JP2001011041A - Treatment and device of sulfur trioxide-containing gas in non-steady state in sulfonating/sulfating reaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat sulfur trioxide-containing gas efficiently by feeding specific sulfur dioxide into an oxidation catalyst-filled converter, feeding the obtained sulfur trioxide- containing gas into a reaction vessel for sulfonating/sulfating an organic compound, introducing the above sulfur trioxide gas in a non-steady state into a sulfur trioxide absorbing column to form sulfuric acid and bringing the residual gas in contact with a specific amount of an aqueous alkaline solution. SOLUTION: This method for treating sulfur trioxide-containing gas is provided by feeding SO2 generated by the combustion of sulfur into a converter filled with an oxidation catalyst to convert it to SO3, feeding a gas containing SO3 exhausted from the above converter into a reaction vessel to produce a sulfonated/sulfated organic compound, introducing the gas exhausted from the above converter into a SO3- absorbing column to form sulfuric acid until that the conversion rate of SO2 to SO3 in the converter reaches to a prescribed steady state value, preferably 98% and then bringing the residual gas in contact with an aqueous alkaline solution in a fed amount in accordance with the temperature difference with an inlet port temperature of the converter to remove SO2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a sulfonated product / sulfuric acid oxide by performing a sulfonation / sulfation reaction of an organic compound using sulfur trioxide, and a method for producing a sulfur trioxide-containing gas in an unsteady state. Regarding the processing method.

[0002]

2. Description of the Related Art Conventionally, sulfur dioxide generated by combustion of sulfur is supplied to a converter filled with an oxidation catalyst to convert it into sulfur trioxide, and a gas containing sulfur trioxide discharged from the converter is converted into a reactor. At the start-up of a production plant for producing a sulfonated product / sulfuric acid by conducting a sulfonation / sulfation reaction of an organic compound, until the gas containing sulfur trioxide reaches a steady state. Since this gas cannot be used in the reaction, sulfur trioxide is recovered as sulfuric acid during that time, and sulfur dioxide is absorbed in an aqueous alkaline solution, and this is treated as a waste liquid. Particularly, in a sulfation / sulfonation reaction step for producing a surfactant material such as linear alkylbenzene sulfonic acid, α-olefin sulfonic acid, alkyl sulfate, α-sulfofatty acid alkyl ester, a gas containing sulfur trioxide is used. The time to reach steady state is as long as about 2-3 hours,
Since the amount of sulfur dioxide in the gas fluctuates greatly and its content is unknown, the treatment is carried out using a large excess of an aqueous alkaline solution, so that the amount of this solution is large and the burden of waste liquid treatment is heavy.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an efficient method for treating a sulfur trioxide-containing gas in an unsteady state, which can reduce the load of waste liquid treatment.

[0004]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies and as a result, have found that the temperature difference between the inlet and outlet temperatures of the converter and the sulfur dioxide in the gas containing sulfur trioxide. It was found that there was a correlation between the amount and the amount, and based on this, the present invention was completed.

[0005] The method and apparatus for treating a sulfur trioxide-containing gas in an unsteady state in the sulfonation / sulfation reaction of the present invention include: (1) supplying sulfur dioxide produced by combustion of sulfur to a converter filled with an oxidation catalyst; Then, a gas containing sulfur trioxide discharged from the converter is supplied to a reactor to perform a sulfonation / sulfation reaction of an organic compound to produce a sulfonated product / sulfur oxide. When the conversion from sulfur dioxide to sulfur trioxide in the converter reaches a predetermined steady-state value, the gas discharged from the converter is introduced into the sulfur trioxide absorption tower to produce sulfuric acid. Then, the remaining gas is brought into contact with an amount of an aqueous alkali solution supplied in accordance with the temperature difference between the inlet temperature and the outlet temperature of the converter to remove sulfur dioxide. Method for treating a sulfur trioxide-containing gas in an unsteady state in a sulfuration / sulfation reaction. (2) At least one converter for converting sulfur dioxide to sulfur trioxide with an oxidation catalyst, a temperature sensor for measuring an inlet temperature and an outlet temperature of the converter, and a sulfur trioxide absorption tower for absorbing sulfur trioxide in water. A scrubber for absorbing sulfur dioxide in the gas discharged from the absorption tower with an alkaline aqueous solution, and means for controlling a supply amount of the alkaline aqueous solution to the scrubber, wherein a temperature difference between an inlet temperature and an outlet temperature of the converter is provided. An apparatus for treating a sulfur trioxide-containing gas in an unsteady state in a sulfonation / sulfation reaction, wherein the supply amount of the alkaline aqueous solution to a scrubber is controlled in accordance with the following conditions. It is characterized by being. Hereinafter, the present invention will be described in more detail.

