DE3610408A1 - Two-stage semi-dry desulphurisation process - Google Patents

Abstract

It is known to bind flue gas by dry hydrated lime in the region of a spray absorber or a contact section. Separating off, e.g., 95% of SO2 means adding moisture in spray absorbers which cools the gas virtually to dew point and, as a consequence, reheating is necessary for delivery of the gas to the stack downstream of the filter. In order to avoid this disadvantage, according to the invention it is proposed that, for gas separation with low temperature decrease, the hydrated lime effects dry at (3) a separation efficiency of about 70% and more, based on the untreated gas loading, and the used lime is transferred at (5) only slightly moistened and at (6) to the spray absorber (2), in order to be separated off from the process at (7) as used lime. <IMAGE>

Description

It is known to dry flue gas through hydrated lime Area of a spray absorber or a contact path to tie.

The separation of e.g. B. by 95% SO ₂ means in spray absorbers the giving up of a moisture which cools the gas almost to the dew point, and as a result a restoration for the delivery of the gas after the filter into the chimney is necessary.

The separation with pure dry lime in contact stretch in front of filter separators or in filter sections separating is with separation rates of 95% and more cannot be reached without adding moisture, and with ent speaking, the addition of moisture becomes the gas  cooled down so that a necessary reheating must be carried out.

In order not to carry out the reheating and despite to achieve the greatest possible separation proposed according to the invention, a two-stage Ab to provide a separation before a fabric filter, where dry technology in the first stage and in the second stage Stage the rest is separated by wet technology, whereby the gas is only cooled down as far as it is for the separation is required, and therefore flue gases with temperatures of e.g. B. 140 ° C after the boiler only must be cooled to about 90 ° C and not how with a wet spray absorption, e.g. B. to 70 ° C, to achieve a 95% separation.

According to the invention, this separation system is achieved despite high temperature maintenance by hydrated lime at ( 3 ), and here with z. B. 60-70% deposition in the contact section ( 3 ) and in the filter ( 4 ) is achieved without adding moisture and without lowering the temperature, since these surfaces of the contact section and the filter are insulated, so that only a deposition of less than 30% must be added in the spray absorber at low humidity.

Here is a temperature z. B. to 90 ° C. hold that is sufficient to correspond to the spread the cleaned exhaust gases without reheating to hand over to the fireplace.

Of course, the invention is not limited to the forms described in detail above, but there are numerous modifications possible, but without deviating from the basic idea of achieving a two-stage deposition of SO ₂ at a low temperature reduction in that the fresh lime at ( 3 ) with The highest contact separation performance is introduced into the contact section ( 3 ) in terms of dry technology, and after contacting below the filter at ( 5 ) the used lime is moistened and at ( 6 ) the spray absorption is supplied.

The drawing shows

with ( 1 ) the raw gas;
with ( 2 ) the spray absorber;
with ( 3 ) the fresh lime supply;
with ( 4 ) a fabric filter;
with ( 5 ) the lime moistening station;
with ( 6 ) the supply of the lime into the spray absorption;
with ( 7 ) the separation of the used lime.

Claims (1)

Process for the separation of acidic pollutants, such as SO ₂ , HCl, HF, etc. from raw gases with a high separation capacity, characterized in that, for gas separation with a low temperature reduction, the lime hydrate dry at ( 3 ) a separation capacity of about 70% and more, based on the raw gas pollution, and the used lime at ( 5 ) is only slightly moistened and at ( 6 ) it is transferred to the spray absorber ( 2 ) in order to be separated from the process as used lime at ( 7 ).