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WO2018186909A1 - Systèmes et procédés pour le contrôle de mercure de post combustion a l'aide d'injection de sorbant et de lavage hydraulique - Google Patents

Systèmes et procédés pour le contrôle de mercure de post combustion a l'aide d'injection de sorbant et de lavage hydraulique Download PDF

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Publication number
WO2018186909A1
WO2018186909A1 PCT/US2017/059606 US2017059606W WO2018186909A1 WO 2018186909 A1 WO2018186909 A1 WO 2018186909A1 US 2017059606 W US2017059606 W US 2017059606W WO 2018186909 A1 WO2018186909 A1 WO 2018186909A1
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Prior art keywords
flue gas
powdered
sorbent
gas desulfurization
mercury
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PCT/US2017/059606
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English (en)
Inventor
David W. Mazyck
Regina Rodriguez
Christine O. VALCARCE
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Carbonxt Inc
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Carbonxt Inc
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Priority to CA3059203A priority Critical patent/CA3059203A1/fr
Publication of WO2018186909A1 publication Critical patent/WO2018186909A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/64—Heavy metals or compounds thereof, e.g. mercury
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/75—Multi-step processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/81—Solid phase processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/102—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/60—Heavy metals or heavy metal compounds
    • B01D2257/602—Mercury or mercury compounds

Definitions

  • This invention relates, in general, to a system for cleaning flue gas, and, in particular, to a system and method for removing mercury with a powdered sorbent injection prior to or into a wet scrubbing system.
  • activated carbon is a high surface area sorbent typically created from the activation of coal (or other material high in carbon content) in a controlled, environment to create a. porous network. This porous network and chemical activity of the AC can be manipulated during activation/manufacturing to create an AC that will preferentially adsorb certain contaminants of concern (e.g., mercury from power plant flue gas to meets MATS standards) . Additionally, post activation treatment can be performed to enhance the chemical reactivity of the AC for the target compound ( s ) of interest.
  • the AC is ground and sized to produce powdered activated carbon (PAC), most typically to 95% passing the 325 mesh for mercury capture from flue gas .
  • PAC powdered activated carbon
  • bromine is a strong oxidant, it can also cause oxidation and corrosion of the duct system and other equipment with which it comes into contact, causing increased maintenance and cost. Further, there are currently no monitoring requirements for bromine compounds; but if emitted to the atmosphere, it would be detrimental to the environment (e.g., ozone depletion in the air and reaction to form carcinogenic compounds in water) . Therefore, it would be advantageous to use alternative methods to reduce sorbent injection rates and still achieve low mercury emissions.
  • Smaller particle size sorbents have negative operational effects. For instance, particle sizes less than 6 microns are difficult to capture with particulate control devices. Small particles escaping capture can lead to opacity issues and compliance issues with particulate emissions (PM) standards. Furthermore, super ⁇ fine sorbents laden with pollutants may be released to the environment .
  • Sorbent injection as applied for control, of mercury for MATS compliance, typically involves the pneumatic conveyance of a powdered sorbent from a storage silo into the process gas of a power plant's flue duct downstream of the boiler and upstream of a particulate control device such as an electrostatic precipitator
  • the powdered sorbent disperses and adsorbs mercury and other unwanted constituents in the flue gas .
  • the powdered sorbent with adsorbed mercury (and other constituents) then is captured and removed from the gas by a particulate control device.
  • mercury capture sorbents typically will be co-collected with other particle matter such as fly ash in an electrostatic precipitator, fabric filter, an electrostatic precipitator in series with a fabric filter, two electrostatic precipitators in series, two fabric filters in series, or similar devices.
  • the sorbents ' capacity for mercury is limited by the temperatures naturally present (e.g., greater them 350° F) as the injected sorbents physically and chemically adsorb mercury through endothermic processes.
  • the time between the injection point and collection point typically is less than three seconds. Therefore, the adsorption of mercury is limited by diffusion and reaction kinetics possible in this short time .
  • a fabric filter is used, as the particulate control device, longer residence times can be realized. This technique is not preferred due to the high cost to install and. operate fabric filters as the primary particulate control device.
  • a drawback to co-collection of sorbents with, fly ash has arisen in some scenarios when fly ash is sold as a commodity product. Comingling the sorbent and fly ash makes the mixture of a quality no longer acceptable to sell.
