METHOD AND DEVICE FOR PROCESSING WASTE WITH A CALORIFIC VALUE

Abstract: Method for processing waste with a calorific value with any degree of humidity whatsoever by means of a thermal treatment, whereby the waste is put in a flow of a hot, heat-resistant, heat-exchanging material which is warmer than 100 DEG C, whereby the material cools off due to heat exchange, the waste dries and the non-evaporated waste components are heated, whereby the cooled, heat-exchanging material is subsequently separated from the dried components, at least a part of the separated dried waste components is joined together with at least a part of the separated heat-exchanging material and whereby these waste components are subsequently subjected to pyrolysis, whereby the heat-exchanging material is heated before being used to dry the waste, characterized in that a granulated material is used as heat-exchanging material, in that the dried waste components which are separated from the granulated material are mixed with only a part of the separated, cooled granulated material and this mixture is subjected to the pyrolysis and in that the rest of the separated, cooled granulated material is mixed directly with granulated material heated by the pyrolysis and in that the thus obtained mixture is used to dry the fresh waste.

Description: Method and device for processing waste with a calorific value. The invention concerns a method for processing waste with a calorific value with any degree of humidity whatsoever by means of a thermal treatment, whereby the waste is put in a flow of hot, heat-resistant, heat-exchanging material which is warmer than 100°C, whereby the material cools due to heat exchange, the waste dries and the non- evaporated waste components are heated, whereby the cooled, heat-exchanging material is subsequently separated from the dried components, at least a part of the separated dried waste components is joined with at least a part of the separated heat-exchanging material and whereby these waste components are subsequently subjected to a pyrolysis, whereby the heat-exchanging material is heated before being used to dry the waste. The invention in particular concerns the processing of solid and liquid, somewhat viscous waste containing organic material, for example waste of animal origin, waste from slaughterhouses, sludge from the cellulose and paper industry, rancid oils, etc. or waste containing combustible mineral components. The largest size of the solid waste particles is preferably smaller than 5 mm. A method of the above-mentioned type is described in US- A-4.248.164. According to this method, the fresh waste is dried by means of hot sand. The dried waste and the cooled sand are removed together from the drying installation and are separated. The separated dried waste is subjected to a pyrolysis, usually with the help of burners, in a combustion chamber in which the separated sand, after being heated by the gases of the pyrolysis, is provided before being supplied to the drying installation. All the sand which is used for the drying is recycled and supplied back to said drying installation at a temperature between 427 and 649°C (800 - 1200°F). This hot sand makes contact with fresh, cold waste, which causes a very great thermal shock. As a result, the sand grains will burst. Because sand is used, the heat- exchange is limited. Due to the high temperature in the drying installation, the life of this drying installation is limited, unless it is made of special materials, which makes it expensive. The invention aims to remedy said disadvantages and to provide a method for processing waste with a calorific value with a high thermal efficiency and a maximum valorization of the processed waste, which method is ecologically sound and can be realized with a relatively cheap device with a long life. This aim is reached according to the invention in that a granulated material is used as heat-exchanging material, in that the dried waste components which are separated from the granulated material are mixed with only a part of the separated, cooled granulated material and this mixture is subjected to the pyrolysis and in that the rest of the separated, cooled granulated material is mixed directly with the granulated material heated by the pyrolysis and in that the thus obtained mixture is used to dry the fresh waste. GB-A-160.422 describes a method for drying material which needs to be ground in a revolving drum, whereby the grinding elements (balls) from the drum are collected and are carried back into the drum via a tube, in which they are heated by a furnace. Said material is no waste and is not subjected to pyrolysis after the drying. Preferably, the dried waste components and the cooled granulated material are separated from one another by collecting them separately to a large extent after the drying. Preferably, all the separated dried waste components are added to a part of the separated granulated material. In order to further diminish the thermal shock of the granulated material, it is recommended to preheat the waste before adding it to the granulated material, for example through heat exchange with steam which is released as the fresh waste is dried. The invention also concerns a device which is particularly suited for applying the method according to the invention. Thus, the invention concerns a device for processing waste with a calorific value which contains a drying installation with at least one drying compartment to which lead a supply for waste and a supply for hot granulated material, a