JPH02232599A - Method and apparatus for disposal of liquid organic waste by sulfuric ore conversion - Google Patents

Abstract

PURPOSE: To keep continuos operation by introducing a liquid organic waste and a nitic acid or a hydrogen peroxide into a reactor which includes a concentrated sulfuric acid and is kept at about 150 deg. and adjusting a flow rate by using the optical concentration of the measured liquid medium as a function. CONSTITUTION: A reactor 1 is partly filled with a sulfuric acid 5 and an organic liquid waste to be processed is introduced into the reactor 1 through a pipe 7. The flow rate of the liquid waste is adjusted by a gear pump 9 and a small stream is introduced so as not to clog the pipe 7 due to carbonization of organic substance in the pump 9. A nitric acid or hydrogen peroxide used for reaction is introduced through a tube 11 immersing in a sulfuric acid 5 and its flow rate is adjusted by a pump 13. The reactor 1 is proved with a preheating means 14, a turbine 15 as a stirring means, a probe 17 for measuring the concentration of liquid medium, and optical concentration measuring means 21 and 23. A gas generating through reaction is discharged from an enclosing body through a pipe 19. The pipe 19 passes through a gas processing assembly and then it is connected with the ventilating circuit of a sealed body of nuclear facility. The means 21 is connected with a microprocessor 27 for controlling the pump 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for treating liquid organic waste. The invention particularly relates to the treatment of liquid organic wastes, which are constituted by organic solvent liquid wastes contaminated with radioactive or toxic substances, e.g. from nuclear installations or chemical industry laboratories, which must be kept in stable conditions. Applies to. Coating with bitumen in known waste preparation methods is undesirable because liquid organic products lower the softening point of the bitumen. Concrete coating is also undesirable since it is extremely difficult to dilute the waste to prevent leaching phenomena. Incorporation into polymerizable products is also possible, but it is difficult to apply to liquid organic products. Therefore, the most reliable treatment method for treating organic waste consists of converting it into V1-free substances in order to maintain its long-term condition. This can be carried out by incineration or dry pyrolysis of the waste.

Ashing organic liquid waste contaminated with radioactive elements has an alpha activity higher than 10-'Ci/s' and 10"'
Processing wastes with β or γ activity higher than Ci/m′ in this way is difficult and therefore necessarily problematic. Additionally, if the liquid waste is composed of organophosphorus compounds, combustion produces phosphoric acid droplets which must be neutralized by adding calcium formate to the flame. Calcium birophosphate is then formed, which increases the ash volume considerably and clogs the filter. In order to further avoid exceptional operating conditions, the phosphorus content of the solvent must be limited to 0.1%. Dry pyrolysis methods involve handling highly active ash, which is difficult to implement on highly contaminated liquid wastes. Another method of treating organic waste is mineralization with sulfuric acid, but this has so far only been used to treat solid 1iHli waste. The method consists of carbonizing the waste with sulfuric acid and oxidizing the carbon formed with nitric acid and/or hydrogen peroxide. This is the formula C
．． +1. In organic waste, the reaction: C, fl. ,+n/2H,SO4 nll20+
n/2SO2+Chicken C (1)? +2H, So, →
211■0+2SO2+CO2 (υ3C+
4HNO, →2}1,0+4NO+3CO2(3)
? C + 21180 3 →LO+2NO+ 3C
O (4)C+H2SO. →B20+SO. +
Corresponds to CO (5). The rate constants of reactions (2) to (5) at 255°C are: K2 = 0.0018 min Km + K3 + K4 + Ks = 0.016 min - 1 K, = 0.011 min Km. +
Ks = 0.0029/1. Oxidation of carbon is i! is carried out faster by nitric acid than by acid (K
s>>Kt>. The method thus includes two steps: 1. H. S.O. 2. Carbonization of carbon with nitric acid and CO. There is oxidation to The gases formed in the above reaction are SO■, CO2, N
O and CO, but SO2 can be oxidized and converted to sulfuric acid by the formed nitrogen oxides and nitric acid. Therefore, the li required for carbonization! It is possible to regenerate the acid.

