Field of Invention
The present invention relates to a rotary reactor for maximizing hydrogen gas
generation by utilizing waste heat from molten slag. More particularly, the
invention relates to a rotary reactor for production of hydrogen and other gases
in a continuous manner by thermo-chemical decomposition of water or steam in
presence of carbonaceous material such as coal or coke or carbon.
Background of the invention
Basic oxygen steelmaking process in LD converter generates about 160 to 200
kg of high temperature (~1600°C) molten slag per ton of steel. Also the
Ferrochrome production process in submerged arc furnace generates about
1100-1200 kg of molten slag (1700-1800°C) per ton of Ferrochrome metal.
In the previous patent application from the applicant 900/KOL/2005,
387/KOL/2006, 803/KOL/2007, WO 2007/036953 Al, WO 2007/125537 Al,
PCT/IN06/00198, US 2012/0171080 and 536/KOL/2009, a novel method and a
set-up for producing hydrogen gas was disclosed wherein the thermo-chemical
decomposition of water or steam by the waste heat from FeO or CrO containing
molten slag was disclosed. This setup comprised of a reaction hood disposed
over a crucible containing molten slag, a steel tube for collecting and transferring
the produced hydrogen gas from said hood into a condenser tank. In the
current patent application, a rotary reactor design is proposed to practice the
method in above patent applications in a continuous manner. In the new rotary
reactor the design limitations in the setup are improved further such that the
hydrogen gas production may be enhanced and the design is suitable for
application in a typical steel or Ferrochrome production process conditions. The
improvements over the earlier design are increased molten slag-steam contact
area, solidification of slag does not hamper the process and the new design is

highly suitable for operating the process in continuous manner. The rotary
reactor is especially suitable to provide the required controlled cooling of molten
slag to maximize hydrogen gas generation and also to enable rapid quenching of
slag towards exit cell in order to enable quick flushing of the molten or solidified
or granulated slag.
PRIOR ART
Various processes to utilize the sensible heat from molten slag and molten iron
are disclosed in the prior art methods. For example, in patent application number
US 5984985A a method for producing carbon monoxide rich gas using a multiple
vessel molten metal gasifieris disclosed wherein iron from molten metal is
primary source of iron. Molten iron with a carbon at least 2 wt% from blast
furnaces is used. The molten iron containing carbon circulates between two
zones (lower zone at high pressure and upper zone at lower pressure) of the
invention. Thus US 5984985A is directed to an at least two zone process
involving molten metal to facilitate the reaction of a carbon-containing material
to one or more oxides of carbon. In patent application number US 2953445, a
process for gasification of fuels and decomposition of gases is disclosed; wherein
slag bath at temperature of 1700°C is used as heat transferring agent as well as
medium to accelerate the gasification of fuels. High temperature liquid slag
containing iron oxide is contacted with fuel containing carbon. A method of
producing combustible gas comprising of carbon monoxide and hydrogen is
disclosed JP 2006-036804A, wherein organic system waste and water is brought
into contact with high temperature slag obtained as by-product of steel making
process in a reaction vessel. The organic system waste can be used in fine
powder form and contains halogen and molten slag is steel slag. In this process,
the carbon and hydrogen of an organic compound in organic system decomposes

