JPS5845660B2 - Trace sulfur analysis method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an analytical method and apparatus for easily, quickly, and accurately quantifying trace amounts of sulfur compounds contained in steel or the like.

In recent years, there has been a demand for higher quality metal materials such as steel, and efforts are being made to reduce the sulfur content, which has a negative effect on mechanical strength and other properties of the material.

Along with this, there is a need for an analytical method that can accurately and quickly quantify trace amounts of sulfur of 10 pp111 or less.

As an analysis method for sulfur in metal materials, taking iron and steel as an example, the Japanese Industrial Standards method for determining sulfur in iron and steel (JI
SG1215), 0.00
As a method to be applied when containing 5% or more sulfur,
Three methods have been established: the barium sulfate gravimetric method, the combustion neutralization titration method, and the combustion iodine titration method, and the pararose aniline spectrophotometry method has been stipulated as the method to be applied when sulfur content is 0.02% or less. ing.

Among these, the method suitable for analyzing trace amounts of sulfur is pararose aniline absorption spectrophotometry, but in this analysis method, the sample is burned in an oxygen gas stream and sulfur dioxide gas is converted into sulfur dioxide gas and absorbed into the absorption liquid. It is difficult to apply this method to the analysis of trace amounts of sulfur below ioppm due to loss due to gas adsorption, etc., and the problem of reagent blank testing in coloring operations using pararose aniline reagents.

Currently, due to the need to quantify trace amounts of sulfur, methods such as spectrophotometric analysis are being considered, in which sulfur compounds in a sample are generated as hydrogen sulfide, this is absorbed, and then a color is developed using a para-aminodimethylaniline reagent. Currently, it is difficult to obtain accurate quantitative values due to the complicated process.

As mentioned above, various methods of analyzing sulfur have been studied for a long time.
Although there are many analytical methods, 10 pI) In
There is no suitable analytical method or apparatus for the analysis of trace amounts of sulfur as described below, and the development of these methods is strongly required.

In view of this, the present inventor conducted research and development focusing on the determination of trace amounts of sulfur in steel, and based on the basic principle of hydrogen sulfide generation - circulation absorption - ultraviolet absorption method, the method principle and device structure are simple and quick. Moreover, the present invention has led to the provision of a new highly accurate trace sulfur analysis method and device.

In the present invention, hydrogen sulfide gas generated by thermally decomposing sulfur compounds in a sample with a reducing solution is absorbed into an alkaline solution and dissociated as sulfide ions (S). The basic method is to continuously measure this absorption to determine the sulfur content in the sample, taking advantage of the fact that the sulfur content has a maximum absorption wavelength in the sample.

The present invention will be described in detail below with reference to explanatory diagrams of an embodiment of the present invention shown in FIGS. 1 and 2.

As shown in the figure, the apparatus of the present invention includes a hydrogen sulfide generation/absorption section W that heats and melts an analysis sample to generate hydrogen sulfide and absorbs it, and circulates the absorption liquid from the hydrogen sulfide absorption tube 1b to the flow cell 6 of the photometer. Absorbent circulation to measure absorbance while
Ultraviolet absorption measuring section It consists of an automatic control section Z.

1 is a hydrogen sulfide generator, and the details of this part are shown in FIG.

1a is a hydrogen sulfide generation container in which an analysis sample and a reducing solution are placed and heated from the bottom to generate hydrogen sulfide.

At the top of this hydrogen sulfide generating container 1a, there is a hydrogen sulfide absorption pipe 1 for storing an alkaline solution and absorbing hydrogen sulfide.
It is attached so that b can be removed.

The hydrogen sulfide gas generated from the hydrogen sulfide generation container 1a is transferred to a hydrogen sulfide generation port 1d, a check valve 1e for preventing backflow of the absorption liquid, and a check valve 1e for the purpose of completely absorbing the hydrogen sulfide gas sent together with the inert gas. It passes through a glass filter 1f for dispersing air bubbles and is absorbed into the absorption liquid in the absorption tube 1b.

A water cooling pipe 1c is attached around the hydrogen sulfide absorption pipe 1b to prevent the temperature of the absorption liquid from rising.

At the top of the hydrogen sulfide absorption pipe 1b is an inlet 1 for the circulating absorption liquid.
g and an air vent pipe 11, and an outlet 1h for the absorption liquid is provided at the bottom.

Further, an inert gas blowing pipe 1j is attached below the absorption pipe 1b so as to be in contact with the bottom of the hydrogen sulfide generating container 1a.

It is desirable that each of the above parts be made of quartz glass due to corrosion caused by the reducing solution and processing convenience.

In addition, it is appropriate that the hydrogen sulfide generator 1 be small-sized, with the hydrogen sulfide generation container 1a having an internal volume of about 100m/about 100m to accelerate the generation rate of hydrogen sulfide, and the hydrogen sulfide absorption pipe 1b having a small amount of absorption liquid. In order to lower the lower limit of quantification, it is appropriate that the internal volume be approximately 10 rIll or less.

