US2867195A - Apparatus for the recovery of heat and chemicals - Google Patents

Description

APPARATUS FOR THE RECOVERY OF' HEAT AND CHEMICALS Filed May 9, 1955 Jan. 6, 1959 E. J. HAUCK ET AL 3 Sheets-Sheet l INVENTORS EDWIN J. HAUCK By STANLEY SuDA ATTORNEY Jan- 6, 1959 E. J. HAUCK ETAL. 2,867,195

APPARATUS FOR THE RECOVERY 0F HEAT AND CHEMICALS Filed May 9, 1955 5 Sheets-Sheet 2 FIG.2

INVENTORS EDWIN J. HAUCK STANLEY SUDA ATTORNEY Jan. 6, 1959 E. J. HAUCK ET AL APPARATUS FOR THE RECOVERY OF' HEAT AND CHEMICALS Filed May 9, 1955 3 Sheets-Shea?l 3 FIG.4

INVENTORS EDWIN J. HAUCK BY STANLEY suoA ATTORNEY bul APPARATUS F OR THE RECQVERY F HEAT AND CHEMICALS Edwin J. Hauck, Fair Lawn,` N. J., and Stanley Suda, Astoria, N. Y., assignors to The Babcock & Wilcox lCompany, New York, N. Y., a corporation of 'New York Application May 9, 19ss,sena1N0. 506,856

s claims. (ci. 122-440) The present invention relates to the construction and operation of vapor generators, and more particularly to a steam boiler and superheater constructed and arranged to be tired by separate fuels where valuable chemicals and heat are obtained from the combustion of one fuel and heat only is obtained from thecombustion of the other fuel.

In the digestion of cellulostic materials in the production of paper pulp it has been economically feasible to incinerate the residual liquor obtained for example in the sulphate or Kraft Process for the recovery of chemicals for reuse and theA production of heat for the generation of superheated steam. In most pulp plants it has been necessary to provide separate steamrgenerating and superheating units iired by oil or gas to supply steam to supplement the steam produced in the boilers of the chemical recovery unit. In small plants it has been difficult to economically justifyvthe installation of separate chemical recovery waste heat boiler units with a separate power boiler. Furthermore, when a single steam generating unit has been installed for the simultaneous combustion of both residual liquor and fuel oil, for example, the results have not been satisfactory. With conjoint fuel combustion the furnace temperatures are higher than attained with the combustion of the residual liquor alone, resulting in the sublimation of chemicals, high dust losses and difficulties in maintaining the heating surfaces of the associated boiler in a clean condition.

Those skilled in the art of steam generating will readily understand the diiiculties encountered in high temperature incineration of residual liquors. However, when furnace temperatures resulting from the incineration of residualv liquors have been maintained at relatively low values with the combustion product temperatures entering the superheater bank being in the range of 1600 to 1700 F., the chemical losses during the incineration have been held at a minimum and the chemical and heat recovery process has proven to be highly efiicient. Even with relatively low furnace temperatures it has proven desirable to construct the heating tube banks of the steam generating unit with the tubes installed on a relatively widespacing so as to facilitate cleaning of the unit. On the-contrary, in steam generating units supplied with fuels such las oil or gas, it is economically desirable to construct the banks of the heat exchange tubes on a relatively close spacing since the cleaning problem is not diicult and higher eficiency of heat transfer can be attained.

In accordance with our present invention we provide a steam generating andY superheating unit having a common setting which is divided into two entirely separate sections by a common iluid cooled division wall. The furnace and gas pass construction of kone section is speciiically designed for the combustion of residual liquor, and for the generation and superheating of steam by the products -of the residual liquor combustion. The other .section of the furnace is specifically designed forthe combustion of an oil or gas fuel with the heating surfaces particularly designed for eicient heat transfer purposes under such conditions of fuel firing. In effect the drums and the division wall of the steam` generating and superheating unit are the only parts of the unit which are common in the utilization of both fuels. The invention is accordingly well suited for economical installation in small plants where the installation of separate steam generating units is not economically justified.

The various features of novelty which characterize Vour invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained vby its use, reference should be had to the accompanying drawings and descriptive matter inwhich we have illustrated and described and embodiment of our invention.

