A Burning Apparatus

Abstract

A burning apparatus for wet substances to be burnt up such as dewatered slurry from a filtering apparatus wherein a fluidized bed of particles unable to be burnt is formed in a series or several series of drying chamber and burning chamber or these two chambers and heating chamber therebetween, said fluidized bed is circulated continuously through said chambers in a direction from the drying chamber toward the burning chamber, and powder or particlelike substances to be burnt up are fed into the drying chamber and are carried with said fluidized bed so that the substances are dried in the drying chamber and then are burnt up in the burning chamber. At least one of the communicating passages between the drying chamber and the burning chamber is so designed that it opens to one chamber at a higher level then to the other, so that the particles of the fluidized bed form a particle pile in the latter chamber, which pile closes said passage so as to preserve a pressure differential between the chambers and facilitate circulation of the fluidized bed.

Description

DISCLOSURE

This invention relates to novel burning apparatus and more particularly to burning apparatus for wet substances possibly burnt up and possibly crushed into powder or particle such as dewatered slurry still containing a small amount of water from a filtering apparatus.

It is well known that, when particles are placed on a perforated plate and air or another gas is supplied from under the plate with a certain rate, said particle is generally floated and mixed homogeneously with the air or the gas to form a layer which is ready to flow transversely, that is, so-called a fluidized bed. When such fluidized bed is formed with particles unable to be burnt such as sand in a burning furnace and substances to be burnt up such as filtered and dewatered slurry are thrown into said fluidized bed with maintaining the temperature of the bed high, said substances can be burnt up continuously with exhausting ashes together while exhausted gas.

However, the burning method and apparatus thereof utilizing a fluidized bed according to the prior art are so designed that substances to be burnt are fed directly into a fluidized bed of sand and the like formed in a burning furnace, so that extremely large quantities of heat is always required so as to maintain the temperature of the bed high enough to dry and burn up water containing substances such as slurry cakes containing about 70 percent of water immediately after filtration in a furnace. However, to maintain the temperature of the fluidized bed in a furnace so high is very uneconomical from the point of heat efficiency and also to burn up wet substances under such conditions is still very difficult.

Accordingly, it is the primary object of the present invention to provide burning apparatus for wet substances by utilizing a fluidized bed of particles unable to be burnt wherein the aforementioned defects are fully avoided so as to improve heat efficiency and to maintain the temperature of the fluidized bed in the furnace high with ease so that the substances to be burnt up can be burnt rapidly and fully.

The above object is achieved according to the present invention by forming a fluidized bed of particles unable to be burnt in a series or several series of drying chamber and burning chamber or drying chamber, heating chamber and burning chamber which chambers are communicated so as to allow the flowing of the fluidized bed through the chambers, and said fluidized bed being flowed and circulated continuously from the drying chambers toward the burning chambers, substances to be burnt up being fed into said drying chamber and being carried with said fluidized bed so that said substances are dried in said drying chamber, then are heated in said heating chamber, and finally are burnt up in said burning chamber during they are circulated through the chambers. Ashes produced in the burning chamber are exhausted out of said chamber with exhausted gas and the fluidized bed is recircled into the drying chamber.

Still a further object of the present invention is to provide novel means for controlling the pressure differential between the respective chambers which produces circulation of the fluidized bed. That is, the apparatus of the present invention is constructed such that at least one communicating passage between adjacent chambers is designed so that it opens to one chamber at a higher level than to the other chamber, with the floor adjacent said opening to the other chamber being free from pores, or the like so that the particles will accumulate adjacent said opening to block same.

The present invention and its advantages will become more readily apparent as the specification is considered in conjunction with the accompanying drawings in which:

FIG. 1 is a transverse sectional view of one embodiment of the burning apparatus according to the present invention taken along line 1--1 of FIG. 2;

FIG. 2 is a side view of the apparatus shown in FIG. 1 vertically sectioned and developed along line II-0 -II of FIG. 1;

FIG. 3 is a developed view along the cylinder circumference shown with imagined line III in FIG. 1;

FIG. 4 is a developed view of an another embodiment of the burning apparatus according to the present invention showing the similar part to the one shown in FIG. 3;

FIG. 5 is a developed view of the prior art means employed in providing for communication between the burning chamber and the drying chamber while maintaining the desired pressure differential.

