OA18500A

OA18500A - Multi-level gas scrubber with multiple flooded scrubber heads.

Info

Publication number: OA18500A
Application number: OA1201700469
Authority: OA
Inventors: Kenneth James Mcclelland
Original assignee: Pacific Green Technologies Inc.
Priority date: 2015-06-02
Filing date: 2015-11-02
Publication date: 2018-12-04

Abstract

The present invention relates to a wet scrubbing head design whose horizontal orientation and flooded operating characteristics allow complete wet scrubbing at multiple interaction zones each with different neutralizing reagents. The capacity for multiple scrubbing zones improves overall pollutant removal efficiency by adding polishing interaction zones for particulate and acid gas removal systems or by broadening the range of pollutants being removed by operating with a different neutralizing solution or a combination of these operating conditions. The flooded head design approach allows a single scrubber to accomplish high levels of removal efficiency for multiple pollutants which reduces cost, and footprint interaction complexities of the multiple devices it replaces. Flooded head scrubbers have application in combustion flue gas pollutant removal and in chemical and industrial applications that generate dust, odors and acid gases.

Description

MULT1-LEVEL GAS SCRUBBER WITI1 MULTIPLE FLOODED SCRUBBER HEADS

FIELD OF INVENTION

The invention relates to the removal of air pollution émissions and particularly relates to an 5 apparatus for scrubbing multiple contaminants from gases.

BACKGROUND OF INVENTION

The air pollution émissions resulting from the combustion of coal, municipal solid waste and biomass, and air émissions from chemical and industrial processes hâve been încreasingly restricted by govcmmental environmental agencies as a resuit of greater public demand for environmental 10 protection coupled with advancements in pollution abatement technologies which allow more restrictive standards to be implemented. The restrictions vary by nation, région and proximity of the air pollution source to population centers. The régulations target a wide range of combustion byproducts including particulate matter; acid gases such as sulphur dioxide, hydrogen chloride and hydrogen fluoride and metals such as mercury and métal groups known for their dctrimental effects 15 on human health. Many of the pollution abatement Systems in use today by utilities and industrial processcs hâve a history of development datîng from the establishment of the first environmental régulations. These devices employ known chemical and mechanical processes to remove the regulated pollution components from gas streams. The stringent émission limits in force today and those more stringent limits pending implémentation requtre alternative approaches. These alternative 20 approaches include adding refinements to existing technologies to enhance their pollutant removal efficiency.

The émissions resulting from the combustion of diesel fuels in marine and power génération applications are also sources of regulated émissions. General cargo and container ships that carry the goods of international trade are buming bunker grade fuels that contain in the range of 2.5% to 25 2.7% sulphur. ln addition, these marine diesel engines produce large amounts of ash, soot and unbumed fuel that are emitted to the atmosphère on the world’s océans. The sulphur and particulate émissions arc greater than permitted by the environmental régulations for land based operations.

Régulations for these émissions in territorial waters as well as dockside arc being implemented by régional and national environmental agencies and in international waters by the International Marine ί *

Organization. The options available to mcet the demands of these régulation include adding scrubbing technologies or clianging the fuel supply for sliips to low sulfur fuels.

Emission technologies for the combustion processes noted above generally can be dividcd into wet and dry Systems. Dry Systems utilize different technologies to address the removal of acid gases and 5 particulatc. Dry flue gas dcsulphurization is commonly accomplished by devices such as a spray drycr tower. Common among the dry particulatc Systems are bag filters and electrostatic precipitators.

Wet Systems used in conjunction with combustion flue gases commonly use aqucous based slurry containing an alkaline material such as limestonc, lime, hydrated lime or enhaneed lime as a 10 neutralizing agent. Wet scrubbing Systems employ several methods to create an interaction between the aqueous slurry and the contaminatcd flue gas. A simple approach uses sprayers in a spray tower or similar device to distribute the slurry into the flue gas to remove sulphur dioxide, hydrogen chloride and hydrogen fluoride through reaction with the slurry to form calcium based compounds. The interaction between the flue gas and the sprayed slurry is general in nature and is not as efficient 15 or effective as forced wet scrubbing Systems.

Forecd wet scrubbing Systems employ design approaches which force the (lue gas into alkaline reagents contained in an aqueous slurry. The design of these Systems créâtes a turbulent reaction zone that increases réaction time, and ensures complété interaction between the (lue gas and alkaline slurry wlitch improves acid gas removal efficiency. In addition, the turbulent zone créâtes an 20 environment for the transfer of particulate matter from the (lue gas to the scrubbing solution. These turbulent zones are generated by scrubbing heads containing ports submerged in a body of scrubbing fluid. The (lue gas passes through the ports at high velocity which créâtes a turbulent zone în the scrubbing solution that transfers the particulate and provides a reaction zone for chemical interactions.

