NZ626934B2 - Starting a smelting process - Google Patents
Starting a smelting process Download PDFInfo
- Publication number
- NZ626934B2 NZ626934B2 NZ626934A NZ62693412A NZ626934B2 NZ 626934 B2 NZ626934 B2 NZ 626934B2 NZ 626934 A NZ626934 A NZ 626934A NZ 62693412 A NZ62693412 A NZ 62693412A NZ 626934 B2 NZ626934 B2 NZ 626934B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- main chamber
- forehearth
- carbonaceous material
- smelting
- oxygen
- Prior art date
Links
- 238000003723 Smelting Methods 0.000 title claims abstract description 102
- 238000000034 method Methods 0.000 title claims abstract description 49
- 239000002184 metal Substances 0.000 claims abstract description 86
- 229910052751 metal Inorganic materials 0.000 claims abstract description 86
- 239000001301 oxygen Substances 0.000 claims abstract description 76
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 76
- MYMOFIZGZYHOMD-UHFFFAOYSA-N oxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims abstract description 73
- 239000007789 gas Substances 0.000 claims abstract description 65
- 239000003575 carbonaceous material Substances 0.000 claims abstract description 52
- 239000000463 material Substances 0.000 claims abstract description 49
- 238000010438 heat treatment Methods 0.000 claims abstract description 14
- 238000004519 manufacturing process Methods 0.000 claims abstract description 6
- 238000007599 discharging Methods 0.000 claims abstract description 5
- 238000010309 melting process Methods 0.000 abstract 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 46
- 239000003245 coal Substances 0.000 description 30
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 29
- 239000002893 slag Substances 0.000 description 29
- 241001062472 Stokellia anisodon Species 0.000 description 24
- 229910052742 iron Inorganic materials 0.000 description 23
- 241001088417 Ammodytes americanus Species 0.000 description 11
- 238000002347 injection Methods 0.000 description 9
- 239000007924 injection Substances 0.000 description 9
- 239000007787 solid Substances 0.000 description 9
- 238000002485 combustion reaction Methods 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 235000019738 Limestone Nutrition 0.000 description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000003546 flue gas Substances 0.000 description 5
- 239000006028 limestone Substances 0.000 description 5
- 230000001603 reducing Effects 0.000 description 5
- 230000004907 flux Effects 0.000 description 4
- 230000002269 spontaneous Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000007792 addition Methods 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 239000002817 coal dust Substances 0.000 description 3
- 238000004880 explosion Methods 0.000 description 3
- 239000003638 reducing agent Substances 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- SZVJSHCCFOBDDC-UHFFFAOYSA-N Iron(II,III) oxide Chemical compound O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000005755 formation reaction Methods 0.000 description 2
- 239000002737 fuel gas Substances 0.000 description 2
- 238000004868 gas analysis Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 241000894007 species Species 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 206010022114 Injury Diseases 0.000 description 1
- 241001417490 Sillaginidae Species 0.000 description 1
- 235000015450 Tilia cordata Nutrition 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 229910052595 hematite Inorganic materials 0.000 description 1
- 239000011019 hematite Substances 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 238000011068 load Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 230000001960 triggered Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B11/00—Making pig-iron other than in blast furnaces
- C21B11/08—Making pig-iron other than in blast furnaces in hearth-type furnaces
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0006—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state
- C21B13/0013—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state introduction of iron oxide into a bath of molten iron containing a carbon reductant
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
- C21B2100/28—Increasing the gas reduction potential of recycled exhaust gases by separation
- C21B2100/282—Increasing the gas reduction potential of recycled exhaust gases by separation of carbon dioxide
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/40—Gas purification of exhaust gases to be recirculated or used in other metallurgical processes
- C21B2100/42—Sulphur removal
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/60—Process control or energy utilisation in the manufacture of iron or steel
- C21B2100/66—Heat exchange
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C2200/00—Recycling of waste material
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/56—Manufacture of steel by other methods
- C21C5/567—Manufacture of steel by other methods operating in a continuous way
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/10—Dry methods smelting of sulfides or formation of mattes by solid carbonaceous reducing agents
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/12—Dry methods smelting of sulfides or formation of mattes by gases
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D3/00—Charging; Discharging; Manipulation of charge
- F27D3/16—Introducing a fluid jet or current into the charge
- F27D2003/168—Introducing a fluid jet or current into the charge through a lance
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D3/00—Charging; Discharging; Manipulation of charge
- F27D3/16—Introducing a fluid jet or current into the charge
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D3/00—Charging; Discharging; Manipulation of charge
- F27D3/18—Charging particulate material using a fluid carrier
