Systems and methods for removing gaseous pollutants from a gas stream

[0001] This application claims priority to US Patent Application No. 11 / 868,904, filed on October 8, 2007 entitled "SYSTEMS AND METHODS FOR REMOVAL OF GASEOUS POLLUTANTS FROM GAS STREAMING".

FIELD OF THE INVENTION The present invention relates to systems and methods for removing gaseous pollutants, such as sulfur dioxide, from a waste gas stream (e.g., industrial waste gas) via a horizontal gas-liquid scrubber.

BACKGROUND OF THE INVENTION [0003] Gases containing impurities, such as sulfur dioxide, are produced in many industrial processes. One way to remove gaseous pollutants from such gases involves the use of vertical scrubbers. Such vertical scrubbers can be expensive to operate due to the investment costs and operational requirements of such towers. Horizontal scrubbers are also known. For example, U.S. Patent No. 5,403,568 by Stowe Jr. discloses a horizontal washer intended in particular to control sulfur dioxide emissions, which uses an aqueous cleaning agent that flows parallel to the direction of gas flow. Stowe Jr. predicts the use of elements changing the direction of flow, which impedes the flow of gases through the scrubber, causing a pressure drop in the scrubber and providing additional gas-liquid contact.

US 2002/0110511 A1 relates to a scrubber that allows a substantially horizontal gas flow pathway to be treated. Patents EP 0613713 A1 and WO 2006/104304 A1 also apply to horizontal wet cleaning systems.

SUMMARY OF THE INVENTION [0004] In general, the present invention relates to horizontal gas-liquid scrubbers for removing gaseous pollutants from gases, and relates to systems and methods relating to these scrubbers. Scrubbers usually do not generally have flow alteration elements between the liquid inlet manifold and a demister located downstream of the inlet liquid collector. Scrubbers can remove at least 71% vol. sulfur dioxide, with an L / G ratio of less than 20.

[0005] In independent claim 1 includes a system for removing gas pollutants from gas. Independent claim 5 includes a suitable method for removing gaseous pollutants from gas. Preferred embodiments are described in the dependent claims.

[0006] These and other aspects, advantages and new features of the invention are set forth in part in the description which follows and will become apparent to those skilled in the art upon reading the following description and figures or may be learned from the practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS [0007]

FIG. 1 is a schematic depiction of one embodiment of a horizontal gas-liquid cleaning system.

FIG. 2 is a partial perspective view of the horizontal gas-liquid cleaning system of FIG. 1, in a view from the bottom housing towards the gas inlet.

FIG. 3 is a schematic representation of one embodiment of a horizontal ducted gas-liquid cleaning system.

FIG. 4 is a graph showing the removal of sulfur dioxide as a function of the liquid-to-gas flow rate indicator for a horizontal gas-liquid cleaning system using a 50% contactor, compared to a horizontal gas-liquid cleaning system that does not contain flow-changing elements.

FIG. 5 is a graph showing the removal of sulfur dioxide depending on the basicity of a horizontal gas-liquid cleaning system using a 50% contactor, compared to a horizontal gas-liquid cleaning system that does not contain flow-changing elements.

FIG. 6 is a graph showing the removal of sulfur dioxide depending on the distance between the nozzles and the defogger.

FIG. 7 is a graph showing the removal of sulfur dioxide depending on the basicity for different sizes of the housing.

FIG. 8a-8c is a schematic representation of the implementation of the nozzle arrangement configuration.

FIG. 9a is a graph showing the removal of sulfur dioxide depending on the basicity for the nozzle configurations of FIG. 8a and 8b.

FIG. 9b is a graph showing the removal of sulfur dioxide depending on L / G for the nozzle configurations of FIG. 8b and 8c.

FIG. 10 is a graph showing the removal of sulfur dioxide depending on L / G for different types of nozzles.

FIG. 11 is a graph showing the removal of sulfur dioxide as a function of L / G for a waste gas stream containing 80 ppm SO2.

FIG. 12 is a graph showing the removal of sulfur dioxide depending on L / G for a waste gas stream containing 200 ppm SO2.

FIG. 13 is a graph showing the removal of sulfur dioxide depending on L / G for waste gas streams containing 425, 600 and 1200 ppm SO2.