Thus, this form of wet system has the capacity to remove multiple pollutants in a single pass. It is however, limited to operating with a single interaction în the scrubbing (luid réservoir, typically

Iocated at the base of the scrubbcr. Its approach does not allow stacking the scrubbing heads so as to attain multiple scrubbing zones as the gas rises through the scrubber.

i I

The more restrictive émission limits being imposed on industry to control air pollutanls from combustion, industrial and chemical processcs rcquirc enhanced approachcs in order to provide high efficiency and cost-effcctivc abatement Systems.

SUMMARY OF INVENTION

There is provided a vertical ly-oricntcd scrubbcr apparatus for removing a pluralîty of distinct contaminants from a contaminated gas stream, having a scrubbcr vessel having a ceiling, a floor, a cylindrical wall connecting the ceiling to the floor, a pluralîty of vertical ly-spaced heads, a volume above each head, a gas inlet, an induccd drafl fan, and a gas outlet; a submerged lower head positîoned horizontally across the lower end of the scrubbcr vessel, wherein the submerged lower 10 head includes a horizontal plate having a pluralîty of narrow slots extending throughout; a first scrubbing fluid réservoir disposed within the bottom end of the scrubber vessel below the submerged lower head, and a first reaction zone volume to a desired level above the submerged scrubbing head, the first scrubbing fluid selected to remove a first group of contaminants from the contaminated gas stream; a first scrubbing fluid inlet extending into a first volume above the 15 submerged head, first spraying means in fluid connection with the first scrubbing fluid inlet for spraying the first scrubbing fluid into the first scrubbing fluid reaction zone volume, and a first scrubbing fluid outlet in the floor; a first flooded head extending horizontally across the entire crosssection of the scrubber vessel at a position above the first scrubbing fluid inlet, wherein the first flooded head comprises a plate having a pluralîty of narrow slots extending throughout; a second 20 scrubbing fluid reaction zone volume disposed to a desired level above the first flooded head, the second scrubbing fluid selected to remove a second group of contaminants from the contaminated gas stream; and a second scrubbing fluîd inlet extending into a second volume above the first flooded head, second spraying means in fluid connection with the second scrubbing fluid inlet for spraying the second scrubbing fluid into the second scrubbing fluid reaction zone volume, and a 25 second scrubbing fluid outlet above the first flooded head passing through the scrubber vessel wall.

There îs further provided a vertically-oriented scrubbcr apparatus for removing a pluralîty of distinct contaminants from a contaminated gas stream, having a scrubber vessel having a ceiling, a floor, a cylindrical wall connecting the ceiling to the floor, a pluralîty of vertically-spaced heads, a volume above each head, a gas inlet, an înduced drafl fan, and a gas outlet; a first scrubbing fluid réservoir 30 disposed within the bottom end of the scrubber vessel to a desired level, the first scrubbing fluid selected to remove a first group of contaminants from the contaminated gas stream; a first flooded i I head extending horizontally across the scrubber vessel al a position above the gas inlet, dcfinîng a first volume between the first scrubbing fluid réservoir and the first floodcd head, wherein the first flooded head comprises a plate having a plurality of narrow slots extending throughoul; a first scrubbing fluid reaction zone volume disposed to a desired level above lhe first flooded head, the 5 réaction zone volume in fluid connection with the réservoir via one or more overflow tubes, each extending from lhe first scrubbing fluid réservoir through lhe first flooded head to a desired level above lhe first flooded head; a first scrubbing fluid inlet extending through lhe wall into a second volume above lhe first flooded head, first spraying means in fluid connection with lhe first scrubbing fluid inlet for spraying lhe first scrubbing fluid into lhe second scrubbing fluid réaction 10 zone volume, and a first scrubbing fluid outlet in lhe floor; a second flooded head extending horizontally across lhe entire cross-section of lhe scrubber vessel at a position above lhe first flooded head, defining a second volume between lhe first scrubbing fluid réaction zone volume and lhe second flooded head, wherein lhe second flooded head comprises a plate having a plurality of narrow slots extending throughoul; a second scrubbing fluid réaction zone volume disposed above 15 lhe second flooded head (o a desired level, the second scrubbing fluid selected to remove a second group of contaminants from lhe contaminaled gas stream; and a second scrubbing fluid inlet extending into a third volume above lhe second flooded head, second spraying means in fluid connection with lhe second scrubbing fluid inlet for spraying lhe second scrubbing fluid into the second scrubbing fluid réaction zone volume, and a second scrubbing fluid outlet above the second 20 flooded head passing through lhe wall of lhe scrubber vessel.

The scrubber apparatus may hâve one or more additional flooded heads extending horizontally across lhe entire cross-section of lhe scrubber vessel and stacked vertically above lhe other heads, each defining an additional volume in relation to lhe head below; one or more additional scrubbing fluid réaction zone volumes, each disposed above a corresponding flooded head to a desired level, 25 each additional scrubbing fluîd selected to remove a desired additional group of contaminants from lhe contaminaled gas stream; and one or more additional scrubbing fluid inlels extending through lhe wall into lhe corresponding additional volume above lhe corresponding additional flooded head, additional corresponding spraying means in fluid connection with lhe additional scrubbing fluid inlet for spraying lhe additional scrubbing fluid into lhe corresponding additional scrubbing fluid 30 réaction zone volume, and one or more corresponding additional scrubbing fluid oullels above lhe corresponding flooded head passing through lhe wall ofthe scrubber vessel.

