Drying and gas or vapor contact with solids – Process – With treated material recirculation
Patent
1999-09-08
2000-10-31
Gravini, Stephen
Drying and gas or vapor contact with solids
Process
With treated material recirculation
34131, 422168, 422172, 423242, 42324303, F26B 700
Patent
active
061383783
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention concerns a wet gas processing method and apparatus to remove from exhaust gas certain targeted components such as those which are harmful. More specifically, it concerns a apparatus which brings about effective liquid-vapor contact between the absorption liquid and the exhaust gas resulting from combusting coal or heavy oil.
TECHNICAL BACKGROUND
Heretofore, various types of liquid-gas contact apparatuses have been employed to remove sulfur dioxide from exhaust smoke using a wet-gas method. These would typically be used to remove harmful substances like sulfur dioxide from the exhaust smoke of a coal-burning boiler. One such apparatus, a previous design by the present petitioners which employs a liquid-column method, is described in Japanese Utility Patent Publication (Koukai) 59-53828.
This apparatus has a number of spray nozzles arranged in an absorption tower. An absorption liquid such as lime slurry is sprayed upward from these spray nozzles to form an absorption column. When exhaust smoke is forced into the center of this flow, the sulfur dioxide in the smoke is absorbed and particulate like fly ash are effectively removed.
A basic design for such a tower is shown in FIG. 24 (A). In the upper portion of absorption tower 2 is exhaust path 8; in its lower portion is smoke inlet 3, the entry port for exhaust gases 1. A number of rows of head pipes 190 are arranged in the lower portion of absorption tower 2. On the pipes 190 are numerous upward-facing spray nozzles, which may, for example, be arranged in a matrix, as shown in FIG. 24(B).
The bottom of absorption tower 2 is made into a funnel shape to form liquid recovery vessel 56. Here the lime slurry or other absorption liquid 5 is collected, after which it is routed to liquid storage tank 57 by pump 21a. This collected absorption liquid 5 is again circulated through spray pump 21b, volume control valve 60 and head pipes 190 back to spray nozzles 4.
The spray nozzle array consisting of all the upward-facing spray nozzles 4 arranged in the matrix forces absorption liquid 5 upward and causes it to assume the form of liquid column jets 5a. At the same time, exhaust gases 1 are brought in via the smoke inlet 3 and forced upward. The flow carries these gases along with the jets of absorption liquid 5 to the top of the tower, where they must pass through jets 5a, now distributed in an umbrella shape. In this way the liquid and vapor are brought into contact with each other.
Subsequently, mist eliminator 6, located in the top of absorption tower 2 around the highest point reached by the jets, separates the absorption liquid 5 which has accompanied exhaust gases 1 and recycles it into liquid storage tank 57. The liquid 5 which falls directly into recovery vessel 56 is transported by recirculation pump 21a into liquid storage tank 57.
With a liquid-vapor contact apparatus of this configuration, when pump 21b is operated, absorption liquid 5 travels through volume control valve 60 and head pipes 190 and is sprayed upward through spray nozzles 4. The exhaust gases 1 which are introduced through entry port 3 are forced to pass through jets 5a to effect liquid-vapor contact. The processed (scrubbed) exhaust gas 7, from which the sulfur dioxide and other noxious components have been removed, is expelled via exhaust path 8.
When this technique is used, by which absorption liquid 5 is sprayed upward, the vapor and liquid are in contact for the entire time that liquid 5 travels up and down the tower. In addition, when liquid 5 reaches the top and spreads into an umbrella shape for its descent, it assumes the form of droplets. This enhances the effect of liquid-vapor contact. When the exhaust gases contain only minimal sulfur dioxide, greater operating economy can be achieved by changing the height of the column of liquid. This method offers a number of benefits over what is known as the packing method, in which the liquid flows into a tower packed with a grid and is there brought into contact with the gases. One such benefit is that wit
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Inoue Kenji
Iwashita Koichiro
Kamiyama Naoyuki
Nagayasu Hiromitsu
Nakamura Satoshi
Gravini Stephen
Mitsubishi Heavy Industries Ltd.
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