EP0132526A2 - Process for coal hydrogenation incorporating a refining step - Google Patents

Abstract

According to the invention, the high-boiling liquid components are separated from the lower-boiling vapor components after leaving the hot separator head by partial condensation in an intermediate separator, so that the gas phase reactor obtains a better service life and optimum reaction conditions and furthermore an improved solvent quality for the hydrogenation with bottom phase hydrogenation and subsequent gas phase hydrogenation the bottom phase hydrogenation occurs.

Description

The invention relates to the production of liquid hydrocarbons from coal hydrogenation, with refined products having a comparatively low boiling point being produced in one operation.

The raw coal oils produced by the bottom phase hydrogenation of coal or high-boiling coal-based products (tars, pitches, etc.) require further processing steps in order to obtain refined, storage-stable liquid hydrocarbons. In order to increase the thermal efficiency and the economy of the overall process, it is advisable to connect the bottom phase hydrogenation and the refining stage in series; because the process parameters (pressure, temperature) required for the refining stage are automatically obtained after the bottom phase hydrogenation.

Since the refining of raw coal oils from the bottom phase hydrogenation also results in a conversion to lighter boiling cuts, the overall process can be optimized with regard to the desired product quality. The service life and the optimal reaction conditions of the fixed bed catalyst in the refining stage play a decisive role for economical process control with high availability of the entire system. The quality of the solvent required for mashing the coal is also important.

For the production of refined liquid hydrocarbons from coal, coal-based products (pitches, tars, etc.) and petroleum-derived heavy oils, several processes for the direct connection in series of bottom phase hydrogenation and gas phase hydrogenation (fixed bed catalyst) are known. In the "Kombi-Hydrierkammer" according to W. Urban (magazine: ERDÖL UND KOHLE ", 8th year; Nov. 1955, No. 11 pages 780-782) the hydrocarbons produced in the bottom phase reactors, which are light, medium and contain heavy settling areas, passed at about 430 ° C. and about 300 bar over gas phase reactors with a fixed bed catalyst filling. This process, known today as "VEBA-COMBI-CRACKING", was also transferred to coal hydrogenation (magazine: "ENERGIE", year 34 , No. 6, June 82, pages 172-173) In the combined process according to L. Raichle and W. Krönig (laid-open publication No. 2654635), the coal oil vapors generated in the bottom phase hydrogenation are divided into two parts: one part is about the gas phase - reactors with lumpy catalyst performed, wherein the lighter boiling ranges are discharged as products after subsequent liquid separation and distillation, and the heavy Siedela ^g ene (aufhydriertes medium and light oil), a part of the solution form means for mashing the coal. The other part is condensed directly after leaving the bottom phase hydrogenation (hot separator) and supplies the necessary remaining amounts of medium oil and heavy oil for the mashing of the coal. In this way, a solvent is formed which is composed of a mixture of hydrogenated (in the gas phase reactor) and non-hydrogenated medium and heavy oils. In this respect, this process differs from other hydrogenation processes (eg EXXON process), in which the entire solvent is hydrated. A disadvantage of the Ver drive from Raichle and Krönig that the directly condensed coal oil vapors also contain a considerable part of the light oil produced, which is obtained as a finished product.

All the above methods have the disadvantage that the over the _G-phase reactor with fixed bed catalyst as-run crude hydrocarbon vapors a large proportion of high-boiling oils contain, which lead to the increased coke formation and thereby reduce the life of the particulate catalyst.

The invention has for its object to reduce the proportion of high-boiling oils in the raw hydrocarbon vapors.

The invention is based on the idea of using an intermediate separator. Such intermediate separators are known per se for pure bottom phase hydrogenation (without downstream gas phase hydrogenation). There the intermediate separator is located behind the hot separator.

The latter is operated with respect to temperature and pressure in such a way that the amount of solvent, consisting of medium and heavy oil, is obtained in the intermediate separator sump, which is necessary in order to be admixed as a partial flow to another partial flow originating from a vacuum column to ensure the solvent self-sufficiency of the bottom phase hydrogenation. (U. Bönisch, B. Strobel: Offenlegungsschrift No. DE 30 22 158 A 1). Since the top products of the intermediate separator only contain product oils consisting of light and medium oils (possibly a small amount of heavy oil), the otherwise usual distillation stage for the separation of product and solvent oils is omitted. It is disadvantageous, however, that in the intermediate separator sump too a - albeit small - amount of light oil is withdrawn, which is returned to the bottom phase hydrogenation in the solvent.

