FR3025523A1 - METHOD FOR DISTILLATION OF HARD TAR AND DEVICE FOR ITS IMPLEMENTATION - Google Patents

Abstract

The invention relates to a coal tar distillation process comprising a primary distillation characterized in that it comprises: a flash distillation of a mixture of dehydrated coal tar and pitch to obtain at the top of the column flashed vapors and at the bottom of the pitch column, a portion of said pitch obtained during the flash distillation being used in the mixture of dehydrated coal tar and starting pitch; . immediately after the flash distillation, a stripping and rectification flashed vapors to obtain a carbon black oil and a large naphthalenic oil cut, and on the device for its implementation.

Description

TECHNICAL FIELD The invention relates to a process for the distillation of coal tar intended to produce three hydrocarbon cuts directly at the level of a primary distillation. , a broad naphthalenic cut, a carbon black oil and a pitch, the last two cuts being without added alkali.

Examination of the Prior Art Coal tar is a mixture of aromatic monocyclic and polycyclic aromatic hydrocarbons. It is obtained after treatment by condensation and decantation of the pyrolysis vapors of coals and anthracites at the outlet of the coke oven batteries. The organic phase recovered after decantation is coal tar. Coal tar is a complex mixture estimated at more than 10,000 different compounds [H.-G. Franck]. Some are present in larger amounts such as naphthalene, anthracene, phenanthrene, or compounds including a heteroatom such as carbazole or quinoline. The heavier compounds having a normal boiling point above about 360 ° C are generally referred to as pitch. The pitch represents about 45 to 55% by mass share of the tar. It can not be further fractionated into differentiated sections using traditional means such as distillation because of its very high molecular weight, high boiling temperature and temperature responsiveness. which tends to make it polymerize.

The different hydrocarbon fractions obtained from tar are defined according to the compounds they contain: - Light oil (LO) or BTX, rich in benzene, toluene and xylenes, - Carbolic (CO) oil, rich in phenol, cresols, indane and coumarone, - Naphthalenic (NO) oil, consisting mainly of naphthalene and to a lesser extent xylenols, - Washing oil (VVO), including methylnaphthalenes, - Anthracene oil (AO), including anthracene, carbazole and phenanthrene. This section can sometimes be separated into two sections, anthracenic oils I and II, having normal boiling temperatures different from about 280 ° C and about 340 ° C., respectively, - heavy oil (HO), sometimes called chrysenic oil when it is rich in chrysene, having a mean normal boiling temperature of the order of 350-360 ° C, - pitch, which contains all compounds of high molecular weight and having normal temperatures boiling point greater than 360 ° C. Pitch is characterized in that it consists of different resins (alpha, beta and gamma) more or less soluble in selective solvents. The proportion of each of the resins constituting the pitch is a criterion of quality. Pitch is a reactive mixture. When subjected to temperatures above about 350-360 ° C, it tends to spontaneously polymerize as a so-called reforming or self-reforming reaction. This reaction tends to change the distribution of the resins, in particular by increasing the proportion of alpha resin. Beyond a certain amount of alpha resin and a certain balance between beta and alpha resin, the pitch quality, with respect to certain specifications of use whose major applications of production of anodes for primary aluminum industry, is degraded.

This nomenclature of the different types of oils may be modified according to the applications and types of coal tar refineries: - Carbon black oil (CBO) is a broad cut which generally includes anthracene oils and heavy oil. It may also include a portion of the wash oil and the pitch. The sum of all the oils of the heavy oil carbolic oil is sometimes considered a broad oil (WFO). Alternatively, the section combining the fractions from the washing oil to the heavy oil may be designated as a creosote oil (CRO).

All these denominations may vary from one refinery to another according to local usage, in particular by introducing notions of "head" cuts or "light" or "heavy" attributes characterizing boiling temperature ranges. successive normal ... Different distillation schemes of tars have been described and used. By way of example, mention may be made of the Wilton and Ab der Halden historical processes, the headings, the modern distillations known as "circulation at the bottom of column" and the multi-flash distillations. Each distillation scheme corresponds either to specific production objectives in terms of number and quality of cuts targeted or to choices made due to technological limitations existing at the time of their development. The oldest continuous distillation scheme for tars is described in the literature as the Wilton process (Fig. 1) or Ab der Halden [Romovacek]. It consists of three stages of treatment: 1. dehydration of the crude tar, to obtain a dehydrated tar; 2. a rectification of dehydrated tar to produce several cuts of hydrocarbons: one or two chemical oils, a creosote oil and a pitch; 3. In some particular embodiments, the pitch is then reheated and held in a polymerization reactor or maturation reactor to controllably modify its properties by controlling the progress of the pitch polymerization. The Ab der Halden variant differs from that of Wilton operated under atmospheric pressure by the addition of a steam train. It makes it possible to obtain a better exhaustion of the pitch as well as a better control of its intrinsic properties. In fact, at the final softening point of the identical pitch, the bottom of the column in the Ab der Halden configuration is cooler than in the Wilton configuration, which makes it possible to limit the spontaneous and uncontrolled polymerization of the pitch. Both Wilton and Ab der Halden processes are usually operated on a single distillation equipment. They have the advantage of being simple and robust but do not allow a rise in capacity beyond about 100,000 tonnes per year of dehydrated tar. In addition, the quality of the collected sections and the recovery yields are not optimal. It will be appreciated that the dehydration step is a preliminary treatment of crude tar common to all continuous distillation processes of tars. When the objective is not primarily to produce chemical oils, simplified variants of these processes are usable. Those skilled in the art refer to it as topping or topping processes. In these embodiments, the dehydration is followed by a simplified distillation whose sole purpose is to separate a light phase from a heavy phase. For phenol-poor tars, H.G. Franck describes steamed "topping" to recover naphthalene at the column head and heavy tar at the bottom of the column (Fig. 2). The latter is then used as a fuel. A distillation unit located in Hamilton, Canada, is described in [Kirk] as being able to separate during a vacuum "topping" an oily fraction containing all the compounds of normal distillation point between 140 ° C and about 340-350 ° C and a pitch at the bottom of the column (Fig. 3). The oily fraction is used as a carbochemical fuel comparable, for example, with fuels of class FA to FE according to standard NF EN 14156. The properties of the pitch can be adjusted by performing an intermediate cleaning cut allowing the point of rotation to be adjusted. softening by removing some heavy oil. This cleanliness cut represents only 1 to 5% maximum of the tar feed. Part of the fatty pitch is then recycled to the feed of the distillation column after being aged / reformed in a maturator. The rest of the fat pitch represents the net output at the end of the unit.

