CA1053008A - Method of operating converter furnace for treating matte - Google Patents

Abstract

ABSTRACT
A method of operating converter furnace for treating matte, in which the blowing air volume supplied per unit time is controlled within a predetermined range such that the supply of a scheduled total blowing air volume for one of a plurality of stages of one cycle in the converter operation ends at a time possibly nearest to a scheduled end time of the blowing for said stage on the basis of the remaining air volume obtained by subtracting the real brown air volume for said stage at a desired time between the start and end of said stage from a scheduled total air volume to be supplied for said stage.
In such method, when the blowing air volume supplied per unit time gets beyond said predetermined range at a time in a stage at least prior to the last stage subject to said cycle, the average blowing air volume to be supplied for the rest of said stage and the remaining stage or stages is determined by dividing the sum of the air volume of the remaining for said stage at a desired time and the total scheduled air volume to be supplied for the remaining stages or stage by the sum of the remaining blowing time for said stage and the scheduled blowing time for the remaining stage or stages, and a time required for carring out the subsequent blowing in said stage is determined by dividing the remaining air volume for said stage by said blowing air volume supplied per unit time, by using said blowing air volume supplied per unit time whereby the actual blowing rate is controlled to said average blowing rate such that the supply of the scheduled total air volume for said stage ends at a time possibly nearest to the scheduled end time of the blowing for said stage.

Description

53~$

Thi q invention relate~ to the smeltin~ o~
non-ferrous metal~ and, more particularly, to a method of operating converter furnaces for treating the matte produced in ~melting furnace ~uch a-~ bla~t ~urnace and flash ~meltin~ furnace.
Or~ obtained f~om mine~ are treated to obt~ined concentrate~ containing more ~aluable metals by mean~
of the flotation proces~, and such concentrate~ ara refined to final metal product in the ~melter.
The ¢opper or nickel ~ulfide concentrate i~
treated in a ~melting furnace to produce matt~, which i~ further treated in converter furnaces to obtain, in ca~e of copper ~mel*in$, the blister copper, while the S02 ga~ prod~ced in the smelting furnace and o~nverter fu~ace i9 recovered a~ ~ulfuric acid.
Usually, the matte produced in the ~melting furnace i~ ohar$ed into converter furnace~ in~talled at near the ~melting furnace in mvlten state, altho~gh in ~ome ca~e~
it i~ tranaported into remote converter~ or other ~melter.
In the f~rmer ca~e, it i~ of cour~e most effective and ~conomical frsm the ~tand point of the economy of in~e~tment that the con~erter ha~ the ~ame tre~ting capacity a~ the ~meltin~ furnace. Thi~ al~o applie~ tc the ~ulfuric acid plant.
In the converter, unde~ired metal~ contai~ed in the matte are oxidized by blowing air, and react~d with a ~la~ formins agent added ~ch a~ ~ilicate ore to tran~form them into the ~lag or eliminated by vapori~ation. Sulphur in the ~a~te i~ also oxidized by the blowing air to eliminate afi S02 ga~. Further, ~3~313~3 ~olid material at roo~ temperatur~ ~uch a~ flu~ du~t and ~crAp ~etal are added ~ cold charge ~or pre~ent-ing the temperature ri~ing of the malt~
In the operation of the converter, th2 amount o~ the matte charged at a time i~ limited by ~uch factor a~ the inner volume of the converter. Con~equently, th~ matt~ to be treated in one cycle i~ charged by dividing into severAl portion~ although the copper ~rade of matte i~ a factor. At each time of charging matte, the 31ag forming a~ent and, i~ nece~sary, cold material~ are charged~ When a major portion of the components to be eliminated a~ slag are changed to the ~lag, the produced slag i~ di~charged by tilting the converter. Then, ~upplementary matte and ~lag forming agent are charged into the converter, and the treatment of the ~upple-mentary matte is carried out and for~ed ~lag i~ di~charged again. In the ~melting of nickel, the concentr~tion of 25 to 30 percent nickel i~ further concentrated through thi~ proces~ to about 75 percent. While in the ~meltin~ of copper, the white metal (Cu2S) obtained in the above proee~s i~ further subject to copper forming reaction to obtain the bli~ter copper.
The above individual period~ of ~lag forming reaction3 ~nd the period~ of copper for~ing reaction~
are each commonly termed a ~tage9 ~ld a ~erie~ of the~e individual 3tage~ i~ called one cycle o~ converter.
In u~e of the converter furnaoe, depending on the treating capacity of the conv~rter ~urnace against the ~melting furnace and number of the furnace~
in~talled two converter ~urnaces are ~lternately used , ~53~
80 a~ to ~ave th~ down time between the completion of copper forming period and th~ tran~fer to next cycle, ~,hereby increa~ing the treating amount per hour. To thi~ ~nd, many method~ have be~n propo~0d, the method~ of which are, ~or cxample, cycle alternating blowing method in which immediately after the aompletion of copper forming period of one conYert~r ~urnace, another converter furnace which i 8 r~ady for operation i~ .
s~cce~i~ely u~ed and the former converter furnace ~hich ~u~t compl0ted the copper forming rsaction gets ready ~or next operation9 ~tage alternating blowin~
method in which two converter furnace~ ~re u~cd to alternately e~ect the ~tage~; and method in which t~o convarter furnace~ out of three furnace3 are alway~
under the operating condition for blowing.
The matte production 0peed of th~ ~melting ~urn~ce ~uch ~ fla~h ~melting furnace can be obtained throu~h th~ material balance calculated from ~uch factor~
as the an~ly~i~ value~ of char~e, the amo~nt of charge and the pre~et matte grade with r~fersnce to the a~erage of the actual production rate. Th~ con~ert~r~
arc provided ~o that they Are sufficiently able to proce~ the a~ount of matte produced by the ~melting furnac~. The treating capaci*y of the converter i~
decidQd from the inner ~olu~ of the conv~rter an~ the number of tuyer~ providod th~reto it. The period of one cycle, though it diff~r~ dependin$ upon the Cu ~rade of matte, i~ about 4 hour~ ~ith a nominal 28 to~s furnace, about 5 hours with a nominal ~5-tons furnRc~
30 and about 8 hour~ ~ith a nominal capa¢ity of 150 to 180 t~nqO
.~ 5 -- .

