CS263537B1 - A method of drying air in the production of sulfuric acid - Google Patents

Abstract

Method of drying air in the production of sulfuric acid from sulfur by the contact method, in which the air flow at the outlet of the drying tower is brought into contact with sulfuric acid with an inlet concentration x of 93 to 98.5% by mass and a temperature lower than the temperature t given by the relationship t = 0.011589 . e°,°9412.xj where tax have the above-mentioned meaning, and in the range of inlet concentration 94<x<98% by mass of sulfuric acid the temperature is higher than 70 °C and at inlet conc. of sulfuric acid 93 to 94% by mass and 98 to 98.5% by mass the temperature is higher than 50 °C.

Description

(54)

Method of air drying in sulfuric acid production

A method of drying air in the production of sulfuric acid from sulfur by a contact process, wherein the air stream at the point of exit from the drying tower is contacted with sulfuric acid having an inlet concentration x 93 to 98.5% hin. and a temperature lower than the temperature t given by t = 0.011589. _e °, ° 9412.x _j wherein tax are as defined above, wherein in the inlet concentration range 94 < x < sulfuric acid, the temperature is above 70 ° C and at the inlet conc. % sulfuric acid 93 to 94 wt. and 98 to 98.5 wt. the temperature is above 50 ° C.

- /) 263 537

The invention relates to a process for drying air in the production of sulfuric acid from sulfur by a contact process.

by contacting the air in contact with 9 3 < % H S 0. Drying

When producing sulfuric acid from sulfur, it is necessary to reduce the moisture content in the air before entering the sulfur furnace or before entering the blower, typically below 0.1 g / Nm \. A higher moisture content would increase corrosion of the reactor and other apparatus at low conversion temperatures. gas. Drying with sulfuric acid is carried out in absorbers of various types, most often in anti-screw packed columns, but Venturi buckles and other apparatuses are also used. In packed columns, the transfer of moisture from olefin to sulfuric acid takes place on the interfacial surface formed by acid running down the filling bodies of scrapers such as Raschig or Pa 11-rings, various types of saddles, etc. The filling bodies can be made of porcelain, or plastic. The flow temperature of the acid is traditionally chosen to be 40®50 ° C and is limited from above due to fear of corrosion of the dryer circuit apparatus due to hot sulfuric acid, as well as by increasing the dew point of sulfuric acid in the conversion gases. Countercurrent dryer towers of a sulfuric acid plant usually have a sufficiently high filler layer so that at the top of the filler there is practically a temperature equalization between the flowing liquid and the exiting gas, and the water vapor content of the exiting gas approaches .

The disadvantage of drying the air with sulfuric acid at a temperature of 40 to 50 ° C is, among other things, the high demands on the need for cooling water

265 537 and the cooling surfaces due to the small temperature difference between the cooling water and the acid and the correspondingly low temperature of the dried air causes an increased risk of corrosion of the device. These deficiencies are only partially remedied by the procedure according to MS. AO No. 193 743, wherein the drying is carried out with sulfuric acid at a flowing acid concentration of 94 to 98% by weight. and a temperature of 50 to 70 ° C.

SUMMARY OF THE INVENTION The present invention relates to a process for drying air in the production of sulfuric acid from sulfur by a contact process, wherein the air stream at the outlet of the drying tower is contacted with sulfuric acid at a feed concentration of x 93 to 98.5% by weight. and a temperature lower than the temperature t given by t = 0.011589. θ ^θ ζ ° 9412.χ ^ where tax have the meaning given above, wherein the inlet concentration range is 94 x <(98 7% by weight sulfuric acid, the temperature is above 70 ° C and the rest in the inlet concentration range 93 to 98,5% by weight) The sulfuric acid is at a temperature greater than 50 [deg.] C. Thus, the above formula gives a curve of the highest usable temperatures of the flowing sulfuric acid as a function of its concentration.

The part of the sulfuric acid flowing out of the drying tower can be cooled without adjusting the acid concentration event. water, preferably to be re-contacted with the dried air stream at the point of its exit from the drying tower.

It is also preferred that at least one of the dryer circuit apparatuses is anodically protected against corrosion. This allows higher temperatures to be used in dryer circuits without the risk of corrosion of the equipment. In addition, temperature increases in dryer circuits are made possible, for example, by the use of efficient mist separators inserted behind the dryer or by the use of new construction materials such as anti-corrosion alloys, polytetrafluoroethylene and the like.

The highest usable temperatures of the flowing acid increase with its concentration, since the corrosion resistance of most construction materials in the range of sulfuric acid concentration 93 to

263> 57

98.5 7 wt. increases with increasing concentration of sulfuric acid.

