JPH047087A - Treatment of waste water containing sulfur compound - Google Patents

Abstract

PURPOSE:To efficiently treat waste water over a long period of time by adding a metal ion such as an Na (I) ion to waste water and subsequently subjecting said waste water to wet oxidizing treatment at temp. of below 370 deg.C under pressure holding the waste water to a liquid phase under the supply of gas containing oxygen using a wet oxidizing reactor packed with a solid catalyst. CONSTITUTION:In treating waste water containing a sulfur compound, a metal ion such as an Na (I) ion and/or a K(I) ion is preliminarily added to said waste water and, subsequently, the waste water is subjected to wet oxidizing treatment at temp. of below 370 deg.C under the supply oxygen-containing gas under pressure holding waste water to a liquid phase using a wet oxidizing reactor packed with a solid catalyst. The affinity of a sulfate ion with a carrier is suppressed and the adhesion of the sulfate ion to the carrier is prohibited and the sulfate ion bonded to the carrier can be also removed. Therefore, waste water containing a sulfur compound can be stably treated over a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for purifying wastewater containing sulfur compounds by wet oxidation in the presence of a solid catalyst. In detail, when wastewater containing sulfur compounds is subjected to wet oxidation treatment in the presence of a solid catalyst, the catalyst is not susceptible to the effects of sulfur catalyst poison, thereby enabling stable wastewater treatment over a long period of time. Regarding the law.

(Prior Art) Known wastewater treatment methods include a biochemical method called an activated sludge method and a wet oxidation method called a Zimmerman method.

In wet oxidation methods, methods using various oxidation catalysts have been proposed in order to speed up the reaction rate.

Furthermore, when wastewater containing sulfur compounds is subjected to wet oxidation treatment in the presence of an oxidation catalyst, sulfur is adsorbed onto the catalyst surface and covers the active sites, resulting in a decrease in treatment efficiency over time, and eventually the catalyst is lost. There is a problem with sulfur being a catalytic poison.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a method for efficiently treating wastewater containing sulfur compounds over a long period of time using a wet oxidation reactor filled with a solid catalyst.

(Means for Solving the Problems) As a result of extensive research to solve the above-mentioned problems, the present inventors have found that when wet oxidation treatment of wastewater containing sulfur compounds is carried out in the presence of an oxidation catalyst. It has been found that by adding metal ions such as Na(1) ions and/or K(I) ions to wastewater in advance, excellent effects as described below can be obtained.

That is, in the present invention, when treating wastewater containing sulfur compounds, metal ions such as Na(1) ions and/or K(I) ions are added to the wastewater containing sulfur compounds in advance, and then a wet method is used which is filled with a solid catalyst. 3 using an oxidation reactor
A method for treating wastewater characterized by wet oxidation treatment under the supply of oxygen-containing gas at a temperature below 70'C and a pressure such that the wastewater maintains a liquid phase.

More specifically, by adding the above-mentioned metal ions, the sulfate ions react with these substances, for example, as shown in the following formula.

2Na" + 304"-+ Na, 5O42K"
+ So, 2- → K2SO3 On the other hand, sulfuric acid ions are adsorbed on the catalyst surface and cause a decrease in activity when the sulfur component is 5o42-, H5O.

This phenomenon occurs when it exists in an ionic state such as sulfuric acid. The former reaction, that is, the affinity between the metal ion and the sulfate ion, is stronger than the latter adhesion reaction, that is, the affinity between the carrier and the sulfate ion. Therefore, by allowing the former reaction to occur, it is possible to prevent the attachment of sulfate ions to the carrier. It also has the effect of suppressing and further removing sulfate ions attached to the carrier due to its affinity. Therefore, adsorption onto the catalyst does not occur and passes through. Furthermore, when treating wastewater containing solids such as sludge, the sulfur compounds contained in the solids undergo a solubilization reaction under warm oxidation conditions to produce sulfate ions, but Na(I) ions and/or When K (1) ions are present in wastewater, the effect of the ions suppresses the adsorption of helium on the catalyst.

Therefore, by adding the above-mentioned metal ions to wastewater in advance, stable catalytic activity can be maintained over a long period of time.

Further, in the present invention, the metal ions to be added to the wastewater in advance are preferably added before heating the wastewater. Examples of the Na(1) ions and/or K(I) ions to be added include sodium hydroxide, sodium nitrate, Any water-soluble salt such as sodium nitrite, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, potassium nitrate, potassium nitrite, potassium carbonate, potassium hydrogen carbonate, etc. may be used, but preferably sodium hydroxide, sodium hydroxide Potassium can be used.

In addition, Na(I) ions and/or K added to wastewater
(1) The injection rate of metal ions is preferably set to an equivalent ratio of 1 or more, preferably 1.1 to 5, relative to the sulfur concentration in wastewater (including the concentration in solid content).

Catalysts according to the present invention include titania, silica, zirconia, alumina, activated carbon, which are generally used for wastewater treatment,
A carrier such as diatomaceous earth can be used. In particular, since titania easily binds to sulfur and is susceptible to sulfur poisoning, the method of the present invention is particularly effective for carriers containing titania. Also titania, titania
Silica supports are preferred for use in this method due to their heat resistance.

To be more specific, manganese, iron, cobalt,
Catalyst-active component metals such as nickel, tungsten, copper, cerium, metal, gold, platinum, palladium, rhodium, ruthenium, and iridium, or their water-insoluble or sparingly soluble compounds, such as oxides, chlorides, and sulfides. is used.

