DE2517869C2 - - Google Patents

Description

The invention relates to a method for decommissioning of a catalyst filled reactor for the catalytic Hydrogenation of a liquid or gaseous feed using Passing the feed over the catalyst in the presence of added hydrogen. Such hydrogenation is common carried out at temperatures above 300 ° C. In many In some cases, the feed contains sulfur-containing compounds which are formed during hydrogenation.

The aforementioned catalytic hydrogenation is often used in refining  of mineral oil, but also in other areas of application carried out.

An example of using a liquid feed for catalytic Hydrogenation is the catalytic desulfurization of certain Petroleum fractions, such as distillate or residue fractions, In this process, the feed is combined with hydrogen through one with the desulfurization catalyst filled reactor at a temperature at which the Infeed not yet or only slightly by splitting or Isomerizing is converted. Those in the liquid feed Sulfur compounds contained are formed with the formation of hydrogen sulfide hydrated. One receives as products on the one hand the desulfurized feed and on the other hand a hydrogen sulfide and unreacted hydrogen-containing gas, which from be withdrawn from the reactor. The latter gas can e.g. B. in a Claus system described below can be transferred.

An example using the aforementioned catalytic hydrogenation a gaseous feed represents the catalytic reduction of a Claus exhaust gas from a Claus plant for production of elemental sulfur by reacting sulfur dioxide and hydrogen sulfide. The Claus exhaust gas contains another certain percentage of unreacted sulfur compounds, which usually have to be removed, by reduction all sulfur compounds with hydrogen to hydrogen sulfide can be achieved and then the hydrogen sulfide formed separated from the Claus exhaust gas (e.g. by absorption) and to the Claus system  is returned. Claus systems are not only found in Refineries, but also - to process the separated from natural gas Hydrogen sulfide - in natural gas fields.

An almost inevitable in catalytic hydrogenation The appearance of sulfur compounds is the deposition of carbon on the catalyst. That carbon often comes from either the hydrocarbons in the feed (e.g. in the desulfurization of petroleum fractions) or from to Heating admixed combustion gases (e.g. during the reduction from Claus exhaust gas). When desulfurizing liquid products are also z. B. tar-like products deposited on the catalyst.

Solid particles such as slag, silicon dioxide, metal salts and Iron particles are usually found at the beginning of the catalyst bed deposited while the sulfides and carbon all over Length of the catalyst bed are available.

When this catalyst is regenerated, the carbon and the tar-like products burned down, and this is used to maintain an acceptable temperature in the reactor in any case an adequate one, with large amounts of steam or nitrogen mixed amount of oxygen added. In practice they are common Temperatures of 300 to 500 ° C applied because the carbon at lower temperatures is not burned. With this regeneration the sulfides are simultaneously with the carbon and  oxidized the tar, due to the desired limited heat generation this oxidation can only be carried out very carefully may. Accordingly, regeneration usually requires one very long time that with large reactors up to a few days can be.

In some cases, e.g. B. in the desulfurization of petroleum residue fractions, the reactor contains very large amounts of catalyst from Z. B. 500 tons. In this case, the amount of catalyst on which no solid particles are deposited, absolutely very large compared to the amount of catalyst on which such Particles have been deposited. This leads to the disadvantage that burning the carbon and tar-like products the metal sulfides of the entire amount of catalyst are oxidized.

If the reactor has to be opened for certain reasons, as expected, it is not sufficient to cool the reactor and flush with an inert gas. It was found that when opening of the reactor after flushing with an inert gas of lower Temperature the catalyst in the air begins to glow and, if the feed contained sulfur compounds, sulfur dioxide releases. Under these conditions, the catalyst shows accordingly pyrophoric properties on and the implementation working on or in the reactor is therefore impossible or dangerous.

So far, this problem has been solved by completely regenerating the  Dissolved catalyst before opening the reactor. This solution is however expensive and time consuming. The aim of the present invention it is therefore to find another solution.

In practice it happens e.g. B. before that a reactor be opened must, although the activity of the catalyst has not decreased so far has that regeneration is required. Another one The aim of the present invention is therefore a method to provide, in which in these cases no regeneration is required, and in which the reactor can still be opened can.