granulated material heater which opens into the drying device and in which granulated material is heated and dried waste components are moreover subjected to a pyrolysis, and means to- collect the granulated material and the dried waste components from this drying compartment and to supply at least a part of the collected dried waste components and at least a part of the collected granulated material to the granulated material heater, characterized in that the drying installation is a horizontal installation and in that the means to collect the granulated material and the dried waste components and to at least partially supply them to the granulated material heater are means to collect the granulated material and the dried waste components almost separately from the drying compartment and contain a pipe to directly recycle a part of the collected granulated material and to mix it with the hot granulated material which is carried from the granulated material heater via the supply into the drying installation. Practically, the drying installation contains an ash separation compartment at the supply side of the granulated material in relation to the drying compartment so as to separate the ashes produced during the pyrolysis of the waste components in the granulated material heater from the hot granulated material via openings in the drum wall. The granulated material heater may consist of two coaxial standing cylinders which are provided with openings and are erected in a chamber, whereby the means to supply the mixture of part of the granulated material and the dried waste components to the granulated material heater bring this mixture in the space between the cylinders, and whereby the above-mentioned chamber is connected on the one hand to the incinerator and on the other hand to the heat exchanger. In order to better explain the characteristics of the invention, the following preferred embodiment of a method and a device for processing waste with a calorific value is given as an example only without being limitative in any way, described according to the invention with reference to the accompanying drawing which schematically represents such a device. The figure shows a device for processing industrial sludge with for example 10% dry components having a calorific value of some MJ/kg, for example 15 MJ/kg. The device represented in the figure contains a reservoir 1 for storing the sludge to be processed, a drying installation 2 with which the reservoir 1 is connected, a granulated material heater 3 which is connected to the drying installation 2 for heating the granulated material 4, and an incinerator 5 which is connected to the granulated material heater 3. This granulated material 4 consists of heat-resistant granules which are resistant to temperatures required for the pyrolysis of the waste, preferably to temperatures above 850°C, and which easily absorb and give out heat. This granulated material preferably consists of ceramic material. Suited materials are for example burnt clay or calcium aluminate with an aluminium alloy which depends on the temperature. The radiation capacity of such materials is usually about 201 J/m .°K.h. The size of the grains is for example such that they are detained by a sieve with meshes of 9 x 9 mm, but can pass through a sieve with meshes of 11 x 11 mm. The specific surface of the grains must be as large as possible. For grains made of the above-mentioned materials and with the above-mentioned size, this specific surface is about 750 m 2 /ιrι 3 . The drying installation 2 has the shape of a horizontal, slightly inclined drum dryer which contains an actual drum 6 which is mounted revolvable around its axis in a thermally and acoustically insulating jacket 7 and which is divided in five compartments by ring-shaped partitions 8, 9, 10 and 11 standing on the inside. Seen from the highest end, these compartments subsequently form a homogenization compartment 12, an ash separation compartment 13, an actual drying compartment 14, a separation compartment 15 for separating the dried waste components and a granulated material discharge compartment 16. The reservoir 1 connects to the drying compartment 14 via a supply consisting of a pipe 17 and an axial supply pipe 18. The wall of the drum 6 is provided with openings at the height of the ash separation compartment 13, so that it forms a sieve through which ashes can fall, but not the granulated material 4 used. In order to collect the ashes, a receiving device consisting of a funnel 19 is mounted under this part of the drum. In an analogous manner, the wall of the drum 6 is provided ' with openings at the height of the separation compartment 15, so that the corresponding wall part forms a sieve through which dried solid waste components can fall, but not the granulated material 4. In order to collect these waste components, a receiving device, namely a funnel 20, is erected under the above-mentioned wall part . The granulated material discharge component 16 situated at the lowest end is provided with openings 21 for the granulated material 4, and is situated above another receiving device, namely a funnel 22. A number of air supply lines 23 open into the jacket 7, whereas the jacket is provided at the top at its highest point with a steam exhaust 24 which connects via a pipe 25 to a serpentine curve situated in the reservoir 1 which forms a heat exchanger 26. At the highest end of the drum 6 is connected a supply for granulated material formed of the supply pipe 27 in which is erected a screw 28. The funnel 