PRODUCING HOT REDUCING GAS

PRODUCTION DE GAZ CHAUDS REDUCTEURS

English Abstract

ABSTRACT
Hot reducing gas (e.g. at 1000 to 1100°C) suitable
for use in reducing oxidic ores is produced by reforming
and partially oxidizing a fluid hydrocarbonaceous fuel
(e.g. fuel oil) with a gaseous oxidant (e.g. oxygen or
H20) in a plasma medium at approximately 2000°C, to
form a high temperature gas comprising a major pro-
portion of C0 and H2 and a minor proportion of C02 and
H20, and then adding a hydrocarbonaceous gas (e.g.
CH4) to the high temperature gas so that further
reforming reactions occur which reduce the proportion
of C02 and H20.

Claims

The embodiments of the invention in which an
exclusive property or privilege is claimed are defined
as follows:-
1. A method of producing hot reducing gas which
mainly comprises CO and H2 and is suitable for use in
reducing oxidic ores, comprising the sequential steps
of:
(a) reforming and partially oxidizing a fluid
hydrocarbonaceous fuel by reacting the fuel with a
gaseous oxidant in a plasma medium at approximately 2000°C,
whereby a high temperature gas comprising a major
proportion of CO and H2 and a minor proportion of CO2
and H2O is formed; and
(b) adding a hydrocarbonaceous gas to the high
temperature gas, whereby further reactions occur which
reduce the proportion of CO2 and H2O.
2. A method as claimed in claim 1, in which the
hot reducing gas is at 1000 to 1100°C.
3. A method as claimed in claim 1, in which the
fuel and the gaseous oxidant are pre-heated.
4. A method as claimed in claim 1, in which the
gaseous oxidant comprises steam, CO2, or oxygen.
5. A method as claimed in claim 1, in which the
fuel comprises a liquid hydrocarbon.
6. A method as claimed in claim 5, in which the
fuel is fuel oil.
7. A method as claimed in claim 1, in which the
hydrocarbonaceous gas is methane.

Description

10~9699
~he present invention relates to a me-tho'd of producing
hot reducing gas which mainly comprises CO a~d H2 ~d is
desi~ned to be used in reducing oxidic ores a~d particularly
iron ores either directly or by injecting the reducing gas
into a shaft furnace such as a blast furnace.
- It is kno~m to obtain hot reducing gas ~rom hydrocarbo-
naceous fuels ~hich are caused to undergo partial oxidation,
catalytic reforming in the presence of steam, or pyrolisis.
More recentl~, it has been suggested to produce reducing
gas by means of a plasma medium. Reforming reactions are
assisted by the high temperatures to which th0 gas is thus
brou~ht. Such a way of proceeding has the advantage of
obtaining minimally oxidized mixtures of CO and H2, i.e.
mixtures containing very small quantities of C02 and H20~
practically with no formation of soot (non~oxidized carbon
from decomposition of the fuel).
Other methods, i.e. methods without a plasma medium~
do not easily produce such gas mixtures, without the latte~
undergoing very high temperatures of the order of 2000C.
~ese reducing gas may be used, in principle, in ore reducing
processes, particularly for reducing iron ores, either in a
blast furnace or according to a direct reduction process.
Rowever, in a number of cases, and particularly in the
two cases referred to above of direct reduction of iron
oxides or of injection into the shaft of a blast furnace, it
is suggested to use reducing gas whose temperature is not
higher than 1000C to 1100C.
What is required is a method which allows this object
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to be attained by modifying the technique of producing
reducing gas by means of a plasma medium in su.ch a way as
to keep its advantages, that is low oxidation level and
small quantity of soot, which results in a decrease in
its temperature do~m to a esired level with no need for
specifically cooling it, i.e. by removing heat.
It is a well-known fact that, when a mixture of
hydrocarbonaceous fuel and supporter of combustion is fed
to a zone at very high temperature (e.g. 2000C) reforming
reactions such as
C~4 + C02 ~ 2 C0 + 2 H2
CE4 + H20 > C0 + 3 E2
2 C$4 + 2 ~ 2 C0 + 4 H2
easily take place in the direction indicated, without the
need for a catalyst~
~he present invention provides a method of producing
'I hot reducing gas which mainly comprises C0 and H2 and is
suitable for use in reducing oxidic ores, comprising the
sequential steps of:
(a) reforming and partially oxidizing a fluid hydro-
. carbonaceous fuel by reacting the fuel with a gaseous
. oxidant in a plasma medium at appro~imately 2000C,
whereby a high temperature gas comprising a major pro-
portion of C0 and H2 and a minor proportion of C02 and H20
is formed; and
(b) adding a hydrocarbonaceous gas to the high
temperature gas, whereby further reactions occur which
reduce the proportion of C02 a d E20. ~he hot reducing
gas produced is preferably at a temperature of 1000C
to 1100C.
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` 1069699
j The fuel and the gaceous oxidant may advantageously
be pre-heated. ~:
~he gaseous oxidant may comprise steam, C02, pure
ox~gen, or air; ~r residual or non-residual reducing
gas comprising an excess of oxygen in the fo~m of C02
and H20; or blast-furnace throat-gas; or gas from a
direct reduction furnace; or fumes recovered at the
outlet of a combustion furnace (for example fumes from
cowpers).
As far as the fuel is concerned, it is possible to
use a liquid or gaseous (e..g. natural gas) hydrocarbon,
or a gas (such as gas from a coke furnace) including .
C0, H2, and CH4 in sufficient quantities to react with
the gaseous oxidant.
EXA~IE
Fuel oil was reacted with oxygen and water in a
plasma medium at about 2000C, in the following
proportions:- -
1 kg fuel oil : 1 Nm3/02 : 0.18 kg H20,
which gave rise to a gas (at 2000C) wnose composition
was H20, 15%; H2, 36%; C02, 3%; C0, 46%. For each
kilogre~me of fuel oil, 3.3 ~m3 of g3~ were produoed.
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1069699
Methane (CII,;) wa,s added to the gas (0.5 Nm3 C~ per
kilogramme of f~el oil) and the resulting gas (after
reforming reactions had taken place) had the composition :
X20~ 3.6%., H2, 49.6%~ C02 1.4%~ C0, 42.2%~ CH4, 3.2%-
This gas was at 1100C and was produced at the rate of
4.5 Nm3 per kilogramme of fuel oil.
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