JPS5918118B2 - Wet oxidation reaction tank - Google Patents

Description

Detailed Description of the Invention: Japanese Patent Application No. 47-98803 (filing date: October 2, 1972) and Japanese Patent Application No. 7033-1979 owned by the applicant company.
No. 7 (filing date: 1976.6.21) describes a wet oxidation method and its reactor for burning organic substances dissolved or suspended in an aqueous medium or other liquids. There is.

Wet oxidation is a safe, efficient, and economical technique for destroying organic wastes such as live or ooze-like organic matter or other forms of organic matter, especially unlike the torrefaction techniques currently in use. There is no need for expensive evaporation of water or drying before burning.

For example, when destroying sewage waste by roasting, it is absolutely necessary to reduce the water content, which is usually 90 parts or more, in advance.

As a result, most of the energy required for roasting and destruction is consumed to remove this water, and a large amount of space, labor, and equipment must be used because a large amount of material is handled in the step of removing this water. It will not happen.

Wet oxidation can also be used as a suitable method to dispose of potentially hazardous organic materials such as toxic organic materials, many organic plastics, explosives and other combustible organic materials without the risk of air pollution or explosion. However, this is because oxidation is always carried out in water and can therefore be controlled.

The amount of combustible organic matter suspended or dissolved in an aqueous medium is determined by the amount of oxygen theoretically required to react with it to destroy it, or in practice, COD (chemical oxygen demand). hoax
It is usually expressed by what is called nd).

The term BOD is also very similar to this,
This refers to the biological oxygen demand required to eliminate organic matter by biological means.

The removal or destruction of organic matter by chemical or biological means is measured by the percentage reduction in COD or BOD, respectively.

A 100% reduction in COD means that the combustible organic matter contained therein has been completely destroyed by chemical oxidation.

Wet oxidation is an exothermic chemical oxidation process in which the combustion rate depends more or less on the concentration of flammable organic matter dissolved or suspended in the aqueous medium, the availability of oxygen in the liquid system, and the organic molecules. It varies depending on the size.

However, what most clearly influences the reaction rate is the temperature and pressure at which the wet oxidation reaction is carried out.

First, in terms of molecular size, organic macromolecules appear to react much more easily than molecules with lower molecular weights.

In contrast, oxidation reactions of lower oxidation reaction products such as acetic acid are experienced as extremely difficult.

Therefore, the rate of decrease in COD increases rapidly at first, but this is because the macromolecules present in a high proportion in the stock solution are first oxidized and broken down into smaller molecular weight molecules, but these smaller molecular weight molecules can be reduced under the same conditions. This is because they are much more difficult to oxidize under these conditions, so they tend to accumulate gradually.

That is, the rate of wet oxidation slows as the concentration of small organic molecules dissolved or suspended in the aqueous medium increases.

This rate change is generally noticeable when the COD reduction rate is in the range of 60-70%.

Temperature and also pressure are important factors regarding the rate and amount of oxidation.

Traditionally, wet oxidation methods require very high temperatures of about 550-600°F (288-316°C) and correspondingly high temperatures to destroy almost all organic matter.
This could only be accomplished using high pressures in the psig (105-140 kg/i gauge) range.

For this reason, such wet oxidation methods require excessively expensive equipment to withstand these conditions during the reaction, as well as the highly corrosive nature of the materials being treated, resulting in the production of organic waste. It has not gained sufficient acceptance as a commercially viable method for treating.

U.S. Patent Nos. 2,665,249, 2,824,058, 2,903,425, 2,932,613, 32,727
Zimmerman and Zimmerman et al. patents such as Zimmerman and Zimmerman et al.
A wet oxidation method called ss) is already in use.

This method uses a reaction tower filled with wastewater, and the amount of organic matter in the waste is maintained at 3 to 6% by weight, and air is usually used as oxygen. Use less oxygen than the theoretical COD requires.

500-550°F (2
60-288°C) and typically 1500°C
~2000psig (105~140kg/i gauge)
The reaction takes place under a pressure within the range of .