4

The gas inlet may be located at the top end of the vessel and a gas inlet duct conducts the gas to a position below the lowermost head; or at the side of the vessel and a gas inlet duct conducts the gas to a position below the lowermost head; or below the lowermost head ofthe vessel.

The apparatus may further comprise a mist eliminator consisting of an absorbent mesh extending across the scrubber vessel. Each of the spraying means may be one or more spray nozzles. The size of the slots in the ilooded lieads may be selected to prevent passage therethrough of scrubbing fluid in the presence of pressurized gas below the head.

There is further provided the use of such a scrubber apparatus remove multiple contaminants from a contaminatcd gas stream according to a method comprising the steps of introducing a first scrubbing 10 fluid into the apparatus to a desired fluid level above the lowermost scrubber head; introducing a second scrubbing fluid into tlie apparatus to a desired level above the next highest scrubber head; cooling a contaminated process gas using a prior art gas conditioner; introducing the cooled contaminated gas under pressure from an induced draft fan into tlie apparatus at a position below the lowermost scrubber head; allowing the gas to pass upwardly through the lowermost scrubber head (o 15 transfer a first group of contaminants from the contaminated gas into the first scrubbing fluid in a first scrubbing fluid reaction zone volume above tlie lowermost scrubber head; allowing the gas to continue passîng upwardly through the next highest scrubber head to transfer a second group of contaminants from the contaminated gas into tlie second scrubbing fluid in a second scrubbing fluid reaction zone volume above the next highest scrubber head; spraying tlie exiting gas to remove 20 additional contaminants and slow the gas flow velocity; allowing the exiting gas to exit tlie scrubbing apparatus; separately removing first and second scrubbing fluids from the scrubber vessel to maîntain a desired level of each scrubbing fluid; and cleaning drained scrubbing fluids for rcuse în the scrubbing apparatus.

Tlie invention provides a scrubber apparatus for removing multiple contaminants from a 25 contaminated gas stream, comprising a scrubber vessel having a sériés of vertically-stacked scrubber heads, each scrubber head flooded with a different scrubbing fluid, each scrubbing fluid selected to remove a desired group of contaminants from the contaminated gas stream, wherein the contaminated gas flows under pressure from below tlie lowermost scrubber head upwardly through the sériés of flooded scrubber heads.

The apparatus may bc used to remove from a contaminated gas stream multiple contaminants selected from the group of contaminants comprising particulatc matter, mctals, hydrogen chloride, hydrogen fluoride, nitrous oxide, nitric oxide, carbon dioxide, and sulfur dioxide.

The présent invention employs a proprietary flooded horizontal scrubbing head that occupics the entire scrubber cross section. The polluted gas passes from below to above the head through an array of ports eut into the head. Scrubbing fluid is supported above the head by the gas as the gas passes through ports at high velocity to create a turbulent réaction zone within the supported scrubbing fluid. The level of scrubbing fluid is controllcd by overflow pipes or troughs and fluid is constantly added by distribution nozzles located above the turbulent zone. Further flooded horizontal heads can be added above the initial head at vertical intervals in the scrubber’s crosssection. Using the flooded head approach, the présent invention allows complété wet scrubbing at multiple levels, each level capable of operating with different neutralizing reagents. The capacity for multiple scrubbing zones provides the opportunîty to improve overall removal efTiciencics by adding polisliing réaction zones for particulatc and acid gas removal or by broadening the range of pollutants being removed by operating with a different neutralizing solution, or a combination of thèse operating conditions.

The présent invention takes a novel approach to the création of a turbulent scrubbing reaction zone at each of multiple levels with the capacity to use different neutralizing reagents at each level. Whcreas traditional approaches use pressure differential across a scrubbing head to force gas through an array of ports submerged în a body of fluid, the présent invention uses pressure differential to support the scrubbing fluid on top of a horizontal scrubbing head. The horizontal scrubbing head contains an array of ports through which the gas passes vertically upward into the flooded zone. The pressure differential and port design accélérâtes the gas sufficiently to create the desired highly turbulent réaction in the flooded zone above the head. The horizontal orientation of the scrubbing head allows multiple heads to be stacked within the same scrubber body. The flooded scrubber heads occupy the entire cross section of the scrubber body which dévotes 100% of the scrubber’s cross sectiona! area to scrubbing and the transit of gas. The horizontal orientation allows the scrubbing head to bc any shape required by the space available for the scrubbing equipment. Because it has the capacity to remove multiple pollutants in a single pass the system has a smaller footprint than the accumulation of equipment that it replaces and as a single unit it is more costeffectîve than multiple single purpose units. The flooded head can be incorporated into new scrubber designs or retrofitted into existing wet scrubbers using a submerged head design approach at its low est level.

