JP4780992B2 - Method for inactivating residual alkali metal - Google Patents

Description

  The present invention relates to a treatment method for decomposing and extinguishing a remaining alkali metal after dehalogenating an organic halogen compound such as polychlorinated biphenyl (hereinafter referred to as PCB) with an alkali metal. is there.

  Conventionally, a method of decomposing PCB (hereinafter referred to as SD method) by reacting an organic halogen compound such as PCB with an alkali metal dispersion such as metal sodium dispersion (hereinafter referred to as SD) has been known. Yes. In this SD method, the amount of SD used for the reaction with PCB is larger than the minimum amount necessary for the dehalogenation treatment. In particular, when PCB is processed at a high concentration (content of 1% or more, particularly 10% or more), since the amount of SD used is large, a large amount of SD remains in the reaction solution after the PCB decomposition treatment, The handling of metallic sodium in this SD becomes a problem. Metallic sodium is extremely active in air and easily ignites, so it is dangerous to leave it as it is. Therefore, a method of adding water to the reaction solution after the PCB treatment to inactivate is performed (Patent Documents 1 to 3). When attention is paid to the water to be added, there are a method (Patent Document 4) in which the addition amount is defined, a method of adding by spraying (Patent Document 5), and the like.

JP2002-12561 JP 2002-65888 A JP 2002-97159 JP 2002-121155 A JP-A-2005-7285

Patent Documents 1 to 3 describe a method of adding water to the treatment solution after dehalogenation to inactivate the residual sodium metal, but do not describe a specific method of adding water.
Patent Document 4 describes a method using 1 to 1.2 mol of water with respect to 1 mol of residual metallic sodium. This requires an activated carbon adsorption treatment or the like for the waste water treatment after the inactivation treatment, and suppresses the amount of water to be added, thereby reducing the cost of the waste water treatment. The addition of 1 to 1.2 moles of water per mole of residual metallic sodium theoretically terminates the inactivation process. In fact, in the beaker test, it can be treated with about 1 mole of water per 1 mole of residual sodium metal after PCB treatment, but in an industrial plant or demonstration facility, in order to add water with theoretical values, It has been found that due to the stirring efficiency of the treatment liquid and the treatment temperature when the treatment volume is large, about 1 mol of water does not completely treat metallic sodium within the range of general operation time. In fact, as described in Examples of the present invention, hydrogen is generated over a long period of time even after adding 1.2 mol or more of water.
When water is added to the remaining metallic sodium and reacted, hydrogen is generated. The generated hydrogen is discharged out of the treatment tank and sent to an exhaust gas treatment apparatus such as activated carbon adsorption treatment for treatment. Since a large amount of hydrogen is generated, it causes a load on the exhaust gas treatment device, and thus the exhaust gas treatment device needs to be scaled up. In addition, the hydrogen concentration in the exhaust gas increases due to rapid hydrogen generation, and it mixes with oxygen in the air near the exhaust gas discharge port. Depending on the conditions, there is a risk of ignition and explosion, which is very dangerous. As the hydrogen is generated, the solution foams, and the bubbles are sent to the exhaust gas treatment device, which may hinder the operation.
Metallic sodium is very active with respect to water, and even if it is a general addition method, the reaction is easily performed and hydrogen is rapidly generated. Therefore, it is preferable to advance the reaction by adding water excessively. Absent. The method of Patent Document 5 in which water is introduced by spraying or finely flowing has an effect of facilitating the reaction, but by making water finer, the reaction with metallic sodium becomes excessively active, and hydrogen rapidly increases. Will lead to the occurrence. Since bubbles are generated in proportion to the generation of hydrogen, Patent Document 5 controls foaming by controlling the number of revolutions of the stirrer. Moreover, although the method of adjusting the input amount of water is described, the specific adjustment method is not suggested.
Therefore, an object of the present invention is a treatment of the remaining alkali metal after the dehalogenation reaction, which controls abrupt generation and foaming of hydrogen by specific adjustment of water addition, suppresses foaming, and is safe. It is an object of the present invention to provide a method for inactivating a residual alkali metal capable of performing a reaction treatment operation.

