Apparatus and Method for Gasifying Solid Fuel

Abstract

Apparatus for gasifying a solid fuel that supplies a solid fuel such as coal by dry condition to a gasification furnace of an entrained-bed type is constructed so as to be able to collect the char discharged from the gasification furnace and re-supply the char to the furnace without using a lock hopper and without changing the char into slurry form. The char discharged from the gasification furnace along with produced gases 53 produced in the gasification furnace is brought into contact with water by a gas cooler 9 and collected. After being dehydrated by a dehydrator 10, the collected char is loaded into a mill 2 or a raw-coal bunker 1. For loading into the raw-coal bunker 1, the char is dried by a drying machine 14, preferably, after the dehydration. According to the present invention, a mixture of the collected char and water can be re-supplied to the gasification furnace without using a lock hopper or a dry feeder. After being dehydrated, the char preferably is further dried and then supplied to the gasification furnace. Since a great deal of moisture is not supplied to the inside of the gasification furnace, it is possible to prevent a temperature of the gasification furnace from decreasing, and thus improve gas conversion efficiency.

Description

TECHNICAL FIELD

The present invention relates to apparatus and method for loading a solid fuel such as coal into a gasification furnace by pneumatically transporting the solid fuel using a carrier gas, and then gasifying the solid fuel by causing the solid fuel to react upon a gasifying agent.

BACKGROUND ART

Some types of gasifiers gasify coal, plastic waste, and/or other solid fuels composed primarily of hydrocarbon employ various gasification furnaces such as fixed beds, fluidized beds, or entrained beds. Of these gasifiers, furnaces referred to as the entrained-bed type have the features that they can be operated at high temperatures from above 1,000° C. to 1,500° C. and that they convert solid fuels into gases at high efficiency. These gasification furnaces of the entrained-bed type suspend a loaded solid fuel in the furnace and bring the solid fuel into contact with a gasifying agent in order to gasify the solid fuel. For this reason, the entrained-bed type may also be called the spouted-bed type.

Before being loaded into a gasification furnace of the entrained-bed type, a solid fuel is usually entrained in a carrier gas or changed into the slurry formed up of the fuel and water. Of the two loading forms, the former by transporting the solid fuel pneumatically before loading it into the gasification furnace is advantageous over the latter in that since moisture is not supplied to the furnace, heat value of the produced gases will correspondingly increase.

When a gasification furnace of the entrained-bed type is used, the carbon components of char, such as unreacted-upon flammable components, are discharged together with produced gases from the gasification furnace. The char and/or other solid substances that have been discharged from the gasification furnace are usually collected and then re-supplied thereto for enhanced gasification efficiency of the solid fuel.

For a gasifier that pneumatically transports a solid fuel and loads the fuel into a gasification furnace of the entrained-bed type, the methods outlined below, for example, are usable to collect the solid substances discharged together with produced gases from the gasification furnace and then re-supply the discharged solid substances. One method is to collect discharged solid substances by using a cyclone or a filter and then returning the solid substances to the gasification furnace via a lock hopper (this method is described in Patent Document 1, for example). Other method is to collect discharged solid substances by using a scrubber and then directly supplying the solid substances in a state of slurry to the gasification furnace (this method is described in Patent Document 2, for example).

Patent Document 1: Japanese Application Patent Laid-Open Publication No. 2000-328074 (Paragraph No. 0013)

Patent Document 2: Japanese Application Patent Laid-Open Publication No. 2-003-231888 (What is Claimed is:)

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

Compared with the method of collecting solid substances by discharging the solid substances from the gasification furnace and then re-supplying the solid substances thereto in slurry form, the method of collecting solid substances by returning discharged solid substances to the gasification furnace via a lock hopper is advantageous in that the heat value of the produced gases can be increased. At the same time, however, the latter method has the problem that a lock hopper of a large capacity is required. In contrast to this, although the former method does not require a lock hopper, this method has a problem in that the heat value of the produced gases will decrease because of moisture being supplied to the gasification furnace.

An object of the present invention is to provide a gasifier that supplies an pneumatically transported solid fuel to a gasification furnace of an entrained-bed type, the gasifier being able to re-supply collected solid substances to the gasification furnace without requiring a lock hopper and without changing the solid substances into slurry.

Means for Solving the Problems

A first aspect of the present invention exists in that produced gases that have been discharged to the outside of the gasification furnace of an entrained-bed type are brought into direct contact with water, then the solid substances, such as char, that has been entrained in the produced gases is collected, and a mixture of the collected solid substances and water is dehydrated before the mixture is loaded into a solid-fuel storage device or a solid-fuel crushing mill.

In order to separate and collect from the produced gases the char and/or other solid substances discharged from the gasification furnace along with the produced gases, the gasifier of the present invention includes at least a solid-substances collecting device of a type which brings water into direct contact with the produced gases.

The gasifier of the present invention also has a dehydrator to dehydrate the mixture of the solid substances and water collected by the solid-substances collecting device. After the mixture of the collected solid substances and water has been dehydrated into gel form, the mixture is desirably dried before being loaded into the solid-fuel storage device or the solid-fuel mill. Desirably, therefore, the gasifier of the present invention further includes a drying machine.

The drying machine is not always required for loading the collected solid substances into the solid-fuel crushing mill. For loading into the solid-fuel storage device, however, the gasifier desirably has the drying machine and dries the solid substances prior to loading.

