FR2515978A1 - Flue gas wet scrubbing system - comprises scrubber and crystalliser for conversion of acidic pollutants to calcium salts - Google Patents

Abstract

Flue gas wet scrubbing system comprises a scrubber vessel through which a suspension of finely-divided CaCO3 in water is circulated in countercurrent flow against flue gases containing acidic components. A crystallisation vessel at the base of the scrubber collects crystals which are pumped to a suitable solids discharge location. Water from the scrubbing liquor lost by vaporisation is recovered in an external heat exchanger and returned to the crystalliser for recirculation. For the removal of acid gases from flue gases and their conversion to solid materials.

Description

 The object of the invention relates to a device for washing and neutralizing combustion gases.

 It is intended to ensure the protection of the exchangers in order to obtain a better analysis of the calories entrained at a temperature level close to the dew point, but is also usable for all washing of hot burnt gases.

 Experience has shown that dirt from heat recuperators using certain polluted heat sources quickly makes these devices unusable.

In addition, gas scrubbers currently on the market are very expensive and generally used to trap more dust than acids. They remove air pollution, but cause pollution of the water which flows abundantly into the sewers.

 The object of the invention eliminates these drawbacks and makes it possible to wash the gases before their admission into the exchanger by capturing the strong acids starting from an inexpensive reagent and ensuring separation and decantation of the soot and sulphates eliminated by the route. solid non-polluting for the environment.

 It is constituted by a judiciously distributed circulation of a colloidal suspension constituted mainly by calcium carbonate producing its effects in a crystallizer of preferentially cylindro-conical shape.

 In the accompanying drawing, given by way of nonlimiting example of one of the embodiments of the object of the invention, the device is shown as a whole seen in section and in elevation.

 The hot gas inlet 1 is located at the base of the washing column 2.

 The gases are evacuated via line 3, located at the top of this column which includes a flow regulator 6.

 The saturation in water vapor, the washing and the neutralization of the acids are obtained by the combination of sprays 5 and 5 'at different heights and in sparging 4 by means of a calcium carbonate slip micronized and constantly recycled by the pump 10 in the surface collector 9 of a reactor settling tank 8.

 In the central part of the decanter is arranged a collecting chamber 7 collecting the saturated salts in the process of precipitation. This chamber brings them into the regeneration zone of insoluble salt crystals, which can be extracted by the automaton 11.

 The constant decanter is supplied at a constant level by condensates 13 which extract calcium carbonate placed in colloidal suspension when passing through the dissolver 12.

 The gas which saturates with water vapor goes by yielding its calories in the recuperator 14 of condensing heat, it will produce purified condensed water, of which it will be possible on the one hand to use the calories in exchangers, and on the other hand be collected in a tank 15 supplying via line 16 the loop of the self-supplied saturator washer.

 This device can also be used for all washing of hot acid gases, of all exhaust fumes from boilers or heat production devices using solid or liquid fuels highly charged with sulfur, fluorides, etc.

 It is thus possible to treat all hot, recoverable gaseous emissions which are currently harmful to the environment.

 These devices are available in all suitable metals and materials.

 However, the shapes, dimensions and arrangements of the various elements may vary within the limit of equivalents, without thereby changing the general design of the invention which has just been described.

Claims (4)

 10 Device intended more particularly for washing and neutralizing the combustion gases supplying the exchangers, but also usable for all washing of hot gases with the use of agents of low cost, characterized by a judiciously distributed circulation of a colloidal suspension based on calcium carbonate producing its effects in a crystallizer (8) of preferably cylindro-conical shape.  20 Device according to claim 1 characterized by a supply of hot gases (1) located at the base of a washing column (2) with outlet (3) connected to the exchanger (14).  30 Device according to claim 1, characterized in that the washing column (2> comprises sprayers (5, 5 ') at different heights and bubbling (4) of a calcium carbonate slip pumped by your pump (10) connected to a reactor settling tank (8) provided axially  from a collecting chamber (7) and at its lower part of a  extraction machine (11).  4 Device according to claim 1 are characterized in that the water supply to the reactor settling tank 8? is carried out by the line (16) connected to the tank t15) of the recuperator via a dissolver (12)