COMPOSITIONS FOR PREVENTING POLYTHIONIC ACID (PTA) STRESS CORROSION CRACKING ON 300 SERIES STAINLESS STEEL AND METHODS OF USING THE SAME

Abstract

Compositions, systems and methods for treating stainless steel vessels to prevent polythionic acid stress corrosion cracking are described. Compositions include pre-mixed K.sub.2CO.sub.3 solutions that can be diluted on-site to desired K.sub.2CO.sub.3 concentrations via in-line mixing with water prior to placement within a stainless steel vessel to be treated.

Claims

1. A system for treating a stainless steel vessel for prevention of stress corrosion cracking, the system comprising: a storage container configured to store a pre-mix K.sub.2CO.sub.3 treatment solution and fluidically coupled with a first conduit; a water source fluidically coupled with a second conduit; a third conduit fluidically coupled with each of the first conduit, the second conduit and a stainless steel vessel to be treated; and a waste vessel fluidically coupled with the stainless steel vessel, wherein, when the system is in use, the pre-mix K.sub.2CO.sub.3 treatment solution is transmitted from the storage container to the third conduit via the first conduit, water is transmitted from the water source to the third conduit via the second conduit, and the pre-mix K.sub.2CO.sub.3 treatment solution and the water mix in the third conduit to form a diluted K.sub.2CO.sub.3 treatment solution, the diluted K.sub.2CO.sub.3 treatment solution receivable by the stainless steel vessel via the third conduit.

2. The system of claim 1, wherein the first conduit further comprises an injection pump.

3. The system of claim 1, wherein the first conduit further comprises an injection rate control valve.

4. (canceled)

5. The system of claim 1, wherein the second conduit further comprises a water injection rate control valve.

6. The system of claim 1, wherein the second conduit further comprises a flow meter.

7. (canceled)

8. The system of claim 1, wherein the storage container is configured to store a pre-mix K.sub.2CO.sub.3 treatment solution having a K.sub.2CO.sub.3 concentration of between about 200 g and about 1120 g of K.sub.2CO.sub.3 per liter of water.

9-17. (canceled)

18. The system of claim 1, wherein the system is configured to prepare a diluted K.sub.2CO.sub.3 treatment solution that contains from about 0.1 to about 10 w/w % K.sub.2CO.sub.3.

19-22. (canceled)

23. A system for treating a stainless steel vessel for prevention of stress corrosion cracking, the system comprising: a storage container configured to store a pre-mix K.sub.2CO.sub.3 treatment solution and fluidically coupled with a first conduit; a water source fluidically coupled with a second conduit; an educator coupled with each of the first conduit and the second conduit; a third conduit fluidically coupled with each of the eductor a stainless steel vessel to be treated; and a waste vessel fluidically coupled with the stainless steel vessel, wherein, when the system is in use, the pre-mix K.sub.2CO.sub.3 treatment solution is transmitted from the storage container to the eductor via the first conduit, water is transmitted from the water source to the eductor via the second conduit, and the pre-mix K.sub.2CO.sub.3 treatment solution and the water mix in the eductor to form a diluted K.sub.2CO.sub.3 treatment solution, the diluted K.sub.2CO.sub.3 treatment solution receivable by the stainless steel vessel from the eductor via the third conduit.

24. The system of claim 23, wherein the first conduit further comprises an injection rate control valve.

25. The system of claim 23, wherein the second conduit further comprises a water injection rate control valve.

26. The system of claim 23, wherein the second conduit further comprises a flow meter.

27. (canceled)

28. The system of claim 23, wherein the storage container is configured to store a pre-mix K.sub.2CO.sub.3 treatment solution having a K.sub.2CO.sub.3 concentration of between about 200 g and about 1120 g of K.sub.2CO.sub.3 per liter of water.

29-37. (canceled)

38. The system of claim 23, wherein the system is configured to prepare a diluted K.sub.2CO.sub.3 treatment solution that contains from about 0.1 to about 10 w/w % K.sub.2CO.sub.3.

39-42. (canceled)

43. A method of treating a stainless steel vessel for prevention of stress corrosion cracking, the method comprising: a) incorporating a stainless steel vessel into a system according to claim 1; b) injecting a diluted K.sub.2CO.sub.3 treatment solution into the stainless steel vessel until the stainless steel vessel is filled or substantially filled with the diluted K.sub.2CO.sub.3 treatment solution; c) maintaining the diluted K.sub.2CO.sub.3 treatment solution in the stainless steel vessel for a predetermined period of time; d) removing the diluted K.sub.2CO.sub.3 treatment solution from the stainless steel vessel.

44. The method of claim 43, wherein the diluted K.sub.2CO.sub.3 treatment solution is removed from the stainless steel vessel to a waste vessel.