into CO and H2. Thus the combustible gas is obtained by decomposition of
organic system waste. In patent application number US 6196479 Bl a method
for granulating and comminuting slag containing metal oxides is disclosed
wherein the molten slag is injected into an expansion chamber or granulating
chamber and pressurized oil is used to create a jet of molten slag from lance
with which water and or oxygen and/or CO2 containing waste gas is brought into
contact in expansion and decomposition chamber. US 6685754 discloses a
method for the production of a hydrogen containing gas, such as a synthesis gas
consisting of hydrogen and carbon monoxide that includes a controlled ration of
hydrogen to carbon monoxide by contacting a carbonaceous material and
reactive metal with steam wherein a portion of the steam reacts with the
carbonaceous material and a portion of the steam reacts with the reactive metal.
The reactive metal is iron in molten metal. The process can be carried out in a
single reactor or two separate reactors in order to generate the synthesis gas
substantially in continuous manner. Two separate reactors were used to carry
out the process consisting of steam reduction reactor and metal oxide reduction
reactor. JP 55120696 discloses a process to effectively utilize the sensible heat of
molten blast furnace slag, by continuously feeding molten blast furnace slag and
slack coal and gasifying agent steam at high velocity towards the molten slag
thereby producing (CO+H2) gas. The blast furnace slag cooled by liberation of
heat becomes semisolid and discharged from the gasifier by a water cooled
screw feeder. In patent application JP 52-041606A, a method for gasification of
coal by using molten slag and molten iron is disclosed wherein the molten iron is
placed in a sealed furnace and coal was fed along with molten converter slag,
oxygen and water into the furnace in order to decompose the coal into H2 or CO
mixed gas. GB 20882621 discloses a method for economic production of gas in
ferrous-bath reactor, wherein reactant fuel (coal) is introduced below the bath
surface and oxygen, and air or a mixture thereof is introduced below or above

the ferrous melt slag. High sulphur containing coals can be gasified using this
method and still product gas having very low sulphur contents can be produced
since the sulphur bearing or sulphide capacity of the slag is high. JP 61083653
discloses a method of producing a gas comprising carbon monoxide and
hydrogen during the slag granulation process. The fixed carbon from the
carbonaceous material coke is gasified to carbon monoxide, part of which further
produces hydrogen and carbon dioxide by reacting with water by the water gas
shift reaction. In patent application US 3709997 an electric furnace installation is
disclosed in which a simple interchangeability of electrodes can be mounted to
facilitate rapid removal and rapid connection of electrodes on the upper part or
hood of the furnace or crucible. US 2003/0089481 discloses a method and
apparatus for melting metals which uses microwave energy as the primary
sources of heat. The ceramic casket insulation used surrounding the microwave
chamber is utilized for preventing heat loss or as heat protection. A smoke
exhaust installation or exhaust hood for evacuating off-gas from electric metal
melting furnace is disclosed in US 2908737. In patent application number US
4696680 a method for purification of gases from a conventional coal gasifieris
disclosed wherein steam and oxygen are utilized and the gases are further
purified using distillation process.
In all the above prior art technologies, efforts were made to utilize the sensible
heat of molten slag or metal to produce carbon monoxide rich gas or to effect
the coal gasification process. Also in most of the above methods either the FeO
(deoxidizing constituent) in molten slag was insignificant or these processes were
operated in such a manner that the activity of deoxidizing constituent (FeO) was
much lower than metallic iron due to use of excessive carbon in the system.
However, in patent application number WO 2007/036953, a method for
producing hydrogen gas was disclosed by splitting water or steam or mixture of

the two in presence of carbonaceous material utilizing the heat from steel plant
wastes such as FeO containing molten slag. A setup for production of hydrogen
gas by thermo-chemical decomposition of water using steel plant slag and waste
materials was then disclosed in patent application number US 2012/0171080 and
WO 2007/125537. The setup comprised of a hood with water line for spraying
the water on molten slag followed by a condenser for separation of steam in
product gas. About 40% by volume hydrogen containing gas was produce. In the
current patent application, a novel rotary reactor is disclosed which overcomes
the design limitations of the previous setup and enables to practice the method
in continuous manner with enhanced production of hydrogen and other gases.
Thus an improved design is disclosed in current application which provides
efficient contact between molten slag and steam for maximizing the hydrogen
gas generation. The rotary reactor also minimizes the air ingress into the system
and the operation is not hampered or limited due to solidification of slag inside
the reactor.
PRIOR ART REACTOR DESIGNS
In patent application 900/KOL/2005 & 387/KOL/2006, a method of producing
hydrogen gas was disclosed wherein the molten slag is contained within a
reactor or slag pit and a hood is placed on the reactor for spraying the water
and carbonaceous material. A setup comprising of reactor, movable hood,
condenser and gas collection tank was disclosed. Handling of solidified slag and
its removal in continuous manner is difficult using the reactor setup especially
based on a crucible or slag pit. Also the water or steam comes in contact with
only the top layer of the slag which may result in inefficient utilization.of heat
from the bottom layers of molten slag contained in the reactor. In patent
application 536/KOL/2009, an apparatus for generating hydrogen rich gas/steam