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/122—Reduction of greenhouse gas [GHG] emissions by capturing or storing CO2
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
Disclosed is a method of starting a molten-bath based melting process for smelting a metalliferous feed material in a smelting apparatus includes commencing supplying cold oxygen-containing gas and cold carbonaceous material into a main chamber of a smelting vessel within at most 3 hours after completing a hot metal charge into the vessel and igniting the carbonaceous material and heating the main chamber and molten metal in the main chamber. The apparatus includes a smelting vessel that includes a main chamber for containing a molten bath, a forehearth for discharging molten metal from the main chamber during a smelting campaign, and a forehearth connection that connects the main chamber and the forehearth. The method of starting a molten-bath based process includes the steps of (a) preheating the main chamber, the forehearth, and the forehearth connection and (b) pouring a charge of hot metal into the main chamber via the forehearth. The method includes (c) commencing supplying cold oxygen-containing gas and cold carbonaceous material into the main chamber within at most 3 hours after completing the hot metal charge and igniting the carbonaceous material and heating the main chamber and molten metal in the main chamber; then step (d) includes continuing supplying oxygen-containing gas and carbonaceous material into the main chamber and combusting carbonaceous material and heating the main chamber and molten metal in the main chamber for a period of at least 10 minutes; and (e) commencing feeding a metalliferous material into the main chamber in order to initiate metal production. The method includes verifying ignition of oxygen-containing gas and carbonaceous material in the main chamber. eting a hot metal charge into the vessel and igniting the carbonaceous material and heating the main chamber and molten metal in the main chamber. The apparatus includes a smelting vessel that includes a main chamber for containing a molten bath, a forehearth for discharging molten metal from the main chamber during a smelting campaign, and a forehearth connection that connects the main chamber and the forehearth. The method of starting a molten-bath based process includes the steps of (a) preheating the main chamber, the forehearth, and the forehearth connection and (b) pouring a charge of hot metal into the main chamber via the forehearth. The method includes (c) commencing supplying cold oxygen-containing gas and cold carbonaceous material into the main chamber within at most 3 hours after completing the hot metal charge and igniting the carbonaceous material and heating the main chamber and molten metal in the main chamber; then step (d) includes continuing supplying oxygen-containing gas and carbonaceous material into the main chamber and combusting carbonaceous material and heating the main chamber and molten metal in the main chamber for a period of at least 10 minutes; and (e) commencing feeding a metalliferous material into the main chamber in order to initiate metal production. The method includes verifying ignition of oxygen-containing gas and carbonaceous material in the main chamber.
Description
STARTING A SMELTING PROCESS
TECHNICAL FIELD
The present invention relates to a method of starting a process for smelting a
metalliferous material.
The term “metalliferous material” is understood herein to include solid feed
material and molten feed material. The term also includes within its scope partially
reduced metalliferous material.
BACKGROUND ART
The present invention relates particularly, although by no means exclusively, to
a method of starting a molten bath-based smelting process for producing molten metal
from a metalliferous feed material in a smelting vessel that has a strong bath/slag
fountain generated by gas evolution in the molten bath, with the gas evolution being at
least partly the result of devolatilisation of carbonaceous material in the molten bath.
In particular, although by no means exclusively, the present invention relates to
a method of starting a process for smelting an iron-containing material, such as an iron
ore, and producing iron.
The present invention relates particularly, although by no means exclusively, to
a method of starting a smelting process in a smelting vessel that includes a main
chamber for smelting metalliferous material.
A known molten bath-based smelting process, generally referred to as the
HIsmelt process, is described in a considerable number of patents and patent
applications in the name of the applicant.
Another molten bath-based smelting process, referred to hereinafter as the
“HIsarna” process, is described in International application PCT/AU99/00884 (WO
00/022176) in the name of the applicant.
5412976_1 (GHMatters) P88933.NZ 7/09/15
The HIsmelt process and the HIsarna process are associated particularly with
producing molten iron from iron ore or another iron-containing material.
The HIsarna process is carried out in a smelting apparatus that includes (a) a
smelting vessel that includes a main smelting chamber and lances for injecting solid
feed materials and oxygen-containing gas into the main chamber and is adapted to
contain a bath of molten metal and slag and (b) a smelt cyclone for pre-treating a
metalliferous feed material that is positioned above and communicates directly with the
smelting vessel.
The term “smelt cyclone” is understood herein to mean a vessel that typically
defines a vertical cylindrical chamber and is constructed so that feed materials supplied
to the chamber move in a path around a vertical central axis of the chamber and can
withstand high operating temperatures sufficient to at least partially melt metalliferous
feed materials.
