CA1210238A - Furnace wall cooling arrangement - Google Patents

Abstract

FURNACE WALL COOLING ARRANGEMENT
ABSTRACT

A furnace wall cooling arrangement comprises banks of cooled pipes with refractory inserts interposed therebetween.
These banks are arranged over the periphery of the furnace wall and attached to the furnace shell. Each bank is divided along its vertical extent into sections, each including the cooling pipes welded to a metal sheet divided into separate parts with-in this section.

Description

lZ~3~

~ CE ~L~ COOLI~G AR~A-iJG~ J~

The present invention relates to cooling s~Jstems o~ metallurgical ~urnaces, and more particularly, to an arrangement for cooling the walls of such furnaces.
~ he invention is especially well suited ~or cool-ing the walls o~ a sha~t ~urnace.
One o~ the major problems .DLacing the present-day metallurgy is to increase service li~e of metallurgial ~urnaces by enhancin~ durability of their cooled walls with a wiew to reducing the shut-down period of the fur-nace and ~acilitatin~ its serviceO
~ or e~ample, there i5 known a ~urnace wall cooling arrangement which comprises cooling pipes arranged aro-und the periphery and alo~ the 1DU11 vertical extent OL
the IJurnace shaYt and welded together throughou~ their le~gth by mean3 o~ metal plates and connected to coolant inlet and outlet ring mains arranged i~ the upper and low-er parts of the furnace (cf. Japa~ese Patent ~pplication No 45-14642 clo 10 A 521, published in 1970) D
The term "cooling pipes" is referred to ~he pipes along which a coolant is supplied and which serve to re-move heat from the inserts in the ~urnace wall.
~ he cooling o~ the ~urnace wall is e~ected by means of a coolant ~ed from a supply ring main to each of the cooling pipes in which the coolant removes heat from the refractory inserts, arranged between these pipes, and then passes as a flow o~ hot water (in case of a direct-~low ' ~2~ 38 coolirAg system) or the steam-water mi~ture (in case GD
evaporation cooling) to an outlet ring main.
~ he prior-art cooling arrange~en~ operates under conditions of variable heat loads which come into bein~
in the process of the ~urnace operation with the result-ant changes in geometric dimensions o~ the cooling arrange-ment. The cooling arrangement is attached to the ~urnace wall the dimensions o~ which remain practically unchanged in the course of ~peration. This means that the heat loads re~erred to above may cause break-away o~ the cooling pipes froM the metal plates along with the ~ailure o~ gas tight-ness of the cooling arranKement as a whole A damage to at least one o~ the cooling pipes will upset the operation of the whole cooling arrangement by reason o~ the ~act that the pipes are closed into a cir-cuit by means o~ common inlet and outlet ri~g mains.
~ urthermore, a great leng-th o~ the cooling pipes causes their considerable thermal expansion, which is ~o be compensated ~or ~y special devices.
Since the metal plates are arra~ged along the centre-line o~ the cooling pipes7 running in parallel with the a~is o~ the ~urnace shell in transverse section, the re-fractory inserts are cooled only by a hal~ o~ the sur~ace area of these pipes 7 which causes untimely damage of the insert pieces.
There is also known a ~urnace ~all cooling arrange-ment which comprises banks arranged around the periphery o~ t~e ~urnace wall and attached to the furnace shell, which banks are made up o~ cooling pipe~ and refractGx~J
in~ert pieces interposed between these pipes (c~. USS~
Inventor's Certi~icate NO 222 ,L~10, cl . C21 ~ 7/06, pU'5-lished in 1966).
In the ~bove-described cooli~g arrangement each o~
the coolin~ pipes is made to e~tend throughout the cool-ing zone of the ~urnace sha~t, with the wor'~ing and later-al parts of these pipes being ~ormed with tenons to permit fi~ed positioning o~ the re~ractory inserts. ~he coolant inlet pipe is introduced in-to the cooling pipe.
A coolant is ~ed along the inside pipe into the lower part o~ the cooling pipe and, on taXing up the ~urnace heat therefrom, is heated up its~elL to be t~ereafter raised under the action of natural head along the interspace bet-ween the wall of the coolant inlet pipe and the wall o~
the cooling pipe. Illhe coolant is then passed to discharg-ing pipelines positioned e~terna~ly o~ the furnace wall~
In case o~ failure o~ one o~ the cooling pipes~ a great section of the ~urnace shell is cut o~ ~rom coolin~, as a result of which it is overheated 9 de~ormed and ~ompletely damaged.
The abovc-de~cribed cooling arrangement i3 co~plicat-ed in construction and is di~icult ~o mount especiall~ dur-ing overhaul periods, which hampers construction and erec-tion works and lmpairs operatin~ reliability o~ the cool-ing arrange~ent as a whole.
In additio~, the refrac-tory insert pieces provided between the cooling pipes o~ the prior-art cooling arrange-men-t have insu~ficient durabilit~.
The reason for this being t~e abrasive aqd cae..,ic-al effect of the charge materials on the middle portion of the cooled wall (over the vertical exten~ of the fur-nace shalt) wherein the refractory insert pieces are da-maged very rapidly~ The upper part of these insert ~ieces is also liable to rapid destruction due to the absence o~ backing.
