FI91129C - Device for desulfurization by wet method and circulation tank - Google Patents

Description

i 91129

Wet desulphurisation device and recycling tank

Divided by application 850 681 5

The invention relates to the desulfurization of markka-type flue gas. More specifically, the invention relates to a recirculation tank device for desulfurizing an exhaust gas from a brand process, into which the device enters an absorption slurry into which the sulfur oxide compound of the exhaust gas is absorbed to form calcium sulfite. The invention relates to a myds device for the desulfurization of an exhaust gas for a process, which device comprises arc cooling means, pdlyn removal means, means for absorbing and removing the sulfur oxide compound and defroster means. Hereinafter, sulfur oxides are commonly labeled S0X.

The wet type flue gas desulphurisation device now in use is essentially a device using a calcium absorber, and gypsum is obtained as a by-product. It is a device that operates according to the limestone-gypsum process (or the lime-gypsum process) and uses limestone, quicklime or slaked lime as an absorbent. Figure 8 shows a conventional device for flue gas desulphurisation, in which limestone is used as an absorbent, and gypsum is obtained as a by-product. The exhaust gas 1 from the boiler or the like is led to the dust removal tower 2, where it is cooled, the oil is removed and the sulfur is partially removed. The resulting gas is then passed to an absorption tower 3, where it is brought into contact with the circulating slurry 30, the frost is removed in a defroster 4 and discharged from the absorption tower. On the other hand, the limestone slurry 20 is fed as an absorption slurry by means of a limestone slurry pump 21 to a recirculation tank 5 and an absorption tower, from which it is then pumped by a recirculation pump 7 to removes the SOx in the exhaust gas and then returns it to the recycle tank and reuses with recycle 5. The sludge from the absorption fraction is introduced into the recirculation tank 6 of the effluent tower 2 by means of the absorption tower drain pump 8 and is further contacted with the effluent gas in the effluent tower, whereby SOX in the effluent gas is removed and the amount of unreacted limestone in the sludge is reduced. The resulting slurry is charged to a by-product recovery system, i. to the sybt-tb tank 10 of the oxidation tower 12, where the unreacted limestone is converted to calcium sulfite with additional sulfuric acid and the pH of the slurry is adjusted to be suitable for oxidation. The slurry having a pH of Saadet-15 ty is deposited in the tower of the oxidation tower 12 by a sybttb pump 11, where the calcium sulfite is oxidized with air to gypsum and then passed through a channel 13 to a thickener 14 where it is concentrated. The resulting gypsum slurry is dewatered with a centrifugal separator 17 to obtain a gypsum-20 powder 18. The filtered water from the thickener 14 and the centrifugal separator 17 is recycled and reused.

However, according to a prior art device, the absorption tower and the dust removal tower are separate and require an unreacted limestone neutralization device, which unreacted limestone is in the sludge leaving the absorption system (tank, pump, etc. for sulfuric acid) and a calcium sulfite oxidizer; Thus, such disadvantages have arisen that the surface area of the system increases and the equipment becomes complex. There is still a need for equipment for unreacted limestone (excess limestone) and added sulfuric acid.

For overriding reasons, there has been a need for a compact desulfurization device that does not require equipment for these chemicals, which simplifies equipment 35 and requires a small surface area.

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The device according to the invention and the recirculation tank for flue gas desulphurisation of the mSrkfi type eliminate the above-mentioned disadvantages of the prior art, so that there are no special means for the absorption tower and the neutralization and oxidation means can be omitted.

The recirculation tank according to the invention is characterized in that the recirculation tank comprises at least one lower mixing means for mixing the absorbent slurry, at least one upper mixing means located above the lower mixing means for mixing the absorbent slurry or mixing the absorber sludge. the device. Preferred embodiments of a recirculation tank according to the invention are set out in claims 2 to 5. The device according to the invention is characterized in that all said silencers are located inside a single absorption tower and that the device is provided with a recirculation tank comprising at least one lower mixing tank. 20 for mixing the absorbent slurry, at least one upper mixing means for mixing the absorbent slurry located above the lower mixing means, means for supplying air to the absorbent slurry and means for removing or circulating the treated absorbent slurry to said device.

Figure 1 shows an apparatus for desulfurizing a flue-type flue gas as an embodiment of the present invention.

Figures 2-5 each show drawings illustrating an apparatus for desulfurizing wet type flue gas 30 in other embodiments of the present invention;

Fig. 6 is a side view showing an implementation of arranging the mixer inside the sludge circulating tank of the exhaust pipe and the location of the air intake pipe.