FIG. 14 is a graph showing the removal of sulfur dioxide depending on L / G for waste gas streams, with partial humidification or without wetting the inlet gas.

DETAILED DESCRIPTION OF THE INVENTION [0008] A detailed reference will now be made to the accompanying drawings that at least help illustrate various respective embodiments of the present invention. Referring to FIG. 1 and 2, one embodiment of a horizontal gas-liquid cleaning system is presented. In the embodiment shown, the horizontal gas-liquid cleaning system 1 comprises a horizontally arranged housing 10 comprising a waste gas inlet 12 receiving a waste gas stream 24 and a gas outlet 14 after the treatment, discharging the gas stream 26 after treatment. In the shown embodiment, the GS gas flow flows from the waste gas inlet 12, through the horizontally oriented housing 10 and exits through the gas outlet 14 after treatment. The horizontally arranged housing 10 further comprises a liquid inlet manifold 16 located downstream of the waste gas inlet 12. The liquid inlet manifold 16 includes at least one inlet lance 17, each inlet lance 17 being at least partially hollow, which facilitates the passage of liquid therethrough. Each inlet lance comprises at least one nozzle 18 connected to it, and sometimes a plurality of nozzles 18 connected thereto ("nozzle, nozzles"). A plurality of nozzles 18 are arranged in a horizontally arranged housing 10 in such a way as to facilitate the spraying of the purifying mist co-currently with the flowing gas stream GS. Accordingly, the nozzles 18 are fluidly connected to the purge liquid reservoir (not shown) through the inlet lances 17 of the liquid inlet manifold 16. The horizontally arranged housing 10 further includes a demister 20 located downstream of the liquid inlet port 16. The extinguisher 20 is adapted to remove entrapped droplets of liquid from the GS gas stream before the GS gas stream leaves the horizontally positioned housing 10 as a gas stream 26 after treatment, through the gas outlet after treatment. The liquid removed exits the horizontally positioned housing 10 via the liquid outlet 22.

[0009] The horizontally positioned housing 10 essentially has no flow-changing elements between the liquid inlet port 16 and the demister 20, thus constituting an essentially unrestricted gas-liquid contact zone 28. The present inventors have found that even in the absence of flow-changing elements in the gas-liquid contact zone 28, the removal of gaseous pollutants from the GS gas stream can be significantly increased in a relatively small space. The term "gaseous pollutants" as used herein means any undesired gaseous compound found in GS. In one embodiment, the gaseous pollutants are acidic compared to the cleaning liquid. In one embodiment, the gaseous pollutants contain sulfur compounds, such as sulfur dioxide and sulfur trioxide. In one embodiment, the gaseous impurities contain one or more NOx (e.g., NO, NO2) and halogenated hydrogen compounds (e.g., HF, HCl). In one embodiment, the gaseous pollutants comprise volatile organic compounds ("VOCs"), such as hydrocarbons, aldehydes and ketones, to name a few.

[0010] In one embodiment, the inlet gas stream comprises SO2. In this embodiment, the system 1 may be able to remove at least about 65% by volume. SO2 from the GS gas stream. In other embodiments, the system 1 may be able to remove at least about 70% by volume. SO2 from a GS gas stream (e.g., at least about 71% by volume SO2), such as at least about 75% vol. SO2, or even at least about 80% by volume SO2, or even at least about 85% vol. SO2, or even at least about 90% by volume SO2, or even at least about 95% vol. SO2 (e.g., at least about 96 vol% SO2).

[0011] Said degree of SO2 removal can be obtained for a relatively large range of SO2 inlet concentrations. In one embodiment, the inlet concentration SO 2 in the GS gas stream is not greater than 2000 ppm SO 2. In other embodiments, the SO2 concentration is no greater than about 1500 ppm, e.g. not greater than about 1000 ppm, or even no more than about 500 ppm, or even no more than about 200 ppm, or even no more than about 100 ppm, or even no more than about 80 ppm, or even no more than about 50 ppm, or even no more than about 35 ppm.

