FIELD OF THE INVENTION
The present Invention relates to up gradation of high volatile and decrepitatable
manganese ores in vertical shaft furnace by partial reduction roasting utilizing
off-gas of sub-merged arc furnace (SAF) for producing ferro-manganese.
BACKGROUND OF THE INVENTION
In the existing practice ferromanganese is produced from high grade to low
grade manganese ores and manganeseferrous iron ores. Most of those
manganese ores are susceptible to decrepitation.
Another disadvantage associated with the said ore is due to dissociation of MnO2
to Mn3O4 liberating free oxygen upon heating to as low temperature as 550° C.

Chemical Equations & Heat Reactions in the Dissociation of MnO2 into Mn3O4 is
explained as follows:
Although the exhaust gas coming from the reaction zone rises the charge
temperature in top zone, which is common phenomenon, the main reason for
overheating and sintering of charge is due to the type of Mn-ore used in the
process. The mineral pyrolusite (MnO2) is major constituent in MnO.
Thermodynamically MnO2 is not stable at high temperature and in reducing
atmospheres, and decomposes into sub-oxides via following reactions:

In sub-merged arc furnace (SAF) top zone, atmosphere is highly reducing as
exhaust gas coming from reaction zone is CO. The reducing atmosphere further
enhances the decomposition of MnO2 in the ore.

The oxygen formed during decomposition reacts instantly with CO in exhaust gas
in the sub-merged arc furnace (SAF) top zone and combustion of CO gas
generates excessive heat in the top zone.

Decomposition of MnO2 liberates 9.2 % oxygen in reaction (1) at 600 C
temperature. The calculation of thermal energy generated by these reactions
revealed that decomposition of 1 tonne Mn-ore at 600 C temperature and
burning of CO gas by liberated oxygen generates ~ 300 kWh i.e. - 1080 MJ
energy. This localized generation of excessive energy increases the temperature
of the charge surface and trigger the sintering of charge by forming siliceous
liquid phase with gangues.
Thermodynamics of reactions of MnO2 with CO gas:


The aforesaid two disadvantageous properties of manganese ores as envisaged
from the above reaction behaviours spose problem in their direct use in a sub-
merged arc furnace (SAF) due to generation of ultrafine materials inside the
furnace and as a consequence overheating the charge materials at the furnace
top due to combustion of the upcoming hot carbon monoxide gas with pure
oxygen freed at high temperatures.
This reaction involved in sintering result further disadvantage by diminishing the
reduction potential of the carbon monoxide gas and masks the natural potential
of the ores to lose oxygen.

The production of ferro manganese is further aggravated due to the use of as received
wet ore which generate series of problems due to its moisture content which besides
demanding additional heat, results in the formation of cold lumps at the top most layer
due to its recondensation, thus additionally reducing a permeability of the bed and
causes channeling.
SUMMARY OF THE INVENTION
The present invention is provided with a treatment of decrepitable manganese ore by
waste heat of arc furnace adaptable for ferro-manganese production comprising the
steps of charging manganese ore from the top of a vertical shaft by means of a
belt/skip/elevator through a double gas sealed inlet and moving the manganese ores
subsequently downward through following zones: (a) preheating zone at a temperature
of 300-500°C (b) a combustion zone at a temperature of 600-900°C (c) a dissociation
zone at a temperature of 570-600°C (d) a gaseous reduction zone at a temperature of
400-500°C and introducing hot-of gas emits from a SAF top after dry cleaning and
boosting through the bottom of vertical shaft and taking out the manganese ores after
passing through a cooling zone at a temperature of 100-300°C on a -5mm screen
disposed below the vertical shaft through double gas seal outset and charging the
partially reduced and screened manganese ore in a sub-merged arc furnace for
production of ferro-manganese and the fines are available at the bottom of the screen
which are briquetted characterised in that upgoing gas dissociates MnO2 content of the
ore to M3O4 at 570-600°C, in dissociation zone and liberates free oxygen which is
autogeneously utilized for combusting residual carbon monoxide and hydrogen gases
available in the off gas in the combustion zone at 600-900°C and heat produced in
combustion zone being utilized for drying, pre-heating and dissociation of the ores.
DESCRIPTION OF THE INVENTION
To remove the above disadvantages of prior art associated with ferromanganese
production in sub-merged arc furnace (SAF) a novel method has been developed with
main aim to remove the moisture as well as fines from manganese ores in a separate
installation.
Another main objective of the invention is to develop and supply slightly preheated and
pre-reduced charge material to the sub-merged arc furnace (SAF).

A further objective of the invention is to eliminate disadvantages associated
with increased temperature at the furnace top while processing low SiO2
containing manganese ores, which have high loss on ignition (LOI), mainly in
the form of oxygen, which is liberated at around 550° C and generates large
amounts of heat at higher temperatures.
A still further objective of the invention is to reduce significant amount of
electricity as well as coke consumption in the production of ferromanganese
in the sub-merged arc furnace (SAF) by using prepared burden suitable for
the sub-merged arc furnace (SAF).
A yet another objective of the invention is the optimized use of a sub-merged
arc furnace (SAF) by eliminating shut down for dust clean-ups and gas
cleaning plant (GCP).

