JP2001240879A - Method for desulfurization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for desulfurization usable as a dry method for desulfurization in a gasification system of a combustible material by which a stable CaSO4 can be formed as a desulfurization product by using a calcium compound particles as a desulfurization agent while suppressing the discharge of the unreacted calcium compound. SOLUTION: This dry method for desulfurization in the gasification system of the combustible material comprises using the calcium compound as the desulfurization agent particles, mixing the calcium compound with a sulfur mixture at a high temperature and circulating the materials within the region carrying out two chemical reactions of oxidation and reduction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desulfurization method for removing sulfide generated when burning coal or municipal waste, and more particularly to a desulfurization method using a calcium compound.

[0002]

2. Description of the Related Art In order to recover energy from combustible materials containing sulfur, such as coal, with high efficiency, there is a need for a technology of gasifying at high temperature and desulfurizing in a dry manner so as not to waste sensible heat of the gas. Have been. Technologies that use iron oxide and zinc oxide are being developed as what is expected as a desulfurization technology in the dry process.However, these technologies require the regeneration of the reaction products resulting from the desulfurization reaction, that is, iron sulfide and zinc sulfide. The situation is far from the level of practical use for commercial machines due to the difficulty of running and the rise in running costs for increasing the desulfurization rate.

Conventionally, calcium carbonate has been used as a desulfurizing agent. Since calcium carbonate is inexpensive and its running cost can be kept low, attempts are still being made to use calcium carbonate as a dry desulfurizing agent for gasification gas, but the desulfurization efficiency is inevitably higher than that using zinc oxide or iron oxide. However, it was difficult to obtain the expected performance.

[0004] It is considered that calcium carbonate is inactivated due to insufficient performance in the desulfurization method using calcium carbonate. The following two formulas can be considered as the desulfurization mechanism of calcium carbonate under a reducing atmosphere. 1) CaCO ₃ → CaO + CO ₂ decarboxylation reaction CaO + H ₂ S → CaS + H ₂ O desulfurization reaction 2) CaCO ₃ + H ₂ S → CaS + H ₂ O + CO ₂ direct desulfurization reaction 1), 2) Both calcium carbonate becomes CaS and calcium carbonate ( It is conceivable that this CaS film covers the surface of CaCO ₃ ) and inactivates calcium carbonate to suppress the reaction.

In the desulfurization method using calcium carbonate, not only is it not possible to obtain sufficient desulfurization performance, but also in spite of using inexpensive calcium carbonate, unreacted calcium carbonate is produced in large quantities as waste. This causes a problem that the cost of waste disposal increases. In addition, CaS formed on the surface of calcium carbonate may react with water vapor in the atmosphere when exposed to the air, generating a highly toxic hydrogen sulfide gas, requiring a sufficient management during handling. Had also occurred.

Therefore, when desulfurizing with calcium carbonate,
It is effective to use calcium carbonate, which is usually used with a diameter of several millimeters, in a state where the particle size is reduced to about several tens of microns, the specific surface area is increased, and the reaction area is increased. Increased energy for finely crushing calcium, difficulty in handling fine powder particles, and especially in the case of fine powder particles, do not stay in the gasification furnace for a sufficient time necessary for the reaction, precious reaction area The fact is that you cannot make the most of it.

[0007] Therefore, sufficient desulfurization performance can be exhibited even if calcium carbonate having a relatively large particle size of about several millimeters is used.
In addition, a desulfurization technique that does not suppress generation of unreacted calcium carbonate as much as possible and that is stable CaSO ₄ instead of CaS, which is a danger of generating hydrogen sulfide as a desulfurization reaction product, has been desired.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and as a dry desulfurization method in a gasification system for combustibles, calcium carbonate particles are used as a desulfurizing agent, and unreacted calcium carbonate is used. It is an object of the present invention to provide a desulfurization method capable of suppressing the emission of sulfur and producing stable CaSO ₄ as a desulfurization reaction product.

[0009]

According to a first aspect of the present invention, there is provided an integrated fluidized bed gasification furnace comprising a gasification chamber and a char combustion chamber, wherein a fluidized medium is circulated therebetween. A desulfurization method comprising charging a calcium compound into a fluid medium, performing a reduction reaction in the gasification chamber at a high temperature, and performing an oxidation reaction in the char combustion chamber.

[0010] Thus, the reaction activity on the surface of the calcium compound can be always maintained, the discharge of unreacted calcium compound is suppressed, and stable C as a desulfurization reaction product is obtained.
aSO ₄ can be generated separately from the calcium compound surface. Therefore, high desulfurization efficiency can be achieved by increasing the effective use efficiency of the desulfurization agent and exposing many active surfaces.

Unreacted calcium carbonate CaCO ₃ resident in the gasification furnace, and CaO, an intermediate stage of the reaction,
And CaS, which is a reduction desulfurization reaction product, moves from the gasification furnace and is supplied to the oxidation furnace. In the oxidation furnace, a part of CaS is oxidized to CaSO ₄ and unreacted CaC
CaO is produced by the decarboxylation reaction of O ₃ . In the oxidation furnace, CaO reacts with sulfur oxides generated from sulfur contained in fixed carbon (so-called char) supplied to the oxidation furnace, and also produces CaSO ₄ . The desulfurizing agent staying in the oxidation furnace 2 includes CaSO ₄ , CaSO ₃ , Ca
O, CaCO ₃ , and in some cases, CaS appear on the surface, and each of them is non-uniformly laminated on the surface of the desulfurizing agent, so that the external appearance is considered to be pock-like. Portion outermost layer is CaSO ₄ such desulfurization agent surface long as exist CaCO ₃ to the layer immediately beneath thin that layer, CO ₂ from CaCO ₃ by decarboxylation
Can break the CaSO ₄ layer to expose a new active reaction surface.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a reaction and a circulation route of a desulfurizing agent in a high-temperature oxidation region and a high-temperature reduction region according to an embodiment of the present invention. The present invention is characterized by using calcium compound particles as desulfurizing agent particles and circulating two regions of redox with respect to an atmosphere when a chemical reaction such as oxidation or reduction is performed.
Thereby, the reaction activity of the calcium carbonate surface can be always maintained. The regions where calcium carbonate is circulated are a high-temperature oxidation region (A region) and a high-temperature reduction region (B region) shown in Table 1.