[0006] The treatment method of the present invention is preferably carried out when the conversion of sulfur dioxide to sulfur trioxide in the converter is less than 98%. Therefore, sulfur trioxide contains sulfur trioxide and sulfur dioxide in the air, and the total concentration of sulfur trioxide and sulfur dioxide is 5 to 15 V%, preferably 6 to 12 V%. In the present invention, raw material sulfur is supplied to a sulfur burner in a molten state and burned to generate sulfur dioxide. The sulfur dioxide is then fed to a converter filled with an oxidation catalyst and converted to sulfur trioxide.

[0007] The converter is a device in which vanadium pentoxide-based particles, columnar particles having a diameter of 4 to 25 mm or rings are packed in the tower as an oxidation catalyst.
Those connected in four to four stages are preferable. For example, in the case of a four-stage converter, the conversion ratio of sulfur dioxide gas to sulfur trioxide gas is 35 to 65% in the first stage converter, 85 to 92% in the second stage, and 95 to 97% in the third stage. %, 4th stage 98 ~
It is preferably 99%, and in the case of a two-stage converter, it is preferably 85-92% in the first stage and 95-99% in the second stage. The reaction temperature is 400 to 600 ° C., preferably,
420-570 ° C., for a four-stage converter, 1
400-600 ° C in the second stage converter and 440 in the second stage
~ 550 ° C, 440-500 ° C in the third stage, 42 in the fourth stage
0 to 440 ° C., preferably 400 to 600 ° C. in the first stage and 440 in the second stage in the case of a two-stage converter.
~ 500 ° C is preferred.

In the above converter, there is a correlation between the temperature difference between the inlet and outlet temperatures of the converter and the conversion of sulfur dioxide gas to sulfur trioxide gas.
Measure these relationships in advance. When two or more converters are used, the correlation between them is checked in advance for each stage, and the conversion rate from sulfur dioxide to sulfur trioxide is estimated from the temperature difference between the inlet temperature and the outlet temperature for each stage. I can do it.
For example, in the case of three stages, since the change in the conversion of the third stage is small, the temperature difference between the first stage and the second stage converter can be used. In the present invention, the correlation between the temperature difference between the inlet and outlet temperatures of the converter and the conversion from sulfur dioxide gas to sulfur trioxide gas is stored in a computer, and the inlet and outlet temperatures of the converter are measured. The conversion rate is estimated from the temperature difference, and the supply rate of the aqueous alkali solution to the scrubber for absorbing and removing sulfur dioxide in a later step is controlled in accordance with the conversion rate. As a result, it is possible to perform control that quickly follows fluctuations in the contents of sulfur trioxide and sulfur dioxide in an unsteady state.

The sulfur trioxide-containing gas discharged from the converter is introduced into the sulfur trioxide absorption tower until the conversion from sulfur dioxide to sulfur trioxide reaches a predetermined steady-state value. At this time, the gas containing sulfur trioxide is preferably introduced before it is introduced into the sulfur trioxide absorption tower.
Cool to a temperature of 5-45 ° C.

[0010] The sulfur trioxide absorption tower is a packed tower in which a predetermined packing is packed in a cylindrical tower. Water or sulfuric acid is supplied from the upper part of the tower as an absorbing solution of sulfur trioxide gas and discharged from the lower part of the tower, and the discharged liquid is adjusted to a predetermined temperature via a pump and a heat exchanger, and is returned to the upper part of the tower. Form a circulation line to be circulated. Water or sulfuric acid is preferably supplied by a shower ring at the top of the tower. The gas containing sulfur trioxide is supplied from the lower part of the tower and discharged from the upper part of the tower, and the sulfur trioxide is absorbed by countercurrent contact between sulfuric acid and the gas containing sulfur trioxide, Concentrated sulfuric acid is produced and discharged from the bottom of the column. Water is supplied to the circulation line in accordance with the discharge amount of concentrated sulfuric acid, and the supply amount of the water is preferably controlled in accordance with the temperature difference between the inlet temperature and the outlet temperature of the converter as described later.

The sulfuric acid circulated to the column has a concentration of 9 at the column inlet.
7 to 98% by weight, the temperature is preferably 30 to 40 ° C at the inlet of the tower and 40 to 50 ° C at the outlet, and the concentration of concentrated sulfuric acid discharged from the lower part of the tower is 95% or more, preferably 98% or more. . The concentration of sulfur trioxide in the gas containing sulfur trioxide is:
5 to 15 V%, preferably 6 to 12 V%, in order to promote gas absorption, the internal pressure of the column is 3 to 10 kg / cm ² ,
The volume ratio of the gas to the flow rate of sulfuric acid is preferably 4 to 6 kg / cm ² , and 3 to 20, preferably 5 to 15. The inner surface of the tower is SS41 to prevent corrosion
Are preferably Teflon-lined.

