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

FIELD OF THE INVENTION

The present invention relates to compositions for preventing polythionic acid stress corrosion cracking on 300 series stainless steel and methods of using the same. More specifically, the present invention relates to pre-mixed solutions that can be diluted on-site and used to treat austenitic stainless steel or austenitic alloy for the prevention of stress corrosion cracking.

BACKGROUND OF THE DISCLOSURE

Historically, to prevent polythionic acid stress cracking, operators have treated stainless vessels with soda ash (i.e., sodium carbonate, or Na₂CO₃). In such instances, a large capacity steel tank (for example, a frac tank) of clean water in which hundreds of pounds of dry soda ash is inserted is used. The soda ash and water are mixed in the tank to form a treatment solution. The tank is then placed “upstream” of the stainless vessel in need of treatment.

The treatment solution is then injected into the bottom of the stainless equipment to be treated until full, at which point the solution exits the top of the vessel and is then pumped back into the large capacity tank. This mixture-injection-return circulation process is performed in a closed loop.

Once the treatment solution returns to the large capacity tank, an operator measures the solution for pH. Based on the measured pH, the operator is able to determine whether the treatment process was effective. If the measurement shows a pH level less than 9, the closed-loop circulation application will need to be continued while adding more soda ash to raise the pH level. If the measurement shows greater than 9, and the closed-loop application process can be terminated after a minimum of two hours, the treated tank can be drained, and pumping equipment can be disconnected from the treated tank. The closed-loop circulation approach is dictated by three main realities.

First, perpetual circulation of the treatment solution is necessary. Otherwise, the soda ash will precipitate and a fall out of solution due to the limited solubility of the soda ash within the treatment solution.

Second, NACE international standards require that in the absence of a clean unit and peripheral piping (i.e., if petroleum contaminants, such as deposits of sludge, and fouling are present), the treatment must be performed on a circulatory basis (see, NACE SP0170-2018, Item No. 21002, Approved Date 2018-09-10, ISBN 1-57590-039-4) Specifically, the NACE international standard requires 1) any equipment to be treated should be filled with the soda ash-containing treatment solution under an inert atmosphere to minimize oxygen contamination, 2) the equipment is treated with the treatment solution by vigorous circulation for a minimum of two hours, and 3) circulating treatment solution should be analyzed at appropriate intervals to ensure pH and chloride limits are maintained.

Third, the efficacy of the treatment process can only be ascertained by testing the soda ash-containing treatment solution on a “before” and “after” basis. In other words, the operator needs to measure the pH of the solution before it travels into and through the vessel to be treated as compared to the pH measurement afterward. To obtain that comparative measurement, the operator must circulate within a closed loop. Moreover, this measurement and testing need precludes even the thought of a once-through application.

Based on the above operational realities and requirements, perpetual circulation within a closed-loop has stood as a longstanding and fixed concept for refiners.

SUMMARY OF THE DISCLOSURE

Systems for treating a stainless steel vessel for prevention of polythionic acid stress corrosion cracking according to various aspects of the disclosure comprise a storage container configured to store a pre-mix K₂CO₃treatment 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 K₂CO₃treatment 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 K₂CO₃treatment solution and the water mix in the third conduit to form a diluted K₂CO₃treatment solution, the diluted K₂CO₃treatment solution receivable by the stainless steel vessel via the third conduit. In some instances, the first conduit further comprises an injection pump. In some instances, the first conduit further comprises an injection rate control valve. In some instances, the first conduit further comprises an injection pump and an injection rate control valve. In some instances, the second conduit further comprises a water injection rate control valve. In some instances, the second conduit further comprises a flow meter. In some instances, the second conduit further comprises a water injection rate control valve and a flow meter. In some instances, the storage container is configured to store a pre-mix K₂CO₃treatment solution having a K₂CO₃concentration of between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water. In some instances, the system is configured to prepare a diluted K₂CO₃treatment solution that contains about from 0.1 to about 10 w/w % K₂CO₃, alternatively from about 0.25 to about 8 w/w % K₂CO₃, alternatively from about 0.5 to about 7 w/w % K₂CO₃, alternatively from about 0.75 to about 6 w/w % K₂CO₃, alternatively from about 1 to about 5 w/w % K₂CO₃, and alternatively from about 1 to about 2 w/w % K₂CO₃.

