U.S. patent number 4,604,215 [Application Number 06/595,821] was granted by the patent office on 1986-08-05 for wet oxidation system.
This patent grant is currently assigned to Kenox Corporation. Invention is credited to Robert P. McCorquodale.
United States Patent |
4,604,215 |
McCorquodale |
August 5, 1986 |
Wet oxidation system
Abstract
A process for oxidizing an aqueous suspension of organic matter
at elevated temperature and pressure includes exposing the organic
matter to an oxygen-containing gas in a reactor for a period
sufficient to reduce chemical oxygen demand of the organic matter
to a predetermined desired level. An aqueous suspension of organic
matter and bubbles of oxygen containing gas is split, rearranged
and combined by an arrangement of vanes within the reactor
core.
Inventors: |
McCorquodale; Robert P. (West
Hill, CA) |
Assignee: |
Kenox Corporation (Toronto,
CA)
|
Family
ID: |
25670337 |
Appl.
No.: |
06/595,821 |
Filed: |
April 2, 1984 |
Current U.S.
Class: |
210/762 |
Current CPC
Class: |
B01F
5/0609 (20130101); B01F 5/061 (20130101); C02F
11/08 (20130101); B01J 19/1875 (20130101); B01J
19/10 (20130101) |
Current International
Class: |
B01J
19/18 (20060101); B01J 19/10 (20060101); B01F
5/06 (20060101); C02F 11/08 (20060101); C02F
11/06 (20060101); C02F 011/08 () |
Field of
Search: |
;210/761-763,748,151,150 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wyse; Thomas
Attorney, Agent or Firm: Sim & McBurney
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A process for oxidizing an aqueous suspension of organic matter
at elevated temperature and pressure by exposing the organic matter
to an oxygen-containing gas in a reactor for a period sufficient to
reduce chemical oxygen demand of the organic matter to a
predetermined desired level, said reactor having a reactor core
housing a static mixer vane arrangement and means for circulating
said aqueous suspension of organic matter over said static mixer
vane arrangement within said reactor core, said static mixer vane
arrangement comprising an arrangement of vanes extending along a
majority of and within said reactor core, said process comprising
operating said reactor at said elevated temperature and pressure
which promotes the oxidation in the aqueous medium of organic
matter with minimal generation of steam, introducing an
oxygen-containing gas into said aqueous suspension of organic
matter; splitting, rearranging and combining the aqueous suspension
of organic matter and bubbles of oxygen-containing gas by the
aqueous suspension of organic matter and bubbles of oxygen
containing gas over said arrangement of vanes within said reactor
core to react said organic matter with said oxygen; withdrawing
treated organic matter from said reactor.
2. A process of claim 1, wherein a plurality of said reactor cores
are provided within said reactor, circulating said aqueous
suspension of organic matter through said reactor cores.
3. A process of claim 2, wherein said reactor cores extend
generally parallel with one another within said reactor, returning
said aqueous suspension along the reactor cores' exterior for
recirculation through said reactor cores.
4. A process of claim 3, wherein said circulating means is located
at one end of the cores for returning said aqueous suspension along
the reactor cores' exterior.
5. A process of claim 1, wherein said aqueous suspension of organic
matter is withdrawn from said reactor after passage through said
reactor core, passing said withdrawn aqueous suspension through
said circulating means located outside of said reactor and
returning said aqueous suspension from said circulating means to
said reactor core for recirculation therethrough.
6. A process for oxidizing an aqueous suspension of organic matter
at elevated temperature and pressure by exposing the organic matter
to an oxygen-containing gas in a reactor for a period sufficient to
reduce chemical oxygen demand of the organic matter to a
predetermined desired level, said reactor being vertically oriented
and having an inner reactor core separated from and surrounded by
an outer reactor chamber where said reactor core communicates at
its upper and lower regions with said outer reactor chamber, said
process comprising operating said reactor at said elevated
temperature and pressure which promotes the oxidation in the
aqueous medium of organic matter with minimal generation of steam,
by means of a pump located in the region of the lower end of said
reactor core circulating continuously said aqueous suspension and
oxygen-containing gas downwardly of said outer reactor chamber and
upwardly of said reactor core, introducing separately an aqueous
suspension of untreated organic matter and an oxygen-containing gas
into the upper region of said outer reactor chamber and below said
reactor core upper region, said untreated organic matter and
oxygen-containing gas are introduced at a temperature and pressure
proximate said operating temperature and pressure, said organic
matter and oxygen mixing and reacting as they flow downwardly to
establish a first reaction zone in said outer reactor chamber, said
reactor core having a static mixer vane arrangement along a
majority of its length, splitting, rearranging and combining the
aqueous suspension of organic matter and bubbles of
oxygen-containing gas by said static mixer as they are circulated
upwardly by said pump to react further said organic matter with
said oxygen to establish a second reaction zone, and withdrawing
treated aqueous suspension of organic matter and gases at a rate at
least equal to the rate of said introduction of organic matter and
gases.
