United States Patent [19]
Stephens, Jr.
[11]
[45]
4,053,301
Oct. 11, 1977
[54] PROCESS FOR THE DIRECf PRODUCI10N
OF STEEL
[75] Inventor: Frank M. Stephens, Jr., Lakewood,
Colo.
[73] Assignee: Hazen Research, Inc., Golden, Colo.
[21] Appl. No.: 622,101
[22] Filed: Oct. 14, 1975
[51] Int. Cl.2 C21C 5/52; C22BlIlO
[52] U.S. Cl 75/11; 75/26;
423/148
[58] Field of Search 75/11, 26, 60, 32;
423/148
[56] References Cited
U.S. PATENT DOCUMENTS
228,329 1/1880 Edison 75/1
2,780,537 2/1957 Stelling 423/148
2,894,831 7/1959 Old 75/26
3,140,168 7/1964 Halley 75/26
3,364,009 1/1968 Kemmetmiiller 75/25
Primary Examiner-P. D. Rosenberg
[57] ABSTRACf
A process for the direct production of steel from partic-
. ulate iron oxides or concentrates including two major
steps in which in Step (1) the iron oxides are converted
to iron carbide and in Step (2) steel is produced directly
from the carbide in the basic oxygen furnace or the
electric furnace. In the production of the carbide the
oxides are reduced and carburized in a single operation
using a mixture of hydrogen as a reducing agent and
carbon bearing substances such as propane primarily as
carburizing agents. Iron carbide thus produced is introduced
as all or part of the charge into a basic oxygen
furnace to produce steel directly without the blast furnace
step. In order to make the steel making process
auto-thermal, heat is supplied either by using the hot
iron carbide from Step (1) or preheating the iron carbide
or by including sufficient fuel in the iron carbide to
supply the required heat by combustion.
53 Claims, 1 Drawing Figure
SCHEMATIC FLOWSHEET FOR DIRECT STEELMAKING PROCESS
IRON ORE
CONCENTRATE
FLUIDIZED
BED UNIT
HEAT
EXCHANGE
PREHEATER
SCRUBBER
'---H-=2+-_CO_+C0-=2+-_C.H.:.4..L MHA2K+ECUOP ..
II
SCRAP HOT
CO COOL AND
CLEAN
METAL FLUX
SLAG ------I MODIFIED
BDF
STEEL
u.s. Patent Oct. 11, 1977 4,053,301
SCHEMATIC FLOWSHEET FOR DIRECT STEELMAKING PROCESS
IRON ORE
CONCENTRATE
CO+C02+CH4+ H2 +HiJ HEAT
EXCHANGE
PREHEATER
SCRUBBER
H2+CO+C02+CH4 H2 +CO
L---=-__-=-----'-..L- MAKEUP •II
SCRAP HOT
CO COOL AND
CLEAN
METAL FLUX
SLAG __---I MODIFIED
BOF
STEEL
BRIEF DESCRIPTION OF THE DRAWING
The single drawing is a schematic flowsheet for the
direct steel making process of the invention.
DESCRIPTION OF PREFERRED
EMBODIMENTS
The invention will be described in detail in conjunction
with the accompanying drawing.
The basic oxygen and electric furnace processes referred
to herein for making steel are well known in the
prior art. The basic oxygen process or basic oxygen
furnace process differs chiefly from Bessemer converters
and open hearth furnaces in that the reactant used to
oxidize the carbon and certain impurities (sulfur, phosphorus,
etc.) in the charge is not air, but oxygen. The
oxygen is introduced by blowing it with a lance onto or
below the surface of the molten iron.
4,053,301
1
PROCESS FOR mE DIRECf PRODUCfION OF
STEEL
BACKGROUND OF THE INVENTION
2
ture range being about 900·-1200· F. The carburizing of
the reduced iron to carbide may be conducted so that
enough carbon is left in the iron carbide product to
supply sufficient heat upon combustion in the basic
5 oxygen furnace to make the process auto-thermal. The
1. Field of the Invention CO/C02 and hydrogen to water vapor ratios of the
The invention lies in the field of the pyrometallurgy gases in the reaction of Step (1) are maintained at a point
of ferrous metals. below which oxidation of iron carbide occurs.
2. Description of the Prior Art Off-gases from the steel making step, about 90 percent
The increasing necessity of using low grade iron ores 10 carbon monoxide, may be circulated for use as part of
for making steel because of the depletion of high grade the reducing gas for the reduction and carburizing step
ores, and economic factors, have created a demand for in the fluidized bed. Material balance calculations show
reduction of the costs in producing steel from iron ore. that the carbon content of the off-gas is sufficient to
Efforts to reduce costs have been directed to the elimi- supply all of the carbon necessary for the reduction and
nation of the use of the highly fuel-consuming blast 15 carburization step. Accordingly, when Steps 1 and 2 are
furnace. The present invention is directed to elimination performed in conjunction with each other as one conof
the use of the blast furnace by converting the iron tinuous operation, all ofthe carbon necessary for Step 1,
oxide to the carbide followed by producing steel di- subject to slight operating losses, may be provided by
rectly from the carbide in the basic oxygen furnace. The continuous cycling of the off-gas from Step 2 to Step 1.
conversion of iron oxides to carbides for various pur- 20 This eliminates the necessity for adding carbon to Step
poses has received some attention in the past but there 1 with the exception of small losses occurring in normal
has been no known activity toward producing steel operations. The result is that the carbon originally
directly from the carbide in a basic oxygen furnace. added to Step 1 to make iron carbide may be used over
U.S. Pat. No. 2,780,537, the closest prior art known, and over by recovering it in Step 2 in the off-gas as steel
discloses a process for converting iron oxides to car- 25 is produced and reusing it in Step 1 to make more carbides
in a fluidized bed process in which carbon monox- bide. When the steps are performed in conjunction with
ide is used as the chief reducing and carburizing gas. each other added heat is not required to make the pro-
The patent teaches that the reducing gas cannot contain cess auto-thermal, as the product going directly from
hydrogen in an amount more than 50 percent by volume Step 1to Step 2 is at a temperature which eliminates the
of the carbon monoxide content. It also refers to the 30 necessity for adding heat. When Steps 1 and 2 are perprior
art disclosing the use of hydrogen in a fluidized formed separately then the hot off-gas from Step 2 may
bed as a reducing gas for iron oxides having a low iron be used for preheating iron carbide or heat added by
content. The reference alludes to use of the iron carbide other means as necessary to make the steel making proproduct
for making "metallic iron" and in an "iron cess auto-thermal.