Other systems for treating a stainless steel vessel for prevention of polythionic acid stress corrosion cracking in accordance with various aspects of the disclosure comprise a storage container configured to store a pre-mix K₂CO₃treatment 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 K₂CO₃treatment 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 K₂CO₃treatment solution and the water mix in the eductor to form a diluted K₂CO₃treatment solution, the diluted K₂CO₃treatment solution receivable by the stainless steel vessel from the eductor via the third conduit. In some instances, the first conduit further comprises an injection rate control valve. In some instances, the second conduit further comprises a water injection rate control valve. In some instances, the second conduit further comprises a flow meter. In some instances, the second conduit further comprises a water injection rate control valve and a flow meter. In some instances, the storage container is configured to store a pre-mix K₂CO₃treatment solution having a K₂CO₃concentration of between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water. In some instances, the system is configured to prepare a diluted K₂CO₃treatment solution that contains about from about 0.1 to about 10 w/w % K₂CO₃, alternatively from about 0.25 to about 8 w/w % K₂CO₃, alternatively from about 0.5 to about 7 w/w % K₂CO₃, alternatively from about 0.75 to about 6 w/w % K₂CO₃, alternatively from about 1 to about 5 w/w % K₂CO₃, and alternatively from about 1 to about 2 w/w % K₂CO₃.

Methods of treating a stainless steel vessel for prevention of polythionic acid stress corrosion cracking according to various aspects of the disclosure comprise incorporating a stainless steel vessel into a system according to various aspects of the disclosure; injecting a diluted K₂CO₃treatment solution into the stainless steel vessel until the stainless steel vessel is filled or substantially filled with the diluted K₂CO₃treatment solution; maintaining the diluted K₂CO₃treatment solution in the stainless steel vessel for a predetermined period of time; and removing the diluted K₂CO₃treatment solution from the stainless steel vessel. In some instances, the diluted K₂CO₃treatment solution is removed from the stainless steel vessel to a waste vessel. In some instances, the predetermined period of time is at least two hours. In some instances, maintaining the diluted K₂CO₃treatment solution in the stainless steel vessel for the predetermined period of time is performed at a temperature of up to 50° C. In some instances, injecting the diluted K₂CO₃treatment solution into the stainless steel vessel until the stainless steel vessel is filled or substantially filled with the diluted K₂CO₃treatment solution is performed under an inert atmosphere. In some instances, maintaining the diluted K₂CO₃treatment solution in the stainless steel vessel for the predetermined period of time further comprises measuring the pH of contents within the stainless steel vessel, the contents comprising the diluted K₂CO₃treatment solution.

A first embodiment is the disclosure is a system for treating a stainless steel vessel for prevention of polythionic acid stress corrosion cracking, the system comprising a storage container configured to store a pre-mix K₂CO₃treatment 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 K₂CO₃treatment 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 K₂CO₃treatment solution and the water mix in the third conduit to form a diluted K₂CO₃treatment solution, the diluted K₂CO₃treatment solution receivable by the stainless steel vessel via the third conduit.

A second embodiment of the disclosure is a system according to the first embodiment, wherein the first conduit further comprises an injection pump.

A third embodiment of the disclosure is a system according to the first or second embodiment wherein the first conduit further comprises an injection rate control valve.

A fourth embodiment of the disclosure is a system according to any one of the first through third embodiments, wherein the first conduit further comprises an injection pump and an injection rate control valve.

A fifth embodiment of the disclosure is a system according to any one of the first through fourth embodiments, wherein the second conduit further comprises a water injection rate control valve.

A sixth embodiment of the disclosure is a system according to any one of the first through fifth embodiments, wherein the second conduit further comprises a flow meter.

A seventh embodiment of the disclosure is a system according to any one of the first through sixth embodiments, wherein the second conduit further comprises a water injection rate control valve and a flow meter.

An eighth embodiment of the disclosure is a system according to any one of the first through seventh embodiments, wherein the storage container is configured to store a pre-mix K₂CO₃treatment solution having a K₂CO₃concentration of between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water.

A ninth embodiment of the disclosure is a system according to any one of the first through eighth embodiments, wherein the system is configured to prepare a diluted K₂CO₃treatment solution that contains from about 0.1 to about 10 w/w % K₂CO₃, alternatively from about 0.25 to about 8 w/w % K₂CO₃, alternatively from about 0.5 to about 7 w/w % K₂CO₃, alternatively from about 0.75 to about 6 w/w % K₂CO₃, alternatively from about 1 to about 5 w/w % K₂CO₃, and alternatively from about 1 to about 2 w/w % K₂CO₃.