A still another objective of the invention is to improve productivity of a sub-
merged arc furnace (SAF) by using pre-reduced charge and increased power
input by minimization of the dangers of sintering and channeling at top
causing sudden eruptions.
According to the invention there is provided a process of upgradation of high
volatile and decrepitatable manganese ores in a vertical shaft furnace by
partial reduction roasting utilizing sup-merged are furnace sub-merged arc
furnace (SAF) off-gas during production of ferromanganese comprising the
steps of charging the cleaned and warm off-gas from a sub-merged arc
furnace (SAF) in the gaseous reduction zone of a vertical shaft fu
rnace charged with decrepitatable manganese ores to simultaneously
accomplish cooling of the outgoing charge material and pre reduce it partially
by dint of carbon monoxide containing in the charged ore, the said upcoming
gas is carried through the dissociation zone of the shaft furnace wherein the
MnO2

content of the ore is dissociated to Mn3O4 at 570-600° C and liberates free
oxygen which is autogenously utilized for combusting the residual carbon
monoxide and hydrogen gases available in the off-gas of the sub-merged arc
furnace (SAF) in the combustion zone maintained at 600-900° C, the heat
produced in the combustion zone being utilized for drying, preheating and
dissociation of the ores, the ores discharged at the bottom of the furnace
being screened to separate fines which are briquetted and sintered and the
dried partially reduced manganese ore obtained to be charged in the sub-
merged arc furnace (SAF) for producing ferromanganese optimizingly.
The present invention is developed by combustion of off-gas of submerged
arc furnace for production of ferromanganese with pure oxygen available at
high temperature around 600° C from the manganese ore charged in an
external vertical shaft furnace instead of combustion by atmospheric air
associated with nitrogen. The decreptatable manganese ore is upgraded by
preheating the ore in a vertical shaft furnace thus taking care of fines

generated outside the sub-merged arc furnace (SAF) and separating the fines
easily and utilizing the fines by agglomerating and charging in the sub-
merged arc furnace (SAF).
The natural property of the manganese ore is exploited optimizingly in the
shaft furnace by utilizing the natural dissociation property of manganese
oxide (MnO2) to lose oxygen (around 25 % of its total oxygen) on simply
heating the manganese ore without consuming any reductant upto the stage
of conversion to Mn2O3.
A vertical shaft furnace is equipped with a skip / belt / bucket charging
arrangement from the top and a bottom discharge device coupled with a
screen is provided at the bottom of the shaft furnace to screen out fines from
partially pre reduced Fe-Mn ores. The said fines are briquetted and sintered
to be used as a charge material in a sub-merged arc furnace (SAF). The sub-
merged arc furnace (SAF) off-gas and composition at the furnace sub-merged

arc furnace (SAF) top is admitted into the vertical shaft furnace which cool
the charge materials and at the same time partially pre reduce the charge
materials by carbon monoxide emitted form the charge itself. Remaining
carbon monoxide content in the upcoming gas combines with the oxygen
liberated from the down coming Mn-ores and generates the major portion of
heat required for the drying, preheating and dissociation process.
The present invention will be better understood from the following description
with the help of the accompanying drawing in which
Figure 1 represents a flow sheet for partial reduction roasting of high
volatile and decrepitatable manganese ores in a vertical shaft furnace utilizing
the sub-merged arc furnace (SAF) off-gas.
The charge materials are passed through seven zones of the shaft furnace as
shown in the flow sheet namely drying zone (100-200° C), preheating zone
(300-500° C), combustion zone (600-900° C), dissociation zone (570-600° C),
gaseous reduction zone (400-500° C), cooling zone (400-500° C) and
discharge zone (100-300° C).

The shaft furnace is equipped with skip / belt / bucket charging facility from
the top and bottom discharge device coupled with -5mm screen below the
furnace such that screening is accomplished in one go and double handling of
the material is avoided. Gas seal valves are provided at the materials
charging as well as discharge points to prevent the furnace gases to come
out of the system unabated. The sub-merged arc furnace (SAF) off-gas at
the available temperature and composition at the sub-merged arc furnace
(SAF) top is dry cleaned and boosted and the clean and warm gas
(100-300° C) is fed in the gaseous reduction zone as shown in the flow sheet.
For this purpose dry type electrostatic precipitator (ESP) wherein doubly
sealed gas boasters are employed. The admitted cleaned gas accomplish
cooling of the outgoing charge materials and simultaneously pre reduce the
charge partially by dint of carbon monoxide content in it
Moist waste gas escapes from the chimney after passing through streams of
water to separate out the fines with the gases. The shaft furnace operates
on counter current flow of gases from the bottom.