~.~53~3~t~3 A~uming now that two nominal 200-tons converter~ are u~ed as "cycle altern~ting blowing method" wlth 585 ton~ of molten matte ~upplied from the ~meltin~ furnace per d~y, the matte production rate of the omelting furnace i~ balanced by three cycle~ of matte treating if about 195 ton~ of matte i~ treated in one cycle of about 8 hours.
If the matte i8 charged in two divi~ion~ into the converter for each cycle, ~ith an actual weight of molten matte of 120 ton~ charged for the first -qtage, ~nd the air supply i~ 3$arted at 0; 00, th~ amount of matte to be charged for the ~econd ~ta~e i~ 75 tons.
A~sumin$ a period o~ 30 minute~ req~ired between the end of the fir~t ~tage and the start o~ the ~econd sta$e for di~charging the slag and charging the matte, a period of 40 minutes req~ired for discharging the Ylag ~fter the end o~ the ~econd ~tage and a down time of 20 minutes required between the end of the third ~tage, iOe., the copper refining ~tage, ~nd the ~tart of the ~ir3t sta~e in the other ¢o~v0rter, th~
total blo~ing time in thi~ cycle i9 480 minute~ - (30 ~ 40 ~ 20) minute3 = 390 minut~.
In thi~ ca~e, the total air ~olume t~ be ~upplied for the individual ~tage~ are determined by the theoretical air vol~me calculated from m~terial balance taking the ratio o~ non-;reacted air and ratio of leakage air into con~ideration and al~o empirically R~:
60,000 Nm3 for the first ~tags, 3~ 55,000 Nm3 for the ~econd ~tag3 ~L~53~

100,000 Nm for the thir~ ~tag~.
In th~ third 3ta~e which i8 the copper forming ~tage, the oxygen in the supplied ~ir n~ed not oxidize iron but i~ exclu~ively re~cted with thc ulur in the ~hite metal, ~o that the concentration of the S0? ga~
produced in thi~ stage i~ higher than that of the fir~t and ~econd 9tage~. In the ~ulfuric ~cid plant, this g~ withdrawn together with mixed air to m~ke the S2 ga~ concentration and the introducing vol~me nearly e~ual to that in the fir~t and ~econd stage~. F~r thi~
purpo~e, the blowing volume per unit time in the third ~t~ge i~ made to be 5 perce.nt le~ than, th~ rate in the fir~t and ~econd ~t~ge8~ that i~ 95 per cent.
In thi~ ca~e, the di~tribution of blowing time, ~uch a~-tn pro~ide ~or an equal blowing r~te for the individual ~tage~ follow~:
For the fir~t stage = 106 ( ) 0,000 ~ 55,000 ~ 100,000 ~ 0.95 mlnute~