7. A process of claim 6, wherein said upper region of said reactor
core is above said second reaction zone, said process further
comprising exposing upwardly moving organic matter and
oxygen-containing gases to ultrasonic energy waves in said upper
region of the reactor core to break up remaining organic matter and
mix the broken up organic matter with the oxygen-containing gas
bubbles to oxidize further said organic matter thereby forming a
third reaction zone, recirculating at least a major portion of the
material emerging from the upper end of said reactor core.
8. A process of claim 6, wherein said static mixer vanes have an
external surface of a catalyst for oxidation reaction of said
organic matter with said oxygen.
9. A process of claim 8, wherein said catalyst is selected from the
group consisting of manganese/chromium/zinc, ammomium vanadate,
copper oxide, nickel oxide, cobalt oxide, chromium oxide, cerium
oxide, silver oxide; copper oxide/zinc oxide, copper oxide/chromium
oxide/magnesium chromate and nickel oxide/nickel chromate.
10. A process of claim 6, wherein said elevated temperature and
pressure is in the range of 200.degree. C. to 370.degree. C. and 35
to 210 kg/cm.sup.2.
11. A process of claim 6, 7 or 9, wherein a plurality of said
reactors are interconnected in series, said withdrawn treated
aqueous suspension of organic matter and gases from an upstream
reactor being introduced to said outer reactor chamber of a
downstream reactor separately of a fresh supply of heated and
pressurized oxygen-containing gas, and disposing of treated aqueous
suspension of organic matter and gases withdrawn from the last of
said plurality of reactors.
12. A process of claim 6, 7 or 9, wherein said treated aqueous
suspension of organic matter and gases are withdrawn from the upper
region of said outer reactor chamber above the area of said point
of introduction of organic matter and oxygen-containing gas.
13. A process of claim 6, 7 or 9, wherein said treated aqueous
suspension of organic matter and gases are withdrawn from the upper
region of said outer reactor chamber above the area of said point
of introduction of organic matter and oxygen-containing gas,
inducing said treated aqueous suspension of organic matter and
gases as they emerge from said reactor core to flow away from said
reactor core to flow away from the region where such treated
organic matter and gases are withdrawn.
14. A process of claim 6, 7 or 9, wherein said reactor is formed
with a cylindrical reactor core and concentric outer annular
reactor chamber, said pump being located adjacent the bottom of
said reactor core for circulating said aqueous suspension of
organic matter and gases downwardly of said annular reactor chamber
and upwardly of said reactor core.
15. A process of claim 6, 7 or 9, wherein said reactor is operated
on a continuous basis, introducing continuously untreated aqueous
suspension of organic matter and oxygen-containing gas, the rate of
introduction providing a residence time of such organic matter in
said reactor sufficient to reduce the chemical oxygen demand of the
organic matter to the desired level.
16. A process of claim 6, 7 or 9, wherein said reactor is operated
on a batch basis, heating and pressurizing said reactor into the
range of operating temperature and pressure and introducing a batch
of aqueous suspension of organic matter and oxygen-containing gas
proximate the operating temperature and pressure, continuously
introducing oxygen-containing gas until the chemical oxygen demand
of the organic matter has been reduced to said desired level.
Description
FIELD OF THE INVENTION
This invention relates to process and apparatus for the wet
oxidation of organic matter using oxygen-containing gases such as
air.
