1. A system (100) for treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃), comprising: a) sour water inlet (102) connected to a first column (106) via a flash drum (104) to pass sour water; b) pre-heated sour water inlet (102-1) is connected from the flash drum (104) via a heat exchanger to provide preheated sour water into the first column (106); c) the first column (106) is connected to the flash drum (104) via the heat exchanger on one side, and is connected to the pre-heated sour water inlet (102-1) to receive preheated sour water on another side, wherein the first column includes an upper portion (106-1) and lower portion (106-2); d) an outlet (108) for H2S removal upon stripping from the upper portion of the first column (106-1); e) a second column (110) fluidly connected to the bottom of the first column (106-2) to receive NH₃-rich liquid feed via a feed preheater (112); f) a reboiler (114) is connected to the second column (110) to generate vapours of steam, remaining H2S, and ammonia contained in the preheated ammonia rich liquid feed; g) an absorber section (116) is connected to the upper portion (110-1) of the second column to receive NH₃-rich gas from the second column (110) to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106); and h) a caustic treater (117) fluidly connected to the absorber section (116) on one side, and inlet of caustic material (117-1) on another side to remove trace H₂S by treating the caustic material with the NH₃ stream in the caustic treater, producing clean NH₃.

2. The system (100) as claimed in claim 1, wherein the lower portion (106-2) comprises a plurality of trays (106-3) for stripping H₂S and an external reflux system using stripped water; and the top portion (106-1) comprises a vertical exchanger heater (106-5) and condenser (106-4) to condense ammonia (NH₃) and water from the treated preheated sour water.

3. The system (100) as claimed in claim 1, wherein the second column (110) includes an upper portion (110-1), lower portion (110-2), trays (110-3), and at least two pump(s) (110-4, 110-5).

4. The system (100) as claimed in claims 1 and 3, wherein the at least one portion of the preheated ammonia rich liquid feed is routed through trays (110-3) from the bottom of the second column (110-2) for NH3 stripping; and the at least two pump(s) (110-4, 110-5) connected to the second column (110) are selected from a high-temperature pump (110-4) and a top pump (110-5).

5. The system (100) as claimed in claims 1 and 4, wherein the high-temperature pump (110-4) is connected at the lower portion (110-2) of the second column (110) for heat recovery to preheat the feed; and the top pump (110-5) is connected to the upper portion (110-1) of the second column (110) to maintain a temperature in the range of 80 to 100°C in order to prevent salt desublimation.

6. The system (100) as claimed in any of claims 1 to 5, wherein a portion of NH₃-rich liquid from the first column (106) or the stripped water from second column (110) is passed and connected to the absorber section (116) to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106).

7. The system (100) as claimed in any of claims 1 to 6, wherein the lower portion of the first column (106-2) includes trays (106-3) to ensure maximum removal of H2S gases; and a vertical exchanger of the vertical exchanger heater (106-5) and condenser (106-4) system in the first column (106) reheats H₂S vapor above its dew point to prevent corrosion.

8. The system (100) as claimed in any of claims 1 to 7, wherein the stripped water from the second column (110) is partially recycled as external reflux to the first column (106) to minimize NH₃ slippage.

9. A method of treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃), comprising: a) passing a sour water through inlet (102) connected to a first column (106) via a flash drum (104); b) pre-heating the sour water (102-1) by passing the sour water from the flash drum (104) via a heat exchanger; c) passing the preheated sour water into the first column (106) in order to strip the H2S at upper portion of the first column (106-2) to obtain stripped H2S and ammonia rich feed and water; d) removing the stripped H2S from outlet (108) from the upper portion of the first column (106-1); e) passing and treating the ammonia rich feed water into second column (110) fluidly connected to the bottom of the first column (106-2) via a feed preheater (112) to heat the ammonia rich feed; f) generating vapours of steam, remaining H2S, and ammonia contained in the preheated ammonia rich liquid feed using a reboiler (114) connected to the second column (110); g) passing NH₃-rich gas from the second column (110) into absorber section (116) connected to the upper portion (110-1) of the second column to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106); and h) removing trace H₂S by treating the NH₃ rich stream with caustic material in caustic treater (117) fluidly connected to the absorber column (116) on one side, and inlet of caustic material (117-1) on another side, to obtain clean NH₃.

10. The method as claimed in claim 9, wherein the method overall operates at a pressure in the range of 0.5–2 kg/cm²g, and at a low-pressure steam at temperature in the range of 125–130°C.

Description:FIELD OF THE PRESENT DISCLOSURE
[0001] The present disclosure generally relates but not limited to the petrochemical and refinery industry. Preferably, the present disclosure relates to system and method for separation and recovery of hydrogen sulfide (H2S) and ammonia (NH3) from sour water generated in refinery processing.

