KR20050024449A - Reactor system for several reactor units in parallel - Google Patents

Abstract

The present invention relates to a reactor system suitable for carrying out a chemical reaction, wherein the reactor system comprises at least one common reactant feed line, at least two single unit operated reactor sections, and at least one common product discharge line. The reactor system is particularly suitable for producing hydrocarbons from syngas using catalysts.

Description

Reactor system for several reactor units arranged in parallel {REACTOR SYSTEM FOR SEVERAL REACTOR UNITS IN PARALLEL}

The present invention relates to a reactor system suitable for carrying out chemical reactions, the system comprising two or more single unit operated reactor parts. More specifically, the present invention relates to the catalytic conversion of syngas to long chain hydrocarbons in a reactor system comprising a plurality of tubular fixed bed reactor portions.

In many cases, this has been and still remains of interest in the scale-up of chemical processes that lead to scale-up of chemical reactors. It is usually more efficient (economical) to use one large scale reactor than many smaller reactors that operate independently.

An important requirement for larger reactors (particularly chemical reactors) is that commercial reactors, which can be 10,000 times larger than laboratory and development room reactors, must be operated in a predictable manner. It is important for the reactor to operate within a set of safety conditions to have predictable output and quality at predictable cost. Changing the reaction scale changes the heat removal and mixing characteristics of the reaction zone, which may lead to changes in temperature distribution and concentration distribution. This results in a change in chemical properties, thus affecting the productivity, selectivity of the reactor, deactivation of the catalyst and the like. This means that it is difficult to predict the performance of large reactors based on the performance of small reactors. Thus, not only for new chemical reactions, but also for existing chemical reactions, extensive scale-up testing, reactor modeling and basic reactor research are generally required for new and / or existing chemical reactors.

It seems that natural maximums are quite often present in the scale-up process of chemical reactors. Further scaling up introduces too much uncertainty in the estimates based on the developed reactor model and / or is simply not practical.

The present invention seeks to find other ways to realize chemical reactors that are scaled up or beyond. Rather than simply expanding the size of existing reactors (including inside reactors, catalyst beds, inside mixers, cooling systems, feed lines / feed distributions, product recovery, etc.), it is desirable (in terms of diameter and / or height) Is preferably operated by combining two or more reactors of the same size into one single unit. Common feed lines, ie gas and / or liquid reactor system feed lines, are split into equal streams of reactor numbers and introduced into other equivalent reactors. The cooling and / or heating system is shared between the reactors. There will be one or more common product discharge lines. The reactor is operated as one single unit. Control of the reactant feed to the reactor system is accomplished by adjusting the feed flow (quantity, temperature, composition, pressure, etc.) in one or more common reactant feed lines. There is no individual control of each reactor section in single unit operation. In a single unit operated, the total product flow of the reactor system is controlled by adjusting the product flow in one or more common product discharge lines. In this kind of operation, there is no individual control over the product release of each reactor section. Thus, it is impossible to deactivate one or more reactors. Only all of the reactor systems can be deactivated. The conditions of one of the reactors cannot be influenced differently than in one of the other reactors. Switching one of the reactant feed lines will no longer cause the reactor to receive the reactant feedstream anymore. Closing one of the product release lines will no longer allow any reactor to release the product. Independent heating or cooling of the reactor section is not possible. Reactor control will be based on information obtained from all reactors present. Departure from one of the reactors cannot be resolved by closing the associated reactor. You will have to shut down the entire system. The feedstream is controlled by controlling a common feed gas / liquid reactant feed line.

Accordingly, the present invention relates to a reactor system suitable for carrying out a chemical reaction, wherein the system comprises at least one common reactant feed line, at least two single unit operated reactor sections, and at least one common product discharge line.

