid aqueous fraction is directed to purge.

[0070] This has the associated benefit of continuously removing an amount of impurities and produced water from the process, but centralizing the purification of the purged water in a process plant water treatment system.

[0071] A sixth aspect relates to a process according to the fifth aspects wherein the fraction of liquid aqueous fraction is directed to purge is more than 5%, 10% or 15%.

[0072] This has the associated benefit of a high purge corresponding to a process in which the net production of water is higher than the amount required as wash water, which typically would be the case for thermally decomposed biological feedstocks, with 5%, 10% or even up to 50% oxygen content.

[0073] At the same time the amount directed to purge must be limited such as less than 95% or 90% to provide a remaining amount of liquid aqueous fraction for recycle.

[0074] A seventh aspect relates to a process according to the fifth or sixth aspect wherein the amount of liquid aqueous fraction is directed to purge is less than 50%, 25% or 15% with the associated benefit of a moderate purge corresponding to a process in which the net production of water is less than the amount required as wash water, which typically would be the case for thermally decomposed feedstocks with a low content of biological materials and having less than 5% oxygen content. The amount of liquid aqueous fraction is directed to purge may be more than 2%, 5% or 10% to ensure salts and other impurities are withdrawn from the process.

[0075] An eighth aspect relates to a process according to the fifth, sixth or seventh aspect wherein the amount of liquid aqueous fraction directed to purge is separated in a concentrated salt brine or precipitate and an amount of purified water by use of evaporation, membrane separation or precipitation.

[0076] This has the associated benefit of reducing the amount of water directed to waste.

[0077] A ninth aspect relates to a process plant configured for carrying out a process according to any of the aspects above.

Examples

[0078] To illustrate the benefits of the present disclosure, a process has been studied with pure make up wash water and with recycled wash water.

[0079] The process studied is a process where the liquid feedstock produced in hydrothermal liquification of forest waste is partially hydroprocessed with the objective of producing a fuel comprising hydrocarbons and oxygenates (HC+Oxyg). The liquid feedstock comprises an amount of chloride and washing to remove the chloride is required to obtain a satisfactory product. The hydroprocessed product stream has the composition shown in Table 1 , stream 12, and is subsequently washed and separated in gas, sour water and product, either in Example 1 using recycled wash water according to the present disclosure and Fig.1 , or in Example 2 using pure or purified wash water according to the comparative process of Fig.2. For practical reporting, the amount of nitrogen and chloride are reported as NHs and HCI respectively even though the aqueous solutions would contain this in ionic form such as NH4 ⁺ and Cl'.

[0080] The performance of Example 1 is reported in Table 1 . Here it is seen that with recycle of wash water, 896 kg/hr of sour water is still withdrawn in stream (30) as purge from the process, and that this water contains about 1 kg/hr of Cl. The heavy product stream (14) contains 1.9 kg/hr, corresponding to 166 ppm Cl and the light product stream (24) contains 3 g/hr HCI, corresponding to 2.4 ppm Cl. The purge of water (30) contains 1.1 kg/hr (1232 ppm) Cl and 145 kg/hr dissolved hydrocarbons and oxygenates. Due to the residual Cl, especially in the heavy product stream, it is necessary to direct the product to a stripper.

[0081] The corresponding performance of Example 2 is reported in Table 2. Here it is seen that with recycle of wash water, 1312 kg/hr of sour water is withdrawn in stream (30) as purge from the process, and that this water contains about 1.1 kg/hr of Cl. The heavy product stream (14) contains 1 .9 kg/hr Cl, corresponding to 166 ppm Cl and the light product stream (24) contains 1 g/hr HCI, corresponding to 1 .0 ppm Cl. The purge of water (30) contains 1.1 kg/hr (842 ppm) Cl and 160 kg/hr dissolved hydrocarbons and oxygenates. As for Example 1 the heavy product stream dictates a requirement to direct the product to a stripper.

[0082] Since significant amounts of CO2 are present in the hydrogen rich gas stream (32), both process layouts would typically involve purification of this stream, e.g. by amine wash.

[0083] From these data it is seen that recycle of the wash water without purification results in lower removal of compounds soluble in water; both Cl and oxygenate product. Washing with pure or purified wash water will reduce the Cl concentration in the light product from 2.4 ppm Cl to 1.0 ppm Cl, but since the heavy product requires stripping, this difference is not of significance. At the same time, washing with pure wash water will withdraw an extra 15 kg/hr product to waste as dissolved oxygenates.

Table 1

Stream 12 14 16 18 20 30 24 32

Phase Mixed Liquid Vapor Mixed Mixed Liquid Liquid Vapor

Temp. 274 240 240 47 214 50 50 50

Total 16753 11927 4826 400 5226 896 1239 2691

H ₂ 1167 328 839 331 1170 741 89 10 N 10.9 1.3 9.6 2.6 12.2 5.9 0.5 3.2 H ₂ 13.5 1.5 12.0 0.1 12.1 0.2 1.4 10.4 C 532 29 503 1 505 3 17 483

658 11 647 0 647 0 1 646 H 3.0 1.9 1.1 0.5 1.6 1.1 0.003 0.002 HC+Oxy 14371 11556 2815 65 2880 145 1131 1538 184 166 230 1232 306 1232 2.4 0.6

Table 2

Stream 12 14 16 18 20 30 24 6

Phase Mixed Liquid Vapor Mixed Mixed Liquid Liquid Vapor

Temp. 274 240 240 50 214 50 50 50

Total 16753 11927 4826 400 5226 1312 1224 2689

H 1167 328 839 400 1239 1142 87 10

N 10.9 1.3 9.6 0.0 8.6 6.2 0.3 2.0

H 13.5 1.5 12.0 0.0 11.9 0.3 1.3 10.3

C 532 29 503 0 503 4 16 482

658 11 647 0 647 0 1 646

H 3.0 1.9 1.1 0.0 1.1 1.1 0.001 0.001 HC+Ox 14371 11556 2815 0 2815 160 1117 1538 184 166 230 0 212 842 1.0 0.2