JPH0813325B2 - Dry simultaneous desulfurization / dust removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a plurality of stages of moving beds using granular desulfurization / dust removing materials, and makes the moving speed of the front stage higher than the moving speed of the rear stage, The present invention relates to a dry simultaneous desulfurization / dust removal method in which high temperature gas containing hydrogen sulfide and dust is passed through these moving beds to simultaneously perform desulfurization and dust removal of the high temperature gas.

[Conventional technology]

Hot gas containing hydrogen sulphide and dust, for example
When the gas produced by gasification of coal is used as a fuel for combined cycle power generation or molten carbonate fuel cells, most of the dust and hydrogen sulfide in the gas must be removed. In the prior art, it is common to cool the gas once and purify it by a wet method. However, this method reduces the thermal efficiency by cooling the gas. Therefore, a dry gas refining technology that performs desulfurization and dust removal at a high temperature of 500 ° C or higher is currently being developed.

Among the dry gas refining technologies, for desulfurization, we developed a fixed bed using a metal oxide powdery desulfurization agent or a fluidized bed type desulfurization device, and a desulfurization device of the type in which metal oxide is supported on honeycomb etc. Is being promoted. Each of these is characterized in that the desulfurizing agent is regenerated and repeatedly used. Further, as the dust removing device, a moving bed dust removing device (granular bed filter) using a granular filter material and a high temperature filter using a metal or ceramic porous body or a woven fabric have been developed.

The moving bed dedusting (granular bed filter) is a method of dedusting by letting a gas flow in a horizontal direction and a filter medium in a vertical direction to make a cross flow contact, and taking in dust in the gas into the filter medium. Normally, a particle size of 1-2 m as a filter material
By using particles of about m, it is possible to remove dust up to about several microns. The number of moving beds may be one, but when multiple stages are connected in series, rough removal of dust is performed in the previous stage with a fast flow rate of the filter medium, and in the latter stage the flow velocity of the filter medium is reduced to achieve a precise finish. Collect dust. The filter material that has finished contact with the gas is separated from dust by mechanical separation or airflow separation, and is recycled again to the upper part of the dust collector. There are not many restrictions regarding the shape of the particles and the surface characteristics of the particles, and any filtering material that has a certain level of strength can be used so that it does not become powdered or worn inside the equipment, and usually cheap silica sand is used. Be seen. The flow rate of the filter material depends on the dust concentration in the gas, dust particle size, target dust collection efficiency, etc., but it is generally operated within a range of several m / h or less.

In dry desulfurization, a gas is brought into contact with a solid having a hydrogen sulfide absorbing ability (desulfurizing agent) to remove hydrogen sulfide in the gas. As a desulfurizing agent, a metal oxide is generally used, and desulfurization occurs by reacting with hydrogen sulfide as shown below to replace oxygen in the oxide with sulfur.

MO _X ＋ aH ₂ S ＋ bH ₂ → MS _Y ＋ cH ₂ O By selecting the appropriate metal species and operating conditions, the used desulfurization agent can be regenerated by the oxidation reaction shown below and can be used repeatedly.

MS _Y + aO ₂ → MO _X + bSO ₂ There are many potential metal species, but iron, zinc, etc. are particularly suitable because of their sulfurization reactivity and ease of regeneration. As the form of the desulfurizing agent, the mineral itself containing the above metal, a molded product thereof, a carrier in which these metals are supported, and the like can be considered. There are various methods for contacting the desulfurizing agent with the treated gas, such as a fixed bed, a fluidized bed, and an airflow bed, but it is also possible to use a moving bed. When iron is used as the metal species, the desulfurization reaction is 400-600 ℃, and the oxidation regeneration is
It is suitable to carry out in the range of 600 to 800 ° C.

The applicant of the present invention, as an apparatus for simultaneously performing desulfurization and dedusting of coal gasification gas, as shown in JP-A-60-18582, has a reaction tower having a desulfurization / dust collecting layer and a lower part of the reaction tower. An apparatus consisting of a regeneration tower connected to the regenerator and a dust separator connected to the lower part of the regeneration tower has already been developed and applied for a patent.

[Problems to be Solved by the Invention]

Generally, in the separation of dust by a moving bed, dust is roughly removed in a state where the dedusting material flowing speed (moving speed) is fast in the previous stage,
It is desirable to reduce the flow rate of the dedusting material in the latter stage so as to perform fine dust collection for finishing. Further, in the desulfurization using a moving bed, it is necessary to reduce the desulfurizing agent flow rate and to bring the desulfurizing agent and gas into sufficient contact to carry out the desulfurization reaction.
As described above, the downflow rate of the dedusting material in the case of dedusting does not match the downflow rate of the desulfurizing agent in the case of desulfurization.

However, in the coal gasification gas desulfurization / dust collector described in JP-A-60-18582, since the moving bed in the reaction tower has one layer, it is optimal for both desulfurization and dust removal. There is the inconvenience that it is difficult to achieve a high flow rate.

The present invention has been made in view of the above points, and the moving bed is provided in a plurality of stages in the gas flow direction, and in the preceding stage, the function mainly of dedusting is performed in a state where the desulfurization / dedusting material downflow speed (moving speed) is high. It is an object of the present invention to provide a dry simultaneous desulfurization / dust removal method in which a desulfurization / dedusting material flow rate is slow in the latter stage so that the function mainly of desulfurization is exerted.

[Means and Actions for Solving the Problems]

In order to achieve the above-mentioned object, the dry simultaneous desulfurization / dust removal method of the present invention provides a plurality of moving beds using granular desulfurization / dedusting materials, and the desulfurization / dedusting materials flow down of each moving bed. The speed is adjustable so that it becomes larger as it goes to the front stage, and in the method of performing desulfurization and dedusting of gas by the dry simultaneous desulfurization and dedusting device with an independent discharger provided under the moving bed of each stage, Part of the desulfurization / dust removal material after being used in the moving bed is continuously regenerated after separating the dust, and the regenerated desulfurization / dedusting material is first supplied to the last moving bed, and then the front stage It is characterized in that it is circulated and used in a moving bed, and with the sulfur content increased, it is extracted and regenerated.

Further, in this method, it is preferable that a part of the desulfurizing / dust removing material after being used in the moving bed in the front stage is separated from the dust and then further extracted and regenerated, and the extraction ratio is variable. .

The appropriate flow rates of gas and desulfurization agent when performing desulfurization in a moving bed differ depending on operating conditions, but as described above, generally, the flow rates of both gas and desulfurization agent are slower (residence time) compared to moving bed dedusting. Is longer) is preferable. The reason for lowering the gas flow velocity is to increase the desulfurization rate of gas,
In order to reduce the gas flow velocity, it is necessary to take a large cross-sectional area of the gas flow channel, which increases the scale of the apparatus for a given amount of processing gas. It is more economical to regenerate the desulfurizing agent after increasing the sulfur content to a certain level or more.However, if the moving speed of the desulfurizing agent is made small to increase the sulfurization reaction rate, if the dust concentration in the gas is high, The amount of dust retained in the
Ventilation pressure loss on the moving floor becomes too large. In such a case, it is necessary to take measures to recycle the desulfurizing agent several times before regenerating it without lowering the moving speed.

In this way, it is possible in principle to simultaneously perform dry dust removal and desulfurization by the moving bed method, but in terms of operating conditions, the two do not completely match, and each has its own constraints. Therefore, it is important to determine the optimal operating conditions that balance the performance, efficiency, and economic efficiency of both dust removal and desulfurization. In addition, both dust removal and desulfurization are not operated under a constant load, and both must be able to handle independent load fluctuations.
In the present invention, in order to efficiently perform both dedusting and desulfurization, a plurality of moving beds are used and the front is operated mainly for dedusting and the rear is operated mainly for desulfurization.

In the front stage, the flow rate of the desulfurization / dust removal material is set to a large value with respect to the gas amount within the range where the bed pressure loss does not increase and the dust removal efficiency is maintained. Therefore, the dust removal effect can be obtained in the front stage, but the reaction rate of the desulfurizing agent does not become so high. On the other hand, in the rear stage, desulfurization /
Reduce the moving speed of the dedusting material. Since most of the dust has already been removed in the front stage, the pressure loss does not increase significantly even if the desulfurizing / dedusting material is moved at a low speed. In the case of two stages, the front / rear stage filter medium flow ratio is preferably in the range of 3 to 20. Further, the rear stage may be an intermittent moving bed, and desulfurization may be performed in a fixed bed state. The required gas retention time is secured for all stages. Therefore, the "moving bed" in the present invention includes "intermittent moving bed".

FIG. 1 shows an example in which two moving beds are provided.
An ejector 3 such as a roll feeder is provided below the first moving bed 1.
In addition, a discharging device 4 such as a roll feeder is provided below the second moving bed 2, and the discharging devices 3 and 4 are adjusted to increase the flow rate (moving speed) of the desulfurizing / dedusting material on the first moving bed 1. ,
The flow rate of the desulfurization / dust removal material in the second moving bed 2 is set to be small. 5 is a dust separator, 6 is a variable means such as a damper, 7 is a regenerator, 8 and 10 are lift pipes, and 11 is a regenerator bypass line. The broken line indicates the flow of gas. Further, the regenerator is configured to be supplied with an oxidant (oxygen-containing gas).

Further, as shown in FIG. 2, a precision dust removing section 18 having a filter 17 made of a porous material such as a ceramic filter or a woven fabric is connected to the downstream side of the dry simultaneous desulfurization / dust removal apparatus shown in FIG. In some cases. In this case, the precision dust removal unit
18 The dust concentration at the inlet is extremely low, so the precision dust removal unit
There is an advantage that the 18 can be downsized.

In addition, a part of the desulfurization / dust removal material after being used in the moving bed at the front stage is continuously regenerated after separating the dust, and the regenerated desulfurization / dedusting material is first supplied to the moving bed at the last stage. Then, it is circulated to the moving bed in the front stage and used, and with the sulfur content increased, it is extracted and regenerated again.

In the method of the present invention, it is necessary to make the moving speeds of the desulfurizing / dedusting material largely different between the front stage and the rear stage. For this reason, it is necessary to make the circulation system for sulfurization regeneration of the desulfurization agent independent in the front stage and the rear stage, or to make the circulation system one and change the number of recycles in the front stage and the rear stage. Therefore, in order to simplify the equipment, a single circulation system is adopted and an operation method including a filtration medium circulation method capable of exhibiting high desulfurization performance is adopted.

The desulfurization performance of the desulfurization agent naturally decreases as the sulfurization rate of the desulfurization agent increases. Therefore, in a moving bed mainly composed of desulfurization, it is desirable to use a fresh desulfurization agent having a low sulfurization rate as much as possible. On the other hand, the regeneration of the desulfurization agent is more efficient because the required treatment amount decreases as the sulfurization rate is increased as much as possible. Further, when it is necessary to perform regeneration at a higher temperature than desulfurization like an iron-based desulfurizing agent, if the sulphidation rate is a certain value or more, the temperature can be raised to a desired temperature range by the regeneration (oxidation) reaction heat without external heating. In the case of an iron-based desulfurizing agent, if the sulfur concentration in the desulfurizing agent is 3% or more, it is possible to raise the temperature without supplying heat from the outside.

In the method of the present invention, the desulfurization / dedusting material is recycled and used in the front moving bed mainly for dedusting among a plurality of moving beds, and a part of the desulfurizing / dedusting material is extracted and sent to the regenerator for regeneration. The entire amount of the regenerated desulfurization / dust removal material is supplied to the rear moving bed mainly composed of desulfurization, used only once, and then sent to the front moving bed composed mainly of dust removal. In this way, in the moving bed at the rear, high desulfurization performance is obtained by the fresh desulfurization / dust removal material, while the desulfurization / dedusting material has a high sulfurization rate while being repeatedly used in the moving bed at the front. It can be played after that.