[0012] The above SO2 removal efficiencies can be obtained with relatively small L / G ratios. As used herein, L / G is the mean flow of purge liquid to the inlet fluid collector 16 measured in gallons ("L") per minute, measured close to the inlet to the inlet manifold 16, to the flow of water-saturated gas stream per 1000 The actual gas flux ("G") can be measured directly or can be calculated, for example, by measuring the total flow rate of the gas stream near the inlet 12 of the waste gas, including water evaporation and depression. temperature. According to the claimed invention, the L / G ratio is less than 20. In some embodiments, the L / G index is not more than about 18,

[0013] As already mentioned, the nozzles 18 are fluidly connected to each other at the liquid inlet manifold 16. The nozzles 18 are used to inject cleaning liquid into the housing 10 to create a purifying mist that flows co-currently with the GS gas stream. Thus, the nozzles 18 are substantially shaped in such a way that their ejection end is set towards the demister 20. The nozzles 18 are usually able to produce a purifying mist from the purifying liquid. The nozzles 18 may be adapted to spray the cleansing liquid according to any suitable spray pattern, forming a cleaning purge within the housing. In general, it is desirable that the nozzles 18 produce a cleaning purge that substantially covers the cross-sectional area of ​​the horizontally oriented housing 10. In this way, nozzles 18 can apply spraying acc. full cone model, spraying acc. empty cone model, fan atomization, or spraying acc. any combination of them.

[0014] The relative distance between each nozzle 18 can be chosen so that the purge mist from one nozzle coincides with the purifying mist of one or more adjacent nozzles 18. The purge mist may thus comprise a substantially cross-sectional area of ​​the horizontally arranged housing 10. The leaving step the purge mist nozzle can be selected such that a significant amount of purge mist remains in the air over a considerable length of the gas-liquid contact zone 28. In this way, significant amounts of cleaning mist may substantially cover the cross-sectional area of ​​the horizontally positioned housing 10 and the length of the gas-liquid contact zone 28, thereby ensuring direct contact between the GS gas stream and the purge mist in a substantially unrestricted gas contact zone 28. liquid. Such direct contact may facilitate the reaction of the gaseous pollutants present in the GS gas stream with the purifying agents contained in the purge mist. As a result, you can achieve high efficiency of removing gas pollutants.

In the case of the liquid inlet manifold 16, any number of nozzles 18 may be used with any number of spray patterns and / or droplet sizes and any combination to facilitate the operation of the horizontal gas liquid cleaning system 1. As a basic example, all nozzles 18 may have the same ability to generate cleansing mist (e.g., the ability to produce the same spray, the ability to produce the same momentum and / or the ability to produce the same droplet size). As an additional example, the first set of nozzles may have one mist generating capacity (e.g., one spray pattern, ability to produce one momentum and / or ability to produce one droplet size), and the second set of nozzles may have a second mist generating capacity (e.g., a second pattern of jets) . ability to produce a second shoot and / or the ability to produce a second droplet size). As a result, you can use other additional sets of nozzles (eg, third, fourth, etc.). In addition, any number of nozzles per lance 17 of the liquid inlet manifold 16 may be used. In the embodiment shown, three nozzles 18 are used for the lance 17 of the liquid inlet manifold 16. However, other configurations may also be used. Furthermore, as shown, the adjacent nozzles 18 can be set in a similar up, down and / or side direction (e.g., in the same vertical and / or horizontal plane), or the adjacent nozzles 18 can be offset in relation to one or several other nozzles 18. any number of nozzles per lance 17 of the liquid inlet collector 16 may be used. In the embodiment shown, three nozzles 18 are used for the lance 17 of the liquid inlet manifold 16. However, other configurations may also be used. Furthermore, as shown, the adjacent nozzles 18 can be set in a similar up, down and / or side direction (e.g., in the same vertical and / or horizontal plane), or the adjacent nozzles 18 can be offset in relation to one or several other nozzles 18. any number of nozzles per lance 17 of the liquid inlet collector 16 may be used. In the embodiment shown, three nozzles 18 are used for the lance 17 of the liquid inlet manifold 16. However, other configurations may also be used. Furthermore, as shown, the adjacent nozzles 18 can be set in a similar up, down and / or side direction (e.g., in the same vertical and / or horizontal plane), or the adjacent nozzles 18 can be offset in relation to one or several other nozzles 18.