BACKGROUND OF THE INVENTION
Destructive oxidation of organic materials in an aqueous medium has
been employed because it provides a useful process for reducing the
chemical oxygen demand of organics in water systems. This avoids
the need to de-water the system in order to burn in a fuel system
the organics. British Pat. No. 706,686 discloses a self-sustaining
process for the destructive oxidation of organic materials in an
aqueous medium. The system operates at a temperature above
450.degree. F. and a pressure sufficient to maintain the water in
liquid form so as to cause the organic material to be oxidized.
Such pressures may be in the range of 1400 to 1500 pounds per
square inch and the temperatures may be as high as 625.degree.
F.
Catalysts have been used in the system to catalyze the oxidation
reaction, such as disclosed in U.S. Pat. No. 2,690,425. The system
is operated at temperatures in the range of 100.degree. C. to
350.degree. C. under pressures of between 400 to 2500 pounds per
square inch.
The reactor design for the wet oxidation system has been provided
in many forms, such as disclosed in U.S. Pat. No. 3,870,631. The
reactor is horizontally oriented and has several compartments to
provide a series reactor arrangement. Agitators are used to provide
a rubbing or abrasive contact between the combustible organic
matter and the oxygen over a maximum area by reason of the high
state of movement during agitation by the agitators. The agitators
are power intensive in view of the speeds at which they must rotate
to generate the degree of agitation required in the wet oxidation
process of that patent, e.g. they may be rotated at speeds of 1300
rpm.
Another approach in agitating a liquid system is to use ultrasonic
energy as disclosed in U.S. Pat. No. 4,013,552. Ultrasonic energy
is transmitted to sewage which is at standard temperature and
pressure. This treatment reduces the liquid particle size and
enrobes the reduced water particles with air to enhance the
biochemical oxidation by the aerobic bacteria. However, this patent
does not contemplate the use of ultrasonic energy in the chemical
oxidation of organic matter. Although U.S. Pat. No. 4,003,832
discloses the use of ultrasonic energy in chemical oxidation of
organic matter, this patent requires the use of large
concentrations of ozone in the area of the ultrasonic energy
generator.
U.S. Pat. No. 4,155,848 discloses a vertical reactor tower for use
in the wet oxidation of organic matter. The vertical tower has an
outer cyclindrical vessel with a smaller diameter concentric tube
therein. The introduced organic matter and oxygen are circulated
downwardly of the annular portion of the vessel and upwardly of the
interior of the reactor core. The oxygen is introduced into the
base of the inner tube so that in flowing upwardly it causes a
circulation of the aqueous medium in the system. This requires
considerably increased supply of compressed air to cause the
necessary circulation. The process, therefore, become cost
ineffective because of the high capital and energy intensive system
needed to compress this air. The system is normally operated at
temperatures in the range of 250.degree. C. to 374.degree. C. The
pressure is high enough to maintain the effluent in liquid
phase.
SUMMARY OF THE INVENTION
According to an aspect of the invention, the process for oxidizing
an aqueous suspension of organic matter in reducing the chemical
oxygen demand of the organic matter to a predetermined level is
carried out at an elevated temperature and pressure by exposing the
organic matter to an oxygen containing gas for a sufficient period
of time.
The process is carried out in a reactor having a reaction zone
consisting of a static mixer vane arrangement and means for
circulating the aqueous suspension of organic matter through the
static mixer vane arrangement. The process comprises operating the
reactor at the elevated temperature and pressure which promotes the
oxidation in the aqueous medium of organic matter with minimal
generation of steam. An oxygen containing gas is introduced into
the aqueous suspension of organic matter. The aqueous suspension of
organic matter and bubbles of oxygen containing gas are split,
rearranged and combined in the static mixer as they are circulated
through the static mixer by the circulating means to react the
organic matter with the oxygen. The treated organic matter is
withdrawn from the reactor reducing the chemical oxygen demand to
the predetermined desired level.
According to another aspect of the invention, the apparatus having
the reaction zone consists of the static mixer vane arrangement
with the means for circulating the aqueous suspension of organic
matter through the static mixer vane arrangement. Means is provided
for introducing an oxygen containing gas into the reactor and means
for introducing an aqueous suspension of organic matter into an
area of the reactor separate from where the oxygen containing is
introduced. The static mixer comprises a plurality of vanes
arranged within the reaction zone to split, rearrange and combine
the aqueous suspension of organic matter and oxygen containing gas
bubbles. Means is provided for withdrawing treated organic matter
in aqueous suspension and gases from the reactor.