is disclosed comprising of rollers which receives the molten slag and water is
sprayed on the molten slag on the roller surface. The hydrogen rich gas is
collected in a stack and the solidified slag is discharged using a bell mechanism.
While the roller design provides more surface area, the necessary residence time
for controlled cooling and efficient contact between the molten slag and water is
limited. A new rotary design is disclosed in the present application which
maximizes the molten slag and steam contact, minimizes the air ingress into the
system, handles the solidified slag in a continuous manner and provides
controlled cooling of the molten slag in the horizontal rotary reactor which is
highly suitable for continuous hydrogen production from molten slag in a typical
steelmaking or ferro alloy plant.
In patent application US 5984985, a multiple vessel reactor comprising of two
zones (upper zone-low pressure and lower zone-high pressure) is disclosed
wherein the two zones, the first and the second, are at different vertical heights
and circulation from one zone to the other occurs as a result of difference in
density between the molten bath in the lower zone compared to that the upper
zone. The current design treats only molten slag, is horizontal and the molten
slag movement is achieved by gravity flow enhanced due to rotation of the
reactor. In patent application number US 6196479 a method of granulating and
comminuting liquid slags is disclosed wherein the liquid slag is transferred into an
expansion and granulation chamber and subsequently into a mill, especially a jet
or impact mill. The device comprise of slag tundish tube is designed as a hole-
type nozzle. Devices for applying carbon carriers and/or water nozzle are
arranged radially outside of the mouth of the tundish tube. The primary objective
of the design is to generate the granulated slag and the water jet is injected to
the slag bath in tundish. The design is suitable for rapid cooling and generating
the granulated slag in the desired size range. The desired size range is also
obtained by the disintegration of slag particles due to armored impact plate and

also high amount of water is required to effect the atomization of molten slag.
The current design provides high contact area between slag and water and
allows controlled cooling of the molten slag. In patent application number US
6685754, two separate reactors are used to carry out the synthesis gas
production comprising of steam reduction reactor and metal oxide reduction
reactor. The reactor uses molten iron metal in the process and requires use of
oxygen injection to increase the temperature of the molten iron, however the
present reactor treats the molten slag in continuous manner without use of
external oxygen injection to the slag bath. The reactor in US 6685754 is not
suitable for treating the molten slag since handling of solidified slag is difficult in
the setup. In patent application number US 4696680, a distillation setup is
provided for purification of gases typically obtained by gasification of coal
whereas the present setup is used for generating the hydrogen gas. In patent
application number US 4389246, wherein the carbonaceous material, oxygen and
steam are top blown using a non-submerged lance on to a molten iron bath. The
reactor requires high velocity oxygen and steam jet which is to be injected. The
reactor deals with molten iron whereas in the current invention the reactor
disclosed user molten slag. Also the handling and removal of solidified slag is
difficult in the reactor disclosed in US 4389246. The present reactor however can
be operated in a continuous manner without any limitation on handling and
removal of solidified slag during the process of hydrogen gas generation. Also
the changes of produced gas entrapment in the molten slag bath are minimized
due to contact of thin layer of molten slag with the water or steam instead of
injecting oxygen and steam in the molten iron batch.
Hence, there exists a necessity to invent a rotary reactor that will maximize
generation of hydrogen gas by utilizing waste heat from molten slag.

Objects of the invention
Therefore, it is an object of the invention to propose a rotary reactor for
maximizing hydrogen gas generation by utilizing waste heat from molten slag
which is capable of enhancing the generation of hydrogen gas by thermo-
chemical decomposition of water or steam in presence of carbonaceous material
and molten FeO and/or CrO containing slag.
Another object of the invention is to propose a rotary reactor for maximizing
hydrogen gas generation by utilizing waste heat from molten slag which is able
to produce hydrogen gas in a continuous manner.
A further object of the invention is to propose a rotary reactor for maximizing
hydrogen gas generation by utilizing waste heat from molten slag which
minimises entrapment of hydrogen gas in slag.
A still further object of the invention is to propose a rotary reactor for maximizing
hydrogen gas generation by utilizing waste heat from molten slag which can
prevent the sticking of molten slag with the inner surface of rotary reaction
chamber.
A still another object of the invention is to propose a rotary reactor for
maximizing hydrogen gas generation by utilizing waste heat from molten slag
which is capable of preventing air ingress into the system comprising of molten
slag reservoir and molten slag feeding arrangement.
A still further object of the invention is to propose a rotary reactor for maximizing
hydrogen gas generation by utilizing waste heat from molten slag which is able
to avoid any pressure built up inside the rotary reactor by continuous withdrawal
of hydrogen gas through exit cell.