[0016] According to the claimed invention, the nozzles are spiral nozzles. The spiral nozzles can be nozzles with a full conical or cone-shaped cone stream. The spiral nozzles may have a spraying angle of 60 degrees or 90 degrees. According to the claimed invention, the spiral nozzles eject the liquid under pressure in the range of about 377 kilopascals (40 psig) to about 550 kilopascals (65 psig). Furthermore, according to the claimed invention, the spiral nozzles have a liquid throughput ranging from about 57 liters per minute (15 gpm) to about 189 liters per minute (50 gpm). Spiral nozzles can be made of durable materials to increase the time of use. Accordingly, ceramics or other abrasion-resistant materials, such as stainless steel or silicon carbide, may be used to build the nozzles.

[0017] In general, the nozzles 18 should be arranged to reduce or reduce the amount of purge mist in contact with the housing walls 10. Accordingly, the housing 10 should generally be selected to reduce or reduce the purge mist being in contact with its walls. In any case, the cross-sectional area should not be too large so that the pressure drop across the housing 10 is not excessive.

[0018] The substantially unrestricted gas-liquid contact zone 28 can allow a slight pressure drop to be obtained along the horizontally positioned housing 10. The pressure drop is a function of several variables, but it is anticipated that in some embodiments, the pressure drop along the housing 10 may not be greater than 2.0 kilopascals (8 inches H2O). In one embodiment, the pressure drop is no more than 1.5 kilopascals (6 inches H2O). In other embodiments, the pressure drop in the housing is no more than 1.0 kilopascal (4 inches of water) or even no more than 0.5 kilopascal (2 inches of H2O) or even no more than 0.4 kilopascal (1.5 inches of H2O) ), measured by a GS gas stream flow rate of between about 3.7 meters per second (12 feet per second) and 13.7 meters per second (45 feet per second).

[0019] As already mentioned, the horizontally arranged housing 10 does not substantially have flow-altering elements between the liquid inlet manifold 16 and the demister 20, constituting a substantially unrestricted gas-liquid contact zone 28. The length of the gas-liquid contact zone 28 is dependent on the application and may be a function of e.g. the flow rate of the GS gas stream through the housing, the inlet concentration of the sulfur compounds, the cross-sectional area of ​​the housing and / or the concentration / alkalinity of the cleaning liquid, to name a few . In general, the length of the gas-liquid contact zone 28 must be long enough to facilitate effective interaction between the GS gas stream and the scavenger liquid, so that an adequate SO2 removal capacity can be achieved (e.g., at least about 90% by volume SO2),

[0020] The demister 20 may be any suitable liquid removal apparatus capable of removing liquid from the GS gas stream at the ranges of flow rates used. A particularly useful gas stream defogger with velocities ranging from about 3.7 to 8.2 meters per second (about 12 to about 27 feet per second) is a reducer / defogger with 2 chevron dividers.

[0021] The inlet gas stream GS may have a velocity so suited as to allow the removal of sulfur compounds during their residence in the purification system 1. In one embodiment, the aggregate velocity of the gas stream (average along the housing) is in the range of about 3.0 meters per second (m / s) to about 13.7 m / s (about 10 feet per second (fps) to 45 feet per second). In one embodiment, the collective gas stream velocity is in the range of about 6.7 m / s (22 fps) to about 8.2 m / s (27 fps). A gas velocity of 8.2 m / s (27 fps) or less may be suitable for a demister with 2 chevron partitions. Other types of demisters may be used at higher gas velocities or a depressurization zone may be used to reduce the aggregate velocity of the gas stream as described below.