BACKGROUND OF THE PRESENT DISCLOSURE
[0002] Sour water is an inevitable byproduct generated in diverse industrial processes, for example, within refineries equipped with primary and secondary processing facilities. Its composition primarily comprises hydrogen sulfide (H₂S) and ammonia (NH₃), accompanied by traces of cyanides, phenols, and hydrocarbons. The specific concentrations of these components vary based on the source of water generation. For instance, the water derived from separators in the reaction section of the hydrocracker unit (HCU) may exhibit high concentrations of H₂S (20,000–50,000 ppmw) and NH₃ (15,000–25,000 ppmw). In contrast, water from the atmospheric distillation column reflux drum contains lower concentrations, with H₂S at 300–500 ppmw and NH₃ at approximately 100–150 ppmw. The key sources include reflux drums of atmospheric distillation columns in Crude Distillation Units (CDUs), hot wells in Vacuum Distillation Units (VDUs), reflux drums of fractionators in Vis-breaker Units (VBUs), Fluid Catalytic Cracking Units (FCCUs), Delayed Coker Units (DCUs), strippers in Naphtha Hydro-Desulfurization Units (NHDS) or Naphtha Hydro-treaters (NHT), and separators in Hydrocracker Units (HCUs) and Diesel Hydro-Desulfurization Units (DHDS) or Diesel Hydro-treaters (DHT).
[0003] The necessity to treat sour water arises from its potential environmental impact. Regulatory compliance demands the removal of H₂S and NH₃ before final treatment in Effluent Treatment Plants (ETPs) or reuse in process units, with typical specifications set at ≤10 ppmw for both contaminants, though some standards allow ≤50 ppmw or ≤25 ppmw NH₃ and ≤10 ppmw H₂S. Untreated sour water poses risks such as toxicity to aquatic ecosystems, corrosion in downstream equipment, and air pollution from volatile emissions.
[0004] Conventional treatment method employs either steam-reboiled, refluxed stripping columns, configured as single-stage or two-stage systems (refer, FIG. 2A and 2B). In a single-stage stripper, sour water is preheated via heat exchange with stripped water bottoms and fed to a low-pressure column (0.7–0.9 kg/cm²g) with trays for stripping and for heat transfer. The reboiler, heated by low-pressure (LP) steam, maintains a temperature of 125 °C, volatilizing H₂S and NH₃ into the overhead vapor. This vapor is cooled to ~90°C using pump-around reflux or condensers, producing a mixed acid gas stream sent to a Sulfur Recovery Unit (SRU). Stripped water, meeting the required specifications, is recycled or directed to ETP. This design is energy-efficient due to LP steam use but cannot separate H₂S and NH₃, resulting in operational challenges in the SRU where NH₃ concentrations (>5 wt%) cause catalyst poisoning, salt deposition (e.g., ammonium bisulfide), and reduced sulfur recovery efficiency.
[0005] For NH3 richer sour water streams (e.g., from HCUs), a two-stage configuration is employed. The first column operates at a higher pressure (~8 kg/cm²a) to preferentially strip H₂S while retaining NH₃ in the liquid phase, using medium-pressure (MP) steam in the reboiler. This column typically features stripping trays and wash trays, with overhead H₂S-rich gas (low NH₃ slippage) routed to the SRU. The bottoms liquid, enriched with NH₃, is depressurized and fed to a low-pressure second column for NH₃ stripping, producing NH₃-rich vapor for incineration (often with SRU tail gas) and stripped water for reuse or ETP.
[0006] Alternate technologies, such as flue gas or fuel gas stripping, use non-condensable gases instead of steam, potentially reducing energy but introducing inefficiencies like lower stripping factors and higher compression needs. Caustic injection for pH control or pre-concentrators for dilute feeds are also options, though they add complexity and cost.
[0007] Despite their effectiveness, conventional systems face significant challenges. Fouling remains a significant challenge, as contaminants such as hydrocarbons, phenols, cyanides, and ammonium salts accumulate on trays, reboilers, and heat exchangers, particularly under elevated temperatures, thereby diminishing mass transfer efficiency and necessitating frequent maintenance to mitigate buildup. Corrosion is exacerbated by the combined effects of the H₂S/NH₃ mixture and high-temperature conditions, leading to pitting, stress cracking, and material degradation, which requires the use of corrosion-resistant alloys such as 316L stainless steel, consequently elevating capital costs. In single-stage systems, the inability to separate H₂S and NH₃ results in SRU operational choking, while two-stage systems demand high energy due to MP steam and elevated pressures, raising both operational (OpEx) and capital expenditures (CapEx).
[0008] Thermodynamic inefficiencies from pressure differentials and stream remixing further elevate steam usage, contributing to greenhouse gas emissions. Variable feed compositions challenge consistent stripped water quality, with pH swings. Further, in a conventional two-stage sour water stripper system, producing near-pure NH₃ and H₂S necessitates a greater number of unit operations, including separate high-pressure and low-pressure columns, pre-treatment units, and auxiliary purification equipment. This configuration increases operational complexity, elevates resource demands, and results in higher energy consumption due to the use of medium-pressure steam and elevated operating pressures.
[0009] Therefore, there is a need in the art to arrive at the an energy-efficient and environmentally sustainable system and method for the separation and purification of hydrogen sulfide (H₂S) and ammonia (NH₃), operating at low pressure with LP steam, achieving higher purity of H₂S and NH₃, and reducing energy use by 20–40%, thus addressing the shortcomings of traditionally known apparatuses and methods including as discussed above.

OBJECTS OF THE PRESENT DISCLOSURE
[0010] Some of the objects of the present disclosure, which at least one embodiment herein satisfies are as listed herein below.
[0011] An object of the present disclosure is to provide system for the separation and purification of hydrogen sulfide (H₂S) and ammonia (NH₃).
[0012] Another object of the present disclosure is to provide a method for the separation and purification of hydrogen sulfide (H₂S) and ammonia (NH₃).
[0013] Yet another object of the present disclosure is to provide system and method for the separation and purification of hydrogen sulfide (H₂S) and ammonia (NH₃) from sour water obtained in refinery processing.

