JP3371692B2 - Coal gasifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasification furnace for coal and other hydrocarbon sources to obtain a combustible gas by gasifying a coal or other hydrocarbon source with a gasifying agent. The present invention relates to a gasification furnace structure and an operating method suitable for a spouted bed gasification furnace.

[0002]

2. Description of the Related Art The construction of a spouted bed gasification furnace is of the reaction mode (1
Various forms are conceivable from the combination of two-stage / two-stage reaction type), burner arrangement (single / multiple, opposite / swirl), and overall furnace structure (single furnace chamber / multiple furnace chamber), but applicable coal type and operation The flexibility of the operating range is high, the scale-up is relatively easy, and the reliability of the furnace wall is taken into consideration. As a result, it is based on a combination of two-stage reaction type / swirl burner / single furnace chamber. In particular, in order to cause the two-stage reaction to occur simultaneously in the single furnace chamber,
The structure is simple and the improvement of gasification rate can be expected mainly (Japanese Patent Application Laid-Open No. 59-176391, Japanese Patent Application No. 59-28552). Also,
High-temperature molten ash (hereinafter referred to as slag) in which the produced gas exhaust port located in the upper part of the furnace and the coal located in the lower part of the furnace are melted
The cross-sectional area of each of the exhaust ports is smaller than the cross-sectional area of the gasification reaction region, which is a gasification furnace structure with a throttle structure. The swirling burner makes it easy to achieve high gasification efficiency, but conversely, the swirling causes fine slag to flow in the vicinity of the center without being mixed with the surroundings, which is a factor that adheres to the furnace wall surface on the downstream side.

As a second example, there is also a gasification furnace having a two-chamber structure, which is also a two-stage reaction type and uses a plurality of burners (combined use of swirling and facing each other). In the first chamber at the bottom of the gasification furnace, the coal is reacted at a high air ratio to raise the temperature to melt and discharge the ash,
In the upper second chamber, only coal is supplied, or coal is supplied at a low air ratio, and the heat of the high temperature gas from the lower one chamber and H ₂ O and CO ₂ contained therein are mainly used as a gasifying agent. It is a method to do.

However, unlike the first conventional example, the second chamber of this system does not directly react oxygen with coal, so the gasification reaction itself is slow, and char containing unreacted carbon is considerably generated. In order to increase the gasification efficiency, it was essential to collect this large amount of char and return it to the gasifier because it is discharged together with the produced gas from the gasifier. Therefore, the structure becomes complicated, and the amount of circulation increases due to the generation of a large amount of char, which causes a problem of increasing ancillary equipment.

[0005]

The above-mentioned prior art, particularly the first example, is aimed at improving the carbon gasification rate, and the swirling burner system is, in view of that point, a large particle retention time. Although it is an excellent method such as eliminating temperature unevenness, conversely, due to the swirling force, it is not easy to mix a gas having a large difference in density with solid particles such as char.

[0006] For example, since the diameter is narrowed just downstream of the upper burner, the inner portion of the narrowed portion has a low temperature and also becomes a gas stagnation region. Especially, coal from the upper burner has a low temperature region. Since it passes through the gasification reaction, it is difficult for the gasification reaction to proceed, resulting in the problem that the char discharged from the gasification furnace increases. This is due to the mixture of char from the upper burner and the hot gas from the lower stage, which is considered to have a great influence on the adhesion of char and slag, that is, the temperature distribution in the cross section of the furnace determined by the mixture distribution. However, since no consideration was given to the carbon concentration in the char, the presence of local hot and cold parts at the gasification chamber outlet and the presence of fine particles that tend to adhere As high-temperature molten slag and char with a low carbon ratio scatter as it is, ash adhesion on the wake side is unavoidable, and in the worst case, it will be blocked by slugging above the narrowed part of the conventional gasification chamber outlet. There was a possibility. Further, char with a large amount of ash discharged from the gasification furnace was liable to cause a trouble due to adhesion to the heat recovery boiler section located in the subsequent stream.