During the dehydration of the mixture of the solid substances and the water, the dehydrator discharges the water, which is then desirably returned to the water-contact collecting device for reuse. In this case, the gasifier further desirably has a water treatment device constructed so that before the water is returned to the water-contact collecting device, salt, char, and/or other substances contained in the separated water are removed therefrom. Reusing the dehydrator-separated water by returning the water to the water-contact collecting device renders the water reusable inside a gasification system and makes it possible to suppress consumption of the water and discharge of the water drained.

A second aspect of the present invention is to provide a method that includes the steps of: producing gases whose major components are hydrogen and carbon monoxide, by causing a reaction between oxygen or air and a pulverized solid fuel inside a gasification furnace; using a collector and a collecting liquid together to collect particulates contained in the produced gases discharged from the gasification furnace; and extracting a slurry mixture of the collecting liquid and the particulates from a bottom section of the collector, and then supplying the mixture to the gasification furnace. The collector preferably includes a container for introducing the produced gases threinto, means for collecting the internal particulates of the produced gases by bringing the produced gases and a liquid into contact with each other inside the container, and a stirrer for stirring the collecting liquid dwelling in a bottom section of the container.

According to this second aspect of the invention, the particulates in the produced gases are captured by the liquid and after dropping into the bottom section of the collector, dwell as a collecting liquid therein. This collecting liquid is stirred to generate slurry formed by dispersion of the particulates into the liquid. That is to say, after dropping into the container bottom, the particulates that have been captured by the liquid are dispersed into the liquid during the stirring operation, and coagulation of the particulates can thus be suppressed. In addition, if the slurry formed by the dispersion of the particulates is supplied to the inside of the furnace, the particulates will be gasified efficiently for improved carbon conversion efficiency.

A method of spraying the liquid into the produced gases, a method of applying the produced gases to a wet wall, or a method of circulating the produced gases through the liquid are usable as the means for collecting the particulates.

The gasification furnace may be a two-stage gasification furnace with a burner at both an upper stage and a lower stage, and the burners may be disposed facing in a tangent direction of the gasification furnace such that the produced gases form a swirling stream.

EFFECTS OF THE INVENTION

According to the present invention, solid substances can be re-supplied to a gasification furnace without using a lock hopper for returning the solid substances, and without changing the solid substances into slurry.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a first embodiment of a gasifier according to the present invention;

FIG. 2 is a block diagram showing a second embodiment of a gasifier according to the present invention;

FIG. 3 is a block diagram showing a third embodiment of a gasifier according to the present invention;

FIG. 4 is a block diagram showing a fourth embodiment of a gasifier according to the present invention;

FIG. 5 is a block diagram showing a fifth embodiment of a gasifier according to the present invention;

FIG. 6 is a block diagram showing a sixth embodiment of a gasifier according to the present invention;

FIG. 7 is a block diagram showing a seventh embodiment of a gasifier according to the present invention;

FIG. 8 is a block diagram showing an eighth embodiment of a gasifier according to the present invention;

FIG. 9 is a conceptual diagram showing an example of a solid-substances crushing mill used in a gasifier of the present invention;

FIG. 10 is a graph showing a relationship between char concentration in char slurry and pressure loss of pipeline transport;

FIG. 11 is a graph showing a relationship between char concentration in a water/char mixture supplied to a solid-fuel crushing mill, and cold gas efficiency that indicates gas conversion efficiency of a gasification furnace; and

FIG. 12 is a schematic of a coal gasifier, showing a further embodiment of the present invention.

LEGEND

1 . . . Raw-coal bunker, 2 . . . Mill, 8 . . . Gasification furnace, 9 . . . Gas cooler, 10 . . . Dehydrator, 13 . . . Water treatment device, 14 . . . Drying machine, 19 . . . Crushing roller, 22 . . . Dry dust remover, 23 . . . Stirring tank, 24 . . . Condenser, 51 . . . Raw coal, 52 . . . Transport pipe, 53 . . . Produced gas, 54 . . . Coarse gas, 55 . . . Cleaning water, 56 . . . Char transport pipe, 57 . . . Gel-like char, 58 . . . Gasifying agent, 59 . . . Pulverized coal, 60 . . . Pulverized coal, 61 . . . Drying air, 63 . . . Water transport pipe, 64 . . . Dry char, 66 . . . Char, 80 . . . Wet char collector, 83 . . . Stirrer, 90 . . . Pump, 99 . . . Gasification furnace.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of a gasifier adapted to partially oxidize coal by making the coal react to a gasifying agent, and produce flammable gases formed up mainly of carbon monoxide and hydrogen, will be described hereunder using the accompanying drawings. The present invention, however, is not limited to or by these embodiments.

First Embodiment

In the present embodiment, hydrating solid substances, such as char, that has been collected by a water-contact collecting device, and then loading the solid substances into a solid-fuel crushing mill after dehydrating is described using FIG. 1. FIG. 1 shows as a block diagram a schematic configuration of a gasifier according to the present invention.