The flooded scrubbing head system îs based upon a vertical orientation of the scrubber body and the horizontal orientation of the flooded scrubbing heads. The gas enters a plénum area above the 5 scrubbing fluid réservoir in the base of the scrubber body and below the first flooded head, The gas is moved lo the plénum by an induced draft fan capable of providing the volume required for lhe flue gas émission and pressure differential required to support the multiple réaction zones above lhe scrubbing head levels in the design. The pressure in the plénum is sufficient to force the gas through ports in lhe head and into a turbulent reaction zone above the head. The size, shape and plurality of 10 the ports in the head are such that lhe gas is sufficiently accelerated to create the desired depth and vigorof turbulence above the head.

The fluid on each head is continuously circulated. The scrubbing lluid is pumped from a fluid réservoir to a network of fluid distribution nozzles that deliver scrubbing fluid to the area above each head. Retum to the réservoir is provided by fluid level controls such as overflow troughs or 15 standpipes thaï pipe lhe fluid back lo the réservoir. The condition of lhe rcturning fluid is monitored for control factors such as pH and the réservoir is conditioned with additional neutralizing reagents lo rcturn the fluid to its optimum reaction condition before redistribution above the head. ln addition, the fluid may be processed by solids removal devices such as hydrocyclones to remove particulate matter collected by the scrubbing lluid.

As the gas continues lo rise in the flooded head scrubber it encounters additional flooded scrubbing heads with the same configuration of ports, fluid distribution and overflows to fluid réservoirs, ln cases where different scrubbing fluids are employed, the overflows direct the alternative scrubbing fluid to tankage with appropriate handling equipment for that fluid.

Upon exiting the turbulent zone of lhe final head the gas rises through demisters or similar devices 25 to remove free water from lhe gas. The gas is available to be ducted to the stack or further processes if required.

The flooded head system can also be used in conjunclion with submerged scrubbing heads al lhe base level of the scrubber. After exiting the turbulent zone above the submerged scrubbing head the i a gas riscs under pressure to a floodcd hcad(s) that operate in the full cross section of the scrubber in the same manner as described above.

BR1EF DESCRIPTION OF DRAWINGS

Λ detailed description of the preferred embodiment is provided below by way of example only and 5 with reference to the following drawings in which:

Figure IA is a top view ofa schematic drawing ofone embodiment ofthe floodcd scrubber head of the présent invention;

Figure IB is a latéral cross-sectional view through IB—IB ofthe floodcd scrubber head depicted in Fig. IA;

Figure IC is a blow-up schematic view of one corner of the embodiment of a flooded scrubber head shown in Fig. IA;

Figure 2 is a cross-sectional view of a multiple level scrubber having the flooded scrubber head of the présent invention at each scrubbing level; and

Figure 3 is a schematic of an embodiment of a system where initial scrubbing is performed by a 15 submerged scrubbing head and the flooded scrubber head of the présent invention is used for scrubbing on subséquent levels above the initial head.

DETAILED DESCRIPTION OF THE INVENTION

The présent invention provides a means of crcaling multiple wet scrubbing interaction levels 2, 4 within a single scrubber vcsscl 11, each level of which is capable of scrubbing 100% of the gas fiow 20 with a different scrubbing fluid. The présent invention uses a scrubber head design whose horizontal orientation and flooded operating characteristics allow the stacking of multiple heads within a single uct scrubber body. The ability to incorporate additional scrubbing interaction zones in a single system provides lhe opportunity to increase overall removal efficiency for pollutants such as particulate malter, acid gases or metals by adding polishing steps or to remove additional 25 regulated pollutants by utilizing other neutralizing rcagents. By incorporating the flooded scrubber heads of the présent invention în wet scrubber designs the resulting system will bave lower capital costs, a smaller footprînt and higher efficiency removal of multiple pollutants.

Referring to Figures ΙΛ lo IC, llic scrubbing head 50 is shown as a generic form to demonstrate the cléments of the head. The head 50 opérâtes in a horizontal orientation. The head may be manufactured from any sheet or plate material with sufficient strength, stiffncss, and thermal and chemical résistance properties. Typical matcrials are métal plate with the preferred matcrials being stainless steel. The horizontal cross-sectional shape of the head conforms to the shape of the scrubber body so as to allow a sealed fit between the periphery ofthe scrubbcr head and the inner circumference of the scrubber vessel. The head contains a plurality of ports 61 that may be in any shape, number and orientation to the head. The preferred port shape is a slot with length in the range of 125 to 200mm with a preferred width of 2mm. The spacing 63 of the ports is typically in the range of 20 to 25mm. The margins 65 between the ports and the edge of the head arc uniform with a preferred distance of 40mm. The head may contain accelerator plates 71 oriented at right angles to the head. The accelerator plates equally divide the space between the rows of ports 61. The margin 65 between the accelerator plates and the ports 61 is maintained at a preferred distance of 40mm. The accelerator plates are typically 150mm in height and contain scuppcrs at the head deck level to allow the latéral transfer of scrubbing fluid. The accelerator plate is of the same material as the scrubber head. Other parameters for the ports, margins, and accelerator plates are permitted within the scope ofthe invention.