  • two particulate control devices may be employed in series with the second being a fabric filter and sorbent injection for mercury control between the two. This technique segregates the sorbent from fly ash collection and allows for longer contact times for the sorbent to collect mercury. While effective, the capital expenditure, additional operational costs, and pressure drop of the additional fabric filter unit are exorbitant and increase the cost of control.
  • sorbent might be injected into the later sections of an electrostatic precipitator so as to try to segregate fly ash material and sorbent. This method, however, even further limits residence time for the carbon to remove mercury, as compared to traditional injection upstream of the electrostatic precipitator, so often would not improve mercury removal or injection rates necessary to substantially reduce mercury emissions .
  • the process gas continues through flue gas ducts with decreased levels of mercury and other constituents. At this point, it is either emitted out of the stack or perhaps passes through a wet flue gas desulfurization ( FGD) unit when installed.
  • FGD wet flue gas desulfurization
  • Wet flue gas desulfurization units are currently installed on over 50% of the MW capacity in the United States to reduce sulfur dioxide (SO 2 ) emissions. While intended for SO 2 capture, mercury also can be captured in the wet flue gas desulfurization units . A high percentage of mercury in the flue gas will partition to a wet flue gas desulfurization liquid when it is found in the oxidized form, but the elemental mercury will pass through without capture.
  • Sorbent injection is a proven effective way to remove mercury; however, for some applications, the amount of PAC required can be very high and, therefore, costly (e.g., because of the high temperatures, short residence times, and numerous other complicating factors ) .
  • the present invention disclosed herein is directed to systems and methods for post combustion mercury control using sorbent injection and wet scrubbing .
  • the present invention is directed to a sorbent composition for removing mercury from flue gas, including a powdered sorbent having a fifty percent distribution particle size of from about 20 micrometers to about 75 micrometers.
  • the powdered sorbent may have a fifty percent distribution particle size of from about 25 micrometers to about 75 micrometers.
  • the powdered sorbent may have a fifty percent distribution particle size of from about 30 micrometers to about 75 micrometers .
  • the powdered sorbent may be powdered activated carbon.
  • the powdered activated carbon may improve mercury removal without halogens.
  • the powdered sorbents may reduce mercury concentrations in the air phase.
  • the powdered sorbents may reduce mercury concentrations in the liquid phase .
  • the present invention is directed to a method of cleaning flue gas, the method including removing particulates from flue gas using a particulate removal system; and injecting a powdered sorbent into the flue gas, wherein the powdered sorbent has a fifty percent distribution particle size of from about 20 micrometers to about 75 micrometers .
  • the method may also include removing the powdered sorbent from dewatered slurry in a flue gas desulfurization system using a hydrocyclone in communication with the flue gas desulfurization system.
  • the hyrocyclone is followed by a vacuum filter.
  • the powdered sorbent may be powdered activated, carbon.
  • the powdered activated carbon may improve mercury removal without halogens .
  • the present invention is directed to a method of cleaning flue gas, the method including removing particulates from flue gas using a particulate removal system; and injecting a powdered sorbent into the WFGD liquor, wherein the powdered sorbent has a fifty percent distribution particle size of from about 20 micrometers to about 75 micrometers.
  • the method may also include removing the powdered sorbent from dewatered slurry in a flue gas desulfurization system using a hydrocyclone in communication with the flue gas desulfurization system.
  • the hydrocyclone is followed by a vacuum filter.
  • the powdered sorbent may be powdered activated carbon.
  • the powdered activated carbon may improve mercury removal without halogens .
  • FIG. 1 is an illustration of a post combustion mercury control using sorbent (in many cases, activated carbon injection (A.CI) system) and wet scrubbing according to an embodiment
  • Figure 2 is a chart showing improved, mercury capture when using an Improved Sorbent Injection System according to an embodiment
  • Figure 3 is a diagram of the improved results of mercury removal after injection of the activated carbon according to an embodiment.
  • Figure 4 is a flowchart of a process for controlling mercury from process gas according to an embodiment .
  • the Improved Sorbent Injection System includes injecting the sorbent at an improved point in the post-combustion cleaning system of a coal-fired, power plant (or, in alternatives, other types of power plants and exhaust systems ⁇ .
  • the Improved Sorbent Injection System includes injecting the sorbent at a point in the system where it later can be filtered, out without affecting other cleaning processes.
  • the sorbent injected is activated carbon; however, in alternatives, other sorbents may be used. When the term "sorbent" is used herein, in many embodiments this may be activated carbon, although other sorbents may be used.
