Process for cleaning a compressor in a continuous process for the epoxidation of an olefin

Abstract

The present invention relates to a process for cleaning a compressor in a continuous process for the epoxidation of an olefin and a unit for carrying out the process according to the present invention.

Description

[0001] Process for cleaning a compressor in a continuous process for the epoxidation of an olefin

[0002] The present invention relates to a process for cleaning a compressor in a continuous process for the epoxidation of an olefin and a unit for carrying out the process according to the present invention.

[0003] Ethylene oxide production processes using ethylene and oxygen for direct reaction are known in the art and disclosed for example in Ullmann’s Encyclopedia “Ethylene oxide”, 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, in WO 2014 / 157698 A1 , and in WO 00 / 17177 A1. Ethylene and oxygen are not completely reacted during the process which requires a recycling of the residual raw materials to increase overall yield and profitability. To recycle the non-reacted ethylene and oxygen, the remaining gases after ethylene oxide separation are sent to a gas compressor prior to be sent back to the reactor. The recycled gas not only includes methane, ethylene and oxygen but also other compounds in gaseous or liquid state. These compounds in gaseous or liquid state are very fine liquid droplets and / or mist. They are forming salts that will deposit on the compressor blades and impair the gas compressor performance. As result the recycle gas compressor must be cleaned to improve efficiency.

[0004] Such cleaning process is described in WO 2005 / 024095 using a mixture of a glycol alkyl ether compound, an alkoxylated surfactant with an alkyl chain length of from about 3 to 18 carbons and a metal corrosion inhibitor component. Nevertheless, such compositions would lead to unfavorable side reactions within the ethylene oxide reactor in case of usage during the running process. In DE 2807449 B1 , the cleaning liquid is injected successively into the different stages of a multistage turbo compressor starting with the stage of highest pressure, the stages are thus cleaned in succession. The cleaning liquid is taken-off preferably via discharged vessels directly after the compressor.

[0005] The same is true for CN 205858800 U which relates to the cleaning of a multistage compressor system with intermediate coolers in between the compressor stages. The compressor is cleaned to prevent the gas-liquid separators being blocked by dust or other impurities. To do so, the liquid cleaning agent run through the compressor and is afterwards separated using a bypass. Also, for this document, a cleaning within the running production process is not possible and a separation of the dirty cleaning agent is required.

[0006] EP 2 177 514 A1 discloses a process for producing epoxy compound comprising reacting an olefin and molecular oxygen (O2) in an epoxidation unit comprising a series of epoxidation reactors. The stream exiting the last reactors of the series is separated into a liquid stream comprising the epoxide compound and a gaseous stream comprising O2 and the unreacted olefin which is recycled into the epoxidation unit using a compressor or a blower.

[0007] GB 2 017 213 A discloses a process for cleaning a multi-stage turbo-compressors for gases. In particular said document discloses that the cleaning can be done without having the necessity to stop the compressor. Further, it disclosed that water can be used as the cleaning agent. The reference requires that the cleaning be done step by step (in successive steps for each stages of the compressor). Further, discharge vessels (7a, 7b, 7c, 4) are used for removing the cleaning liquid laden with soiling matters. Cleaning of one compartment of a multi-stage turbo-compressor can be done without stopping the complete multi-stage turbo-compressor, however, the portion or compartment that is cleaned cannot do any compression work during cleaning.

[0008] Therefore, there is a need to provide an improved process for cleaning compressors in particular in processes for the epoxidation of olefins which permits to simplify the cleaning while not affecting the production rate and reducing unfavorable by-products generation.

[0009] Surprisingly, it has been found that with the process of the present invention, namely a process for cleaning a compressor in a continuous process for the epoxidation of an olefin, it was possible to avoid the removal and thus separation of the cleaning composition after the cleaning preventing the stop of the ethylene oxide production running process. Hence, the production rate is not affected and the yield of the process is maintained based on the plant requirements thanks to the periodical cleaning in a continuous ethylene oxide production process.

[0010] Therefore, the present invention relates to a process for cleaning a compressor in a continuous process for the epoxidation of an olefin, the process comprising

[0011] (i) preparing an epoxide from the olefin, wherein (i) comprises feeding the olefin and oxygen into an epoxidation reactor comprising an heterogeneous epoxidation catalyst; bringing in contact the olefin, the oxygen and said catalyst in the epoxidation reactor, obtaining a gaseous stream A comprising the corresponding epoxide and one or more of the olefin and oxygen; passing the gaseous stream A into a separation unit, obtaining a stream B comprising said epoxide and a stream C comprising the one or more of the olefin and oxygen;

[0012] (ii) recycling the one or more of the olefin and oxygen obtained according to (i) into the epoxidation reactor, wherein (ii) comprises introducing the stream C at the inlet end of a compressor, removing a compressed gaseous stream D at the outlet end of the compressor and subsequently introducing the compressed stream D into the epoxidation reactor in (i), the stream D comprising the one or more of the olefin and oxygen; the process further comprising

[0013] (iii) periodically cleaning the compressor used in (ii), wherein (iii) comprises introducing a cleaning liquid consisting of water at the inlet end of the compressor during the recycling of the one or more of the olefin and oxygen according to (ii), the compressed stream D removed from the compressor and subsequently introduced into the epoxidation reactor in (i) further comprising the cleaning liquid.