45. (canceled)

46. The method of claim 43, wherein step c) is performed at a temperature of up to 50? C. and/or the predetermined period of time is at least two hours.

47. The method of claim 43, wherein step b) is performed under an inert atmosphere.

48. The method of claim 43, wherein step c) further comprises measuring the pH of contents within the stainless steel vessel, the contents comprising the diluted K.sub.2CO.sub.3 treatment solution.

49. A method of treating a stainless steel vessel for prevention of stress corrosion cracking, the method comprising: a) incorporating a stainless steel vessel into a system according to claim 23; b) injecting a diluted K.sub.2CO.sub.3 treatment solution into the stainless steel vessel until the stainless steel vessel is filled or substantially filled with the diluted K.sub.2CO.sub.3 treatment solution; c) maintaining the diluted K.sub.2CO.sub.3 treatment solution in the stainless steel vessel for a predetermined period of time; d) removing the diluted K.sub.2CO.sub.3 treatment solution from the stainless steel vessel.

50. The method of claim 49, wherein the diluted K.sub.2CO.sub.3 treatment solution is removed from the stainless steel vessel to a waste vessel.

51. (canceled)

52. The method of claim 49, wherein step c) is performed at a temperature of up to 50? C. and/or the predetermined period of time is at least two hours.

53. The method of claim 49, wherein step b) is performed under an inert atmosphere.

54. The method of claim 49, wherein step c) further comprises measuring the pH of contents within the stainless steel vessel, the contents comprising the diluted K.sub.2CO.sub.3 treatment solution.

55-72. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a schematic illustration of a prior art system for the treatment of a stainless steel vessel for the protection thereof from stress corrosion cracking;

[0036] FIG. 2 is a schematic illustration of a system according to various aspects of the present disclosure the treatment and protection thereof from stress corrosion cracking;

[0037] FIG. 3 is a schematic illustration of another system according to various aspects of the present disclosure for the treatment and protection thereof from stress corrosion cracking;

[0038] FIG. 4 is a flowchart of a method according to various aspects of the present disclosure for the treatment and protection thereof from stress corrosion cracking; and

[0039] FIG. 5 is a flowchart of another method according to various aspects of the present disclosure for the treatment and protection thereof from stress corrosion cracking.

DETAILED DESCRIPTION

[0040] The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the subject matter of the present disclosure, their application, or uses.

[0041] As used throughout, ranges are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. Unless otherwise specified, all percentages and amounts expressed herein and elsewhere in the specification should be understood to refer to percentages by weight.

[0042] For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term about. The use of the term about applies to all numeric values, whether or not explicitly indicated. This term generally refers to a range of numbers that one of ordinary skill in the art would consider as a reasonable amount of deviation to the recited numeric values (i.e., having the equivalent function or result). For example, this term can be construed as including a deviation of ?10 percent, alternatively ?5 percent, alternatively ?1 percent, alternatively ?0.5 percent, and alternatively ?0.1 percent of the given numeric value provided such a deviation does not alter the end function or result of the value. Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present invention.

[0043] It is noted that, as used in this specification and the appended claims, the singular forms a, an, and the, include plural references unless expressly and unequivocally limited to one referent. As used herein, the term include and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items. For example, as used in this specification and the following claims, the terms comprise (as well as forms, derivatives, or variations thereof, such as comprising and comprises), include (as well as forms, derivatives, or variations thereof, such as including and includes) and has (as well as forms, derivatives, or variations thereof, such as having and have) are inclusive (i.e., open-ended) and do not exclude additional elements or steps. Accordingly, these terms are intended to not only cover the recited element(s) or step(s), but may also include other elements or steps not expressly recited. Furthermore, as used herein, the use of the terms a or an when used in conjunction with an element may mean one, but it is also consistent with the meaning of one or more, at least one, and one or more than one. Therefore, an element preceded by a or an does not, without more constraints, preclude the existence of additional identical elements.

[0044] For the purposes of this specification and appended claims, the term coupled refers to the linking or connection of two objects. The coupling can be permanent or reversible. The coupling can be direct or indirect. An indirect coupling includes linking or connecting two objects through one or more intermediary objects. The term substantially, as used herein, is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder.

[0045] In accordance with various aspects of the disclosure, methods for the protection of austenitic stainless steel or austenitic alloy refinery equipment from polythionic acid stress corrosion cracking during shutdown operations are described herein. Methods according to various aspects of the present disclosure allow for the protection of said refinery equipment stress corrosion cracking without the need for application of treatment solutions via closed-loop circulation approaches.