~ ow durabilitg o~ the insert pieces result in that the unprotected sections o~ the ~urnace snell are exposed to the action of the hot charge materials and furnace gas-es, causinK overheating and deformatioh of the furnace shell.
~ urthermore 9 since the lower part of each cooling pipe ~as a small cross-sectional area9 the -travelling velo-city of the coolant ~lo~ will be the smallest in this part o~ the pipe ands therefore, it will be first to be clogged up with slime and to burn through because o~ the cooling failure.
It is the primary object o~ t~e invention to provide a ~urnace wall cooling arrangement of lsnger service life and improved gas tightness, whose construction and instal~
lation will bR less time- and labour-consuming~
Another obaect o~ the iavention is to enhance dur-ability of refractory inserts.
Still another object of the inve~tion is to lower stresses in the ~urnace shellO
Y~t another object o~ the inve~tion i9 to ensure 12~ 38 uni~orm distribution o~ heat loa~s over the Lull ver-tical exten~t of the furnace shaft.
These and other objects of -the invention are ac-complish~d by the provision o~ a furnace wall cooling arrangement comprising ban~s made up of cooling pipes and refractory inserts placed between these pipes, ~hich ba~ks being arranged over the periphery o~ the furnace ~all and attached to the ~urnace shell, ~herein, accord-ing to the invention, each bank i5 divided along its ver-tical e~tent into sections each including cooling pipes welded to a metal sheet divided into separate parts ~ith-in this section.
B~ dividinæ each bank into sections and each metal shee-t into separate parts~ it becomes possible to compen-sate ~or the stresses which come into being in the process of operation and to thereby completely eliminate t~e pos-sibility o~ de~ormation of the cooling pipes. Such con-struction o~ the cooling arrangement makes it possible to prolong its uninterrupted serYice li~e, to improve gas tightness thereof, and save time and labour required rOr its manufacture and installation~
~he vertically adjacent sections o~ the cooling ar-rangement are pre~erably placed relative to o~e anot~er so as to permit staggered arrange~ent o~ the cooling pip-es and re~ractory inserts.
Such structural arrang~ent makes it possible to substantially reduce the extent o~ wear o~ the re~racto~y ~2~3'~3 inserts and thus to protect the ~urnace shell lrom be-ing overheated by the charge ~aterial and ~urnace gases, as well as to prec~ude the de~ormation o~ the ~urnace shell and its subsequent damage.
The adjacent sections OL the cooling arrangement are pre~erably o~set relative to each other in the ver-tical, which permits the cut-outs, provided in the ~urnace shsll as outlets ~or the cooling pipes~ to be uni~ormly distributed over the ~urnace shell with a view to enhanc-i~g its strengrth.
The cooling pipes oi each section are preferably spac-ed in parallel arrangement with the furnace shell a-t an angle o~ 30 to 75 to its generatrix, which ensures therm-al co~tact between the cooling pipes in one bank and the ~low gas in -the ~urnace during its nonuni~orm distribution over the cross-sectional area of t~e furnace.
The angle o~ 75 7 at which the cooling pipes are inclined to the generatrix is sel~G~ed, in -the event of eva-poration cooling, by reason of the ~act that with natural circulation any angle larger than that o~ 75 will not permit a su~ficient head to be produced in the cooled cir-cuit to enable circulation.
In addition, the vapour phase will extend along the upper Keneratrix o~ the cooling pipes, which causes over-heating and burning-through o~ the latter.
The ~inimum angle o~ inclination o~ the cooling pipe is determined by the nece~sity o~ providing such con-ditions under which -the flow of ~as will traverse all the cooling pipes within each section, not~uithstandirg its nonuni~orm peripheral dis~ribution in the furnace.
Provided the dimensions o~ each section are stand-ard, the upward flow of gas will traverse all the cool-in~ pipes wit~in this section with a minimum angle of their inclination being not less than 30. I~ the angle of in-clination is less tha~ ~0, not all of the cooling pipes in o~e section will be traversed by the gas flow, which will result in overheating o~ some o~ the pipes and under-j heating o~ others and, eventually, in their thermal defor-mation.
Advantageously, each part oi the metal sheet is form-ed with a slit through which the cooling pipes are welded to this part OL the sheet.
In doin~; so it becomes possible to ensure e~fective cooling ol~ the metal she2t~ reliable gas tightnes~ of the whole arrangement, as well as good p~otection to the ~ur-nace shell against overheating and subsequent deformatio~.
In the event o~ large-capacity furnaces with flat ; walls, the parts o~ a metal sheet may be made ~lat in cross section, wherea~ for small-capacity furnaces, each part of the metal sheet may have an arched shape with the radius o~ curvature corresponding to the radius of circum~erence o~ the ~urnace shell in a respective section.
'~hus, it becomes possible to ~ill in the gap bet-ween the furnace shell and the metal sheets of the cool-ing arran~emont, which also facilitates the mountin~ o~
the latter.