In a lower section of a gasification furnace 8, the gasifier shown in FIG. 1 has a supply port for coal which is a solid fuel, and a supply port for air which serves as a gasifying agent, and in an upper section of the gasification furnace, the gasifier has a discharge port for gases which have been produced inside the furnace. The coal loaded into the gasification furnace is accepted in a bulk state of raw coal 51 by a raw-coal bunker 1 that operates as a solid-fuel storage device. The raw coal 51 that has been stored into the raw-coal bunker 1 is supplied to a mill 2 that is the solid-fuel crushing mill, at a desired rate. In addition to the raw coal supplied from the raw-coal bunker 1, a mixture of water and the solid substances such as char, is loaded in a gel-like condition into the mill 2. Loading the mixture of water and the solid substances such as char, is later described herein. The gel-like mixture is hereinafter called the gel-like char.

In the mill 2, the raw coal 51 is crushed into an average size of about 40 μm to become pulverized coal, which is then mixed with the gel-like char 57 that is fed in through a feeder. Dry air 61 is introduced into the mill 2, and the dry air serves to further remove moisture from the gel-like char 57. The pulverized coal and char that have been obtained by crushing the raw coal inside the mill 2 are transported to bag filters 4, 4a through a transport pipe 52 using air or any other appropriate gas stream, as a carrier gas. The present embodiment has the two bag filters so that the pulverized coal can be supplied at two split stages, upper and lower, to the gasification furnace.

Inside the bag filters 4, 4a, the pulverized coal is separated from the carrier gas, and then collected into normal-pressure hoppers 5, 5a. After the pulverized coal has been stored in required quantities into the normal-pressure hoppers 5, 5a, valves at lower sections of the normal-pressure hoppers 5, 5a are opened to drop the pulverized coal drops into pressure hoppers 6, 6a. After the pulverized coal inside the normal-pressure hoppers 5, 5a has been transferred to the pressure hoppers 6, 6a, the valves at the lower sections of the normal-pressure hoppers 5, 5a are closed, whereby a gas such as a nitrogen gas is then supplied and a pressure higher than an operating pressure of the gasification furnace 8 is applied to the pressure hoppers 6, 6a. When the pressurization thereof is completed and feed hoppers 7, 7a run short of the pulverized coal, the pressure hoppers 6, 6a open respective valves at bottom to drop the pulverized coal into the feed hoppers 7, 7a. After the pulverized coal inside the pressure hoppers 6, 6a has been transferred to the feed hoppers 7, 7a, the pressure hoppers 6, 6a close the respective valves located at bottom. The pulverized coal within the feed hoppers 7, 7a is entrained in the gas stream transported by the carrier gas, such as nitrogen gas, that has been supplied to sections near the bottom sections of the feed hoppers. After that, the pulverized coal is supplied as pulverized coal 59, 60 to the gasification furnace 8. The char that has been supplied to the mill 2 is also loaded into the gasification furnace together with the stream of the carrier gas. In addition, oxygen or the gasifying agent 58, such as air, are supplied to the gasification furnace 8. Since the pulverized coal is supplied at the two split stages, upper and lower, to the inside of the gasification furnace, the gasifying agent is also supplied at two split stages, upper and lower, to the gasification furnace.

Inside the gasification furnace, the pulverized coal is partially combusted using oxygen and generates heat and flammable gases such as carbon monoxide and hydrogen. Ash components contained in the pulverized coal after heat has been generated are molten and then discharged as a slag from the gasification furnace 8. Produced gases 53 that are the flammable gases are usually discharged from the gasification furnace 8 at about 1,000° C. The produced gases, after being discharged from the gasification furnace, are introduced into a gas cooler 9, the water-contact solid-substances collecting device, in which the discharged gases then come into direct contact with water and are cooled. The produced gases 53 include soot such as the char that contains carbon components which have not been gasified in the gasification furnace 8. Inside the gas cooler 9, the produced gases and water come into direct contact with each other and thus the soot is separated from the produced gases. Coarse gases 54, after being cooled by the gas cooler 9 and cleared of the soot and other dust particles, are discharged from the system. After being separated from the produced gases in the gas cooler 9, the mixture of the water and the solid substances such as char is discharged in char slurry form from the gas cooler 9, from which the mixture is carried towards the mill 2 through a char transport pipe 56. Cleaning water 55 is cyclically supplied to the gas cooler 9, and the produced gases are cleaned and cooled by the cleaning water.

Concentration of the char in the char slurry must be enhanced to ensure that the char that has been collected into the gas cooler 9 is efficiently transported to the mill 2. Too high char concentration in the char slurry, however, causes the char to be solidified within the transport pipe 56 and hence to block the pipe. The char concentration is desirably controlled below 30% by weight to ensure fluidity of the char slurry. The reason for this is described below using FIG. 10. FIG. 10 is a graph showing a relationship between the char concentration in the char slurry and pressure loss of the pipeline transport. FIG. 10 indicates that when the char concentration in the char slurry is 30% or more by weight, the pressure loss in the pipeline is very significant, that is, that since the char slurry lacks fluidity, such char concentration is not suitable for pipeline transport powered by a pump or the like. Conversely, too low char concentration in the char slurry deteriorates transport efficiency of the char. With these factors taken into account, it is desirable that the char concentration in the char slurry should be as high as possible within a range that does not degrade fluidity, and more specifically, it is desirable that the char concentration be controlled to range from 20% to 30% by weight. The amount of char occurring can be empirically estimated from operating conditions of the gasification furnace, and char slurry with a char concentration of 20%-30% by weight can be obtained by regulating a supply rate of the cleaning water 55 to the gas cooler 9 according to the particular amount of char occurring. When the char concentration in the char slurry obtained in the gas cooler 9 is controlled below 30% by weight, the char slurry can be handled as a liquid, and this makes pump-based transport and pressurization possible.

