FI125977B - Method and apparatus for incinerating sludge - Google Patents

Description

FIELD OF THE INVENTION Field of the Invention

The invention relates to a method for the incineration of sludge as defined in the preamble of claim 1 and to an apparatus for incineration of the sludge as defined in the preamble of claim 18.

BACKGROUND OF THE INVENTION In the context of the present invention, the closest prior art is represented by fluidized bed drying methods using hot water or steam as a heat source for drying, and fluidized bed combustion methods provided by several equipment manufacturers.

Further, it is known to dry the wet slurry by drying the wet slurry in a fluid bed dryer in which hot water or steam is introduced into the fluidized bed tubular heat exchanger tubing or into the jacket surrounding the fluidized bed. It is also known to burn slurry in a fluidized bed reactor which may additionally produce some or all of the hot water or steam needed for drying.

For example, the above-mentioned known sludge combustion processes have the following disadvantages. All hot water or steam powered dryers require a pressurized hot water or steam system, which significantly increases the cost of manufacturing a sludge incinerator. Hot-water or steam-powered dryers require a pressurized hot-water or steam system that requires the operator to have the qualifications specified in the pressure vessel. In hot-water or steam-fired sludge combustion plants, a separate post-combustion heat recovery section is required to cool the flue gas, which significantly increases the cost of manufacturing the sludge incineration plant. The heat exchanger of the rotary dryer must be designed and implemented as a pressure vessel, which makes the dryer heavy and expensive. When hot water or steam is used as the heat source for the dryer, the temperature difference between the heat exchanger is small, in practice only 30-40 ° C, leaving the heat density in the heat exchanger low, being only about 2-3 kW / m2. This results in high costs for the dryer and thus also for the sludge incinerator. When the height of the heat exchanger tubes has to be limited to 6 meters due to, for example, serviceability, this, together with a low heat transfer power density, results in a large specific tube month, i.e. pipe number / drying power, and the specific cross section of the riser channel, i.e. cross-sectional area / drying power. This, in turn, results in a high specific self-propulsion power of the sludge incineration plant, i.e. omakäyttöteho / drying power.

CA 2727638 discloses a method for burning biomass, and JP 2002317180 discloses a method and apparatus for burning a slurry.

PURPOSE OF THE INVENTION

It is an object of the invention to provide a solution by which the above-mentioned drawbacks of the known sludge combustion and sludge drying technology can be substantially reduced, the most important of which is the high investment and operating costs of the equipment.

It is an object of the invention to provide a new type of method and apparatus for treating wet sludge in a cost-effective, easy-to-use and efficient manner.

SUMMARY OF THE INVENTION

The method and apparatus of the invention are characterized by what is stated in the claims.

The invention is based on a method for burning sludges. According to the invention, the wet slurry is dried in a circulating pulp dryer, the dried slurry is burned in a circulating pulp reactor, and the flue gas is passed from the circulating pulp actor to the circulating pulp dryer to transfer heat to the drying slurry. Preferably, at least a portion of the flue gas formed in the circulating pulp reactor is fed to the circulating pulp dryer.

Further, the invention is based on an apparatus for burning sludges. According to the invention the apparatus comprises kiertomassakuivuri, wherein drying the wet slurry, the first feed means for feeding the wet slurry kiertomassakuivuriin, the circulating fluidized bed reactor for the incineration of dried sludge, second feeder means for the dried sludge into kiertomassakuivuril-O kiertomassareaktorille, and the flue gas recirculation intermediate for venting the flue gas in the circulating fluidized bed reactor kiertomassakuivuriin heat transfer material to be dried to transfer heat from the slurry.

As used herein, slurry means any slurry raw material formed by a liquid and a solid.

In one embodiment, the flue gas is provided at a temperature of 500-900 ° C, preferably 500-700 ° C. Preferably, the flue gas is cooled downstream of the circulating reactor. In one embodiment, the temperature of the flue gas is controlled by a heat exchanger. In one embodiment, the separated flue gas is led from the circulating pulp reactor to a heat exchanger, e.g. to cool the flue gas by means of combustion air, wherein the temperature of the flue gas is controlled between 500 and 700 ° C. In one embodiment, the flue gas is introduced into a separator, e.g. a cyclone separator, at a temperature of 500 to 700 ° C. In one embodiment, the cooled flue gas is introduced into a circulating dryer after a heat exchanger or after a separator such as a cyclone separator.

In one embodiment, a circulating dryer having two parallel circulating systems which are in heat transfer relationship to one another, the first circulating system being the drying side of the slurry and the second circulating system being the heat transfer side, and feeding the wet slurry to the first circulating system and the flue gas. In one embodiment, fluidized material, wet sludge and gas are provided in the fluid chamber of the first circulating mass system, fluidizing or transporting wet sludge with fluidized material and gas in the fluidized space while drying the at least one elongated first riser, and removing the dried slurry containing the fluidized material by means of the dried slurry removal means from the dryer. The first recirculation duct may include an upper portion of the duct side upstream duct, a separator for separating gas from the solid, and a solid return duct. The separated gas can be recycled as a recycle gas back into a recirculating pulp dryer or alternatively can be fed to a condenser or recycled pulp reactor. From the condenser, non-condensed gas can be fed to a circulating pulp reactor or circulating pulp dryer. In one embodiment, the second circulating pulp system feeds the flue gas, fluidizes the flue gas together with the fluidized material in at least one elongated second riser, and circulates the fluidized material through a second circulating duct. The second recirculation duct may include a separator for separating the flue gas from the solid and a solids return duct. In this context, the riser channel may be any tubular channel, tube or the like in any form in which the material compositions can be carried in an upwardly closed space in a dryer.

One embodiment utilizes a rotary dryer as defined in the patent application filed on the same date by the same applicant or any application of said rotary dryer.

In one embodiment, the temperature of the lower portion of the second riser of the circulating dryer is controlled by adjusting the flow of fluidized material passing through the return channel of the second recirculation channel.

In one embodiment, the dried slurry containing the fluidized material is passed from a circulating pulp drier to a circulating pulp reactor.

In one embodiment, derived from the dried sludge, which contains fluidised material in the circulating fluidized dry-Rista circulating fluidized reactor, the dryer the drying side of the differential pressure asetusarvosäätönä.

In one embodiment, a circulating mass actor is used to supply dried slurry containing fluidized material, from a circulating dryer to a lower combustion chamber of a circulating mass reactor, to provide a fluidized material and gas upstream of the fluidized bed reactor, burning the dried slurry in a device assembly formed by a lower combustion chamber, a flow channel and an upper combustion chamber, separating the fluid material from the flue gases after the upper combustion chamber, e.g. by means of a separator, and circulating the fluid material through the return conduit to the lower combustion chamber. In one embodiment, the return duct includes a cooled return duct. In one embodiment, the return duct includes an uncooled return duct. In one embodiment, the return duct includes a cooled and non-cooled return duct, wherein the fluidized material is recycled to the lower combustion chamber via a cooled and / or non-cooled return duct in the desired ratio. In one embodiment, the fluidized material, or at least a portion thereof, is cooled by a heat exchanger before being recycled back to the lower combustion chamber via a return conduit. Preferably, the dried slurry is burned substantially in a device assembly formed by the lower combustion chamber, the flow passage and the upper combustion chamber before the flue gases leave the upper combustion chamber.

In one embodiment, a rotary mass actuator as defined in PCT / FI2012 / 050057 or an application thereof is used.

In one embodiment, the temperature of the circulating mass actor is controlled by controlling the circulating mass flow of the heat exchanger fitted to the return channel of the fluidized material recirculation.

In one embodiment, at least a part of the heat contained in the flue gas generated in the circulating mass reactor is transferred for utilization in the circulating mass reactor, e.g. by means of a fluidized material. The heat can be recovered from the flue gas, for example by means of a heat exchanger, and transferred to the fluidized material. In one embodiment, the heat is recovered from the flue gas when the flue gas is cooled before being fed to a circulating dryer, e.g. by means of a heat exchanger.

In one embodiment, the volume fraction of fluidized material in the upper combustion chamber of the rotary solar reactor is provided in the range of 0.005 to 0.05.

In one embodiment, a horizontal gas velocity component is provided in the lower combustion chamber of the rotary solar reactor between 0.5 and 7.0 m / s.

In one embodiment, the vertical velocity component of the gas is provided in the flow channel of the rotary solar reactor between 3 and 20 m / s, more preferably between 3 and 15 m / s.

In one embodiment, the recycled mass actor, preferably regenerated and hot, fluidized material is supplied to the circulating mass dryer, preferably to the drying side of the circulating mass dryer, to supplement the amount of heat required for drying. In one embodiment, derived from the circulating fluidized bed reactor, fluidised material in the circulating fluidized-dryer of the dryer side of the fluidized bed dryer temperature asetusarvosäätönä.

Preferably, the invention is based expressly drying the slurry reactor by passing combustion flue gas to the dryer heat emitting side of the circulating fluidized bed reactor system and the combustion fluidised bed dryer heat receiving side of the circulating fluidized bed system, and the dried sludge incineration based technologies in said circulating fluidized combustion reactor.

In the prior art circulating dryers, problems have been caused, in principle, by the use of hot water or steam as a heat source instead of the combustion gas of the combustion reactor and / or that the suspended material is formed by a dried slurry.

The process of the invention substantially reduces the disadvantages of known sludge incineration methods. In the process according to the invention, the thermal energy of the flue gas of the combustion reactor is utilized by directing the flue gas directly to the circulating dryer for drying as a heat release agent. This arrangement provides significant benefits. The heat transfer of the dryer can be carried out in a non-pressurized structure, whereby the heat transfer solution becomes substantially lighter and less expensive compared to the pressurized heat exchanger. The average temperature difference in heat transfer can be increased 4 to 5 times that of a water or steam heated dryer, whereby the required surface area for the same heat transfer power is only about 25% of the equivalent heat or water heated steam dryer. When the dryer power is proportional to the heater surface, only about 25% of the fan power of an equivalent water or steam heater is required for a flue gas dryer. By fan power is meant here, when the heat output of the dryer is proportional to the heat surface, the tube size selected is proportional to the heat surface, and when the flow rate of the blower fan is proportional to the tube number, the fan flow rate and hence the fan power is proportional to the heat surface. The post-combustion heat recovery section is significantly reduced and in many cases even redundant, which significantly reduces the cost of manufacturing the sludge incinerator.

Furthermore, when according to the invention, the sludge-incineration process uses fluidized bed material combustion reactor fluidized material, which is supplied to the dryer is preferably a dryer temperature of the fluidised gun tusarvosäätönä and the dryer is passed polttoreakto-Riin slurry coating the fluidized material or a mixture of the slurry and fluidized bed material dryer heat receiving side of a drainage side of a differential pressure set and many important benefits are achieved. If the thermal energy of the flue gas after the combustion reactor covers only a part of the heat demand of the dryer, the remainder of the heat demand of the dryer can be brought to the dryer by introducing hot fluidized material from the combustion reactor to the dryer. This will further reduce the heat transfer surface area of the dryer and its own power output. In the dryer, particle growth and agglomeration is prevented because the slurry-coated fluid material introduced from the dryer to the incinerator is regenerated in the incinerator to its original size before being returned to the dryer.

In the past, the use of hot gas as a heat source for dryers has been perceived as problematic. The introduction of the post-combustion gas into the heat exchanger of the dryer may cause structural problems in different parts of the process due to different thermal expansion. In order to achieve a high power density, the gas after the combustion reactor should preferably be introduced into the drier at a temperature above 500 ° C, whereby the surface temperature of the drier heat exchanger may be temporarily and locally high for the durability of the structure. The gas after the combustion reactor contains a large amount of ash, which causes the need for the soot to be cleaned, which results in a low packing density of the heat surface and the need for a soot cleaning equipment. The above problems have been solved in the slurry combustion process according to the invention by circulating on the heat-releasing gas side of the dryer a powdered material, e.g. sand or other suitable fluidized material, preferably having a particle size between 0.1 and 0.5 mm. The fluidizing material circulating on the heat release gas side of the dryer continuously scrubbing the heat release side, keeping it clean, thus maintaining a high packing density of the heat surface. In addition, the dryer the heat emitting side of the maximum temperature of the fluidized bed material may limit the mass flow rate by adjusting to a desired value regardless of the temperature of the incoming gas. A further advantage may be mentioned that the drier leijumassavirta more gas side heat-mönläpäisylukua.

Sludges are generally defined as waste, in which the flue gas of sludge combustion must be at a temperature of at least 850 ° C for a minimum of 2 seconds. On the other hand, rising temperatures substantially higher than required cause problems in the form of ash melting and shortening of the service life of the structures. Therefore, controlling the temperature of the burner actor is essential. Therefore, in the process of the invention, the combustion reactor flue gas temperature is maintained at its set point, e.g. by passing a portion of the fluid material stream circulating in the combustion reactor to a heat exchanger fitted to the combustion reactor return duct, e.g. When the fluidized material cooled in the intercooler is returned to a substantially thermally insulated combustion chamber, it provides adiabatic cooling, which allows the combustion reactor flue gas temperature to remain at its setpoint despite changes in fluid exchange between the dryer and the combustor.