[0014] The process of the present application preferably requires

[0015] (a) cleaning the compressor with a cleaning liquid consisting of water used for recycling unreacted olefin and molecular oxygen into the epoxidation reactor; (b) periodical cleaning;

[0016] (c) cleaning during compressing and thus without stopping the process for the epoxidation of an olefin; (d) no discharge of the cleaning liquid.

[0017] Preferably, step (iii) is free of discharge and does not employ discharge vessels. Thus, the compressed stream D removed from the compressor and subsequently introduced into the epoxidation reactor in (i) does preferably not pass one or more discharge vessels and is not discharged.

[0018] Cleaning of one compartment of a multi-stage turbo-compressor can be done without stopping the compressor, however, according to the present invention the portion or compartment that is being cleaned can continue to do its supposed work. In the process of the present invention this is possible since, e.g. unlike the process of GB 2 017213 A, there is no discharge and the cleaning liquid (water) is recycled with the one or more of the olefin and oxygen into the epoxidation reactor. There is no need to stop the feed of the medium to be compressed, i.e. one or more of the olefin and oxygen, into the compressor during the cleaning according to the present invention. This is especially important for single-stage compressors like single-stage turbo compressors.

[0019] These distinguishing features permit to not only to clean the compressor in a continuous epoxidation process but also permit to reduce the units used for cleaning a compressor and thus the costs of this operation in particular thanks to its periodical repetition and the absence of discharge of the cleaning liquid after its injection in the compressor.

[0020] Preferably, each period of cleaning according to (iii) is operated for a duration in the range of from 15 seconds to 1 hour, more preferably in the range of from 30 seconds to 40 minutes, more preferably in the range of from 30 seconds to 30 minutes.

[0021] In the context of the present invention, it is however noted that the skilled person may adapt the frequency of the cleaning in the continuous process based on the needs of the particular plant.

[0022] Preferably, the periodicity of the cleaning according to (iii) is determined based on data obtained from one or more testing units and / or one or more production plants.

[0023] Preferably periodically cleaning according to (iii) is performed every 4 hours to 48 hours, more preferably every 10 hours to 30 hours, more preferably every 22 to 26 hours.

[0024] Preferably periodically cleaning according to (iii) is performed once a day.

[0025] Preferably the cleaning liquid consists of deionized water, more preferably recycled deionized water.

[0026] Preferably, (iii) comprises periodically cleaning the compressor used in (ii), wherein (iii) comprises introducing one cleaning liquid consisting of water at the inlet end of the compressor during the recycling of the one or more of the olefin and oxygen according to (ii), the compressed stream D removed from the compressor and subsequently introduced into the epoxidation reactor in (i) further comprising the cleaning liquid.

[0027] Preferably the process further comprises measuring downstream of the outlet end of the compressor and upstream of the inlet end of the epoxidation reactor the flow rate of the stream D removed from said compressor, more preferably measuring is performed continuously.

[0028] Preferably, according to (iii), the ratio of the flow rate of the cleaning liquid, fw, in m3(liquid) / h, entering the compressor relative to the flow rate of the stream C, fc, in Nm3(gas) / h, entering the compressor, fw(m3(liquid) / h):fc(Nm3(gas) / h), is in the range of from 108:1 to 103: 1 m3 / Nm3, more preferably in the range of from 107: 1 to 104:1 m3 / Nm3, more preferably in the range of from 107:1 to 105:1 m3 / Nm3.