Referring now to the drawings, in which like reference numerals designate like parts throughout the several views thereof, there is shown a preferred embodiment of the burning apparatus according to the present invention in FIGS. 1, 2 and 3. The burning apparatus comprises a drying chamber 6 and a burning chamber 8 which chambers are formed by dividing the annular space formed with a pair of concentrically arranged cylindrical sidewalls 1 and 2 with dividing wall members 3 and 5. The bottom plate members 9 and 11 of respective chambers 6 and 8 are substantially in the same horizontal plane and a number of pores 12 are perforated through said plate members 9 and 11 for injecting air into the chambers from under said members so as to form a fluidized bed A of powders or particles having a suitable height in each chamber 6 and 8 with air or another gas injected and supplied through said pores 12.

In the apparatus according to the present invention, the fluidized bed A is formed in the drying chamber 6 and the burning chamber 8 above the bottom plate members 9 and 11 respectively with particles unable to be burnt such as sand or particles of iron with small grain sizes and said bed A is moved from the drying chamber 6 into the burning chamber 8 and also from burning chamber 8 into the drying chamber 6 so as to circulate the fluidized bed A in the clockwise direction in the apparatus shown in FIG. 1. For communicating the chambers 6 and 8 so as to allow the above-mentioned circulation of the fluidized bed A, the dividing wall member 5 is provided with a communicating window 13 at its lowermost portion and the dividing wall member 3 is provided with a passage 14 which is equipped with suitable means for moving the bed A from the burning chamber 8 into the drying chamber 6. The fluidized bed A is moved from the drying chamber 6 into the burning chamber 8 through said communicating window 13 by keeping the pressure in the former chamber 6 higher than that in the latter chamber 8, as detailed after. Therefore, gas streaming from the chamber 6 into the chamber 8 through the passage 14 due to the pressure difference between these chambers must always be prevented with suitable means. For achieving this purpose, in the apparatus shown in FIGS. 1, 2 and 3, said passage 14 is opened in the burning chamber 8 at the opening 14 a with a definite level and is opened in the drying chamber 6 at the opening 14 b positioned lower than said opening 14 a, and the bottom plate member 9 is remained unperforated in a definite area 9 a near the downside of the opening 14 b , so that the sand in the fluidized bed A formed in the burning chamber 8 streams down through the passage 14 from the opening 14 a toward the opening 14 b and piles up on the unperforated area 9 a of the plate member 9 so as the opening 14 b to be always closed with the pile of sand B. Said sandpile is fluidized at its front portion with the injected air through the pores 12 to form the fluidized bed A as the volume of the pile B increases. Thus, the sandpile B always closes the opening 14 b while maintaining its volume constant and also is always fluidized at its front portion, so that the fluidized bed A in the burning chamber 8 is moved into the drying chamber 6 after being changed once into the sandpile B.

Under the bottom plate member 9 of the drying chamber 6, there are provided lower and upper chambers 15 and 16. Hot air introduced into the lower chamber 15 is supplied into the upper chamber 16 through suitable numbers of inlets 17 provided in the dividing wall between the chambers 15 and 16. The reference character 18 designates dampers which are provided for each of the inlets 17 for regulating the flow rate of the hot air supplied from the lower chamber 15 into the upper chamber 16. Said hot air is introduced into the lower chamber 15 through a conduit 19 from a heating apparatus for the air (not shown in the drawings). Similarly, there are provided lower and upper chambers 25 and 26 under the bottom plate member 11 of the burning chamber 8 and hot air introduced into the lower chamber 25 through a conduit 29 is supplied into the upper chamber 26 through the inlets 27 provided with dampers 28 for regulating the flow rate of the air and then is supplied into the burning chamber 8 through the aforementioned pores 12 in the plate member 11. Dampers 32 are provided in gas-exhausting ducts 30 which are connected to the uppermost portion of the drying chamber 6. Thus, the pressure in the drying chamber 6 can be controlled by regulating the rate of the hot air supplied into the chamber 6 with dampers 18 and the rate of the exhausted gas out of the chamber 6 through the ducts 30 with the dampers 32. Similarly, there is provided a damper 36 in gas-exhausting ducts 35 connected to the uppermost portion of the burning chamber 8, so that the pressure in the burning chamber 8 can be controlled by regulating the rate of the hot air supplied into the chamber 8 with the damper 28 and the rate of exhausted gas out of the chamber 8 through the duct 35 with the damper 36 in relation to each damper.

