PROCESS FOR TREATMENT OF PYROLYSIS OILS FOR VALORIZATION IN A STEAM CRACKER UNIT

Abstract

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

Description

Description Title of the invention: PROCESS FOR TREATING PYROLYSIS OILS FOR RECYCLING IN A UNIT STEAM CRACKING Technical field

[0001] = The present invention relates to a method for treating a pyrolysis oil from plastics and / or tires and / or solid recovered fuels (SRF) in order to to obtain a partially hydrotreated pyrolysis oil which can be recovered in as a co-feed with petroleum feedstocks in a steam cracking unit. More In particular, the present invention relates to a method of treating an oil pyrolysis for the elimination of its halogenated compounds in order to be able to easily recover this oil in a steam cracking unit. Prior art

[0002] = Plastic waste is generally mixtures of several polymers, for example example of mixtures of polyethylene, polypropylene, polyethylene te- rephthalate, polyvinyl chloride, polystyrene. In addition, depending on the uses, Plastics may contain, in addition to polymers, other compounds, such as plasticizers, pigments, dyes or even residues of poly- catalysts merization. Plastic waste may also contain, in small quantities, biomass from, for example, household waste. The treatment of waste on the one hand, including storage, mechanical treatment, sorting, pyrolysis, and also the storage and transportation of pyrolysis oil on the other hand can also induce corrosion.

[0003] — As for tires, they are mainly made of rubber for their property elastic (mixture of elastomers of natural and synthetic rubber type crosslinked, with the addition of adjuvants such as silica, resin, sulfur, zinc oxide, carbon black carbon, etc.) and textile and metal fibers for their reinforcing properties.