According to another aspect of the invention, ultrasonic energy
waves may be used in the reactor to further enhance the oxidation
reaction by breaking up already partly oxidized organic matter. In
addition, the static mixer vanes may have at least portions thereof
coated with a catalyst for the oxidation reaction.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings
wherein:
FIG. 1 is a schematic view of the reactor and heat exchanger for
use in the wet oxidation of organic matter and in which the
process, according to this invention, is carried out;
FIG. 2 is a schematic view of an alternative embodiment of the
reactor having a plurality of reaction zones defined therein in
which the process, according to this invention, is carried out;
and
FIG. 3 is a section along lines 3--3 of FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The process and apparatus, according to this invention, is useful
in most wet oxidation applications such as in the disposal of
sewage, slime, sludges and other organic waste including organic
plastics and explosives. The oxidative combustion is controlled, as
carried out under water, where the pressure is sufficient to
minimize the production of steam during the reaction. By use of the
static mixer vane arrangement in the reactor core, the overall
reactor configuration is considerably simplified compared to the
power intensive type such as disclosed in U.S. Pat. No.
3,870,631.
Considering the process as carried out in a preferred embodiment
for the apparatus of FIG. 1, a vertically oriented reactor 10
comprises an outer cylindrical pressure vessel 12 with closed upper
and bottom end portions 14 and 16. According to this construction,
the upper end 14 comprises an outer plate 18 bolted to an annular
ring 20 which is welded to the outer pressure vessel 12. Sealing
material 22 is used in sealingly engaging the outer plate 18 to the
annular ring 20. An ultrasonic probe 24 extends through the plate
14 and is sealingly engaged with the gasket material 22 as it
extends into the reactor 10.
The bottom 16 is similarly sealed with an outer plate 26 bolted to
an annular ring 28 which is welded to the outer vessel 12. A gasket
30 is used in sealingly engaging the outer plate 26 with the vessel
12. A bearing and sealing arrangement 32 is provided for the drive
shaft 34 which drives the vanes 36 of the pump unit 38 which,
according to this embodiment, is located at the bottom portion of
the reactor 13. The seals and bearing arrangement 32 is such to
withstand the temperatures and pressures at which the reactor 10
operates. A pulley 40 is provided on the drive shaft which is
connected by way of appropriate V-belt to a drive motor. The
reactor 10 includes, interior and concentric with the cyclindrical
outer pressure vessel 12, an inner tube 42. The inner tube is
shorter than the outer vessel 12 to define an upper space 44 and a
lower space 46, thereby providing communication between the reactor
core 48 defined in the interior of the inner tube 42 and the outer
annular reactor chamber 50 which surrounds the reactor core.
The circulating pump 38 is located in the lower region 46 with the
vanes 36 extending upwardly into the interior portion 52 of the
inner tube 42. The vanes are so configured to circulate the aqueous
suspension and gases upwardly of the inner core in the direction of
arrows 54. As the suspension and gases emerge from the upper region
56 of the reactor, they flow over the rear portion 58 of the inner
tube in the direction of arrow 60, thus flowing downwardly for
recirculation upwardly of the inner core in the direction of arrow
54.
On start-up of the reactor 10, it is heated to the operating
temperatures and pressurized to the operating pressures. In order
to treat common industrial wastes, the operating temperatures are
normally in the range of 200.degree. C. to 230.degree. C. and
pressures in the range of 35 to 45 kg/cm.sup.2. However in treating
waste from oil recovery systems to thereby generate energy, the
systems may operate at pressures in the range of 210 kg/cm.sup.2
and temperatures in the range of 320.degree. C. in treating waste
from heavy oil and tar sands bitumen recovery systems. The outer
vessel 12 is reinforced and made of a material which can withstand
the operating pressures and temperatures with added safety margin.
Normally the reactor 10 is elevated to the operating temperature by
purging the system with live steam and then pressurized as the high
pressure aqueous waste stream and oxygen-containing gas are
introduced to the reactor. A heat exchanger 62 is used to heat
exchange the hot treated waste liquid and gases with incoming waste
materials and the oxygen-containing gas which may be air. The waste
to be treated is introduced to the heat exchanger 62 via line 64.