[0046] FIG. 1 is a schematic illustration showing the prior art system 100 for treating stainless steel vessel with a soda ash treatment solution for protection of the vessel from stress corrosion cracking, where the soda ash treatment solution is produced on site. In practice, the soda ash treatment solution cannot be produced off-site due to the limited solubility of soda ash in water (about 212.5 grams/L at 20? C.; or a 17.5 wt % soda ash saturated solution at room temperature), the thousands of gallons of treatment solution required to treat stainless steel vessel, and the continued need to add fresh soda ash to the treatment solution during the treatment process. The system 100 includes a treatment solution storage vessel 110 and a vessel 170 which are coupled with each other in a closed-loop. The vessel 170 contains interior surfaces which may become compromised over time due to polythionic acid stress corrosion cracking. Water is supplied to the vessel 110 from source 120 via conduit 130. Soda ash is supplied to the vessel 110 from a soda ash source 140. The soda ash source 140 is generally a soda ash containment means such as a hopper, bags, drums etc. The soda ash is supplied to the vessel 110 from the soda ash source 140 either in an automated fashion at the control of an operator, or manually by the operator. Soda ash and water are combined in the vessel 110 such that the resulting soda ash treatment solution contains from 1 to 5 wt % soda ash and has a pH greater than 9. The vessel 110 may include further components such as internal or external heating elements and/or means for stirring or agitating the contents of the vessel 110 to aid in preparation of the soda ash treatment solution within the vessel 110, and to promote continued dissolution of the soda ash within the water.

[0047] Once formed, the soda ash treatment solution is transmitted from the vessel 110 to a bottom portion of the contaminated vessel 170 via pump 150 and conduits 160,180. While the contaminated vessel 170 is maintained under an inert atmosphere, the soda ash treatment solution is injected into the vessel 170, filling the vessel 170. Injection of the treatment solution into the contaminated vessel 170 is continued such that the treatment solution exits a top portion of the vessel 170 via conduit 190 and is transmitted back to vessel 110. In this closed-loop arrangement, the treatment solution is vigorously circulated through the vessel 170 for a minimum of two hours. During circulation, the treatment solution is analyzed from time to time to ensure the pH and chloride limits of the solution are maintained. Generally, the treatment solution is analyzed prior to reentry into the vessel 110 and prior to transmission from vessel 110 to the contaminated vessel 170. In most instances, additional soda ash will need to be added to the treatment solution from the soda ash source 140 to maintain the required properties of the treatment solution.

[0048] Unlike the prior art use of soda ash, the present disclosure is directed to the use of K.sub.2CO.sub.3. In accordance with various aspects of the present disclosure, K.sub.2CO.sub.3 treatment solutions are provided as pre-mixed solutions, obviating the need for preparing the treatment solutions on-site in a vessel. Unlike soda ash, which has limited solubility in water under ambient conditions (212.5 g/L), K.sub.2CO.sub.3 has a solubility (1120 g/L at 20? C.) that allows for preparation of incredibly concentrated pre-mixed solutions (up to about 52.8 wt % K.sub.2CO.sub.3 at 20? C.). In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution is a saturated solution. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 100 g and about 1120 g of K.sub.2CO.sub.3 per liter of water. In other instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 200 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 300 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 400 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 500 g and about 1100 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 600 g and about 1080 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 700 g and about 1060 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 800 g and about 1040 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 900 g and about 1020 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 920 g and about 1000 g of K.sub.2CO.sub.3 per liter of water, and alternatively between about 940 g and about 980 g of K.sub.2CO.sub.3 per liter of water. Preferably, the pre-mixed K.sub.2CO.sub.3 treatment solution contains about 49 wt % K.sub.2CO.sub.3.

[0049] In some instances, diluted forms of concentrated pre-mixed K.sub.2CO.sub.3 treatment solutions in accordance with various aspects of the disclose can further be mixed with one or more corrosion inhibitors to decrease the possibility of chloride stress corrosion cracking. When one or more corrosion inhibitors are used, the diluted form of the concentrated pre-mixed K.sub.2CO.sub.3 treatment solution, used as described in the methods below, should contain a sufficient amount of corrosion inhibitor such that when the treatment solution is diluted, as described herein, the diluted solution contains between about 0.1 to about 1 wt %, preferably, about 0.2 to about 0.8 wt %, more preferably from about 0.25 to about 0.6 wt %, even more preferably from about 0.3 to about 0.5 wt %, and even more preferably about 0.4 wt % corrosion inhibitor. In some instances, the one or more corrosion inhibitors can include sodium nitrate.

