EA041091B1 - INTEGRATED WET SCRUBBING SYSTEM - Google Patents

Description

Technical field

The invention relates to air quality equipment. In particular, the invention relates to the removal of air emissions from industrial processes.

State of the art

As more and more is known about the harmful effects on human health, the environment and global warming from emissions from combustion, chemical and industrial processes, environmental protection agencies create and enforce restrictions that set the levels of permitted emissions of air pollutants. In order to meet not only current but also future regulations, advanced technologies are required to provide air emissions management systems for the global industry. In addition, these technologies must be energy efficient and must use consumables efficiently to minimize operating costs and environmental impact.

Emissions resulting from the combustion of coal, municipal solid waste, and biomass have been substantially limited by environmental protection agencies as a result of increased societal demand for environmental protection, together with improvements in pollution control technologies that enable more restrictive standards to be met. Restrictions may vary by nation, region, and the proximity of the fire source to population centers. The regulations address a wide range of combustion by-products, including particulate matter; acid gases such as sulfur dioxide, hydrogen chloride and hydrogen fluoride; metals from groups that are known to be harmful to health, such as mercury vapor and greenhouse gases, of which carbon dioxide and nitrogen oxides are the main ones. Most of the devices currently used in utilities and industrial processes to control pollutants are known for their development, beginning with the approval of the first standards for environmental protection. These devices use known chemical and mechanical processes to remove regulated contaminants from exhaust gases to acceptable levels. In addition, new technologies have been introduced that use alternative means to achieve the required emission concentrations. Emissions controls currently in place, as well as those awaiting implementation, require systems whose approach is more focused on meeting standards. The approach requires optimization of each stage of the control process by improving existing technologies, introducing more efficient approaches and combination systems to achieve a significant increase in removal efficiency.

The abatement technologies for the combustion technologies mentioned above can generally be divided into wet and dry systems. Dry systems use a variety of technologies to ensure the removal of acid gases and particulates. The desulfurization of dry flue gas is generally carried out by controlled spraying of an aqueous lime slurry into the gas stream as it rises through the spray drying tower. The lime slurry reacts with the sulfur and the process is controlled so that the water component of the slurry is completely evaporated, leaving a dry solid that can be recovered from the bottom of the column or removed using the selected particulate removal technology. Among dry particle removal systems, bag filters and electrostatic precipitators are common.

Wet systems used with combustion exhaust gases generally use an aqueous slurry containing alkaline material such as limestone, lime, slaked lime and/or lime with additives. Basic wet systems use nebulizers to propagate the slurry to react with the exhaust gas to remove oxides of sulfur, chlorine and fluorine by forming solid calcium salts such as calcium sulfites and sulfates, calcium chloride and calcium fluoride, which are produced by reaction with alkaline reagent as it rises through the irrigation column or similar device.

Brief description of the drawings

A detailed description of preferred embodiments is provided below by way of example only and with reference to the following drawings, in which:

fig. 1 is a schematic view of a system representing the present invention;

fig. 2 is a schematic view of another embodiment of the system of the present invention;

fig. 3 is a schematic view of another embodiment of the system of the present invention;

fig. 4 is a schematic view of another embodiment of the system of the present invention;

fig. 5 is a schematic view of another embodiment of the system of the present invention.

In the drawings, each embodiment of the invention is shown by way of example only. Should

- 1 041091 clearly understand that the description and drawings are intended only to illustrate and assist in understanding, and not to define the limitations of the present invention.

Detailed description of the invention

Alternative wet scrubbing systems use design approaches that force the exhaust gas to react with an alkaline agent, generally one or more of limestone, lime, slaked lime, or lime with additives. By forcing exhaust gas/slurry interaction, these systems create a vortex reaction zone, which increases reaction time, ensures complete interaction between exhaust gas and alkaline slurry, which improves acid gas removal efficiency. In addition, the vortex zone creates an environment for the transfer of particulates from the exhaust gas to the scrubbing solution. Thus, some forms of wet systems are designed to remove multiple contaminants in a single pass.

Advanced gas scrubbers have multiple levels of interaction, each with a vortex reaction zone that further treats 100% of the exhaust gas. Each of the reaction zones is configured to use a different reagent, which may be selected to improve the removal efficiency of the target contaminants or to allow additional contaminants to be removed in a single pass system.

Emissions resulting from the combustion of diesel fuels in the marine industry and power generation are also sources of regulated emissions. General cargo and container ships that carry goods for foreign trade burn high quality bunker fuels that contain up to 4.5% sulfur, although this is typically in the range of 2.5 to 2.7%. In addition, these marine diesel engines produce large amounts of soot, soot and unburnt fuel that are released into the oceans. The sulfur and particulate content is outside the environmental regulations for onshore mining operations. Emission limits on land are set by regional and national environmental agencies, and in international waters by the International Maritime Organization. Options include adding scrubber technologies or replacing ship fuel supplies with low sulfur fuels.