Brief description of the accompanying drawings:
Fig.l : Shows a schematic diagram of rotary reactor according to the invention.
The different parts of the invented rotary reactor are referred with
numerals as shown below.
1. Reservoir for molten slag.
2. Molten slag.
3. Stopper rod.
4. Lifting lever.
5. Stationary entry cell.
6. Refractory lined rotary reaction chamber
7. Vertical plate sealing (one end attached to rotary chamber and other end
attached to stationary cell of the reactor).
8. Baffle for setting the spiral motion of molten slag.
9. Baffle.
10. Nozzles for water or mist spray.
11. Rotary reaction chamber (no refractory lining).
12. Hollow steel pipe.
13. Stationary exit cell.
14. Product gas withdrawal.
15. Projected bottom attached to exit cell and dipped in water.
16. Solidified or granulated slag.
17. Product gas comprising hydrogen.
18. Girth gear.
19. Roller support.
20. Roller support.

Detailed Description of a preferred embodiment of the invention.
A novel method for producing hydrogen and/or other gases from steel plant
wastes and waste heat was claimed by the applicant in patent application
numbers 900/KOL/2005, 387/KOL/2006, 803/KOL/2007, WO 2007/036953 Al,
WO 2007/125537 Al, PCT/IN06/00198, US 2012/0171080 and 536/KOL/2009.
The method comprised of providing molten ferrous slag containing FeOor CrOat
a temperature of overl600°C in a reactor; contacting the molten ferrous slag
with water and/or steam in order to form a gas stream comprising of hydrogen
and other gases by combining FeO in slag with oxygen from water and/or steam;
and extracting said stream of gas from said reactor comprising hydrogen and
carbon monoxide in the volume ratio of between ratio of between 1:0.2 to 1:1.
The molten ferrous slag was selected from the group comprising
desulphurization slag from steel making or converter slag from steel making or
from ferrochrome or ferromanganese slag in a submerged arc furnace (SAF). A
carbonaceous material was injected into the said reactor along with said water
and/or steam such that the ration of water to carbonaceous material was 1: 0.1
to 1:1 by weight. The product gas obtained from the process comprised of
carbon monoxide not greater than about 15% by volume. A device comprising of
a movable reaction hood disposed over the slag pit attached to a chain-pulley
block means with a water inlet line to spray water on the slag was disclosed by
the applicant to produce gas stream comprising of hydrogen by thermo-chemical
decomposition of water utilizing the waste heat from molten slag.
In the current patent application, a rotary reactor design is proposed by the
applicant in order to enhance the hydrogen gas production in the production in
the product gas stream and also to practice the method of above inventions in
continuous manner and process large volumes of molten slag.

