Method For Cleaning A Compressor Using Dry Ice

Abstract

A method for cleaning a compressor having at least one compressor stage and serving to compress an operating medium. In at least one compressor stage of the compressor, during the compression operation, dry ice, or solid CO.sub.2, is used for the operating medium for abrasive cleaning of assemblies of the respective compressor stage to be cleaned.

Claims

1.-9. (canceled)

10. A method for cleaning a compressor, which comprises at least one compressor stage, comprising: compressing a working medium by the compressor; using dry ice (solid CO.sub.2) to abrasively clean of assemblies of a respective compressor stage of the compressor to be cleaned, during the compression of the working medium.

11. The method according to claim 10, wherein the dry ice is introduced into the respective compressor stage via a carrier gas, wherein the dry ice via the carrier gas is directed on assemblies of the respective compressor stage to be cleaned by the abrasive cleaning.

12. The method according to claim 10, further comprising: introducing liquid CO.sub.2 into the respective compressor stage; and converting the liquid CO.sub.2 into dry ice and carrier gas through isenthalpic expansion; and directing the dry ice via the carrier gas at assemblies of the respective compressor stage to be cleaned.

13. The method according to claims 11, wherein for cleaning the at least one compressor stage the dry ice used for cleaning the respective compressor stage is extracted one of internally and during the compression operation of the compressor and the carrier gas is extracted one of internally and during the compression operation of the compressor is.

14. The method according to claim 13, wherein the compressor is configured to compress CO.sub.2, wherein downstream of a high-pressure side compressor stage supercritically compressed CO.sub.2 is initially liquefied and subsequently converted into solid CO.sub.2 and gaseous CO.sub.2, and wherein the gaseous CO.sub.2 extracted and used as carrier gas and the solid CO.sub.2 is extracted and used as dry ice for cleaning a low-pressure side compressor stage.

15. The method according to claim 14, wherein the liquid CO.sub.2 is divided into two partial flows, wherein a first partial flow (18a) is converted into solid CO.sub.2 and gaseous CO.sub.2, and wherein a second partial flow (18b) is cooled through expansion to further cool down the first partial flow prior to conversion into solid CO.sub.2 and gaseous CO.sub.2.

16. The method according to claim 10, wherein for cleaning the at least one compressor stage at least one of: dry ice obtained one of externally and outside the compression operation of the compressor is used for cleaning the respective compressor stage, and carrier gas obtained one of externally and outside the compression operation of the compressor is used for cleaning the respective compressor stage.

17. The method according to claim 16, wherein for cleaning at least one compressor stage the dry ice and the carrier gas is used for cleaning the respective compressor stage.

18. The method according to claim 16, wherein for cleaning at least one compressor stage the dry ice obtained externally or outside the compression operation of the compressor and the carrier gas extracted one of from the compressed working medium internally and during the compression operation of the compressor is used for cleaning the respective compressor stage.

19. The method according to claim 14, wherein downstream of a high-pressure side compressor stage downstream of a last compressor stage the supercritically compressed CO.sub.2 is initially liquefied.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Preferred further developments of the invention are obtained from the subclaims and the following description. Exemplary embodiments of the invention are explained in more detail by way of the drawing without being restricted to this. There it shows:

[0011] FIG. 1 is a block diagram for illustrating a method for cleaning a compressor;

[0012] FIG. 2 is a block diagram for illustrating a method for cleaning a compressor;

[0013] FIG. 3 is a block diagram for illustrating a method for cleaning a compressor;

[0014] FIG. 4 is a block diagram for illustrating a method for cleaning a compressor; and

[0015] FIG. 5 is a block diagram for illustrating a method for cleaning a compressor.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0016] FIG. 1 shows an exemplary embodiment of a compressor 10 with three compressor stages 11, 12, and 13, wherein in the compressor stages 11, 12, and 13 a working medium 14 is gradually compressed. Downstream of each compressor stage 11, 12, 13 a cooler 15, 16, 17 is arranged to cool the working medium 14, which has been partly compressed in the respective upstream compressor stage 11, 12, 13.

[0017] In FIG. 1, the front-most compressor stage 11 of the compressor 10 is cleaned during the compression operation for the working medium 14, namely with dry ice, i.e. with solid CO.sub.2, which is introduced via a carrier gas into the compressor stage 11. By way of the carrier gas, the dry ice is directed at assemblies of the compressor stage 11 to be cleaned for abrasively cleaning the same.

[0018] In the exemplary embodiment of FIG. 1, dry ice extracted internally and carrier gas extracted internally is used for cleaning the compressor stage 11. Here, the compressor 10 of FIG. 1 serves for compressing working medium in the form of CO.sub.2, wherein downstream of the rear-most or last compressor stage 13 supercritically compressed CO.sub.2 is present. This supercritically compressed CO.sub.2 is cooled down in the cooler 17, wherein downstream of the cooler 17 CO.sub.2 is present, which can be liquid but also supercritical. From the working medium 14, a part is conducted via a recirculation line 18, in which an expansion valve 19 is arranged. In the expansion valve 19, an expansion of the CO.sub.2 takes place for the further cooling of the same. If appropriate, the CO.sub.2 is already isenthalpically expanded so far in the region of the expansion valve 19 or alternatively only downstream of the expansion valve 19 in the region of the compressor stage 11 to convert liquid CO.sub.2 into solid CO.sub.2, i.e. dry ice, and gaseous CO.sub.2, i.e. carrier gas. Accordingly, from the compressed working medium 14 a part is branched off in order to obtain from the same by cooling and expansion on the one hand gaseous CO.sub.2 as internally extracted carrier gas and on the other hand solid CO.sub.2 as internally extracted dry ice and to utilise this for cleaning the compressor stage 11.

[0019] A further development of the exemplary embodiment of FIG. 1 is shown by FIG. 2, wherein in the exemplary embodiment of FIG. 2 the liquid CO.sub.2 branched off into the recirculation line 18 is divided into two part flows 18a, 18b. The part flow 18a is converted by cooling and expansion into solid CO.sub.2 and gaseous CO.sub.2 for providing internally extracted dry ice and internally extracted carrier gas. The second part flow 18b is conducted via a further expansion valve 20 for the expansion and cooling of the same, in order to further cool the first part flow 18a via this second part flow 18b using a cooler 21 positioned upstream of the expansion valve 19 prior to the conversion into solid CO.sub.2 and gaseous CO.sub.2. By way of this, compared with FIG. 1, the formation of internally extracted dry ice can be improved. The second part flow 18b utilised for cooling the first part flow 18a according to FIG. 2 is recirculated into or admixed to the working medium 14 upstream of the first compressor stage 11.

[0020] As already explained, the exemplary embodiments of FIGS. 1 and 2 are in particular employed with a compressor that compresses CO.sub.2 as working medium.

[0021] In FIGS. 1 and 2, dry ice extracted internally or during the compression operation of the compressor from the working medium compressed in a higher or in a high-pressure side compressor stage and carrier gas extracted internally or during the compression operation of the compressor from the working medium compressed in the higher or in the high-pressure side compressor stage are utilised in each case for cleaning a lower or low-pressure side compressor stage. Dependent on the process pressures in the compressor stages of the compressor, only a part quantity of the compressor stage can be cleaned with dry ice extracted internally or during the compression operation of the compressor in the versions of FIGS. 1 and 2.

[0022] FIGS. 3 to 5 show further configurations of the invention, again on the example of a compressor 10 with the three compressor stages 11, 12, and 13 and coolers 15 to 17 connected downstream of the compressor stages 11 to 13. In the versions of FIGS. 3 and 5, all compressor stages can be cleaned with externally obtained dry ice.

[0023] FIG. 3 shows a form of the invention, in which assemblies of each of the compressor stages 11, 12, 13 are abrasively cleaned with the help of dry ice, wherein the dry ice is introduced into the respective compressor stage 11, 12, 13 via a carrier gas. In FIG. 3, carrier gas obtained externally or outside the compression operation of the compressor and not carrier gas extracted from the working medium compressed by the compressor and dry ice obtained externally or outside the compression operation of the compressor and not extracted from the working medium compressed by the compressor is used. Accordingly, in FIG. 3, a line 22, 23, 24 in which a valve 25, 26, and 27 respectively is integrated in each case leads to each of the compressor stages 11, 12, 13 to be cleaned. Dependent on the opening position of the valve 25, 26, 27, dry ice kept ready externally can be conducted via the respective line 22, 23, 24 by way of carrier gas kept ready externally can be conducted in the direction of the respective compressor stage 11, 12, 13 to be cleaned.