22 is connected via a first pipe 29, in which is. mounted a lift mechanism which is not represented in the figures, to the top of the vertically erected granulated material heater 3, and it is connected via a second pipe 30, in which are also erected such a lift mechanism and a sieve 31, to the above-mentioned supply pipe 27. The above-mentioned funnel 20 opens into the pipe 29, whereas the end of the sieve 31 is also connected to this pipe. Together with the partition wall 11 and the sieve-forming wall parts of the drum 6, the funnels 20 and 22 form means to collect the granulated material and dried waste components separately. The granulated material heater 3 consists of two vertical, co-axially perforated cylinders 32 and 33 which are situated in a room 34 which is divided in three compartments 35, 36 and 37 around the outer cylinder 33. The space 38 inside the inner cylinder 32 is closed at the top and at the bottom, whereas the ring-shaped interspace 39 between the cylinders 32 and 33 opens at the top into a common entry to which the above-mentioned pipe 29 is connected, and it opens into a conveyor line 40 at the bottom, in which is mounted a screw 41, and which connects to the above-mentioned supply pipe 27. The top compartment 35 and the bottom compartment 37 connect via a common pipe 42 over a fan 43 to the incinerator 5 and over a second ventilator 44 to the secondary part of a heat exchanger 45. The incinerator 5 itself is connected to the primary part of the heat exchanger 45. This primary part opens into the outlet 47. The secondary part of the heat exchanger 45 is connected via the pipe 48 to the middlemost compartment 36 of the granulated material heater 3. At the end of the pipe 42 which connects to the incinerator 5 is also connected an open burner 49. The above-described device works as follows: In the reservoir 1 is stored a mixture of sludge with different calorific values so as to be able to guarantee the heat required for the method. The more solid components the sludge contains, the higher the calorific value. In this reservoir 1, the sludge mixture is heated to about 80°C by means of heat exchange with the steam which is generated during the drying of the waste and which flows through the heat exchanger 26. The preheated sludge is brought via the pipe 17 and the axial supply pipe 18 in the drying compartment 14 of the drying installation 2, whose drum 6 is continuously rotated. Here, the sludge is exposed to the hot granulated material 4 which is moved in the drum 6 from the highest to the lowest end. This granulated material has a temperature between 200 and 300°C, for example a temperature of about 250°C when it arrives over the ring- shaped partition 9 in the drying compartment 14. Due to the heat exchange the sludge dries, whereby the non-evaporated waste components are heated to 100°C or more, and the granulated material cools to preferably the same temperature. From the mixture of cooled granulated material and dried waste components which end up in the separation compartment 15 over the ring-shaped overflow formed by the partition 10, the dried waste components are separated as they fall through a sieve-forming wall part of the drum 6. These waste components are collected in the funnel 20 and subsequently supplied to the pipe 29. Over the overflow formed by the smaller, ring-shaped partition 11 falls practically only granulated material in the granulated material discharge compartment 16 from where it falls through openings 21 in the funnel 22. The major part of the granulated material 4, normally 75 to 85 wt %, and for example 80 wt %, is directly supplied to the supply pipe 27 via the pipe 30, after it has been purified from the waste components in the sieve 31. By means of the screw 28, this part of the granulated material is mixed with the mixture of hot granulated material and ashes at a temperature of about 750°C coming from the granulated material heater 3, and it is put in the homogenization compartment 12, where the mixing continues. In this homogenization compartment 12, the difference between the temperatures of the core and the outside of the granules of the granulated material drops below 40°K, and the average temperature of the mass of granulated material is brought at 200 to 300°C, for example at about 250°C. From the homogenous mixture which falls over the overflow formed by the partition 18 in the ash separation compartment 13, the ashes are separated as these ashes fall through the openings in the drum wall part. These ashes are collected in the funnel 19. Over the overflow 9 falls practically pure granulated material 4 with an average temperature of about 250°C in the drying compartment 14. The part of the waste components which is removed from the granulated material in the pipe 36 by means of the sieve 31 is added to the steam in the pipe 29. Through this pipe 29 is supplied a small part between 15 and 25 wt %, for example 20%, by means of a screw not represented here, after the waste components from the funnel 20 were added to it, to the interspace 39 of the granulated material heater 3. In this interspace 39, the mixture of granulated material and waste components falls down due to the force of gravity. In the middlemost zone of the interspace 39 is put preheated air at a temperature of about 750°C, coming from the secondary part of the heat exchanger 45, via the pipe 48 and the compartment 36. The supplied air flows from the outside to the inside through the cylinders 33 and 32 and thus through the granulated material. This air allows for