The catalyst composition is 75 to 99.95% by weight of the carrier, preferably 85 to 99.9% by weight, 0.05 to 25% by weight of the metal or compound thereof as the catalyst active component element,
Preferably it is in the range of 0.1 to 15% by weight. Preferably, among the catalyst active component elements, manganese, iron, cobalt, nickel, tungsten, copper, cerium, and silver are used in an amount of 0 to 15% by weight as a compound, and platinum, palladium, rhodium, ruthenium, and iridium are used in an amount of 0 to 15% by weight. The amount is 0 to 5% by weight as metal (however, the total amount of both is 0.1 to 15% by weight). Furthermore, a catalyst in which the above-mentioned platinum group metal is supported on a titania-zirconia carrier is preferable. In particular, in this catalyst titania 2
When a binary composite oxide or a mixture consisting of 0 to 90 mol% and 10 to 80 mol% of zirconia is used, it has excellent activity, hot water resistance, acid resistance, and durability.

In addition, the shape of the catalyst carrier is pellet-like, spherical,
Both honeycomb and ring shapes can be used, but when dealing with wastewater containing suspended matter such as excess sludge,
A honeycomb shape is particularly preferred since the catalyst layer may be clogged due to solid matter, precipitation, etc.

As the wet oxidation reactor according to the present invention, a commonly used single-tube cylindrical reactor, a multi-tube reactor, etc. are used depending on the wastewater to be treated.

Further, in order to maintain the liquid phase state of the wastewater, the reaction temperature is set to a temperature lower than 370° C. and a pressure higher than that which maintains the liquid phase state at this temperature.

In the reaction, an oxygen-containing gas is used, but air is preferable since it is inexpensive, except in special cases such as when making the apparatus more compact.

Next, the present invention will be explained in more detail with reference to Examples.

Note that the present invention is not limited to these Examples unless it goes against the spirit of the present invention.

Example I FIG. 1 is a schematic diagram of an apparatus for treating wastewater containing phosphorus compounds according to the present invention. The reactor 1 used has an inner diameter of 50rrIfrI and a tube length of 10m, and inside the tube are:
Pellet catalyst with an average particle size of 51Ilffl and a length of 6mm (
A titania-zirconia carrier containing 0.5 wt% of Pt supported on the catalyst layer was packed to a catalyst layer length of 8 m.

A sodium hydroxide solution was added by pump 4 to a flowing wastewater line 10 with a concentration of 40 g/j2 of C0D(Cr) containing sulfur compounds (500 ppm H2SO4 equivalent to sulfuric acid).

On the other hand, air was pressurized by a compressor 9, mixed with waste water supplied from a waste water supply pump 3, and after being preheated by a heat exchanger 2, was supplied to the reactor 1.

The wastewater treated in reactor 1 is discharged from line 12,
After being cooled in the heat exchanger 7, it was supplied to the gas-liquid separator 5, where it was separated into harmless gas and water. In this gas-liquid separator 5, a liquid level controller LC detects the liquid level and operates a liquid level control valve 6 to maintain a constant liquid level, and a pressure controller PC detects pressure and operates a pressure control valve 6. 7 to maintain a constant pressure.

At this time, the processing conditions in the reactor 1 are as follows: reaction temperature 25
0°C, reaction pressure cuff 5kg/aflG, and wastewater supply amount 30j! /fir, a sodium hydroxide solution added in advance to the wastewater at a supply rate of 6,100 ppm, 3f/Hr, and an air flow rate of 4,800 Nl/Hr. The COO reaction rate under these conditions was 99%, and no decrease in the COD reaction rate was observed even during continuous operation at 2,000)1r.

Comparative Example 1 Contains sulfur compound (H2SO4500ppm in terms of sulfuric acid) 00 (C:r) 40 g/I! Continuous operation was carried out under the same treatment conditions using the same apparatus used in Example 1, without adding metal ions in advance to wastewater having a concentration of .

Table 1 shows the change in COD reaction rate over time.

Table 1 Example 2 A sulfur compound (H2SO in terms of sulfuric acid) was prepared according to Example 1.

40 g/C0D (Cr) containing 500 ppm)
Potassium hydroxide solution was added by pump 4 to the flowing waste water line 10 at a concentration of IV.

Continuous operation was carried out under the same treatment conditions except that the concentration of the potassium hydroxide solution was 3.600 ppm and the feed rate was 31/Hr.

The COD reaction rate under this condition was 99%, and 2,000
No decrease in COD reaction rate was observed even during continuous operation for 0 hours.

(Effects of the Invention) As described above, according to the present invention, by adding metal ions in advance to wastewater containing sulfur compounds, the affinity between sulfate ions and the carrier is suppressed, and the attachment of sulfate ions to the carrier is prevented. In addition, it is also possible to remove sulfate ions attached to the carrier.

Therefore, stable wastewater treatment for a long period of time can be realized for wastewater containing sulfur compounds.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one embodiment of the present invention. 1... Single tube cylindrical reactor 2... Heat exchanger 3... Waste water supply pump 4... Sodium hydroxide solution supply pump 5... Gas-liquid separator 6... Liquid level control valve 7...Pressure 8...Air supply line 9...Compressor 10...Wastewater supply line 11...Sodium hydroxide solution supply line 12...
Processing liquid line

Claims (2)

[Claims] (1) When treating wastewater containing sulfur compounds, metal ions such as Na(I) ions and/or K(I) ions are added to the wastewater containing sulfur compounds in advance, and then a wet oxidation reactor is filled with a solid catalyst. A method for treating wastewater, characterized in that wet oxidation treatment is carried out at a temperature of less than 370° C. and under a pressure such that the wastewater maintains a liquid phase while supplying an oxygen-containing gas. (2) The method for treating wastewater according to claim (1), wherein the solid catalyst is a catalyst whose carrier component is an oxide containing titania.