Circulating mass dryer and method for drying wet sludge

Abstract

The invention relates to a circulating mass dryer for drying wet sludge. According to the invention, the circulating mass dryer includes two adjacent circulating mass systems in heat exchange communication with one another, wherein the first circulating mass system is a sludge drying side and the second circulating mass system is a heat releasing side, and the first and the second circulating mass system each comprises at least one elongated riser (3, 16), and the riser (3) of the first circulating mass system and the riser (16) of the second circulating mass system are adjacent in such a way that a common heat exchange surface is formed therebetween. In addition, the invention relates to a corresponding method.

Claims

1. A circulating mass dryer for drying wet sludge, the dryer comprising: a first circulating mass system and a second circulating mass system in heat exchange communication with one another, the first circulating mass system being a sludge drying side comprising: a first elongated riser with a sludge inlet port, a first fluidization material port, and a gas feeding port; and a return channel in fluid communication with the first riser; and the second circulating mass system being a heat releasing side comprising: a second elongated riser with a second fluidization material port, and a heat releasing material feeding port; the first elongated riser of the first circulating mass system and the second elongated riser of the second circulating mass system being adjacent and separated by a heat exchange surface therebetween.

2. The dryer according to claim 1, wherein the first circulating mass system further comprises a fluidization chamber and a dried sludge discharge port for discharging dried sludge from the dryer.

3. The dryer according to claim 1, wherein the first circulating mass system includes a first separator part for separating a mixture formed by dried sludge and fluidization material.

4. The dryer according to claim 3, wherein the first separator part comprises a separator arrangement including a substantially vertical separator inlet channel, a flow guide, a substantially horizontal separator chamber, a substantially horizontal central tube and a conical part of the first separator part.

5. The dryer according to claim 1, wherein the second circulating mass system further comprises a fluidization chamber and a fluidization material outlet for discharging the fluidization material from the dryer.

6. The dryer according to claim 1, wherein the second circulating mass system includes a second separator part for separating a heat releasing material and fluidization material from one another.

7. The dryer according to claim 6, wherein the second separator part comprises a separator arrangement including a substantially vertical separator inlet channel, a flow guide, a substantially horizontal separator chamber and a substantially horizontal central tube and a conical part of the second separator part.

8. The dryer according to claim 1, wherein the second circulating mass system further comprises a fluidization chamber, a second separator part, a second return channel, and a regulating device fitted in the return channel for regulating fluidization material flow in the return channel.

9. The dryer according to claim 1, wherein the heat releasing material feeding port is constructed to feed hot gas into the second elongated riser for use as a heat releasing material.

10. The dryer according to claim 9, wherein the hot gas is a flue gas.

11. The dryer according to claim 1, wherein the first and the second circulating mass system form a tubular heat exchanger, wherein the first circulating mass system is provided on a tube side of the heat exchanger and the second circulating mass system is provided on a jacket side of the heat exchanger.

12. A method for drying wet sludge in a circulating mass dryer comprising a first circulating mass system and a second circulating mass system in heat exchange communication with one another, wherein the first circulating mass system is a sludge drying side comprising a first elongated riser, a sludge inlet port, a first fluidization material port, and a gas feeding port, and a return channel in fluid communication with the first riser, wherein the second circulating mass system is a heat releasing side comprising a second elongated riser with a second fluidization material port, and a heat releasing material feeding port, and wherein the riser of the first circulating mass system and the riser of the second circulating mass system are adjacent in such a way that a common heat exchange surface is formed therebetween, the method comprising: feeding wet sludge, a first fluidization material, and gas to the first circulating mass system; and feeding heat releasing material and a second fluidization material to the second circulating mass system.

13. The method according to claim 12, wherein the first fluidization material is fed through the first fluidization material port, the wet sludge is fed through the sludge inlet port and the gas is fed through the gas feeding port to a fluidization chamber of the first circulating mass system, the wet sludge is conveyed upwards together with the fluidization material and the gas while being dried in at least one elongated first riser, the first fluidization material and dried sludge are returned by the return channel to the first fluidization chamber and dried sludge is discharged through a dried sludge discharge port from the drier.

14. The method according to claim 12 further comprising separating a mixture formed by dried sludge and fluidization material by a first separator part in the first circulating mass system.