Chemical and industrial processes produce contaminants that can be removed by chemical interaction with neutralizing agents or transport mechanisms in the case of particulate matter.

A range of acid, odor and harmful chemical emissions from industrial processes require scrubbing technologies that can effectively remove multiple contaminants in a single pass. Environmental regulations are once again imposing limits on emissions that regulate harmful gases and dust emissions in these industrial sectors, which include the production of chemicals, pulp and paper, and the production of composite wood panels.

Stricter emission limits on air pollutants from combustion, industrial and chemical processes require technology improvements and integration to ensure that abatement systems meet future industrial requirements.

One application of the present invention is to remove particulate matter; acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride, from combustion and industrial processes. The system includes the following steps:

(1) cooling the hot gas and removing part of the acid gases by passing the exhaust gas through a chamber containing spray heads emitting an aqueous suspension formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives to water;

(2) introducing gas into the wet scrubber using the same aqueous slurry containing an alkaline agent such as limestone, slaked lime, lime or lime with additives as the scrubbing solution therein to remove the remaining acid gases and most of the particulate matter ;

(3) circulating the scrubbing solution through solids separators such as hydrocyclones to remove solids for further processing in dewaterers and directing the reduced solids component of the circulating stream to the scrubber heads followed by the addition of neutralizing agents;

(4) passing the gas stream into a wet electrostatic precipitator to remove the remaining solids;

(5) transferring the exhaust gas to the chimney;

(6) directing the effluent from the cooler, wet scrubber, and wet electrostatic precipitator to a solids settler;

(7) transferring the settled high density solids from the settler to a solids separation device such as a hydrocyclone;

- 2 041091 (8) treatment of a high solids overflow in a dewatering device such as a vacuum belt filter or a decanter centrifuge. The solids are sent to a landfill and the liquid portion is returned to a sump and (9) directing the low solids drain from the solids separator to a cooling block followed by conditioning with a neutralizing agent.

Another application of the present invention is to remove particulate matter; acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride; dioxins, VOCs (Volatile Organic Compounds) and mercury from combustion and industrial processes, and reheating as needed. The system includes the following steps:

(1) processing the contaminated exhaust gas stream through a primary particle removal device such as a multicyclone or the like to remove large particles;

(2) directing the exhaust gas to a heat exchange device;

(3) cooling the hot gas and removing part of the acid gases by passing the exhaust gas through a chamber containing spray heads emitting an aqueous suspension formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives to water;

(4) introducing gas into the wet scrubber using an aqueous slurry containing an alkaline agent such as limestone, slaked lime, lime or lime with additives as the scrubbing solution therein to remove the remaining acid gases and most of the particulate matter.

(5) circulating the scrubber solution through solids separators such as hydrocyclones to remove solids for further processing and directing the fluid balance to the scrubber heads followed by the addition of neutralizing agents;

(6) introducing the gas into a vessel where it reacts with granular activated carbon to remove dioxins, VOCs, and metals, the primary purpose being to remove mercury;

(7) passing the gas stream into a wet electrostatic precipitator to remove remaining solids;

(8) transferring exhaust gas to a heat exchanger; (9) supplying heated gas from a heat exchanger to a chimney.

(10) directing the effluent from the cooler, wet scrubber, and wet electrostatic precipitator to a sump.

(11) transferring the settled high density solids from the settler to a solids separation device such as a hydrocyclone.

(12) treating the high solids overflow in a dewatering device such as a vacuum belt filter or a decanter centrifuge. The solids are sent to a landfill and the liquid part is returned to the sump.

(13) directing the low solids drain from the solids separator to a cooling block, followed by conditioning with a neutralizing agent.

The design goal of the present invention includes the integration of compatible technologies in such a way that it significantly increases the regulatory limits for target air pollutants, while remaining cost-effective and adaptable. The present invention provides a system for removing targeted pollutants, including particulate matter, acid gases and mercury, from combustion and industrial process exhaust gases by integrating wet scrubber and gas scrubbing technologies with a wet electrostatic precipitator.