This method will be specifically described with reference to FIG. A gas containing hydrogen sulfide and dust is passed through a first moving bed in which the desulfurization / dedusting material moves at a large downflow speed to perform a dedusting-based treatment. The desulfurization / dedusting material after being used in the first moving bed 1 is extracted at a high speed by the discharger 3, and a part is supplied to the dust separator 5 to separate the dust and the powdered desulfurization / dedusting material, and then regenerated. It is introduced into the container 7 and reproduced. The regenerated desulfurization / dust removal material is supplied by the lift pipe 8 to the second moving bed 2 in which the desulfurization / dedusting material moves at a small downflow speed, and the gas from the first moving bed 1 is supplied to the second moving bed 2. And desulfurization-based treatment is performed. The desulfurization / dedusting material after being used in the second moving bed 2 is extracted at a low speed by the discharger 4, together with the desulfurization / dedusting material extracted from the first moving bed 1 and not introduced into the dust separator 5. , Lift pipe on the first moving floor 1
Circulated by 10. In this way, the sulfur content is increased and extracted and regenerated. Although not shown in FIG. 1, a fresh desulfurization / dust removal material supply pipe is connected to the first moving bed 1 or the second moving bed 2.

In the above method, it is preferable that a part of the desulfurizing / dedusting material after being used in the moving bed at the front stage is separated from the dust and then regenerated by extracting a part of the desulfurizing / dedusting material, and the extraction ratio is variable. That is, a regenerator bypass line is provided in the desulfurization / dedusting material flow path in the front stage → (partially withdrawn) → regenerator → rear stage to regenerate only part of the desulfurizing agent supplied to the rear stage. .

This method will be specifically described with reference to FIG. The desulfurization / dedusting material after being used in the first moving bed 1 is extracted at a high speed by the discharger 3, and a part thereof is supplied to the dust separator 5 to separate the dust and the powdered desulfurization / dedusting material, and then the damper. Only a part is extracted by the variable means 6 such as and reproduced by the regenerator 7. The desulfurizing / dedusting material from the dust separator, which has not been supplied to the regenerator 7, is supplied to the second moving bed 2 through the regenerator bypass line 11.

Since the method of changing the extraction ratio is configured in this way, the following effects are achieved.

(1) When using a desulfurization / dust removal material that can maintain the desulfurization performance even if the sulfurization rate becomes considerably high,
Regeneration can be performed after further increasing the sulfurization rate without changing the operating conditions of the dedusting layer.

(2) When a desulfurization load change (such as a change in the hydrogen sulfide concentration in the gas) occurs, the operating conditions of the desulfurization / dust removal layer can be changed by changing the proportion of desulfurization / dust removal material used for regeneration by this method. It is possible to perform regeneration at a constant sulfurization rate without changing. Conversely, even if the dust removal load changes independently, it can be dealt with without affecting the desulfurization agent regeneration.

〔Example〕

 Examples of the present invention will be given below.

Example 1 As a test gas, a gas having the following composition simulating a coal gasification gas was prepared and treated with the apparatus shown in FIG.

H ₂ : 15 vol% CO: 15 〃 CO ₂ : 10 vol% H ₂ O: 10 〃 H ₂ S: 1500ppm Dust: 3g / Nm ³ Desulfurization temperature in the second moving bed is 500 ℃, as desulfurization / dedusting material For, crushed iron ore with a grain size of 1.0 to 1.41 mm was used. Regeneration of desulfurization / dust removal material was performed by oxidation at 50 ° C with 50% diluted air.

First, the above gas was treated by the method according to claim 1. Of the desulfurization / dust removal material circulation amount in the first moving bed, 8% by weight was extracted, regenerated, and supplied to the second moving bed. The mass balance of gas and desulfurization / dust removal materials was as shown in Tables 1 and 2. The hydrogen sulfide concentration of the second moving bed outlet gas had dropped to 100 ppm. Dust decreased to ³ mg / Nm ³ in the second moving bed outlet gas, and the dedusting rate was 99.9
%Met.