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Figure 7 shows a cross-section of the plane of the above arrangement.

Fig. 8 is a drawing illustrating a flow chart of a conventional apparatus for removing sulfur-5 of a flue gas type.

The present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows, as described above, a view of an apparatus for desulfurizing a wet type of flue gas as an embodiment of the present invention. In this figure, the device comprises a vertical cylindrical tower body 50; a deaeration portion 34 and an absorption portion 35 formed in the lower portion and the upper portion within the tower body 50, respectively; a dust removal section 36 of the recirculation tank, which tank 15 is in the bottom part of the tower frame; mixing equipment 32 inside the recycling tank 36; an air supply pipe 30 having some holes for supplying air to the liquid surface of the recirculation tank 36 of the dust extraction section; for oxidizing the screen 31, which screen is above the air intake pipe 30; a pump device 37 and spray means 22 for supplying and spraying the absorbent liquid into the removal tank 36 of the removal portion into the dust removal portion 34; a port 45 for supplying exhaust gas 1 located in the polynomial section 34; a piping 39A for feeding a portion of the absorbent liquid 25 to the absorbent liquid recycle tank 38, the dust removal section 36 to the recycle tank; a spray apparatus 22 for the absorbent liquid, disposed in the absorbent portion 35; a collector 33 for the absorbent liquid located below the spray apparatus 22; An absorbent liquid recirculation tank 38, and this absorbent liquid is collected in a collector 3 and circulated through a downcomer 40; a pump 39 for supplying absorbent liquid from inside the tank 38 to the spray apparatus 22 in the absorption section 35; a mixing apparatus 43 disposed within the recirculation tank 38 of the absorption section; apparatus for feeding absorbent (CaCO 3) to the recirculation tank 38 of the absorption section; an outlet 46 for the exhaust gas located at the top of the tower frame; a defroster 4 disposed on the outlet 5 of the spray device 22 and the outlet 46 in the absorption section 35; and a line 13 for removing the gypsum-containing liquid from the dust removal section of the recirculation tank 36, the pump 37 and the line 13.

Exhaust gas 1 from a boiler or the like is led to a polynomial section 34 through an exhaust gas outlet 45 10 in the lower part of the absorption tower, where it is removed, cooled and partially broken.

The resulting gas rises through the ceramic of the absorbent liquid 33 and the diffusion plate 49 and is passed to the absorbent portion 35 in an absorption tower where the SO 2 contained in the exhaust gas is absorbed and the calcium absorbent (CaCO 3, Ca (OH) 2) is removed.

CaO) by means of a sludge. The resulting debris is removed from the obtained exhaust gas by a defroster 4 and discharged through an outlet in the yia part of the absorption tower. On the other hand, the absorbent (CaCO 3, etc.) slurry is placed 20 in the tank 38 of the absorbent part 35, where the slurry is mixed with a mixer 43, then charged to the absorbent part 35 by a circulating pump 39 to remove SOx in the exhaust gas, collected by a collector 33, returned to the absorbent part reused round-25 miles. Such a coater is implemented in the form of U-shaped ceramic vessels (the shape of a trough or the shape of a semi-bubble tube) in cross-section and arranged knee-like in several layers, as described in JP Patent Application No. Sho 58-126363 / 1983, which is incorporated herein by reference. (U.S. Patent Application No. 51,065, January 16, 1984). The collector may consist of several funnel-shaped water collection devices. A portion of the excess slurry is removed via line 39A to the recirculation tank 36 of the pb-lynching portion in an amount corresponding to 35 absorbed amounts of absorbent slurry (CaCO 3). The sludge fed to the recycle tank 36 of the dedusting section 6 is mixed in the tank by a mixer 32 and recirculated by a pump 37 to the descaling section 34, where it is brought into contact with the exhaust gas, whereby the slurry content of the slurry is reacted. Further, air is supplied through an air-supply pipe 30 located above the deaeration section recirculation tank 36, and further above the air-discharge pipe 30 there is a screen 31 for oxidation, in which screen the exhaust gas recirculation liquid (i.e., the recirculation liquid is and whose pH has been lowered) is effectively contacted with air, whereby the calcium sulfite formed during the absorption of SO 2 gas is oxidized to gypsum. The resulting gypsum-containing slurry is removed by a circulating pump 37 15 of the dust removal section to a thickener and a centrifugal separator, whereby the gypsum is concentrated and separated, and finally the gypsum is recovered in powder form with 10% or less water. As the above oxidation screen 31, any type of screen can be used which promotes the contact efficiency in the presence of calcium sulfite (slurry) and air, such as those consisting of a metal mesh, filler or the like. A smooth metal mesh, filler or the like can be formed or coated with metal. , which act as oxidation catalysts.

