RU2332357C1 - Method of sewage water neutralisation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used for neutralisation of sewage water containing dissolved explosive substance, for instance, octogen. Method of sewage water purification lies in decomposition of explosive substance dissolved in it in presence of sulphuric acid under action of ultraviolet rays in bath by circulation according to scheme tank - peristaltic pump-nutsch filter - peristaltic pump - bath - tank. Distance between source of ultraviolet rays and surface of sewage water in bath does not exceed 11 cm, thickness of water layer in it does not exceed 3 cm, and total duration of irradiation is from 0.33 to 0.5 hour.

EFFECT: intensification of sewage water neutralization process.

1 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of neutralization of industrial wastewater.

A known method of neutralizing an aqueous solution of explosive, patent RU No. 2233257, IPC С06В 21/00 [1], which is adopted as a prototype.

According to this patent, the neutralization of an aqueous explosive (BB) solution is carried out by decomposing it under the action of ultraviolet rays in the presence of sulfuric acid. The neutralization process is carried out during the circulation of an aqueous explosive solution in the presence of sulfuric acid according to the tank-peristaltic pump-bath-tank scheme. A source of ultraviolet rays, a DRT-2500 mercury-quartz lamp, is installed above the bathtub. The distance between the source of ultraviolet rays and the surface of the wastewater in the bath is not more than 11 cm, the thickness of the water layer in it is not more than 3 cm, the total duration of irradiation is from 0.33 to 0.5 hours. The solution is circulated according to the indicated scheme to a mass fraction of explosive below the maximum permissible concentration (MPC) for water bodies.

However, the method of neutralizing an aqueous explosive solution according to the above patent has some disadvantages.

According to the mentioned scheme of the circulation process, the neutralized aqueous solution of the explosive after the bath is returned to the same tank from where it is taken for disposal. In this case, the neutralized portion of the aqueous explosive solution is concentrated when it enters the tank and is mixed with wastewater with a higher concentration of explosives and its mass fraction gradually decreases during circulation.

Therefore, multiple and prolonged circulation is required to achieve the mass fraction of explosive in an aqueous solution to the MPC level.

In the manufacture of charges from a mixed solid rocket fuel from powerful explosives, octogen has found primary use, the neutralization of which in the waste water extends the claimed method.

An object of the invention is to intensify the process of neutralizing wastewater with an explosive dissolved in it by decomposing it under the influence of ultraviolet rays and improving the circulation scheme.

The technical result of the method of neutralizing wastewater with the decomposition of the octogen dissolved in it in the presence of sulfuric acid under the influence of ultraviolet rays in the bath during circulation according to the tank-peristaltic pump-bath-tank scheme (with a distance between the source of ultraviolet rays and the surface of the wastewater in the bath is not more than 11 cm, the thickness of the water layer in it is not more than 3 cm, with a total irradiation duration of 0.33 to 0.5 hours) is achieved by including an additional nutsche filter in the circulation circuit and neutralizing circulation of wastewater according to the scheme tank - peristaltic pump - suction filter - peristaltic pump - bath - tank. The scheme of wastewater neutralization proposed in the patent (prototype) is close to the scheme of external circulating mixing, presented in the book "General Course of Processes and Apparatuses of Chemical Technology" edited by V. G. Aishtein, M .: Logos, higher school, 2002, vol. .1, p. 444 [2]. From this source it follows that to ensure the quality of mixing, it is necessary to find the pump capacity V, m ³ / s, at a certain empirically determined multiplicity of circulation K according to the formula V = K _c · V,

where V is the volume of the vessel, m ³ .

According to the literature ("Devices for mixing liquid media" E.A. Vasiltseva, V. S. Ushakova, Reference manual, Leningrad, Leningrad branch, 1979, p. 157 [3]) to achieve the required degree of mixing ideality is required K _c ≥10, i.e. it is necessary to carry out at least 10 circulations in the volume of the apparatus.

Thus, for perfect mixing conditions, the pump capacity should be 10 times the volume of the vessel.

However, in the circulation scheme during the neutralization of wastewater containing explosives, this condition is difficult to fulfill for the following reasons:

- the existing product range does not include pumps that meet specific requirements to ensure safe operating conditions during the processing of explosives;

- with the required use of a pump with high productivity, it is necessary to design a large bath with a powerful radiation source, taking into account the provision, at the same time, of a sufficiently large residence time of treated wastewater.

It seems possible to intensify the process of decomposition of explosives in wastewater by providing two vessels in the scheme: one for supplying wastewater to the bath for decomposition, and the other for receiving after passing through the bath. In the wastewater treatment scheme, a tank will be used as the first vessel, and a suction filter as the second vessel.

The possibility of using a nutsche filter is due to the fact that it is used at the initial stage to separate explosives from insoluble particles. When performing subsequent operations at the stage of neutralization, the nucht filter is not involved in the process. In this regard, it can be used as a receiving tank at the stage of wastewater treatment. In this case, it is necessary to replace the filter cloth before use. In the wastewater treatment scheme, a filter cloth is required to separate possible foreign matter, to protect the peristaltic pump, since the ingress of solid particles into the membrane zone of the pump can disrupt its normal operation.