In view of the above points, an object of the present invention is to maintain a high gasification rate and minimize the amount of char circulation, and at the same time, from the viewpoint of reducing the amount of slag scattered and preventing adhesion, a high slag rate. In addition to achieving the above, the high temperature gas generated in the lower stage is cooled so that there is no temperature distribution as much as possible below the predetermined outlet gas temperature, that is, the melting point of ash, and high temperature fine slag and low carbon content char in the air flow are generated. In particular, it is to provide a gasification furnace structure and an operating method for preventing adhesion on the upper side wall of the gasification chamber, the outlet gas outlet throttle portion and the downstream side.

[0008]

In order to solve the above-mentioned problems, the temperature distribution in the gasification furnace is set to a high temperature in the slag downflow portion, and above the upper burner, the temperature at which slag is hard to adhere and the inside of the furnace are high. The gasification reaction of char must be promoted by eliminating the low temperature part at. What is more important is the following findings obtained from basic experiments. It is about 10 to 15% by weight of carbon in char.
If it is above, it is a result that ash content does not adhere even if the gas temperature is 1000 to 1200 ° C. Therefore, the proportion of carbon in the scattered char is such that the char does not adhere to at least 1
It is to suppress the unevenness of the carbon concentration in the char so as not to become less than 0%, and to keep it within the ideal range as much as possible.

To this end, it is necessary to 1) achieve a high slag conversion rate, and 2) sufficiently mix high-temperature gas and char in the furnace. Also, from the viewpoint of preventing adhesion, it is related to 2), but 3) the fine slag and char are cooled in the airflow before contacting the structure, at least those of high temperature are cooled, or the slag To prevent the decrease of carbon concentration, based on the above three points,
The one-chamber two-stage reaction type gasification furnace structure of the present invention is as follows.

1) Upper and lower burners are arranged in the gasification chamber, and each burner is of a swirl type. Then, the lower burner is made larger than the average oxidizer / coal flow rate ratio in the entire conversion furnace.

2) The amount of the oxidizing agent supplied to the char burner for supplying the circulating char is such that the combustion heat of the char completely melts the ash content in the recycled char. 3) The upper burner should be smaller than the average oxidizer / coal flow rate ratio in the entire gasification furnace.

4) Unlike the conventional case, without providing a throttle portion downstream of the upper burner, a sufficient distance is provided between the upper burner and the gasification furnace outlet gas outlet throttle portion, and no throttle portion is provided during that time. Have the same diameter.

5) The recycle gas, which is the produced gas, is ejected from the top to the bottom along the side wall from the canopy in the vicinity of the narrowed portion of the outlet of the gasification furnace of the above 4).

6) A water cooling pipe is arranged on the downstream side in the vicinity of the gas outlet narrowing portion of the gasification furnace outlet of the above 4) in a form orthogonal to the gas flow direction to cool the central portion by radiation.

Specifically, it has the following features.

More specifically, a gas outlet narrowing portion having a diameter smaller than the inner diameter of the gasification chamber is provided at the upper part of the gasification chamber which is a pulverized coal gasification reaction region, and a gas having a slag outlet at the bottom is provided. In the gasification furnace, the gasification chamber is one chamber,
With placing the burner to supply a mixed fluid of the pulverized coal and the oxidant in the gasification chamber into upper and lower stages, so that the upper and lower burner for ejecting the mixed fluid in the tangential direction of the virtual circle and the virtual to the gasification chamber And above the gasification chamber
Heaven connecting the narrowed diameter of the gas outlet
The generated gas from the gasifier from the lid is used as recycled gas.
It is characterized by being introduced .

In addition, the amount of the oxidizer added to the upper and lower burners is set so that the ratio of the oxidizer to the coal of the lower burner is larger than the ratio of the oxidizer to the total coal which is the average value of the upper and lower burners, and conversely the average value of the upper stage It is characterized in that it is controlled to be smaller.

In addition, a circulation char discharged from the coal gasification furnace and a char burner for supplying an oxidant are arranged in the lower part of the gasification chamber, and carbon content in the char is burned to generate CO ₂ . It is characterized in that the amount of oxidant input is determined according to the char component so that the amount of heat generated when it is generated corresponds to the amount of heat capable of melting the ash in the char.

