Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Including external recycle loop
Reexamination Certificate
1999-03-11
2001-11-27
Knode, Marian C. (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Including external recycle loop
C422S129000, C422S139000, C422S140000, C422S145000, C422S147000, C422S231000, C588S253000
Reexamination Certificate
active
06322761
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
1. Field of the Invention
This invention relates to a reactor for use in a system for decomposing organic oil or fat containing PCB (polychlorobiphenyl) and thereby making it nonpoisonous. More particularly, it relates to a PCB decomposition reactor for mixing PCB with water, an oxidizing agent and sodium hydroxide and effecting its thermal decomposition at high temperature and under elevated pressure.
2. Description of Related Art
FIG. 3
illustrates an example of a conventional reactor for use in PCB decomposition system. In this reactor, a feed pipe
23
for feeding a mixture
22
of water, PCB, mineral oil and sodium carbonate to a hollow reaction vessel
21
is connected to the lower part of its side wall. Moreover, reaction vessel
21
is equipped with pipes
24
and
25
which connect the upper part of its sidewall and feed pipe
23
in flow communication relationship, and a circulating pump
26
for agitating purposes is installed between pipes
24
and
25
.
An outlet pipe
28
for supplying the reaction fluid to a cyclone separator
27
is provided at the top of reaction vessel
21
. The top of cyclone separator
27
is equipped with a discharge pipe
29
, which is connected to the equipment constituting the downstream side of the PCB decomposition system. The bottom of cyclone separator
27
is equipped with a recirculation pipe
30
, the other end of which is connected to reaction vessel
21
. Moreover, a gas supply nozzle
32
for supplying air or oxygen
31
is connected to the bottom of reaction vessel
21
.
When the PCB decomposition reactor having the above-described construction is operated, reaction vessel
21
is supplied with water at 250 kgf/cm
2
and 380° C., and also with PCB, mineral oil and sodium carbonate. Circulating pump
26
serves to agitate the reaction fluid within reaction vessel
21
, and also introduce the reactant mixture
22
of water, PCB, mineral oil and sodium carbonate having a temperature of 200 to 250° C. from the outside into reaction vessel
21
by mixing it with the steam of the fluid driven by circulating pump
26
. This mixture
22
undergoes an exothermic reaction within reaction vessel
21
and causes sodium carbonate to precipitate.
At the bottom of reaction vessel
21
, air or oxygen
31
is injected from gas supply nozzle
32
. This air or oxygen
31
serving as an oxidizing agent dissolves in the reaction fluid while it goes up through reaction vessel
21
in the form of gas bubbles, thus causing an agitation flow within reaction vessel
21
. The sodium carbonate precipitated within reaction vessel
21
is agitated into contact with PCB by the circulation flow caused by circulating pump
26
and the stream of gas bubbles injected from gas supply nozzle
32
, so that the decomposition reaction of PCB is accelerated.
As described above, the conventional reaction vessel
21
has used sodium carbonate in order to decompose PCB. The solubility of sodium carbonate decreases with rising temperature, and it scarcely dissolves at temperatures above 350° C. Consequently, it has been conventional practice to feed the mixture
22
of water, PCB, mineral oil and sodium carbonate having a temperature of 250° C. to reaction vessel
21
having a temperature of 380° C. and thereby precipitate the sodium carbonate within reaction vessel
21
in the form of solid particles. The precipitated sodium carbonate, together with the introduced fluid, is agitated by gas bubbles of oxygen. Thus, a so-called three-phase fluidized bed consisting of a solid, a gas and a liquid is formed to accelerate the decomposition reaction of PCB.
OBJECT AND SUMMARY OF THE INVENTION
The reactor having the above-described construction has the following problems.
A circulating pump which can be used under high-pressure temperature and high-pressure conditions (e.g., at 380° C. and 250 kgf/cm
2
) is expensive and hence raises the overall equipment cost. Since the combustion rate of oil in a liquid is high, the reactant mixture fed through the feed pipe reacts with oxygen dissolved in water and causes heat evolution in the feed pipe. If sodium carbonate alone is supplied, the sodium carbonate produced by the oxidation reaction is converted into sodium bicarbonate, resulting in a reduction in the rate of the decomposition reaction of PCB. If sodium carbonate is introduced into the reaction fluid, the solubility of oxygen is reduced and a gas phase is produced at the top of the reaction vessel. This causes a mixed gas-liquid phase to flow into the cyclone separator, resulting in a reduction in the separation efficiency of the cyclone separator.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a PCB decomposition reactor which does not involve unduly high equipment cost and which can decompose PCB efficiently.
In order to accomplish the above object, the present invention provides a PCB decomposition reactor comprising a reaction vessel for decomposing PCB therein and a cyclone separator disposed in flow communication with an outlet of the reaction vessel for separating sodium carbonate particles from the reaction fluid withdrawn through the outlet, wherein the outlet is formed in the sidewall of the reaction vessel.
Moreover, in order to accomplish the above object, the present invention also provides a PCB decomposition reactor comprising a reaction vessel for decomposing PCB therein and a cyclone separator disposed in flow communication with an outlet of the reaction vessel for separating sodium carbonate particles from the reaction fluid withdrawn through from the outlet, wherein the reaction vessel is equipped with an injector for injecting water and sodium hydroxide from the outside to the inside of the reaction vessel, and a pipe for introducing the sodium carbonate particles separated by the cyclone separator into the suction chamber of the injector.
Furthermore, in order to accomplish the above object, the present invention also provides a PCB decomposition reactor comprising a reaction vessel for decomposing PCB therein and a feed pipe for feeding PCB and a solvent therefor to the reaction vessel, wherein an injector for injecting water and sodium hydroxide from the outside to the inside of the reaction vessel is connected to the reaction vessel, and the feed pipe is connected to the flow path between the connected end of the injector and the suction port of the injector for supplying water and sodium hydroxide therethrough.
Additionally, in order to accomplish the above object, the present invention also provides a PCB decomposition reactor comprising a reaction vessel for decomposing PCB therein with the aid of sodium carbonate, wherein the molar amount of sodium hydroxide supplied to the reaction vessel in order to form sodium carbonate is controlled so as to fall within a range which does not cause any excess sodium carbonate to precipitate.
Specifically, in the PCB decomposition reactor of the present invention, sodium hydroxide and sodium bicarbonate are dissolved in water, and this solution is mixed with PCB, mineral oil serving as a solvent therefor, and sodium carbonate particles formed as the reaction product. To the resulting mixture, oxygen is supplied from a gas supply nozzle. The resulting reaction fluid is fed to a cyclone separator through an outlet pipe connected to the reaction vessel at a position below the top thereof, so that the precipitated sodium carbonate particles are separated. The reaction fluid from which sodium carbonate has been removed is discharged to the downstream side of the cyclone separator through a discharge pipe. The separated sodium carbonate particles are supplied to the flow path of an injector through a downcomer for the fluid separated by the cyclone separator. A mixture of water and sodium hydroxide is supplied to the injector as a driving fluid. Moreover, a mixture of PCB and mineral oil is fed to the flow path of the injector.
REFERENCES:
patent: 4931260 (1990-06-01), Molerus et al.
patent: 6124
Fukuzumi Tadatsugu
Hokao Nobuhiro
Ikeda Nobuyuki
Iwao Mitsuji
Moribe Takashi
Knode Marian C.
Mitsubishi Heavy Industries Inc.
Myers Bigel & Sibley & Sajovec
Varcoe Frederick
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