For the ~cond ~tags 60~0-oo -~ 55--~-0-0-O-+-10~,00o ~'o.95 = 97 (minute~) ~or the third ~ta$e 100~00 ~ o~25 ~_~9~ ~ - 186 ~inute~) ' + 55~ + 10~00 ~ 0.95 Thu~, the ~cheduled ~tarting ~ndr~n~ time~
and blowing rate~ for the indi~idual ~tage~ of thi~
cycl~ are aR follow~:

3o - 7 - . :

1~53~8 First ~tage Second ~tage Third ~tage St~rting time 0;00 2:16 4:33 Ending t.ime 1:46 3:53 7~39 Blowing r~te 566Nm3/min~ 567Nm3/min. 537Nm3/min.

It i~ now a~umed that ~fter the fir~t stage, the ~econd ~tage i~ started with ~n actual weight of 78 ton3 o~ molten matte charged in the converter at a time of 2~23, which i8 delayed 7 minute~ from the ~cheduled time.
In thi~ ca~e, by lengthening the treating period according to th~ amount of the matte ch~rged in the oon~erter in exces~ of the ~chedule~ amount, the rate of the matte productio~ in the smeltin~ furnace i~
balanced b~ th~ rate ~f treating in the converter. Al~o, a~ the increa~e of the amount of charged matte re~ults in the incr~a~e ~f the total blowing volume to be ~upplied in the se~ond atage and the amount o~ ~hite metal to be treated in the third ~ta~e, blo~ing ~olu~e ~or the third ~tAge i~ increa~ed.
Thu , a period o~

1~205~578 ~ 24 ~ 60 = 487 (minute~

may be taken till the end vf this cycle. Becau e fir~t 25 ~tag~ start~ at 0:00, thi~ cycle end~ at ~:07. Since 20 minute~ i~ taken a~ the down time period after the end of the third ~tage, i.e~, copper formin$ ~ta~e, the and point cf thi~ ~ta~ is 7247.
Alao~ ~ince the do~n time of 40 minuta~ i required between the ~econd and third ~tage3, the total : `

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bl~wing ti~e Por both iffecond and third ~tage iiY
7 x 60 ~ 47 - (2 x 60 ~ 23) - 40 = 284 (~inute~) Mean~hile, due to the increa~e of the amount of matte, the tot~l air volume required for the ~econd ~nd third ~tage i~7 re-calculated to be 57,000 Nm3 for the ~econd ~ta$e 102,000 Nm3 ~or the third i~tage.
Thu~, the bl~wing timei~ for the econd ~nd third stage~ are re-determined ~imilar to the previouis dii~tribution to be ai~ ~ollow~:
For the i~econd ~tage 57,000 ~ 102,000 ~ 0.95 = 98-5 ~ 99 (minutes) For the third stage 5j i0o1jO0Oo2 oo95~xo2~54 = 185.5 _ 185 (minute~) Thui~, the re-schedule ~n and ~fter the ~cond tsta~e iY ai~ follow~:
Second ~tage Third stage Starting time - 2:23 4:~2 Endin~ *ime 4:02 7:47 Bl~w~;ng rate575 Nm3/min. 549.4 Nm3/min.
It i~ now a~i~umed that the atar*ing time o~
:, . .
third i~ita$e after ~lag of~ in the second ~tage is 4:38, 4 minute3 earlier th~n the ~cheduled time~ In thiis case, it iii~ nece~Yary to reduce the blowing rate ~or correi~pondin~ the endin~ time to the i~ehedule time.
Accordingly9 the blowin~ rate i~
1027000 ~ (l8s ~ 4) = 539.7 Nm3/min.
By Dper~ti~lg the co~verter ln the above w~y, the tr~i~tment of matte in the conv0rter can bs cArried _ 9 _ . , . . , . . ,, ~ . . . . ,, .. , ., ,. ...

