Method of removing sulfur dioxide from gas

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

 

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

The known method of gas purification from sulfur dioxide suspension of limestone or lime with the addition of carboxylic acid and manganese sulfate by means of absorption, oxidation, neutralization and filtration emitting plaster. Absorption of sulfur dioxide from gas is carried out in counter-current mode (Rodionov A.I., closin V.N., Torasession NS - Tech environmental protection, - M, Chemistry, 1989, p.77, 1-25).

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

The closest technical solution to the claimed design is the limestone (lime) method. This method includes the absorption of gas in counter-current mode with lime slurry, the crystallization of the precipitated sludge and its subsequent conclusion (Smooth AV Absorption methods for cleaning gases from sulfur dioxide. Overview - Industrial and sanitary gas cleaning. - M, CONTAINERTYPES, 1978, series HM-14, p.3-7) - prototype.

The method of purification of g is the call dioxide (dioxide) sulfur under this scheme is simple and accessible, however, it does not provide high efficiency process for cleaning exhaust process gases from sulfur dioxide. In addition, with this method the reliability of the installation of low-pollution absorber salt deposits: sulfates and sulfites of calcium.

The objective of the invention is to improve the lime method of cleaning 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 installation of gas cleaning.

The technical result is achieved in that in the method of purification of process gas from sulfur dioxide by absorption of lime suspension, crystallization and removal of sludge gas before absorption is cooled in the evaporative mode until the dew point of water. Water is supplied from the calculation 0,08-0,12 l/m3gas. The water temperature by 10°higher than the dew point temperature of the cooled gas.

The absorption of gas is carried in suspension in the form of drops applied perpendicular to the gas flow.

The invention consists in increasing the efficiency of absorption of sulfur dioxide from pre-cooled and saturated with water vapor process gas.

It was established experimentally that the cooling is their gas before absorption in the evaporator mode until the dew point of water, supplied in quantities of 0,08-0,12 l/m3gas temperature (water), 10°exceeding the dew point temperature of the cooled gas, allows to achieve the efficiency of absorption of sulfur dioxide to 95%. On the inner surface of the absorber does not occur salt deposits, as at 100%relative humidity gas water does not evaporate from absorbing saline wet absorber. As a result of this not happening satiety absorbing solution of these areas and, as a result, no deposition of salts on the walls of the absorber.

It was also established that the most efficient process of absorption takes place when contacting the gas stream with drops of suspension and water supplied (flying) perpendicular to the gas flow, as the absence of the liquid column and a large horizontal velocity provides a low hydraulic resistance, high speed, gas, greater bandwidth suspensions and water and a small residence time of the droplets of the suspension and the water in the contact zone. Increasing the degree of gas purification from sulfur dioxide and increases operational reliability of the installation.

From the analysis of scientific-technical and patent literature inventive combination of features that ensure the achievement of the technical result of the detection is prohibited, that allows to conclude that under the given technical decision criteria of "novelty" and "inventive step".

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

The installation includes a multi-stage absorber 1, which consists of five steps 2, 3, 4, 5, 6, the mold 7, the output node cuttings 8, the reactor for the preparation of lime suspensions 9, crusher 10, the mill 11 and classifier dry limestone (lime) 12.

The invention is carried out as follows.

Example 1. Gas sinter production in the amount of 290 thousand nm3/h with a temperature of 125°containing (g/nm3): sulfur dioxide -3,54, carbon dioxide - 46,0, oxygen - 184, served after dedusting in the bottom of the multi-stage (in this case, 5-speed column absorber 1. In the upper part of the absorber serves pre-made from limestone or lime lime slurry. Supplied process gas to the first 2 and second 3-stage absorber 1 is in contact with water droplets formed by the dispersion of the water supplied perpendicular to the flow of gas. After passing through these stages, the gas is cooled to the dew point - 56°C. the gas is Then fed to the following three-stage absorber 4, 5, 6, which are perpendicular to the gas flow is known the new slurry from crystallizer (circulation collection) 7. Lime slurry previously prepared from lime or limestone by grinding in a crusher 10, where served in a ball mill 11 and the classifier 12. After classifying coarse particles are returned to the ball mill 11, and the fine particles of limestone or lime served in the reactor 9, which together add water, mix and get a lime slurry, which is then supplied to the crystallizer 7.

The gas is in contact with drops of lime slurry applied perpendicular to its flow. The absorbed sulfur dioxide reacts with the lime slurry (Ca(OH)2and as sulfite or calcium sulfate together with waste lime suspension, all-speed flows down to the bottom of the absorber 1, is withdrawn from the bottom of the absorber 1 and enters the mold 7. From the last part of this absorbing solution is sent to the output node cuttings 8, where it is filtered or centrifuged. The filtered sludge is removed and the filtrate is returned to the reactor 9.

Purified from sulfur dioxide gas is withdrawn from the upper part of the absorber. Examples of cleanup other process emissions similar to that shown. The dew point of the flue gas, depending on the chemical composition can vary from 32 to 52°C, dew point sinter gases is 40-46°C, dew point those is technological gas from incinerators of waste 39-48°C.

Properties of this method of cleaning waste gases from sulfur dioxide in the table.

Table
No.

p/p
Carried the Manager of the installation of gas, tysm3/hThe specific cooling water flow rate, l/m3gasThe difference between the water temperature and the dew point of the cooled gas, °The degree of purification of gas, %The continuity of the installation, monthsThe ener-GOSAT rata %
12900,061076661
22900,0810941382
32900,10109514100
42900,12109514126
52900,14109514158
62900,1089211100
72900,10 129314100
8 proto-type290--806145

As can be seen from the table, the best performance is observed in examples 2-4 with the declared parameters of the water flow. In examples 1 and 5 with the beyond the values observed deterioration in example 1, the insufficient degree of gas purification from sulfur dioxide, and example 5 - high energy costs.

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

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

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

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 the absorption gas is cooled in the evaporative mode to dew point of water supplied in the number 0,08-0,12 l/m3gas and temperature above the dew point of the cooled ha is and on 10° C.

2. The method according to claim 1, characterized in that the absorption gas is carried in suspension in the form of drops applied perpendicular to the gas flow.



 

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