  • the Improved Sorbent Injection System additionally includes the revelation that the available electrostatic precipitators may be on the hot side of an air-heater, which is a more challenging environment for sorbents to remove mercury because of the elevated temperatures and short residence times. Therefore, the Improved Sorbent Injection System includes the use of alternative injection strategi ⁇ s wit,h longer residence times, better mixing, and lower temperatures that are more advantageous .
  • SO3 sulfur trioxide
  • SO3 also can be found in substantial quantities when power plants inject it to condition fly ash aiding in its removal.
  • PAC and most sorbents traditionally lose their capacity for mercury removal with increasing concentrations of SO 3 .
  • SO3 concentration will be highest right after the boiler and will decrease through the duct system as it sorbs and reacts with fly ash.
  • a standard power plant setup typically includes a boiler, followed by an air heater, and followed by a particulate control device ⁇ electrostatic precipitator or fabric filter) that exits in an exhaust stack.
  • a particulate control device ⁇ electrostatic precipitator or fabric filter
  • SCR selective catalytic reduction
  • NO x s nitrogen oxides
  • FGD flue gas desulfurization units
  • Embodiments of Improved Sorbent Injection System provide that PAC will no longer accumulate with the fly ash, since the overwhelming majority of fly ash viill occur in the traditional particulate capture equipment (i.e., electrostatic precipitator, fabric filter) . Therefore, this fly ash byproduct can be used, and sold for various purposes, such as for use in concrete. Since the injection point typically is further downstream, effluent v/ill be cooler . The longer residence time and cooler temperature will lead to improved removal of mercury. After the electrostatic precipitator or other particulate control device, gases that might compete with the activity of the PAC in the removal of the mercury v/ill be lessened.
  • the re-emission of mercury likely is reduced, since more of the mercury will be captured in the PAC and is not available for the reaction in the slurry. Since the mercury will not be as available in the slurry, when the slurry is dewatered, the residual mercury and other reaction byproducts in the dewatered slurry will be lessened.
  • the wet flue gas desulfurization solids byproduct integrity can be maintained for reuse, recycling, or disposal.
  • Embodiments of the Improved Sorbent Injection System were not known or expected, since the wet flue gas desulfurization system is used for control of SO 2 gases; and using it for particulate removal of powdered sorbent s is an unexpected application.
  • the wet flue gas desulturization unit is quite suited for the removal of powders, even though this is not a typical application.
  • Mercury removal v/ill occur in the gas phase, and then be retained during contact in the wet flue gas desulturization unit .
  • Those in the art focus on capturing mercury from the liquid phase of a wet flue gas desulfurization unit.
  • the position of the injection of powdered sorbent provides gas phase capture of mercury in parallel with liquid phase mercury capture.
  • SO 3 will be lower downstream of the particulate control devices, thereby reducing the exposure of the sorbent to this detrimental acidic compound and thereby eliminate the need to apply dry sorbent injection to eliminate S0 3 before it comes into contact with the sorbent. Also, since the temperature of the flue gas will be cooler at the point of injection, the activity of S0 3 is reduced. Also for wet flue gas desulfurization units, the powdered sorbent materials contribute to the reduction of other unwanted reactions and constituents in the discharged liquid (such as heavy metals and nutrients) after contact with the slurry. In this way, there is the advantage of serving as two treatment processes (one for mercury removal and the other for wastewater treatment) encompassed by one material and system.
  • specifically engineered PACs for mercury removal are applied with sorbent injection for mercury removal from coal-fired power plant flue gas .
  • sorbent injection for mercury removal from coal-fired power plant flue gas In concert with the engineered PACs, complimentary improvements to the overall system are provided.
  • PAC is utilized as the sorbent, it can be engineered also to improve wet flue gas desulfurization slurry chemistry and improve the quality of the discharged wastewater.
  • some systems may teach that merely the injection of PAC prior to the flue gas desulfurization is sub-optimal and call for the injection of additional materials and other treatments .
  • the proper positioning of the injection site of the PAC at proper temperatures and after the removal of much particulate, with the proper PAC selection an advantageous system is achieved.
  • System 100 may be a coal-fired electric power generation plant, in one embodiment.
  • System 100 may include a boiler 102, such as for a coal-fired power plant.
  • the process gas or flue gas to be treated may originate from many industrial facilities such as a power plant, cement plant, v/aste incinerator, or other facilities that will occur to one skilled in the art .
  • Boiler 102 may be a coal-fired boiler that burns or combusts coal to heat water into superheated steam for driving steam turbines that produce electricity. These types of power plants are common throughout the U.S. and elsewhere. Boiler 102 may further include an economizer 104, in one embodiment. Economizer 104 may be used to recover heat produced from boiler 102.