In one form of the HIsarna process, carbonaceous feed material (typically coal)
and optionally flux (typically calcined limestone) are injected into a molten bath in the
main chamber of the smelting vessel. The carbonaceous material is provided as a
source of a reductant and a source of energy. Metalliferous feed material, such as iron
ore, optionally blended with flux, is injected into and heated and partially melted and
partially reduced in the smelt cyclone. This molten, partly reduced metalliferous
material flows downwardly from the smelt cyclone into the molten bath in the smelting
vessel and is smelted to molten metal in the bath. Hot reaction gases (typically CO,
CO , H , and H O) produced in the molten bath is partially combusted by oxygen-
2 2 2
containing gas (typically technical-grade oxygen) in an upper part of the main chamber.
Heat generated by the post-combustion is transferred to molten droplets in the upper
section that fall back into the molten bath to maintain the temperature of the bath. The
hot, partially-combusted reaction gases flow upwardly from the main chamber and enter
the bottom of the smelt cyclone. Oxygen-containing gas (typically technical-grade
oxygen) is injected into the smelt cyclone via tuyeres that are arranged in such a way as
to generate a cyclonic swirl pattern in a horizontal plane, i.e. about a vertical central
axis of the chamber of the smelt cyclone. This injection of oxygen-containing gas leads
to further combustion of smelting vessel gases, resulting in very hot (cyclonic) flames.
Finely divided incoming metalliferous feed material is injected pneumatically into these
flames via tuyeres in the smelt cyclone, resulting in rapid heating and partial melting
5412976_1 (GHMatters) P88933.NZ 7/09/15
accompanied by partial reduction (roughly 10-20% reduction). The reduction is due to
both thermal decomposition of hematite and the reducing action of CO/H in the
reaction gases from the main chamber. The hot, partially melted metalliferous feed
material is thrown outwards onto the walls of the smelt cyclone by cyclonic swirl action
and, as described above, flows downwardly into the smelting vessel below for smelting
in the main chamber of that vessel.
The net effect of the above-described form of the HIsarna process is a two-step
countercurrent process. Metalliferous feed material is heated and partially reduced by
outgoing reaction gases form the smelting vessel (with oxygen-containing gas addition)
and flows downwardly into the smelting vessel and is smelted to molten iron in the
smelting vessel. In a general sense, this countercurrent arrangement increases
productivity and energy efficiency.
The above description is not to be taken as an admission of the common general
knowledge in Australia or elsewhere.
The applicant has proposed that the HIsarna process and an oxygen-blown
version of the HIsmelt process be started up in a smelting vessel by feeding hot metal
(from an external source) into the main chamber of the vessel via the forehearth of the
vessel, commencing supplying oxygen-containing gas (typically technical grade
oxygen) and solid carbonaceous material (typically coal) and generating heat in the
main chamber. This hot start-up method generates heat via spontaneous ignition of
combustible material in the main chamber. The applicant has proposed that this initial
step in the hot start-up method be followed by the addition of slag-forming agents and,
later on, by the addition of metalliferous feed material (such as ferruginous material
such as iron ore) into the main chamber.
In pilot plant trials of the HIsarna process that were based on cold technical-
grade oxygen as the oxygen-containing gas, coal as the solid carbonaceous material,
and iron ore fines as the metalliferous material, the applicant found that such a start-up
can fail under certain conditions. By inadvertently allowing a long period of time to
pass between charging hot metal and admitting oxygen/coal into the main chamber of
the smelting vessel, it was found that coal-oxygen ignition could fail despite that fact
that fresh hot metal had recently been poured into the main chamber. This led to an un-
combusted mixture of coal and oxygen leaving the smelting vessel, and this in turn
triggered a coal dust explosion in a downstream waste heat boiler.
5412976_1 (GHMatters) P88933.NZ 7/09/15
The applicant believes that this type of situation must be avoided since it can
lead to serious injury and/or equipment damage. As a consequence of this failed start-
up, the applicant subsequently installed a camera in the smelting vessel to observe
directly what was causing ignition failure.
Video footage showed that, when hot metal is poured into the main chamber of
the smelting vessel, there are spontaneous sparks and small splashes of hot metal which
are easily capable of igniting a cold oxygen-coal mixture in the main chamber.
However, as time passes, a thin layer of slag builds on the hot metal surface, and hot
metal splashing activity gradually dies down. Eventually, the metal becomes
completely blanketed with a slag crust, and metal splashing activity stops. If oxygen
and coal are fed under these conditions, it is believed that ignition can fail.
The slag is believed to come from two sources: (1) slag left behind in the main
chamber of the smelting vessel from previous operations, such as previous smelting
campaigns, and (2) oxidation of certain metal species (particularly silicon) in hot metal.
The degree to which the latter occurs is a function of how much silicon is present in the
charge metal and, in cases where silicon is deliberately increased as part of start-up, this
effect is intensified. The important practical conclusion is that a slag layer can always
form, and a safe start-up method must accommodate this possibility.