[0004] Solid recovered fuels (SRF), also called “refuse derived fuel” (RDF), or “solid recovered fuels” (SRF) according to Anglo-Saxon terminology, are solid non-hazardous waste prepared for energy recovery, whether they come from household and similar waste, from waste from eco- economic or construction and demolition waste. CSRs are generally a mixture of any combustible waste such as used tires, sub- food products (fats, animal flours, etc.), viscose waste and wood, light fractions from shredders (e.g. from used vehicles, of electrical and electronic equipment (WEEE), household and commercial waste commercial, residues from the recycling of various types of waste, including certain municipal waste, plastic waste, textiles, wood among others. CSR generally contains plastic waste. Plastics from collection and sorting channels, recycled tires, or even CSR can undergo a pyrolysis step to obtain, among other things, pyrolysis oils. These oils generally contain many impurities, particularly halogenated compounds, including chlorine-based compounds, but also diolefins, olefins, metals, including iron and silicon, or heteroelements such as sulfur, oxygen, and nitrogen, and insolubles. These pyrolysis oils from plastics and / or tires and / or CSR are generally burned to generate electricity and / or used as fuel in industrial or district heating boilers. Another way of valorizing pyrolysis oils is to use them as feedstock for a steam cracking unit to (re)create olefins, the latter being monomers that make up certain polymers. However, plastic and / or tire pyrolysis oils often contain high levels of impurities that are incompatible with steam cracking units or units located downstream of steam cracking units, in particular polymerization processes and selective hydrogenation processes. One way to remove these impurities from pyrolysis oils is to carry out hydrotreatment in the presence of catalysts. Steam cracking units require very high feed purities, including low chlorine, diolefin, olefin, metal, and sulfur contents. The specification for the chlorine content at the inlet of a steam cracking unit is typically 3 ppm by weight maximum, preferably 1 ppm by weight maximum. Hydrotreatment upstream of steam cracking is then often carried out in several stages and under fairly advanced conditions, particularly 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. The present invention proposes a process for the gentle hydrotreatment of a pyrolysis oil from plastics and / or tires and / or CSR, making it possible in particular to reduce its content of halogenated compounds, and in particular chlorine, in order to obtain a pyrolysis oil freed from most of the halogenated compounds and which can then be sent as a co-charge with petroleum charges to a steam cracking unit. Unlike the hydrotreatment processes described in the state of the art, the process according to the invention aims at gentle hydrotreatment, in particular at low pressure and moderate temperatures. The mild operating conditions in hydrotreatment, combined with a separation step with washing, make it possible to largely eliminate halogenated compounds. The process according to the invention is mainly focused on the elimination 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 does not necessarily aim at a complete hydrotreatment of the oil. The other impurities contained in the pyrolysis oils (metals, silicon, nitrogen, etc.) are not necessarily completely eliminated during the process according to the invention, although the operating conditions make it possible to eliminate at least some of them. The residual levels of impurities contained in the oil are compatible with the specifications for a steam cracking unit by diluting the oil with the petroleum feedstock. The "mild" hydrotreatment of the present invention is a hydrotreatment carried out under conditions of pressure, temperature and hourly volumetric flow rate which are judiciously chosen and generally more moderate compared to the conventional hydrotreatments known from the state of the art aimed at eliminating all impurities. The hydrotreatment of the present invention makes it possible in particular to largely eliminate halogenated compounds. The objective of the present invention is therefore to propose a process for treating plastic and / or tire pyrolysis oils that is inexpensive, easy to carry out and easily integrated into existing steam cracking units. The use of mild operating conditions makes it possible to minimize hydrogen consumption, thus minimizing the cost of this purification and also operating and investment costs while eliminating the chlorine content as much as possible. Furthermore, 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 content of halogenated compounds sufficiently low to be sent directly for co-processing in a steam cracking unit. Summary of the invention More specifically, the invention relates to a method for treating a so-called pyrolysis charge, comprising a pyrolysis oil from plastics and / or tires and / or recovered solid fuels comprising halogenated compounds, said method comprising: a) a hydrotreatment step carried out in a hydrotreatment reaction section comprising at least one hydrotreatment catalyst, said hydrotreatment reaction section being fed at least with the pyrolysis feedstock and a gas stream comprising hydrogen, said hydrotreatment reaction section being operated at an average temperature between 100 and 220°C, a hydrogen partial pressure between 1.0 and 3.0 MPa abs. and an hourly volumetric flow rate between 0.05 and 5 h-!, the hydrogen coverage being between 5 and 50 Nm? of hydrogen per m° of pyrolysis feedstock, to obtain a partially hydrotreated effluent having hydrocarbon compounds with a reduced halogen content, b) a separation stage, fed with the partially hydrotreated effluent from stage a) and an aqueous solution to obtain at least one gaseous effluent, one aqueous effluent and one partially hydrotreated hydrocarbon effluent, c) a step of steam cracking a petroleum feedstock in which at least a 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 hydrotreatment step carried out at a temperature and / or pressure higher 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. According to a variant, the mass ratio between the flow rate of the partially hydrotreated hydrocarbon effluent from step b) and the flow rate of petroleum feedstock introduced into step c) is less than 1. According to one variant, the pyrolysis feedstock consists of a pyrolysis oil from plastics and / or tires and / or solid recovered fuels. According to one variant, the content of halogenated compounds in said pyrolysis charge is between | and 5000 ppm by weight. According to one variant, a stream containing a nitrogen compound and / or a sulfur compound is injected upstream of step a). According to a variant, said hydrotreatment catalyst of step a) comprises a support chosen from alumina, silica, silica-aluminas, magnesia, clays and their mixtures and a hydro-dehydrogenating function comprising either at least one element from group VIII and at least one element from group VIB, or at least one element from group VIII. According to a variant, said method comprises at least one step a0) of pretreatment of the pyrolysis feedstock comprising a pyrolysis oil from plastics and / or tires and / or CSR, 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 decantation step and / or an electrostatic separation step and / or a step of washing using an aqueous solution and / or a gas stripping step. According to one variant, the petroleum feedstock introduced into steam cracking step c) is chosen from naphtha, kerosene, diesel, or mixtures of such feedstocks. According to a variant, the reaction section of step a) uses at least two reactors operating in switchable mode. According to one variant, the steam cracking step c) is carried out in at least one pyrolysis furnace at a temperature between 700 and 900°C and at a pressure between 0.05 and 0.3 MPa relative in the presence of water vapor. According to a variant, in steam cracking step c) the residence time of the hydrocarbon compounds is less than or equal to 1.0 seconds and the quantity of water introduced, in the form of water vapor, is between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds entering step c). In the following text, "pyrolysis oil" means oil resulting from the pyrolysis of plastics and / or tires and / or CSR, unless otherwise indicated. According to the present invention, the pressures are absolute pressures, also noted abs., and are given in absolute MPa (or MPa abs.), unless otherwise indicated. According to the present invention, the expressions "between ... and ..." and "between .