Therefore, the present invention has been made in view of the background as described above, and succeeded in solving the above problems by employing the following method for inactivating a residual alkali metal. That is, the present invention
(1) A method for inactivating a residual alkali metal, wherein a dehalogenation treatment is performed by reacting an organic halogen compound and an alkali metal, and the remaining alkali metal is treated by adding water to the alkali metal remaining after the treatment. In
Adding by dividing the total amount 1.2 to 2 times moles of water to a plurality of times relative to the total number of moles of the alkali metal content remaining that features a.

And it is preferable that the above invention is embodied as follows.
(2) you added portionwise total amount 1.5 to 2 times moles of water to a plurality of times relative to the total number of moles of the alkali metal content remaining.
(3) a primary additive, you 1 to 1.5-fold mol relative to the total number of moles of the alkali metal content remaining.
(4) the primary additive, you 1.1 to 1.5-fold mol relative to the total number of moles of the alkali metal content remaining.
(5) between the primary addition and secondary addition, Ru provided added stopping step.
(6) intends rows secondary added after the hydrogen generation amount per unit in the processing bath time has decreased.
(7) The rate of addition, Ru constant speed der.
(8) is divided into two times you added to the water.
(9) adding by dividing the water into a plurality of times, the primary includes a second adding step, the addition rate of water in the secondary addition, have faster than the rate of addition of water in the primary additive.

In the above (1) and (2) , by defining the total amount of water to be added, the residual metal sodium can be completely decomposed and inactivated. If more water is added, it is natural that the reaction solution shifts to the inactivated region. However, by defining 2 times mole as the maximum required amount, excessive addition can be suppressed and residual metal sodium decomposition can be suppressed. Waste water treatment after treatment can be suppressed. Moreover, by adding 1.2 times mol or more, preferably 1.5 times mol or more of water as the minimum necessary level, the processing capacity is large as in industrial plants and demonstration facilities, and the efficiency of stirring, processing temperature, etc. Even if it affects the decomposition treatment, the residual metallic sodium can be completely treated. And by satisfying the conditions of these addition amounts and adding in multiple portions, the generation of hydrogen gas as a reaction product can be suppressed and controlled, and the hydrogen concentration in the exhaust gas does not reach the explosion limit. Can be.
In the above (3) and (4) , most of the residual metallic sodium can be inactivated by the primary addition. Suspending and stopping the addition until most of the metallic sodium is processed has a great influence on the operation of temperature control, exhaust gas control, etc., and is 1 per 1 mol of alkali metal remaining in the primary addition. It is preferable to continuously add 1 mol, preferably 1.1 mol or more of water. In addition, as most metal sodium is decomposed by the primary addition, the maximum hydrogen generation amount can be grasped at the time of the primary addition, and the hydrogen generation amount in the subsequent addition steps can be easily controlled. It becomes. Then, in the subsequent addition, that is, in the steps after the secondary addition, the residual metallic sodium that has not been decomposed by the primary addition can be more completely decomposed into a safe form.
In the above (5) and (6) , troubles such as sudden hydrogen generation, load of the exhaust gas treatment device due to foaming, danger of explosion can be prevented. By grasping the hydrogen generation state and confirming a decrease in hydrogen generation amount, so-called peaking, hydrogen generation at the time of secondary addition can be controlled, and trouble can be minimized.
In the above (7) , by performing the addition rate constant, there is no work for arbitrarily changing the conventional addition rate, and the addition process and control become easy. Further, it is possible to facilitate operation control due to generation of hydrogen accompanying the addition and temperature rise.
In (8) above, the time for the inactivation treatment step can be shortened by defining the divided addition to be twice. Since most of the remaining metallic sodium can be treated by the primary addition, there is no need to increase the number of subsequent additions unnecessarily, and two additions are preferred.
In (9) above, it is possible to further reduce the time of the inactivation processing step. As most residual metal sodium is treated in the primary addition, the maximum amount of hydrogen generated reaches a peak at the time of the primary addition, and even if the rate of water addition thereafter is increased, the amount of hydrogen generated is reduced. It can be controlled well. And addition time can be shortened safely.

