CS257594B1 - A method of refining a redox wash solution - Google Patents

Abstract

The solution concerns the removal of sulphide from gases obtained from the combustion of fossil fuels by oxidation with oxygen from the oxidizing gas. Its essence lies in the fact that 1.10"7 to 4 g/l of surfactant is added to the washing solution and the regeneration is carried out at a temperature of 5 to 85 °C.

Description

The invention relates to a process for the regeneration of an oxidation-reducing scrubbing solution for the removal of sulfane from gases obtained by burning fossil fuels by oxidation with oxygen contained in the oxidizing gas.

The suitability of metal chelates for the removal of sulfane from heating, waste, coke oven and other gases results from their physicochemical properties, as they are highly soluble in aqueous scrubbing solution and convert easily the sulfane gas into solid elemental sulfur which falls out of the oxidation reduction return cycle. solution in a very filterable form.

In the desulphurization of gases with chelated iron complexes, in the first phase the absorption of H.sub.3 in the alkaline solution takes place to form HS, in the second stage the reaction is carried out with Fe bound in the form of a complex with tetrasodium ethylenediaminotetraacetic acid e.g.

(Fe ³⁺ EDTA ⁴ ~) + HS ^- + H 2 O = 2 (Fe ² + EDTA ⁴ ) ^{2 -} + S + H 30 ⁺

The reaction takes place almost immediately upon contact of the sulfane-containing gas with the scrubbing solution. To completely convert the reduced form of the scrubbing solution (Fe? + EDTA?) 2 back to the active oxidized form (Fe EDTA), air oxygen oxidation is used according to the equation.

(Fe ²⁺ EDTA ⁴ ) ² + 4 H ₃₀ ⁺ + 02 = 4 (Fe ³⁺ EDTA ⁴ ~) + 6 H ₂ 0

In order to guarantee the proper functioning of the scrubbing solution, its pH must be maintained in the range of approximately 7 to 9 by the addition of buffering compounds.

A disadvantage of this process is that the oxidation of the reduced form to the active oxidized form is slow. For re-oxidation, it is therefore necessary to inject a large amount of oxygen-containing gas into the scrubbing solution, which entails a large consumption of electricity for gas compression. To ensure proper operation of the desulfurization plant, it is necessary to work with large volumes of scrubbing liquid, which also requires large volumes of the oxidation tank.

According to the invention, these processes are overcome by a process for the regeneration of an oxidation-reducing scrubbing solution to remove sulfane from gases obtained by burning fossil fuels with oxygen in an oxidizing gas. It is based on the addition of 1.10-4 g / l of surfactant to the wash solution and regeneration at a temperature of from 5 to 85 ° C.

The process according to the invention has the advantage of substantially accelerating the oxidation which occurs when the scrubbing liquid contacts the oxygen-containing gas. By using a surfactant it is also possible to advantageously influence the form of solid sulfur which is deposited in the presence of the latter in solution in a coarser-grained form and is thus more easily transportable from the scrubber. Washes better and thus reduces the loss of chemicals. Surfactants which may be used are surfactants of various types and / or mixtures thereof, for example oxoethylenated alkylamine or polyarylamine having from 5 to 25 moles of bound ethylene oxide, the alkyl having from 8 to 20 carbon atoms and aryl being phenyl or oxoethylated higher fatty acid alkanolamides with 5 to 25 moles. 25 moles of bound ethylene oxide containing 11 to 17 carbon atoms in the fatty acid alkyl chain and 2 to 3 carbon atoms in the alkyl linked to the amide group. As oxoethylated alkanonamide, oxoethylated stearic acid diaethanolamide with 6 moles of bound ethylene oxide is added. The acceleration of the oxidation will also make it possible to reduce the consumption of the oxidizing gas and the electrical energy associated with its compression and injection into the scrubbing liquid. A further advantage is that it is not necessary to have such large tanks for their oxidation.

Another suitable surfactant is a copolymer of ethylene oxide and propylene oxide containing a polypropylene glycol moiety having a molecular weight of 1,500 to 2,500, preferably 1,800 and 7 to 15% by weight of bound ethylene oxide, preferably 10% by weight.

The process of the invention is further described in the following examples.

Example 1

Gas containing 3% by volume of sulfane was desulfurized with a solution of 0.12 mol.l ^-3 EDTA, 0.09 mol.l ¹ Fe and 65 gL ³ NaHCO ³ . 12 liters of sulfane-containing gas were bubbled through one liter of solution at 22 ° C regularly. 100 l of air was always required to fully recover the scrubbing solution.

Example 2

To the scrubbing solution shown in Example 1 was added C 10 -C 20 alkylaminopolyethylene glycol ether and 7 moles of bound ethylene oxide in an amount of 0.35 g ^-1 solution. 12 liters of gas containing 3 3 vol. 23 liters of air were always required to fully recover the scrubbing solution.

Example 3

The scrubbing and oxidation processes described in Example 2 were carried out at 60 ° C. 18 liters of air were always required to fully recover the scrubbing solution.

Example 4

To vypiracimu solution mentioned in Example 1 was added to a copolymer of ethylene and propylene containing polypropylene glycol moiety having a molecular weight of 1800 and 10% by weight of combined ethylene at 0.3 gl ³ wash solution. 12 liters of gas containing 3% by volume of sulfane was regularly bubbled through one liter of solution. 22 liters of air were always required to fully recover the scrubbing solution.

Claims (1)

SUBJECT OF THE INVENTION Method for regenerating an oxidation-reducing scrubbing solution for removing sulfane from gases obtained by burning fossil fuels by oxidation with oxygen from an oxidizing gas, characterized in that 1.10-4 g / l of surfactant is added to the scrubbing solution and regeneration is carried out at a temperature of 5 to 85 ° C.