[0029] Therefore, the present invention preferably relates to a process for cleaning a compressor in a continuous process for the epoxidation of an olefin, the process comprising

[0030] (i) preparing an epoxide from the olefin, wherein (i) comprises feeding the olefin and oxygen into an epoxidation reactor comprising an heterogeneous epoxidation catalyst; bringing in contact the olefin, the oxygen and said catalyst in the epoxidation reactor, obtaining a gaseous stream A comprising the corresponding epoxide and one or more of the olefin and oxygen; passing the gaseous stream A into a separation unit, obtaining a stream B comprising said epoxide and a stream C comprising the one or more of the olefin and oxygen;

[0031] (ii) recycling the one or more of the olefin and oxygen obtained according to (i) into the epoxidation reactor, wherein (ii) comprises introducing the stream C at the inlet end of a compressor, removing a compressed gaseous stream D at the outlet end of the compressor and subsequently introducing the compressed stream D into the epoxidation reactor in (i), the stream D comprising the one or more of the olefin and oxygen; the process further comprising

[0032] (iii) periodically cleaning the compressor used in (ii), wherein (iii) comprises introducing a cleaning liquid consisting of water at the inlet end of the compressor during the recycling of the one or more of the olefin and oxygen according to (ii), the compressed stream D removed from the compressor and subsequently introduced into the epoxidation reactor in (i) further comprising the cleaning liquid; wherein the ratio of the flow rate of the cleaning liquid, fw, in m3(liquid) / h, entering the compressor relative to the flow rate of the stream C, fc, in Nm3(gas) / h, entering the compressor, fw(m3(liquid) / h):fc(Nm3(gas) / h), is in the range of from 108: 1 to 103: 1 m3 / Nm3, more preferably in the range of from 107: 1 to 104:1 m3 / Nm3, more preferably in the range of from 107:1 to 105:1 m3 / Nm3. In the context of the present invention, preferably the ratio fw(m3(liquid) / h):fc(Nm3(gas) / h) is essentially similar for each periodic cleaning according to (iii) or preferably the ratio fw(m3(liq- uid) / h):fc(Nm3(gas) / h) is varying from a cleaning to another but remains in the range of from 108: 1 to 103: 1 m3 / Nm3, more preferably in the range of from 107:1 to 104: 1 m3 / Nm3, more preferably in the range of from 107: 1 to 105:1 m3 / Nm3.

[0033] In the context of the present invention, the aforementioned flow rate ratio will be adapted by the skilled person to the need of the process, depending on different factors of the plant, such as the type of compressor, the volume of the epoxidation reactor, the reactor load, etc.

[0034] Preferably the process of the present invention comprises using one or more heat exchangers using H2O.

[0035] Preferably the water used according to (iii) is at least partially recycled water, more preferably from one or more heat exchangers. In this regard, the one or more heat exchangers use water in gaseous state (water steam), the water steam is condensed and introduced into a collective drum. Hence, the water used according to (iii) is taken from the collective drum for being introduced into the compressor according to (iii).

[0036] Preferably no solvent other than water is used for cleaning according to (iii).

[0037] Preferably, according to (iii), the cleaning liquid is introduced into the compressor at a temperature in the range of from 10 to 80 °C, more preferably in the range of from 20 to 60 °C, more preferably in the range of from 25 to 50 °C.

[0038] The compressor can be a single-stage compressor or a multiple or multi-stage compressor. Preferably the compressor is a single-stage compressor.

[0039] Preferably the compressor is one or more of a rotary compressor, a single-stage turbo compressor, a multi-stage turbo compressor, a screw compressor and a piston compressor.

[0040] More preferably, the compressor is a single-stage turbo compressor.

[0041] Preferably the epoxidation reactor temperature is in the range of from 180 to 350 °C, more preferably in the range of from 190 to 300 °C.

[0042] It should however be noted that the epoxidation reactor temperature is varying during the operation time to adjust production capacity and / or to compensate the reduction in catalyst activity, as well known in the art by the skilled person.

[0043] Preferably the epoxidation in the epoxidation reactor is performed at a pressure in the range of from 10 to 30 bar(abs), more preferably in the range of from 15 to 30 bar(abs), more preferably in the range of from 15 to 20 bar(abs). Preferably the epoxidation reactor is one or more of a multi-tube reactor and a salt bath reactor, more preferably a multi-tube reactor.

[0044] In the context of the present invention, the stream C is a gaseous stream. The stream C may however contain small amounts of liquid or solid(particle) impurities as known by a skilled person.

[0045] Preferably at most 0.5 weight-%, more preferably at most 0.3 weight-% of water is comprised in the stream C based on the weight of the stream C.

[0046] Preferably, the stream B is a liquid stream.

[0047] In the context of the present invention, the stream D comprises a gaseous phase from the stream C and a liquid phase from the cleaning liquid.

[0048] Preferably, during the continuous process, excluding the cleaning according to (iii), at most 0.5 weight-%, more preferably at most 0.3 weight-% of water is comprised in the stream D based on the weight of the stream D, said water being from stream C. As may be understood by the skilled person, said water content in the compressed stream D will be (slightly) increased during the periodic cleaning according to (iii) by the addition of the cleaning liquid according to the ratio fw(m3(liquid) / h):fc(Nm3(gas) / h) disclosed herein.

[0049] Preferably the olefin is ethylene.