  First, in addition to PCB as an organic halogen compound to be subjected to the dehalogenation treatment of the present invention, a hardly decomposable organic halogen compound such as dioxins, polychlorinated dibenzofurans, polychlorinated benzene, chlorofluorocarbon, DDT, and BHC is used. These organic halogen compounds may be used as they are, but can be used as an organic halogen compound solution adjusted to a concentration suitable for treatment by dissolving in a solvent. For example, in the case of PCB, it is preferable that the concentration is adjusted to 50 wt% or less. When the concentration is high, the viscosity becomes high and handling becomes difficult.

  As the solvent for dissolving the organic halogen compound, aliphatic hydrocarbons, aromatic hydrocarbons or alicyclic hydrocarbons which are inert to alkali metals or low in activity are preferable. For example, hexane, cyclohexane, benzene, kerosene, As substitutes for decalin, transformer oil (trans oil described in JIS C 2320-1993), heavy oil (described in JIS K2205), liquid paraffin or cleaning oil (fluorocarbon, trichloroethane, kerosene, etc., automobiles, electronic parts, precision equipment And a hydrocarbon-based solvent used for cleaning), and these can be used alone or as a mixture. Among these solvents, trans oil can be particularly preferably used in terms of stabilizing SD.

  Examples of the alkali metal include potassium, lithium, cesium, rubidium, and alloys thereof in addition to sodium, but sodium is most preferable in view of ease of handling and reactivity. SD is most preferable in consideration of sex. In particular, SD produced in electrical insulating oil is excellent in stability, dispersibility, and reactivity. The electrical insulating oil is an oil for electrical insulation used for 1 to 7 types of capacitors described in Japanese Industrial Standard JIS 2380, and among them, the first type electrical insulating oil is preferable. Further, the alkali metal concentration in the alkali metal dispersion can be arbitrarily selected, but is preferably about 1 to 50%. The average particle size of the alkali metal dispersion is 20 μm or less, preferably 10 μm or less. SD is added in an amount of 1 to 50 times mol, preferably 1 to 20 times mol, per mol of halogen atom in the organic halogen compound.

  In the process of decomposing an organic halogen compound, for example, when PCB contained in electrical insulating oil is decomposed at a high concentration, PCB is contained in a reaction tank in which SD and trans oil as a solvent are stored. The oil to be treated is supplied and dehalogenated. The reaction temperature here is 150 to 200 ° C, preferably 160 to 180 ° C. By the chemical reaction between PCB and metallic sodium, biphenyl is bonded, and PCB is rendered harmless to the polymer. Excess metal sodium remains in the reaction solution after the treatment, and water is added to inactivate the remaining metal sodium. Since the amount of residual metallic sodium is calculated based on the amount of metallic sodium in the SD used in the dehalogenation process, the amount of metallic sodium that reacts with PCB, etc., the amount of water actually added is theoretically The amount corresponds to the calculated residual metal sodium. The addition of water is performed in a plurality of times, preferably in two times. By adding water, sodium and water react to produce sodium hydroxide and hydrogen, and the residual metallic sodium is inactivated. Then, the treated solution is sent to a waste water treatment device and the exhaust gas such as hydrogen is sent to an exhaust gas treatment device and the like for treatment.

  Further, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a processing apparatus according to an embodiment of the present invention. The processing apparatus for processing the residual metallic sodium is composed of a reaction tank 1, a processing solution tank 2, a decomposition water tank 3, a control device 4, and the like. The control device 4 connects the valve 3 b provided in the middle of the pipe 3 a that connects the reaction tank body 10 and the decomposition water tank 3, the exhaust gas treatment device 5 that processes the exhaust gas in the reaction tank 1, and the reaction tank 1. It consists of a concentration meter 5c for measuring the hydrogen concentration in the exhaust gas provided in the middle of the pipe 5a and a thermometer (not shown) for measuring the temperature in the tank. The measurement value of the densitometer 5c is received by the control device 4 through the wiring 41. Moreover, the wiring 42 which transmits the signal which switches the valve | bulb 3b from the control apparatus 4 is provided. The reaction vessel body 10 is provided with a jacket 11 for controlling the temperature, a stirrer 12 and an inert gas supply device 13.