Referring to Figure 2, there is depicted an example of a scrubber system incorporating the flooded scrubber heads of the present invention which is comprised of a scrubbing vessel (11) containing two flooded heads 12, 14.

The process of gas contamination removal using the system of Figure 2 begins with introduction of the contaminated gas I from a combustion or industrial process that generates particulate matter, acid gases and metals that require removal. The gas enters a lowermost plénum 3 bounded by a réservoir of a first scrubbing fluid 31 (or a solid membrane) below and a flooded head 12 above. The gas enters under positive pressure created by an induced draft fan (not shown). The gas pressure is sufficient to support a desired depth of a first scrubbing fluid on the heads 12, 14 and to overcome the pressure drop incurrcd by the gas as it passes through the ports în the heads. Preferred pressure at the lowermost plénum 3 is 450mm of water. The gas rîses through the ports în the lowermost head 12 at a velocity in the range of 20 to 25 meters per second. The gas enters a turbulent first scrubbing fluid reaction zone volume 33 where the gas and first scrubbing fluid are aggressively mixed. The first scrubbing fluid is selected for it rcactivity with a first group of « I contaminants targctcd for removal. The first serubbing fluid level on the lowermost head 12 is controlled by overflow tubes that pass through the head to the first serubbing fluid réservoir 31 that is typically located in the base ofthe serubber vessel 11. The overflow first serubbing fluid 37 is replaced by conditioned first serubbing fluid 34 from a first serubbing fluid inlet distribution header 5 13 in order to maintain fluid level and rcactivity with the contaminants being removed. In addition to chemical reactivity, the aggressive turbulence created in the wet serubber will cfTiciently remove particulate matter from the gas and transfer it to the serubbing fluid. After exiting the turbulent first serubbing fluid reaction zone volume the gas rïses under the remaining pressure to repeat the process, passing through a second flooded head 14 into a turbulent second serubbing fluid reaction 10 zone volume 35. For illustrative purposes the depth of the second serubbing fluid réaction zone volume 35 is controlled by a second serubbing fluid outlet, which may be a plurality of overflow troughs 23 that transfer the second serubbing fluid from the serubber vessel and route it to a second serubbing fluid réservoir not shown. Using this approach, the second serubbing fluid on head 14 can bc a different serubbing fluid than that on head 12, thus allowing polishîng or alternative 15 contaminants to be removed. Second serubbing fluid on head 14 is constantly replaced with conditioned serubbing fluid 36. The decontaminated gas 7 exiting the second serubbing fluid reaction zone volume 35 can bc ducted to the stack or further processes. Using this same approach, additional flooded serubbing heads may be serially added vertically within the serubber body for further polishîng or removal of other air pollutants as required by the process.

Referring to Figure 3, there is shown an example of a system comprising a serubbing vessel 11 containing a submerged lowermost head 22 beneath a flooded head 14 functioning as a second serubbing head.

The process in Figure 3 begins with the contaminatcd gas 1 from a combustion or industrial process that generates particulate matter, acid gases and mctals that requirc removal. The gas is ducted to the 25 submerged serubber head 22. The gas enters under positive pressure created by an induced draft fan (not shown). The gas pressure is sufficient to overcomc the pressure created by the depth of a first serubbing fluid on the lowermost head 22 and support the depth of a second serubbing fluid to bc supported on the second flooded head 14. Additional gas pressure is incorporated into the design to overcomc the pressure drop incurred by the gas as it passes through the ports in the heads and losses incurred in the duetîng of the gas. Preferred pressure at the lowermost plénum 3 is 450mm of water.

The gas rises through the ports in the submerged head 22 at a vclocity determined by the design of » t the head. The gas enters a turbulent first scrubbïng fluid réaction zone volume 33 where the gas and first scrubbïng fluid are aggressively mixed in a turbulent first scrubbing fluid reaction zone volume. The first scrubbing fluid is selected for its reactivity with a first group of contaminants targeled for removal. The first scrubbing fluid level on the submerged head 22 is controlled by sensors such as 5 differential pressure sensors which activate control valves to regulate the flow of fluid exiting for recirculation via a first scrubbing fluid outlet 32 in the floor of the vessel. Conditioned first scrubbing fluid 34 is added through a first scrubbing fluid inlet distribution header 13 in order to maintain reactivity with the contaminants being removed. ln addition to chemical reactivity, the aggressivc turbulence created in the wet scrubber will efficiently remove particulate matter from the 10 gas and transfer it to the scrubbing fluid. After exiting the turbulent first scrubbing fluid reaction zone volume 33 the gas riscs under the remaining pressure to repeal the process, passing through flooded head 14 into a turbulent second scrubbing fluid reaction zone volume 35. For illustrative purposes the depth ofthe second scrubbing fluid reaction zone volume 35 is controlled by a second scrubbing fluid outlet, which may be a plurality of overflow troughs 23 that transfer the second 15 scrubbing fluid from the scrubber vessel and roule il to a second scrubbing fluid réservoir (not shown). Using this approach, the upper flooded head 14 can operate with a different scrubbing fluid than is used on the submerged head 22 thus allowing polishing or the addition of alternative reagents to remove other regulated contaminants. Second scrubbing fluid on the flooded head 14 is constantly replaced with conditioned second scrubbing fluid 36 carried by second scrubbing fluid 20 inlet distribution header 15. The decontaminated gas 7 exiting the second scrubbing fluid réaction zone volume can be ducted to the stack or further processes. Using this same approach, additional flooded scrubbing heads may be serially added vertically within the scrubber vessel for further polishing or removal of other air pollulants as requîred by the process.