There are several methods for generating hydrogen sulfide gas from sulfur compounds in analysis samples such as steel, but in the present invention, a small amount of iron is added and an inert gas is blown in until white smoke is generated. The most suitable method was to use heat-treated phosphoric acid as a reducing solution.

That is, an analysis sample is placed in a hydrogen sulfide generating container 1a, and after blowing argon gas or nitrogen gas through an inert gas blowing pipe 1j to expel the air inside the container, the above-mentioned phosphoric acid reducing solution is added and the heater is heated. 2 to dissolve the analysis sample and continue heating until white smoke of phosphoric acid is generated, the sulfur compounds in the sample are converted into hydrogen sulfide and generated.

The reducing power of this method is very strong, and even if the sulfur in the sample forms a sulfide, such as iron sulfide, or even if it exists in the form of a sulfate, it can be easily reduced to hydrogen sulfide. I can do it.

However, in the case of metal samples that are more stable and less soluble than iron, etc., it may take a long time to dissolve and it may be difficult to completely generate hydrogen sulfide. is appropriate.

That is, first, the sample is heated and decomposed with aqua regia, then evaporated to dryness, the sulfur compound is replaced with sulfate, hydrochloric acid is added several times, heated to drive out the nitric acid, and metal aluminum pieces are added to reduce iron and other substances. Then, this sample solution is placed in the hydrogen sulfide generation container 1a, and a reducing solution is added and heated in the same manner as described above to generate hydrogen sulfide.

However, since the sample solution in this case will be a hydrochloric acid solution of about 10 -, use a solution containing sodium hydroxide in an amount equivalent to or more than this amount of hydrochloric acid as the absorption liquid, and use a hydrogen sulfide absorption tube 1b with a large capacity. There is a need.

In addition, when performing pretreatment to dissolve the sample in advance and replace the sulfur compound with sulfate as described above, a mixed solution of hydroiodic acid and hypophosphorous acid may be used as the reducing solution.
In this case, some of the iodine will volatilize, so it is necessary to provide a cleaning tube with a walking capacity containing water for cleaning the hydrogen sulfide gas between the hydrogen sulfide generation container 1a and the hydrogen sulfide absorption tube 1b.

In this way, the hydrogen sulfide absorption tube 1b can have a walking capacity as shown in FIG. 2, and the amount of absorption liquid can be reduced.

Furthermore, since the generated hydrogen sulfide gas tends to adhere to and remain on tube walls, it is suitable to keep the distance between the hydrogen sulfide generation container 1a and the absorption tube 1b as short as possible.

When a conduit is provided between 1a and 1b, it is necessary to heat the conduit by wrapping a heater around it.

Hydrogen sulfide generated by the above method is absorbed by the absorption tube 1b, and an alkaline solution such as sodium hydroxide, potassium hydroxide or aqueous ammonia is suitable as the absorption liquid. In the example, a sodium hydroxide solution of about 0.2 N was used.

The absorbed hydrogen sulfide dissociates into sulfide ions, and these sulfide ions have a maximum absorption wavelength near 232 nm in the ultraviolet region.

At wavelengths around 232 nm, dilute aqueous solutions such as sodium hydroxide used as absorption liquids show almost no absorption, and absorbance is proportional to the sulfide ion concentration. The content of sulfur compounds can be determined.

In this case, the measurement wavelength is preferably 232 nm, which is the maximum absorption wavelength, but the range of this absorption peak is average, for example, 220 nm to 232 nm.
Measurements can also be carried out at a wavelength of 252 nm.

However, since sulfide ions are easily changed by air oxidation, it is inappropriate to absorb the sulfide ions in the hydrogen sulfide absorption tube 1b and then take out the absorption liquid and transfer it to an absorption cell to measure the absorbance.

The present invention solves this problem by injecting inert gas and absorbing pipe 1b.
In addition to installing a cooler 1c around the photometer, a more fundamental solution is to circulate the absorption liquid through the flow cell of the photometer and quickly measure the absorbance in an atmospheric shielding system that does not allow the absorption liquid to come into contact with the air. It was adopted.

3 is a circulation pump that circulates the absorption liquid, and the amount of absorption liquid is approximately 5-
A constant flow pump with little pulsation is suitable because of the small amount and the need to stably measure absorbance.

5 is a device that can measure ultraviolet absorption with a photometer and is equipped with a circulation cell 6, which has an optical path length as long as possible and an internal volume of about 0.17727! A small amount is preferable.

Reference numerals 9a and 9b are flow path switching devices for sequentially injecting, loading, and discharging the absorption liquid, and an automatic solvent switching device used in liquid chromatographs and the like is suitable.

