RU2256603C1 - Method for treatment of smoke gas from sulfur dioxide - Google Patents

Abstract

FIELD: heat technology.

SUBSTANCE: invention relates to technology for treatment of smoke gases from sulfur dioxide. Method for treatment of smoke gases from sulfur dioxide involves passing smoke gases through countercurrent scrubber with absorption liquid based on ammonia aqueous solution for preparing ammonium sulfite followed by oxidation of ammonium sulfite to ammonium sulfate. Then one part of absorption solution removing after oxidation is mixed with fresh ammonium aqueous solution and fed to treatment of smoke gases and another part is fed to utilization. Oxidation is carried out with smoke gases oxygen in indicated scrubber in addition initiating agent for oxidation to absorption liquid as azocompounds. Invention provides simplifying the process and to reduce time for accumulation of ammonium sulfite by 1.8-2.0-fold.

EFFECT: improved method for treatment.

Description

The invention relates to heat engineering, and in particular to a technology for the purification of flue gases from sulfur dioxide.

A known method (German application No. 19731062, B 01 D 53/77, 1999 - prototype) remove sulfur dioxide from flue gases, based on the use of aqueous ammonia solution (absorption solution). Flue gases containing sulfur dioxide are passed through a countercurrent scrubber with aqueous ammonia to produce ammonium sulfite. Ammonium sulfite is oxidized to ammonium sulfate in an apparatus for oxidation, supplying compressed air to it. Part of the absorption solution leaving after oxidation is mixed with a fresh aqueous ammonia solution and sent to the flue gas treatment, and another part of the absorption solution leaving after oxidation is disposed of. This mode provides optimal pH values of 5-6.5, which increases the degree of purification of sulfur dioxide. The disadvantage of this method is the need to use an apparatus for oxidation, as well as additional equipment (pumps, pipelines) for supplying compressed air to this apparatus.

The achieved result of the invention is to simplify the method.

This is ensured by the fact that in the method of purifying flue gases from sulfur dioxide, namely, flue gases are passed through a countercurrent scrubber with an absorption liquid based on an aqueous solution of ammonia to produce ammonium sulfite, the ammonium sulfite is oxidized to ammonium sulfate, then one part of the effluent after the oxidation of the absorption solution is mixed with a fresh aqueous solution of ammonia and sent to the flue gas treatment, and the other part is disposed of, the oxidation according to the invention is carried out with flue oxygen s gases in said scrubber with the addition of the initiator into the absorption liquid oxidation in the form of azo compounds.

Azo compounds are compounds containing one or more azo groups, which consist of two nitrogen atoms linked together by a double bond (-N = N-). The azo group can be between different, mainly aromatic groups. The compounds proposed in this technical solution may contain, along with the azo group, aryl (Ar), alkyl (Alk) and phenyl (R) groups. Such compounds decompose into radicals, and therefore they are the initiators of radical oxidation reactions. With the decay of azo compounds, the formation of radicals occurs according to the scheme:

Ar-N = N-R → Ar * + N + R *

Where N is nitrogen

Ar is an aryl group,

R is a phenyl group,

Ar *, R * - radicals

The resulting radicals, in turn, initiate the formation of radical ions SO ₃ *, SO ₄ *, SO ₅ *, leading the oxidation chain of ammonium sulfite. The presence of initiating additives allows purification of flue gases from sulfur dioxide without the use of an apparatus for oxidation, the supply of compressed air into it and the necessary additional equipment for this.

The method according to the invention can be illustrated by the following example.

Flue gases from a pulverized coal boiler with a temperature not exceeding 120 ° C in an amount of 1000 nm ³ / h, with a sulfur concentration of 0.15 vol.% Are fed for cleaning to the lower part of the scrubber. The scrubber operates in countercurrent mode of gas and liquid interaction. Scrubber irrigation is carried out in a closed cycle with a solution containing an azo compound in an amount of 0.0015 wt.% Of the sulfite ion content in the solution. When ammonium sulfate is accumulated in a solution of 300-350 g / l, part of it is taken away and sent for disposal. When flue gas is cleaned with solutions without the addition of an oxidation initiator, the accumulation of ammonium sulfate to a concentration of 300 g / l occurs within 25-30 hours. When an azo compound is introduced into the solution, the accumulation time of ammonium sulfate, respectively, decreases by 1.8–2.0 times. In this mode, the use of an apparatus for oxidation, as well as additional equipment (pumps, pipelines) for supplying compressed air to this apparatus is not required. And the optimal pH of the solution is observed to obtain a high degree of purification from sulfur dioxide flue gases.

Claims (1)

The method of purification of flue gases from sulfur dioxide, which consists in the fact that the flue gases are passed through a countercurrent scrubber with an absorption liquid based on an aqueous solution of ammonia to produce ammonium sulfite, oxidation of ammonium sulfite to ammonium sulfate is carried out, then one part of the exhaust solution after oxidation is mixed with fresh aqueous ammonia solution and sent to the flue gas treatment, and the other to the disposal, characterized in that the oxidation is carried out with flue gas oxygen in the specified scrubber p When an oxidation initiator is added to the absorption liquid as azo compounds.