Referring first to FIG. 1, the system comprises a gas conditioning chamber (22); wet scrubber (23); and wet electrostatic precipitator (25). The process shown in Fig. 1 begins with a gas stream (1) from a combustion or industrial process that produces particulate matter, acid gases and metals to be removed. The gas (1) is sent to a gas conditioning chamber (22) containing spray nozzles or the like emitting an aqueous suspension (47) formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives to water. In the case of hot exhaust gases, the gas conditioning chamber (22) will cool the inlet gas from temperatures in the range of 120 to 200°C to a range of 50 to 60°C, with 55°C being the preferred outlet temperature. The conditioning chamber (22) also functions to remove some of the acid gases, typically sulfur dioxide, hydrogen chloride and hydrogen fluoride, by reacting the gases with the alkaline slurry (47). In addition, the conditioning chamber serves to moisten the solids, making them heavier and more reactive in the wet scrubber phase (23). The effluent (41) of the conditioning chamber contains reaction products and solid particles. In cases where an aqueous suspension (47) formed by adding an alkaline agent such as limestone, slaked lime,

- 3 041091 lime or lime with additives, the reaction products are solids, which include calcium sulfite, calcium sulfate, calcium chloride and calcium fluoride. These salts are sent to solids separation operations (26) for processing and recycling. Immediately after conditioning and cooling, the gas (4) is fed into a wet scrubber (23) configured to remove particles, acid gas and metals. The wet scrubber functionality is suitable for efficient removal of these target contaminants. The improved wet scrubber is the preferred embodiment due to the design of its head with multiple forcing functions, and its operation will be described in the process diagram. An aqueous slurry (47) is fed to the head of the improved gas scrubber (23) at each level, formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives. Inside the wet scrubber (23), the gas (4) is forced upward through the scrubber head, which contains a series of holes that provide a path for the gas to pass through the scrubber head. The gas passes through the holes at high velocity into the scrubbing solution (47), which creates a high vortex interaction zone above the head. The preferred depth of vortex motion is between 300 and 400 nm. After the gas exits the vortex zone on the first head, it rises in the scrubber and the process is repeated on the second head. The interaction removes acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride, by forming solid calcium compounds. The interaction also removes particulate matter from the gas and transfers it to the scrubbing fluid (47). The scrubbing fluid, with entrained salts and particles, is continuously pumped out of the scrubber as an effluent (41). The operating temperature of the wet scrubber will reflect the inlet gas temperature (4) of approximately 55°C. The gas (5) passes through the anti-fog device (28) as it exits the wet scrubber and is fed to the wet electrostatic precipitator (25) to remove the remaining solids, with particular emphasis on extra fine particles. As the gas passes through the wet electrostatic precipitator (25), it is subjected to a high voltage electric field, while at the same time the opposite charge is applied to the device. Operating voltage levels and flow direction vary between comparative designs. As a result of the electrostatic charge, solid particles are removed from the gas stream and are held on the charged wall of the device. Through a combination of moisture from the wet scrubber and occasional washing of the walls of the electrostatic precipitator, particles are removed as an effluent (41). The gas (7) leaves the wet electrostatic precipitator and is fed into the chimney. At the time of exit, the gas (7) contains practically no target contaminants.

The effluent (41) from the gas conditioning chamber, wet scrubber and wet electrostatic precipitator is directed to processes capable of separating solids from effluents, such as a hydrocyclone or the like. The waste (44) with a high content of particles is transferred to a dewatering device such as a vacuum belt filter or a decanter centrifuge (27). The filter cake (61) is sent to a landfill. The liquid component (46) from the dehydrator (27) and the drain (42) from the solids separation process are conditioned with an alkaline agent (45) and make-up water (43) as required to maintain the solution pH in the preferred range of 6.25 up to 6.75. The resulting conditioned slurry (47) is circulated to the wet scrubber and gas conditioning chamber. A portion of the clean drain (46) from the dewatering process is discarded, typically for use in other processes on site. The volume of discharge and the loss of evaporation during the cooling process with the addition of water (43) are compiled as part of the slurry conditioning process.

Referring to FIG. 2, the system configuration contains the following components: a device (20) for removing solids; chamber (22) for gas conditioning; wet scrubber (23); and wet electrostatic precipitator (25). The process shown in Fig. 2 begins with a gas stream (1) from a combustion or industrial process that produces particulate matter, acid gases and metals to be removed. In this iteration of the present invention, the gas (1) is sent to a solids removal device (20), such as a multicyclone, to remove most of the large particles. Solid particles (61) are collected in the device and transferred to a landfill. After exiting the solids removal device (20), the gas (2) is sent to a gas conditioning chamber (22) containing spray nozzles or the like emitting an aqueous suspension (47) formed by adding an alkaline reagent such as limestone, slaked lime, lime or lime with additives, into water. In the case of hot exhaust gases, the gas conditioning chamber (22) will cool the inlet gas from temperatures in the range of 120 to 200°C to a range of 50 to 60°C, with 55°C being the preferred outlet temperature. The conditioning chamber (22) also functions to remove some of the acid gases, typically sulfur dioxide, hydrogen chloride and hydrogen fluoride, by reacting the gases with the alkaline slurry (47). In addition, the conditioning chamber serves to moisten the solids, making them heavier and more reactive in the wet scrubber phase (23). The effluent (41) of the conditioning chamber contains reaction products and solid particles. In cases where water is used

- 4 041091 suspension (47), formed by adding an alkaline reagent such as limestone, slaked lime, lime or lime with additives, the reaction products are solids, which include calcium sulfite, calcium sulfate, calcium chloride and calcium fluoride. These salts are sent to solids separation operations (26) for processing and recycling. Immediately after conditioning and cooling, the gas (4) is fed into a wet scrubber (23) configured to remove particles, acid gas and metals. The wet scrubber functionality is suitable for efficient removal of these target contaminants. The improved wet scrubber is the preferred embodiment due to the design of its head with multiple forcing functions, and its operation will be described in the process diagram. An aqueous slurry (47) is fed to the head of the improved gas scrubber (23) at each level, formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives. Inside the wet scrubber (23), the gas (4) is forced upward through the scrubber head, which contains a series of holes that provide a path for the gas to pass through the scrubber head. The gas passes through the holes at high velocity into the scrubbing solution (47), which creates a high vortex interaction zone above the head. The preferred depth of vortex motion is between 300 nm and 400 nm. After the gas exits the vortex zone on the first head, it rises in the scrubber and the process is repeated on the second head. The interaction removes acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride, by forming solid calcium compounds. The interaction also removes particulate matter from the gas and transfers it to the scrubbing fluid (47). The scrubbing fluid, with entrained salts and particles, is continuously pumped out of the scrubber as an effluent (41). The operating temperature of the wet scrubber will reflect the inlet gas temperature (4) of approximately 55°C. The gas (5) passes through the anti-fog device (28) as it exits the wet scrubber and is fed to the wet electrostatic precipitator (25) to remove the remaining solids, with particular emphasis on extra fine particles. As the gas passes through the wet electrostatic precipitator (25), it is subjected to a high voltage electric field, while at the same time the opposite charge is applied to the device. Operating voltage levels and flow direction vary between comparative designs. As a result of the electrostatic charge, solid particles are removed from the gas stream and are held on the charged wall of the device. Through a combination of moisture from the wet scrubber and occasional washing of the walls of the electrostatic precipitator, particles are removed as an effluent (41). The gas (7) leaves the wet electrostatic precipitator and is fed into the chimney. At the time of exit, the gas (7) contains practically no target contaminants.

The effluent (41) from the gas conditioning chamber, wet scrubber and wet electrostatic precipitator is directed to processes capable of separating solids from effluents, such as a hydrocyclone or the like. The waste (44) with a high content of particles is transferred to a dewatering device such as a vacuum belt filter or a decanter centrifuge (27). The filter cake (61) is sent to a landfill. The liquid component (46) from the dehydrator (27) and the drain (42) from the solids separation process are conditioned with an alkaline agent (45) and make-up water (43) as required to maintain the solution pH in the preferred range of 6.25 to 6.75. The resulting conditioned slurry (47) is circulated to the wet scrubber and gas conditioning chamber. A portion of the clean drain (46) from the dewatering process is discarded, typically for use in other processes on site.

The volume of discharge and the loss of evaporation during the cooling process with the addition of water (43) are compiled as part of the slurry conditioning process.

Referring to FIG. 3, the system configuration contains the following components: a device (20) for removing solids; heat exchanger (21); chamber (22) for gas conditioning; wet scrubber (23); and wet electrostatic precipitator (25). The process shown in Fig. 3 begins with a gas stream (1) from a combustion or industrial process that produces particulate matter, acid gases and metals to be removed. In FIG. 3 also shows an exhaust gas reheat option (7) for applications where plume visibility is to be minimized. In this iteration of the present invention, the gas (1) is sent to a solids removal device (20), such as a multicyclone, to remove most of the large particles. Solid particles (61) are collected in the device and transferred to a landfill. The outlet gas (2) is fed into the heat exchanger (21) where it is cooled as it gives off heat to the colder countercurrent gas (7). The type of heat exchanger (21) and materials are chosen for the requirements for the working environment and heat transfer. The gas (3) exits the heat exchanger and is transferred to a gas conditioning chamber (22) containing spray nozzles or the like emitting an aqueous suspension (47) formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives , in water. In the case of hot exhaust gases, the gas conditioning chamber (22) will cool the inlet gas from temperatures in the range of 120 to 200°C to dia.