As the number of hydrocarbon fractions to be recovered is increased and requirements for higher recovery efficiency or quality become apparent, the tars distillation units evolve to more complex systems. The original method employed at Clairton (Fig. 4) and described in [Kirk] is an example of this type of evolution. After the dehydration, the continuous distillation is carried out on several fractionation columns in series. Each column makes it possible to recover a particular hydrocarbon cut, its quality being adjusted in particular by controlling the reflux ratio of each distillation column. The bottom of the column is then sent to the next column where it is subjected to further distillation to recover the next cut and so on. The hydrocarbon cuts are recovered in an order corresponding to an increasing normal boiling temperature. The pitch is recovered at the bottom of the last column after passing successively in each distillation apparatus. The pitch therefore has a relatively long residence time and undergoes a thermal history which contributes to its spontaneous and uncontrolled polymerization. In order to limit the associated thermal stress, the different equipment is operated under reduced pressure, which makes it possible to reduce the temperature of the column foot and to mitigate, but only in part, the self-reforming of the pitch. This self-reforming mitigation is indeed only partial because it is influenced by the capacity modulations of the distillation units: the column bottoms act as polymerization reactors for recycling pitch.

When the capacity of the unit is decreased, the residence time in the bottom of the columns increases mechanically. At low capacity, the pitch is therefore more reformed than high capacity. In the case of load modulation, the pitch quality and the quality of the oils can not therefore be maintained simultaneously and arbitrations may be required as to the qualities and productivities of certain products / cuts to be sacrificed for the benefit of others. This type of distillation is often described in the literature as column bottom distillation or "bottom circulation distillation" [Romovacek].

In order to overcome the drawbacks of bottom-column distillation, an alternative strategy is to employ a flash or multi-flash distillation technique (Fig. 5 - [H.-G. Franck]). In this type of process, the dehydration is followed by a first flash called primary distillation. It makes it possible to separate a more or less fatty pitch from an oily fraction at the earliest point in the process. As for the example of Hamilton-based distillation, a cleanliness cut allowing a small amount of anthracene oil II or a heavy oil to be recovered makes it possible to adjust the properties of the pitch collected at the bottom of the column. This intermediate withdrawal produces a heavy oil comparable to a carbon black oil. However tonnages remain very low: these cuts are in fact so-called "cleanliness" cuts allowing only caller differentiation net quality of the pitch, including lowering the amount of residual volatile oils. Consequently, these "cleanliness" cuts represent only a few percent (1 to 5% by weight) of the tar feed while the productivity objective is of the order of 20 percent by weight for a tar distillation. producing a carbon black oil. The oils collected at the top are then treated by fractional distillation to recover different cuts. Depending on the case, the primary distillation is carried out under atmospheric pressure as described in Chinese patent CN 102161901B, under reduced pressure [Ullmann] or under steam distillation as in the continuous distillation scheme Ab der Halden for capacities greater than 100 000 tons a year. The use of distillation strategies under reduced pressure or steaming can reduce heat stress on the pitch. After distillation under steam distillation, the oils collected in heads are washed, condensed and dehydrated while the aqueous condensates are stripped.

These different operations take place simultaneously, which thus makes it possible: - to recover the corrosive species in the aqueous condensates, and thus to increase the lifetimes of the equipment and columns of the fractional distillation of the oils, with respect to the duration of life of alternative technologies; Recovering the organic substances which would otherwise have dissolved in the water, which thus makes it possible to avoid significant losses of yield which would otherwise take place because of the bringing into contact between the aqueous and organic phases; dehydrating the organic phase, which will not induce additional yield loss at the fractional distillation column heads of the downstream oils due to the formation of volatile water / tar compound azeotropes.

The pitch recovered at the bottom of the column may then be polymerized under controlled conditions of temperature, pressure and residence time in one or more reforming reactors in series in order to adjust its properties. The primary distillation under reduced pressure is immediately followed by fractional distillation. This is carried out using a distillation train composed of several columns in series with the primary distillation. The columns are supplied with vapor phase directly. The reflux is controlled by recirculation of the feet of the downstream columns to the upstream columns. Since corrosive species are not recovered prior to fractional distillation, these column legs must be cooled and washed with water. This induces a wetting of the reflux. Since some of the tar compounds form azeotropes with water, the leakage of water into the vapors at the top of the last column induces a contribution to a loss of yield compared to distillation under steaming. The oils are recovered in descending order of their normal boiling point. In the scheme proposed by [H.G. Franck] or [Ullmann], the vacuum source is propagated from the last fractional distillation column to the first primary distillation column. Due to the pressure losses all along the columns, the resulting pressure at the bottom of the primary column may not be sufficiently low to allow a depletion of the pitch comparable to that obtained for example during a primary distillation with 20 training at the steam. The pitch produced may then be a little fatter than required and an additional downstream additional flash depletion unit may be required depending on the properties targeted. Alternatively, and as for primary distillation under steaming, the pitch collected at the bottom of the column can then be subjected to additional reforming treatment.

The primary distillation operated under atmospheric pressure does not make it possible to obtain the same cut-off rates as the primary distillations under steam or under reduced pressure: the pitch collected at the bottom of the column is much lighter and the oils collected at the top of the column. column have a shorter boiling temperature range. This fraction of oil stops with the washing oils (fraction containing the methyl-naphthalenes) whereas the compounds with three or more aromatic rings remain in the pitch (anthracenes, homologues of the anthracene and heavier products). The foot of the column of the primary distillation is comparable to a heavy tar. Therefore, in order to produce a pitch that meets the specifications, a second flash operation is required (Figures 6 and 7). CN102161901 refers to this foot of the column as "carbon black oil"; this "carbon black oil" contains in this case about 60% pitch. It is then distilled under reduced pressure in order to collect the pitch at the bottom of the column and the heavy oils at the top 3025523 7 (Figure 6.a). The name "oil for carbon black" used is however misleading because not in accordance with the practice of those skilled in the art and the specifications of the industries employing it. Indeed, the oils thus identified must meet strict specifications especially with respect to their coking power (evaluated using a BMCI index - "Bureau of Mines Coking Index"). The value of the BMCI is, beyond a certain pitch content estimated at 30%, penalized by the amount of pitch. The method described in CN102161901 is ultimately only a modified version of "topping" processes, embellished with a traditional additional separation unit providing no particular element of remarkable or non-obvious performance. Thus, CN102161901 describes an implementation of an old concept (as illustrated in Figure 7 - [Romovacek]) by making modifications accessible to those skilled in the art. In order to limit the corrosion phenomena of the materials constituting the equipment, the various processes described above resort to additions of neutralizing bases in order to treat either crude tar or certain oil cuts. The neutralizing bases employed are in general, and in this order of priority, sodium hydroxide, sodium carbonates, potassium hydroxide, potassium carbonates or calcium carbonates. Depending on the type of process, the addition is made at a different point. The sodium, potassium or calcium salts formed as a result of these additions are not volatile. They then tend to concentrate in the heavy fractions. If these fractions have a high permissible limit imposed by their specifications, then the maximum amount of neutralizing agent is limited. The processes for the continuous distillation of "bottom-of-column circulation" type tars require that the addition be carried out in the feed tar. As a result, the salts concentrate in the pitch. Since the pitch is subject to a binding specification on the maximum acceptable amount of sodium (500 ppm maximum, 250 ppm in general), the amount of salts containing the sodium ion that can be added is therefore limited. In addition, the tar already contains sodium which further decreases the amount of neutralizer allowed. In fact, in this scheme of operation, the neutralization can not be complete. In a multi-flash scheme under reduced pressure, the neutralization is carried out on the reflux of the first fractional distillation column, reflux constituted by the fraction "washing oil". As mentioned above, this induces a water introduction contributing to a loss of yield. In addition, this does not make it possible to treat all the corrosive species, the vaporized oils introduced into the fractionation column leading to the production of naphthalenic oil being loaded in a non negligible quantity of species causing selective corrosion in the range. temperatures of 180-220 ° C.