production furnace" operating below the melting point 35 The iron carbide produced in Step 1 is added directly
of iron or steel, however, there is no teaching of use of as the charge to the basic oxygen or electric furnace
the product for introduction into a fully molten steel along with fluxing agents, alloying material and other
system such as the basic oxygen furnace or electric conventional additives to produce steel directly with
furnace. Other somewhat remote prior art discloses elimination of the conventional blast furnace step. Heat
processes for converting metallic iron to iron carbide 40. is supplied to the charge when necessary in various
rather than conversion of iron oxide to the carbide. ways to make the process auto-thermal. These ways
Still other prior art discloses fluid bed processes for may include direct heating, addition of fuel such as
the direct reduction of iron oxides to metallic iron carbon, or producing sufficient free or combined carwhich
in turn could be further converted to carbide. bon in the carbide as it is produced, or others. Sensible
However, these other direct reduction processes have 45 heat from the off-gas of the BOF may be used and the
the disadvantages that the product may be pyrophoric off-gas may be partially burned to provide heat to the
in some cases requiring briquetting, and stickiness is not charge. If the latter is done the CO/C02 ratio in the
completely eliminated in some processes so that difficul- combustion gases must be maintained below that at
ties arise with the fluid bed process. which iron carbide will decompose at the required pre-
It is an object of this invention to provide a process 50 heat temperature.
for making steel from iron oxide without the use of a
blast furnace.
It is another object of this invention to provide a
successful process for making steel from iron oxide by
first converting the oxide to the carbide, followed by 55
introducing the carbide directly into the basic oxygen
furnace to produce steel.
SUMMARY OF THE INVENTION
A process for the direct production of steel from 60
particulate iron oxides or concentrates which comprises
(1) converting the oxides to iron carbide in a single step
in a fluidized bed at low temperatures with a mixture of
reducing and carburizing gases followed by (2) direct
conversion of the carbide to steel in a basic oxygen or 65
electric furnace.
The reducingand carburizing temperature of Step (1)
cannot exceed about 1300· F with a preferred tempera4,053,301
4
be used so long as they supply carbon to form iron
carbide.
By proper balancing of the ratios of the hydrogen and
carbon bearing materials, it is possible to restrict the
5 hydrogen to a reducing function and the carbon to a
carburizing function. This can readily be done by maintaining
quantities of hydrogen bearing gases which are
in excess of the quantities of the carbon bearing gases.
Because of the equilibrium conditions in.volved in
10 hydrogen-carbon-oxygen gas systems, the required hydrogen-
carbon ratios will automatically require that
methane be present in the gas system. The quantity of
methane present will be a function of carbon to hydrogen
ratios, as well as temperature and pressure condi15
tions.
Representative tests and results from an extensive test
program using the reduction and carburization procedure
described above in a fluid bed reactor are presented
in the following Table I.
TABLE I
3
The iron carbide produced by the process described
herein is a mixture of carbides having the molecular
formulas Fe2C and Fe3C with the Fe3C content being
predominant.
The fluidized bed reactor referred to herein is of the
conventional type in which finely divided feed material
on a grate or other perforate support is fluidized by
upwardly flowing gases which may include or entirely
comprise the reactant gases. Auxiliary equipment includes
heating and temperature control and monitoring
equipment, heat exchangers, scrubbers, cyclones, gas
cycling equipment, and other conventional equipment.
Some of this auxiliary equipment is shown schematically
in the flowsheet.
In this specification and the claims the reduction and
carburization step is referred to as Step 1 and the steel
making step as Step 2. The term "hydrogen bearing
gas" includes hydrogen gas alone and the term "carbon
containing material" includes carbon alone.
EXAMPLES OF Fe1C PRODUCTION
Gas Additions Off-gas Analysis· Pro-
Hz C3Hs N z Temp Hz N z CH4 CO COz duct
IImin IImin IImin • F % % % % % %C Remarks
Final red in
reactor 5.02% C
Good clean Fe3C
produced
Good Fe3C saturated
with excess C
Good Fe3C
Good Fe3C
Good Fe3C
Good Fe3C
Good Fe3C
5.02
8.96
4.94
4.67
4.77
4.69
5.42
77.0 0.5 6.3 8.9 2.0
72.0 5.2 13.2 2.9
72.1 6.5 7.8 3.4
72.6 6.4 10.6 4.0
69.3 7.9 12.2 4.4
62.5 6.7 16.1 6.7
67.5 6.0 11.6 3.9
58.3 6.1 21.4 6.8
1168 4.35
1170
1018
1081
1108
1112
1103
1130
2.5 1.0 0.5
2.5 1.0 0.5
2.5 1.0 0.5
2.5 1.0 0.5
2.5 1.0 0.5
2.5 1.0 0.5
2.5 1.0 0.5
2.5 1.0 0.5
Test Feed
No. Type Mesh Rate
FB- of Ore Size Ore g/min
30 Hematite -'-20+100 0
36 Hematite -20+100 0
37B Hematite -20+100 0
38B Hematite -20+100 0
39B Hematite -20+100 0
40 Hematite -20+100 2.7
41B Magnetite -20+100 0
41C Magnetite -325 3.8
·The balance of gas is water vapor.
The carbon content in the final product varies as the
percent iron oxide in the feed materials varies. Lower
grade ores with lower iron contents will automatically
yield products with lower carbon contents.
The volume of hydrogen in the hydrogen-carbon
monoxide reducing and carburizing mixture in the fluidized
unit should exceed the volume of carbon monoxide,
the preferred amount of hydrogen being over about
60 percent by volume of the carbon monoxide present.
The results show production by Step 1 of the process
of clean iron carbide which is highly suitable for use in
the basic oxygen or electric furnace. X-ray diffraction
analysis showed the carbon to be present as iron carbide
50 with no free carbon or metallic iron. The product was
found to be nonpyrophoric. Simulated weathering tests
showed that the product was stable in oxidizing atmospheres
containing water vapor up to a temperature of
2500 C.
The results also show that Step 1 of the process is
highly successful in producing iron carbide directly
from iron oxides when operated within temperature
ranges of about 10200 F - 11700 F using hydrogen to
water vapor ratios between 5 to 1 and 8 to 1 and CO/CO2ratios
between about 1 to 1 and 5 to 1. As stated
herein, Step 1 can be successfully operated within a
temperature range of about 9000 _13000 F, a hydrogen to
water vapor ratio of about 2.5 to 1 to about 8 to 1 and
a CO/C02 ratio of about 1 to 1, up to about 4 to 1.
Under these conditions, methane will be present in
quantities ranging from 1to 70 percent by volume of the
gas system containing the prescribed amounts of hydrogen,
water vapor, CO, and CO2. It was found that Step
Step 1 of the overall process is the conversion of the 35
oxides in the iron ore concentrate to iron carbide in the
fluidized bed unit shown in the flowsheet. The conversion
process must be carefully controlled to provide a
product suitable for use in the basic oxygen or electric
furnace. The iron carbide is desirable for use in these 40
processes because it is non-pyrophoric and resistant to
weathering which permits transport for long distances
and storage for reasonable periods.
