JPS60112890A - Apparatus for gasification of coal or the like - Google Patents

Abstract

PURPOSE:To promote the gasification reaction of char, by contracting the lower part of the fluidized layer column to decrease the diameter of the diffusion plate, and supplying an oxygen-containing gas through a feed nozzle to the column, thereby extending the combustion zone of char and increasing the temperature of the whole fluidized layer. CONSTITUTION:A fluidized layer gasification furnace 1 is furnished with a diffusion plate 8 at its bottom, and a coal-water slurry supplying nozzle 4 to inject coal 3, oxygen 10 and steam 11 simultaneously into the furnace is attached to the middle part of the fluidized layer 2. The inner diameter of the gasification furnace 1 is enlarged gradually from its bottom toward the upper part. The oxygen 5 used as the gasification agent and the steam 6 for dilution are supplied through the diffusion plate 8, and oxygen 10 and steam 11 are ejected through the coal-water slurry nozzle 4. The space tower velocity of the fluidizing particle is maintained at a proper level considering the amount of the gasification agent introduced under the diffusion plate 8, the amount of the gas ejected through the nozzle 4, and the content of water in the slurry medium. A desirable fluidized state can be attained by contracting the bottom part of the gasification furnace 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a gasification apparatus for gasifying coal, and more particularly to a gasification apparatus for fluidized gasification using a partial oxidation method using a gas containing oxygen and steam.

[Background of the invention]

Since coal is a fossil fuel with the largest reserves, its use as an energy alternative to oil is being reconsidered. In particular, conversion to fluid energy is required from the viewpoint of handling and environmental protection.In particular, gasification can be used to produce fuel gas, synthesis gas for chemical raw materials, hydrogen gas for oil refining and coal liquefaction, reducing gas for the steel industry, and even larger applications. It is a technology that can be widely used in gasification power generation, etc., and its development is viewed as important.

Gasification can be roughly divided into partial oxidation methods that use air or oxygen and water vapor, and hydrogen gasification methods that use hydrogen. Hydrogen is produced by reacting char with water vapor, so it is considered a modification of the partial oxidation method. You can also do that. On the other hand, the reaction types are fixed bed, fluidized bed, and spouted bed.

It is classified as a molten layer. In particular, the fluidized bed allows the use of powdered coal, which is a disadvantage of the fixed bed, and since the particles in the furnace are mixed by the gas flow, it is easier to equalize the temperature, making it difficult to form a low-temperature region in the furnace, and decomposing tar. This has the advantage of promoting and reducing the amount of generation. Furthermore, since the particle size of the coal used is small and the surface area is large, there is also the advantage that the reaction rate is large and the throughput can be increased.

However, in the fluidized bed method, when the ash content in the coal melts, it coagulates with each other to form lumpy ash, which causes so-called talin car trouble, making stable operation of the gasifier impossible. Generally, the oxygen-containing gas of the gasifying agent is blown into the furnace through a distribution plate such as a perforated plate.
The oxygen concentration at these inlets is high and a carbonaceous combustion reaction occurs with intense heat generation. For this reason, a high temperature region is generated locally, and the ash content in the coal tends to become molten.

Therefore, in order to suppress the oxygen concentration to a certain level or less, a method has been adopted in which water vapor is supplied in excess to prevent localized increases in temperature. However, methods are being used to reduce clinker production by modifying the shape of the dispersion plate to activate the movement of particles directly above the dispersion plate, thereby quickly dispersing the heat generated by the reaction.

On the other hand, it is advantageous for a coal gasifier to operate under a pressure of several tens of atmospheres in terms of improving throughput, increasing gasification efficiency, or using the generated gas. However, special measures are required to feed solid coal into a pressurized system, and generally a lock hopper system is used, which supplies coal stored in a hopper maintained at a pressure equal to or higher than that of the gasifier. ing. In this system, coal is filled into a hopper at normal pressure, pressurized gas is pumped into it to increase the pressure, the system is transferred to the hopper that supplies the gasifier, and then the pressure is reduced again and the coal is filled. Although this method is simple, it has the disadvantage that the pressurizing power of the hopper is large and the switching valve is extremely worn, making it unreliable.

