CS257595B1 - A method of regenerating an oxidation-reducing solution - Google Patents

Abstract

The solution concerns the removal of sulphonate from biogas by oxidation with oxygen contained in the oxidizing gas. Its essence lies in the fact that a surfactant is added to the washing solution in an amount of 1.10-7 to 4 g/1 of 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 removing sulfane from a biological gas by oxidation with oxygen contained in the oxidizing gas.

In the first phase, the absorption of H ₉ S in the alkaline solution takes place at 3+ ^from HS, and in the second phase the reaction is carried out between Pe bound in the form of a complex, for example with tetrasodium ethylenediaminotetraacetic acid (EDTA):

(Fe ³⁺ EDTA ⁴ ~) ~ + HS ^- + H 2 O = 2 (Fe ²⁺ EDTA ⁴ ~) ^2_ + S + H30 ⁺

This reaction takes place almost immediately upon contact of the sulfane-containing gas with the scrubbing solution.

To completely convert the reduced form of the wash solution

2+ 4- 2 (Fe EDTA) back to the active oxidized form 3+ 4- (Fe EDTA) is used by oxygen oxidation according to the equation:

(Fe ²⁺ EDTA ⁴ ) ² "+ 4 H 30 ⁺ + C> 2 = 4 (Fe ³⁺ EDTA ^4_ ) + 6 HjO

In order to guarantee the proper functioning of the scrubbing solution, it is necessary to maintain its pH in the range of approximately 7 to 9 by adding buffering compounds.

The disadvantage of this process is the very high consumption of the gas to be re-oxidized, that is to say, that during the oxidation there is a large consumption of electrical energy required to compress the oxygen-containing gases. Due to the slow oxidation to ensure the correct functioning of the scrubber, it is necessary to work with a large volume of washing liquid, which also requires very bulky tanks.

According to the invention, the above mentioned drawbacks are overcome by a method of regenerating an oxidation-reducing scrubbing solution for removing sulfane from the biological gas by oxidation with oxygen contained in the oxidizing gas. Its essence consists in adding to the scrubbing solution a surfactant in an amount of 1.10? up to 4 g / l of washing solution and regeneration are carried out at a temperature of from 5 to 85 ° C.

The advantage of the process according to the invention lies in the acceleration of the oxidation which occurs when the liquid is in contact with the gas. A further advantage is that it is possible to reduce the amount of recirculating solution in order to accelerate the oxidation. Thus, oxidation is less expensive and the same amount of gas can be desulfurized in a smaller plant. The use of a surfactant can also advantageously influence the form of solid excreted sulfur. In the presence of a surfactant, the precipitated solid sulfur is easier to transport and more easily washed. This also reduces losses of the scrubbing solution.

Surfactants which may be used are surfactants of various types and / or mixtures thereof, for example oxoethylated alkylamine or alkylarylamine having 5 to 25 moles of bound ethylene oxide, the alkyl having 8 to 20 carbon atoms and aryl being phenyl or oxyethylated higher fatty acid alkanolamides having 5 to 25 moles. 25 moles of bound ethylene oxide containing from 11 to 17 carbon atoms in the fatty acid alkyl chain and from 2 to 3 carbon atoms in the alkyl linked to the amide group. As oxoethylated stearic acid diethanolamide with 6 moles of bound ethylene oxide.

Another type of 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 according to the invention is described in more detail in the following examples.

Example 1

Gas containing 2.5% by volume of sulfane was desulfurized with a 0.13 mol solution.

-1 -1 -1 .1 EDTA, 0.09 mol.l Fe and 60 gl NaHCO _third After passing 12 liters of gas through 1 liter of 20 ° C scrubbing solution, 100 liters of air were required to fully recover it.

Example 2

To the scrubbing solution shown in Example 1 was added a C 10 to C 20 alkylaminopolyethylene glycol ether and 7 moles of bound ethylene oxide in an amount of 0.4 g / L bath. The amount of air required to regenerate the same amount of solution after washing the same amount of sulfane was reduced 5-fold.

Example 3

To the scrubbing solution of Example 1 was added a C 1 -C 20 alkylaminopolyethylene glycol ether and 7 moles of bound ethylene oxide in an amount of 1 g of bath. Washing and regeneration were performed at 70 ° C. 18 liters of air were required to fully recover 1 liter of solution after washing 12 liters of gas containing 2.5% by volume of sulfane.

Example 4

Ethylene oxide / propylene oxide copolymer containing a 1,800 molecular weight propylene glycol moiety with 10% by weight was added to the scrubbing solution of Example 1 in an amount of 0.32 g / l. bound ethylene oxide. 20 liters of air were required to fully recover the 12 liter gas scrubbing solution containing 2.5% by volume of sulfane.

Claims (1)

SUBJECT OF THE INVENTION Method for regenerating an oxidation-reducing scrubbing solution for removing sulfane from a biogas by oxidation with oxygen contained in the oxidizing gas, characterized in that the scrubbing solution is added with a surfactant in an amount of 1.10 ⁷ to 4 g / l of scrubbing solution and regenerated at a temperature of 5 ° C to 85 ° C.