EP0318903B1 - Process for the hydrogenation of liquid carbon-containing feedstocks - Google Patents

Description

The invention relates to a process for the hydrogenation of liquid carbonaceous feedstocks such as heavy oils, oil residues, top or vacuum residues, syncrude from oil shale, tar sands, tars and pitches from hard coal or lignite, with hydrogen-containing gases as hydrogenation gas under the conditions of a phase-phase hydrogenation at elevated temperature and increased pressure in the presence of an additive or a catalyst with a downstream hot separator stage with separate heating of a feed stream formed from the feed materials and a partial stream of the hydrogenation gas and a second partial stream of the hydrogenation gas. The feedstocks are liquid either at normal temperature or at elevated temperatures.

Temperatures in the bottom phase reactor of approximately 400 to 500 ° C. are typical, and the process pressure can be selected between 150 to 1200 bar.

The invention is based on a method as specified above, in which heavy oil is fed as a feed product to a preheater and in which a partial flow of the total amount of hydrogenation gas required in a gas heat exchanger through which the hot separator head product flows precedes the preheated mixture of heavy oil, possibly additive and hydrogenation gas Entry into the bottom phase reactor is added (see. DE 35 23 709 A1).

The publication DE 35 05 553 A1 relates to a process for pretreating the feed products for the coal hydrogenation and is otherwise analogous to the above Process according to DE 35 23 709 A1.

In the known processes of the type mentioned at the outset, the feed products are heated to the temperature required for entry into the reaction system of the bottom phase hydrogenation by means of a heating furnace provided in the feed product stream. This heating furnace is one of the most critical components of any sump phase hydrogenation system. This is due in particular to the operating conditions, which are characterized by high hydrogen partial pressure in the pipe, high pipe wall temperatures and high total pressure, and which set operational limits beyond the material that can be used.

According to "The catalytic pressure hydrogenation of coal, tars and mineral oils", Springer-Verlag, Berlin / Göttingen / Heidelberg 1950, page 232, the reaction participants were basically heated in heat exchangers and in the tip preheater. "Bundle" regenerators were generally used as the heat exchanger, and hairpin-shaped pressure tubes of 90 or 110 mm in diameter and approximately 30,000 mm in total length were used for the tip preheating by means of the externally heated heating furnace, the product feed stream being conducted within the tubes which were heated by means of roller gas heating .

The process conditions, which are characterized by a multi-phase flow of gases and vapors, liquid and solid in the tube, result in considerable uncertainties in the design of the heating furnace, both when calculating the pressure loss and the heat transfer.

The use of such tip preheaters is associated with procedural disadvantages which result from high pressure loss in the preheater, poor heat transfer and undefined conditions due to the three-phase system present in the tube.

Operational disadvantages result from the tendency to incrust the inside of the furnace tubes and from coking reactions of the product in the tubes. Associated with this are a limitation of the runtime of the hydrogenation plant as a whole and also safety-related problems such as the occurrence of so-called "hot spots" which can lead to pipe tears.

Accordingly, the task of the invention is to improve the overall heat management of the process by recovering the heat of reaction. In the document DE 26 51 253 A1 it is stated that in a procedure similar to that at the beginning The specified process of the preheater heated by external heat can be considerably reduced or even completely omitted under certain circumstances, but it is intended that a distillate fraction to be returned to the feed product is reheated in a heat exchanger heated by external heat. The additional heating of the distillates brings the advantage of the significantly lower tendency to coke compared to the heating of the coal pulp in a preheater.

A similar procedure, namely heating a coal-oil mixture in the swell range from 290 to 340 ° C by means of direct heat exchange by adding part of the hot liquid-solid hydrogenation residue and the entire condensate of the gas-vaporous hydrogenation products obtained at 390 to 440 ° C can also be found in the document EP 0 058 327 A3.

According to the invention, the above object is achieved in the method of the type mentioned above in that the hot separator head product emits its heat to the feed streams mentioned in indirect heat exchange and that by further heating the separately conducted part of the hydrogenation gas in a hydrogenation gas heater and then combining it with the indirect heat exchange heated feed stream the necessary inlet temperature is reached in the bottom phase reactor.

The specified method is suitable for hydrating liquid carbon-containing feedstocks such as heavy oils, oil residues (top and vacuum residues), syncrude from e.g. B. oil shale, tar sands, heavy oils, tars and pitches from hard coal or lignite u. to process.