… and ..." are equivalent and mean that the limit values ​​of the interval are included in the range of values ​​described. If this were not the case and the limit values ​​were not included in the range described, such precision will be provided by the present invention. For the purposes of the present invention, the different parameter ranges for a given step such as pressure ranges and temperature ranges may be used alone or in combination. For example, for the purposes of the present invention, a range of preferred pressure values ​​may be combined with a range of more preferred temperature values. In the following, particular and / or preferred embodiments of the invention may be described. They may be implemented separately or combined with each other, without limitation of combination when technically feasible. In the following, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief DR 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. The metal content is measured by X-ray fluorescence. DETAILED DESCRIPTION The pyrolysis charge According to the invention, a "plastic pyrolysis oil or pyrolysis oil of tires or CSR pyrolysis oil” is an oil, advantageously in liquid form at room temperature, resulting from the pyrolysis of plastics, preferably plastic waste from collection and sorting channels, or from the pyrolysis of used tires or from the pyrolysis of CSR. It comprises in particular a mixture of hydrocarbon compounds, in particular paraffins, olefins (mono- and / or diolefins), naphthenes and aromatics. At least 80% by weight of these hydrocarbon compounds preferably have a boiling point below 700°C, and preferably below 550°C. In particular, depending on the origin of the pyrolysis oil, it may 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, naphthenes, olefins and aromatics is equal to 100% by weight of the hydrocarbon compounds. Pyrolysis oil may contain diolefins. The diolefin content is commonly determined indirectly as the maleic anhydride value (MAV). The method is based on the Diels-Alder addition reaction between conjugated diolefins and maleic anhydride. The method for determining MAV is described in C. Lôpez-Garcfa 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. MAV is expressed as mg of maleic anhydride reacted with 1 g of sample (mg / g). MAV ranges from 5 to 100 mg / g in pyrolysis oils. The density of pyrolysis oil, measured at 15°C according to the ASTM D4052 method, is generally between 0.75 g / cm* and 0.99 g / cm?, preferably between 0.75 g / cm* and 0.95 g / cm:. Pyrolysis oil may include, and most often does include, additionally impurities such as metals, in particular iron, silicon, halogenated compounds, in particular chlorinated compounds. These impurities may be present in the pyrolysis oil at high levels, for example up to 500 ppm by weight or 700 ppm by weight or even 1000 ppm by weight, and even 5000 ppm by weight, of halogenated elements (in particular chlorine but also bromine, fluorine, iodine or astatine) provided by halogenated compounds, and generally between 1 and 1000 ppm by weight or between 1 and 700 ppm by weight or between 1 and 500 ppm by weight of halogenated elements. Pyrolysis oil can contain up to 500 ppm by weight or 700 ppm by weight or even 1000 ppm by weight or even 5000 ppm by weight of chlorine element provided by chlorinated compounds, and generally between 1 and 1000 ppm by weight or between 1 and 700 ppm by weight or even between 1 and 500 ppm by weight of chlorine elements. The oil can contain up to 200 ppm by weight, or even 1500 ppm by weight of elements metallic or semi-metallic, and generally between 1 and 200 ppm by weight or between 1 and 1500 ppm by weight of metallic or semi-metallic elements. Alkali metals, alkaline earth metals, transition metals, poor metals and metalloids can be assimilated to contaminants of a metallic nature, called metallic or semi-metallic metals or elements. In particular, the metallic or semi-metallic metals or elements include silicon, iron or both of these elements. Pyrolysis oil may in particular comprise up to 200 ppm by weight or 1000 ppm by weight of silicon, and generally between 1 and 200 ppm by weight or between 1 and 1000 ppm by weight or between 1 and 500 ppm by weight of silicon. Pyrolysis oil may in particular comprise up to 50 ppm by weight or 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.Pyrolysis oil may also include phosphorus, sodium, calcium, potassium and magnesium. The pyrolysis oil may also comprise other impurities such as heteroelements provided in particular by sulfur compounds, oxygenated compounds and / or nitrogen compounds, at contents generally less than 40,000 ppm by weight of heteroelements and preferably 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. The sulfur compounds are generally present in a content of less than 15,000 ppm by weight and preferably 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. Oxygenated compounds are generally present in a content of less than 15,000 ppm by weight and preferably 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 oxygenated compounds. Nitrogen compounds are generally present in a content of less than 10,000 ppm by weight and preferably less than 5,000 ppm by weight, and generally between 1 and 10,000 ppm by weight or between 1 and 5,000 ppm by weight of nitrogen compounds. The content of sulfur, oxygenated and / or nitrogen compounds often depends on the origin of the oil. Thus, tire pyrolysis oils generally contain more heteroelements than plastic pyrolysis oils, particularly sulfur compounds. Pyrolysis oil may also include other impurities such as heavy metals such as mercury, arsenic, zinc and lead, for example up to 100 ppb by weight or 200 ppb by weight of mercury or arsenic, and generally between 1 and 200 ppb by weight or between 1 and 100 ppb by weight of heavy metals. The pyrolysis feedstock of the process according to the invention comprises at least one pyrolysis oil from plastics and / or tires and / or CSR. Said feedstock may consist of only pyrolysis oil(s). Preferably, said feedstock comprises at least 50% by weight, preferably between 70 and 100% by weight, of pyrolysis oil relative to the total weight of the feedstock, i.e. preferably between 50 and 100% by weight, preferably between 70% and 100% by weight of plastic pyrolysis oil. Particularly preferably, the pyrolysis feedstock of the process according to the invention consists solely of pyrolysis oil(s) from plastics and / or tires and / or CSR. In the case of a mixture of plastic pyrolysis oil, tire pyrolysis oil and / or CSR pyrolysis oil, this mixture can be carried out in any proportion. According to another variant, the pyrolysis feedstock of the process according to the invention introduced in step a) may comprise, in addition to the pyrolysis oil or oils, a conventional petroleum feedstock or a feedstock resulting from the conversion of biomass which is then co-treated with the pyrolysis oil of the feedstock. The conventional petroleum feedstock introduced in step a) may advantageously be a cut or a mixture of cuts of the naphtha or diesel type. The feedstock resulting from the conversion of the biomass introduced in step a) may advantageously be chosen from vegetable oils, algae or algal oils, fish oils, used edible oils, and fats of vegetable or animal origin; or mixtures of such feedstocks. Said vegetable oils may advantageously be crude or refined, totally or partially, and derived from plants chosen from rapeseed, sunflower, soybean, palm, olive, coconut, copra, castor, cotton, peanut, linseed and crambe oils and all oils derived for example from sunflower or rapeseed by genetic modification or hybridization, this list not being exhaustive. Said animal fats are advantageously chosen from lard and fats composed of residues from the food industry or from the catering industries.Frying oils, various animal oils such as fish oils, tallow, lard can also be used. The feedstock resulting from the conversion of biomass can also advantageously be chosen from methyl esters of fatty acids of vegetable and / or animal origin or even methyl esters of fatty acids from used edible vegetable oils. The feedstock from biomass conversion may also be selected from feedstocks from thermal or catalytic biomass conversion processes, such as oils that are produced from biomass, particularly lignocellulosic biomass, with various liquefaction methods, such as hydrothermal liquefaction or pyrolysis. The term "biomass" refers to material derived from recently living organisms, which includes plants, animals and their by-products. The term "lignocellulosic biomass" refers to biomass derived from plants or their by-products. Lignocellulosic biomass is composed of carbohydrate polymers (cellulose, hemicellulose) and an aromatic polymer (lignin). The feedstock from biomass conversion can also advantageously be chosen from feedstocks from the paper industry. The pyrolysis oil from plastics and / or tires and / or CSR can come from a thermal or catalytic pyrolysis treatment or can be prepared by hydropyrolysis (pyrolysis in the presence of a catalyst and hydrogen). Pre-treatment (optional) Said pyrolysis feedstock comprising a plastic and / or tire and / or CSR pyrolysis oil can advantageously be pretreated in at least one optional pretreatment step a0), prior to hydrotreatment step a), to obtain a pretreated feedstock which feeds step a). According to a variant, this optional pretreatment step a0) makes it possible to reduce the quantity of contaminants and solid particles, in particular the quantity of iron and / or silicon and / or chlorine, possibly present in the feed comprising a pyrolysis oil. This optional step a0) makes it possible in particular to eliminate sediments which may form due to the unstable nature of the pyrolysis oils and / or a compatibility problem between two different feeds. Thus, an optional step a0) of pretreatment of the feed comprising a pyrolysis oil is advantageously carried out in particular when said feed comprises more than 10 ppm by weight, in particular more than 20 ppm by weight, more particularly more than 50 ppm by weight of metallic elements and / or solid particles, and in particular when said feed comprises more than 5 ppm by weight of silicon, more particularly more than 10 ppm by weight, or even more than 20 ppm by weight of silicon.Likewise, an optional step a0) of pretreatment of the feed comprising a pyrolysis oil is advantageously carried out in particular when said feed comprises more than 10 ppm by weight, in particular more than 20 ppm by weight, more particularly more than 50 ppm by weight of chlorine. Said optional pretreatment step a0) may be implemented by any method known to those skilled in the art for reducing the quantity of contaminants. It may in particular comprise an adsorption step and / or a filtration step and / or a centrifugation