CS269260B1 - Method of hydrogen fluoride and hydrogen chloride removal from sour gas - Google Patents

Abstract

It is a method of removing hydrogen fluoride and hydrogen chloride from gas rich in sulfur dioxide during desulphurization of flue gases, cyclic magnesia - method. The essence, the solution is, that hydrogen fluoride and hydrogen chloride are removed by partial condensation of water vapor, contained in sulfur gas by cooling and / or or compressing pure gas under dew, point. Can be used to remove flu- / hydrogen chloride and hydrogen chloride from gases little water soluble.

Description

EN 269 260 B1

T

The invention relates to a process for the removal of hydrogen fluoride and hydrogen chloride from a gas rich in sulfur dioxide in flue gas desulfurization by a cyclic magnesia method and the coupling of the process.

The flue gas desulfurization with magnesium oxide-rich feedstock is effected by contacting the flue gases with the aqueous suspension of the magnesium feedstock. In doing so, the substantial part of the sulfur dioxide is removed by the following reaction mechanism: M SO, + SO, + H, Og 0 2 2 Mg (HSO 3) 2 (1) Mg (HSO 3) 2 + MgO 2 MgSO 3 ♦ H 2 O (2) MgSO 3 + xH2O and MgSO4 + xHgO (3) 1 (x may be 3 or 6)

The resulting tri- or hexahydrate suspension is concentrated, and the aqueous phase is returned to the absorber system and the concentrated suspension is freed from free and crystalline condensation by reaction.

MgSO 4. xH 2 O MgSO 3 + X H 2 O (4) and then subjected to thermal decomposition (calcination at 800-1000 ° C.

MgSO MgO + S02 (5)

The decomposed magnesium oxide is reused as the active ingredient in the slurry wash and the sulfur dioxide rich gas is used in the sulfuric acid production process by the contact method.

Together with the sulfur dioxide removed, the entire range of other flue gas substances is trapped in the absorbent suspension. These include fly ash, fluorine-hydrogen gas and hydrogen chloride. These impurities are then thundering in the closed process and their increased concentrations cause operational difficulties. In case of increasing the concentration of ash in the absorption slurry, the desulfurization efficiency is reduced and the possibility of the equipment being deposited due to cementation reactions is increased.

The increased content of fluoride and chloride ions in the wash circuit results in an increase in the concentration of hydrogen fluoride gas and hydrogen chloride in the sulfur gas and in the production of sulfuric acid since, in addition to the basic decomposition reaction (5), a partial decomposition of the resulting fluoride and magnesium chloride also takes place. This increases the corrosion attack of the lining of the decomposer and the sulfuric acid production device.

These issues of cyclic desulphurisation technology using magnesium raw material are still being solved in two ways.

The first option is to include a technological node called the prewash, in which the flue gases are sprayed with process water, removing a substantial portion of the ash and water-soluble impurities such as hydrogen fluoride and hydrogen chloride. These admixtures trapped in the process water are discharged for disposal. Only then is the absorption with a suspension of magnesium raw material carried out by desulfurization according to the reaction, (2), (3), thickening and dewatering of the absorption suspension and its calcination. 2 EN 269 260 B1

A disadvantage of the method is; that, although a substantial part of the impurities is removed, they are succinctly collected in the absorption circuit, which is carried out by the scrubbing of sulfur dioxide and which is largely closed. Furthermore, the process results in a significant cooling of the flue gas prior to entering the absorbent portion, thereby increasing the energy requirements for re-heating to achieve sufficient climbing and preventing corrosion in the flue gas ducts.

The second variant envisages the removal in the water of insoluble directs by the inclusion of the technological node of the uninvolved acid refining. This knot consists of a shower tray with accessories and a filter. A 10% thickened slurry is vented from the stream entering the slurry into the tower; the slurry ranks and the countercurrent is sprayed with sulfur dioxide gas from the magnesium sulphite calcining node. This results in the reaction of sulfur dioxide with magnesium sulphite according to (1), the resulting magnesium bisulphite goes into solution and the solid ash-forming phase can be filtered on the filter and discharged to the landfill. as well as the impurities achieved in the refilled salt su-plane. The filtrate returns to the absorption cycle where magnesium bisulfite neutralizes according to equation (2).

Thus, this variant does not address the removal of impurities from water-soluble flue gases, in particular hydrogen fluoride and hydrogen chloride. As a result, this deficiency causes the accumulation of these substances and their salts in the circuit, a change in the composition of the absorption suspension of the corrosive attack of the apparatuses of the decomposition furnace and the acid refining node, eventually. the loss of hydrogen hydrogen to the sulfuric acid contact node, the loss of vanadium catalyst, the volatile compounds and the quality of the sulfuric acid produced.

Both of the above mentioned contaminant removal methods from the flue gas desulfurization system by cyclic method could be combined in a single desulfurization line, which would contain both a prewash node and a sulfur refining node. However, the shift thus obtained would be very complicated.

