JPS5982999A - Treatment of waste caustic soda liquid - Google Patents

Abstract

PURPOSE:To remove efficiently phenol, etc. by adding a mineral acid to a waste caustic soda liquid from a petroleum refining device, etc. to neutralize the liquid then supplying the same to a crude oil desalting device to control phenol to a specific content or below then supplying the liquid to an activated sludge device. CONSTITUTION:Sulfuric acid is added to a waste caustic soda liquid to adjust the pH in the inlet of a desalting device 5 to 3.5-7. The neutralized waste caustic soda liquid is diluted by the waste process water which is removed of hydrogen sulfide and ammonia by steam stripping in a deaerator 2. The liquid is then mixed with the crude oil which is heated with a heat exchanger and is supplied to the device 5. The desalting device is operated at 4.0-7.5pH and 120-150 deg.C. The waste liquid is drawn from a flow passage 6 after stagnation for 3-4hr. The waste liquid after the treatment is supplied through a cooler 8 and an oil separator 9 to an activated sludge device 10. The waste water decreased of harmful material is released from a guard basin 12 into a river.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating caustic soda wastewater containing phenol and COD substances discharged from petroleum refineries, petrochemical plants, etc. To be more detailed, 1
The present invention consists of: 1. Caustic soda waste containing harmful substances such as phenol discharged from petroleum refineries, etc. is supplied to a crude oil desalter (hereinafter abbreviated as desalter), treated, and then treated in an activated sludge equipment. The present invention relates to a method for treating caustic soda waste liquid, the purpose of which is to treat and purify the waste liquid.

In petroleum refineries and petrochemical plants, a method of washing with caustic soda is generally employed to remove impurities such as hydrogen sulfide, mercaptans, and phenol contained in various exhaust gases and petroleum fractions. The caustic soda waste liquid used for this cleaning contains harmful substances such as sulfur compounds and phenol extracted from various exhaust gases and petroleum fractions. If the water is not released into rivers, it will cause enormous damage to fish, shellfish, and seaweed.

Therefore, in order to purify the caustic soda waste liquid containing harmful substances, the caustic soda waste liquid has been treated in an activated sludge apparatus.

As a result of extensive research into these problems, the present inventors have found that harmful substances such as phenol and COD substances in the neutralized caustic soda waste liquid can be removed by treating the waste liquid with a desalter. After confirming the facts, the present invention was completed.

Therefore, the main purpose of the present invention is to effectively remove phenol and COD substances contained in caustic soda waste liquid discharged from petroleum refining and petrochemical equipment in a factory without installing special equipment. be.

Another object of the present invention is to efficiently and stably treat caustic soda waste containing phenol COD substances in an activated sludge apparatus without causing spring shock.

1. Another object of the present invention is 1. phenol in caustic soda waste liquid discharged from petroleum refining and petrochemical equipment;
The objective is to remove COD substances with simple operations.

Still another object of the present invention is to prevent corrosion in the desalter by introducing caustic soda waste into the desalter.

The present invention involves neutralizing sumo isoda waste fluid containing phenol and COD substances discharged from two petroleum refineries, two petrochemical plants, etc., by adding mineral acid, and then supplying it to a desalination machine for secondary treatment. Is phenol less than 100 pp+n?
) The present invention relates to a method for treating caustic soda waste liquid, characterized in that demineralizer waste water whose COD has been reduced to 500 ppm or less is supplied to an activated sludge apparatus for treatment.

In other words, the present invention (1) neutralizes a caustic soda waste liquid containing a large amount of phenol and COD substances by adding mineral acid, and (2) sends the neutralized caustic soda waste liquid as desalination water to a demineralizer. Phenol and CO from supply and waste liquid
(3) supplying the caustic soda waste liquid whose content of harmful substances such as phenol and COD substances has been reduced below the permissible value to an activated sludge device to purify the waste liquid; The present invention provides a method for treating caustic soda waste liquid, which includes the following steps.

The caustic soda waste liquid treated in the present invention is produced from petroleum refineries, petrochemical factories, etc. The caustic soda waste used for cleaning petroleum fractions usually contains about 3 to 15 ml of sodium sulfide, sodium bisulfide, soda carbonate, etc.
In addition to the weight ratio, mercaptans are about 05 to 5 weight ratio, phenol and cresols are sodium salts,
and about 05 to 25% of each. According to the conventional method, a certain amount of impurities such as phenol and mercaptan are decomposed by the activated sludge, so that the caustic soda waste liquid can be purified. However, when caustic soda containing a considerable amount of impurities such as phenol and mercaptan is supplied, microorganisms in the sludge are killed, and the activated sludge equipment is often unable to operate normally. Since the activated sludge equipment is installed at the end of the wastewater treatment system, malfunction of the activated sludge equipment will have a great negative impact on the wastewater treatment work. Furthermore, the surplus sludge produced in large quantities by charging the activated sludge cannot be easily disposed of because it contains harmful substances. I have many problems like this.