The air is introduced to the heat exchanger via line 66 which flows
upwardly of the heat exchanger. The heated waste stream emerges
from the heat exchanger in line 68 and is introduced to the outer
reactor chamber 50 via inlet 70 at the rear of the reactor 10. The
inlet 70 has a nozzle portion which directs the introduction of the
waste stream circumferentially of the annular chamber 50 so that
the aqueous suspension circulates downwardly of the outer chamber
50 in a spiral manner.
The heated air exits the heat exchanger in line 72 and is
introduced at the first location by inlet 74 for mixing with the
downwardly travelling aqueous suspension. Optionally, there may be
a second inlet 76 for introducing additional fresh
oxygen-containing gas to the outer chamber 50 further downstream of
the inlet 74.
The treated waste liquid and gases are removed from the upper
region 44 of the reactor via outlet 78 which passes the treated
liquid and gases downwardly of the heat exchanged via line 80. The
hot waste liquid and gases are heat exchanged with the incoming
untreated waste stream and air. As the waste liquid and gas is
cooled, the gases separate and exit from the heat exchanger via
line 82. The condensed liquids emerge from the heat exchanger via
line 84.
The reactor core 48 includes a static mixer vane arrangement 86
which is secured and remains stationary within the inner tube 42.
The circulating pump 38 circulates upwardly the aqueous suspension
and gases over the vanes 88 and 90 of the static mixer. The vanes
are shaped and configured as shown by the different arrangements of
88 and 90 to split, rearrange and combine the stream. The flow
rates upwardly of the reactor core are such that the organic matter
and bubbles of oxygen-containing gas, which may be air, are
subdivided so as to expose fresh surfaces of the organic matter to
oxygen and further oxidize the organic compounds. The static mixer
vane arrangement extends from the lower region of the inner tube
upwardly of a majority of the inner tube. Above the static mixer is
the upper region 92 which is left vacant.
According to a preferred embodiment of the invention, an ultrasonic
probe 24 is located in the upper region 92. By way of the
ultrasonic energy, the already oxidized particles of organic matter
are further broken up to expose fresh surfaces which are oxidized
by the bubbles of air. The air bubbles may be imploded by the
ultrasonic energy to expose more oxygen to the fresh organic
surfaces in enhancing the oxidation of the organic matter.
The upper end of the inner tube is sloped to provide a lowermost
portion which defines the weir 58. Thus the treated materials flow
over the weir in a direction away from the outlet 78 to enhance the
circulation of the materials. The liquid level in the reactor may
be slightly above the outlet 78 so that the treated organic matter
and entrained gases are removed. Above the outlet, there is the
upper space 44 where some gases may remain, but principally in all
reaction zones within the outer chamber 50, the inner core along
the static mixer and at the ultrasonic probe, there are no vapour
regions.
Thus the reactor 10 provides, according to this preferred
embodiment, three reaction zones. A first reaction zone is provided
in the outer core 50 where the introduced untreated organic matter
is exposed to oxygen at inlets 74 and 76 for the incoming fresh
air. The second reaction zone is defined in the static mixer 86
along its length whereby additional splitting and refolding of the
materials, further oxidation of the organic matter takes place. The
third reaction zone is in the region of the ultrasonic probe 24
which breaks up the remaining oxidized organic matter, particularly
the small organic molecules, to further oxidize the materials to
the extent in forming carbon dioxide and carbon monoxide. It has
been found that produced acetic acid, which is most difficult to
break down in other types of prior wet oxidation systems, can be
broken down by this system.
Violent agitation of the system is avoided in each of the reaction
zones. The circulating pump 38 merely circulates the fluid
downwardly of the outer annular reactor chamber 50 and upwardly
over the static mixer vanes 86. There is no violent agitation in
the area of the pump 38 and the air, as introduced, is at spaces
remote from the vanes of the pump 38.
The static mixer may have a variety of vane configurations which
are readily available in the marketplace. For example, the
"Statiflo" (trademark) motionless mixers as distributed by Statiflo
Inc. provide an acceptable static mixer. Another example is the
static mixer distributed by Koch Engineering Company Inc.
Additional details of static mixers and their applications may be
found in International Chemical Engineering, Volume 22, No. 2,
April 1982, 1977.