Of the drawings:

Fig. l is an elevation view, in section, of a steam generating and superheating unit constructed in vaccordance with the invention; v v

Figs. 2 and 3 are sections of the apparatus shown in Fig. l, taken on lines'Z-Z and 33, respectively; and

Fig. 4 is a section of Fig. 1, taken on line 4-4, and turned l 4 As'shown in the drawings the invention is illustrated as applied to a Steam generating unit for the incineration of residual black liquor in one furnace and fuel oil in a separate furnace. The gaseous products of combustion from each fuel pass through convection heating surfaces and steam superheating surfaces with the gaseous prod'- ucts combined for discharge to a common outlet from the unit and thence to the atmosphere. It will be understood that the vgaseous products of combustion leaving the unit can be passed through an air heater for the further recoveryof heat. v The air heater (not shown) can,

usefully supply preheated air to both furnaces to*aid in the combustion of the fuels.Y The steam kgenerated -and superheated in the separate sections of the furnace is combined externally of the unit-setting for use in a common prime mover or for process use.

As shown in Fig. 1 the vapor generator includes an upper steam and water drum 10 spaced above a lower drum 11. The drums 10 and 11 are connected by rows of convection heating tubes which are arranged inY tubeto-tube spacing as hereinafter described.

Connected in the circulatory system of the steam generator is an upper horizontally disposed header 12 which extends. outwardly from the drum 10 and is provided with a row of tubes 13 extending downwardly to a lower horizontally disposed header 14 forming a division wall 1S normal to and intermediate the length of the drums 10 and 11. The division wall is providedwith well known refractory material positioned between adjacent tubes 13 to form a gas tight structure, one side of which forms one side wall of a black liquor incinerating furnace 16 while the opposite side-forms one side of the fuel oil burning furnace 17.

The division wall 15 extends rearwardly of the setting to continue the separation of the convection gas passes receiving heating gases from the separate furnaces 16 and 17, as shown particularly in Fig. 4. The division wall extends from the front to the rear of the setting and is fluid cooled'to provide a gas tight separation between convection tubes 48 in the black liquor incinerating portion of the unit and the tubes of the convection banks 77 --of the fluid fuel iired portion of the unit.

The black lliquor incinerating furnace 16 is providedV with a second side wall 18 which includes an upright row of tubes 20 extending from an upper header 21 which is parallel with the header 12 and positioned at the same elevation, and a lower header 22 which is horizontally disposed'and positioned'parallel to the header 14. The` transversehorizontally disposed header 27 positioned up` wardly adjacent the headers 14 and 22. The row ofl Y ItubesV not 'only defines the front wall 25 -of the liquor incineratin'gjfurrnace V1'6`b'ut also forms.V the roof k28rof the f1 1rn'ac'e. Suitable refractory.materialismounted be-` tween lthetubl'ves126, fand the customary insulation and casingjis installed' outwardly of the' tube row to form a assign u l vA jow of tubesilfis 4inclined 'upwardly' from the transverse 'heade 27 'to cooperate 'with refractory 'Irriate- 'rial Ato formthej hearth 131 'of 'the liquor'ncinerating furnace 16. Thet'ubes 30 'eXterrd'upwai-dly to'ap'osition intermediate the height of the furnace and 'are'bent inwardlyj'ofthe furnace'and reversely towards the c'onvection-tube bank as at `32 "and"33 vrespectively to deilne a nose baille 34. The tubesr30 Yare provided'with refractory materialya'nd the customary -insulation vand exterior metallic casingtofo'rm ja gas tightf'rea'r' wall 35 of the liquor "incineratingefurnace Above the 'nose baille 34 the refractory material is omitted and tubes 30 are ex-` tended inan :upward direction and then rearward of the furnace 1r6`rt'ofopen tothe upper steam and water drum 10. The upright eXtension'of the tubes 30 are alternately `spaced'to provide a lgas outlet 36 from the furnace 16. 1 In the incineration of residual black liquor the liquor is projected through a spray type burner 37 positioned 1nthe"-front -wall 25 ofthe furnace at a position inter` mediate-the hearth k31 and the nose baille 34. The sprayed liquor delivered'to the 'furnace is partially dried 'and 'deposited upontherear wall'30 and side' walls 15 van'dflS 'ofthe 'furnace 'from which lthe dried liquor or charjffalls under the inlluen'ceof gravityto the'hearth 31 whereitfburns, to vsmelt'the chemicals and to completethecornbustionA ofthe 'carbonaceous matter therein. 1 'lPrimary'eombustionair is delivered to the furnace 16 at a position upwardly adjacent the`hearth'31 throughV a seriesofv'air p orts -40 which'are `supplied with heated combustion` aiuthrough.an'insulated duct 41 from an air heaterprthellike (not shown). Positioned upwardly oftheprimary airports I40 is a second row of air inlet ports 42 throu-ghwhich secondary combustion air is f deliveredto' thefu'rnace 16 through the separate duct 43 :with-airflow controlled so that the Yproportions of primaryand 'secondary air may be regulated forproper combustion conditions onlthe hearth t31.