The drawbacks of the present invention are the fact that fluorine-hydrogen and hydrogen chloride are removed by partial condensation of the water vapor contained in the sulfur gas by cooling and / or compressing the purified gas below the dew point. This will remove a significant portion of the water-soluble components. If the gas vapor purge vapor content is too low, it may increase before cleaning, eg by adding saturated steam. The advantage of this method of separating water-soluble impurities is that a relatively small volume of concentrated waste is obtained which is well disposed of. In a small amount of hot condensate, the bulk of the hydrogen fluoride and hydrogen chloride resulting from the decomposition of magnesium salts remain, while sulfur dioxide dissolves only slightly. Another advantage is the possibility of using otherwise waste heat contained in the sulfur gas stream to various technological heating systems.

A particular embodiment of the invention is shown in the drawing in the circuit diagram.

The wiring consists of an absorber 6 with an inlet flue gas duct 2 and a desulfurized flue gas outlet flue. The absorber is connected to the circulation tank J, into which the magnesium feed dispenser of the calcined feedstock 2, connected to the intermediate reservoir 6, and the water supply pipe 2 of the process water. Circulation. the reservoir is connected to a sedimentation tank 8 connected to a rotary kiln 2 connected to the heating gas conduit 10. The rotary specimen 2 is connected to a condenser 11 connected to a separator 12 and a condensed condensate outlet conduit 13 and to a sulfur dioxide rich conduit 14.

The function of the invention is that the flue gases are introduced through the inlet duct 2 to the absorber 1, in which sulfur dioxide, but also hydrogen fluoride and hydrogen chloride is trapped by scrubbing the wash suspension. Desulphurized flue gases escape through the outlet flue 4 into the atmosphere. A portion of the wash suspension in which the pollutants are trapped proceeds from the circulation tank J to the settling tank 8 where it is thickened. The overflow with the settling tank goes back to the circulation tank, while the thickened suspension proceeds to the calcining rotary kiln 2.

Claims (3)

C ^ 269 2 60 B1 3 * Magnesium, Intermediate * 6 and Line 2 Process Water to Refill Leaks. In the rotary kiln 2 heated by the fuel gas supplied via line 10, the suspens crystals decompose to form a gaseous phase and a solid phase. Solid Phase, Recycled Magnesium Oxide Returns to Intermediate 6, from where Feeder 2 Feeds to Recirculation Tank 2 · The gaseous phase enters the cooler 11. it is cooled below the dew point. The resulting caps are separated in the separator 12 and the trapped condensate is discharged via line 13 for disposal. The high sulfur dioxide gas is discharged via line 14 to further processing. Example Flue gases from the combustion of brown coal in an amount of 1200 m ^ · h -1, comprising: 7,200 mgm-3 of sulfur dioxide, 30 mg of hydrogen fluoride and 60 mg of hydrogen chloride, were continuously introduced into a filler-free absorber in which the absorption susceptibility was desulphurized. The exhausted flue gas was discharged into the atmosphere. The absorber was sprayed with the suspension administered from the circulation container at a volume of 4 to 1. The circulation suspension at a density of 1250 kg nT contained 10% solids and 90% liquid phase. The water waste was fed into the circulation tank at a rate of 0.1 ml / l. This water was used to flush the additional calcined feedstock in an amount of 7.5 kg of h-1 from the calcining furnace from the feeder to the circulation tank. The crude contained 80% by weight magnesium oxide. A portion of the absorbent slurry at 0.20 h -1 was discharged from the circulation pump outlet to the thickened node of the slurry from which the clear liquid was recycled to the circulation tank and a 1,500 kg m 2 thick slurry was charged. kg m < 3 > was discharged to a rotary kiln heated by the gas to 800 [deg.] C. The calcinate formed was discharged and transported to the intermediate container and from there the dosing container was dispensed. -3-3 Gases and calcination with a content of 270 g of sulfur dioxide, 1100 mg of hydrogen fluoride and 2000 mg of m 3 of hydrogen chloride were charged to the cooler and cooled to 45 ° C. In the separator disposed downstream of the condenser, 0.0015 h of condensate containing 1.8 wt. % F, 3.5 wt% Cl, 5 wt% C; Mg 2+, 2.5 wt. SO2 and 0.3 15 wt. SO2-. This condensation was intended to be disposed of while the sulfur dioxide-rich gas was used as its source. The invention can be used to remove hydrogen fluoride and hydrogen chloride from low-water gases, preferably in a flue gas desulfurization process using a cyclic method using a magnesium feedstock. OBJECT OF THE INVENTION A method for removing hydrogen fluoride and hydrogen chloride from sulfur gas by desulfurizing the flue gas by a magnesite method, characterized in that hydrogen fluoride and hydrogen chloride eliminate partial condensation of water vapor contained in the sulfur gas by cooling and / or pushing the purified gas below the dew point. 1 drawing