According to the invention this is avoided in that the crude coal oils from the bottom phase hydrogenation after leaving the hot separator head are divided by partial condensation in the intermediate separator into a high-boiling liquid fraction and a lower-boiling vapor fraction. The low-boiling coal oil vapors, which are passed over the gas phase reactor, consist of light, medium and possibly a comparatively small amount of light heavy oil. This division can be varied by changing the intermediate separator temperature. This ensures that the bottom phase hydrogenation is combined in one working process with the gas phase hydrogenation, so that only the crude coal oils which tend to boil less (with only a little heavy oil content) are passed over the gas phase reactors. The crude coal oils, which tend to be high boiling, are largely drawn off upstream of the gas phase reactor and serve as part of the solvent for the pulp mashing. The result of this is that the gas phase reactor, on the one hand, has a better service life and optimal reaction conditions for the production of (partially) refined and low-boiling products and, on the other hand, is relieved of the proportion of coal oil (especially heavy oil) which is required as a solvent for mashing the coal . In addition, the reaction conditions for a catalyst can be adjusted more optimally if the starting products are not too broad. The use for the gas phase reactor occurs in the desired boiling point. The overall process is optimized in such a way that on the one hand an optimal refining and conversation of raw coal oils (light, medium and some heavy oil) _? u refined hydrocarbons takes place with a lower boiling point and, on the other hand, the service life and the reaction conditions for the catalyst in the gas phase reactor are optimized. Furthermore, in the event that more coal oils are passed through the gas phase reactor than the product quantity, only light and medium oils and the lighter boiling cuts of the heavy oil in the gas phase reactor are hydrated. As a result, the catalyst is gently stressed on the one hand and a hydrated solvent part consisting of medium oil and light heavy oil cuts is produced on the other hand. It is shown that the solvent quality that is decisive for the hydrogenation process is essentially determined by the type and amount of the middle oil and possibly the light heavy oil (eg donor effect of the relatively easily hydrolyzed middle oils and light heavy oil fractions).

The part of the solvent thus produced and returned to the pulp mashing then consists on the one hand of the rehydrated solvent oil (free of heavy oil) with a higher boiling point) and on the other hand of the heavy-boiling intermediate separator sump product, which is not hydrated. This results in an improved solvent quality for the hydrogenation process.

Since the liquid portion in the intermediate separator still contains small amounts of light oil, stripping with hydrogen-containing gases and partial evaporation of the liquid portion and / or by flash evaporation of the above can be used. Light oil components are largely separated and added to the use for gas phase hydrogenation.

Various examples of the hydrogenation according to the invention are shown below.

1 to 6 show flow diagrams of various operating modes according to the invention. According to Figure 1, the products from the Sumpfphasehydrierung 1 in hot separator 2 at about 450 ^o C in a liquid / solid phase (bottom) and a gas / vapors phase (head) are separated. This gas / vapor phase, which contains the actual coal oils, is partially cooled in heat exchangers 3, as a result of which the tendentially heavier boiling cuts of the coal oils largely condense out. The separation of the liquid phase on the one hand and the gas / vapor phase on the other hand takes place in the intermediate separator 4 at 320 to 420 ° C.

The temperature of the intermediate separator 4, which determines the thermodynamic equilibrium and thus the separation of the coal oil into a lower-boiling vapor phase and a heavier-boiling liquid phase, can be varied by alternative connection of the feed-product heat exchangers 3, which recover a large part of the waste heat of the products .

• Fahrweise a:

Six process variants are provided in order to set the optimum reaction conditions for the gas phase hydrogenation depending on the product quantities and boiling points of the coal oil from the bottom phase hydrogenation:

• Driving style a:

The hot separator head products are cooled in the heat exchanger 3 to the reaction temperature of the gas phase reactor 6. Here, a considerable part of the heavy oil (e.g. 70%) from the hot separator top product is produced in vapor form. Almost all of the light oil and most of the middle oil are also produced in vapor form.