The neutralization is therefore only partial. Finally, since sodium is nonvolatile, it can not be introduced in too large quantities. Indeed, the sodium tends to concentrate in the condensed phases that flow back to the sections of anthracene oil I, II and pitch.

In a multi-flash production scheme under steam or atmospheric pressure, the neutralization is carried out on the fully condensed broad cut withdrawn at the top of the primary column. In these production schemes, the pitches produced are therefore without added sodium, since only the oils are treated. On the other hand, the treatment of the broad oil cut implies the presence of added sodium in the heavier cuts resulting from the fractional distillation: anthracene oils, creosote oils or heavy oils according to the denominations used. If these oils are used as oil for carbon black, then the presence of sodium, potassium or calcium becomes critical, the specifications, 50 ppm maximum, being up to ten times more severe than for pitch. As a result, not all of the heavy oils collected can be directly used to formulate a carbon black oil: the heavy oil portion must be removed by distillation and the carbon black oil cut stops at the fraction of anthracene oil II. The sodium is thus purged in the heavy oil, but the carbon black oil thus obtained is lighter and therefore less good with respect to the specifications, in particular as regards the boiling temperature range and the performance characteristics. coking. The production of carbon black oil represents an outlet of interest for the coal tar distillation industries. Given the configurations mentioned, if the objective is to produce such an oil at the same time as pitch, then a simple unit such that the flow at the column bottom introduced by [Romovacek] would appear particularly suitable. However, it does not necessarily achieve the right economic balance between chemical oils, pitch and carbon black oil, the profitability of the process being achieved only on chemical oils. The best equilibrium is achieved for processes which make it possible to produce a pitch having stable properties, and whose recovery rate of recoverable chemical products, ie mainly naphthalene, is maximal while allowing a formulation of carbon black oil in the binding limits of the associated specifications. The two types of multi-flash process under reduced pressure or steam are therefore the most appropriate among those described in the literature. However, none of them makes it possible to achieve optimum performance: the steam-driven process, because of the mode of neutralization used, induces a loss of heavy oil which is highly loaded with salts which can not contribute. oil formulation for carbon black; the reduced partial pressure process does not allow an optimum recovery yield of naphthalene and in case of overdosage or too much sodium transfer in the neutralization of the washing oil reflux, the anthracene oil fractions I and II are found to be contaminated with sodium, which leads to the same consequences as for the heavy oils of the steam process.

In addition, whatever the process scheme considered, the carbon black oil will have to be formulated: this means that it will be obtained after mixing previously distilled fractions. Energetically, the power consumed during the distillation is wasted and additional consumption to reconstitute a mixture will be necessary. Whatever the methods described and employed, it appears that no solution described is optimal for producing, on units of capacities greater than 100,000 tons per year in dehydrated tar equivalent, and simultaneously, the three types of slices. : - Sodium-free added pitch preserving its native properties, - Sodium-free carbon black oil added with maximum yield, - Chemical oils, including for example naphthalene, with optimal yield. The distillation of coal tars for the simultaneous production of pitch, carbon black oil and large naphthalenic cut subsequently fractionated into 25 individual cuts therefore requires the use of a specially designed process to obtain products in accordance with specifications and overcoming the aforementioned drawbacks. This specific process was set up by the inventors and is the basis of the present invention. The principle of the invention lies in the definition of a primary distillation of coal tar coupling a flash effect and a rectification of the volatile oils in order to simultaneously produce three polyaromatic hydrocarbon cuts without the effect of thermal aging and without the addition of salts containing alkalis. The three generated sections thus retain intrinsic properties derived from the raw material employed without undergoing undesirable aging effect or concentration of added nonvolatile salts for pitch and carbon black oil. Primary distillation is conducted without the addition of alkalis and alkaline earths.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a diagram according to the prior art which shows the typical configuration of a tar distillation according to the Wlton method. Figure 2 is a scheme according to the prior art which shows the typical configuration of a tar distillation according to the method of topping. Figure 3 is a schematic diagram of the prior art which shows the typical configuration of a tar distillation according to the method employed in Hamilton for producing a pitch and a carbochemical fuel. Figure 4 is a schematic diagram of the prior art showing the typical configuration of so-called "bottom-of-column" tar distillation as used at Clairton. Figure 5 is a scheme according to the prior art which shows the typical configuration of a multi-flash tar distillation with oil neutralization on the wash oil reflux.

Figure 6 is a schematic diagram of the prior art showing the typical configuration of a tar distillation according to CN102161901B. Figure 7 is a diagram according to the prior art which shows the typical configuration of a so-called "bottom-of-column circulation" tar distillation supplemented with a pitch flash.

Figure 8 is a diagram illustrating a device for carrying out the method according to the invention. DESCRIPTION OF THE INVENTION The present invention provides a tar distillation process which produces in one primary distillation step three streams: pitch, carbon black oil, and large naphthalenic oil cut. By this method, it is possible to produce a carbon black oil without the addition of alkalis of any kind (such as Na or K) or alkaline earth metals (for example Ca). The amount of carbon black oil produced according to the invention reaches tonnages comparable to or greater than those obtained in a state-of-the-art tar distillation supplemented by a carbon black oil formulation station. by mixing. The method according to the invention makes it possible to manage the cutoff between the pitch and the carbon black oil so as to adjust the properties of the pitch. Said method also makes it possible, by its organization, to produce a pitch without adding alkalis of any kind (such as Na or K) or alkaline earth (for example Ca). It makes it possible to modulate the productivities of the three cuts produced (pitch, oil for carbon black and chemical oils) in adjustment to the market demand and without recourse to methods of blending sections of previously distilled hydrocarbons. Furthermore, the process according to the invention makes it possible to condense the chemical oil vapors and to neutralize them without inducing contamination, leading to a loss of yield of valuable chemical species in the downstream treatment of fractional distillation of the oils.