[0024] As carrier gas, a gas can be taken for example that corresponds to the compressed working medium 14 (but not necessarily so).

[0025] A further configuration of the invention is shown by FIG. 4, wherein in the version of FIG. 4 dry ice obtained externally or outside the compression operation of the compressor and not extracted from the working medium compressed by the compressor but carrier gas extracted internally or during the compression operation of the compressor from the compressed working medium is conducted to the compressor stage 11 for cleaning. For providing the internally extracted carrier gas, a part is branched off from the compressed working medium 14 via the recirculation line 18 and expanded in the expansion valve 19.

[0026] This expanded working medium, which provides the internally extracted carrier gas, is mixed in FIG. 4 with dry ice obtained externally or outside the compression operation of the compressor and not extracted from the working medium compressed in the compressor, which is provided via the line 28 dependent on the opening position of a valve 29 integrated in the line 28. The internally extracted carrier gas is mixed with the externally provided dry ice and then conducted for the cleaning of the compressor stage 11.

[0027] A further configuration of the invention is shown by FIG. 5. In FIG. 5, each compressor stage 11, 12, 13 is again cleaned. Carrier gas required for this purpose is branched off from the respective working medium to be compressed via recirculation lines 30, 31, 32 and extracted through expansion of the same in the region of an expansion valve 33, 34, and 35 respectively assigned to the respective recirculation lines 30, 31, 32. Accordingly, the carrier gas needed in the compressor stage 11 is branched off downstream of the cooler 15 and conducted via the recirculation line 30 and the expansion valve 33 assigned to the recirculation line 30. The carrier gas, which is needed in the region of the compressor stage 12, is branched off in the region of the recirculation line 31 downstream of the cooler 16 connected downstream of said compressor stage 12 and in the region of the expansion valve 34 converted into carrier gas. Carrier gas, which is needed for cleaning the compressor stage, 13 is branched off via the recirculation line 22 downstream of the cooler 17 connected downstream of the compressor stage 13 and in the region of the expansion valve 35 assigned to this recirculation line 32 converted into carrier gas. Accordingly, in the region of each compressor stage 11, 12, 13, internally extracted carrier gas is utilised, which is extracted through an expansion of the working medium, partly compressed in the respective compressor stage 11, to be cleaned in the region of the respective expansion valve 33, 34, and 35 respectively. The respective carrier gas is mixed with externally provided dry ice, which can be conducted via the lines 36, 37, 38 and the valves 39, 40, 41 assigned to these lines 36, 37, 38 in the direction of the respective compressor stage 11, 12, 13. The respective dry ice is mixed with the respective carrier gas and then conducted to the respective compressor stage 11, 12, 13 for cleaning the same.

[0028] Accordingly, according to the invention, dry ice, solid CO.sub.2 is used for cleaning a compressor stage of a compressor 10, which is preferentially introduced into the respective compressor stage via a carrier gas. The dry ice can be internally extracted dry ice or externally provided dry ice. Likewise, the carrier gas can be internally extracted carrier gas or externally provided carrier gas.

[0029] In the case of compressors that serve for compressing CO.sub.2, both the carrier gas and also the dry ice can be extracted through isenthalpic expansion of liquid CO.sub.2 from a high pressure to a low pressure. The proportion of the extracted solid CO.sub.2, i.e. the proportion of the extracted dry ice in this case depends on the pressure and the temperature of the liquid CO.sub.2, wherein by cooling the liquid CO.sub.2 prior to the expansion of the same the proportion of the extractable dry ice can be increased (see above version of FIG. 2).

[0030] The solid particles of the dry ice are transported by the carrier gas and directed onto the assemblies of the respective compressor stage to be cleaned with high velocity. In the process, the solid particles of dry ice strike contaminations in the region of the assemblies of the respective compressor stage and detach the same by way of an abrasive action. During the further process operation, the dry ice evaporates or sublimates so that no washing medium has to be separated out.

[0031] The invention can be employed with all types of compressors for example radial compressors and axial compressors. With the invention, a particularly advantageous and effective cleaning of a compressor is possible.

[0032] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.