JP4543629B2 - Exhaust gas treatment apparatus, calcium fluoride recovery method, and fluorine recovery method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a process for recovering fluorine from the exhaust gas.
[0002]
[Prior art]
As a device for removing hydrogen chloride and hydrogen fluoride from combustion exhaust gas containing hydrogen chloride and hydrogen fluoride, slaked lime was blown into the flue and the slaked lime that reacted with hydrogen chloride and hydrogen fluoride was collected by a bag filter. An apparatus is described in Japanese Patent Application Laid-Open No. 2000-153130.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-153130
[Problems to be solved by the invention]
The present invention aims to provide a method capable of efficiently recovering fluorine from the exhaust gas.
[0005]
[Means for Solving the Problems]
The fluorine recovery method of the present invention is a method for recovering fluorine from exhaust gas, in the reaction step of exhaust gas and lime-based reactant particles in the reactor, and for the particles taken out from the reactor, A separation step for separating the rich surface portion and the unreacted core portion in the separation device, and classifying the surface portion separated by the separation device to obtain a fine particle having a particle size of a predetermined particle size or less. A calcium fluoride is recovered by a calcium fluoride recovery method including a classification step of sorting, and fluorine is recovered from the recovered calcium fluoride .
[0006]
In the according the onset Ming, the exhaust gas is contacted with lime reactant particles limestone, etc. in the reactor, reacts with the fluorine component and lime reactant particles such as hydrogen fluoride in exhaust gas, fluoride Hydrogen and the like are removed from the exhaust gas. The lime-based reactant particles are taken out from the reactor and separated into a surface portion and a core portion by a separation device. Since the core portion hardly reacts with hydrogen fluoride or the like, it is returned to the reactor and reused for exhaust gas treatment.
[0007]
This surface portion contains a lot of fluorine components such as hydrogen fluoride. In the present invention, the surface portion separated by the separation device is classified, and the fine particles are collected. This fine-grained portion has a higher fluorine content than those having a larger particle size, and the recovery efficiency of fluorine or calcium fluoride is improved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments will be described with reference to the drawings. Figure 1 is a system diagram of an exhaust gas processing device that is used to an embodiment.
[0011]
The reactor 1 has a limestone receiving port 1a in the upper part, and a screw-type limestone take-out device 2 is provided in the lower part. An exhaust gas inlet 1b and a treated gas outlet 1c are provided in the middle of the reactor 1 in the vertical direction on opposite sides of the reactor.
[0012]
The reactor 1 is filled with limestone particles, and the exhaust gas introduced into the limestone 1 from the inlet 1b passes through the limestone packed bed to the outlet 1c, during which the exhaust gas contacts the limestone, Acid gas components such as hydrogen fluoride and hydrogen chloride in the exhaust gas react with limestone and are removed from the exhaust gas.
[0013]
In this embodiment, the exhaust gas is supplied into the reactor 1 through the exhaust gas introduction chamber 1B provided on the inlet 1b side, and reaches the outlet 1c through the extraction chamber 1C on the outlet 1c side. It is configured.
[0014]
In this embodiment, gas guide members 1e and 1f having a mountain-shaped cross section are implemented from the chambers 1B and 1C.
[0015]
The gas guide member 1e extends from the chamber 1B toward the chamber 1C, but does not reach the chamber 1C. The gas in the chamber 1B is blown to the lower side of the gas guide member 1e and flows out into the gap between the limestone particles. The gas that has passed through the gap between the limestone particles is collected in a space below the gas guide member 1f, and is introduced into the chamber 1C through this space.
[0016]
The gas guide member 1f extends from the chamber 1C toward the chamber 1B, but does not reach the chamber 1B.
[0017]
The gas guide members 1e and 1f are arranged in a staggered manner in upper and lower stages.
[0018]
The take-out device 2 at the bottom of the reactor 1 is configured such that the screw is rotated by a motor 2m, and limestone is cut out. The already-reacted limestone taken out from the take-out device 2 is introduced into the surface peeling machine 3, and the surface portion and the core portion of the limestone particles are separated.
[0019]
In the surface peeling machine 3, a perforated cylindrical body 3a made of punching metal or the like is disposed in a cylindrical outer casing, and the cylindrical body 3a is rotated around its axis by a motor 3b. . The already reacted limestone is introduced into the base end side (left end side in FIG. 1) of the cylindrical body 3a. Since the surface portion of the limestone particles that reacted with hydrogen fluoride or the like in the exhaust gas is brittle compared to the unreacted core portion, the limestone particles surface portion is rubbed with each other as the cylindrical body 3a rotates. Separated from the core portion of the particles, such as scraped or stripped.
