WO2022115682A1

WO2022115682A1 - Direct contact cooler column

Info

Publication number: WO2022115682A1
Application number: PCT/US2021/060971
Authority: WO
Inventors: Richard Axelbaum; Zhiwei Yang; Piyush Verma
Original assignee: Washington University
Priority date: 2020-11-30
Filing date: 2021-11-29
Publication date: 2022-06-02

Abstract

Described herein is a direct contact cooler column. Also described herein is a method for using a direct contact cooler column for removing a contaminant from a gas stream. The direct contact cooler column simultaneously recovers flue gas heat and removes SOx and NOx from flue gas.

Description

DIRECT CONTACT COOLER COLUMN

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application Serial No. 63/119,369, filed on November 30, 2020, the content of which is hereby incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE [0002] Described herein is a direct contact cooler column. Also described herein is a method for using a direct contact cooler column for removing a contaminant from a gas stream. The direct contact cooler column simultaneously recovers flue gas heat and removes SO_x and NO_x from flue gas.

GOVERNMENT SUPPORT CLAUSE

[0003] This invention was made with government support under grant number DE-FE0025193 awarded by the Department of Energy. The government has certain rights in the invention.

BACKGROUND OF THE DISCLOSURE:

[0004] SO_x and NO_x are both major pollutants from fossil fuel combustion. In conventional fossil fuel plants, the removal of SO_x and NO_x is achieved in two steps - a selective catalytic reduction (SCR) unit to remove NO_x and a flue gas desulfurization (FGD) unit to remove SO_x. In recent years, the desire to decarbonize the electricity grid has led to tremendous interest in carbon capture and storage (CCS) technologies for power plants, and oxy-combustion has emerged as a promising option for CCS. An oxy- combustion process has a much smaller volumetric flow of flue gas than a conventional air- fired process due to the elimination of N2, leading to more compact pollutant removal units. Furthermore, CCS has brought out the opportunity for an alternative pollutant removal technology - integrated pollutant removal (IPR) technology, which removes SO_x and NO_x simultaneously in a pressurized water wash column, i.e., direct contact cooler (DCC). Because the CO2 product needs to be compressed downstream for transportation and storage, there is no additional cost for pressurizing flue gas. Overall, this new technology is expected to be more cost-effective than SCR and FGD for oxy-combustion processes. [0005] IPR technology is especially cost-effective for pressurized combustion systems, which offer the advantage of the moisture in the flue gas condensing at a higher temperature, resulting in the recovery of the latent heat that can be integrated into the steam cycle to increase the plant efficiency. Pressurized combustion is of particular interest for carbon capture as the CO2 product often has to be compressed anyway for further utilization and hence there is no additional cost for pressurization of the combustion system.

[0006] For atmospheric pressure oxy-combustion, the flue gas must be cooled such that the majority of the moisture is removed before compression to prevent acid condensation in the compressors. Therefore, previous attempts regarding IPR technology have focused on removal at a temperature lower than 50 °C with a high L/G ratio, where the heat transfer from latent and sensible heat is not a variable affecting the mass transfer and reaction kinetics. This confirmed the possibility of pressuring the flue gas and then removing SO_x and NO_x using a water contact column. It has been suggested that pressurizing the gas to 30 bar can lead to better removal.

[0007] Recently, pressurized oxy-combustion has received significant attention due to its potential for efficiency improvement. At atmospheric pressure, moisture in the flue gas condenses at a low temperature, and thus the latent heat is not useable. However, under pressure, the moisture condenses at a higher temperature, allowing the latent heat to be integrated into the steam cycle and improving plant efficiency. Pressurized oxy- combustion also benefits the IPR technology because moisture condensation and SO_x and NO_x removal can occur concurrently in the DCC column, thereby further reducing complexity and cost. In this case, the DCC acts both as a heat exchanger to recover latent and sensible heat from the flue gas and as an absorber for SO_x and NO_x. To maximize plant efficiency, the water temperature exiting the DCC must be maintained at a relatively high temperature, which is accomplished by limiting the L/G ratio, making scrubbing a high-temperature process.

[0008] A conventional DCC column is a counter-current packed column with just one input for water coming from the top and one input for gas from the bottom of the column. Based on the L/G ratio, the column diameter is sized for a 75% approach to the flooding velocity for optimum mass transfer. The height of the column is sized based on the outlet concentration of SO_x and NO_x, which depends on the residence time of the gas.