If the char slurry loaded into the mill 2 is high in moisture content, the mill will slip, failing to crush the raw coal properly. Before being loaded into the mill, therefore, the char slurry is introduced into a dehydrator 10 and dehydrated. The dehydrator 10 is desirably provided at a location as close as to the mill 2 in order to minimize a transport distance from the dehydrator to the mill. In the dehydrator 10, the char in the slurry and part of the water are separated from each other and the char slurry is condensed into gel-like char 57. The dehydrator can use a press method, a filtering method, a centrifugal separation method, or the like, depending on particular needs. In the dehydrator 10, the char concentration in the gel-like char is desirably controlled above 70% by weight. The reason for this is described below using FIG. 11. FIG. 11 is a graph showing a relationship between char concentration in a water/char mixture supplied to a solid-fuel crushing mill, and cold gas efficiency that indicates gas conversion efficiency of a gasification furnace, this relationship being based on application of the present invention to a plant. The cold gas efficiency is a relative heat value of produced gases with respect to the heat value of generated from the fuel loaded into the gasification furnace, and indicates the gas conversion efficiency of the gasification furnace.

Cold gas efficiency=(Gas production rate by weight×heat value of produced gases)/(Heat value of solid fuel×Feed rate by weight of solid fuel)

It can be seen from FIG. 11 that as the char concentration in the water/char mixture decreases, the cold gas efficiency of the plant decreases, and that as the char concentration increases, the cold gas efficiency increases. A cold gas efficiency of 80% almost equal to the cold gas efficiency of the plant in the case that the plant uses a dry scheme to re-supply char to the gasification furnace can be obtained when the char concentration in the water/char mixture increases above 70% by weight.

The gel-like char 57 that has been obtained in the dehydrator 10 is supplied to the mill 2 via a char feeder 12 without being stored within the dehydrator 10. A screw feeder, a pusher, or the like can be used as the char feeder.

An example of a solid-fuel crushing mill for use in the present embodiment is shown in FIG. 9. FIG. 9 shows a schematic configuration of the solid-fuel crushing mill. The mill has its entirety shrouded with a housing 17, and internally has a rotary table 21, crushing rollers 19, a rotary classifier 16, roller brackets 18, and other elements. The raw coal 51, after being introduced into the housing 17 via a solid-fuel supply pipe 15, drops onto the rotary table 21. The rotary table 21 includes crushing rings 20, to the surface of which the raw coal 51 next moves. The crushing rollers 19 are installed on the crushing rings 20. Rotation of the rotary table 21 inserts the raw coal 51 between the crushing rollers 19 and the crushing rings 20, and crushes the coal by grinding. A pipe with the char feeder 12 inserted therein is installed in the housing 17 in such a form as to penetrate sidewalls thereof. The gel-like char 57 is supplied to the inside of the mill via the pipe. The pipe with the inserted char feeder 12 is disposed so as to be supplied the gel-like char 57 to the surface of each crushing ring 20. Also, the above pipe is installed in places as many as there actually are the crushing rollers 19, and the gel-like char 57 is distributed to each of the pipes before being supplied to the mill. It is possible, by supplying the gel-like char 57 to the mill by branching a flow of the char according to the particular number of crushing rollers 19, to distribute uniformly the char and raw coal contained in a mixture 62 of both that has been supplied to the mill. The above also makes it possible to prevent the crushing rollers from idling/racing. Absence of nonuniformly distributed char in the mill yields uniform friction between each crushing roller 19 and each crushing ring 20, thus making vibration suppressible.

The present invention uses a water-contact collecting device to collect the soot and dust arising from the char entrained in the gases produced by the gasification furnace, so the invention makes it possible to cool the produced gases without using a large boiler-type gas cooler.

In addition, since char free of water is supplied as a char/solid fuel mixture prior to supply to the gasification furnace, it is possible to use the lock hopper or the feeder for supplying the solid fuel, and hence to dispense with a special lock hopper or feeder for the char.

Furthermore, before being supplied to the gasification furnace, the char is dehydrated or further dried, so a great deal of moisture is not supplied to the gasification furnace, and this prevents reduction in internal temperature thereof and improves the amount of heat generated by the produced gases. In rare cases, coarse particles ranging from several hundreds of micrometers (μm) to several millimeters (mm) in size are included in the char loaded, and if that is the case, the coarse particles may block a loading pipeline and/or nozzle disposed on the way to the gasification furnace. In the present embodiment, however, since char is loaded into a special mill for crushing raw materials, coarse particles of the char are also crushed, which makes it possible to avoid the above trouble of blocking the loading pipeline and/or nozzle.

Loading all collected char into the solid-fuel crushing mill, regardless of a gasification furnace load, makes it possible to construct a gasification system not requiring a large hopper or tank for storage of char whose bulk specific gravity is roughly as small as from 0.1 to 0.3.

Second Embodiment

In the present embodiment, an example of loading gel-like char into a raw-coal bunker after the char obtained in a dehydrator has been dried by a drying machine is described below using FIG. 2. FIG. 2 is a block diagram showing a schematic configuration of a gasifier according to the present embodiment. The following describes structural differences from the first embodiment, and some of features of the present embodiment.