- 5 041091 range from 50 to 60°C, with the preferred outlet temperature being 55°C. The conditioning chamber (22) also functions to remove some of the acid gases, typically sulfur dioxide, hydrogen chloride and hydrogen fluoride, by reacting the gases with the alkaline slurry (47). In addition, the conditioning chamber serves to moisten the solids, making them heavier and more reactive in the wet scrubber phase (23). The effluent (41) of the conditioning chamber contains reaction products and solid particles. In cases where an aqueous slurry (47) formed by adding an alkaline reagent such as limestone, slaked lime, lime or lime with additives is used, the reaction products are solids which include calcium sulfite, calcium sulfate, calcium chloride and calcium fluoride . These salts are sent to solids separation operations (26) for processing and recycling. Immediately after conditioning and cooling, the gas (4) is fed into a wet scrubber (23) configured to remove particles, acid gas and metals. The wet scrubber functionality is suitable for efficient removal of these target contaminants. The improved wet scrubber is the preferred embodiment due to the design of its head with multiple forcing functions, and its operation will be described in the process diagram. An aqueous slurry (47) is fed to the head of the improved gas scrubber (23) at each level, formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives. Inside the wet scrubber (23), the gas (4) is forced upward through the scrubber head, which contains a series of holes that provide a path for the gas to pass through the scrubber head. The gas passes through the holes at high velocity into the scrubbing solution (47), which creates a high vortex interaction zone above the head. The preferred depth of vortex motion is between 300 and 400 nm. After the gas exits the vortex zone on the first head, it rises in the scrubber and the process is repeated on the second head. The interaction removes acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride, by forming solid calcium compounds. The interaction also removes particulate matter from the gas and transfers it to the scrubbing fluid (47). The scrubbing fluid, with entrained salts and particles, is continuously pumped out of the scrubber as an effluent (41). The operating temperature of the wet scrubber will reflect the inlet gas temperature (4) of approximately 55°C. The gas (5) passes through the anti-fog device (28) as it exits the wet scrubber and is fed to the wet electrostatic precipitator (25) to remove the remaining solids, with particular emphasis on extra fine particles. As the gas passes through the wet electrostatic precipitator (25), it is subjected to a high voltage electric field, while at the same time an opposite charge is applied to the device. Operating voltage levels and flow direction vary between comparative designs. As a result of the electrostatic charge, solid particles are removed from the gas stream and are held on the charged wall of the device. Through a combination of moisture from the wet scrubber and occasional washing of the walls of the electrostatic precipitator, particles are removed as an effluent (41). The gas (7) leaves the wet electrostatic precipitator and is fed into the chimney. At the time of exit, the gas (7) contains practically no target contaminants.

The effluent (41) from the gas conditioning chamber, wet scrubber and wet electrostatic precipitator is directed to processes capable of separating solids from effluents, such as a hydrocyclone or the like. The waste (44) with a high content of particles is transferred to a dewatering device such as a vacuum belt filter or a decanter centrifuge (27). The filter cake (61) is sent to a landfill. The liquid component (46) from the dehydrator (27) and the drain (42) from the solids separation process are conditioned with an alkaline agent (45) and make-up water (43) as required to maintain the solution pH in the preferred range of 6.25 to 6.75. The resulting conditioned slurry (47) is circulated to the wet scrubber and gas conditioning chamber. A portion of the clean drain (46) from the dewatering process is discarded, typically for use in other processes on site. The volume of discharge and the loss of evaporation during the cooling process with the addition of water (43) are compiled as part of the slurry conditioning process.

Referring to FIG. 4, the system comprises a gas conditioning chamber (22); wet scrubber (23); a reaction chamber (24) with granular activated carbon and a wet electrostatic precipitator (25). The process shown in Fig. 4 begins with a stream of (1) gas from a combustion or industrial process that produces particulate matter; acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride; dioxins, VOCs and metals, including mercury, to be removed. In this iteration of the present invention, the gas (1) is directed to a gas conditioning chamber (22) containing spray nozzles or the like emitting an aqueous suspension (47) formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives to water. In the case of hot exhaust gases, the gas conditioning chamber (22) will cool the inlet gas from temperatures in the range of 120 to 200°C to a range of 50 to 60°C, with 55°C being the preferred outlet temperature. Conditioni