It was found that the pyrophoric properties of the catalyst by means of a fully controlled oxidation in which the temperature is continuously below using suitable measures 300 ° C is kept, can be completely eliminated.

Surprisingly, this "passivation" of the catalyst can without simultaneous oxidation of the active sulfides, such as cobalt, Perform nickel, molybdenum and / or tungsten sulfide. Accordingly, the passivation is much less time consuming than required for traditional regeneration treatments in which the active sulfides are oxidized.

It has also been found that the carbon and tar-like Products passivated hardly or not at all during passivation will. There are certain signs that the pyrophoric  Properties of the catalyst on the presence of fine distributed iron and / or iron sulfide is oxidized at low temperatures.

The registration is based on the task of a procedure for decommissioning of a catalyst filled reactor for the catalytic Hydrogenation of a liquid or gaseous feed by passing the feed over the catalyst, which contains cobalt sulfide and / or nickel sulfide together with molybdenum sulfide and / or tungsten sulfide on a carrier material consisting at least in large part of silicon dioxide and / or aluminum oxide, in the presence of added hydrogen.

The object is achieved by a method having the characterizing features of claim 1.

In the dependent claims 2-8 training of the Method according to claim 1 specified.  

Since the catalytic hydrogenation is generally at temperatures the temperature is above 300 ° C in the reactor in the reactor in most cases by cooling to below 300 ° C can be reduced.

If the feeding of the feed before lowering the temperature interrupted in the reactor, it is possible the temperature by means of the supplied hydrogen or by means of the purge gas belittling. Especially when a heavy feed, like a petroleum residue fraction, it is hydrogenated advisable to feed the feed at high temperatures interrupt to prevent the feed in the reactor from solidifying.

If a liquid feed has been processed, it is possible immediately before decommissioning the reactor to another, lighter feed, such as heavy gasoline or gas oil, transition and the temperature in the reactor by feeding to reduce this slight infeed. This is a preferred Embodiment. In this way, if necessary remaining residues of the residue product removed, the may have deposited on the catalyst particles. A liquid also leads to a faster cooling of the Catalyst as a gas.

It is also possible to adjust the temperature in the reactor during or partly during the interruption of the feeding of the feed decrease, the interruption of the feed gradually  takes place and accordingly takes a long time. The simultaneous cooling and interrupting the feed will e.g. B. performed when hydrogen is fed to the reactor and then the supply of the feed is gradually interrupted or if a colder feed is subsequently initiated becomes.

The supply of the feed can also be interrupted after cooling be, the cooling at least partially by means of the feeding can be brought about. In this case, of course only a small part of the feed hydrogenated so that it may be advisable during cooling under certain conditions can use a feed that is not hydrogenated got to.

Preferably the temperature in the reactor is by means of a hydrocarbon oil and especially with heavy gasoline or gas oil reduced.

Finally, the aim of all the measures according to the invention is one a temperature below 300 ° C and neither feed still have hydrogen-containing reactor available. The Removal of the hydrogen and the feed is done by flushing of the reactor with an inert gas before, during and after cooling reached. As an inert gas z. B. carbon dioxide and preferably Nitrogen used.

After practically complete removal of the hydrocarbon  and hydrogen residues from the reactor except for z. B. less than 1 volume percent sufficient purging with inert gas makes a low one Amount of air or oxygen added to the purge gas. Initially In any case, only as much air or oxygen as Purge gas are added so that its oxygen content is less than 1 volume percent and the oxygen content of the purge gas must also be low enough to ensure that the temperature in the reactor does not exceed 300 ° C. Passing through of the purge gas having a low oxygen content through the reactor now continues. One of observed oxygen consumption accompanied by a rise in temperature, which, however, is limited to a maximum of 300 ° C in all cases got to.

The oxygen content of the purge gas is preferably regulated in such a way that the temperature of the purge gas withdrawn from the reactor remains below 150 ° C. This temperature of the used Purge gas is a reliable indicator of temperature in the reactor and is easy to determine.