. lThe .residual liquor gaseous Vcombustion products pass upwardlythr'ough -the yopening '44between the front wall 2S and-the -nose baille 34, turn to flow in -a generally horizontalfdirection over superheating elements 45 and pass throughj the gas outlet -36 to enter the convection passes of t-hesteam generator. The superheater tubes flare for example,V 2`in diameter, and are positioned m widely spaced rows for ease o f cleaning. Saturated steam Lis-passed through arow vrof conduits 46 from thev ,47 positionedyabove beneath the lower end of the bale and move upwardly through 'the rear portion vof the convectionbank and'to discharge through a heating gas outlet 51 positioned rearwardly in the upper portion of the setting. As is customary in a black liquor incinerating furnace, a dust hopper 52 is positioned'beneath lthe lower. drum 11 and is provided with a,` depending baille 53 extending .downwardly from the lower drum l11`to a position closely I adjacent the outlet 52 from the hopper 52. With this construction-there is little tendency for heating l gases to by-pass the tubes 48 oftheconvection banks-since suilicient dust'is usually maintained in the dusthopper 52 to form a seal around the lower end ofthe baffle `53.

The fuel oil furnace 17 is. bounded onone side by a wall 54 including tubes SS-parallel to the division wall 15. and transversely spacedy therefrom.' The; row of tubes 5S extends from an upper header 56 which is connected with the uppersteainwandwater drumlt) to a lwer. header .57 which Ais parallel t0 the lower headers 14.and:22.andupwardly 'spaeedrfromrpthe level thereof. Th'e l'sidewall 54l is providedL with` refractory-heatinsulata ing material "'58land an 'exterior'v metal casing 6l).v

.The front wall 61 of the=furnace 17 shown irl-Fig.V 2 is 'de'ne'd'by ftube and refractory material whereinthe tubes62 extendforwardl-y Yand downwardlyfrom the .U'Pr' feiern 'sind waterdrum 10 to' formaninciined roof 63 'anti' ebent' toextend' downwardly ,toa lowerfspaced position. The 'tubes .are thereafter bent to incline rearwardly toahoriz'ontally 'disposedftransverserear header Y then loweredge of the nsebaille 6Sson1eofthe tubes- 66 of Ithe 'rear'wall extend forwardlyand upwardlyand thence rearwardly to thesteam and Water0 drum 10V to delinea sla'g'scr'een 70. Othertubes 66 from therear walleite'nd upwardly and rearwardlyfto "a lposition spaced [from the upright portions ofthe slag screen 70 and thereafter extendiupwardly and rearwardlyto the steam and water drum 10. Thev refractory Ir'naterial 71 supportedbythe latter tbesends atgafpois'it'iondownwardlyspaced from the roofA of .the furnacefprovding a gas outlet 72 therebetween.. v Y Y The space between therslagl sien 70 Y supporting tubes is prov' ed.'with' a.'depehdenft series of 'superheatergtubes 7g3 whi'cfli'farecon'riected witha steam inletheader 74,'receivingfst .frlnlhdrlim'10`through thefrowrofclouduits 75,`and 'a 'slprh'e'a'te'd steam outlet header'76. The inletand 'outl'etheadefrsQTfl ,and 76, re-v spectively, are p'ositi'ol'ledv abovethe' roof '63 'of the furnaceiu. Y 'j The heating gases discharged 'through' the furnace out let 72 move in jafge'rerally'horizontal position into the convection banks "77fof'jth'e boiler. A depending baille 78extends'downwardlyjfrom the's'team and water drum 10 toa position spaced above the lowerv drurn 11 so as toV dellectthe heating gases lin a downward/direction throug'hthe lforwardrows of .the convection bank l77. Thereafter the 'gases pass'throught the openingj80 between the lower end ofthe baffle .78 and the lower drum 11 to move lt'lpwardly"throughfthe rearward :portion of the convection bankj'77 and discharge 'through an upper gas outlet'8`1. 'The convectionbank'of the unit is provided withv a dust hopper' 82 which is positioned beneath the lower vdrumL 1 1. As intherblack liquor incinerating portion of Athe unit, a baille member83 extends downi wardlyifr'om the lower l'drurn -1'0v`to" amposition adjacent incinerating porti'on of '.theunit are-arranged in widely spacedtube rows Awhere the tube spacing' 'between tubes irl-.each V. row'is also .widely spaced; A-depending baffle 50 extends `from ,the upper steam andfwater drum 10 torv deflect the heating gases in a downward direction to. pass the outlet '84 -of the hopper82. Y LVery. littlekdfust is. 'collectedin-theho'pper ,Sp2 A:but -oil 'orr Y'gas lfuels'Y ordinarily contain somelii'onico' bustibl'ernaterial and some ash will )In the embodiment fof 'the -inve'ntion shOWnimFig'S. 1 and 2, fuel oil 4is burned -inwth'e furnace 17, and for `this andthe baille 71 f purpose ports 85 are provided in the Wall 61 and an oil atomizer 86 inserted through each of the ports. 'Each oil atomizer is provided with a combustion air register 87 which is supplied with a controlled amount of preheated air through a duct 88 from an air heater (notshown) to maintain proper combustion conditions in the furnace 17.