Further, the distance between the upper burner and the gas outlet narrowing portion of the gasifier is at least twice the distance between the upper burner and the slag outlet, and the high temperature gas generated in the lower burner and the coal of the upper burner are separated. The structure is such that a sufficient space region is provided in the upper burner from the mixing surface with the char generated from the cooling surface and the cooling surface by the radiation and mixing to the side wall surface. In addition, the temperature at the gas outlet narrowing portion in the upper part of the gasification chamber is set to be equal to or lower than the melting point of ash. Furthermore, it is necessary to prevent the generation of char having a carbon concentration of 10%.

[0020]

Further, the invention is characterized in that the injection nozzle for the recycle gas is divided into a plurality of nozzles, and the nozzles are intermittently switched for injection.

Further, a cold water pipe is newly provided between the gasification furnace and the heat recovery boiler located downstream of the gas recovery port on the downstream side near the narrowed portion of the gas outlet to prevent uneven flow and to radiate gas so that it is relatively solid. It is characterized by cooling the high temperature region in the central part of the gasification furnace, which consumes less gas. By the above 1), the temperature can be raised to a temperature higher than the pour point of the slag, and the generated slag is made to adhere to the side wall and the lower slag tap by the turning force of the burner and flow down. Since the carbon content in the char has a high oxygen concentration, it is almost gasified and becomes all CO and CO ₂ . However, the fine slag rides in the central updraft and flows upward.

Further, from the above 2), the ash contained in the circulating char is completely melted by its sufficient combustion heat, and the wall surface is made to flow down by the swirling force, so that the high slag is combined with the lower burner. Achieve

Next, according to the above 3), a part of the coal from the upper burner, which has a low oxidant ratio to the coal, comes into contact with the high temperature rising gas from the lower stage, and gasification proceeds. Further, the remaining coal becomes an upward flow along the side wall due to the burner swirling force due to the elimination of the throttling part that was conventionally near the upper burner in the above 4), but since the oxygen concentration is low,
The reaction becomes difficult to proceed, and as a result, the temperature in the region close to the side wall becomes low, so that relatively large char and carbon-rich char are likely to be generated, and they are biased to the side wall by the swirling force. Therefore, the finer the slag formed by part of the lower and upper coals, the closer to the periphery, and if the amount of char is larger, part of the slag will be taken into the char and it will be difficult to adhere to the side wall. In addition, even if the amount of adhesion increases, the possibility of spontaneous fall increases. That is, it is possible to prevent the high temperature slag generated from the lower burner from adhering to the wall surface in this vicinity. However, if the char flowing along the side wall does not react and flows to the gas outlet as it is, the gasification rate will decrease, so it will react with high-temperature gas containing a large amount of oxidizing agents such as CO ₂ and H ₂ O. I have to let you.

By the way, according to the above 4), since the throttle portion which has been located directly above the upper burner is separated from the upper burner to the gas outlet on the upper side, there is no possibility of clogging due to slag adhesion near the throttle portion. . Further, since the space from the upper burner to the narrowed portion becomes long, the gas containing the high temperature fine slag has a better chance of coming into contact with the chars containing a large amount of unburned carbon present around the gas. However, since the swirling force remains in the region from the upper burner on the downstream side to the gasifier outlet, mixing is inevitably bad and it flows to the outlet as it is, and the temperature near the center of the furnace remains high and the temperature approaches the wall surface. descend. Contrary to the temperature distribution, the carbon content in the char mainly generated from the coal flowing upward from the upper burner has a distribution that increases toward the wall surface.

Therefore, it is the most important of the present invention that the gasification reaction of the peripheral char is caused by promoting the mixing of the high temperature gas and the upper burner generating char by some means, and the central high temperature part is cooled at the same time. That's the point.

In order to improve the temperature and concentration distribution as described above, the char adhering to the side wall is blown off by the recycle gas blowing described in 5) above, or a circulating flow of gas containing a large amount of char flowing near the side wall is formed. The blown char advances the gasification reaction (C + CO ₂ = 2CO) while mixing with the mainstream gas in the center. Therefore, the gasification efficiency is improved and the high temperature gas containing the fine slag is cooled by the endothermic reaction. Further, the temperature of the mainstream gas decreases due to the mixture of the low temperature recycled gas and char with the mainstream gas, and the temperature distribution in the cross section tends to be uniform. Furthermore, by mixing the blown-off wall-attached char and the fine slag, it is possible to prevent the high-temperature fine slag from adhering.

