US2397262A - Metallurgical process - Google Patents

Description

I PatentedhMar. 26,. 1946 METALLURGICAL PROCESS Charles H. Heist, Buffalo, N. Y., assignor to National Steel Corporation, a corporation of Delaware No Drawing. Application March so, 1943,. I

Serial No. 481,147 1 4 Claims.

This invention relates to an improved process for making ferrosilicon.

In the present practice of making ferrosilicon or silvery iron a highly silicious ore is used together with a high hearth temperature. About one-third of the ore charge is normally Richmond ore or some other highly silicious ore. In the case of Richmond ore the silica runs about. 40%. The coke burden is kept heavy in order to maintain a high temperature at the smelting zone. As the charge descends in the furnace the silica which is present mostly in the form of silicates melts and part immediately combines with limey substances to form slag. Of that portion which continues downwardly through the furnace the majority goes to the slagto satisfy the lime before reaching the smelting zone. Of that which does reach the smelting zone a portion.

depending among other things upon the hearth temperature, is reduced to silicon which enters the iron. Silica is reduced in the presence of coke at a temperature of about 3200 and 3300 F.

Ferrosilicon usually runs from 7 to 15% silicon. An optimum proportion of silicon is 10% due to economic factors of blast furnace operation. In order to get 10% silicon into the iron under present. operating conditions, a quantity of silica equal to about 22% of the ore charge must be available. When using a highly 'silicious ore the silicon, being present in the form of silicates, is melted at relatively low temperatures and is thus available for slagging and side reactions over a'considerable part of the descent in the furnace. Additionally, a large body of these melted silicates are held in the burden by the blast and, when the blast is reduced for tapping purposes this large body of liquid silicates rushes down through the smelting zone to -join the slag without suiiicient time for reduction. in the smelting zone of some of the silica to silicon. This results in loss of silica to-the slag besides the objectionable factors of a too highly silicious' slag.

In view of thefact that silicon is reduced at the proper temperature when it is in intimate contact with the incandescent coke, the applitains its form'right down to the point of combustion. Thus in the present process the silica is held within the interstices of the coke until i the coke body reaches the smelting zone temperature and is consumed by combustion. At this point by maintaining the temperature between 3200 and'330'0 F. the silica intimately held in contact with the coke is reduced to silicon and enters the iron. In the present process sufficient silica for fluxing is supplied by the ores used. If there is not suflicient silica present in theores, sand may be added to the burden for fiuxing purposes, the silica in the coke being destinedfor the iron. If the economics of the process demands that some highly silicious ores beused in the charge, less silica can be added to the coke or more lime used in the charge, the

proportion of silica in the coke being maintained I the proportion of coke charged is increased. The

applicant has found that 10% silicon in the iron is still the most economical proportion under present operating conditions. To increase the silicon appreciably over this necessitates the use of an amount of coke which makes the process uneconomic.

In producing his new metallurgical charging stock the applicant determines the amount of silica in the coke ash and addssufflcient fine sand to the coal charged to the coking process TABLE 1 Stock analysis in per cent Stock Fe Phos SiOa Mn A1203 OeO MgO 55% Hill Bessemer 55.33 0. 034 7.77 0. 12 0.37 Rii'hmrmd 35. 32 045 42. 55 i 08 1. 6% (Crude) Portsmouth 39. 95 177 9. 99 2. 76 3% Amsden 51. 53 613 4. 61 2. 96 200# Ro1lscale.. 73. 30 036 70 21 600# Borings 85.00 050 5. 00 20M Ferrosilicon scrap 64.45 500 20. 42 Donner m 020 4. 80 HM Stone .011 .92

Hill Bessemer 49. 89 27. 017 3. 87 Richmond 31. 11. 20 014 13. 49 (Crude) P 5. 66 2. 26. 010 57 Amsden 3. 40 1. .021 16 Roll scale- 1. 89 1. 39 001 01 Borin 5.66 4.81. .003 28 Ferrosilieon scrap 1. 89 1. 22 009 39 Average ore 100.00 50. 18 075 18.77 41 1 00 17 18 Weight of charge, pounds 6.30 ore 10, 600 5, 319 8. 0 1, 990 43 106 18 19 3.55 mlm 7, 097 1. 4 220. 25 11 1.15 500119 2,300 .3 20 1, 097 122 Ore per net ton pig iron 3,476 lbs. equals 1.74 tons net.

Total charge, lbs. 810: for 10.00% Si in pig 1,074 I Slag composition 111 lbs. per charge theoretical S10: 1, 278 42. 51 39. 50 A 346 11. 51 54. 02 12. 20 51. 70 Slag volume 49. 257 C30 1, 37. 92 38. 75 Pounds stone per ton mg 754 MgO 152 5. 06 42. 98 6. 89 45. 64 Pounds slag per ton pig.-- 9861! Add. 3% 91 3. 00- 2. 66 Pig iron tons per charge 3.05 I Total slag 3, 007 100. 00 100.00 I I I Yield 5o.1s+s7.11%-57.e1 I Pig m analysis reg 1g) B101 to bases equals .99

Per cent re... 87.11

Stone required 2,266 lbs.