Slag layer formation is a function of vessel geometry, charge metal
temperature/composition and vessel condition (e.g. thickness of existing freeze layers
on side walls of vessels). When hot metal is poured into a main chamber of a smelting
vessel, there is an immediate loss of heat by radiation from the relatively quiescent bath
surface to the side walls of the main chamber that are above the hot metal. These side
walls may be refractory walls. In the case of the smelting vessel of particular interest to
the applicant, the side walls include water-cooled panels. Metal, by virtue of having a
high density and a relatively low viscosity under these conditions, tends to circulate
within itself. This suppresses any initial tendency to form a solidified or highly viscous
uniform crust across its top surface. Slag, on the other hand, tends to float as a more or
less uniform thin layer on top of the metal. As it loses heat by radiation, its viscosity
rises and it becomes sticky. Under these conditions an insulating slag crust (in effect an
insulating “blanket”) is effectively formed on top of the hot metal. This is considered by
the applicant to be the key mechanism associated with the ability of slag to compromise
oxygen-coal ignition under start-up conditions. This is a time-related mechanism.
5412976_1 (GHMatters) P88933.NZ 7/09/15
Understanding the time-scale associated with the formation of this slag crust is
critical for safe plant operation. For the pilot plant described herein, the (metal) bath
diameter was around 2.6 m and the top space was defined by fully water-cooled panels
in the side walls and the roof of the smelting vessel. A provisional (sacrificial)
cast/gunned refractory layer was present on the water panels at the time. In the trial
involving the failed start-up (leading to the coal dust explosion), metal was charged into
the main chamber of the vessel and 7 separate attempts were made to start the process
by adding oxygen and coal to the main chamber. Of these, 6 were made within the first
2 hours after charging, and each time it was possible to show that ignition had indeed
taken place (from water panel heat load and gas composition data) but the start-up
attempt had subsequently failed for reasons unrelated to ignition. The 7th (and last)
attempt was made around 2.5 hours after completion of the hot metal charge. It is this
attempt that led to final ignition failure and the resulting coal dust explosion.
For this particular smelting facility, there appears to be a “safe” ignition time-
window of around 1-2 hours after completion of hot metal charging (during which
spontaneous ignition of oxygen and coal can be reasonably assured). Beyond this, safe
ignition is not assured and an alternate cold start-up method needs to be followed. The
cold start-up method is described in a companion International application entitled
“Starting a Smelting Process” lodged in the name of the applicant on the same day as
the International application for the present invention.
Translation of this specific time-window to other smelting facilities must be
undertaken with care, giving due consideration to the factors discussed above (vessel
geometry, charge metal conditions etc).
SUMMARY OF THE DISCLOSURE
The method of starting a smelting process of the present invention is applicable
to starting any molten bath-based smelting process when a fresh hot metal charge has
been added as part of start-up from an empty-vessel condition.
According to the present invention there is provided a method of starting a
molten-bath based process for smelting a metalliferous feed material in a smelting
apparatus, with the apparatus including a smelting vessel that includes a main chamber
5412976_1 (GHMatters) P88933.NZ 7/09/15
for containing a molten bath, a forehearth for discharging molten metal from the main
chamber during a smelting campaign, and a forehearth connection that connects the
main chamber and the forehearth, and with the method including the steps of:
(a) preheating the main chamber, the forehearth, and the forehearth
connection;
(b) pouring a charge of hot metal into the main chamber via the forehearth;
(c) commencing supplying cold oxygen-containing gas and cold
carbonaceous material into the main chamber within at most 3 hours after
completing the hot metal charge and igniting the carbonaceous material and
heating the main chamber and molten metal in the main chamber;
(d) continuing supplying oxygen-containing gas and carbonaceous material
into the main chamber and combusting carbonaceous material and heating the
main chamber and molten metal in the main chamber for a period of at least 10
minutes; and
(e) commencing feeding a metalliferous material into the main chamber in
order to initiate metal production.
By way of explanation of the selection of an upper ignition time limit of 3 hours
in step (c), as is described above, the upper time limit of 2 hours for safe ignition arising
from the pilot plant trials was subject to various factors associated with the size and
operating conditions of the pilot plant. Taking into account these factors for the pilot
plant and having regard to factors that are relevant to other molten bath-based smelting
facilities, the applicant concluded that under conditions other than those used in the
pilot plant this time period for safe ignition could expand to as much as 3 hours in other
smelting facilities.
5412976_1 (GHMatters) P88933.NZ 7/09/15
The term “cold” in the context of oxygen-containing gas is understood herein to
mean cold in the sense that the gas is at a temperature below that required for
spontaneous ignition of the carbonaceous material and the oxygen-containing gas
mixture (i.e. below about 700-800°C in the case of a coal-oxygen mixture).
The term “cold” in the context of carbonaceous material is understood herein to
mean solid material below 150°C.