The oxides are reduced to iron and the iron converted
to the carbide in a continuous process in the fluid bed 45
reactor in which the reducing the carburizing gases are
added together. In order to prevent any sticking caused
by the transient presence of metallic iron the temperature
is maintained below about 13000 F at all times and
preferably in the range of about 9000 _12000 F.
Hydrogen is preferably· used as the reducing gas although
carbon monoxide or hydrocarbon gases or mixtures
of hydrogen with CO and hydrocarbon gases may
be used. The flowsheet shows the use of hydrogen and
carbon monoxide with water being given off. Hydrogen 55
is preferred as the reducing gas because the oxidation
product of hydrogen, which is 'water, may be easily
removed from the furance off-gas thus permitting recycling
of the balance of the gas without the need for
extensive complicated and expensive chemical systems 60
for removing the oxidation products of carbon which
are carbon monoxide and carbon dioxide when carbon
containing reducing gases are used.
The preferred carburizing gas which is mixed with
the reducing gas is propane, although carbon monoxide 65
or other hydrocarbon gases, or solid carbon, may be
used with the lower alkyl hydrocarbon gases being
preferred. A wide range of carbonaceous materials may
4,053,301
5
I would not operate outside these ranges to successfully
produce iron carbide.
Step 2 of the overall process is the conversion of the
iron carbide to steel in the basic oxygen furnace. Because
of the nature of the basic oxygen furnace process, 5
special conditions apply to the processing of iron carbide
to steel by this process as compared to other steel
making processes in furnaces.
If Steps I and 2 are close-coupled so that the iron
carbide comes out of the fluid bed unit at an elevated 10
temperature ofabout 1100·-1300· F and at that temperature
is added directly to the basic oxygen furnace, then
the heat calculations show that no added heat is required
and the process is continuous and auto-thermal.
The modification shown in the flowsheet wherein the 15
off-gases are being sent directly to the fluidized bed unit
is used when Steps I and 2 are close-coupled in time. In
this modification of the process substantially all of the
carbon used in the fluidized bed unit to convert the
oxides to iron carbide is recovered as CO in the furnace 20
and recycled to the fluidized bed unit to be reused in
again making iron carbide.
If for purposes of transport or storage the Step I
product becomes or is cooled before Step 2, then heat
must be readded either in the form of reheating the 25
product or adding extra fuel to Step 2.
Heat balance calculations show that at ambient temperature
iron carbide does not contain sufficient fuel
value so that the reaction taking place in the basic oxygen
furnace is autothermal without adding heat to the 30
charge.
The additional heat required to make the reaction
self-sustaining may be supplied in a number of ways.
The off-gas from the basic oxygen furnace produced by
the processing of iron carbide contains about 90 percent 35
carbon monoxide in addition to substantial sensible heat.
The sensible heat may be used through heat exchangers
or otherwise to heat the incoming iron carbide. By
burning part of the off-gas, sufficient heat is achieved
for augmenting the sensible heat to effect the required 40
preheating of the incoming iron carbide charge to make
the process auto-thermal. Under some conditions the
sensible heat alone is sufficient. The heat for the preheating
can be obtained entirely from combustion of the
off-gas. The preferred preheat temperature range is 45
from about BOO· F to about 2000· F.
Tests conducted with iron carbide in a gaseous me·
dium simulating that of the combustion products from
partial combustion of the off-gas showed that the iron
carbide is not only stable under these conditions but 50
actually increased in carbon content from 5.9 to 7.1
percent due to the formation of the Fe2C carbide from
the normally predominant Fe3C, To achieve this result
the CO/C02 ratio in the combustion gas must be between
I to I and 2 to I when attaining preheat tempera- 55
tures of 900·-1300· F.
Added heat to make the process auto-thermal can be
supplied wholly or in part by direct heating of the Fe3C
charge with an external heat source. Sufficient carbon
may be added to the iron carbide to provide the re- 60
quired additional heat by combustion during the process.
The amount of carbon added varies from about 3
to 5 weight percent of the iron carbide charge. The
carbon may be added directly· to the iron carbide by
preheating the iron carbide in carbon bearing gases 65
having a CO/C02ratio greater than I to 1.
Heat may be supplied by reaction of the basic oxygen
furnace off-gas with incoming iron carbide. The neces-
6
sary carbon content of the iron carbide to furnish the
required heat upon combustion can be supplied during
Step I of the process described above by adjusting the
content of the carbonaceous material in the reacting gas
mixture of the fluidized bed to provide for the production
of suffiCient Fe2C in the Fe3C product. As shown in
the flowsheet, hot scrap metal may be added to the basic
oxygen furnace charge.
Step 2 of the process may also include the addition of
pig iron carbide charge in the basic oxygen and electric
furnaces. A significant advantage of this feature is that
iron carbide can then be added for cooling in an amount
three times that of scrap iron which can be added to
conventional basic oxygen furnace processes for cooling.
Iron carbide for this purpose can be added in' an
amount up to about 60 percent by weight of the iron
carbide-pig iron charge. One advantage of this is that
present pig iron furnaces can be continued in operation
in conjunction with the present process.
The invention includes all of the above procedures
alone or combined for providing the necessary heat for
the iron carbide charge to make the reaction in the basic
oxygen furnace auto-thermal.
If Step 2 is conducted in the electric furnace, any
extraneous heat required may be supplied by means of
the electrical evergy normally used in this type of furnace.
Step I of the process provides a convenient and effective
means for concentrating low grade non-magnetic
ores to separate the iron ore from the gangue. As the
iron carbide produced from non-magnetic ores is magnetic
it is only necessary to process non-magnetic ore,
such as, oxidized taconites, in accordance with Step I to
convert the iron oxide therein to iron carbide and subject
the treated ore to magnetic separation to separate
the magnetic iron carbide from the gangue. The iron
carbide recovered may then be used in Step 2 of the
process of the invention.
A number of advantages of the invention are apparent
from the above description. Its principal advantage is
that it eliminates the expensive intermediate blast furnace
step in converting iron ore to steel. When the two
steps are performed in conjunction no added heat is
necessary for the second step and carbon monoxide
from the second step provides the necessary carbon for
carbonization of reduced iron in the first step so that the
carbon can be reused continuously in both steps. Step I
includes the production of water as a by-product, thus
simplifying the recovery of by-product carbon containing
gases. This step can be performed to give a product
having a high enough ratio of Fe2C to Fe3C to provide
a high enough carbon content in the charge for the basic
oxygen furnace to make the steel making process autothermal.