[0013]

[Table 1]

Before describing the reaction of calcium carbonate as a desulfurizing agent in each region, the reaction in the case where calcium carbonate is used as a desulfurizing agent will be summarized, and the main reaction occurring in each region will be described. <Thermal decomposition / reverse reaction> CaCO ₃ → CaO + CO ₂ decarboxylation reaction CaO + CO ₂ → CaCO ₃ recarboxylation reaction (1) <Oxidation reaction> CaCO ₃ + SO ₂ + 0.5O ₂ → CaSO ₄ + CO ₂ Direct desulfurization reaction CaO + SO ₂ +0 0.5O ₂ → CaSO ₄ oxidative desulfurization reaction CaO + CO + 0.5O ₂ → CaCO ₃ recarboxylation reaction (2) CaS + 2O ₂ → CaSO ₄ desulfurization product oxidation reaction <Reduction reaction> CaO + H ₂ S → CaS + H ₂ O reduction desulfurization reaction

In the region A, a high temperature of 850 ° C. or more is maintained and the oxygen concentration is high. In a gasification system, this is almost the same as the condition in a so-called oxidation furnace such as a char combustion chamber, and a decarboxylation reaction and an oxidation reaction occur. Because it is an oxidizing atmosphere, combustibles burn,
When the pressure of the system is high, the partial pressure of carbon dioxide increases, so that the recarboxylation reaction (1), which is the reverse reaction of the thermal decomposition reaction, may occur, in which case the direct desulfurization reaction prevails.

The zone B is a carbonizer in the gasification system, a so-called gasification furnace. In the region B, since the oxygen concentration is low and the carbon dioxide concentration is low, the temperature is 800
Above ℃, a decarboxylation reaction which is a thermal decomposition reaction occurs. The desulfurization reaction is a reductive desulfurization reaction.

FIG. 1 shows an effective method of using the desulfurizing agent CaCO ₃ taking advantage of the characteristics of the chemical reaction in the regions A and B described above. The reactions described below can be used in a pressure range from normal pressure to 10 MPa.

FIG. 1 shows a circulation route of the desulfurizing agent in the above two regions in the present invention. How the calcium compound can maintain the desulfurization function in this circulation route will be described below. The sulfur content in the combustibles supplied to the gasification furnace 1 as a gasification raw material generates hydrogen sulfide in the gasification furnace 1. The gasification furnace 1 corresponds to the region B in the above description, and the conditions are the same as those in the above description. On the other hand, part of the calcium carbonate also supplied to the gasification furnace 1 as a desulfurizing agent becomes CaO by a decarboxylation reaction in the furnace (reaction), and reacts with hydrogen sulfide H ₂ S in the furnace to form CaS ( reaction).

Unreacted calcium carbonate CaCO ₃ staying in the gasification furnace 1 and Ca which is an intermediate stage of the reaction
O and CaS, which is a product of the reductive desulfurization reaction, move, for example, via a communication path 21 from the gasification furnace, and are supplied to the oxidation furnace 2. The oxidation furnace 2 corresponds to the region A in the above description, and the conditions are the same as those in the above description. Part of CaS is oxidized to CaSO ₄ inside the oxidation furnace 2 (reaction)
At the same time, decarbonation of unreacted CaCO ₃ causes C
Produces aO (reaction). CaO in oxidation furnace 2
Is the fixed carbon (so-called char) supplied to the oxidation furnace 2
Reacts with the sulfur oxides generated from the sulfur content contained in the sulfuric acid to produce CaSO ₄ (reaction). When the operating pressure is low, unreacted CaCO ₃ is also decarbonated inside the oxidation furnace 2 (reaction).

The desulfurizing agent staying in the oxidation furnace 2 includes CaS
O₄, CaSO₃, CaO, CaCO₃, In some cases
Indicates that each of the CaS appears on the surface, and each of these
Layered on the surface of the desulfurizing agent unevenly, so to speak
It is considered to be in a state. Of such desulfurizing agent surface
The outermost layer is CaSO₄Part is no more in the oxidation furnace
The reaction hardly proceeds, but CaSO₄Layer is thin
And the layer immediately below it is CaCO 2₃Exists
If this is the case, CaCO₃To CO ₂Missing
When CaSO₄Breaks the layer to expose a new active reaction surface
Can be done.

However, unlike the present invention, in a general system for recovering energy by gasifying combustibles, gasification is performed at a pressure higher than the atmospheric pressure, specifically, a pressure higher than about 1 MPa at which the gas turbine can be driven. In many cases, the furnace is operated. In this case, the CO ₂ partial pressure of the oxidation furnace is 0.1.
Since the pressure becomes about 5 MPa or more, the decarboxylation reaction of CaCO ₃ is suppressed, the CaSO ₄ layer continues to exist on the surface of the desulfurizing agent as it is as an inactive surface, and the Ca component in the lower layer remains without functioning as a desulfurizing agent. It will be lost.