  • the flue gets or process gas 106 exiting boiler 102 and/or economizer 104 may then be flowed, transported, ducted, piped, etc. via one or more process lines 108 to a selective catalytic reduction unit 110 for the removal, of nitrogen containing compounds, in one embodiment .
  • selective catalytic reduction unit 110 may convert NO x compounds to diatomic nitrogen ( 2 ) and water (H 2 0) using a catalyst and a gaseous reductant, such as an ammonia containing compound.
  • Process gas 106 may then be flowed, transported, ducted, piped, etc. to a heat exchanger, pre-heater, and/or air heater 112 where heat is transferred from process gas 106 to a feed of air to be fed back into boiler 102.
  • Process gas 106 may then be transferred via process line 108 to an electrostatic precipitator 114 for removal of particulates contained in process gas 106, in one example.
  • System 100 may also include an additive injection device/unit 116 for injecting one or more compounds, chemicals, etc., such as organosulfides , inorganic sulfides, acids, bases, metal oxides, oxides, metals, photocatalysts , and/or minerals to aid with sorbent performance.
  • additive injection unit 116 is located downstream of electrostatic precipitator 114 for injecting these compounds and/or chemicals prior to injection of activated carbon products as discussed herein.
  • System 100 may further include one or more activated carbon injection ("ACT") devices, units, systems, etc. (ACI unit 118 ⁇ .
  • ACI unit 118 may include an activated storage vessel, such as a powdered activated carbon (PAC) storage vessel.
  • PAC powdered activated carbon
  • Such vessels may be silos, and the like where activated carbon, such as PAC, may be stored for use in system 100.
  • Activated carbon silo (not shown) may be any type of storage vessel such that it is capable of containing a supply and/or feedstock of activated carbon, such as PAC, for supplying the activated carbon to process gas 106 of system 100.
  • Some additional exemplary activated carbon silos may include supersacs, silos, storage vessels, and the like.
  • Activated carbon may be injected anywhere along process line 108 downstream of additive injection unit 116, preferably.
  • system 100 may include one or more fluidizing nozzles 120 that may assist in providing activated carbon in a fluidized form, such that it may be transported in a substantially fluid form dov/nstream in system 100.
  • system 100 may include one or more control valves (not shown ) that may be disposed and/or located substantially proximal to the exit or outlet of activated carbon and/or fluidizing nozzles 120 for controlling the flow of activated carbon from ACI unit 118 to system 100.
  • the feed of activated carbon can also be controlled by a series of additional control valves, movable barriers, etc. (not shown) .
  • fluidization assistance may be applied in the form of physical agitation or the use of fluidizing nozzles.
  • system 100 may include other types of control valves, such as manual valves (not shown) , and the like as would be known to those skilled in the art.
  • the treated process gas 106 may then be sent to a flue gas desulfurization unit 122 via process line 108 for removal of sulfur compounds, in one embodiment. After being treated in flue gas desulfurization unit 122, treated process gas 106 may then be sent to a stack 124 for emission into the environment.
  • flue gas desulfurization unit 122 may have an gas/air phase and a liquid/water phase; system 100 described herein reduces mercury concentrations in the air phase and liquid. phase of flue gas desulfurization unit 122, such that the discharge water of flue gas desulfurization unit 122 has a lower concentration of mercury in the process or flue gas than prior to upstream of ACI unit 118.
  • activated carbon is used to target reduced concentrations of nitrates/nitrites and heavy metals, such as mercury, arsenic, lead, and selenium in the liquid or wet phase of flue gas desulfurization unit 122 such that the discharge water of flue gas desulfurization unit 122 has lower concentrations of these contaminants in the process or flue gas than prior to upstream of ACI unit 118,
  • activated carbon of system 100 is used to target reduced concentrations of mercury in the gas /air phase and reduced concentrations of nitrates/nitrites and heavy metals such as mercury, arsenic, lead, and selenium in the wet phase of flue gas desulfurization unit 122.
  • System 100 may also include a hydrocyclone 126 for further removal of particulates in the vjet flue gas desulfurization unit liquor prior to discharges.
  • Hydrocyclone 126 may be used to remove activated carbon, powdered sorbent, powdered activated carbon, and the like from the wastewater of the wet flue gas desulfurization unit 122.
  • Hydrocyclone 126 may also be followed by a vacuum filter that will further remove particulates/solids prior to liquor discharge.