The apparatus is provided with a screw feeder 37 disposed in an opening 38 which opens into the drying chamber 6 at a suitable level. Under the opening 38 there is provided in the drying chamber 6 a crusher 39 for crushing wet substances to be burnt up fed with the feeder 37. Said crusher 39 comprises a number of crushing rods 41 fixedly mounted on a rotating shaft 40 which is rotated with an electric motor 42, so that the substances fed into the chamber 6 above the shaft 40 are crushed finely with the rods 41 into powders or particles and are scattered in the chamber 6 without forming lumps. In the burning chamber 8, there is provided a burner 43 at a suitable position. Further, the inner wall of the burning chamber 8 is covered with fireproof material 44 such as firebrick. To the gas-exhausting duct 35, there is connected a cyclon 45 for recovering ashes which are exhausted out of the chamber 8 together with exhausted gas. 46 designates an exhausted gas recovering conduit which is connected to the duct 35.

When the burning-up of wet substances to be burnt up is intended, suitable amounts of particles unable to be burnt such as particles of sand are fed into the drying chamber 6 and hot air is supplied from under the bottom plate members 9 and 11 into the drying chamber 6 and the burning chamber 8 through pores 12 with a suitable pressure of injection to form a fluidized sand bed A. In this case, the dampers 17, 28, 32 and 36 are suitably adjusted so as to regulate the rates of the hot air supplied into the chambers 6 and 8 from under the bottom plate members 9 and 11 and the rates of the exhausted air out of the chambers 6 and 8 through the ducts 30 and 35 so that the air pressure in the drying chamber 6 is maintained somewhat higher, for example 10 -25 mm. waterhead, than the air pressure in the burning chamber 8. Owing to the above-stated air pressure difference in the chambers 6 and 8, the fluidized sand bed A flows continuously from the drying chamber 6 toward the burning chamber 8 through the communicating window 13. The fluidized sand bed A in the burning chamber 8 is passed through the passage 14 in the dividing wall 3, is changed once into a sandpile B which closes one opening 14 b of the passage 14, and then is fluidized in the drying chamber 6 continuously. Thus, the fluidized sand bed A is circulated through the drying chamber 6 and the burning chamber 8 continuously in one direction.

Therefore, when substances to be burnt up containing about 70 percent in weight of water such as slurry cakes from a filtering apparatus are fed continuously into the drying chamber 6 with the feeder 37, said substances are crushed into fine particles or powders and are scattered in the chamber 6 by the crusher 39 so that the substances in the form of powders or particles are mixed with the fluidized sand bed A and are carried with said bed A. Said substances flow toward the burning chamber 8 and at the same time are dried with the aid of the heated sand bed and the hot air injected through the pores 12 in the bottom plate member 9. Thus, the substances to be burnt up are transferred continuously into the burning chamber 8 through the communicating window 13 with the aid of the bed A after having been dried sufficiently and having been heated to a considerably high temperature. As soon as the substances enter the burning chamber 8, they are heated to a temperature above the firing one of said substances or are fired with the burner 43 arranged in the chamber 8 so that they are burnt up fully.

Ashes produced during the burning-up of the substances in the burning chamber 8 are exhausted out of said chamber 8 together with exhausted gas through the exhausting duct 35 and are recovered with the cyclon 45. The heat content of the exhausted gas from the exhausting ducts 30 is recovered by means of a suitable heat exchanger and is used for preheating the air supplied into the chambers 6 and 8. Because the exhausted gas from the conduit 46 contains no moisture, said gas may be supplied directly into the conduit 19 for supplying hot air into the drying chamber 6. Thus, the fluidized sand bed A containing no substances to be burnt up is returned into the drying chamber 6 from the burning chamber 8 through the passage 14.

FIG. 4 shows an another preferred embodiment of the burning apparatus according to the present invention. In this embodiment, there is provided between the drying chamber 6 and the burning chamber 8 a heating chamber 7 which heats the fluidized bed A of sand and substances to be burnt up to a sufficiently high temperature for making easy the burning-up of said substances in the burning chamber 8. Under the perforated bottom plate member 10 of the heating chamber 7, there are provided a lower chamber 20 and an upper chamber 21. The hot air introduced into the lower chamber 20 through a conduit 24 enters the upper chamber 21 through an inlet 22 which is equipped with a damper 23 and then is injected into the heating chamber 7 through the pores in the bottom plate member 10 for forming a fluidized sand bed A in the chamber 7, and exhausted gas leaves the chamber at the top through a gas-exhausting duct 33 equipped with a damper 34. The pressure in the heating chamber 7 can be regulated by regulating the rate of the hot gas supplied into the chamber 7 with the damper 23 and the rate of the exhausted gas leaving the chamber 7 with the damper 34. The dividing wall member 4 between the drying chamber 6 and the chamber 7 is provided with a communicating window 13 a at the lowermost portion and also the dividing wall member 5 between the chamber 7 and the burning chamber 8 is provided with a communicating window 13 b at the lowermost portion, respectively. In this case, the air pressure in the chamber 7 is kept somewhat lower than the one in the chamber 6 and further the air pressure in the chamber 8 is kept somewhat lower than the one in the chamber 7, so that the fluidized bed A is moved continuously from the drying chamber 6 toward the heating chamber 7 and then from here toward the burning chamber 8. Said fluidized bed A is recirculated from the burning chamber 8 into the drying chamber 6 with the means detailed before relating to the first embodiment shown in FIGS. 1, 2 and 3.

Therefore, in the burning apparatus shown in FIG. 4, substances to be burnt up such as slurry cakes are heated up to the burning temperature with the hot air from under the bottom plate member 11 to be burnt up very rapidly immediately after they enter the burning chamber 8 from the heating chamber 7. In this case, exhausted gas from the ducts 33 and 35 contains no moisture so that said gas may be supplied into the conduit 19 after having removed ashes therein.

The advantage of the apparatus according to this embodiment consists in the fact that heat required for drying the substances to be burnt up is very little because the temperature in the drying chamber 6 may be maintained at such that the substances are dried most effectively and there is no need for preheating the substances up to a temperature near the burning one of said substances, and the temperature of the substances to be burnt up can be raised to the one near their burning temperature very easily in the heating chamber 7.

One of the particular advantages of the present invention resides in the fact that the fluidized bed of the substances to be burnt up can be formed very smoothly and said bed of the substances is dried and heated in the drying chamber 6 and the heating chamber 7 very rapidly and sufficiently, because the fluidized bed of the particles unable to be burnt is preformed in the drying chamber 6 and the burning chamber 8 or said two chambers and the heating chamber 7 therebetween so as to circulate through the chambers and then the fine particles of the substances to be burnt up are mixed to the fluidized bed so as to be carried with said bed. As the substances to be burnt up are fully fluidized and then are carried into the burning chamber 8 in such a state that they can be burnt up immediately, said substances are fired immediately and are burnt up fully in said burning chamber 8. Another important advantage of the present invention consists in the fact that calorie required for maintaining the temperature in the burning chamber 8 is little and the fluidized bed of the particles unable to be burnt circulated through the chambers is returned without any loss of heat content so that the drying and heating of the substances to be burnt up in the drying chamber 6 are performed very effectively.

While two preferred embodiments of the invention have been illustrated by way of example in the drawings and particularly described, the invention is in no way limited to the embodiments shown. Moreover, the features of the two embodiments shown in the drawings are mutually interchangeable in so far as they are compatible.