Further, by providing the water cooling pipe of the above 6), the particle concentration in the central part of the gasification furnace is relatively low, and the radiation in the vertical direction becomes more effective than in the side wall. Effective for cooling. In addition to cooling, the char that has been scattered from the gasification chamber will most often adhere to this water-cooled pipe, so ash adhesion to the regular water-cooled pipe installed on the downstream side of this water-cooled pipe will be reduced. This enhances the cooling effect of the regular water cooling pipe. It also plays a role of rectifying the swirl flow from the lower part of the furnace by the swirl burner, and can be expected to improve the heat transfer performance of the heat transfer tube on the downstream side.

[0029]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. The gasifier of the present invention is used in the coal gasification flow shown in FIG. In FIG. 1, coal 1
Is pulverized by a crusher 2, and then gas is conveyed, and is collected by a cyclone 3 and a bag filter 4,
Stored in hopper 5. The pulverized coal thus stored is supplied to the upper part of the gasification chamber 70 of the gasification furnace 6 by the supply gas 20 (nitrogen, carbon dioxide, air, part of the generated gas, etc.),
It is sent down. In the gasification chamber 70, a mixed fluid of pulverized coal 21 and oxygen 22A and steam 22B as a gasifying agent is ejected from the upper burner 8, and the lower burner 7 is also discharged.
Also, a mixed fluid of pulverized coal, oxygen, and steam is jetted. Normally, steam is not used, but steam may be supplied to both stages or only one of the stages depending on operating conditions.

The pulverized coal is gasified in the gasification chamber 70, the details of which will be described later with reference to the longitudinal sectional view of the main part of the gasification furnace of the present invention shown in FIG.

The coal ash contained in the pulverized coal 21 is melted to form slag, which flows down through the furnace wall and the slag outlet 9 into the water tank 10. In the water tank, it is cooled in the slag cooling section 11 by the cooling water 23 pressurized and sent by the pump 30, stored in the slag hopper 12, and then separated and discarded by the slag separator 13. The cooling water 23 that has cooled the slag is reused by the recirculation pump 31. The water tank 10 is kept at a low temperature by circulating the water, and it is possible to prevent the water from evaporating due to the temperature rise due to the radiant heat transfer from the furnace and the sensible heat brought in by the slag.

After the heat of the produced gas 24 is recovered by the water cooling pipe 17, the heat is recovered by the heat recovery boiler 13 at 300 to 400 ° C.
Is cooled down. After that, the char in the produced gas is collected by the cyclone 14, stored in the char hopper 15, and again supplied to the char burner 33 provided near the lower burner arranged in the lower part of the gasification chamber 70, and the char in the gasification furnace. And the unreacted carbon is gasified. Cyclone 1
The produced gas 25 that has passed through 4 passes through a dust filter (not shown) and is passed through a gas purification device (not shown) to burn chemical raw materials, hydrogen sources, industrial gas generators, and other gas turbines. Be used for.

Of the purified gas discharged from the gas refining apparatus, preferably about 5% of the purified gas 26 is gasified from the gasification chamber 70 of the gasification furnace 6 and the vicinity of the upper gas extraction port narrowing portion 16. It is designed to eject into the furnace.

The high-pressure steam 28 generated in the water cooling pipe 17 and the heat recovery boiler 13 in the gasification furnace is sent to the steam turbine (not shown) through the high-pressure drum 18, the steam pipe 27, and finally. Will contribute to power generation.

Next, details of the inside of the gasification furnace of the present invention will be described with reference to FIG. The upper part of the gasification chamber 70 communicates with the heat recovery boiler via the generated gas outlet 19, and the lower part communicates with the slag cooling unit 11 via the slag outlet 9. The cross-sectional area of each outlet is smaller than the cross-sectional area of the gasification chamber. The entire circumference from the lower part of the gasification chamber 70 to the vicinity of the upper burner 8 is surrounded by a heat insulating material or a refractory material 32. However, in order to protect the inner wall of the furnace from damage due to high temperature gas or molten slag, the heat insulating material or the refractory material 32 is used. The water cooling pipe 17A is embedded to cool the side wall surface 105 of the furnace so that the damage does not progress to a certain extent. Further, since the temperature of the wall surface from the upper part of the upper burner 8 to the generated gas outlet 19 becomes lower than that of the lower part of the gasification chamber, the entire circumference is covered with the water cooling pipe 17B, and steam is generated by heat exchange with the generated gas 24. Then, the generated gas is cooled.