According to one embodiment of the method according to the invention the oxygen-containing purge gas after passing through the reactor cooled, again mixed with oxygen and then returned to the reactor. It is readily apparent that this embodiment is opposite saving only the use of fresh purge gas represents.

If the purge gas contains less than 1 volume percent oxygen  the temperature rise in the reactor begins to decrease the oxygen content of the purge gas gradually to above 1 percent by volume elevated. It must continue to be ensured continuously be that the temperature in the reactor does not reach values above 300 ° C rises.

Also during this period, in which the oxygen content of the Purge gas is above 1 volume percent, the purge gas is preferred returned and the oxygen (s) consumed or Air replaced. In this period the temperature is rising because of the advanced controlled oxidation generally lower. The oxygen consumption is also included less.

In one embodiment of the invention, the oxygen content the purge gas is increased at a predetermined rate, however, the increase is always postponed as long as the Temperature in the reactor exceeds a predetermined value. Thereby can passivation in a relatively simple manner to be controlled.

The oxygen content of the returned purge gas is preferred by adding a higher temperature rise in the Reactor corresponding lower amount of air and vice versa replaced. This completely controls the oxidation and the temperature rise limited to a relatively constant value, because in the event of excessive temperature rise, the cause of this increase, namely an excessively high oxygen content, is eliminated and in the case of too low a temperature rise, the insufficient one  Oxygen supply is increased. An excessive rise in temperature has the disadvantage that components in the reactor be oxidized, which need not be oxidized, and one too low Temperature rise means that the controlled oxidation runs slower than absolutely necessary.

According to the oxygen partial pressure in the purge gas finally to at least 0.2 kg / cm² and in particular to at least 0.8 kg / cm² raised and this pressure for some time before opening the reactor maintained. The reactor will preferably continue to be some Flushed time, with practically no further heat development observed becomes. Depending on the circumstances, this takes place at an oxygen partial pressure of at least 0.2 kg / cm² or less. The latter two measures guarantee the best possible Security level.

Under certain conditions, there is a risk of a local The coal burns off, causing an uncontrolled rise in temperature in the zone with the spent coal and also to spread the undesirable temperature rise to others Set the catalyst can result. This phenomenon occurs e.g. B. in conditions such as the presence of large amounts of pyrophoric compounds in the reactor or in cases where in the catalytic hydrogenation and / or in the cooling of the reactor not all places of the catalyst from the coolant (like Heavy gasoline or gas oil) have been wetted and therefore dry Zones exist. The latter phenomenon can in particular  occur in cases where the catalyst to a significant extent is contaminated, resulting in poor distribution of the Coolant leads over the catalyst.

At every risk of an uncontrolled temperature increase in the reactor To avoid, the reactor is preferably with a hydrocarbon oil purged together with the purge gas. Particularly suitable a petroleum-based hydrocarbon oil such as heavy fuel or preferably gas oil. The feed rate of the Hydrocarbon oil to the reactor can fluctuate considerably. Preferably at least 5 percent of that during the catalytic Hydrogenation fed to the reactor into the reactor initiated. In particular, at least 10 percent of the aforementioned amount of hydrocarbon oil fed into the reactor. The circulation speed of the gas oil is during the Purge gas circulation approximately to the amount of the normal operation of the Reactor feed to be catalytically increased.

For complete wetting of the catalyst, it is advantageous the reactor containing the catalyst completely or practically completely fill with a hydrocarbon oil (especially with a gas oil) before using the oxygen-containing purge gas feeds into the reactor. It is particularly advantageous after the reactor is filled with the hydrocarbon oil from below the hydrogen is almost completely removed from the reactor has been. After the subsequent removal of the hydrocarbon oil from the reactor with the introduction of the purge gas began. This purge gas can be used immediately or after some time  A circulating hydrocarbon oil can be added.

It is desirable that the reactor be relatively low low temperature is opened. The temperature when opening is preferably at most 60 ° C. This temperature can achieved by rinsing, but it is also possible cool the reactor further after rinsing. This ensures that the highest possible conversion of z. B. iron sulfide as long as possible at relatively high temperatures is carried out. In the latter case there is pressure cooling e.g. B. preferred with air, since the reactor itself is very slow cools down.