step and / or a decantation step and / or an electrostatic separation step and / or a washing step using an aqueous solution and / or a gas stripping step. The optional pretreatment step a0) is advantageously carried out at a temperature between 20 and 400°C, preferably between 40 and 350°C, and at a pressure between 0.15 and 10.0 MPa abs, preferably between 0.2 and 7.0 MPa abs. According to a variant, said optional pretreatment step a0) is implemented in an adsorption section operated in the presence of at least one adsorbent. The adsorbent may 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 m? / g, preferably greater than or equal to 200 m? / g. The specific surface area of ​​said at least one adsorbent is advantageously less than or equal to 600 m' / g, in particular less than or equal to 400 m? / g. The specific surface area of ​​the adsorbent is a surface area measured by the BET method, i.e. the specific surface area determined by nitrogen adsorption in accordance with ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of the American Chemical Society", 6Q, 309 (1938). Advantageously, said adsorbent comprises less than 1% by weight of metallic elements, preferably is free of metallic elements. By metallic elements of the adsorbent, it is meant the elements of groups 6 to 10 of the periodic table of elements (new IUPAC classification). The residence time of the load in the adsorption section is generally between 1 and 180 minutes. Said adsorption section of optional step a0) comprises at least one adsorption column, preferably comprises at least two adsorption columns, preferably between two and four adsorption columns, containing said adsorbent. When the adsorption section comprises two adsorption columns, an operating mode may be a so-called "swing" operation, according to the established English term, in which one of the columns is online, i.e. in operation, while the other column is in reserve. When the absorbent of the online column is used up, this column is isolated while the column in reserve is put online, i.e. in operation. The used absorbent can then be regenerated in situ and / or replaced with fresh absorbent so that the column containing it can be put back online once the other column has been isolated. Another operating mode is to have at least two columns operating in series. When the absorbent in the column placed at the head is worn out, this first column is isolated and the worn absorbent is either regenerated in situ or replaced with fresh absorbent. The column is then put back online in the last position and so on. This operation is called permutable mode, or according to the English term "PRS" for Permutable Reactor System or "lead and lag" according to the English term. The association of at least two adsorption columns makes it possible to overcome the possible and possibly rapid poisoning and / or clogging of the adsorbent under the joint action of metallic contaminants, diolefins, gums from diolefins and insolubles possibly present in the pyrolysis oil to be treated. The presence of at least two adsorption columns facilitates the replacement and / or regeneration of the adsorbent, advantageously without stopping the pretreatment unit, or even the process, thus reducing the risk of clogging and therefore avoiding stopping the unit due to clogging, controlling costs and limiting adsorbent consumption. According to another variant, said optional pretreatment step a0) is implemented in a washing section with an aqueous solution, for example water or an acidic or basic solution. This washing section may comprise equipment for bringing the feedstock into contact with the aqueous solution and separating the phases so as to obtain the pretreated feedstock on the one hand and the aqueous solution comprising impurities on the other hand. Among this equipment, there may be for example a stirred reactor, a decanter, a mixer-decanter and / or a co- or counter-current washing column. According to another variant, said optional pretreatment step a0) is implemented by filtration. The filtration step makes it possible to remove inorganic solids, sediments and / or fines contained in the feed, in particular metals, metal oxides and metal chlorides. A filter is generally used whose pore size (for example the diameter or equivalent diameter) 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, a filter may be used whose pore size is less than 25 μm but greater than 5 μm. A series of filters with different pore sizes may also be used, in particular a series of filters having pore sizes decreasing in the direction of flow of the feed. These filter media are well known for industrial uses.Cartridge filters, self-cleaning filters, are suitable for example. The dry extract can be measured for example by the Heptane Insolubles test, Method ASTM D-3279. The content of insolubles in heptane should be reduced to less than 0.5% by weight, preferably less than 0.1%. According to a particular embodiment, the pretreatment step a0) by filtration comprises at least one filter whose pore size is less than 10 microns, and preferably greater than 5 um, optionally followed by a filtration system whose pore size is less than 2 um and preferably less than 1 um. According to another particular embodiment, the pretreatment step a0) by filtration comprises at least one filter whose pore size is less than 10 um, and preferably greater than 5 um, followed by an electrostatic precipitation system. According to another particular embodiment, the pretreatment step a0) by filtration comprises at least one filter whose pore size is less than 10 μm, and preferably greater than 5 um, followed by a filter system(s) using filter aids such as sand or diatomaceous earth. According to another variant, said optional pretreatment step a0) is implemented by centrifugation. According to another variant, the pretreatment step a0) comprises centrifugation and filtration. According to another variant, said optional pretreatment step a0) is implemented by decantation. According to another variant, the pretreatment step a0) comprises decantation and filtration. According to another variant, said optional pretreatment step a0) is carried out by gas stripping, thereby reducing the oxygen content in the feedstock. The gas stripping may remove oxygen (Oz) that may be dissolved in the feedstock thereby reducing the likelihood of free radical formation leading to polymerization in downstream steps. The method generally involves contacting the feedstock with a stripping gas (e.g. H>, N; or a mixture thereof), thereby transferring at least some of the dissolved oxygen from the feedstock to the stripping gas, followed by separation of the stripping gas from the feedstock. The volume of stripping gas relative to the volume of feedstock (both volumes measured under gas stripping conditions) is generally greater than 1, and preferably at least 3. In particular embodiments, the stripping gas may contain at least 60% (molar percentage) Hz.Any dissolved H; remaining in the feed after the gas stripping step is not a problem, given the downstream hydroprocessing. Preferably, the gas stripping step is completed before any (pre)heating of the feed, to minimize potential fouling. Said optional pretreatment step a0) generally comprises one or more, preferably several treatments described above. It may in particular comprise a sequence of a washing step using an aqueous solution and / or an adsorption step, followed by a gas stripping step, followed by a filtration step and / or a centrifugation step. All these steps are preferably carried out before any (pre)heating of the load. Said optional pretreatment step a0) thus makes it possible to obtain a pretreated feed which then feeds the mild hydrotreatment step a). Step a) of hydrotreatment According to the invention, the method comprises a step a) implemented in a hydrotreatment reaction section comprising at least one hydrotreatment catalyst, said hydrotreatment reaction section being supplied at least with the pyrolysis feedstock and a gas stream comprising hydrogen, said hydrotreatment reaction section being implemented at an average temperature between 100 and 220°C, a hydrogen partial pressure between 1.0 and 3.0 MPa abs. and a volumetric velocity hourly between 0.05 and 5 h!, the hydrogen coverage being between 5 and 50 Nm? of hydrogen per m°* of pyrolysis feedstock, to obtain a partially hydrotreated effluent having hydrocarbon compounds with a reduced halogen content. Step a) is in particular carried out under mild hydrogen pressure and temperature conditions allowing in particular the elimination of halogens, and in particular chlorine, in order to make the pyrolysis oil compatible as a co-feedstock in the steam cracking unit. The other impurities contained in the pyrolysis oils (metals, silicon, nitrogen, etc.) are not necessarily completely eliminated during the process according to the invention, although the operating conditions make it possible to eliminate at least some of them. Step a) thus mainly uses hydrogenation reactions of halogenated compounds, and to a lesser extent also other hydrotreatment reactions well known to those skilled in the art, particularly hydrotreatment reactions such as the hydrogenation of aromatics, hydrodesulfurization and hydrodenitrogenation, as well as the hydrogenation of olefins and diolefins. Said hydrotreatment reaction section is advantageously carried out at a medium temperature (or WABT as defined below) of hydrotreatment between 100 and 220°C, preferably between 120 and 200°C, at a partial pressure of hydrogen 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 volumetric velocity (HVV) between 0.1 and 5 h-!, preferably between 0.1 and 2 h!, preferentially between 0.1 and 1.0 h". The hydrogen coverage in step a) is