[0022] In the embodiment shown, the housing 10 has a substantially equal cross-sectional area. However, in other embodiments (not shown), the housing 10 may have different cross-sectional area areas. For example, one part of the housing 10 may have one cross-sectional area and the second portion of the housing 10 may have a second cross-sectional area that differs from the first cross-sectional area. In one embodiment, the second cross-section area may be larger than the first cross-section area. In this embodiment, the second cross-sectional area may be considered as an expansion zone that may reduce the gas velocity. In one approach (not shown), the expansion zone is incorporated into the housing, facilitating a reduction in the inlet gas flow rate from a first speed (e.g., greater than about 8.2 m / s (27 fps)) to a second gas flow rate (e.g., not more than about 8.2 m / s (27 fps)). Thus, in some cases, the inlet velocity of the GS gas stream may be greater than the speed of the gas stream close to the defogger. In some cases, the velocity of the gas stream may be about 13.7 m / s (45 fps), and an expansion zone may be located in the housing in order to be able to reduce the velocity of the gas stream before it contacts the demister. In other embodiments, the combined gas stream velocity is greater than 8.2 m / s (27 fps) and no expansion zone is used, but a suitable demister is used. 2 m / s (27 fps)) to the second gas flow rate (e.g., not more than approximately 8.2 m / s (27 fps)). Thus, in some cases, the inlet velocity of the GS gas stream may be greater than the speed of the gas stream close to the defogger. In some cases, the velocity of the gas stream may be about 13.7 m / s (45 fps), and an expansion zone may be located in the housing in order to be able to reduce the velocity of the gas stream before it contacts the demister. In other embodiments, the combined gas stream velocity is greater than 8.2 m / s (27 fps) and no expansion zone is used, but a suitable demister is used. 2 m / s (27 fps)) to the second gas flow rate (e.g., not more than approximately 8.2 m / s (27 fps)). Thus, in some cases, the inlet velocity of the GS gas stream may be greater than the speed of the gas stream close to the defogger. In some cases, the velocity of the gas stream may be about 13.7 m / s (45 fps), and an expansion zone may be located in the housing in order to be able to reduce the velocity of the gas stream before it contacts the demister. In other embodiments, the combined gas stream velocity is greater than 8.2 m / s (27 fps) and no expansion zone is used, but a suitable demister is used. than the speed of the gas stream near the defogger. In some cases, the velocity of the gas stream may be about 13.7 m / s (45 fps), and an expansion zone may be located in the housing in order to be able to reduce the velocity of the gas stream before it contacts the demister. In other embodiments, the combined gas stream velocity is greater than 8.2 m / s (27 fps) and no expansion zone is used, but a suitable demister is used. than the speed of the gas stream near the defogger. In some cases, the velocity of the gas stream may be about 13.7 m / s (45 fps), and an expansion zone may be located in the housing in order to be able to reduce the velocity of the gas stream before it contacts the demister. In other embodiments, the combined gas stream velocity is greater than 8.2 m / s (27 fps) and no expansion zone is used, but a suitable demister is used.

[0023] The purification liquid can be any liquid suitable for producing the purge mist by means of nozzles 18 and for removing the sulfur compounds from the waste gas stream 24 as a result of its interaction (eg by reaction / absorption / co-radiation). The mismatched cleaning liquid may allow removal of any of the above-described gaseous pollutants before the GS gas stream leaves the horizontal casing 10 as a gas stream 26 after treatment, for example with any of the above described sulfur dioxide removal efficiencies. The mismatched cleaning liquid should allow removal of such gaseous pollutants at relatively low L / G ratios, such as any of the above-described L / G indices. In one embodiment, the purification liquid is a basic feed liquid, such as a sodium-based liquid and may contain, for example, sodium sulfite. In one embodiment, sodium hydroxide dust and / or sodium dust is used to form sodium sulfite in the cleaning liquid. In other embodiments, the cleansing liquid may contain other basic liquids, such as one or more of sea water, seawater enriched with lime, magnesium lime, and soda lime, to name a few. Thus, in some embodiments, the horizontal gas-liquid cleaning system may be integrated with existing water-containing / treatment systems to produce a cleaning liquid and / or regenerate the cleaning liquid used. In other embodiments, the cleansing liquid may contain other basic liquids, such as one or more of sea water, seawater enriched with lime, magnesium lime, and soda lime, to name a few. Thus, in some embodiments, the horizontal gas-liquid cleaning system may be integrated with existing water-containing / treatment systems to produce a cleaning liquid and / or regenerate the cleaning liquid used. In other embodiments, the cleansing liquid may contain other basic liquids, such as one or more of sea water, seawater enriched with lime, magnesium lime, and soda lime, to name a few. Thus, in some embodiments, the horizontal gas-liquid cleaning system may be integrated with existing water-containing / treatment systems to produce a cleaning liquid and / or regenerate the cleaning liquid used.

[0024] In one embodiment, the purification liquid is sodium-based and is regenerated by the mode of a dilute two-component alkaline agent or a concentrated two-component alkaline mode mode in which the first reagent (e.g., sodium sulfite) is used to remove sulfur dioxide from the gas stream 24 waste. The other reagent (e.g., slaked lime) is used to regenerate the waste liquid in order to use it as a cleansing liquid.