Advantages of Step 2 are that it provides sources of
heat for making this step auto-thermal without the use
of extra materials, i.e., sensible heat from the off-gases
can be used or the CO in the off-gases can be burned to
provide the necessary heat, or the CO can be reacted
with the iron carbide from Step I to raise the ratio of
Fe2C to Fe3C in the charge so that sufficient carbon will
be available for combustion to supply the augmenting
heat to make Step 2 auto-thermal. When pig iron is
added to the charge, large amounts of iron carbide can
be added for cooling. The overall process is practically
pollution-free and provides for maximum conservation
and reuse of non-product reactants. A further advantage
of the overall process is that it results in a saving in
4,053,301
7 8
transportation costs when the carbide is made near the 16. The process of claim 14 in which at least part of
mine before transport to the steel making furnace as iron the heat for the preheat step is derived from off-gases
carbide represents a higher percentage of usable mate- from step (b).
rial than the oxide. 17. The process of claim 14 in which at least some of
What is claimed is: 5 the heat for the preheat step is derived from sensible
1. A process for the direct production of steel from heat in the off-gases.
iron oxides which comprises: 18. The process of claim 14 in which at least some of
a. converting the iron in the oxides to iron carbide; the heat for the preheat step is derived from combustion
and of CO in the off-gases.
b. converting the iron in the iron carbide directly to 10 19. The process of claim 18 in which the' CO/C02
steel in the basic oxygen furnace. ratio in the gas combustion products is maintained from
2. The process of claim 1 in which in step (b) the about 1:1 to about 2:1 when attaining preheat temperaconversion
is accomplished by oxidizing the carbon in tures of 900·_BOO· F.
the iron carbide to carbon monoxide with the heat re- 20. The process of claim 14 in which the heat for the
leased thereby providing heat for operation of the basic 15 preheat step is provided by reacting at least part of the
oxygen furnace. off-gas to produce Fe2C in the iron carbide from step
3. A process for the direct production of steel from (a~l. The process of claim 20 in which the composition
iron oxides which comprises: of the reactive medium of step (a) is adjusted to provide
a. reducing the oxides and converting the iron to iron 20 the required amount of Fe2C in the iron carbide charge.
carbide in one step in a fluidized bed with a mixture 22. The process of claim 3 in which the iron carbide of
of hydrogen bearing gas and a carbon containing step (a) has lost heat before step (b) is performed and
material which provides carbon for the iron car- sufficient fuel is added to it to provide additional heat
bide, the hydrogen being present in an amount ex- upon combustion in the process to render the reactions
ceeding 50% of the CO present; and 25 occurring in the conversion of the iron carbide to steel
b. adding the iron carbide to a basic oxygen furnace in the basic oxygen furnace autothermal.
and processing it to steel by the basic oxygen fur- 23. The process of claim 22 in which the fuel is carnace
process without the addition of external heat. bon.
4. The process of claim 3 in which steps (a) and (b) are 24. The process of claim 23 in which the carbon is
performed in conjunction and the iron carbide of step 30 added in an amount from about 3 to 5 weight percent of
(a) is added directly to the basic oxygen furnace without the iron carbide charge.
substantial heat loss so that the process is auto-thermal. 25. The process of claim 23 in which the carbon is
5. The process of claim 4 in which the iron carbide is added directly to the iron carbide charge.
at a temperature between about 900· F to 1300· F when 26. The process of claim 3 in which molten pig iron is
it leaves step (a). 35 added to the iron carbide charge in step (b) and iron
6. The process of claim 4 in which off-gas is cycled carbide is used to control the temperature of the melt.
from step (b) to step (a). 27. The process of claim 26 in which the temperature
7. The process of claim 6 in which the off-gas pro- controlling iron carbide is added in an amount up to
vides substantially all of the carbon for step (a). about 60 weight percent of the iron carbide-pig iron
8. The process of claim 3 in which in step (a) the ratio 40 charge.
of hydrogen to formed water in the reaction medium of 28. A process for conversion of iron oxides to iron
the fluidized bed is maintained from about 2.5 to 1 to carbide which comprises reducing the oxides and conabout
8 to 1 and the CO/C02ratio is maintained from verting the iron to iron carbide in one step in a fluidized
about 1 to 1 to about 4 to 1, the prescribed CO/C02_ bed with a mixture of hydrogen and a carbon containing
hydrogenIH20 ratios being essentially in· equilibrium 45 material which provides carbon for the iron carbide, the
with methane. mixture containing hydrogen in an amount over 60
9. The process of claim 3 in which the volume of percent by volume of the carbon monoxide present.
hydrogen exceeds the volume of CO in said fluidized 29. The process of claim 28 in which the ratio of
hydrogen to formed water in the reaction medium of
bed. . 50 the fluidized bed is maintained from about 2.5 to 1 to
10•.The process of claim 3 in which the carbon con- about 8 to I and the ratio ofCO/C02is maintained from
taining material is solid carbon.
11. The process of claim 3 in which the carbon con- about I to I to about 4 to I, the prescribed CO/C02hydrogen/
H20 ratios being essentially in equilibrium
taining material is lower alkyl hydrocarbon gas. with methane.
12. The process of claim 11 in which the gas is pro- 55 30. The process of claim 28 in which the carbon conpane.
taining material is solid carbon.
13. The process of claim 8 in which the temperature 31. The process of claim 28 in which the carbon conof
the reaction gas mixture is between about 900· F and taining material is a lower alkyl hydrocarbon gas.
BOO· F. 32. The process of claim 31 in which the gas is pro-
14. The process ofclaim 3 in which the iron carbide of 60 pane.
step (a) has lost heat before step (b) is performed and 33. The process of claim 28 in which the temperature
sufficient heat in a preheat step is added to it for step (b) of the mixture is between about 1100· F and about BOO·
to render the reactions occurring in the conversion of F.
the iron carbide to steel in the basic oxygen furance 34. A process for converting iron carbide to steel in
auto-thermal. 65 the basic oxygen furnace by the basic oxygen furnace
15. The process of claim 14 in which the iron carbide process, said process comprising the step ofaugmenting
charge is preheated to a temperature between about the heat produced in the conversion process which is
BOO· F and about 2000· F. produced by oxidizing the carbon in the iron carbide,
4,053,301
9
with additional heat, to make the process in the basic
oxygen furnace autothermal.
35. The process of claim 34 in which the heat is added
in a preheat step.
36. The process of claim 35 in which the temperature 5
of the iron carbide charge is between about BOO· F and
about 2000· F before it is added to the basic oxygen
furnace.
37. The process of claim 35 in which the preheat step 10
is performed by directly heating the iron carbide
charge.
38. The process of claim 35 in which at least some of
the heat for the preheat step is derived from sensible
heat in the off-gases. 15
39. The process of claim 35 in which at least some of
the heat for the preheat step is derived from combustion
of CO in the off-gases.