In the dissociation zone the MnO2 content of the ores is dissociated into
Mn3O4 liberating free oxygen which is autogenously utilized for combusting
the residual carbon monoxide and hydrogen gases available in the off-gas
from semi closed or closed type sub-merged arc furnace (SAF) treating
ferromanganese ore and fed in the gaseous reduction zone of the shaft
furnace.
Supplementary combustion air via combustion air fan is fed at the combustion
zone to provide the heat requirement of the process and such supplementary
atmospheric air is necessary largely during start-up of the process.
The carbon monoxide content in the up coming gas combines with the
oxygen liberated from the down-coming MnO at about 600-700° C and
generates major portion of the heat required for the drying, preheating and
dissociation process.

The process becomes almost autogenous with regard to the oxygen
requirement and very little amount of it have to be supplemented from fresh
combustion air.
The invention as described and illustrated hereinabove should not be read in
a restrictive manner as various modifications, alternations and changes are
possible within the scope and limit of the invention as encampused in the
appended claims.

WE CLAIM:
1. A treatment of high volatile and decrepitable manganese ores in a vertical
furnace by partial reduction roasting uitilizing off-gas emits from sub-
merged arc furnace for production of ferro-manganese comprising the
steps of:
- raw materials of manganese ores are charged from the top of a
vertical shaft by means of a belt/skip/elevator through a double gas
sealed inlet;
- the manganese ores are passed through a drying zone (Temp 100-
200°C) at the top of the vertical shaft;
- the manganese ores are moving downward and passed through a
pre-heating zone (Temp 300-500°C) after passing from drying
zone;
- after combustion zone, the manganese ore are passed through a
dissociation zone (Temp 570-600°C);
- the manganese ores are passed to a gaseous reduction zone
(Temp 400-500°C) after dissociation zone wherein hot off gas are
introduced from SAF top after dry cleaning and boosting;
- the manganese ores are taken out after passing through a cooling
zone (Temp 100-300°C) on a -5mm screen disposed below the
vertical shaft through double gas seal outset;

characterized in that upgoing gas dissociated MnO2 content of the
ore to M3O4 at 570-600°C, in dissociation zone and liberates free
oxygen which is autogeneously utilized for combusting residual
carbon monoxide and hydrogen gases available in the off gas in the
combustion zone at 600-900°C and heat produced in combustion
zone being utilized for drying, pre-heating and dissociation of the
ores.
2. The treatment as claimed in claim 1, wherein the charge materials in the
shaft furnace are passed through seven zones namely drying zone (100-
200°C), pre-heating zone (300-500°C), combustion zone (600-900°C),
dissociation zone (570-600°C), gaseous reduction zone (400-500°C),
cooling zone (400-500°C) and discharge zone (100-300°C).
3. The treatment as claimed in claim 1, wherein the shaft furnace is
equipped with skip/belt/bucket charging facility from the top and bottom
discharge device coupled with -5mm screen such that screening of
resulted partially reduced ore and fines are carried out in one go through
the screen.
4. The treatment as claimed in claim 1, wherein the bottom discharge device
is couple with -5mm screen below the shaft furnace and gas valves and
the sintered fines are charged with the manganese ores in the sub-
merged arc furnace (SAF).

5. The treatment as claimed in preceding claims, wherein off gas of the sub-
merged arc furnace (SAF) before admitting in the shaft furnace is cleaned
in a dry type electrostatic precipitator.
6. The treatment as claimed in preceding claims, wherein supplementary
atmospheric air is fed at the combustion zone via combustion air fan
during start up of the process.
7. The treatment as claimed in preceding claims, wherein moist waste gas
from the top of the furnace escapes in the atmosphere via GCP.
8. A treatment of high volatile and decrepitable manganese ores in a vertical
furnace by partial reduction roasting utilizing off-gas emits from sub-
merged arc furnace for production of ferro-manganese substantially as
herein described and illustrated.

ABSTRACT

A TREATMENT OF HIGH VOLATILE AND DECREPITABLE
MANGANESE ORES IN A VERTICAL FURNACE BY PARTIAL
REDUCTION ROASTING UTILIZING OFF-GAS EMITS FROM
SUB-MERGED ARC FURNACE FOR PRODUCTION OF FERRO-
MANGANESE
The present invention relates a treatment of decrepitable manganese ore by
waste heat of arc furnace adaptable for ferro-manganese production comprising
the step of charging manganese ore in a vertical shaft from top by an elevator
which passes downwardly through a preheating zone and thereafter a
combustion zone followed by a dissociation zone and finally passes a gaseous
reduction zone wherein introducing clean hot of gas, emitting from a SAF top,
through the bottom of vertical shaft and taking out manganese ore from a
cooling zone on a -5mm screen disposed below vertical shaft and charging
reduced and screened manganese ore in a submerged arc furnace for production
of ferro-manganese and the fines are available at the bottom of the screen which
are briquetted.