Methods for minimizing fouling, corrosion and solvent degradation in cryogenic refineries and natural gas processing

Abstract

A method of oxygen scavenging, the method comprising (i) providing an oxygen scavenger composition; and (ii) adding the oxygen scavenger composition to an aqueous feed and / or a hydrocarbon feed in a hydrocarbon processing system.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 62 / 951,076, filed on December 20, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The disclosed technology generally provides oxygen scavenger compositions and methods of oxygen scavenging, and more specifically provides oxygen scavenger compositions and methods of oxygen scavenging to minimize corrosion, fouling and / or chemical degradation in refinery or natural gas processing applications. Background Art

[0004] It is well known that the presence of dissolved oxygen in refineries and natural gas processing can lead to a number of serious adverse effects, including scaling and corrosion. Examples of adverse effects caused by dissolved oxygen are: (1) scaling caused by the polymerization of unstable hydrocarbon compounds, in which oxygen is an initiating or contributing factor; (2) degradation of amines and glycols to organic acids, such as formic acid, acetic acid, oxalic acid, glycolic acid and other degradation products, such as aldehydes and N-bicine; and / or (3) corrosion caused by direct oxygen attack on metal surfaces, or indirectly by the action of organic acids produced by the degradation of amines and glycols and other corrosive compounds (such as thiocyanide, thiosulfate, chlorides, etc.) that enter with the feed to these processes.

[0005] For example, sour water stripping is a refining process where external steam or steam generated by a reboiler is used to remove ammonia and H2S from sour water. The heater, reboiler, and column internals of a phenolic sour water stripper column foul significantly in a short period of time and must be removed from the line for cleaning. The primary cause of organic fouling in such a process is the polymerization of phenols triggered by dissolved oxygen in the sour water feed and accelerated by corrosion products and higher temperatures.

[0006] Acidic hydrocarbon liquids and gases are processed in amine processing plants, which, depending on the specific application, primarily remove hydrogen sulfide, carbon dioxide, carbonyl sulfide, and carbon disulfide. Such applications include, but are not limited to, refineries, natural gas plants, natural gas liquids (NGL) plants, coal gasification plants, ammonia plants, and hydrogen production.

[0007] Similar to the sour water stripper, when unstable hydrocarbons (e.g., olefins) are present in the feed to the gas / liquid and liquid / liquid amine absorbers, dissolved oxygen triggers the fouling mechanism. The formed polymers accumulate in the bottoms and trays of the amine contactors, foul the lean / rich exchangers, and find their way to the amine regenerators. Excessive fouling reduces processing capacity, may result in amine losses due to carryover, and may force the refinery or gas facility to reduce production capacity, ultimately resulting in both expensive and time-consuming online and offline cleaning operations.

[0008] In addition, similar to amine gas processing equipment, the dissolved oxygen entering the glycol dehydration unit tends to decompose the circulating glycol-based dehydrating agent (mainly triethylene glycol), which leads to the formation of organic acids such as formic acid, acetic acid, oxalic acid and glycolic acid. These acids reduce the pH of the glycols, thereby accelerating the corrosion rate. The dissolved oxygen also triggers the polymerization of unstable gaseous components, which is very similar to the situation of the acidic water stripper. The combination of corrosion products and polymers ultimately leads to reduced productivity, excessive glycol losses due to entrainment, and related downstream problems. The glycol dehydration unit is very similar to the amine processing unit in that the glycol absorbs water in the contactor and releases water in the regenerator by applying heat at a lower pressure.

[0009] Oxygen scavengers have long been used in boiler water and steam systems to inhibit corrosion. Recognizing the effective use of oxygen scavengers in boiler water systems, various oxygen scavengers have been applied to amine gas processing equipment to inhibit corrosion. However, oxygen scavengers are rarely used in sour water strippers and are almost never used in glycol dehydration units to reduce the potential for corrosion.