The inventive method can, for. B. in a reactor Catalytic desulfurization of a liquid hydrocarbon feed be applied. Examples of such desulfurization processes are the desulfurization of light petroleum distillate fractions and the desulfurization of petroleum residue fractions.

However, the method according to the invention can also be used in other methods, as in the catalytic reduction of sulfur compounds in a gaseous feed to hydrogen sulfide, be applied.

In the latter case, the feed z. B. from the exhaust gas from a Claus plant for the production of elemental sulfur consist of gases containing sulfur compounds.  

In the aforementioned desulfurization processes, the catalyst contains particularly expediently cobalt sulfide and / or nickel sulfide together with molybdenum sulfide and / or tungsten sulfide a carrier material that is at least largely made of silicon dioxide and / or aluminum oxide. It was found, that such catalysts have pyrophoric properties. It however, all other types of catalysts that have pyrophoric properties, by means of the invention Procedure are treated.

The invention provides an improvement to the process for continuous catalytic hydrogenation of one or more sulfur compounds in a liquid or gaseous feed with the formation of hydrogen sulfide, at which the feed for hydrogenation through a reactor filled with a catalyst in the presence of added hydrogen at temperatures above 200 ° C is passed. The improvement is that at the time a predetermined pressure drop across the reactor as As a result of the contamination of the catalyst layer at the end of the feed the reactor the reactor using one or more the aforementioned embodiment (s) of the method according to the invention is decommissioned, after which the contaminated catalyst layer replaced and the reactor started again becomes. An advantage of this method is that it does not know how so far, the entire amount of catalyst replaced or regenerated must become. The method according to the invention has in particular: for the catalytic desulfurization of petroleum residue fractions  reactors used have special advantages because in these cases very large amounts of catalyst are used. In practice total amounts of catalyst per reactor are currently approximately 750 m³ used, where the steam-air regeneration is common leads to difficulties because per ton of catalyst ever Approximately 0.5 to 1.0 tons of steam required for regeneration per hour are what the refinery in many cases represents very high peak loads. In this case, that The inventive method has the advantage that the purge gas is recycled can be.

The pressure drop in particular increases with liquid feeds over a reactor for catalytic hydrogenation often because of the Deposition of slag on the first catalyst layer. This deposit often contains high levels of metals such as metallic iron or metal salts coming from the plant or come from the feed. The deposition of slag means but not that the catalyst has been deactivated. At The desulphurization of liquid feeds becomes the catalyst in a reactor for the desulfurization of petroleum residue fractions e.g. B. blocked so far after about half a year, that the top catalyst layer must be replaced while at blocking the desulfurization of petroleum distillate fractions only occurs after a period of approximately 3 months to 2 years. In addition, an excessively high pressure drop occurs repeatedly before the deactivation of the catalyst.  

An advantage over the passivation method according to the invention over the conventional regeneration of catalysts in that the catalyst then does not sulfide again must become. In the case of catalysts containing molybdenum the conventional regeneration also has the disadvantage that them at significantly higher temperatures under oxidative conditions must be carried out, which leads to the risk of sublimation leads from Molydäntrioxyd. It is also noted that burning off in general during conventional regeneration Temperatures of 370 to 470 ° C is carried out. Also goes the aforementioned embodiment of the method according to the invention on the observation that the catalytic activity by the burning of the carbon is not significantly increased, provided the carbon is present in the usual percentages and that it is pretty quick after restarting the reactor to re-deposit carbon on the reactor comes without high activity of the catalyst Extent is affected. This is why it burns down of carbon is not essential for regeneration.

The aforementioned improvement of the process for continuous Catalytic hydrogenation is preferably done in this way performed that when the reactor is shut down Carbon dioxide content in the purge gas leaving the reactor during the time is controlled during which to the reactor fed purge gas oxygen is added and the amount of oxygen  in the purge gas is reduced or completely oxygen-free Purge gas used as long as the amount of carbon dioxide exceeds a predetermined value. As soon as the carbon dioxide content in the purge gas drawn off from the reactor becomes too high this excessive carbon dioxide content as such is an indication that too much carbon burned off becomes. The carbon dioxide content is preferably at values below 0.04 volume percent held.

