JPS631089B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry flue gas desulfurization apparatus having a novel structure and used for collecting and removing sulfur oxides contained in flue gas from a boiler or an industrial furnace.

The spread of flue gas desulfurization equipment in Japan has been remarkable over the past 10 years. At the stage of developing flue gas desulfurization equipment, various technologies were proposed, including dry methods, but currently commercially operated plant equipment, especially large-capacity ones, do not collect the absorbent liquid and flue gas within the absorption tower. The so-called wet method, which involves contact, is the mainstream.

However, the wet method requires a large amount of process water, including evaporated water, and the temperature of the exhaust gas after treatment increases.
Because the temperature is low (50 to 70℃) and there is a lot of moisture, if the exhaust gas is released directly from the chimney, the water vapor will become noticeable as white smoke, so it may be necessary to reheat the exhaust gas. Requires fuel. Furthermore, if the exhaust gas is released at a low temperature, the diffusion effect of the exhaust gas from the chimney to the atmosphere is poor.

Further, there are drawbacks such as the need for equipment to treat wastewater used for cooling exhaust gas and removing dust prior to desulfurization. In particular, the fuel used for reheating exhaust gas after wet treatment reaches 2 to 3% of the main fuel in boilers for large-capacity power plants, and has become a major problem from the point of view of energy conservation.

On the other hand, various dry methods have been proposed, and although activated carbon adsorption has a high desulfurization effect, there are few practical applications of activated carbon that has adsorbed sulfur oxides.
The cycle of adsorption, heating, desorption, and cooling is repeated by heating to 250 to 700°C and releasing sulfur oxides using inert gas, then cooling to the processing gas temperature and reusing it. This cycle is automatically performed. Furthermore, the adsorption performance of activated carbon deteriorates with repeated use, so it needs to be updated at regular intervals, and this replenishment and replacement requires a lot of manpower. There were drawbacks such as the possibility of accidents such as dust explosions or combustion due to the powdering of the activated carbon after the cycle. Furthermore, the dust in the exhaust gas adheres to the activated carbon adsorption layer, causing clogging of the adsorption layer, leading to a decrease in adsorption performance and an increase in gas pressure loss in the adsorption layer.

The present inventors previously proposed an exhaust gas desulfurization device that adsorbs and removes sulfur oxides from exhaust gas using an adsorption layer. The outside and inside of the cage are divided into five zones: adsorption, heating, desorption, cooling, and adsorbent exchange using a casing and sealing device, and the adsorbent is supplied and discharged corresponding to the adsorbent exchange zone. "An exhaust gas desulfurization device characterized by comprising a device" was proposed (Japanese Patent Application No. 150133/1983), but the present invention also adds improvements to this device with regard to measures against dust in the exhaust gas. It is something.

The amount of dust in the exhaust gas from a coal-fired boiler is approximately 10 to 20 g/m ³ N, which is extremely large. If this exhaust gas is directly passed through the exhaust gas desulfurization equipment, problems such as dust adhesion and blockage will occur, making stable operation impossible. Furthermore, from the viewpoint of secondary pollution prevention, it is not permissible to entrain a large amount of dust into the exhaust smoke from the chimney. For these reasons, before passing the exhaust gas through the exhaust gas desulfurization device, an electrostatic precipitator or the like is installed to remove dust beforehand, and then the exhaust gas is passed through the exhaust gas desulfurization device.
However, the dust concentration in exhaust gas treated with an electrostatic precipitator or the like is still about 100 to 500 kg/m ³ N.

The exhaust gas desulfurization equipment proposed earlier has various features, but if there is a high concentration of dust in the exhaust gas, there is a risk that dust will adhere to the adsorption layer and block it, making stable operation impossible. It was hot.

The present invention was made in order to eliminate the above-mentioned drawbacks of the previously proposed device, and includes a packed bed (hereinafter referred to as this layer) made of a filler with a smaller particle size than the adsorbent before the packed bed of adsorbent. By setting up a dummy layer (called a dummy layer) and adjusting the amount of filler exchanged from the dummy layer depending on the dust concentration in the exhaust gas, troubles such as dust adhesion and clogging of the adsorbent filled layer are prevented. This is what I am trying to do.