In the present invention, as shown in FIG. 1, the oxidation furnace 2 is provided with a communication path 22 to the gasification furnace 1, and the desulfurizing agent (calcium carbonate and its derivatives) in the oxidation furnace 2 is gaseous. It can be returned to the furnace 1 again. In general, since almost no combustion occurs in the gasification furnace, the partial pressure of CO ₂ is low, and the decarboxylation of CaCO ₃ is not suppressed. Therefore, CaSO ₄ , CaSO ₃ , CaO, CaC
Even if a layer of O ₃ , and in some cases, a layer of CaS is unevenly laminated in a pock-like manner, CaCO ₃ in the desulfurizing agent releases CO ₂ by a reaction of CaCO ₃ → CaO + CO ₂ decarboxylation reaction. Thus, it is possible to expose a new reaction surface by peeling off the layer of each component, especially the layer of CaSO ₄ .

The part whose surface is covered by CaS is Ca
Since the density of the product is lower than that of the portion covered by SO ₄ , the opening ratio of the pores is large and CO ₂ can be released from the inside through the pores, so that the coating is hardly destroyed. However, when the desulfurizing agent particles circulate again from the gasification furnace 1 to the oxidation furnace 2 and return, the pores in the oxidation furnace 2 are closed by the generated CaSO ₄ , so that the gasification furnace and the oxidation furnace are connected. While circulating many times, the CaSO ₄ coating can always be destroyed by the release of CO ₂ , exposing a new reactive surface.

Since CaS has a smaller volume per mole than CaSO ₄ , the portion covered by CaS is Ca
The porosity is higher than the part covered by SO ₄ ,
The pore opening ratio is also large. Therefore, since the CO ₂ can be released from the inside through the pores, the CaS coating is hardly destroyed, but the desulfurizing agent particles circulate again from the gasification furnace 1 to the oxidation furnace 2 and return. At this time, since the pores are closed by the generated CaSO ₄ in the oxidation furnace 2, the CaSO ₄ film is always formed on the surface of the desulfurizing agent while circulating the gasification furnace and the oxidation furnace many times. , the coating if it is destroyed by the release of CO ₂ by thermal decomposition of the interior of CaCO _3, it is possible to expose a new reaction surface.

FIG. 2 is a schematic cross section showing the history of desulfurizing agent particles.
It is a representation. Is C immediately after being put into the gasifier
aCO₃Particles. Is put into the gasifier and decarbonated
CO from the surface by the reaction₂To form a layer of CaO,
Further, the surface of the CaO layer is H ₂Reacts with S to form CaS
It is in the state of doing. Return to the oxidation furnace from this state for a long time
After a while, the solid CaSO₄Membrane
Form and inactivate. In the state of desulfurizer particles
Was returned to the oxidation furnace, and it has been a while. On the surface
CaSO₄Is formed, and a CaO layer is formed thereunder.
Can be seen. The desulfurizer particles are returned to the gasifier
It has been a while. CaSO on the surface₄Is decarburized
Peeled off due to acid reaction. And likewise
Desulfurizing agent by repeating gasification furnace → gasification furnace → oxidation furnace
Particles react more and more from the surface.

The desulfurizing agent from which the mixed layer of CaSO ₄ and CaCO ₃ has peeled off in the gasification chamber 1 is further decomposed by thermal decomposition to decompose the base material CaCO ₃ to form CaO on the surface. This CaO functions as a new active reaction surface, reacts with hydrogen sulfide in the gasification furnace to form CaS, and is returned to the oxidation furnace 2 again. In this way, the desulfurizing agent is gradually consumed from the surface and is effectively used.

As described above, part or all of the substances (sulfides) containing CaO, CaS, CaSO ₄ and sulfur are passed from the reducing atmosphere B to the oxidizing atmosphere A, and then passed again through the reducing atmosphere B. Calcium carbonate can be effectively used as a desulfurizing agent. In the above description, the case where calcium carbonate was used as the desulfurizing agent was described, but it goes without saying that minerals such as limestone and dolomite, which are mainly composed of calcium carbonate, can also be used as the desulfurizing agent like calcium carbonate particles. .

Next, a specific embodiment of the present invention will be described. FIG. 3 is a conceptual diagram of an integrated fluidized bed gasification furnace in which the functions of the gasification furnace and the oxidation furnace invented by the present inventors are integrated into one.

FIG. 3 schematically shows the basic structure of the integrated gasification furnace. The gasification chamber has three functions of pyrolysis, that is, gasification, char combustion, and heat recovery. 1, a char combustion chamber 32, and a heat recovery chamber 33 are housed in, for example, a cylindrical or rectangular furnace. Gasification chamber 31, char combustion chamber 32, heat recovery chamber 33
Is divided by partition walls 41, 42, 43, 44, 45, and a fluidized bed, which is a dense layer containing a fluidized medium, is formed at the bottom of each. Fluidized bed of each chamber, i.e. gasification chamber fluidized bed,
In order to make the fluidized medium in the fluidized bed of the char combustion chamber and the fluidized bed of the heat recovery chamber flow, a diffuser for blowing fluidized gas into the fluidized medium is provided at the bottom of the furnace, which is the bottom of each of the chambers 31, 32, and 33. Have been. The air diffuser is configured to include, for example, a perforated plate laid on the bottom of the furnace, the perforated plate is divided into a plurality of rooms by dividing the perforated plate in the width direction, and to change the superficial velocity of each part in each room. In addition, the flow rate of the fluidizing gas blown out from each room of the air diffuser through the perforated plate is changed. Since the superficial velocity is relatively different in each part of the chamber, the flowing state of the fluid medium in each chamber is also different in each part of the chamber, so that an internal swirling flow is formed. In the drawing, the size of the white arrow shown in the air diffuser indicates the flow velocity of the fluidized gas to be blown out. For example, a thick arrow at a portion indicated by 32b has a larger flow velocity than a thin arrow at a portion indicated by 32a.