One or more flooded scrubbing heads as embodied in the présent invention offer advantages over 25 the current art represented by submerged scrubbing heads. Among the advantages is the ability to supply wet scrubbing of 100% of the gas at multiple levels of interaction zones with different neutralizing reagents within a single scrubbing body. This attribule allows a single scrubbing device to remove a broader range of pollutants al higher removal efficiencies. Scrubbers utilizing the flooded head design will bave a smaller and liighly flexible footprînt, lower capital cost, scalabilîty 30 and capacity to remove multiple pollutants in a single device. The flooded head has application in combustion processes including coal, biomass and municipal solid waste where the primary pollutants targeled for removal are particulate matter, acid gases including sulphur dioxide, hydrogen chloride and hydrogen fluoride, mêlais including mercury. In addition, scrubbers used in chemical and industrial processcs requîring the removal of dust, odors and acid gascs arc candidates for flooded head designs in both new and retrofit installations.

From the foregoing, it will be seen that this invention is one well adapted to attain ail of the ends and objectives herein set forth, together with other advantages which are obvious and which arc inhérent to the system. It will be understood that certain features and sub-combinations are of utilîty and may be employed with reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims. Many possible embodiments may be made of the invention without departing from the scope of the claims. It is to be understood that ail matter herein set forth 10 and shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense. It will be apprecîated by those skilled in the art that other variations of the preferred embodiment may also be practiced without departing from the scope of the invention.

Claims

Wliat is claimed is:

I. A vertically-oriented scrubber apparatus for removing a plurality of distinct contaminants from a contaminated gas stream, comprising:

5 a) a scrubber vessel having a ceïling, a floor, a cylindrical wall connecting the cciling to the floor, a plurality of vertically-spaced heads, a volume above each head, a gas inlet, an induced drafl fan, and a gas outlet;

b) a submcrged lower head positioned horizontally across the lower end of the scrubber vessel, wherein the submerged lower head includes a horizontal plate having a plurality of narrow ! 0 slots extending throughout;

c) a first scrubbîng fluid réservoir disposed within the bottom end of the scrubber vessel below the submerged lower head, and a first réaction zone volume lo a desired level above the submerged scrubbîng head, the first scrubbîng fluid selected to remove a first group ofcontaminants from the contaminated gas stream;

15 d) a first scrubbîng fluid inlet extending into a first volume above the submerged head, first spraying means in fluid connection with the first scrubbîng fluid inlet for spraying the first scrubbîng fluid into the first scrubbîng fluid réaction zone volume, and a first scrubbîng fluid outlet in the floor;

e) a first flooded head extending horizontally across the entire cross-section of lhe 20 scrubber vessel at a position above the first scrubbîng fluid inlet, wherein the first flooded head comprises a plate having a plurality of narrow slots extending throughout;

f) a second scrubbing fluid réaction zone volume disposed to a desired level above the first flooded head, the second scrubbing fluid selected to remove a second group of contaminants from lhe contaminated gas stream; and

25 g) a second scrubbing fluid inlet extending into a second volume above the first flooded head, second spraying means in fluid connection with lhe second scrubbing fluid inlet for spraying the second scrubbing fluid into the second scrubbing fluid reaction zone volume, and a second scrubbing fluid outlet above the first flooded head passing through the scrubber vessel wall.
2. A vcrtically-oriented scrubber apparatus for removing a plurality of distinct contaminants from a contaminated gas stream, comprising:

a) a scrubber vessel having a cciling, a floor, a cylindrical wall connecting the cciling to the floor, a plurality of vertically-spaced heads, a volume above each head, a gas inlet, an induced draft fan, and a gas outlet;

b) a first scrubbing fluid réservoir disposed within the bottom end of the scrubber vessel to a desired level, the first scrubbing fluid selected to remove a fïrst group of contaminants from the contaminated gas stream;