By use of the static mixer, the mixing of the components is
accomplished with a minimum of power input, approximately one tenth
of that required to operate the agitating devices of other units
and achieve adequate mixing to oxidize extensively the
materials.
The use of a motionless mixer providing extended surface area along
its length lends itself readily to the use of catalysts for the
oxidation reaction. The surface of the vanes of the static mixer
can be formed of or include catalysts which, at these temperatures
and pressure, catalyze the oxidation reaction. Suitable catalysts
are metallic oxides of copper, nickel, cobalt, chromium, manganese,
platinum, palladium, iron, cerium or silver. Mixtures of such
oxides are useful, such as copper oxide/zinc oxide (50:50), copper
oxide/chromium oxide/magnesium chromate (1:1:.004 by weight) and
nickel oxide/nickel chromate (50:50). Other catalysts include
magnesium sulphate and ammonium vanadate. Another catalyst mixture
includes manganese/chromium/zinc (80/47/20).
The dimensions of the inner tube and the outer vessel are selected
such that with the particular circulation rate of the pump 38, the
flow of the aqueous suspension downwardly of the outer annular
chamber is increased relative to the upward flow through the static
mixer. This increased flow down the outer reaction chamber ensures
that the oxygen-containing gas, as introduced at points 74 and 76,
is entrained in the suspension and moves downwardly with the
aqueous suspension so as to be present in the suspension when
travelling upwardly through the static mixer.
According to a preferred embodiment of the invention in treating
normal organic industrial waste, the dimensions of the inner tube
to the outer tube provides volume ratios in the range of 2:1.
Because of the unique reactor design, there is considerably lower
capital costs in equipment as compared to other arrangements,
higher yields are realized in chemical oxygen demand reduction
compared to other reactor designs. The arrangement, according to
this invention, involves fewer valves and control equipment. The
modular approach to the reactor provides for multiples thereof in
providing series reactors. In arranging for a series of reactors,
the treated waste liquid and gas in line 80 would be introduced to
a downstream reactor corresponding to reactor 10 at inlet 70. Air
would be introduced to the downstream reactor again at point 74 and
76. A plurality of reactors may be so arranged where the treated
waste liquid from each reactor is transferred to the next. The
treated waste liquid and gas removed from the last reactor in the
series would then be returned through the heat exchanger. Multiples
of reactors may be used in the circumstances where extended
oxidation reactions are required to fully reduce the chemical
oxygen demand in the introduced waste liquid.
The use of ultrasonic energy in association with a multiple reactor
system provides additional benefits. The use of the ultrasonic
energy to break up the organic matter, as it emerges from the
static mixer reactor zone, provides fresh surfaces for oxidation
which when transferred to the downstream reactor, is contacted with
fresh oxygen containing gas to expedite the oxidation of the broken
up organic materials in the downstream reactor. It is appreciated
that a wide range of ultrasonic frequencies may be used, such as
from 10 kilohertz to 100 kilohertz.
The apparatus may be operated on either a batch or continuous
basis. For a batch basis, the reactor 10 is initially heated to the
operating temperature by use of live steam which may be introduced
via inlet 70 and removed via outlet 78. Once the reactor is up to
operating temperature, the aqueous suspension of organic matter is
introduced via inlet 70 at the operating pressure until the
predetermined batch volume of aqueous suspension is introduced to
the reactor. The heated air is introduced at operating temperature
and pressure via inlets 74 and 76 to commence the oxidation of the
organic matter. The air is continuously introduced during the
operation of the apparatus until the chemical oxygen demand of the
organic matter is reduced to a desired level. At that time, the
reactor is purged of the treated material in preparation for
treating the next batch or shutdown.
When the reactor 10 is operated on a continuous basis, the aqueous
suspension of organic matter and oxygen-containing gas are
introduced at rates which provide a residence time for the organic
matter in the reactor to reduce the COD (chemical oxygen demand) to
the desired level. The treated waste liquid and gases are
continuously removed from outlet 78 in the manner previously
discussed.
The alternative embodiment for the reactor design is schematically
shown in FIG. 2. The reactor 100 comprises an outer shell 102 only
the lower section of which is shown. In view of the prior
discussion of the complete reactor of FIG. 1, the upper portion
would be similar with respect to the location of means for
withdrawing treated organic matter from the upper region of the
reactor along with location of an ultrasonic probe above the
reactor cores 104, 106 and 108 which are positioned within the
reactor shell 102 as shown in the section of FIG. 3. The reactor
tubes 104, 106 and 108 are very similar to the reactor tube of FIG.