In order to recover good quality gypsum, it is necessary to reduce the concentration of unreacted limestone in the slurry after the slurry has entered the dewatering section from the recycle tank to the thickener, and to achieve complete oxidation of the calcium sulfite in the slurry. In order to achieve this, it is necessary to select the pH of the slurry in the dewatering section of the dewatering section, the capacity of the tank and the amount of air supplied for oxidation.

In the blocked embodiment in Figure 1, a flow air method 35 is used as the oxidizing air supply pipe 30 towards the liquid surface of the recirculation tank, taking the scale

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91129 7, but as illustrated in Figure 2, a myds method may be used in which the air intake pipe 30 is immersed in the liquid in the tank and air is drawn into it. According to this method, since the circulating liquid is in contact with the air in the tank, the oxidation rate increases, making it possible to reduce the amount of oxidizing air. Further, as illustrated in Fig. 6, the air ignition tube 30 and the oxidation screen 31 can each be immersed in the liquid of the recirculation tank. According to such a construction, the oxidation screen 10 31 prevents the air injected into the liquid from rising, whereby it is possible to keep the contact time of the air with the circulating liquid sufficient. Furthermore, in the case where the oxidation screen is in many layers, its efficiency can be improved.

In the present invention, as an air ignition device disposed in the recirculation tank of the dust extraction section, in addition to a barrel 30 having holes as shown in Fig. 1, those shown in Fig. 6 or Fig. 7 are used, the air ignition nozzles 30A to 30G being arranged in mixers 32A to 32D. proximity accordingly. It is preferred that such nozzles 30A to 30G be arranged to face the blades of the mixers 32A to 32D so that the injected air can spray against the blades, be finely divided and dispersed in the liquid. When 25 such devices are used, the mixing of the slurry and the fine distribution and dispersion of the ignited air are achieved at the same time, whereby it is possible to achieve the oxidation of calcium sulfite uniformly and with high efficiency. In Fig. 6, a stirrer 32E located below the air core 30 nozzle 30G prevents the pump 37 from causing air cavitation.

As for the mixers 32A to 32D, in addition to those arranged in a rainy position in the recirculation tank 36 (i.e., directed to its center), as shown in the female 35 figures, the mixers can be positioned obliquely so that the flow formed by mixing can form a circular flow. Further, when the air supply pipe is fixed along the axis of the agitators and air is supplied along the axis behind the rotating blade of the agitators, then the efficiency of the gas-liquid contact is further improved. It has been found that with respect to the rotating blade, propeller-type ones are more desirable than wing-type ones.

The embodiments described in Figures 1, 2 and 3 relate to a device in which the recirculation tank 38 of the absorbent part is located separately outside the absorption tower. However, as illustrated in Figure 4, when the lower part of the tower is divided into two partition walls 42, the recirculation tank 36 of the dewatering part and the recirculation tank 38 of the absorbent part may be in the same tower to make the device compact, in addition to said efficiency. In the figure, numeral 41 refers to a sludge downcomer.

The above embodiments in which only p61y in the exhaust gas removes the absorbent-containing slurry are called polysynthesis systems, but the pG-20 lyner separation system described in Figure 5 can also be used.

The device shown in Figure 5 comprises the following parts: a vertically arranged, cylindrical tower structure 50; the pGly removal portion 34 and the absorption portion 35 formed in the lower space 25, and the upper space of the tower body, respectively; a recycling tank 36 for the pGly removal section; formed in the bottom portion of the tower frame 50; a tube 51 for supplying water to the dewatering section recirculation tank 36; a pump device 37 and a spray device 22 for injecting and spraying water 30 into the recirculation tank 36 of the dewatering section, the dewatering section 34; a port 45 for introducing an exhaust gas located in the deaeration section 34; a spraying apparatus 22 for the absorption liquid, attached to the absorption section 35; a collector 33 for the absorbent liquid, located under the spray device 35; defroster 4A located below the ceramic 33; a recirculation tank 38 for the absorbent liquid, for receiving the liquid collected by the collector 33; a pump device 39 for an absorbent liquid recirculation tank 38, an absorbent liquid spray apparatus 22; mixing equipment 32 5 located in the recirculation tank 38 of the absorption section; an air feeder to the surface of the liquid inside the recirculation tank 38 of the absorption section or to the inside; a tube 52 for feeding the absorbent slurry to the recirculation tank 38 of the absorption section; an outlet 46 for the exhaust gas, at the top of the tower frame; and an apparatus 10 for removing the gypsum-containing slurry from the recirculation tank 38 of the absorption section.

