JPS58172204A - Method for removing metallic sulfide from alkali hydrosulfide solution - Google Patents

Abstract

PURPOSE:To accelerate flocculation and settling and to enhance the work efficiency of filtration by adding anionic polyacrylamide having a prescribed mol.wt. to an alkalie hydrosulfide soln. contg. fine particles of metallic sulfide and org. matter and having a prescribed spent rate. CONSTITUTION:When the spent rate of an alkali hydrosulfide soln. contg. fine metallic sulfide, org. matter, etc. recovered from a chemical plant is below a prescribed value, the soln. is reacted with H2S to adjust the spent rate to >=90.1%. Anionic polyacrylamide having >=2 millions mol.wt. is then added to the soln. After agitating the soln., formed flocks are settled, and the fine precipitate is filtered off. Thus, the fine metallic sulfide and org. matter in the alkali hydrosulfide soln. are easily filtered off.

Description

[Detailed Description of the Invention] The present invention utilizes alkali sulfide (
The present invention relates to a method for efficiently separating fine metal sulfides and organic substances coexisting in a solution (mainly sodium hydrogen sulfide).

Alkaline hydrosulfide liquid is obtained from waste soda liquid discharged from chemical factories such as petroleum refining, petrochemistry, coal chemistry, cellophane rayon, and sufu, from H2S-containing gas, and from waste noda liquid and H2S-containing gas. Alkaline hydrosulfide solution is being recovered. However, this recovered alkaline hydrosulfide solution contains fine metal sulfides (hereinafter referred to as "fine sulfides") mainly composed of iron sulfide from waste soda solution, H, S gas, and lines.

Father, waste soda liquid contains phenols, thiophenols,
Organic substances such as mercaptans and low polymers (hereinafter referred to as ``organic substances'') are dissolved, and these organic substances are converted into alkali hydrosulfide by reaction with waste soda solution and H2S.
Therefore, it can be separated and removed from the alkaline hydrosulfide solution based on the difference in specific gravity (Patent Nos. 401527 and 80040).
(See No. 1) However, it is unavoidable that a small amount of it be mixed into the alkaline hydrosulfide solution. This trace amount of organic matter adheres to the fine sulfides mentioned above, forming a suspended state with poor sedimentation.

When attempting to separate and remove such fine sulfides and organic substances from an alkaline hydrosulfide solution, the fine particle filtration surface becomes clogged with organic matter, resulting in a significant increase in the amount of filter aids and, furthermore, the filtration process. The prolongation of this situation is no longer possible.

If a method is used in which fine sulfides are precipitated and then separated, it usually takes 15 to 30 hours for the fine sulfides to settle, and in some cases it may take more than 2 days.
Furthermore, if some organic matter is attached, complete sedimentation cannot be expected, and the clogging problem remains unsolved.

The reason why separating and removing fine sulfides, organic substances, etc. from the alkaline hydrosulfide solution is extremely difficult and takes a long time is that
Since this filtration operation is a pretreatment step for the continuous concentration operation of the alkali hydrosulfide solution, the delay in p-filtration makes it necessary to reduce or temporarily stop the supply to the concentration step. Therefore, in such a case, not only the work efficiency will be lowered but also the capital investment will be increased, so those involved are struggling to find a countermeasure against this problem, and there is a strong need for an easy and quick separation method.

Therefore, the present inventors attempted various experiments in order to quickly and easily separate fine sulfides, organic substances, etc. from an alkaline hydrosulfide solution containing them.

Inorganic flocculants are themselves acidic liquids, but because they become acidic when dissolved, they are inconvenient and rarely used for alkaline hydrosulfide alkaline liquids, so organic flocculants are generally used for alkaline liquids containing inorganic suspensions. We proceeded with the study of the anionic flocking agent used.

Among them, we have considered anionic flocculants that are said to be effective for relatively strong alkaline liquids, but because the pH range in which they can be used is outside the 1-pa range limit for floccants, they cannot be used for long periods of time or under heated conditions. In this case, alteration effect due to the alkali of the flocculant was observed.

However, in this experiment, the present inventors found that floccants with larger molecular weights flocculated more quickly and flocculated once.
We discovered the phenomenon that flocs do not easily become dispersed.