  • Example 1 Preparation of PAC
  • a magnetic activated carbon sample with 6% by weight of magnetite (FesC ) was prepared with PAC treated with a wet method, to precipitate ferric chloride and. ferrous sulfate in 200 lb. batches followed by dewatering and drying at 200° C. The dried product was sieved, and. resulted in about 95% of the final product passing through a 325-mesh sieve.
  • the product was tested at the Mercury Research Center (MRC) .
  • the MRC removes a constant flow 7 of approximately 20,500 actual cubic feet per minute (acfm) of flue gas (representative of a 5 mega watt [MW] boiler) from the Southern Company Plant Christ Boiler (78 MW) .
  • the boiler runs on a low-sulfur bituminous coal blend from varying sources .
  • the typical SO 3 concentration of the fuel blends resulted in about 2 parts per million (ppm) of SO 3 .
  • Figure 2 shows improved mercury capture when using an embodiment of an Improved Sorbent Injection System.
  • the product was pneumatically injected at increasing injection rates upstream of the electrostatic precipitator (ACI 1 in Figure 2) and downstream of the electrostatic precipitator (ACI 2 in Figure 2) .
  • Particulate removal was achieved with the electrostatic precipitator for ACI 1.
  • Particulates remained uncaptured for ACI 2, and returned to the Christ process train.
  • Mercury concentrations were monitored at the MRC inlet and the MRC outlet, and the observed concentrations were converted to pounds per trillion British thermal units (lb/Tbtu) using the standard EPA Method 19.
  • Mercury removal by the AC was calculated as the inlet mercury concentration minus the outlet mercury concentration and is illustrated in Figure 2. At typical injection rates and above, less AC is necessary to remove the same amount of AC which would result in significant cost savings for the utility.
  • a coal-fired power plant with a 540 MW unit was conducting a trial to inject a powdered sorbent into the wet scrubber sump which was subsequently pumped into the absorber vessel.
  • the powdered sorbent met the typical 95% passing the 325 mesh with a d50 particle size of 15 microns.
  • Albeit vapor phase mercury emissions went down based on continuous emissions monitoring equipment, the unit began experiencing elevated levels of mercury in their sorbent traps. This was because Hg bound to the fine PAC particles was escaping past the mist eliminators and being captured in the sorbent trap. Furthermore, the fine PAC particles began clogging the rotary vacuum filters, causing the system to shut down.
  • a pov/dered sorbent with 50% passing the 325 mesh and a d50 particle size of 45 microns was added to the sump and subsequently injected into the absorber.
  • FIG. 3 data shows the improved mercury capture when using an embodiment of an Improved Sorbent Injection System.
  • the larger particle size sorbent decreased dusting during handling and injection of the sorbent into the sump.
  • the rotary vacuum filters remained operational without any issues.
  • sorbent trap data matched the continuous emissions monitor data to indicate that no opacity issues with sorbent past the mist eliminators was observed .
  • FIG 4 a method for controlling mercury removal in flue gas or process gas is schematically illustrated and generally designated 400.
  • process or flue gas may be transferred to a pre-heater for heat transfer to an air source to be fed. back into a particular unit, such as boiler 102.
  • This step may also include transferring the process or flue gas to an economizer prior to transferring it to a SCR, such as selective catalytic reduction unit 110.
  • the process or flue gas may be transferred to a particulate collection device/unit, such as electrostatic precipitator 114.
  • This step may include removing particulates from the process or flue gas.
  • a chemical and/or compound may be injected into process or flue gas downstream of the particulate collection device/unit, such as electrostatic precipitator 114.
  • This step may include contacting the process and flue gas with one or more of organosulf ides, inorganic sulfides, acids, bases, metal oxides, oxides, metals, photocatalyst and/or minerals to aid with activated carbon/sorbent performance.
  • step 408 the process or flue gas may be contacted with activated carbon, such as from ACI unit 118.
  • activated carbon may be PAC .
  • step 410 the process or flue gas is transferred to a wet flue gas desulfurization unit, such as flue gas desulfurizatiori unit 122, where the powdered sorbent material contributes to the reduction of other unwanted reactions and constituents in the discharged liquid (such as heavy metals and nutrients) after contact with the slurry in flue gas desulfurization unit 122.
  • a wet flue gas desulfurization unit such as flue gas desulfurizatiori unit 122
  • the powdered sorbent material contributes to the reduction of other unwanted reactions and constituents in the discharged liquid (such as heavy metals and nutrients) after contact with the slurry in flue gas desulfurization unit 122.