  The material of the reaction vessel main body 10 and the jacket 11 is appropriately selected from steel (SS), stainless steel (SUS), and the like according to the heat medium temperature, equipment cost, and the like. The stirrer 12 only needs to have sufficient ability to stir the reaction solution. For example, a paddle blade or a turbine blade is preferable in the shape of a stirring blade. In some cases, it is possible to provide a defoaming plate for defoaming above the liquid level of the treatment solution and on the stirring shaft in the gas phase. In order to increase the stirring efficiency, a baffle is provided in the tank. The densitometer 5c detects the amount of hydrogen generated in the tank, and there is no particular problem as long as the hydrogen concentration can be measured. However, as a place to be installed, a pipe 5a led out to the exhaust gas treatment device 5 or the like. It is preferable to provide it at the location of the occlusion system, such as in the middle. Moreover, since it takes time until hydrogen gas is generated and exhaust gas is discharged and the hydrogen concentration in the exhaust gas is measured as the distance from the reaction vessel 1 increases, it is preferably provided as close to the reaction vessel 1 as possible. The thermometer (not shown) is installed so as to be immersed in the reaction solution, but depending on the reaction state, there are some places where the temperature rise is significant locally, so several places are placed and the temperature change is made. It is preferable to be in a state where it can be confirmed in more detail.

  Regarding the deactivation treatment method of the present invention in the case of adding water, first, nitrogen, argon or helium, which is an inert gas, is preliminarily applied to the reaction vessel main body 10 and the piping accompanying it by the inert gas supply device 13. Then, the processing solution is supplied from the processing solution tank 2 to the reaction tank main body 11 under an inert gas atmosphere. The total amount of the processing solution is supplied so that the processing solution is not added again after the start of water addition. This uses a method in which only water is added during the deactivation treatment in order to facilitate control of the temperature due to the amount of hydrogen generated in the tank and heat generation. In addition, a solvent such as insulating oil may be injected into the treatment solution to reduce the temperature before adding water.

  The reaction solution after the dehalogenation treatment is as high as 150 to 180 ° C., and the treatment solution is cooled to 70 to 100 ° C., preferably 80 to 90 ° C. for treatment. This is because if the temperature in the tank rises to 100 ° C. or more due to an exothermic reaction in which the remaining metallic sodium reacts with water, the added water rapidly evaporates, and sufficient reaction with metallic sodium is not performed. In addition, if the reaction temperature is too low, the reaction is carried out slowly and the inactivation treatment time becomes long. Therefore, the reaction temperature is as high as possible, and the temperature range of 70 to 100 ° C. is the temperature at which water does not evaporate. It is preferable to control it. And since it is an exothermic reaction, if the temperature in the tank is too close to 100 ° C, the temperature rise due to heat generation cannot be suppressed well by temperature control with a cooling medium or the like, and the temperature is controlled within the range of 80 to 90 ° C. Is preferred. As the temperature control, a method of controlling the temperature in the tank by passing a heating medium / cooling medium or the like through a jacket provided in the reaction tank, such as the method of the present applicant (Japanese Patent Laid-Open No. 2004-209432), is preferable.

  While stirring with a stirrer 12, a cooling medium is allowed to flow through the jacket 11 attached to the reaction vessel main body 10, and the valve 3 b is opened by a signal from the control device 4, and water from the cracked water tank 3 is kept at a predetermined constant rate. Then, the primary addition is made in the reaction vessel main body. The primary addition amount is a predetermined amount defined in advance and is 1 to 1.5 times mol, preferably 1.1 to 1.5 times mol of water relative to the total number of moles of remaining alkali metal. Control. Here, as additives other than water, alcohols such as methanol, ethanol, propanol and butanol, organic acids, or a mixture thereof can achieve the same effect, but water is optimal in consideration of cost and handling. is there. As a method of adding water, even if it is a method of injecting and adding piping into the processing solution so that it is smoothly added to the processing solution, or a method of adding water along the inner wall of the tank, A method of adding directly from the gas phase part in the tank may be used, and there is no particular limitation. When added, metal sodium in the treatment solution reacts with water to generate hydrogen, so the inert gas is added while always being injected. The generated exhaust gas such as hydrogen passes through the pipe 5a, is led to the exhaust gas processing device 5, and is processed by activated carbon adsorption or the like.

