RU2046756C1 - Sulfuric acid production method - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: method involves the use of utilization tank 2 to cool gases evolved in the process of burning liquid sulfur in furnace 1. Upon cooling, the gases enter the first step of contact apparatus 3. The gases from the first plate of contact apparatus 3 are cooled in heat exchanger 4, and they are supplied to the second plate of contact apparatus 3. The gases from the second plate of contact apparatus 3 are cooled in heat exchanger 5, and they are supplied to the third plate of contact apparatus 3. The gases from this plate are cooled in heat exchangers 6 and 7, then they enter scrubber WAI. The gases from scrubber WAI are heated in heat exchangers 6, 5 and 4, and they enter the fourth plate of contact apparatus 3. The gases from this plate are cooled in economizer 8, and they are supplied to absorption tower WAII. From this tower the gases are supplied to the fifth plate of contact apparatus 3 upon preliminary heating. The process of heating has two steps: first the gases are heated in heat exchangers 9 and 10, then they are heated in heat exchanger 11 by hot gases coming from furnace 1. The gases from the fifth plate of contact apparatus 3 enter absorption tower WAIII, and from this tower they are released in the atmosphere upon removal of sulfur trioxide. EFFECT: higher efficiency. 2 dwg

Description

 The invention relates to methods for producing sulfuric acid using a three-stage oxidation of sulfur dioxide with the intermediate elimination of the resulting sulfur trioxide.

A known method of producing sulfuric acid through a three-stage conversion with intermediate absorption of sulfur trioxide [1] according to which the oxidation process is carried out in a five-plate apparatus in which the first three plates form the first contact stage, the fourth and fifth plates, respectively, the second and third contact stage. After the first and second contact stages, intermediate absorption of the sulfur trioxide formed is carried out, and after the third contact stage, gases are sent to the final absorption, then released to the atmosphere. In order to maintain the appropriate temperature conditions of the process of oxidation of sulfur dioxide, the gases from the first and second stages of contact primarily subjected to absorption and then warmed in heat exchangers to 430 ^C. The heating process proceeds in two stages: first by a gas from the third contact tray apparatus, ie. The gases from the third plate of the contact apparatus primarily heat the gases after the second absorption stage, and then the gases after the first absorption stage. In addition, the gases after the first absorption stage are heated by gases from the first plate of the contact apparatus, the gases after the second absorption stage by gases from the second plate of the contact apparatus.

 The process of oxidation of sulfur dioxide on all plates of the contact apparatus is carried out on a solid catalyst bed, and the removal of sulfur trioxide can be carried out by absorption or condensation, or by absorption and condensation.

 There is also known a method for the production of sulfuric acid by means of a three-stage oxidation of sulfur dioxide at an intermediate stage of removal of the resulting sulfur trioxide [2] according to which the gases from the first or second contact stage after the intermediate process of eliminating sulfur trioxide are re-heated in three stages to the required temperature. First, it is heated with gases from the first contact stage, then with gases from the second and / or third contact stage, the final heating of the gases conducted to the second stage is carried out by the gases leaving the first plate, and the final heating of the gases conducted to the third stage is carried out by means of the contact apparatus leaving the second plate gases.

 However, the solution presented above does not guarantee complete autothermal conditions of the sulfuric acid production process, since it does not take into account a significant reduction in the degree of conversion of sulfur dioxide to sulfur trioxide at the first contact stage in the case of the traditional equipment of the plate with a catalyst in a cylindrical form. Another disadvantage of this solution is the impossibility of its application in the modernization of installations without a fundamental restructuring of existing thermal systems.

 A method for producing sulfuric acid by means of a three-stage oxidation of sulfur dioxide with an intermediate elimination of sulfur trioxide, in which the gases carried to the second contact stage are heated by gases from the first contact stage, according to the invention is characterized in that the gases supplied to the third stage are heated by means of leaving the second or third contact stage gases, after which they are heated by hot gases from the furnace for burning sulfur.