On the other hand, if powdered coal is made into a slurry, it becomes possible to stably supply it with a pump, and it becomes extremely easy to handle in terms of transportation and supply. The present inventors have previously studied a process in which coal is mixed with petroleum-based heavy oil to form a slurry, supplied to a pressurized fluidized bed gasifier, and gasified at the same time. Various proposals have been made regarding this. If coal is mixed with heavy oil under heating, it can be transported as a slurry and both can be gasified at the same time. Furthermore, even when the coal is coking coal, the formation of agglomerates due to adhesion is suppressed, which is not only advantageous for raw material supply, but has also been confirmed to be effective in terms of compatibility with coal types.

Depending on the raw material situation, petroleum is expensive and heavy oil may be converted into light oil rather than gasified, but in this case water can be used as a slurry medium. However, the maximum coal concentration as a water slurry is 60 to 75%, and 25 to 40% of water is supplied to the gasifier. Water as a slurry medium evaporates in the furnace, absorbing a large amount of heat and lowering the temperature inside the furnace. Therefore, compared to the case where coal is dry-supplied using a single lock hopper, oxygen as a gasifying agent must be supplied in excess.

Also, if the amount of dilution steam is not increased in accordance with the amount of oxygen, clinker will be formed.

Generally, when coal is supplied as a water slurry, it is necessary to increase the amount of oxygen and steam supplied compared to dry supply, and the gasification efficiency (generated gas calorific value/coal calorific value) is There is a drawback that it deteriorates drastically. Therefore,
Water slurry is supplied to a pressurized system using a pump, the water is evaporated, and then sent to a gasifier. A method of sending it as a medium has also been proposed.

However, all of these methods involve complicated processes, and it is considered difficult to implement efficient gasification due to operability.

In a fluidized bed reactor, the fluidizing gas (or gasifying agent in the case of a coal gasifier) is generally fed through a dispersion plate placed at the bottom of the gasifier. 9
As shown in Japanese Patent Application No. 7605, a method of feeding from a nozzle is also known.

When this method was applied to a coal gasifier, compared to the method of blowing through tiny holes in the dispersion plate, the bubbles became larger and the movement of particles around the bubbles became slower.9 The combustion reaction within the bubbles There is a possibility that clinker will be generated more easily than when using a dispersion plate, and that a large amount of diluting steam may be required. In addition, if a gasification agent is inserted near the inlet of raw coal, the gas generated by thermal decomposition of the raw material will be burned preferentially than the char gasification, and even if the same amount of oxygen is supplied, unburned char will burn. The amount may increase and the gasification efficiency may decrease.

As described above, in a fluidized bed coal gasifier using a dispersion plate, it is necessary to supply excess steam as a diluent to avoid clinker formation, and to simplify the supply system. When coal is slurried using water as a medium,
The amount of heat required to evaporate and heat water in the gasifier increases,
A decrease in furnace temperature and gasification efficiency cannot be avoided. Even if water slurry is supplied into the furnace, if the amount of water vapor for dilution can be reduced, gasification efficiency can be expected to improve. Even when supplying
If dilution steam can be reduced without producing clinker, it will be effective in improving gasification efficiency.

[Purpose of the invention]

An object of the present invention is to solve the various drawbacks of the pressurized fluidized bed coal gasifier described above and to provide a highly efficient fluidized bed gasifier.

[Summary of the invention]

The results of various studies on the effects of the amount and injection position of oxygen and steam supplied as gasifying agents on the temperature in the fluidized bed gasifier, the amount of gas produced, gasification efficiency, and clinker production. , we obtained the following findings.

