JPS6241703A - Sulfuric acid concentration apparatus - Google Patents

Abstract

PURPOSE:To prevent generation of sulfur trioxide and reduce contamination, by covering a sulfuric acid concentration tank and a connection pipe thereof to a cooling part with a heat insulating material. CONSTITUTION:A sulfuric acid concentration apparatus formed from a single or plural concentration tanks containing undiluted sulfuric acid, heating device, cooling device for condensing the generated vapor, receiving tank for collecting the condensate and connection pipe with a cock. The above-mentioned connection pipe is provided between the concentration tanks and the cooling part and covered with a heat insulating material.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an apparatus for evaporating and concentrating sulfuric acid.

(Prior Art) High purity of sulfuric acid is required in various fields such as the electronic industry, and as a result, it has become necessary to improve the technology for evaluating the purity of sulfuric acid. The concentration of impurities contained in sulfuric acid can be analyzed and evaluated with high sensitivity using various spectroscopic analyzers, but it is difficult to directly introduce sulfuric acid into an analyzer for analysis, and the matrix must be separated before introducing it into the analyzer. There is a need. In the case of sulfuric acid, the matrix is generally separated and removed by evaporation concentration, the vapor residue is dissolved in pure water, and then impurity analysis is performed.

Conventionally, in the evaporative concentration method of sulfuric acid, a sulfuric acid stock solution is placed in an evaporating dish made of platinum or quartz, and heated to the boiling point of sulfuric acid (approximately 31
It was as simple as heating it above 7°C.

Although evaporation and concentration can be carried out using a conventional vacuum distillation apparatus, an example of such apparatus is shown in FIG. It has a structure in which a sulfuric acid stock solution 2 is put into a concentrating tank 1, heated by a heating device 3, and the steam is cooled and condensed in a cooling section 8 having a cooling water inlet/outlet 9.10 and held in a receiving tank 2. The inside of the device is evacuated through the pressure reduction port 13 attached to the side pipe 11 for pressure reduction, and a capillary 27 and a thermometer 2 are connected to the connection pipe 26 that connects the concentration tank 1 and the cooling section 8.
8 could be attached.

(Problem to be solved by the invention) Sulfuric acid generates sulfur trioxide at 290°C and
It boils at C. Therefore, conventional sulfuric acid concentration methods have disadvantages such as generating toxic sulfur trioxide, requiring a long time, and being an open system, which is likely to cause contamination. In addition, the vacuum distillation apparatus shown in FIG. 4 has poor distillation efficiency for sulfuric acid, which has a high boiling point, due to the structure of the connecting pipe 26, it is not possible to install multiple concentration tanks, and external air is drawn from the capillary 27 provided to prevent bumping. After evaporation and concentration, which is likely to cause contamination because it is introduced into the stock solution,
It had drawbacks such as the difficulty of removing the concentration tank. Also,
A rotary evaporator is used as a vacuum evaporation concentration device for substances with a relatively low boiling point, but it has been difficult to apply it to sulfuric acid, which has a high boiling point, due to problems such as the material of the rotating parts.

The object of the present invention is to eliminate the drawbacks of the conventional methods and devices, and to quickly, without generating sulfur dioxide,
Moreover, it is an object of the present invention to provide a sulfuric acid concentrator that can evaporate and concentrate a single or multiple sulfuric acid samples without causing contamination.

(Means for Solving the Problems) According to the present invention, a concentrating tank containing a sulfuric acid stock solution is heated by a heating device, the generated steam is condensed in a cooling section, and the condensed liquid is collected in a receiving tank. A vacuum evaporation concentration device having a structure that includes a single or multiple concentration tanks, and a structure in which the concentration tank and a part of the connecting pipe with a cock provided between the concentration tank and the cooling section are covered with a heat insulating material. A sulfuric acid concentrator is obtained, which is characterized by having:

(Action) Sulfuric acid does not generate sulfur dioxide under vacuum and reduced pressure.
Evaporates quickly. Efficient evaporation and concentration can be achieved by improving the connecting pipe and covering the parts that come in contact with outside air with heat insulating material. Sulfuric acid does not bump when heated without water, so
There is no need for a capillary to prevent bumping, and the device can be sealed, reducing contamination from the outside.