This type of method has been described by Lereh et al.
dChemical WasLe Management
T, Vol. 2, 1981, pp. 265-277. The present invention relates to a method for treating liquid organic waste by sulfuric acid mineralization, which has the advantage of overcoming the drawbacks of known dry pyrolysis and ashing methods and can be carried out continuously. The present invention comprises: in a reactor maintained at a temperature of at least 150° C. and containing f4 sulfuric acid; b) the liquid organic waste to be treated; and b) nitric acid and hydrogen peroxide in the reactor. Then, carbonization of the introduced liquid waste with sulfuric acid and oxidation of carbon and SO2 formed during carbonization are carried out, and at the same time sulfuric acid is introduced at a flow rate such that sulfuric acid is regenerated, and the liquid present in the reactor is regenerated. continuously measuring the optical density of the medium and adjusting the flow rate of the introduced liquid organic waste and/or of the nitric acid and/or hydrogen peroxide as a function of the measured optical density; Provides a method for treating organic waste. That is, in the present invention, in the same reactor,
The two stages of carbonization and oxidation of the sulfuric acid mineralization process and the stage of regenerating sulfuric acid by oxidizing 302 with nitric acid and/or hydrogen peroxide introduced into the reactor are carried out simultaneously. Furthermore, as a function of the measured optical density, the flow rate of the introduced liquid waste and/or oxidizer is adjusted. The optical density varies as a function of the elemental carbon concentration of the reaction medium. Additionally, when the optical density exceeds a set level corresponding to an acceptable elemental carbon concentration in the reaction medium, the organic liquid waste feed rate may be reduced or stopped, or an excess of organic liquid waste may be added to the reaction medium. Increase the feed rate of nitric acid and/or hydrogen peroxide to oxidize the carbon present. As soon as the optical density is again below the set level, the liquid waste or nitric acid and/or hydrogen peroxide feed rate is returned to its starting value.
The process of the invention can thus be carried out continuously without the addition of sulfuric acid.

In the present invention, the flow rate of liquid organic waste, nitric acid and/or hydrogen peroxide to be introduced into the reactor is fixed at a predetermined value, and when the measured optical density exceeds the set value, the liquid waste is It is preferred to interrupt the introduction of the liquid waste into the reactor and automatically restart the feed after a stoppage time depending on the values set for the liquid waste stream, in particular. If the flow rate is low, the stop time will be a few seconds, e.g. 1-3 seconds; if the flow rate is higher, the stop time will be longer.6 The sulfuric acid used for waste carbonization is generally concentrated VfL acid, e.g. at 250°C. It is 16-18M sulfuric acid. The nitric acid used for the oxidation of carbon and SO2 is also concentrated nitric acid, e.g.
~14M nitric acid is preferred. If hydrogen peroxide is used, it is preferably 30% hydrogen peroxide (110 volumes). The method of the present invention is particularly applicable to the treatment of liquid organic wastes evaporated by organic solvents, such as those used in irradiated nuclear fuel reprocessing facilities. Examples of such solvents include at least one compound selected from organic phosphorus compounds such as tributyl phosphate and amines such as trilaurylamine, and mixtures thereof. If the liquid organic solvent to be treated is an organic solvent possibly containing an organic diluent, (
the volume of liquid to be treated by pre-neutralization (to remove any acids and nitrate ions that may be present) and by removing diluents and alcohols, which are light products that are susceptible to partial vaporization during mineralization; In order to reduce the amount of water, it is preferable to perform concentration by distillation. Neutralization can be carried out at ambient temperature by contacting the solvent with a sodium carbonate solution. This sodium carbonate solution makes it possible to remove any acid and nitrate ions that may be present, which would cause undesirable reactions during distillation. It can also dissolve cations such as uranium or plutonium. Distillation and concentration operations are almost always carried out under reduced pressure. However, if the liquid waste contains highly volatile products such as ethanol, probanol and brobionic acid, it is preferred to carry out the 'distillation at ambient temperature. By this distillation, the distillate is decontaminated and the volume of solvent to be mineralized can be reduced,
Diluents and chlorine derivatives, which are generally highly volatile, can also be removed to avoid unwanted hydrochloric acid formation within the reaction funnel system. This distillation is preferably carried out in a closed body, using equipment with short residence times to prevent solvent degradation and limit tar formation. This device is preferably equipped with a rotating belt for discharging the deposits remaining during evaporation to prevent cleaning waste from adhering. It is possible to collect the concentrated organic residue obtained in the container and heat it again if it has a high viscosity and/or if necessary to prevent precipitation. The concentrate is discharged into a separate enclosure to prevent any radioactive recontamination during its testing. If the solvent originates from an irradiated fuel reprocessing facility, all these operations should be performed in a glove box under a nitrogen atmosphere. To carry out the treatment of the invention, the organic residue is then introduced into a reactor heated to a suitable level of temperature, for example 200° C. or higher if the oxidizing agent used is nitric acid. Organic nitro derivatives cannot be formed above 200°C. In this case, it is preferable to operate at a temperature of 220 to 270°C, for example 250°C. In the case of hydrogen peroxide, the temperature is 150-200°C, e.g.
70℃ is appropriate. The invention further provides a reactor, means for heating the reactor, means for introducing the organic liquid waste to be treated into the reactor, and means for introducing nitric acid and/or hydrogen peroxide into the reactor. as in a conventional device, but further comprising means for measuring the optical density of the liquid medium present in the reactor and, as a function of the measured optical density, the flow rate of the organic liquid waste introduced as well as 7 or and means for regulating the flow rate of nitric acid and/or hydrogen peroxide.