[0020]
This scraped or peeled surface portion is a powdered product in which powder and particles are mixed. This particulate matter passes through the hole of the cylindrical body 3a and is taken out from the particulate matter outlet 3d. In addition, the screw blade | wing is provided in the outer periphery of the cylindrical body 3a, and a granular material is scraped up by the screw outlet 3d by this screw blade | wing.
[0021]
The particulate matter taken out from the outlet 3d is introduced into the classification device 7 and classified into fine particles and medium particles having a larger particle size. This classifier may be a sieve type or an air classifier using a difference in specific gravity, and the type is not limited.
[0022]
The cylindrical body 3a has a downward slope toward the distal end side (the right side in FIG. 1), and the limestone particles gradually move toward the distal end side as the cylindrical body 3 rotates. Done. In addition, the hole diameter of the side peripheral surface of the cylindrical body 3a is set to about 2-3 mm, and a core particle larger than this reaches the front end side of the cylindrical body 3a. An outlet is provided on the axial center side of the distal end surface of the cylindrical body 3a, and the core particles flow out of the cylindrical body 3a from the outlet and are then taken out from the core particle outlet 3c of the surface peeling machine 3. . Since the core particles are mainly composed of unreacted limestone, they are reintroduced into the reactor 1.
[0023]
In this embodiment, the core particles from the outlet 3 c are entrained by the airflow from the blower 5 through the rotary damper 4 and supplied to the limestone inlet 1 a at the top of the reactor 1.
[0024]
In the exhaust gas treatment apparatus configured as described above, Newfeed limestone and reused limestone are supplied to the upper part of the reactor 1, the exhaust gas is circulated through the reactor 1, and contacts the limestone in the reactor 1. Acidic components such as hydrogen chloride and hydrogen fluoride react with the limestone particles and are removed from the exhaust gas. The treated exhaust gas is sent to the chimney through the induction fan 8, and may be further treated with a bag filter or the like in the middle. When the acidic component in the exhaust gas is mainly hydrogen fluoride, the surface of the limestone particles is rich in calcium fluoride.
[0025]
The limestone taken out from the bottom of the reactor 1 through the take-out device 2 is subjected to surface peeling treatment by the surface peeling machine 3, and the core portion mainly composed of unreacted limestone is returned to the reactor 1 and peeled off. The derived granular material is separated into fine particles and medium particles by the classifier 7. The fine granules are sent to a fluorine or calcium fluoride recovery process. The fine particles have a higher fluorine content than the medium particles and can efficiently recover fluorine or calcium fluoride. The method for recovering fluorine from calcium fluoride is arbitrary. The medium grain is used for manufacturing raw materials such as cement and ceramics, and fertilizers.
[0026]
In the case of limestone, the fractional particle size of the fine particles and medium particles in the classifier 7 is preferably 0.1 to 1.5 mm, particularly 0.5 to 1.5 mm, for example, about 1 mm.
Moreover, the hole diameter of the cylindrical body 3a of the surface peeling machine 3 is preferably about 2 to 3 mm, for example, about 2.5 mm. The limestone particle size of Newfeed is preferably about 4 to 6 mm.
[0027]
In the above embodiment, limestone is used as the reactant particles, but dolomite may be used.
[0028]
The configurations of the reactor 1 and the surface stripper 3 are examples, and it is obvious that reactors and surface strippers having configurations other than those described above may be employed.
[0029]
【The invention's effect】
As described above, according to the present invention, it is possible to efficiently recover the fluorine.
[Brief description of the drawings]
1 is a configuration diagram of an exhaust gas processing device that is used to an embodiment.

Claims (1)

In the method of recovering fluorine from exhaust gas ,
A reaction process in the reactor of exhaust gas and lime-based reactant particles;
A separation step for subjecting the particles taken out from the reactor to separation in a separation device of a surface portion rich in already reacted components and a core portion rich in unreacted components;
A classification step of classifying the surface portion separated by the separation device to fractionate fine particles having a predetermined particle size or less;
Calcium fluoride recovered by the method of recovering calcium fluoride comprising comprising a recovered fluorinated method recovering characterized that you recover fluorine from calcium fluoride.

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