When the wastewater is circulated with intake after the bath into the suction filter, it is excluded from mixing it in the tank with the wastewater to be neutralized, thereby reducing the duration of the neutralization process.

The present invention is recommended to be used for a method of neutralizing wastewater containing a dissolved nitroamine substance - HMX, by circulation according to the scheme (drawing): tank - peristaltic pump - suction filter - peristaltic pump - bath - tank.

According to this scheme, the wastewater from the suction filter 1 with open gates 6 (5) and 6 (2) is pumped by a peristaltic pump 2 into the tank 3. At the same time, the gates 6 (1), 6 (3) and 6 (4) are closed. After stirring, if necessary, with the introduction of sulfuric acid with a peristaltic pump 2, with the open gates 6 (1) and 6 (3), the gates 6 (2), 6 (4) and 6 (5) are closed from the tank, the water is pumped into the suction filter after replacement filter cloth. Next, the wastewater from the suction filter 1 with a peristaltic pump 2 with open gates 6 (4) and 6 (5) and closed gates 6 (1), 6 (2) and 6 (3) is passed through bath 4 when irradiated with ultraviolet rays to the tank 3. In the above-described way, the circulation of wastewater is continued according to the scheme: tank - peristaltic pump - suction filter - peristaltic pump - bath - tank until the mass fraction of explosive decreases to the MPC level and below.

The main operation in the wastewater treatment scheme is its irradiation with ultraviolet rays in the bath. When working according to the recommended scheme, it is possible to use the simplest option - a single pass of wastewater through the bath. This option is implemented if the residence time of the wastewater in the bath is ensured equal to the required duration for the decomposition of HMX to its mass fraction below MPC. This option corresponds to the circulation coefficient K _c = 1 according to the formula:

where g is the pump capacity, l / h;

τ is the required residence time in the bath for the decomposition of explosives to a level below the MPC, hours;

V is the working volume of the bath, l.

In this case, for small installations with a small bath volume, which is limited by the small area of ultraviolet light scattering by a single lamp, it becomes difficult to select a pump due to its unstable operation.

For example, with the required time for the disposal of wastewater with an octogen of 0.5 hours

т.е производительность должна быть не более двух рабочих объемов ванны.

i.e. productivity should be no more than two working volumes of the bath.

When using a larger pump, multiple wastewater circulation through the bath is required. However, in this case, there is also a restriction on the performance of the peristaltic pump. With greater pump performance, the residence time of wastewater in the bath is reduced, which will lead to turbulence in the flow. For practical use, it is advisable that the circulation ratio K _c <5. With a greater multiplicity of circulation, the technical process is complicated due to the need for multiple gate control. In this case, the maximum pump capacity is

When neutralizing wastewater according to the claimed method, the frequency of circulation through the bath will correspond to the frequency of exchange of contents in the tank or suction filter of the volume of wastewater.

The duration of emptying the tank or filling the suction filter will be

where t is the duration of a single expenditure of wastewater from the tank, hours;

Q is the volume of wastewater in the tank, l;

g - productivity of the peristaltic pump, l / h.

The total duration of the neutralization T will be:

Reducing the total duration of disposal can

provide by parallel installation of several sources of ultraviolet radiation.

Comparative indicators of the neutralization of wastewater with HMX by the present method and the prototype are shown in the table.

Comparative indicators Circulation pattern Duration of disposal, hour According to the prototype 150 and more According to the claimed method 67-90

Comparative indicators were obtained when testing the installation with the following parameters: the distance from the lamp to the surface of the wastewater in the bath is 11 cm; the thickness of the water layer in the bath is 3 cm; volume of neutralized wastewater 500 l; bath volume - 2.8 l; peristaltic pump capacity - 20 l / h; the source of ultraviolet radiation - one mercury-quartz lamp DRT-2500; the maximum mass fraction of dissolved HMX in wastewater is 15 mg / l.

From the table it is seen that according to the claimed method, the neutralization of wastewater with octogen is carried out more efficiently.

Example. Initial data:

bath volume V = 2.8 l,

the required residence time of wastewater in the bath t = 0.5 hours,

By circulating the multiplicity _n = 5,

the volume of neutralized wastewater V = 500 l.

With these parameters, the pump capacity will be:

At this capacity, the decontamination time T will be

The proposed method of disposal of wastewater containing HMX was tested with a positive result in the conditions of the Perm Perm Powder Plant.

Claims (1)

A method of neutralizing wastewater, including the decomposition of an explosive dissolved in it in the presence of sulfuric acid under the influence of ultraviolet rays in the bath by circulating according to the tank-peristaltic pump-bath-tank scheme with a distance between the source of ultraviolet rays and the surface of the wastewater in the bath not more than 11 cm , the thickness of the water layer in it is not more than 3 cm and the total duration of irradiation is from 0.33 to 0.5 hours, characterized in that an additional nutsche filter and decomposition of explosives are introduced into the circulation circuit in the waste water is carried out according to the scheme: Tank - peristaltic pump - nutsche filter - peristaltic pump - bath - tank.