The air drying method according to the invention has a number of advantages. The cooling water consumption for acid cooling is reduced, the process can be operated with a smaller cooling surface. In special cases (in the winter months), acid cooling can be completely disabled. The amount of heat not transferred between the acid and the cooling water compared to the prior art process is used to produce steam.

It has been calculated that an increase in the temperature of the dried air of 10 ° C corresponds to an increase in steam production of about 1%, so that, for example, if drying is carried out at a temperature flowing at 98% by weight. acid 80 ° C, steam production will increase compared to the current state / same concentration, but the flowing acid temperature 50 ° C / by 3%.

In the following, the invention is explained in more detail in the drawing, in which one of the possible process flow diagrams is illustrated, and by way of example embodiments.

The atmospheric air 7 enters the countercurrent of the drying tower where it comes into contact with the flowing sulfuric acid 3. The dried air enters the heat exchanger 5 where it is heated by the conversion gas Nr. The exiting conversion gas 7, after the heat has been given off, goes to an absorption tower, which is no longer shown in FIG. The air stream 8 from the exchanger 5 is used to burn the sulfur 9 in the sulfur dioxide furnace 10, which in the stream 11 proceeds for further processing to the plant.

From the drying tower 2, dilute sulfuric acid 12 flows into the mixer 13, where the acid concentration is adjusted to the desired value (stream 16) by the addition of process water 14 and absorption acid 15 and a water balance is maintained. In the cooler 17 excess acid heat is transferred to the cooling water 18 (heated water 19). From here, cooled acid 21 is pumped through pump 22 back to drying tower 2 (stream 3), with part of the acid 23 being discharged from the circuit as a production acid.

By utilizing the invention, the amount of heat transferred in the cooler 17 by the acid 16 to the cooling water 18 is reduced

263 537 If there is no need for acid stream 1 6 to cool at all 3, cooler 17 is saved.

Example 1

Sulfuric acid 3 flowing into the drying tower 2 at a concentration of 94 wt. has a temperature of 80 _from 5 ° C. Molar fraction value

30 ^ 11 in the gas stream exiting from the kiln 1 0 _f is 0.1, and vý- MALL works with a conversion of 0.98. The absorbent acid 15 flows from the absorber circuit to a mixer 13 having a temperature of 50 ° C and a concentration of 98.5% by weight. Water 14 is not added to the mixer 13. In the cooler 17, heat Q = 10500 kJ per 1 kmol of sulfur sulfur (stream 9) is removed from the acid stream 16. The air exiting the £ £ drying tower has a temperature _of 80 ° C _from 5 thereby to produce steam is converted to the commonly used method of / 4 air temperature of 40 ° C / about 11700 kJ / kmol more sulfur.

Example 2

Sulfuric acid 8 flows into the drying tower 2 at a concentration of 95% by weight. H ^ SO ^ and a temperature of _from 88 5 ° C. The plant operates with a degree of conversion of 0 _{out of} 98 and the molar fraction SO ^ at the outlet of the furnace (stream 11) is 0.1. or water (stream 14) _{from the} absorber circuit 15 has a temperature of 50 ° C and a concentration of 98 _{out of} 5 wt. H 2 SO 4. Thereafter, the acid stream 16 is not cooled and the condenser 17 is saved. The heat released in the absorber is transferred to the air stream vystup exiting the drying tower £ at 88.6 ° C and will be used to produce steam. Compared to the current state (air temperature 4 = 40 ° C) with air 4, it converts 14045 kJ of steam per kilogram of sulfur to be burned.

Claims (3)

SUBJECT OF THE INVENTION A method of drying air in the production of sulfuric acid from sulfur by a contact method, wherein the air stream at the outlet of the drying tower is contacted with sulfuric acid, characterized in that the air stream is contacted with sulfuric acid of inlet concentration x 93 % to 98.5 wt. and a temperature lower than the temperature t given by t = 0.011589. _e ° / ⁰⁹⁴¹² - * _z where tax are as defined above, wherein in the inlet concentration range 94 <<χ <ζ 98 7 wt. of sulfuric acid, the temperature is above 70 ° C and at the inlet conc. of sulfuric acid 93 to 94 7. wt. and 98 to 98.5 7 wt. the temperature is above 50 ° C. 2. A method according to claim 1, characterized in that, after adjusting the concentration without cooling, a portion of the sulfuric acid flowing out of the drying tower is re-contacted with a stream of dried air at its outlet from the drying tower. 3. Process according to claim 1 or 2 _f, characterized in that at least one APA RATU sušičového circuit anodic protection against corrosion.