FIELD OF INVENTION
The present invention relates to an apparatus for producing hydrogen-rich
gas/steam through efficient waste heat recovery from molten slag discharged
from metallurgical furnaces such as converters, blast furnace and submerged arc
furnace.
A generic principle for the production of hydrogen gas using waste heat of
molten slag including a system for carrying out the process of the invention is
disclosed in WO 2007/125537, Indian Patent Application 803/KOL/07 entitled: a
novel method for production of hydrogen gas by catalytic thermochemical
decomposition of water using waste heat by metallic slag, all of which are
incorporated by way of reference.
BACKGROUND OF THE INVENTIQN
Integrated steel plants are one of the major consumers of fossil fuels, and
release about 5% of that energy in the form of waste heat, which gives rise to
environmental problems. Although several studies have been conducted, no
alternative process has been commercialized to recover waste heat from moltenslag discharged by various furnaces in steel plants, in spite of its huge potential.
The extremely high temperature (> 1500C) of slag prevents the efficient
recovery by conventional technology. Presently, the molten slag is treated by
conventional quenching/granulating. Generation of hydrogen-rich gas by thermochemical
decomposition of water using waste heat of molten steel slag out of it
could be a viable solution in this direction. Handling of molten slag becomes a
problem in extracting the waste heat efficiently. A set-up for extracting the waste
heat should provide maximum surface area of slag with minimum heat loss to
environment, better steam/water-slag contact with maximum residence time,
and should preferably be a continuous process. This gave rise to come up with
an innovative design of the apparatus to extract the waste heat more efficiently.
This patent presents the design of the apparatus.
OBJECTS OF THE INVENTION
It is therefore, an object of the invention to propose an apparatus which is
capable of generating hydrogen-rich gas/steam through efficient waste heat
recovery from molten slag.
Another object of the invention is to propose an apparatus which is capable of
hydrogen gas by the molten slag reacting with one of water and steam through
catalytic thermo-chemical decomposition of water and/or steam. A still another object of the invention is to propose an apparatus which is capable
of hydrogen-rich gas adaptable as fuel by molten slag reacting with one of water
and steam which is capable of recovering even the sensible heat of the molten
slag to make the process further cost-effective.
Yet another object of the invention is to propose an apparatus which is capable
of hydrogen-rich gas/steam through efficient waste heat recovery from molten
slag, which is also capable of granulating the slag.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a design of the apparatus to
produce hydrogen-rich gas/steam from molten slag of metal industry by
extracting the waste heat out of it in an economical and efficient way.
The present invention is featured by an apparatus to carry out water
decomposition to produce hydrogen-rich gas/steam wherein the water or steam
is in contact with molten metal slag. The apparatus houses multiple rollers in
series to distribute the molten slag over its surface as the slag fall on it. The
roller rotates to have uniform distribution of slag heat on the entire surface. A
distributor cum buffer makes the slag fall all over the surface of the rotatingroller along the length at a flow rate. As the molten slag comes down along the
roller surface., nozzles sprays water/steam on it with a prefixed pressure so as to
disintegrate the molten slag into droplets to expose maximum area available for
heat extraction. At the bottom of the apparatus a bell mechanism may be
adapted to maintain a pressure within the apparatus. Other side of apparatus
has a gas collection zone separated by a wall from the roller zone as to have
minimum distraction in gas flow from falling slag as well as the entrainment of
the water/steam into hydrogen-rich gas/steam stream.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig.l - shows a schematic diagram of the apparatus for producing hydrogen-rich
gas/steam according to invention
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The objects, features and advantage of the invention and manner of attaining
them will become more apparent, and the invention itself will best be
understood, from the following description of preferred embodiment taken in
connection with the attached drawing. Figure 1 is a schematic diagram
illustrating elements of the apparatus (A) for producing hydrogen-rich gas/steam
according to the invention. Referring to Figure 1, an apparatus (A) consists of multiple rotating rollers (1) in
series andior in parallel for receiving the molten slag through a distributor (2)
when the rollers receives the slag one by one exposing maximum possible area
for heat transfer/reaction with water or steam being sprayed in form of jets
coming from multiple nozzles (3) arranged in the apparatus (A). The molten slag
once discharged from the metallurgical furnace can be transferred to pouring
location by well known practice of ladle car and a pan/pot be utilized as a
pouring buffer or be directly pour onto the rollers (1). The distributor (2) of the
apparatus works as a receptor cum distribution system to uniformly distribute
poured molten slag over rotating rollers.