[0050] FIG. 2 is a schematic illustration showing a system 200 according to various aspects for the treatment and protection of a vessel from stress corrosion cracking, where a K.sub.2CO.sub.3 treatment solution is provided as a pre-mixed solution. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution is a saturated solution. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 100 g and about 1120 g of K.sub.2CO.sub.3 per liter of water. In other instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 200 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 300 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 400 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 500 g and about 1100 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 600 g and about 1080 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 700 g and about 1060 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 800 g and about 1040 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 900 g and about 1020 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 920 g and about 1000 g of K.sub.2CO.sub.3 per liter of water, and alternatively between about 940 g and about 980 g of K.sub.2CO.sub.3 per liter of water. Preferably, the pre-mixed K.sub.2CO.sub.3 solution contains about 49 wt % K.sub.2CO.sub.3. The system 200 generally includes a pre-mixed K.sub.2CO.sub.3 treatment solution storage container 210, a water source 220, a vessel 230, and a waste vessel 240. Water is transmitted from the water source 220 through conduits 255,265 at a controlled rate that is regulated by a water rate control valve 270. The rate at which the water is transmitted through conduit 255 can be monitored using a flow meter 280 that is coupled with conduit 255. The container 210 is coupled with an injection pump 250 via a conduit 215. The type of pump used as the injection pump 250 is not limited to any particular type of pump. The pre-mixed K.sub.2CO.sub.3 treatment solution is pumped through a conduit 225 to an injection rate control valve 260. The injection rate control valve 260 can be acted upon to regulate the amount of concentrated K.sub.2CO.sub.3 treatment solution transmitted to the conduit 265 via a conduit 235. Water and concentrated K.sub.2CO.sub.3 treatment solution mix in the conduit 265, which originates at the intersection of conduit 235 and conduit 255, to form a diluted K.sub.2CO.sub.3 treatment solution. The diluted K.sub.2CO.sub.3 treatment solution is delivered to an inlet (not shown) of the vessel 230 via conduit 265. The diluted K.sub.2CO.sub.3 treatment solution is then pumped into the vessel 230 until the vessel is filled with the diluted K.sub.2CO.sub.3 treatment solution and is allowed to soak for a predetermined period of time. After the predetermined period of time, the used diluted K.sub.2CO.sub.3 treatment solution is transmitted to the waste vessel 240 via a conduit 275, where the conduit 275 is coupled with an outlet (not shown) of the vessel 230 and an inlet (not shown) of the waste vessel 240. In some instances, the outlet of the vessel 230 is located in a lower or bottom portion of the vessel 230 and the outlet is located in an upper or top portion of the vessel 230. In some instances, the outlet of the vessel 230 is located in an upper or top portion of the vessel 230 and the outlet is located in a lower or bottom of the vessel 230.

[0051] In system 200, one or more corrosion inhibitors can be incorporated in the diluted K.sub.2CO.sub.3 treatment solution such that the diluted K.sub.2CO.sub.3 treatment solution contains from about 0.1 to about 1 wt %, preferably from about 0.2 to about 0.8 wt %, more preferably from about 0.25 to about 0.6 wt %, even more preferably from about 0.3 to about 0.5 wt %, and even more preferably about 0.4 wt % corrosion inhibitor. In some instances, the one or more corrosion inhibitors can be added to the water at water source 220. In some instances, the one or more corrosion inhibitors can be added to the diluted K.sub.2CO.sub.3 treatment solution in conduit 265. In some instances, the one or more corrosion inhibitors can be added to the diluted K.sub.2CO.sub.3 treatment solution in the vessel 230.

[0052] FIG. 3 is a schematic illustration showing another system 300 according to various aspects of the present disclosure for the treatment and protection of a vessel from stress corrosion cracking, where a K.sub.2CO.sub.3 treatment solution is provided as a pre-mixed solution. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution is a saturated solution. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 100 g and about 1120 g of K.sub.2CO.sub.3 per liter of water. In other instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 200 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 300 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 400 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 500 g and about 1100 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 600 g and about 1080 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 700 g and about 1060 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 800 g and about 1040 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 900 g and about 1020 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 920 g and about 1000 g of K.sub.2CO.sub.3 per liter of water, and alternatively between about 940 g and about 980 g of K.sub.2CO.sub.3 per liter of water. Preferably, the pre-mixed K.sub.2CO.sub.3 solution contains about 49 wt % K.sub.2CO.sub.3. The system 300 generally includes a pre-mixed K.sub.2CO.sub.3 treatment solution storage container 310, a water source 320, a vessel 330, and a waste vessel 340. Water is transmitted from the water source 320 to an eductor 380 through conduits 335,345 at a controlled rate that is regulated by a water rate control valve 360. The rate at which the water is transmitted through conduit 345 can be monitored using a flow meter 370, which is coupled with the conduit 345. The container 310 is coupled with an injection rate control valve 350 via a conduit 315. A concentrated K.sub.2CO.sub.3 treatment solution is transmitted to the eductor 380 via a conduit 325. Water and pre-mixed K.sub.2CO.sub.3 treatment solution mix in the eductor 380 to form a diluted K.sub.2CO.sub.3 treatment solution. The diluted K.sub.2CO.sub.3 treatment solution is delivered to an inlet (not shown) of the vessel 330 via conduit 365. The diluted K.sub.2CO.sub.3 treatment solution is pumped into the vessel 330 until the vessel is filled with the diluted K.sub.2CO.sub.3 treatment solution and is allowed to soak for a predetermined period of time. After the predetermined period of time, the diluted K.sub.2CO.sub.3 treatment solution is transmitted to the waste vessel 340 via a conduit 375, where the conduit 375 is coupled with an outlet (not shown) of the vessel 330 and an inlet (not shown) of the waste vessel 340. In some instances, the outlet of the petroleum-contaminated vessel 330 is located in a lower or bottom portion of the vessel 330 and the outlet is located in an upper or top portion of the vessel 330. In some instances, the outlet of the vessel 330 is located in an upper or top portion of the vessel 330 and the outlet is located in a lower or bottom of the vessel 330.

