RU2286836C1 - Method of removing sulfur dioxide from gas - Google Patents

Abstract

FIELD: purification of gases.

SUBSTANCE: method comprises absorbing sulfur dioxide by means of a lime suspension, crystallization, and removing slime. The gas is cooled before absorbing up to the dew point by water evaporating. The ratio of the volume of water to that of the gas should be 0.08-0.12 l/m³. The water temperature exceeds that of the dew point by 10°C of the cooled gas. The gas is absorbed by the suspension made of droplets supplied perpendicular to the gas flow.

EFFECT: enhanced quality of purification.

1 cl, 1 dwg, 1 tbl

Description

The invention relates to the field of chemical technology and can be used for purification of waste process gases at enterprises of the energy, metallurgical and chemical industries.

A known method of purifying gas from sulfur dioxide with a suspension of limestone or lime with the addition of carboxylic acid and manganese sulfate by absorption, oxidation, neutralization and filtration with the release of gypsum. The absorption of sulfur dioxide from gas is carried out in countercurrent mode (Rodionov A.I., Klushin V.N., Torocheshnikov N.S. - Environmental protection technology, - M., Chemistry, 1989, p. 77, Fig. 1-25 )

The disadvantage of this method is the use of additional absorbers, which complicates the technology of purification of exhaust (technological) gases from sulfur dioxide and significantly increases the capital and current costs of the cleaning process.

The closest technical solution to the claimed is the scheme of the limestone (calcareous) method. This method includes absorption of gas in countercurrent mode with a lime slurry, crystallization of the deposited sludge and its subsequent withdrawal (Gladky A.V. Absorption methods for cleaning gases from sulfur dioxide. Overview - Industrial and sanitary cleaning of gases. - M., TSINTIHIMNEFTEMASH, 1978, series XM-14, p.3-7) - prototype.

The method of purification of gases from sulfur dioxide (dioxide) according to this scheme is simple and affordable, however, it does not provide high efficiency for the process of purifying process gases from sulfur dioxide. In addition, with this method, the reliability of operation of the installation is low due to contamination of the absorber with salt deposits: calcium sulfates and sulfites.

The objective of the invention is to improve the calcareous method of purification of gases from sulfur dioxide.

The technical result that will be achieved from the use of this invention is to increase the degree of gas purification from sulfur dioxide and increase the reliability of operation of the gas purification plant.

The technical result is achieved by the fact that in the method for purifying process gas from sulfur dioxide by absorption with a lime suspension, crystallization and sludge removal, the gas is cooled before absorption in an evaporative mode to dew point with water. Water is supplied at the rate of 0.08-0.12 l / m ^{3 of} gas. The water temperature is 10 ° C higher than the dew point temperature of the cooled gas.

Gas absorption is carried out by a suspension in the form of droplets supplied perpendicular to the gas flow.

The essence of the invention is to increase the efficiency of absorption of sulfur dioxide from pre-cooled and saturated with water vapor process gas.

It was experimentally established that gas cooling before absorption in the evaporative mode to a dew point of water supplied in an amount of 0.08-0.12 l / m ^{3 of} gas with a temperature of (water) 10 ° C higher than the dew point of the cooled gas allows reaching sulfur dioxide absorption efficiency up to 95%. In this case, salt deposition does not occur on the inner surface of the absorber, because at 100% relative humidity of the gas, water does not evaporate from the absorbing saline solution of the wet areas of the absorber. As a result of this, there is no saturation of the absorption solution of these areas and, as a result, the deposition of salts on the walls of the absorber is excluded.

It was also established that the most rational process of absorption occurs when the gas stream is in contact with droplets of suspension and water supplied (flying) perpendicular to the gas stream, because the absence of a liquid column and a large horizontal speed provides low hydraulic resistance, high permissible gas velocities, large throughput of the suspension and water, and a short residence time of droplets of suspension and water in the contact zone. As a result, the degree of purification of gas from sulfur dioxide increases and the reliability of operation of the installation increases.

From the analysis of scientific, technical and patent literature, the claimed combination of features ensuring the achievement of this technical result was not revealed, which allows us to conclude that this technical solution meets the criteria of "novelty" and "inventive step".

The invention is illustrated in the drawing, which shows a diagram of a process gas treatment plant.