~53~g`~

out in keeping balance with the a~ount of matte production in the ~melting furnace, and also it i~ po~ible to provide for oub~tantially uni~orm ~upply of the S02 ga~
to the ~ulfuric acid plant.
The air blowing into the converter i8 made through ~ number of tuyeres provided in the ~ide wall of the converter. Since solid matter build~ up at the opening of each tuyere opened to the interior of the refractory brickY and eventually clo~e~ the tuyera, during the blowlng, th~ ~olid matter i~ frequently removed by ~ punching rod from the out~ide into the interior of the furnace to provide for ~ufficient blow-ing.
Since the blocking of the tuyere~ varie~
depending upon their location, temperature distribution withi~ the ~urnac0 and other variou~ factor~, the blowing rate into the converter i~ ~ubject to Pluctuation~.
There~ore, occurrence of difference between ~cheduled total blowin~ ~olume and actual blowin$
volume i~ unavoidable, cau~in~ deviationY of the ~cheduled blowing~;time ~or completing the converter reactionO
If one cycle ends earlier than a ~shedul~d time, it mean~ a hi~her average blowing rate than the ~cheduled rate. I~ this ca~e, excessi~e ga~ i3 ~upplied to the ~9 sulfuric acid pl~nt, and the S~2 tre~t~ng cap~city of the sulfuric acid plant ~o~Qd-b~ ~ometimcs ~urp~s~ed. Al~o ~ince the matte production rate in the smeltin$ furnace i~ not chan~ed, the down time in *he operatio~ of the converter io extended, leading to increa~ed heat lo~s till the otart of the ne~t cy¢le. Fuxther, ~ince the , - ~53~
capacity of the sulfuric acid plant is fixed, an increase of the converter exhaust gas volume beyond a scheduled volume forces reduction of the exhaust gas from the smelting furnace, necessarily leading to reduction of the eed rate of ore to the smelting furnace.
On the other hand, if the cycle takes a longer time than the treating time corresponding to the amount of the charged matte, the treating capacity of the converter becomes insufficient with respect to the smelting furnace, so that it becomes unavoidable to reduce the matte production rate in the smelting furnace, which also leads to insufficient supply of exhaust gas to the sulfuric acid plant and results in the reduction of the conversion efficiency. If such fluctuations are taken into consideration, considerable redundancy has to be provided for the capacity of the plant which is inefficient from the standpoint of the equipment economy.
This invention has an object of providing a method of operating one or more converters, which permits to keep well balanced with smelting furnace and sulfuric acid plant and to exhibit fully as possible the capacities of the related equipment.
According to the invention there is provided a method of operating at least one converter furnace for treating molten matte, which comprises adjusting the blowing air volume supplied per unit time within a predetermined range such that the supply of a scheduled total blowing air volume for one of a plurality of stages of one cycle in the converter operation ends at or close to a scheduled end time of the blowing for said stage, said adjustment being effected by subtracting the real blown air volume . i, ,,: .: -53~
from said scheduled total air volume at a suitable time between the start and end of said stage to obtain a remaining air volume and adjusting the blowing air vclume supplied per unit time to ensure that said remaining air volume is completely supplied at or close to said scheduled end time.
The invention will now be described in conjunction with an example thereof. `. ;
Example The amount of molten matte supplied from a smelting furnace into a-converter was 591 tons per day. This matte was treated in the converter in three cycles, ~ .

-- lla - ~

1~5~

that wa~, 197 ton~ of matte was treated in each eycle with a treating time of 8 hours. Similar to the above di~cription, the blowing time in ona cycle excluding the down time wa~ #et to 390 minute~;
Al~o, ~cheduled total air volume ~ere 61,500 Nm3 for the fir~t ~tage 55,000 Nm for the ~econd ~tage 101,000 Nm3 for the third stage.
The amount~;of matte charged for the fir~t ~tag~ wa~ ~et to be 122 tons, ~ith the matte amount for the s~cond stage being thu~ set to 75 tonY. Similar to the above, the bl~wing time~ in the individual ~tages allotted ~o tha$'~the blowing rate per unit time WA
~ifor~ were a~ follow~:
For the fir~t ~ta$e 61~500 + 55,000 + lo1,ooo ~-0.~5 = 108 (minute~) For the ~econd ~taga 61~500 + 55.~00 + lO1,Ooo x-0-.95 = 96 (minu*e~) For the third ~tage . 101?000 ~ 0.95 x 390 ~1,500 ~ 55,000 ~ lb~,000 x-0.95 = 1~6 (mlnute~) Thun, the ~chedul~d starting and ending tim~s and blo~ing rate~ for the indi~idual ~tag~ were ~et a~ follo~: .
~ir~t ~taga Second stage Third stage Starting time 3:20 5:38 7:54 ~ndin~ time 55o8 7:14 11.00 Blowinggrate 569 ~m3/min. 573 Nm3/~in. 543 Nm3/min.