In this mode of operation, more products are run through the gas phase reactors 6 than the end products cnt speaks; ie some of the refined products (medium and heavy are used as the hydrated solvent portion.

example 1

Based on 100 kg of coal (on) in the bottom phase reactors 1 (480 ° C, 300 bar) and a solvent quantity of 150 kg (50% medium oil, 50% heavy oil), the result is in the intermediate separator 4 at a temperature of 390 ° C - 400 ° C following product separation: The bottom phase of the intermediate separator contains 15.8 kg of oils (1.5% light oil, 24% medium oil, 74.5% heavy oil), which are recirculated as a solvent component. The top phase of the intermediate separator 4 (use for the gas phase reactor 6) consists of the hydrogenation gas from the bottom phase hydrogenation and 126 kg of oil vapors (14.5% light oil, 55.5% medium oil, 30% heavy oil). In the gas phase reactor 6, the crude coal oils are refined by refining on a fixed bed catalyst at 390 ° C. and 280 bar and partially converted to lighter boiling points. With a specific catalyst load of 1 kg Kl / 1 kg catalyst · h, the product distribution is approx. 30% light oil, 43.5% medium oil and 26.5% heavy oil. The coal oils from the gas phase reactor 6 are condensed out by cooling 7 and separated from the residual gases in the separator 8. In a subsequent distillation, the pre-refined coal oils are divided into gasoline, medium oil and heavy oil. All petrol and 22% of the middle oil are released as products. All of the heavy oil and the remaining medium oil (78%) are recirculated as a solvent component, which is hydrated, for mashing the coal. Based on the total solvent, the hydrogenated solvent is 50%.

• Die Heißabscheider-Kopfprodukte werden im Wärmeaustauscher 3 auf eine Zwischenabscheidertemperatur abgekühlt, welche unterhalb der Reaktionstemperatur des Gasphasereaktors 6 liegt. Hierdurch wird erreicht, daß ein großer Teil des Schweröls auskondensiert. Die Gas-/Dämpfe-Phase enthält vergleichsweise wenig Schweröl und ermöglicht somit optimale Reaktionsbedingungen für den stückigen Katalysator im Gasphasereaktor 6. Vor Eintritt in den Gasphasereaktor wird die Gas-/Dämpfephase auf Reaktionstemperatur des Gasphasereaktors 6 durch Aufheizung 5 - hitzt. Nach Verlassen des Gasphasereaktors 6 werden die Produkte und Gase über einen Kühler 7 einem Abscheider 8 zugeführt.

Driving style b):

• The hot separator head products are cooled in the heat exchanger 3 to an intermediate separator temperature which is below the Reaction temperature of the gas phase reactor 6 is. This ensures that a large part of the heavy oil condenses out. The gas / vapor phase contains comparatively little heavy oil and thus enables optimal reaction conditions for the lumpy catalyst in the gas phase reactor 6. Before entering the gas phase reactor, the gas / vapor phase is heated to the reaction temperature of the gas phase reactor 6 by heating 5. After leaving the gas phase reactor 6, the products and gases are fed to a separator 8 via a cooler 7.

Example 2

With the same operating conditions as example 1, the following product separation results in the intermediate separator 4 at a temperature of 330 ° C - 340 ° C: The bottom phase of the intermediate separator contains 70.5 kg of oils (2.5% light oil, 40.5% medium oil, 57% Heavy oil), which are recirculated as a solvent component. The top phase of the intermediate separator 4 (use for the gas phase reactor 6) consists of the hydrogenation gas from the bottom phase hydrogenation and 71 kg of oil vapors (23% light oil, 63.5% middle oil, 13.5% heavy oil), which in the heating 5 to the reaction temperature 390 ° C of the gas phase reactor 6 are heated. In the gas phase reactor, the crude coal oils are refined at 390 ° C and 280 bar by means of refining on a fixed bed catalyst and partially converted to lighter boiling points. With a specific catalyst load of 1 kg oil / 1 kg catalyst h, the product distribution is approx. 34% light oil, 53.5% medium oil and 12.5% heavy oil. The coal oils from the gas phase reactor 6 are condensed out by cooling 7 and separated from the residual gases in the separator 8. In a subsequent distillation, the pre-refined coal oils are divided into gasoline, medium oil and heavy oil. All petrol and 63.5% of the middle oil are released as a product. All of the heavy oil and the remaining medium oil (36.5%) are recirculated as a solvent component, which is hydrated, for mashing the coal. Based on the total solvent, the hydrogenated solvent is 15%. The other modes of operation (cf) represent modifications of the mode of operation b). A small amount of light oil is also produced in the intermediate separator sump. In order to prevent this - even if small - light oil portion from being returned to the bottom phase hydrogenation as a solvent, this light oil is largely separated from the intermediate separator bottom product and added to the use for the gas phase hydrogenation.