Preferably the means for measuring optical density are complementary such that the light beam guided in the first light guide is guided into the second light guide after passing through the path in the liquid medium of the reactor. a first optical waveguide and a second optical waveguide arranged;
It includes means for introducing a light beam into the first optical waveguide, and means for measuring the intensity of the light beam exiting from the second optical waveguide. The invention will now be explained in more detail by way of non-limiting examples with reference to the accompanying drawings, in which: FIG. FIG. 1 shows that the organic solvent to be mineralized is introduced through a pipe 7 with a pump 9 and a pipe 1 with a pump 13.
1 shows an installation comprising a reactor 1 through which nitric acid is introduced. Reactor 1 can be heated by heating means 14. The gas generated by the reaction is exhausted through the vibrator 19. The pipe 19 is connected to a first rectification column R associated with a condenser C into which air is introduced. At the outlet of condenser C, dilute HNO. and H, S.O. is collected and stored. On the other hand, the recovered gas containing nitrogen oxide and air is sent to a catalytic recombination column (caLalytic rec).
oaibination? The nitric acid is catalytically recombined in the column 20 with water introduced from the top of the column 20 to form nitric acid. The gas from which the nitrogen oxides have been removed is transferred to the sodium trap 22, where it collects CO■ and the last traces of impurities ([803, }180■ and ]1SO.
> is captured by Soda. FIG. 2 shows an apparatus according to the invention comprising a reactor 2S1, for example made of Pyrex glass, which is sealed on top by a cover 3 made of, for example, rigid polytetrafluoroethylene. A part of the reactor 1 is filled with sulfuric acid 5 and the organic liquid waste to be treated is introduced through a pipe 7.
Vibe 7 is not immersed in sulfuric acid 5. The flow rate of liquid waste is regulated by gabonbu 9. The gear bomb 9 also introduces a small air flow to prevent the pipe 7 from clogging due to carbonization of organic matter.

The nitric acid or hydrogen peroxide used in the reaction is introduced by a tube 11 immersed in sulfuric acid 5, the flow rate of which is controlled by the bomb 1.
Adjusted by 3. Furthermore, the reactor has heating means 14;
For example, a turbine 1 made of polytetrafluoroethylene
5, a probe l7 for measuring the temperature of the liquid medium, and optical density measuring means 21, 23.
It is equipped with the following. The gas generated by the reaction is vibrator 1.
9 is ejected from the enclosure. Vibrator 19 is the first
After passing through the gas handling assembly shown in the figure, it is connected to the ventilation circuit of the enclosed enclosure of the nuclear facility. In the embodiment shown in FIG. 2, the optical density is determined by a photoelectric sensor 2 installed at the end of the reactor opposite a light source 23 installed in a transparent tube 25 to separate it from the liquid medium.
It is measured by 1. The light source can be a quartz iodine lamp. The light source 23 is generally approximately 1c+++ from the wall of the reactor 1, which in this case is clearly transparent. The photoelectric cell 21 is connected to a microprocessor 27 which displays the optical density of the solution and controls the bomb 9 which supplies the liquid waste to be treated.

The microprocessor 27 temporarily stops or reduces the feed stream of the waste material to be treated if the optical density exceeds a set level corresponding to, for example, the carbon content of the reaction medium from 1 to 59/1. It is programmed to activate bomb 9 for this purpose.