1. By providing a multiplicity of the reactor tubes in the reactor
100, variations on the circulation can be achieved employing a pump
which may be located either internally or externally of the reactor
100. Each reactor tube 104, 106 and 108 has corresponding tubular
wall portions 110, 112 and 114. A static mixer vane arrangement
generally indicated at 116 in tube 104 is located in each of the
tubes to define a corresponding reaction zone. The aqueous
suspension of organic matter and oxygen-containing gas are
introduced to the reactor 100 in a manner similar to that with the
reactor 10 of FIG. 1. The flow of the material, according to this
embodiment, is upwardly of each of the reactor cores 104, 106 and
108. By arranging the reactor cores contiguous one another and
surrounded by the reactor shell 102, three discrete and independent
channels 118, 120 and 122 are provided. The material overflows
these tubes and flows downwardly of the reactor via the channels
118, 120 and 122. This circulation is induced by pump 124 which
removes the downwardly flowing organic material in suspension via
the respective outlets 126, 128 and 130. The outlets, in
communication with conduits 132, 134 and 136, transfer the
materials to the inlet side 138 of the pump 124. The pump 124 is
driven by motor 140 connected by a drive shaft 142. The pump has a
single outlet 140 which is connected to a manifold 142 consisting
of a cage network 144 which divides the output of 140 into three
outlet portions 146, 148 and 150. The outlet portions extend into
the respective tubes as shown in FIG. 3. By circulating pump 124
located exterior of the reactor 100, a circulation of the aqueous
suspension of organic matter and oxygen-containing gas is achieved
without violent agitation at the base of the reactor 100. Depending
upon whether the reactor 100 is operated on a batch or continuous
basis, the flows are prescribed so as to provide the necessary
residence time of the organic matter in the reactor 100 to achieve
the desired reduction in chemical oxygen demand of the materials
being treated.
As with the static mixer vane arrangement of the reactor of FIG. 1,
the static mixer vane 116 in each reactor tube may be coated with
suitable catalysts for the oxidation reaction. An ultrasonic probe
may be located above the grouping of three reactor tubes in the
upper region of the reactor or a probe provided for each of the
tubes similar to the manner shown in FIG. 1. It is understood in
keeping with the alternative embodiment of FIG. 2 that many other
configurations internally of the reactor may be provided to achieve
a plurality of reaction zones effected by the static mixer vane
arrangements.
The process of the invention has been carried out in the reactor
design of FIG. 1 having two towers in series using a sugar water
test stream having a 7% COD. The reactor system was operated on a
continuous basis with a reactant residence time of one hour.
Samples of treated oxidized stream were collected. The collected
samples were analyzed to reveal at steady state condition a COD
reduction of 91%. With the ultrasonic probe activated, a further 5%
reduction of COD was achieved to realize an overall COD reduction
of 96% during steady condition. It is appreciated that the use of
an appropriate catalyst of the type previously discussed would
further increase the overall percentage COD reduction.
The apparatus and process of this invention is capable of operating
at the reduced temperatures and pressures for a wet oxidation
system as compared to the substantially higher temperatures and
pressures used in many of the prior art systems. In view of the
unique aspects of the reactor, the system is considerably more
economic and compared to some systems will cost one third of the
prior systems. By using the modular concept for the reactors,
larger volumes of waste material can be processed by simply adding
more units to the system. The modules can be inventoried, thereby
shortening delivery time. Heat exchange within the reactor is
facilitated by the design of having an inner reactor core
surrounded by an outer reactor chamber. The downflow section of the
reactor removes heat from the energy created in the upflowing
material of the central core. Thus less demand is placed on the
heat exchanger in heating the waste materials to be introduced to
the reactor. The circulation pump for use in circulating the
aqueous medium requires about 10% of the power required to drive
the agitators of the more complex, multi-chamber systems, such as
disclosed in U.S. Pat. No. 3,870,631.
Although preferred embodiments of the invention have been described
herein in detail, it will be understood by those skilled in the art
that variations may be made thereto without departing from the
spirit of the invention or the scope of the appended claims.
* * * * *