The invention provides a reduction in the cost of manufacturing and operating a sludge combustion plant up to less than half the cost of manufacturing and operating a sludge combustion plant which uses water or steam of the same power as the heat source of the dryer.

The process according to the invention can be utilized in the treatment of any kind of sludge, e.g. in the treatment of sludges in waste water treatment plants.

LIST OF FIGURES

Figure 1 illustrates a process according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by means of detailed application examples with reference to the accompanying figure.

Example 1

Figure 1 illustrates a process according to the invention with its equipment. The wet slurry (104) is fed from the silo (1) to the fluidized bed (5) of the rotary mass dryer (100) by a first feeding device (2), where the wet slurry (104) is mixed with the fluidized bed material. In a preferred embodiment, the fluidizing gas is steam formed in the dryer (100) containing some non-condensable gases, such as air, and organic compounds, which are recirculated from the central tube (9) of the dryer cyclone separator (8) via a secondary gas fan (3). 105) to the gas cabinet (4) of the dryer, from which the circulating gas is distributed through the grate (18) to the fluidized bed of the fluidized bed (5). Leijukammiosta (5) wet slurry kiertokaa- mixture of gas and fluidised material rise of the dryer the drying side of the elongated riser channel (6), which has a heat transfer surface (121) with the heat emitting side of the elongated riser channel (12) through the dry machine side upper part of the riser (7) , and from there tangentially to the cyclone separator (8). In the cyclone separator (8), the recycle gas is separated from the mixture of fluid particles and slurry, and the recycle gas is led from the cyclone separator (8) through the central tube (9) to the secondary cyclone (24) and gravitationally . The steam generated in the dryer may be led from the secondary cyclone (24) to the condenser (21) by separating the flow to the condenser (21) from the circulating gas stream to the dryer (100) after the circulation fan (3) and before the dryer gas cabinet (4). In the condenser (21), most of the steam condenses and the resulting condensate is removed from the condenser. The dust separated in the secondary cyclone (24) is introduced into the feed tube (25) of the circulating reactor (101). The non-condensed gas is led from the condenser (21) by means of a gas blower (22) to the flow passage (33) of the reactor (101) where the hydrocarbon compounds of the non-condensable gas are oxidized to odorless oxides.

The circulating dryer (100) comprises two parallel circulating systems which are in heat transfer communication with each other, the first circulating system being the drying side of the wet slurry (104) as described above and the second circulating pulping system being the heat releasing side fed to the flue gas (103). a circulating mass reactor (101) as a heat transferring heat transfer medium for transferring heat through a common heat transfer surface (121) to a slurry (104) to be dried. In a preferred embodiment, the flue gas is arranged at a temperature of 500 to 700 ° C before being fed to the dryer.

The dried slurry (106) in combination with the dryer dry machine side fluidised material supplied leijukam-chamber (5), preferably to its bottom fitted through present in the discharge-pipe (19) of the dryer conveyor (20) for transporting the slurry and fluidized reactor (101), the feed tube (25) of the dryer the dryer side of the differential pressure setting value adjustment DPC1 controller. The dryer the drying side leijukammion (5) is maintained at asetusarvos-I by passing the reactor (101) regenerated and preferably hot fluidized material (102) through a tube (26) of the dryer fluidized bed (5) by controlling the connecting tube (26) leijumateriaalivirtaa actuator (27) to control the temperature of the fluidized bed (5) TC2 as a setpoint control. The recovered fluidized material (102) is used to supplement the amount of heat required for drying.

The dried slurry and fluidized particles (106) are directed through the feed tube (25) into the lower combustion chamber (32) of the reactor (101), which includes a fluidized chamber and also feeds combustion air through the reactor grate (31). Additional fluidized material may be fed to the lower combustion chamber (32). The slurry (106) is oxidized in the lower (32) and upper (34) combustion chamber, whereupon the fluidized particles are regenerated. The coarse solids accumulating in the reactor in the lower combustion chamber (32) are removed by means of an exhaust pipe (42) and a conveyor (43), controlled by the pressure difference in the lower combustion chamber (32). It is preferable that the inlet pipe (25) and the flow passage (33) are located at opposite ends of the lower combustion chamber (32), whereby a significant horizontal gas velocity component is generated in the lower combustion chamber (32), the combustion air / sludge ratio constantly changing.