Therefore, the present inventors proceeded with the following experiment with the belief that the influence of the alkali of the flocculant can be suppressed when coagulation and sedimentation is performed quickly by using a flocculant with a large molecular weight.

That is, anionic polyacrylamide with a molecular weight of approximately 500,000, 1,002,005,000,000 was used as the flocculant, and the amount added was varied to determine the sedimentation status of fine sulfides in the sodium bisulfide solution. The sedimentation time was investigated and the results shown in Table 1 were obtained.

Table 1. Molecular weight of flocking agent and sedimentation time Note: Sedimentation time is 2 minutes, NaBH solution: Na5H2-'5.4'76 N
a2S2, 3% Na5H fine sulfide in solution: α5
vo1% (3000 rpm, 20 minutes) In this experiment, the size of the molecular weight influenced the sedimentation time more than expected.Th
We were able to confirm that e.

At this time, turbidity (fine suspended particles of sulfide) was observed in the sodium hydrogen sulfide solution with a molecular weight of 500,000, but this phenomenon was not observed in all those with a molecular weight of 1,000,000 or more.This experimental result is noteworthy. This is an effective phenomenon.

This turbidity phenomenon is presumed to be due to the fact that the flocculant was affected in some way by the alkali, such as decomposition or alteration, which affected the flocculation effect.

Therefore, the present inventors conducted the following experiments regarding the influence of alkali on the flocking agent.

Add H2S to NaOH solution (approximately 30 cm) to which iron chloride solution has been added.
The spent rate of NaOH, that is, the consumption rate, (NaOH is consumed by I'I2S and completely N
The spent rate when it becomes a8H is 100ch, for example: Na
The spent rate when all of the OH content becomes Na2S is 5.
Place each Na5H solution with a molecular weight of 85 to 95 mm in a 100 mm colorimeter tube, and add 0.1 mm each of anionic polyacrylamide with a molecular weight of approximately 500,000, 1 million, 2 million, and 5 million as a flocking agent. After adding 500 ppm of the liquid solution and stirring the mixture and leaving it for 120 minutes, the condition of the supernatant liquid was examined and the results shown in Table 2 were obtained.

Table 2 Effect of alkali on flocking agent Molecular weight approx. 500
10,000,2 million has a spent rate of 90.1% or more, 10
It was confirmed that 0,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000, 92,7,00,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000000 type type type type form type form, 500,000,000,00000 type items have been confirmed that they do not become cloudy at 92.7 geeches or higher. Although an increase in the spent rate means a decrease in alkalinity, the fact that flocculation is effectively observed even in the pH range of 1'3 or higher as a result of an increase in H8- ion concentration is due to other factors other than alkalinity. It seems that some factor was at play. This means that the spent rate of Na5H solution with no turbidity observed when using floccants with molecular weights of 5 million and 2 million is 90.
．． 1%, compared with recovered Na5, which was developed earlier by the present inventors.
Coincidentally, this coincides with the spent rate of 90, at which organic matter separates from the Na5H solution in the reaction process of the H solution (see Patent No. 800,401 above), and when the spent rate is around this, the flocculation effect is promoted due to some factor. It is considered that

The fact that the spent rate at which turbidity, which is thought to be caused by the alkali of the flocculant, does not occur, and the spent rate at which organic matter is separated from the alkali hydrosulfide solution coincides with each other. It is believed that this improves separation, reduces contamination with the alkaline hydrosulfide solution, and provides favorable conditions for the use of floccants.

Therefore, the degree of polymerization of the flocking agent used is inseparably related to the spent rate of the alkali hydrosulfide solution.l) The solution with a high spent rate allows the use of a low molecular weight flocking agent.
means. However, the most preferred flocking agent (anionic polyacrylamide) has a molecular weight of 200.
It is appropriate to use an alkali hydrosulfide with a spent ratio of 90.14 or more.