_ 12 -~0530~B
At 4:15 after the start of the first stage, the re~l blown air Yolume wa~ found to be 30,389 Nm3.
At this time, there was left 53 minu*e~ until the ocheduled time of end of thi~ ~tage, and the total air volume of remaining to be ~upplied was 61,500 ~ 30,389 =
31,111 Nm3. Gon~equently, the aub~equent blo~ing rate W~8 adjusted to 31,111 ~ 53 = 587 Nm3/min.
Since the range of the blowing r~te we~ ~et to be 530 to 600 Nm3/min., ~he rate of 587 Nm3/min.
10 waff olightly below the upper limit of blowing rate, the blowin~ was continue~ at that rate, which was thereafter repea*edly adju~ted at an inter~al of 5 minutes. At the time of eaoh o~ these adju~tment~, the new rate WA8 within the afore-men-ioned predetermined rat~, ~o that the fir~t ~tage could be ended at the ~cheduled e~ding time.
After the fir~t stage and di~charging the ~lag, 77 ton~ o~ m~tte wa~ charged into the converter, And the bl~ing for the second stage wa~ ~tar~ed at 20 5:36.
Since the ~mou~t of the charged matte and the ~tarting time of the serond ~ta~e dif~ered fro~ the ~cheduled on0a, the corrected ending ti~e of the third ~tage wa~ calculated.

12259177 x 1440 = 485 (minute~) Thus, the c~rreeted ending time of the +hird stage wa~
3s20 + 485 minute~ - 20 mi~utes = il:05 Al30, with the increa~e of the ~a*te, the - 13 ~

.
:. ' ,' :. ::
:: , .,., ,. . . ,; ,.

.: " .. . , , , , . ~ :

~53~

~cheduled total air volume~ for the ~cond and third ~tage~ were altered to be 57,000 Nm3 for the ~econd ~tage 102,000 Nm3 for the third ~tage.
The total blowing time for the ~econd and third ~tage~ was 11 x 60 ~ 5 - (5 x-60 + 36) - 40 = 289 (minutes) ~nd the di~tribution of thi~ time wa~

57.000 + 102,000 ~ o.95 = 100 ~minute~) ~or the ~eoond ~tage and 102,000 ~ 0.95 x 289 57,000 -l~102,00o ~ 0.95 = 189 (minute~) for ~he third tage From the above, the ~chedule on and ~fter ~econd ~tage w~ altered to be a~ follow~:
Second ~tage Third stag~
Starting time 5:36 7:56 Endin$ time 7.16 11:05 Blo~ing rat~ 570 Nm3/min. 539 Nm3/min.
In the ~econd ~tage, similar to the fir~t ~tage, the blowing rate wa~ adJu~ted at the interval of S minute~ by obtainin~ the re~l blo~n air volume for the 3tage, ~ubtracti~g thi3 volume from the scheduled total air volum~ to be ~upplied for thi~ stage to obtAin the total air volume o~ the remaining, and dividing the l~t obtain~d volume by the r~idual ti~e o~ this stage. At 6:21, the real blown air volu~e wa~

~ound to be 23~120 Nm3. At this tim~, the rem~ining time until the ~nd of thi~ ~tage wa~ 55 minute~, ~o thAt - 14 w ,::

~53~

for ending thi~ ~t~ge at the ~ched~led ending tim0, the blowin~ rate had to be made to (57,000 - 23,120l ~ 55 = 618 Nm3/min.
Howev0r, ~ince the s~eltin~ furnace and ~ul~uric acid plant were combined with th~ upper limit of the blowin~ rate ~et to 600 Nm3/min., if blowing effected at thi~ upper limit, the ending time of thi~
~tage would be extended and~lwould result in out-of~
balance with reApect to the ~melting furnance.
Accordingly, the aver~ge blowing rate for the re~t of the cycle wa~ calculated by addi~g 55 minute~, the remaining blowing time o~ thi~ ~tage, to 189 minute~, the ~cheduled blowing time of the third ~tage, adding 33,880 Nm3, the total air volume of the remaining to ~5 be su~plied for this ~tage~ to 102,000 Nm3, the total air volume to be ~upplied ~or the third ~t~, and dividin~ the seGond ~um of 135,880 Nm3 by the fir~t ~um of 244 minute~ (and taking the m~a~ure for redu~ing the blowin$ rate as the rea~on ~hat the third ~ta~e wa~ the c~pper ~srming st~$e as mentioned earlier).