The main advantage of the reactor system is that it is easier to scale up. For example, if a reactor of any size proves to work well, scaling up further reactors is unnecessary. By combining multiple similar reactors and operating them as one single unit with a common reactant feed line and a common product discharge line, the desired scale-up will be possible. Alternatively, if some (large) scale-up is required for a particular reactor, the scale-up can be limited, for example, using three or four reactor sections operated as a single unit. Scale-up is reduced by three or four factors. Another advantage is the weight reduction of the reactor, which makes transportation / handling / lifting easier. The size of the reactor may be limited by workplace limits, passage limits, bridge limits, hoisting limits, and the like. As reactors get smaller, more companies may produce them. In addition, simultaneous production by more than one vendor is possible. Since the reactor system operates as a single unit, no additional manpower is required to operate the unit in the control room. In terms of process control, there is no difference between one large reactor and the reactor system of the present invention: The reactor system of the present invention operates in the same way as one single large reactor. In general, the heating / cooling rate for the reactor system according to the invention will be faster than for one single large reactor. Some additional maintenance may be required, and some larger planning space may be required. However, it is clear that these minor drawbacks can be offset by this benefit. In addition, since the work will be distributed to several places, the repair in the reactor may be done faster.

The reactor system described above is particularly useful for strong exothermic reactions. One example is the conversion of a mixture of carbon monoxide and hydrogen, a synthesis gas, to methanol or hydrocarbons. These conversions are highly exothermic and require extensive cooling. This requires a relatively large amount of cooling inside the reactor and quickly reaches the natural limits of scaling up the reactor. Another example is the oxidation of (low) olefins, for example catalytic conversion of ethylene to ethylene oxide in a multi-tubular fixed bed reactor. The reactor system is also suitable for biochemical reactions.

The reactor system according to the invention suitably comprises 2 to 20 single unit operated reactor parts, preferably 3 to 8 single unit operated reactor parts, more preferably 4 parts. Usually the reactor portion will comprise a rather conventional reactor, an elongated cylindrical reactor that will be a vertical reactor in use. Suitable reactor parts are known chemical reactors such as tank reactors, (c) tube reactors, tower reactors, fluidized bed reactors and slurry phase reactors. See, for example, Perry's Chemical Engineers' Handbook (MgGrawHill Book Company, 6th Edition, 4-24-4-27) and Chemical Reactor Design and Operation (Westerterp, Van Swaaij an Beenackers, John Wiley & Sons, 1984). Can be. In addition, the reactor portion may be located in one large reactor. This will solve many of the problems associated with scaling up, but some of the benefits described above will be lost. It is preferred that all reactor parts have the same size. However, this is not essential and other size reactors may be used. In this case, steps must be taken to distribute the feed in the desired proportions to the reactor. Cooling / heating systems may also require adaptation. Single unit operated reactor parts will be operated in parallel. The reactor system does not include a portion of the reactor operated in series. Each reactor portion is preferably a separate chemical reactor, suitably comprising a shell (or tube) and one or more reaction zones.

In most cases, each reactor portion will comprise one or more catalyst beds. Slurry reactors may also be used. In view of the large heat generation in synthesizing hydrocarbons from syngas, the slurry reactor may have an advantage over fixed bed reactors in terms of heat transfer. On the other hand, the main technical problems associated with slurry reactors include hydrodynamic solids treatment. In a preferred embodiment, the reactor portion comprises a multi-tubular fixed bed catalyst arrangement. The tube is filled with catalyst particles and the tube is surrounded by a coolant, in particular a mixture of water and steam. Thus, each of the reactor parts comprises an indirect heat exchange system, the heat exchange system being operated jointly. It is preferred that known thermosiphon systems be used.

Depending on the chemical reaction to be performed, gas and / or liquid feeds will be introduced into the reactor. All possible reactor flow modes may be used, namely upflow and / or downflow, cocurrent and / or counterflow. Gas and / or liquid recycle may also be used. For the synthesis of hydrocarbons, one common gas reactant feed line will introduce syngas into the reactor system. This feed is divided into as many streams as necessary for the number of reactor sections attached and fed to different reactor sections. If gas and liquid are to be introduced in the reactor section, it is preferred that the gas feed line and the liquid feed line are provided separately. In the system according to the invention it is recommended to use reactors of the same kind, preferably reactors of the same size. In the case of heterogeneous catalysis, although not essential, it is preferred that the same catalyst be used for all reactor parts.

Depending on the chemical reaction to be performed, gas and / or liquid must be released from the reactor. In some cases, a slurry, for example a mixture of catalyst and liquid, must be discharged from the reactor. When gas and liquid are to be discharged from the reactor, this may be done by a single discharge line, but the reactor system preferably includes one common gas product discharge line and one common liquid reactant discharge line. The reactor system described above may include a gas and / or liquid recycle line between the common product discharge line and the common reactant feed line.