The method may include verifying ignition of oxygen-containing gas and
carbonaceous material in the main chamber. The verification may be via water panel
heat loads and/or an on-line gas analysis system for the smelting apparatus and/or direct
observation using a camera or a suitable opening in the vessel (if process conditions
allow this).
Step (a) may include preheating a hearth of the vessel, the forehearth, and the
forehearth connection for example using a suitable fuel gas, such that an average
surface temperature of the hearth, the forehearth, and the forehearth connection is above
1000°C, preferably above 1200°C.
The charge of molten metal in step (b) may include multiple individual ladles of
hot metal.
Step (b) may include selecting the amount of the charge of hot metal into the
main chamber via the forehearth such that the metal level in the main chamber is at
least 100 mm above the top of the forehearth connection.
Step (b) may include selecting the amount of the charge of hot metal into the
main chamber via the forehearth such that the metal level in the main chamber is at
least 200 mm above the top of the forehearth connection.
5412976_1 (GHMatters) P88933.NZ 7/09/15
Step (c) may include commencing supplying oxygen-containing gas and
carbonaceous material into the main chamber within 2 hours after completion of the hot
metal charge into the main chamber.
Step (c) may include commencing supplying oxygen-containing gas and
carbonaceous material into the main chamber within 1 hour after completion of the hot
metal charge into the main chamber.
Step (c) may include commencing supplying coal carbonaceous material into the
main chamber before commencing supplying oxygen-containing gas into the main
chamber.
Step (c) may include commencing supplying coal carbonaceous material and
oxygen-containing gas into the main chamber at the same time.
Step (c) may include commencing supplying oxygen-containing gas into the
main chamber before commencing supplying coal carbonaceous material into the main
chamber.
Step (c) may include selecting the ratio of solid carbonaceous material and
oxygen-containing gas to ensure complete combustion of the solid carbonaceous
material.
Step (d) may include increasing the ratio of solid carbonaceous material and
oxygen-containing gas.
Step (d) may include heating the main chamber for a period of 30-60 minutes by
combusting carbonaceous material and oxygen-containing gas in the main chamber.
The initial feed rates of oxygen-containing gas and carbonaceous material into
the main chamber in step (c) above are preferably calculated such that there is sufficient
oxygen to fully combust the carbonaceous material. This is generally consistent with
maximum heat generation and highest probability of achieving good ignition.
5412976_1 (GHMatters) P88933.NZ 7/09/15
Once this initial ignition step (c) has been completed, the rates of oxygen-
containing gas and carbonaceous material are preferably adjusted in step (d) from the
step (c) rates such that there is roughly half, preferably at least 40% of the amount of
oxygen for complete combustion of the carbonaceous material. This brings the oxygen
potential of the main chamber more or less into its normal range for smelting and
prevents excessive oxidation of molten materials.
The method may include, following step (d) and before step (e), feeding slag or
slag-forming agents into the main chamber in order to establish a suitable slag
inventory for smelting metalliferous material in the main chamber.
The smelting vessel may include a refractory-lined hearth.
The forehearth may be a refractory-lined forehearth.
The smelting vessel may include partially water-cooled side walls that define a
top space of the main chamber of the vessel.
The smelting vessel may include lances/tuyeres for injecting carbonaceous
material into the bath in the main chamber of the vessel.
The smelting vessel may include lances/tuyeres for injecting oxygen-containing
gas into the top space of the main chamber of the vessel.
The apparatus may include (i) the above-described smelting vessel that is
adapted to contain a bath of molten metal and (ii) a smelt cyclone that is positioned
above and communicates with the smelting vessel. In that event, step (e) may include
commencing supplying metalliferous feed material and additional oxygen-containing
gas into the smelt cyclone and generating a rotating flow of material in the cyclone and
combusting combustible gas flowing upwardly into the cyclone from the vessel and
partially reducing and melting the metalliferous feed material in the cyclone, whereby
the partially reduced molten metalliferous feed material flows downwardly from the
5412976_1 (GHMatters) P88933.NZ 7/09/15
cyclone into the molten bath of metal and slag in the main chamber of the smelting
vessel and is smelted to molten metal in the bath.
The method of present invention is applicable to a molten bath-based smelting
apparatus that includes (a) a smelting vessel that has a main chamber that is adapted to
contain the bath of molten metal and slag, (b) lances or other suitable means for
supplying the carbonaceous material into the bath, (c) lances or other suitable means for
supplying the oxygen-containing gas into the bath (d) lances or other suitable means for
supplying the metalliferous material into the bath, either directly or indirectly via a
smelt cyclone, and (e) at least 40%, typically at least 50%, of the wall region of the
smelting vessel above the bath being covered by water-cooled panels with frozen slag
layers.