[0010]

[0006] Therefore, there is a need in the art for methods for minimizing corrosion, fouling, and / or chemical degradation due to oxygen in refinery or natural gas processing applications. Summary of the invention

[0011] The disclosed technology generally provides oxygen scavenger compositions and methods of oxygen scavenging, and more specifically provides oxygen scavenger compositions and methods of oxygen scavenging to minimize corrosion, fouling and / or chemical degradation in refinery or natural gas processing applications.

[0012] In one aspect of the disclosed technology, a method of oxygen scavenging includes: (i) providing an oxygen scavenger composition; and (ii) adding the oxygen scavenger composition to an aqueous feed and / or a hydrocarbon feed to a hydrocarbon processing system.

[0013] In some embodiments, the oxygen scavenger composition comprises a hydroxyalkylhydroxylamine and a catalyst. In some embodiments, the hydroxyalkylhydroxylamine is N,N-bis(2-hydroxypropyl)hydroxylamine (HPHA). In some embodiments, the oxygen scavenger composition is a blend.

[0014] In some embodiments, the catalyst is a quinone catalyst. In some embodiments, the quinone catalyst is hydroquinone, benzoquinone, or a blend thereof. In some embodiments, the hydroxyalkylhydroxylamine is N,N-bis(2-hydroxypropyl)hydroxylamine (HPHA), and the catalyst is hydroquinone. In some embodiments, the oxygen scavenger composition further comprises N,N-bis(2-hydroxyethyl)hydroxylamine (HEHA), N,N-bis(2-hydroxybutyl)-hydroxylamine (HBHA) and / or diethylhydroxylamine (DEHA). In some embodiments, the ratio of N,N-bis(2-hydroxypropyl)hydroxylamine (HPHA) to hydroquinone is from about 0.0001:100 to about 100:0.0001.

[0015] In some embodiments, the oxygen scavenger composition is added to the aqueous and / or hydrocarbon feed in an amount of 0.0001 ppm to about 50,000 ppm. In some embodiments, the aqueous and / or hydrocarbon feed contains dissolved oxygen in the range of about 0.0001 ppm to about 50,000 ppm.

[0016] In some embodiments, the aqueous feed comprises hydrocarbons, hydrogen sulfide, carbon dioxide, organic acids, phenols, dissolved minerals, alkanolamines, glycols, and / or oxygen. In some embodiments, the hydrocarbon feed is an acid gas or liquid stream or a blend thereof.

[0017] In some embodiments, the hydrocarbon processing system is a refinery, a natural gas processing system, a coal gasification plant, or an ammonia plant. In some embodiments, the aqueous and / or hydrocarbon processing system comprises a sour water stripper, a glycol dehydration unit, or a hydrocarbon gas processing unit.

[0018] In some embodiments, the hydrocarbon processing system operates at a temperature range of about 40° F. to about 500° F. In some embodiments, the temperature range is less than 300° F. DETAILED DESCRIPTION

[0019] The disclosed technology generally provides oxygen scavenger compositions and methods of oxygen scavenging, and more specifically, provides oxygen scavenger compositions and methods of oxygen scavenging to minimize corrosion, fouling and / or chemical degradation in refinery or natural gas processing applications. The present technology can be used in applications such as, but not limited to, 1) amine processing, in both upstream and downstream applications in refineries and gas plants, or other applications such as coal gasification, ammonia plants, hydrogen production, etc.; 2) glycol dehydration in upstream and midstream applications; 3) sour water strippers; and / or 4) feed / effluent exchangers in desalters, hydrotreaters, and other refinery applications where oxygen alone or in combination with other compounds is suspected of participating in the fouling mechanism may be beneficial.

[0020] The present technology minimizes the severe adverse effects caused by dissolved oxygen entering a sour water stripper, a gas sweetening process using alkanolamines, and / or a glycol dehydration unit by using catalytic hydroxyalkylhydroxylamines as low temperature oxygen scavengers. The disclosed scavenger compositions and methods exhibit faster reaction rates (i.e., improved kinetics) with oxygen than other types of catalytic hydroxyalkylhydroxylamines (e.g., DEHA / HQ) currently in use. Due to such improved kinetics, dissolved oxygen will be consumed before it can cause the deleterious effects of scaling, corrosion, and solvent degradation in refinery or natural gas processing applications. In addition, the faster reaction rate will ensure that a more uniform magnetite protective layer is formed on the equipment.

[0021] In addition, the present technology provides protection from the formation of polymers (or oxygen triggered polymerization), which leads to fouling deposits in equipment and on heat transfer surfaces. Such protection will be more complete than with other conventional technologies, as it is believed that the oxygen will be completely consumed before the process reaches higher temperatures and the fouling rate accelerates rapidly. Therefore, the fouling tendency in refinery or natural gas processing applications will be significantly reduced because by having a system that is uniformly protected from corrosion, the flux of corrosion products (which act as polymerization catalysts) will be significantly reduced.

[0022] In one aspect of the disclosed technology, a method of oxygen scavenging is provided. The method comprises (i) providing an oxygen scavenger composition; and (ii) adding the oxygen scavenger composition to an aqueous feed and / or a hydrocarbon feed of a hydrocarbon processing system.

[0023] In one embodiment, the oxygen scavenger composition comprises a hydroxyalkylhydroxylamine and a catalyst. The oxygen scavenger composition will form a corrosion-resistant magnetite layer because it is believed that the catalyzed hydroxyalkylhydroxylamine (e.g., HPHA) reacts faster with oxygen and therefore reacts faster with metal oxides present in the system, converting non-protective hematite to magnetite. Due to the corrosion-resistant magnetite layer, corrosion products will be minimized. The oxygen scavenger composition as disclosed herein provides less available dissolved oxygen and corrosion products present in applications such as, but not limited to, sour water stripping, amine treatment, and / or glycol dehydration applications.

[0024] In some embodiments, the oxygen scavenger composition is a blend. In some embodiments, the hydroxyalkylhydroxylamine is N,N-bis(2-hydroxypropyl)hydroxylamine (HPHA). It is believed that because HPHA is a highly branched molecule (i.e., more than DEHA and others), the disclosed oxygen scavengers may react faster and more efficiently with dissolved oxygen.

[0025] In some embodiments, the catalyst is a quinone catalyst. In some embodiments, wherein the quinone catalyst is hydroquinone, benzoquinone, or a blend thereof. In some embodiments, the hydroxyalkylhydroxylamine is N,N-bis(2-hydroxypropyl)hydroxylamine (HPHA), and the catalyst is hydroquinone.

[0026] In some embodiments, the oxygen scavenger composition further comprises N,N-bis(2-hydroxyethyl)hydroxylamine (HEHA), N,N-bis(2-hydroxybutyl)-hydroxylamine (HBHA), and / or diethylhydroxylamine (DEHA).

[0027] In some embodiments, the ratio of N,N-bis(2-hydroxypropyl)hydroxylamine (HPHA) to hydroquinone is from about 0.0001:100 to about 100:0.0001, in other embodiments, from about 50:0.0001 to about 0.0001:100, and in other embodiments, from about 20:3 to about 30:3.

[0028] The method further provides adding the oxygen scavenger composition to an aqueous feed and / or a hydrocarbon feed in a hydrocarbon processing system. It should be understood that hydrocarbon processing systems include, but are not limited to, refineries, natural gas processing systems (including upstream and / or midstream applications), coal gasification plants, ammonia plants, and the like.

[0029] In some embodiments, the oxygen scavenger composition is added to the aqueous and / or hydrocarbon feed in an amount of 0.0001 ppm to about 50,000 ppm (in other embodiments, in an amount of 1 ppm to about 10,000 ppm, and in other embodiments, in an amount of about 1 ppm to about 100 ppm). It should be understood that the oxygen scavenger composition can be added to one or more aqueous and / or hydrocarbon feeds by most any conventional chemical addition means. In some embodiments, the chemical addition and / or injection system comprises an injection quill of a material and design suitable for the particular application.

[0030] In some embodiments, the aqueous and / or hydrocarbon feed comprises dissolved oxygen in the range of about 0.0001 ppm to about 50,000 ppm. In some embodiments, the aqueous feed comprises hydrocarbons, hydrogen sulfide, carbon dioxide, organic acids, phenols, dissolved minerals, alkanolamines, glycols, and / or oxygen. In some embodiments, the hydrocarbon feed is an acidic gas or liquid stream or a blend thereof.

[0031] In some embodiments, the aqueous and / or hydrocarbon processing system comprises a sour water stripper, a glycol dehydration unit, or a hydrocarbon gas processing unit.

[0032] The disclosed oxygen scavenger compositions and methods minimize scaling, corrosion, and solvent degradation in cryogenic applications. By utilizing the disclosed oxygen scavenger compositions in cryogenic environments, the degradation rates of amines and diols are greatly reduced by effectively removing dissolved oxygen at the low temperature end of these processes. Such removal is due to the faster reaction rate of the disclosed oxygen scavenger compositions with oxygen compared to other conventional technologies, which prevents oxygen from complexing with the amines and diols when they come into contact with each other.

[0033] In some embodiments, the hydrocarbon processing system operates at a temperature range of about 40° F. to about 500° F. In some embodiments, the temperature range is less than 300° F.

[0034] In the foregoing description, the invention has been described with reference to specific embodiments of the invention. Although embodiments of the disclosed technology have been described, it should be understood that the disclosure is not limited thereto and may be modified without departing from the disclosed technology. The scope of the disclosed technology is defined by the appended claims, and all devices, processes and methods within the meaning of the claims, whether literally or by equivalents, are intended to be encompassed therein.

Claims

1. A method for oxygen scavenging, the method comprising: (i) providing an oxygen scavenger composition, wherein the oxygen scavenger composition comprises a hydroxyalkylhydroxylamine and a catalyst; and (ii) adding the oxygen scavenger composition to an aqueous feed and / or a hydrocarbon feed in a hydrocarbon processing system, wherein the hydroxyalkylhydroxylamine is N,N-bis(2-hydroxypropyl)hydroxylamine, and the catalyst is hydroquinone; wherein the ratio of N,N-bis(2-hydroxypropyl)hydroxylamine to hydroquinone is 20:3 to 30:3; wherein the aqueous feed comprises hydrocarbons and dissolved oxygen; and wherein the hydrocarbon feed comprises dissolved oxygen.

2. The method of claim 1, wherein the oxygen scavenger composition is a blend.

3. The method of claim 1, wherein the oxygen scavenger composition further comprises N,N-bis(2-hydroxyethyl)hydroxylamine, N,N-bis(2-hydroxybutyl)-hydroxylamine and / or diethylhydroxylamine.

4. The method of claim 1, wherein the oxygen scavenger composition is added to the aqueous and / or hydrocarbon feed in an amount of 0.0001 ppm to 50,000 ppm.

5. The process of claim 1, wherein the aqueous and / or hydrocarbon feed comprises dissolved oxygen in the range of 0.0001 ppm to 50,000 ppm.

6. The method of claim 1, wherein the aqueous feed further comprises at least one of hydrogen sulfide, carbon dioxide, organic acids, phenols, dissolved minerals, alkanolamines, and glycols.

7. The process of claim 1, wherein the hydrocarbon feed is a sour gas or liquid stream or a blend thereof.

8. The method of claim 1, wherein the hydrocarbon processing system is a refinery, a natural gas processing system, a coal gasification plant, or an ammonia plant.

9. The method of claim 1, wherein the aqueous and / or hydrocarbon processing system comprises a sour water stripper, a glycol dehydration unit, or a hydrocarbon gas processing unit.

10. The method of claim 1 wherein the hydrocarbon processing system operates at a temperature range of 40°F to 500°F.

11. The method of claim 10 wherein the temperature range is less than 300°F.