The installation includes a multi-stage absorber 1, consisting of five stages 2, 3, 4, 5, 6, a mold 7, a slurry output unit 8, a reactor for the preparation of lime slurry 9, crusher 10, mill 11 and dry lime classifier (lime) 12 .

The invention is as follows.

Example 1. Gas sinter production in an amount of 290 thousand nm ³ / h with a temperature of 125 ° C, containing (g / nm ³ ): sulfur dioxide -3.54, carbon dioxide - 46.0, oxygen - 184, is fed after dust cleaning to the bottom of a multi-stage (in this case 5-stage) column absorber 1. A lime slurry previously prepared from limestone or lime is fed into the upper part of the absorber. The supplied process gas in the first 2 and second 3 stages of the absorber 1 is in contact with water droplets resulting from the dispersion of water supplied perpendicular to the movement of the gas stream. After passing through these stages, the gas is cooled to a dew point of 56 ° C. Then the gas enters the next three stages of the absorber 4, 5, 6, to which the lime suspension is fed perpendicular to the gas stream from the mold (circulation collector) 7. The lime suspension is preliminarily prepared from lime or limestone by grinding it in a grinder 10, from where it is fed to a ball mill 11 and classifier 12. After classification, large particles are returned to the ball mill 11, and small particles of limestone or lime are fed into the reactor 9, to which water is added at the same time, mixed and limes are obtained suspension, which then enters the mold 7.

The gas is in contact with drops of a lime slurry supplied perpendicular to its flow. The absorbed sulfur dioxide reacts with the lime suspension (Ca (OH) ₂ ) and, in the form of calcium sulfite or calcium sulfate, together with the spent lime suspension, which flows from all stages to the bottom of the absorber 1, is discharged from the bottom of the absorber 1 and enters the crystallizer 7 From the last part of this absorption solution is sent to the outlet unit of the sludge 8, where it is filtered or centrifuged. The filtered sludge is removed and the filtrate is returned to the reactor 9.

The gas purified from sulfur dioxide is discharged from the upper part of the absorber. Examples of purification of other process gases are similar to the above. Depending on the chemical composition, the dew point of flue gases can vary from 32 to 52 ° С, the dew point of sinter gases is 40-46 ° С, and the dew point of the process gas from waste incineration plants is 39-48 ° С.

The properties of this method of purification of process gases from sulfur dioxide are shown in the table.

Table №№
p / p Gas production capacity, thousand nm ³ / h Specific consumption of cooling water, l / m ³ gas Differences between water temperature and dew point of the cooled gas, ° С The degree of gas purification,% Installation continuity, months Energy-gosat-rats,% one 290 0.06 10 76 6 61 2 290 0.08 10 94 13 82 3 290 0.10 10 95 fourteen one hundred four 290 0.12 10 95 fourteen 126 5 290 0.14 10 95 fourteen 158 6 290 0.10 8 92 eleven one hundred 7 290 0.10 12 93 fourteen one hundred 8 prototype 290 - - 80 6 145

As can be seen from the table, the most optimal indicators are observed in examples 2-4 with the claimed parameters of water flow. In examples 1 and 5 with exorbitant values, performance deterioration is observed: in example 1 there is an insufficient degree of purification of gas from sulfur dioxide, and in example 5, high energy costs.

In examples 6 and 7 with exorbitant values of water temperature (excess of dew point temperature of less than or more than 10 ° C), the degree of gas purification worsens.

Compared with the prototype (example 8), the inventive method will increase the degree of purification of gases from sulfur dioxide in 1, 2 times.

This invention can dramatically reduce the salt deposits of sulfates and calcium sulfites on the walls of the absorber. The degree of purification of the process gas from sulfur dioxide is 95%.

Claims (2)

1. The method of purification of process gas from sulfur dioxide by absorption of lime suspension, crystallization and removal of sludge, characterized in that before absorption the gas is cooled by evaporation to the dew point of water supplied in an amount of 0.08-0.12 l / m ³ gas and with a temperature exceeding the dew point temperature of the cooled gas by 10 ° C. 2. The method according to claim 1, characterized in that the gas is absorbed by a suspension in the form of droplets supplied perpendicular to the gas flow.