-In the operation of the unit described both of the furnaces 16 and 17 will ordinarily be fired at the VIsame time by residual liquor and fuel oil, respectively, so as to supply the steam required for the paper pulping plant. The residual liquor fired portion of the unit will usually be fired at a generally uniform rate to consume the residual liquor and to recover the chemicals therein, while changes in total steam requirements will be accommodated by changes in the oil firing rate. Under these conditions there will be little or no relative movement between the division wall and the abutting edge of the floor 65 of the furnace 17. However, the furnace 17 may not be supplied with fuel under some conditions, and expansion ofthe division wall tubes 13 would occur, while the level of the floor 65 Would not change. Thus, the jointv between the wall and the oor 65 is provided with a'sealed slip joint to permit differential movement therebetween while at the same time preventing leakage of air or gas through the joint. Since the superheaters 45 and 73 are separated and each receive saturated steam from a common source, i. e. the dum 10, it is desirable to avoid flow .of steam through the superheater element not supplied superheated steam outlet duct from each header.

In the embodiment shown, the furnaces 16,and 17 are proportioned for the production of approximately 10,000# of steam per hour from the incineration of residual liquor, and approximately 40,000# of steam per hour from the combustion of fuel oil, at rated capacity. It will be understood that the proportions of the furnaces can be altered for the combustion of two fuels to meet the specific steam requirements for a particular installation Without departing from concept of the present invention, and still retain the economic advantages of the common drums and furnace wall disclosed.

While in accordance with the provisions of the statutes we have illustrated and described herein a preferred embodiment of the invention, those skilledin the art will understand that changes may be made in the method of operation and form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

l. A vapor generator comprising upper and lower drums, fluid cooled means defining a combustion chamber and a convection gas-pass, a common fluid cooled imperforate division wall separating said combustion chamber and convection gas-pass into separate gas-passes through said vapor generator, at least a portion of said division wall being subjected to heat on both sides thereof, means in one of said furnaces for the incineration of residual liquor and the recovery of chemicals in molten form therefrom, means in the second of said furnaces for the combustion of a fluent fuel for the generation of high temperature heating gases, banks of widely spaced fluid heating tubes positioned in the convection gas-pass of said first furnace, banks of relatively closely spaced fiuid heating tubes positioned in the convection gas-pass of said second furnace, separate superheaters positioned in the separate gas-passes, means for introducing vapor separately intov said superheaters from said upper drum, and means for separately discharging the superheated vapor from said superheaters whereby the vapor generator can be operated as a chemical recovery unit and produce .more

steam than obtainable from the-.incineration of the residual liquor alone without altering the efficiency of chemical recovery.