  After completion of the primary addition, the valve 3b is closed, and the hydrogen concentration and temperature are confirmed with the concentration meter 5c and the thermometer. By the inactivation treatment, the amount of hydrogen gas in the reaction vessel main body 10 increases. After confirming that the amount of hydrogen gas has reached its peak, the valve 3b is opened and secondary addition is started. The secondary addition is performed at a constant rate with a higher flow rate than the primary addition. And it added so that the total addition amount of water might be 1.2-2 times mole with respect to the total number of moles of the remaining alkali metal before primary addition, Preferably it is in the range of 1.5-2 times mole. Thereafter, the valve 3b is closed to finish the inactivation process. The treated solution after the inactivation treatment is transferred to an oil / water separation step (not shown) and processed separately.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples, and the present invention only needs to satisfy the requirements of the claims. It is possible.

Example 1
About 4000 kg of the treatment solution (100 ° C.) after the dehalogenation treatment was charged into a 4000 L reaction vessel from the treatment solution vessel and stirred, and simultaneously cooled by a cooling medium. Simultaneously with cooling to 85 ° C., water was firstly added from a cracked water tank at a constant rate of 53 kg (1.5 times the amount of residual metallic sodium) over 4 hours. Meanwhile, the hydrogen concentration was confirmed by a densitometer. Then, after about 5 hours from the start of the addition, it was confirmed that the hydrogen concentration reached its peak and the generation amount decreased, and then the secondary addition was started. The secondary addition was performed at a flow rate three times that of the primary addition. Until the end of the secondary addition, the hydrogen concentration was gradual, and the secondary addition was terminated after the addition of a total amount of 70 kg of water (2 times the amount of residual sodium before the primary addition).
(Example 2)
The same dehalogenation treatment was performed in the same equipment as in Example 1, and about 4000 kg of the treatment solution after the dehalogenation treatment was charged from the treatment solution tank and cooled to 85 ° C. From the cracked water tank, 42 kg of water (1.2 mol of the amount of residual metal sodium) was added primarily at a constant rate over 3.2 hours. After confirming the hydrogen concentration with a densitometer, secondary addition was started. The secondary addition was performed at a flow rate three times that of the primary addition. After the addition of a total amount of 53 kg (1.5 times the amount of residual sodium before the primary addition) of water, the secondary addition was terminated.
(Comparative Example 1)
The same dehalogenation treatment was performed in the same equipment as in Example 1, and about 3000 kg of the treatment solution after the dehalogenation treatment was charged from the treatment solution tank and cooled to 85 ° C. From the cracked water tank, 28 kg of water (0.8 moles of residual metal sodium amount) was added primarily at a constant rate. After confirming the hydrogen concentration with a densitometer, secondary addition was started. The secondary addition was performed at a flow rate three times that of the primary addition. After the addition of a total amount of 53 kg (1.5 times the amount of residual sodium before the primary addition) of water, the secondary addition was terminated.
(Comparative Example 2)
The same dehalogenation treatment was performed in the same equipment as in Example 1, and about 3000 kg of the treated solution after the dehalogenation treatment was charged from the treatment solution tank, and this time it was cooled to 60 ° C. First, 53 kg of water (1.5 times the amount of residual metal sodium) was added at a constant rate from the decomposition water tank. After confirming the hydrogen concentration with a densitometer, secondary addition was started. The secondary addition was performed at a flow rate three times that of the primary addition. The secondary addition was completed after adding a total amount of 70 kg of water (2 moles of residual sodium before the primary addition).