The upper and lower pulverized coal burners are installed above and below the gasification chamber (7, 8), respectively, while the char burner 33 is installed in the lower part of the gasification chamber. In the present invention, the number of burners is four at equal intervals in the direction in contact with the turning circle. The upper burner and the char burner are basically turning in the same manner as the lower burner. Also, the number of burners is four. The size of the swirl circle diameter and the number of burners are determined by the amount of coal supply, the stability of the swirl flow, and the complexity of operation control. Furthermore, the residence time of the coal particles can be adjusted by changing the ratio of the diameters of the swirling circles of the upper and lower burners.

In the present invention, the amount of coal supplied to the upper and lower burners is the same, and the flow rate ratio of the oxygen 22A, 22B (gasifying agent) which is the oxidant supplied to the lower burner 7 and the coal 21 (oxidizer / coal. ) Is larger than the total (oxidizer / coal). That is, the flow rate of the oxidizing agent in the lower stage is consequently higher than that of the oxidizing agent supplied in the upper stage. As a result, in the lower part of the gasification chamber 70, since the coal supplied from the lower burner 7 has a large amount of oxygen, it is possible to form a state sufficiently higher than the melting point of ash and the pour point of ash. Then, this molten ash, that is, slag, is pushed to the side wall surface 105 by the swirling flow of the lower burner 7, so that it easily flows down. Further, since carbon in the char has a high oxygen concentration, gasification progresses rapidly and is gasified into CO ₂ , CO and H ₂ O. In order to obtain a strong swirling force, it is necessary to increase the ratio d / D of the swirling circle diameter d and the furnace diameter D, but if it is too large, the side wall surface may be exposed to high-temperature flames and the slag tap Since the slag tends to adhere to the cooling section 11 of No. 3, it is desirable to keep it within the optimum range.

With respect to the so-called circulating char 29 that has been recycled, the amount of the oxidant 53 supplied to the char burner 33 is the amount of heat generated when the carbon in the circulating char is burned to generate CO _2. However, the charging amount of the oxidizer 53 is determined according to the char component so as to correspond to the amount of heat capable of melting the ash contained in the circulating char, and the mixing of char and oxygen is as good as possible. To In addition, d /
Since there is a small amount of D, there is no problem if d / D is set to be equal to or larger than the lower burner.

As described above, in the lower part of the gasification chamber 70, the oxygen concentration is increased to form a high temperature state, and the swirling force is utilized to promote the adhesion of the slag to the side wall surface 105, whereby the lower burner 7 and the char. The ash in the coal char supplied from the burner 33 can be slagged at a very high rate. Conversely, since less ash goes up, the possibility of ash adhesion can be reduced accordingly. However, in order not to damage the side wall surface 105 of the gasification furnace due to the temperature rising too much, the oxygen 22
It may be necessary to control the A, 22B and 53 flow rates or in some cases steam addition. Note that the fine high-temperature slag in the molten ash does not adhere to the wall in the swirling flow and flows upward as it is.

Here, FIG. 3 shows a schematic diagram of the analysis result of the gas flow in the gasification furnace of the present invention. The area 100 near the center of the lower part of the gasification furnace becomes a high temperature area, and the fine slag flows upward along the ascending air current near the center. Further, the side wall surface 105 between the upper burner and the lower burner causes the slag pushed down by the side wall due to the turning force to flow down, and the slag outlet 9
It flows down to the aquarium.

Next, regarding the coal supplied from the upper burner, since the upper burner is smaller than the total oxidizer / coal ratio, oxygen is insufficient near the burner.
However, since the amount of oxygen is small, there is unreacted carbon, but the temperature of the particles themselves does not reach the melting temperature of ash,
And the surface of the char is highly reactive. Some of the coal from the upper stage burner is CO ₂ or of H ₂ O hot rising gases from the lower by a flow 101 formed by using a two-stage burner turning scheme proceeds contact gasified with carbon, C
O and H ₂ are produced. Further, the remaining coal becomes an upward flow along the side wall 103 as shown in the figure, and the temperature is relatively low, so that a relatively large char is likely to be generated and adheres to the side wall 103 by the swirling force.