(1) When oxygen is blown only from the dispersion plate, if the oxygen concentration in the supplied gasifying agent (oxygen + steam or air + steam) is 20 VO 1% or more, clinker tends to be generated. On the other hand, the gasifying agent (oxygen concentration 2
0 yot%) When injecting the gasifying agent directly into the fluidized state of the particles in the furnace, increase the oxygen concentration to 4%.
No clinker formation was observed around the blowing nozzle even at 0 to 50 VOj. This is thought to be due to the fact that the particle motion in the fluidized bed above the dispersion plate is more intense than the particle movement directly above the dispersion plate, and thermal diffusion is large.

(2) When a coal-water slurry was used as a raw material, no clinker was generated near the raw material supply nozzle even if the raw material slurry did not contain diluent steam and only oxygen was separately supplied.

Since the moisture in the raw material slurry plays the same role as the diluting steam, it is thought that clinker is difficult to form even if 100% oxygen is used. Note that if the water in this slurry medium is calculated as steam, it means that the gasifying agent with an oxygen concentration of 50 or more is blown into the slurry medium.

Furthermore, if raw materials and gasifying agents are injected from the same nozzle in this way, there is a concern that useful combustible gas components such as methane produced by thermal decomposition of coking coal will come into contact with oxygen and be preferentially burned and dissipated. However, as shown in Figure 1, it is clear that the amount of methane or the total amount of hydrocarbon gas containing methane (C1-C3) is dominated by the fluidized bed temperature, and that the presence or absence of oxygen blown from the nozzle has little effect. became. That is,
・、Mu indicates that the raw material and oxygen are supplied from the same nozzle, and ○、Δ
The mark shows that the raw material and oxygen were blown into the container from separate nozzles. The oxygen blown from the nozzle contributes to the combustion and gasification of the char, which is a fluidized particle, and therefore increases the temperature of the fluidized bed at the blown part, promoting thermal decomposition of the raw material, and is thought to be effective in suppressing tar by-products. It will be done.

Figure 2 shows the hydrocarbon gas yield when the coal-heavy oil mixed feedstock was gasified. When gasifying a coal-heavy oil slurry, it is necessary to feed the raw material fed by a pump into the fluidized bed while atomizing it at the tip of the nozzle, and generally steam is used as the atomizing agent. . In Fig. 2, oxygen is mixed with this atomizing steam, but in this case as well, almost no disappearance of hydrocarbon gas due to oxygen injection is observed, as in the case above.

As shown in Figures 1 and 2, the hydrocarbon gas yield is controlled by temperature, and the hydrocarbon gas (CI-03
) is 70'O to 800C, and methane has a very thick value around 800C. This indicates that as the temperature increases, methane production increases due to the cutting of hydrocarbons, but as the temperature rises further, steam reforming of methane is promoted, resulting in a decrease in methane.

In accordance with (1) and (2) above, even if the oxygen concentration is higher when oxygen is blown through the nozzle than when blown through the dispersion plate, that is, even if the amount of steam is small, clinker is not generated. However, even if the raw material supply port is used in conjunction with the gasifying agent supply port, there is almost no disappearance of target useful gas components such as methane, but rather it contributes to the combustion and gasification of the fluidized char around the injection port, and the temperature rises. It has been found that this is effective in accelerating the thermal decomposition of raw materials and reducing the amount of tar by-products.In this way, when the raw material supply nozzle is used in conjunction with the gasification agent supply nozzle, the following results can be achieved. Advantages (1) When processing a fixed amount of raw material, compared to blowing the gasifying agent only through the dispersion plate, it is better to blow the gasifying agent through the nozzle, since the amount of oxygen blown through the nozzle is blown through the dispersion plate. The amount of oxygen can be reduced, and the amount of water vapor for dilution can be reduced accordingly.

(11) When dealing with a water slurry, the water in the slurry medium acts as a local heating inhibitor, so there is no need to add new diluting steam to the nozzle-blown oxygen, and even if it is necessary, it can be done in a very small amount. Water as a medium evaporates in the furnace and also serves as a fluidizing gas for the particles.