c) a first flooded head extending horizontally across the scrubber vessel at a position above the gas inlet, defining a first volume between the first scrubbing fluid réservoir and the first flooded head, wherein the first flooded head comprises a plate having a plurality of narrow slots extending throughout;

d) a first scrubbing fluid reaction zone volume disposed to a desired level above the first flooded head, the reaction zone volume in fluid connection with the réservoir via one or more overflow tubes, each extending from the first scrubbing fluid réservoir through the first flooded head to a desired level above the first flooded head;

f) a first scrubbing fluid inlet extending through the wall into a second volume above the first flooded head, first spraying means in fluid connection with the first scrubbing fluid inlet for spraying the first scrubbing fluid into the second scrubbing fluid reaction zone volume, and a first scrubbing fluid outlet in the floor;

g) a second flooded head extending horizontally across the entire cross-section of the scrubber vessel at a position above the first flooded head, defining a second volume between the first scrubbing fluid reaction zone volume and the second flooded head, wherein the second flooded head comprises a plate having a plurality of narrow slots extending throughout;

h) a second scrubbing fluid réaction zone volume disposed above the second flooded head to a desired level, the second scrubbing fluîd selected to remove a second group of contaminants from the contaminated gas stream; and

i) a second scrubbing fluid inlet extending into a third volume above the second flooded

5 head, second spraying means in fluid connection with the second scrubbing fluid inlet for spraying the second scrubbing fluid into the second scrubbing fluid réaction zone volume, and a second scrubbing fluid outlet above the second flooded head passing through the wall of the scrubber vessel.
3. The scrubber apparatus of claim I, further comprising:

10 a) one or more additional flooded heads extending horizontally across the entire crosssection of the scrubber vessel and scrially stacked vertically above the other heads, each defining an additional volume in relation to the head below;

b) one or more additional scrubbing fluîd réaction zone volumes, each disposed above a corresponding flooded head to a desired level, each additional scrubbing fluid selected to remove a

15 desired additional group of contaminants from the contaminated gas stream; and

c) one or more additional scrubbing fluid ïnlets extending through the wall into the corresponding additional volume above the corresponding additional flooded head, additional corresponding spraying means in fluid connection with the additional scrubbing fluid inlet for spraying the additional scrubbing fluid into the corresponding additional scrubbing fluid reaction

20 zone volume, and one or more corresponding additional scrubbing fluid outlets above the corresponding flooded head passing through the wall of the scrubber vessel.
4. The scrubber apparatus of claim 2, further comprising:

a) one or more additional flooded heads extending horizontally across the entire crosssection of the scrubber vessel and serially stacked vertically above the other heads, each defining an

25 additional volume in relation to the head below;

b) one or more additional scrubbing fluid reaction zone volumes, each disposed above a corresponding flooded head to a desired level, each additional scrubbing fluîd selected to remove a desired additional group of contaminants from the contaminated gas stream; and

c) one or more additional scrubbing fluid inlets extending through the wall into the corresponding additional volume above the corresponding additional floodcd head, additional corresponding spraying means in fluid connection with the additional scrubbing fluid inlet for spraying the additional scrubbing fluid into the corresponding additional scrubbing fluid réaction
5 zone volume, and one or more corresponding additional scrubbing fluid outlcts above the corresponding flooded head passing through the wall ofthe scrubber vessel.

5. The scrubber apparatus of claim 2, wherein the gas inlet is located at the top end of the vessel and a gas inlet duct conducts the gas to a position below the lowermost head.
6. The scrubber apparatus of claim 2, wherein the gas inlet is located at the side of the vessel 10 and a gas inlet duct conducts the gas to a position below the lowermost head.
7. The scrubber apparatus of claim 2, wherein the size of the slots in the flooded heads arc selected to prevent passage thercthrough of scrubbing fluid in the presence of pressurized gas below the flooded heads.
8. Λ method of removing multiple contaminants from a contaminated gas stream, the method 15 comprising the steps of:

a) introducing a first scrubbing fluid into the apparatus of claim I to a desired fluid level above the submerged scrubber head;

b) introducing a second scrubbing fluid into the apparatus of claim I to a desired level above the flooded scrubber head;

20 c) cooling a contaminated process gas using a prior art gas conditioner;

d) introducing the cooled contaminated gas under pressure from an induced draft fan into the apparatus of claim I at a position below the submerged scrubber head;

e) allowing the gas to pass upwardly through the submerged scrubber head to transfer a first group of contaminants from the contaminated gas into the first scrubbing fluid in a first

25 scrubbing fluid reaction zone volume above the submerged scrubber head;

f) allowing the gas to continue passing upwardly through the ilooded head to transfer a second group of contaminants from the contaminatcd gas into the second scrubbing fluid in a second scrubbing fluid reaction zone volume above the flooded head;

g) spraying the exiting gas to remove additional contaminants and slow the gas flow 5 velocity;

h) allowing the exiting gas to exil the scrubbing apparatus;

i) separately removing first and second scrubbing fluids from the scrubber vessel to maintain a desired level of each scrubbing fluid; and

j) cleaning drained scrubbing fluids for rcuse in the scrubbing apparatus.
10 9. The use of the scrubber apparatus of claim I to remove multiple contaminants from a contaminated gas stream according to the method of claim 8.