A tenth embodiment of the disclosure is a system for treating a stainless steel vessel for prevention of polythionic acid stress corrosion cracking, the system comprising a storage container configured to store a pre-mix K₂CO₃treatment 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 K₂CO₃treatment 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 K₂CO₃treatment solution and the water mix in the eductor to form a diluted K₂CO₃treatment solution, the diluted K₂CO₃treatment solution receivable by the stainless steel vessel from the eductor via the third conduit.

An eleventh embodiment of the disclosure is a system according to the tenth embodiment, wherein the first conduit further comprises an injection rate control valve.

A twelfth embodiment of the disclosure is a system according to the tenth or eleventh embodiment, wherein the second conduit further comprises a water injection rate control valve.

A thirteenth embodiment of the disclosure is a system according to any one of the tenth through twelfth embodiments, wherein the second conduit further comprises a flow meter.

A fourteenth embodiment of the disclosure is a system according to any one of the tenth through thirteenth embodiments, wherein the second conduit further comprises a water injection rate control valve and a flow meter.

A fifteenth embodiment of the disclosure is a system according to any one of the tenth through fourteenth embodiments, wherein the storage container is configured to store a pre-mix K₂CO₃treatment solution having a K₂CO₃concentration of between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water.

A sixteenth embodiment of the disclosure is a system according to any one of the tenth through fifteenth embodiments, wherein the system is configured to prepare a diluted K₂CO₃treatment solution that contains from about 0.1 to about 10 w/w % K₂CO₃, alternatively from about 0.25 to about 8 w/w % K₂CO₃, alternatively from about 0.5 to about 7 w/w % K₂CO₃, alternatively from about 0.75 to about 6 w/w % K₂CO₃, alternatively from about 1 to about 5 w/w % K₂CO₃, and alternatively from about 1 to about 2 w/w % K₂CO₃.

A seventeenth embodiment of the disclosure is a method of treating a stainless steel vessel for prevention of polythionic acid stress corrosion cracking, the method comprising: a) incorporating a stainless steel vessel into a system according to any one of the first through sixteenth embodiments; b) injecting a diluted K₂CO₃treatment solution into the stainless steel vessel until the stainless steel vessel is filled or substantially filled with the diluted K₂CO₃treatment solution; c) maintaining the diluted K₂CO₃treatment solution in the stainless steel vessel for a predetermined period of time; d) removing the diluted K₂CO₃treatment solution from the stainless steel vessel.

An eighteenth embodiment of the disclosure is a method according to the seventeenth embodiment, wherein the diluted K₂CO₃treatment solution is removed from the stainless steel vessel to a waste vessel.

A nineteenth embodiment of the disclosure is a method according to the seventeenth or eighteenth embodiment, wherein the predetermined period of time is at least two hours.

A twentieth embodiment of the disclosure is a method according to any one of the seventeenth through nineteenth embodiments, wherein step c) is performed at a temperature of up to 50° C.

A twenty-first embodiment of the disclosure is a method according to any one of the seventeenth through twentieth embodiments, wherein step b) is performed under an inert atmosphere.

A twenty-second embodiment of the disclosure is a method according to any one of the seventeenth through twenty-first embodiments, wherein step c) further comprises measuring the pH of contents within the stainless steel vessel, the contents comprising the diluted K₂CO₃treatment solution.

BRIEF DESCRIPTION OF THE DRAWINGS

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;

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;

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;

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

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

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.

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.

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.

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.

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.

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.

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.

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.

Unlike the prior art use of soda ash, the present disclosure is directed to the use of K₂CO₃. In accordance with various aspects of the present disclosure, K₂CO₃treatment 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), K₂CO₃has a solubility (1120 g/L at 20° C.) that allows for preparation of incredibly concentrated pre-mixed solutions (up to about 52.8 wt % K₂CO₃at 20° C.). In some instances, the pre-mixed K₂CO₃treatment solution is a saturated solution. In some instances, the pre-mixed K₂CO₃treatment solution comprises between about 100 g and about 1120 g of K₂CO₃per liter of water. In other instances, the pre-mixed K₂CO₃treatment solution comprises between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water. Preferably, the pre-mixed K₂CO₃treatment solution contains about 49 wt % K₂CO₃.

In some instances, diluted forms of concentrated pre-mixed K₂CO₃treatment 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 K₂CO₃treatment 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.