The schematic view of the rotary reactor is shown in Fig. 1. The rotary
reactor comprises of a reservoir (1) where the molten slag (2) over temperature
of 1600°C from the LD converter or from Ferrochrome production is collected.
The molten slag reservoir (1) is a refractory lined vessel and a bottom opening
(2) which is connected to a hollow entry cell (5) of the rotary reactor (R). An
upward or downward movable vertical stopper rod (3) is provided which opens
or blocks the bottom opening of the reservoir. A lifting lever means (4) controls
the vertical upward or downward movement of the stopper rod. The rotary
reaction chamber (11) of the rotary reactor ® has an entry cell (5). Molten slag
(2) from the reservoir (1) is fed to the rotary reaction chamber (11) through its
entry cell (5). The cylindrical rotary reaction chamber (11) has part of its inner
wall refractory lined (6). The refractory lined wall (6) of the rotary reaction
chamber (11) is lined with special ceramic coating to prevent sticking of molten
slag (2) to the wall of rotary reaction chamber (11).
A baffle (8) is mounted on the refractory lined part (6) of rotary reaction
chamber (11) and it holds the molten slag. The refractory lined part of rotary
reaction chamber also has a spiral baffle (8) which sets the spiral motion of
molten slag for making it thin. On the inner wall of the rotary reaction chamber
multiple baffles (9) are mounted at distance which ensures the continuous and
smooth flow of molten as well as solidified slag (16) towards the exit cell of
rotary reactor. Water or steam or water containing carbonaceous material is
passed through a concentric pipe (12) which is provided with jets or nozzle
means (10) along its length to spray water or steam or water containing
carbonaceous material on the molten slag layer formed on the inner wall of
rotary reaction chamber (11). The stationary exit cell (13) is provided with a
projected bottom (15) which is dipped in water bath (16). The exit cell is also
provided with continuous gas withdrawal provision (14) from the rotary reaction
chamber such that the product gas is discharged through outlet pipe (17). The

solidified or granulated slag with water moves towards the exit cell and
discharged in to the projected bottom (15) of stationary exit cell. The air ingress
in to the system from the exit cell is minimized since the projected bottom of exit
cell is dipped into the water bath (16). The rotary reaction chamber (11) is
provided with roller support (19,20) and the rotation of the rotary reaction
chamber (11) is carried out by girth gear (18) means for varying the rotational
speed as well as the inclination of rotary reaction chamber (11). Molten slag from
the reservoir enters the rotary reaction chamber (11) and collected into the
chamber created by baffle (8). During rotation of the rotary reaction chamber
(11) the molten slag (2) is set into a spiral motion and moves towards the exit
cell (13) of the reactor by forming a thin layer partly or completely covering the
inner surface of the rotary reaction chamber (11). The water or steam or water
containing carbonaceous material is sprayed on the thin molten slag layer. The
thermo-chemical decomposition of water is carried out by the heat from molten
slag. The oxygen present in the system reacts with the oxide (FeO or CrO) in
molten slag thus an oxygen free environment is created in the immediate vicinity
of the slag. The carbonaceous material may also be injected into the said reactor
separately in order to maintain an oxygen free environment in the rotary reaction
chamber (11). The molten slag moves towards the exit cell (13) of rotary reactor
(R) and gets solidified and or granulated. Additional excess water may be added
by controlled water flow from the nozzles towards the exit end (13) of rotary
reaction chamber (11) in order to effect rapid removal or flushing of solidified or
granulated slag. The length of the rotary reaction chamber (11) may be kept as
per the molten slag residence time requirement or properties (temperature,
viscosity, solidification rate) of the molten slag. The product gas comprising of
hydrogen and other gases is continuously withdrawn from the rotary reaction
chamber (11) to avoid pressure buildup. The solidified or granulated slag is

continuously discharged to the water containing chamber (16) for removal from
the system.
The distinguishing features of the invented rotary reactor are as follows:
i) The design of the reactor enhances or maximizes the contact area
between molten slag and steam or water.
ii) It ensures continuous flow and discharge of molten and/or solidified or
granulated slag in the set up.
iii) It minimises entrapment of hydrogen gas in slage due to contact of water
or steam with thin layer of molten slag.
iv) It enhances production of hydrogen gas by increased contact area
between molten slag and water or steam due to formation of a thin
layer of molten slag in the rotary reaction chamber and spraying of water
or steam or containing water on the thin layer of molten slag and
production is also enhanced due to controlled cooling of the molten slag
by spraying controlled quantity of water or water containing carbon so
that maximum slag heat is utilized for production of hydrogen gas instead
of steam. This controlled cooling in the present invention is in contrast to
conventional slag granulation processes where rapid or sudden quenching
of molten slag is practiced in excessive quantity of water which mostly
results in utilization of slag hear to produce steam instead of hydrogen
gas. Thus the invented rotary reactor is aimed to provide controlled
cooling of molten slag and also provides higher contact area for heat
transfer between molten slag and water or steam.
V) It enhances production of hydrogen gas through control cooling of the
molten slag by spraying controlled quantity of water or water containing
carbon so that maximum slag heat is utilized for production of hydrogen
gas instead of steam.