The examples illustrate the invention.

Example 1

The drawing shows a diagrammatic representation of the oxygen content of the purge gas in the course of the present Example of passivation carried out.

In a semi-technical plant for catalytic desulfurization petroleum residue fractions become 1470 tons of petroleum residue fraction desulfurized. The system consists of one with a catalyst filled desulfurization reactor. The catalyst contains 3.2% by weight of cobalt and 9.2% by weight of molybdenum a carrier material consisting mainly of aluminum oxide, which was previously sulfided are. The reactor contains the catalyst as a fixed bed and the treating residue fraction is fed into the top of the reactor and withdrawn from the bottom of the reactor. Flows through hydrogen the reactor in parallel flow for feeding.

Immediately before the passivation according to the invention, the  Catalyst 3.2 weight percent cobalt and 9.2 weight percent Molybdenum. The catalyst at the top of the reactor contains 10.2 percent by weight Vanadium, 4.4 weight percent nickel, 0.7 weight percent Sodium and 0.40 weight percent iron. The catalyst at the bottom of the reactor contains 0.8 weight percent vanadium, 0.3 weight percent nickel, 0.2 weight percent sodium and 0.04 Weight percent iron.

The reactor is now passivated, starting with the Residue fraction passes on to gas oil as feed and thereby continuously supplies a hydrogen-rich gas mixture. The reactor is cooled in the course of 10 hours. While cooling down the temperature decrease is continuously less than 40 ° C per hour. The temperature of the gas fed to the reactor is 15 ° C, and after cooling a gas with a temperature also withdrawn from the reactor at 15 ° C. The gas oil feed is now interrupted and the reactor with a hydrogen-rich gas purged for about 6 hours. The hydrogen is then replaced by nitrogen and the reactor until a hydrogen concentration below 1 volume percent is reached purged with nitrogen. The nitrogen pressure will then increased to 6 kg / cm² and the nitrogen by means of a compressor returned.

Then air is injected into the returned nitrogen stream. The oxygen content of the purge gas fed into the reactor is measured continuously and is shown in the figure. In this figure, the time "t" is plotted in hours on the abscissa against the oxygen content in volume percent on the ordinate. The curve shows that oxygen is injected discontinuously into the purge gas. However, the duration of the oxygen injection increases continuously.

In the table are for the same period of time as in the figure, the pressure used in the process (increased pressure), the Duration of the individual air injection processes and the carbon dioxide content specified in the purge gas leaving the reactor.

table

The figure shows that passivation consumes oxygen becomes. The passivation process is also continuous Determination of the carbon dioxide content of the reactor controlled purge gas checked. It was found that between 2.5 and 4 hours after the start of rinsing a big one Oxygen consumption occurs. It was also observed that the carbon dioxide content of the purge gas when air is injected into the purge gas because of the carbon dioxide content in the air.

The temperature of the purge gas when leaving the reactor is continuously 15 ° C. The passivation process according to the above Accordingly, the example is carried out very carefully.

After rinsing for 7.5 hours using the oxygen-containing nitrogen stream with increasing increase in oxygen content the passivation process after 30 minutes of compressed air circulation completed by the reactor and then opened the reactor. The catalyst shows no pyrophoric at this time Properties more on.

A subsequent analysis of the catalyst reveals that depending on the point in the reactor from which the catalyst was removed the catalyst is about 7 to 15 weight percent carbon and contains about 7 to 8 weight percent sulfur.

Example 2

In the semi-technical plant described in Example 1  Desulphurized 106,000 tons of petroleum residue fraction. The catalyst gets pretty dirty and contains a big one Amount of pyrophoric material.

The reactor is cooled to 40 ° C, hydrogen through nitrogen replaced, the nitrogen pressure increased to 6 kg / cm², oxygen to Purge gas added and the oxygen content of the purge gas gradually, as described in Example 1, increased.