SUMMARY OF THE PRESENT DISCLOSURE
[0014] This summary is provided to introduce a selection of concepts in a simplified form that is further described below in the detailed description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0015] An aspect of the present disclosure is to provide a system (100) for treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃), comprising:
a) sour water inlet (102) connected to a first column (106) via a flash drum (104) to pass sour water;
b) pre-heated sour water inlet (102-1) is connected from the flash drum (104) via a heat exchanger to provide preheated sour water into the first column (106);
c) the first column (106) is connected to the flash drum (104) via the heat exchanger on one side, and is connected to the pre-heated sour water inlet (102-1) to receive preheated sour water on another side, wherein the first column includes an upper portion (106-1) and lower portion (106-2);
d) an outlet (108) for H2S removal upon stripping from the upper portion of the first column (106-1);
e) a second column (110) fluidly connected to the bottom of the first column (106-2) to receive NH₃-rich liquid feed via a feed preheater (112);
f) a reboiler (114) is connected to the second column (110) to generate vapours of remaining H2S, and ammonia contained in the preheated ammonia rich liquid feed;
g) an absorber section (116) is connected to the upper portion (110-1) of the second column to receive NH₃-rich gas from the second column (110) to absorb residual H₂S using ammonia rich liquid or stripped water, and recirculating H₂S-rich liquid back to the first column (106); and
h) a caustic treater (117) fluidly connected to the absorber section (116) on one side, and inlet of caustic material (117-1) on another side to remove trace H₂S by treating the caustic material with the NH₃ stream in the caustic treater (117), producing clean NH₃.
[0016] In some embodiments, a portion of the vapours generated from the reboiler (114) is sent to the first column bottom section (106-2) as a vapor source for stripping.
[0017] In some embodiments, the lower portion (106-2) comprises a plurality of trays (106-3) for stripping H₂S and an external reflux system using stripped water.
[0018] In some embodiments, the top portion comprises a vertical exchanger and condenser system (106-4 & 106-5) to condense ammonia (NH₃) and water from the treated preheated sour water.
[0019] In some embodiments, a reheater (106-5) is connected above to a condenser (106-4) to heat the gas above its dew point.
[0020] In some embodiments, the second column includes an upper portion (110-1) and lower portion (110-2)
[0021] In another aspect, the present disclosure provides a method of treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃), comprising:
a) passing a sour water through inlet (102) connected to a first column (106) via a flash drum (104);
b) pre-heating the sour water (102-1) by passing the sour water from the flash drum (104) via a heat exchanger;
c) passing the preheated sour water into the first column (106) in order to strip the H2S at upper portion of the first column (106-2) to obtain stripped H2S and ammonia rich feed water;
d) removing the stripped H2S from outlet (108) from the upper portion of the first column (106-1);
e) passing and treating the ammonia rich feed water into second column (110) fluidly connected to the bottom of the first column (106-2) via a feed preheater (112) to heat the ammonia rich feed;
f) generating vapours of remaining H2S, and ammonia contained in the preheated ammonia rich liquid feed using a reboiler (114) connected to the second column (110);
g) passing NH₃-rich gas from the second column (110) into absorber column (116) connected to the upper portion (110-1) of the second column to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106); and
h) removing trace H₂S by treating the NH₃ rich stream with caustic material in caustic treater (117) fluidly connected to the absorber section (116) on one side, and inlet of caustic material (117-1) on another side, to obtain clean NH₃.

BRIEF DESCRIPTION OF ACCOMAPANYING DRAWINGS:
[0022] FIG. 1 shows the representative line drawing of the system (100) as disclosed in the present disclosure.
[0023] FIG. 2A shows representative line drawing of the conventionally known single-stage sour water stripper configuration.
[0024] FIG. 2B shows representative line drawing of the conventionally known two-stage sour water stripper configuration.

DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE
[0025] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.
[0026] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0027] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0028] In some embodiments, numbers have been used for quantifying weight percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0029] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0030] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0031] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.
[0032] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.
[0033] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0034] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0035] The term “dew point of H2S” refers to a temperature at which it condenses from gas to liquid, which depends heavily on pressure. At atmospheric pressure (1 atm), the dew point/boiling point of H2S is -59.55 ℃.
[0036] The term “LP steam” refers to low-pressure (LP) steam, where the steam is produced at pressures up to 15 psi (or roughly 3.5–4.5 bar in industrial settings), commonly used for heating, sterilization, and light processing.
[0037] The term “CapEx/OpEx” refers to CapEx (Capital Expenditure) involving major investments in physical assets like building units, upgrading infrastructure, or purchasing machinery to increase capacity and long-term value, which are depreciated over time, and the OpEx (Operating Expenditure) refers to day-to-day costs such as crude oil, catalysts, labor, maintenance, and utilities, which are expensed immediately.
[0038] In general embodiments, the present disclosure addresses the challenges inherent in conventional sour water treatment (covered in FIG. 2A and 2B) by introducing a multi-column configuration (106, 110) that optimizes resource utilization, enhances operational flexibility, and ensures compliance with stringent environmental regulations. It is submitted that the system and method of the present disclosure can be applicable across diverse refinery units such as Crude Distillation Units (CDUs), Hydrocracker Units (HCUs), and Diesel Hydro-Desulfurization Units (DHDS). Also, the system and method of the present disclosure is designed to handle sour water streams with varying compositions, from lean sources (e.g., 300–500 ppmw H₂S, 100–150 ppmw NH₃) to rich streams (e.g., 20,000–50,000 ppmw H₂S, 15,000–25,000 ppmw NH₃).
[0039] An embodiment of the present disclosure is to provide a system (100) for treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃), comprising:
a) sour water inlet (102) connected to a first column (106) via a flash drum (104) to pass sour water;
b) pre-heated sour water inlet (102-1) is connected from the flash drum (104) via a heat exchanger to provide preheated sour water into the first column (106);
c) the first column (106) is connected to the flash drum (104) via the heat exchanger on one side, and is connected to the pre-heated sour water inlet (102-1) to receive preheated sour water on another side, wherein the first column includes an upper portion (106-1) and lower portion (106-2);
d) an outlet (108) for H2S removal upon stripping from the upper portion of the first column (106-1);
e) a second column (110) fluidly connected to the bottom of the first column (106-2) to receive NH₃-rich liquid feed via a feed preheater (112);
f) a reboiler (114) is connected to the second column (110) to generate vapours of steam, remaining H2S, and ammonia contained in the preheated ammonia rich liquid feed;
g) an absorber section (116) is connected to the upper portion (110-1) of the second column to receive NH₃-rich gas from the second column (110) to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106); and
h) a caustic treater (117) fluidly connected to the absorber section (116) on one side, and inlet of caustic material (117-1) on another side to remove trace H₂S by treating the caustic material with the NH₃ stream in the caustic treater, producing clean NH₃.
[0040] In some embodiments, the flash drum (104) is connected to the sour water inlet (102) on one side and to the first column (106) on another side.
[0041] In some embodiments, the lower portion (106-2) comprises a plurality of trays (106-3) for stripping H₂S and an external reflux system using stripped water.
[0042] In some embodiments, the top portion comprises a vertical exchanger and condenser system (106-4 & 106-5) to condense ammonia (NH₃) and water from the treated preheated sour water.
[0043] In some embodiments, a reheater (106-5) is connected or provided above a condenser (106-4) to heat the gas above its dew point.
[0044] In some embodiments, the maintenance of temperature in the upper portion (106-1) of the first column top is done by the top pump (106-6) in order to prevent salt desublimation, wherein the temperature maintained is in the range of 80 to 100°C.
[0045] In some embodiments, the second column includes an upper portion (110-1) and lower portion (110-2)
[0046] In some embodiments, the at least one portion of the stripping vapours rich in steam is routed through trays (110-3) from the bottom of the second column (110-2) to the first column (106) for H₂S stripping.
[0047] In some embodiments, the at least one portion is routed as stripped sour water via an outlet (120).
[0048] In some embodiments, at least two pump(s) (110-4, 110-5) that are connected to the second column (110).
[0049] In some embodiments, the at least two pump(s) (110-4, 110-5) are selected from but not limited to a high-temperature pump (110-4) and a top pump (110-5).
[0050] In some embodiments, the high-temperature pump (110-4) is connected at the lower portion (110-2) of the second column (110) for heat recovery to preheat the feed.
[0051] In some embodiments, the high-temperature pump (110-4) recovers 10–20% of the energy used for feed preheat, reducing overall steam consumption by 20–40% compared to conventional two-stage strippers (FIG. 2B).
[0052] In some embodiments, the top pump (110-5) is connected to the upper portion (110-1) of the second column (110) to maintain a temperature in the range of 80 to 100°C in order to prevent salt desublimation.
[0053] In some embodiments, a portion of the vapours generated from the reboiler (114) is sent to the first column bottom section (106-2) as a vapor source for stripping.
[0054] In some embodiments, a portion of NH₃-rich liquid from the first column (106) or the stripped water from second column (110) is passed and connected to the absorber column (116) to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106).
[0055] In some embodiments, the system (100) overall operates at a pressure in the range of 0.5–2 kg/cm²g.
[0056] In some embodiments, the system (100) overall operates at a low-pressure steam at temperature in the range of 125–130°C.
[0057] In some embodiments, the separated H₂S from said system (100) has a purity greater than 95%.
[0058] In some embodiments, the separated NH₃ from said system (100) has a purity greater than 90%.
[0059] In some embodiments, the stripped water comprises concentration of each of H₂S and NH₃ less than 10 ppmw.
[0060] In some embodiments, the lower portion of the first column (106-2) includes trays (106-3) to ensure maximum removal of H2S gases.
[0061] In some embodiments, a vertical exchanger (106-5) of the vertical exchanger heater and condenser system (106-4 & 106-5) in the first column (106) is to condense NH3 & water vapor, and then reheats H₂S vapor above its dew point to prevent corrosion.
[0062] In some embodiments, the reboiler’s (114) vapor split is adjustable to provide a turndown capability of 50–120% based on feed composition variability.
[0063] In some embodiments, the absorber section (116) comprises stripped water as the absorbing liquid when H₂S levels in the NH₃ rich stream are below a predetermined threshold.
[0064] In some embodiments, the system (100 - FIG. 1) is configured as a retrofit to the conventional two-stage sour water stripper (FIG. 2B) by modifying column internals and adding the absorber and caustic treater, reducing downtime to 2–4 weeks.
[0065] In some embodiments, the system additionally comprising automated controls for adjusting vapor and liquid flows between the first and second columns (106, 110) to handle feed rates.
[0066] In some embodiments, the stripped water from the second column (110) is partially recycled as external reflux to the first column (106) to minimize NH₃ slippage.
[0067] In some embodiments, the system (100) is adapted to process sour water from high-nitrogen crudes, maintaining Sulfur Recovery Unit (SRU) compatibility by minimizing NH₃ in the H₂S stream.
[0068] In some embodiments, the system (100) is a hybrid stripper-absorber system for treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃).
[0069] In some embodiments, the sour wate comprises concentration of H₂S in the range of 300–50000 ppmw.
[0070] In some embodiments, the sour wate comprises concentration of ammonia in the range of 100–25000 ppmw.
[0071] In some embodiments, the sour wate comprises concentration of H₂S in the range of 300–500 ppmw.
[0072] In some embodiments, the sour wate comprises concentration of H₂S in the range of 15000–50000 ppmw.
[0073] In some embodiments, the sour wate comprises concentration of ammonia in the range of 100–150 ppmw.
[0074] In some embodiments, the sour wate comprises concentration of ammonia in the range of 15000–25000 ppmw.
[0075] In another aspect, the present disclosure provides a method of treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃), comprising:
a) passing a sour water through inlet (102) connected to a first column (106) via a flash drum (104);
b) pre-heating the sour water (102-1) by passing the sour water from the flash drum (104) via a heat exchanger;
c) passing the preheated sour water into the first column (106) in order to strip the H2S at upper portion of the first column (106-2) to obtain stripped H2S and ammonia rich feed water;
d) removing the stripped H2S from outlet (108) from the upper portion of the first column (106-1);
e) passing and treating the ammonia rich feed water into second column (110) fluidly connected to the bottom of the first column (106-2) via a feed preheater (112) to heat the ammonia rich feed;
f) generating vapours of steam, remaining H2S, and ammonia contained in the preheated ammonia rich liquid feed using a reboiler (114) connected to the second column (110);
g) passing NH₃-rich gas from the second column (110) into absorber section (116) connected to the upper portion (110-1) of the second column to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106); and
h) removing trace H₂S by treating the NH₃ rich stream with caustic material in caustic treater (117) fluidly connected to the absorber section (116) on one side, and inlet of caustic material (117-1) on another side, to obtain clean NH₃.
[0076] In some embodiments, the stripping H₂S and an external reflux system using stripped water is done in the lower portion (106-2) containing plurality of trays (106-3).
[0077] In some embodiments, the heating and condensing of the ammonia generated in the first column (106) from the treated sour water is done in the top portion of the first column using the vertical exchanger heater (106-5) and condenser (106-4) system.
[0078] In some embodiments, the second column (110) includes an upper portion (110-1), lower portion (110-2), trays (110-3), and at least two pump(s) (110-4, 110-5).
[0079] In some embodiments, the at least one portion of the stripping vapours rich in steam is passed through trays (110-3) from the bottom/lower portion of the second column (110-2) to the first column (106) for H₂S stripping.
[0080] In some embodiments, the at least one portion is passed out as stripped sour water via an outlet (120).
[0081] In some embodiments, the at least two pump(s) (110-4, 110-5) connected to the second column (110) are selected from but not limited to a high-temperature pump (110-4) and a top pump (110-5).
[0082] In some embodiments, the heat recovery to preheat the feed is done by using the high-temperature pump (110-4) connected to the lower portion (110-2) of the second column.
[0083] In some embodiments, the high-temperature pump (110-4) recovers 10–20% of the energy used for feed preheat, reducing overall steam consumption by 20–40% compared to conventional two-stage strippers (FIG. 2B).
[0084] In some embodiments, the maintenance of temperature in the upper portion (110-2) of the second column top (110-5) is done by the top pump (110-5) in order to prevent salt desublimation, wherein the temperature maintained is in the range of 80 to 100°C.
[0085] In some embodiments, the method additionally comprises passing and connecting a portion of NH₃-rich liquid from the first column (106) or the stripped water from second column (110) to the absorber column (116) to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106).
[0086] In some embodiments, the method overall operates at a pressure in the range of 0.5–2 kg/cm²g.
[0087] In some embodiments, the method overall operates at a low-pressure steam at temperature in the range of 125–130°C.
[0088] In some embodiments, the separated H₂S by said method has a purity greater than 95%.
[0089] In some embodiments, the separated NH₃ by said method has a purity greater than 90%.
[0090] In some embodiments, the stripped water comprises concentration of each of H₂S and NH₃ less than 10 ppmw.
[0091] In some embodiments, the method additionally comprises reheating of the H₂S vapor generated in the first column (106) above its dew point is done to prevent corrosion, wherein the reheating is done using a vertical exchanger of the vertical exchanger heater (106-5) and condenser (106-4) system for reducing NH3 & water content in the H2S vapours.
[0092] In some embodiments, the reheating temperature is in the range of 50 to 70 ℃.
[0093] In some embodiments, the stripped water is used as the absorbing liquid in the absorber column (116) when H₂S levels in the NH₃ rich stream are below a predetermined threshold.
[0094] In some embodiments, the method additionally comprises automated controls for adjusting vapor and liquid flows between the first and second columns (106, 110) to handle feed rates.
[0095] In some embodiments, the method additionally comprises partial recycling of stripped water from the second column (110) is done to the first column (106) to minimize NH₃ slippage.
[0096] In some embodiments, the method is adapted to process sour water from high-nitrogen crudes, maintaining Sulfur Recovery Unit (SRU) compatibility by minimizing NH₃ in the H₂S stream.
[0097] In some embodiments, the sour wate comprises concentration of H₂S in the range of 300–50000 ppmw.
[0098] In some embodiments, the sour wate comprises concentration of ammonia in the range of 100–25000 ppmw.
[0099] In some embodiments, the sour wate comprises concentration of H₂S in the range of 300–500 ppmw.
[00100] In some embodiments, the sour wate comprises concentration of H₂S in the range of 15000–50000 ppmw.
[00101] In some embodiments, the sour wate comprises concentration of ammonia in the range of 100–150 ppmw.
[00102] In some embodiments, the sour wate comprises concentration of ammonia in the range of 15000–25000 ppmw.
[00103] In specific embodiments, the hybrid column system (100), as depicted in FIG. 1, which integrates stripping and absorption functionalities within a single vessel or as a retrofit to existing two-stage strippers (FIG. 2B). The columns are architecturally divided into key sections: a bottom stripping zone (106-2, 110-2), and a top section for H₂S and NH₃ fractionation zones (106-1, 110-1). Each zone is equipped with specialized trays or packing (106-3, 110-3) tailored for specific functions—H₂S stripping, NH₃- H₂O condensation, NH₃ stripping, and H₂S absorption—enabling precise control over vapor and liquid flows. According to FIG. 1 disclosed system, features a strategic flow scheme where sour water enters the H₂S fractionation zone (106-1) at the top, undergoes initial H₂S stripping, and flows downward to the bottom stripping section (106-2) for maximum H₂S gas removal. The liquid from the bottom (106-2), rich in NH₃, is routed to the second column (110) via tray internals (106-3), where it is stripped and absorbed, while H₂S-absorbed liquid from the absorber (116) is gravity-fed back to the H₂S zone.
[00104] According to FIG. 1 and the present disclosure, another pivotal element of the system (100) is the absorber section (116) positioned above the NH₃ fractionation zone (110-1), which utilizes NH₃-rich or stripped water to capture residual H₂S, ensuring high purity in the NH₃ stream. The H₂S fractionation zone incorporates an integrated vertical exchanger heater (106-5) and condenser (106-4) system, as shown in FIG. 1, which condenses NH₃ and water from the overhead vapor, reheats the H₂S gas above its dew point (50–70°C) to mitigate corrosion, and returns any slipped NH₃ to the process. This innovative routing of streams minimizes thermodynamic remixing, a common inefficiency in conventional systems, and produces near-pure H₂S (>95% purity) for Sulfur Recovery Unit (SRU) feed and NH₃ (>90% purity) for potential industrial applications, with optional caustic scrubbing to remove trace H₂S.
[00105] In specific embodiments, the system (100) operates at low pressure in the range of 0.5–2.5 kg/cm²g, leveraging abundant low-pressure (LP) steam at reboiler temperatures of 125–140°C, akin to single-stage strippers, while achieving the selective separation of two-stage designs. This low-energy approach reduces steam consumption by 20–40% compared to traditional two-stage systems (FIG. 2B) which rely on medium-pressure (MP) steam and high-pressure operation. Heat integration is a key feature, converting wasted pump-around duty (110-4 and 110-5) into usable feed preheat, while a vapor equalization line from the feed surge drum (104) to the low-pressure NH₃ zone (106-2) manages flashing without energy-intensive remixing. These enhancements, clearly depicted in the FIG. 1, contribute to significant operational expenditure (OpEx) and capital expenditure (CapEx) savings.
[00106] The FIG. 1 indicating outlet for stripped water (120) confirms the system’s and method’s environmental benefit as the stripped water meets specification of <10 ppmw of H₂S and NH₃, suitable for reuse or safe discharge to Effluent Treatment Plants (ETPs).
[00107] In a nutshell, the present disclosure provides a system and method covering hybrid stripper-absorber system, as illustrated in FIG. 1 and it represents a paradigm shift in sour water treatment, where it combines innovative column design, precise flow management, and energy-efficient operation. It also surpasses conventional single- and two-stage systems (FIG. 2A and 2B) in efficiency, cost-effectiveness, and environmental impact.
[00108] In specific embodiment, the present disclosure provides a system for sour water treatment, featuring a two-columns optimized for energy-efficient separation of hydrogen sulfide (H₂S) and ammonia (NH₃). The system comprises passing sour water via inlet (102), then from the feed surge drum (104), preheated via heat exchange, entering the top of the first column (106-1). While the flashed gases from feed surge drum (104) is routed to first column (106) via equalization line. Here, maximum H₂S is stripped off in the upper portion of first column (106-1), while NH₃ is absorbed back toward the column bottom (106-2, 106-3) using top external reflux with stripped water and a top vertical heat exchanger (106-5) for NH₃-H₂O condensation. The NH₃-rich liquid from the first column bottom (106-2) flows to the second column (110), where the NH₃ is stripped from the reboiled water. The reboiler (114) vapor splits: one portion finalizes NH3 stripping, while the other, drawn after several trays (110-3) from the second column bottom (110-2), is routed to the first column (106) to enhance H₂S stripping. The second column (110) includes two pump-arounds (110-4 and 110-5) where a high-temperature one (110-4) recovering heat for feed preheat, and a top one (110-5) maintaining 90°C to prevent salt desublimation. The NH₃-rich gas, with minimal H₂S, enters an absorber section (116) where NH₃-rich liquid (a portion from first column, 106) or stripped water (a portion from second column, 110) absorbs residual H₂S, recirculating it to the first column (106). The NH₃ stream, with trace H₂S, is treated in a caustic treater (117) to produce clean NH₃.
[00109] The FIG. 1 highlights low-pressure operation, strategic vapor/liquid routing, and heat integration, yielding near-pure H₂S (>95%) and NH₃ (>90%), with stripped water (<10 ppmw contaminants) exiting.
[00110] While the foregoing description discloses various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope of the disclosure. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES AND INDUSTRIAL APPLICABILITY OF THE PRESENT DISCLOSURE
[00111] The present disclosure provides a new and effective system and method for recovery of hydrogen sulfide and ammonia from the sour water usually generated in refinery processing.
[00112] It provides an energy-efficient and environmentally sustainable solution for the separation and purification of hydrogen sulfide (H₂S) and ammonia (NH₃) from the sour water, where operating at low pressure with LP steam, it achieves >95% H₂S and >90% NH₃ purity, reducing energy use by 20–40% and CapEx/OpEx, enhancing sustainability and flexibility.
[00113] The system and method offer remarkable adaptability such as adding partitions and rerouting flows—thus minimizing downtime and leveraging existing infrastructure. This flexibility extends to handling variable feed compositions, including high-nitrogen crudes like Nigerian, which impact NH₃ levels and SRU efficiency.
[00114] The system’s turndown capability ensures robust performance across a wide range of capacities, supported by automated controls for vapor and liquid splits.
[00115] The production of near-pure H₂S and NH₃ streams optimizes SRU performance, reduces emissions, and enables byproduct recovery, enhancing sustainability.
[00116] Operationally, the low-pressure and temperature conditions reduce fouling and corrosion risks, lowering maintenance needs and extending equipment life. The strategic use of LP steam aligns with refinery energy profiles, while the elimination of separate purification units for NH₃ further reduces costs.
[00117] The system and method ensure the simultaneous and precise separation of hydrogen sulfide (H₂S) and ammonia (NH₃) into near-pure streams, with H₂S purity exceeding 95% and NH₃ purity surpassing 90%. This is achieved through the first column’s targeted H₂S stripping, supported by external reflux with stripped water and NH₃-H₂O condensation, followed by the second column’s dedicated NH₃ stripping. The absorber column further refines the NH₃ stream by removing residual H₂S, ensuring compliance with stringent environmental specifications (<10 ppmw in stripped water) and enabling the production of marketable NH₃ for industrial applications, such as fertilizer production.
[00118] The system and method operate at low pressure (0.5–2 kg/cm²g) with low-pressure (LP) steam at 125–130°C, and reduce energy consumption by 20–40% compared to conventional two-stage systems that rely on medium-pressure (MP) steam and high-pressure operation (FIG. 2B).
[00119] The strategic use of reboiler vapor from the second column (110), split to finalize NH3 stripping in the second column (110) and enhance H₂S stripping in the first column (106), minimizes steam demand. The high-temperature pump-around (110-4) in the second column recovers heat for feed preheat, converting wasted energy into usable heat, while the top pump-around (110-5) maintains 90°C to prevent salt desublimation, optimizing overall energy efficiency.
[00120] The system and method covering two-column design, retrofittable into existing units, leverages current infrastructure, reducing the need for new high-pressure equipment and lowering CapEx by 15–30%. The low-pressure operation decreases equipment rating requirements, further cutting costs. OpEx is also reduced by 20–35% due to lower steam and utility usage, with the elimination of separate NH₃ purification units saving additional operational costs. The simplified flow scheme, with integrated heat exchange and vapor routing, also minimizes maintenance needs, extending equipment lifespan.
[00121] The system and method accommodate a wide range of sour water compositions, from lean streams (e.g., 300–500 ppmw H₂S, 100–150 ppmw NH₃) to rich streams (e.g., 20,000–50,000 ppmw H₂S, 15,000–25,000 ppmw NH₃), including high-nitrogen crudes like Nigerian. The adjustable vapor split from the second column reboiler (114) and the dual pump-around system (110-4, 110-5) provide a turndown range of 50–120%, allowing the process to adapt to fluctuating refinery feed rates and crude slates.
[00122] The low-temperature operation (e.g., 90°C top temperature via pump-around, 106-6 & 110-5) and strategic use of stripped water reflux reduce the deposition of ammonium salts, hydrocarbons, and other foulants on trays and exchangers, a common issue in conventional strippers. The reheating of H₂S vapor above its dew point in the first column’s vertical exchanger (106-5) prevents dew point corrosion, enhancing equipment reliability and reducing maintenance frequency compared to high-pressure, high-temperature systems.
[00123] By producing stripped water with <10 ppmw H₂S and NH₃ (120), the system and method ensured compliance with environmental regulations, facilitating safe reuse or discharge to Effluent Treatment Plants (ETPs). The near-pure H₂S stream optimizes SRU performance by minimizing NH₃-related choking, reducing emissions and improving sulfur recovery efficiency. The clean NH₃, post-caustic treatment, supports byproduct recovery, lowering the overall environmental footprint of refinery operations.
[00124] The high-temperature pump-around’s (110-4) heat recovery for feed preheat transforms a typically wasted energy stream into a productive resource, saving 10–20% of energy. The vapor equalization from the second column to the first column eliminates the need for energy-intensive remixing in feed surge drums, enhancing thermodynamic efficiency. This integrated approach aligns with refinery energy profiles, utilizing abundant LP steam and reducing greenhouse gas emissions.
[00125] The caustic treater (117) ensures trace H₂S removal, producing high-purity NH₃, addressing the challenge of variable feed quality that often complicates conventional stripping. , Claims:1. A system (100) for treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃), comprising:
a) sour water inlet (102) connected to a first column (106) via a flash drum (104) to pass sour water;
b) pre-heated sour water inlet (102-1) is connected from the flash drum (104) via a heat exchanger to provide preheated sour water into the first column (106);
c) the first column (106) is connected to the flash drum (104) via the heat exchanger on one side, and is connected to the pre-heated sour water inlet (102-1) to receive preheated sour water on another side, wherein the first column includes an upper portion (106-1) and lower portion (106-2);
d) an outlet (108) for H2S removal upon stripping from the upper portion of the first column (106-1);
e) a second column (110) fluidly connected to the bottom of the first column (106-2) to receive NH₃-rich liquid feed via a feed preheater (112);
f) a reboiler (114) is connected to the second column (110) to generate vapours of steam, remaining H2S, and ammonia contained in the preheated ammonia rich liquid feed;
g) an absorber section (116) is connected to the upper portion (110-1) of the second column to receive NH₃-rich gas from the second column (110) to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106); and
h) a caustic treater (117) fluidly connected to the absorber section (116) on one side, and inlet of caustic material (117-1) on another side to remove trace H₂S by treating the caustic material with the NH₃ stream in the caustic treater, producing clean NH₃.

