CS234151B1 - A method for increasing the concentration of sulfur dioxide in gases and apparatus for carrying out the process - Google Patents

Abstract

The invention relates to a method for increasing the concentration of sulfur dioxide in gases from the thermal decomposition of magnesium sulfite. obtained during the desulfurization of flue gases of an aqueous suspension of magnesite in connection with the use of these gases for the production of sulfuric acid. The essence of the invention lies in the fact that a part of the gases from the thermal decomposition of magnesium sulfite after their cooling is freed from sulfur dioxide in an SOg absorber, after which these gases are mixed with undissolved flue gases after absorption before their desulfurization, while the desorption of SOg, captured in the SOg absorber, produces a gas rich in SOg, which is combined with the remaining part of the gases from the thermal decomposition of magnesium sulfite, for the purpose of processing for the production of sulfuric acid. The invention can be used in the desulfurization of flue gases and in sulfuric acid production plants.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for increasing the concentration of sulfur dioxide (SO2) in gases from the thermal decomposition of magnesium sulphite (MgSO4) obtained by flue gas desulfurization with an aqueous magnesite slurry in connection with the use of these gases for sulfuric acid production.

These gases are now utilized such that magnesium sulphite crystals of MgSO 4 .SHgO are roasted in a furnace at temperatures of about 900 ° C after removal of water using a direct flame generated by the combustion of gaseous or liquid fuels. The gases leaving the furnace contain approximately 8 to 9% by volume of SO2, but often also fall below 7% by volume, significantly reducing the performance of the sulfuric acid plant. This problem is solved so that the low content of SO ₂ in the gas is increased by the addition SOG formed either from evaporation of liquefied SOg | or by combustion of elementary sulfur. Both methods have the disadvantage that it is necessary to ensure the supply of these raw materials and to ensure the equipment required to obtain S0 _2, including the energy supply to either evaporation S0 _2, or the burning of sulfur.

These deficiencies are eliminated method for increasing the concentration of the invention, whose principle consists in that part of the gases from the thermal decomposition of magnesium sulfite after cooling, freed from sulfur dioxide absorber S0 _2, whereupon the gases after absorption, is mixed with neodsířenými flue gas before desulfurization, wherein desorption SOG trapped in the absorber ₂ S0 is obtained rich gas S0 _2, which is combined with the remaining part of the gas from the thermal decomposition sulfite hořečnatéhojza to process for the manufacture of sulfuric acid.

Disclosure of the device according to the invention consisting of SOg absorber flue gas furnaces for decomposition MgSOg and devices for the production of sulfuric acid according to the invention consists in that the furnace for decomposition MgSOg is connected to the absorber ₂ S0 on which

2234 151 continues desorber and the desorber is coupled to a device for manufacturing sulfuric acid, S0 ₂ absorber is connected with the conduit for feeding exhaust gas into the adsorber neodsířených S0 ₂ from flue gases.

This has the advantage that the dimensions of the absorbent device are significantly reduced. Any sorbent, whether solid or liquid in consistency, for example active coke, sodium sulfite solution or organic solvents, can be used for absorption. However, it is most advantageous to use a MgSO4 solution which is produced by the flue gas desulphurization process using the magnesite process. When absorbed in the absorber SOg arises magnesium bisulfite Mg (HS0 _{3) 2,} which is again in a desorber converted to MgSOg + SOg. It is advantageous to carry out the gas distribution downstream of the roasting furnace automatically according to the selected optimum SO ₂ concentration in the gases prior to the sulfuric acid production (eg 13%), so that as the SO ₂ content of the gas downstream of the roasting furnace decreases. An advantage of increasing the concentration of the present invention are lower capital and operating costs, and to ensure the optimum concentration of SO ₂ prior to the manufacture of sulfuric acid from the resources that are available in the actual flue gas desulfurization.

An example of a device for carrying out the method according to the invention is shown in the drawing, which is a production diagram. The device according to the invention in the drawing consists of a flue gas absorber 10, a crystallizer 2, a drying device 3, an MgSO 4 decomposition furnace 4 and a sulfuric acid production plant 7. Oven 4 for decomposing MgSOg is connected to the absorber 5 S0 ₂ to which is connected desorber 6 and the desorber 6 is connected to means 7 for the production of sulfuric acid, wherein the absorber 5 SOg is connected to the supply line neodsířených flue gas into the absorber 1, S0 ₂ from the flue gas. The absorber 10 is connected to the chimney 8.

