Method for the treatment of pyrolysis oils in order to use same in a steam-cracking unit

Abstract

Process for treating a feedstock comprising a plastic and / or tyre and / or solid recovered fuel pyrolysis oil comprising halogenated compounds, comprising:a) a hydrotreating step in order to obtain a partially hydrotreated effluent having a reduced content of halogenated compounds,b) a separation step, fed with the partially hydrotreated effluent from step a) and an aqueous solution in order to obtain a gaseous effluent, an aqueous effluent and a partially hydrotreated hydrocarbon effluent,c) a step of steam cracking of a petroleum feedstock in which at least one portion of the partially hydrotreated hydrocarbon effluent is introduced as a co-feedstock without first undergoing another hydrotreating step carried out at higher temperature and / or pressure, said mixture of said petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) having a halogenated compound content of less than or equal to 3 ppm by weight.

Description

TECHNICAL FIELDThe present invention relates to a process for treating a pyrolysis oil of plastics and / or tyres and / or solid recovered fuels (SRFs) to obtain a partially hydrotreated pyrolysis oil which can be upgraded as a co-feedstock with petroleum feedstocks in a steam cracking unit. More particularly, the present invention relates to a process for treating a pyrolysis oil with a view to eliminating the halogenated compounds thereof in order to be able to easily upgrade this oil in a steam cracking unit.PRIOR ARTPlastic waste is generally a mixture of several polymers, for example mixtures of polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride or polystyrene. Furthermore, depending on the uses, the plastics may contain, in addition to the polymers, other compounds, such as plasticizers, pigments, dyes or else polymerization catalyst residues. Plastic waste may additionally contain, in a minor amount, biomass originating, for example, from household waste. The treatment of the waste, on the one hand, notably the storage, the mechanical treatments, the sorting, the pyrolysis, and also the storage and the transportation of pyrolysis oil, on the other hand, can also cause corrosion.With regard to tyres, they are mainly constituted of rubbers, for their elastic property (mixture of elastomers of the type of crosslinked synthetic and natural rubbers, with the addition of adjuvants of the type of silica, resin, sulfur, zinc oxide, carbon black, and the like), and of textile and metal fibres, for their reinforcing property.

[0004] Solid recovered fuels (SRFs), also called refuse-derived fuel (RDF), are solid non-hazardous wastes prepared with a view to energy upgrading, whether they originate from household and similar waste, from waste from economic activities or from waste from construction and demolition. SRFs are generally a mixture of any combustible waste, such as used tyres, food by-products (fats, animal meal, and the like), viscose and wood waste, light fractions resulting from shredders (for example from used vehicles, electrical and electronic equipment (WEEE), household and commercial waste, residues from the recycling of various types of waste, including certain municipal wastes, plastic waste, textiles or wood, inter alia. SRFs generally contain plastic waste.

[0005] Plastics resulting from collection and sorting channels or recycled tyres or else SRFs can undergo a step of pyrolysis in order to obtain, inter alia, pyrolysis oils. These oils generally comprise a lot of impurities, in particular halogenated compounds, notably chlorine-based compounds, but also diolefins, olefins, metals, notably iron, silicon, or else heteroelements such as sulfur, oxygen and nitrogen, and insoluble materials.

[0006] These plastic and / or tyre and / or SRF pyrolysis oils are generally incinerated in order to generate electricity and / or used as fuel in industrial or district heating boilers.

[0007] Another route for upgrading pyrolysis oils is the use of these pyrolysis oils as feedstock of a steam cracking unit in order to (re)create olefins, the latter being constituent monomers of certain polymers. However, plastic and / or tyre pyrolysis oils have impurities at often high contents that are incompatible with steam cracking units or units located downstream of steam cracking units, notably polymerization processes and selective hydrogenation processes.

[0008] One way of removing these impurities contained in the pyrolysis oils is to carry out a hydrotreating in the presence of catalysts. Steam cracking units require very high feedstock purities, notably low contents of chlorine, diolefins, olefins, metals and sulfur. The specification of the chlorine content at the inlet of a steam cracking unit is typically 3 ppm by weight at most, preferably 1 ppm by weight at most.

[0009] Hydrotreatment upstream of steam cracking is then often carried out in several steps and under quite stringent conditions, notably in terms of temperature and pressure, in order to achieve the required specifications. Such processes are for example described in WO2016 / 142808, WO2016 / 142809, WO2018 / 055555, WO2021 / 110395 or WO2021 / 165178.

[0010] The present invention proposes a process for mild hydrotreatment of a plastic and / or tyre and / or SRF pyrolysis oil making it possible notably to reduce its content of halogenated compounds, and notably of chlorine, in order to obtain a pyrolysis oil stripped of most of the halogenated compounds and which can then be sent as co-feedstock with petroleum feedstocks into a steam cracking unit.

[0011] Unlike the hydrotreating processes described in the prior art, the process according to the invention is directed toward a mild hydrotreatment, notably at low pressure and moderate temperatures. The mild operating conditions in the hydrotreatment, combined with a separation step with washing, make it possible to largely remove halogenated compounds.

[0012] The process according to the invention is mainly focused on the removal of halogenated compounds in order to make the pyrolysis oil compatible as a feedstock in a steam cracking unit. The process according to the invention is not necessarily directed toward complete hydrotreatment of the oil. The other impurities contained in the pyrolysis oils (metals, silicon, nitrogen, etc.) are not necessarily completely removed during the process according to the invention, although the operating conditions make it possible to remove at least a portion thereof. The residual contents of impurities contained in the oil are compatible with the specifications for a steam cracking unit by diluting the oil with the petroleum feedstock.

[0013] The “mild” hydrotreatment of the present invention is a hydrotreatment carried out under carefully chosen pressure, temperature and hourly space velocity conditions that are generally more moderate compared to conventional hydrotreatments known from the prior art aimed at removing all the impurities. The hydrotreatment of the present invention makes it possible notably to remove a large part of the halogenated compounds.

[0014] The objective of the present invention is then to propose a process for treating plastic and / or tyre pyrolysis oils that is inexpensive, easy to carry out and can easily be integrated into existing steam cracking units. The fact of using mild operating conditions makes it possible to minimize the hydrogen consumption, thus minimizing the cost of this purification and also the operating and investment costs while removing the chlorine content as much as possible.

[0015] In addition, the process according to the invention can be carried out in a unit dedicated to pyrolysis oils, and therefore in a low-capacity unit making it possible to obtain a partially hydrotreated pyrolysis oil with a low enough content of halogenated compounds to be sent directly to co-processing in a steam cracking unit.SUMMARY OF THE INVENTION

[0016] More specifically, the invention relates to a process for treating a “pyrolysis” feedstock, comprising a plastic and / or tyre and / or solid recovered fuel pyrolysis oil comprising halogenated compounds, said process comprising:

[0017] a) a hydrotreating step carried out in a hydrotreating reaction section comprising at least one hydrotreating catalyst, said hydrotreating reaction section being fed at least with the pyrolysis feedstock and a gas stream comprising hydrogen, said hydrotreating reaction section being used at an average temperature of between 100° C. and 220° C., a partial pressure of hydrogen of between 1.0 and 3.0 MPa abs. and an hourly space velocity of between 0.05 and 5 h−1, the hydrogen coverage being between 5 and 50 Nm3 of hydrogen per m3 of pyrolysis feedstock, in order to obtain a partially hydrotreated effluent having hydrocarbon compounds with a reduced halogen content,

[0018] b) a separation step, fed with the partially hydrotreated effluent from step a) and an aqueous solution in order to obtain at least a gaseous effluent, an aqueous effluent and a partially hydrotreated hydrocarbon effluent,

[0019] c) a step of steam cracking of a petroleum feedstock in which at least one portion of the partially hydrotreated hydrocarbon effluent from step b) is introduced as a co-feedstock, said partially hydrotreated hydrocarbon effluent from step b) being introduced without first undergoing another hydrotreating step carried out at higher temperature and / or pressure than the temperature and / or pressure of step a), said mixture of said petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) having a halogen content of less than or equal to 3 ppm by weight.

[0020] According to one variant, the weight ratio of the flow of the partially hydrotreated hydrocarbon effluent from step b) to the flow of petroleum feedstock introduced in step c) is less than 1.