advantageously between 5 and 50 Nm* of hydrogen per m* of fresh charge, and preferably between 10 and 40 Nm* of hydrogen per m* of fresh charge, preferably between 15 and 30 Nm* of hydrogen per m° of fresh charge. . According to the invention, the "average temperature" of a reaction section corresponds to the Weight Average Bed Temperature (WABT) according to the established Anglo-Saxon term, well known to those skilled in the art. The average temperature is advantageously determined according to the catalytic systems, the equipment, and the configuration thereof, used. The average temperature (or WABT) is calculated as follows: [Math.1] WABT = (Terute + Tsorie 2 with Tenré: the temperature of the flow at the inlet of the reaction section and T,orie: 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 start of cycle conditions. The hourly volumetric velocity (HVV) is defined here as the ratio between the hourly volumetric flow rate of the feedstock including the pyrolysis oil, possibly pretreated, by the volume of catalyst(s). The hydrogen coverage is defined as the ratio of the volume flow rate of hydrogen taken under normal temperature and pressure conditions to the volume flow rate of "fresh" load, i.e. the load to be treated, possibly pre-treated, without taking into account a recycled fraction, at 15°C (in normal m 3, noted Nm°, of H, per m° of load). The gas stream comprising hydrogen, which feeds the hydrotreatment reaction section may consist of a hydrogen make-up and / or 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 from the second catalytic bed of the reaction section. These additional gas streams are also called cooling streams. They make it possible to control the temperature in the reactor in which the reactions carried out are generally very exothermic. The gas stream containing hydrogen can come from a fossil source or a renewable source, for example from the gasification of plastic waste or produced by electrolysis. Advantageously, the gas stream comprising hydrogen comes from a compressor used in the refinery to supply another hydrorefining unit using hydrogen such as a hydrocracking, hydrotreatment or hydroconversion unit. This has the advantage of eliminating the need for a dedicated compressor for recycling hydrogen from step b) and therefore saving on investment costs. Optionally, the reaction section of said step a) may also be additionally supplied with a portion of the partially hydrotreated hydrocarbon effluent from step b) (recycle) as described below. Preferably, the process according to the invention comprises a hydrotreatment step a) implemented in a hydrotreatment reaction section, implementing at least one fixed bed reactor having n catalytic beds, n being an integer greater than or equal to 1, preferably between one and ten, preferably between two and five, each comprising at least one hydrotreatment catalyst. Said hydrotreatment reaction section is supplied at least with the pyrolysis feedstock, optionally pretreated, and a gas stream comprising hydrogen, advantageously at the level of the first catalytic bed of the first reactor in operation. An injection of at least a portion of the pyrolysis feedstock and / or at least a portion of hydrogen between the different catalytic beds is also possible. The hydrotreatment reaction section using at least one fixed bed reactor can operate with a descending or ascending flow of gas and liquid. 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 hydrotreatment 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 catalytic bed(s) and therefore to avoid stopping the unit due to clogging. According to this embodiment, the hydrotreatment reaction section of step a) comprises two reactors operating in permutable mode, called "PRS" for Permutable Reactor System or "lead and lag". The association of at least two reactors in PRS mode makes it possible to isolate a reactor, unload the spent catalyst, reload the reactor with fresh catalyst and put said reactor back into service without stopping the process. The PRS technology is described, in particular, in patent FR2681871. According to another embodiment, said hydrotreatment reaction section comprises a single fixed bed reactor containing n catalytic beds, n being an integer greater than or equal to one, preferably between one and ten, more preferably between two and five. Advantageously, reactor internals, for example of the filter tray type, can be used to prevent clogging of the reactor(s). An example of a filter tray is described in patent FR3051375. Preferably, step a) may use upstream of the hydrotreatment catalyst(s) at least one guard bed containing adsorbents of the alumina, silica, silica-alumina, zeolite and / or activated carbon type possibly containing metals from group VIB and / or VIII. It is also possible to use a series of guard beds with particles of different diameters, in particular a series of guard beds having decreasing diameters in the direction of circulation of the feedstock (also called "grading" according to English terminology). Advantageously, said hydrotreatment catalyst comprises a support, preferably mineral, and a hydro-dehydrogenating function. According to one variant, the hydro-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 metallic elements from groups VIB and VIII is preferably between 1% and 40% by weight, preferably 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 MoO- and WO; respectively. The weight ratio expressed in metal oxide between the metal (or metals) of group VIB relative to the metal (or metals) of group VIII is preferably between 1 and 20, and preferably between 2 and 10. According to this variant, the reaction section of said step a) comprises for example a hydrotreatment 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 MoO relative to the weight of said catalyst) on a preferably mineral support, preferably on an alumina support. According to another variant, the hydro-dehydrogenating function comprises, and is preferably constituted of, at least one element from group VIII, 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. The support of said hydrotreatment catalyst is preferably chosen from alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof. Said support may contain doping compounds, in particular oxides chosen from boron oxide, in particular boron trioxide, zirconia, ceria, titanium oxide, phosphoric anhydride and a mixture of these oxides. Preferably, said hydrotreatment catalyst comprises an alumina support, optionally doped with phosphorus and optionally boron. When phosphoric anhydride P,O;5 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 B,O; 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 be, for example, a y (gamma) or n (eta) alumina. Said hydrotreatment catalyst is for example in the form of extrudates or in the form of beads. Very preferably, step a) can use, in addition to the hydrotreatment catalyst(s) described above, also at least one hydrotreatment 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 oxide. of nickel 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 MoO; relative to the weight of said catalyst, on an alumina support. This catalyst with a low metal content can preferably be placed upstream or downstream of the hydrogenation catalyst(s) described above, preferably upstream. The preparation of the catalyst for hydrotreatment step a) is known and generally comprises a step of impregnation of the metals of group VIII and group VIB when present, and optionally phosphorus and / or boron on the support, followed by drying, then optionally calcination. The catalyst for step a) may also be a catalyst used in its reduced form, thus involving a reduction step in its preparation. Before their use in a process step, the catalysts are generally subjected to sulfurization 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 sulfurizing agent may be injected upstream of the optional pretreatment step a0) or of the hydrotreatment step a), preferably upstream of the hydrotreatment step a) in order to ensure a sufficient quantity of sulfur to form the active species of the catalyst (in sulfide form). This activation or sulfurization step is carried out by methods well known to those skilled in the art, and advantageously under a sulfide-reducing atmosphere in the presence of hydrogen and hydrogen sulfide.The sulfurizing agents are preferably HS gas, elemental sulfur, CS, mercaptans, sulfides and / or polysulfides, hydrocarbon fractions with a boiling point below 400°C containing sulfur compounds or any other compound containing sulfur used for the activation of hydrocarbon feedstocks in order to sulfurize the catalyst. Said sulfur-containing compounds are advantageously chosen from alkyl disulfides such as, for example, dimethyl disulfide (DMDS), alkyl sulfides, such as, for example, dimethyl sulfide, thiols such as, for example, n-butyl mercaptan (or 1-butanethiol) and polysulfide compounds of the tert-onyl-polysulfide type. The catalyst may also be sulfurized by the sulfur contained in the feedstock to be desulfurized. Preferably, the catalyst is sulfurized in situ in the presence of a sulfurizing agent and a hydrocarbon feedstock.Very preferably, the catalyst is sulfurized in situ in the presence of the additive charge of dimethyl disulfide. The sulfurizing agent can be injected continuously. The partially hydrotreated effluent obtained at the end of hydrogenation step a) is sent, preferably directly, to washing / separation step b). Separation step b) According to the invention, the treatment method comprises a step b) of separation, advantageously implemented 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 one gaseous effluent, one aqueous effluent and one partially hydrotreated hydrocarbon effluent. This separation step b) makes it