[0025] In the case of a one pass system, the scavenging liquid may exhibit a basicity that allows removal of sulfur dioxide from the waste gas stream 24. The alkalinity of the purifying liquid varies depending on the application and generally refers to the inlet concentration of SO2 and CO2. In one embodiment, such as for a waste gas stream containing no more than 80 ppm SO2, the alkalinity of the purge liquid can be at least about 300 ppm CaCO3, but no more than 500 ppm CaCO3. In another embodiment, such as for a waste gas stream with an inlet concentration of no more than 200 ppm SO2, the alkalinity of the purge liquid can be at least about 750 ppm CaCO3, but not more than about 1200 ppm CaCO3. Similarly, The pH of the cleaning liquid can be adjusted according to the inlet concentration of the sulfur compounds. The alkalinity and pH can be controlled in a manner known in the art for use with a waste gas stream containing more than 200 ppm SO2.

[0026] The horizontal gas-liquid cleaning system 1 can be used in many different applications. In one embodiment, the horizontal gas and liquid cleaning system 1 is used in a transmission duct line, in which the waste gas inlet 12 and the gas outlet after treatment are directly connected to each other in the waste gas transfer channel in the industrial installation. One implementation of such a configuration is shown in FIG. 3. In the illustrated embodiment, the waste gas 24 from the industrial plant (not shown) exits the industrial plant through the duct 50. The horizontal gas-liquid cleaning system 1 is seamlessly connected to the duct 50 via a conduit 51 and a gas inlet 12. As described above . such waste gas 24 may be treated in the gas-liquid cleaning system 1 and the gas 26 after treatment may be discharged through the gas outlet after treatment. Accordingly, the gas-liquid purification system 1 may comprise one or more transition zones (described above) for achieving a suitable gas flow rate and / or may include suitable demisters. In turn, the gas outlet 14 after treatment can be fluidly connected to the outlet channel 54 via a pipe line 53. Such a treated gas 26 can be discharged into the atmosphere. Accordingly, in one embodiment the duct 50 and the outlet duct 54 exist before the installation of the horizontal gas-liquid cleaning system 1, and the duct 52 connecting the duct 50 and the outlet duct 54 can be removed, facilitating the introduction of a horizontal gas-liquid cleaning system 1. Thus, in some embodiments, the horizontal gas-liquid purification system 1 can be added to an existing plant with relatively little adaptation of the existing waste gas cleaning system. In other embodiments, the horizontal liquid gas cleaning system is used in non-refurbishment applications, such as newly constructed gas scrubbers.

[0027] The waste gas stream 24 may be any waste gas stream requiring removal of gaseous pollutants therefrom. For example, the waste gas stream may be waste gas from an aluminum smelting plant, industrial steam boilers, or steelworks, to name a few. In one approach, the waste gas stream may be a stream of concentrated waste gas from an aluminum smelting plant, such as a concentrated waste gas stream from a dry dust extraction con centration operation, as disclosed in PCT Application No. PCT / FR2006 / 000415.

[0028] In one embodiment, the waste gas stream comprises SO 2 at a concentration of not more than an average of about 2000 ppm. In a particular embodiment, the waste gas stream contains no more than an average of about 200 ppm SO2 (e.g. waste gas from an aluminum smelting plant) and the scavenging liquid contains sodium dust. In another embodiment, the waste gas stream contains, on average, no more than 2,000 ppm SO2, and it is possible to use the mode of a dilute two component alkaline agent, a concentrated two component alkaline agent mode, and a method for purification with sodium lime or magnesium lime.