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 K₂CO₃treatment solution is provided as a pre-mixed solution. In some instances, the pre-mixed K₂CO₃treatment solution is a saturated solution. In some instances, the pre-mixed K₂CO₃treatment solution comprises between about 100 g and about 1120 g of K₂CO₃per liter of water. In other instances, the pre-mixed K₂CO₃treatment solution comprises between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water. Preferably, the pre-mixed K₂CO₃solution contains about 49 wt % K₂CO₃. The system 200 generally includes a pre-mixed K₂CO₃treatment 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 K₂CO₃treatment 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 K₂CO₃treatment solution transmitted to the conduit 265 via a conduit 235. Water and concentrated K₂CO₃treatment solution mix in the conduit 265, which originates at the intersection of conduit 235 and conduit 255, to form a diluted K₂CO₃treatment solution. The diluted K₂CO₃treatment solution is delivered to an inlet (not shown) of the vessel 230 via conduit 265. The diluted K₂CO₃treatment solution is then pumped into the vessel 230 until the vessel is filled with the diluted K₂CO₃treatment solution and is allowed to soak for a predetermined period of time. After the predetermined period of time, the used diluted K₂CO₃treatment 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.

In system 200, one or more corrosion inhibitors can be incorporated in the diluted K₂CO₃treatment solution such that the diluted K₂CO₃treatment 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 K₂CO₃treatment solution in conduit 265. In some instances, the one or more corrosion inhibitors can be added to the diluted K₂CO₃treatment solution in the vessel 230.

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 K₂CO₃treatment solution is provided as a pre-mixed solution. In some instances, the pre-mixed K₂CO₃treatment solution is a saturated solution. In some instances, the pre-mixed K₂CO₃treatment solution comprises between about 100 g and about 1120 g of K₂CO₃per liter of water. In other instances, the pre-mixed K₂CO₃treatment solution comprises between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water. Preferably, the pre-mixed K₂CO₃solution contains about 49 wt % K₂CO₃. The system 300 generally includes a pre-mixed K₂CO₃treatment 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 K₂CO₃treatment solution is transmitted to the eductor 380 via a conduit 325. Water and pre-mixed K₂CO₃treatment solution mix in the eductor 380 to form a diluted K₂CO₃treatment solution. The diluted K₂CO₃treatment solution is delivered to an inlet (not shown) of the vessel 330 via conduit 365. The diluted K₂CO₃treatment solution is pumped into the vessel 330 until the vessel is filled with the diluted K₂CO₃treatment solution and is allowed to soak for a predetermined period of time. After the predetermined period of time, the diluted K₂CO₃treatment 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.

In system 300, one or more corrosion inhibitors can be incorporated in the diluted K₂CO₃treatment solution such that the diluted K₂CO₃treatment 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 K₂CO₃treatment solution in conduit 365. In some instances, the one or more corrosion inhibitors can be added to the diluted K₂CO₃treatment solution in the vessel 330.

An exemplary method 400 for treating a stainless steel vessel with a K₂CO₃treatment 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 K₂CO₃treatment 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.

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 K₂CO₃treatment solution therein, and by coupling a fluid outlet of the vessel 230 with conduit 275, to transmit used K₂CO₃treatment 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.

In step 420, a K₂CO₃treatment solution storage container 210 containing a pre-mixed K₂CO₃solution 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 K₂CO₃treatment 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 K₂CO₃treatment solution in the storage container 210 is a saturated solution. In some instances, the pre-mixed K₂CO₃treatment solution comprises between about 100 g and about 1120 g of K₂CO₃per liter of water. In other instances, the pre-mixed K₂CO₃treatment solution comprises between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water. Preferably, the pre-mixed K₂CO₃solution contains about 49 wt % K₂CO₃. To minimize the amount pre-mixed K₂CO₃treatment 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 K₂CO₃treatment 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.

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.

In step 430, a controlled amount of pre-mixed K₂CO₃treatment 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 K₂CO₃treatment solution and water mix in-line in conduit 265 to form a diluted K₂CO₃treatment solution. The pre-mixed K₂CO₃treatment solution and water should be transmitted to the conduit 265 in relative amounts such that the resulting diluted K₂CO₃treatment solution contains about from about 0.1 to about 10 w/w % K₂CO₃, preferably from 0.25 to about 8 w/w % K₂CO₃, more preferably from about 0.5 to about 7 w/w % K₂CO₃, even more preferably from about 0.75 to about 6 w/w % K₂CO₃, and even more preferably from about 1 to about 5 w/w % K₂CO₃. In some instances, a diluted K₂CO₃treatment solution having about 1 to about 2 w/w % K₂CO₃is formed. After step 430 is completed, the method 400 may proceed to step 440.