FIG. 2 differs from FIG. 1 in that the gel-like char 57 obtained in the dehydrator 10 is introduced into the drying machine 14 via the char feeder 12 and dried in that the dry char 64 is loaded into the raw-coal bunker 1, not a mill 2.

When char that has been collected by a gas cooler 9 is loaded into the raw-coal bunker 1, if moisture is contained in the char, the coal will be wet and stick too strongly to be removable from the bunker. For this reason, the char requires prior drying. According to the present embodiment, since the collected char is supplied in a dry condition to the inside of the mill 2 via the raw-coal bunker 1, entry of moisture into the mill 2 can be suppressed for improved crushing capabilities thereof.

Third Embodiment

In the present embodiment, the gasifier shown in FIG. 1 is constructed so that after water has been separated by the dehydrator 10, the water is returned to a gas cooler 9 for reuse. A block diagram of the gasifier according to the present embodiment is shown in FIG. 3. Differences from FIG. 1 are described below.

The gasifier in FIG. 3 includes a water transport pipe 63 disposed between the dehydrator 10 and the gas cooler 9.

During dehydration of char slurry by the dehydrator 10, water is separated from the slurry by and discharged from the dehydrator 10. The water is then returned to the gas cooler 9 through the water transport pipe 63 and reused. Thus, the water that has been separated by the dehydrator 10 can be reused in the gasification system. In addition, consumption of the water and a discharge level of the water drained can be suppressed.

Fourth Embodiment

In the present embodiment, the configuration of the gasifier shown in FIG. 2 includes, as in FIG. 3, a water transport pipe 63 provided between the dehydrator 10 and the gas cooler 9. A block diagram of the gasifier of the present embodiment is shown in FIG. 4.

In the present invention, water that has been separated by the dehydrator 10 can also be reused in the gasification system. In addition, consumption of the water and a discharge level of the water drained can be suppressed.

Fifth Embodiment

In the present embodiment, the gasifier shown in FIG. 3 includes a water treatment device midway on the water transport pipe 63 that interconnects the dehydrator 10 and the gas cooler 9. A block diagram of the gasifier of the present embodiment is shown in FIG. 5.

When the gas cooler 9 is used to collect char by bringing water into direct contact with gases produced in a gasification furnace, water-soluble components included in the produced gases, such as chlorine and ammonium, are likely to dissolve in the water. While water that has been separated by the dehydrator 10 is being returned to the gas cooler 9 and recycled, the chlorine and ammonium components are condensed and then precipitated as salt. If the salt sticks to pipes and/or various devices, this is liable to corrode the pipe and the like. The water treatment device 13 is therefore provided to remove the chlorine and ammonium components, and even the char that may have been entrained. The sticking of salt to the pipe and other devices due to the chlorine and ammonium components can thus be suppressed.

The present embodiment is very effective in a gasification system which, after separating water using the dehydrator 10, returns the separated water to the gas cooler 9 and recycles the water.

Sixth Embodiment

The present embodiment is an example in which the gasifier of the configuration shown in FIG. 4 includes essentially the same type of water treatment device 13 as shown in FIG. 5, and in the present example, essentially the same advantageous effects as those of the fifth embodiment can be obtained. A block diagram of the gasifier of the present embodiment is shown in FIG. 6.

Seventh Embodiment

The present embodiment uses both a gas cooler and a dry dust remover to collect solid substances as the solid-substances collecting device in the gasifier of FIG. 1. In the embodiment, char and other solid substances that have been collected from both devices are mixed before being loaded into the mill 2 through the dehydrator. A block diagram of the gasifier of the present embodiment is shown in FIG. 7.

In the present embodiment, produced gases 53 that have been produced in the gasification furnace enter the gas cooler 9, in which the char is then removed and cooled before being introduced as coarse gases 54 into a dry dust remover 22. The char and the like are further separated within the dry dust remover 22 and discharged as high-quality coarse gases 67. The dry dust remover 22 can be, for example, a cyclone or a filter, or both thereof. The coarse gases 54, after being discharged from the gas cooler 9, are heavily laden with moisture. A transport pipe for transporting the coarse gases 54 to the dry dust remover 22, therefore, is desirably heated beforehand to prevent the moisture from condensing.

Because of its own gravity, char 66 that has been collected by the dry dust remover 22 drops into a stirring tank 23. A mixture of the char and water that have been discharged from the gas cooler 9 is also introduced into the stirring tank 23, in which both the char and the water are then mixed and stirred. A mixture of the char and water that have been mixed in the stirring tank 23 is transported as char slurry towards the mill 2 through the char transport pipe 56.

According to the present embodiment, even the 10-μm or smaller-size char that is difficult to remove can be removed from the coarse gases almost completely. Since a collecty ratio of char improves, gas conversion efficiency also improves.

The dry dust remover 22 can also be provided in the gasifier of the configuration shown in FIG. 2. Additionally, while in FIG. 7 the dry dust remover 22 is provided downstream with respect to the gas cooler 9, it is possible to provide the dry dust remover 22 upstream with respect to the gas cooler 9, and the gas cooler 9, downstream with respect to the dry dust remover 22. In this case, however, the produced gases 53 within the gasification furnace are desirably cooled before being introduced into the dry dust remover 22.