Under normal operating conditions, the molten bath-based smelting process
includes the steps of:
(a) supplying carbonaceous material and metalliferous material (which may
be solid or molten) into the molten bath and generating reaction gas and
smelting metalliferous material and producing molten metal in the bath,
(b) supplying oxygen-containing gas into the main chamber for above-bath
combustion of combustible gas released from the bath and generating heat for
in-bath smelting reactions, with the oxygen-containing gas typically being
technical-grade oxygen which is “cold” in the sense that it is at a temperature
significantly below that required for safe ignition of a coal-oxygen mixture (i.e.
below about 700-800°C); and
(c) producing significant upward movement of molten material from the
bath by gas upwelling in order to create heat-carrying droplets and splashes of
molten material which are heated when projected into the combustion region in
the top space of the main chamber and thereafter fall back into the bath,
5412976_1 (GHMatters) P88933.NZ 7/09/15
whereby the droplets and splashes carry heat downwards into the bath where it
is used for smelting of the metalliferous material.
The oxygen-containing gas may be air, oxygen, or oxygen-enriched air.
According to the present invention there is provided a method of starting a
molten-bath based process for smelting a metalliferous feed material in a smelting
apparatus, with the apparatus including a smelting vessel that includes a main chamber
for containing a molten bath, a forehearth for discharging molten metal from the main
chamber during a smelting campaign, and a forehearth connection that connects the
main chamber and the forehearth, and with the method including the steps of:
(a) preheating the main chamber, the forehearth, and the forehearth
connection;
(b) pouring a charge of hot metal into the main chamber via the forehearth;
(c) commencing supplying cold oxygen-containing gas and cold
carbonaceous material into the main chamber and igniting carbonaceous
material and heating the main chamber and molten metal in the main chamber
within a time period before an insulating layer of crusty slag forms on the metal
charge to an extent that it prevents molten metal igniting carbonaceous material;
(d) continuing supplying oxygen-containing gas and carbonaceous material
into the main chamber and combusting carbonaceous material and oxygen-
containing gas and heating the main chamber and molten metal in the main
chamber for a period of at least 10 minutes; and
(e) commencing feeding a metalliferous material into the main chamber in
order to initiate metal production.
BRIEF DESCRIPTION OF THE DRAWINGS
5412976_1 (GHMatters) P88933.NZ 7/09/15
An embodiment of a method of starting a smelting process in a smelting vessel
in accordance with the present invention is described with reference to the
accompanying drawings, of which:
Figure 1 is a diagrammatic view of a HIsarna apparatus for smelting a
metalliferous material and producing molten metal in accordance with one embodiment
of the HIsarna process;
Figure 2 is an enlarged cross-sectional view of the smelting vessel shown in
Figure 1 which illustrates the condition of the smelting vessel shortly after supplying a
charge of molten metal into a main chamber of a smelting vessel of the apparatus
shown in Figure 1 and there is crusty layer forming on the molten metal and molten slag
layers in the vessel.
DESCRIPTION OF EMBODIMENT(S)
The HIsarna process smelts metalliferous feed material and produces process
outputs of molten metal, molten slag, and an off-gas. The following description of the
HIsarna process is in the context of smelting metalliferous material in the form of iron
ore. The present invention is not limited to this type of metalliferous material.
The HIsarna apparatus shown in Figure 1 includes a smelt cyclone 2 and a
molten bath-based smelting vessel 4 having a main chamber 19 located directly beneath
the smelt cyclone 2, with direct communication between the chambers of the smelt
cyclone 2 and the smelting vessel 4.
With reference to Figure 1, during steady-state operation of a smelting
campaign, a blend of magnetite-based ore (or other iron ore) with a top size of 6 mm
and flux such as limestone 1 is fed, via an ore dryer, and with a pneumatic conveying
gas 1a, into the smelt cyclone 2. Limestone represents roughly 8-10 wt% of the
combined stream of ore and limestone. Oxygen 8 is injected into the smelt cyclone 2
via tuyeres to preheat and partly melt and partly reduce the ore. The oxygen 8 also
5412976_1 (GHMatters) P88933.NZ 7/09/15
combusts combustible gas flowing upwardly into the smelt cyclone 2 from the smelting
vessel 4. The partly melted and partly reduced ore flows downwardly from the smelt
cyclone 2 into a molten bath 25 of metal and slag in the main chamber 19 in the
smelting vessel 4. The partly melted and partly reduced ore is smelted to form molten
iron in the molten bath 25. Coal 3 is fed, via a separate dryer, to the main chamber 19
of the smelting vessel 4. The coal 3 and a conveying gas 2a are injected via lances 35
into the molten bath 25 of metal and slag in the main chamber 19. The coal provides a
source of a reductant and a source of energy. Figures 1 and 2 show the molten bath 25
as comprising two layers, of which layer 25a is a molten metal layer and layer 25b is a
molten slag layer. The Figures illustrate the layers as being of uniform depth. This is
for illustration purposes only and is not an accurate representation of what would be a
highly agitated and well-mixed bath in operation of the HIsarna process. The mixing of
the molten bath 25 is due to devolatilisation of coal in the bath, which generates gas,
such as CO and H , and results in upward movement of gas and entrained material from
the molten bath into a top space of the main chamber 19 that is above the molten bath
. Oxygen 7 is injected into the main chamber 19 via lances 37 to post-combust some
of these gases, typically CO and H , generated in and released from the molten bath 25
in the top space of the main chamber 19 and provide the necessary heat for the smelting
process in the bath.