Molten slag while put into apparatus remains at high temperature say up to >
1250 C. The roller made preferably of iron should have sufficient strength so as
not to sag under its own or falling hot slag. The rollers are supported at ends. To
keep the roller cool, water may be passed through a passage at roller center
axis. The rollers are rotated by a suitable prime mover (not shown in the Figure)
in the direction as indicated by the arrow along the horizontal axis. Speed of the
roller is kept such that the poured molten slag flows along the roller surface.
Number of nozzles (3) are placed in front of the roller surface to have
water/steam jets hitting against the roller surface at a reqUired flow rate. The
molten slag is cooled and granulated, as jets strikes onto it. The gradually cooled
and granulated slag falls from one roller (1) to another roller (1) out of multiplerollers arranged in series. Necessary hardware such as valves, pressure release
valves, pipes, connectors etc. and control instruments like flow controller,
temperature, pressure and gas sensors etc are installed to operate and carry out
hydrogen rich gas generation process. Through the contact and subsequent
reaction hydrogen-rich gas/steam is generated. The generated gas is collected
through stack (4) for further separation of hydrogen-rich gas from steam. The
location and shape of the stack is designed for complete, smooth and safe
collection of the product gas from the chamber (7). The proper collection of the
gas from all the sides of the chamber (7) is essential for maintaining uniform
pressure inside the apparatus and also to avoid generation of any excess
pressure and/or backpressure. Solidified slag granules fall on the bottom of the
chamber (7) where it is discharged through a bell mechanism. The pressure
within the chamber (7) is controlled by the bell mechanism (5) as bell remains in
closed position when gas is being produced from molten slag thereafter solidified
slag is discharged by opening the bell by up and down movement. The apparatus
has leak proof close chamber (7) by mean of walls boundaries (6), wherein all
the devises for gas generation are fitted. The material of the wall may be
preferably of steel or any other material which can sustain the operation and is
heat resistant. To reduce the heat loss to surrounding atmosphere from the
operating apparatus peripherals, insulating material is used to cover up the walls
from outside. The apparatus and the system, as described in the present invention, enable the
maximum and uniform recovery of the waste energy of the molten slag in the
form of hydrogen rich gas and steam. However, it will be appreciated that other
types of system can also be utilized in accordance with the present invention.
The selection and type of system is dictated by properties of slag (temperature,
fluidity, composition etc.),scale, economics and plant operations, at which
maximum heat recovery is possible with required safety and minimum
operational problems.
It is particular noteworthy, in accordance with the foregoing description, that
essentially the same system can be utilized to produce various gas streams i.e.
hydrogen gas, steam and hydrocarbons by simply altering the input stream
combination to the reactor and recovering the waste heat of slag, based on the
plant requirement and techno-economic parameters.
WE CLAIM
1. An apparatus (A) for generating hydrogen-rich gas/steam through
efficient recovery of waste heat from slag comprising:
a plurality of rotating rollers (1) in series and/or in parallel for receiving
molten slag;
at least one distributor (2) for uniformly distributing poured molten slag
over rotating rollers (1);
a plurality of nozzles (3) for supplying water/steam jets on the roller
surface;
a stake (4) for collecting hydrogen rich/steam gas;
a movable bell.(5) mechanism for discharging solidified slag granules;
a chamber (7) for enclosing all the devises for gas generation;
characterised in that the rotating rollers (1) carrying an uniformly
distributed molten slag are injected with water jet to produce hydrogenrich
gas/steam.
2. An apparatus (A) as claimed in claim 1, wherein the rollers (1) are
supported at ends and rotated by prime movers.
3. An apparatus (A) as claimed in claim 1, wherein the rollers are made
preferably of iron.
4. An apparatus (A) as claimed in claim 1, wherein the wall of the chamber
(7) is made preferably of steel.
5. An apparatus (A) as claimed in claim 1, wherein the chamber (7) is leak
proof.
6. An apparatus (A) as claimed in claim 1, wherein the walls of the chamber
(7) is covered by insulating materials to reduce the heat loss.