the pyrolysis and the final burning of the waste components which are mixed with the granulated material. Part of the gases coming from the middlemost zone flows upward in the inner space 38 and through the top zone. The gasification and the first pyrolysis of the waste components takes place in the top zone of this interspace 39, whereby a gaseous fuel is produced of relatively inferior quality. This gaseous fuel is removed via the compartment 35 and carried via the pipe 42 by means of the fans 43 and 44, partly to the incinerator 5 and partly behind the secondary part of the heat exchanger 45. Another part of the gases coming from the middlemost zone flows downward in the space 38 and subsequently through the lower zone of the interspace 39. The entire combustion of all combustible elements in the waste components takes place in this lower zone. Also the temperature variations in the granulated material are attenuated in this lower zone. The gases from this lower zone are collected in the compartment 37, from where they are mainly supplied to the incinerator 5 and to a lesser extent to the secondary part of the heat exchanger 45 via the pipe 42 and the above-mentioned fans 43 and 44. The mixture of granulated material and ashes is removed from the lower end of the granulated material heater 3 and is carried through the conveyor pipe 40 to the supply pipe 27 at a temperature of about 750°C by means of a screw 41. The mixture of gases at about 300°C from the compartment 35 and the air with a large excess air of 30 to 40% which is partly polluted by combustion gases from the lower zone in the interspace 39 which is discharged at about 750°C via the compartment 37 is burnt in the incinerator 5. A possible surplus of these gases is burnt in the open burner 49. The combustion gases of the incinerator 5 at a temperature of about 850 °C are carried via the pipe 46 through the primary part of the heat exchanger 45, so that they heat the air supplied to the middlemost compartment 36 to about 750°C. The heat exchanger 45 provides the necessary pressure and underpressure for the working of the granulated material heater 3 /incinerator 5 /heat exchanger 45 as a whole. In order to start the device, a high-grade fuel is combusted in the incinerator 5 which is carried from outside in the incinerator 5. As soon as the temperature of the granulated material which is collected from the drying installation 2 is higher than 100°C, the waste is gradually supplied to the drying installation 2. As soon as hot granulated material is supplied to the drying installation 2 at a temperature of 200 to 250°C, the normal flow of waste can be supplied. In the meantime, the supply of fuel from the outside to the incinerator 5 has been reduced to zero. This starting procedure requires one hour at the most. The steam which is produced during the drying in the drying installation 2, and which is collected via the steam exhaust 24 can be partly used for preheating the sludge. A possible surplus of steam can be efficiently used for preheating water for domestic use. Depending on the composition, the condensate of this steam can be chemically neutralized or mixed with 5 vol.% preheated air and heated up to 800°C in a regeneration heat exchanger which works uninterruptedly with granulated material. The thermal agent of the heater is the heater agent itself after a flow of gaseous fuel was led through it coming for example from the top zone of the granulated material heater 3. The fuel is burnt at the air dispersed in the steam mass. During the period in which the steam has a high temperature, the oxidizing effect of the air contributes to the detoxication of the steam. In order to prevent that condensate is formed inside the jacket 7, hot air can be blown through the air supply pipes 23 in this jacket. This air can be heated by the heat exchanger 45. According to the above-described method and with the above-described device is obtained a complete treatment of all harmful materials in the processed waste. The potential energy which is stored in the waste is efficiently valorized. Only in the case of waste with a high degree of humidity must be added fuel from outside. In the case of relatively dry waste, for example waste which contains 25% of water and which has a heating value of more than 2 MJ/kg, fuel from outside is not even required. Only when starting or re-starting the device, fuel is required, but the consumption is relatively low. The produced steam is entirely valorized. The ashes can be directly collected via the funnel 19 and they do not disperse in the gases. The collected ashes have a temperature of only 200°C, which implies that the considerable heat of these ashes is fully used in this device . The intensive heat transfer of the granulated material results in a cheap, compact and very efficient device. The present invention is by no means limited to the embodiments described above and represented in the accompanying drawings; on the contrary, such a method and device for processing waste can be made in all sorts of variants while still remaining within the scope of the invention. In particular, the waste does not necessarily need to be sludge. It can also be other, solid or liquid waste. What is advantageous, however, is that by possibly mixing different sorts of waste, one makes sure that the waste which is supplied to the drying installation has enough calorific value to supply the heat, once the installation is working, required to preserve the method without any supply of fuel from outside being required.

