FIELD OF APPLICATION
The present Invention relates to a method for producing hydrogen and/or other
gases from steel plant wastes and waste heat The gas stream produced may
also comprise hydrogen, carbon morraxide and other gases.
BACKGROUND OF THE INVENTION
With tiie increasing use and d^}l^ion of non-renewable sources of er^rgy, such
as petroleum, natural gas and coal, hydrogen is being Increasingly looked upon
as a viable alternative fuel. Quite a few processes exist for separation and
collection of hydrogen gas. Among these the most popular are electrolysis and
the use of high temperatures of nuclear reactors or petroleum processing plants
to ^It water (H2O) into hydrogen and oxygen. These proc^ses are expensive
as they involve use of electricity or other chemicals such as sulphuric acid,
hydrogen iodide, metallic zinc and zinc oxide, which need clc^ed-ioop
regeneration and handling. This makes the production of hydrogen a costly
process.
In the steel plant the generated wastes, like molten slag from basic oxygen
converters called LD slag, at a temperature of about 1600° C to 1700° C are
dumped into pits for removal and further processing. In the present invention
the heat of tiiis wa^e material can be used for the production of a gas stream
comprising hydrogen gas or hydrogen and carbon monoxide.
SUMMARY OF THE INVENTION
The main object of the present inventton therefore, is to use the heat of steel
plant wastes, like molten slags for gener^ing hydro^n by splitting water and/or
steam or a mixture of the two in the presence of a reducing agent.
Another object of the present invention is to use the heat of steel plant waste for
generating hydrogen, carbon monoxide and/or other gases by splittir^ water or
steam or a mixture of the two in the presence of a carbonaceous n^terial.
Water splits into hydrogen and oxygen at 1800° K, I.e., at 1527° C. In the
present invention water and/or steam can be split into hydrogen and oxygen by
using heat available in steel plant wastes like molten slags.
The waste material of molten slag may comprise steel making slag like
desulphurisatlon, converter, electric arc furnace (EAF), blast furnace slags,
ferrochrome and ferromanganese slags in submerged arc furnace (SAF), or a
mixture of these slags.
Water and/or steam is contacted with molten slag in the presence of reducing
agents in a reactor, like for examples a carbonaceous material.
Presence of FeO and/or other reducing agents such as carbon in the form of
coal, coke or refractory bkx:ks enhance the process of hydrogen generation. At
the operating temperature (above 1500° C), it is still possible for hydrogen to
recomblne with oxygen to form water. However, FeO present in the slag reacts
with the oxygen to form higher valence oxides such as Fe2O3 and Fe3O4. The
thermodynamic activity of oxygen in the immediate vicinity of slag is reduced,
thus reducing the chances of recombination of hydrogen and oxygen.
Presence of strong deoxidizers such as carbon (in the form of coal, coke or
graphite blocks) enhances the kinetks of removal of oxygen, further improving
the efficiency of the hydrogen generatbn process. Waste materials as reducing
agents like carbonaceous materials, are abundantly available in steel plants for
use in this process to assist the generation of hydrogen by contacting water
and/or steam with molten slag In the presence of a reducing agent in the
reactor.
Thus the present invention provides a method for producing hydrogen and/or
other gases from steel plant wastes and waste heat, comprising the steps of
providing molten waste from a steel plant, like molten slag, in a reactor;
contacting the molten slag with water and/or steam in the presence of a
reducing agent to form a stream of hydrogen and/or other gases; and extrorting
hydro^n and/or other gases from saki stream.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The invention can now be described in detail with the help of the figure of the
accompanying drawing in which:
Figure 1 shcMS a schematic set up for producing a stream
of gases using steel plant wastes and their waste
heat in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Water and/or steam is sprayed on LD slag, or other steel plant wastes with
temperature above 1600° C. The waste is either static, for example in a static
reactor or a ladle or a pot 1 or on ground or moving (e.g., being poured or in
fluid motion down a slope or on a conveyor). The water sprayed through a
water line 3 immediately splits when it comes in contact with the hot slag. The
emanating gases are funneied through a hood 2 placed over the area and
collected using a gas collection pipe 4.
The preferred temperature of the molten slag in the reactor is greater than
about 1250°C when water is sprayed into the molten slag.
The oxygen generated from splitting of water will react with the carbon present
forming carbon monoxide. The gas stream comprising hydrogen and carbon
monoxide can then be collected from the reactor.
The hydrogen gas is formed by two reactions a) decomposition of water and
simultaneous absorption of oxygen by carbon and/or Fe, FeO in the slag and b)
water-gas-shift reaction i.e. water and carbon monoxide formed during first
reaction. On the other hand, carbon monoxide is formed by reaction of
carbonaceous flux with nascent oxygen generated by water decomposition
reaction. The air infiltration in the system also generates CO gas by burning C-
flux. The ratio of H2 and CO can be controlled by different ways i) by adjusting
the input ratio of water and carbon flux, ii) by adjusting the product gas
retention time in reaction hood iii) by controlling the air infiltration in the
system, and iv) by controlling the water-gas-shift reaction. The metallic and
metal sub-oxides present in the molten slag are used novel way to trap the
nascent oxygen formed by water decomposition reaction. The innovative
approach helps to control the generation of CO gas.
In the present invention the production of gas stream comprises hydrogen and
carbon monoxide in the volume ratio of between 1:0.2 to 1:1.