Eighth Embodiment

In the present embodiment, an example in which, before being transported towards the mill 2 through the char transport pipe 56, char slurry that has been discharged from the gas cooler 9 is condensed by a condenser is described below as the present embodiment. A block diagram of the gasifier thereof is shown in FIG. 8. The char slurry that has been discharged from the gas cooler 9 in the gasifier of FIG. 8 is enhanced in char concentration in the condenser 24 before being transported through the char transport pipe 56.

It has already been discussed in the description of the first embodiment that too high char concentration in the char slurry blocks the char in the char transport pipe and thus blocks the pipe itself. In the first embodiment, the char concentration in the char slurry is regulated by regulating the amount of cleaning water supplied to the gas cooler 9. The eighth embodiment, however, includes independent condenser 24 to raise the char concentration in the char slurry. It is possible, by enhancing the char concentration in the char slurry to 20%-30% by weight with the condenser 24 before transporting the char slurry towards the mill 2 through the char transport pipe 56, to reduce a fluid flow rate of the char slurry within the transport pipe without causing the blocking thereof, and improve transport efficiency. The present embodiment can also be applied to the gasifier of the configuration shown in any one of FIGS. 2 to 7.

Ninth Embodiment

A further example of the present invention is described as a ninth embodiment below. As shown in FIG. 12, a gasifier of the present embodiment includes a raw materials hopper 31, a gasification furnace 99, a wet dust collector 80, a pump 90, and a flow regulator 35. The raw materials hopper 31, a vertical container whose bottom has a shape of an inverted cone tip, has a feeder 36 coupled at a discharge port formed centrally in a bottom section of the container. The feeder 36 is connected through a pipe 37 to a burner (not shown) that is disposed on a lower sidewall of the gasification furnace 99. The flow regulator 35 for regulating a flow rate of an oxidizing agent is disposed midway on a pipe 38, which is connected to the pipe 37. The gasification furnace 99 is, for example, a cylindrical container coupled at a bottom central section thereof to a slag discharge pipeline 39. An upper sidewall of the gasification furnace 99 has a coupled pipe 71, through which the furnace is connected to the wet dust collector 80.

The wet dust collector 80 includes a cylindrical container 82 whose top has a shape of a dome, and nozzles 81 arranged each inside the container 82. The wet dust collector 80 also includes a stirrer 83 and guides 84. A pipe 87 for discharging gases from the container 82 to system exterior is connected a top inside the container 82. The plurality of nozzles 81 for spraying water downward are arranged in an upper section of the container 82, and the nozzles 81 are each connected to a pipe 85 provided to supply the water. A connection port for the pipe 71 is formed on a side face of the container 82, below the nozzles 81. The guides 84, each formed protrudingly, for example, from an inner wall of the container 82 towards a central section thereof and having a conical shape with an approximately circular opening in a central portion, are disposed at positions further below the connection port. Each guide 84 is inclined downward towards the opening and constructed so that water droplets drop towards the opening, for example. The stirrer 83 of a screw type is disposed horizontally below the guides 84, that is, in a bottom section of the container 82, and the stirrer 83 has a rotating shaft coupled to a driving shaft of a motor 86 provided outside the container. The container 82 further has a pipe 88 coupled to a section on a sidewall of the container, near the bottom thereof, and the pipe 88 is connected to a suction port of the pump 90. The pump 90 is coupled at a discharge port thereof to a lower sidewall section of the gasification furnace 99 via a pipe 89.

Operation of the gasifier device thus constructed is described below. The raw materials hopper 31 is stocked with, for example, coal that has been crushed into fine particle form (hereinafter, the coal is referred to simply as pulverized coal). When the feeder 36 is operated, a necessary amount of pulverized coal is delivered, then carried through the pipe 37 by pneumatic transport, for example, and loaded from each nozzle into the gasification furnace 99. At this time, the oxidizing agent (e.g., oxygen) that has been flow-regulated by the flow regulator 35 is supplied to the inside of the pipe 37 via the pipe 38.

After being loaded into the gasification furnace 99, the pulverized coal and the oxidizing agent are subjected to partial combustion and gasification of the pulverized coal are simultaneously conducted, and the pulverized coal reacts upon the oxidizing agent at a high temperature (e.g., about 1,500° C.) and under a high pressure. Flammable gases composed mainly of substances such as hydrogen and carbon monoxide are thus produced (these gases are hereinafter referred to simply as the produced gases). The produced gases include unburnt char, which is then entrained in the produced gases and moves upward while, for example, swirling inside the gasification furnace. Thus, the produced gases including the char are discharged from a discharge port of the gasification furnace 99 and introduced into the wet char collector 80 via the pipe 71. Meanwhile, inorganic substances included in the raw materials, such as ashes, sand, or glass, are changed into slag form (molten ashes), and the slag flows downward into a lower-stage internal region of the gasification furnace 99, from which the slag is then discharged from the system via the slag discharge pipeline 39.

Next, collection of the char included in the produced gases is described below. The char within the produced gases that have been introduced into the container 82 of the wet char collector 80 is captured using very fine water droplets sprayed from the plurality of nozzles 81, and the captured char flows downward. In the meantime, the produced gases arrive at a top section of the container 82 through surroundings of the nozzles 81 and are discharged from the system via the pipe 87.