That is, by way of example, though only a series of the drying chamber 6 and the burning chamber 8 or said two chambers and the heating chamber 7 therebetween are provided in the apparatuses according to hereinbefore illustrated two embodiments, plural series of such chambers may be provided and the fluidized bed may be circulated through such several series of the chambers. Further, in the above embodiments, the transfer of the fluidized sand bed A from the burning chamber 8 having a lower pressure into the drying chamber 6 having a higher pressure is performed by changing said bed A once into the sandpile B and the transfers of said fluidized bed between the other two adjacent chambers are performed by utilizing the gas pressure differences therebetween, but each of such transferring means may be applied to the transfer of the fluidized bed between optional two adjacent chambers. The primary advantage of the burning apparatus according to the present invention is provided by the fact that at least one of the communicating passages between the burning chamber 8 and the drying chamber 6 is so designed that it opens to chamber 8 at a higher level than to chamber 6 so that the opening of the passage 14 is always closed by the sandpile B, the particles of which form the fluidized bed. That is, the closing of passage 14 by the particles of sand pile B guarantees the maintenance of the pressure differential between the two chambers and the smooth transfer of particles from the burning chamber 8 into the drying chamber 6 without a backflow of the chamber with the higher pressure into the chamber with the lower pressure. It is known in the art to employ driven transferring means for the fluidized bed as is shown in FIG. 5. In this regard, an impeller or rotary valve 48 is provided in a passage 47 formed in the wall dividing burning chamber 8 and the drying chamber 6. This arrangement suffers from several disadvantages in that the impeller or rotary valve 48 is exposed to the high temperature of the burning chamber and it must be constructed so as to operate in the presence of these high temperatures and thus is extremely expensive. The present apparatus on the other hand, employs no moving parts or the like and thus does not suffer from the deficiencies of the prior art constructions.

Claims

What is claimed is:

1. Burning apparatus for wet powder or particlelike substances comprising: at least one series of annularly arranged chambers including a drying chamber, a heating chamber and a burning chamber, each said chamber including a perforated bottom plate member means for providing a horizontally flowing fluidized bed of material by the injection of a gas stream through the perforations in said bottom plate member, communicating passages for said flowing fluidized bed being provided in dividing walls between adjacent chambers, means for continuously circulating said fluidized bed horizontally through said chambers, means for feeding the substances to be burned into said drying chamber, and means for expelling exhaust gases from said burning chamber, whereby said substances are carried with said fluidized bed so that the substances are dried, heated and subsequently burned up, with the ashes thus produced being expelled with said exhaust gases.

2. Apparatus as defined in claim 1 wherein at least one of said communicating passages between adjacent chambers includes means constructed such that it opens to one chamber at a higher level than to the other chamber, with said bottom plate member being free from perforations or the like below the opening of said passage to said other chamber, such that the material of such fluidized bed can accumulate to block said passage and thereby maintain a pressure differential within said chambers.

3. Burning apparatus for wet powder or particlelike substances comprising at least one series of annularly arranged chambers, including a drying chamber and a burning chamber, said chamber including a perforated bottom plate member, means for providing a horizontally flowing fluidized bed of material by the injection of a gas stream through the perforations of said bottom plate member, dividing walls disposed between adjacent chambers and having communicating passages for the fluidized bed formed therein, and means for feeding the substance to be burned into said drying chamber, the improvement wherein at least one of said communicating passages between adjacent chambers includes means constructed such that it opens to one chamber at a higher level than to the other chamber, and the bottom plate member of said other chamber being free from perforations or the like, through which the gas stream is injected, in the area immediately adjacent said passage, such that the material of said fluidized bed can accumulate to block said passage and maintain a pressure differential between said chambers.

4. Apparatus as defined in claim 3, further including a heating chamber disposed intermediate said drying and burning chambers.

5. The burning apparatus according to claim 3 wherein gas pressure regulating means are provided in each of the chambers.

6. The burning apparatus according to claim 5 wherein the passage which opens in one chamber at a higher level than in the other chamber is provided in the dividing wall between the burning chamber the gas pressure of which is regulated so as to maintain a gas pressure lower than in the drying chamber and said drying chamber, and the particles for forming the fluidized bed are transferred from the burning chamber into the drying chamber with a higher gas pressure through the aforementioned passage.