Thus, the invention relates to a coal tar distillation process comprising a primary distillation characterized in that it comprises: a flash distillation of a mixture of dehydrated coal tar and pitch, making it possible to obtain flashed vapors at the top of the column and at the bottom of the pitch column, a part of the pitch obtained during the flash distillation being used in the mixture 10 dehydrated coal tar and starting pitch; . immediately after flash distillation, stripping and rectification and flash vapors to obtain a carbon black oil and a large naphthalenic oil cut. Primary distillation is conducted without the addition of alkalis and alkaline earths. The primary distillation may be carried out under partial vacuum, under steaming or under a combination of partial vacuum and steam entrainment. The broad naphthalenic oil fraction obtained by the process according to the invention comprises the tar compounds having normal boiling temperatures of between 70 and 300 ° C. The carbon black oil obtained by the process of the invention comprises the tar compounds having normal boiling temperatures of between 300 and 450 ° C. According to a particular embodiment, the process according to the invention comprises, before the primary distillation, a step of dehydration of a coal tar. According to another particular embodiment, the process comprises, after the primary distillation, the successive stages of condensation, neutralization and distillation of the large naphthalenic oil section, making it possible to obtain different chemical oils. Neutralization can be carried out without reflux to the condensation and primary distillation stages. In the process according to the invention, before distillation, a light oil, composed of a mixture of benzene, toluene and xylenes, is added to the condensed and neutralized broad naphthalenic oil. The invention also relates to a dehydrated coal tar distillation device implementing the method described above, in which the equipment for the primary distillation comprises: a flash column, a stripping column and a stripping column; heating system. The device according to the invention may also comprise a vacuum condensation device downstream of the stripping and stripping column.

It may also comprise, upstream of the flash column, a column for dehydration of coal tar. The following description illustrates a particular embodiment of the invention in which there are four main elements: Dehydration of coal tar to remove the water contained in the feed tar and produce a dehydrated tar, A primary distillation of tars allowing the simultaneous production of pitch, carbon black oil (CBO) and a broad naphthalenic oil section comprising in a single fraction the cuts usually referred to as carbolic oils, Naphthalenic and washing, - Neutralization of the condensed large naphthalenic oil section during the primary distillation, fractional distillation of the condensed and neutralized broad naphthalenic oil for recovery of the separated fractions of carbolic oil, oil naphthalenic and washing oil. The dehydration of the tar is carried out by means of a heteroazeotropic distillation employing a light oil as a dehydrating agent. The water contained in the tar is mixed with the light oil and forms at a low temperature an azeotrope which preferably distils. This gaseous azeotrope is then condensed. The latter being heterogeneous, it then separates by demixing in the form of two phases: an organic phase of light oil and an aqueous phase. The light oil thus obtained is the result of a form of regeneration of the dehydrating agent, optionally supplemented with the benzene, toluene and xylene compounds present in the tar and used in the composition of the light oil. This regenerated light oil can then be reused as a desiccant. The excess is kept for later use in the unit. This dehydration is operable in this form within the limit of a water content of up to about 7% by weight in the tar. Beyond this, it must be preceded by mechanical separation by centrifugation to lower the water content in the tar to less than 7% by weight. Dehydrated tar, having a maximum water content of 0.5%, is mixed with recirculation of the pitch produced in the flash column. This mixture between the dehydrated tar and the pitch, which comes out hot from the flash column and can be kept hot by a heating system, allows: on the one hand, to preheat the supply of dehydrated tar and to bring it at the temperature required to preferentially vaporise in the flash column all the compounds of normal distillation temperature greater than or equal to 350-360 ° C, on the other hand, to dilute the volatile species in a non-volatile pitch ballast and in such proportions that the vaporized volume fraction does not have sufficient energy to cause pitch in the flashed vapor distillation column which is directly in series with the flash column. The heating system makes it possible to maintain the pitch at a temperature below 360 ° C. The amount of pitch added to the dehydrated coal tar is determined in such a way that the heating system increases its energy to a level sufficient to bring the dehydrated and pitched tar mixture to a feed temperature in the flash column allowing the flash to occur, without exceeding a temperature greater than 350-360 ° C. The dehydrated tar treated in this way is such as obtained at the bottom of the dehydration column: it contains no addition of neutralizing species such as soda or potash, for example. The flash column is connected directly to the input of the rectification and stripping column. This connection is made to allow a vapor phase supply. In order to promote the vaporization of the heavy species without requiring too much temperature at the bottom of the flash column, the series systems of the two columns (flash column and stripping and stripping column) and the condenser are operated under vacuum. Thus, the temperature at the bottom of the flash column is maintained at a sufficiently high temperature to allow good separation but low enough not to induce self reforming pitch. The excess pitch is evacuated at the bottom of the flash column. Depending on the final specifications required and the properties of the raw material, this pitch may then be subjected to controlled reforming in dedicated reactors and / or a softening point adjustment in accordance with the usual rules and processes available for the production of the raw material. skilled in the art. The flashed stripping and stripping column permits a clear and clean break between a controlled specification carbon black oil and a lighter cut of chemical oil comparable to a large naphthalenic oil cut. This broad naphthalenic oil cup is a cut comprising carbolic, naphthalenic and wash oils. Its naphthalene titer is lower than for a rectified naphthalenic oil because of the dilution effects associated with the presence of the carbol and wash fractions. In order to control the quality of the oils produced, it can be applied a controlled reboil at the bottom of the column and controlled reflux at the top of the column. For example, the reboiling power is provided by means of a reboiler system forming part of the heating system such as a network of economizers recovering energy on oven fumes. Reflux can be controlled by returning a portion of the condensed chemical oil to the top of the column or incorporating a dephlegmator into the actual construction of the carbon black oil rectification column. According to a particular embodiment, the heating system consists of one or more radiant furnaces, each being provided with a single helical coil for circulating the fluid to be heated and one or more sections of economizers on the fumes. to recover the energy available to provide the reboiling energy of the carbon black oil rectification column, to preheat the dehydrated tar feed, to preheat the furnace combustion air, to generate steam, etc.