From the combustion chamber (32), the slurry, gas and fluidized particles ascend through the flow passage (33) to the upper combustion chamber (34). In the flow passage (33) fitted at the end of the lower combustion chamber (32), the vertical velocity of the gas is much higher than that of the lower Leigh chamber (32) and preferably in the range of 3 to 20 m / s, most preferably 3 to 15 m / s. From the upper combustion chamber (34), the flue gas and fluidized material are led to a separation cyclone (35) where the flue gas and fluid particles are separated, and the fluid particles drop gravitatively into the return passage (37) and the flue gas exits the separation cyclone (35). For the circulating mass reactor (101) of the invention, it is preferable that the combustion chambers (32,34) and the flow channel (33) connecting them are substantially thermally insulated.

After the return channel (37), return channels (38) and (40) are arranged, of which the return channel (40) includes heat transfer surfaces (39) and the return channel (38) is non-cooled. Through the return passages (38) and (40), the fluidized material is returned to the lower combustion chamber (32). The fluidized material flow through the heat exchanger (39) is controlled by an actuator (41) fitted to the lower part of the return duct (40), which in turn is controlled by the set temperature (TC3) of the upper combustion chamber (34). Preferably, the fluidized material is cooled by a heat exchanger (39). The portion of the fluidized material that is not directed to the return passage (40) is directed to the lower reactor combustion chamber (32) through the return passage (38) as a setpoint differential pressure control of the flow passage (33).

The flue gas separated from the central pipe (36) of the reactor separation cyclone (35) is led to a LUVO heat exchanger (29). In the heat exchanger (29), the flue gas is cooled to a temperature of 500 to 700 ° C by means of combustion air, which is supplied to the heat exchanger (29) by means of an air blower (28). The combustion air heated from the heat exchanger (29) is introduced as combustion air into the air chamber (30) of the circulating mass reactor (101), from where it is distributed to the reactor via a grate (31). The cooled flue gas (103) passing air preheater, the heat exchanger (29) via a hot cyclone (23) of the dryer (100) of the flue gas cabinet (11), from which the flue gas is conducted to the lower part of the hearth (17) of the dryer heat emitting side of the riser (12) with a fluidized material. The flue gas (103) and the fluidized particles rise upwardly along the riser channel (12) to the cyclone separator (13), where the flue gas and fluidized particles are separated. The flue gas exits the central pipe (14) of the cyclone separator (13) and the separated fluidized particles enter the return passage (15) where the fluidized particles are kept in a packed state. From the return channel (15), fluid particles are introduced into the lower part of the riser channel (12) by means of an actuator (16) as a setpoint control of the temperature TC1 of the riser channel (12). The flue gas discharged from the dryer (100) can be treated by means of the flue gas filter (44) and fed to the pipe (46) by the flue gas fan (45).

In an alternative embodiment, the dry sludge may be burned in a conventional fluidized bed or circulating fluidized bed boiler. In an alternative embodiment, the steam generated in the dryer may be led to combustion without condensation; in the alternative embodiment, the dryer riser ducts (6,12) and the heat transfer surface (121) separating them are formed by a tubular heat exchanger such that the first riser duct (6) from the diaper sheath.

The method and apparatus of the invention are suitable as various applications for use in the treatment of a wide variety of sludges.

The invention is not limited to the above examples only, but many modifications are possible within the scope of the inventive idea defined by the claims.

Claims (18)