The gasification chamber 31 and the char combustion chamber 32 are partitioned by a partition wall 41, and the char combustion chamber 32 and the heat recovery chamber 33 are separated.
Is partitioned by a partition wall 42, and the gasification chamber and the heat recovery chamber are partitioned by a partition wall 43. That is, they are not configured as separate furnaces, but are integrally configured as one furnace. In this gasification furnace, the partition wall 41 constitutes the second partition wall of the present invention. Furthermore, the gasification chamber 3 of the char combustion chamber 32
A settling char combustion chamber 34 is provided near the surface in contact with 1 so that the flowing medium descends. That is, the char combustion chamber 32 is divided into a settled char combustion chamber 34 and a main body of the char combustion chamber other than the settled char combustion chamber 34. For this reason, a partition wall 44 is provided for partitioning the settling char combustion chamber 34 from other parts of the char combustion chamber (char combustion chamber main body). Further, the settling char combustion chamber 34 and the gasification chamber 31 are separated by a partition wall 45 as a first partition wall of the present invention.

Here, the fluidized bed and the interface will be described.
The fluidized bed comprises a thick bed containing a fluid medium (e.g., silica sand) which is placed in a fluidized state by the fluidizing gas in a vertically lower part thereof, and a fluid bed which is located vertically above the rich bed. It consists of a splash zone in which a large amount of gas coexists and the flowing medium is vigorously splashing. Above the fluidized bed, that is, above the splash zone, there is a gas-free freeboard section containing almost no fluidized medium.
The interface in the present invention refers to the splash zone having a certain thickness, but may be regarded as a virtual surface intermediate between the upper surface and the lower surface (the upper surface of the dense layer) of the splash zone. Also, when "the partition is separated by a partition wall so that there is no gas flow above the interface of the fluidized bed in the vertical direction", it is preferable that there be no gas flow above the upper surface of the dense layer below the interface. preferable.

The partition wall 41 between the gasification chamber 31 and the char combustion chamber 32 is almost completely partitioned from the furnace ceiling 49 toward the furnace bottom (perforated plate of the air diffuser). There is no second bottom 51 near the furnace bottom. However, the upper end of the flow part 51 does not reach the upper part of any of the interface of the fluidized bed of the gasification chamber and the interface of the fluidized bed of the char combustion chamber. More preferably, the distribution unit 5
The upper end of 1 does not reach above the top of the rich bed of the gasification chamber fluidized bed or the top of the rich bed of the char combustion chamber fluidized bed. In other words, the distribution unit 51
Is preferably configured to always dive into the dense layer. That is, the gasification chamber 31 and the char combustion chamber 32 are separated from each other by a partition wall at least in the freeboard section, more specifically, above the interface, and more preferably, above the upper surface of the dense layer. You will be partitioned.

The upper end of the partition wall 42 between the char combustion chamber 32 and the heat recovery chamber 33 is located near the interface, that is, above the upper surface of the dense layer, but below the upper surface of the splash zone. The lower end of the partition wall 42 extends to the vicinity of the furnace bottom. Like the partition wall 41, the lower end does not contact the furnace bottom, and there is an opening 52 near the furnace bottom that does not reach above the upper surface of the dense layer. A partition wall 43 between the gasification chamber 31 and the heat recovery chamber 33 is completely partitioned from the furnace bottom to the furnace ceiling. The upper end of a partition wall 44 that partitions the inside of the char combustion chamber 32 to provide the settling char combustion chamber 34 is near the interface of the fluidized bed, and the lower end is in contact with the furnace bottom. The relationship between the upper end of the partition wall 44 and the fluidized bed is the same as the relationship between the partition wall 42 and the fluidized bed. The partition wall 45 that separates the settling char combustion chamber 34 from the gasification chamber 31 is similar to the partition wall 41, and almost entirely partitions from the furnace ceiling to the furnace bottom, and the lower end is not in contact with the furnace bottom. Instead, there is a first circulation part 55 near the furnace bottom, and the upper end of this opening is below the upper surface of the dense layer. That is, the relationship between the first circulation unit 55 and the fluidized bed is the same as the relationship between the second circulation unit 51 and the fluidized bed.

The combustibles containing sulfur and the like, which are fed into the gasification chamber, receive heat from the fluid medium, and are pyrolyzed and gasified. Typically, the fuel does not burn in the gasification chamber, but is so-called carbonized. The remaining dry distillation char flows into the char combustion chamber 32 together with the fluid medium from the flow portion 51 below the partition wall 41. The char thus introduced from the gasification chamber 31 is burned in the char combustion chamber 32 to heat the fluid medium. The fluid medium heated by the combustion heat of the char in the char combustion chamber 32 crosses over the upper end of the partition wall 42 and the heat recovery chamber 33.
After being cooled by the in-layer heat transfer tube 71 disposed below the interface in the heat recovery chamber, and then cooled again through the lower opening 52 of the second partition wall 42. It flows into the chamber 32. The volatile matter of the combustibles charged into the gasification chamber 31 is instantaneously gasified, and subsequently, the gasification of solid carbon (char) occurs relatively slowly. Therefore, gasification chamber 3
The residence time of the char in 1 (time until the char charged into the gasification chamber 31 passes through the char combustion chamber 32) can be an important factor that determines the gasification ratio (carbon conversion rate) of the fuel.

