Combustion – Heated line section feeds flame holder – Distinct exhaust products line heats feed line
Reexamination Certificate
2002-05-10
2003-04-15
Bennett, Henry (Department: 3743)
Combustion
Heated line section feeds flame holder
Distinct exhaust products line heats feed line
C431S011000
Reexamination Certificate
active
06547555
ABSTRACT:
TECHNICAL FIELD
This invention relates to a regenerator for regenerative combustion burner, particularly, to a regenerator for regenerative combustion burner which has a long operation life, a capability of stable and high yield heat recovery during an extended term, and a possibility of realizing a reduced pressure loss.
BACKGROUND ARTS
Now, referring to drawings, the regenerative combustion burner will be explained by an example where the regenerative combustion burners are installed in the heating furnace.
FIG. 1
is a schematic sectional view of the heating furnace that the regenerative burners are installed. In
FIG. 1
, the numeral
1
denotes a heating furnace; the numerals
2
a
,
2
b
denote paired regenerative burners, respectively, wherein the paired burners are arranged on the furnace wall and face each other; and the numeral
3
a
,
3
b
denote a regenerator, respectively, wherein each regenerator is established at the regenerative burner
2
a
, or
2
b
. The regenerators
3
a
and
3
b
are preferably to have a large specific surface, and are generally made of plural honeycomb structure bodies. The numeral
4
a
and
4
b
denote a fuel shut-off valve respectively, and pressurized fuel is supplied from a fuel supply source which is not shown to burners
2
a
and
2
b
at a predetermined flow rate, while these valves have opened. The numeral
5
a
and
5
b
denote a combustion air valve respectively, and pressurized air is supplied from air supply source which is not shown to burners
2
a
and
2
b
at a predetermined flow rate, while these valves have opened. The numeral
6
a
and
6
b
denotes a flue gas valve respectively, and the flue gas (hereinafter, referred as “furnace internal gas”) which has passed through the regenerator
3
a
and
3
b
is drawn at a predetermined flow rate by an exhaust blower which is not shown, and it is discharged to the atmosphere, while this valve has opened.
In
FIG. 1
, when, for example, one burner
2
a
is in the fired condition, the fuel shut-off valve
4
a
is opened in order to supply the fuel thereto. And, the combustion air valve
5
a
is opened and the flue gas valve
6
a
is closed in order to push the air into one regenerator
3
a
. The air which has passed through the regenerator
3
a
, by taking a heat from the regenerator, becomes high-temperature tempered air, and then, it is supplied to the burner
2
a.
At the same period, in the other burner
2
b
, both of the fuel shut-off valve
4
b
and the combustion air valve
5
b
are closed, and flue gas valve
6
b
has opened. The furnace internal gas is drawn from burner
2
b
, and it is exhausted by the exhaust blower, after it passes through the regenerator
3
b
so that its heat is stored to the regenerator
3
.
In the case of regenerative combustion in the heating furnace
1
using above mentioned regenerative burner
2
a
and
2
b
, alternate combustion which alternately switches the combustion burner
2
a
and
2
b
every the fixed time is done.
When the combustion is changeover and the other burner
2
b
is in the fired condition, the combustion fuel shut-off valve
4
b
and combustion air valve
5
b
are opened together and the flue gas valve
6
b
is closed so as to supply the air to the other regenerator
3
b
. The air which passed through the regenerator
3
b
being in high-temperature absorbs heat from the regenerator
3
b
, and it becomes the high-temperature tempered air to be supplied to the burner
2
b.
In the meantime, in the burner
2
a
, the fuel shut-off valve
4
a
and combustion air valve
5
a
are closed together, and the flue gas valve
6
a
is opened, and thus the furnace internal gas is drawn from burner
2
a
, and it is exhausted by the exhaust blower, after it passes through the regenerator
3
a
so that its heat is stored to the regenerator
3
a.
At a separate pair of burners
2
a
1
,
2
b
1
, which are adjacent to the foregoing paired burners
2
a
,
2
b
, in the longitudinal direction of the furnace, a similar alternate combustion is done. However, the timing of the combustion is different. That is to say, when the burner
2
a
is in combustion, the adjacent burner
2
a
1
is in heat storage condition.
Generally, as a material of the regenerator, ceramics such as alumina and cordierites, etc. are used. The life of the regenerator is greatly changed by temperature of the flue gas and use environments such as the existence of the metal dust in the flue gas. When the choice of material for the regenerator is improper, therefore, fuse or cracking of regenerator may be happened and/or clogging of regenerator may be caused, which are followed by the drastically shortened lifetime of regenerator, and at worst led into the condition of inoperative due to the reduced heat-recovery and the heightened pressure loss.
Especially, in case of the alumina, that has the alumina purity of about 97% and the porosity of over 30% is usually used. Thus, in case that the high-temperature exhaust gas involves metal dust and being in amply high temperature, the fuse of regenerator can be happened by the reaction with the metal dust, and which is followed by the inoperative result. In addition, the life of the regenerator is greatly affected by alumina purity and porosity. Incidentally, the porosity showed the volume ratio of the pore in the material.
When comparing alumina with cordierite, the price of the alumina is generally higher than that of the cordierite. Further, as the purity goes up, and as the porosity goes down, the alumina tends to costlier.
The present invention, therefore, aims to provide a regenerator for the regenerative combustion burner capable of maintaining a stable heat recovery and low pressure loss in the long term, in keeping with low cost and by adopting an optimum construction, after clarifying the durability of alumina under a given alumina purity, given porosity, given atmosphere temperature and given condition for existence or nonexistence of the metal dust, or after clarifying the working condition of cordierite under a given atmosphere temperature and given condition for existence or nonexistence of the metal dust.
DISCLOSURE OF THE PRESENT INVENTION
The first invention is characterized by the fact that, in a regenerator made of the materials each comprising alumina as a main ingredient, wherein the regenerator is used in a regenerative combustion burner being fired with alternately and repeatedly operations of heat storage by the passage of high-temperature flue gas in a fixed time and heating of combustion air by passage of the combustion air in a next fixed time; and the regenerator is used under the condition that the aforesaid flue gas includes metal dust;
the alumina purities in the materials for the regenerator are lowered in the order, the high-temperature, medium-temperature and low-temperature parts of the regenerator.
The second invention is characterized by decreasing the porosity of the aforesaid high temperature part in comparison with the porosity of the medium temperature part.
The third inventions is characterized by the fact that, in a regenerator made of the materials each comprising alumina as a main ingredient, wherein the regenerator is used in a regenerative combustion burner being fired with alternately and repeatedly operations of heat storage by the passage of high-temperature flue gas in a fixed time and heating of combustion air by passage of the combustion air in a next fixed time; and the regenerator is used under the condition that the aforesaid flue gas includes metal dust;
the alumina purity in the material for the high-temperature part of the regenerator where the flue gas is exceeding 1200° C. is not less than 98%, that for the medium-temperature part of the regenerator where the flue gas is exceeding 1100° C. and not higher than 1200° C. is 95%, and the material for the low-temperature part of the regenerator where the flue gas is not higher than 1100° C. is cordierite.
The fourth invention is characterized that the porosity in the high-temperature part is not more than 20%, and the porosity in
Kasai Yoshiyuki
Mori Isao
Sudo Jun
Suzukawa Yutaka
Basichas Alfred
Bennett Henry
Frishauf Holtz Goodman & Chick P.C.
NKK Corporation
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