  • activated carbon is used to target reduced concentrations of nitrates/nitrites and heavy metals, such as mercury, arsenic, lead, and selenium in the liquid or wet phase of flue gas desulfurization unit 122 such that the discharge water of flue gas desulfurization unit 122 has lower concentrations of these contaminants in the process or flue gas than prior to upstream of ACI unit 118.
  • the process or flue gas may be transferred to a stack for emitting to the environment.
  • the particle size of the sorbent may be increased to reduce or eliminate the issues of increased dusting and opacity issues, long wetting times, plugging of vacuum filters, and the like.
  • the particle size for environment 50% distribution (d50) of the sorbent particles may be from about 20 micrometers to about 75 micrometers. This means that approximately 50% of the sorbent particles have a particle size of less than this range and 50% of the sorbent particles have a particle size of more than this range.
  • the systems and sorbents described herein may decrease the distribution and/or amount of sorbent having particle sizes of less than 20 micrometers, less them 15 micrometers, less than 10 micrometers, and less than 5 micrometers .
  • such sorbents having a d.50 of from about 20 micrometers to about 75 micrometers may be injected in the flue gas just upstream, of flue gas desulfurization unit 122. In another embodiment, such sorbents may be injected into the absorber vessel of flue gas desulfurization unit 122.
  • Embodiments of this disclosure may be further illustrated by the following Items :
  • Item 1 A system for cleaning flue gas, the system comprising: a particulate removal system; an additive injector positioned downstream of the particulate removal system, for injecting an additive into the flue gas; a powdered sorbent injector positioned downstream of the additive injector, for injecting powdered sorbents, wherein no powdered sorbent injectors are positioned upstream of the particulate removal system; and
  • a flue gas desulfurization system positioned downstream from the powdered sorbent injector, wherein no other processing apparatus is located between the powdered, sorbent injector and the flue gas desulfurization system.
  • Item 2 The system of Item 1, wherein the particulate removal system is a fabric filter.
  • Item 3 The system of any of the preceding items, wherein the particulate removal system is an electrostatic precipitator,
  • Item 4 The system of any of the preceding items, wherein no other substance is injected between the powdered activated carbon injector and the flue gas desulfurization system.
  • a method of cleaning flue gas comprising: removing particulates from flue gas using a particulate removal system, injecting an additive into the flue gas downstream of the particulate removal system, injecting powdered sorbent into the flue gas downstream of said injection of the additive, wherein no powdered sorbent is injected upstream of the particulate removal system, and treating the flue gas in a flue gas desulfurization system positioned downstream from a point where the powdered sorbent is injected, wherein no other processing is done between the powdered sorbent injector and the flue gas desulfurization system.
  • injecting an additive comprises: injecting into the flue gas one or more of the group consisting of organosul.fid.es, inorganic sulfides, acids, bases, metal oxides, oxides, metals, photocataiysts, and minerals.
  • a sorbent composition for removing mercury from flue gas comprising: a powdered sorbent having a fifty percent distribution particle size of from about 20 micrometers to about 75 micrometers.
  • a method of cleaning flue gas comprising: injecting a powdered sorbent into the flue gas, wherein the powdered sorbent has a. fifty percent distribution particle size of from about 20 micrometers to about 75 micrometers; and collecting the powdered, sorbent in a flue gas desulfurization system.
  • a method of cleaning flue gas comprising: injecting a powdered sorbent into the liquor/slurry of a flue gas desulfurization system, wherein the powdered sorbent has a fifty percent distribution particle size of from about 20 micrometers to about 75 micrometers.

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Abstract

Un système de nettoyage de gaz de combustion, le système comprenant un système d'élimination de particules; un injecteur d'additif positionné en aval du système d'élimination de particules, pour l'injection d'un additif dans le gaz de combustion; un injecteur de sorbant en poudre positionné en aval de l'injecteur d'additif, pour l'injection de sorbants en poudre, dans lequel aucun injecteur de sorbant en poudre n'est positionné en amont du système d'élimination de particules; et un système de désulfuration de gaz de combustion positionné en aval de l'injecteur de sorbant en poudre, aucun autre appareil de traitement n'étant situé entre l'injecteur de sorbant en poudre et le système de désulfuration de gaz de combustion.
PCT/US2017/059606 2017-04-05 2017-11-01 Systèmes et procédés pour le contrôle de mercure de post combustion a l'aide d'injection de sorbant et de lavage hydraulique Ceased WO2018186909A1 (fr)

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