[0012] The gas discharged from the sulfur trioxide absorption tower mainly contains sulfur dioxide.
This gas is introduced into a scrubber that absorbs sulfur dioxide with an aqueous alkaline solution. Before introducing this gas into the scrubber, it is preferable to remove sulfur trioxide / sulfuric acid accompanying the gas through a cotrel (electric precipitator).

A scrubber is a packed tower in which a cylindrical column is filled with a predetermined packing material. An alkaline aqueous solution is supplied from the upper portion of the column, discharged from the lower portion of the column, and a gas containing sulfur dioxide is supplied from the lower portion of the column. And discharged from the top of the tower. Inside the tower, sulfur dioxide is absorbed and removed by countercurrent contact between the aqueous alkali solution and the gas containing sulfur dioxide, and the sulfur dioxide is discharged from the lower part of the tower and treated as a waste liquid.

In the scrubber, a circulation line is formed for supplying an alkaline aqueous solution from the upper part of the tower, discharging the aqueous solution from the lower part of the tower, and recirculating the alkaline aqueous solution to the upper part of the tower through a pump. Is connected to a line (new charge) for supplying water for concentration adjustment. The concentration of the alkaline aqueous solution in the circulation line is 0.0
1-0.5% by weight is preferred. If it exceeds 0.5% by weight, an inorganic substance such as Na ₂ SO ₄ may precipitate and adhere to the packing, deteriorating the gas-liquid contact efficiency. In addition,
As the high-concentration aqueous alkaline solution to be supplied to the circulation line, a concentrated aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, or the like can be used. , 4
A 0-48% aqueous solution is preferred.

In the present invention, the supply amount of the alkaline aqueous solution supplied to the circulation line is controlled according to the temperature difference between the inlet temperature and the outlet temperature of the converter. That is, the correlation between the temperature difference between the inlet and outlet temperatures of the converter and the conversion rate from sulfur dioxide to sulfur trioxide is stored in a computer, and the inlet and outlet temperatures of the converter are measured, and this temperature difference is measured. The conversion rate is estimated from the above, and the supply amount of the aqueous alkali solution to the scrubber for absorbing and removing the sulfur dioxide gas in the subsequent process is controlled in accordance with the conversion rate. Qualitatively, when the temperature difference increases, the conversion rate from sulfur dioxide gas to sulfur trioxide gas increases and the amount of sulfur dioxide gas decreases, so the supply amount of the alkaline aqueous solution decreases, and the temperature difference decreases. If it decreases, the supply amount of the aqueous alkali solution is increased. The amount of water supplied to the sulfur trioxide absorption tower can be controlled in a similar manner.

The temperature of the aqueous alkali solution circulated through the scrubber is 30 to 40 ° C. at the entrance of the tower and 32 to 4 at the exit.
In the 2 ° C tower, the temperature is preferably from 32 to 42 ° C, and in order to promote gas absorption, the internal pressure of the tower is 1.1 to 1.5 kg / c.
m ² , preferably 1.3 to 1.5 kg / cm ² , the volume ratio between the gas and the flow rate of the aqueous alkali solution is 50 to 200,
Preferably, it is set to 90 to 140. The inner surface of the tower is preferably one in which SS41 is FRP-lined to prevent corrosion.

In the present invention, the gas treated by the scrubber can be released to the atmosphere as it is. The alkaline aqueous solution having absorbed the sulfur dioxide is discharged from the lower part of the tower, sent to a waste liquid treatment tank, and treated.

[0018]

According to the present invention, the amount of supply of the aqueous alkali solution to the scrubber that absorbs and removes sulfur dioxide can be reduced in order to efficiently treat the gas containing sulfur trioxide in an unsteady state. The processing load can be reduced.