Under these conditions, the material is highly corrosive;
Due to the high pressure and high temperature at which the reaction is carried out, the initial equipment is extremely expensive and the operating life of the equipment is relatively short. The method is simply not commercially acceptable.

Using the reaction process and reactor described in the aforementioned applicant's proprietary patent application, temperature and pressure conditions as well as reaction times can be maintained without a corresponding reduction in the amount or rate of combustion of organic matter. A significant reduction in COD can be achieved, thereby allowing efficient and economical production of effluents with low levels of COD.

The object of the present invention is to introduce greater efficiency and economy into a reactor of the type described in the above-mentioned patent application in the possession of the applicant.

By doing this, greater efficiency is achieved.
The effluent from the reactor can be introduced into the reactor to increase the exposure time of the organic material to wet oxidation under more favorable high concentration conditions without increasing the size of the reaction space. subjected to after-treatment to recover the useful components contained, and thereby involve the treatment of organic matter by cities and ships, the treatment of propellants, or the recovery of silver, terephthalic acid, and other components. A process and reaction vessel is provided that is highly commercially acceptable for processing organic waste and materials, such as processing waste photographic film.

These and other objects and advantages of the invention will become apparent from the following description, and one embodiment of the invention is illustrated by the accompanying drawings, which do not serve to explain the invention. However, this is not intended to be limiting.

FIG. 1 is a front cross-sectional view of a wet oxidation reactor of the type described in the above-referenced patent application.

FIG. 2 is a process flow diagram of an apparatus embodying features of the present invention for use in combination with a modified embodiment of the reactor of FIG.

FIG. 3 is a schematic diagram showing an alternative route for treating effluent vapor.

FIG. 4 is a schematic cross-sectional view of a weir-type reaction tank used to carry out the present invention.

FIG. 5 is a process flow chart showing the features that are implemented when carrying out the present invention.

And FIG. 6 shows the residue after continuous wet oxidation of digester sludge by practicing the present invention.

The wet oxidation reaction tank (FIG. 1) used in carrying out the present invention consists of a cylindrical reaction chamber 10 arranged horizontally.

The interior 12 of the reaction cylinder is subdivided by vertical walls 1416 and 18 into a series of adjacent compartments 2022, 24 and 26, each in the shape of a cylindrical compartment.

The cylindrical reactor is of various dimensions depending somewhat on the desired capacity of the apparatus, and the compartments can vary in size or volumetric capacity, with the first compartment having a larger capacity than the other compartments. It is preferable that there be.

Each compartment is provided with its own agitator, preferably in the form of a starter consisting of a pair of disc-shaped members 28 and 30, fixedly spaced vertically on a shaft 32.

A shaft 32 passes through the cylindrical reactor 10, is shaft sealed, mounted on a bearing 34 for rotation about a vertical axis, and is located in the center of each compartment of the cylindrical reactor 10. The outwardly extending portion of the shaft is provided with means such as a pulley 36 for rotating the shaft by a belt driven by a motor, or means such as an electric motor mounted on each shaft.

Each of the discs 28 and 30 is provided with a plurality of wings 37 that are provided downward from the bottom side thereof and extend in the radial direction.

When using pairs of vertically spaced disks as shown, the lower disk should be placed at about 1/3 of the height of the compartment, and the other disk should be placed at about 1/3 of the height of the compartment. 2
It is preferable to arrange it at a level of /3.

However, only one disc stirrer or more than one disc stirrer can be used, with the lowest disc scoop located away from the bottom of the compartment and the uppermost disc scoop located away from the top of the compartment.

Preferably each starter is 1/2 inch from the top within the compartment.
4 or less and is held in the space below the water surface.

Air, oxygen or other oxygen-containing gas may be added to the compartment where the oxidation reaction is desired to occur, in order to introduce the oxygen-containing gas or air directly into the maximum stirring zone created in the lowest scoop. It is introduced through an inlet in the form of a more nozzle.

