WO2019018671A1 - Systèmes et procédé d'élimination de gaz acide dans un épurateur à sec à lit fluidisé circulant - Google Patents

Systèmes et procédé d'élimination de gaz acide dans un épurateur à sec à lit fluidisé circulant Download PDF

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Publication number
WO2019018671A1
WO2019018671A1 PCT/US2018/042926 US2018042926W WO2019018671A1 WO 2019018671 A1 WO2019018671 A1 WO 2019018671A1 US 2018042926 W US2018042926 W US 2018042926W WO 2019018671 A1 WO2019018671 A1 WO 2019018671A1
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WO
WIPO (PCT)
Prior art keywords
particles
microns
equal
flue gas
less
Prior art date
Application number
PCT/US2018/042926
Other languages
English (en)
Inventor
Curtis Biehn
Mark Degenova
Eric Van Rens
Randy Griffard
Original Assignee
Mississippi Lime Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US15/655,201 external-priority patent/US10155227B2/en
Priority claimed from US15/655,527 external-priority patent/US10046273B1/en
Application filed by Mississippi Lime Company filed Critical Mississippi Lime Company
Publication of WO2019018671A1 publication Critical patent/WO2019018671A1/fr

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Classifications

    • 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
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/508—Sulfur oxides by treating the gases with solids
    • 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
    • B01D53/68—Halogens or halogen compounds
    • B01D53/685—Halogens or halogen compounds by treating the gases with solids
    • 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
    • B01D53/83—Solid phase processes with moving reactants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/40—Alkaline earth metal or magnesium compounds
    • B01D2251/404—Alkaline earth metal or magnesium compounds of calcium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/60—Inorganic bases or salts
    • B01D2251/604—Hydroxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases

Definitions

  • the invention relates generally to air pollution control processes aimed at controlling acid gases that are emitted from industrial, utility, incineration, or metallurgical process. Specifically the invention concerns the mitigation of Sulfur Dioxide (SCh), Hydrochloric acid (HQ), and Sulfur Trioxide (SO3) using a high reactivity calcium hydroxide (hydrated lime) in a circulating dry scrubber (CDS).
  • SCh Sulfur Dioxide
  • HQ Hydrochloric acid
  • SO3 Sulfur Trioxide
  • CDS circulating dry scrubber
  • Flue gases are generally very complex chemical mixtures which comprise a number of different compositions in different percentages depending on the material being combusted, the type of combustion being performed, impurities present in the combustion process, and specifics of the flue design.
  • the release of certain chemicals into the atmosphere which commonly appear in flue gases is undesirable, and therefore their release is generally regulated by governments and controlled by those who perform the combustion.
  • Some of the chemicals that are subject to regulation are certain acid gases.
  • a large number of acid gases are desired to be, and are, under controlled emission standards in the United States and other countries. This includes compounds such as, but not limited to, hydrogen chloride (HCl), sulfur dioxide ($02) and sulfur trioxide (SO3).
  • Sulfur trioxide can evidence itself as condensable particulate in the form of sulfuric acid (H2SO4). Condensable particulate can also he a regulated emission.
  • Flue gas exhaust mitigation is generally performed by devices called "scrubbers". Scrubbers introduce chemical compounds into the flue gas. The compounds then react with the undesirable compounds which are intended to be removed.
  • the undesirable compounds are either captured and disposed of, or turned into a less harmful compound prior to their exhaust, or both.
  • SO2 is a gas mat contributes to acid rain and regional haze. Since the 1970's, clean air regulations have been designed to reduce emissions of SO2 from industrial processes at great benefit to the environment and human health. For large emitters, the use of wet and dry scrubbing has led to the reduction of SO2. Smaller emitters, however, seek out less costly capital investment to control SO2 emissions in order to remain operating and produce electricity or steam. Similarly, halides in fossil fuels (such as chlorine and fluorine) are combusted and form their corresponding acid in the flue gas emissions. The halogenated acids also contribute to corrosion of internal equipment or, uncaptured, pollute the air via stack emissions.
  • halides in fossil fuels such as chlorine and fluorine
  • Flue gas treatment has become a focus of electric utilities and industrial operations due to increasingly tighter air quality standards. As companies seek to comply with air quality regulations, the need arises for effective flue gas treatment options.
  • Alkali species based on alkali or alkaline earth metals are common sorbents used to neutralize the acid components of the flue gas. The most common of these alkalis are sodium, calcium, or magnesium-based.
  • a common method of introduction of the sorbents into the gas stream is to use dry sorbent injections.
  • the sorbents are prepared as a fine or coarse powder and transported and stored at the use site. Dry sorbent injection systems pneumatically convey powdered sorbents to form a fine powder dispersion in the duct. The dry sorbent neutralizes and protects equipment from corrosion while eliminating acid gas emissions.
  • Common sorbents used are sodium (trona or sodium bicarbonate) or calcium (hydrated lime based.
  • Hydrated lime One commonly used material for the scrubbing of acid gases is hydrated lime. It has been established thai hydrated lime can provide a desirable reaction to act as a mitigation agent. Hydrated lime reacts with SO3 to form calcium sulfate in accordance with the following equation: [012] Hydrated lime systems have been proven successful in many full scale operations. These systems operate continuously to provide utility companies with a dependable, cost- effective means of acid gas control.
  • Lime hydrate meeting the above described characteristics, properties, and reactivity has generally been manufactured according to a commonly known and utilized process.
  • a lime feed of primarily calcium oxide commonly known as quicklime
  • quicklime a lime feed of primarily calcium oxide
  • a desired size e.g., 95% or smaller than 100 mesh.
  • all of the lime feed is ground together (lime and impurities), without any removal of particles during the grinding, until the batch of lime feed (both the lime and impurities) meets the desired particle size requirements.
  • This continuous grinding is not surprising as the conventional wisdom is that small particles are better and, thus, the more the calcium oxide is grinded, the better.
  • the quicklime meeting the desired size requirements is then fed into a hydrator, where the calcium oxide reacts with water (also known as slaking), and then flash dried to form calcium hydroxide in accordance with the following equation:
  • the resultant calcium hydroxide (also known as hydrated lime) is then milled and classified until it meets a desired level of fineness and BET surface area.
  • a system for removal of sulfur dioxide (SO2) from a flue gas comprising: a flue gas duct including a circulating dry scrubber (CDS); and an injection system for injecting a highly reactive lime hydrate (HRH) into the flue gas in the CDS.
  • SO2 sulfur dioxide
  • CDS circulating dry scrubber
  • HRH highly reactive lime hydrate
  • a method for removal of sulfur dioxide (SO2) from a flue gas comprising: providing a flue gas duct including a circulating dry scrubber (CDS); and injecting a highly reactive lime hydrate (HRH) into the flue gas in the CDS.
  • SO2 sulfur dioxide
  • HRH highly reactive lime hydrate
  • FIG. 1 provides a conceptual block diagram of an embodiment of a flue gas duct system as may be used is, for example, in a coal fired power plant including common components.
  • FIG. 2 provides a conceptual block diagram of a circulating dry scrubber (CDS).
  • CDS circulating dry scrubber
  • FIG. 3 provides a table illustrating increased reduction of SO2 with a high reactivity lime hydrate (HRH) compared to a more traditional hydrated lime composition in a circulating dry scrubber to control stack SO2 emissions.
  • HRH high reactivity lime hydrate
  • FIG.4 provides a graph showing average feed rates of HRH and traditional lime hydrate at a full load.
  • FIG. 5 provides a bar chart showing relative feed rates of HRH and traditional lime hydrate at different load conditions.
  • FIG. 1 shows a loose block diagram of an arrangement of a flue gas duct system such as can be used in a coal fired power plant.
  • major components include the boiler (101), a selected catalytic reduction (SCR) system for reducing NO* emissions (103), an air preheater (APH) (105), a bag house or electrostatic precipitator (ESP) (107), a Flue Gas Desulfurization (FGD) unit (109), and then the exhaust stack (111).
  • SCR selected catalytic reduction
  • APH air preheater
  • ESP electrostatic precipitator
  • FGD Flue Gas Desulfurization
  • WFGD wet flue gas desulfurization
  • chlorides can attack even the most exotic and expensive metal alloys causing major damage to an WFGD system.
  • chloride purge it is common practice to control the level of chlorides present in the scrubber slurry by removing or "purging ** a portion of the scrubber slurry. This process is often referred to as a "chloride purge”.
  • WFGD is a very effective technology for scrubbing S02
  • the WFGD purge stream is an aqueous solution and generally contains a wide variety of pollutants making it a rather toxic material to handle and dispose of. it, includes gypsum, along with heavy metals. chlorides, magnesium and dissolved organics. Jn many applications, WFGD purge water is first treated by dewatering to separate synthetic gypsum cake which can be a valuable secondary product. The remaining WFGD purge water is then recycled back to the scrubber.
  • chloride purge A portion of this water (still containing dissolved chlorides) is removed from the recycle stream (the "chloride purge"), and is subjected to various forms of water treatment (as required) to reduce or eliminate dissolved metals and other contaminants of concern prior to discharge back into the environment in accordance with the applicable permits and laws.
  • chloride purge the recycle stream
  • water treatment as required
  • CDS circulating dry scrubbing
  • a CDS is also referred to as circulating fluid bed (CFB).
  • the technology of a CDS is relatively straightforward and is illustrated in FIG. 2.
  • flue gas (200) is directed into the reaction vessel (201) where hydrated lime (203) (possibly with additional water (205)) is directed into the flue gas stream. This causes the hydrated lime to react with the SCh to produce calcium sulfite according to Equation 1.
  • the calcium sulfite may further react with available oxygen to produce calcium sulfate
  • HRH highly reactive lime hydrate
  • HRH can be manufactured in accordance with a number of processes. In an embodiment, it may be manufactured in accordance with, and/or have the properties discussed in, United States Patent Application Serial Numbers: 13/594,538, 14/180,128, 14/289,278, and 15/344,173 the entire disclosure of all of which is herein incorporated by reference.
  • HRH is notably different from other hydrated lime as it has an improved removal rate of acidic pollutants present in the flue gas where the sorbent is delivered and the rate of removal is generally substantially higher.
  • the use of a high purity, highly reactive hydrated lime such as HRH will have faster
  • the HRH is a dry solid free of excess moisture.
  • the product used may be described by having citric acid reactivity of less than 15 sec, preferentially less than 10 sec, optimally less than 7 sec.
  • the product used may also be described by having available calcium hydroxide concentration of greater than 92% wt, preferentially greater than 94%, and optimally greater man 95%.
  • the product used may also be described by having at least 90% of particles less than 10 microns, preferentially less than 8 microns. At least 50% of the particles are less than 4 microns, preferentially less man 3 microns.
  • the product may also be described as having a BET surface area of at least 18 m 2 /g, preferentially at least 19 m 2 /g, 20 m 2 /g, or 30 m 2 /g.
  • 90% percent of the particles are less than or equal to about 10 microns and greater than or equal to about 4 microns and a ratio of a size of particle 90% of the particles are below to a size of particle 10% of the particles are below is less than about 8.
  • the particles preferably have a BET surface area of about 18 m 2 /g or greater or about 20 m 2 /g or greater.
  • the d90/dl0 ratio is less than 6, between 4 and 7, or between 5 and 6.
  • 90% percent of the particles may be less than or equal to about 8 microns and greater than or equal to about 4 microns, less than or equal to about 6 microns and greater than or equal to about 4 microns, or less than or equal to about 5 microns and greater than or equal to about 4 microns.
  • 50% of the particles are less than or equal to about 4 microns, less man or equal to about 2 microns, and may be greater than 1 micron.
  • the reactivity to a weak acid provides for a reactivity time that is measurable with commercial instruments.
  • the problem with determining reaction time to stronger acids is that the reaction can be too quick to effectively measure at laboratory scaling. Thus, it is difficult to predict compositions mat will function well without performing large scale pilot testing.
  • the citric acid reactivity of a particular hydrated lime composition the amount of time it took 1.7 grams of time hydrate to neutralize 26 grams of citric acid was measured. As a measurement of effectiveness, it is preferred that this value be less than or equal to 15 seconds in order to have a hydrated lime composition which is classified as being an HRH.
  • the HRH will generally be used as part of circulating dry scrubber system of the off gas of an industrial plant, incinerator, or boiler that combusts sulfur and/or halogenated fuels.
  • Hydrated lime (203) is fed from a silo into a conveying line that disperses the fine powder into the bottom of a reactor (201) in the off gas piping.
  • a predetermined amount of recycled ash (211) is also fed into the reactor (201), as is a quantity of spray water (20S) designed to wet the solid particles and drop flue gas temperature.
  • the floe gas travels through the duct into a BH (207)/(l07), where ash collects on the bags while clean flue gas (209) flows through the ash/bag layers.
  • Automated mechanical means dislodge the ash from the bag exterior and this ash is either recycled (211) to the reactor (201) or sent (213) to a landfill or other beneficial use as deemed appropriate.
  • a plant fueled with PRB coal uses a CDS to control stack SO2 emissions.
  • the plant compared a traditional hydrated lime against performance of an HRH.
  • the CDS operates under a logic-based controller that adjusts the lime feed rate in order to maintain a near constant SO 2 emission as determined by a CEMS monitor in the stack flue gas.
  • the unit and scrubber were operated normally over several days with each type of hydrated lime. Results are outlined in FIG. 3.
  • HRH provides a method of removing SCk from flue gas of boiler firing sulfur-containing fuel that is advantageous over prior art due to tighter particle size distribution of the hydrated lime sorbent.
  • Advantageous generally refers to reduced sorbent quantities required to achieve similar reduction in concentration of SO* that end user requires for traditional hydrated lime.
  • this also provides a method of removing S0 2 from flue gas of boiler firing sulfur containing fuel that is generally advantageous due to more rapid reactivity of hydrated lime sorbent, as characterized by acid reactivity test.
  • advantageous refers to greater reductions in concentration of S ( 1 ⁇ 2 that end user experiences when using standard hydrated lime.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Treating Waste Gases (AREA)