[0050] Preferably the heterogeneous catalyst comprised in the epoxidation reactor comprises silver and one or more of a support oxidic material and one or more promoters.

[0051] Preferably, the promoters comprise one or more of tungsten, rhenium, potassium, lithium and caesium.

[0052] Preferably, the support oxidic material preferably comprises alumina, more preferably a-alu- mina.

[0053] Preferably from 95 to 100 weight-%, more preferably from 97 to 100 weight-%, of the support oxidic material consists of alumina, more preferably ct-alumina.

[0054] Preferably, the support oxidic material substantially consists of, or consists of, alumina, more preferably ct-alumina

[0055] In the context of the present invention, the silver catalyst used in the present invention can be any silver containing catalyst known in the art. Preferably, the catalyst is as disclosed in EP 3 866 972 B1 , which is incorporated herewith by reference. Preferably in addition to the olefin and oxygen, at least one saturated hydrocarbon is introduced in the epoxidation reactor according to (i). Preferably the at least one saturated hydrocarbon is one or more of ethane, methane, propane, and cyclopropane, more preferably is one or more of ethane and methane.

[0056] Preferably the olefin, oxygen, and more preferably the at least one saturated hydrocarbon as defined in the foregoing, fed into the epoxidation reactor according to (i) are comprised in an inlet gas composition, the olefin being present in an amount in the range of from 1 to 50 mole-%, more preferably in the range of from 5 to 40 mole-%, based on the total moles of the inlet gas composition.

[0057] Preferably the inlet gas composition comprises up to 10 mole-% of oxygen, more preferably from 1 to 9 mole-%, based on the total moles of the inlet gas composition.

[0058] Preferably the separation unit is an absorption unit, more preferably comprising an epoxide absorption unit.

[0059] Preferably (i) further comprises subjecting the stream B comprising the epoxide to one or more purification steps.

[0060] Preferably the one or more purification steps comprise one or more of a stripping step, a dehydration step and one or more separation steps.

[0061] Preferably one or more of (i), (ii) and (iii) are at least partially executed by using a computer or a computer network.

[0062] The present invention further relates to a unit for carrying out the process according to the present invention, the unit comprising an epoxidation reactor comprising the heterogeneous catalyst; a means for introducing the olefin into the reactor; a means for introducing oxygen into the reactor; a means for removing the gaseous stream A from the reactor; a separation unit; a means for introducing the stream A into the separation unit; a means for removing the stream B from the separation unit; a means for removing the stream C from the separation unit; a compressor; a means for introducing the stream C into the compressor at its inlet end; a means for introducing water into the compressor at its inlet end; a means for removing the compressed stream D from the compressor; a means for introducing the compressed stream D into the epoxidation reactor. Preferably the epoxidation reactor is one or more of a multi-tube reactor and a salt bath reactor, more preferably a multi-tube reactor.

[0063] Preferably the means for introducing the olefin into the reactor is one or more nozzles.

[0064] Preferably the means for introducing oxygen into the reactor is one or more nozzles. It is conceivable that the means for introducing the olefin into the reactor is also the means for introducing oxygen into the reactor.

[0065] Preferably the separation unit is an absorption unit, more preferably comprising an epoxide absorption unit.

[0066] Preferably the means for introducing the stream A into the compressor at its inlet end is the means for introducing water into the compressor at its inlet end.

[0067] Preferably the compressor is one or more of a rotary compressor, a single-stage turbo compressor, a multi-stage turbo compressor, a screw compressor and a piston compressor, more preferably a single-stage turbo compressor.

[0068] Preferably the unit further comprises one or more heat exchangers, more preferably functioning with water, more preferably water steam.

[0069] Preferably the unit further comprises a collective drum for collecting recycled water and a means for transporting the water from the one or more heat exchangers to the drum.

[0070] Preferably the unit further comprises one or more condensers for condensing water used in the one or more heat exchangers.

[0071] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0072] 1 . A process for cleaning a compressor in a continuous process for the epoxidation of an olefin, the process comprising

[0073] (i) preparing an epoxide from the olefin, wherein (i) comprises feeding the olefin and oxygen into an epoxidation reactor comprising an heterogeneous epoxidation catalyst; bringing in contact the olefin, the oxygen and said catalyst in the epoxidation reactor, obtaining a gaseous stream A comprising the corresponding epoxide and one or more of the olefin and oxygen; passing the gaseous stream A into a separation unit, obtaining a stream B comprising said epoxide and a stream C comprising the one or more of the olefin and oxygen;