  Table 1 summarizes the processing temperatures and addition amounts of the examples, and FIG. 2 shows the amount of hydrogen generated in the tank by water addition based on the examples.

(Evaluation)
From the results of Examples 1 and 2, the maximum hydrogen generation amount can be set at the time of the primary addition, and there is no trouble due to foaming and no load on the exhaust gas treatment device. Residual metallic sodium could be inactivated. Further, from Examples 1 and 2, when the primary addition amount was defined as 1.2 times mole, the processing time could be shortened as the primary addition time decreased. And when the primary addition amount which is Example 1 is 1.5 times mole, the peak of hydrogen generation amount can be reliably put into the primary addition, and hydrogen generation in the subsequent secondary addition is controlled. I was able to. From this, it is preferable to determine the amount of addition and the temperature so as to fall within the scope of the claims in advance by trial operation or the like, and to select the optimum operation state. Moreover, it can be seen that the amount of hydrogen generation is also caused by the addition of 1.2 times mol or more by the primary addition, so that the residual sodium is not completely decomposed only by the addition of 1.2 times mol or less. That is, it can be said that metallic sodium is not treated unless the amount of water added is 1.2 times mol or more.
On the other hand, from Comparative Example 1, when the primary addition was performed at a ratio of 1.2 times or less, the allowable hydrogen generation amount was exceeded during the secondary addition, and the bubbles spread throughout the piping led to the exhaust gas treatment device. Oops. From this result, it can be said that in the primary addition, it is preferable to add 1.2 times mole or more of water in consideration of foaming and load on the exhaust gas treatment device.
From Comparative Example 2, the hydrogen generation amount could be provided at the time of the primary addition, and the treatment could be performed smoothly until the end. However, the reaction became dull due to the treatment temperature being 60 ° C., and the treatment time was considerably consumed. It became the result. The longer the treatment time, the greater the burden on personnel due to operation, the thermal efficiency of operation control, cooling medium, etc., so it can be said that the treatment temperature is preferably in the range of 70 to 100 ° C.

It is the schematic which shows the decomposition processing apparatus which shows one Embodiment of this invention. Hydrogen generation amount after water addition in Examples

Explanation of symbols

1 ... Reaction tank (10 is the main body, 11 is the jacket)
DESCRIPTION OF SYMBOLS 12 ... Stirrer 13 ... Inert gas supply device 2 ... Treatment solution tank 3 ... Decomposition water tank (3a is piping, 3b is valve)
4. Control device (41 and 42 are wiring)
5 ... Exhaust gas treatment device (5a is piping)

Claims (6)

In the deactivation treatment method of the remaining alkali metal, the dehalogenation treatment is performed by reacting the organic halogen compound and the alkali metal, and the remaining alkali metal is treated by adding water to the alkali metal remaining after the treatment.
At 70 to 100 ° C., water with a total addition amount of 1.2 to 2 times the total amount of moles of the remaining alkali metal is added in two portions, and the first addition (hereinafter referred to as primary addition) ) To 1 to 1.5 times the total number of moles of the remaining alkali metal, and secondary addition is performed after the amount of hydrogen generated per unit time in the treatment tank has decreased. Residual alkali metal inactivation treatment method. 2. The residual alkali metal concentration according to claim 1, wherein water having a total addition amount of 1.5 to 2 times moles is added in two portions with respect to the total number of moles of the remaining alkali metal. Activation processing method. The inertness of the remaining alkali metal according to any one of claims 1 and 2 , wherein the primary addition is 1.1 to 1.5 times the total number of moles of the remaining alkali metal. Processing method. Between the primary additive and second additive (hereinafter referred to as secondary additive), inactivation treatment method of the residual alkali metal according to any one of claims 1 to 3, characterized by providing the additive stopping step. The method for inactivating a residual alkali metal according to any one of claims 1 to 4 , wherein the addition rate is a constant rate. The step of adding water dividedly in a plurality of times includes primary and secondary addition steps, wherein the water addition rate in the secondary addition is faster than the water addition rate in the primary addition. Item 6. The method for inactivating a residual alkali metal according to Item 1 to 5 .

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