2. The system (100) as claimed in claim 1, wherein
the lower portion (106-2) comprises a plurality of trays (106-3) for stripping H₂S and an external reflux system using stripped water; and
the top portion (106-1) comprises a vertical exchanger heater (106-5) and condenser (106-4) to condense ammonia (NH₃) and water from the treated preheated sour water.

3. The system (100) as claimed in claim 1, wherein the second column (110) includes an upper portion (110-1), lower portion (110-2), trays (110-3), and at least two pump(s) (110-4, 110-5).

4. The system (100) as claimed in claims 1 and 3, wherein
the at least one portion of the preheated ammonia rich liquid feed is routed through trays (110-3) from the bottom of the second column (110-2) for NH3 stripping; and
the at least two pump(s) (110-4, 110-5) connected to the second column (110) are selected from a high-temperature pump (110-4) and a top pump (110-5).

5. The system (100) as claimed in claims 1 and 4, wherein
the high-temperature pump (110-4) is connected at the lower portion (110-2) of the second column (110) for heat recovery to preheat the feed; and
the top pump (110-5) is connected to the upper portion (110-1) of the second column (110) to maintain a temperature in the range of 80 to 100°C in order to prevent salt desublimation.

6. The system (100) as claimed in any of claims 1 to 5, wherein a portion of NH₃-rich liquid from the first column (106) or the stripped water from second column (110) is passed and connected to the absorber section (116) to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106).

7. The system (100) as claimed in any of claims 1 to 6, wherein
the lower portion of the first column (106-2) includes trays (106-3) to ensure maximum removal of H2S gases; and
a vertical exchanger of the vertical exchanger heater (106-5) and condenser (106-4) system in the first column (106) reheats H₂S vapor above its dew point to prevent corrosion.

8. The system (100) as claimed in any of claims 1 to 7, wherein the stripped water from the second column (110) is partially recycled as external reflux to the first column (106) to minimize NH₃ slippage.

9. A method of treating sour water to separate hydrogen sulfide (H₂S) and ammonia (NH₃), comprising:
a) passing a sour water through inlet (102) connected to a first column (106) via a flash drum (104);
b) pre-heating the sour water (102-1) by passing the sour water from the flash drum (104) via a heat exchanger;
c) passing the preheated sour water into the first column (106) in order to strip the H2S at upper portion of the first column (106-2) to obtain stripped H2S and ammonia rich feed and water;
d) removing the stripped H2S from outlet (108) from the upper portion of the first column (106-1);
e) passing and treating the ammonia rich feed water into second column (110) fluidly connected to the bottom of the first column (106-2) via a feed preheater (112) to heat the ammonia rich feed;
f) generating vapours of steam, remaining H2S, and ammonia contained in the preheated ammonia rich liquid feed using a reboiler (114) connected to the second column (110);
g) passing NH₃-rich gas from the second column (110) into absorber section (116) connected to the upper portion (110-1) of the second column to absorb residual H₂S, and recirculating H₂S-rich liquid back to the first column (106); and
h) removing trace H₂S by treating the NH₃ rich stream with caustic material in caustic treater (117) fluidly connected to the absorber column (116) on one side, and inlet of caustic material (117-1) on another side, to obtain clean NH₃.

10. The method as claimed in claim 9, wherein the method overall operates at a pressure in the range of 0.5–2 kg/cm²g, and at a low-pressure steam at temperature in the range of 125–130°C.