[0029] The temperature and humidity of the incoming waste gas stream 24 may affect the efficiency of the system 1. In one embodiment, a cooling water jet is applied upstream of the inlet liquid collector 16 to at least partially moisturize and / or cool the incoming waste gas stream, sometimes referred to as preliminary wetting. With respect to, for example, FIG. 1, a horizontal gas-liquid cleaning system 1 may optionally comprise a cooling sprayer 40 arranged before the inlet liquid collector 16 for spraying water (or other suitable cooling means) in the incoming waste gas stream 24 to cool such waste gas stream 24. Sprayer the cooling unit 40 can spray the cooling water countercurrently or co-currently with respect to the waste gas stream 24, to facilitate such cooling. The volume flow rate of such a cooling liquid stream is usually dependent on the application. The use of pre-wetting can lead to at least about 2% vol. SO2 removal efficiency, or even at least about 3% vol. increase, or even around 4% vol. growth. In some embodiments, the use of pre-wetting may allow system 1 to run at lower L / G ratios, while still obtaining adequate SO2 removal efficiency.

[0030] As noted above, the system can remove gaseous pollutants other than SO2 from the waste gas stream. For example, the system may remove one or more of NOx, HCl, HF, SO3, and VOC to name a few. In this range, various cleaning liquids can be used. In any case, the cleansing liquid may have a basic pH as compared to gaseous pollutants (in addition to volatile organic compounds), so as to facilitate their removal.

Examples

Example 1 - Test for SO2 removal with and without flow direction elements [0031] A horizontal gas-liquid purification system similar to that shown in FIG. 1, is manufactured in two configurations. The first system includes a 50% open contactor placed between the nozzles and the demister. The second system does not contain any elements changing the flow direction between the nozzles and the demister. The dehumidifier is a demister with 2 chevron partitions. Waste gas with an average SO2 concentration of about 80 ppm is delivered to the system with a volumetric flow rate of about 990 to 1400 real cubic meters per minute (3500 to 5000 ACFM), with an average velocity of about 6.7 m / s (22 feet for a second). Different types of nozzles, including vortex types, were used during the test, also known as W-type and jet-type nozzles, also known as BSL type or spiral nozzles with a 90 ° spray angle and the shape of a hollow cone splash. The purge liquid purification feed containing sodium sulfite and sodium carbonate feeds the nozzles at an L / G ratio ranging from about 15 to about 18.

[0032] In FIG. 4 shows the efficiency of removing SO2 depending on the L / G ratio using both the first configuration (50% contactor) and the second configuration (without the elements changing the direction of flow). In FIG. 5 shows the effectiveness of removing SO2 depending on alkalinity, both in the first configuration (50% contactor) and in the second configuration (without the elements changing the direction of flow). Higher average SO2 removal efficiencies are achieved with the second configuration, with no flow changing elements placed between the nozzles and the dehumidifier.

Example 2 - Testing the distance between nozzles and the defogger [0033] A horizontal gas-liquid cleaning system similar to that shown in FIG. 1. A waste gas with an SO2 concentration of approximately 77 ppm on average and a flow rate of approximately 7.0 m / sec (23 feet per second) is supplied to the system. The L / G indicator is around 16. The demister is a demister with 2 chevron partitions and is located about 6.1 m (20 ft) behind the nozzles. The concentration of SO2 in the gas is measured between the nozzles and the demister, the results of which are shown in FIG. 6. The efficiency of SO2 removal increases dramatically at a distance from 0 m to 2.4 m (0 ft to 8 ft) between the defogger and the nozzles, and then the level does not change.

Example 3 - Examination of Case Size and Number of Nozzles [0034] Various horizontal gas-liquid purification systems similar to those shown in FIG. 1. The size of the housing and the number of nozzles in the housing is varied. An inlet gas containing between about 100 ppm and 200 ppm SO2 is used and having a velocity of about 6.7 m / s (22 fps). A sodium-based purification liquid with a basicity ranging from about 600 ppm CaCO3 to about 1400 ppm CaCO3 is used. The system operates at an L / G ratio of 17. As shown in FIG. 7, over 90% of volume SO2 removal is achieved in systems with a larger cross-sectional area and more spray nozzles, with moderate alkalinity corresponding to (600-800 ppm) CaCO3, while 90% vol. SO2 removal is not achieved in smaller housings with fewer nozzles, even with alkalinity corresponding to 1000 ppm CaCO3 and higher. It is believed that the smaller housings have a larger "edge effect" in which a larger percentage of the mists collide with the housing walls, thereby reducing the effective amount of mist available for interaction with the waste gas stream.