In addition to the heavy materials intended as starting materials, the present process is also advantageous Oils or heavy mineral oil residues Mixtures of finely ground coal and the feedstocks provided according to the invention are supplied as so-called foreign oils ("co-processing"). Such a procedure has the advantage that the recycle streams required for the mashing of the finely ground coal are largely or completely eliminated. Weight ratios of coal and foreign oil of 1 to 5 to 4 to 5 are preferred. All types of coal which can be economically hydrogenated, for example, are suitable as the coal to be used. B. typical gas flame coals of the Ruhr area.

It has been found that the process can be designed by recovering the thermal energy of the reaction products as far as possible so that a hydrogenation gas heater is sufficient for a separate partial flow of the hydrogenation gas in order to apply the start-up temperature of the hydrogenation reaction required when starting up into the hydrogenation reactor in the bottom phase and to compensate for heat losses . This result could only be achieved by optimizing the process control of the reaction products and the feed products in countercurrent, and it is surprising that the thermal energy to be supplied can be introduced into the process via a partial stream of the hydrogenation gas without external heating of the liquid or solid-liquid feed products.

Circulation furnaces come as hydrogenation gas heaters, hereinafter also referred to as hydrogenation gas furnaces, but preferably also radiation ovens, in which heating to a temperature of 300 to 650 ° C., preferably 490 to 550 ° C. takes place.

In a further embodiment of the proposed method, the feed stream (3) through three heat exchangers (18, 19, 20) and the separately heated hydrogen gas stream (5) before entering the hydrogenation gas furnace (24) through three heat exchangers (21, 22, 23) in countercurrent led to the hot separator head product.

When dividing the total amount of hydrogenation gas between the two partial streams, it is also possible to proceed in such a way that the circulating hydrogenation gas is provided for the feed stream fresh hydrogen as feed and for the second partial stream of the hydrogenation gas.

In this case, stream (9) in the downstream direction comes into heat exchange relationship with the feed stream (3) in the heat exchanger (20) and the partial stream of the hydrogenation gas (5) in the heat exchanger (23) and passes through a reactor (27) for hydrogenation in the gas phase at a fixed bed contact . The product stream refined in reactor (27) passes as stream (10) heat exchanger (19) and heat exchanger (22) in heat exchange relationship with stream (3) or stream (5) and an intermediate separator (28) with separation of a hot oil fraction (11). The residual stream (12) drawn off by the separator (28) gives the rest of the heat exchangers (18) and (21) for heating the Use products utilizable heat to electricity (3) and electricity (5) and is fed to a cold separator (29), in which a separation of waste water and exhaust gas as well as the recovery of a cold oil fraction (13) and recycling of the cycle hydrogenation gas as stream (15) via compressor (30) done in the process.

For temperature control in the bottom phase reactor (25) and in the hot separator (26), part of the circulating gas stream (16) is advantageously kept available as a quench gas stream and fed in if necessary.

Following the cold separator (29), a gas scrubber can be provided in the usual way for working up the circulating hydrogen gas fraction. Such a work-up ensures a sufficient hydrogen partial pressure in the hydrogenation gas system by removing the C₁ to C₄ components which are soluble in the gas scrubbing by means of washing liquid.

The separate partial stream from the total amount of hydrogenation gas to be used can make up 20 to 95, preferably 40 to 80% of the total amount of hydrogenation gas required.

The present method is explained in more detail below with the aid of the diagram of the drawing with the specified reference numerals.

The stream of feedstocks (1) consisting of a suspension with the additive or catalyst is mixed with a partial stream of the hydrogenation gas (2) composed of cycle hydrogenation gas, stream (15), via compressor (30) while feeding in fresh hydrogen, stream (17). combined to form stream (3) and preheated to the conditions of stream (4) by means of indirect heat exchange in the apparatuses (18), (19) and (20).

The separate hydrogenation gas stream (5) is also preheated in indirect heat exchange in the apparatuses (21), (22) and (23) and heated to the necessary temperature in hydrogenation gas heater (24), so that in the mixture of material stream (6) with the Material flow (4) the required reactor inlet temperature in reactor (25) for stream (7) is reached.

The desired products are obtained in the reactor (25) or in a cascade of reactors connected in series, which are separated in the hot separator (26) into a residue stream (8) and into a top stream (9).