23~

At the places o~ joints o~ ~wo vertically a~,oin-ing sections, a part of th~ ~qetal sheet 01 each lof~er section is made L-shaped in form9 whereby the durabilit-J
ol re~ractory inserts i~ enhanced and, in case o~ damage o~ these inserts, the lower part o~ the metal sheet thus ~ormed will serve as a sup~orting membar for a skull ac-cumulated in the ~urnace.
The horizontal sections o~ the ~-shaped part o~ the metal she~t have cooling pipes welded thereto with a view to ensuring good cooling o~ these ~ections and, consequent-ly, their high durability.
The inventio~ will now be described, by way o~ ex-ample only, with re~erence to the accomPanying drawin~s, wherein:
~ IGo 1 is a general view o~ the sectio~ o~ a bank incorporated in an arran~eme~t ~or cooling the ~urnace wall, with a partial cut-awa~ view of re~ractory inserts, ~ IG. 2 is a side view o~ FIG~ 1, also showing the ~urnace shell;
FIG, 3 is an embodiment o~ joinin~ a part o~ the me-tal sheet with cooling pipes by welding ef~ected throu~h Slit9;
FIG~ 4 is another embodiment æ joining a part o~
the metal sheet with cooling pipes by welding;
FIG. 5 shows an embodiment o~ the furnace wall coo~-ing arrangement wherein the cooling pipes and re~ractory inserts are staggered, with a partial cut-away view o~ re-~ractory inserts;

~ IGo 6 is a.side view o~ FIG. 5, also shol~7ing the furnace shell;
FIG. 7 shows an embodiment o~ the Lurnace wall coGl-ing arrangement with the sections thereo~ being verticall~
o~set relative to one another, with a partial cut-away view o~ refrastory inserts;
FIG~ 8 shows an embodiment of the furnace ~vall cool;
ing arrangement wherein the cooling pipes are placed in pa-rallel with the furnace shell at an an~le to its genera-trix, ~ IG~ 9 is a side view o~ ~IG. 8; and ~ IG. 10 shows a metal sheet divided into separate parts with slits formed ther~i~ to permit the cooling pipes ~o be welded thereto~
~ he ~urnace wall cooLing arrangement, as illustrated, comprises banks wni¢h are vertically divided into sections 1, such as shown in ~IG. lo Each seotion 1 includes a me-tal sheet 2 welded to cooling pipes ~, each havin~ a cool-ant inlet pipe 4 and a coolant outlet pipe 5 (~IG. 2), and re~ractory inserts 6 (FIG. 1) placed betwee~ the cooling pipes 30 W~thin each section 1 the metal shee~ 2 is divided into parts 7. 'lhe æections 1 are placed one above the other over the ~ull v`ertical e~tent o~ the ~urnace wall cooling zone.
~ ach o~ th~ bank sections 1 is attached to the fur-nace s~ell 9 by maans o~ fixing members such as s~own at 8 in FIG. 2.
Shown in FIGo 3~ 4 are embodiments o~ joining the Jf~

metal sheet with the cooling pipes b~welding.
'~he ve~tically adjoining sections 1 (~IGS.5,6~ are placed one relative to another so as to permit sta~gered arran$ement of the cooling pipes 3~and refractory inserts 6 with a view to enhancing durability o~ the refractory inserts and preventing possible overheating of the furnace shell 90 A gap 10 between the ~urnace shell 9 (~IG. 6) and the sections 1 o~ the banks is filled in with an expansion material; as is the common practicev Since the adjoinin~ sections 1 (FIG. 7~ are oL~set relative to each other in the vertical9 the cut-outs pro-vided in the ~urnace shell 9 to receive the coolant inlet and outlet pipes ~ and 5 can be uni~ormly distributed over the ~urnace shell 9 with a view to increasing its s~rength.
~ he cooling pipes 3 (~IG~. 8 and 9) are spaced in parallel arrangement with the ~urnace shell 9 at an angle o~ 30 to 75 to it~ ~eneratri~, a~ a result o~ which the steam-water mixture is ea~ier discharged in the event o~ , evaporation cooling~ and the operating reliabilit~ of the cooling arrangement is improved~
- D2pending on the con~iguration o~ the ~urnace shell 9, the metal sheet~ 2 may be made either ~lat or bow-shap-ed, with the radius o~ curvature corresponding to the ra-dius o~ circum~erence o~ the ~ur,nace shell in a respective s,ection. '~his is done to permit the gap between the furnace shell 9 and the sections 1 o~ the cooling arrangement to be reliably ~ealed.