Operations related to circulation of the absorption liquid will be explained.

First, the flow path switch 9a is switched to the side where the flow path is stopped, the flow path switch 9b is switched to connect the absorption liquid tank 4 and the circulation pump 3, and the circulation pump 3 is operated for a certain period of time.

The absorption liquid passes through the pump 3, the circulation cell 6, and the absorption liquid circulation pipe 8 made of a Teflon tube with an inner diameter of approximately 0.5 to 1 mφ, which connects the absorption liquid inlet 1g at the upper part of the hydrogen sulfide absorption pipe 1b, and is constantly supplied to the absorption pipe 1b. The correct amount of absorption liquid is injected.

Next, inert gas is blown in and heated to start generating hydrogen sulfide.

The generated hydrogen sulfide is absorbed by the absorption liquid, and the inert gas as a carrier gas is passed through the air vent pipe 11 at the upper part of the absorption pipe 1b.
More exhaust.

At the same time as the hydrogen sulfide generation operation starts, the switching pump 3 is operated to connect the switching device 9a to the switching device 9b, and to connect the switching device 9b to the switching device 9a and the circulation pump 3, and the absorption liquid is transferred to the absorption pipe. The absorption liquid is circulated through a circulator 8 that connects the absorption liquid outlet 1h at the lower end of the absorbent tube 1b, the switch 9a, the switch 9b, the circulation pump 3, the circulation cell 6, and the absorption liquid inlet 1g at the upper part of the absorption pipe 1b.

As time passes, the absorbance of the absorption liquid at around 232 nm increases depending on the sulfur content in the sample, and after a certain period of time, the absorbance stops increasing and becomes a constant value.

This change in absorbance is recorded by the recorder 7, and the sulfur content in the sample is measured.

Next, the switch 9b is switched, the pump 3 is operated, each path is cleaned with the absorption liquid, and the absorption liquid is discharged into the waste liquid tank 14a.

As described above, the method of circulating the absorption liquid and measuring the absorbance of the absorption liquid at the same time as the hydrogen sulfide generation operation is performed in an atmosphere-shielded system and in order to quickly measure the absorbance. Analytical operations can be speeded up and simplified because hydrogen sulfide generation, absorption, and absorbance measurement operations can be performed at the same time. There are many advantages.

As for the circulation path of the absorption liquid, it is effective to circulate it in the direction of the pump 3, the photometer flow cell 6, and the absorption tube 1b for absorbing hydrogen sulfide, cleaning the inside of the absorption tube 1b, and discharging the entire amount of absorption liquid. there were.

Therefore, the absorption liquid inlet 1g, which is the connection point of the absorption liquid circulation pipe, needs to be attached to the upper part of the absorption pipe 1b, and the absorption liquid outlet 1h needs to be attached to the lower part of the absorption pipe 1b.

Further, the air vent pipe 11 needs to be attached to the upper part of the absorption pipe 1b.

The inert gas injection/residual sample discharge section Y serves to supply a constant flow of inert gas during the operation of generating hydrogen sulfide in the hydrogen sulfide generator 1, and to supply the remaining sample liquid in the hydrogen sulfide generation container 1a at the end of analysis. This is the part that works to collect and discharge.

10 is an inert gas cylinder that uses argon, nitrogen, etc.

Reference numeral 11 denotes a flow meter that normally blows inert gas at a rate of about 100 ml/vtirt.

Reference numeral 9c is a flow path switching device that switches the path for inert gas injection and sample residual liquid discharge.

Reference numeral 12 denotes a water flow cooler for lowering the temperature of the remaining sample liquid to some extent when discharging the remaining sample liquid.

13 is a suction pump, and 14b is a waste liquid tank.

Injecting inert gas during hydrogen sulfide generation prevents air oxidation of the reducing solution and increases the efficiency of hydrogen sulfide generation.
As a carrier gas to send hydrogen sulfide to the absorption tube 1b,
It also plays an important role in stirring the reducing solution to promote dissolution of the sample and generation of hydrogen sulfide.

The automatic control section Z is mainly composed of an automatic controller 15,
It functions to automatically perform all operations except for charging the sample and reducing solution into the hydrogen sulfide generating container.

Heater 2, circulation pump 3, photometer 5, flow path switch 9a
, 9b + 9c s The suction pump 13 and other control points are terminals 15a, 15b l 15c of an automatic controller 15 using a generally commercially available sequence programmer.
... and automatically controls each operation in sequence according to a predetermined operation program.

That is, after putting the sample and reducing solution into the hydrogen sulfide generation container 1a, the flow path switch 9C is switched to transfer the inert gas to the cylinder 10, the flow meter 11, the switch 9c, the cooler 12, and the inert gas blowing pipe 1. ” and sent to the hydrogen sulfide generating container 1a.

