CS215900B1 - Apparatus for desulphurizing combustion products by wet limestone or lime method - Google Patents

Description

The present invention relates to an apparatus for desulphurization of flue gases by wet limestone or lime processes and solves the problem of the interaction of this technology with the preparation of boiling acid in the production of pulp by the calcium bisulfite technology.

There is known a process for preparing a solution for obtaining a boiling acid for the production of pulp by the calcium sulphite sulphate process (U.S. Pat. No. 215,899), which replaces natural limestone or precipitated calcium carbonate by sludge from flue gas desulphurisation by a wet limestone or lime process. Sulfur combustion or roasting of pyrite converts the unreacted calcium carbonate and calcium sulphite into the acidic calcium sulphite from which the cooking acid for pulp production is produced by the calcium sulphite sulphite process.

According to this solution, the calcium sulfite solution is produced in a plant which is part of a boiling acid production plant and requires a min. 50% of the sulfur dioxide required for the required reaction.

These disadvantages are overcome by the device according to the invention. In accordance with the invention, in order to prepare a calcium sulphite solution for obtaining boiling acid for pulp production, in the flue gas desulphurisation technology by limestone or lime method, at least one additional absorber is included between the wet flue gas cooler and the desulfurization plant absorber. from flue gas desulphurisation.

It is an advantage of the invention that there is no need to prepare especially the sulfur dioxide needed to convert calcium carbonate and calcium sulfite into acidic calcium sulfite.

A further advantage is that there is no need to build an acidic plant in new plants where flue gas desulphurisation is simultaneously carried out by wet limestone or lime in order to comply with the prescribed emission limits for sulfur dioxide, and where expansion of bunioin production by the calcium bisulfite method is not possible of the existing plant. From the point of view of desulfurization technology, the invention has the advantage that less lime or limestone is required than in the case of flue gas desulfurization without the use of sludge, due to the reaction of unreacted calcium carbonate and calcium sulfite with sulfur dioxide to form acidic calcium sulfite.

Example

The device according to the invention is shown in the drawing.

The flue gas desulfurization apparatus including the recovery of the boiling acid solution is shown in the drawing where the cooler X is coupled to the newly incorporated absorber 2, for preparing the calcium sulfite solution, which is further coupled to the desulfurizer absorber 2 and the circulation tank 4 waste sludge. The absorber 2 is also connected to the filtration device 2 and the sedimentation device 2.

The flue gases coming from the colleague cool down to a temperature of about 50 ° C in the flue gas cooler χ, which simultaneously serves for ash removal, respectively. separation of soot from flue gas. The ash-flue gas enters the absorber 2, where at the same time the waste sludge from the circulation tank 5 belonging to the absorber 2 is introduced, in which the process of absorbing sulfur dioxide in the limestone resp. lime suspension. The sludge from the circulation tank 6, which in addition to the unreacted calcium carbonate, also contains calcium sulfite, is converted to the acidic calcium sulfite according to the equations! CaCO4 + 2 SOg + HgO = Ca (HSC > ₃ ) ₂ + COg

CaSO ₃ + · SO ₂ + 1I ₂ O = C _and (HSO ₃ ) ₂

The calcium sulphite solution thus prepared is freed from the ballast calcium sulfate and the remainder of the fly ash not separated from the flue gas in the flue gas cooler, either by filtration in apparatus 6 or by sedimentation in apparatus 2, or a combination of both principles. The flue gas, partially devoid of sulfur dioxide, is fed to the absorber 2 where it is sprayed with an aqueous suspension of lime or limestone and then, if necessary, introduced into a chimney.

Claims (1)

Apparatus for desulphurization of the flue gas with a limestone or lime method while obtaining a solution of calcium sulphite for the preparation of boiling acid in the production of pulp by calcium sulphite technology, characterized in that at least one further absorber (2) is incorporated between the wet cooler (1). ) to spray cooled and ash-free flue gas with sludge from the flue gas desulphurisation.