40. The process of claim 39 in which the CO/C02
ratio in the gas combustion products is maintained from 20
about 1:1 to about 2:1 when attaining preheat temperatures
of 900·-1300· F.
41. The process of claim 35 in which the heat for the
preheat step is provided by reacting at least part of the
off-gas with the iron carbide from step (a) to produce 25
Fe2C,
42. The process of claim 34 in which said heat is
augmented by adding a fuel to the iron carbide charge
for combustion during the conversion step.· 30
43. The process of claim 42 in which sufficient fuel is
added to the charge to provide additional heat upon
combustion in the process to raise the temperature of
the charge to at least about 1100· F.
44. The process of claim 42 in which the fuel is car- 35
bon.
45. The process of claim 44 in which the carbon is
added in an amount from about 3 to 5 weight percent of
the iron carbide charge.
46. A process of making steel from iron carbide in the 40
basic oxygen furnace which comprises adding pig iron
10
to the iron carbide charge and controlling the temperature
of the charge by the addition of iron carbide.
47. The process of claim 46 in which the pig iron is
added in an amount up to about 40 weight percent ofthe
charge and the temperature controlling iron carbide is
added in an·amount up to about 60 weight percent ofthe
iron carbide-pig iron charge. .
48. A process for concentrating non-magnetic low
grade iron ores ·which comprises converting the iron
oxide in the ores to iron carbide and separating the iron
carbide and gangue by subjecting the treated ores to
magnetic separation.
- 49. The process of claim 48 in which the iron oxides
are converted to iron carbide in one step in a fluidized
bed with a mixture of hydrogen bearing gas and a carbon
containing material which provides carbon for the
iron carbide.
50•. The process of claim 49 in which hydrogen is
present in an amount of over 60 percent by volume of
carbon monoxide in the fluidized bed.
51. A process for the direct production of steel from
iron oxides which comprises:
a. converting the iron in the oxides to iron carbide;
and
b. converting an iron in the iron carbide directly to
steel in an electric furnace.
52. A process for the direct production of steel from
iron oxides which comprises:
a. reducing the oxides and converting the iron to iron
carbide in one step in a fluidized bed with a mixture
of a hydrogen bearing gas and a carbon containing
material which provides carbon for the iron carbide,
the hydrogen being present in an amount exceeding
50% of the CO present; and
b. adding the iron carbide to the electric furnace and
processing it to steel in an electric furnace.
53. The process of claim 52 in which steps (a) and (b)
are performed in conjunction and the iron carbide produced
in step (a) is added directly to the electric furnace
without substantial heat loss.
* * * * '"
45
50
55
60
65
le='�b~p-i��font-family:"Times New Roman","serif";mso-fareast-font-family: HiddenHorzOCR'>stripping using alkaline-NaEDTA solution.
Palladium is stripped from the loaded organic using a 45
water soluble reducing agent in an acidified aqueos
solution. An important criteria in selecting a suitable
reductant reagent is that is should not contribute any
Product
Aqueous feed
Raffinate
Loaded Organic
Amount Assay, gil Grams
inml. Pt Pd Ir Rh Ru Fe Pt Pd
1050 0.40 3.30 1.10 3.80 4.10 0.002 0.42 3.5
1050 0.04 1.00 1.10 3.78 4.05 0.002 0.04 1.1
1575 0.24 1.58 0.02 0.003 0.05 0.004 0.38 2.5
foreign metals to the organic which might eventually
cause fouling or a reduction in loading capacity. Satisfactory
reductant stripping agents for use in the present
invention include acidified solutions of hydrazine salts,
hydroxylamine salts, and conventional organic reduc- 60
ing agents, i.e., thiourea. The reductant stripping solutions
are acidified to between 0.1 to about 3 N HCI and
are preferably employed as 0.5 N solutions. The preferred
reducing solution is 50 g/l hydrazine dihydrochloride
(N2lL.2HCI) acidified to 0.5 N HCI. AI- 65
though suggested concentrations of strippant solutions
have been described herein, those skilled in the art will
appreciate that these may be varied depending upon the
It will be seen from the above Table that platinum and
palladium were selectively extracted from an aqueous
hydrochloric acid solution containing iridium, rhodium,
ruthenium and iron by an organically substituted secondary
amine. The minute quantities of iridium, rhodium,
ruthenium andiron which are extracted along with
platinum and palladium are relatively insignificant.
EXAMPLE II
The tests in this Example illustrate that a variety of
alkaline reagents at different concentrations may be
EXAMPLE III
8
Test No.5. In all instances it was possible to obtain strip
solutions in which platinum was at a relatively high
concentration with respect to palladium as compared to
the original aqueous solutions from which they were
separated. .
4,041,126
7
used to selectively strip platinum from an organic extraction
solvent loaded with platinum and palladium.
A ten percent (%) by volume Amberlite-LA-I solution
in kerosene (AMSCO 175) containing 3% by volume
isodecanol (and conditioned to chloride form as in 5
Example I) was loaded with platinum and palladium by
contacting with an aqueous hydrochloric acid solution
assaying (in gil) gold 0.007, platinum 2.86, palladium The extraction and selective stripping tests in Exam-
8.40, iridium 0.031, rhodium 0.038 and ruthenium 1.13. pIe III were performed to illustrate that the sequence of
The loaded organic assayed in (gil) platinum 1.12 and 10 stripping platinum and palladium from a loaded seconpalladium
3.55. Predetermined quantities of the loaded dary amine organic is not important and either metal
organic were treated with solutions of NaZC03, NaH- may be stripped first through the process of the present
C03 and NaOH in separatory funnels at room tempera- invention.
ture (plus or minus 25° C) at an 01A ratio of 2 to 1. The To carry out Example III a 10% by volume solution
contact times and alkaline concentration of the stripping 15 of Amberlite LA-I in 3 volume percent (%) isodecanol
solution were varied as noted in Table II. Following and 87 volume percent (%) kerosene (AMSCO 175)
each contact period, the phases were separated, filtered was loaded with platinum and palladium in a single
and assayed for platinum distribution. Results of the contact with a hydrochloric acid solution assaying (in
respective assays are indicated in Tables II and IIA gil) gold 0.004, platinum 2.90, palladium 8.20, iridium
below. 20 0.024, ruthenium 1.13 and rhodium 0.036. Prior to the
TABLE II
Loaded organic: 1.12 gil Pt + 3.55 gil Pd
Stripping: 0/A = 211
Contact Assays 1/ % UK"
(concen-
Test Strip Volumes Taken, ml Time Temp Strip Org.,gll Strip Soln, g/I Stripped tration) Ratio Pt/Pd
O/A
No. Solution Organic Aqueous min °C Pd Pd Pt Pd Pt Pd Pt Pd in Strip
I 50 gil Na2C03 30 IS 5 ±25 0.03 . 3.30 2.19 0.49 97 7< I 7 4.5/1
2 50 gil NaOH 30 IS 5 ±25 0.03 2.80 2.06 0.91 97 21< I 3 2/1
3 11 gil Naif03 30 IS IS ±25 1.17 3.45 0.007 0.002< 1< I> 100> 100
4 50 gil Na C03 30 IS IS ±25 0.18 3.52 1.80 0.004 84< 1< 1> 100 450/1
5 50 gil NaHC03 50 25 15 ±40 0.25 3.52 1.80 0.038 78 1< 1 93 47/1
6 50 gil NaHC03 + 30 15 15 ±25 0.20 3.45 1.91 0.17 82 3< 1 20 11/1
5 gil NaEDTA2/
7 75 gil NaHCO; + 50 25 IS ±25 0.21 3.40 1.87 0.18 81 4< 19 10/1
5 gil EDTA3
50 gil NaHC03 + 50 25 15 ±25 0.28 3.44 1.76 0.17 75 3< 20 10/1
5 gil EDTA
IIAll assays were on filtered products and do not include losses, if any, in scum products.
21NaEOTA = (Ethylenedinitrilo), tetra-acetic acid disodium salt.
'lEOTA = (Ethylenedinitrilo), tetra-acetic acid.
_=- TABLE IIA 40
Test
No.
extraction of emf of the aqueous solution was reduced
Physical Observations to _ 525 millivolts by the addition of hydroquinone.
Scum suspended thru aqueous. Poor phase The extraction organic was preconditioned to chloride
separation.
2 Scum suspended thru aqueous. Poor phase form by two contacts at an 01A ratio of 2 to 1 with 100
3 ~~:~al~~queous, poor phase separation. 45 grams per liter NaCI in IN HCI followed by washing
4 ( Scum suspended in aqueous, settles in with 20 grams per liter NaCI adjusted to pH 1.5 with
( aqueous, clear organic. Same problem, HCI. The extraction was carried out by allowing the
5 ( both tests.
6 Trace scum, no phase separation problem. aqueous solution to contact the organic for three min-
7 Clear organic + aqueous phases, no scums. utes at 24°C and at an 01A ratio of 2 to 1. Following
__8__C_l_e_ar_o_r_ga_n_ic_+_a...;q_ue_o_us_p_h_a_se_s,_n_o_s_cu_m_s_. 50 the contact period the phases were separated and the
loaded organic phase scrubbed by contacting with pH 1
HCL for three minutes at 24° C at an 01A ratio of 2 to
1. The phases were again separated and the scrubbed
platinum and palladium loaded organic was analyzed,
and assayed (in gil) platinum 1.06, palladium 3.52, iridium
0.002, ruthenium 0.002 and rhodium less than 0.001.
The loaded organic solution was then divided into three
approximately equal portions (labeled organic 1, 2 and
3) which were each contacted once with an aqueous
strip solution containing 50 gil NaHC03 for a period of
5 minutes at 25° C. After contacting the first loaded
organic portion, the phases were separated and sufficient
NaHC03 added to the aqueous phase to restore it
to 50 grams per liter NaHC03, and the restored solution
used to contact the second and third portions of loaded
organic in sequence. All contacts were carried out at an
01A ratio of 2 to 1 and the phases separated and analyzed
after each contact. The platinum pregnant aque-
The results of the tests illustrated in Table II indicate
that a variety of alkaline reagents can be used to selectively
strip platinum from an amine organic loaded with
platinum and palladium. The poor stripping action of 55
Test No.3 is attributable to use of a weak alkaline solution
(11 gil). The insoluble scums formed in Tests Nos.
1 through 5 resulted in poor phase separation. The
emulsion forming scum was solubilized by addition of a
chelating agent [NaEDTA (ethylene dinitrillo)tetraa- 60
cetic acid disodium salt] to the alkaline stripping solution
prior to contact with the loaded organic. As indicated
in the results of Tests Nos. 6 through 8, this entirely
eliminated the scum formation in most instances
or reduced it to trace levels and also alleviated the 65
physical problem of phase separation. A 50 gil solution
of NaHC03 provided optimum selective stripping of
platinum from palladium as illustrated in the results of
10
4,041,126
9
ous strip solution was then acidified to pH 1 with l2N TABLE IV-continued
HC!. Analyses of the scrubbed-loaded organic, each Amount Assay,gll
stripped organic portion and the acidified platinum .:.P.:'ro:::d~u::::ct~_...,---__...,---~m,;;-I O;-:/;;-A_-----;:;-:P:;rt~_,,-:Pdm_
pregnant strip solution were carried out and the results Ramnate 850 1.0 0.70 1.70
found to be as follows: 5 Loaded Organic 850 1.04 2.60
TABLE III
Amount Assay, gil Grams
Product ml O/A Au Pt Pd Ir Ru Rh Pt Pd
Scrubbed organic 1400 0.005 1.06 3.52 0.002 0.002 <0.001 1.48 4.9
Stripped organic I 440 2.0 0.05 3.52 0.02 1.5
Stripped organic 2 470 ! 0.06 3.52 0.03 1.6
Stripped organic 3 490 0.09 3.52 0.04 1.7
Pt pregnant strip 232 0.002 6.00 0.004< 0.001 0.001 <0.001 1.39< 0.001
(acidified) 1.48 4.8
Pt Pd
% stripped 94 0.03
Ratio Pt/Pd in pregnant strip = 1000/1
Amount Assay,gll Grams % Stripped
Product ml Pt Pd Pt Pd Pt Pd
Scrubbed
orlianic
stnpped 700 1.04 2.60 0.728 1.82
Combined
Pd/organic 700 1.00 0.56 0.700 0.39 <I 78
Pd pregnant
strip 200 0.10 6.90 0.020 1.38
0.720 1.77
The scrubbed loaded organic (assaying in gil) platinum
1.04 and palladium 2.60 was then subdivided into
two separate portions. The first portion was conJa~ted
with a 50 gil aqueous solution of N2lL.2 HCl.acldified
to 0.5N with HCL for 3 minutes at an 01A ratio of 2 to
1. Following phase separation the aqueous raffinate
phase was used to contact the second portion of scrubbed
organic (at an 01A ratio 1.5 to 1) for 3 minutes at
25°C. The palladium pregnant aqueous raffinate was
separated from the organic extract phase which was
then combined with the previously stripped first organic
portion. As in the initial ~est, th~ percentages and
amounts of platinum and palladIUm strIpped were determined
by analysis of the respective separated phases as
indicated in the following table:
TABLE IVA
Product
Aqueous
EXAMPLE IV
This test was conducted to illustrate that platinum The combined palladium stripped organic was then
and palladium may be stripped from a loaded secondary contacted with pH 1 HCl at an 01A ratio of 2 to 1 for
amine organic in the order (1) palladium, (2) platinum. 50 3 minutes at 25° C to scrub the organic phase. Follow-
An organic extraction solution was prepared and ing phase separation, the scrubbed organic phase was
preconditioned to chloride form as in Example III and analyzed and found to assay (in gil) platinum 1.00, and
used to contact an aqueous hydrochloric acid solution palladium 0.56. The scurbbed organic phase was .t~en
assaying (in gil) gold less than 0.001, platinum 1.70, contacted with a 50 gil solution of NaHC03contammg
pallaadium 4.59, iridium 0.025, ruthenium 1.10, and 55 5 gil EDTA which was prepared ~y adjusting an
rhodium 0.036. The emf of the aqueous solution was EDTA suspension in water to l?H 8 With NaOH s?lureduced
to - 525 millivolts by the addition of dry hy- tion to dissolve the EDTA, addmg NaHC03 and ddut.