When silica sand or the like is used as the fluid medium, the char is concentrated mainly on the upper part of the layer because the specific gravity of the char is smaller than the specific gravity of the fluid medium. When the inflow of the fluid medium into the gasification chamber and the outflow of the fluid medium from the gasification chamber to the char combustion chamber occur from the flow section below the partition wall as described above, mainly the char existing at the upper part of the bed However, the fluid medium mainly present in the lower part of the bed is more likely to flow out of the gasification chamber into the char combustion chamber, and conversely, the char is less likely to flow out of the gasification chamber into the char combustion chamber. Accordingly, the average residence time of the char in the gasification chamber can be maintained longer than that in the case where the gasification chamber is a completely mixed layer. In that case, the fluidized medium flowing into the gasification chamber from the settling char combustion chamber 34 passes mainly through only the lower part of the gasification chamber to the char combustion chamber without being widely mixed in the bed in the gasification chamber. However, even in this case, the fluidizing gas supplied from the gasification chamber hearth exchanges heat with the fluidizing medium and transfers heat from the fluidizing gas to the char, thereby indirectly causing the fluid to flow. It is possible to supply the heat used for gasification of the char from the sensible heat of the flowing medium. Also, by controlling the fluidized gas velocity in the gasification chamber and controlling the aspect of the swirling flow of the gasification chamber, it is possible to change the mixing state of the flowing medium and the char in the gasification chamber, thereby Thus, the average residence time of the gasification chamber of the char can be controlled.

On the other hand, in the present furnace structure, the height of the fluidized bed in the gasification chamber can be freely changed by controlling the pressure difference between the gasification chamber and the char combustion chamber.
Even with this method, it is possible to control the char residence time in the gasification chamber. Here, the heat recovery chamber 33 is not essential for the fuel gasification system of the present invention. That is, if the amount of char mainly composed of carbon remaining after gasification of the volatile components in the gasification chamber 31 is substantially equal to the amount of char required for heating the fluidized medium in the char combustion chamber 32, the flow Heat recovery chamber 3 that takes away heat from the medium
3 is unnecessary. If the difference in the amount of the char is small, for example, the gasification temperature in the gasification chamber 31 becomes higher, and the amount of CO gas generated in the gasification chamber 31 increases, so that the balance state is maintained. It is.

However, as shown in FIG.
In the case of equipping 3, coal with a large amount of generated char
It can handle a wide variety of fuels, even urban garbage that generates almost no char. That is, for any fuel, by adjusting the amount of heat recovery in the heat recovery chamber 33, the combustion temperature of the char combustion chamber 32 can be appropriately adjusted, and the temperature of the fluidized medium can be appropriately maintained. On the other hand, the fluid medium heated in the char combustion chamber 32 flows into the settling char combustion chamber 34 over the upper end of the fourth partition wall 44,
Next, the gas flows into the gasification chamber 31 from the circulation part 55 below the partition wall 45.

Here, the flow state and movement of the flowing medium between the respective chambers will be described. The vicinity of a surface in contact with the partition wall 45 between the settling char combustion chamber 34 inside the gasification chamber 31 is as follows:
The strong fluidization region 31b maintains a strong fluidization state as compared with the fluidization of the settling char combustion chamber 34. As a whole, it is preferable to change the superficial velocity of the fluidizing gas depending on the location so that the mixed diffusion of the injected fuel and the fluidized medium is promoted. For example, as shown in FIG.
In addition to 1b, a weak fluidization zone 31a is provided to form a swirling flow of the fluid medium.

The char combustion chamber 32 has a weak fluidized zone 3 in the center.
2a, having a strong fluidization region 32b in the peripheral portion, and the fluid medium and the char form an internal swirling flow. Gasification chamber 31,
The fluidization speed in the strong fluidization zone in the char combustion chamber 32 is 5 Umf
As described above, it is preferable that the fluidization speed of the weak fluidization zone is 5 Umf or less, but if a relatively clear difference is provided between the weak fluidization zone and the strong fluidization zone, the fluidization speed is particularly large even when exceeding this range. No problem. It is preferable to arrange a strong fluidization zone 32b in a portion in contact with the heat recovery chamber 33 and the settling char combustion chamber 34 in the char combustion chamber 32. If necessary, the furnace bottom may be provided with a gradient such that it falls from the weak fluidized region 32a to the strong fluidized region 32b. Here, Umf is a unit in which the minimum fluidization speed (the speed at which fluidization starts) is 1 Umf. That is, 5 Umf is five times the minimum fluidization rate.

As described above, the fluidized state on the char combustion chamber side near the partition wall 42 between the char combustion chamber 32 and the heat recovery chamber 33 is relatively stronger than the fluidized state on the heat recovery chamber 33 side. , The flowing medium flows from the char combustion chamber 32 side to the heat recovery chamber 33 side over the upper end of the partition wall 42 near the interface of the fluidized bed, and the flowing medium flows into the heat recovery chamber 33. The heat recovery chamber 3 moves downward (toward the bottom of the furnace) due to the relatively weak fluidized state, that is, the high-density state, and passes through the lower end (the flow portion 52) of the partition wall 42 near the furnace bottom.
It moves from the third side to the side of the char combustion chamber 32.

Similarly, the fluidized state of the main body portion of the char combustion chamber near the partition wall 44 between the main body portion of the char combustion chamber 32 and the settling char combustion chamber 34 is relatively smaller than the fluidized state of the settled char combustion chamber 34 side. By maintaining the fluidized state as strong as possible, the fluid medium moves and flows from the main body of the char combustion chamber 32 to the settled char combustion chamber 34 over the upper end of the partition wall 44 near the interface of the fluidized bed. Settling char combustion chamber 34
Flow medium moves downward (furnace bottom direction) due to the relatively weak fluidized state, that is, the high-density state in the settling char combustion chamber 34, and the lower end of the partition wall 45 near the furnace bottom. Through the (opening 55), the sedimentary char moves from the combustion chamber 34 side to the gasification chamber 31 side. Here, the gasification chamber 3
The fluidization state on the gasification chamber 31 side near the partition wall 45 between 1 and the settling char combustion chamber 34 is maintained in a relatively stronger fluidization state than the fluidization state on the settling char combustion chamber 34 side.
This assists in the movement of the flowing medium from the settling char combustion chamber 34 to the gasification chamber 31 by the attraction effect. Similarly, the fluidized state on the side of the char combustion chamber 32 near the partition wall 41 between the gasification chamber 31 and the char combustion chamber 32 is a relatively stronger fluidized state than the fluidized state on the gasification chamber 31 side. Is kept. Accordingly, the fluid medium flows through the flow section 51 below the interface of the fluidized bed of the partition wall 41, preferably below the upper surface of the dense layer (submerged in the dense layer).
2 side.

