METHOD FOR TREATING POSSIBLY CONTAMINATED BIOLOGICAL MATERIAL PRIOR TO A PYROLYSIS PROCESS

Abstract: The present invention concerns a method for treating possibly contaminated biological material prior to a pyrolysis process (11), comprising removing of free water in a preheating step (1) at a temperature < 100 DEG C and then all bound water in a heating step (6) at a temperature from about 100 DEG C to about 200 DEG C. The invention is characterized in that all water vapour formed is condensed, received condensed water is subjected to electro flotation (3, 8), whereby formed flock is separated from the water and returned to said preheating step (1) and the water thus received is further led through an activated carbon filter (5, 10) in order to receive absolutely clean water (W1, W2). The used activated carbon is returned to the preheating stage (1), and the remaining, absolutely dry biological material from the heating stage (6) is subjected to a pyrolysis process (11) in absence of oxygen at a temperature of above 700 DEG C.

Description: Method for treating possibly contaminated biological material prior to a pyrolysis process The present invention concerns a method for treating possibly contaminated biological material prior to a pyrolysis process, comprising removing of free water in a preheating step at a temperature < 100°C and then all bound water in a heating step at a temperature from about 100°C to about 200°C. In a pyrolysis process the biological material is thermally broken down in absence of oxygen at high temperatures of above 700°C, whereby carbon and hydrocarbon compounds are recovered. Due to the high temperature used in the pyrolysis process it will also be possible to destroy contaminated wastes, without any dangerous exhaust. Beacause the BSE disease already appears in many countries there will be a risk that possibly all slaughterhouse waste is contaminated. Testing of sick and dead animals does not guarantee that prione, the agent causing said BSE disease, would not appear in slaughterhouse waste from so called healthy animals. Prione is spread to healthy animals by fodder manufactured from slaughterhouse waste. The germination period of said disease at cows is generally longer than the age for slaughter (about 3 years) . Fodder made of slaughterhouse waste will also spread prione to other animals. The prione is transferred from contaminated, necessarily not sick animals to human beings sudstantially with the food (the germination period at a human being is 5 to 15 years) . Materials made of animal brain and spinal marrow tissues have already for a long time been used in washing-materials and cosmetics. Most priones will exist in these types of tissues. Although the risk of contamination through these materials is less than through the food, the priones will finally end into waters and thus finally in all animals and also in human beings . Due to the fact that prione does not split nor multiply outside a nerve tissue the BSE as well as the deadly disease caused by it at human beings will gradually disappear almost completely, if the use of slaughter waste as fodder and as raw material in the industry cease. Prione is a plaited, crystalline protein, which foremost will destroy brain and other nerve tissue. What is known there are priones in all species of animals. Prione protects a specie from cannibalism. The prione guarantees that a cannibal will die before a whole specie is destroyed, because only the cannibal dies. The other members of the specie will remain alive, because prione does not multiply quickly outside a nerve tissue. Prione is a special disease causing agent and a special molecule. When other life molecules are destroyed very easily prione stands extreme conditions very well. All living organisms and protein molecules will generally be destroyed when they are cooked in water. Hot saturated water vapour destroys all other known disease producers but not priones. Incineration also destroys many organisms and protein molecules but not necessarily priones. They may remain in the ashes as contamination. In the European patent specification EP 0771318 a method for treatment of minicipal waste sludge or animal slurry is disclosed wherein a combination of a compostor and a flotation process is used. However there is no chance to destroy priones in a process based on such a combination. The only way to securely and finally destroy slaughterhouse waste has proven to be by means of a pyrolysis process as described in the international patent application PCT/FI00/01048. Prior to the pyrolysis stage all free as well as bound water has to be removed from the biological material, which is carried out in a preheating stage at a temperature below 100°C and a heating stage at a temperature range from about 120°C to about 200°C. The object of the invention is to provide a method for preventing any contaminated water, vapour, or gas from escaping from the process during any stage of it. This is achieved with a method, which is characterized in that all water vapour formed is condensed, received condensed water is subjected to electro flotation, whereby possible contamination is flocked, formed flock is separated from the water and returned to said preheating step and the water thus received is further led through an active carbon filter in order to receive absolutely clean water, and the remaining, absolutely dry biological material from the heating stage is subjected to a pyrolysis process in absence of oxygen at a temperature of above 700°C. By this method all possibly contaminated material will be returned to the process and finally be subjected to the pyrolysis process, where all biological material is degraded to carbon, hydrocarbon gas and an oil fraction. In the enclosed dependent claims 2 to 6 further characteristics of the invention will be disclosed. The invention will now be described in more detail with reference to the drawing, Fig.l showing schematically an example of a preferred embodiment of the invention. In the method according to the invention a batch of possibly contaminated biological material, having a dry content of about 20 % or less, is fed, as illustrated by arrow A, to a preheating stage 1 maintaining a temperature below 100°C, in order to remove all free water from the biological material. The water vapour generated in to preheating stage 1 is led to a condenser 2, wherein the vapour is condensed to liquid water. Said liquid water is then led, as illustrated by arrow B to an electro flotation cell 3, wherein the water is subjected to electro flotation on passing between electrified electrodes. During the electro flotation process possible contamination in the water will be flocked. The water together with the flock is led to a flock separator 4, wherein said flock is separated from the water. The flock having a dry content of about 15 % is the returned to the preheating stage 1 as shown by arrow C and the water is led through an activated carbon filter 5, whereby quit pure water is received at Wi. When all free water has been removed from the batch of biological material said batch is fed to a heating stage 6 wherein a temperature range from about 100° to about 200°C is maintained in order to remove all bound water from the biological material. The water vapour generated during the heating stage 6 is led, as illustrated by arrow D to a second condenser 7, wherein the vapour and gases are condensed into liquid form. Such liquid is then led, as illustrated by arrow E to an electro flotation cell 8, wherein the liquid is subjected to electro flotation on passing between electrified electrodes. During the electro flotation process possible contamination in the liquid will be flocked. The liquid and flock is then led to a flock separator 9 wherein said flock is separated from the liquid. The separated flock, having a dry content of about 15 % is returned, as illustrated by arrow F, to the preheating stage 1, where a next batch of biological material is treated, in order to remove free water. The liquid i.e. water from the flock separator 9 is led through an activated carbon filter 10, whereby absolutely clean water is received at W 2 . At the end of the heating stage 6 an absolutely dry batch of biological material is received which is then fed to an pyrolysis chamber 11, where the batch is subjected to a pyrolysis process in absence of oxygen at a temperature above 700°C. The biological material is then degraded to a pyrolysis gas and solid carbon, the pyrolysis gas is led to a fractionating condenser 12 wherein condensable fractions a, b of the pyrolysis gas is separated from the thus purified pyrolysis gas being stored in a gas tank 16. The solid rest of the biological material, i.e. carbon, in the pyrolysis chamber 11 is then cooled in at least a pre-cooling stage 13 and a cooling stage 14. The cooled carbon at 15 is then led to a storage before it is refined to carbon black or activated carbon. According to a somewhat more simple embodiment the condensed liquids from the condensers 2 and 7 can be fed to a common electro flotation cell 3 or 8, whereby only one set of electro flotation cell, flock separator and activated carbon filter is required. Active carbon used in the active carbon filters 5 and 10 can be fed to the pyrolysis process together with a batch of new biological material in the preheating stage 1. Solid carbon received from the pyrolysis process can be refined to carbon black or activated carbon to be used for instance in the activated carbon filters 5, 10. A preferred temperature in the preheating stage is about 80°C and a prefered temperature range of the heating stage is from about 160°C to about 180°C. A part of the clean water received from the active carbon filters 5 and 10 at i and W 2 , respectively can preferably be used as cooling agent in the condenser 2 and 7, respectively, as indicated by the arrows 17 and 18.