As shown in the drawing, the fluid recirculation systems of the dewatering section 34 and the absorbent section 35 are separated by a pile wall 42 and water is circulated to the dewatering section 34 to remove and cool the dust, while the absorbent slurry is fed to the absorption section 35 and air is supplied. The frost (or pfily) in the exhaust gas is taken by a defroster 4A.

In the device of Figure 5, the silencers 42 can be replaced by a horizontal screen with which the tank is divided into upper and lower parts. An air ignition tube and a tube for removing gypsum-containing liquid are provided in the upper part, whereby the pH of the upper part is made lower, while a tube for inserting the absorbent slurry and a tube for circulating the absorbent slurry to the absorption part are placed in the lower part.

According to the above embodiment, high efficiencies in SOx absorption and calcium sulfite oxidation are obtained.

30 Example

An example of exhaust gas treatment was performed using the apparatus shown in Figure 1 for desulfurization of a markka type gas.

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The test conditions are as follows:

Gas volume: 3,000 Nm3 / h, SO2 content: 1,000 ppm, desulphurisation percentage: 90 or higher, p61y concentration at the inlet: 200 mg / Nm3, pdly concentration at the outlet: 5 15 mg / Nm3 or lower.

The test results were as follows:

Gas volume: 3,000 Nm3 / h, SO2 content: 1,000 ppm, desulphurisation percentage: 98, p61y concentration at inlet: 200 mg / Nm3, pGly concentration at exit: 7 mg / Nm3, percentage of lime-10 scale: 0 .01%, amount of sulfuric acid used: 0 kg / h, purity of by-product gypsum: 96.3%.

According to the device of the present invention, a tank for feeding the absorbent liquid to the oxidation tower can be omitted and the devices around the oxidation tower and thus made the device compact, and since the limestone and sulfuric acid equipment can be it is possible to reduce the use of electric power. 20 Furthermore, since the polynomial section, the absorption section, and the recirculation tank of the pdlyn removal section are kept in one tower, the throughput of the feed of gases from one tower to another through the piping can be reduced. When the exhaust gas is fed to the absorption section and passed through the collector and the diffusion plate after cooling in the dewatering section, the material used to build the collector and the diffusion plate need not be heat-resistant and may be inexpensive.

Claims (4)

91129 11 A recirculation tank (36) for an apparatus for burning sulfur from a flue gas by means of a mark process, into which a absorption slurry into which the exhaust gas sulfur oxide compound is absorbed to form calcium sulphite is introduced, characterized in that the recirculation tank (36) (32E) for agitating the absorbent slurry, an upper agitator (32A, 32B) disposed on the upper side of the agitator slurry for agitating the at least one downcomer, agitators (30A-30G) adapted to air-blade the upper agitator (32A to 32D) absorbing-15 to the sludge, and means (37) for removing the treated absorbing sludge or circulating it to said bed. A recirculation tank according to claim 1, characterized in that it has a plurality of upper mixing devices (32A to 32D) at a distance from the defined circumferential distance 20 and at least one lower mixing device on the opposite side of the circulation pump (37). A recirculation tank according to claim 1, characterized in that the air sybttbla device (30A to 30G) is located on the shaft of the vane mixers of the upper mixing device (32A to 32D). An apparatus for desulphurisation of exhaust gas for a process comprising gas cooling agents, degassing agents (34), agents for absorbing and removing sulfur oxide compound and defroster agents (4), characterized in that all said agents are placed in a single absorber. and that the apparatus is provided with a recirculation tank (36) including at least one lower mixing means (32E) for mixing the absorbent slurry, at least one upper mixing means (32A, 32B) located above the lower mixing means 12 for mixing the absorbent slurry, means (30) for supplying air absorbent slurry and means (37) for removing the delayed absorbent slurry 5 or circulating it to said device. 91129 13