The water droplets including the char drop onto the guides 84, then flow downward from the openings formed centrally therein, and dwell in a stirring section formed in the bottom section of the container 82. The char-collecting fluid that has flown downward into the stirring section is stirred by the stirrer 83, whereby the char and the water are mixed into slurry form. After this, the slurry is suctioned by the pump 90 via the pipe 88 and reloaded into the gasification furnace 99 via the pipe 89, and the char included in the slurry is gasified.

Although decreases in diameter of the water droplets used to capture the char increase a contact area and render the water droplets easier to capture, since too small water droplets may evaporate before dropping onto the guides 84, the water droplets are preferably adjusted to a diameter that allows for the above factors.

According to the embodiments described above, char particles that have a strong hydrophobic property and elude mixing with water are wet-collected by water droplets, and after dropping onto the bottom section of the container 82, the collected char particles are stirred. The char is thus dispersed in the water and coagulation of the char can be suppressed. This, in turn, prevents the char from blocking, for example, an exit and vicinity of the wet char collector 80, thus making stable char recycling possible.

In addition, for the wet char collector 80 in any one of the embodiments, unlike the wet char collector of the conventional lock hopper scheme, since an element for wet-collecting the char and an element for forming the char into slurry are integrally constructed, wet collection and the formation of slurry are simultaneously conducted and in addition to the above advantageous effects, system cost reduction coupled with simplification of plant equipment becomes possible.

Furthermore, the slurry formed by dispersion of the char is suctioned by the pump, so a riser and other sections of the supply pipeline, for example, can be prevented from becoming blocked. Re-supplying such slurry to the furnace also leads to efficient gasification of the char, improves carbon conversion efficiency, and makes manufacture of high-concentration hydrogen possible.

While a method of collecting char by spraying water into produced gases is applied to the above embodiments, the present invention is not limited to or by the embodiments and, for example, a char collection method by applying produced gases onto a wet wall or by introducing the produced gases into water may be used instead. In addition, the gasification furnace 99 in any one of the embodiments may be a single-chamber two stage gasification furnace with a burner disposed at an upper stage and lower stage of the gasification furnace 99, in which case, the burners may be oriented in a tangent direction of the gasification furnace 99 such that the produced gases form a swirling stream.

INDUSTRIAL APPLICABILITY

According to the present invention, in a gasification furnace that uses an entrained-bed type to transport a solid fuel pneumatically and supply to the gasification furnace, a char discharged from the gasification furnace can be re-supplied thereto without using a lock hopper and without changing the char into slurry form. The gasifier of the present invention is very simple in structure, so the gasifier can be applied to various such types of fuel-gas plant or equipment as: electric power-generating equipment using an internal-combustion engine, a gas turbine, or the like; a plant for manufacturing a liquefied synthetic fuel from the carbon monoxide, hydrogen, and/or other substances contained in fuel gases; an ammonium-synthesizing plant; and a plant for synthesizing a nitrogen fertilizer.

Claims

1. Apparatus for gasifying a solid fuel comprising:

a gasification furnace for gasifying a solid fuel pneumatically transported by causing a reaction thereof upon a gasifying agent;

a solid-fuel storage device for storing the solid fuel to be loaded into the gasification furnace;

a solid-fuel crushing mill for crushing the solid fuel pneumatically transported from the solid-fuel storage device before the solid fuel is loaded into the gasification furnace; and

a solid-substances collecting device for collecting a solid substances discharged from the gasification furnace along with produced gases produced therein;

wherein the solid-substances collecting device includes at least a collecting device of a type which brings the produced gases and water into direct contact with each other, and the solid-substances collecting device is adapted such that a mixture of the water and the solid substances collected by the collecting device is re-supplied at least into either the solid-fuel storage device or the solid-fuel crushing mill after dehydrating of the mixture.

2. The apparatus for gasifying a solid fuel according to claim 1, the apparatus further comprising:

a transport pipe for transporting the mixture of water and the solid substances collected by the solid-substances collecting device at least to either the solid-fuel storage device or the solid-fuel crushing mill; and a dehydrator disposed midway on the transport pipe.

3. The apparatus for gasifying a solid fuel according to claim 2, wherein the mixture dehydrated by the dehydrator so as to obtain a solid-substances concentration therein greater than 70% by weight is re-supplied to the solid-fuel crushing mill.

4. The apparatus for gasifying a solid fuel according to claim 1, the apparatus further comprising:

a transport pipe for transporting the mixture of water and the solid substances collected by the solid-substances collecting device to the solid-fuel storage device; a dehydrator and a drying machine for drying the mixture dehydrated by the dehydrator are disposed midway on the transport pipe.

5. The apparatus for gasifying a solid fuel according to claim 1, the apparatus being constructed such that:

the solid-substances collecting device includes the water-contact type of collecting device and a dry type of dust-removing device; and

the solid substances collected by the solid-substances collecting devices are mixed and then re-supplied at least to either the solid-fuel storage device or the solid-fuel crushing mill.

6. The apparatus for gasifying a solid fuel according to claim 5, the apparatus further comprising:

a stirring tank for mixing the solid substances collected by the water-contact type of collecting device and the dry type of dust-removing device.