The gas stream produced in the reactor, comprises at least at least 10 volume
percent of hydrogen gas and not greater than about 15 volume percent of
carbon dioxide.
In another embodiment the extracted gas stream may comprise hydrogen and
caibon monoxide in the ratio of i: 1 to about 8:1.
The water present may be extracted from the gas stream for recycling.
The water is contacted with the molten slag in the reactor by spraying water
using a spray rK)zzle. Steam can also be injected into the molten slag in the
reactor, using a lance.
The reducing agent or the carbonaceous material can be injected into the molten
slag in the reactor along with the water and/or steam.
The carbonaceous material to be injected into the molten slag may comprise
material selected from a group consisting of coal, coke, steel plant waste,
municipal waste and coal mine waste. The ratio of water to carbonaceous
material injected may be from about 1:0.1 to 1:1.
For promoting the formation of hydrogen, a flux may be added to the molten
slag and the carbonaceous material.
From the stream of hydrogen and/or other gases produced by the method of the
present invention, the hydrogen and carbon monoxide can be separated.
The use of steel plant wastes and their waste heat Is a cost effective method for
generation of hydro^n or hydrogen and carbon monoxide. 90 million tones of
LD slag produced annually can be a major source for supply of hydrogen gas
worldwide.
WE CLAIM;
1. A method for producing hydrogen and/or other gases from steel
plant wastes and waste heat, comprising the steps of:
-providing molten waste from steel plant like molten slag, in a
reactor;
-contacting the molten slag with desired amount of water
and/or steam in the presence of a reducing agent to form
stream of hydrogen and other gases such as oxygen, extracting
hydrogen and/or other gases from said stream,
characterized in that the heat energy of molten slag is used to
convert water/stream into a stream of hydrogen and other
gases and metal and metal oxides in the slag combines with the
oxygen to form higher oxides and prevents the recombination
thereof with hydrogen.
2. The method as claimed in claim 1, wherein said molten slag is
one of, or a mixture of blast furnace slag, desulphurization slag
of steel making, converter slag of steel making, ferrochrome or
ferromanganese slag in submerged arc furnace (SAF).
3. The methcxj as claimed in claim 1, wherein said contacting step comprises
spraying water into said molten slag using a water line with a spray
nozzle.
4. The method as claimed in claim 3, wherein the temperature of said
molten slag during said water spraying step is greater than 1250° C.
5. The method as claimed in claim 1, wherein said contacting step comprises
injecting steam into said molten slag using a lance.
6. The method as claimed in preceding claims, wherein said contacting step
comprises injecting said reducing agent along with injecting said water
and/or steam into said molten slag.
7. A method for production of a stream of hydrogen and/or carbon
monoxide, and other gases comprising the steps of:
- providing molten waste from a steel plant, like molten slag. In a
reactor;
- contacting the molten slag with water and/or steam in the presence
of a carbonaceous material to form a stream of hydrogen and or
other gases; and
- extracting said stream of gases from said reactor.
8. The method as claimed in claim 7, wherein said molten slag is one of or a
mixture of blast furnance slag, desulphurisation slag of steel making,
converter slag of steelmaking, ferrochrome or ferro-manganese slag in
submerged arc furnace (SAF).
9. The method as claimed in claim 7, wherein said contacting step comprises
spraying water into said molten slag using a spray nozzle.
10.The method as claimed In claim 9, wherein the temperature of said
molten slag during said water injecting step is greater than 1250° C.
11.The mehod as claimed in claim 7, wherein said contacting step comprises
injecting steam into said molten slag using a lance.
12.The method as claimed in claim 7, wherein said contacting step comprises
injecting said carbonaceous material along with injecting said water
and/or steam into said molten slag.
13.The method as claimed in claim 7, wherein said carbonaceous material
comprises a material selected from a group consisting of coal coke, steel
plant waste, municipal waste and coal mine waste.
14. The method as claimed in claim 7, wherein the ratio of water to
carbonaceous material is between 1:0.1 to 1:1.
15.The method as claimed in claim 7, wherein a flux is added to said molten
slag and said carbonaceous material for promoting the formation of
hydrogen.
16.The method as claimed in claim 7, wherein the volume ratio of hydrogen
and carbon monoxide produced is in the range of 1:0.2 to 1:1.
17.The method as claimed in claim 7, wherein said gas stream extracted
from said reactor comprises at least 10 volume percent of hydrogen.
18.The method as claimed in claim 7, wherein said gas stream produced in
the reactor comprises not greater than 15 volume percent of carbon
dioxide.
19.The method as claimed in claim 7, wherein said gas stream comprises a
hydrogen / carbon monoxide ratio of 1:1 to about 8:1.
20. A method for production of a gas stream of hydrogen and carbon
monoxide, substantially as herein described and illustrated in the
accompanying drawing.

A method for producing hydrogen and/or other gases from steel plant wastes and waste heat, comprising the steps of -providing molten waste from steel plant like molten slag, in a reactor;
-contacting the molten slag with desired amount of water and/or steam in the presence of a reducing agent to form stream of hydrogen
and other gases such as oxygen, extracting hydrogen and/or other gases from said stream,
characterized in that the heat energy of molten slag is used to convert water/ stream into a stream of hydrogen and other gases and
metal and metal oxides in the slag combines with the oxygen to form higher oxides and prevents the recombination thereof with hydrogen.