That is, the present invention has a cylindrical cage whose axis is substantially vertical and is rotatable around the coaxial line, a packed layer of adsorbent is formed in the cage, and the outside and inside of the cage are sealed by a casing and a sealing device. It is divided into at least four zones along the circumference: adsorption, desorption, cooling, and adsorbent exchange, and the adsorbent adsorbs and removes sulfur oxides in the exhaust gas, and the rotation of the cage creates a packed bed of adsorbent. In this apparatus, the adsorbent is sequentially moved and circulated through each zone for desorption, cooling, and exchange of the adsorbent, in which a packing material having a particle size smaller than that of the adsorbent is placed in a cage around the outer periphery of the packed bed of the adsorbent. A packed bed is provided so that the exhaust gas passes sequentially from the packed bed of the packing material to the packed bed of the adsorbent, and the adsorbent and the packing material of each packed bed are exchangeable independently of each other. The gist of this invention is an exhaust gas desulfurization device characterized by the following features.

The filler of the dummy layer, which is an improvement of the present invention, may be an inert substance or the adsorbent itself as long as the particle size is smaller than that of the adsorbent.

Hereinafter, the present invention will be described in further detail with reference to the accompanying drawings.

In Fig. 1, numeral 1 denotes a rotary cage, which has a vertical cylindrical shape and is fixed on a strong rotary table 2 on a disk, and the rotary table 2 is supported at its lower part by a plurality of rotatable rollers 3. There is. Reference numeral 4 indicates a central support, and reference numeral 5 indicates a plurality of arms radially extending toward the center of the rotary table 2. The center is fixed to the rotary table 2, and the center is determined by side rollers 6 fixed to each arm 5. The drive device 8 moves the rotary table 2 and the rotary cage 1 at a slow speed (for example, for 5 hours or more) around the central column 4.
It rotates at a rate of 1 rotation in 10 hours). The rotation speed can be adjusted to suit gas processing conditions. Since the structure of the rotating cage 1 is 10 to 20 m in diameter and 10 to 25 m in height when used in a large-scale commercial plant, it is desirable to make it as light as possible. Metal threads 27 and 27' are placed in the intermediate portion, and an adsorbent 26 is filled inside the rotary cage 1, and a filler 26' is filled outside the rotating cage 1 to form a cylindrical packed bed.
9 is an external casing, 10 is a processing gas inlet, 1
0' is a current plate, 11 is a processing gas outlet, 12 is a desorption gas inlet, 13 is a desorption gas outlet, 14 and 14'
15 and 15' are electric or pressure-operated gate valves, 16 and 16' are material seals that prevent the process gas from leaking to the top, and 17 and 17' are adsorption layers installed in the rotating cage 1. Blitz prevention plate for materials and fillers, 18 and 1
8' is the adsorbent and filler discharge gate, 19 and 1
9' is a discharge hopper, 20 and 20' are discharge conveyors, and 21 is a gas seal.

FIG. 2 shows a - cross section of FIG. 1. In FIG. 2, b is a preheating zone provided as necessary, 22 is a heating gas inlet, and 23 is a heating gas outlet. 24 is a cooling gas inlet, and 25 is a cooling gas outlet.

In addition, the adsorbent and filler supply device shown in FIG.
4,14'.

FIG. 3 is an enlarged view of section A in FIG. 2, showing the structure of the rotating cage 1 and the structure of the gas seal. As mentioned above, the rotating cage 1 has an assembled structure of pipes, and is made of metal thread 27.
and 27', and filled with adsorbent 26 and filler 26'.

Considering pressure loss, the particle size of the adsorbent is preferably 5 to 20 mm and the layer thickness is 500 to 1200 mm.The particle size of the filler is smaller than that of the adsorbent, and the layer thickness is 100 mm.
~1000mm is suitable.

Further, the rotating cage 1 is partitioned by partition plates 28, and a heat insulating material 29 is filled between the partition plates 28 to prevent heat transfer between each section. Reference numeral 30 denotes a sealing plate made of an asbestos plate provided on the rotating cage 1, which serves as a gas seal between the inner and outer casings 9, and sealing gas is blown out from a pipe 31 in order to further improve the gas sealing. In addition, the inner and outer casings 9 are also lined with a heat insulating material 34 to relieve thermal stress on the casing due to high temperature heating and desorption gas.

FIG. 4 shows a device for discharging the adsorbent and filler.
32 and 32' are air cylinders for operating the discharge gates 18 and 18', which open the gates 18 and 18' at the positions of the discharge hoppers 19 and 19' to discharge the adsorbent and filler.

Note that 33 is a reinforcing material for the rotary table 2.

Next, to explain the operation with reference to FIG.
and passes through the adsorbent 26 and exits from the outlet 11. The rotating cage 1 rotates at a slow speed in the direction of the rotation arrow, but the filler and adsorbent of the packed bed remove dust and sulfur oxides from the process gas passing through the packed bed in the adsorption zone a during one rotation. The sulfur oxides are adsorbed and then heated in heating zone b by an inert hot gas from 22 to the appropriate temperature for desorption, and then adsorbed in desorption zone c by a desorption gas consisting of a mixture of an inert gas and water vapor from 12. The desorbed gas becomes a gas rich in sulfur oxides, and is sent from the outlet 13 to a sulfur recovery device (not shown). It goes without saying that the heated gas discharged is also sent to the sulfur recovery device. Next, the adsorbent after desorption enters the cooling zone d, where it is cooled down to the same temperature as the process gas by an inert gas at a lower temperature than 24, and then enters the adsorption zone a again by rotation of the gauge. In the explanation regarding FIGS. 1 and 2, heating zone b is explained, but those skilled in the art will understand that heating zone b is not necessarily necessary if the desorption gas in desorption zone c is heated. It should be obvious.

As explained above, as the cage 1 rotates, the adsorbent repeats the cycle of adsorption, (heating if necessary), desorption, and cooling, but the performance of the adsorbent decreases with the number of repeated uses. Therefore, for example 5~
After 15 repeated uses, the old adsorbent is discharged from gate 1.
8, and new adsorbent is supplied from the supply tank 14 to prevent performance deterioration. Therefore, an adsorbent exchange zone e is provided, and the adsorbent is updated while taking into account the performance deterioration of the adsorbent.

Similarly, the filler to which dust in the exhaust gas has adhered is also replaced in the exchange zone e in an amount suitable for preventing an increase in pressure loss when the exhaust gas passes through. The rotation of the rotating cage 1 may be continuous, and the partition plate 28 may be rotated continuously.
Intermittent rotation may also be used, in which only one section partitioned by is rotated and then stopped. As for the adsorbent, in the case of the device according to the present invention, a relatively long passage time can be obtained due to the large passage area, so there is no need to use high-grade activated carbon, and inexpensive semi-formed coke etc. can be used, so the cost is reduced. Furthermore, if adsorbent waste is used as fuel, desulfurization costs can be further reduced. In addition, since the adsorbent remains stationary except for replenishment during the cycle, there is little powdering loss due to mutual friction.

The features of the device according to the present invention explained in detail above are summarized below.

(1) It is vertical and requires less site area.

(2) Since it is essentially a continuous type and there is no pressure fluctuation of the processing gas, there is no effect on the combustion equipment.

(3) Optimum desulfurization conditions can be ensured by controlling the rotation speed in response to fluctuations in the concentration of sulfur oxide gas and dust concentration.

(4) Since the adsorbent does not come into contact with the atmosphere during the cycle, accidents such as dust explosions and combustion can be prevented.

(5) Since the filling material is replaced periodically after a certain period of time, clogging due to dust can be prevented.
There is no problem even if the processing gas contains dust, and pressure fluctuations due to dust are small.

(6) The conversion of adsorbents and fillers is easy to mechanize, and unmanned operation is also possible.

(7) Since the gas passage area can be large, there is no need to use high-grade adsorbents, and inexpensive semi-formed coke can be used as the adsorbent.
Furthermore, since used adsorbent can be used as fuel, desulfurization costs can be reduced.

(8) It does not require large amounts of water or reheating fuel like the wet method.

[Brief explanation of the drawing]

Figures 1 and 2 are a side view and a plan view of an embodiment of the present invention, Figure 3 is an enlarged explanatory view of section A in Figure 2, and Figure 4 is the discharge of the adsorbent and filler of the present invention. FIG. 3 is a partial diagram of the device.

Claims (1)

[Claims] 1. It has a cylindrical cage whose axis is almost vertical and is rotatable around the coaxial line, a packed layer of adsorbent is formed in the cage, and the outside and inside of the cage are sealed along the circumference by a casing and a sealing device. At least it absorbs,
Divided into four zones: desorption, cooling, and adsorbent exchange, the adsorbent adsorbs and removes sulfur oxides from exhaust gas, and the rotation of the cage sequentially moves and circulates the packed bed of adsorbent to each zone. hand,
In an apparatus for desorbing, cooling, and exchanging the adsorbent, a packed bed of a filler having a particle size smaller than that of the adsorbent is provided in a cage around the outer periphery of the packed bed of the adsorbent, so that the exhaust gas is absorbed by the packed bed. 1. An exhaust gas desulfurization apparatus characterized in that the exhaust gas is sequentially passed from a packed bed of material to a packed bed of adsorbent, and that the adsorbent and filler of each packed bed are exchangeable independently of each other.