In the upper part 102 near the upper burner, if the amount of fine slag formed by the lower and upper descending flows 101 is larger than the amount of the adhered char, part of the slag is taken into the char and the adherence becomes difficult. Further, even if the amount of adhesion increases, there is a high possibility that it will fall spontaneously, and it is possible to prevent deterioration of the heat transfer performance of the water cooling pipe due to adhesion of ash to the wall surface 103.

Next, from the upper burner to the outlet of the gasification furnace, a gas containing fine slag that easily adheres at a high temperature flows in the vicinity of the center of the furnace, and as shown in the temperature distribution in the cross section of the furnace shown in FIG. The temperature decreases as it approaches. Contrary to the temperature distribution, the C content in the char is also shown in the same figure, but in the center the fine slag that is not collected by the turning force of the lower stage passes, and as the peripheral part is closer to the center, it spouts from the upper stage. The coal is discharged in a downward flow and reacts with the high temperature gas from the lower stage to reduce the amount of carbon due to the gasification reaction, and some of the ash is melted. The proportion of unreacted carbon that has not been gasified increases as it approaches the periphery. That is, the distribution is such that the amount of carbon increases from the center toward the wall surface. The most important point in the present invention is promotion and cooling of the gasification reaction by mixing the high temperature gas containing the fine slag and the char containing a small amount of carbon and the upper stage burner generated char.

In the gasifier of the present invention, the distance from the upper burner 8 shown in FIG. 2 to the narrowed portion 16 of the produced gas outlet of the gasifier is set to be twice or more than the distance from the upper burner 8 to the slag outlet 9. There is. For this reason, as can be seen from the gas flow in Fig. 3, the high-temperature gas in the center of the gasifier tends to spread to the periphery, promoting gasification by mixing with unreacted char from the upper burner and the endothermic phenomenon that occurs at that time. This cools the gas. Regarding the cooling of the gas, radiation to the water-cooling pipe provided on the side wall should be expected, but the effect of radiation is relatively small because there are many char particles between the central part and the periphery. In order to enhance the effect of radiation, it is important not only to gasify the unreacted char but also to attach ash to the side wall to reduce the particle concentration in the gas. If the high-temperature molten ash adheres to the wall surface as it is, the amount of adhesion gradually increases.However, in the present invention, since the sufficient space is provided on the downstream side of the upper burner, the temperature of the ash can be reduced by cooling such as mixing and radiation. It is lowered and can prevent large adhesion.

Further, promotion of cooling by mixing in the furnace and elimination of a local high temperature portion, and promotion of gasification of unreacted carbon existing around the side wall and cooling due to the endothermic effect accompanied therewith, To improve the distribution shown in Fig. 4,
Recycled gas 26, which is generated gas, is jetted from top to bottom along the side wall 103 from the canopy 106 of the gas outlet throttle unit 16 shown in FIG. 2 to blow off the char adhering to the side wall 103, and the circulation shown in FIG. A basin 104 is formed. As a result, the blown-off char advances the gasification reaction (C + CO ₂ = 2CO) while being mixed with the mainstream gas.
The endothermic reaction at this time cools the mainstream high temperature gas. Further, the temperature of the produced gas 24 decreases due to the mixture of the low-temperature recycled gas 26 and char with the produced gas 24 which is the mainstream gas, and the temperature distribution of the cross section of the gasification furnace proceeds in the direction of homogenization. As a result, there is no local high temperature portion, and it is possible to prevent slag from adhering in the vicinity of the produced gas outlet narrowing portion 16.

Further, since the char containing a large amount of carbon is attached to the surface of the slag by mixing the blown-off wall-adhered char and the fine slag contained in the generated gas 24, the ratio of the carbon concentration on the slag surface to 10% or more increases. This also leads to prevention of adhesion of high temperature fine slag on the downstream side. Further, by blowing the char attached to the side wall 103, the surface of the water-cooled pipe 17B, which is a bare pipe that makes the periphery vertical, is washed, and as a result, the effect of gas radiation is increased, and the water-cooled bare pipe 17B is increased. The amount of heat transferred to Therefore, the load on the heat recovery boiler on the downstream side is reduced, and the heat recovery boiler can be made more compact than before.