In general, the movement of the fluid medium between the two chambers (a) and (b) is performed when the chambers (a) and (b) are partitioned by a partition wall c whose upper end is near the height of the interface. Comparing the fluidized state of the chamber A and the chamber B near the partition C, for example, if the fluidized state of the chamber A is maintained stronger than the fluidized state of the chamber B, the fluid medium Flows from the room a to the room b over the upper end of the chamber. In addition, when the lower chamber is partitioned by a partition wall d whose lower end is below the interface, preferably below the upper surface of the dense layer (in other words, dips into the dense layer), in other words, the opening is formed below the interface. Or, when partitioned by a partition wall d having an opening sunk in the dense layer, comparing the fluidized state of the chamber A and the chamber B near the partition wall d, for example, the fluidized state of the chamber A side If the fluidized state is kept stronger than the fluidized state on the chamber side, the fluid medium flows through the opening at the lower end of the partition wall d and moves from the chamber side to the chamber side. It can be said that this is due to the attraction effect of the relatively strong flow state of the fluid medium in the chamber A, and that the density of the fluid medium in the chamber B due to the relatively weak flow state in the chamber B is higher than that of the chamber A. It can also be said that. In order to maintain the equilibrium state of the mass balance between the chambers that are about to collapse due to the movement of the fluid medium between the chambers at one place as described above, the fluid medium between the chambers at other places is maintained. May occur.

As for the relative relationship between the upper end of the partition wall C as a partition wall that defines one room or as the partition wall in one room and the lower end of the same partition wall d, the upper end is similarly described. The upper end of the partition wall C for moving the fluid medium over the partition wall is located vertically above the lower end of the partition wall for moving the fluid medium under the lower end. With this configuration, when the chamber is filled with the fluid medium and fluidized, if the amount of the fluid medium to be filled is appropriately determined, the upper end is located near the interface of the fluidized bed, and the lower end is The fluid medium can be moved in a predetermined direction with respect to the partition C or the partition D by setting the fluidization strength near the partition appropriately as described above. Can be done. In addition, it is possible to eliminate gas flow between the two chambers partitioned by the partition wall d.

The above description is applied to the case of FIG. 1. Explaining that, the char combustion chamber 32 and the heat recovery chamber 33 have a partition wall 42 whose upper end is near the height of the interface and whose lower end is buried in the dense layer.
The char combustion chamber 32 near the partition wall 42
The fluidized state on the side is kept stronger than the fluidized state on the heat recovery chamber 33 side near the partition wall 42. Therefore, the flowing medium flows from the char combustion chamber 32 side to the heat recovery chamber 33 side over the upper end of the partition wall 42, and passes through the lower end of the partition wall 42 from the heat recovery chamber 33 side to the char combustion chamber 32 side. Moving.

Further, the lower end of the char combustion chamber 32 and the gasification chamber 31 is partitioned by a first partition wall 45 immersed in the dense layer. Is provided with a settling char combustion chamber 34 defined by a partition wall including a partition wall 44 and a partition wall 45 near the height of the partition wall 44. The fluidized state of the main body of the char combustion chamber 32 near the partition wall 44 is determined by a partition. It is kept stronger than the fluidized state on the settling char combustion chamber 34 side near the wall 44. Therefore, the fluid medium flows from the main body side of the char combustion chamber 32 to the settling char combustion chamber 34 side over the upper end of the partition wall 44. With this configuration, the fluid medium flowing into the settling char combustion chamber 34 moves from the settling char combustion chamber 34 to the gasification chamber 31 through the lower end of the partition wall 45 so as to maintain at least mass balance. At this time, if the fluidized state on the side of the gasification chamber 31 near the partition wall 45 is more strongly maintained than the fluidized state on the side of the settling char combustion chamber 34 near the partition wall 45, the movement of the fluid medium by the attracting action is performed. Is promoted.

Further, the gasification chamber 31 and the main body of the char combustion chamber 32 are partitioned by a second partition wall 41 whose lower end is buried in a dense layer. From the settling char combustion chamber 34 to the gasification chamber 31
Is moved to the char combustion chamber 32 through the lower end of the partition wall 41 so as to maintain the mass balance, but at this time, the fluidized state on the side of the char combustion chamber 32 near the partition wall 41 Is the gasification chamber 31 near the partition wall 41
If the fluidized state is maintained stronger than the fluidized state on the side, not only the mass balance is maintained, but also the fluidized medium is attracted and moved toward the char combustion chamber 32 by the strong fluidized state.

In the embodiment of FIG. 3, the settling of the fluid medium is performed in the settling char combustion chamber 34 which is a part of the char combustion chamber 32. Specifically, it may be provided in a part of the circulation part 51 in a form which may be called a settling gasification chamber (not shown). That is, the fluidized state of the settling gasification chamber is made relatively weaker than that of the adjacent gasification chamber main body, and the fluidized medium of the gasification chamber main body passes over the upper end of the partition wall to the settling gasification chamber. The flowing and settled fluid medium moves to the char combustion chamber through the flow section 51. At this time, the settling char combustion chamber 34 may or may not be provided with the settling gasification chamber. If a settling gasification chamber is provided, as in the case of FIG. 2, the fluidized medium flows from the char combustion chamber 32 to the gasification chamber 31 through the circulation section 55 and from the gasification chamber 31 to the char combustion chamber 32 through the circulation section 51. And move.