[0009] Described herein is a novel design for a direct contact cooler column. The column simultaneously recovers heat and removes SO_x and NO_x from the flue gas. [0010] An optimized design with multiple water inlets in accordance with the present disclosure enhances the scrubbing of NO_xby about 9% and SO_x by about 3.5% by increasing the residence time in the same sized column by 35%. It is also observed that the liquid-phase reaction between absorbed SO_x and NO_x plays a significant role in the removal of SO2 from the flue gas for high-temperature scrubbing compared with low- temperature scrubbing. The design reinforces the potential of high -temperature SO_x-NO_x removal and heat recovery and suggests a means of reducing capital costs for such columns.

BRIEF DESCRIPTION OF THE DISCLOSURE

[0011] In one embodiment, the present disclosure is directed to a direct contact cooler column comprising a lower region comprising a gas inlet, an upper region comprising a gas outlet, a first liquid inlet between the upper region and the lower region, and a second liquid inlet between the upper region and the lower region, wherein the first liquid inlet is located substantially below the second liquid inlet, wherein the direct contact cooler is configured to operate at high temperature and high pressure.

[0012] In another embodiment, the present disclosure is directed to a method for removing a contaminant from a gas stream, the method comprising (i) introducing a gas stream comprising a contaminant into a gas inlet of a direct contact cooler column, (ii) introducing a first liquid stream into a first liquid inlet of the direct contact cooler column, (iii) contacting the gas stream comprising a contaminant with the first liquid stream, (iv) introducing a second liquid stream into a second liquid inlet of the direct contact cooler column, wherein the first liquid inlet is located substantially below the second liquid inlet,

(v) contacting the gas stream comprising a contaminant with the second liquid stream, and

(vi) recovering the gas stream. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A is a comparative embodiment of a conventional direct cooling column.

[0014] Figure IB is an exemplary embodiment of a direct cooling column in accordance with the present disclosure. [0015] Figure 2 is an exemplary embodiment of gas temperature profiles for a conventional direct cooling column and a direct cooling column in accordance with the present disclosure.

[0016] Figure 3 is an exemplary embodiment of gas volumetric flow profiles for a conventional direct cooling column and a direct cooling column in accordance with the present disclosure.

[0017] Figure 4 is an exemplary embodiment of gas residence times for a conventional direct cooling column and a direct cooling column in accordance with the present disclosure.

[0018] Figure 5 is an exemplary embodiment of NO_x and SO2 removal for a conventional direct cooling column and a direct cooling column in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0019] Described herein is a direct contact cooler column comprising a lower region comprising a gas inlet, an upper region comprising a gas outlet, a first liquid inlet between the upper region and the lower region; and a second liquid inlet between the upper region and the lower region. The first liquid inlet is located substantially below the second liquid inlet. The direct contact cooler is configured to operate at high temperature and high pressure.

[0020] In some embodiments, the direct contact cooler column comprises additional liquid inlets. In some embodiments, the direct contact cooler column comprises two, three, four, five, six, seven, eight, nine, ten, or more than ten liquid inlets. [0021] In some embodiments, the direct contact cooler column is configured to operate at a temperature in the range of from about 25 °C to about 600 °C. In some embodiments, the direct contact cooler column is configured to operate at a temperature in the range of from about 25 °C to about 200 °C.

[0022] In some embodiments, an input gas stream is introduced into the gas inlet at a temperature in the range of from about 100 °C to about 600 °C. In some embodiments, an input gas stream is introduced into the gas inlet at a temperature of about 200 °C.

[0023] In some embodiments, an output gas stream exits the gas outlet at a temperature in the range of from about 25 °C to about 100 °C. In some embodiments, an output gas stream exits the gas outlet at a temperature in the range of from about 25 °C to about 50 °C.

[0024] In some embodiments, the direct contact cooler column is configured to operate at a pressure in the range of from about 1 bar to about 30 bar, from about 5 bar to about 25 bar, from about 10 bar to about 20 bar, or about 15 bar.

[0025] In some embodiments, a first liquid stream is introduced into the first liquid inlet or a second liquid stream is introduced into the second liquid inlet at a pressure in the range of from about 1 bar to about 30 bar. In some embodiments, a first liquid stream is introduced into the first liquid inlet or a second liquid stream is introduced into the second liquid inlet at a pressure of about 15 bar.