droquinone prior to contacting the extraction o~ganic. ing with water to final volume. The organ~c was di-
A single organic/aqueous contact was then carned out vided into two equal aliquots. The first ahquot was
for three minutes at 25° C at an 01A ratio of 1/1. Fol- 60 contacted with the alkaline stripping solution for 10
lowing phase separation the organic extract phase was minutes at 25° C. Following phase separation, 5.1 grams
scrubbed by contacting pH 1 HCl for three minutes at of NaHC03 was dissolved in the aqueous phase to rean
organic to aqueous ratio of2 to 1. Analysis of each of store the alkaline solution.to 50 gil NaHC03
• The rethe
respective phases gave the following results. stored strippant solution was then used to contact the
TABLE IV 65 second aliquot for 10 minutes at 25° C. Both of the -------...,---A-m.:.o.:.u=nt=-=--:.---A-::s~Sa~y:-,g/::-;;--1 --- preceding contacts were carried out at an organic. to
ml O/A Pt Pd aqueous ratio of 2 to 1. No scum was observed dUrIng
850 1.70 4.59 the first contact and only trace scums were apparent at
Table III indicates that 94% of the platinum was Aqueous Scrub 412 2.0 0.009 0.02
stripped from the loaded organic while. less tha~ 0.03% 20 :::S::::cr~ub::::b::e=-d-=:O:.:.rg~a::n:::ic~_---.:8:..:2_5 1_.04 2_.6_O _
of the palladium was removed. The ratio of platmum to
palladium in the pregnant strip solution ~as gre~ter
than 1,000 to 1. Platinum stripped orgamc portions
(Nos. 1, 2 and 3) were combined and assayed (in. gil)
platinum 0.070 and palladium 3.48: The platmum 25
stripped organic was then scrubbed with IN HCl for 3
minutes at 25° C at an 01A ratio of 2 to 1. After phase
separation, the scrubbed organic phase was analy.zed
and found to assay (in gil) platinum 0.070 and palladIUm
3.50. The scrubbed organic was then contacted three 30
times in succession with a fresh solution of 50 gil
N2lL.2HCl in 0.5N HCl at an organic aqueous ratio of
2 to 1 for a period of 5 minutes, the phases being sep~.
rated after each contact. The separated aqueous strIp
solutions were combined and an analysis ofthe.aqueous 35
strip solution revealed that 75% of the palladIUm present
in the scrubbed organic and less than 2% of the
platinum had been stripped into the aqueous solution by
the acidic strip treatment.
The results of this test indicate. that an or~anicallr 40
substituted secondary amine orgamc loaded with platinum
and palladium may be selectively stripped from a
loaded secondary amine organic ina stripping sequence
in which platinum is first removed followed by pallailium.
~
4,041,126
50
55
12
separating said organic extract phase from said aqueous
raffinate phase,
contacting said organic extract phase with an acidified
aqueous solution of a. water soluble reducing
agent to form an aqueous phase loaded with palladium
and a platinum containing organic extract
phase,
separating said platinum containing organic phase
from said palladium containing aqueous phase,
contacting said platinum containing organic extract
phase with at least the stoichiometric quantity of an
aqueous alkaline stripping agent required for neutralization
of said extract phase, said contact resulting
in the formation of an queous phase loaded with
platinum and a stripped organic phase.
2. The process of claim 1 wherein R1 is a fatty alkyl
group.
3. The process of claim! wherein said aqueous acidic
medium is hydrochloric acid.
4. The process according to claim 3 wherein said
alkaline solution contains between about 5 and 100
grams per liter of an alkaline reagent.
5. The process of claim 4 wherein said alkaline reagent
is a water soluble member selected from the
group consisting of the carbonates, bicarbonates and
hydroxides of alkali and alkaline earth elements.
6. The process of claim 5 wherein a metal chelating
agent is added to said aqueous alkaline solution prior to
contacting said organic extract phase.
7. The process of claim 6 wherein said metal chelating
agent is an amino carboxylic acid compound:
8. The process of claim 1 wherein said reducing agent
is selected from the group consisting of acidified solutions
of hydrazine salts, hydroxylamine salts, and thiourea.
9. The process of claim 8 wherein said acidified reducing
agent is hydrazine dihydrochloride.
10. The process of claim 9 wherein said acidified
reducing solution is adjusted to between 0.1 and 3.0 N
HCI.
11. The process of claim 3 wherein said aqueous solution
is extracted in plurality of times by contacting the
aqueous raffinate phase and subsequent raffinates with
said organic extractant.
12. A continuous process for the selective separation
and recovery of platinum and palladium dissolved in an
aqueous chloride solution which comprises:
reducing said solution to an emf between about -425
mvand -650 mv,
contacting said aqueous chloride solution with a
mixed extraction reagent comprising a water immiscible
organic solvent having dissolved therein an
organically substituted secondary amine compound
of the general formula:
11
the interface of the second stripping contact. After
phase separation following the second stripping
contact, the stripped organic phases were combined and
the platinum pregnant strip solution was adjusted to pH
1 by addition of 12N HCI to stabilize the solution. As 5
in the preceding test, the percentage of platinum and
palladium stripped was determined by analysis of the
separated phases as indicated below:
Amount Assay, gil Grams % Stripped
Product ml Pt Pd Pt Pd Pt Pd
Pd stripped
organic
(scrubbed) 600 1.00 0.56 0.60 0.336
Pt stripped 15
organic 600 0.15 0.55 0.09 0.330 85 <2
Pt pregnant
strip 151 3.20 0.071 0.48 0.011
0.57 0.341
TABLEIVB
-----------::-----=,.------:c--::c-:--.,--10
The tabulated data indicate that the initial stripping 20
operation resulted in the strip of 78% of the palladium
and less than 1% of the platinum from the loaded organic.