Claims: CLAIMS : 1. Method for treating possibly contaminated biological material prior to a pyrolysis process, comprising removing of free water in a preheating step at a temperature < 100°C and then all bound water in a heating step at a temperature from about 100°C to about 200°C, characterized in that all water vapour formed is condensed, received condensed water is subjected to electro flotation, whereby formed flock is separa- ted from the water and returned to said preheating step and the water thus received is further led through an activated carbon filter in order to receive absolutely clean water, and the remaining, absolutely dry biological material from the heating stage is subjected to a pyrolysis process in absence of oxygen at a temperature of above 700°C. 2. Method according to claim 1, characterized in that used activated carbon from the activated carbon filter is fed to the pyrolysis process together with the dry biological material. 3. Method according to claim 1, characterized in that carbon received from the pyrolysis process is refined to carbon black or activated carbon to be used in the activated carbon filter. 4. Method according to claim 1, characterized in that the preheating stage is carried out at a temperature of about 80°C. 5. Method according to claim 1, characterized in that the heating stage is carried out at a temperature from about 160°C to about 180°C. 6. Method according to claim 1, characterized in that during the pyrolysis process a solid carbon fraction and a pyrolysis gas fraction is received, said pyrolysis gas being subjected to a fractionating condensation in order to remove all condensable fractions from said pyrolysis gas separately and recovering thus purified pyrolysis gas.

Inventors: SUOMINEN HANNU L, SUOMINEN, HANNU, L.
Applicants: BCDE GROUP WASTE MAN LTD OY, SUOMINEN HANNU L, BCDE GROUP WASTE MANAGEMENT LTD OY, SUOMINEN, HANNU, L.
Application year: 2001
Main classification: C10B53
IPC codes: A61L2, A61L11, C02F1, C02F11, C10B53