Examples and Comparative Examples Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 In a sulfonation plant for producing a linear alkylbenzene sulfonic acid, sulfur dioxide produced by combustion of molten sulfur is supplied to a converter filled with a vanadium pentoxide catalyst to be converted into sulfur trioxide. Until the conversion reaches 98%, the gas discharged from the converter is
Was introduced into a processing device for a sulfur trioxide-containing gas shown in the following. The sulfur trioxide-containing gas is supplied to a sulfur trioxide absorption tower, and sulfur trioxide is recovered as concentrated sulfuric acid. The sulfur is absorbed and removed, and is released as a clean gas to the atmosphere. The sulfur trioxide-containing gas has a temperature of 40 ° C. and a flow rate of 45 Nm ³ / min. , Sulfur trioxide and sulfur dioxide in the gas were 8.4 V% in total. The sulfur trioxide absorption tower is a packed tower in which a packing having a capacity of about 40 m ³ is packed in a cylinder. Was circulated and supplied to 40 ° C., and 98% by weight of concentrated sulfuric acid was obtained from the bottom of the column. Water is supplied to the sulfuric acid circulation line according to the amount of concentrated sulfuric acid discharged from the lower part of the tower. The scrubber was a packed tower in which packing was packed in a cylinder having an internal volume of about 50 m ³ , and an aqueous solution of sodium hydroxide having a concentration of 0.04% by weight was circulated and supplied at a predetermined flow rate (40 t / hr). The liquid temperature in the scrubber was 40 ° C.
A 48% sodium hydroxide aqueous solution (new charge) and water for adjusting the concentration to a predetermined concentration are supplied to the sodium hydroxide circulation line so as to balance the amount of waste liquid discharged from the scrubber. The amount of new charge of the aqueous sodium hydroxide solution to be supplied to the scrubber was changed based on the correlation between the temperature difference and the conversion as follows by measuring the inlet and outlet temperatures of the converter with a temperature sensor. The converter has four stages, and the temperature difference is the sum of the temperature differences between the inlet and outlet of the first, second and third stages ((1st stage outlet temperature-1 stage inlet temperature) + (2nd stage outlet temperature-2 stage inlet) Temperature) + (3rd stage exit temperature−3rd stage entrance temperature)). The relationship between the temperature difference (ΔT) and the conversion (ΔX) was as shown in the equation (1).

Embedded image ΔT = 234.7 ΔX (1) ΔT: ° C. ΔX: mole fraction The amount of sulfur dioxide is calculated by an arithmetic unit based on the formula (1), and the hydroxylation to be supplied to the scrubber is calculated. The flow rate of the aqueous sodium solution was determined, and the amount of the new charge of the aqueous sodium hydroxide solution was controlled so as to reach this flow rate. The new charge amount of the aqueous sodium hydroxide solution is 20 to 30.
The flow rate range was kg / hr. Although not shown in FIG. 1, the amount of water supplied to the sulfur trioxide absorption tower was controlled based on the above equation (1). Such a process was performed for about 2 hours. The packing of the scrubber was obtained by inserting a cross-shaped plate (a 10 mm × 46 mm × 2 mm thick plate into a cylinder having a diameter of 50 mm, a length of 50 mm, and a thickness of 2 mm) so that the plates face each other. It is installed in the axial direction of a single cylinder and has a plurality of quadrangular channels (axial direction 10 mm × circumferential direction 30 mm) on the side wall (material: polyethylene).

Comparative Example 1 In Example 1, the control according to the temperature difference was not performed, and the amount of the new charge of the aqueous sodium hydroxide solution was supplied to the scrubber at a constant flow rate of 30 kg / hr.

Evaluation In the Examples and Comparative Examples, the amount of waste liquid during the above treatment (the ratio when Example 1 was set to 1) was used as a measure of the load of waste liquid treatment corresponding to the amount of alkaline aqueous solution discharged from the scrubber. When the pH of the waste liquid was measured, as shown in Table 1, the load of the waste liquid treatment was reduced in the example since the amount of the waste liquid was smaller and the pH was lower.

[0023]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for treating a sulfur trioxide-containing gas of the present invention.

Claims (2)

[Claims] (1) sulfur dioxide produced by combustion of sulfur;
It is supplied to a converter filled with an oxidation catalyst to convert it into sulfur trioxide, and a gas containing sulfur trioxide discharged from the converter is supplied to a reactor to perform a sulfonation / sulfation reaction of an organic compound. When producing the sulfonate / sulfuric acid, the gas discharged from the converter is subjected to sulfur trioxide absorption until the conversion ratio of sulfur dioxide to sulfur trioxide in the converter reaches a predetermined steady-state value. It is introduced into the column to produce sulfuric acid, and then the remaining gas is contacted with an amount of an aqueous alkali solution supplied according to the temperature difference between the inlet and outlet temperatures of the converter to remove sulfur dioxide. A method for treating a sulfur trioxide-containing gas in an unsteady state in a sulfonation / sulfation reaction. 2. At least one converter for converting sulfur dioxide to sulfur trioxide with an oxidation catalyst, a temperature sensor for measuring an inlet temperature and an outlet temperature of the converter, and sulfur trioxide for absorbing sulfur trioxide in water. An absorption tower, a scrubber for absorbing sulfur dioxide in the gas discharged from the absorption tower with an alkaline aqueous solution, and means for controlling a supply amount of the alkaline aqueous solution to the scrubber, wherein an inlet temperature and an outlet temperature of the converter Controlling the supply amount of the alkaline aqueous solution to a scrubber according to the temperature difference,
Equipment for treating sulfur trioxide-containing gas during unsteady state in sulfation reaction.