The entire heat recovery chamber 33 is fluidized evenly,
Normally, it is maintained so as to be in a fluidized state weaker than the fluidized state of the char combustion chamber 32 in contact with the heat recovery chamber at the maximum.
Therefore, the superficial velocity of the fluidizing gas in the heat recovery chamber 33 is 0 to 3
Controlled between Umf, the fluidized medium forms a settling fluidized bed while flowing slowly. Here, 0 Umf is a state in which the fluidizing gas has stopped. In this state,
Heat recovery in the heat recovery chamber 33 can be minimized. That is, the heat recovery chamber 33 can arbitrarily adjust the amount of recovered heat within a range from the maximum to the minimum by changing the fluidized state of the fluid medium. Further, in the heat recovery chamber 33, the fluidization may be uniformly started and stopped or the strength of the fluidization may be adjusted throughout the chamber, but the fluidization of a part of the area may be stopped and the other fluidized state may be set. Then, the strength of the fluidized state of a part of the region may be adjusted.

Further, relatively large non-combustible substances contained in the fuel are discharged from a non-combustible substance discharge port 63 provided at the furnace bottom of the gasification chamber 31. Further, the furnace bottom of each chamber may be horizontal, but the furnace bottom may be inclined in accordance with the flow of the fluid medium near the furnace bottom in order to prevent a stagnant portion of the flow of the fluid medium. The incombustible discharge port may be provided not only at the bottom of the gasification chamber 31 but also at the bottom of the char combustion chamber 32 or the heat recovery chamber 33.

The most preferable fluidizing gas for the gasification chamber 31 is that the generated gas is pressurized and recycled. In this way, the gas leaving the gasification chamber is purely gas generated from the fuel, and very high quality gas can be obtained. If that is not possible,
It is preferable to use a gas containing as little oxygen as possible (oxygen-free gas). If the bed temperature of the fluidized medium decreases due to the endothermic reaction during gasification, oxygen or a gas containing oxygen, such as air, is supplied as necessary to burn a part of the product gas in addition to the oxygen-free gas. You may make it do. The fluidizing gas supplied to the char combustion chamber 32 supplies a gas containing oxygen necessary for char combustion, for example, air, a mixed gas of oxygen and steam. As the fluidizing gas supplied to the heat recovery chamber 33, air, steam, combustion exhaust gas or the like is used.

The portion above the upper surface (upper surface of the splash zone) of the fluidized bed of the gasification chamber 31 and the char combustion chamber 32, that is, the free board portion, is completely partitioned by a partition wall. Furthermore, since the portion above the upper surface of the dense bed of the fluidized bed, that is, the splash zone and the free board portion are completely partitioned by the partition wall, the pressures P1, P2 of the char combustion chamber 32 and the gasification chamber 31, respectively. Is slightly disturbed, the disturbance can be absorbed only by a slight change in the difference in the position of the interface between the two fluidized beds or the difference in the position of the upper surface of the dense bed, that is, the difference in the bed height. That is, since the gasification chamber 31 and the char combustion chamber 32 are partitioned by the partition wall 45, even if the pressures P1 and P2 of the respective chambers fluctuate, this pressure difference can be absorbed by the layer height difference. The absorption can be performed until such a layer descends to the upper end of the flow section 55. Accordingly, the upper limit of the pressure difference (P1-P2 or P2-P1) between the free space of the char combustion chamber 32 and the freeboard of the gasification chamber 31 that can be absorbed by the difference in bed height is determined by the flow rate of the lower part of the partition wall 45 that separates each other. From the top, it is approximately equal to the head difference between the head of the gasification chamber fluidized bed and the head of the char combustion chamber fluidized bed.

In the integrated gasification furnace described above, a gasification chamber, a char combustion chamber, and a heat recovery chamber are provided inside a single fluidized bed furnace through partition walls, respectively. The gasification chamber, the char combustion chamber, and the heat recovery chamber are provided adjacent to each other. This integrated gasifier enables a large amount of fluidized medium to circulate between the char combustion chamber and the gasification chamber, so that the sensible heat of the fluidized medium alone can supply a sufficient amount of heat for gasification, It is most easily possible to obtain a product gas having a high calorific value. Further, since the seal between the char combustion gas and the product gas is completely completed, the pressure balance between the gasification chamber and the char combustion chamber is well controlled, and the combustion gas and the product gas are not mixed, and the properties of the product gas are reduced. There is no lowering. The fluid medium and the char as the heat medium flow from the gasification chamber 31 into the char combustion chamber 32, and the same amount of the fluid medium flows from the char combustion chamber 32 into the gasification chamber 31. Since it is configured to return, the mass is naturally balanced, and there is no need to mechanically convey the fluid medium from the char combustion chamber 32 side to the gasification chamber 31 side using a conveyor or the like. There are no problems such as difficulty in handling particles and large sensible heat loss.

As described above, as shown in FIG.
In one fluidized bed furnace, the three functions of pyrolysis and gasification of fuel, char combustion, and in-bed heat recovery are made to coexist, and the high-temperature fluidized medium in the char combustion chamber is supplied with heat from a heat source for pyrolysis and gasification. An integrated gasification furnace for supplying a gasification medium as a medium, wherein the gasification chamber and the heat recovery chamber are completely separated from the furnace bottom to the ceiling by a partition wall, or are arranged so as not to be in contact with each other; And the char combustion chamber are completely partitioned by a partition wall above the interface of the fluidized bed, and the relative strength between the fluidized state on the gasification chamber side near the partition wall and the fluidized state on the char combustion chamber side is determined. By maintaining such a relationship as a predetermined relationship, the flow medium is moved from the char combustion chamber side to the gasification chamber side through the flow portion provided near the furnace bottom of the partition wall. Further, the fluid medium including the char is moved from the gasification chamber to the char combustion chamber.