Next, regarding the method for blowing the recycled gas, from the viewpoint of power reduction, the recycled gas flow rate is naturally small. However, if the flow rate is too low, the above-mentioned blow effect is weakened.

The recycled gas injection structure and injection method of this embodiment will be described. As shown in FIGS. 2, 5 and 6, a ring-shaped recycled gas header 47 is provided on the outer peripheral portion of the canopy 106 in the vicinity of the generated gas outlet narrowing portion 16, and the header is divided into eight by a partition plate 50. The injection nozzles 49 are inserted one by one from the chamber through the canopy 106 into the gasification furnace. Two recycled gas manifolds 4 are provided outside the recycled gas header 47.
Surrounded by two.

The recycled gas 26 introduced from the gas purifier is branched from the gas header 40 into two, and the branched pipe 4
Through 1 into the recycled gas manifold 42. Each manifold and the recycled gas header 47 are connected by a communication pipe 48, and electromagnetic shutoff valves 43A and 43B are provided therein. For injection of the recycled gas, as shown in FIG. 5, for example, only one pair of shutoff valves, such as shutoff valves 43A and 43B, which are opposed to each other, are opened and other valves are closed at that time. That is, the recycle gas is not blown from all nozzles at once, but is always blown from only two nozzles facing each other. Then, the shutoff valve is closed at a predetermined time interval by an electric signal, and the valve that is currently open is closed and the next set of adjacent valves is opened. In this way, each nozzle is not continuous, and the recycled gas is intermittently injected in a certain cycle.

By this method, even if the amount of recycled gas flowing into the header 40 is small, a gas having kinetic energy sufficient to obtain the above-mentioned effect flows near the blown wall surface. From the viewpoint of blowing the char attached to the wall surface, the effect is sufficiently obtained if the fluid has a large kinetic energy even if it is not continuous.

Further, one pair of facing nozzles is selected as a combination of nozzles in order to prevent the flow and temperature distribution from being asymmetrically biased in one direction.

Next, as shown in FIG. 2, a water cooling pipe 51 is arranged in the vicinity of the generated gas outlet throttle portion 16 so that its longitudinal direction is orthogonal to the gas flow of the mainstream gas 24, and the cooling water 35 is supplied.
Is introduced to generate steam 36. Since the central part of the gasification furnace has a relatively low particle concentration and the vertical radiation in the central part of the gasification furnace is more effective than the side walls, this water cooling pipe is effective in radiative cooling of the high temperature gas in the central part of the gasification furnace. Yes, it prevents slag from adhering near the narrowed portion 16 of the generated gas outlet. In addition to the cooling, most of the char scattered from the gasification chamber 70 is attached to the water cooling pipe. Therefore, the adhesion of ash to the regular water cooling pipe (not shown) provided on the downstream side of this water cooling pipe will be reduced as much as possible, and the deterioration of the heat transfer performance of the regular water cooling pipe will be suppressed to reduce the cooling effect. It also works to increase Further, it also plays a role of rectifying the swirling flow by the upper and lower burners 8 and 7 which are swirl burners from the gasification chamber (lower part of the gasification furnace) 70, and improves the heat transfer performance of the heat transfer tube on the downstream side. Can be expected. The char adhering to the water-cooled pipe removes the adhering matter by thermal shock such as temperature change due to cooling water at night.

[0053]

According to the present invention, since sufficient high temperature gas and char are mixed in the furnace, a high gasification rate can be obtained to reduce the amount of char recycling, and the cost of the gasification plant can be reduced. It greatly contributes to the reduction. Also, from the viewpoint of preventing slag adhesion, a high slag rate can be obtained, so the amount of ash scattering itself is reduced, and due to the above mixing effect, the fine slag and low carbon char are exposed to air flow before they contact the structure. Therefore, at least the high temperature one is cooled, and the slag is prevented from adhering to the gas outlet narrowing portion at the gasification chamber outlet and the downstream side thereof, which has the effect of enhancing the reliability of the gasification furnace. Further, since the amount of slag adhering is reduced, the heat transfer characteristics are improved, and the cost can be reduced by making the heat recovery boiler compact.