In this implementation R, the flow of nitric acid or hydrogen peroxide introduced by pipe 11 is regulated by bomb 13 to a fixed value. It is clear that the bomb 13 could also be made to follow the microprocessor 27 in order to increase the flow of nitric acid or hydrogen peroxide when the optical density exceeds a set level. FIG. 3 shows another implementation of the means for measuring the optical density of the liquid medium present in the reactor. In this case, the second
The drop or dip tube 25 shown has been replaced by the assembly 30 of FIG. The assembly 30 comprises a holder or envelope 29 made of, for example, polytetrafluoroethylene, the envelope 29 having an orifice 31 through which the reaction medium can flow back into the envelope 29. Within the envelope 29 is its lower part 3
A first optical waveguide 33 in which 3a is curved is provided.
Its lower portion 33g reaches the height of the orifice 31, and above it a second optical waveguide 35 is provided, and a space corresponding to the optical path T in the reaction medium is provided between these two waveguides. ing. Although not shown in the figure, a light generator is installed outside the reactor to direct the light beam to the first optical waveguide 33.
The light beam is then arranged to introduce the liquid medium along the red iT! and is guided by the second optical waveguide 35. The second optical waveguide 35 is
Measure the intensity of the emitted light beam and use that value to determine the optical path T.
in combination with a photoelectric cell external to the reactor to induce the optical density of the liquid medium present in the reactor. The photoelectric cell associated with the optical waveguide 35 is connected to a microprocessor 27 which controls the amount of liquid waste introduced to be treated as described above. As mentioned above,
The optical path T corresponds to a solution approximately lean. This second device is particularly suited for operation in compact bodies, since both the optical waveguide and the optoelectronic cell for detection can be installed outside a closed body, for example a glove box.

The device of the invention can be equipped with safety or auxiliary devices to avoid any accidents in case of failure of the light source, photoelectric cell or nitric acid supply. In all cases the supply of organic liquid waste will be stopped. In the event of a temperature drop, the supply of a-liquid waste can be stopped. The following example is given to illustrate the method of the invention. 1: In this example, the phosphorus triple was heated to 250°C and 18M sulfuric acid was used. 0
,5! 14N nitric acid was introduced through the pipe 11 at a flow rate of 197±Zml hours, and the turbine 15 was set at a speed of 300 r.m. p. m. I got it working. Flow rate of triptyl phosphate (TBP) 100m through Vibe 7
// hours, microprocessor 27 is introduced at an optical density of 1 g/! of carbon in a liquid medium. Adjustments were made so that the supply of tributyl phosphate would be stopped if the value corresponding to was exceeded.
The supply of tributyl phosphate is automatically restored again after a few seconds. After 4 hours of operation, the average TOP flow rate, the consumption levels of IINO and I1SO4 on carbon, and the zero consumption level on carbon in the sodium trap were measured. The amount of carbon was determined based on the amount of TBP introduced. The results obtained are shown in Table 1. This example follows the same method as Example 1, except that a visual inspection of the reaction was performed and the tributyl phosphate feed was started and stopped manually. Table 1 shows the results obtained outside these conditions. Comparing these results with those of Example 1 shows that the optical sensor control benefits throughput, reduces the consumption of nitric acid and sulfuric acid, and reduces the consumption of reagents in the case of alkaline cleaning of gases.

2 to 6: Lint Bull Process In these examples, the effect of the nitric acid flow rate on the throughput of the reactor was investigated. maintained at 250°C and 188°C
i! Eleven reactors containing 0.51 of the acid were used. 14N nitric acid from 208 to 300 aa1 as a function of flow rate in the example.
It was changed and introduced at 7 o'clock. Tributyl phosphate was supplied at a flow rate of 100 ml/hour, and the detector 21 was supplied in the same manner as in Example 1.
is 1g of carbon #! The supply of tributyl phosphate was stopped when an optical density higher than that corresponding to . Table 2 shows the flow rate of nitric acid, the average flow rate of tributyl phosphate, and the nitric acid consumption relative to carbon obtained under these conditions. From Table 2, 2
50K*There is no increase in processing capacity after 17:00, so 1
1 reactor, the optimum value of nitric acid flow rate is 250s+1/
It turns out that it's time. In these examples, various organic solvents were treated by keeping the flow rate of nitric acid constant and using an optical sensor to stop the flow of the solvent as in Example 1. Table 3 shows the results and processing conditions.