Driving style c):

According to FIG. 2, the light oil is separated from the intermediate separator sump product by partial evaporation and / or stripping with hydrogenation gas, cycle gas or fresh hydrogen (approx. 97% H ₂ ). The evaporation temperature, which lies between the intermediate separator and the gas phase reactor temperature, and the amount and quality of the stripping gas (for example hydrogenation cycle gas, fresh hydrogen, approx. 97% _H2 . Determine the amount of the low-boiling fractions to be evaporated. For example, heat recovery of the waste heat of the hot separator head product) or in a heating furnace (for example parallel to the heating of the intermediate separator head products) The gas / oil vapors are separated from the bottom product in a further separator 9 and fed to the feed for the gas phase hydrogenation.

Example 3

70,5 kg ölen, welche noch ca. 1,7 kg Leichtöl enthalten. Mittels Strippen mit Frischwasserstoff (97 % H₂) und Erwärmung im Aufheizofen 5 auf ca. 390°C ergibt sich im Abscheider 9 eine öldämpfemenge von ca. 18 kg (1,3 kg Leichtöl), welche dem Einsatz im Gasphasereaktor 6 zugeschlagen werden.Based on the numerical values of Example 2, the bottom product of the intermediate separator 4 consists of 330 ° - 340 ° C

Oil 70.5 kg, which still contains approx. 1.7 kg light oil. Stripping with fresh hydrogen (97% H ₂ ) and heating in the heating furnace 5 to approx. 390 ° C. results in an oil vapor quantity of approx. 18 kg (1.3 kg light oil) in the separator 9, which are added to the use in the gas phase reactor 6.

Driving style-d):

The separation of the light oil from the bottom product of the intermediate separator 4 is carried out according to FIG. 3 by relaxing the bottom product with subsequent distillative removal of the low-boiling fractions. In the distillation column 10, either only light oil or a mixture of light oil and medium oil can be drawn off, which is compressed again to process pressure by means of a high-pressure pump 11, heated and added to the insert for the gas phase hydrogenation. The procedural justification for this procedure is that the light oil is completely separated from the bottom product of the intermediate separator; also depending on the temperature of the intermediate separator 4 by adding light oil and medium oil in the gas phase reactor 6, a two-phase flow can be generated if op-. maximum reaction conditions in the gas phase reactor require this. Finally, the boiling cut in the distillation 10 can be set so that not only the amount of product, but also a solvent fraction (medium oil and possibly heavy oil with a low boiling point) is passed through the gas phase reactor in order to achieve a desired solvent quality (increased hydrated fraction).

Example 4

Based on the numerical values of Example 2, the bottom product of the intermediate separator 4 at 330-340 ° C. consists of 70.5 kg of oils, which still contain approx. 1.7 kg of light oil. By relaxing the oils to atmospheric pressure, some of the oils evaporate, but these are converted back into the liquid phase by condensation. The gases released during the expansion of the oils are removed. In the distillation column 10, the light oil (1.7 kg) is completely separated from the residual oil (solvent content 68.8 kg) and fed to the use of gas phase hydrogenation via the pump 11 and the heating device 5. This creates a solvent that is practically free of light oil.

Driving style e):

This method variant according to FIG. 4 is based on fan code d. The lighter fractions are separated from the sump by flash evaporation 12. After condensation of these lighter fractions and separation of the gases, they are compressed to high pressure in the liquid phase, heated and then used in the gas phase reactor. The separation of the lighter fractions in the flash evaporation 12 can optionally be enhanced by stripping.

Example 5

Based on the numerical values of Example 2, the bottom product of the intermediate separator 4 at 330-340 ° C. consists of 70.5 kg of oils, which still contain approx. 1.7 kg of light oil. By relaxing these oils to about atmospheric pressure in the flash evaporator 12, a division into 15.5 kg of oil vapors (1.5 kg of light oil) and 55 kg of oil (0.2 kg of light oil) takes place. The 15.5 kg of oil vapors with 1.5 kg of light oil are condensed out, separated from the expansion and stripping gases and fed into gas phase hydrogenation via a high-pressure pump 11 and heating device 5.

Driving style f):

This method variant according to FIG. 5 represents an expansion of the mode of operation e). The lighter fractions are separated from the sump by the flash evaporation 12, possibly by supporting stripping gas. After condensation of these lighter fractions and separation of the gases, they are divided in a subsequent distillation 13 into a low-boiling fraction, which contains virtually all of the light oil, and a heavy-boiling fraction (solvent fraction). The lower-boiling fraction is compressed to high pressure by means of compression 11, heated and added to the use of the gas phase reactor.

Example 6

Based on the numerical values of Example 5, the 15.5 kg of oil vapors from the flash evaporator 12 consist of 1.5 kg of light oil and 14 kg of medium / heavy oil. In the subsequent distillation 13, the 1.5 kg of light oil are separated off, compressed, heated and added to the use of gas phase hydrogenation. The remaining 14 kg medium / heavy oil are added to the solvent.

Claims (8)

1.) Process for coal hydrogenation with bottom phase hydrogenation and downstream gas phase hydrogenation, characterized in that the coal oils from the bottom phase hydrogenation are divided by partial condensation in an intermediate separator (4) under process pressure into a higher-boiling liquid fraction and a low-boiling vapor fraction, and the vapor fraction is passed over gas-phase reactors and converted to (partially) refined products with a lower boiling point, the liquid fraction, which contains the majority of the high-boiling fractions, is drawn off in front of the gas phase reactor and fed to the coal mash as part of the solvent. 2.) Method according to claim 1, characterized in that a hydrated solvent portion is generated, which consists either only of medium oil or from a mixture of medium oil and heavy oil with a low boiling point and more coal oils are driven in quantities than the product quantities via the gas phase reactor. 3.) Method according to claim 1, characterized in that the intermediate separator temperature corresponds approximately to the reaction temperature of the gas phase reactors (6) of 350-420 ° C. 4.) Method according to claim 1, characterized in that the intermediate separating temperature is below the reaction temperature of the gas phase reactors and intermediate separator head product is heated in gaseous form together with the gases to the reaction temperature of the gas phase reactors and fed to the gas phase reactor. 5.) Method according to claim 1, characterized in that the intermediate separator temperature is below the reaction temperature of the gas phase reactors, the light oil obtained in the intermediate separator sump product under process pressure by partial evaporation and / or stripping (with hydrogenation cycle gas or fresh hydrogen) for the most part separated from the liquid phase and used for gas phase hydrogenation and heated to reaction temperature before entering the gas phase reactors. 6.) Process according to claim 1, characterized in that the intermediate separator temperature is below the reaction temperature of the gas phase reactors, the liquid phase is expanded and separated from the low boilers in a distillation fractionation column or simple top column, the low boilers (condensate) are compressed to process pressure and heated to the reaction temperature and is added to the insert for the gas phase reactors. 7.) Method according to claim 1, characterized in that the intermediate separator temperatures are below the reaction temperature of the gas phase reactors, the liquid phase - optionally under stripping - in the flash evaporation is separated into a low-boiling vapor phase and a high-boiling bottom phase (solvent), the low-boiling vapor phase is condensed out is separated into a low-boiling fraction (further solvent fraction) in a subsequent distillation and the low-boiling fraction is compressed, heated and fed to the gas phase reactors. 8.) Method according to claim 6 and 7, characterized in that in order to generate a two-phase flow in the fractionating column or top column, in addition to the light oil, medium-boiling fractions are withdrawn and added to the use for the gas phase reactors.

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