The reactor parts in the reactor system of the present invention are suitably the same. Similar in size, catalyst, design and cooling performance. Reactor production in this case is a simple choice since it is a simple replication process. However, it is not essential that the reactor parts should be identical. Other types of catalyst may be used, as well as other sizes. Depending on the design, catalyst, etc., steps must be taken to ensure correct feed distribution to the reactor. In addition, cooling performance can vary from reactor to reactor, which leads to different conditions in the reactor portion of one reactor system. If different conditions occur in one or more reactor parts of the system according to the invention, it should be taken into account that the system is operated as one single unit, so that the conditions cannot be changed in one or more of the reactors.

The aforementioned hydrocarbon synthesis may be any suitable hydrocarbon synthesis step known to those skilled in the art, but is preferably a Fischer Tropsch reaction. Syngas to be used for hydrocarbon synthesis reactions, in particular Fischer Tropsch reactions, is obtained from hydrocarbonaceous feeds, in particular by partial oxidation, catalytic partial oxidation and / or steam / methane reforming. In a suitable embodiment a self-heating modifier is used, or a hydrocarbonaceous feed is introduced into the reforming zone followed by partial oxidation of the product, which process is used to heat the reforming zone. As the hydrocarbonaceous feed, it is appropriate that it is a mixture of methane, natural gas, side gas or C _1-4 hydrocarbons, in particular natural gas.

To control the H ₂ / CO ratio in the syngas, carbon dioxide and / or steam may be introduced into the partial oxidation process and / or the reforming process. The H ₂ / CO ratio of the synthesis gas is suitably 1.3 to 2.3, and preferably 1.6 to 2.1. If desired, additional (small) amounts of hydrogen may be additionally obtained by steam / methane reforming (preferably in combination with a water shift reaction). Additional hydrogen may also be used in other processes, for example hydrocracking.

Syngas obtained in the manner described above usually has a temperature of 900 to 1400 ° C., which has a temperature of 100 to 500 ° C., suitably a temperature of 150 to 450 ° C., preferably a temperature of 300 to 400 ° C. As it cools, it generates power, for example in the form of steam. Further cooling to a temperature of 40 to 130 ° C., preferably to 50 to 100 ° C., is carried out in a conventional heat exchanger, in particular in a tubular heat exchanger.

The purified gas mixture, which mainly contains hydrogen and carbon monoxide, is usually contacted with a suitable catalyst in the catalytic conversion stage in which liquid hydrocarbons are formed.

Catalysts used to catalyze a mixture comprising hydrogen and carbon monoxide to hydrocarbons are known in the art and are commonly referred to as Fischer-Tropsch catalysts. Catalysts used in this process often include metals belonging to Group 8 of the Periodic Table of Elements as catalytically active components. Particular catalytically active metals include ruthenium, iron, cobalt and nickel. Cobalt is the preferred catalytically active metal.

The catalytically active metal is preferably supported on a porous carrier. The porous carrier may be selected from one of the suitable refractory metal oxides or silicates or combinations thereof known in the art. Particular examples of preferred porous carriers are silica, alumina, titania, zirconia, ceria, gaul and combinations thereof, with silica, alumina and titania being particularly preferred.

The amount of catalytically active metal on the carrier is preferably 3 to 300 pbw, more preferably 10 to 80 pbw, particularly preferably 20 to 60 pbw, per 100 pbw of carrier material.

If desired, the catalyst may also comprise one or more metals or metal oxides as promoters. Suitable metal oxide promoters may be selected from groups 2A, 3B, 4B, 5B and 6B, or actinides and lanthanum series of the Periodic Table of Elements. In particular, oxides of magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, cerium, titanium, zirconium, hafnium, thorium, uranium, vanadium, chromium and manganese are very suitable promoters. In particular, particularly preferred metal oxide promoters for the catalyst used to prepare the wax for use in the present invention are manganese oxide and zirconium oxide. Suitable metal promoters may be selected from Groups 7B or 8 of the Periodic Table. Rhenium and Group 8 precious metals are particularly suitable, with platinum and palladium being particularly preferred. The amount of accelerator present in the catalyst is suitably 0.01 to 100 pbw per 100 pbw of carrier, preferably 0.1 to 40 pbw, more preferably 1 to 20 pbw. Most preferred promoters are selected from vanadium, manganese, rhenium, zirconium and platinum.