[0074] (ii) recycling the one or more of the olefin and oxygen obtained according to (i) into the epoxidation reactor, wherein (ii) comprises introducing the stream C at the inlet end of a compressor, removing a compressed gaseous stream D at the outlet end of the compressor and subsequently introducing the compressed stream D into the epoxidation reactor in (i), the stream D comprising the one or more of the olefin and oxygen; the process further comprising

[0075] (iii) periodically cleaning the compressor used in (ii), wherein (iii) comprises introducing a cleaning liquid consisting of water at the inlet end of the compressor during the recycling of the one or more of the olefin and oxygen according to (ii), the compressed stream D removed from the compressor and subsequently introduced into the epoxidation reactor in (i) further comprising the cleaning liquid. The process of embodiment 1 , wherein each period of cleaning according to (iii) is operated for a duration in the range of from 15 seconds to 1 hour, preferably in the range of from 30 seconds to 40 minutes, more preferably in the range of from 30 seconds to 30 minutes. The process of embodiment 1 or 2, wherein periodically cleaning according to (iii) is performed every 4 hours to 48 hours, preferably every 10 hours to 30 hours, more preferably every 22 to 26 hours. The process of any one of embodiments 1 to 3, wherein the cleaning composition consists of deionized water. The process of any one of embodiments 1 to 4, further comprises measuring downstream of the outlet end of the compressor and upstream of the inlet end of the epoxidation reactor the flow rate of the stream D removed from said compressor, preferably measuring is performed continuously. The process of any one of embodiments 1 to 5, wherein, according to (iii), the ratio of the flow rate of the cleaning liquid, fw, in m3(liquid) / h, entering the compressor relative to the flow rate of the stream C, fc, in Nm3(gas) / h, entering the compressor, fw(m3(liq- uid) / h):fc(Nm3(gas) / h), is in the range of from 108:1 to 103:1 m3 / Nm3, preferably in the range of from 107:1 to 104:1 m3 / Nm3, more preferably in the range of from 107:1 to 10-5:1 mW.

[0076] 7. The process of any one of embodiments 1 to 6, wherein the water used according to (iii) is at least partially recycled water, preferably from one or more heat exchangers.

[0077] 8. The process of any one of embodiments 1 to 7, wherein no solvent other than water is used for cleaning according to (iii).

[0078] 9. The process of any one of embodiments 1 to 8, wherein, according to (iii), the cleaning liquid is introduced into the compressor at a temperature in the range of from 10 to 80 °C, preferably in the range of from 20 to 60 °C, more preferably in the range of from 25 to 50 °C.

[0079] 10. The process of any one of embodiments 1 to 9, wherein the compressor is one or more of a rotary compressor, a single-stage turbo compressor, a multi-stage turbo compressor, a screw compressor and a piston compressor, preferably a single-stage turbo compressor.

[0080] 11 . The process of any one of embodiments 1 to 10, wherein the epoxidation reactor temperature is in the range of from 180 to 350 °C, preferably in the range of from 190 to 300 °C.

[0081] 12. The process of any one of embodiments 1 to 11 , wherein the epoxidation in the epoxidation reactor is performed at a pressure in the range of from 10 to 30 bar(abs), preferably in the range of from 15 to 30 bar(abs), more preferably in the range of from 15 to 20 bar(abs).

[0082] 13. The process of any one of embodiments 1 to 12, wherein the epoxidation reactor is one or more of a multi-tube reactor and a salt bath reactor, preferably a multi-tube reactor.

[0083] 14. The process of any one of embodiments 1 to 13, wherein the olefin is ethylene.

[0084] 15. The process of any one of embodiments 1 to 14, wherein the heterogeneous catalyst comprised in the epoxidation reactor comprises silver and one or more of a support oxidic material and one or more promoters.

[0085] 16. The process of any one of embodiments 1 to 15, wherein in addition to the olefin and oxygen, at least one saturated hydrocarbon is introduced in the epoxidation reactor according to (i), wherein preferably the at least one saturated hydrocarbon is one or more of ethane, methane, propane, and cyclopropane, more preferably is one or more of ethane and methane.

[0086] 17. The process of any one of embodiments 1 to 16, wherein the olefin, oxygen and preferably the at least one saturated hydrocarbon as defined in embodiment 16 fed into the epox- idation reactor according to (i) are comprised in an inlet gas composition, wherein the olefin is present in an amount in the range of from 1 to 50 mole-%, preferably in the range of from 5 to 40 mole-%, based on the total moles of the inlet gas composition.

[0087] 18. The process of embodiment 17, wherein the inlet gas composition comprises up to 10 mole-% of oxygen, preferably from 1 to 9 mole-%, based on the total moles of the inlet gas composition.

[0088] 19. The process of any one of embodiments 1 to 18, wherein the separation unit is an absorption unit, preferably comprising an epoxide absorption unit.