Normal operation of the HIsarna process during a smelting campaign involves
(a) coal injection via lances 35 and cold oxygen injection via lances 37 into the main
chamber 19 of the smelting vessel 4 and (b) ore injection 7 and additional oxygen
injection 8 into the smelt cyclone 2.
The operating conditions, including but not limited to, coal and oxygen feed
rates into the main chamber 19 of the smelting vessel 4 and ore and oxygen feed rates
into the smelt cyclone 2 and heat losses from the main chamber 19, are selected so that
offgas leaving the smelt cyclone 2 via an offgas outlet duct 9 has a post-combustion
degree of at least 90%.
5412976_1 (GHMatters) P88933.NZ 7/09/15
Offgas from the smelt cyclone 2 passes via an offgas duct 9 to an offgas
incinerator 10, where additional oxygen 11 is injected to burn residual CO/H and
provide a degree of free oxygen (typically 1-2%) in the fully combusted flue gas.
Fully combusted offgas then passes through a waste heat recovery section 12
where the gas is cooled and steam is generated. Flue gas then passes through a wet
scrubber 13 where cooling and dust removal are achieved. The resulting sludge 14 is
available for recycle to the smelter via the ore feed stream 1.
Cool flue gas leaving the scrubber 13 is fed to a flue gas desulphurisation unit
Clean flue gas is then vented via a stack 16. This gas consists mainly of CO
and, if appropriate, it can be compressed and geo-sequestered (with appropriate removal
of residual non-condensable gas species).
With particular reference to Figure 2, the smelting vessel 4 includes a
refractory-lined hearth 33 and side walls 41 defined predominantly by water-cooled
panels that define the main chamber 19. The smelting vessel 4 also includes a
forehearth 21 which is connected to the main chamber 19 via a forehearth connection
23. During the course of a smelting campaign of the HIsarna process, molten metal
produced in the main chamber 19 discharges from the main chamber 19 via the
forehearth connection 23 and the forehearth 21.
One embodiment of the method for starting the HIsarna process for ironmaking
in accordance with the present invention is described below.
At the commencement of the start-up method, the main chamber 19, the
forehearth 21, and the forehearth connection 23 of the vessel 4 are empty.
The start-up method includes preheating the hearth 33, the forehearth 21, and
the forehearth connection 23, for example using a suitable fuel gas, such that an average
5412976_1 (GHMatters) P88933.NZ 7/09/15
surface temperature of the hearth 33, the forehearth 21, and the forehearth connection
23 is above 1000°C, preferably above 1200°C
After the preheating step is completed, the start-up method includes pouring a
selected amount of molten iron into the main chamber 19 via the forehearth 21 and the
forehearth connection 23 to establish a molten iron bath 25a in the hearth 33 of the
vessel 4. Typically, the amount of the charge is selected such that the molten iron level
in the main chamber 19 is at least 100 mm above the top of the forehearth connection
As soon as the molten iron is charged into the main chamber 19, a crusty frozen
slag layer 29 begins to form on the surface of the molten iron bath 25a. Figure 2
illustrates the smelting vessel 4 at this stage in the start-up method. Heat is lost from a
top surface of the molten iron bath 25a shown in Figure 2 by (mainly) radiation to
water-cooled panels of the side walls 41 that define the upper section of the main
chamber 19.
After completing the step of charging molten iron into the main chamber 19, the
start-up method includes supplying coal and oxygen into the main chamber 19 via the
lances 35 and 37, respectively.
In a successful start-up method, coal ignites and heat is generated in the main
chamber 19.
The key to a safe start-up of the HIsarna process is admission of oxygen 37 and
coal injection 35 within a nominal “safe” time-period of less than 3 hours (1-2 hours in
this example).
In more general terms, the time window is the period of time before the crusty
frozen slag layer 29 forms to an extent that sparks and splashes of molten iron from the
molten iron bath 25a into the top space in the main chamber 19 above the molten bath
25a cannot ignite oxygen 37 and coal 35 and there is no other ignition source.
