WO1995004245A1 - REDUCTION DES EMISSIONS DE NOx DANS DES LITS FLUIDISES - Google Patents

REDUCTION DES EMISSIONS DE NOx DANS DES LITS FLUIDISES Download PDF

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Publication number
WO1995004245A1
WO1995004245A1 PCT/US1994/006295 US9406295W WO9504245A1 WO 1995004245 A1 WO1995004245 A1 WO 1995004245A1 US 9406295 W US9406295 W US 9406295W WO 9504245 A1 WO9504245 A1 WO 9504245A1
Authority
WO
WIPO (PCT)
Prior art keywords
fluidized bed
urea
emissions
bed
reduction
Prior art date
Application number
PCT/US1994/006295
Other languages
English (en)
Inventor
Lewis W. Clark
Richard L. Samu
Original Assignee
Dorr-Oliver Incorporated
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
Application filed by Dorr-Oliver Incorporated filed Critical Dorr-Oliver Incorporated
Publication of WO1995004245A1 publication Critical patent/WO1995004245A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
    • F23G5/30—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having a fluidised bed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J7/00—Arrangement of devices for supplying chemicals to fire
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2209/00—Specific waste
    • F23G2209/12—Sludge, slurries or mixtures of liquids

Definitions

  • the invention is directed to the reduction of NO x levels in the flue gas from fluidized bed incinerators, particularly fluidized bed incinerators of the bubbling bed type.
  • Fluidized bed reactors are well-known means for generating heat and, in various forms, can carry out the processes of drying, roasting, calcining, incineration and heat treatment of solids in the chemical, metallurgical and other material processing fields. They are also used for the generation of hot gases, including steam, for use in driving electric power generation equipment, for process heat, for space heating, or for other purposes.
  • Fluidized bed reactors typically comprise a vessel having a substantially horizontal air distributor or constriction plate, which supports a bed of particulate solids in the reaction chamber and separates the reaction chamber from a windbox below the air distributor. Combustion air is introduced into the windbox and passes through the air distributor in sufficient volume to achieve a gas velocity that expands or fluidizes the solids bed, suspending the particulate solids of the bed in the flowing air stream and imparting to the individual particles a continuous random motion.
  • a fluidized bed in appearance and properties resembles a boiling liquid.
  • Conducting a combustion reaction in a fluidized bed has important advantages which include attainment of a substantially uniform bed temperature, combustion at relatively low temperatures, say 1350°-1700°F, and a high heat transfer rate.
  • Nitrogen oxides are generated when fuel is burned, both from thermal fixation of nitrogen in the air and from conversion of nitrogen present in the fuel.
  • the former reaction is favored at high temperatures (above 1800°F) while the latter occurs at all temperatures.
  • the problem of NO x reduction in flue gas has hitherto been addressed by injection of ammonia into the effluent stream with and without catalysts.
  • U.S. Patent No. 3,900,554 suggests non-catalytic removal of NO x from flue gases by injecting ammonia into a gas stream at a temperature in the range 1600°-2000°F.
  • U.S. Patent No. 4,208,386 is directed to a process in which an effluent stream is contacted with urea (as a solid or in solution) at a temperature in the range 1600°-2000°F to reduce NO x .
  • U.S. Patent 4,719,092 calls for reducing the concentration of NO x in oxygen-rich combustion effluents by injecting an aqueous solution of urea and an oxygenated hydrocarbon into the effluent at a temperature above 1600°F.
  • U.S. Patent No. 4,756,890 suggests injection of ammonia or an ammonia precursor into the gas stream within a high temperature cyclone separator at a location where there is a strong vortex region to obtain an efficient mixing of the NO x reducing agent and the combustion product flue gas.
  • This arrangement is particularly suitable for those fluidized bed reactors of the circulating bed type where large volumes of gas and solids are returned to the combustion reactor through a cyclone. It is not suitable for fluidized bed reactors of the bubbling bed type serving as incinerators because the incinerators generally do not employ cyclone separators.
  • FIG. 1 is an elevational view, partially in section, of a fluidized bed incinerator in which the process of the invention can be carried out.
  • a fluidized bed reactor 10 having a vessel wall 11 which comprises a steel shell 13 and a refractory lining 14.
  • the reactor 10 is supported by grillage beams 36 which rest on a concrete pad or foundation 38.
  • the reaction chamber 16 in the main portion of the fluid bed reactor 10 is separated from the windbox 17 in the lower portion of the fluid bed reactor by a perforated steel constriction plate or the perforated refractory dome 21 as shown.
  • a steel constriction plate is suitable for cold windbox operation while the perforated refractory dome is used when the incoming air is heated; that is, for "hot windbox" operation.
  • the freeboard region of the reaction chamber is designated by the reference character 16.
  • the refractory dome 21 is provided with a number of tuyeres 22 for providing communication between the windbox 17 and the reaction chamber 16.
  • a conduit 27 is provided for introducing feed stock into the reaction chamber 16.
  • a fluidized bed 24 is illustrated in the reaction chamber 16 and a conduit 26 is provided for draining the bed material or removal of solid particulate products if required.
  • a conduit 29 is provided for supplying air to the windbox 17.
  • a duct 34 is provided for the off-gases emanating from the reaction chamber 16.
  • a conduit 28 may be provided for introducing secondary air into the reaction chamber 16.
  • the fluidized bed reactor 10 has within the reaction chamber 16 a body of particulate material 24 which is supported by the perforated dome or constriction element 21.
  • Air supplied by a blower (not shown) through conduit 29 to the windbox 17 moves upward through the tuyeres 22 of the constriction element 21 into the bed material 24 and expands that bed to a substantial height within the combustion chamber 16, forming a fluidized bed of the bubbling bed type.
  • Above the expanded bed 24 is the freeboard region of the combustion chamber 16 into which gas and fine particles are ejected from the bed 24. Secondary air may be introduced into the freeboard region just above the expanded bed 24 through conduit 28.
  • Combustion takes place primarily in the expanded bed 24 at temperatures of 1350°F to 1600°F and at the level of secondary air introduction and thereabove in reaction chamber 16 where gases and suspended fine solid particles are burned at temperatures of 1350°F to 1700°F.
  • the sludge to be incinerated is supplied directly into the fluidized bed through conduit 27.
  • the dry urea is injected directly into the fluidized bed through supply hose 41. The amount of injected urea used is somewhat in excess of that required to complete the desired reactions.
  • a fluidized bed reactor about 30 feet high and having a maximum diameter at the rea ⁇ ion chamber of about 27 feet is provided with a refractory combustion dome separating the reaction chamber from the windbox below.
  • a bed comprising inert material i.e. silica sand
  • inert material i.e. silica sand
  • it is fluidized in the combustion zone of the reaction chamber by introducing a flow of air from the windbox sufficient to establish an air flow of from 2.0 ft/sec to 4 ft/sec.
  • This air flow expands the charge in the reaction chamber and forms a fluidized bed of the bubbling bed type.
  • Waste material containing organics i.e., waste water sludge
  • the dry urea is also injected into the fluidized bed. Combustion of the organic material in the charge takes place at a temperature of from 1350°F to 1600°F. There is excess air present in the process so that emissions from the rea ⁇ or contain about 4-10% by volume of oxygen.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Treating Waste Gases (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)