The top stream (9) is used for preheating in countercurrent to the feed stream (3) and hydrogenation gas stream (5) in the aforementioned apparatuses (18), (19), (20), (21), (22) and (23). The circuit shown in the figure provides an integrated gas phase reactor (27) for the purpose of refining and further removal, in particular of the O, S and N-containing heteroatom components. Gas phase reactor (27) is advantageously connected between apparatus (23) and apparatus (19).

The products condensed in the heat exchangers due to the removal of heat are collected in intermediate separators (28) and in cold separators (29). The condensates are discharged from the high-pressure circuit as hot oil (11) and cold oil (13). After the hot oil has been drawn off, water can be injected in order to avoid the salinization of the downstream heat exchangers.

The water of reaction formed in the hydrogenation process is optionally separated together with the injection water in the cold separator (29) and discharged as stream (14) from the high-pressure circuit. It contains u. a. the heteroatom compounds removed by refining in the form of the simple hydrogen compounds H₂S and in particular NH₃ dissolved in the waste water.

Depending on the design of the heat exchanger or the arrangement of the intermediate separator, the temperature in the intermediate separator can be freely selected within a certain range.

The residual gas going overhead in the cold separator (29) is returned with a circuit compressor (30), if necessary after a certain proportion has been discharged. The return gas is cold gas as a stream for temperature control of the reactors and the hot separator (16) taken. The fresh hydrogen required for the reaction is added as stream (17). Provision can also be made to add stream (2) as a fresh hydrogen stream.

Claims (7)

1. A process for the hydrogenation of liquid carbon containing batch materials such as heavy oils, oil residues, top or vacuum residues, syncrude from oil slate, tar sands, tars and pitches of pit coal or lignite with hydrogen containing gases as the hydrogenation gas in the conditions of a sump phase hydrogenation at a temperature of 400 to 500°C and a pressure of 150 to 1200 bar, possibly in the presence of an additive or a catalyst with a connected hot separator stage, with the separate heating of a batch flow formed from the batch materials and a component flow of the hydrogenation gas and of a second component flow of the hydrogenation gas, no externally heated batch product furnace being used for heating the batch flow of the carbon-containing batch materials, the hot separator head product giving off its thermal energy to said batch flows in indirect heat exchange, characterized in that the necessary temperature of entry into the sump phase reactor is achieved by further heating of the second component flow of the hydrogenation gas in a hydrogenation gas heater, followed by combination with the batch flow heated by indirect heat exchange.
2. A process according to claim 1, characterized in that the batch materials are used mixed with finely ground coal.
3. A process according to claim 1, characterized in that heating is performed in the hydrogenation gas heater to a temperature of 300 to 650°C, preferably 490 to 550°C.
4. A process according to one of claims 1 to 3, characterized in that the batch flow (2) is passed in contraflow to the hot separator head product flow (9) through heat exchangers (18, 19, 20), while the separately heated second component flow of the hydrogenation gas (5) is passed through heat exchangers (21, 22, 23) prior to entry into the hydrogenation gas furnace (20), the flow (9) is subjected in the downflow direction successively to heat exchange with the batch flow (3) in a heat exchanger (20) and with the hydrogenation gas flow (5) in a heat exchanger (23) and passes through a reactor (27) for hydrogenation in the gaseous phase on a solid bed contact and then passes as a flow (10) to a heat exchanger (19) and a heat exchanger (22) for heat exchange with flow (3) and flow (5) respectively and also through an intermediate separator (28) for the separation of a hot oil fraction (11), and then the flow (12) gives off a residual heat in a heat exchanger (18) and a heat exchanger (21) to flow (3) and flow (5) respectively and is fed to a cold separator (29), where the waste water and waste gas are separated and a cold oil fraction is recovered and a proportion of the circuit hydrogenation gas is returned.
5. A process according to one of claims 1 to 4, characterized in that a proportion of the circuit hydrogenation gas is fed as a quenching gas flow (16) for temperature regulation to the sump phase reactor (25), the hot separator (26) and the gaseous phase reactor (27).
6. A process according to one of claims 1 to 5, characterized in that downstream of the cold separator (29) the gas is scrubbed for the processing of the proportion of circuit hydrogenation gas.
7. A process according to one of claims 1 to 6, characterized in that the separately heated component flow (5) amounts to 20 to 95, preferably 40 to 80% of the total quantity of hydrogenation gas to be used.

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