7. The apparatus for gasifying a solid fuel according to claim 1, the apparatus further comprising:

a condenser for enhancing a concentration of the solid substances by condensing the mixture of water and the solid substances collected by the solid-substances collecting device; and

a dehydrator with a transport pipe for transporting the mixture condensed by the condenser at least to either the solid-fuel storage device or the solid-fuel crushing mill, the dehydrator being disposed midway on the transport pipe.

8. The apparatus for gasifying a solid fuel according to claim 7, wherein the mixture condensed by the condenser so as to obtain a solid-substances concentration greater than 20%-30% by weight is transported to the dehydrator through the transport pipe.

9. The apparatus for gasifying a solid fuel according to claim 1, the apparatus further comprising:

a mill as the solid-fuel crushing mill having a plurality of crushing rollers;

wherein a flow of the mixture of water and the solid substances collected by the solid-substances collecting device is branched off according to the particular number of crushing rollers, and the branched flow of the mixture is loaded into the mill.

10. The apparatus for gasifying a solid fuel according to claim 2, the apparatus further comprising:

a water transport pipe for transporting the water separated by the dehydrator to the water-contact type of solid-substances collecting device.

11. The apparatus for gasifying a solid fuel according to claim 2, the apparatus further comprising:

a water treatment device for removing salt or char by treating the water separated by the dehydrator; and a water transport pipe for transporting the water treated by the water treatment device to the water-contact type of solid-substances collecting device.

12. Apparatus for gasifying a solid fuel comprising:

a gasification furnace for gasifying a solid fuel pneumatically transported by causing a reaction thereof upon a gasifying agent;

a solid-fuel storage device for storing the solid fuel to be loaded into the gasification furnace;

a solid-fuel crushing mill for crushing the solid fuel pneumatically transported from the solid-fuel storage device before the solid fuel is loaded into the gasification furnace;

a water-contact type of solid-substances collecting device for cooling gasification furnace produced gases discharged from the gasification furnace by bringing the produced gases into direct contact with water and collecting the solid substances entrained in the produced gases;

a pipe for transporting a mixture of the water and the solid substances collected by the water-contact type of solid-substances collecting device to the solid-fuel crushing mill; and

a dehydrator for forming gel-like solid substances from the mixture transported through the pipe by dehydrating the transported mixture before the mixture is loaded into the solid-fuel crushing mill.

13. Apparatus for gasifying a solid fuel comprising:

a gasification furnace for gasifying a solid fuel pneumatically transported by causing a reaction thereof upon a gasifying agent;

a solid-fuel storage device for storing the solid fuel to be loaded into the gasification furnace;

a solid-fuel crushing mill for crushing the solid fuel pneumatically transported from the solid-fuel storage device before the solid fuel is loaded into the gasification furnace;

a water-contact type of solid-substances collecting device for cooling gasification furnace produced gases discharged from the gasification furnace by bringing the produced gases into direct contact with water and collecting the solid substances entrained in the produced gases;

a pipe for transporting a mixture of the water and the solid substances collected by the water-contact type of solid-substances collecting device to the solid-fuel crushing mill;

a dehydrator for forming gel-like solid substances from the mixture transported through the pipe by dehydrating the transported mixture before the mixture is loaded into the solid-fuel crushing mill; and

a drying machine for drying the gel-like solid substances obtained by the dehydrator.

14. A method for gasifying a solid fuel comprising the steps of:

a gasifying process for gasifying a solid fuel pneumatically transported by causing a reaction thereof upon a gasifying agent;

a collecting process for collecting solid substances along with gasification furnace produced gases discharged from the gasification furnace, by bringing the produced gases into direct contact with water;

a dehydrating process for dehydrating a mixture of the water and solid substances collected in the collecting process; and

a transporting process for transporting the mixture whose solid-substances concentration has been enhanced in the dehydrating process at least into either a solid-fuel storage device for storing the solid fuel or a solid-fuel crushing mill for crushing the solid fuel.

15. The method for gasifying a solid fuel according to claim 14, wherein, the transporting process is transporting the mixture dehydrated in the dehydrating process to the solid-fuel crushing mill.

16. The method for gasifying a solid fuel according to claim 14, wherein, the drying process is drying the mixture dehydrated in the dehydrating process; and

the transporting process is transporting the mixture dried in the drying process to the solid-fuel storage device.

17. The method for gasifying a solid fuel according to claim 14, wherein, regardless of a load of the gasification furnace, an overall amount of solid substances collected in the collecting process is loaded at least into either the solid-fuel storage device or the solid-fuel crushing mill,

18. Apparatus for gasifying a solid fuel, comprising:

a gasification furnace for producing produced gases with main components of hydrogen and carbon monoxide by causing oxygen or air to react upon a pulverized solid fuel; and

a particle collector for collecting particulates contained in the produced gases discharged from the gasification furnace;

wherein the particle collector includes a container for introducing the produced gases thereinto, means for collecting particulates in the produced gases by bringing the produced gases and liquid into contact with each other in the container, a stirrer for stirring collection liquid dwelling in a bottom section of the container, and

a pump for extracting slurry formed up of the collection liquid and the particulates from a bottom section of the collector and supplying the slurry to an interior of the gasification furnace.

19. The apparatus for gasifying a solid fuel according to claim 18, wherein the gasification furnace is a two stage gasification furnace with a burner disposed at an upper stage and lower stage thereof, the burners being oriented in a tangent direction of the gasification furnace such that the produced gases form a swirling stream.