JPS6362250B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry desulfurization method, and particularly to a dry desulfurization method for recovering sulfur dioxide gas (hereinafter referred to as SO ₂ ) in exhaust gas as elemental sulfur.

Currently, the wet method is the main flue gas desulfurization method used in coal-fired power plants. However, this method has secondary problems such as securing water, post-treatment of wastewater, and measures to prevent white smoke, and also requires importing a large amount of coal stone as an absorbent, resulting in an oversupply of gypsum as a by-product stone. is expected in the future, so it is not necessarily the best method.

In particular, in order to promote new coal-fired power generation amidst the difficulty in finding a power source, it is necessary to develop a new desulfurization method that can solve the problems of these wet methods.

Therefore, (1) the amount of water used is small, (2) the temperature drop of the treated gas is small, (3) the amount of processing agent used and the amount of by-products generated is small, and (4) the comprehensive exhaust system including denitrification and dust prevention is used. Dry desulfurization methods for recovering elemental sulfur are attracting attention because they have advantages such as being easily compatible with smoke treatment systems.

An object of the present invention is to provide a dry flue gas desulfurization method that can efficiently recover SO ₂ in flue gas as elemental sulfur.

The gist of the present invention is to pass exhaust gas containing SO ₂ through a γ-alumina adsorbent layer, take out the γ-alumina adsorbent that has adsorbed SO ₂ from the system, and remove separately generated hydrogen sulfide (hereinafter referred to as H ₂ S). The γ-alumina adsorbent was brought into contact with the γ-alumina adsorbent, and the γ-alumina adsorbent was adsorbed.
It is characterized by generating elemental sulfur through a Claus reaction between SO ₂ and H ₂ S, taking out the γ-alumina adsorbent to which the elemental sulfur is attached, heating it to at least 500°C, and recovering elemental sulfur from the γ-alumina adsorbent. This is a dry desulfurization method.

Embodiments of the present invention will be described in detail below with reference to the drawings. Coal transported from a coal storage site 1 is burned in a coal-fired boiler 2, and exhaust gas 3 is discharged. The heat possessed by this exhaust gas is recovered by an air preheater (not shown), but in order to avoid low-temperature corrosion caused by SOx, the exhaust gas temperature at the outlet of the air preheater is usually approximately
It is controlled so that the temperature does not drop below 120℃. The exhaust gas contains 1-3% _SO2 . Exhaust gas 3 is γ
It is sent to an adsorption tower 4 filled with an alumina adsorbent 5, and the SO ₂ contained therein is adsorbed by the adsorbent 5. SO ₂
The exhaust gas from which dust has been removed is removed by a bag filter 14 and discharged into the atmosphere from a chimney 15. The adsorbent 5 that has adsorbed SO ₂ is taken out from the adsorption tower 4 and sent to the Claus furnace 9, where it is brought into contact with H ₂ S that is separately generated in the furnace 9, and the SO 2 is adsorbed by the adsorbent 5.
Elemental sulfur is generated by the Claus reaction shown by the following formula between SO ₂ and H ₂ S.

2H ₂ S + SO ₂ → 3/8S ₈ + 2H ₂ O The adsorbent 5 that adsorbed SO ₂ in the adsorption tower becomes at a temperature of around 120°C, which is almost the same as the exhaust gas, due to the exhaust gas during adsorption, and is sent to the Claus furnace. Claus furnace 9
The temperature is controlled at 120℃. Further, the SO ₂ adsorbent 5 must be effective as a Claus reaction catalyst as it is, and γ alumina is suitable for this purpose. Furthermore, the activity of γ-alumina as a Claus reaction catalyst reaches its maximum at around 100°C, decreases as the temperature rises, and reaches its minimum at around 500°C, so the appropriate temperature range for the Claus reaction is 100 to 250°C. be.

In the illustrated embodiment, the source of H ₂ S is sought in the exhaust gas itself. That is, a part of the exhaust gas 3 discharged from the boiler 2 and before entering the adsorption tower 4 is transferred to the H ₂ S generator 6.
The SO ₂ in the exhaust gas is converted to H ₂ S by the hydrogen 7 introduced here. this
The H ₂ S-containing gas 8 from the H ₂ S generator 6 is introduced into the Claus reactor 9 and subjected to the Claus reaction with SO ₂ as described above. Processed at The temperature of the adsorbent taken out from the adsorption tower is around 120°C, which is close to the temperature at which gamma alumina is highly active within the temperature range in which it is used as a Claus reaction catalyst, so heating for the Claus reaction is not necessary. An efficient Claus reaction can be carried out without the need for

The adsorbent 5 adhering to elemental sulfur produced in the Claus furnace 9 is then sent to a desorption tower 10 . In the desorption tower 10, the adsorbent 5 on which elemental sulfur is attached is heated to a temperature of about 500°C, which is about 60°C higher than the boiling point of sulfur.
The attached sulfur is desorbed from the adsorbent 5 and sent to the sulfur condenser 11 as vapor. Since the adsorbent 5 with sulfur attached is heated to a temperature approximately 50°C higher than the boiling point of sulfur, the elemental sulfur attached to the pores of the porous γ alumina also evaporates easily, reducing the surface area used as an adsorbent. is restored to the state before SO ₂ adsorption.

The adsorbent 5 from which elemental sulfur has been desorbed in the desorption tower 10 is
It is returned to the adsorption tower 4 again and used to adsorb SO ₂ in the exhaust gas 3. On the other hand, the sulfur vapor sent to the sulfur condenser 11 is cooled below its melting point by the cooling water 12.
It is cooled to 100°C and recovered sulfur 13 is recovered in solid form.

As described above, the method of the present invention involves absorbing SO ₂ in exhaust gas into a γ-alumina absorbent, converting SO ₂ into elemental sulfur through a low-temperature Claus reaction using γ-alumina as a catalyst, and then heating it to at least 500°C to desorb it. It is possible to recover elemental sulfur without introducing special chemicals from outside the system. Furthermore, the adsorbent that also serves as a catalyst for γ-alumina is economical because unlike activated carbon, etc., it is not burned, can be used repeatedly, and does not reduce its adsorption power. In addition, since the conversion of adsorbed SO ₂ to elemental sulfur is carried out at lower temperatures, the structure and handling of the equipment is easy, and there is less heat loss. Since the reactions are carried out separately, it is easy to control the temperature to suit each reaction.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the method of the present invention. 2... Coal-fired boiler, 4... Adsorption tower, 5... Adsorbent, 6... _H2S generator, 9... Claus furnace, 1
0...Desorption tower, 11...Sulfur condenser, 13...Recovered sulfur, 15...Chimney.

Claims (1)

[Claims] 1. Pass the exhaust gas containing sulfur dioxide gas through the γ-alumina adsorbent layer, take out the γ-alumina adsorbent that has adsorbed sulfur dioxide gas from the system, and bring separately generated hydrogen sulfide into contact with the γ-alumina adsorbent. The sulfur dioxide gas and hydrogen sulfide adsorbed on the alumina adsorbent generate elemental sulfur through the Claus reaction, and the γ-alumina adsorbent with the elemental sulfur attached is taken out and heated to at least 500°C to convert the elemental sulfur into γ.
A dry desulfurization method characterized by desorption and recovery using an alumina adsorbent.