The vacuum condensation system consists of a series of low pressure drop heat exchangers for fully condensing the vaporized chemical oil exiting the head of the carbon black oil rectification column. This system utilizes a closed loop heat transfer fluid to recover energy and utilize it at other points in the refinery such as, for example, the preheating of the large neutralized naphthalenic oil with light oil oil. upstream of the first rectification column of the fractional distillation train. The condensates are collected in a tank. The entire equipment chain is kept under vacuum, the vacuum being applied at the collection tank condensed oil and propagating against the current to the foot of the flash column.

The condensed oils are then neutralized in a biphasic contactor. During this neutralization, the organic phase, i.e. the condensed oils, is intimately mixed with an aqueous phase containing a neutralizing base. The two phases are then decanted and the organic phase can be treated in distillation.

The aqueous phase is, in turn, mixed with the process water from the dehydration of the tars to be treated. During this neutralization, the corrosive species (such as chlorides, fluorides, chlorocyanates, thiocyanates, etc.) contained in the oils are captured by the alkali and / or alkaline earth metals provided by the base and solubilized in the water. In a specific embodiment in which the tar is rich in tar acids (naphthenic species and phenol derivatives), the neutralization is carried out with a more concentrated base in order to attack also the labile hydrogens of these corrosive organic species. Salts are formed, for example sodium salts (such as sodium phenolates) soluble in water. In this case, the process water collected at the end of the neutralization is treated separately from the process water resulting from the dehydration, in particular in order to recover the phenolic species by means of complementary water treatment processes. Following this neutralization, the fraction of decanted oil can be subjected to a fractional distillation. Prior to the distillation, and in order to overcome the drawbacks of having a neutralized oil saturated with water which, during the distillation, would cause the formation of azeotropes contributing to the loss of recovery yield of naphthalene, the neutralized oil is added the excess light oil collected at the dehydration level in proportions that only form, given the limited solubility of water in this neutralized oil, a water + light oil heteroazeotrope. Since this heteroazeotrope has distillation temperatures lower than the lightest of the organic compounds contained in the neutralized oil fraction, no yield loss will be experienced. The neutralized oil added with light oil is then subjected to fractional distillation according to a conventional principle. The cuts are distilled according to an order of increasing normal distillation temperatures. The top fraction of the first column makes it possible to recover a carbolic oil. Condensation at the top is partial to allow the water heteroazeotrope + light oil to remain in the vapor phase. The first condensates are therefore collected as being only carbolic oil. The non-condensed vapors under these conditions are then cooled to complete condensation of the heteroazeotrope. The condensates are returned to the decanters of the dewatering section for recycling the light oil as a desiccant. The bottom of the first column is then distilled in a second column to produce a concentrated naphthalenic oil at the top and a washing oil at the bottom.

As with any distillation, the control of the reboiling and reflux rates makes it possible to control the quality of the outgoing flows. These bettings are carried out according to the techniques available to those skilled in the art. Similarly, depending on the case, those skilled in the art may be required to modify, by means of well-known techniques, the operating conditions of these distillation systems; in particular, the type of column internals, the level of pressure, the number of equipment, the type of heat exchange and condensation system, etc. Where appropriate, these modifications are required because of the special implementation requirements of the method specific to a production context such as, for example, the nature of available cooling fluids.

A detailed description of the coal tar distillation process according to the invention carried out in a device according to the invention will be given below with reference to FIG. 8. A coal tar 101 containing up to 7 % by weight of water is mixed with a light oil 102 consisting of a mixture of benzene, toluene and xylenes. The amount of light oil is determined exactly according to the water content of the tar and the composition of the light oil in order to achieve proportions of water and benzene, toluene and xylenes such as the amounts of benzene, toluene and xylene are sufficient for all the water present to form azeotropes with these compounds. These proportions are governed by the laws of thermodynamics. The resulting mixture 103 is then preheated to a temperature such that the azeotropic water + light oil compounds flash in the dehydration column 10. In the dehydration column 10, the water azeotropic vapors plus benzene, toluene and The xylenes are vaporized and discharged as steam 104. These vapors are then condensed using any suitable heat exchange system. Thus, in a current embodiment, the condensation can be carried out using a tube / shell heat exchanger using a cold fluid such as a cooling water to condense the azeotrope vapors. In an alternative embodiment, the azeotrope vapors can be condensed using an air cooler.

The condensed vapors are then decanted and separated. The organic phase is reused, partly to be re-mixed with the tar 101, partly to be mixed with the wide naphthalenic oil 302, and the excess is discharged at the unit outlet. The aqueous phase is discharged at the unit outlet to then undergo treatment in industrial purification plant.

The dehydrated tar collected at the bottom of the dewatering column 10 is then mixed with a stream of hot pitch 212. This mixture 201 is fed into the flash column 20. This flash column 20 is in series with the rectification column. carbon black oils 22, the vacuum condenser 24 and the storage tank 25. This series of equipment is kept under reduced pressure by means of a vacuum system. The vacuum is applied to the storage tank 25 and propagates counter-current through the condenser 24, the carbon black oil rectification column 22 and the flash column 20. This vacuum system is, for example, consisting of a liquid ring pump, the ring liquid being selected as having a low vapor pressure and compatibility with polycyclic aromatic and organic aromatic organic compounds. A washing oil type oil within the meaning of the definitions of the present invention is particularly suitable. The vacuum can also be achieved using a screw compressor or a lobe pump ("roots"). Vapor ejector or liquid ejector ("Hi-jet") vacuum systems may also be employed. In the former case, medium or high pressure steam is employed. In the latter case, a liquid having a low vapor pressure and compatibility with polycyclic aromatic and organic aromatic organic compounds is employed. For the "Hi-jet" application this liquid may for example be a washing oil type oil, an anthracene oil or a heavy oil in the sense of the definitions of the present invention.

Other alternative embodiments are possible such as the combination of vapor ejectors employing low or medium pressure steam combined with liquid ring pumps where the liquid is water or cooled condensates from the ejectors. These various embodiments are not limiting and those skilled in the art can adapt the vacuum system.

The mixture 201 of pitch and dehydrated tar is flashed in the flash column 20. During this flash, the vaporizable elements 221 are separated from the pitch which constitutes the part of the feed which remains liquid at the temperature conditions and The pitch is collected at the bottom of the column 20 in the form of a stream 202. The stream 202 is separated in two: a portion 211 is recycled through the heating system 21 while the rest is discharged at the outlet of unit 203. The amount recycled through the heating system 21 is determined in such a way that the heating system 21 increases its energy to a level sufficient to bring the dehydrated tar stream to a temperature of 25.degree. supply in the column 20 allowing the flash to occur, without exceeding the output of the heating system 212 a temperature greater than 350-360 ° C. The heating system 21 is, for example, consisting of a radiant furnace where the flow of fatty pitch is circulated in a single helical coil protected from the flame of the hearth of the radiant furnace with the aid of a heat shield. It may also consist of two or more radiant furnaces placed in parallel. In an alternative embodiment, the heating system 21 consists of an electric oven. In an alternative embodiment, the heating system 21 consists of one or more electric furnaces placed in series. These various embodiments are not limiting and those skilled in the art can adapt the heating system. Organic vapors 221 flashed into the flash column 20 are fed into the rectification column of the carbon black oil 22. The rectification column of the carbon black oil 22 controls the separation between the oils. 241, and the carbon black oil 222. This cut is ensured by controlling the reflux and reboiling rates. The reflux ratio is controlled by ensuring a return of a portion of the condensate flow recovered at the outlet of the vacuum condenser 24. In an exemplary embodiment, the condenser 24 consists of two equipment in series: a partial condenser , or dephlegmator, mounted on the column 22 and a total condenser mounted on the accumulator 24. In an alternative embodiment, the condenser 24 consists of two equipment in series: a partial condenser surmounting a storage capacity, is equipped with a dedicated reflux pump to the top of the column 22 is positioned so that the reflux can be achieved by gravity, and a total condenser mounted on the accumulator 25. In an alternative embodiment, the total condenser 24 consists of a single total condenser surmounting the accumulator 25; reflux is ensured to the column head 22 either by gravity effect or with the aid of a dedicated pump. In each of these embodiments, the system 24 may consist of tube / shell heat exchangers, plate heat exchangers, spiral heat exchangers or a combination of heat exchangers of these technologies. The reboiling rate is controlled by providing a modulation of the thermal load at the reboiler 23. In a particular embodiment, the reboiler 23 consists of a heat exchanger type smoke economizer 35 installed at the output of the radiant oven 21 In an alternative embodiment, the reboiler 3025523 19 23 consists of a radiant furnace. In another alternative embodiment, the reboiler 234 consists of a tube / shell heat exchanger where the heat load is provided by a heat transfer oil heated in a boiler. These various embodiments are not limiting and those skilled in the art can adapt the heating system. Reboiler 23 is fed with a flow of carbon black oil 231 punctured on stream 222. The derived amount is calculated to achieve the required reboil rate without increasing the temperature of the carbon black oil. above 350 ° C at the reboiler outlet 23. The excess carbon black oil 223 is discharged at the unit outlet. The broad naphthalenic section 251 collected in the accumulator 25 is fed into the neutralization unit 30 in the form of a stream 301 where it is brought into contact with a neutralizing base solution. In a particular embodiment, the contacting is performed within a stirred column. In an alternative embodiment, the contacting is performed within a pulsed column. In another alternative embodiment, the contacting is carried out in a settling mixer, the settling mixer may consist of a static mixer and a decanter. In another alternative embodiment, the contacting is carried out in a cascade of settling mixers, the cascade being able, for example, to comprise from 2 to 5 settling mixers. In another particular embodiment, the neutralizing base solution is prepared from demineralised water and sodium hydroxide. In alternative embodiments, the soda is replaced by another inorganic neutralizing base such as potassium hydroxide, sodium carbonates, calcium or potassium. These various embodiments are not limiting and those skilled in the art can adapt the neutralization system or the nature of the neutralizing base. The neutralized large naphthalenic cup 302 is mixed with a light oil 401. The amount of light oil is determined exactly as a function of the water content of the neutralized large naphthalenic cut and the composition of the light oil in order to achieve proportions of water and benzene, toluene and xylenes such as the amounts of benzene, toluene and xylenes are sufficient for all the water present to form azeotropes with these compounds. These proportions are governed by the laws of thermodynamics. The resulting mixture 402 is then fed into the rectification column 40.

The rectification column 40 proceeds from the usual fractional distillation equipment. Within the distillation column 40, three sections are separated: i) a light oil vapor and water phase with the compositions of the azeotrope water + benzene, toluene and xylenes 421, ii) a liquid cut of oil carbolic 422 and iii) the remainder of the oils in the form of a wide cut 404 collected at the bottom of the column. The distillation column 40 is provided with a reflux system and a reboiling system. The quality of the carbolic oil is controlled using the reflux system. This reflux system consists of a partial condenser 42 for condensing only the carbolic oil, the azeotropic mixture water + light oil 421 passing through the partial condenser 42 without being condensed. In a particular embodiment, the partial condenser is a tube / shell heat exchanger mounted directly on the column 40. Thus, the carbolic oil is condensed in the tubes, falls by gravity effect at the top of the column 40 where a part is The flow rate of stream 422 is controlled by a temperature control of the draw off to ensure that the column is at the correct operating point for the desired quality of the desired oil. According to this embodiment, the condensation of the carbolic oil is carried out by evaporating in the shell of the exchanger a condensate at a pressure chosen to be that of a saturated vapor whose temperature is higher than the condensation temperature of the azeotrope water + composed of the lightest volatile oil. Thus, the azeotropic mixture passes through the tubes without being condensed. It can then be condensed according to an embodiment as previously described for the case of the azeotropic mixture of dehydration. In an alternative embodiment, the condenser 42 consists of a remote exchanger surmounting an accumulation capacity. This accumulation capacity is either positioned in such a way that the condensates can be re-circulated partly towards the top of the column 40 by gravity or it is provided with a fixed lifting pump allowing to re-circulate a part of the condensates towards the top of the column 40. According to this particular embodiment, any heat exchanger technology is conceivable. As before, the partial condensation can be carried out by vaporizing the cooling fluid.

As before, the partial condenser will only condense the carbolic oil, the vapors of water and light oil remaining in the vapor phase. These vapors are then condensed and collected according to an embodiment comparable to those described above for the case of the azeotropic mixture of dehydration. The reboiling is ensured by heating the flow 411 circulated through the reboiler 41. In a particular embodiment, the reboiler 41 consists of a radiant furnace. In an alternative embodiment, the reboiler 41 consists of a tube / shell heat exchanger where the heat load is provided by a heat transfer oil heated in a boiler. These various embodiments are not limiting and those skilled in the art can adapt the heating system.