possible in particular to eliminate halogens (chlorine) in the form of hydrogen halides (HCI in particular) 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. Separation step b) is advantageously carried out at a temperature between 20 and 200°C, preferably between 50 and 180°C, preferably between 80 and 150°C. Advantageously, 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 necessary. The separation step can advantageously be implemented by any method known to those skilled in the art such as, for example, the combination of one or more separator(s) (drum(s)), and / or one or more stripping column(s), this or these separator(s) (drum(s)) and / or columns optionally being able to be supplied with a stripping gas, for example a hydrogen-rich gas stream. The washing / separation section of step c) can at least partly be carried out in common or separate washing and separation equipment. Advantageously, 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 in part and preferably all of the hydrogen halides (HCl in particular) and any salts present. The aqueous solution can be water. It can also be a basic aqueous solution (by adding NaOH for example). Using a basic solution helps neutralize hydrogen halides and any dissolved salts. In a possible embodiment of the invention, 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 making it possible to obtain at least one aqueous effluent loaded with hydrogen halides (HCl in particular) and any dissolved salts, 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 settling tank in order to obtain said washed partially hydrotreated effluent and said aqueous effluent. Said partially washed gaseous effluent can in parallel be introduced into a washing column where it circulates countercurrent to an aqueous flow, preferably of the same nature as the aqueous solution injected into the partially hydrotreated effluent, which makes it possible to eliminate at least in part, preferably in full, the hydrochloric acid contained in the partially washed gaseous effluent and thus to obtain said gaseous effluent, preferably comprising essentially hydrogen, and an acidic aqueous stream. Said aqueous effluent from the settling tank may optionally be mixed with said acidic aqueous stream, and be used, optionally in a mixture with said acidic aqueous stream in a water recycling circuit to supply step b) of separation into said aqueous solution upstream of the washing / separation section and / or into said aqueous stream in the washing column. Said water recycling circuit may comprise a make-up of water and / or a basic solution and / or a purge making it possible to remove impurities. Hydrotreatment step a) mainly involves hydrogenation reactions of halogenated compounds, and to a lesser extent also other hydrotreatment reactions such as hydrodenitrogenation which generates NH; by hydrogenation of nitrogen compounds and hydrodesulfurization which generates H2S by hydrogenation of sulfur compounds. When NH; is present in the partially hydrotreated effluent from step a), separation step b) also makes it possible to eliminate ammonium chloride salts, which are formed by reaction between chloride ions, released by the hydrogenation of chlorinated compounds in HCI form, in particular during step a), and ammonium ions, generated by the hydrogenation of nitrogen compounds in NH; form during step a) by dissolving them in the aqueous solution. When HS is present in the partially hydrotreated effluent from step a), separation step b) also makes it possible to eliminate ammonium sulfide salts ((NHL)2S) which are formed by reaction between the H»S resulting from the hydrodesulfurization of sulfur compounds and the NH, by dissolving them in the aqueous solution. According to one embodiment, and depending on the content of chlorinated 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 monodie-ethanolamine, may be injected upstream of the hydrotreatment step a) in order to ensure a sufficient quantity of ammonium ions to combine the chloride ions formed during the hydrotreatment step in the form of ammonium chloride salts, thus making it possible to limit the formation of hydrochloric acid and thus to limit corrosion downstream of the separation section. The gaseous effluent obtained at the end of step b) advantageously comprises hydrogen, preferably comprises at least 80% by volume, preferably at least 85% by volume, of hydrogen. The gaseous effluent obtained at the end of step b) contains very little chlorine, generally at a content of less than 3 ppm chlorine weight, which allows it to be sent to a refining unit requiring hydrogen. According to one embodiment, said gaseous effluent can at least partly be recycled to the hydrotreatment step a), the recycling system being able to comprise a purification section (for example adsorption of heavy metals such as mercury). 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, hydrotreatment or hydroconversion unit of the refinery. This has the advantage of being able to do without a compressor dedicated to recycling hydrogen from step b) and therefore a saving in investment costs. As for the partially hydrotreated hydrocarbon liquid effluent from step b) and according to a 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 (gum formation) and / or the formation of coke. Advantageously, the quantity of partially hydrotreated hydrocarbon effluent from step b) recycled, i.e. the fraction of product obtained recycled, is adjusted so that the weight ratio between the recycle stream from step b) and the feed comprising a pyrolysis oil, i.e. the feed to be treated feeding the overall process, is less than or equal to 10, preferably less than or equal to 7, and preferably greater than or equal to 0.001, preferably greater than or equal to 0.01, and more preferably greater than or equal to 0.1. Preferably, the quantity of partially hydrotreated hydrocarbon effluent from step b) recycled is adjusted so that the weight ratio between the recycle stream and the feed comprising a pyrolysis oil is between 0.01 and 10, preferably between 0.1 and 7, and more preferably between 0.2 and 5.This recycle rate makes it possible in particular to control the temperature rise in step a). Indeed, when the recycle rate is high, the dilution rate of the feedstock is high, and the temperature rise at the start 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 level of the first catalytic bed of the reaction section of step a) or between the different catalytic beds. When the reaction section- . hydrotreatment plant of step a) comprises two reactors operating in permutable mode, at least part of the partially hydrotreated hydrocarbon effluent from step b) can be recycled between the two reactors. According to another preferred embodiment, the partially hydrotreated hydrocarbon effluent from step b) is sent in part and preferably in full, directly to the inlet of a steam cracking unit as a co-charge with an oil charge. This has the advantage of not requiring a recycle compressor. 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-charge into a steam cracking unit. The partially hydrotreated hydrocarbon effluent from step b) is in particular an effluent with a reduced content of halogenated compounds, and in particular chlorine. Preferably, at least 50%, and more preferably at least 75% of the halogenated compounds of the initial charge are removed during steps a) and b). The other impurities contained in the pyrolysis oils (metals, silicon, nitrogen, etc.) are not necessarily completely eliminated during steps a) and b) of the process according to the invention, although the operating conditions make it possible to eliminate at least a portion of them. Indeed, the pyrolysis oil, which is the partially hydrotreated hydrocarbon effluent, does not need to be fully hydrotreated in order to be able to introduce it as a co-feed into a steam cracking unit. In particular, it does not need to undergo another hydrotreatment carried out at a higher temperature and / or pressure 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 feed injected in step c). Preferably, at least 50%, and more preferably at least 75% of the metallic elements of the initial charge are eliminated during steps a) and b). Generally, a maximum of 50%, and more preferably a maximum of 25% of the sulfur compounds in the initial charge are eliminated during steps a) and b). Preferably, at least 25%, and more preferably at least 50% of the oxygenated compounds of the initial charge are eliminated during steps a) and b). Generally, a maximum of 30%, and more preferably a maximum of 15% of the nitrogen compounds of the initial charge are eliminated during steps a) and b). The content of heavy metals such as mercury, arsenic, zinc and lead remains largely unchanged. The contents are given in relative weight concentrations, percentage (%) by weight, part(s) per million (ppm) by weight or part(s) per billion (ppb) by weight, by relative to the total weight of the flow considered. Step c) of steam cracking According to the invention, the process comprises a step c) of steam cracking a petroleum feedstock in which at least a 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 hydrotreatment step carried out at a 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. Thanks to the hydrotreatment step a) allowing the release of halogenated compounds (for example chlorine) mainly in gaseous form (hydrogen halides of the HCl type in particular), followed by the washing / separation step b) allowing the dissolution and elimination of the hydrogen halides, the partially hydrotreated hydrocarbon effluent from step b) has a sufficiently reduced content of halogenated compounds to be able to inject it as a co-feed into a petroleum feedstock steam cracking unit. The partially hydrotreated hydrocarbon effluent from step b) is introduced into the steam cracking unit of a petroleum feedstock in such a quantity 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. Generally, the mass ratio between the flow rate of the partially hydrotreated hydrocarbon effluent from step b) (pyrolysis oil) and 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. 