From the table, it can be seen that the performance is significantly reduced when the solvent contains trilaurylamine. That is, the long carbon chains of trilaurylamine are more resistant than those of tributyl phosphate. The results of Example 8 show that it is preferable to treat trilaurylamine mixed with tributyl phosphate. Todoroki” Test number RHO, flow rate (I11・hr−1) Average TOP flow rate I×hr”》 Comparative example 1 Example 1 C(1) (1) The amount of carbon was calculated based on the chemical formula of the introduced TBP. (2) Sodium trap is @ amount of FINO,,HNO
．． and +12SO. and all CO. pl
+ Once it reached about 8, I replaced the soda. Furthermore, CO
is captured in the form of IICO,-, and only 011- is CO
Consumed by 2. Example number 148 1180, flow rate (ml/hour-1) Table 1 Example number 7 8 9
10 (mol/hour゛1》) (1) The amount of carbon was calculated based on the chemical formula of the introduced TBP. 'and/or T.I.
Calculated based on the chemical formula of ^.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the equipment, and Fig. 2 is a diagram of the present invention C! ') Schematic diagram of remounting, Figure 3 is a diagram of a modified ellipse of the optical density measuring means. 1... Reactor, 5... Sulfuric acid, 7.19... Pipe, 9.13... Pump, 11... Tube, ]4... Addition means, 20... Contact re- Coupling tower, 22... sodium trap, 23... light source, 29... envelope, 3... orifice, 33... first optical waveguide,
35...Second light guide path, C...Condenser, R.
...Rectification tower. Yoshito Goki

Claims (9)

[Claims] (1) in a reactor maintained at a temperature of at least 150° C. and containing concentrated sulfuric acid, a) the liquid organic waste to be treated, and b) nitric acid and/or hydrogen peroxide in said reactor; introducing at a flow rate such that the carbonization of the introduced liquid waste with sulfuric acid and the oxidation of the carbon and SO_2 formed during carbonization take place at the same time that the sulfuric acid is regenerated, and the liquid medium present in said reactor continuously measuring the optical density of the liquid organic waste, and adjusting the flow rate of the introduced liquid organic waste and/or the flow rate of nitric acid and/or hydrogen peroxide as a function of the measured optical density. A method of continuously processing waste. (2) The flow rate of liquid organic waste, nitric acid and/or hydrogen peroxide introduced into the reactor is fixed at a predetermined value, and the introduction of the liquid waste into the reactor is measured. 2. The method of claim 1, wherein the method is stopped when the optical density is above a set level. (3) The method according to claim 1 or 2, wherein the liquid organic waste is an organic solvent. (4) The method according to claim 3, wherein the organic solvent contains at least one compound selected from tributyl phosphate and trilaurylamine. (5) The method according to claim 3 or 4, wherein the organic solvent contains an organic diluent. (6) Before introducing the organic solvent into the reactor, first neutralize the organic solvent to remove any acid and nitrate ions that may be present, and then convert the neutralized organic solvent into a highly volatile 6. Process according to claim 3, characterized in that it is subjected to a pretreatment consisting of concentration by distillation in order to remove the substances. (7) that the reactor has 15
7. A method according to any one of claims 1 to 6, characterized in that the temperature is maintained between 0 and 200<0>C or between 220 and 270<0>C. (8) comprising a reactor, means for heating the reactor, means for introducing the organic liquid waste to be treated into said reactor, and means for introducing nitric acid and/or hydrogen peroxide into said reactor. An apparatus for treating organic liquid waste, the apparatus comprising:
Furthermore, means for measuring the optical density of the liquid medium present in said reactor and for determining the flow rate of the introduced liquid organic waste and/or the flow rate of nitric acid and/or hydrogen peroxide as a function of the measured optical density. A device characterized in that it includes means for adjusting. (9) the optical density measuring means are mutually positioned such that the light beam guided in the first optical waveguide can be guided in the second optical waveguide after passing through the path in the liquid medium of the reactor; a first optical waveguide and a second optical waveguide, means for introducing a light beam into the first optical waveguide, and means for measuring the concentration of the light beam exiting from the second optical waveguide. 9. The device according to claim 8, characterized in that: