STATIC FURNACE FOR THE THERMAL DECOMPOSITION OF SOLIDS AT HIGH TEMPERATURES BY THERMAL RADIATION

FOUR STATIQUE POUR LA DECOMPOSITION THERMIQUE DE MATIERES SOLIDES PAR IRRADIATION THERMIQUE A HAUTE TEMPERATURE

English Abstract

The thermal radiation furnace, according to the present invention comprises
the following main parts: a solids feeding system; a solids pre-heating system
and at the same time a gas/vapor cooling system; a reactor for the thermal
radiation thermal decomposition; a solid products of the reaction cooling
system and at the same time a solid thermal energy recovery system; a solid
products discharge system; a furnace heating system to the thermal radiation
temperatures; a gas/vapor collecting system for the gases/vapors formed in the
reaction; and a flue gases heat recovery system when combustion is the energy
source for the thermal radiation.

French Abstract

Four à irradiation thermique comportant principalement un système d'amenée de matières solides, un système de préchauffage de ces matières solides, et de refroidissement des gaz et vapeurs engendrés, un réacteur de décomposition thermique par irradiation thermique, un système de refroidissement des produits réactionnels solides, et de récupération de l'énergie thermique des produits solides, un système d'évacuation des produits solides, un système de chauffage servant à porter le four à une température d'irradiation thermique, un système de récupération des gaz et vapeurs engendrés au cours de la réaction, et, au cas où la source d'énergie de l'irradiation thermique serait la combustion, un système de récupération des gaz brûlés.

Claims

"CLAIMS"
1. Static furnace for the thermal decomposition of
solids at elevated temperatures by thermal radiation,
characterized by the fact that it comprises the following main
parts: a system to feed the solids into the furnace; a system
for preheating the solids and to cool the gases/vapors formed;
a reactor for the thermal radiation thermal decomposition; a
system to cool the solid products and to recover energy from
the solid products of the reaction; a system to discharge the
solid products; a furnace heating system to heat the furnace
to the temperatures of thermal radiation; a gas/vapor
collecting system for the gas/vapor formed in the reaction; a
flue gas energy recovery system when combustion is the source
of energy for the thermal radiation.
2. Furnace according to the claim 1., characterized by
the fact that the solids are fed on the upper part of the
furnace and their movement down to their removal from the
furnaces, is made by action of gravity, by means of the
solids storage (1), in the uppermost part of the equipment,
which discharges the solids through a mechanism of feeding
the furnace (2).
3. Furnace according to the claim (1)., characterized by
the fact that the heat to heat up the ceramic plates (4) is
supplied by burners (3) assembled in chambers (5), which are
completely tight and isolated from the reactions/reaction
zones of the furnace.
4. Furnace according to the claim 1., characterized by
the fact that the cooling is made by a waterwall system, in
the production of hot water and/or the production of steam, in
which tuber (6) in the vertical position, formed with fins or

compounding a waterwall, are filled up with water, coming from
a lower water header (8b) and receiving the heat from the
solid products inside the furnace, by thermal radiation, heat
up the water and/or generate steam which is then diverted to
the upper hot water or steam header (8a).
5. Furnace according to the claim 1; characterized by
the fact that the solids, continue their motion down by action
of gravity, allowed by a discharge mechanism (7) of the
solids.
6. Furnace according to the claim 1., characterized by
the fact that the flue gases, formed in the combustion
chambers, are collected in a channel (9) in the furnace and,
after pre-heating the combustion air, are vented to the
atmosphere.

Description

r ~ ~ ~ ~
- 21 94675
USTATIC FURNA OE FOR THE THERMAL DECOMPOSITION OF SOLIDS AT
HIGH TEMPERATURES BY THERMAL RADIATION~.
5 Techni~l Fiel~
The present invention refers to a static furnace, more ~
specifically to a static furnace for the thermal decomposition ~n
of solids at high temperatures by thermal radiation. ~
Sllmm~ry of the inv~ntion
The furnace of the present invention is characterized by i~
the utilization of essentially thermal radiation as the source
of the heat needed in the process. Hence, the direct contact
with the hot gases is avoided, these hot gases being generated
in the combustion of fuels in the furnace environment, also
avoided is the cont~mi~tion of the CO2 or of the sulfur
(vapor) formed in the thermal decomposition of the limestone
or of the pyritic substances, and of the solid residue formed
in the furnace.
The source of thermal radiation can be electric energy,
combustion of fossil andjor renewable fuels, externally to the
furnace environment and other forms of heating the furnace
chamber by thermal radiation.

21q~675
~rief nescrlption of the nr~w;~gs:
- Figure 1 represents the front elevation of a static
furnace for the thermal decomposition of solids at high
temperatures by thermal radiation of the present invention.
Figure 2 represents a back elevation of the furnace of
the invention.
Figure 3 represents the plant of the furnace of the
invention.
Figure 4 represents a section according to the plane
A - A in figure 3.
Figure 5 represents a section according to the plane
B - B in Figure 4.
C~
15 Disclosllre of the Inv~nt'on C
This furnace is intended for the decomposition of solids
at a temperature range from 500~C to 1200~C, for, for C~
instance, limestone calcination (CaCO3), to produce a lime
(CaO) of high reactivity and pure carbonic gas (CO2), at 100%,
20 or the thermal decomposition of iron and copper pyrites, such
as the pyritic rejects of coal, and the pyritic concentrates
of iron and copper, to produce sulfur 100~~ pure and a residue
of iron sulfide of industrial application.
The thermal radiation furnace, according to the present
25 invention comprises the following main parts:
a solids feeding systemi
a solids pre-heating system which is also used in the
cooling of the formed gases/vapors;
a reactor for the thermal decomposition by thermal
30 radiation;
a cooling system for the solid products of the reaction
and for the solids thermal energy recovery;

o 3
3 2! 94675
a system for the discharge of the solid productsi a
system for the heating of the furnace to the temperatures of
- thermal radiation;
a system to collect the gas/vapors formed in the
reaction; and
a system to recover the energy of the flue gases
whenever this is the source of energy for the thermal
radiation.
Sol;~.s Fee~i ng Syst~m
The solids are fed through the top of the furnace and ~a
are moved in their path by gravity action until their ~e...~v~l
from the furnace. A feeding hopper 1, silo or other means to
store the solids, in the highest part of the assembly, o
discharges the solids through a rotating valve 2, for example, O
or other feeding mechanism to the furnace, which defines O
tightness, preventing the gases/vapors formed in the
environment to escape. C~
Soli~ pre-he~t; ng ~n~ g~ses/v~pors cool~ ng syst~m
The solids are fed to the furnace at ambient temperature
and they require to be heated up to the process temperature of
the thermal decomposition, in the range 500~C to 1200~C. On
the other hand, the gases/vapors formed in the thermal
2S decomposition which occurs in the reactor by thermal radiation
being in the range of temperatures between 500~C and 1200~C,
must be cooled down to temperatures suitable to their recovery
and utilization in the following steps.
Therefore, the solids pre-heating takes place
simultaneously to the gases/vapors cooling in the upper
regions of the furnace, where the solids descend by gravity
and the gases/vapors rise in counter-flow and in direct

2194675 PC~ R ~ 500003~
contact with the solids, thus producing the desired effects.
Once heated to the desired temperature of operation, the
- solids enter the thermal decomposition reaction zone, which i9
strictly maintained at this defined temperature, rigorously
controlled by the heating sources of those thermal radiation
surfaces. The downflow in the reactor is cauged by the gravity
action. The solids remain in this reaction zone the necessary
time for their complete conversion and the production of the
desired products, that is, the regidence time which i8 ~0
controlled by the solids movement by gravity through a
mechanism of solids motion at the bottom of the furnace. To
keep the quality or the purity of the gas/vapor formed, a ~
slight overpressure is maintained in the furnace to prevent ~n
the contamination of the furnace atmosphere by external O
gases/vapors. Three reaction zones are shown in the figures. O
The heat to heat up the ceramic plates 4 is provided by O
burners 3 located in completely isolated chambers 5 from the
reactions/reaction zones of the furnace to avoid the C~
contamination of the reaction products with the combustion
products of the fuel and of the excess air. The chamber walls,
where the burners are installed, are vertical and the
refractory plates will be heated up to transfer the heat
received via combustion to the solids (limestone or pyrites,
pending upon the application) by thermal radiation.
The figures present four chambers and twelve burners
each chamber, as an example. The number of burners for maximum
energy efficiency will be defined as function of the flame
intensity, shape and temperature.
Soli~ Pro~llcts of th~ re~ctio~ cooling systPm ~n~ the sol i~R
therm~l ~nergy recovery.
After completion of the thermal decomposition reaction,

- 2194675 Fcil~R ~ ~3000~3~JD
s
the solids in the temperature range 500~C - 1200~C will be
cooled to temperatures suitable for their handling, discharge
~ and/or further utilization in other process steps downstream
the furnace. The heat recovery from the solid products with
their consequent cooling, can be made, for example, also by
thermal radiation to a system of water cooled wall, to produce
hot water and/or steam. Such water wall is similar to those
existing in boilers in which the tubes 6 in a vertical
position, united by fins or composing the waterwall, are
filled up with water, from a lower water header 8b and
receiving the heat of the solid products within the furnace,
by thermal radiation quantity, the water is heated up and/or
steam is produced which is guided then to the upper hot water
or steam header 8a. In this system, the solids follow their ~
movement downwards by the action of gravity, allowed by a 0
mechanism, for example, rotary valves 7 actuated by low energy 0
consumption motors at the lowest part of the furnace or by an
endless screw, which at the same time, makes the sealing and C~
tightness of the furnace against the intake of air and/or
other gases to the interior of the furnace, which would
contaminate the desired gases/vapors and/or solid products.
Hence, the same heat transfer mechanism is used, that is, the
thermal radiation, to supply the heat of reaction of thermal
decomposition, in the reactor, and for the thermal energy
recovery and cooling of the reaction solid products.
Another way to recover the thermal energy contained in
the solids and their simultaneous cooling, can be to send the
solids to an air tight compartment, a silo for example, with
double sealing and send air into it, cooling the solids and
heating up the air which would serve as combustion air to the
fuel burners.

21 94675 ~l18R 9 ~~ ~~ ~3~
nisch~r~e of Soli~ Pro~l~cts ~yRtem.
Once the solids are cooled, these reaction products are
discharged from the furnace, by gra~ity, through the rotary
valve 7, or endless screw, to the desired site.
-
~ting of the fllrn~ce to th~ Th~rm~l RA~iAt;nn T~m~er~tllr~cSyst~m
To reach the temperatures which are needed to the
conduction of the process by thermal radiation, the external
10 source of heat to the furnace surfaces can be electric energy ~,
or any other, for example, the burning of fossil fuels or C3
renewable energy, for example, in burners localized in
compartments, adequately designed, to optimize the heating '~
process to the walls/surfaces of the furnace. Those burners
and the burning compartments must be in a sufficient num.ber O
for the desired production rate, and their specification is a O
function of the temperature to be reached for the reaction ~
process to take place. The utilization of the temperature and C~
the flame radiant surface of the burners must be optimized,
for the desired heating of the surfaces/walls of the furnace.
G~ Collect;ng/V~por Collecti ng Syst~m
The gas/vapor of interest, formed in the reaction of
thermal decomposition, should be recovered under conditions of
their further utilization. An induction blowing system,
downstream the furnace, defines the needed conditions to
remove that gas/vapor. Care should be taken that the gas/vapor
be at a temperature above its condensation at the exit to the
furnace, or a partial condensation of one of its components,
or above the dew point if it is a mixture of gases/vapors.
The gas/vapor formed, after its cooling and pre-heating
of the solids before the reaction, enters a gas/vapor

21 94675
collector/header, at the uppermost part of the furnace, from
where it is removed from the furnace. The collecting system
for the gas/vapors must maintain a slight overpressure in the
furnace atmosphere, to avoid its cont~m;n~tion with
5 gases/vapors from outside.
Fll~e ~ es ~nergy Recovery .~ystPm
One of the possible external sources of heat, for
heating of the surfaces/walls of the furnace to the
10 temperature of radiation for the process, is the combustion of -~
fossil or renewable fuels, liquid, with specially selected
burners for the desired application, so that the fuel energy aU
use will be optimized, by means of the high temperature of the
flame and of its surface, and of the temperature of the flue
15 gases. O
The burners are placed in the front part of the furnace ~
in compartments specially designed for this application, in an o
adequate number to reach the temperature of the surfaces/walls G~
of the furnace, suitable to the process. The flue gases are C~
20 removed for example, from the rear part of those compartments
and, might be used, in conventional equipments already
available in the marketplace, for the pre-heating of the
necessary air to the combustion which was itself the source of
these flue gases.
The electric energy as source of external heat could
only find practical application in those economic situations,
in which, for example, the electric energy is cheap or can be
generated at the site at low costs, or even, close to the
furnace.
The figures present the typical configuration of the
thermal radiation furnace, in which the several parts which
make it, or its systems can be easily identified. The

8 PCTI~R 9 50 ~~ 03 ~,6
dimensions are typical and will depend upon the process and
its characteristics, such as: size of the solid particles,
- process temperature, external source of heat, nature of the
formed products, level of the energy recovery desired, and of
the nature and characteristics of the solid particles.
The flue gases produced in the combustion chambers are
collected in a ~h~nnel 9 in the furnace, and, after pre-
heating of the combustion air, the gases are vented to the
atmosphere.
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Representative Drawing