Catalytically active metals and promoters, if present, may be distributed on the carrier material by appropriate treatment, such as infiltration, kneading and extrusion. After distributing the catalytically active metal and (if appropriate) the promoter on the carrier material, the loaded carrier typically undergoes calcination. As an effect of the calcining treatment, crystal water is removed, volatile decomposition products are decomposed, and organic and inorganic compounds are converted into their respective oxides.

After firing, the final catalyst may be activated by contacting the catalyst with hydrogen or a hydrogen containing gas, generally at a temperature of about 200 to 350 ° C. Other processes for the preparation of Fischer Tropsch catalysts include kneading / mixing followed by extrusion, drying / firing and activation.

The catalytic conversion process can be carried out under conventional synthetic conditions known in the art. In general, the catalytic conversion can be carried out at a temperature of 150 to 300 ℃, preferably 180 to 260 ℃. Typical voltage forces for catalytic conversion processes are 1 to 200 bar, more preferably 10 to 70 bar in absolute pressure. In the catalytic conversion process in particular at least 75% by weight of C ₅ ⁺ , preferably at least 85% by weight of C ₅ ⁺ hydrocarbons are produced. Depending on the catalyst and conversion conditions, the amount of heavy wax (C ₂₀ ⁺ ) can be up to 60% by weight, often up to 70% by weight, even up to 85% by weight. Preferably a cobalt catalyst is used, and also a low H ₂ / CO ratio and low temperature (190-230 ° C.). In order to prevent coke generation, the H ₂ / CO ratio is preferably 0.3 or more. Fischer Tropsch reaction is carried out under the above conditions such that the SF-alpha value for the product obtained with 20 or more carbon atoms is 0.925 or more, preferably 0.935 or more, more preferably 0.945 or more, even more preferably 0.955 or more. Is especially good.

Preferably a Fischer-Tropsch catalyst is used, which results in a significant amount of paraffins, more preferably substantially unbranched paraffins. The most suitable catalyst for this purpose is a cobalt containing Fischer-Tropsch catalyst. Such catalysts are for example introduced in AU 698392 and WO 99/34917.

The Fischer Tropsch process may be a slurry FT process or a fixed bed FT process, in particular a multi-tubular fixed bed.

The present invention also relates to a process for reacting carbon monoxide with hydrogen in the presence of a catalyst at high temperature and high pressure to obtain a hydrocarbon, wherein the reactor system described above is used. The invention also relates to products made in the Fischer Tropsch process. The present invention also relates to the process for catalytic conversion of ethane to ethylene oxide, as well as the preparation of methanol and the methanol obtained.

Claims (10)

A reactor system suitable for conducting a chemical reaction, the reactor system comprising at least one common reactant feed line, at least two single unit operated reactor portions, and at least one common product discharge line. Reactor system according to claim 1, wherein the reactor system comprises 3 to 8, preferably 4 single unit operated reactor sections, each reactor section being preferably a separate and independent chemical reactor. . 3. Reactor system according to claim 1 or 2, wherein each reactor portion comprises at least one catalyst bed and preferably comprises a multi-tubular fixed bed catalyst arrangement. 4. Reactor system according to any one of the preceding claims, wherein each reactor portion comprises an indirect heat exchange system, the heat exchange system being operated jointly, preferably comprising a thermosiphon system. 5. The reactor system of claim 1, wherein the reactor system comprises one common gas reactant feed line. 6. 6. The reactor system of claim 1, wherein the reactor system comprises one common gaseous product discharge line. 7. 7. Reactor system according to any one of the preceding claims, characterized in that the reactor system comprises one common liquid reactant discharge line or one common liquid product discharge line. 8. The reactor system of any of claims 1 to 7, wherein the reactor portion comprises a cobalt catalyst for use in Fischer Tropsch synthesis. 9. Reactor system according to any one of the preceding claims, wherein each reactor portion is contained in a separate reactor. Process for obtaining a hydrocarbon, characterized in that the carbon monoxide and hydrogen are reacted in the presence of a catalyst at a high temperature and a high pressure using the reactor system according to any one of claims 1 to 9.