The Palladium containing aqueous strip solution
had a palladium/platinum ratio of 69/1. The platinum 25
stripped organic contained 0.15 gil platinum and 0.55
gil platinum (85% and less than 2% stripped, respectively)
and the aqueous platinum containing strip solution
had a platinum/palladium ratio of 46/1. Compared
to the starting feed liquor of the process, the Pd/Pt ratio 30
was increased from 2.7/1 to 6911 and the Pt/Pd ratio
was increased from 0.4/1 to 46/1. Overall recovery
from the loaded organic was 85% for platinum and 79%
for palladium.
The platinum and palladium values may be won from 35
the respective aqueous stripping solutions using techniques
well known in the art (e.g., precipitation of ammonium
chloroplatinate with NILCI to recover platinum,
or precipitation of dichlorodiaminopalladium by
sequential addition of ammonium hydroxide and hydro- 40
chloric acid solutions to recover palladium).
What is claimed is:
1. A process for the separation and selective recovery
of platinum and palladium values from an aqueous
acidic medium which comprises: 45
contacting the medium with a mixed organic extraction
reagent comprising a water immiscible solvent
having dissolved therein an organically substituted
secondary amine compound of the general formula:
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said com-
65 pound having a solubility of at least 1% in said solvent
and being capable of forming complexes of platinum
and palladium that are preferentially soluble in the organic
solvent and whereby the contacting results in the
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said compound
being sufficiently soluble in said solvent to make 60
a 1% solution and capable of forming complexes with
platinum and palladium that are preferentially soluble in
said solvent and whereby said contacting results in the
formation of an organic extract phase and an aqueous
raffinate phase,
maintaining said medium at an emf of between about
-425 and -650 millivolts during said contacting
operation,
4,041,126
13
creation of an organic extract phase and an aqueous
raffinate phase,
separating said organic extract phase from said aqueous
raffinate phase,
contacting said organic extract phase with an aqueous 5
solution containing at least the stoichiometric quantity
of sodium bicarbonate required for neutralization
of said organic phase and the disodium salt of
ethylenediaminetetraacetic acid to form a stripped 10
organic extract phase and an aqueous platinum
containing strip solution,
contacting said stripped organic extract phase with an
aqueous solution containing from about 5 to about
100 grams per liter of hydrazine dihydrochloride to 15
remove palladium from said stripped organic extract
phase, and
contacting a fresh platinum and palladium containing
aqueous chloride solution with said platinum and
palladium stripped organic extract phase. 20
13. A continuous process for the separation and selective
recovery of platinum dissolved in aqueous chloride
solutions with palladium which comprises:
reducing said aqeuous chloride solution to an emf
between about -425 mv and -650 mv, 25
contacting said aqueous chloride solution for a predetermined
time period with an organic solvent containing
at least 1% by weight of an organically
substituted secondary amine compound of the general
formula 30
35
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said compound
having a solubility of at least 1% in said solvent 40
and being capable of forming complexes of platinum
and palladium that are preferentially soluble in the organic
solvent and whereby the contacting results in the
creation of an organic extract phase and an aqueous 45
raffinate phase,
isolating said extract phase from said raffinate phase,
14
contacting said extract phase with at least the stoichiometric
quantity of an aqueous alkaline solution
required to neutralize the chloride form of said
amine to selectively separate said platinum values
from said palladium values in said organic extract
phase. and form a platinum stripped organic extract
phase and an aqueous platinum containing strip
solution, and
isolating said aqueous solution from said platinum
extract phase.
14. A continuous process for the separation and selective
recovery of palladium dissolved in aqueous chloride
solutions with platinum which comprises:
reducing said solution to an emf between about -425
mvand -650 mv,
contacting said aqueous chloride solution for a predetermined
time period with an organic solvent containing
at least 1% by weight of an organically
substituted secondary amine compound of the general
formula:
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said compound
capable of forming complexes of platinum and
palladium that are preferentially soluble in the organic
xolvent and whereby said contacting results in the creation
of an organic extract phase and an aqueous raffinate
phase, •
separating said organic extract phase from said aqueous
raffinate phase,
contacting said organic extract phase with an aqueous
solution containing a reducing agent acidified to
between about 0.1 to about 3.0 N-HCl to strip
palladium values from said organic extract phase,
said contact resulting in the formation of a palladium
loaded aqueous phase and a stripped organic
phase containing said platinum,
separating said loaded aqeuous phase and said
stripped organic phase, and recovering palladium
from said loaded aqueous phase.
* * * * *
50
55
60
65
no<ĩet0�(D�e:none'>point of elemental sulfur.
* * * * *
14
ture between about 500 C and the melting point of
sulfur to convert substantially all of the sulfide
sulfur to elemental sulfur in solid form and to effect
conversion of the metal compounds to metal chlorides,
and recovering metal from the chlorides.
22. The process of claim 21 in which chlorination is
performed at a temperature between about 800 C and
the melting point of sulfur.
23. The process of claim 2] in which the minerals
10 contain silver.
24. The process of claim 23 in which the silver containing
mineral is tetrahedrite.
25. The process of claim 21 in which sulfur chlorides
formed during dry chlorination are reacted with the
15 metal sulfides to form metal chlorides and elemental
sulfur.
26. The process of claim 25 in which the process is
performed by introducing the metal sulfides and dry
chlorine gas countercurrently into the reaction zone
20 and an inert sweep gas is introduced into the reaction
zone to bring sulfur chlorides formed during the dry
chlorination into contact with metal sulfides entering
the reaction zone.
4,011,146
13
lead, silver recovered from the leach solution by cementation,
the leach solution after removal of lead and
silver therefrom recycled to the sodium chloride leaching
step, the improvement comprising preventing the
build-up of zinc in the leach solution in the leaching 5
step by removing a bleed stream from the lead and
silver depleted leach solution, removing zinc from the
bleed stream and recycling the bleed stream to the
leaching solution in the leaching step.
19. The process of claim 18 including subjecting the
bleed stream to electrolysis after removal of zinc therefrom
to produce chlorine gas and recycling the chlorine
gas to the dry chlorination step.
20. The process of claim 19 in which the zinc is removed
by precipitating it as zinc carbonate by the addition
of sodium carbonate, the sodium hydroxide produced
in the electrolyis is carbonated to sodium carbonate
and the sodium carbonate recycled to the zinc
precipitation step.
21. The process of recovering metal values from
minerals of the polymorphic series of complex metal
sulfides tetrahedrite-tennantite comprising:
a. subjecting the minerals to dry chlorination with
chlorine gas in the absence of oxygen at a tempera-
25
30
35
40
45
50
55
60
65