[0089] 20. The process of any one of embodiments 1 to 19, wherein (i) further comprises subjecting the stream B comprising the epoxide to one or more purification steps.

[0090] 21 . The process of any one of embodiments 1 to 20, wherein one or more of (i), (ii) and (iii) are at least partially executed by using a computer or a computer network.

[0091] 22. A unit for carrying out the process according to any one of embodiments 1 to 21 , the unit comprising an epoxidation reactor comprising the heterogeneous catalyst; a means for introducing the olefin into the reactor; a means for introducing oxygen into the reactor; a means for removing the gaseous stream A from the reactor; a separation unit; a means for introducing the stream A into the separation unit; a means for removing the stream B from the separation unit; a means for removing the stream C from the separation unit; a compressor; a means for introducing the stream C into the compressor at its inlet end; a means for introducing water into the compressor at its inlet end; a means for removing the compressed stream D from the compressor; a means for introducing the compressed stream D into the epoxidation reactor.

[0092] 23. The unit of embodiment 22, wherein the epoxidation reactor is one or more of a multi-tube reactor and a salt bath reactor, preferably a multi-tube reactor.

[0093] 24. The unit of embodiment 22 or 23, wherein the separation unit is an absorption unit, preferably comprising an epoxide absorption unit.

[0094] 25. The unit of any one of embodiments 22 to 24, wherein the means for introducing the stream A into the compressor at its inlet end is the means for introducing water into the compressor at its inlet end. 26. The unit of any one of embodiments 22 to 25, wherein the compressor is one or more of a rotary compressor, a single-stage turbo compressor, a multi-stage turbo compressor, a screw compressor and a piston compressor, preferably a single-stage turbo compressor.

[0095] 27. The unit of any one of embodiments 22 to 26, further comprising one or more heat exchangers, preferably functioning with water, more preferably water steam.

[0096] 28. The unit of embodiment 27, further comprising a collective drum for collecting recycled water and a means for transporting the water from the one or more heat exchangers to the drum.

[0097] 29. The unit of embodiment 27 or 28, further comprising one or more condensers for condensing water used in the one or more heat exchangers.

[0098] It is explicitly noted that the above set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0099] In the context of the present invention, the term “reactor temperature” refers to the average temperature in the reactor and in particular in the catalyst bed.

[0100] In the context of the present invention, the term “gas stream” or “gaseous stream” means that the stream has a gas phase under the process conditions. Similarly, the term “liquid stream” means that the stream has a liquid phase under the process conditions.

[0101] In the context of the present invention, a term “X is one or more of A, B and C”, wherein X is a given feature and each of A, B and C stands for specific realization of said feature, is to be understood as disclosing that X is either A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. In this regard, it is noted that the skilled person is capable of transfer to above abstract term to a concrete example, e.g. where X is a chemical element and A, B and C are concrete elements such as Li, Na, and K, or X is a temperature and A, B and C are concrete temperatures such as 10 °C, 20 °C, and 30 °C. In this regard, it is further noted that the skilled person is capable of extending the above term to less specific realizations of said feature, e.g. “X is one or more of A and B” disclosing that X is either A, or B, or A and B, or to more specific realizations of said feature, e.g. “X is one or more of A, B, C and D”, disclosing that X is either A, or B, or C, or D, or A and B, or A and C, or A and D, or B and C, or B and D, or C and D, or A and B and C, or A and B and D, or B and C and D, or A and B and C and D.

[0102] The present invention is further illustrated by the following example.

[0103] Example For the ethylene oxide production according to the invention, ethylene was subjected to catalytic gas phase oxidation using a molecular oxygen-containing gas in the presence of a silver catalyst. The process comprises the introduction of ethylene, oxygen and at least one saturated hydrocarbon (methane) together with the introduction of the recycled gas stream (stream D) from ethylene oxide absorption column, the recycled gas stream containing among others unreacted ethylene, unreacted oxygen. The product gas containing ethylene oxide (stream A) as products was sent to ethylene oxide absorption column (separation unit), where the ethylene oxide is absorbed by an absorption liquid (mainly containing water). In addition to ethylene oxide, ethylene, oxygen, carbon dioxide, an inert gas (nitrogen, argon, methane, ethane, or the like), a low boiling point impurity such as formaldehyde, and a high boiling point impurity such as acetaldehyde or acetic acid, produced as byproducts, are also absorbed at the same time in the absorption column. EO rich absorption liquid (stream B) was then discharged to ethylene oxide stripper for further purification processes.