The desulphurization plant operates by flue-gas desulphurization to the SO ₂ absorber from the flue gas, where it is freed from aqueous MgO suspensions of the vast majority of SOg to form MgSO ₃ .3H ₂ O, which is crystallized in crystallizer 2. Desulphurized flue gas is removed! to chimney eighth crystals in a drying device 3 and dewatered in a furnace 4 for decomposing MgSOg the combustion of liquid or gaseous fuels, obtaining a product gas containing up to 10% by volume S0 _2, which is according to the old technology leads directly to the device 7 for the production of acid sulfuric. According to the invention, a portion of the flue gas fed to the absorber 5, S0 ₂ wherein the solution is freed from the more frequent MgSOg 5,234,151 SOg then the exhaust gas from the absorber 5 SOg added to the desulfurized flue gas stream before the absorber χ S0 ₂ from flue gases. The Mg ₂ SO 4, formed in the absorber 5 SO _2, is fed to a desorber 6 where SOg is released at approximately 95% by volume, which is added to a stream of gases fed to the sulfuric acid production plant 7. The re-sorbed sorbent from desorber 6 is returned to the absorber 2 SOg.

Example 1

The flue gas containing 0.3% by volume of S0 ₂ enters the absorber X S0 ₂ from flue gases and after purification on a content of 0.03% by volume SOg are discharged into a chimney eighth gas exits from the furnace 4 for decomposing MgSO ^ containing 7% by volume of S0 _2, and part of them is withdrawn into the absorber 5 S0 _2, wherein the cooling is carried out first and then the absorption of S0 ₂ in solution MgSOg, whereupon gas from the absorber 2 SOgjS containing about 1 vol.% S0 _2J are returned into the stream of desulfurized flue gas. In the absorber 5 S0 ₂ the solution of Mg (HS0 _{2) 2} is subjected in desorber 2 desorption by heating and the resulting S0 ₂ Jo content of 95% objemovýchjse added before the device 7 for the production of sulfuric acid into the second portion of gases from the furnace 4 for decomposing MgSO ^ containing 7% vol SOG so that the sulfuric acid plant to enter a gas containing 13 volume% S0 ₂ ·

Example 2

The flue gas containing 0.3% by volume of S0 ₂ is desulfurized in a similar manner as in Example 1. The gas exits from the furnace 4 for decomposing MgSO ^ containing 7% by volume of S0 ₂ and a part of them, after previous cooling adiabatic evaporation of water at 120 ° C is drawn into the absorber 2 SO ₂ , sorption of SO ₂ ^is carried out by means of active carbon material, eg active coke. The saturated sorbent containing SO ₂ in the form of H ₂ SO ₄ is subjected to thermal decomposition at 650 ° C in desorber 6, and the resulting SO ₂ is added again before the sulfuric acid production plant 7 to the second part of the gases from £ furnace for decomposition MgSO ^, so that in the sulfuric acid plant receives the mixture containing 13% by volume of _{the second}

The invention can be used in flue gas desulfurization and in sulfuric acid plants.

Claims (2)

Process for increasing the concentration of sulfur dioxide in gases from the thermal decomposition of magnesium sulphite, MgSO 4, for the production of sulfuric acid, characterized in that part of these gases, after cooling, is freed from sulfur dioxide in the SO ₂ absorber. flue gas before desulfurization, wherein the desorption SOG trapped in the absorber ₂ S0 is obtained rich gas S0 ₂ who ry is combined with the remaining part of the gas from the thermal decomposition MgSO ^ jza to process for the manufacture of sulfuric acid. 2. Apparatus for performing the method according to claim 1, comprising the absorber of S0 ₂ from flue gas, furnace to decompose MgSOg and devices for the production of sulfuric acid, characterized in that the furnace (4) for decomposing MgSOg is connected to the absorber (5) to which SOg ₉ the desorber (6) is connected and the desorber (6) is connected to the sulfuric acid production device (7), the absorber (5) SOg is connected to the supply line neodsířených flue gas into the absorber (1) S0 ₂ from flue gases.