In the variant illustrated, the nozzle 38 extends upwardly from the bottom side of the compartment to the vane member 37 of the lowest starter.

A stream of air or oxygen-containing air is therefore introduced upwards towards the bottom side of the starter, and the introduced air or gas is directly exposed to the torsional forces generated by the rapidly rotating starter.

The air is thereby broken up into fine increments as it is directly sparged with turbulent liquid.

The nozzle 38 can be placed at the center of the starter or off-center.

However, it is preferably within the wingspan of the starte so as to be introduced into the vortices generated thereby.

Air or a gas containing oxygen is supplied to the nozzle through a head 40 communicating with a compressor or accumulator which compresses the air or gas to a high pressure equal to or greater than the pressure conditions existing in the reaction compartment. Introduced below.

The first compartment 20 is equipped with an inlet 42 at one end of a tube member 44 for introducing a liquid for wet oxidation of organic matter;
Preferably, the liquid is preheated in the manner described below.

The first compartment is equipped with a series of electric heaters or heat exchange coils 48.

This is provided for the purpose of introducing sufficient heat for the heat exchange liquid to initiate the reaction and for circulating it through the head 50 to remove the heat generated by the exothermic reaction.

This also maintains temperature control of the materials within the reactor.

The last compartment, shown as the withdrawal zone, has an outlet 52 communicating with the vapor area in the upper part of the compartment for discharging vapor and another outlet 54 communicating with the liquid area in the lower part of the compartment for removing effluent liquid from the compartment. It is equipped with.

The plurality of compartments are in communication with each other for fluid flow from one compartment to another.

For example, by means of a hollow tubular member 56 extending laterally from an inlet 58 at the top of a previous compartment to a vertically disposed downward pipe in the next compartment.

The inlet 58 of each preceding compartment is located at the top of the compartment, thereby subdividing the compartment into a liquid area rising to the level of the outlet and a vapor area above the outlet.

In practicing the invention, the withdrawal zone 61 communicates with the final reaction zone 26 through one or more channels at the level of the vapor-liquid interface in the preceding reactor.

For example, it communicates with the hollow tube member 56 through a corresponding tube member regardless of whether there is a downward vibro 0 or not.

However, it is preferred to form a weir with a wall 62 extending upwardly to a level corresponding to the vapor-liquid interface.

Over this weir, liquid flows from the pre-reaction zone to the withdrawal zone 61.

It also includes an open area above the weir for free flow of vapor from the reaction zone to the withdrawal zone.

The liquid or vapor phase material entering the separation zone is not preferably agitated by the introduction of oxygen or other oxygen-containing gases or by the use of stirrers or mechanical means to maintain agitation.

This allows for virtually complete phase separation into an upper vapor phase and a lower liquid phase.

In order to achieve a sharp separation between the several phases in the breakaway zone, it is desirable to subdivide the breakaway zone by baffles 66, which move the breakaway zone horizontally and laterally away from the weir 62. It extends near the far end of the zone to subdivide the withdrawal zone into an upper vapor zone 68 and a lower liquid zone 70.

In operation, liquid flows from the weir horizontally aft over baffle plate 66 to opening 72 at the far end and then down through opening 72 to the liquid zone.

The absence of agitation and the presence of baffle flow provide quiescence for a sharp separation between the upper vapor phase and the lower liquid phase.

The coexistence of solid and liquid substances within the vapor phase is therefore minimized.

Outlet 52 connects upper vapor zone 68 to conduit 74 for removing vapor from the upper vapor zone, substantially free of coexistence of liquid and solid materials.

Another outlet 54 communicates the liquid zone with line 76 .

The liquid collected in the liquid zone by its line 76 is removed by subsequent processing.

A wet oxidation tank as shown in FIG. 4 used in carrying out the present invention consists of a cylindrical reaction chamber 100 arranged horizontally.

Its interior has vertical walls or partitions 102, 103, 10
A series of adjacent compartments 1 by 4, 105 and 106
07, 108° 109. Subdivided into 110, 111 and 112.