(Hi) In cases where spray supply is required, such as coal-heavy oil slurry, by adding oxygen to the spraying steam, there is no need to add new diluting steam. Rather, these oxygens also act as atomizing agents, so
It is also possible to reduce the atomizing water vapor.

As mentioned above, the method of blowing oxygen through a nozzle is less likely to generate clinker than the method of blowing oxygen through a dispersion plate, so it is possible to reduce the amount of water vapor and is effective in improving gasification efficiency. As a result of examining the angle of , it became clear that if the gasifier 1 is oriented so as to form a swirling flow, it becomes even more difficult to generate clinker.

In other words, as shown in Figs. 3 and 4, if four gasifying agent injection nozzles are arranged 90° from the furnace radial direction and 45° from the furnace center, the blown gas will flow into this area. As a swirling flow occurs and the fluidized particles have velocity not only in the vertical direction but also in the circumferential direction, particle motion becomes more active, heat diffusion is promoted, and clinker is difficult to form even at high oxygen concentrations. Seem.

In addition, as mentioned in (1) above, it is possible to reduce oxygen and water vapor from the distribution plate by blowing oxygen from the nozzle, but if the column diameter is the same, the gasification from these distribution plates The gas flow rate becomes faster as the amount of agent is reduced, and particle motion in this area also decreases, and in some cases, fluidization may not occur. When the momentum of particles decreases in this way, even if the oxygen concentration is kept low, thermal diffusion may not occur and clinker may be formed. Therefore, as a result of reducing the column diameter in proportion to the reduction in the amount of gasifying agent and ensuring that the gas flow rate did not decrease,
It has become clear that a good fluidity state can be maintained and clinker formation can be avoided.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, but before that, a conventional gasification apparatus will be explained with reference to FIGS. 5 and 6. Fig. 5 shows a method in which all of the gasifying agent is supplied from the bottom of the dispersion plate 8, which tends to generate clinker on the dispersion plate 8, and in order to avoid this, a large amount of diluting steam must be supplied from the dispersion plate 8. This has the disadvantage that the gasification efficiency decreases as a result. FIG. 6 shows a system in which the gasifying agent is branched into several nozzles 12 together with the dispersion plate 8 and is directly supplied into the fluidized bed 2. Although the gasification efficiency is higher than that in FIG. The gas flow rate decreases by the amount that the gasifying agent is blown into, and if the oxygen concentration in the gasifying agent from the dispersion plate 8 is slightly increased, that is, the amount of water vapor is reduced, clinker tends to form easily. Ta.

On the other hand, the gasifier shown in FIG. 7 shows an embodiment of the present invention which solves these drawbacks of the prior art. A dispersion plate 8 is provided at the bottom of the fluidized bed gasifier 1, and a coal-water slurry supply nozzle 4 that simultaneously spouts out coal 3, oxygen 10, and steam 11 is installed in the middle part of the fluidized bed 2. has a structure in which the inner diameter gradually increases from the bottom to the top. Oxygen 5 as a gasifying agent and water vapor 6 for dilution are supplied from the dispersion plate 8, and oxygen 10 and water vapor 11 are also blown from the coal-water slurry supply nozzle 4 as described above. In addition, 7 is a discharge port for char and ash. As shown in FIG. 7, the fluidization start speed U of the fluidized particles (char) is adjusted by considering the amount of gasifying agent introduced from the lower part of the dispersion plate 8, the amount of gas blown from the nozzle 4, and the amount of water in the slurry medium. f3~
By narrowing down the diameter of the column at the bottom of the gasifier 1 so that a superficial velocity of 5 times or more can be maintained, a good fluidization state is obtained, and clinker formation directly above the distribution plate 8 and at the nozzle blowing part is suppressed. Further, a temperature drop in the vicinity of the coal-water slurry supply nozzle 4 due to evaporation of water in the medium is also suppressed. Furthermore, if these coal-water slurry supply nozzles 4 are arranged to form a swirling flow as shown in FIG.
5wt% water slurry IK2 units! No clinker formation was observed at the tip of the coal-water slurry supply nozzle 4 even when 40 kg of oxygen was blown into the coal-water slurry supply nozzle. If it is not arranged in a swirling flow type but placed towards the center, 0.32Kg/9-
When more oxygen was supplied than the water slurry, clinker was easily generated around the coal-water slurry supply nozzle 4, but this was because the movement of particles around the nozzle 4 was less active than in the case of the swirl flow type arrangement. Seem.