There is a strong desire for a method to effectively treat caustic soda waste.

The method of the present invention (=, effective for the treatment of caustic soda waste liquid from coconuts, containing 10,000 ppw or more of phenol,
Caustic soda waste liquid having a COD of 50,000 pprr or more can be targeted.

Sulfuric acid is suitable as the mineral acid for neutralizing the caustic soda waste solution, and for example, it is economically preferable to use the sulfuric acid waste solution discharged from an alkylation device or the like. The amount of mineral acid added to neutralize the caustic soda waste liquid must be sufficient to reduce the pH of the waste liquid to 7 or less ('i
However, if the pH of the waste liquid remains above 7 even after the addition of mineral acid, the acidic substances in the caustic soda waste liquid will decrease in the demineralizer, causing the pH value to rise and the operating efficiency of the demineralizer to decrease. be. In general, the desalination efficiency of crude oil increases as the D/H becomes more pebble, but if the PU is less than 35, this is not preferable because the problem of corrosion of the desalter will occur.

In the present invention, process wastewater refers to all wastewater containing impurities and harmful substances generated from equipment such as oil refineries.

For example, it can be used to drain oil-containing wastewater from tank yards, cooling water used for heat exchange of crude oil and petroleum fractions, and steam condensate from wheelers and distillation towers. Process wastewater often contains impurities such as COD, BOD, and oil, but these are effectively removed in the desalter at the same time as the caustic soda wastewater, reducing the burden on the activated sludge equipment. The amount of Pro-7 waste to be added to the caustic soda waste after neutralization may vary depending on the amount of caustic soda waste to be treated and the alkali concentration.For example, if the free alkali concentration is 5 to 15% by weight, the process It is preferable that the volume of the waste water is 10 to 40 times that of the caustic soda waste liquid.

The diluted caustic soda waste is brought into contact with crude oil in a desalter. Caustic soda waste liquid weighs approximately 1 to 15% by weight relative to crude oil.
Preferably, the contact can be made in a ratio of about 3 to 10 times.

The crude oil is not particularly limited, and any type of crude oil can be used. In other words, from light crude oil to heavy crude oil,
It can be used regardless of its properties, from low-sulfur crude oil to high-sulfur crude oil.

The desalter used in the 4r invention is a device for chemically or electrically separating water, muddy substances, etc. containing salts such as sodium chloride and calcium chloride dispersed in crude oil from crude oil.

Desalting methods include chemical desalting, in which chemicals are added to a stable emulsion of crude oil and water to facilitate the separation of crude oil and water, and chemical desalting, in which a high voltage is applied to the crude oil to be treated to destroy the emulsion. electrical desalination method to separate salt-containing water;
Alternatively, there are desalting methods that use a drawing method in combination, but the present invention can be applied to any desalting method. recent years.

A two-stage desalination method in which two desalters are connected to desalinate crude oil has been explored, but in the present invention, sufficient waste liquid treatment effects can be obtained by using only one of the desalters. be able to.

Caustic soda waste liquid.

The heated crude oil is vigorously mixed with the mixing knob at the desalter inlet. The resulting emulsion of crude oil and waste liquid is ejected from the distributor of the desalter into a high-voltage electric field.

Through this operation, the emulsion-like caustic soda waste liquid loses most of its fuels and COD substances to the crude oil, while at the same time dissolving the salt and mud in the crude oil and turning it into huge water droplets due to the high-voltage electric field between the electrodes. It settles to the bottom of the salter.

Ru. In general, the higher the temperature of crude oil, the higher the desalting effect, and the better the purification rate of waste liquid, so higher temperatures are more suitable for carrying out the present invention. The desalination machine.

In order to suppress the escape of low boiling point components and water vapor in crude oil, the desalter is usually operated at a pressure of 5 to 25 mm (especially about 1 - I Sυ). It has been pointed out that crude oil desalters are generally susceptible to corrosion due to the naphthenic acid originally contained in the crude oil and hydrogen chloride newly generated during the ring removal process. Corrosion of the demineralizer due to such acidic components can be prevented by supplying caustic soda waste to the demineralizer according to the present invention.For this purpose, the pt (pt) of the demineralizer should be set to 40 or more.

need to be managed. However, p) I is 7
If it exceeds 5, the desalting effect 11 will decrease and the removal rate of phenol etc. from the caustic soda waste will also decrease, so it is necessary to adjust the amount of acid added in the neutralization step. The residence time of the caustic soda waste in the desalter is approximately 3 to 4 hours.