A method for burning slurry, characterized in that the wet slurry (104) is dried in a rotary dryer (100) having a slurry drying side and a heat transfer side which are in heat transfer relationship with one another and having a common heat transfer surface (121). slurry (106) in a circulating pulp reactor (101), and introducing the flue gas (103) from the circulating pulp reactor into a circulating dryer as a heat transfer medium to the heat transfer side to transfer heat through the heat transfer surface (121) to the sludge to be dried. Method according to Claim 1, characterized in that the flue gas is provided at a temperature of 500 to 700 ° C. Method according to Claim 1 or 2, characterized in that a rotary mass dryer (100) is used which comprises two parallel rotary systems which are in heat transfer communication with one another, the first of which being the drying side of the slurry and the second circulating mass. the system (11,12,13,14,15) is the heat-releasing side, and wet sludge (104) is supplied to the first circulating system and the flue gas (103) to the second circulating system. Method according to Claim 3, characterized in that fluidized material (102), wet slurry (104) and gas (105) are provided in the fluid chamber (5) of the first circulating mass system, the wet slurry is conveyed upwardly together with the fluidized material and gas. in the elongated first riser channel (6), the mixture of solid fluidized material and dried slurry is returned to the fluidized bed (5) by a first recirculation channel (7.8.9.10) and removed the dried slurry (106) containing fluidized material by the dried slurry removal means (19). Method according to claim 3 or 4, characterized in that flue gas (103) is introduced into the second circulating pulp system, fluidized with the fluid material upwards in at least one elongated second riser channel (12) and circulated the fluid material by a second circulating duct (13,14,15). . Method according to one of Claims 1 to 5, characterized in that the dried slurry (106) containing the fluidized material is introduced from the rotary mass dryer (100) to the rotary mass reactor (101). 7. A method according to claim 6, characterized in that the dried sludge is passed (106) containing fluidized material, kiertomassakuivurista (100) of the circulating fluidized bed reactor (101) to the dryer dry machine side pressure difference asetusarvosäätönä. Method according to one of Claims 1 to 7, characterized in that the dried slurry (106) containing the fluidized material is fed from the rotary mass dryer (100) to the lower combustion chamber (32) of the rotary mass reactor (101), the fluidized material and gas are arranged feeding the dried slurry (106) with the fluid material and gas upwardly along the flow passage (33) to the upper combustion chamber (34), incinerating the dried slurry (106) in the lower combustion chamber, flow passage and upper combustion chamber, fluidized material from the flue gases after the upper combustion chamber (34) and recirculating the fluidized material through the return duct (37,38,39,40) to the lower combustion chamber (32). Method according to Claim 8, characterized in that the fluidized material is cooled by means of a heat exchanger (39) before being returned to the lower combustion chamber (32) via a return conduit (40). Method according to one of Claims 1 to 9, characterized in that the separated flue gas (103) is introduced from the circulating pulp reactor (101) to a heat exchanger (29), wherein the temperature of the flue gas is adjusted between 500 and 700 ° C. A method according to any one of claims 1 to 10, characterized in that fluidised material (102) is introduced from the circulating pulp reactor (101) to the circulating dryer (100) on the drying side thereof. 12. A method according to claim 11, characterized in that the rotary mass is passed from the reactor (101) fluidized material (102) kiertomassakuivuriin (100) of the dryer side of the fluidized bed dryer temperature asetusarvosäätönä. Method according to one of Claims 1 to 12, characterized in that the temperature of the lower part of the second riser channel (12) of the circulating dryer (100) is controlled by adjusting the flow of fluidized material passing through the return channel (15) of the second recycling channel. Method according to one of Claims 1 to 13, characterized in that the temperature of the circulating mass reactor (101) is controlled by controlling the circulating mass flow of the heat exchanger (39) fitted to the return channel (37,38,39,40) of circulating fluidized material. Method according to one of Claims 1 to 14, characterized in that a volume fraction of fluidized material in the upper combustion chamber (34) of the circulating mass reactor (101) is provided in the range of 0.005 to 0.05. Method according to one of Claims 1 to 15, characterized in that a horizontal velocity component of the gas in the lower combustion chamber (32) of the circulating mass reactor (101) is arranged between 0.5 and 7.0 m / s. Method according to one of Claims 1 to 16, characterized in that a vertical velocity component of the gas in the flow channel (33) of the circulating mass reactor (101) is provided in the range of 3 to 20 m / s. Apparatus for incineration of slurry, characterized in that the apparatus comprises a circulating mass dryer (100) for drying the wet slurry (104) and including a drying side and a heat transfer side of the slurry which are in heat transfer communication with each other and having a common heat transfer surface (121) first feed means (2) for supplying wet sludge to a circulating pulp dryer (100), a circulating pulp reactor (101) for burning dried slurry (106), second supply means (20) for feeding dried sludge (106) from a circulating pulver (103) for transferring heat from the rotary mass reactor (101) to the rotary mass dryer (100) as a heat transfer medium to the heat transfer side for transferring heat to the slurry to be dried via the heat transfer surface (121). claim