In step 440, the diluted K₂CO₃treatment 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 K₂CO₃treatment solution is injected into the stainless steel vessel 230 until the vessel 230 is filled or substantially filled with the diluted K₂CO₃treatment 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.

In step 450, the diluted K₂CO₃treatment 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.

In step 460, the used diluted K₂CO₃treatment 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 K₂CO₃should 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.

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.

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

An exemplary method 500 for treating a stainless steel vessel with a K₂CO₃treatment 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 K₂CO₃treatment 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.

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 K₂CO₃treatment solution therein, and by coupling a fluid outlet of the vessel 330 with conduit 375, to transmit K₂CO₃treatment solution from the vessel 330 to the waste vessel 340 after a soaking step discussed below.

In step 520, a K₂CO₃treatment 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 K₂CO₃treatment 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 K₂CO₃treatment solution in the storage container 310 is a saturated solution. In some instances, the pre-mixed K₂CO₃treatment solution comprises between about 100 g and about 1120 g of K₂CO₃per liter of water. In other instances, the pre-mixed K₂CO₃treatment solution comprises between about 200 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 300 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 400 g and about 1120 g of K₂CO₃per liter of water, alternatively between about 500 g and about 1100 g of K₂CO₃per liter of water, alternatively between about 600 g and about 1080 g of K₂CO₃per liter of water, alternatively between about 700 g and about 1060 g of K₂CO₃per liter of water, alternatively between about 800 g and about 1040 g of K₂CO₃per liter of water, alternatively between about 900 g and about 1020 g of K₂CO₃per liter of water, alternatively between about 920 g and about 1000 g of K₂CO₃per liter of water, and alternatively between about 940 g and about 980 g of K₂CO₃per liter of water. Preferably, the pre-mixed K₂CO₃solution contains about 49 wt % K₂CO₃. To minimize the amount K₂CO₃solution 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 K₂CO₃treatment 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.

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.

In step 530, a controlled amount of pre-mixed concentrated K₂CO₃treatment 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 K₂CO₃treatment solution and water mix in educator 380 to form a diluted K₂CO₃treatment solution which exits the educator 380 through conduit 365. The pre-mixed K₂CO₃treatment solution and water should be transmitted to the educator 380 in relative amounts such that the resulting diluted K₂CO₃treatment solution contains about from 0.1 to about 10 w/w % K₂CO₃, preferably from about 0.25 to about 8 w/w % K₂CO₃, more preferably from about 0.5 to about 7 w/w % K₂CO₃, even more preferably from about 0.75 to about 6 w/w % K₂CO₃, and even more preferably from about 1 to about 5 w/w % K₂CO₃. In some instances, a diluted K₂CO₃treatment solution having about 1 to about 2 w/w % K₂CO₃is formed. After step 530 is completed, the method 500 may proceed to step 540.

In step 540, the diluted K₂CO₃treatment 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 K₂CO₃treatment solution is injected into the stainless steel vessel 330 until the vessel 330 is filled or substantially filled with the diluted K₂CO₃treatment 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.

In step 550, the diluted K₂CO₃treatment 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.

In step 560, the used diluted K₂CO₃treatment 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 K₂CO₃should 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.

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.

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

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 K₂CO₃solutions 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 K₂CO₃solutions and systems according to the present disclosure, such as systems 200 and 300, in-line mixing of water and the pre-mixed K₂CO₃solutions facilitates easy preparation of diluted pre-mixed K₂CO₃solutions 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 K₂CO₃solutions and systems according to the present disclosure, such as systems 200 and 300, on the other hand, the pH of the K₂CO₃solutions can easily be measured in the vessel to determine whether additional round(s) of soaking with newly diluted K₂CO₃solutions are required.

While various aspects of the disclosure are directed to pre-mix K₂CO₃treatment 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.

In some instances, pre-mix K₂CO₃treatment 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.

In some instances, pre-mix K₂CO₃treatment 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.

In some instances, pre-mix K₂CO₃treatment 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 K₂CO₃treatment 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.

In some instances, pre-mix K₂CO₃treatment 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 K₂CO₃treatment 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.

In some instances, pre-mix K₂CO₃treatment 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 K₂CO₃treatment 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.

In some instances, pre-mix K₂CO₃treatment 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 K₂CO₃treatment 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.

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.

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

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