15. The method according to claim 12, wherein the second fluidization material is fed through the second fluidization material port and the heat releasing material is fed through the heat releasing material feeding port to a fluidization chamber of the second circulating mass system, the method further comprising fluidizing the heat releasing material upwards together with the fluidization material in the second elongated riser, and returning the second fluidization material by a second set of return channels to the second fluidization chamber and discharging the second fluidization material as needed through a fluidization material outlet from the drier.

16. The method according to claim 15, wherein the heat releasing material is separated from fluidization material by a second separator part in the second circulating mass system.

17. The method according to claim 12, further comprising regulating flow of the second fluidization material in a return channel of the second circulating mass system with a regulating device fitted in the return channel.

18. The method according to claim 12, wherein hot gas is used as the heat releasing material.

19. The method according to claim 18, wherein the hot gas used is a flue gas.

20. The method according to claim 12, wherein the heat releasing material comprises a gas having a vertical free surface speed from 0.5 to 2 m/s in the second fluidization chamber of the second circulating mass system.

21. The method according to claim 12, wherein each of the first and second circulating mass systems comprise a separator part, and wherein gas arriving at the separator part has a vertical free surface speed from 5 to 15 m/s.

Description

LIST OF FIGURES

(1) FIG. 1 illustrates one circulating mass dryer according to the invention as a sectional view from a first side,

(2) FIG. 2 illustrates the circulating mass dryer according to FIG. 1 as a sectional view from a second side which is perpendicular to the first side, and

(3) FIG. 3 illustrates the circulating mass dryer according to FIG. 1 as a horizontal sectional view.

DETAILED DESCRIPTION OF THE INVENTION

(4) The invention will be described below by way of detailed embodiment examples with reference to the accompanying figures.

Example 1

(5) FIG. 1, 2, 3 illustrate one embodiment of the dryer based on two circulating mass systems according to the invention. FIGS. 1 and 2 illustrate a side view of the dryer according to the invention in cross-section and FIG. 3 illustrates the dryer in a horizontal cross-section. The drying process is carried out in a first circulating mass system including a fluidization gas inlet connection (31) and a gas distribution grate (1) with distribution nozzles for distributing the fluidization gas to the fluidization chamber (2) of the first circulating mass system, to which fluidization chamber a separate fluidization material feed connection (12) and a feed connection (13) for the sludge material to be dried as well as a dried sludge outlet connection (14) are connected. From the fluidization chamber (2), the suspension formed by fluidization gas, sludge material to be dried and fluidization material rises in first risers (3), which are elongated vertically disposed tubular risers, to an overlying upper chamber (4).

(6) The upper chamber (4) is connected to the separating cyclone of a first separator part for separating the mixture formed by dried sludge and fluidization material from the rest of the suspension with gas. The first separating cyclone includes a substantially vertical separator inlet channel (5), a flow guide (6), a substantially horizontal separator chamber (7), a substantially horizontal central tube (8) and a conical section (9) of the separator. The inlet end of the vertical, cross-sectionally rectangular separator inlet channel (5) of the separator cyclone is fitted in the upper chamber (4). The longer side of the horizontal cross-section of the separator inlet channel (5) is most suitably more than two times the length of the shorter side. To intensify the vortex that is formed in the substantially horizontal separator chamber (7), a flow guide (6) is fitted at the outlet end of the inlet channel (5). The advantage of this separator arrangement is that most of the solid material is gravitationally separated even before the separator chamber (7), whereto only dusty solid material is passed, by virtue of which the pressure loss and wearing of the separating cyclone are minimized. Said dust is concentrated on the wall of the separator chamber (7) by the effect of the vortex that is formed in the separator chamber (7) and the concentrated dust flow is gravitationally directed to the conical part (9) of the separator with the rest of the solid material. The gas that contains only a small amount of fine solid material exits through the horizontal central tube (8). The solid material directed to the conical part (9) is gravitationally directed to the upper end of a set of return channels (10,11) fitted at the bottom end of the cone. The mixture formed by solid fluidization material and dried sludge is returned to the fluidization chamber (2) of the first circulating mass system through the return channel (10) and the lower connection (11) of the return channel. The lower connection (11) of the return channel is fitted to connect the return channel (10) to the fluidization chamber (2).

(7) What has been stated above concerning the operation of the circulating mass system of the dryer side, i.e. the first circulating mass system, is also mostly applicable to the heat releasing gas circulating mass system, i.e. the second circulating mass system. The second circulating mass system includes heat releasing gas feeding means (15). The gas feeding means (15) include a gas delivery connection and means for distributing the gas, e.g. a gas distribution grate and distribution nozzles through which the heat releasing gas is distributed to the fluidization chamber (25) of the second circulating mass system. The horizontal cross-sectional surface of the fluidization chamber (25) is so dimensioned that the vertical free surface speed of the gas as calculated according to the free cross-sectional surface most suitably ranges from 0.5 to 2 m/s. Most suitably, the means for distributing the gas are formed by pipes with spray orifices at the bottom. In addition, a fluidization material feed connection (26) and outlet connection (27) are connected to the fluidization chamber (25).

(8) From the fluidization chamber (25) of the second circulating mass system, the suspension formed by heat releasing gas and fluidization material rises in a second elongated riser (16), in this connection a jacket surrounding the first risers (3), to the top part of the dryer. An opening (17) is fitted at the top part of the dryer for conveying the suspension formed by heat releasing gas and fluidization material to the separator cyclone of a second separator part for separating the heat releasing gas and fluidization material from one another. The second separator cyclone includes a substantially vertical separator inlet channel (18), a flow guide (19), a substantially horizontal separator chamber (191), a substantially horizontal central tube (20) and a conical part (21) of the separator. The horizontal section of the separator inlet channel (18) is rectangular. The free cross-sectional surface of the second riser, i.e. jacket (16), is so dimensioned that the vertical free surface speed of gas as calculated according to it most suitably ranges from 5 to 15 m/s, preferably as the gas arrives at the separator part. The longer side of the horizontal cross section of the separator inlet channel (18) is most suitably more than two times the length of the shorter side. To intensify the vortex formed in the substantially horizontal separator chamber (191), a flow guide (19) is fitted at the bottom end of the inlet channel (18). The free cross-sectional surface of the inlet channel (18) is so dimensioned that the speed of gas as calculated according to it most suitably ranges from 5 to 15 m/s. More than 99% of the solid fluidization material is thus gravitationally separated even before the separator chamber (191), whereto only a small portion of the solid fluidization material is passed. Said fine fluidization material is concentrated on the wall of the separator chamber (191) by the effect of the vortex that is formed in the separator chamber (191) and is gravitationally directed to the conical part (21) of the separator. The gas exits through the central tube (20). The fluidization material directed to the conical part (21) of the separator is gravitationally directed to the top end of the set of return channels (22,23,24) fitted at the bottom end of the cone. The fluidization material moves through a return channel (22) to a circulating mass regulating device (23) fitted at the bottom thereof and therefrom through a fluidization material opening (24) to the fluidization chamber (25) of the second circulating mass system.

(9) The fluidization material flow that passes through the return channel (22) of the second circulating mass system is controlled and regulated by means of the regulating device (23) as a set point for the temperature of the fluidized bed which, depending on the material to be dried, most suitably ranges from 150 to 450 C., in the fluidization chamber (25). While the circulating fluidization material flow keeps the temperature of the fluidized bed at the desired set point, it also keeps the jacket side of the dryer clean. The fluidization material flow regulating device (23), such as an actuator, is most suitably pneumatic. From the regulating device (23), the fluidization material gravitationally moves in a non-packed state through the opening (24) to the fluidization chamber (25).

(10) Although, in the example described above, the heat releasing gas circulating mass system is fitted on the jacket side of the dryer also operating as the heat exchanger, the solution according to the invention can be also carried out in such a way that the heat releasing gas circulating mass system is fitted on the tube side of the dryer.

(11) In an embodiment of the dryer according to the invention which is preferred in terms of the flow, thermal and structural characteristics, the separator of the fluidization material used is a horizontal separator (5,6,7,8,9) and (18,19,191,20,21), wherein the most suitably cross-sectionally rectangular inlet channel (5) and (18) of the horizontal separator is directed substantially perpendicularly downwards for discharging the separated fluidization material from the separator, and the bottom of the substantially horizontal separator chamber is coupled to the top part of the return channel by the cone, and the horizontal cross-sectional shape of the circulating mass dryer is most suitably rectangular.

(12) The circulating mass dryer and method according to the invention are applicable as different embodiments for use in carrying out the most diverse dryer solutions and for use in connection with drying of the most different kinds of sludges.

(13) The invention is not limited merely to the examples described above; instead, many modifications are possible within the scope of the inventive idea defined by the claims.