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. The petroleum feedstock used in the steam cracking unit is preferably selected from naphtha, kerosene, diesel, or mixtures of such feedstocks. Said steam cracking step c) is advantageously carried out in at least one pyrolysis furnace at a temperature of between 700 and 900°C, preferably between 750 and 850°C, and at a pressure of between 0.05 and 0.3 MPa relative in the presence of water vapor. The residence time of the hydrocarbon compounds is generally less than or equal to 1.0 seconds (denoted s), preferably between 0.1 and 0.5 s. Advantageously Typically, water vapor is introduced upstream of steam cracking step c) and after separation (or fractionation). The amount of water introduced, in the form of water vapor, is advantageously between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds entering step c). Steam cracking step c) can be carried out in several pyrolysis furnaces in parallel so as to adapt the operating conditions to the different streams feeding step c), and also to manage the decoking times of the tubes. A furnace comprises one or more tubes arranged in parallel. A furnace can also designate a group of furnaces operating in parallel. For example, one furnace can be dedicated to cracking the middle distillate cut. The effluents from the various steam cracking furnaces are generally recombined before separation in order to constitute an effluent. It is understood that the steam cracking step c) comprises the steam cracking furnaces but also the sub-steps associated with steam cracking well known to those skilled in the art. These sub-steps may include in particular heat exchangers, columns and catalytic reactors and recycles to the furnaces. A column generally makes it possible to fractionate the effluent in order to recover at least a light fraction comprising hydrogen and compounds having 2 to 5 carbon atoms, and a fraction comprising pyrolysis gasoline, and possibly a heavier fraction. Columns make it possible to separate the different constituents of the light fractionation fraction in order to recover at least one cut rich in ethylene (C2 cut) and a cut rich in propylene (C3 cut) and possibly a cut rich in butenes (C4 cut).Catalytic reactors are used in particular to carry out hydrogenation of C2, C3 and even C4 cuts and pyrolysis gasoline. Saturated compounds, in particular saturated compounds with 2 to 4 carbon atoms, are advantageously recycled to steam cracking furnaces in order to increase overall olefin yields. 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), at 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 in question. Said C2, C3 and C4 olefins can then be advantageously used as polyolefin monomers. Analysis methods used The analysis methods and / or standards used to determine the characteristics of the various flows, in particular the load to be treated and the effluents, are known to those skilled in the art. They are in particular listed below for information purposes in Table 1. Other methods deemed equivalent may also be used, in particular equivalent IP, EN or ISO methods: [Tables 1] Description Density @15°C Sulfur Content Nitrogen Content Acid Number [Bromine Number] Maleic Anhydride Number (MAV) [Oxygen Content] Paraffin Content Naphthenes and Olefins Content | Aromatics Content Halogen Content Chlorine Content Metals Content: the Fe si Na B [Simulated distillation |ASTM D2887 (1) MAY method described in the article: C. Lépez-Garcfa 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 LIST OF FIGURES The mention of the elements referenced in [Fig. 1] allows a better understanding of the invention, without it being limited to the particular embodiments illustrated in [Fig. 1]. The different embodiments presented can be used alone or in combination with each other, without limitation of combination. [Fig 1] [Fig. 1] represents the diagram of a general embodiment of the method of the present invention, comprising: - a step a) hydrotreatment of a pyrolysis oil 1 in the presence of a hydrogen-rich gas 2 and optionally an amine supplied by stream 3 and optionally a sulfurizing agent by stream 4; -a separation / washing step b) supplied with the partially hydrotreated effluent 5 from the hydrotreatment step a) and in the presence of an aqueous solution 6 to obtain at least one gaseous effluent 7, one aqueous effluent 8 and one partially hydrotreated hydrocarbon effluent 9, a part 9a of which can be recycled in step a); - a step c) of steam cracking of a petroleum feedstock 10 in which at least a portion and preferably all of the partially hydrotreated hydrocarbon effluent from step b) 9 is introduced as a co-feedstock, said partially hydrotreated hydrocarbon effluent from step b) 9 being introduced without undergoing another hydrotreatment step carried out at higher temperature and / or pressure beforehand. Only the main steps, with the main flows, are shown in the Figure, in order to allow a better understanding of the invention. It is understood that all the equipment necessary for operation is present (tanks, pumps, exchangers, furnaces, columns, etc.), even if not shown. It is also understood that hydrogen-rich gas flows (make-up or recycle), as described above, can be injected at the inlet of each reactor or catalytic bed or between two reactors or two catalytic beds. EXAMPLES 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 2: Characteristics of the pyrolysis charge [Tables 2] Description Methods Unit Load |Density @ 15°C ASTM D4052 fem 0.820 Sulfur Content ISO 20846 ppm wt 320 Nitrogen Content ASTM D4629 ppm wt 730 Acid Number ASTM D664 mg KOH / g LS Bromine Number ASTMDI1159 |g / 100g 80 Maleic Anhydride Number MAV Method mg / 100g 10 Oxygenates Content Combustion + wt % I Infrared Paraffins Content UOP990-11 wt % 45 |Naphthenes Content UOP990-11 wt % # Olefins Content “ |UOP990-11 wt % 5 Aromatics Content UOP990-11 wt % 10 Halogens Content ASTM D7359 |ppmwt | |97 Chlorine Content ASTM D7536 ppm weight 95 Metals Content: [ASTM DS185 Olefins Content UOP990-11 % wt | Aromatics Content UOP990-11 % wt 10 Halogens Content ASTM D7359 |ppmwt | |97 Chlorine Content ASTM D7536 ppm wt 95 Metals Content: - |ASTM D5185 |P [ppm wt 10 Fe ppm wt 25 si ppm wt 45 - ppm wt 2 Bu 1 ' 1 ppm wt E FIRE EF ASTM D2887 °C AT qe |ec qe qe qe I The pyrolysis feedstock is subjected to a hydrotreatment step a) carried out in a fixed bed reactor and in the presence of hydrogen and a NiMo on Alumina hydrotreatment catalyst under different operating conditions and indicated in Table 3. Table 3: Conditions of hydrotreatment step a) [Tables 3] Example | Example 2 Example 3 (non-compliant) |[(compliant) (compliant) I [20 140 140 [MPa abs |3 E |2 Average temperature °C 230 — 140 140 Partial Pressure |MPa abs |3 [3 |? of Hydrogen H / HC [Nm |s [ 5 (Volume coverage of hydrogen relative to the | volume of charge) VVA M jos jo.s [0.35 (volume flow rate of charge volume of catalysts) At the end of hydrogenation step a), the conversion rates (= (initial concentration - final concentration) / initial concentration) observed in chlorine, diolefins and olefins are indicated in Table 4. Table 4: Species conversions during hydrotreatment step a) [Tables 4] Example [Example 2 | Example 3 1 (compliant | (compliant) (non-) compliant ) 0 Ja 75 [26 |60 |21 [12 fe is jo Le Conversion rate of fe jo | |75 chlorine Conversion rate of |æ [60 [1 | 12 diolefins Conversion rate of qe ju qe Jo olefins [Consumption H % weight relative to [0.18 “Jooi “Jo -Jo.1 0.01 % weight relative to [0.18 to the weight of the fresh load The effluent from hydrotreatment step a) is subjected to a separation step b): a stream of water is injected into the effluent from hydrotreatment step a); the mixture is then treated in an acid gas washing column and separator drums. The yields of the different fractions obtained after separation are indicated in Table 5 (the yields correspond to the ratios of the mass quantities of the different products obtained in relation to the mass of charge upstream of step a), expressed as a percentage and noted % m / m). Table 5: Yields of the different products obtained after separation [Tables 5] |Gas fraction (NH; + H,S + H20 + C1-C4) % m / m 2.42 Liquid fraction % m / m 99.31 The characteristics of the liquid fraction obtained after separation step b) are presented in table 6: Table 6: Liquid fraction characteristics [Tables 6] [mg / 100g 8 [79 8.8 [Tables 6] |Description |Methods |Unit Example 1 |Example 2 [Example 3 (non- (compliant) |(compliant) compliant) Sulphur Content [ISO 20846 | |ppm weight 250 279 286 [Nitrogen Content |ASTM |ppm weight 72 730 730 D4629 Bromine Index |ASTM | g / 100g “fr6 80 80 D1159 Index Method [mer 100g 4 |7a 8.8 of MAV (1) Maleic Anhydride I ( ÿ 1._ a 1 [ppm weight [10 [17 [24 ASTM D7536 ASTM D2887 qe qe qe [°c qe qe |°c 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 mass proportion of 10% oil / 90% petroleum feedstock. A mixture is obtained which contains less than 3 ppm by weight of chlorine (for all examples) which is introduced into a fluidized bed catalytic steam cracking unit. Less energy is used according to examples 2 and 3 (temperatures of step a)) and less hydrogen (consumption H>). Example 3, carried out under very mild temperature and pressure conditions, shows that it is possible to obtain an oil sufficiently free of chlorine while using less pressure (and therefore less energy) than in Example 2.