[0053] In system 300, one or more corrosion inhibitors can be incorporated in the diluted K.sub.2CO.sub.3 treatment solution such that the diluted K.sub.2CO.sub.3 treatment solution contains from about 0.1 to about 1 wt %, preferably from about 0.2 to about 0.8 wt %, more preferably from about 0.25 to about 0.6 wt %, even more preferably from about 0.3 to about 0.5 wt %, and even more preferably about 0.4 wt % corrosion inhibitor. In some instances, the one or more corrosion inhibitors can be added to the water at water source 320. In some instances, the one or more corrosion inhibitors can be added to the diluted K.sub.2CO.sub.3 treatment solution in conduit 365. In some instances, the one or more corrosion inhibitors can be added to the diluted K.sub.2CO.sub.3 treatment solution in the vessel 330.

[0054] An exemplary method 400 for treating a stainless steel vessel with a K.sub.2CO.sub.3 treatment solution for protection of the vessel from stress corrosion cracking during a shutdown operation using system 200 is shown diagrammatically in FIG. 4, the method 400 can proceed according to the following method steps. As one of ordinary skill in the art may appreciate one or more steps may be omitted, and/or one or more steps may be added, to method 400, and one or more elements from system 200 may be added or omitted, in the ordinary course of treating a stainless steel vessel with a K.sub.2CO.sub.3 treatment solution for protection of the vessel from stress corrosion cracking without departing from the scope of the method. In some instances, the method 400 can begin at step 410.

[0055] In step 410, a stainless steel vessel 230 is incorporated into the system 200 for treating and protecting the vessel 230 from stress corrosion cracking. The vessel is incorporated into the system 200 by coupling a fluid inlet of the vessel 230 with conduit 265, to receive a K.sub.2CO.sub.3 treatment solution therein, and by coupling a fluid outlet of the vessel 230 with conduit 275, to transmit used K.sub.2CO.sub.3 treatment solution from the vessel 230 to the waste vessel 240 after a soaking step discussed below. After step 410 is completed, the method 400 may proceed to step 420.

[0056] In step 420, a K.sub.2CO.sub.3 treatment solution storage container 210 containing a pre-mixed K.sub.2CO.sub.3 solution is coupled with conduit 215 and a water source 220 is coupled with conduit 245. The type of container 210 that is used to store the pre-mixed K.sub.2CO.sub.3 treatment solution is not particularly limiting. Any container that is capable of storing basic (i.e., pH>7) media for extended periods of time is suitable. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution in the storage container 210 is a saturated solution. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 100 g and about 1120 g of K.sub.2CO.sub.3 per liter of water. In other instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 200 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 300 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 400 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 500 g and about 1100 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 600 g and about 1080 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 700 g and about 1060 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 800 g and about 1040 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 900 g and about 1020 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 920 g and about 1000 g of K.sub.2CO.sub.3 per liter of water, and alternatively between about 940 g and about 980 g of K.sub.2CO.sub.3 per liter of water. Preferably, the pre-mixed K.sub.2CO.sub.3 solution contains about 49 wt % K.sub.2CO.sub.3. To minimize the amount pre-mixed K.sub.2CO.sub.3 treatment solution required for any particular treating and protection process and the amount of raw product to be delivered to the vessel site, and to reduce the number of times storage containers 210 may need to be replaced during a single treating and protection process, it is preferred to use pre-mixed K.sub.2CO.sub.3 treatment solutions having concentrations as high as practicable in view of environmental and/or processing considerations, such as surrounding air temperature or extent or type of petroleum contamination within the vessel 230.

[0057] In some instances, step 420 can be performed prior to step 410. In some instances, steps 410 and 420 are performed contemporaneously. After step 420 is completed, the method 400 may proceed to step 430.