10. The method ofclaim 9, further comprising the additional step (ÎT) after step (f) of:

fl) allowing the gas to continue passing upwardly through one or more serially vertically stacked additional flooded heads to transfer one or more additional groups of contaminants from the 15 contaminated gas into one or more additional scrubbing fluids in each of one or more additional scrubbing fluid réaction zone volumes above each of the corresponding flooded heads.
11. A method of removing multiple contaminants from a contaminated gas stream, the method comprising the steps of:

a) introducing a first scrubbing fluid into the apparatus of claim 2 to a desired fluid level above 20 the first flooded scrubber head;

b) introducing a second scrubbing fluid into the apparatus of claim 2 to a desired level above the second flooded scrubber head;

c) cooling a contaminated process gas using a prior art gas conditioner;

d) introducing the cooled contaminated gas under pressure from an induced draft fan 25 into the apparatus of claim 2 at a position below the first flooded scrubber head;

e) allowing the gas to pass upwardly through the first flooded head to transfer a first group of contaminants from the contaminated gas into the first scrubbing fluid in a first scrubbing fluid réaction zone volume above the first flooded head;

f) allowing the gas to continue passing upwardly through the second flooded head to transfer a second group of contaminants from the contaminated gas into the second scrubbing fluid in a second scrubbing fluid reaction zone volume above the second flooded head;

g) spraying the exitîng gas to remove additional contaminants and slow the gas flow velocîty;

h) allowing the exitîng gas to exit the scrubbing apparatus;

i) separately removing first and second scrubbing fluids from the scrubber vcssel to maintain a desired level of each scrubbing fluid; and

j) cleaning drained scrubbing fluids for reuse in the scrubbing apparatus.
12. The use of the scrubber apparatus of claim 2 to remove multiple contaminants from a contaminated gas stream according to method of claim 11.
13. The method of claim 11, further comprising the additional step (Π) after step (f) of:

fl) allowing the gas to continue passîng upwardly through onc or more serially vertically stacked additional flooded heads to transfer one or more additional groups of contaminants from the contaminated gas into one or more additional scrubbing fluids in each of one or more additional scrubbing fluid réaction zone volumes above each ofthe corresponding flooded heads.
14. The use of the apparatus of claim 1 to remove from a contaminated gas stream multiple contaminants selected from the group of contaminants comprising particulate matter, metals, hydrogen chloride, hydrogen fluoride, nitrous oxide, nitric oxide, carbon dioxide, and sulfur dioxide.
15. The use of the apparatus of claim 2 to remove from a contaminated gas stream multiple contaminants selected from the group of contaminants comprising particulate matter, metals, hydrogen chloride, hydrogen fluoride, nitrous oxide, nitric oxide, carbon dioxide, and sulfur dioxide.

»
16. A method of removing multiple contaminants from a contaminated gas stream, the method comprising the steps of:

a) introducing a first scrubbing fluid into the apparatus of claim 2 to a desired fluid level above the first flooded head;

b) introducing a second scrubbing fluid into the apparatus of claim 2 to a desired level above the second flooded head;

c) cooling a contaminated process gas using a prior art gas conditioner;

d) introducing the cooled contaminated gas under pressure from an induced draft fan into the apparatus ofclaim 2 at a position below the first flooded head;

e) allowing the gas to pass upwardly through the first flooded head to transfer a first group of contaminants from the contaminated gas into the first scrubbing fluid in a first scrubbing fluid reaction zone volume above the first flooded head;

f) allowing the gas to continue passîng upwardly through the second flooded head to transfer a second group of contaminants from the contaminated gas into the second scrubbing fluid în a second scrubbing fluid reaction zone volume above the second flooded head;

g) spraying the exiting gas to remove additional contaminants and slow the gas flow velocity;

h) allowing the exiting gas to exit the scrubbing apparatus;

i) separately removing first and second scrubbing fluids from the scrubber vessel to maintain a desired level of each scrubbing fluid; and

j) cleaning drained scrubbing fluids for reuse in the scrubbing apparatus.
17. A flooded scrubber head for a wet gas scrubbing vessel, the flooded head comprising:

a) a horizontal plate extending across the entire latéral cross-section of the scrubbing vessel, the head having one or more rows of ports for the upward passage thercthrough of contaminated gases into a scrubbing fluid reaction zone volume above the head, wherein the entire perimeter ofthe head is adjacent to the inner circumfercncc ofthe scrubbing vessel, and the size, shape and angle of the ports is selected to prevent the scrubbing fluid from passing downward through the ports in the presence of pressurized gas below the head; and

b) one or more accelerator plates extending upwardly perpendicular to the head between 5 the one or more rows of ports into the scrubbing fluid réaction zone volume.