(Example) Hereinafter, the present invention will be described with reference to the drawings showing one example. FIG. 1 is a side view showing the apparatus of the embodiment. A sulfuric acid stock solution 2 is put into a concentration tank 1 and heated by a heating device 3 to evaporate it. The sulfuric acid vapor enters the cooling section 8 through the connecting pipe 5 and is condensed. The condensed liquid passes through the depressurizing side pipe 11 and is collected in the receiving tank 12 . The inside of the apparatus is evacuated via a pressure reduction port 13 attached to a side pipe 11 for pressure reduction. In this apparatus, in order to increase the efficiency of sulfuric acid distillation, the connecting pipe 5 is structured so that sulfuric acid vapor can easily pass therethrough, and a part of the concentrating tank 1 and the connecting pipe 5 are covered with a heat insulating material 4.

In addition, in order to prevent contamination due to elution from equipment constituent materials, the concentration tank 1 and the connecting pipe 5 are made of quartz. After evaporation and concentration, the concentration tank 1 is removed, and the evaporation residue in the tank is collected with a pipette or the like and used for impurity analysis. In order to make it easier to remove the concentration tank 1, the connecting pipe 5 is equipped with two cocks. . That is, when removing the concentration tank 1,
To prevent the condensate from flowing back, first close the cap, then open the cock 7 to bring it to atmospheric pressure, and then remove it.

With this device, concentration could be carried out at a distillation rate of about 150 ml/H with almost no sulfur trioxide being generated, and the rate was several to 30 times faster than the conventional method and device. Furthermore, due to the reduction of contamination, the lower limit of detection shown in the table was achieved in analysis using graphite furnace atomic absorption spectrometry.

A perspective view of another embodiment of the concentration tank 1 and connecting pipe 5 shown in FIG. 1 is shown in FIGS. 2 and 3. The device shown in Figure 2 is a connecting pipe 16.
It has a structure in which it is branched into two and can be provided with two concentration tanks 14 and 15. Three or more concentration tanks can be provided by increasing the number of branches of the connecting pipe. Since a plurality of concentration tanks can be provided in this way, a plurality of sulfuric acid samples can be evaporated and concentrated simultaneously, and the processing time can be significantly reduced.

FIG. 3 shows another embodiment. This device has a cock at the branched part of the connecting pipe 21. For example, when the concentration in the concentration tank 19 is finished, the cock 22 is closed and the cock 23 is opened, and when the concentration tank 20 is finished, the cock 24 is closed.
By closing the cock 25 and opening the cock 25, each concentration tank can be attached and detached independently. Also in this case, three or more concentration tanks can be provided by increasing the number of branches.

(Effects of the Invention) As shown in the examples above, by performing evaporation concentration using the apparatus of the present invention, toxic sulfur trioxide is not generated, and the concentration is several times to 30 times that of the conventional method and conventional apparatus. Concentration was possible at variable speed. In addition, since it is a closed type, contamination from the outside can be reduced, and analysis of metal impurity elements in sulfuric acid using graphite furnace atomic absorption spectrometry was possible down to an extremely trace concentration of about 0.019 g/l. If you have multiple sulfuric acid samples,
By using a device equipped with multiple concentration tanks, the processing time could be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a side view of an apparatus showing one embodiment of the present invention, FIGS. 2 and 3 are partial perspective views of other embodiments, and FIG. 4 is a side view of a conventional vacuum distillation apparatus. In the figure, 1. 14, 15, 19. 20... concentration tank, 2... sulfuric acid stock solution, 3... heating device, 4... heat insulating material, 5, 16
, 21, 26... Connecting pipe, 6.7.17, 18.22
~25...Cock, 8...Cooling section, 9...Cooling water inlet, 10...Cooling water outlet, 11...Side pipe for pressure reduction,
12...Receiving tank, 13.・, Decompression port, 27... Capillary, 28... Thermometer. Closed? Figure 3

Claims (1)

[Claims] In a sulfuric acid concentrator that has a concentration tank containing a sulfuric acid stock solution, a heating device that heats the concentration tank, a cooling section that condenses the generated steam, and a receiving tank that collects the condensed liquid, a single or multiple concentration tanks are used. 1. A sulfuric acid concentrator, comprising: a sulfuric acid concentrator, and a structure in which a part of the concentrating tank and a connecting pipe with a cock provided between the concentrating tank and the cooling section are covered with a heat insulating material.