[0026] In some embodiments, the direct contact cooler column comprises a packing material. Any suitable packing material known in the art may be used. In some embodiments, the direct contact cooler column comprises a packing material selected from the group consisting of random packings, trays, and combinations thereof.

[0027] The direct contact cooler column has a height and a diameter. The height and the diameter are independent of each other. The diameter of the direct contact cooler column typically depends on the gas-to-liquid ratio. The height typically depends on the NO_x concentration in the inlet gas. As one non-limiting example, for a 550 MWe pressured oxy-combustion power plant, the diameter is about 5.6 m and the height is about [0028] In some embodiments, the direct contact cooler column has a height in the range of from about 1 m to about 100 m. In some embodiments, the direct contact cooler column has a height in the range of from about 5 m to about 100 m, from about 10 m to about 80 m, from about 25 m to about 75 m, or from about 30 m to about 60 m. In some embodiments, the direct contact cooler column has a diameter in the range of from about

2.5 m to about 6 m.

[0029] In many embodiments, the first liquid inlet is located substantially below the second liquid inlet to influence the scrubbing properties of the reactor. In some embodiments, the relative and absolute positions of the liquid inlets influence one or more of the temperature, pressure, volumetric flow rate, chemical reaction kinetics, residence time, and/or density of gas streams flowing through the direct contact cooler column.

[0030] In some embodiments, the first liquid inlet is positioned at a height that is less than about 50%, less than about 45%, less than about 40%, less than about 35%, less than about 30%, less than about 25%, less than about 20%, less than about 15%, or less than about 10% of the column height. In some embodiments, the first liquid inlet is positioned at a height that is less than about 50% of the column height.

[0031] In some embodiments, the second liquid inlet is positioned at a height that is greater than about 50%, greater than about 55%, greater than about 60%, greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, greater than about 85%, or greater than about 90% of the column height. In some embodiments, the second liquid inlet is positioned at a height that is greater than about 80% of the column height.

[0032] The direct contact cooler column in accordance with the present application is useful in a variety of combustion systems known in the art. Such systems include those described in US20200049343, US20190368722, and US10731847, which are incorporated by reference herein.

[0033] In some embodiments, a boiler comprises the direct contact cooler column. In some embodiments, a high pressure boiler comprises the direct contact cooler column. [0034] In some embodiments, the direct contact cooler column is used in a combustion process. In some embodiments, the direct contact cooler column is used in an oxy-combustion process. In some embodiments, the direct contact cooler column is used in a chemical process.

[0035] Also described herein is a method for removing a contaminant from a gas stream. The method comprises (i) introducing a gas stream comprising a contaminant into a gas inlet of a direct contact cooler column, (ii) introducing a first liquid stream into a first liquid inlet of the direct contact cooler column, (iii) contacting the gas stream comprising a contaminant with the first liquid stream, (iv) introducing a second liquid stream into a second liquid inlet of the direct contact cooler column, wherein the first liquid inlet is located substantially below the second liquid inlet, (v) contacting the gas stream comprising a contaminant with the second liquid stream, and (vi) recovering the gas stream.

[0036] In some embodiments, a method for removing a contaminant from a gas stream is disclosed. The method includes introducing a gas stream comprising a contaminant into a gas inlet of a direct contact cooler column; introducing a first liquid stream into a first liquid inlet of the direct contact cooler column; contacting the gas stream comprising a contaminant with the first liquid stream; introducing a second liquid stream into a second liquid inlet of the direct contact cooler column, wherein the first liquid inlet is located substantially below the second liquid inlet; contacting the gas stream comprising a contaminant with the second liquid stream; and recovering the gas stream, wherein the amount of the contaminant in the recovered gas stream is less than the amount of the contaminant in the gas stream introduced into the gas inlet of the direct contact cooler column.

[0037] That is, through the interaction and steps of the liquid stream and gas stream introductions as disclosed, the contaminant in the gas stream is removed. In some embodiments, the contaminant is removed completely from the gas stream. In some embodiments, the contaminant is removed partially from the gas stream. In some embodiments, multiple contaminants are removed - either partially or wholly - from the gas stream. [0038] In some embodiments, the gas stream comprises a gas selected from the group consisting of flue gas, air, CO₂, N₂, SO_x, SO₂, SO₃, NO_x, NO, NO₂, N₂O, HC1, Hg, CO, H₂, COS, H₂S, NH₃, HCN, and combinations thereof.

[0039] In some embodiments, the gas stream comprises a contaminant selected from the group consisting of SO_x, NO_x, and combinations thereof.