Claims: Claims . 1. Method for processing waste with a calorific value with any degree of humidity whatsoever by means of a thermal treatment, whereby the waste is put in a flow of hot, heat-resistant, heat-exchanging material which is warmer than 100°C, whereby the material cools due to heat exchange, the waste dries and the non-evaporated waste components are heated, whereby the cooled, heat- exchanging material is subsequently separated from the dried components, at least a part of the separated dried waste components is joined with at least a part of the separated heat-exchanging material and whereby these waste components are subsequently subjected to a pyrolysis, whereby the heat-exchanging material is heated before being used to dry the waste, characterized in that a granulated material is used as heat-exchanging material, in that the dried waste components which are separated from the granulated material are mixed with only a part of the separated, cooled granulated material and this mixture is subjected to the pyrolysis and in that the rest of the separated, cooled granulated material is mixed directly with the granulated material heated by the pyrolysis and in that the thus obtained mixture is used to dry the fresh waste. 2. Method according to claim 1, characterized in that the dried waste components and the cooled granulated material are separated by collecting them separately to a large extent after the drying. 3. Method according to any of the preceding claims. characterized in that the gases released during the pyrolysis are burnt and in that the heat produced by combustion is recycled and used for the pyrolysis via heat exchange with the air which is used for the pyrolysis. 4. Method according to any of the preceding claims, characterized in that all the separated dried waste components are added to a part of the separated granulated material. 5. Method according to any of the preceding claims, characterized in that the waste is preheated before being added to the granulated material, for example by means of heat exchange with steam which is released as the fresh waste is dried. 6. Method according to any of the preceding claims, characterized in that the granulated material is heated by the pyrolysis of the waste components to more than 250 to 300°C and in that such a part of the cooled separated granulated material is mixed with this heated granulated material that the temperature of the mixture which is used for drying the fresh waste is situated between 200 and 300°C. 7. Device for processing waste with a calorific value which contains a drying installation (2) with at least one drying compartment (14) to which lead a supply (17- 18) for waste and a supply (27) for hot granulated material, a granulated material heater (3) which opens into the drying device (2) and in which granulated material (4) is heated and dried waste components are moreover subjected to a pyrolysis, and means (20-22-29- 30) to collect the granulated material and the dried waste components from this drying compartment (14) and to supply at least a part of the collected dried waste components and at least a part of the collected granulated material to the granulated material heater (3), characterized in that the drying installation (2) is a horizontal installation and in that the means (20-22- 29-30) to collect the granulated material and the dried waste components and at least partially supply them to the granulated material heater (3) are means to collect the granulated material and the dried waste components almost separately from the drying compartment and contain a pipe (30) to recycle a part of the collected granulated material directly and to mix it with the hot granulated material which is carried from the granulated material heater (3) via the supply (27) into the drying installation (2). 8. Device according to claim 7, characterized in that it contains an incinerator (5) for burning the gases released during the pyrolysis in the granulated material heater (3) and a heat exchanger (45) to use the heat produced by combustion in the incinerator (5) for the pyrolysis in the granulated material heater (3) and for heating the granulated material (4). 9. Device according to claim 8, characterized in that the drying installation (2), at the end of which the granulated material heater (3) opens into, contains a homogenization compartment (12) for homogeneously mixing heated granulated material from the granulated material heater (3) with a part of the collected granulated material. 10. Device according to any of claims 7 to 9, characterized in that the drying installation (2) contains an ash separation compartment (13) at the supply side of the granulated material in relation to the drying compartment (14) so as to separate the ashes produced during the pyrolysis of the waste components in the granulated material heater (3) from the hot granulated material via openings in the drum wall. 11. Device according to any of claims 7 to 9, characterized in that the drying installation (2) contains a revolvable horizontal drum (6) and a jacket (7) around it, and in that the drum (6) is divided in compartments (12 to 16) by ring-shaped partitions (8-9-10 and 11) standing on the inside, of which one is the drying compartment (14). 12. Device according to claim 11, characterized in that the jacket (7) is equipped with a steam outlet (24) which is connected with among others a heat exchanger (26) for preheating the waste. 13. Device according to any of claims 8 and 9, characterized in that the granulated material heater (.3) contains two coaxial standing cylinders (32 and 33) which are provided with openings and are erected in a chamber (34), whereby the means to supply the mixture of part of the granulated material and dried waste components to the granulated material heater (3) bring this mixture in the interspace (39) between the cylinders, and whereby the above-mentioned chamber (34) is connected on the one hand to the incinerator (5) and on the other hand to the heat exchanger (45) . 14. Device according to the preceding claim, characterized in that the chamber (34) is divided in three compartments (35-36-37) around the outer cylinder (33) and in that the top compartment (35) and the bottom compartment (37) open into at least the incinerator (5), whereas the outlet of this incinerator (5) is connected to the primary part of the heat exchanger (45), and the secondary part of the latter is connected to the middlemost compartment (36).

Inventors: DE MUYNCK JOSE OMER ARNOLD, DE MUYNCK, JOSE, OMER, ARNOLD
Applicants: DRUWEL NORBERT, GROEP DANIS NV, MUYNCK JOSE OMER ARNOLD DE, DE MUYNCK, JOSE, OMER, ARNOLD, DRUWEL, NORBERT, GROEP DANIS, NAAMLOZE VENNOOTSCHAP
Application year: 1995
Main classification: C10B53
IPC codes: B09B3, C10B1, C10B49, C10B53, F23G5, F23G7, F26B3, F26B11, F26B23