The reboiler is fed with an oil flow punctured on the flow 404. The derived amount is calculated in order to make it possible to reach the required reboiling rate without increasing the temperature of the oil above 350 ° C. at the outlet of the reboiler. The excess oil 501 is fed into the rectification column 50. The rectification column 50 proceeds from the usual fractional distillation equipment 10. Within the distillation column 50, two sections are separated: i) a concentrated naphthalenic oil 521 and ii) a washing oil 504 collected at the bottom of the column 50. The distillation column 50 is equipped with a reflux system and a reboiling system. The quality of the naphthalenic oil is controlled using the reflux system. This reflux system consists of a condenser 52 for condensing the naphthalenic oil. In a particular embodiment, the condenser is a tube / shell heat exchanger mounted directly on the column 50. Thus, the naphthalenic oil is condensed in the tubes, falls by gravity effect at the top of the column 50 where a part is drawn off. in the form of the flow 521. The flow rate of the flow 521 is controlled by a temperature control of the withdrawal to ensure that the column is at the right operating point for the desired naphthalenic oil quality 521. According to this embodiment, the condensation of the naphthalenic oil is carried out by evaporating in the shell of the exchanger a condensate at a pressure chosen to be that of a saturated vapor whose temperature is close to a value under the temperature condensation of the naphthalenic oil. In an alternative embodiment, the condenser 52 consists of a remote exchanger surmounting an accumulation capacity. This accumulation capacity is either positioned in such a way that the condensates can be re-circulated partly towards the top of the column 50 by gravity or it is equipped with a fixed lifting pump allowing to re-circulate a part of the condensates towards the top of the column 50. According to this particular embodiment, any heat exchanger technology is conceivable. As before, the partial condensation can be carried out by vaporizing the cooling fluid. Reboiling is provided by heating a portion of recirculated stream 503 through reboiler 51. In a particular embodiment, reboiler 51 is comprised of a radiant furnace. In an alternative embodiment, the reboiler 51 consists of a tube / shell heat exchanger where the heat load is provided by a heat transfer oil heated in a boiler. These various embodiments are not limiting and those skilled in the art can adapt the heating system. The reboiler is fed with a flow of oil 511 punctured on the flow 503. The amount derived is calculated in order to achieve the required reboiling rate without increasing the temperature of the oil beyond 350 ° C output reboiler 51. The excess oil 504 is discharged at the unit outlet. In an alternative embodiment, the columns 40 and 50 are operated under reduced pressure. The alternative embodiments of the partial vacuum are comparable to those described for the evacuation of the assembly consisting of the accumulator 25, the condenser 24, the carbon black oil rectification column 22 and the flash column of the pyrolytic residues 20. In an alternative embodiment, the column 40 is operated under atmospheric pressure and the column 50 is operated under reduced pressure. The alternative embodiments of the partial vacuum are comparable to those described for the evacuation of the assembly consisting of the accumulator 25, the condenser 24, the rectification column of the carbon black oil 22 and the flash column of the pyrolytic residues 20. According to this embodiment, the reboiling of the column 40 can be provided by means of a radiant furnace completed with a convection section. The hot oil at the outlet of this system 41 is then fed into the shell of a tube / shell heat exchanger used as a reboiler 51 while the flow of recirculated washing oil 211 derived from the stream 503 passes into the tubes. According to this embodiment, a single furnace makes it possible to provide the power required for the reboiling of the two columns 40 and 50. The calculation of the useful power of the common oven is adjusted accordingly in order to take into account the rewetting requirements of the two rectifications.

EXAMPLE OF IMPLEMENTATION OF THE INVENTION The following example of implementation describes a coal tar distillation unit with a capacity of 38,600 kg / h of tar (on a dry basis) according to the invention. The crude tar contains on a dry basis 1.2% insolubles in quinoline and 50 ppm sodium. The crude tar 101 containing 3% by weight of water is mixed in line with a continuous flow rate of 6000 kg / h of light oil 102. The composition of the light oil is 30% by weight of benzene, 30% by weight mass of toluene and 40% by weight of xylenes. The amount of light oil is in slight excess with respect to the water balance, in order to compensate for possible fluctuations in the amount of water in the tar feed. The tar + light oil mixture 103 is preheated by means of a tube / shell heat exchanger. The thermal power is provided by a hot organic fluid Dowtherm A. The hot mixture 103 is flashed in the dehydration column 10. The dehydration column 10 is provided with four dividing plates. The power supplied to the preheating exchanger is controlled in order to obtain a dehydration vapor temperature 104 of 95 ° C. These vapors are constituted by the azeotropic water + compounds of the light oil. These vapors are condensed and cooled to 50 ° C in the shell of a shell / shell heat exchanger. The power of condensation and cooling is provided by a cooling water circulating in the tubes of the exchanger. The condensates with the composition of the heterogeneous azeotropes are then decanted. The aqueous phase is pumped to a water treatment system. The organic phase is recycled partly to the tar feed 101, partly to the supply of neutralized large naphthalenic oil 302, while the excess is made available in unit limits. These recycling are done according to the flow required by the different points of mixing and consumption. At the end of this treatment, the tar collected at the bottom of column 10 contains about 0.5% by weight of bound residual water.