The table below shows the gasification test results using each type of gasifier mentioned above.

In these tests, water slurry containing 60 wt% of domestic sub-bituminous coal was used as the raw material. In Comparative Example 1 using the conventional gasifier shown in FIG. 5, the oxygen amount was 0.7 Kr/? - Coal (units are the same below), clinker was not generated when the water vapor amount was 1.6, but when the oxygen amount was increased to 0.9 as in Comparative Example 2, clinker was generated on the dispersion plate. Gasification efficiency (cold gas efficiency, generated gas calorific value/raw material calorific value) was 43% and 55%, respectively.
%, and the methane yields were also 6.2% and 7.6%.

On the other hand, in Comparative Example 3 in Figure 6, the oxygen amount was set to 0.9 as in Comparative Example 2, of which 0.6 was supplied from the dispersion plate and 0.3 from the raw material nozzle, and water vapor was not supplied from the nozzle. , 1.6 from the distribution plate only. In this case, the supply amount of gasifying agent oxygen and water vapor is the same as in Comparative Example 2, but clinker is not generated on the nozzle rotation or the dispersion plate, and the temperature drop near the raw material supply nozzle is small. The conversion efficiency also increased to 59 inches.

However, when the amount of water vapor from the dispersion plate was reduced to 1.3 (Comparative Example 4), clinker formation was observed. In Comparative Example 2, the amount of gasifying agent from the dispersion plate was 0.9 oxygen, 1.6 water vapor,
That is, clinker was generated at an oxygen concentration of 24 VO 1%, whereas in Comparative Example 4, oxygen was 0.6, water vapor was 1.3,
That is, clinker formation was observed at an oxygen concentration of 20.6 vot. In this way, compared to the gasifier shown in Fig. 5, the gasifier shown in Fig. 6 does not produce clinker even if a large amount of oxygen is supplied with the same amount of steam (1.6 Ky/Ky - coal), but the dispersion plate Looking only at the gasifying agent from the gasifier, as shown in Figure 5, less oxygen is blown in from the dispersion plate by the amount of oxygen supplied by the amount reduced, that is, the amount of oxygen supplied from the nozzle is subtracted, so the amount of water vapor is reduced by the equivalent amount. It was thought that the amount of water vapor could be reduced, but in reality clinker would be generated unless the amount of water vapor was slightly higher than that.

This is because by reducing the amount of oxygen and water vapor blown in from the dispersion plate, the gas flow velocity in this region decreases, making the fluidization state of the char worse, so clinker is generated unless the oxygen concentration is lowered slightly. be.

On the other hand, in the gasifier of the present invention shown in FIG. 7, as shown in Example 1, the oxygen/coal ratio is 0.
In 9, when the water was divided into 0.5 from the dispersion plate and 0.4 from the raw material slurry nozzle, clinker was not generated even if the amount of steam from the dispersion plate (steam/coal) was reduced to 0.9. Ta. Compared to Comparative Examples 2 and 4, the amount of water vapor is 60~
It is clear that because the temperature is reduced by 45 degrees, the temperature inside the furnace also increases by more than 1000 degrees, and the gasification efficiency increases by about 10%.