The temperature in the reactor is measured at some points and the carbon dioxide content of the exhaust gas is determined from time to time. After about 20 hours (with an oxygen concentration in the purge gas 18% by volume) the carbon dioxide concentration increases in the exhaust gas drastically (from 0.03 to 0.3 volume percent) and A sharp rise in temperature is measured in the end part of the reactor (from originally 40 to 50 ° C to 100 ° C). Subsequently the reactor is opened and the catalyst out of the reactor away. The catalyst from the end part of the reactor is hot and releases gas oil vapor and sulfur dioxide. Although the catalyst has no pyrophoric properties, the danger is evident that a further temperature rise to an uncontrolled Burning the coal on the catalyst leads. That danger is avoided when decommissioning the reactor is carried out according to Example 3.

Example 3

One for catalytic desulfurization approximately the same as in Example 2 described amount of the same petroleum residue fraction catalyst used  is cooled and the amount of hydrogen in the reactor Nitrogen as a purge gas, as in Example 2, to a volume percent reduced. The reactor is evacuated and gas oil from pumped down into the reactor until all of its catalyst content is completely immersed in gas oil. Then the gas oil withdrawn from the reactor and nitrogen at a pressure of 6 kg / cm² fed into the reactor. Be through the reactor Nitrogen and at the same time an amount of gas oil of 10 percent of amount of hydrocarbon to be desulfurized during normal operation in the reactor headed. Then becomes A volume percentage of oxygen was added to the purge gas. After one hour the circulation of the nitrogen / oxygen flow is ended and air fed into the reactor at a pressure of 6 kg / cm². The gas oil circulation gradually increases to the value of normal operation the amount of hydrocarbon desulfurized increased. After three hours of circulation of air and gas oil, in which none Temperature rise or unwanted oxidation of coal occurs, the reactor is opened. The catalyst has no pyrophoric Properties on.

Claims (8)

1. Process for decommissioning a reactor filled with catalyst for the catalytic hydrogenation of a liquid or gaseous feed by passing the feed over a catalyst, the cobalt sulfide and / or nickel sulfide (together with molybdenum sulfide) and / or tungsten sulfide on at least a large part of silicon dioxide and / or aluminum oxide, in the presence of added hydrogen, characterized in that the catalyst in the reactor is passivated by the following process steps:

• (a) the temperature in the reactor, if it is more than 300 ° C, is reduced to below 300 ° C and such a low temperature is maintained until the reactor is opened;
• (b) the feeding of the feed is interrupted and the added hydrogen is replaced by an inert gas during or after the lowering of the temperature according to (a);
• (c) the reactor is flushed for a time with a hydrocarbon oil and with a flushing gas consisting of the inert gas mentioned under (b);
• (d) then an amount of oxygen-containing gas is added to the purge gas such that the initial oxygen content of the purge gas is at most 1 volume percent;
• (e) the oxygen content of the purge gas is increased and the purge gas supply is continued until there is practically no heat development in the reactor;
• (f) the oxygen partial pressure of the purge gas is increased to at least 0.2 kg / cm²;
• (g) the reactor is opened.

2. The method according to claim 1, characterized in that the temperature in the reactor in process step (a) by means of a Hydrocarbon oil is reduced. 3. The method according to claim 1 and 2, characterized in that the oxygen content in the purge gas is adjusted so that the temperature of the purge gas drawn from the reactor below 150 ° C is maintained. 4. The method according to claim 1 to 3, characterized in that the oxygen partial pressure in the purge gas at the end before Opening the reactor kept at least 0.8 kg / cm² for some time becomes. 5. The method according to claim 1 to 4, characterized in that the reactor containing the catalyst before being introduced of the oxygen-containing purge gas in the reactor completely or practically completely filled with a hydrocarbon oil becomes.   6. The method according to claim 1 to 5, characterized in that that during the period in which that was fed into the reactor Purge gas has an oxygen content, the carbon dioxide content of the purge gas drawn off from the reactor and that the amount of oxygen added to the purge gas is reduced or is brought to zero as long as the carbon dioxide content of the withdrawn purge gas exceeds a predetermined value. 7. The method according to claim 6, characterized in that the carbon dioxide content of the purge gas withdrawn from the reactor is kept below 0.04 percent by volume. 8. The method according to claim 1 to 7, characterized in that the temperature in the reactor before opening to a maximum of 60 ° C is held.