[0058] In step 430, a controlled amount of pre-mixed K.sub.2CO.sub.3 treatment solution is transmitted to conduit 265 from the storage container 210 through conduits 215,225,235, pump 250 and injection rate control valve 260. Also in step 430, a controlled amount of water, which is monitored by flow meter 280, is transmitted to conduit 265 from the water source 220 through conduits 245,255 and injection rate control valve 270. The pre-mixed K.sub.2CO.sub.3 treatment solution and water mix in-line in conduit 265 to form a diluted K.sub.2CO.sub.3 treatment solution. The pre-mixed K.sub.2CO.sub.3 treatment solution and water should be transmitted to the conduit 265 in relative amounts such that the resulting diluted K.sub.2CO.sub.3 treatment solution contains about from about 0.1 to about 10 w/w % K.sub.2CO.sub.3, preferably from 0.25 to about 8 w/w % K.sub.2CO.sub.3, more preferably from about 0.5 to about 7 w/w % K.sub.2CO.sub.3, even more preferably from about 0.75 to about 6 w/w % K.sub.2CO.sub.3, and even more preferably from about 1 to about 5 w/w % K.sub.2CO.sub.3. In some instances, a diluted K.sub.2CO.sub.3 treatment solution having about 1 to about 2 w/w % K.sub.2CO.sub.3 is formed. After step 430 is completed, the method 400 may proceed to step 440.

[0059] In step 440, the diluted K.sub.2CO.sub.3 treatment solution is injected into the stainless steel vessel 230 through a fluid inlet of the vessel 230 to which the conduit 265 is coupled. The diluted K.sub.2CO.sub.3 treatment solution is injected into the stainless steel vessel 230 until the vessel 230 is filled or substantially filled with the diluted K.sub.2CO.sub.3 treatment solution. The vessel 230 is filled or substantially filled under an inert atmosphere to minimize oxygen contamination. After step 440 is completed, the method 400 may proceed to step 450.

[0060] In step 450, the diluted K.sub.2CO.sub.3 treatment solution is maintained in the stainless steel vessel 230 for a predetermined amount time to allow penetration of the petroleum contaminants into the treatment solution. In some instances, this soak step is performed at room temperature. In some instances, this soak step is performed at elevated temperatures of up to about 50? C. Generally, the predetermined period of time is at least two hours. During step 450, the pH of the contents of the stainless steel vessel is measured. pH measurements can be performed continuously or incrementally over time. Optionally, other chemical analyses such as petroleum contaminant and/or chloride content, can also be conducted during step 450. After step 450 is completed, the method 400 may proceed to step 460.

[0061] In step 460, the used diluted K.sub.2CO.sub.3 treatment solution exits the vessel 230 via a fluid outlet and is dumped into a waste vessel 240. After dumping is complete, a residual film of K.sub.2CO.sub.3 should remain on the internal surfaces of the vessel 230 throughout downtime periods to ensure continued protection from stress corrosion cracking. After step 460 is completed, the method 400 may proceed to step 470.

[0062] In step 470, depending on the outcome of the pH, and optionally any chemical analyses, undertaken in step 450, steps 410-460 can be repeated one or more time until it is established the vessel 230 no longer contains petroleum contaminants. At the conclusion of step 470, the method 400 ends.

[0063] In some instances, one or more corrosion inhibitors, as described herein, can be added in any one of steps 430-450.

[0064] An exemplary method 500 for treating a stainless steel vessel with a K.sub.2CO.sub.3 treatment solution for protection of the vessel from stress corrosion cracking using system 300 is shown diagrammatically in FIG. 5. The method 500 can proceed according to the following method steps. As one of ordinary skill in the art may appreciate one or more steps may be omitted, and/or one or more steps may be added, to method 500, and one or more elements from system 300 may be added or omitted, in the ordinary course of treating a stainless steel vessel with a K.sub.2CO.sub.3 treatment solution for protection of the vessel from stress corrosion cracking without departing from the scope of the method. In some instances, the method 500 can begin at step 510.

[0065] In step 510, a stainless steel vessel 330 is incorporated into the system 300 for treating and protection of the vessel 330 from stress corrosion cracking. The vessel 330 is incorporated into the system 300 by coupling a fluid inlet of the vessel 300 with conduit 365, to receive K.sub.2CO.sub.3 treatment solution therein, and by coupling a fluid outlet of the vessel 330 with conduit 375, to transmit K.sub.2CO.sub.3 treatment solution from the vessel 330 to the waste vessel 340 after a soaking step discussed below.