Abstract

L'invention concerne des systèmes et des procédés pour l'utilisation de chaux hydratée hautement réactive (HRH) dans des épurateurs à sec à lit fluidisé circulant (CDS) pour éliminer le dioxyde de soufre (SO 2) du gaz de combustion.
PCT/US2018/042926 2017-07-20 2018-07-19 Systèmes et procédé d'élimination de gaz acide dans un épurateur à sec à lit fluidisé circulant WO2019018671A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US15/655,201 2017-07-20
US15/655,527 2017-07-20
US15/655,201 US10155227B2 (en) 2012-08-24 2017-07-20 Systems and method for removal of acid gas in a circulating dry scrubber
US15/655,527 US10046273B1 (en) 2014-09-05 2017-07-20 Systems and method for removal of acid gas in a circulating dry scrubber

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WO2019018671A1 true WO2019018671A1 (fr) 2019-01-24

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5492685A (en) * 1990-07-24 1996-02-20 The Board Of Trustees Of The University Of Illinois High surface area hydrated lime and method of removing SO2 from a gas stream
US20090246117A1 (en) * 2008-03-25 2009-10-01 Jean-Yves Tilquin Method of forming a hydrated lime for acid gas removal from flue gas
US8518353B1 (en) * 2012-10-09 2013-08-27 Babcock Power Development LLC Reduced sorbent utilization for circulating dry scrubbers
WO2014186485A1 (fr) * 2013-05-16 2014-11-20 Babcock & Wilcox Power Generation Group, Inc. Transport de matières solides dans un système de désulfuration de gaz de carneau
US20150139882A1 (en) * 2013-11-15 2015-05-21 Babcock & Wilcox Power Generation Group, Inc. Integrated sorbent injection and flue gas desulfurization system
US9517471B1 (en) * 2011-08-26 2016-12-13 Mississippi Lime Company High reactivity lime hydrate and methods of manufacturing and uses thereof
US9751043B1 (en) * 2014-09-05 2017-09-05 Mississippi Lime Company Systems and method for removal of acid gas in a circulating dry scrubber

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5492685A (en) * 1990-07-24 1996-02-20 The Board Of Trustees Of The University Of Illinois High surface area hydrated lime and method of removing SO2 from a gas stream
US20090246117A1 (en) * 2008-03-25 2009-10-01 Jean-Yves Tilquin Method of forming a hydrated lime for acid gas removal from flue gas
US9517471B1 (en) * 2011-08-26 2016-12-13 Mississippi Lime Company High reactivity lime hydrate and methods of manufacturing and uses thereof
US8518353B1 (en) * 2012-10-09 2013-08-27 Babcock Power Development LLC Reduced sorbent utilization for circulating dry scrubbers
WO2014186485A1 (fr) * 2013-05-16 2014-11-20 Babcock & Wilcox Power Generation Group, Inc. Transport de matières solides dans un système de désulfuration de gaz de carneau
US20150139882A1 (en) * 2013-11-15 2015-05-21 Babcock & Wilcox Power Generation Group, Inc. Integrated sorbent injection and flue gas desulfurization system
US9751043B1 (en) * 2014-09-05 2017-09-05 Mississippi Lime Company Systems and method for removal of acid gas in a circulating dry scrubber

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