An activated sludge device is a device for biochemically decomposing and removing impurities contained in caustic soda waste liquid and other process wastewater from a desalter.

The apparatus usually consists of an activated carbon absorption tower, a pretreatment device such as a pre-aeration paddle, an aeration tank, a coagulation sedimentation tank, a treated wastewater tank, an excess sludge treatment device, etc.

However, in the present invention, most of the impurities such as hydrogen sulfide in the caustic soda waste are removed by the demineralizer.
There is no problem even if pretreatment equipment such as an activated carbon absorption tower or pre-aeration tank is not installed.

Inside the llP air tank is activated sludge, that is, bacteria and yeast.

A floc-like colony of aerobic microorganisms such as mold and protozoa is introduced into the tank, and is circulated within the tank by flowing with the waste liquid flowing into the tank and the air being blown in.

Activated sludge is sensitive to impurities such as phenol and sulfur compounds, and if it comes into contact with waste liquid containing large amounts of these components, it will receive a toxic shock, making it impossible to operate the activated sludge equipment stably. It is necessary to strictly control the concentration. Especially phenol is 11
It is desirable to reduce the toxic substances in the waste liquid to 00 ppm or less and COD to 500 ppm or less. More preferably,
Phenol 50 ppm or less, COD 300
It is to be less than ppm. Activated sludge equipment has a pH of 5
It is preferable to operate at a temperature of 30 to 40°C.

In addition, compounds such as phenol and COD substances in the caustic soda waste liquid are transferred to the crude oil side in the desalter and transported to the distillation unit, but they are not removed from hydrogen in subsequent processing equipment such as hydrotreating equipment and hydrodesulfurization equipment. There is no possibility that the quality of petroleum products will ultimately deteriorate as it reacts with the petroleum products and is converted into hydrocarbons, etc.

Next, two embodiments of the present invention will be explained with reference to FIG. The caustic soda waste liquid to be treated is
Adjustments are made. Sulfuric acid is added in an amount sufficient to bring the pH at the demineralizer inlet to 35-7.

This neutralization process is performed by a neutralization drum (1). The neutralization drum is maintained at approximately 30° C. and stirred. Neutralized caustic soda waste liquid.

In the deaerator (2) hydrogen sulfide and ammonia are diluted with steam-stripped process waste water. The caustic soda waste liquid is mixed with crude oil heated in a heat exchanger and supplied to a desalter. The desalter is operated at a pH of 4.0-75 and a temperature of 120-150°C. The caustic soda waste liquid (J) supplied to the demineralizer is extracted from the channel 6 after a residence time of 3 to 4 hours.Then, the desalination treated wastewater passes through the cooler (8) and the oil separator (9). The wastewater passes through and is supplied to the activated sludge equipment (10). The wastewater treated with the activated sludge equipment and reduced in harmful substances is discharged into the river from the guard basin (2). is flow path 7
After being pulled out and heated.

It is supplied to a distillation device (not shown), treated in a conventional manner, and separated into various petroleum fractions.

Here, one embodiment of the present invention will be explained by way of an example.

Example 1 A caustic soda waste liquid discharged from a gasoline washing process in an oil refinery was treated by the method of the present invention. First, 17,480 ppm of phenol and 8 COD substances.
Caustic soda waste liquid containing 3,020 pI”m (first
(Table 1) was neutralized by addition of sulfuric acid.

1 kl of this neutralized caustic soda waste liquid was diluted by mixing it with 30 kl of process waste generated in the same oil refinery. The H of the diluted waste liquid was 65. Next, this diluted waste liquid was mixed with 80% Middle Eastern crude oil that had been preheated in a heat exchanger.
For 0 kl, water for desalination was added at a ratio of 31 parts to 1 part and supplied to the desalter. The demineralizer is heated at 130℃, p
)+7, and the waste liquid was treated in the demineralizer for about 4 hours.

As a result, the caustic soda waste from the desalter contained 20 ppm of phenol (removal rate of 95%) and COD.
The properties were 140 ppm (removal rate 88%).

In addition, there were 90 people in the crude oil desalination room.

Caustic soda waste liquid from the desalter is process wastewater 60
After mixing with kl and treating with an oil separator, it was supplied to an activated sludge unit and treated. The activated sludge unit was operated at 30'C and pH 7 in the presence of aerobic bacteria. Almost no harmful substances such as phenol or COD substances were detected in the waste liquid after activated sludge treatment. The results are shown in Table 1. In addition, the above process wastewater is phenol'E.
It contained 220 ppm of 4ppm4 aoI) substance.