The partition walls of each series are open at the top so that the vapor phase in all the compartments is freely communicated and the liquid level is somewhat different in each successive compartment due to the difference in the height of the weir. It's getting lower.

This ensures that the fluid flows from left to right in the reaction tank as shown in FIG.

In practicing the invention, the sixth section 112 of the horizontal, multi-section pressure cooker is used as a withdrawal zone.

It consists of baffles or weirs separating the various reaction compartments, in other words chambers 102, 103, 104, 105 and 10.
The opening in the gas phase at the top of 6 is divided by diameter from 111 to 10.
It is connected to 7.

The sixth compartment 112 is equipped with a number of stirring disks.

The solid material is then separated from the suspension.

This is to prevent mist and droplets from being introduced into the vapor phase.

The liquid phase is discharged through a channel 116 that sinks to the bottom of the compartment 112.

This can ensure that all sand and heavy sediments are removed from the bottom of the breakaway compartment.

The rate of discharge of the liquid phase is controlled by a level detector 117.

The detector may be karyotype, conductance type or capacitive type.

The liquid and vapor phases are each individually led to respective heat exchangers where thermal energy is transferred to the feed entering compartment 107.

A schematic arrangement of liquid phase and vapor phase heat exchangers and the use of aftercoolers to recover surplus thermal energy in a useful form as hot water or low pressure steam is shown in FIG.

The key idea of the present invention is to extract steam from the vapor zone in the vapor phase under the temperatures and pressures present, which provides many advantages for the wet oxidation process.

The amount of vapor generated during the combustion of organic matter by wet oxidation is
It varies somewhat depending on the amount of organic matter being oxidized and the heat generated by the exothermic reaction.

This introduces many variables but is automatically compensated for in reactors of the type described above.

Thereby, it is desired to minimize conditions that would otherwise be considered dangerous and impose design limitations on the device.

Removing the vapor in the vapor phase without condensing it serves to remove a substantial amount of water introduced into the reactor, thereby significantly increasing the residence time of the liquid phase.

This has the effect of increasing the capacity of the device to further combust organic matter and reduce the COD of the effluent liquid.

The vapor phase consists primarily of oxygen, a carrier gas such as nitrogen from the air, and water vapor produced by heat absorption from the exothermic reaction.

In addition, the steam from the steam zone can contain materials such as grease and paraffin wax that are steam-distilled, low boiling point materials such as ammonia, and boiling point materials such as acetic acid that evaporate under the temperature and pressure conditions present in the reactor. low organic acids,
Contains aldehydes, ketones, etc.

These are removed from the reactor along with the effluent vapors.

Many of these components can be removed by simple and convenient methods to recover useful raw materials and provide a clean effluent.

The effluent is discharged into the atmosphere and is virtually free of contaminants.

The vapor phase condensate is completely free of heavy metals.

Many routes can be taken to treat the effluent vapor.

In one embodiment, the effluent vapor is passed into a heat exchange relationship with other gases or liquids to recover heat that would otherwise escape to the atmosphere.

For example, the incoming liquid to be wet oxidized can be preheated by passing it into a heat exchange relationship with the effluent vapor from the reaction vessel.

It preheats the liquid close to the reaction temperature before entering the reactor.

Alternatively or additionally: 1. The hot effluent steam can be passed to a condenser 80 in heat exchange relationship with water or other heat exchange liquid, and the heat exchange liquid is used for space heaters or power generation.

In the variant shown in FIG. 2 of the drawings, the warm effluent steam is converted into a sugar part to condense the distilled or vaporized condensable substances.

For example, one barrel of grease and paraffin wax was distilled per ten tons of wet oxidation of sludge.

Such wax and other condensates are removed from outlet 82 of vapor phase heat exchanger 80.

Separation of the wax and condensable substances which have come out together in this manner can be effected by expanding the steam from the expansion valve 84 into the expansion chamber 86.

Condensate, liquid, and solid materials can be collected from conduit 88 through a rotary lacrimator 90 or other solid-liquid separation means at the bottom of expansion chamber 86 .