Table 2 is a furnace-mixture for use under present operating conditions which incorporates TABLE 2 Stock analysis in per cent Stoek- Fe Phos SiOa Mn AlzOa CBO MgO 55 Hill Bessemer" 56. 46 0. 033 8. 93 0. l2 0. 37 5 Amsrlan 53. 21 512 4. 77 16 2. 16 1. 11 0. 54 Slnfer 56. 93 106 12. 75 58 2. 20 2. 57 1.50 26 Hanna 49. 06 074 7. 13 I 64 1. 43

.020 15.00 2.94 .40 .14 EM stone" 011 74 79 49. 28 4. 51

Mia-lure ercent Average cre 100.00 55. 80 .079 8 l9 58 94 24 13 Stock Fe Phos s10. Mn 1110. 0110 M30 Weight of charge, pounds I 018 9, 400 5, 246 7. 4 55 88 23 12 Cnlm 7, 157 1. 4 1, 074 210 29 flfnnn 1, 300 1 11. 10 M1 59 Ore per ton pig iron 3,123 lbs. equals 1.56 tons net.

Total charge, lbs. 8101101- 10.00% Si in pig 1,194 Slag composition in lbs. per charge Total slag.-...' -.1, 797 100.00 v 1 Yield 55.80:-87.07%=64.10% Pig i 'on analysis req ugr ed S10; to bases equals .85

"""" "I 10.00 .03 75 Stone required 1,2901? Percent Fe..- 87. 07 I v Table 3 shows a. furnace mixture in which some cally to incorporate up to 15% of silicon into the Richmond ore is used. The coke used contains iron and even higher percentages may be feasible 15% S102 including that in the ash.- with improvedconditions or operation.

' TABLE 3 Stock analysis in per cent Stock Fe Phos s10, Mn 41,0. 050 MgO 70% Hill Bessemer 50.40 0.033 8.93" 0.12 0.37

5 Amsdem. 53.21 .512 4.77 .10 2.10 1 11 0.54 7 50.03 .100 12 75 .58 220 2 57 1.50 7 (Crude Portsmouth 39.95 .177 9.97 4.61 2.70 21 .25 10 31011111011 38.29 .053 37. 34 .13 1.40 34 .44 200;; Roll scale.-. 73.30 .030 .70 .51 .21 600i Borings 85.00 .050 5.00 .70 Silica-coke .020 15. 00 2. 04 1 14 KM stone .011 .34 .70 40.23 4 51 Mixture, percent Hill Bessemer. I 64. 04 36. 16 021 5. 72 4.58 244 .023 .22 .07 .10 .05 .02 0.110v 3.01 .007 .57 .15 .1s .10 0. s0 2. 74 .4012 e0 .32 19 01 .02 0.15 3.50 .005 3.43 .01 13 03 .04 2.13 1. .001 .01 .01 Borings 6. 38 5. 42 003 32 04 Average ore 100.00 73 .072 11 20 57 .27 .28

Wei M char 2 ounde 8,600end8000re of 0.0 1,001 '25 20 00k 1.4 210 20 10 Stone 2 13 838 77 Ore per ton pig iron 3,124 lbs. equals 1.56 tons net.

Total charge lbs. $10,101 10.007 s1 in pig, 1.103. Slag composition in lbs. per chm-Ere 966' 41. 20 200 12.77 54.03 Slag volume 38. 91% 892 38. 11 Pounds stone per ton pig. 565# 113 4. 86 42. 97 Pounds slag per ton pig 7? 71 3.00 Pig iron tons per charge" 3. 01 1 501121112 2,341 100.00

. Yield 5s.7s+s7.07%=04.02 Pig gun analysis rezgltied 310, to bases equals .06.

.1 12 I Stone required 1,0001

Percent Fe... 87.07

It will be understood that the metallurgical I claim: charging stock of the present invention can be 1. In a process for producing ferrosilicon in a used in any process of incorporating silicon in a combustion type metallurgical furnace where metal during reduction. iron ore is reduced and melted bythe heat of in n ygen enriched blast the process of combustion, charging iron ore containing silicon the present invention can be utilized economi- 75 in combined form to the furnace, chargin'gafluxing agent to the furnace in suflicient quantity toremove the major portion of saidsilicon in slag form and charging silica and metallurgical coke to the furnace, the .coke having the silica mechanically held in. its structure in a quantity cient quantity to remove the major portion of suflicient to supply the major portion of the silicon in the ferrosilicon product.

2. A process for producing ferrosilicon includins from about 7% to about 15% silicon in a comheld in its structure in ajquantity sufflcient to bodies consisting of about 15% silica and the remainder coke and incidental impuritie 'to the furnace, the coke having the fine silica mechanically held in its structure in a quantity sumcient .to supply the major portion of the silicon in the product; and burning said coke and causing said fluxing agent to remove the major portionof. said combined silicon in slag form from said ore and causing the molten iron to combine with the silicon of said silica of said bodies in a quantity sufficient to produce said ferrosilicon product.

3. In a process for producing ferrosilicon in-' cluding from 7% to 15% silicon in a combustion. type furnace wherein iron ore is melted by the 80 heat of combustion, charging iron ore containing silicon in combined form to the furnace, charging a fluxing agent to the furnace in sufiisaid combined silicon in slag form and charging bodies consisting of about 15% silica and the remainder coke and incidental impurities to the furnace, the coke having fine silica mechanically supply the major portion of the silicon in the ferrosilicon product. t

4. A process for producing ferrosilicon in a combustion type furnace wherein iron ore is melted primarily by the heat generated by the combustion of coke, said process comprising charging iron ore containing silicon in combined form to the furnace, charging a fiuxing agent to the furnace in suificient quantity to remove the major portion of said combinedsilicon in slag form and charging bodies consisting of silica and coke to the furnace, the coke having fine silica, mechanically held in its structure in a quantity sufiicient to supply the major portion of the silicon in the product; and burning said coke and causing said fluxing agent to remove the major portion of said combined silicon in slag form from said ore and causing the molten iron to combine with the silicon of said bodies in a quantity sufliv cient to produce said ferrosilicon product.

' CHARLES H. HEIST.