Next, operate the flow path switching devices 9a and 9b circulation pump 3,
The absorption liquid is sent into the hydrogen sulfide absorption tube 1b.

Next, the heater 2, photometer 5, and recorder 7 are operated, and the switch 9b is switched to operate the circulation pump to circulate the absorption liquid through the circulation cell 6 of the photometer, thereby changing the absorbance of the absorption liquid. Measure and record.

After the analysis is completed, the switch 9b is switched to operate the circulation pump 3 to discharge the absorption liquid and clean the absorption liquid circulation path.

In addition, the suction pump 13 is operated and the switch 9c is switched to drain the remaining sample liquid in the hydrogen sulfide generating container 1a to the waste liquid tank 14b.
be discharged.

In the apparatus according to the embodiment of the present invention, the injection of an analytical sample into the hydrogen sulfide generating container 1a, the injection of an analytical sample solution, and the injection of a reducing solution were not automated, but an analytical sample loading device or a reagent solution pouring device was connected. These automatic operations are fully possible with current general technology.

According to the present invention, which generates sulfur compounds in a sample as hydrogen sulfide and continuously measures the ultraviolet absorption of the absorption liquid, the sulfide ions in the solution that has absorbed hydrogen sulfide are colored by adding an organic reagent or the like to make them visible. It is possible to avoid the complexity of analysis operations such as measuring the absorbance of a sample, and the operations are very simple and quick.

In addition, in color absorption spectrophotometry using organic reagents, there is generally a large interference with hydrogen chloride, phosphoric acid, etc. that evaporate accompanying the generation of hydrogen sulfide, but these do not affect the present invention because they exhibit almost no ultraviolet absorption. There is no need to perform hydrogen sulfide generation operations under strict operating conditions.

Furthermore, the quantitative sensitivity is extremely high, and by using approximately 0.5 to 1 g of sample, trace amounts of sulfur, typically up to 0.5 ppI+@ degree, can be determined with high accuracy, and the time required for sample analysis is approximately 2.
It is quick and takes 0 minutes.

A certain amount of a solution prepared by dissolving the reagent potassium sulfate in water was placed in a hydrogen sulfide generating container 1a and heated to evaporate water, and then the sulfur in this solution was analyzed according to the procedure of the embodiment of the present invention.

The results of repeated analysis five times are shown in Table 1, and the analysis was able to be performed with high accuracy.

As described above, the present invention is a new invention with a simple method principle and a simple and practical device structure.

The present invention greatly contributes to quality control by analyzing trace amounts of sulfur in metal materials such as steel.

It is also used in the fields of analysis of minerals, plants, etc., and analysis of environmental measures.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams of an embodiment of the present invention. FIG. 1 shows the overall structure of the apparatus of the present invention, and FIG. 2 shows details of the hydrogen sulfide generating apparatus. 1...Hydrogen sulfide generator, 1a...Hydrogen sulfide generation container, 1b...Hydrogen sulfide absorption pipe, 1c...Cooling pipe, 1
d...Hydrogen sulfide generation port, 1e...Check valve, 1f...
・Glass filter, 1g...Absorption liquid inlet, 1h...
・Absorption liquid outlet, 1i...Air vent pipe, 1j...Inert gas blowing pipe, 2...Heater, 3...Circulation pump, 4...Absorption liquid tank, 5...Light intensity Total, 6... Distribution cell, 7... Recorder, 8... Absorbent circulation pipe, 9a
, 9b, 9c...flow path switching device, 10...-inert gas cylinder, 11...flow meter, 12...cooler, 13...suction pump, 14a, 14b...waste tank, 15-1M dynamic controller, 15a, 15b. 15C...Automatic control terminal, W...Hydrogen sulfide generation/
Absorption section, X...absorption liquid circulation/ultraviolet absorption measurement section, Y...
・Inert gas blowing・Sample residual liquid discharge sound 115Z...Automatic control unit.

Claims (1)

[Claims] 1. The analysis sample is thermally decomposed in a reducing solution while blowing inert gas to generate a sulfur compound as hydrogen sulfide gas, and this hydrogen sulfide gas is circulated between an absorption tube and a flow cell of a photometer. A trace amount sulfur analysis method characterized by determining the amount of trace amounts of sulfur compounds in a sample by continuously measuring changes in ultraviolet absorption around 232 nm while sequentially absorbing the sample in an alkaline solution. 2. A hydrogen sulfide absorption pipe with one end of an absorption liquid circulation pipe connecting the flow path switching device, circulation pump, and photometer circulation cell and an air vent pipe connected to the upper part, and the other end of the absorption liquid circulation pipe connected to the lower part; A trace sulfur analyzer characterized by a configuration in which a hydrogen sulfide generator equipped with an inert gas blowing pipe and a heater is connected to the lower part of a hydrogen sulfide absorption pipe.