Wash Oil for Use as an Antifouling Agent in Gas Compressors

Abstract

The present invention relates to wash oil for use as an antifouling agent in gas compressors, in particular in cracked gas compressors, including at least one compound according to formulae (II)

##STR00001##

with the moieties R.sup.2 and R.sup.3 are selected from a group of linear or branched C.sub.1-C.sub.20-alkyl, C.sub.3-C.sub.10-cycloalkyl and linear or branched C.sub.1-C.sub.10-alkyl substituted C.sub.3-C.sub.10-cycloalkyl and C.sub.6-C.sub.12 aryl and C.sub.1-C.sub.10-alkyl substituted C.sub.6-C.sub.12 aryl. The moieties can be interrupted by oxygen or nitrogen. The moieties can be functionalised with hydroxyl groups or amino groups. The moieties can be the same or different. The invention relates also to the use of such wash oil as anti-fouling agent.

Claims

1. A wash oil for use as an antifouling agent in gas compressers comprising; at least one compound according to formulae (II) ##STR00007## wherein the moieties R.sup.2 and R.sup.3 are selected from a group consisting of linear or branched C.sub.1-C.sub.20-alkyl, C.sub.3-C.sub.10-cycloalkyl and linear or branched C.sub.1-C.sub.10-alkyl substituted C.sub.3-C.sub.10-cycloalkyl and C.sub.6-C.sub.12 aryl and C.sub.1-C.sub.10-alkyl substituted C.sub.6-C.sub.12 aryl, and wherein said moieties can be interrupted by oxygen or nitrogen, and wherein said moieties can be functionalised with hydroxyl groups or amino groups, and wherein said moieties can be the same or different, and at least one additive selected from a group consisting of polymerization inhibitor, antioxidant, metal deactivator, metal scavenger, corrosion inhibitor and pH-control additive.

2. The wash oil according to claim 1, wherein the wash oil comprises a mixture of at least two compounds according to formulae (I), (II) and (III) ##STR00008## wherein the moieties R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are selected from a group consisting of linear or branched C.sub.1-C.sub.20-alkyl, C.sub.3-C.sub.10-cycloalkyl and linear or branched C.sub.1-C.sub.10-alkyl substituted C.sub.3-C.sub.10-cycloalkyl and C.sub.6-C.sub.12 aryl and C.sub.1-C.sub.10-alkyl substituted C.sub.6-C.sub.12 aryl, and wherein said moieties can be interrupted by oxygen or nitrogen, and wherein said moieties can be functionalised with hydroxyl groups or amino groups, and wherein said moieties can be the same or different.

3. The wash oil according to claim 1, comprising: 0 to 10 mass % of a monosubstituted benzene according to formulae (I); 60 to 100 mass % of a disubstituted benzene according to formulae (II); and 0 to 5 mass of a trisubstituted benzene according to formulae (III).

4. The wash oil according to claim 2, wherein the mixture comprises at least three of the compounds selected from a group consisting of compounds according to formulae (I), (IIa-b) and (IIIa-c) ##STR00009##

5. The wash oil according to claim 2, wherein the moieties R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are selected from a group consisting of C.sub.1-C.sub.12-alkyl and C.sub.3-C.sub.7-cycloalkyl.

6. The wash oil according to claim 2, wherein the moieties R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are selected from a group consisting of ethyl, propyl, isopropyl, butyl and iso-butyl.

7. The wash oil according to claim 2, wherein the mixture comprises isopropylbenzene (Cumene), at least one diisopropylbenzene-Isomer and at least one triisopropylbenzene-Isomer.

8. The wash oil according to claim 2, wherein the mixture comprises 94-96 mass % diisopropylbenzene (DIPB); 2-4 mass % isopropylbenzene (Cumene), 1-2 mass % triisopropylbenzene (TRIPB) and 0.1-1.0 mass % heavier aromatic hydrocarbons.

9. The wash oil according to claim 1, comprising a boiling point at temperatures between 150° C. and 300° C.

10. The wash oil according to claim 2, wherein the mixture is free of non-aromatic compounds.

11. The wash oil according to claim 1, wherein the wash oil is mixed with other pyrolysis gas mixtures.

12. The wash oil according to claim 1, wherein the ratio of the at least one compound according to formulae (II) or the mixture of the at least two compounds according to formulae (I), (II) and (III) and at least one additive selected from a group consisting of polymerization inhibitor, antioxidant, metal deactivator, metal scavenger, corrosion inhibitor and pH-control additive is between 1000/1 and 10/1.

13. The wash oil according to claim 1, wherein the least one polymerization inhibitor is selected from the group consisting of aromatic and heteroaromatic compounds.

14. A process for applying an antifouling agent to a gas compressor comprising providing a wash oil, according to claim 1.

15. The process according to claim 14, wherein the wash oil is injected continuously or non-continuously into the gas compressor.

16. The process according to claim 14, wherein the gas compressor is a cracked gas compressor.

17. The process according to claim 15, wherein the wash oil is injected with a continuous injection rate of 0.05 to 0.25 per stage as wt % of gas processed.

18. The wash oil according to claim 2, wherein the mixture comprises at least three compounds according to formulae (I), (II) and (III).

19. The wash oil according to claim 10, wherein the mixture is free of non-aromatic compounds including: C1-C8 alkanes, C2-C8 alkenes and/or C3-C8 alkynes.