On the other hand, any material remaining in a gas or vapor state is removed from the top outlet 92.
5 as a clean effluent or recycled to a vapor phase heat exchanger as shown in FIG.

Alternatively or additionally, the effluent vapor may be cooled or placed in a bubble column to separate solids and condensable liquids.
ble cap column), a contact column, a washer or a condenser 80, which can be removed at various stages.

On the one hand, the remaining gaseous material is forced out of the top 94 as clean gas.

In order to reduce the temperature and pressure of the exiting steam according to the expansion route, the expansion occurs through a turbine 96 or other means that converts the released energy or work into power for operating the turbine or for generating electrical energy.

The condensed material can be recovered and processed by various conventional means such as filtration for solid-liquid separation, adsorption for separation between liquids or gases, or solvent fractionation for liquid-liquid, solid-solid separation. can be separated into its components.

The residual gases and vapors remaining after condensation can be treated to recover useful gaseous components before being discharged to the atmosphere.

Useful gas components include organic acids with low boiling points such as acetic acid, nitrogen compounds such as ammonia, and aldehydes such as formaldehyde.

Such recovery can be accomplished by absorption in a suitable solvent or water, or by contacting and reacting the materials in an adsorption reactor 95.

The increased residence time of the liquid phase obtained by removing the vapor phase from the reactor without condensation depends in part on the amount of liquid converted to the vapor phase during combustion of the organic material by wet oxidation.

Reactions sufficient to sustain combustion of organic matter dissolved or suspended in an aqueous carrier convert approximately 10 to 40 parts of water into steam.

As a result, the liquid phase components have a corresponding decrease in volume and
This increases the capacity of the reaction tank.

It also increases the retention time of solid materials in the liquid phase solution.

Removing the vapor phase as effluent from the reactor introduces an additional factor that favors the economics and efficiency of wet oxidation methods for treating organic wastes, as the liquid phase volume is significantly reduced and heavy metal residues are correspondingly reduced. and increasing the concentration of other solid substances.

It also correspondingly reduces the amount of liquid required for the process of removing heavy metals and recovering other materials.

. The following examples are given to illustrate the practice of the invention in the wet oxidation of sewage sludge, as illustrated by Pennsylvania Philadelphia digester sludge with a COD of 70,855~/l, and are therefore intended to limit the scope of the claims. Not.

After the final reaction compartment there is a detachment compartment 112 as shown in FIG.
A reaction tank with

The inner surface of the reactor is made of a material that resists corrosion even when exposed to high-temperature oxidizing liquids and vapors.

Therefore, the walls of the reactor are lined with carbon or corrosion-resistant acid brick.

On the other hand, the stirrer, air inlet, partition wall, baffle plate, etc. are made of titanium, 316 stainless steel, etc.

The test was conducted under the conditions shown in the process diagram in FIG.

Pressure was maintained to give a reaction temperature of about 230°C (about 446°F) in the reactor, and air was pumped into the last compartment at a rate of 2.2 to 2.7 cubic feet per minute for oxygen introduction. It was introduced in all sections except for.

From a mass balance standpoint, 35.7% of the liquid was converted to vapor from the withdrawal zone, while the amount of liquid removed from the liquid zone was about 64.3% of the inflow.

Therefore, the reduction in liquid in the liquid zone is approximately 35.7% of the charge liquid.
%, whereby the residence time of the liquid phase in the liquid zone increased accordingly.

Gas phase condensate contains a grease-in-water emulsion that is easily destroyed.

It is found by nuclear magnetic resonance tests as well as long-term saponification tests to consist of chain aliphatic or paraffin type organic compounds having a boiling point range of 190-250°C.

Sludge is normally treated sludge dry amount per grease 35 ~
50 pounds or 1 barrel of oil per 101 sludge.

This product can be directly combusted or made into more useful petrochemical feedstocks.