2. A vapor generator comprising upper and lower drums, fluid cooled wallmeans defining a combustion chamber and a convection gas-pass, a common Huid cooled imperforate division wall separating said combustion chamber and convection gas-pass into separate gas-passes positioned in the gas-pass of vsaid second furnace, sepa-Y rate superheaters positioned in the separate gaspasses, means for introducing vapor separately into said superheaters from said upper drum, and valve means for controlling the vapor liow through each of said superheaters whereby the Vapor generator can be operated as a chemi cal recovery unit and produce more steam than obtainable from the incineration of the residual liquor alone without altering the efficiency of chemical recovery.

3. A vapor generator comprising upper and lower drums, fluid cooled wall means defining a combustion chamber and a convection gas-pass, a common fluid cooled imperforate division wall separating said combustion chamber and convection gas-pass into separate gas-passes through said vapor generator, at least a portion of said division wall being subjected to heat on both sides thereof, means in one of said furnaces for the incineration of residual liquor and the recovery of chemicals in molten form therefrom, means in the second of said furnaces for the combustion of a fluent fuel for the generation of high temperature heating gases, banks of widely spaced fluid heating tubes positioned in the gas-pass of said first furnace, banks of relatively closely spaced fluid heating tubes positioned in the gas-pass of said second furnace, the lower portion of said first liquor incinerating furnace being extended below vthe floor of said second furnace, and means for introducing combustion air into the lower portion of said first furnace whereby the vapor generator can be operated as a chemical recovery unit and produce more steam than obtainable from the incineration of the residual liquor alone without altering the efficiency of chemical recovery.

4. A vapor generator comprising upper and lower drums, an imperforate division wall including an upright row of fiuid cooled tubes positioned in a plane normal to the longitudinal axisof and intermediate the length of said drums, walls including rows of fluid cooled tubes cooperating with said division wall to define an upwardly elongated furnace and a convection gas pass on one side of said division wall for the incineration of residual liquor, means for incinerating residual liquor in said furnace for the recovery of chemical constituents in molten form from said liquor including spray nozzle means positioned in the wall of said furnace for the introduction of residual liquor to said furnace, means for the introduction of combustion air into said furnace through vertically spaced rows of ports positioned in the lower wall portions of said furnace, walls including rows of fluid cooled tubes cooperating with said division wall to define a second furnace and a second gas-pass on the opposite side of said division wall for the combustion of a separate fuel, the floor of said secondl furnace being spaced above the uppermost row of combustion air inlet produce more steam than obtainable from the incineration of the res'iiualliguor alone Witliout 'altering the efficiency of chemical-recovery.

v i 5. YA vapor generator comprising horizfontallvfdisposed upper and lowver'dr'un'is, animperforatefdivision Wallin- Acludingian upright row of 'uid'cooled "tubes positioned in aplane norrnal to thelong'itudinialaxis of 4and intermediate the lengthv'of t said drurns,` Walls including rows of uid cooled tubes cooperating' With said division wall to dene an. upwardly elongated Lfurnacfps'and a convec` tiongas-'passon one side of Asaididi'visikon vvall Afor the incineration of residual liquor," means "for incinerating residual"liquofiinfsaid furnace for the recovery'of chemt ical constituents in molten forni-from'said Vliquonincluding spray nozzlefrneans positionedin a'jwallof jsaid fur- Ynace and means furthe introduction of combustion'air into "said furnace'through verticallyspaced rows of ports positioned inthe Y*lower Wallfpor'tions of said furnace, convection banks of'vapor generating tubes 4insaid convection gaspass andei'nl thepa'thbf' heatingvg'aseslleaving said residual liquorincineratin'g furnace, `a superhe'ater positioned in said'heating-gas-passreceiving vapor frein said lupper drum, WallsVv including "rows of fluidycooled tubes cooperating with said division vWall to 'define a secl' ond furnace and `a second convection gas-pass onk they. opposite side of said division wall for the combustion oftk al separate fuel,l 'the' '-oor'; of; said second 'furnace'b'eng ports Qof'saidf residual?l 'liquorv incineratingfufrnace;burner meanspositionedfin ka'wall of saidseoondfurnae for the introductionfof fuel thereto, convection "banks `of 'vaporjgenerating tubes'in the second lconvection gaslp'ass and infthe path offheating gases Vleaving said s econd'fur-f nace, and a 'superheater positioned 'inthepath of' heat` References Cited intfie 'le of t'liispatent UNITEDIISTATES .PATENTS Apu-T2 l v1939 -2-,6061103 vvHamm Y 1 Aug. 5, 1952 yFOREIGN PATENTS Svvedenv -a I une 2.0, "1950

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