33 ~80 ~ 102 000 ~ 0.95 3 = 579 (Nm /man~) By thi~ value, the tot~l air voluma of the remainin~ for the sec~nd ~tage ~a~ divided to ~btain the rem~ininS blowing tim~ ~or the ~econd ~ta$e.
33,880 ~ 579 = 59 (minute~) By thi~ v~lue, the total ~ir volume o~ the remainin~ for the second ~tage wa~ divided.
33,880 ~ 59 = 574 (Nm3/min.) The blo~ing rat~ wa~ adju~ted to thi~ value and similar '~5 ~

.. . : . ... : .... ~ ., :., 1~530QB

Adjustment3 were made at the interval of 5 minute~.
In thi~ way, the second stage wa~ended 2 minutes ~fter the ~cheduled ending til~e.
To ~ecover thi~ delay during the third ~tage, the blowing time of the third ~tage wa~ ~horte~ed by

2 minute~ to 187 minute.~, And the third ~tage wa3 ~tarted a-t 7:48, ô minute~ later than the ~cheduled time, at blowing rate of 102,000 ~ 187 = 545 (N~3~min.) The upper limit of blowing rate for the third ~tage had to be kept to 0.95 time~ the previou~ upper limit of 600 Nm3/min., that i~, 600 x 0.95 = 570 (Nm3/min.) Thu~, the blowing wa~ actually made at a ~ate clo~e to the upper limit, namely, 102,000 ~ (187 - 8l = 569.8 (Nm3Jmin.~
At 9:30 the real blown air volume ~upplied for thi~ ~*age wa~ 45,000 Nm3, which wa~ le~ than the ~cheduled volume. EYen at thi~ time, the blowing rate w~q ~et to the ~pper limit of 570 Nm3jmi~. for the third 3tage.
Thu~, the remaining blowing tim~ wa~

102 9 570 45~~ = 100 ( minut e ~ ) Although thi~ time meant that the ~cheduled time was e~ceeded by 5 minute~, ~aid del~yed ending time W8 clo~est to the scheduled ending time of blowi~g for thi~
~tage ina~much a~ the blowing rate was held within the predeterminad range.

Although in the above de~cription of the ~: ', ' . . :., ' ', ' `
. . .. . . ..

~5~

example, the correction of the ~cheduled blowing air volume when there is a dif~erence of thoaamount and composition of the actually char~ed cold material with re~pect to A scheduled ons ha~ been omitt~d for the Dake of ~implicity of the de~cription, in the actual operation such corre~tion is al-qo made.
Al~o, while the above example ha~ concerned with the case of converting the copper matte into bliqter copper, in the case of dealing with the niokel ~atte the blowing rate i3, in the l~t 3tage, not reduced from that in the praceding ~t~geq ~ince the conccntration of the nickel grade is aolely effected~ This situation al30 i~ applicable to the case ~f dealin$ with copper matt~ to produce white metal but not to produce the blister copper. Further, ev~n in the ca~e of producing the bli~ter copper, with som0 ~tage~ carried out by simultaneouoly operating a plurality of co~erter~, the copper forming stage may be carried out without reducing the blowlng rate compared to the preceding Ytage~ becau~e it i~ po~sible to uniformalize the gA~
conoentratlon combining the exhau~t ga~ ~rom one converter with that fr~m ano~her converter.
In c~rryin~ out the invantion~ the nece~ary calculation~ can be effected by u~ing an electronic comput~r, and it i~ po~ible to perform automatic operation by combining th~ computer with aut~matic control equipments. Thu~, by so ~rran~in~ a~ to ad~u~t the blowing rate at a fix~d inte~val, for in~tance 5 minuteq, the operation may be preeis01y oarried out according to *he -~chedule. Furth~rmore, it is pos~ible ~053~
to keep (furnace condition) con-Qtantly by varying the tuyere punching frequency accordin~ to the blowing rate.
A~ ha~ b~en de~cribed, ~ince accordin~ to the invention the blowing rate i~ controlled a~ to end each stag~ at the ~chedu:Led time according tv th~
total air volwne of the remaining to be supplied in the operation of each stage, while keeping the variation~
of the blowing rate within a predetermined range, the matte tr~a*ing rate in the converter may be ad~pted to comply more ~trictly with the ~atte producing rate in the ~malting furnace. Thu~, it i~ pos~ible to improve the operational stability of the ~melting furance, and to minimi~e the variation~ of the rate f ~upply of S02 gA~ from the converter and ~meltin~
furnace to the ~ul~uric acid plant, ~o th~lthe varia-tion for the operational conditiQ~ of the~e equipm~nts may be reduced compared to the conventional method.
Thu~, lt i~ po~ible to increa~e the treating capacity of ths ~meltin~ furnace and ~ulfuric acid plant.
Al~o, as ha~ been ~hown in connection with th~ ~ec~nd stage in the ~bove example, if there i~ any remaining ~tage~ by ~o arran$ing a~ to adjust the blowin~s rate for present :stage by adding the tt~tal ~4ir volume of the remaining to be 3upplied for ths pre~ent sta$e and the total air vQlume to b~ ~upplied for the re~aining ~tage or ~tages, the time required for the whole cycle may be adju~ted more readily compared to the ca~e of adju~ting the blowin~ rate ~ithin the 30 individual qtage~ .