[0104] A gas stream not absorbed in the absorption column containing ethylene, oxygen, carbon dioxide, and others, for example, nitrogen, argon, methane, or ethane (stream C) discharged from the column top part of the absorption column, is circulated into the epoxidation reactor after its passage into a compressor. Indeed, the recycled gas was sent to the epoxidation reactor using the recycled gas compressor (single-shaft & single-stage centrifugal turbo compressor, electrically powered, purchased from Siemens, 9082kW, 50175 m3 / h at 14.3 bar) that continuously runs during the EO production process. To evaluate the efficiency of the recycled gas compressor and indirectly measure the fouling within the compressor, the gas flow rate downstream of the compressor and upstream of the epoxidation reactor was continuously determined (Figure 1). Over time, a reduction in gas flow can be observed reflecting the increasing fouling and reduction of efficiency. About once a day (here: 09.12.2022 at 7:09 and 10.12.2022 at 7:00), water (cleaning liquid) was introduced into the compressor together with the stream exiting the separation unit (absorption unit) in order to clean the gas compressor (here 1stflushing and 2ndflushing). The first flushing was performed for 13 minutes using at a flow rate fw of water entering the compressor of about 1 .5 m3 / h water. The second flushing was performed for 26 minutes at a flow rate fw of water entering the compressor of about 2.5 m3 / h water. The ratio of fw in m3(liquid) / h relative to the flow rate fc of stream C entering into the compressor in Nm3(gas) / h for the different flushing / cleaning was in the range of from 3 x 106: 1 to 5 x 106: 1 m3 / Nm3.

[0105] The effect of the present invention can be directly observed by the increasing gas flow rate measured after the compressor during flushing period and the resulting high gas flow rate after each cleaning with water (cf. Figure 3). Therefore, thanks to the present invention, it is believed that one can operate continuously the production of ethylene oxide while maintaining optimum efficiency by the periodical cleaning of the compressor with water which at these amounts does not have detrimental effect over the overall process. It is also very advantageous in term of reducing water waste since the water used is recycled water obtained from units in the plant, such as heat exchangers.

[0106] Description of the figures Figure 1 is a schematic representation of a unit for carrying out the process according to embodiments of the present invention.

[0107] The unit comprises an epoxidation reactor R(E), a compressor, and a separation unit SU. The stream MS represents the stream(s) of starting materials such as an olefin and oxygen entering the reactor for an epoxidation. The stream A comprising the corresponding epoxide and nonreacted starting materials (olefin and / or oxygen) is removed from R(E) and introduced into SU for separating the product, namely the epoxide, from the non-reacted starting materials. The stream B comprising the epoxide is thus removed from SU and the stream C comprising one or more of the olefin and oxygen is also removed from SU and passed through the compressor for continuous recycling as compressed stream D into R(E). Periodically, the compressor is cleaned a cleaning liquid W(l), namely water, is introduced with the stream C in the compressor for a given time, the compressed stream D comprising the dirty water and the one or more of the olefin and oxygen is recycled into R(E).

[0108] Figure 2 is a schematic representation of a unit for carrying out the process according to embodiments of the present invention.

[0109] The unit comprises an epoxidation reactor R(E), a compressor, and a separation unit SU. The stream MS represents the stream(s) of starting materials such as an olefin and oxygen entering the reactor for an epoxidation. The stream A comprising the corresponding epoxide and nonreacted starting materials (olefin and / or oxygen) is removed from R(E) and introduced into SU for separating the product, namely the epoxide, from the non-reacted starting materials. The stream B comprising the epoxide is thus removed from SU and the stream C comprising one or more of the olefin and oxygen is also removed from SU and passed through the compressor for continuous recycling as compressed stream D into R(E). The stream B is purified in PU obtaining the product P1. Periodically, the compressor is cleaned; a cleaning liquid W(l), namely water, is introduced with the stream C in the compressor for a given time, the compressed stream D comprising the cleaning liquid and the one or more of the olefin and oxygen is recycled into R(E). The water from the cleaning liquid is recycled water which has been collected in CD(Wc). Indeed, CD(Wc) is filled with one or more streams Sx(Wc), with x=1 or more, from one or more heat exchangers HE (not shown in Figure 2) that are running with steam and used in the process.

[0110] Figure 3 is a graphic representing the flow rate of recycled stream D at the outlet of the compressor in function of the time to illustrate the effect of the cleaning phases.