The dehydrated tar is mixed with a hot pitch 222. The pitch of the pitch 212 is set so that the mixture 201 is brought to about 360 ° C. at the inlet of the flash column of the pyrolytic residues 20. This corresponds to at a pitch rate 203 of 300 m3 / h. the flash column of the pyrolytic residues consists of a flash drum for separating the vapors, released during the flash, from the remaining liquid portion 25, the pitch, under the conditions of pressure and temperature of the column 20. The pitch fat is collected at the bottom of flash drum and redistributed on a set of six dividing trays. Column 20 is operated under a reduced pressure of -80 kPa (g). The pitch collected at the bottom of the column 202 is recirculated to the two radiant furnaces 21, operated in parallel, at a total flow rate 211 of 300 m 3 / h, ie 150 m 3 / h per oven. A fat pitch rate 203 of 17.6 m 3 / h is withdrawn continuously. The pitch thus produced has a softening point of 90 ° C Mettler determined according to ASTM D3104. It contains 2.2% of insolubles in quinoline determined according to ASTM D2318. The amount of pitch withdrawn represents 54.7% of the dehydrated diet. In view of the insoluble content in the quinoline tar and the concentration effect due to the flash distillation, this indicates that the pitch produced did not undergo self-reforming leading to the formation of 35 insoluble substances in quinoline. The sodium content of the pitch produced is 92 ppm. This increase is solely related to a concentration effect relative to the amount of sodium initially contained in the diet. The vapors 221 emerging at the top of the column 20 are transferred to the column 22 by the effect of pressure difference. Column 22 is operated under a reduced pressure of -85 kPa (g). The grinding column 22 is provided on the grinding portion with structured packing. On the stripping portion located under the vapor feed 221, the column is provided with 20 slotted trays. The reboiling is provided by means of a vertical tube / shell-and-tube heat exchanger 23 fed, on the tube side, by a carbon black oil loop 231 derived from the flow 222 and, on the shell side, by a thermal fluid flow of The column 22 is equipped at the top with a spiral exchanger designed as a partial condenser. The carbon black oil 223 is withdrawn continuously at an adjustable flow rate of 7720 kg / h. The carbon black oil 223 contains 10 ppm sodium. It complies with the most stringent specifications and standards such as GOST 1126. The vapors 241 not condensed at the set point of the head exchanger of the column 22 are then condensed and cooled in a total vacuum condenser 24, of type spiral exchanger, and collected in a buffer tank 25. These condensates 251 are the fraction of broad naphthalenic oil. The vacuum is applied to the buffer tank 25 by means of a lobe pump ("roots"). The supply of the vacuum pump is protected by two guard condensers. The cooling power is provided by hot water in the first condenser and cold water in the second. The condensates possibly collected on these guard exchangers are redirected to the neutralization 30. The large naphthalenic oil fraction 301 is pumped continuously to the neutralization section 30. The neutralization section 30 consists of a stirred column equipped with a stirrer with multiple tiered blades. The agitator is operated at 10 rpm. The flow of large naphthalenic oil is brought into contact with a solution of sodium hydroxide circulating in the agitated column. 2% sodium hydroxide is used. The amount of injected sodium hydroxide is modulated according to the chloride content measured in the broad naphthalenic oil. The soda is preheated to the temperature of the supply of large naphthalenic oil. The temperature of the neutralization column is kept constant in order to avoid any risk of phase inversion. The neutralized large naphthalenic oil is then separated from the water in a decanter. This organic fraction 302 is mixed with the light oil stream 401 from the dewatering section. The amount of light oil is adjusted according to the water content dissolved in the decanted neutralized large naphthalenic oil. This mixed stream 402 is then fed into the grinding column 40. The grinding column 40 is provided with single slot platens on the grinding portion and 32 double slot platens in the stripping portion. The reboiling is provided by means of a furnace 41 heating the flow 411 derived from the stream 404. The furnace 41 is common to the columns 40 and 50. The reflux is controlled using a tube exchanger / calender 42 mounted vertically on the column 40. The vapors 403 are partially condensed on the tubes side which ensures reflux. The power and temperature of the shell-side exchanger are ensured by evaporating boiler water in the form of steam at a pressure of 100 kPa (g). The flow of non-condensed vapors 421 passing through the exchanger 401 consists of azeotropic water + light oil. These azeotropes are condensed and cooled as previously in a tube / shell heat exchanger where the cold power is supplied by cold water. The condensates are gravity directed to the decanter of the dewatering section where they are separated. A carbolic oil is continuously withdrawn at the top plate in the form of a stream 422 at an adjustable flow rate of 640 kg / h. The neutralized large naphthalenic oil, topped with the contributions of the light oil + water and the carbolic oil fractions, is fed continuously in the form of stream 501 into the column 50.

The grinding column 50 is provided with structured packing on the grinding portion and 40 double slotted trays pass in the stripping portion. The reboiling is provided with the aid of an economizer 51 heating the flow 511 derived in part from the flow 503. The hot power is supplied by the overheated column foot oil 411 at the furnace outlet 41. The reflux is controlled at using a tube / shell heat exchanger 52 mounted vertically on the column 50. The vapors 502 are condensed on the tubes side which ensures the reflux. The power and temperature of the exchanger on the shell side are ensured by evaporating a boiler water in the form of steam at a pressure of 400 kPa (g). A 92% concentrated naphthalenic oil is continuously withdrawn from the top plate in the form of a stream 521. The wash oil collected at the bottom of the column 50 is withdrawn continuously, in the form of stream 504, at a pressure of 50.degree. flow rate of 4250 kg / h. The two rectification columns 40 and 50 are operated under vacuum at a pressure of -85 kPa (g). The vacuum is applied using a liquid ring pump, the liquid being a washing oil at 25 ° C. The streams 203 and 223 are cooled in heat exchangers to their storage temperature by giving up their heat to a Dowtherm thermal oil flow A used to warm the tar at the feed of the column 10. The excess heat is used to generate steam at a pressure of 400 kPa (g). Flows 504 and 521 are circulated through heat exchangers where they are cooled to their storage temperature by heating the feed stream 402.

Variations in the details of implementation of this example are possible without these inducing any deviation from the object of the invention. References [H.-G.Franck]: H.-G. Franck, JW Stadelhofer, in "Industrial Aromatic Chemistry", Springer Verlag, Berlin Heidelberg, 1988 [Kirk]: "Tar and Pitch" in "Kirk-Othmer Encyclopedia of Chemical Technology, "J. Wiley and Sons [Ullmann]: Blümer, G.-P., Colin, G. and Htike, H. 2011. Tar and Pitch. Ullmann's Encyclopedia of Industrial Chemistry. [Romovacek]: G.R. Romovacek, Light Metals, 1985, pp793-803

Claims (10)

REVENDICATIONS1. A process for the distillation of coal tar comprising a primary distillation characterized in that it comprises: a flash distillation of a mixture of dehydrated coal tar and pitch to obtain at the top of the column flashed vapors and at the bottom of the pitch column, a portion of said pitch obtained during the flash distillation being used in the mixture of dehydrated coal tar and starting pitch; . immediately after the flash distillation, stripping and rectification of the flashed vapors to obtain a carbon black oil and a large naphthalenic oil cut. 2. Method according to claim 1, characterized in that the primary distillation is conducted without adding alkali and alkaline earth 3. Process according to claim 1 or 2, characterized in that the broad naphthalenic oil fraction comprises tar compounds having normal boiling temperatures of between 70 and 300 ° C. 4. Method according to any one of claims 1 to 3, characterized in that the oil for carbon black comprises the tar compounds having normal boiling temperatures of between 300 and 450 ° C. 5. Method according to any one of claims 1 to 4, characterized in that it comprises before primary distillation a dehydration step of coal tar. 6. Method according to one of claims 1 to 5, characterized in that it comprises, after the primary distillation, the successive stages of condensation, neutralization and distillation of the naphthalenic oil section broad. 7. Method according to claim 6, characterized in that the neutralization is carried out without reflux to the stages of condensation and primary distillation. 3025523 28 8. Process according to Claim 6 or Claim 7, characterized in that, before the distillation, a light oil, composed of a mixture of benzene, toluene and xylenes, is added to the condensed and neutralized broad naphthalenic oil. 5 9. Process according to any one of claims 1 to 8, characterized in that the primary distillation is carried out under partial vacuum, under steaming or under a combination of partial vacuum and steam entrainment. 10 10. Dehydrated coal tar distillation apparatus implementing the process described in any one of claims 1 to 9, characterized in that the equipment for the primary distillation comprises: a flash column, a rectification column and stripping, a heating system.