[0040] In some embodiments, the method comprises recovering flue gas heat.

[0041] In many embodiments, the method does not require added chemicals. In some embodiments, the method is free of added chemicals. Added chemicals include oxidants, reductants, chemicals used to remove contaminants, and combinations thereof. [0042] In some embodiments, less than about 50%, less than about 45%, less than about 40%, less than about 35%, less than about 30%, less than about 25%, less than about 20%, less than about 15%, less than about 10%, or less than about 5% of the total volume of introduced liquid is delivered via the second liquid inlet. In some embodiments, less than about 25% of the total volume of introduced liquid is delivered via the second liquid inlet.

[0043] In some embodiments, the first liquid stream and the second liquid stream each individually comprise a liquid selected from the group consisting of water, brine, an acidic solution, an alkaline solution, and combinations thereof.

[0044] As used herein, an acidic solution is a solution having a pH value less than about 7.

[0045] As used herein, an alkaline solution is a solution having a pH value greater than about 7.

[0046] As used herein, brine is a solution comprising water and relatively high concentrations of NaCl. [0047] In some embodiments, the brine is brackish water. In some embodiments, the brine has a NaCl concentration in the range of from about 0.05% to about 3%. [0048] In some embodiments, the brine is saline water. In some embodiments, the brine has a NaCl concentration in the range of from about 3% to about 5%.

[0049] In some embodiments, the brine is seawater. In some embodiments, the brine has a NaCl concentration of about 3.5%.

EXAMPLES [0050] Without further elaboration, it is believed that one skilled in the art using the preceding description can utilize the present disclosure to its fullest extent. The following Examples are, therefore, to be construed as merely illustrative, and not limiting of the disclosure in any way whatsoever.

[0051] Example 1. Modeling [0052] Modeling Methodology

[0053] The DCC design is based on the flue gas from a 550 MWe pressurized oxy-combustion plant using PRB coal. The flue gas conditions at the inlet are presented in Table 1. The column is modeled as a rate-based reactive-absorption column in Aspen Plus V9, which includes three interlinked processes with different time constants and constraints - heat transfer, mass transfer, and chemical reactions. The ENRTL is used as the property method because of the electrolytic nature of the liquid phase reaction.

[0054] Table 1. Inlet modeling parameters

[0055] Column Design

[0056] A conventional column design 100, presented in Figure 1A, is a counter- current packed column 102 with water coming from the top and gas from the bottom. Gas enters through a gas inlet 104 and water enters through a water inlet 108. Gas exits through a gas outlet 106 and water exits through a water outlet 110.

[0057] The L/G ratio is determined by fixing the moisture content of the outlet flue gas to be 1% v/v. The resulting L/G ratio is 1.03 kg/kg and the water temperature exiting the DCC is around 160 °C. Based on the L/G ratio, the column diameter is sized for a 75% approach to the flooding velocity for optimum mass transfer. The height of the column 102 is sized based on the outlet concentration of NO_x (<100 ppm) and SO_x (<50 ppm). An 80 mm Raschig ring is employed as the packing material since it provides good mass transfer with a reasonable pressure drop in the column. The calculations are performed over 10 stages for better numerical understanding, with the bottom -most stage numbered as stage 1.

[0058] A modified column design 200, presented in Figure IB, uses the same dimension and packing material as those of the conventional column 102 to highlight the differences in the removal efficiencies with the conventional design. The modified column design 200 includes a counter-current packed column 202. Gas enters through a gas inlet 204 and water enters through a first water inlet 208 and a second water inlet 210. Further water inlets may be present (not shown). Gas exits through a gas outlet 206 and water exits through a water outlet 212.

[0059] Water is split into up to 10 streams, one for each stage. Optimization is performed to maximize NO_x and SO_x removal efficiency by varying the flow rate of each water stream while fixing the L/G ratio and outlet moisture content. The optimization results suggest that a simple design with only two water inlets provides the best removal efficiency, one stream at the top with 23.5% of the total flow, and the remaining entering above the 4^th stage.

[0060] Chemical Kinetics [0061] The reaction mechanism used in the model is presented in Table 2. This reduced mechanism includes all significant reactions in gas and liquid phases. The kinetic model has been verified against experimental data from a pilot-scale system and predicts the SO_x and NO_x removal efficiency at various conditions to a close degree.