From these experiments, the present invention has demonstrated that waste soda liquid discharged from petroleum refining, petrochemical, coal chemical, cellophane, rayon, and sufu chemical factories, as well as H2S-containing gas,
Furthermore, when separating and removing fine sulfides and organic substances mixed in the hydrosulfurized alkali liquid recovered from waste soda liquid and H2S-containing gas, a flocculant with a molecular weight of approximately 2 million is used to promote the sedimentation of these substances. An appropriate amount of the above anionic polyacrylamide was added at a spent rate of 90.1.
The alkaline hydrosulfide solution recovered at 4 or higher, and those with a spent rate lower than that, are further reacted with H2S 'i to 90%
．． A recovered alkaline hydrosulfide solution characterized in that it is added after making the spent ratio 1%, and after stirring, it is allowed to stand or is stirred weakly to the extent that it does not interfere with sedimentation, thereby flocculating and sedimenting the produced flocs and separating them. It can be said that it is a method of removing fine sulfides and organic substances from.

Next, the present invention will be specifically explained using examples.

Example 1 Recovered from waste soda liquid and H2S-containing gas discharged from petroleum refining as shown in Table 6. Na5H solution 100 each
- is placed on a 100 - colorimeter tube with a scale, and anionic polyacrylamide with a molecular weight of approximately 5 million, which is commercially available as a flocking agent [Sumifloc FA-5 manufactured by Sumitomo Chemical Co., Ltd.]
0FA-70 effective pH range former pH 6~9 latter pH 8~
11] was added in an amount equivalent to B o o ppm, inverted stirring was performed 10 times, and the resulting flocs were allowed to coagulate and settle by standing still. The same sample was precipitated in the same manner in advance to determine the amount of sediment. When the sedimentation time until the amount of 5tdK reached the same amount as that of 5tdK was measured, it was 18 minutes for Sumifloc FA-50 and 18.2 minutes for Sumifloc FA-70, which showed that there was almost no difference between the two. At this time, no turbidity was observed in the supernatant liquid in either case.

Table 3 Properties of recovered Na5H solution Na5H25, 32wt% Na2S 2.35
pNa2003 '0.96 7FNa2
SO3'0.24' lNa2S2O30,
12# Spent rate 94.1 Precipitate α5 v01 (5000 rpm, 20 minutes) Comparative Example 1 70 The sedimentation time was examined in the same manner as in Example 1 without adding a thickening agent. Even after 3 hours of standing, there was almost no sedimentation and separation.

As is clear from comparing the results of Example 1 and Comparative Example 1, the effect of using the flocking agent was remarkable.

Example 2 Using a glass Puchner funnel with an inner diameter of about 70 mm and a P paper shop 2, a vacuum of 150 mm of water was applied to the P liquid so that it entered the graduated cylinder, and it was left to stand in the same manner as in Example 1. The supernatant liquid after 40 minutes and the supernatant liquid after 16 hours of standing in the same manner as in Comparative Example 1 were each filtered through 9 omg, and the overspeed was 86.4 m/min and 75.4 d/min, respectively. .

When all the flocking agent is added, it is 11++ higher than that without addition.
The fact that the p-filtration can be carried out as quickly as 1/2 minute can be attributed to the fact that the flocculant prevents the settling of fine sulfides and also acts on the organic matter that causes clogging of the p-filtration surface, resulting in good results.

These examples are merely examples for specifically explaining the present invention, and it goes without saying that the technical idea of the present invention includes many changes and improvements within the limits, and the technical scope of the present invention It is not intended to restrict. ,,.

As explained above, according to the present invention, an appropriate amount of anionic polyacrylamide with a molecular weight of 2 million or more is mixed with fine sulfides, organic substances, etc. recovered from petroleum refining, petrochemical, coal chemical, and chemical factories such as cellophane, rayon, and sufu. It is added to and stirred in the alkaline hydrosulfide solution with a spent ratio of 90.14 or more to settle the formed flocs, thereby facilitating P-filtration of the supernatant liquid and greatly shortening the E-suitability time of the flocs themselves. As a result, workability and economical efficiency can be significantly improved, so the effects are significant.

Agent: 1) Akira Agent Ryo Hagi Hara -

Claims (1)

[Claims] In order to remove fine precipitates of metal sulfides, mainly iron sulfide, and organic matter coexisting in an alkaline hydrosulfide solution, anionic polyacrylamide with a molecular weight of 2 million or more is used as a precipitation-promoting flocking agent to increase the spent rate of alkaline content.
90. A method for removing and separating fine precipitates of metal sulfides coexisting in an alkaline hydrosulfide solution, which comprises adding the solution to an alkaline hydrosulfide solution at a concentration of 90.14 or higher, and coagulating and precipitating the generated flocs after stirring.