[0021] According to one variant, the pyrolysis feedstock consists of a plastic and / or tyre and / or solid recovered fuel pyrolysis oil.

[0022] According to one variant, the content of halogenated compounds in said pyrolysis feedstock is between 1 and 5000 ppm by weight.

[0023] According to one variant, a stream containing a nitrogen compound and / or a sulfur compound is injected upstream of step a).

[0024] According to one variant, said hydrotreating catalyst of step a) comprises a support chosen from alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof and a hydrogenating-dehydrogenating function comprising either at least one group VIII element and at least one group VIB element, or at least one group VIII element.

[0025] According to one variant, said process comprises at least one step a0) of pretreating the pyrolysis feedstock comprising a plastic and / or tyre and / or SRF pyrolysis oil, said pretreatment step being carried out upstream of step a), and comprises an adsorption step and / or a filtration step and / or a centrifugation step and / or a settling step and / or an electrostatic separation step and / or a step of washing with an aqueous solution and / or a gas stripping step.

[0026] According to one variant, the petroleum feedstock introduced in steam cracking step c) is chosen from naphtha, kerosene, gas oil, or mixtures of such feedstocks.

[0027] According to one variant, the reaction section of step a) employs at least two reactors operating in permutable mode.

[0028] According to one variant, the steam cracking step c) is carried out in at least one pyrolysis furnace at a temperature of between 70° and 900° C. and at a pressure of between 0.05 and 0.3 MPa relative in the presence of steam.

[0029] According to one variant, in the steam cracking step c), the residence time of the hydrocarbon compounds is less than or equal to 1.0 second and the amount of water introduced, in the form of steam, is between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds at the inlet of step c).

[0030] In the remainder of the text, the term “pyrolysis oil” is understood to mean an oil resulting from the pyrolysis of plastics and / or of tyres and / or of SRFs, unless otherwise indicated.

[0031] According to the present invention, the pressures are absolute pressures, also denoted abs., and are given in MPa absolute (or MPa abs.), unless otherwise indicated.

[0032] According to the present invention, the expressions “of between . . . and . . . ” and “between . . . and . . . ” are equivalent and mean that the limit values of the interval are included in the described range of values. If such were not the case and if the limiting values were not included in the range described, such a clarification will be introduced by the present invention.

[0033] For the purposes of the present invention, the various parameter ranges for a given step, such as the pressure ranges and the temperature ranges, can be used alone or in combination. For example, for the purposes of the present invention, a range of preferred pressure values can be combined with a range of more preferred temperature values.

[0034] In the text hereinbelow, specific and / or preferred embodiments of the invention may be described. They can be implemented separately or combined together, without limitation of combination when this is technically feasible.

[0035] Subsequently, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, editor-in-chief D. R. Lide, 81st edition, 2000-2001). For example, group VIII (or VIIIB) according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUPAC classification.

[0036] The content of metals is measured by X-ray fluorescence.DETAILED DESCRIPTIONThe Pyrolysis Feedstock

[0037] According to the invention, a “plastic pyrolysis oil or tyre pyrolysis oil or SRF pyrolysis oil” is an oil, advantageously in liquid form at ambient temperature, resulting from the pyrolysis of plastics, preferably of plastic waste originating notably from collection and sorting channels, or resulting from the pyrolysis of used tyres or else from the pyrolysis of SRFs. It comprises in particular a mixture of hydrocarbon compounds, especially paraffins, olefins (mono- and / or diolefins), naphthenes and aromatics. At least 80% by weight of these hydrocarbon compounds preferably have a boiling point of less than 700° C. and preferably of less than 550° C. In particular, depending on the origin of the pyrolysis oil, the latter can comprise up to 70% by weight of paraffins, up to 90% by weight of naphthenes, up to 90% by weight of olefins and up to 90% by weight of aromatics, it being understood that the sum of the paraffins, of the naphthenes, of the olefins and of the aromatics is equal to 100% by weight of the hydrocarbon compounds.

[0038] The pyrolysis oil can comprise diolefins. The content of diolefins is commonly determined indirectly as the maleic anhydride value (MAV). The method is based on the Diels-Alder addition reaction between the conjugated diolefins and the maleic anhydride. The method for the determination of the MAV is described in C. López-Garcla et al., Near Infrared Monitoring of Low Conjugated Diolefins Content in Hydrotreated FCC Gasoline Streams, Oil & Gas Science and Technology—Rev. IFP, Vol. 62 (2007), No. 1, pp. 57-68. The MAV is expressed in mg of maleic anhydride having reacted with 1 g of sample (mg / g). The MAV varies between 5 and 100 mg / g in the pyrolysis oils.

[0039] The density of the pyrolysis oil, measured at 15° C. according to the ASTM D4052 method, is generally of between 0.75 g / cm3 and 0.99 g / cm3, preferably of between 0.75 g / cm3 and 0.95 g / cm3.

[0040] The pyrolysis oil may also comprise, and usually does comprise, impurities, such as metals, notably iron, silicon or halogenated compounds, notably chlorinated compounds. These impurities can be present in the pyrolysis oil at high contents, for example up to 500 ppm by weight or else 700 ppm by weight, or 1000 ppm by weight, and even 5000 ppm by weight, of halogen elements (notably chlorine but also bromine, fluorine, iodine or astatine) contributed by halogenated compounds, and generally between 1 and 1000 ppm by weight or between 1 and 700 ppm by weight or else between 1 and 500 ppm by weight of halogen elements. The pyrolysis oil can contain up to 500 ppm by weight or else 700 ppm by weight, or 1000 ppm by weight and even 5000 ppm by weight of chlorine elements contributed by chlorinated compounds, and generally between 1 and 1000 ppm by weight or between 1 and 700 ppm by weight or else between 1 and 500 ppm by weight of chlorine elements.

[0041] The oil can comprise up to 200 ppm by weight, or 1500 ppm by weight, of metal or semi-metal elements, and generally between 1 and 200 ppm by weight or between 1 and 1500 ppm by weight of metal or semi-metal elements. Akali metals, alkaline-earth metals, transition metals, post-transition metals and metalloids can be put into the same category as contaminants of metal nature, referred to as metals or metal or semi-metal elements. In particular, the metals or metal or semi-metal elements comprise silicon, iron or both of these elements. The pyrolysis oil can notably comprise up to 200 ppm by weight or else 1000 ppm by weight of silicon, and generally between 1 and 200 ppm by weight or between 1 and 1000 ppm by weight or else between 1 and 500 ppm by weight of silicon. The pyrolysis oil can notably comprise up to 50 ppm by weight or else 100 ppm by weight of iron, and generally between 1 and 50 ppm by weight or between 1 and 100 ppm by weight of iron. The pyrolysis oil can also comprise phosphorus, sodium, calcium, potassium and magnesium.

[0042] The pyrolysis oil can also comprise other impurities, such as heteroelements contributed notably by sulfur compounds, oxygen compounds and / or nitrogen compounds, at contents generally of less than 40 000 ppm by weight of heteroelements and preferably of less than 15 500 ppm by weight of heteroelements, and generally between 1 and 40 000 ppm by weight or between 1 and 15 500 ppm by weight of heteroelements.

[0043] The sulfur compounds are generally present in a content of less than 15 000 ppm by weight and preferably of less than 10 000 ppm by weight, and generally between 1 and 15 000 ppm by weight or between 1 and 10 000 ppm by weight of sulfur compounds.

[0044] The oxygen compounds are generally present in a content of less than 15 000 ppm by weight and preferably of less than 10 000 ppm by weight, and generally between 1 and 15 000 ppm by weight or between 1 and 10 000 ppm by weight of oxygen compounds.

[0045] The nitrogen compounds are generally present in a content of less than 10 000 ppm by weight and preferably of less than 5000 ppm by weight, and generally between 1 and 10 000 ppm by weight or between 1 and 5000 ppm by weight of nitrogen compounds.

[0046] The contents of sulfur, oxygen and / or nitrogen compounds often depend on the origin of the oil. Thus, tyre pyrolysis oils generally contain more heteroelements than plastic pyrolysis oils, notably sulfur compounds.

[0047] The pyrolysis oil can also comprise other impurities, such as heavy metals, for example mercury, arsenic, zinc and lead, for example up to 100 ppb by weight or else 200 ppb by weight of mercury or of arsenic, and generally between 1 and 200 ppb by weight or between 1 and 100 ppb by weight of heavy metals.

[0048] The pyrolysis feedstock of the process according to the invention comprises at least one plastic and / or tyre and / or SRF pyrolysis oil. Said feedstock can consist solely of pyrolysis oil(s). Preferably, said feedstock comprises at least 50% by weight, in a preferred way between 70% and 100% by weight, of pyrolysis oil, relative to the total weight of the feedstock, that is to say preferably between 50% and 100% by weight and in a preferred way between 70% and 100% by weight of plastic pyrolysis oil.

[0049] Particularly preferably, the pyrolysis feedstock of the process according to the invention consists solely of plastic and / or tyre and / or SRF pyrolysis oil(s).

[0050] In the case of a mixture of a plastic pyrolysis oil, a tyre pyrolysis oil and / or an SRF pyrolysis oil, this mixture can be produced in any proportion.

[0051] According to another variant, the pyrolysis feedstock of the process according to the invention introduced in step a) can comprise, in addition to the pyrolysis oil(s), a conventional petroleum feedstock or a feedstock resulting from biomass conversion which is then co-treated with the pyrolysis oil of the feedstock.

[0052] The conventional petroleum feedstock introduced in step a) can advantageously be a cut or a mixture of cuts of naphtha or gas oil type.

[0053] The feedstock resulting from the biomass conversion introduced in step a) can advantageously be chosen from vegetable oils, oils from algae or algal oils, fish oils, waste edible oils, and fats of vegetable or animal origin, or mixtures of such feedstocks. Said vegetable oils can advantageously be crude or refined, completely or partly, and obtained from plants chosen from rapeseed, sunflower, soybean, palm, olive, coconut, coconut kernel, castor oil plant, cotton plant, peanut oil, linseed oil and sea kale oil, and all the oils obtained, for example, from sunflower or rapeseed by genetic modification or hybridization, this list not being limiting. Said animal fats are advantageously chosen from blubber and fats composed of residues from the food industry or obtained from the catering industries. Frying oils, various animal oils, such as fish oils, tallow or lard, can also be used. The feedstock resulting from biomass conversion can also advantageously be chosen from fatty acid methyl esters of vegetable and / or animal origin or else fatty acid methyl esters from waste edible vegetable oils.

[0054] The feedstock obtained from the conversion of biomass can also be chosen from feedstocks originating from thermal or catalytic biomass conversion processes, such as oils which are produced from biomass, in particular from lignocellulosic biomass, with various liquefaction methods, such as hydrothermal liquefaction or pyrolysis. The term “biomass” refers to a material derived from recently living organisms, which includes plants, animals and by-products thereof. The term “lignocellulosic biomass” denotes biomass derived from plants or from by-products thereof. The lignocellulosic biomass is composed of carbohydrate polymers (cellulose, hemicellulose) and of an aromatic polymer (lignin).

[0055] The feedstock resulting from biomass conversion can also advantageously be chosen from feedstocks resulting from the papermaking industry.

[0056] The plastic and / or tyre and / or SRF pyrolysis oil can result from a thermal or catalytic pyrolysis treatment or else be prepared by hydropyrolysis (pyrolysis in the presence of a catalyst and of hydrogen).Pretreatment (Optional)

[0057] Said pyrolysis feedstock comprising a plastic and / or tyre and / or SRF pyrolysis oil can advantageously be pretreated in at least one optional pretreatment step a0), prior to the hydrotreating step a), in order to obtain a pretreated feedstock which feedstocks step a).

[0058] According to one variant, this optional pretreatment step a0) makes it possible to reduce the amount of contaminants and of solid particles, in particular the amount of iron and / or of silicon and / or of chlorine, possibly present in the feedstock comprising a pyrolysis oil. This optional step a0) makes possible notably the removal of sediments which can be formed as a result of the unstable nature of the pyrolysis oils and / or of a problem of compatibility between two different feedstocks. Thus, an optional step a0) of pretreatment of the feedstock comprising a pyrolysis oil is advantageously carried out, in particular when said feedstock comprises more than 10 ppm by weight, notably more than 20 ppm by weight, more particularly more than 50 ppm by weight, of metal elements and / or of solid particles, and in particular when said feedstock comprises more than 5 ppm by weight of silicon, more particularly more than 10 ppm by weight, indeed even more than 20 ppm by weight, of silicon. Likewise, an optional step a0) of pretreatment of the feedstock comprising a pyrolysis oil is advantageously carried out in particular when said feedstock comprises more than 10 ppm by weight, notably more than 20 ppm by weight, more particularly more than 50 ppm by weight, of chlorine.

[0059] Said optional pretreatment step a0) can be carried out by any method known to those skilled in the art which makes it possible to reduce the amount of contaminants. It can notably comprise an adsorption step and / or a filtration step and / or a centrifugation step and / or a settling step and / or an electrostatic separation step and / or a step of washing with an aqueous solution and / or a gas stripping step.

[0060] The optional pretreatment step a0) is advantageously carried out at a temperature of between 20° C. and 400° C., preferably between 40° C. and 350° C., and at a pressure between 0.15 and 10.0 MPa abs., preferably between 0.2 and 7.0 MPa abs.

[0061] According to one variant, said optional pretreatment step a0) is carried out in an adsorption section operated in the presence of at least one adsorbent. The adsorbent can be chosen from a zeolite, activated carbon, a clay, a silica or an alumina. Preferably, the adsorbent is an alumina, having a specific surface area greater than or equal to 100 m2 / g, preferably greater than or equal to 200 m2 / g. The specific surface area of said at least one adsorbent is advantageously less than or equal to 600 m2 / g, in particular less than or equal to 400 m2 / g. The specific surface area of the adsorbent is a surface area measured by the BET method, that is to say the specific surface area determined by nitrogen adsorption in accordance with Standard ASTM D 3663-78 drawn up from the Brunauer-Emmett-Teller method described in the periodical The Journal of the American Chemical Society, 6Q, 309 (1938).

[0062] Advantageously, said adsorbent comprises less than 1% by weight of metal elements and preferably is devoid of metal elements. Metal elements of the adsorbent should be understood as meaning the elements from groups 6 to 10 of the Periodic Table of the Elements (new IUPAC classification). The residence time of the feedstock in the adsorption section is generally of between 1 and 180 minutes.

[0063] Said adsorption section of the optional step a0) comprises at least one adsorption column, preferably comprises at least two adsorption columns, preferentially between two and four adsorption columns, containing said adsorbent. When the adsorption section comprises two adsorption columns, one operating mode can be a “swing” operation, in which one of the columns is on-line, that is to say in operation, while the other column is in reserve. When the adsorbent of the on-line column is spent, this column is isolated, while the column in reserve is placed on-line, that is to say in operation. The spent adsorbent can subsequently be regenerated in situ and / or replaced with fresh adsorbent in order for the column containing it to be again able to be placed back on-line once the other column has been isolated.

[0064] Another operating mode is to have at least two columns operating in series. When the adsorbent of the column placed at the head is spent, this first column is isolated and the spent adsorbent is either regenerated in situ or replaced with fresh adsorbent. The column is subsequently brought back on-line in the last position, and so on. This operation is referred to as permutable mode, or as PRS for permutable reactor system or else as “lead and lag”. The combination of at least two adsorption columns makes it possible to overcome the possible and potentially rapid poisoning and / or clogging of the adsorbent due to the combined action of the metallic contaminants, of the diolefins, of the gums obtained from the diolefins and of the insoluble matter that may be present in the pyrolysis oil to be treated. This is because the presence of at least two adsorption columns facilitates the replacement and / or the regeneration of the adsorbent, advantageously without shutdown of the pretreatment unit, indeed even of the process, thus making it possible to reduce the risks of clogging and thus to avoid shutdown of the unit due to clogging, to control the costs and to limit the consumption of adsorbent.

[0065] According to another variant, said optional pretreatment step a0) is carried out in a section for washing with an aqueous solution, for example water, or an acidic or basic solution. This washing section can comprise items of equipment which make it possible to bring the feedstock into contact with the aqueous solution and to separate the phases so as to obtain, on the one hand, the pretreated feedstock and, on the other hand, the aqueous solution comprising impurities. These items of equipment can include, for example, a stirred reactor, a settler, a mixer-settler and / or a cocurrent or countercurrent washing column.

[0066] According to another variant, said optional pretreatment step a0) is carried out by filtration. The filtration step makes it possible to remove the inorganic solids, sediments and / or fines contained in the feedstock, notably the metals, metal oxides and metal chlorides. Use is generally made of a filter, the size (for example the diameter or equivalent diameter) of the pores of which is less than 25 μm, preferably less than or equal to 10 μm, even more preferably less than or equal to 5 μm. According to another variant, use may be made of a filter, the size of the pores of which is less than 25 μm but greater than 5 μm. Use may also be made of a series of filters with different pore sizes, notably a series of filters having pore sizes decreasing in the direction of the circulation of the feedstock. These filtering media are well known for industrial uses. Cartridge filters or self-cleaning filters are suitable, for example. The solids content can be measured, for example, by the Heptane Insolubles test, ASTM D-3279 method. The content of insolubles in heptane has to be reduced to less than 0.5% by weight, preferably to less than 0.1%.

[0067] According to a specific embodiment, the step of pretreatment a0) by filtration comprises at least one filter, the size of the pores of which is less than 10 μm and preferably greater than 5 μm, optionally followed by a filtration system, the size of the pores of which is less than 2 μm and preferably less than 1 μm.

[0068] According to another specific embodiment, the step of pretreatment a0) by filtration comprises at least one filter, the size of the pores of which is less than 10 μm and preferably greater than 5 μm, followed by an electrostatic precipitation system.

[0069] According to another specific embodiment, the step of pretreatment a0) by filtration comprises at least one filter, the size of the pores of which is less than 10 μm and preferably greater than 5 μm, followed by a system of filter(s) using filtration adjuvants, such as sand or diatomaceous earths.

[0070] According to another variant, said optional pretreatment step a0) is carried out by centrifugation. According to another variant, the pretreatment step a0) comprises a centrifugation and a filtration.

[0071] According to another variant, said optional pretreatment step a0) is carried out by settling. According to another variant, the pretreatment step a0) comprises a settling and a filtration. According to another variant, said optional pretreatment step a0) is carried out by gas stripping, thus reducing the content of oxygen in the feedstock. The gas extraction can remove the oxygen (O2) which may be dissolved in the feedstock, thus reducing the probability of formation of free radicals resulting in polymerization in the downstream steps. The process generally involves bringing the feedstock into contact with an extraction gas (for example H2, N2 or a mixture thereof), thus transferring at least one portion of the dissolved oxygen of the feedstock to the extraction gas, followed by the separation of the extraction gas from the feedstock. The volume of extraction gas with respect to the volume of feedstock (the two volumes measured under gas extraction conditions) is generally greater than 1 and preferably at least 3. In specific embodiments, the extraction gas can contain at least 60% (molar percentage) of H2. Any dissolved H2 remaining in the feedstock after the gas extraction step is not a problem, due to the downstream hydrotreating. Preferably, the gas extraction step is finished before any (pre)heating of the feedstock, in order to minimize the potential fouling.

[0072] Said optional pretreatment step a0) generally comprises one or more, preferably several, treatments described above. It can notably comprise a series of a step of washing with an aqueous solution and / or an adsorption step, followed by a gas stripping step, followed by a filtration step and / or by a centrifugation step. All these steps are preferably carried out before any (pre)heating of the feedstock.

[0073] Said optional pretreatment step a0) thus makes it possible to obtain a pretreated feedstock which subsequently feedstocks the mild hydrotreating step a).Hydrotreating Step a)

[0074] According to the invention, the process comprises a step a) carried out in a hydrotreating reaction section comprising at least one hydrotreating catalyst, said hydrotreating reaction section being fed at least with the pyrolysis feedstock and a gas stream comprising hydrogen, said hydrotreating reaction section being used at an average temperature of between 100° C. and 220° C., a partial pressure of hydrogen of between 1.0 and 3.0 MPa abs. and an hourly space velocity of between 0.05 and 5 h−1, the hydrogen coverage being between 5 and 50 Nm3 of hydrogen per m3 of pyrolysis feedstock, in order to obtain a partially hydrotreated effluent having hydrocarbon compounds with a reduced halogen content.

[0075] Step a) is notably carried out under mild hydrogen pressure and temperature conditions enabling notably the removal of the halogens, and notably of chlorine, in order to make the pyrolysis oil compatible as co-feedstock in the steam cracking unit.

[0076] The other impurities contained in the pyrolysis oils (metals, silicon, nitrogen, etc.) are not necessarily completely removed during the process according to the invention, although the operating conditions make it possible to remove at least a portion thereof. Step a) thus mainly involves hydrogenation reactions of the halogenated compounds, and to a lesser extent also other hydrotreating reactions well known to those skilled in the art, particularly hydrotreating reactions such as hydrogenation of aromatics, hydrodesulfurization and hydrodenitrogenation, and also the hydrogenation of olefins and diolefins.

[0077] Said hydrotreating reaction section is advantageously used at an average hydrotreating temperature (or WABT as defined below) of between 100° C. and 220° C., preferably between 120° C. and 200° C., at a partial pressure of hydrogen of between 1.0 and 3.0 MPa abs., preferably between 1.0 and 2.4 MPa abs., preferably between 1.2 and 2.2 MPa abs., and at an hourly space velocity (HSV) of between 0.1 and 5 h−1, preferably between 0.1 and 2 h−1, preferentially of between 0.1 and 1.0 h−1. The hydrogen coverage in step a) is advantageously of between 5 and 50 Nm3 of hydrogen per m3 of fresh feedstock, and preferably between 10 and 40 Nm3 of hydrogen per m3 of fresh feedstock and in a preferred way between 15 and 30 Nm3 of hydrogen per m3 of fresh feedstock.

[0078] According to the invention, the “average temperature” of a reaction section corresponds to the weight-average bed temperature (WABT), which is well known to those skilled in the art. The average temperature is advantageously determined as a function of the catalytic systems, of the items of equipment, of the configuration of these, that are used. The average temperature (or WABT) is calculated in the following way:WABT=(Tentrée+Tsortie) / 2

[0079] with Tinlet: the temperature of the flow at the inlet of the reaction section and Toutlet: the temperature of the effluent at the outlet of the reaction section. Unless otherwise indicated, the “average temperature” of a reaction section is given at cycle beginning conditions.

[0080] The hourly space velocity (HSV) is defined here as the ratio of the hourly volume flow rate of the feedstock comprising the pyrolysis oil, which has optionally been pretreated, to the volume of catalyst(s).

[0081] The hydrogen coverage is defined as the ratio of the volume flow rate of hydrogen, taken under normal temperature and pressure conditions, relative to the volume flow rate of “fresh” feedstock, that is to say of the feedstock to be treated, which has optionally been pretreated, without taking into account a recycled fraction, at 15° C. (in normal m3, denoted Nm3, of H2 per m3 of feedstock).

[0082] The gas stream comprising hydrogen, which feedstocks the hydrotreating reaction section, can consist of a supply of hydrogen and / or of recycled hydrogen. Preferably, an additional gas stream comprising hydrogen is advantageously introduced at the inlet of each reactor, in particular operating in series, and / or at the inlet of each catalytic bed starting from the second catalytic bed of the reaction section. These additional gas streams are also referred to as cooling streams. They make it possible to control the temperature in the reactor in which the reactions carried out are generally highly exothermic.

[0083] The gas stream comprising hydrogen may be derived from a fossil source or from a renewable source, for example derived from the gasification of plastic waste, or produced by electrolysis.

[0084] Advantageously, the gas stream comprising hydrogen originates from a compressor used in the refinery to supply another hydrorefining unit using hydrogen, such as a hydrocracking, hydrotreating or hydroconversion unit. This has the advantage of dispensing with a dedicated compressor for recycling the hydrogen from step b) and therefore saving on investment costs.

[0085] Optionally, the reaction section of said step a) can also be additionally supplied with a portion of the partially hydrotreated hydrocarbon (recycle) effluent from step b) as described below.

[0086] Preferably, the process according to the invention comprises a hydrotreating step a) carried out in a hydrotreating reaction section, using at least one fixed-bed reactor having n catalyst beds, n being an integer greater than or equal to 1, preferably between 1 and 10, preferably between 2 and 5, each comprising at least one hydrotreating catalyst.

[0087] Said hydrotreating reaction section is fed at least with the optionally pretreated pyrolysis feedstock, and a gas stream comprising hydrogen, advantageously at the first catalyst bed of the first reactor in operation. An injection of at least one portion of the pyrolysis feedstock and / or at least one portion of hydrogen between the various catalyst beds is also possible.

[0088] The hydrotreating reaction section using at least one fixed-bed reactor can operate with gas and liquid downflow or upflow.

[0089] Advantageously, the reaction section of said step a) comprises between 1 and 5 reactors, preferably between 2 and 5 reactors, and particularly preferably it comprises two reactors. The advantage of a hydrotreating reaction section comprising several reactors lies in an optimized treatment of the feedstock, while making it possible to reduce the risks of clogging of the catalyst bed(s) and thus to avoid shutdown of the unit due to clogging.

[0090] According to this embodiment, the hydrotreating reaction section of step a) comprises two reactors operating in permutable mode, known as PRS for permutable reactor system or else as “lead and lag”. The combination of at least two reactors in PRS mode makes it possible to isolate a reactor, to discharge the spent catalyst, to recharge the reactor with fresh catalyst and to bring said reactor back into service without shutting down the process. The PRS technology is described in particular in patent FR 2 681 871.

[0091] According to another embodiment, said hydrotreating reaction section comprises a single fixed-bed reactor containing n catalyst beds, n being an integer greater than or equal to 1, preferably between 1 and 10, in a preferred way between 2 and 5.

[0092] Advantageously, reactor internals, for example of filter plate type, can be used to prevent the plugging of the reactor(s). An example of a filter plate is described in patent FR 3 051 375.

[0093] Preferably, step a) can employ, upstream of the hydrotreating catalyst(s), at least one guard bed containing adsorbents of alumina, silica, silica-alumina, zeolite and / or active carbon type optionally containing metals from group VIB and / or VIII. Use may also be made of a series of guard beds with particles of different diameters, notably a series of guard beds having diameters decreasing in the direction of the circulation of the feedstock (also referred to as “grading”).

[0094] Advantageously, said hydrotreating catalyst comprises a support, preferably a mineral support, and a hydrogenating-dehydrogenating function.

[0095] According to one variant, the hydrogenating-dehydrogenating function comprises in particular at least one element from group VIII, preferably chosen from nickel and cobalt, and at least one element from group VIB, preferably chosen from molybdenum and tungsten. According to this variant, the total content, expressed as oxides, of the metal elements from groups VIB and VIII is preferably between 1% and 40% by weight, preferentially from 5% to 30% by weight, relative to the total weight of the catalyst. When the metal is cobalt or nickel, the metal content is expressed as CoO and NiO respectively. When the metal is molybdenum or tungsten, the metal content is expressed as MoO3 and WO3 respectively.

[0096] The ratio by weight, expressed as metal oxide, of the metal (or metals) from group VIB relative to the metal (or to the metals) from group VIII is preferably between 1 and 20 and with preference between 2 and 10.

[0097] According to this variant, the reaction section of said step a) comprises, for example, a hydrotreating catalyst comprising between 0.5% and 12% by weight of nickel, preferably between 0.9% and 10% by weight of nickel (expressed as nickel oxide NiO relative to the weight of said catalyst), and between 1% and 30% by weight of molybdenum, preferably between 3% and 20% by weight of molybdenum (expressed as molybdenum oxide MoO3 relative to the weight of said catalyst), on a preferably mineral support, preferably on an alumina support.

[0098] According to another variant, the hydrogenating-dehydrogenating function comprises, and preferably consists of, at least one group VIII element, preferably nickel. According to this variant, the content of nickel oxides is preferably between 1% and 50% by weight, preferably between 10% and 30% by weight, relative to the weight of said catalyst. This type of catalyst is preferably used in its reduced form, on a preferably mineral support, preferably on an alumina support.

[0099] The support for said hydrotreating catalyst is preferably chosen from alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof. Said support can include dopant compounds, notably oxides chosen from boron oxide, especially boron trioxide, zirconia, ceria, titanium oxide, phosphorus pentoxide and a mixture of these oxides. Preferably, said hydrotreating catalyst comprises an alumina support, optionally doped with phosphorus and optionally boron. When phosphorus pentoxide P2O5 is present, its concentration is less than 10% by weight, relative to the weight of the alumina, and advantageously at least 0.001% by weight, relative to the total weight of the alumina. When boron trioxide B2O3 is present, its concentration is less than 10% by weight, relative to the weight of the alumina, and advantageously at least 0.001%, relative to the total weight of the alumina. The alumina used can, for example, be a γ (gamma) or η (eta) alumina.

[0100] Said hydrotreating catalyst is for example in the form of extrudates or in the form of beads.

[0101] Very preferably, step a) may also use, in addition to the hydrotreating catalyst(s) described above, at least one hydrotreating catalyst used in step a) comprising less than 1% by weight of nickel and at least 0.1% by weight of nickel, preferably 0.5% by weight of nickel, expressed as nickel oxide NiO relative to the weight of said catalyst, and less than 5% by weight of molybdenum and at least 0.1% by weight of molybdenum, preferably 0.5% by weight of molybdenum, expressed as molybdenum oxide MoO3 relative to the weight of said catalyst, on an alumina support. This catalyst, not highly loaded with metals, can be preferably placed upstream or downstream of the hydrogenation catalyst(s) described above, preferably upstream.

[0102] The preparation of the catalyst for the hydrotreating step a) is known and generally comprises a step of impregnation of the group VIII metals and of the group VIB metals when present, and optionally of the phosphorus and / or boron on the support, followed by drying, and then optionally calcining. The catalyst of step a) can also be a catalyst used in its reduced form, thus involving a reduction step in its preparation.

[0103] Before being used in a step of the process, the catalysts are generally subjected to sulfidation in order to form the active species. Depending on the content of sulfur compounds in the initial feedstock to be treated, a stream containing a sulfiding agent can be injected upstream of the optional pretreatment step a0) or of the hydrotreating step a), preferably upstream of the hydrotreating step a), in order to ensure a sufficient amount of sulfur to form the active species of the catalyst (in sulfide form). This activation or sulfidation step is carried out by methods well known to those skilled in the art, and advantageously under a sulfo-reductive atmosphere in the presence of hydrogen and hydrogen sulfide. The sulfiding agents are preferably H2S gas, elemental sulfur, CS2, mercaptans, sulfides and / or polysulfides, hydrocarbon cuts having a boiling point of less than 400° C. containing sulfur compounds or any other sulfur-containing compound used for the activation of hydrocarbon feedstocks with a view to sulfiding the catalyst. Said sulfur-containing compounds are advantageously chosen from alkyl disulfides, such as, for example, dimethyl disulfide (DMDS), akyl sulfides, such as, for example, dimethyl sulfide, thiols, such as, for example, n-butyl mercaptan (or 1-butanethiol), and polysulfide compounds of tert-nonyl polysulfide type. The catalyst can also be sulfided by the sulfur contained in the feedstock to be desulfurized. Preferably, the catalyst is sulfided in situ in the presence of a sulfiding agent and of a hydrocarbon feedstock. Very preferably, the catalyst is sulfided in situ in the presence of the feedstock additivated with dimethyl disulfide. The sulfiding agent can be injected continuously.

[0104] The partially hydrotreated effluent obtained at the end of the hydrogenation step a) is sent, preferably directly, to the washing / separation step b).Separation Step b)

[0105] According to the invention, the treatment process comprises a separation step b), advantageously performed in at least one washing / separation section, fed at least with the partially hydrotreated effluent from step a) and an aqueous solution, to obtain at least a gaseous effluent, an aqueous effluent and a partially hydrotreated hydrocarbon effluent.

[0106] This separation step b) makes it possible in particular to remove the halogens (chlorine) in the form of hydrogen halides (HCl notably) formed by the reaction of hydrogen ions and halide ions released by the hydrogenation of the halogenated compounds during step a) which dissolve in the aqueous solution.

[0107] The separation step b) is advantageously carried out at a temperature of between 20° C. and 200° C., preferentially between 50° C. and 180° C., in a preferred way between 80° C. and 150° C. Advantageously, the separation step b) is carried out at a pressure close to that used in step a), preferably between 1.0 and 2.0 MPa, so as to facilitate the recycling of hydrogen if need be.

[0108] The separation step can advantageously be carried out by any method known to those skilled in the art, such as, for example, the combination of one or more separators (drums) and / or one or more stripping columns, it being possible for this or these separator(s) (drum(s)) and / or columns to be optionally fed with a stripping gas, for example a hydrogen-rich gas stream. The washing / separation section of step c) can, at least partly, be produced from common or separate items of washing and separating equipment.

[0109] Advantageously, the separation step b) comprises an injection of an aqueous solution, preferably an injection of water, into the partially hydrotreated effluent from step a), upstream of the washing / separation section, so as to dissolve at least some and preferably all of of the hydrogen halides (HCl notably) and any salts present.

[0110] The aqueous solution may be water. It can also be a basic aqueous solution (by adding NaOH for example). The use of a basic solution makes it possible to neutralize the hydrogen halides and any dissolved salts.

[0111] In one optional embodiment of the invention, the separation step b) comprises the injection of an aqueous solution into the partially hydrotreated effluent from step a), followed by the washing / separation section advantageously comprising a separation phase for obtaining at least one aqueous effluent loaded with hydrogen halides (HCl notably) and any dissolved salts present, a washed partially hydrotreated effluent and a partially washed gaseous effluent. Said aqueous effluent and the washed partially hydrotreated effluent can then be separated in a knockout drum in order to obtain said washed partially hydrotreated effluent and said aqueous effluent. Said partially washed gaseous effluent can simultaneously be introduced into a washing column where it circulates countercurrentwise relative to an aqueous stream, preferably of the same nature as the aqueous solution injected into the partially hydrotreated effluent, which makes it possible to remove at least some, preferably all, of the hydrochloric acid contained in the partially washed gaseous effluent and to thus obtain said gaseous effluent, preferably essentially comprising hydrogen, and an acidic aqueous stream. Said aqueous effluent resulting from the knockout drum can optionally be mixed with said acidic aqueous stream, and be used, optionally as a mixture with said acidic aqueous stream, in a water recycling circuit for feedstocking separation step b) with said aqueous solution upstream of the washing / separation section and / or with said aqueous stream in the washing column. Said water recycling circuit can comprise a supply of water and / or of a basic solution and / or a bleed making it possible to discharge the impurities.

[0112] The hydrotreating step a) mainly involves hydrogenation reactions of the halogenated compounds, and to a lesser extent also other hydrotreating reactions such as hydrodenitrogenation, which generates NH3 by hydrogenation of nitrogen compounds, and hydrodesulfurization, which generates H2S by hydrogenation of sulfur compounds.

[0113] When NH3 is present in the partially hydrotreated effluent from step a), the separation step b) also makes it possible to remove ammonium chloride salts, which are formed by reaction between the chloride ions, released by the hydrogenation of the chlorinated compounds in the form of HCl notably during step a), and the ammonium ions, generated by the hydrogenation of the nitrogen compounds in the form of NH3 during step a) by dissolving them in the aqueous solution.

[0114] When H2S is present in the partially hydrotreated effluent from step a), the separation step b) also makes it possible to remove ammonium sulfide ((NH4)2S) salts which are formed by reaction between H2S resulting from the hydrodesulfurization of the sulfur compounds and NH3, by dissolving them in the aqueous solution.

[0115] According to one embodiment, and as a function of the content of chlorine compounds in the initial or pretreated feedstock, a stream containing a nitrogen compound such as ammonia or an amine, for example monoethanolamine, diethanolamine and / or monodiethanolamine, can be injected upstream of the hydrotreating step a) so as to ensure a sufficient amount of ammonium ions for combining the chloride ions formed during the hydrotreating step in the form of ammonium chloride salts, thus making it possible to limit the formation of hydrochloric acid and thus to limit the corrosion downstream of the separation section.

[0116] The gaseous effluent obtained on conclusion of step b) advantageously comprises hydrogen, preferably comprises at least 80 vol %, preferably at least 85 vol %, of hydrogen. The gaseous effluent obtained on conclusion of step b) contains very little chlorine, generally at a content of less than 3 ppm by weight of chlorine, which enables it to be sent into a refining unit requiring hydrogen.

[0117] According to one embodiment, said gaseous effluent can at least partly be recycled to the hydrotreating step a), it being possible for the recycling system to comprise a purification section (for example for adsorption of heavy metals such as mercury).

[0118] According to another preferred embodiment, said gaseous effluent can at least partly be recycled upstream of a hydrogen compressor used to supply a hydrorefining unit using hydrogen such as a hydrocracking, hydrotreating or hydroconversion unit of the refinery. This has the advantage of being able to dispense with a dedicated compressor for recycling hydrogen from step b) and therefore saving on investment costs.

[0119] As for the partially hydrotreated hydrocarbon liquid effluent from step b) and according to one variant, a portion of the partially hydrotreated hydrocarbon effluent from step b) can be recycled upstream of step a). The recycling of a portion of the partially hydrotreated hydrocarbon effluent from step b) to or upstream of step a) advantageously makes it possible, on the one hand, to dilute the impurities and, on the other hand, to control the temperature in step a) in which the reactions involved can be highly exothermic. Diluting the impurities makes it possible to limit undesirable reactions such as the polymerization of diolefins (formation of gum) and / or the formation of coke.

[0120] Advantageously, the amount of the partially hydrotreated hydrocarbon effluent from step b) that is recycled, i.e. the fraction of product obtained that is recycled, is adjusted so that the weight ratio of the recycle stream from step b) to the feedstock comprising a pyrolysis oil, i.e. the feedstock to be treated feedstocking the overall process, is less than or equal to 10, preferably less than or equal to 7, and preferentially greater than or equal to 0.001, preferably greater than or equal to 0.01 and in a preferred way greater than or equal to 0.1. Preferably, the amount of the partially hydrotreated hydrocarbon effluent from step b) that is recycled is adjusted so that the weight ratio of the recycle stream to the feedstock comprising a pyrolysis oil is between 0.01 and 10, preferably between 0.1 and 7 and particularly preferably between 0.2 and 5. This recycle ratio makes it possible notably to control the rise in the temperature in step a). This is because, when the recycle ratio is high, the rate of dilution of the feedstock is high, and the rise in temperature at the beginning of the reaction section of step a) is thus controllable by the dilution effect. The injection of the partially hydrotreated hydrocarbon effluent from step b) can be carried out at the first catalyst bed of the reaction section of step a) or between the various catalyst beds. When the hydrotreating reaction section of step a) comprises two reactors operating in permutable mode, at least one portion of the partially hydrotreated hydrocarbon effluent from step b) can be recycled between the two reactors.

[0121] According to another preferred embodiment, the partially hydrotreated hydrocarbon effluent from step b) is partly and preferably entirely sent directly to the inlet of a steam cracking unit as a co-feedstock with a petroleum feedstock. This has the advantage of not needing a recycle compressor.

[0122] Said partially hydrotreated hydrocarbon effluent from step b) thus obtained by treatment according to steps a) and b) of the process of the invention has a composition compatible with being introduced as co-feedstock into a steam cracking unit.

[0123] The partially hydrotreated hydrocarbon effluent from step b) is notably an effluent with a reduced content of halogenated compounds, and notably of chlorine.

[0124] Preferably, at least 50%, and more preferably at least 75% of the halogenated compounds of the initial feedstock are removed during steps a) and b).