[0062] Table 2 Reaction mechanism used in modeling

[0063] Results

[0064] By analyzing the time scales of mass and heat transfer and all chemical reactions, it is found that the oxidation of NO to NO2 in the column is the rate-limiting step for removing NO_x and SO_x. Because the L/G ratio and oxygen content in the flue gas are both fixed, the removal of NO and SO2 depends on the residence time and temperature profile in the column.

[0065] The results indicated that in a conventional column, it is possible to remove SO_x and NO_x to the required standard in about 115 seconds, and heat transfer is faster than the chemical reactions. About 83% of NO_x was scrubbed and about 96.5% of SO_x was scrubbed in that time. A high fraction of cooling and condensation is achieved in around 40% of the column height with the specified L/G ratio. Due to the counter-current design, most of the cooling and condensation takes place at the top part. As shown in Figure 2, compared to the conventional column, the gas temperature in the modified column drops faster in the bottom part (below the second water inlets). The gas outlet temperature is slightly higher than that of the conventional design because a smaller L/G ratio in the upper section leads to a reduced surface area of contact. In some embodiments, a different packing in the upper column yields improved heat transfer.

[0066] In the modified design, the volumetric gas flow rate decreases significantly, as seen in Figure 3, due to 1) earlier condensation and 2) faster cooling down of the gas. In the conventional design, most of the cooling and condensation occurs in the upper section of the column, while in the modified design, they are largely completed by stage 5, leading to a much lower flow rate in the remaining part of the column.

[0067] The different gas flow rates lead to different cumulative gas residence times, as shown in Figure 4. The total residence time in the modified column is 39 seconds longer (or 34% larger) than that in the conventional column.

[0068] Figure 5 summarizes the scrubbing efficiency of SO_x and NO_x in both designs. Since NO removal is limited by the NO oxidation reaction, the increase in residence time in the modified design enhances the scrubbing of NO by almost 9 percentage points. Consequently, the increased production and absorption of NO2 enhances the liquid phase reaction with HSO 3, resulting in higher and faster absorption of SO2 in water. The scrubbing efficiency of SO_x increases by almost 3 percentage points to 99.98%.

[0069] Conclusions

[0070] A direct contact cooler that simultaneously recovers flue gas heat and removes SO_x and NO_x significantly reduces the cost of pollutant removal in pressurized oxy-combustion systems. The present disclosure demonstrates modeling and optimization of a direct contact cooler using a reaction mechanism and kinetic data validated by pilot- scale experiment results. A time scale analysis of the mass and heat transfer and all chemical reactions indicated that the NO removal is limited by the NO oxidation reaction.

[0071] A conventional column design was compared with a novel modified design in accordance with the present disclosure. In the conventional column, gas is fed from the bottom and water from the top. The gas temperature remains high until the upper section, where most moisture condensation and gas temperature reduction occurs. The modified design was obtained by splitting water into multiple streams, one for each column stage, and then optimizing the flow rate of all water streams to maximize the SO_x and NO_x removal efficiency. The optimal design had only two water streams, with 23.5% water fed from the top and the remaining fed from the 4^th stage.

[0072] The modified design proved to be significantly better in SO_x and NO_x scrubbing efficiency. In the modified column, the heat transfer at the lower section is enhanced, leading to faster temperature drop and earlier moisture condensation. The lower temperature and moisture content both contribute to a lower volumetric gas flow rate and hence a long residence time (34% longer). Since the NO oxidation reaction occurred faster at lower temperatures, the modified column had a higher NO oxidation rate and longer time for NO to oxidize, leading to significantly higher SO_x and NO_x removal efficiency (about 3.5% higher and 9% higher, respectively). In addition, the modified design reinforced the potency of high temperature SO_x and NO_x removal and heat recovery and suggested a potential reduction to capital cost for such columns.

[0073] This written description uses examples to illustrate the present disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any compositions or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have elements that do not differ from the literal language of the claims, or if they include equivalent elements with insubstantial differences from the literal language of the claims.

[0074] As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains”, “containing,” “characterized by” or any other variation thereof, are intended to cover a non-exclusive inclusion, subject to any limitation explicitly indicated. For example, a composition, mixture, process or method that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, mixture, process or method. [0075] The transitional phrase “consisting of’ excludes any element, step, or ingredient not specified. If in the claim, such would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase “consisting of’ appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

[0076] The transitional phrase “consisting essentially of’ is used to define a composition or method that includes materials, steps, features, components, or elements, in addition to those literally disclosed, provided that these additional materials, steps, features, components, or elements do not materially affect the basic and novel characteristic(s) of the claimed disclosure. The term “consisting essentially of’ occupies a middle ground between “comprising” and “consisting of’.