Example 4 - Testing the configuration of the nozzle system [0035] A horizontal gas-liquid cleaning system similar to that shown in FIG. 1. The housing has a width of 47.0 cm (18.5 ") and a length of 75.57 cm (29.75"). A single column of nozzles with a different nozzle arrangement is used. These nozzle configurations are shown in FIG. 8a - 8c. The first system is configured as shown in FIG. 8a and includes a 3 x 3 nozzle arrangement BSJ9040 (hollow cone). The second system is configured as shown in FIG. 8a and includes a 3 x 3 nozzle system BSJ9040 (full cone). The third system is configured as shown in FIG. 8b and includes a 3 x 3 BSJ9040 nozzle arrangement (hollow cone). The fourth system is configured as shown in FIG. 8b and includes a 3 x 3 nozzle system BSJ9040 (full cone). The fifth system is configured as shown in FIG. 8c and includes a 3 x 1 nozzle arrangement BSJ90120. The inlet gas containing about 100 ppm SO2 and the alkaline scavenger based on sodium are used. The L / G ratio varies and the inlet gas speed is 6.7 m / s (22 fps). As shown in FIG. 9a and 9b, the configuration of the nozzle arrangement of Fig. 8b leads to a higher removal efficiency of SO2 than the configuration of the nozzle arrangement of FIG. 8a and 8c. In addition, hollow conical nozzles give higher efficiency than full conical nozzles. 8b leads to a higher removal efficiency of SO2 than the configuration of the nozzle arrangement of FIG. 8a and 8c. In addition, hollow conical nozzles give higher efficiency than full conical nozzles. 8b leads to a higher removal efficiency of SO2 than the configuration of the nozzle arrangement of FIG. 8a and 8c. In addition, hollow conical nozzles give higher efficiency than full conical nozzles.

Example 5 - Study of nozzle types [0036] A horizontal gas-liquid cleaning system similar to that shown in FIG. 1. The housing has a width of 70,168 cm (27,625 ") and a length of 70,168 cm (27,625"). The inlet gas containing about 100 ppm SO2 and the alkaline scavenging liquid are used. The L / G ratio varies and the inlet gas speed is around 22 fps. A number of nozzles are used to test the removal efficiency of SO2 through the nozzles. The tested nozzles include spiral jet nozzles, tangential jet nozzles, and eddy stream nozzles. In some nozzles, the spray angle is also diversified (90 ° and 60 °), similarly to the type of cone (hollow cone and full cone). As shown in FIG. 10

Example 6 - Testing of various inlet concentrations of SO2 and purifying liquids [0037] A horizontal gas-liquid cleaning system similar to that shown in FIG. 1. Different waste gas streams with a collective gas velocity of about 6.7 m / s (22 feet per second) and an SO2 concentration of about 80 ppm to about 1200 ppm are treated in a system with L / G ranging from about 11 to about 18. Various purification liquids are used to treat the waste gas stream. In particular, for a concentration test of 80 ppm to 200 ppm, the mode of a dilute two component alkaline agent is used, and when testing concentrations of 425 ppm, 600 ppm, and 1200 ppm, a concentrated two-component alkaline mode is used.SO2, and often at least 90% vol. SO2, with an L / G of less than 18, and often less than 16. FIG. 11 shows the amount of sulfur dioxide to be removed as a function of L / G for a waste gas stream containing 80 ppm SO2. In FIG. 12 shows the amount of sulfur dioxide to be removed as a function of L / G for a waste gas stream containing 200 ppm SO2. In FIG. 13 shows the amount of sulfur dioxide to be removed as a function of L / G for waste gas streams containing 425 ppm, 600 ppm, and 1200 ppm SO2.

Example 7 - Effect of pre-wetting of the waste gas stream. [0038] A horizontal gas-liquid cleaning system similar to that shown in FIG. 1. A waste gas stream with a collective gas velocity of about 6.4 m / s (21 feet per second) and an SO2 concentration of about 80 ppm is treated in a system with an L / G ranging from about 10 to about 16 In the first approach, the waste gas stream is treated without pre-wetting the waste gas stream before treating the waste gas stream with a cleaning liquid. In the second approach, the waste gas stream is pre-wetted before treating the waste gas stream with a cleaning liquid. As shown in FIG. 14, the system removes from about 2.7% by volume using pre-wetting. up to about 4.0% vol.

27487 / EP / 17

EP 2 265 357 B1