- 6 041091 the blowing chamber (22) also functions to remove part of the acid gases, usually sulfur dioxide, hydrogen chloride and hydrogen fluoride, as a result of the reaction of gases with an alkaline suspension (47). In addition, the conditioning chamber serves to moisten the solids, making them heavier and more reactive in the wet scrubber phase (23). The effluent (41) of the conditioning chamber contains reaction products and solid particles. In cases where an aqueous slurry (47) formed by adding an alkaline reagent such as limestone, slaked lime, lime or lime with additives is used, the reaction products are solids which include calcium sulfite, calcium sulfate, calcium chloride and calcium fluoride . These salts are sent to solids separation operations (26) for processing and recycling. Immediately after conditioning and cooling, the gas (4) is fed into a wet scrubber (23) configured to remove particles, acid gas and metals. The wet scrubber functionality is suitable for efficient removal of these target contaminants. The improved wet scrubber is the preferred embodiment due to the design of its head with multiple forcing functions, and its operation will be described in the process diagram. An aqueous slurry (47) is fed to the head of the improved gas scrubber (23) at each level, formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives. Inside the wet scrubber (23), the gas (4) is forced upward through the scrubber head, which contains a series of holes that provide a path for the gas to pass through the scrubber head. The gas passes through the holes at high velocity into the scrubbing solution (47), which creates a highly vortex interaction zone above the head. The preferred depth of vortex motion is between 300 and 400 nm. After the gas exits the vortex zone on the first head, it rises in the scrubber and the process is repeated on the second head. The interaction removes acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride, by forming solid calcium compounds. The interaction also removes particulate matter from the gas and transfers it to the scrubbing fluid (47). The scrubbing fluid, with entrained salts and particles, is continuously pumped out of the scrubber as an effluent (41). The operating temperature of the wet scrubber will reflect the inlet gas temperature (4) of approximately 55°C. The gas (5) passes through the anti-fog device (28) as it exits the wet scrubber and is fed into a reaction vessel (24) containing a granular activated carbon filter bed. Granular activated carbon adsorbs dioxins, VOCs and metals, among which mercury is the primary target. The adsorption capacity of granular activated carbon is limited and the material can be reclaimed or landfilled. The gas (6) exits the reaction vessel and is fed to a wet electrostatic precipitator (25) to remove the remaining solids, with particular emphasis on extra fine particles. And it is fed into a wet electrostatic precipitator (25) to remove the remaining solids, with particular emphasis on extra fine particles. As the gas passes through the wet electrostatic precipitator (25), it is subjected to a high voltage electric field, while at the same time an opposite charge is applied to the device. Operating voltage levels and flow direction vary between comparative designs. As a result of the electrostatic charge, solid particles are removed from the gas stream and are held on the charged wall of the device. Through a combination of moisture from the wet scrubber and occasional washing of the walls of the electrostatic precipitator, particles are removed as an effluent (41). The gas (7) leaves the wet electrostatic precipitator and is fed into the chimney. At the time of exit, the gas (7) contains practically no target contaminants.

The effluent (41) from the gas conditioning chamber, wet scrubber and wet electrostatic precipitator is directed to processes capable of separating solids from effluents, such as a hydrocyclone or the like. The waste (44) with a high content of particles is transferred to a dewatering device such as a vacuum belt filter or a decanter centrifuge (27). The filter cake (61) is sent to a landfill. The liquid component (46) from the dehydrator (27) and the drain (42) from the solids separation process are conditioned with an alkaline agent (45) and make-up water (43) as required to maintain the solution pH in the preferred range of 6.25 to 6.75. The resulting conditioned slurry (47) is circulated to the wet scrubber and gas conditioning chamber. A portion of the clean drain (46) from the dewatering process is discarded, typically for use in other processes on site. The volume of discharge and the loss of evaporation during the cooling process with the addition of water (43) are compiled as part of the slurry conditioning process.

Referring to FIG. 5, the system contains a device (20) for removing solids; heat exchanger (21); chamber (22) for gas conditioning; wet scrubber (23); a reaction chamber (24) with granular activated carbon and a wet electrostatic precipitator (25). The process shown in Fig. 5 begins with a stream of (1) gas from a combustion or industrial process that produces particulate matter; acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride; dioxins, VOCs and metals, including mercury, to be disposed of. In this iteration of the present invention, the exhaust gas (1) is sent to the device (20) to remove