[Brief description of drawings]

FIG. 1 is a flow chart of coal gasification in which a gasification furnace of the present invention is incorporated.

FIG. 2 is a longitudinal sectional view of an essential part showing an embodiment of a gasification furnace.

FIG. 3 is an explanatory diagram of a gas flow inside the gasification furnace of the present invention.

FIG. 4 is a schematic view of temperature and carbon concentration distribution in a cross section of a conventional gasifier.

FIG. 5 is a plan view of a recycled gas injection structure which is a part of the gasification furnace of the present invention.

FIG. 6 is a sectional view taken along line AA.

[Explanation of symbols]

6 ... Gasification furnace, 7 ... Lower burner, 8 ... Upper burner, 10
... water tank, 16 ... gas outlet throttle, 17 ... water cooling pipe, 1
9 ... Gas outlet, 21 ... Pulverized coal, 22A ... Oxygen, 24
… Production gas, 26… Purified gas, 29… Circulation char, 32
... Refractory material, 47 ... Recycled gas header, 49 ... Injection nozzle, 51 ... Water cooling pipe, 70 ... Gasification chamber, 106 ... Canopy.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Atsushi Morihara Jun 1-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Zensuke Tamura 5-10, Jonan-cho, Hitachi-shi, Ibaraki 5 (56) Reference JP-A-59-176391 (JP, A) JP-A-7-97579 (JP, A) JP-A-61-218689 (JP, A) JP-A-61-207492 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C10J 3/46-3/56

Claims (7)

(57) [Claims] 1. A gasification furnace in which a gas outlet narrowing portion having a diameter smaller than the inner diameter of the gasification chamber is provided in the upper part of the gasification chamber, which is a pulverized coal gasification reaction region, and a slag outlet is provided in the bottom portion. , With the gasification chamber as one chamber, the burners for supplying a mixed fluid of pulverized coal and an oxidant to the gasification chamber are arranged in two stages, and each of the upper and lower burners is a virtual circle virtual in the gasification chamber. The mixed fluid is ejected in a tangential direction, and the upper part of the gasification chamber and a smaller diameter than that
Gas from the canopy that connects the gas outlet throttle
A coal gasification furnace characterized in that the produced gas emitted from the gasification furnace is introduced as a recycled gas . 2. The amount of oxidizer charged to the upper and lower burners according to claim 1, wherein the ratio of oxidant to coal in the lower burner is larger than the ratio of oxidant to total coal which is the average value of upper and lower burners. On the contrary, the upper stage is a coal gasification furnace characterized by being controlled to be smaller than the average value. 3. The circulating char discharged from the coal gasification furnace and a char burner for supplying an oxidant are arranged in the lower part of the gasification chamber according to claim 1, and the carbon content in the char is reduced. A coal gasification furnace, characterized in that the amount of oxidant input is determined according to the char component so that the amount of heat generated when burning to generate CO ₂ corresponds to the amount of heat capable of melting the ash in the char. . 4. The method according to claim 1, wherein the distance between the upper burner and the gasification furnace gas outlet narrowing portion is at least twice the distance between the upper burner and the slag outlet, and the lower burner generates the gas. From the mixing surface of the hot gas and the char generated from the coal of the upper burner, and the cooling surface due to the radiation and mixing to the side wall surface, a sufficient space area is provided in the upper burner, and the gasification is performed. A coal gasification furnace characterized in that the temperature at the gas outlet narrowing part in the upper part of the chamber is lower than the melting point of ash. 5. The coal gasification furnace according to claim 1, wherein the carbon concentration of the char discharged from the gasification furnace is 10% or more. 6. The method of claim paragraph 1, wherein the split injection nozzle for the recycle gas in a plurality, the coal gasification furnace which comprises causing the injected by switching the nozzles intermittently. 7. The cold water pipe according to claim 1 or 4 , wherein a cold water pipe is newly provided between the gasification furnace and a heat recovery boiler located on the downstream side of the gasification furnace on the downstream side in the vicinity of the gas outlet narrowing section. ,
A coal gasification furnace characterized by cooling a high temperature region in the central part of the gasification furnace with relatively low solid content by preventing uneven flow and radiating gas.