[0125] The other impurities contained in the pyrolysis oils (metals, silicon, nitrogen, etc.) are not necessarily completely removed during steps a) and b) of the process according to the invention, although the operating conditions make it possible to remove at least a portion thereof. Indeed, the pyrolysis oil, which is the partially hydrotreated hydrocarbon effluent, does not need to be completely hydrotreated in order to be able to introduce it as a co-feedstock into a steam cracking unit. It notably does not need to undergo another hydrotreatment carried out at a temperature and / or pressure higher than those of step a) prior to its introduction into a steam cracking unit. The residual contents of impurities contained in the oil are compatible with the specifications for a steam cracking unit by diluting the oil with the petroleum feedstock injected in step c).

[0126] Preferably, at least 50% and more preferentially at least 75% of the metal elements of the initial feedstock are removed during steps a) and b).

[0127] Generally, at most 50%, and more preferentially at most 25%, of the sulfur compounds in the initial feedstock are removed during steps a) and b).

[0128] Preferably, at least 25%, and more preferentially at least 50% of the oxygen compounds of the initial feedstock are removed during steps a) and b).

[0129] Generally, at most 30%, and more preferentially at most 15%, of the nitrogen compounds of the initial feedstock are removed during steps a) and b).

[0130] The content of heavy metals such as mercury, arsenic, zinc and lead remains essentially unchanged.

[0131] The contents are given as relative concentrations by weight, percentages (%) by weight, part(s) per million (ppm) by weight or part(s) per billion (ppb) by weight, relative to the total weight of the stream under consideration.Steam Cracking Step c)

[0132] According to the invention the process comprises a step c) of steam cracking of a petroleum feedstock in which at least one portion of the partially hydrotreated hydrocarbon effluent from step b) is introduced as a co-feedstock, said partially hydrotreated hydrocarbon effluent from step b) being introduced without first undergoing another hydrotreating step carried out at higher temperature and / or pressure than the temperature and / or pressure of step a), said mixture of said petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) having a halogen content of less than or equal to 3 ppm by weight.

[0133] By virtue of the hydrotreating step a) making it possible to release the halogenated compounds (for example chlorine) mainly in gaseous form (hydrogen halides of HCl type notably), followed by the washing / separation step b) making it possible to dissolve and remove the hydrogen halides, the partially hydrotreated hydrocarbon effluent from step b) has a sufficiently reduced halogenated compound content to make it possible to inject it as a co-feedstock into a unit for for petroleum-feedstock steam cracking.

[0134] The partially hydrotreated hydrocarbon effluent from step b) is introduced into the unit for steam cracking of a petroleum feedstock in such an amount that the chlorine content in the mixture of petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) is less than or equal to 3 ppm by weight, preferably less than or equal to 1 ppm by weight.

[0135] Generally, the weight ratio of the flow rate of the partially hydrotreated hydrocarbon effluent from step b) (pyrolysis oil) to the flow rate of petroleum feedstock introduced into the unit of step c) in the process according to the invention is generally less than 1, and preferably between 0.01 and 0.9, and preferably between 0.02 and 0.5.

[0136] When the content of halogenated compounds is greater than 3, or even 1 ppm by weight in the partially hydrotreated hydrocarbon effluent from step b), the content of 3, or even 1 ppm of chlorine can be achieved by dilution at the inlet of the unit with the petroleum feedstock.

[0137] The petroleum feedstock used in the steam cracking unit is preferably chosen from naphtha, kerosene, gas oil, or mixtures of such feedstocks.

[0138] Said steam cracking step c) is advantageously carried out in at least one pyrolysis furnace at a temperature of between 70° and 900° C., preferably between 75° and 850° C., and at a pressure of between 0.05 and 0.3 MPa relative in the presence of steam. The residence time of the hydrocarbon compounds is generally less than or equal to 1.0 second (noted as s), preferably between 0.1 and 0.5 s. Steam is advantageously introduced upstream of the steam cracking step c) and after the separation (or fractionation). The amount of water introduced, in the form of steam, is advantageously between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds at the inlet of step c). The steam cracking step c) can be carried out in a plurality of pyrolysis furnaces in parallel, so as to adapt the operating conditions to the various streams feedstocking step c), and also to manage the tube decoking times. A furnace comprises one or more tubes arranged in parallel. A furnace can also denote a group of furnaces operating in parallel. For example, a furnace may be dedicated to cracking the middle distillates cut.

[0139] The effluents from the various steam cracking furnaces are generally recombined before separation for the purpose of constituting an effluent. It is understood that the steam cracking step c) includes the steam cracking furnaces but also the substeps associated with the steam cracking that are well known to those skilled in the art. These substeps may notably include heat exchangers, columns and catalytic reactors and recycling to the furnaces. A column generally makes it possible to fractionate the effluent for the purpose of recovering at least a light fraction comprising hydrogen and compounds having from 2 to 5 carbon atoms, and a fraction comprising pyrolysis petrol, and optionally a heavier fraction. Columns make it possible to separate the various constituents of the fractionation light fraction in order to recover at least a cut rich in ethylene (C2 cut) and a cut rich in propylene (C3 cut) and optionally a cut rich in butenes (C4 cut). The catalytic reactors make it possible notably to carry out hydrogenations of the C2, C3, indeed even C4, cuts and of the pyrolysis petrol. The saturated compounds, notably the saturated compounds having from 2 to 4 carbon atoms, are advantageously recycled to the steam cracking furnaces so as to increase the overall yields of olefins.

[0140] This steam cracking step c) makes it possible to obtain at least one effluent containing olefins comprising 2, 3 and / or 4 carbon atoms (i.e. C2, C3 and / or C4 olefins), in satisfactory contents, in particular greater than or equal to 30% by weight of total olefins comprising 2, 3 and 4 carbon atoms relative to the weight of the steam cracking effluent under consideration. Said C2, C3 and C4 olefins can subsequently be advantageously used as polyolefin monomers.Analysis Methods Used

[0141] The analysis methods and / or standards used to determine the characteristics of the various streams, in particular of the feedstock to be treated and of the effluents, are known to those skilled in the art. They are in particular listed below in Table 1 by way of information. Other methods reputed to be equivalent can also be used, notably equivalent IP, EN or ISO methods:TABLE 1DescriptionMethodsDensity @ 15° C.ASTM D4052Sulfur ContentISO 20846Nitrogen ContentASTM D4629Acid numberASTM D664Bromine NumberASTM D1159Maleic anhydride value (MAV)MAV method (1)Content of Oxygen-Containing MoleculesCombustion + InfraredContent of ParaffinsUOP990-11Content of Naphthenes and OlefinsUOP990-11Content of AromaticsUOP990-11Content of HalogensASTM D7359Chlorine contentASTM D7536Content of Metals:ASTM D5185PFeSiNaBSimulated distillationASTM D2887(1) MAV method described in the paper: C. López-García et al., Near Infrared Monitoring of Low Conjugated Diolefins Content in Hydrotreated FCC Gasoline Streams, Oil & Gas Science and Technology - Rev. IFP, Vol. 62 (2007), No. 1, pp. 57-68LIST OF FIGURES

[0142] The information regarding the elements referenced in FIG. 1 enables a better understanding of the invention, without said invention being limited to the particular embodiments illustrated in FIG. 1. The various embodiments presented can be used alone or in combination with one another, without limitation of combination.

[0143] FIG. 1 represents the diagram of a general embodiment of the process of the present invention, comprising:

[0144] a step a) of hydrotreating a pyrolysis oil 1 in the presence of a hydrogen-rich gas 2 and optionally an amine provided by the stream 3 and optionally a sulfiding agent provided by the stream 4;

[0145] a separation / washing step b) supplied with the partially hydrotreated effluent 5 from the hydrotreating step a) and in the presence of an aqueous solution 6 to obtain at least a gaseous effluent 7, an aqueous effluent 8 and a partially hydrotreated hydrocarbon effluent 9, of which a portion 9a can be recycled to step a);

[0146] a step c) of steam cracking of a petroleum feedstock 10 in which at least one portion, and preferably all, of the partially hydrotreated hydrocarbon effluent from step b) 9 is introduced as co-feedstock, said partially hydrotreated hydrocarbon effluent from step b) 9 being introduced without first undergoing another hydrotreating step carried out at higher temperature and / or pressure.

