Furnaces – Process – Treating fuel constituent or combustion product
Reexamination Certificate
2001-02-21
2002-06-04
Esquivel, Denise L. (Department: 3749)
Furnaces
Process
Treating fuel constituent or combustion product
C110S238000, C110S348000, C110S233000, C110S345000, C432S180000, C431S175000, C431S215000, C431S005000, C431S007000
Reexamination Certificate
active
06397766
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for incinerating organic waste water and volatile organic compounds and a method therefor and more particularly, an evaporative and regenerative waste water incineration system for economically and efficiently removing the organic compounds by oxidizing the waste gas generated from evaporated waste water including the organic compounds using a regenerative thermal oxidizer.
2. Description of the Related Art
Generally, volatile organic compounds including a total of hydrocarbon compounds are materials generally created in chemical factories, waste water treatment plants and during the printing works in car manufacturing factories, and cause the photochemical smog, warming of the Earth, destruction of ozone layer in the stratosphere, and so on, and very fatally toxic to human body such as developing cancer, etc. and the human environment.
The known techniques to treat the volatile organic compounds are incineration, absorption for removal, adsorption, cooling condensation, biological treatment and layer separation methods, etc. And especially regenerative thermal oxidation method is widely used.
A Regenerative thermal Oxidizer (now referred to as RTO) is operated by incinerating the waste gas including the volatile organic compounds, and collecting the heat generated during the incineration through a ceramic filler material thereby greatly reducing the operation expenses of the system, and minimizing an installation space. The treatment efficiency of the RTO is very high over 99%, and a second contamination is little, and if the concentration of the volatile organic compounds in the waste gas is over 300 vppm, a supplementary supply of energy is not necessary by using the incineration energy from the system, itself.
Describing its operation more detail, the RTO maximmably collects the waste heat energy discharged from the waste gas and turns the energy to preheat introduced gas. For this purpose, it employs ceramic which is directly heated and cooled for its regeneration instead of a typical heat exchanger.
That is, when using a shell & tube type heat exchanger or a plate type heat exchanger for the heat exchange of gas, the temperature difference of the gas between the inlet and the outlet of the heat exchanger is 100 to 200° C. thereby limiting the usage. However, the ceramic has its maximum service temperature by 950° C., and when regenerating, the temperature difference between the inlet and the outlet can be reduced to 20° C. thereby achieving 98% of the heat recovery rate.
FIGS. 1 and 2
show the operation states of forward/rearward direction in the typical RTO. After heating a furnace placed between ceramic layers
1
,
2
disposed on the left and right sides of the RTO to be appropriate for the operation of the furnace at the start of the operation, the waste gas is introduced.
The waste gas is preheated up to the temperature of the furnace passing the ceramic layer
1
, and the organic gas in the waste gas starts its oxidation and while passing through the furnace for a certain time period, all the organic compounds are oxidized at a temperature of about 800° C.
At this time, while the treated gas at a high temperature passes though the ceramic layer
2
, the gas discharges out almost all heat so that the gas is cooled just down to a temperature of 10 to 30° C. higher than the temperature of the inlet in the ceramic layer
1
.
At this time, after a while, the inlet path for the gas is switched as shown in FIG.
2
.
The switching operation shown in
FIGS. 1 and 2
is repeated with a certain interval of time (about 1.5 to 3 minutes) thereby minimizing the energy for the gas incineration.
The system shown in
FIGS. 1 and 2
is called a 2-bed type RTO, and the 2-bed type RTO is an economical system. However, not-treated gas existing on the ceramics of the RTO during the switching of the valves and other not-treated gas passing through the furnace of the RTO in a roundabout way are discharged at a time during the switching of the valves so that the removal efficiency of the whole organic compounds is around 95% due to the discharge of the not-treated gas.
To address this problem, a 3-bed type RTO or a gas buffer can be used. The case of using the buffer is shown in FIG.
3
.
That is, the incineration system comprises an RTO, a gas buffer and a blower.
The operation of forward direction by using the buffer
12
is described as follows:
The not-treated waste gas from the processes is introduced into a ceramic layer
3
on one side of the 2-bed type RTO with a valve
5
open. The introduced gas at room temperature is heated up to 800° C. for oxidation by the regenerative ceramic so that the organic volatile compounds (VOC) in the air is oxidized. The temperature of the gas after oxidation is about 830° C. which is 30° C. higher than that of the regeneration ceramic. The gas at this temperature is cooled down passing through a ceramic layer
4
at the other side. Most of the heat is transmitted to the ceramic layer
4
thereby increasing the temperature of the ceramic
4
. The cooled-down gas passes through a valve
8
, the blower
13
, and a valve
10
in turn and is discharged to the atmosphere.
As described above, during the operation of the forward direction, the valve
5
,
8
are open and the valves
6
,
7
are closed. A buffer valve
9
at the front of the gas buffer is closed.
While the operation of the forward direction is maintained for about
2
minutes, the ceramic of the ceramic layer
3
preheats the gas and is cooled down. The ceramic layer
4
absorbs the heat of the heated gas and is heated. At this time, the introduction of the gas is started with the operation start of the rearward direction.
The operation conditions in the forward direction and the rearward direction are the same, and the introduction direction of the waste gas is changed to the ceramic layer
4
on the other side. There exists a switching time between the operation of the forward/rearward direction.
Since the valves
5
,
8
of the rearward direction are closed and the valves
6
,
7
are open, not-treated waste gas present between the ceramic layer
3
and the valve
5
passes through the valve
7
by the blower
13
, and is discharged through the valve
10
to the atmosphere.
To prevent this, by using the gas buffer
12
, the buffer valve
9
is open, and the valve
10
of a pipe leading to a smokestack is closed.
Therefore, the not-treated gas is collected into the gas buffer
12
through the buffer valve
9
, and the treated gas on the upper side of the gas buffer
12
is directly discharged out of the smokestack.
After the switching time, the gas path at the back side of the RTO is turned to the discharge pipe, and the buffer valve
9
is closed.
There is provided a diaphragm inside the gas buffer
12
to minimize the mixing of the introduced gas. The lower side of the buffer is connected to the inlet line for not-treated gas, and the upper side of the buffer is in flow communication with the discharge pipe to the atmosphere. The not-treated gas stored in the buffer is automatically circulated to the front of the RTO with the valve
11
open, and the inside of the buffer is changed with a gas introduced from the atmosphere until the next switching time.
Meanwhile, in chemical factories, the waste water treatment and cars manufacturing companies, large amount of other kinds of waste water beside the above organic compounds is generated. When the concentration of the organic compounds in the organic waste wate is low (e.g., COD lower than 5,000 ppm), it is treated with active oil treatment, but in case of high concentration (e.g., COD higher than 10,000 ppm), the active oil treatment is not sufficient and not economical so that it is treated by incinerating.
At this time, the waste water incineration using a typical incineration furnace is operated by introducing the waste water including organic compounds (VOC included) into the incineration furnace, and oxidizing the organic compounds in the
Cantor & Colburn LLP
Esquivel Denise L.
Key Engineering Co., Ltd.
Rinehart K. B.
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