[0077] Where a disclosure or a portion thereof is defined with an open-ended term such as “comprising,” it should be readily understood that (unless otherwise stated) the description should be interpreted to also describe such a disclosure using the terms “consisting essentially of’ or “consisting of.”

[0078] Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0079] Also, the indefinite articles “a” and “an” preceding an element or component of the disclosure are intended to be nonrestrictive regarding the number of instances (i.e. occurrences) of the element or component. Therefore “a” or “an” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

Claims

WHAT IS CLAIMED IS:

1. A direct contact cooler column comprising: a lower region comprising a gas inlet; an upper region comprising a gas outlet; a first liquid inlet between the upper region and the lower region; and a second liquid inlet between the upper region and the lower region, wherein the first liquid inlet is located substantially below the second liquid inlet; wherein the direct contact cooler is configured to operate at high temperature and high pressure.

2. The direct contact cooler column of claim 1, wherein the direct contact cooler column is configured to operate at a temperature in the range of from about 25 °C to about 600 °C.

3. The direct contact cooler column of claim 1, wherein the direct contact cooler column is configured to operate at a temperature in the range of from about 25 °C to about 200 °C.

4. The direct contact cooler column of claim 1, wherein the direct contact cooler column is configured to operate at a pressure in the range of from about 1 bar to about 30 bar.

5. The direct contact cooler column of claim 1, wherein the first liquid inlet is positioned at a height that is less than about 50% of the column height.

6. The direct contact cooler column of claim 1, wherein the second liquid inlet is positioned at a height that is greater than about 50% of the column height.

7. The direct contact cooler column of claim 1, wherein the second liquid inlet is positioned at a height that is greater than about 80% of the column height.

8. The direct contact cooler column of claim 1, wherein the direct contact cooler column is configured to receive a gas stream comprising a gas selected from the group consisting of flue gas, air, C0₂, N₂, SO_x, S0₂, S0₃, NO_x, NO, N0₂, N₂0, HC1, Hg, CO, H₂, COS, H₂S, ML, HCN, and combinations thereof.

9. A boiler comprising the direct contact cooler column of claim 1.

10. A method for removing a contaminant from a gas stream, the method comprising: introducing a gas stream comprising a contaminant into a gas inlet of a direct contact cooler column; introducing a first liquid stream into a first liquid inlet of the direct contact cooler column; contacting the gas stream comprising a contaminant with the first liquid stream; introducing a second liquid stream into a second liquid inlet of the direct contact cooler column, wherein the first liquid inlet is located substantially below the second liquid inlet; contacting the gas stream comprising a contaminant with the second liquid stream; and recovering the gas stream, wherein the amount of the contaminant in the recovered gas stream is less than the amount of the contaminant in the gas stream introduced into the gas inlet of the direct contact cooler column.

11. The method of claim 10, wherein the direct contact cooler column is at a temperature in the range of from about 25 °C to about 600 °C.

12. The method of claim 10, wherein the direct contact cooler column is configured to operate at a temperature in the range of from about 25 °C to about 200 °C.

13. The method of claim 10, wherein the direct contact cooler column is at a pressure in the range of from about 1 bar to about 30 bar.

14. The method of claim 10, wherein the first liquid inlet is positioned at a height that is less than about 50% of the column height.

15. The method of claim 10, wherein the second liquid inlet is positioned at a height that is greater than about 50% of the column height.

16. The method of claim 10, wherein the second liquid inlet is positioned at a height that is greater than about 80% of the column height.

17. The method of claim 10, wherein less than about 25% of the total volume of introduced liquid is delivered via the second liquid inlet.

18. The method of claim 10, wherein the gas stream comprises a gas selected from the group consisting of flue gas, air, CO₂, N₂, SO_x, SO₂, SO₃, NO_x, NO, NO₂, N₂O, HC1, Hg, CO, H₂, COS, H₂S, NH₃, HCN, and combinations thereof.

19. The method of claim 10, wherein the first liquid stream and the second liquid stream each individually comprise a liquid selected from the group consisting of water, brine, an acidic solution, an alkaline solution, and combinations thereof.

20. The method of claim 10, wherein the contaminant removed is selected from the group consisting of SO_x, NO_x, and combinations thereof.