- 7 041091 solids, such as a multi-cyclone, to remove most of the large particles. Solid particles (61) are collected in the device and transferred to a landfill. The outlet gas (2) is fed into the heat exchanger (21) where it is cooled as it gives off heat to the colder countercurrent gas (7). The type of heat exchanger (21) and materials are chosen for the requirements for the working environment and heat transfer. The gas (3) exits the heat exchanger and is transferred to a gas conditioning chamber (22) containing spray nozzles or the like emitting an aqueous suspension (47) formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives , in water. In the case of hot exhaust gases, the gas conditioning chamber (22) will cool the gas from temperatures in the range of 120 to 200°C to a range of 50 to 60°C, with 55°C being the preferred outlet temperature. The conditioning chamber (22) also functions to remove some of the acid gases, sulfur dioxide, hydrogen chloride and hydrogen fluoride, by reaction with the alkaline slurry (47). In addition, the conditioning chamber serves to moisten the solids, making them heavier and more reactive in the wet scrubber phase (23). The effluent (41) of the conditioning chamber contains reaction products and solid particles. In cases where an aqueous slurry (47) formed by adding an alkaline reagent such as limestone, slaked lime, lime or lime with additives is used, the reaction products are solids which include calcium sulfite, calcium sulfate, calcium chloride and calcium fluoride . These salts are sent to solids separation operations (26) for processing and recycling. Immediately after conditioning and cooling, the gas (4) is fed into a wet scrubber (23) configured to remove particles, acid gas and metals. The wet scrubber functionality is suitable for efficient removal of these target contaminants. The improved wet scrubber is the preferred embodiment due to the design of its head with multiple forcing functions, and its operation will be described in the process diagram. An aqueous slurry (47) is fed to the head of the improved gas scrubber (23) at each level, formed by adding an alkaline agent such as limestone, slaked lime, lime or lime with additives. Inside the wet scrubber (23), the gas (4) is forced upward through the scrubber head, which contains a series of holes that provide a path for the gas to pass through the scrubber head. The gas passes through the holes at high velocity into the scrubbing solution (47), which creates a highly vortex interaction zone above the head. The preferred depth of vortex motion is between 300 and 400 nm. After the gas exits the vortex zone on the first head, it rises in the scrubber (23) and the process is repeated on the second head. The interaction removes acid gases, including sulfur dioxide, hydrogen chloride and hydrogen fluoride, by forming solid calcium compounds. The high swirl interaction also removes solids from the gas and transfers them to the scrubbing fluid (47). The scrubbing fluid, with entrained salts and particles, is continuously pumped out of the scrubber as an effluent (41). The operating temperature of the wet scrubber will reflect the inlet gas temperature (4) of approximately 55°C. The gas (5) passes through the anti-fog device (28) as it exits the wet scrubber and is fed into a reaction vessel (24) containing a granular activated carbon filter bed. Granular activated carbon adsorbs dioxins, VOCs and metals, among which mercury is the primary target. The adsorption capacity of granular activated carbon is limited and the material can be reclaimed or landfilled. The gas (6) exits the reaction vessel and is fed to a wet electrostatic precipitator (25) to remove the remaining solids, with particular emphasis on extra fine particles. As the gas passes through the wet electrostatic precipitator (25), it is subjected to a high voltage electric field, while at the same time an opposite charge is applied to the device. Operating voltage levels and flow direction vary between comparative designs. As a result of the polarity of the electrostatic charge, solid particles are removed from the gas stream and are held on the charged wall of the device. Through a combination of moisture from the wet scrubber and occasional washing of the walls of the electrostatic precipitator, particles are removed as an effluent (41). The gas (7) exits the wet electrostatic precipitator practically free of target contaminants and is fed into the chimney or additionally sent to the heat exchanger (21) if reheating is required. In the reheat option, the gas (8) is heated to a level that suits the chimney design and plume visibility requirements.

The effluent (41) from the gas conditioning chamber, wet scrubber and wet electrostatic precipitator is directed to processes capable of separating solids from effluents, such as a hydrocyclone or the like. The waste (44) with a high content of particles is transferred to a dewatering device such as a vacuum belt filter or a decanter centrifuge (27). The filter cake (61) is sent to a landfill. The liquid component (46) from the dehydrator (27) and the drain (42) from the solids separation process are conditioned with an alkaline agent (45) and make-up water (43) as required to maintain the solution pH in the preferred range of 6.25 to 6.75. The resulting condi

- 8 041091 the cationized slurry (47) is circulated to the wet scrubber and gas conditioning chamber. A portion of the clean overflow (46) from the dewatering process is discarded, typically for use in other areas of the process. The volume of discharge and the loss of evaporation during the cooling process with the addition of water (43) are compiled as part of the slurry conditioning process.

The integrated wet scrubbing system of the present invention offers advantages over prior art single technologies and designs whereby a stack of compatible technologies delivers contaminant removal efficiencies far greater than target pollutant, particulate matter, acid gas, dioxin requirements. , VOC, mercury and other metals. The system remains adaptable and, because of its efficiency, can be used to minimize consumption and consumable costs while still removing contaminants within regulatory limits.