In Example 2, the oxygen supply rate from the raw material slurry nozzle was increased, the oxygen from the dispersion plate was decreased, and the water vapor from the dispersion plate was reduced by that amount, but no burnt linker was generated and the amount of water vapor was reduced. Furthermore, the temperature inside the furnace increases by the amount that is reduced, and the υ gasification efficiency also improves.

〔Effect of the invention〕

According to the present invention, when coal is gasified in a fluidized bed,
By reducing the diameter of the lower column of the fluidized bed to reduce the diameter of the dispersion plate, and by providing a raw material supply nozzle at the upper part or another nozzle and supplying the oxygen-containing gas of the gasifying agent from these, char, which is a fluidized particle, can be produced. The combustion area is expanded, localized temperature increase is suppressed, and the temperature of the entire fluidized bed can be increased. This accelerates the gasification reaction of char and also reduces the amount of heat that becomes sensible heat in the produced gas, contributing to improved gasification efficiency and significantly reducing energy consumption to generate steam. . Moreover, such a nozzle blowing device can supply oxygen alone when coal is supplied as a water slurry, and when supplying coal as a slurry with heavy oil etc., it can be mixed with water vapor for spraying. Therefore, water vapor to dilute the oxygen supplied from the nozzle is substantially unnecessary. Furthermore, when coal is supplied to a gasifier in a dry manner, it is necessary to dilute oxygen with steam, but the amount of steam required is smaller than when oxygen is introduced from a dispersion plate.

However, the effect of ejecting coal and gasifying agent together into the fluidized bed is to suppress coking troubles caused by adhesion near the raw material supply nozzle. For example, when supplying a slurry made by mixing coal with heavy oil, it is possible to increase the throughput per unit volume of the sintering furnace by increasing the pressure, but as the load per supply nozzle increases, the nozzle The temperature of the fluidized bed in the surrounding area decreased, and the wet particles tended to aggregate, producing coarse particles, and collided with the wall facing the spray in a wet state, resulting in the formation of carbon-like lumps. . Even under these conditions, if oxygen is mixed into the I]J fog steam, the fluidized char around the raw material supply nozzle will burn, suppressing the temperature drop, and the wet state will almost disappear.
It is effective in avoiding the caulking troubles mentioned above.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the effects of temperature and gasifying agent injection method on hydrocarbon gas yield when coal-water slurry is gasified in a fluidized bed, and Figure 2 is a diagram showing the effects of temperature and gasifying agent injection method on the hydrocarbon gas yield when coal-water slurry is gasified in a fluidized bed. A diagram similar to Figure 1 in the case of gasification in a fluidized bed, Figure 3 is a diagram showing an example of the nozzle arrangement in the case of blowing the gasifying agent from the nozzle, and Figure 4 is a diagram showing A-A in Figure 3. 5 is a schematic diagram of a conventional gasifier that supplies gasifying agent only from a dispersion plate, and FIG. 6 is a needle-shaped one similar to that shown in FIG. FIG. 7 is a schematic view of a coal gasifier according to an embodiment of the present invention. 1... Gasifier, 2... Fluidized bed, 3... Coal, 4
Coal-water slurry supply nozzle, 5.10 Oxygen, 6°11 Steam, 8 Dispersion plate. Agent Patent attorney Akio Takahashi goo 700 & (110900 anti-1 good; quantity degree (°C) - Figure 2 Oo 700 8oo 9o. father trap blue degree (・C) 箭 3 (2)

Claims (1)

[Claims] 1. A fluidized bed gasifier that is formed so that its inner diameter gradually increases from the bottom to the top, a nozzle that blows an oxygen-containing gasifying agent into the furnace from the bottom of the gasifier, and this nozzle. A dispersion plate located at the lower part of the gasifier above the gasifier, which spouts the gasifying agent ejected from the nozzle into the fluidized bed, and a fluidized bed, which jets the coal and oxygen-containing gasifying agent together into the fluidized bed. A coal gasification device characterized by comprising a nozzle provided in a middle position.