[0066] In step 520, a K.sub.2CO.sub.3 treatment solution storage container 310 is coupled with conduit 315 and a water source 320 is coupled with conduit 335. The type of container that is used to store the pre-mixed concentrated K.sub.2CO.sub.3 treatment solution is not particularly limiting. Any container that is capable of storing basic (i.e., pH>7) media is suitable. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution in the storage container 310 is a saturated solution. In some instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 100 g and about 1120 g of K.sub.2CO.sub.3 per liter of water. In other instances, the pre-mixed K.sub.2CO.sub.3 treatment solution comprises between about 200 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 300 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 400 g and about 1120 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 500 g and about 1100 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 600 g and about 1080 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 700 g and about 1060 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 800 g and about 1040 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 900 g and about 1020 g of K.sub.2CO.sub.3 per liter of water, alternatively between about 920 g and about 1000 g of K.sub.2CO.sub.3 per liter of water, and alternatively between about 940 g and about 980 g of K.sub.2CO.sub.3 per liter of water. Preferably, the pre-mixed K.sub.2CO.sub.3 solution contains about 49 wt % K.sub.2CO.sub.3. To minimize the amount K.sub.2CO.sub.3 solution required for any particular treating and protection process and the amount of raw product to be delivered to the petroleum-contaminated vessel site, and to reduce the number of time storage containers 310 may need to be replaced during a single treating and protection process, it is preferred to use K.sub.2CO.sub.3 treatment solution having concentrations as high as practicable in view of environmental and/or processing considerations, such as surrounding air temperature or extent or type of within the vessel 330.

[0067] In some instances, step 520 can be performed prior to step 510. In some instances, steps 510 and 520 are performed contemporaneously. After step 520 is completed, the method 500 may proceed to step 530.

[0068] In step 530, a controlled amount of pre-mixed concentrated K.sub.2CO.sub.3 treatment solution is transmitted to educator 380 from the storage container 310 through conduits 315,325 and injection rate control valve 350. Also in step 530, a controlled amount of water, which is monitored by flow meter 370, is transmitted to educator 380 from the water source 320 through conduits 335,345 and injection rate control valve 360. The pre-mixed K.sub.2CO.sub.3 treatment solution and water mix in educator 380 to form a diluted K.sub.2CO.sub.3 treatment solution which exits the educator 380 through conduit 365. The pre-mixed K.sub.2CO.sub.3 treatment solution and water should be transmitted to the educator 380 in relative amounts such that the resulting diluted K.sub.2CO.sub.3 treatment solution contains about from 0.1 to about 10 w/w % K.sub.2CO.sub.3, preferably from about 0.25 to about 8 w/w % K.sub.2CO.sub.3, more preferably from about 0.5 to about 7 w/w % K.sub.2CO.sub.3, even more preferably from about 0.75 to about 6 w/w % K.sub.2CO.sub.3, and even more preferably from about 1 to about 5 w/w % K.sub.2CO.sub.3. In some instances, a diluted K.sub.2CO.sub.3 treatment solution having about 1 to about 2 w/w % K.sub.2CO.sub.3 is formed. After step 530 is completed, the method 500 may proceed to step 540.

[0069] In step 540, the diluted K.sub.2CO.sub.3 treatment solution is injected into the stainless steel vessel 330 through a fluid inlet of the vessel 330 to which the conduit 365 is coupled. The diluted K.sub.2CO.sub.3 treatment solution is injected into the stainless steel vessel 330 until the vessel 330 is filled or substantially filled with the diluted K.sub.2CO.sub.3 treatment solution. The vessel 330 is filled or substantially filled under an inert atmosphere to minimize oxygen contamination. After step 540 is completed, the method 500 may proceed to step 550.

[0070] In step 550, the diluted K.sub.2CO.sub.3 treatment solution is maintained in the stainless steel vessel 330 for a predetermined amount time to allow penetration of the petroleum contaminants into the treatment solution. In some instances, this soak step is performed at room temperature. In some instances, this soak step is performed at elevated temperatures of up to about 50? C. Generally, the predetermined period of time is at least two hours. During step 550, the pH of the contents of the stainless steel vessel is measured. pH measurements can be performed continuously or incrementally over time. Optionally, other chemical analyses such as petroleum contaminant and/or chloride content, can also be conducted during step 550. After step 550 is completed, the method 500 may proceed to step 560.

[0071] In step 560, the used diluted K.sub.2CO.sub.3 treatment solution, exits the vessel 330 via a fluid outlet and is dumped into a waste vessel 340. After dumping is complete, a residual film of K.sub.2CO.sub.3 should remain on the internal surfaces of the vessel throughout downtime periods to ensure continued protection from stress corrosion cracking. After step 560 is completed, the method 500 may proceed to step 570.

[0072] In step 570, depending on the outcome of the pH, and optionally, chemical analyses, undertaken in step 550, steps 510-560 can be repeated one or more times. At the conclusion of step 580, the method 500 ends.

[0073] In some instances, one or more corrosion inhibitors, as described herein, can be added in any one of steps 530-550.