 The present invention through the use of part of the hot gases from the sulfur combustion furnace guarantees full autothermal process when the contact apparatus is equipped with a ring catalyst, which further makes it possible to increase the operation of the installation. In addition, the invention guarantees a high degree of final conversion and can significantly reduce the emission of sulfur dioxide into the atmosphere during installation startup. An additional advantage of this solution is the ability to add a third contact stage while maintaining the previous two-stage oxidation system, which significantly reduces the modernization work.

 In FIG. 1 shows the installation diagram with the heating of the gases supplied to the third contact stage by gases after the third contact stage; in FIG. 2 installation diagram with the heating of gases carried to the third contact stage by gases after the second contact stage.

Liquid sulfur with a temperature of 145 ^about With is introduced into the furnace 1, in which the process of combustion in dry air. As a result of this process, gases are formed with a content of about 11% sulfur dioxide with a temperature of about 1000 ^about C.

These gases are conducted to a recovery boiler 2, in which cooling is carried out, and then discharged to the contact apparatus 3. The contact apparatus is equipped with five plates that are equipped with a ring catalyst. The first three plates of the contact apparatus form the first contact stage, and the fourth and fifth plates, respectively, the second and third contact stages. The temperature imposed contactor gases is approximately 425 ° ^C. The temperature control is made by adding to the gases after utilizing boiler appropriate amount of hot gases from the furnace 1.

On the first plate of the contact apparatus 3, sulfur dioxide is oxidized. In this process, the temperature of the gases rises to about 600 ° ^C leaving the first contact plate gases are cooled in heat exchanger 4 to a temperature of about 460 ^C via conducted after the second contact step, posleabsorbtsionnyh gases, after which they are held on the second plate contact apparatus 3. after the second plates contact apparatus 3 gases with a temperature of about 530 ^{° C} are carried out in heat exchanger 5, in which the cooling them to about 450 ^{° C} posleabsorbtsionnymi basics conducted after the second contact plate, after that, they are held on the third plate 3. The contact device leaves the third plate contact device gases have a temperature of approximately 480 ° ^C. Further, they are fed to the heat exchangers 6 and 7, in which the cooling takes place to a temperature of approximately 200 ^about C. Then they are brought into the two-stage absorption tower WA I in order to eliminate sulfur trioxide.

The gases from the absorption tower WA I with a temperature of about 70 ^{° C} heated in serially connected heat exchangers 6, 5 and 4 to a temperature of approximately 430 ^{° C} gas from the first contact and the plates are held to the fourth plate contact device 3, which forms the second contact stage. Here, further oxidation of sulfur dioxide is carried out. After the second stage gases contact at a temperature of about 450 ^{° C} are cooled in the economizer 8 and a temperature of about 200 ^{° C,} after which they are fed to the absorption tower WA II, where the removal of sulfur trioxide.

After absorption tower WA II gases with temperatures of about ⁸⁰ ° C after preheating to 425 ^{° C} held on the fifth plate contact device, which forms the third contact stage. The heating process proceeds in two stages: first, the gases are heated in series-connected heat exchangers 9 and 10 by gases from the third contact stage and then they are heated in the exchanger 11 by hot gases from furnace 1. On the fifth plate of the contact apparatus, the sulfur dioxide formed is oxidized, so that the complete conversion is 99.95% and gases with a temperature of about 440 ^{° C,} after cooling the heat exchangers 9 and 10 to a temperature of about 180 ^{° C} are carried out in an absorption tower WA III, where they are after the removal of sulfur trioxide is released into the atmosphere.

 Gases (Fig. 2), conducted after the second absorption tower WA II to the third contact stage, are heated in the heat exchangers 9 and 10 by gases from the second contact stage and then heated in the exchanger 11 with hot gases from the furnace 1.

Claims (1)

 METHOD FOR PRODUCING SULFURIC ACID from elemental sulfur, including burning the last, three-stage conversion of the obtained sulfur dioxide to trioxide with heating the gas before it is fed to each conversion stage and with absorption of sulfur trioxide after each stage, while the gas is heated with gases leaving the second stage from the first stage of conversion, characterized in that the gas before being fed to the third stage is heated with gases leaving the furnace for burning sulfur, with its preliminary heating with gases leaving the second sludge and the third stage of conversion.

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