5412976_1 (GHMatters) P88933.NZ 7/09/15
When oxygen 37 and coal 35 are first admitted, the ratio between the two is
calculated such that there is sufficient oxygen to burn all the coal 35. After ignition, this
condition is only maintained for long enough (5-10 minutes) to verify that ignition is
healthy. Thereafter, the coal-to-ore ratio is subsequently adjusted to approximately
twice the amount of coal 35 (for full combustion) relative to oxygen 37. The purpose of
the increase in the coal-to-ore ratio is to ramp up the levels of carbon for use as a
source of a reductant and energy.
Verifying healthy ignition may be via water panel heat loads and/or an on-line
gas analysis system for the smelting apparatus and/or direct observation using a camera
or a suitable opening in the smelting vessel 4 (if process conditions allow this).
The start-up method may include injecting fluxing agents such as lime or
limestone at any time when coal injection is active. The preferred practice is to wait
until after the initial 5-10 minute ignition verification stage as described above.
Injection of coal and oxygen (plus flux) is maintained for approximately 30
minutes in order to heat the main chamber 19 and the molten metal in the chamber. At
this point crushed slag is pneumatically conveyed into the main chamber 19 via slag
notch 6 in order to rapidly establish a suitable slag inventory for normal operation.
Once crushed slag injection is complete, iron ore and oxygen 8 are injected into
smelt cyclone 2, coal 35 and oxygen 37 are injected into smelting vessel 4, metal
production in the smelting campaign begins, and molten metal is discharged from the
main chamber 19 via the forehearth 21 and the forehearth connection 23.
Many modifications may be made to the embodiment of the process of the
present invention described above without the departing from the spirit and scope of the
invention.
5412976_1 (GHMatters) P88933.NZ 7/09/15
The above description focuses on coal as the carbonaceous material and
technical grade oxygen as the oxygen-containing gas. The present invention is not so
limited and extends to any suitable oxygen-containing gas and any suitable solid
carbonaceous materials.
The above-described embodiment focuses on the HIsarna process. The present
invention is not limited to the HIsarna process and extends to any molten bath-based
process in a smelting vessel. By way of example, the present invention extends to the
oxygen-blown version of the HIsmelt process. As is indicated above, the HIsmelt
process is described in a considerable number of patents and patent applications in the
name of the applicant. By way of example, the HIsmelt process is described in
International application PCT/AU96/00197 in the name of the applicant. The
disclosure in the patent specification lodged with the International application is
incorporated herein by cross-reference.
5412976_1 (GHMatters) P88933.NZ 7/09/15
Claims (3)
1. A method of starting a molten-bath based process for smelting a metalliferous feed material in a smelting apparatus, with the apparatus including a smelting vessel that includes a main chamber for containing a molten bath, a forehearth for discharging 5 molten metal from the main chamber during a smelting campaign, and a forehearth connection that connects the main chamber and the forehearth, and with the method including the steps of: (a) preheating the main chamber, the forehearth, and the forehearth 10 connection; (b) pouring a charge of hot metal into the main chamber via the forehearth; 15 (c) commencing supplying cold oxygen-containing gas and cold carbonaceous material into the main chamber within at most 3 hours after completing the hot metal charge and igniting the carbonaceous material and heating the main chamber and molten metal in the main chamber; 20 (d) continuing supplying oxygen-containing gas and carbonaceous material into the main chamber and combusting carbonaceous material and heating the main chamber and molten metal in the main chamber for a period of at least 10 minutes; and 25 (e) commencing feeding a metalliferous material into the main chamber in order to initiate metal production.
2. The method defined in claim 1 includes verifying ignition of oxygen- containing gas and carbonaceous material in the main chamber.
3. The method defined in claim 1 or claim 2 wherein step (a) includes preheating a hearth of the vessel, the forehearth, and the forehearth connection such that 5412976_1 (GHMatters) P88933.NZ
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2011905068A AU2011905068A0 (en) | 2011-12-06 | Starting a Smelting Process | |
AU2011905068 | 2011-12-06 | ||
PCT/AU2012/001486 WO2013082658A1 (en) | 2011-12-06 | 2012-12-06 | Starting a smelting process |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ626934A NZ626934A (en) | 2016-01-29 |
NZ626934B2 true NZ626934B2 (en) | 2016-05-03 |
Family
ID=
Similar Documents
Publication | Publication Date | Title |
---|---|---|
AU2012350150B2 (en) | Starting a smelting process | |
AU2012350144B2 (en) | Starting a smelting process | |
US9771626B2 (en) | Starting a smelting process | |
AU2012350151B2 (en) | Starting a smelting process | |
NZ626934B2 (en) | Starting a smelting process | |
AU2019240892B2 (en) | Direct smelting process with full combustion | |
NZ626931B2 (en) | Starting a smelting process | |
NZ626933B2 (en) | Starting a smelting process |