Abstract

Dans un processus d'incinération de boues (27) d'eaux usées dans un réacteur (20) à lit fluidisé, on injecte directement des granulés d'urée sèche (41) dans la zone (24) du lit fluidisé du réacteur, ce qui a pour effet de réduire d'au moins 25 % les émissions de NOx.
PCT/US1994/006295 1993-07-28 1994-06-03 REDUCTION DES EMISSIONS DE NOx DANS DES LITS FLUIDISES WO1995004245A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US9896493A 1993-07-28 1993-07-28
US08/098,964 1993-07-28

Publications (1)

Publication Number Publication Date
WO1995004245A1 true WO1995004245A1 (fr) 1995-02-09

Family

ID=22271759

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1994/006295 WO1995004245A1 (fr) 1993-07-28 1994-06-03 REDUCTION DES EMISSIONS DE NOx DANS DES LITS FLUIDISES

Country Status (1)

Country Link
WO (1) WO1995004245A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130333597A1 (en) * 2012-04-19 2013-12-19 Degremont Methods and Systems for Flue Gas Denitrification
JP2014021191A (ja) * 2012-07-13 2014-02-03 Mitsubishi Chemicals Corp トナーの製造装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888193A (en) * 1973-01-16 1975-06-10 Babcock Hitachi Kk Incineration method for combustible industrial wastage and a fluidized bed furnace used therefor
US4208386A (en) * 1976-03-03 1980-06-17 Electric Power Research Institute, Inc. Urea reduction of NOx in combustion effluents
US5055029A (en) * 1990-01-22 1991-10-08 Mobil Oil Corporation Reducing NOx emissions from a circulating fluid bed combustor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888193A (en) * 1973-01-16 1975-06-10 Babcock Hitachi Kk Incineration method for combustible industrial wastage and a fluidized bed furnace used therefor
US4208386A (en) * 1976-03-03 1980-06-17 Electric Power Research Institute, Inc. Urea reduction of NOx in combustion effluents
US5055029A (en) * 1990-01-22 1991-10-08 Mobil Oil Corporation Reducing NOx emissions from a circulating fluid bed combustor

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130333597A1 (en) * 2012-04-19 2013-12-19 Degremont Methods and Systems for Flue Gas Denitrification
US10458650B2 (en) * 2012-04-19 2019-10-29 Degremont Methods and systems for flue gas denitrification
JP2014021191A (ja) * 2012-07-13 2014-02-03 Mitsubishi Chemicals Corp トナーの製造装置

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