For this reason, since the gasification chamber and the char combustion chamber are completely separated from each other by the partition wall above the interface of the fluidized bed, even if the gas pressure in each chamber fluctuates, the pressure balance is lost and combustion takes place. There is no problem that the gas and the product gas are mixed. Therefore, no special pressure balance control is required between the gasification chamber and the char combustion chamber. By maintaining the fluidized state on the gasification chamber side near the partition wall and the fluidized state on the char combustion chamber side in a predetermined state, the flow through the flow portion provided near the furnace bottom of the partition wall allows A large amount of the fluid medium can be stably moved from the combustion chamber side to the gasification chamber side. For this reason, no mechanical high-temperature particle handling means is required for moving the flowing medium from the char combustion chamber side to the gasification chamber side.

In the integrated gasification furnace, the weakly fluidized region provided at a location in contact with the gasification chamber in the char combustion chamber is a settling char combustion chamber, and a partition wall extending from the furnace bottom to the vicinity of the fluidized bed interface is used. It may be configured separately from other char combustion chambers, and the char combustion chamber, the settling char combustion chamber,
A strong fluidization zone and a weak fluidization zone are provided in the gasification chamber, respectively.
It may be configured to generate an internal swirling flow of the flowing medium in each chamber. Further, in the above integrated gasifier, the heat recovery chamber is disposed so as to be in contact with the strong fluidization region of the char combustion chamber, and the heat recovery chamber and the char combustion chamber have a flow portion near the furnace bottom, and The upper end is partitioned by a partition wall that reaches the vicinity of the fluidized bed interface, and the fluidization state of the char combustion chamber near the partition wall is made relatively stronger than the fluidization state of the heat recovery chamber side to generate the circulating force of the fluid medium. The heat recovery chamber may be disposed so as to be in contact with the strong fluidization region of the settling char combustion chamber, and the heat recovery chamber and the settling char combustion chamber include a flow portion near the furnace bottom, and The upper end thereof is partitioned by a partition wall which reaches the vicinity of the fluidized bed interface, and the fluidized state of the settling char combustion chamber side near the partition wall is made relatively stronger than the fluidized state of the heat recovery chamber side to circulate the fluid medium. May be caused. Although an oxygen-free gas is used as the fluidizing gas in the gasification chamber, a gas containing no oxygen such as water vapor may be used as the so-called oxygen-free gas. Further, the furnace bottom of each of the gasification chamber, the char combustion chamber, and the heat recovery chamber may be inclined along the streamline of the fluidized medium near the furnace bottom to make contact with the gasification furnace in the char combustion chamber. The temperature of the gasification chamber may be adjusted by controlling the fluidized state of the weak fluidized region.

Here, in the integrated gasifier C shown in FIG. 3, considering the two regions A and B described above, the fluidized bed portion A 'of the fluidized medium in the char combustion chamber was exactly as described above. Region A, the fluidized medium portion B 'of the gasification chamber 31, also applies to region B. Here, the conditions of the parts A 'and B' are the same as those shown in the area A and the area B in the above description.

The function of the present invention is exerted by supplying calcium carbonate particles, limestone particles or dolomite particles having a size accompanying the fluid medium as a desulfurizing agent into the furnace. The integrated gasifier of FIG. 3 is characterized in that it can use silica sand with little wear due to abrasion as a fluid medium. Naturally, calcium carbonate particles, limestone particles or dolomite particles are used as the fluid medium. No problem. Further, the supply location of the desulfurizing agent particles is not particularly limited, but it is preferable to supply the desulfurizing agent particles to the gasification chamber in the sense that a decarboxylation reaction occurs first. Since the gas supply chamber is provided with a raw material supply port,
It may be supplied together with the raw materials. Particularly when operating at a high temperature, it is preferable that the number of supply ports is as small as possible.
It is good to supply with raw materials.

In the integrated gasifier X, a large amount of fluid medium is circulated between the char combustion chamber and the gasification chamber, and the desulfurizing agent between the A zone (A ') and the B zone (B') is circulated. Mass circulation is easily realized. The integrated gasifier shown in FIG. 3 is one of the ideal embodiments of the present invention.

[0059]

In the desulfurization method using a calcium compound of a sulfur mixture, the calcium compound is mixed with the sulfur mixture, and the mixture is subjected to a circulation treatment by two combinations of high-temperature oxidation (step) and reduction (step), and a desulfurizing agent A high desulfurization efficiency can be achieved by increasing the effective use efficiency of the catalyst and exposing many active surfaces.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circulation route and main reactions of a desulfurizing agent according to an embodiment of the present invention.

FIG. 2 is a diagram showing a history of desulfurizing agent particles in FIG. 1 in a schematic cross section.

FIG. 3 is a conceptual diagram of an integrated fluidized-bed gasifier according to an embodiment of the present invention.

[Explanation of symbols]

1 Low CO ₂ reducing atmosphere (B region: gasification furnace) 2 High temperature oxidizing atmosphere (A region: oxidation furnace) 21, 22 Communication passage

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10J 3/00 ZAB C10J 3/46 K 3/46 F23G 5/30 ZABJ ZABM F23C 10/00 B01D 53/34 124Z F23G 5/30 ZAB F23C 11/02 303 (72) Inventor Fumiaki Ryokaku 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation (72) Inventor Kimishi Narikawa Odaka, Midori-ku, Nagoya-shi, Aichi 20-1 Kita-Sekiyama, Chubu F-term (reference) in Chubu Electric Power Co., Inc. (reference) BB02 BB03 BB22 DD12 FF03 FF13

Claims (1)

[Claims] 1. An integrated fluidized-bed gasification furnace comprising a gasification chamber and a char combustion chamber, wherein a fluid medium is circulated therebetween. A calcium compound is introduced into the fluid medium, A desulfurization method comprising performing a reduction reaction in a gasification chamber and performing an oxidation reaction in the char combustion chamber.