[0147] Only the main steps, with the main streams, are shown in the FIGURE, so as to allow a better understanding of the invention. It is clearly understood that all the items of equipment required for the operation are present (drums, pumps, exchangers, furnaces, columns, and the like), even if they are not represented. It is also understood that hydrogen-rich gas streams (supply or recycle streams), as described above, can be injected at the inlet of each reactor or catalyst bed or between two reactors or two catalyst beds.Examples

[0148] The pyrolysis feedstock treated in the process is a plastic pyrolysis oil (i.e. comprising 100% by weight of said plastic pyrolysis oil) having the characteristics indicated in Table 2.TABLE 2Characteristics of the pyrolysis feedstockFeed-DescriptionMethodsUnitstockDensity @ 15° C.ASTM D4052g / cm30.820Sulfur ContentISO 20846ppm by weight320Nitrogen ContentASTM D4629ppm by weight730Acid numberASTM D664mg KOH / g1.5Bromine NumberASTM D1159g / 100 g80Maleic anhydride valueMAV methodmg / 100 g10Content of Oxygen-Combustion +% by weight1.0Containing MoleculesInfraredContent of ParaffinsUOP990-11% by weight45Content of NaphthenesUOP990-11% by weight20Content of OlefinsUOP990-11% by weight25Content of AromaticsUOP990-11% by weight10Content of HalogensASTM D7359ppm by weight97Chlorine contentASTM D7536ppm by weight95Content of Metals:ASTM D5185Pppm by weight10Feppm by weight25Sippm by weight45Nappm by weight2Bppm by weight2Simulated distillationASTM D2887 0%° C.4010%° C.9830%° C.16150%° C.23270%° C.30990%° C.394100% ° C.432

[0149] The pyrolysis feedstock is subjected to a hydrotreating step a) carried out in a fixed-bed reactor and in the presence of hydrogen and an NiMo-on-alumina hydrotreating catalyst under different operating conditions indicated in Table 3.TABLE 3Conditions of the hydrotreating step a)Example 1Example 2Example 3(not in(in(inaccor-accor-accor-dance)dance)dance)Average temperature° C.230140140Partial pressure ofMPa332hydrogenabs.H2 / HCNm3 / m3555(Hydrogen coverage byvolume, relative to thevolume of feedstock)HSVh−10.50.50.35(volume flow rate offeedstock / volume ofcatalysts)

[0150] On conclusion of the hydrogenation step a), the degrees of conversion (=(initial concentration−final concentration) / initial concentration) observed for chlorine, diolefins and olefins are indicated in Table 4.TABLE 4Conversions of the entities during the hydrotreating step a)Example 1Example 2Example 3(not in(in(inaccor-accor-accor-dance)dance)dance)Degree of conversion%908275of the chlorineDegree of conversion%602112of the diolefinsDegree of conversion%1800of the olefinsH2 consumption% by weight0.180.010.01relative tothe weightof the freshfeedstock

[0151] The effluent from the hydrotreating step a) is subjected to a separation step b): a stream of water is injected into the effluent from the hydrotreating step a); the mixture is then treated in an acid gas washing column and separating drums.

[0152] The yields of the various fractions obtained after separation are shown in Table 5 (the yields correspond to the ratios of the amounts by weight of the various products obtained, relative to the weight of feedstock upstream of the step a), expressed as a percentage and denoted % w / w).TABLE 5Yields of the various products obtained after separationGas fraction (NH3 + H2S + H2O + C1-C4)% w / w2.42Liquid fraction% w / w99.31

[0153] The characteristics of the liquid fraction obtained after the separation step b) are presented in Table 6:TABLE 6characteristics of the liquid fractionExample 1Example 2Example 3(not in(in(inaccor-accor-accor-DescriptionMethodsUnitdance)dance)dance)SulfurISO 20846ppm by250279286ContentweightNitrogenASTMppm by725730730ContentD4629weightBromineASTMg / 100 g76.18080NumberD1159MaleicMAVmg / 100 g47.98.8anhydridemethodvalue(1)ChlorineASTMppm by101724contentD7536weightSimulatedASTMdistillationD2887 0%° C.60656310%° C.98999830%° C.16116216050%° C.23223123170%° C.30930830990%° C.394393394100% ° C.432434433

[0154] The effluent from step b) is then mixed with a petroleum feedstock (naphtha) for steam cracking having a chlorine content of 0 ppm by weight in a weight proportion of 10% oil / 90% petroleum feedstock. A mixture is obtained which contains less than 3 ppm by weight of chlorine (for all the examples), which is introduced into a fluidized-bed catalytic steam cracking unit.

[0155] Less energy (temperatures of step a)) and less hydrogen (H2 consumption) are used according to Examples 2 and 3.

[0156] Example 3, carried out under very mild temperature and pressure conditions, shows that it is possible to obtain an oil sufficiently stripped of chlorine while using less pressure (and therefore less energy) than in Example 2.

Claims

1. Process for treating a pyrolysis feedstock, comprising a plastic and / or tyre and / or solid recovered fuel pyrolysis oil comprising halogenated compounds, said process comprising:a) a hydrotreating step carried out in a hydrotreating reaction section comprising at least one hydrotreating catalyst, said hydrotreating reaction section being fed at least with the pyrolysis feedstock and a gas stream comprising hydrogen, said hydrotreating reaction section having an average temperature of between 100° C. and 220° C., a partial pressure of hydrogen of between 1.0 and 3.0 MPa abs. and an hourly space velocity of between 0.05 and 5 h−1, the hydrogen coverage being between 5 and 50 Nm3 of hydrogen per m3 of pyrolysis feedstock, in order to obtain a partially hydrotreated effluent having hydrocarbon compounds with a reduced halogen content,b) a separation step, fed with the partially hydrotreated effluent from step a) and an aqueous solution in order to obtain at least a gaseous effluent, an aqueous effluent and a partially hydrotreated hydrocarbon effluent,c) a step of steam cracking of a petroleum feedstock in which at least one portion of the partially hydrotreated hydrocarbon effluent from step b) is introduced as a co-feedstock, said partially hydrotreated hydrocarbon effluent from step b) being introduced without first undergoing another hydrotreating step carried out at higher temperature and / or pressure than the temperature and / or pressure of step a), said mixture of said petroleum feedstock and the partially hydrotreated hydrocarbon effluent from step b) having a halogen content of less than or equal to 3 ppm by weight.

2. Process according to claim 1, in which the weight ratio of the flow of the partially hydrotreated hydrocarbon effluent from step b) to the flow of petroleum feedstock introduced in step c) is less than 1.

3. Process according to claim 1, in which the pyrolysis feedstock consists of a plastic and / or tyre and / or solid recovered fuel pyrolysis oil.

4. Process according to claim 1, in which the content of halogenated compounds in said pyrolysis feedstock is between 1 and 5000 ppm by weight.

5. Process according to claim 1, in which a stream containing a nitrogen compound and / or a sulfur compound is injected upstream of step a).

6. Process according to claim 1, in which said hydrotreating catalyst of step a) comprises a support chosen from alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof and a hydrogenating-dehydrogenating function comprising either at least one group VIII element and at least one group VIB element, or at least one group VIII element.

7. Process according to claim 1, comprising at least one step a0) of pretreating the feedstock comprising a plastic and / or tyre and / or SRF pyrolysis oil, said pretreatment step being carried out upstream of step a), and comprises an adsorption step and / or a filtration step and / or a centrifugation step and / or a settling step and / or an electrostatic separation step and / or a step of washing with an aqueous solution and / or a gas stripping step.

8. Process according to claim 1, in which the petroleum feedstock introduced in steam cracking step c) is chosen from naphtha, kerosene, gas oil, or mixtures of such feedstocks.

9. Process according to claim 1, in which the reaction section of step a) includes at least two reactors operating in permutable mode.

10. Process according to claim 1, in which the steam cracking step c) is carried out in at least one pyrolysis furnace at a temperature of between 700 and 900° C. and at a pressure of between 0.05 and 0.3 MPa relative in the presence of steam.

11. Process according to claim 1, in which, in the steam cracking step c), the residence time of the hydrocarbon compounds is less than or equal to 1.0 second and the amount of water introduced, in the form of steam, is between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds at the inlet of step c).

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