We Claim:
1. A Rotary reactor (R) for maximizing hydrogen gas generation by utilizing
waste heat from molten slag, the said Rotary reactor (R) comprising;
a reservoir (1) for collecting molten slag with an opening (21) at the
bottom of the said reservoir connected to hollow entry cell (5) of the
rotary reactor (R);
an upward or downward movable vertical rod (3) connected to a lifting
lever means (4) for controlling the movement of the said rod and for
feeding the molten slag from the reservoir (1);
a rotary reaction chamber (11) for receiving the molten slag (2) through
opening (21) and entry cell (5);
a refractory lined (6) inner wall of the rotary reaction chamber (11);
Characterized in that,
the rotary reactor (R) is provided with roller support and girth gear means
(18) for rotating and varying the spiral speed and inclination of the
reaction chamber (11) creating a thin layer of molten slag when a spiral
baffle (8) is disposed in the reaction chamber (11) for setting a spiral
motion of molten slag and a plurality of baffles (9) are mounted on the
inner wall of the said rotary reaction chamber for ensuring continuous and
smooth flow of molten as well as solidified slag (16) towards the exit cell
of rotary reactor (R) wherein a concentric pipe (12) is disposed in the said
rotary reaction chamber (11) having plurality of nozzles mounted on it for
spraying water or mist on the thin layer of molten slag for controlled
cooling of the said slag when a water tank (16) is disposed at the exit cell
for receiving the solidified and/or granulated slag continuously through
protected bottom (15) providing a water sea for preventing an air ingress
into the rotary reactor (R) wherein the withdrawal provision (14) of the

exit cell (13) allows product hydrogen gas to be discharged through the
exit pipe (17).
2. The rotary reactor (R) as claimed in claim 1, wherein the entry cell (5) of
the rotary reaction chamber (11) is in stationary condition while the
reactor chamber is in rotating condition.
3. The rotary reactor (R) as claimed in claim 1, wherein the refractory lined
surface (6) inside the rotary reaction chamber (11) is coated with heat
resistant ceramic paint for preventing the sticking of molten slag with
refractory lining.
4. The rotary reactor (R) as claimed in claim 1, wherein the molten slag
reservoir (1) is a refractory lined vessel.
5. The rotary reactor (R) as claimed in claim 1, wherein the said reactor is
cylindrical in shape.

ABSTRACT

The present invention relates to a rotary reactor for maximizing hydrogen
gas generation by utilizing waste heat from molten slag. A refractory lined
molten slag reservoir (1) which has a bottom opening (21) connected to a hollow
entry cell (5) of the rotary reactor (R), receives molten slag (2) over temperature
of 1600°C from the L.D. Convertor or from Ferrochrome production. The upward
or downward movement of a stopper rod (3) is actuated by a lifting lever means
(4) which controls the movement of the said rod. The reactor (R) has a
cylindrical rotary reaction chamber which has part of its inner wall refractory
lined (6) and the refractory lined wall is lined with special ceramic coating. The
refractory lined part (6) of the rotary reaction chamber has a baffle (8) mounted
on it which holds the molten slag and also has a spiral baffle (8) which sets the
spiral motion of molten slag for making it thin. In addition to this there are
multiple number of baffles (9) mounted at a distance to ensure continuous and
smooth flow of molten as well as solidified slag (16) towards the exit cell and
moves into a tank through a projected bottom (15) attached to the exit cell and
dipped in water. Water or steam or water containing carbonaceous material is
passed through a concentric pipe (12) which is provided with jets or nozzle
means (10) along its length to spray water or steam on molten slag layer formed
on the inner wall of the rotary reaction chamber. The rotary reaction chamber
(11) is provided with roller support (19,20) and the rotation of the rotary
reaction chamber (11) is carried out by girth gear means. The exit cell is
provided with continuous hydrogen gas withdrawal provision (14) from the
rotary reaction chamber (11) such that the product gas is discharged through
outlet pipe (17).