[0074] Methods according to various aspects of the disclosure exhibit numerous advantages over previous, prior art, processes for protection of austenitic stainless steel or austenitic alloy refinery equipment from polythionic acid stress corrosion cracking during shutdown operations. First, because the use of soda ash requires on-site addition to water and mixing, operators are required to use personal protective equipment, avoid dust formation and breathing of said dust. Soda ash dust is also a known eye irritant. The use of pre-mixed K.sub.2CO.sub.3 solutions according to the present disclosure remove the issues associated with the use of soda ash powder. Also, when preparing soda ash solutions on-site, operators must expend considerable time and effort to accurately add a sufficient amount of the soda ash to a water tank to prepare the required 1-5 wt % soda ash solution having a pH of 9 or greater. When using pre-mixed K.sub.2CO.sub.3 solutions and systems according to the present disclosure, such as systems 200 and 300, in-line mixing of water and the pre-mixed K.sub.2CO.sub.3 solutions facilitates easy preparation of diluted pre-mixed K.sub.2CO.sub.3 solutions prior to placement within a stainless steel vessel. Also, when treating a stainless steel vessel using soda ash solutions in a closed-loop circulation process, operators must periodically measure the pH of soda ash solution exiting the stainless steel vessel to ensure its pH is greater than 9 and, if the pH is not greater than 9, must add fresh soda ash to the solution prior to recirculation to the vessel. When using pre-mixed K.sub.2CO.sub.3 solutions and systems according to the present disclosure, such as systems 200 and 300, on the other hand, the pH of the K.sub.2CO.sub.3 solutions can easily be measured in the vessel to determine whether additional round(s) of soaking with newly diluted K.sub.2CO.sub.3 solutions are required.

[0075] While various aspects of the disclosure are directed to pre-mix K.sub.2CO.sub.3 treatment solutions and related systems within which they are used, as described herein, for treating a stainless steel vessel for prevention of polythionic acid stress corrosion cracking, the disclosure is not limited to such systems and uses.

[0076] In some instances, pre-mix K.sub.2CO.sub.3 treatment solutions (and their methods of use) according to various aspects of the disclosure can be used to treat vessels that are made of materials other than stainless steel, such as other steels or metal alloys, for prevention of stress corrosion cracking that may occur due to the presence of foulants other than or in addition to polythionic acid.

[0077] In some instances, pre-mix K.sub.2CO.sub.3 treatment solutions (and their methods of use) according to various aspects of the disclosure can be used to treat vessels that are made of materials other than stainless steel, such as other steels or metal alloys, in processes for neutralizing the contents (for example acidic compounds) of said vessels.

[0078] In some instances, pre-mix K.sub.2CO.sub.3 treatment solutions (and their methods of use) according to various aspects of the disclosure can be used to treat in modified systems of systems 200 and 330 where the vessel 230 or 330 is a sulfuric acid alkylation unit and the pre-mix K.sub.2CO.sub.3 treatment solutions can be used as described above to neutralize excess and/or unreacted sulfuric acid and/or other acids at various stage of use, remediation and cleaning of said sulfuric acid alkylation unit.

[0079] In some instances, pre-mix K.sub.2CO.sub.3 treatment solutions (and their methods of use) according to various aspects of the disclosure can be used to treat in modified systems of systems 200 and 330 where the vessel 230 or 330 is a catalytic distillation/fractionation unit and the pre-mix K.sub.2CO.sub.3 treatment solutions can be used as described above for catalyst deactivation and/or to neutralize excess and/or unreacted acids at various stage of use, remediation and cleaning of said catalytic distillation unit.

[0080] In some instances, pre-mix K.sub.2CO.sub.3 treatment solutions (and their methods of use) according to various aspects of the disclosure can be used to treat in modified systems of systems 200 and 330 where the vessel 230 or 330 is a catalyst bed and the pre-mix K.sub.2CO.sub.3 treatment solutions can be used as described above for catalyst deactivation and/or to neutralize excess and/or unreacted acids at various stage of use, remediation and cleaning of said catalyst bed, such as during catalyst handling and wet dumping processes.

[0081] In some instances, pre-mix K.sub.2CO.sub.3 treatment solutions (and their methods of use) according to various aspects of the disclosure can be used to treat in modified systems of systems 200 and 330 where the vessel 230 or 330 is any vessel that has been subjected to an acid washing process and the pre-mix K.sub.2CO.sub.3 treatment solutions can be used as described above to neutralize any acid remaining in the vessel after the acid washing process at various stage of use, remediation and cleaning of said acid washed vessel.

[0082] Although the present invention and its objects, features and advantages have been described in detail, other embodiments are encompassed by the invention. All references cited herein are incorporate by reference in their entireties. Finally, those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the scope of the invention as defined by the appended claims.