3~

At the places o~ joints of the two verticall~ ad~oi~-ing sections 1 (~IGs 5, 6 ), each part 7 o~ tne metal sheet

2 is made L-s~aped in order to enhance d~rability o~ the re~ractor~ inserts. The L-shaped parts 7 o~ the metal sheet 2 have t~eir horizontal sections 11 welded to the coolin~ pipe~ 39 which makes ~or their ef~ective cooling and9 consequently, enhances their durabilityO
The cooling pipes 3 are welded to the parts 7 of the metal sh~et 2 through slits 12, such as shown in ~IG. 10.
The ~urnace wall cooling arrangem~nt operates as ~ollow~.
First, a coolant i~ fed along the inlet pipes 4 to the cooling pipes 3 wherein it is heated up and then dis-charged ~rom the ~urnace throu~h the outlet pipes 5.
'~he sectional metal sheets 2 are provided to make up ~or the expan~ion of the cooled pipes 3a~d re~ractory inserts 6~
In addition, b~ w~lding the coo~ing pipe~ ~ to the metal sheets 2 along the back generatrix, it is possible to make ~ull use o~ the entire heat-ab~orbing sur~ace o~
the pipes 3 50 as to e~sure ef ective cooling o~ the re-fractory inserts 6. Since the refractory inserts 6 e~tend beyond the centre line of the cooling pipes 3, they become protected rrom th~ detrime~tal ef~ect o~ the descending charge materials.
With th~ bank~ being divided into separate sections 1, a ~ailure o~ one o~ the cooling pipes ~ will no~ cause ~, overheatin~ o~ the ~urnace shell along, above or belG7 the damaged section 1.
Stagp~ered arrangement o~ the cooling pipes ~ and re-fractory inserts 6 in the vertically adjoining sections 1 protects the re~ractory in~erts 6 o~ tha sections 1 from bein~ damag~ed b~ the charge materials throu~hout the ver-tiCal e~tent o~ the furnace shell.
With the adiacent sections being o~set relative to one another in the vertical, the local stresses in the ~ur-nace shell 9 are lowered and the strength o~ the latter is thereby incrcased.
~ h~ use o~ the metal sheet 2 permits the overheating o~ the ~urnace6 shell 9 to be prevented even ~ith the ~ail-uxe o~ one o~ the coolin6 pipes ~.
With the cooling arrangement of the invention it be-come~ ~easible to substantially enhance durability of thc ~urnace walls, to inarease the ~urnace production campaign, and to ~acilitate its s0rvicing.
~ urthermore, t~e overhaul period o~ the ~urnace can be reduced owing to the possibility o~ ~abricating the sec-tio~s on the outside.

Claims (9)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An arrangement for cooling a furnace wall, com-prising:
- banks of cooling, pipes arranged over the peri-phery of the furnace wall and attached to the furnace shell;
- refractory inserts interposed between the cooling pipes of said banks;
- sections in-to which said banks of cooling pipes are divided along the vertical extent thereof;
- a metal sheet of each said section welded to said cooling pipes;
- parts into which the metal sheet is divided in the horizontal;

2. A cooling arrangement as claimed in claim 1, wherein the vertically adjoining sections are placed re-lative to one another so as to permit staggered arrange-ment of the cooling pipes and refractory inserts.

3. A cooling arrangement as claimed in claim 1, where-in the adjoining sections are offset relative to one ano-ther in the vertical.

4. A cooling arrangement as claimed in claim 1, where-in the cooling pipes of each section are placed in paral-lel with the furnace shell at an angle of 30 to 75° to its generatrix.

5. A cooling arrangement as claimed in claim 19 where-in each part of the metal sheet is formed with a slit through which the cooling pipe is welded to this part of the sheet.

6. A cooling arrangement as claimed in claim 5, wherein each part of the metal sheet is made flat in cross section.

7. A cooling arrangement as claimed in claim 5, wherein each part of the metal sheet is bow-shaped in cross section with the radius of curvature correspond-ing to the radius of circumference of the furnace shell in the respective section.

8. A cooling arrangement as claimed in claims 5 and 6, wherein at the places of joints or two vertically adjoining sections, a part of the metal sheet in each underlying section is L-shaped in form.

9. A cooling arrangement as claimed in claim 8, wherein the L-shaped part of the metal sheet has its horizontal sections welded to the cooling pipes.