Claims

Claims

1. Method for treating a so-called pyrolysis charge, comprising a pyrolysis oil from plastics and / or tires and / or fuels recovered solids comprising halogenated compounds, said method comprising: a) a hydrotreatment step implemented in a reaction section hydrotreatment plant comprising at least one catalyst hydrotreatment, said hydrotreatment reaction section being powered at least by the pyrolysis charge and a gas flow comprising hydrogen, said reaction section hydrotreatment being carried out at an average temperature between 100 and 220°C, a hydrogen partial pressure between 1.0 and 3.0 MPa abs. and an hourly volumetric velocity between 0.05 and 5 h-!, the coverage in hydrogen being between 5 and 50 Nm°* of hydrogen per m* of pyrolysis charge, to obtain a partially hydrotreated effluent having hydrocarbon compounds with halogen content reduced, b) a separation stage, fed by the partially hy- effluent treated product from step a) and an aqueous solution to obtain at least a gaseous effluent, an aqueous effluent and a hydrocarbon effluent by- partially hydrotreated, (c) a steam cracking step of a petroleum feedstock in which at less a portion of the partially hydrotreated hydrocarbon effluent from step b) is introduced as a co-load, said hy- effluent partially hydrotreated carbon from step b) being introduced without first undergoing another hydrotreatment step carried out at temperature and / or pressure higher 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. Method according to the preceding claim, in which the mass ratio between the flow rate of the partially hydrotreated hydrocarbon effluent from of step b) and the flow rate of oil charge introduced in step c) is less than 1.

3. Method according to one of the preceding claims, in which the pyrolysis charge consists of plastic pyrolysis oil and / or tires and / or solid recovered fuels.

4. Method according to one of the preceding claims, in which the content of halogenated compounds in said pyrolysis charge is included between 1 and 5000 ppm weight.

5. Method according to one of the preceding claims in which a flow containing a nitrogen compound and / or a sulfur compound is injected into upstream of step a).

6. A method according to any preceding claim, wherein said ca- hydrotreatment alyst of step a) comprises a selected support among alumina, silica, silica-aluminas, magnesia, clays and their mixtures and a hydro-dehydrogenating function comprising either at least one element from group VIII and at least one element from group VIB, or at least one element from group VII.

7. Method according to one of the preceding claims, comprising at at least one step a0) of pretreatment of the load comprising an oil of pyrolysis of plastics and / or tires and / or CSR, said step of pretreatment being implemented upstream of step a) and includes an adsorption step and / or a filtration step and / or a step of centrifugation and / or a decantation step and / or a se- electrostatic treatment and / or a washing step using a aqueous solution and / or a gas stripping step.

8. Method according to one of the preceding claims, in which the petroleum feedstock introduced in step c) of steam cracking is chosen among naphtha, kerosene, diesel, or mixtures of such charges.

9. Method according to one of the preceding claims in which the reaction section of step a) implements at least two reactors operating in switchable mode.

10. A method according to any preceding claim wherein step c) steam cracking is carried out in at least one pyrolysis furnace at a temperature between 700 and 900°C and at a pressure between between 0.05 and 0.3 MPa relative in the presence of water vapor.

11. | Method according to one of the preceding claims, in which in step c) of steam cracking the residence time of the hydro- compounds carbonaceous is less than or equal to 1.0 second and the amount of water in- introduced, in the form of water vapor, is between 0.3 and 3.0 kg of water per kg of hydrocarbon compounds entering step c).