From the foregoing, it will be clear that the present invention is highly adaptable to achieve all of the intended end goals and objectives, together with other advantages that are obvious and inherent in the system. It should be understood that certain features and subcombinations may be used and implemented with reference to other features and subcombinations. This is provided by the scope of the claims and is within its limits. Many possible embodiments of the invention may be practiced without departing from the scope of the claims. It should be understood that the entire concept presented herein, as shown in the accompanying drawings, should be interpreted as illustrative and not restrictive. One skilled in the art will appreciate that other variations of the preferred embodiment may also be practiced without departing from the scope of the invention.

Claims (15)

CLAIM 1. A method for removing contaminants from a hot exhaust gas stream, comprising the following steps: a) passing an exhaust gas stream through a gas conditioning chamber containing an aqueous slurry; b) passing the waste gas stream exiting the gas conditioning chamber into a wet scrubber containing the same aqueous slurry as in the gas conditioning chamber; c) passing the waste gas stream exiting the wet scrubber into a wet electrostatic precipitator to remove any remaining solids; d) transferring the exhaust gas stream exiting the wet electrostatic precipitator into a chimney; e) directing the effluent from the gas conditioning chamber, wet scrubber, and wet electrostatic precipitator to a solids separator to separate solids from a high solids overflow; e) directing the high solids overflow exiting the solids separation device to the dewatering device; g) disposal of solids exiting the dewatering device in a landfill; h) conditioning the overflow from the dehydrator with an alkaline agent to form an aqueous suspension; And i) circulating the aqueous slurry obtained in the previous step through the wet scrubber and gas conditioning chamber. 2. The method according to claim 1, characterized in that the gas conditioning chamber contains spray heads that emit an aqueous suspension obtained by adding an alkaline reagent selected from the group of alkaline reagents containing limestone, slaked lime, lime or lime with additives, in water. 3. The method according to claim 1, characterized in that the aqueous suspension is obtained by adding an alkaline reagent selected from the group of alkaline reagents containing limestone, slaked lime, lime or lime with additives to water. 4. Method according to claims 1 to 3, characterized in that the solids separator is a hydrocyclone. 5. Method according to claims 1 to 4, characterized in that the dewatering device is selected from the group of dewatering devices comprising a vacuum belt filter and a decanter centrifuge. 6. The method according to claims 1 to 5, characterized in that it comprises an additional step (a1) before step (a), comprising passing the exhaust gas stream through the solids removal device. 7. The method according to claim 6, characterized in that the solids removal device is a multicyclone. 8. The method according to claims 6, 7, characterized in that it includes an additional step (a ₂ ) after step (a1), including passing the exhaust gas stream exiting the solids removal device - 9 041091 substances, through a heat exchanger. 9. The method according to claims 1 to 8, characterized in that it comprises an additional step (c1) before step (c), comprising passing the waste gas stream leaving the wet scrubber to a reaction chamber with granular activated carbon. 10. A system for removing contaminants from a hot exhaust gas stream in accordance with the method according to claims 1-9, containing purifications connected in the technological sequence: a) a gas conditioning chamber, which, among other things, removes part of the acid gases from the stream and moistens the solid particles contained in the stream as a result of spraying an aqueous suspension; b) a wet scrubber containing an aqueous slurry and configured to remove particles, acid gas and metals; c) a solids removal device; d) a wet electrostatic precipitator connected to the wet scrubber, ensuring the removal of the remaining extra fine particles, equipped with e) an exhaust pipe that ensures the removal of the gas flow from the precipitator; e) a dewatering device installed downstream of the solids separation device to receive the high solids overflow from the solids separation device and to remove the solids for disposal in a landfill, as well as the liquid overflow for subsequent conditioning using an alkaline reagent to obtain an aqueous suspension. 11. The system according to claim 10, characterized in that it further comprises a solids removal device used in the implementation of an additional step (a1) before step (a), including passing the exhaust gas stream through the solids removal device in the method according to item 5. 12. The system according to claim 11, characterized in that it further comprises a heat exchanger used in the implementation of an additional step (a ₂ ) after step (a1), including passing the exhaust gas stream exiting the solids removal device through the heat exchanger within method according to claim 8. 13. The system according to claims 10-12, characterized in that it further comprises a reaction chamber with granular activated carbon used in the implementation of an additional step (c1) before step (c), including passing the exhaust gas stream leaving the wet scrubber, the reaction chamber with granular activated carbon within the method according to claim 9. 14. The system according to claims 10-12, characterized in that it is configured to remove from the exhaust gas stream one or more pollutants selected from the group of pollutants containing particles, sulfur dioxide, hydrogen chloride and hydrogen fluoride. 15. The system according to claim 13, characterized in that it is configured to remove from the exhaust gas stream one or more pollutants selected from the group of pollutants containing particles, sulfur dioxide, hydrogen chloride, hydrogen fluoride, dioxins, volatile organic compounds and mercury.