~L~53~
Of cour~e, ~ince the ending time~ of the individual ~tag~ and the cycle can be indicated, the preparation~ for the sub~equent stage or cycle may be made on the ba~i~ of th~ indications~
In the caae of the cycle alternating blowing method, the variation of the down time betw~en cycle~
i~ reduced in the caqe according to the inven*ion compared to the conventional case aa is shown below.

Average Variance Standard Coef`ficient . value deqiation of VariRnCe Conventional 17.86 115.4 11.01 61.6%
method min. min. min.

Method accord- 18.52 69.1 8.51 46.0%
ing to the min. min. min.
invention 15 Since accordin~ to the invention the fluc$uation~ of the volume of the converter exhau~t ga~ are greatly reduced, even ~ith the maximum volume of converter exhaust gas, the ~um of the volu~e of the conv~rter e~hau~t ~as and the volume of the ~la~h ~meltin~ furnace exhaus* gas may be le~s than the maximum suction capacity of the ~ulfuric acid plant if the ~melting amount and exhau~t ga~ volume of the ~la~h smelting furnace are constant. The compari~on of the varia~ions of the copper convert~r exhau~t ~aa volume between the ca~e according to the invention and the conventional ca~e in term~ of numerical figure~

wa~ follows.

~ ~53~38 Average Variance Standard Nm /h. Nm /h. deviation Nm /h.
Con~ention~l method FirYt ~lAg ~ormation55 x 103 13.0 x 106 3.609 x 103 ~; ~tage Second alag 61 x 103 24.9 x 10~ 4.990 x 103 formation ~tage Copper forming 61 x 103 89.5 x 106 9.460 x 103 ~t~g~

Method according to the invention ~ir~t ~ag 62 x 103 4.9 x 10~ 2.213 x 103 formation ~tage Second ~lag 59 x 103 5.0 x 106 2.236 x 103 formation ~tage Copper formin~ 60 x 103 2.6 x 106 1.612 x 103 4tage In this ca~e, the rate of smelting in the fla~h ~melting ~urnace was 42 ton3/h., the volume of the flaah smelting furnaoe exhaust ga3 wa~ 80 ~ 103 Nm3/h., ~nd the ~uction capacity of the .qulfuric acid plant waY
160 x 103 N~3/h. In the ca~e of the conventional method, the total volume of a~hau~t gas withdr~wn into the ~ulfurie acid plant during the first or ~eoond slag for~tion ~tage of con~erter is below the suction capacity of the ~ul~uric acid plant, namely 160 x 103 ~m3/h., even i~ av~ra~e volume of the exhaust gas in the flash ~melting ~urnace, and the ~xhauat ga~ in the converter, and thrae time~ the standard deviation o~

the exhaust ga~ volume in the converter are added together. However, the variati~ are lar~er in the copper forming ~ta~e than in other ~tage; the ~um o~
the averaxe volume exhau~t ga~ in the flaah ~elting . . . . . . .

~053~

furnac~, exhaust ~sas in the converter, and 2 time~ the standard de~riation of the exhauslt ga~ rolume in the converter i~ 159.92 x 103 Nm3/h., ~ubstantially corre~pond to the suction capacity of the slllfuric acid plant~ In the ca~e of the conventional tnethod, there iq no redundancy of the smelting amount of the fla~h smelting furance, and al~o in the copper forming stagQ of the con~rerter it i~ liable that the sum of the exhau~t gaE~ volume in the fla~h ~melting furnace and converter exceeds th~ suction capacity of the ~ulf`laric acid plant.
In contrast, in accordance with the in~rention, the ~um of the a~rerage volume of the flaElh smelting furnace exhau~t gas and converter exhaust ga~, and th~ee time~ the ~tandelrd deviation of the exhaul3t ~as volume in the con~rerter i~
148.639 x 103 Nm3/h. in the fir~t ~a~ formation tag~, 145.708 x 103 Nm3/h. in the ~econd slag formation ~ta~e, and 144 r 836 x 103 Nm3Jh. in the copper forming ~tage.
Thus, a redundancy of 11.361 x 103 ~Im3/h.
even in the first slag formation ~tags ~here the total volume of the e~au~3t ga~ i~s th~ highest one in 25 compari~on ~ith the su¢tion s:apacity of the ~uLPuric acid plant, namely 160 x 103 Nm3~h., is pro~ided.
Consequently, in thi~ ca~e it i~ pos~ible to increai3e the 0~hau~st ~ voluma by increa~ing the ~melting amount in the fla~h smelting ~urnace.
30 (If n~ce~3s~lry, it i~ poe~3alble to operate the c~n~rerter - 21 _ . , .:

~615;~

at the ~ame required air volume rate, while increasing the copper content in the matte by rai~ing the copper ~rade of th~ matte with increa~ad smeltin~ amount in the flaoh ~meltin$ furnac~)~ In a comparative ca~e o~ incre~ng the ~melting amount in *he ~la~h smelting furnRce where matte of the ~me copper grade a~ the conventional one i8 produced, the productiDn amount of matte in the flash ~malting furnace i9 increa~ed, calling for an increa~e of the air volume to b~
~upplied to the converter ~nd hence leading to incre~e of the conYerter exhau~t ga~. If in thi~ ca~e the redundancy of the ~ulfuric acid plant i~ to be filled with the total ~xhau~t ga~ ~olume from the fla~h ~melting ~urnace and converter, the tot~l exhau~t ~a~
volume ~or 1 ton/hr. of the ~melted materi~l to the fla~h -~melting furnace is 148.639 x 103 4 42 = 3.54 x 103 (Nm3~h.) and hence increa~e of the ~malting capacity is 11.361 x 103 ~ 3.54 x 103 = 3.2 (tons/h.) Henca, t~e amount ~f the fe~d m~terial i~
42.0 ~ 3.2 = 45.2 (to~/hr.) Thi~ mean3 that it i~ po~ible to incre~e *he ~malting cap~cigr by about 7.6 percent.

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Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of operating at least one converter furnace for treating molten matte, which comprises adjusting the blowing air volume supplied per unit time within a predetermined range such that the supply of a scheduled total blowing air volume for one of a plurality of stages of one cycle in the converter operation ends at or close to a scheduled end time of the blowing for said stage, said adjustment being effected by subtracting the real blown air volume from said scheduled total air volume at a suitable time between the start and end of said stage to obtain a remaining air volume and adjusting the blowing air volume supplied per unit time to ensure that said remaining air volume is completely supplied at or close to said scheduled end time.

2. The method according to claim 1, wherein the blowing rate to be supplied per unit time for the last stage is 95 percent of the blowing rate for the other stages when converting copper matte into blister copper.

3. The method according to claim 1, wherein the scheduled ending time of blowing for each stage is determined on the basis of a value obtained by dividing the product of the total air volume required for said stage and the total blowing time for the cycle by the sum of the total air volume required for the individual stages.

4. The method according to claim 1, wherein the scheduled end time of blowing for each stage is determined on the basis of a value obtained by dividing the product of the total air volume required for said stage and the total blowing time for the cycle by the sum of the division of the total air volume required for the last stage by 0.95 and the total air volume required for the other stages.

5. The method according to claim 4, wherein the numerator of the fraction for determining the scheduled end time of blowing for the last stage is the product of the division of the total air volume required for the last stage by 0.95 and the total blowing time for the cycle.

6. The method according to claim 1, which comprises a first step of determining, when the blowing air volume supplied per unit time gets beyond said predetermined range at a time in a stage at least prior to the last stage subjected to said cycle, the average blowing air volume to be supplied for the rest of said stage and the remaining stage or stages by dividing the sum of the air volume remaining for said stage at a desired time and the total scheduled air volume to be supplied for the remaining stages or stage by the sum of the remaining blowing time for said stage and the scheduled blowing time for the remaining stage or stages, a second step of dividing the remaining air volume for said stage by said blowing air volume to be supplied per unit time to determine a time required for carrying out the subsequent blowing in said stage by using said blowing air volume to be supplied per unit time, and a third step of controlling the actual blowing rate to said average blowing rate such that the supply of the scheduled total air volume for said stage ends at a time as close as possible to the scheduled end time of the blowing for said stage.

7. The method according to claim 6, wherein in said third step the rate of blowing for said stage is controlled to the limit of said range when the average blowing rate is beyond said range in said stage.

8. The method according to claim 6, wherein in said third step the blowing rate in the last stage is controlled to the limit of said range when the average blowing rate is beyond said range in said last stage.