[0111] Cited Literature

[0112] Ullmann’s Encyclopedia “Ethylene oxide”, 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

[0113] - WO2014157698 A1

[0114] - WOOO / 17177 A1 - W02005 / 024095 A

[0115] - DE 2807449 B1

[0116] - CN205858800 U

Claims

Claims1 . A process for cleaning a compressor in a continuous process for the epoxidation of an olefin, the process comprising(i) preparing an epoxide from the olefin, wherein (i) comprises feeding the olefin and oxygen into an epoxidation reactor comprising a heterogeneous epoxidation catalyst; bringing in contact the olefin, the oxygen and said catalyst in the epoxidation reactor, obtaining a gaseous stream A comprising the corresponding epoxide and one or more of the olefin and oxygen; passing the gaseous stream A into a separation unit, obtaining a stream B comprising said epoxide and a stream C comprising the one or more of the olefin and oxygen;(ii) recycling the one or more of the olefin and oxygen obtained according to (i) into the epoxidation reactor, wherein (ii) comprises introducing the stream C at the inlet end of a compressor, removing a compressed gaseous stream D at the outlet end of the compressor and subsequently introducing the compressed stream D into the epoxidation reactor in (i), the stream D comprising the one or more of the olefin and oxygen; the process further comprising(iii) periodically cleaning the compressor used in (ii), wherein (iii) comprises introducing a cleaning liquid consisting of water at the inlet end of the compressor during the recycling of the one or more of the olefin and oxygen according to (ii), the compressed stream D removed from the compressor and subsequently introduced into the epoxidation reactor in (i) further comprising the cleaning liquid.

2. The process of claim 1 , wherein each period of cleaning according to (iii) is operated for a duration in the range of from 15 seconds to 1 hour, preferably in the range of from 30 seconds to 40 minutes, more preferably in the range of from 30 seconds to 30 minutes.

3. The process of claim 1 or 2, wherein periodically cleaning according to (iii) is performed every 4 hours to 48 hours, preferably every 10 hours to 30 hours, more preferably every 22 to 26 hours.

4. The process of any one of claims 1 to 3, further comprises measuring downstream of the outlet end of the compressor and upstream of the inlet end of the epoxidation reactor the flow rate of the stream D removed from said compressor, preferably measuring is performed continuously.

5. The process of any one of claims 1 to 4, wherein, according to (iii), the ratio of the flow rate of the cleaning liquid, fw, in m3(liquid) / h, entering the compressor relative to the flow rate of the stream C, fc, in Nm3(gas) / h, entering the compressor,fw(m3(liquid) / h):fc(N m3(gas) / h), is in the range of from 108:1 to 103:1 m3 / Nm3, preferably in the range of from 107:1 to 104:1 m3 / Nm3, more preferably in the range of from 107:1 to 10-5:1 m3 / Nm3.

6. The process of any one of claims 1 to 5, wherein the water used according to (iii) is at least partially recycled water, preferably from one or more heat exchangers.

7. The process of any one of claims 1 to 6, wherein no solvent other than water is used for cleaning according to (iii).

8. The process of any one of claims 1 to 7, wherein, according to (iii), the cleaning liquid is introduced into the compressor at a temperature in the range of from 10 to 80 °C, preferably in the range of from 20 to 60 °C, more preferably in the range of from 25 to 50 °C.

9. The process of any one of claims 1 to 8, wherein in addition to the olefin and oxygen, at least one saturated hydrocarbon is introduced in the epoxidation reactor according to (i), wherein preferably the at least one saturated hydrocarbon is one or more of ethane, methane, propane, and cyclopropane, more preferably is one or more of ethane and methane.

10. The process of any one of claims 1 to 9, wherein the olefin, oxygen and preferably the at least one saturated hydrocarbon as defined in claim 9 fed into the epoxidation reactor according to (i) are comprised an inlet gas composition, wherein the olefin is present in an amount in the range of from 1 to 50 mole-%, preferably in the range of from 5 to 40 mole- %, based on the total moles of the inlet gas composition.11 . The process of any one of claims 1 to 10, wherein the separation unit is an absorption unit, preferably comprising an epoxide absorption unit.

12. The process of any one of claims 1 to 11 , wherein (i) further comprises subjecting the stream B comprising the epoxide to one or more purification steps.

13. A unit for carrying out the process according to any one of claims 1 to 12, the unit comprising an epoxidation reactor comprising the heterogeneous catalyst; a means for introducing the olefin into the reactor; a means for introducing oxygen into the reactor; a means for removing the gaseous stream A from the reactor; a separation unit; a means for introducing the stream A into the separation unit; a means for removing the stream B from the separation unit; a means for removing the stream C from the separation unit; a compressor;a means for introducing the stream C into the compressor at its inlet end; a means for introducing water into the compressor at its inlet end; a means for removing the compressed stream D from the compressor; a means for introducing the compressed stream D into the epoxidation reactor.

14. The unit of claim 13, wherein the compressor is one or more of a rotary compressor, a single-stage turbo compressor, a multi-stage turbo compressor, a screw compressor and a piston compressor, preferably a single-stage turbo compressor.

15. The unit of claim 13 or 14, further comprising one or more heat exchangers, preferably functioning with water, more preferably water steam.

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