The organic matter remaining in the gas phase condensate generally consists of 45-55% by weight acetic acid and 15-20% by weight propionic acid, as determined by gas-phase chromocytgelography.

And trace amounts of butyric acid, acetaldehyde, acetone, formic acid, methanol and ethanol are present.

Residual organic matter in the liquid phase effluent ranges from 40 to 70 parts acetic acid, depending somewhat on the treated sludge.

Propionic acid is present in an amount ranging from 5 to 15 parts by weight, with smaller amounts of formic acid and acetone and trace amounts of acetaldehyde present in the liquid.

It will be appreciated that changes may be made in the apparatus and operating conditions without departing from the spirit of the invention, particularly as defined in the claims.

Embodiments of the present invention are shown below.

(1) The claims feature a continuous wet oxidation process in which an aqueous liquid containing organic matter is continuously introduced into a reaction zone, and the separated vapor and liquid are then continuously removed from a withdrawal zone. the method of.

(2) The method according to claim 1 and the preceding paragraph (1), which comprises a step of treating the separated vapor to recover heat and/or useful components.

(3) A method as claimed in the claims and in the preceding paragraphs, comprising the step of subjecting the liquid containing organic material to a state of high agitation while in the reaction zone.

(4) The method described in the claims and the preceding items, wherein the oxygen-containing gas is air.

(5) Claims characterized in that the vapor from the separation zone is passed through an aqueous liquid containing organic matter introduced into the reaction zone while exchanging heat to recover heat from the vapor to produce a charge liquid; The methods described in the previous sections.

(6) treating the steam from the withdrawal zone by expanding the steam to produce work, using this work as a power source, and then separating the condensate from the residual steam; Method.

(7) The method according to the claims and the preceding items, wherein the liquid separated from the separation zone is treated by passing the liquid separated from the separation zone into a solid part and a liquid solute.

(8) treating the additive to precipitate the valuable components in the solution and then separating the precipitate from others;
).

(9) The reaction tank according to claim 2, wherein a stirrer is located in close proximity to the area where the oxygen-containing gas is introduced in order to directly disperse oxygen in the liquid.

(10) Claims consisting of an expansion chamber communicating with a steam outlet and an expansion valve for expanding steam from the outlet into the expansion chamber and separating condensable material from the expanded steam while reducing temperature and pressure accordingly. 2. The reaction tank described in 2.

[Brief explanation of the drawing]

Figure 1 is a schematic front sectional view of the wet oxidation reaction tank, and Figure 2 is a schematic front sectional view of the wet oxidation reaction tank.
Figure 3 is a flow chart of one treatment path for effluent steam, Figure 4 is a schematic cross-sectional view of a weir-type reaction tank, Figure 5 is a process diagram, and Figure 6 is a process diagram combined with the modified form of the reaction tank shown in the figure. is an income and expenditure chart.

Claims (1)

[Scope of Claims] 1. A reaction tank for wet oxidation of an organic substance in the form of a solution or dispersion in an organic liquid, having an inlet at one end for introducing a liquid containing the organic substance to be oxidized; a horizontally disposed enclosure that is laterally subdivided into a plurality of communicating reaction zones and a stationary withdrawal zone located opposite the inlet; means for maintaining the reaction zones under high temperature and pressure;
means for introducing an oxygen-containing gas into said liquid passing through at least a first reaction zone; substantially horizontally the entire distance across the top of the withdrawal zone at a level corresponding to the level of liquid in the preceding reaction zone; Exothermic oxidation of organic matter can be prevented by providing a baffle plate extending in length so that the liquid from the preceding reaction zone flows by gravity into the liquid zone only after it has flowed over the baffle plate. The heat generated changes the liquid into vapor, and in the separation zone, the vapor collects as an upper vapor phase and the liquid collects as a lower liquid phase, separating the liquid and vapor, and further collecting in the vapor zone. A reaction vessel characterized in that it is provided with an outlet at the top of the withdrawal zone for taking out vapor and an outlet at the bottom of the withdrawal zone for taking out the liquid collected in the liquid zone.