Comparative Example I The same caustic soda waste liquid as in Example 1 (see Table 1) was used, except that the pH in the demineralizer was set to 55. It was treated under the same conditions as lJ1. Namely.

7: L / /L' is 17,480 pptn -)
A small plate of fermentation from Example 1 was added to a caustic soda waste solution containing 83,020 ppm of COD substances. This caustic soda waste liquid IKI was mixed with 1 to 30% of Pro-7 wastewater generated within the same oil refinery and diluted. In the text, this diluted waste liquid was preheated with a heat exchanger and
Water for desalination was added at a ratio of 1:30 to t:1 and supplied to the desalter. The temperature of the desalter is 130'C.

The system was operated at pH 8.f, and the waste liquid was treated in the demineralizer for about 4 hours. This is the caustic soda waste from the desalter.

Fx Nord 180 pprn, COD 560p
pm and "D f: o a "iE a Karatsuka 7 I soda waste liquid was treated with an oil separator according to Pro 7 pp water 60 +-x and t, and then supplied to an activated sludge device for treatment. . Activated sludge equipment is operated in the presence of aerobic bacteria for 30 minutes.
°C, D) I-/. Wastewater after activated sludge treatment.

The removal rate of harmful components is 130 ppm for phenol and 300 ppm for COD.

Example).

Example 2 Sumo wrestler Isorg waste iT containing 17,480 ppm of Z, = 7− and 83,020 ppm of COD substances
! :, (see Table 1), a larger amount of sulfuric acid was added than in Example 1. 11 u of this caustic soda waste liquid was mixed and diluted with 30 Kl of Pro-7 wastewater generated within the same oil refinery. Next, this diluted waste liquid was added as desalination water at a ratio of 31) to 800 Kl of Middle Eastern crude oil preheated in a heat exchanger and supplied to a desalter.

The desalter was operated at 130°C and pH 4.1, and the waste liquid was treated in the desalter for about 4 hours. As a result, the phenol in the decyclization wastewater was 18 PDIT'+ coDtj 130
pprn; decreased. Thereafter, the active and '5 mud treatments were carried out in the same manner as in Example 1, and the results shown in Table 1 were obtained.

As explained above, the invention is extremely effective in treating isodium waste liquid that is drained from oil refineries and the like.

That is, by implementing the present invention, 1) phenol and mercaptan contained in caustic soda waste liquid can be decentered by more than o5yx, and COD substances can be more than 85Z.

2) The desalter can prevent corrosion of the desalter without reducing the crude oil removal rate, and the activated sludge device can operate stably, and 3) The activated sludge The work environment around the equipment is improved, and the number of harmful components contained in the surplus sludge can be reduced, making it easier to dispose of the surplus sludge externally. is extremely large.

Applicant Takuya Fuel Industry Co., Ltd. 61 Table 1 pH 13, 86, 88, 44, 3 -J' Lucali (%) 6-fi 2 compound (llpm) 8.000
1.60 160 160/lunobutane j ppm) 10.400
45 45 43 no, L Nord (
1”T'm) 17.480
370 380 360 (Ol) 6 (ppm) 83,020
1,120 +,■:+o 1. +2
On+u+tppm)
58,000 900 9
20 94°, 111 minutes [ppm)
1.6,000 250 260 250
*(・0'') is fi1 oxidized +1 substance in water1 M% consumed by organic matter, nitrite, sulfide, etc.
) Analyzed using JSU method).

Demineralizer 1]'10 Lower for activated sludge equipment B, 6 4.1
7 7 7ku13
<1 + -401<120<1 254<110<1 20180], 8<1130<1 11+056013083007 (Here, JISK O+0
Brief Description of the Drawings Figure 1 is a two-step diagram showing the treatment of caustic soda waste liquid according to the present invention.

1... Neutralization drum 2... Deaerator 5... Demineralizer 9... Oil separator 10... Activated sludge device

Claims (3)

[Claims] (1) After neutralizing caustic soda waste discharged from petroleum refining or petrochemical equipment by adding mineral acid, it is supplied as desalination water or as part of it to a crude oil desalter for treatment, and phenol is removed. A method for treating caustic soda wastewater, which comprises supplying the demineralizer wastewater whose COD content has been reduced to 100 pprn or less and 500 ppm or less to an activated sludge device for treatment. (2) The treatment method according to claim 1, wherein the pH in the crude oil desalter is 7.5 or less. (3) The treatment method according to claim 1, wherein the caustic soda waste liquid is neutralized and then diluted with Pro-7 wastewater.