In addition, the "first moving bed return" in Table 2 means the first
It is a portion of the moving bed extraction unit that is not supplied to the dust separator, that is, the portion A in FIG.

Example 2 As a test gas, a gas having the following composition simulating coal gasification gas was prepared and treated with the apparatus shown in FIG.

H ₂ : 15% by volume CO: 15 〃 CO ₂ : 10 〃 H ₂ O: 10 〃 H ₂ S: 3000ppm Dust: 3g / Nm ³ By the method described in claim 2, using the device shown in FIG. Gas was processed. The desulfurization temperature, desulfurization / dust-removing material, and regeneration conditions were the same as in Example 1. Of the desulfurization / dust removal materials extracted from the first moving bed (the extraction rate was 8% by weight as in Example 1), 75% by weight was recycled to the regenerator. The mass balances of gas and desulfurization / dust removal materials were as shown in Tables 3 and 4. The hydrogen sulfide concentration of the second moving bed outlet gas had dropped to 100 ppm. Also, the dust dropped to ³ mg / Nm ³ in the second moving bed outlet gas,
The dust removal rate was 99.9%.

Example 3 A coal gasification gas containing 1200 ppm of hydrogen sulfide and 3000 mg / Nm ³ of dust from a coal gasification furnace was treated at the high temperature with the apparatus shown in FIG. A ceramic filter was used as the filter made of a porous material. The second moving bed outlet gas contained hydrogen sulfide 20 ppm and dust 100 mg / Nm ³ . As a result of introducing this gas into the precision dedusting section and treating it, hydrogen sulfide and dust in the precision dedusting section outlet gas were reduced to 20 ppm and 0.1 ppm, respectively. This purified gas was supplied to and used in a gas turbine.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

(1) Desulfurization with low sulfur content in the last moving bed
It is possible to efficiently regenerate the dedusting material after exhibiting high desulfurization performance and increasing the sulfur content in the desulfurization / dedusting material.

(2) When the extraction ratio of desulfurization / dust removal material from which dust is separated is variable, the applicable load range of desulfurization / dust removal is wide, and it is possible to cope with both fluctuations independently.

(3) By integrating the desulfurization unit and the dust removal unit, it is possible to reduce the size and simplification of the device and reduce the amount of power used and the amount of utility. In addition, it is possible to adopt optimal operating conditions that balance the performance, efficiency, and economic efficiency of both desulfurization and dust removal.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of an apparatus for carrying out the dry simultaneous desulfurization / dust removal method of the present invention, and FIG. 2 is a system diagram showing another example of an apparatus for carrying out the method of the present invention. 1 ... First moving bed, 2 ... Second moving bed, 3, 4 ... Ejector, 5 ... Dust separator, 6 ... Variable means, 7 ... Regenerator, 8, 10 ... Lift pipe , 11 …… Regenerator bypass line, 17 …… Filter made of porous material, 18 …… Precision dedusting part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuya Ishikawa 1-1 Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries Ltd. Technical Research Institute (56) Reference JP-A-54-56982 (JP, A) JP-A-SHO 63-310624 (JP, A) JP-A-61-291025 (JP, A) JP-A-54-43901 (JP, A)

Claims (2)

[Claims] 1. A plurality of moving beds using granular desulfurization / dedusting material are provided, and the desulfurization / dedusting material flowing speed of each moving bed is adjustable so that it becomes higher toward the front side. In the method for desulfurizing and dedusting gas with a dry simultaneous desulfurization and dedusting device equipped with an independent discharger at the bottom of the moving bed, a part of the desulfurization and dedusting material after being used in the moving bed at the front stage, After separating the dust, it was continuously regenerated, and the regenerated desulfurization / dedusting material was first supplied to the last moving bed, and then circulated to the moving bed at the front to be used, and the sulfur content increased. A simultaneous dry desulfurization / dust removal method characterized by extracting in a state and regenerating it again. 2. A part of the desulfurizing / dedusting material after being used in the moving bed at the front stage, after separating the dust, further extracting and regenerating it, and the extraction ratio is variable. The dry simultaneous desulfurization / dust removal method according to claim 1.