20. The wash oil according to claim 9, comprising a boiling point at temperatures between 190° and 220° C.

Description

[0065] Further details of the invention will be explained in detail by the means of the following example with reference to the Figures. It shows:

[0066] FIG. 1 a process flow diagram for cumene production;

[0067] FIG. 2 a diagram showing boiling point of different wash oils;

[0068] FIG. 3 a diagram showing the efficiency of a compressor depending on the introduction of wash oil,

[0069] FIG. 4 a diagram showing solubility data of fouling samples using different wash oils, and

[0070] FIG. 5A a diagram showing the compressor efficiency without addition of wash oil;

[0071] FIG. 5B a diagram showing the compressor efficiency in the presence of an antifoulant agent;

[0072] FIG. 5C a diagram showing the compressor efficiency in the presence of wash oil comprising aromatic compounds of formulae I, II and III; and

[0073] FIG. 5D a diagram showing the compressor efficiency in the presence of wash oil comprising aromatic compounds of formulae I, II and III and antifoulant additives.

[0074] The overhead product of a DIPB column is used in the provided examples. Said DIPB overhead stream contains 94-96 mass % DIPB, 2-4 mass % Cumene, 1-2 mass % TRIPB and 0.1-1.0 mass % heavier aromatic hydrocarbons. The DIPB stream is obtained as a side product in the Cumene production from benzene and propylene.

[0075] A typical process flow diagram for Cumene production (US 2011/024558 A1) is shown in FIG. 1. Here, a propylene feed and benzene (either fresh or recycled) are charged to the alkylation reactor 1, where the propylene reacts to completion to form Cumene. The effluent from the alkylation reactor 1 is subsequently sent to the depropanizer column 2 for removing propane that entered the process plant with the propylene feed along with any excess of propylene and water. The bottom of the depropanizer column 2 is subsequently sent to a benzene column 3, where benzene is collected overhead. The benzene bottom in turn is sent to the Cumene column 4 where a Cumene product is recovered as an overhead and the Cumene bottom is sent to the DIPB column 5 where DIPB is also recovered as overhead and comprises the above-mentioned composition.

[0076] This DIPB overhead stream is subsequently used in the following tests and examples.

[0077] In the diagram of FIG. 2 the boiling points of the DIPB overhead wash oil, a standard commercial wash oil and a third internal wash oil are compared to the recommended boiling point.

[0078] As can be seen from the diagram, the DIPB overhead stream has an initial boiling point of 195° C. and a final boiling point of 208° C. and fulfils the requirements of the recommended boiling points for wash oil which is for the initial boiling point and the final boiling point 200° C.

[0079] In the diagram of FIG. 3 the compressor relative polytrophic efficiency is plotted against time, before and after commercial wash oil is added. As clearly can be seen, the efficiency of the compressor deteriorates rapidly before the addition of the wash oil but is quickly recovered after wash oil is introduced in the system.

[0080] In the diagram of FIG. 4 experimental data are shown representing the solubility of fouling samples in DIPB wash oil as compared to the internal wash oil and commercial wash oil.

[0081] The solubility experiments were conducted using the following experimental procedure. In a first step, 10 ml of the wash solution DIPB, internal wash oil or commercial wash oil are heated in each case to a temperature of about 80° C. Subsequently, 1 g of the fouling residue from a compressor on a production side of the applicant is added to the 10 ml wash solution, which was pre-heated to 80° C. The mixture of wash solution and fouling residue is stirred for 20 min maintaining a constant temperature of 80° C. After that time period, the wash solution is filtered from the remaining solid and the remaining solid is dried in a vacuum oven for 20 min. The remaining and dried solid is then finally weighted and the value compared to the initial amount of about 1 g. The weight difference to the starting amount of the solid is then calculated as the solid solubilized in the wash solution.

[0082] The results of the solubility tests are summarized in the diagram of FIG. 4. All three wash solution tested show a good solubility efficiency of the fouling polymer sample used. The solubility efficiency of the DIPB wash oil was with 52.1% similar to the previously used internal wash oil and only slightly less than the commercial wash oil making it a good alternative to the presently available wash oils.

[0083] The effect of the wash oil without and with additives on the compressor efficiency is exemplarily shown in the diagrams of FIGS. 5A-D. The diagram of FIG. 5A depict the rather rapid decrease of the compressor efficiency over a time period of 200 days without the addition of any wash oil or antifouling agent.

[0084] When adding only a polymerization inhibitor (e.g. 4-Hydroxy-2,2,6,6-tetramethylpiperidin-N-oxyl) as antifoulant agent the decline of compressor efficiency is slightly reduced (FIG. 5B).

[0085] When adding only a wash oil (here DIPB wash oil which is injected intermittently 3 hours per week) without any further additives or antifouling agents the decrease of compressor efficiency over a period of 200 days was reduced drastically (FIG. 5C) when compared to the data of FIG. 5A.

[0086] An even stronger effect on the compressor efficiency was detectable when the wash oil was combined with a polymerization inhibitor (e.g. 4-Hydroxy-2,2,6,6-tetramethylpiperidin-N-oxyl) in a ratio 1/100 inhibitor/wash oil. When adding the mixture of wash oil/inhibitor (which was injected intermittently 3 hours per week) no decline of the compressor efficiency over a period of 200 days was detectable (FIG. 5C).

[0087] In summary the combination of wash oil and inhibitor increased the compressor efficiency in a synergistic manner that was not predictable for a person skilled in the art. The synergistic effect may be due to specific interaction between wash oil and antifoulant agent as explained previously.