Background In the known methods of charring of organic material, such as fast or slow pyrolysis, the process is typically one-staged. Phased methods are also known, such as screw-shaped dry distillers, but in these, the phasing is not fulfilled with sufficient precision. For example, the publication by David A. Laird, Robert C. Brown, James E. Amonette, Johannes Leh- mann, "Review of the pyrolysis platform for coproducing bio-oil and bio-char", Biofuels, Bioprod. Bioref. 3 (2009) 547-562, see Figure 1, describes a typical dry distiller according to the state of the art. In the known charring methods, the gases which are generated in the process are allowed to mix with the solid matter during the beginning of the process in such a way that the composition of the gas generated is changed. As a consequence, with the known apparatuses it is possible to produce only those carbon and liquid fractions which were the design objectives of the apparatus. If it is desired to change the yield of the process, this can only be done by redesigning the structure of the known apparatus.

In the known fast pyrolysis apparatuses, the raw material fed must be very fine (for example, grain size less than 3 mm), because it should be warmed up to a temperature of more than 650 °C in less than two seconds, in order that the required reactions can be generated. In the known fast pyrolysis methods, the purpose is typically to generate as much raw materials for oily fuel (for example wood wax) as possible, and the yield of carbon is of secondary importance. In the known methods, the process cannot be modified and only the composition of the raw material affects the materials obtained.

In the known slow pyrolysis apparatuses, the reactions take place either in the same gas space or the intention has been to separate the phasing spaces from one another by a screw structure. Such a screw structure works with solid substances, but the gas fractions that are most relevant for the process can pass uncontrollably between the various stages of the process. In this case, the composition of the liquids and gases obtained cannot be determined in a controlled way, and a consequence of this is that it is not possible to predict yields.

The publication WO 2013/039991 Al describes a pyrolysis process, which is based on two-stage reactors, for processing carbon. The gases generated in the different stages of the pyrolysis are separately collected and condensed in one step at a certain temperature. According to the publication, the gases can be recirculated back to the pyrolysis process.

The publication US 2005/0240068 Al describes the processing of organic waste by way of a multi-stage pyrolysis method. The material that has not reacted is recirculated back into the process in order to be re-pyrolysed. In this method, the gases are free to flow between the different parts of the reactor. The publication does not state that the gases obtained from the reactors are kept separate or condensed stepwise. This method does not allow separation of the gases and material condensed from them.

The publication WO 2011/159768 A2 describes a two-stage pyrolysis process in which a slow pyrolysis stage is followed by a flash pyrolysis stage. These steps are carried out in reactors which are connected to each other directly, without preventing the mixing of gases generated in the different stages. The publication does not suggest that the slow pyrolysis stage is phased. Nor does the publication suggest that the condensation stage of the gases is phased or controlled. The purpose of the present invention is to provide an apparatus in which the above- described disadvantages of the state of the art are overcome.

By means of the apparatus according to the present invention it is possible to generate desired end-products, such as various qualities of carbon, as well as different liquids and gases, in a controlled way and reproducibly. Summary of the present invention

The present invention relates to an apparatus according to Claim 1 for charring organic material by using slow pyrolysis, which apparatus comprises:

two or more vertical reactors connected in series by means of conveyors in such a way that each reactor is adapted to receive material to be treated from the conveyor preceding the reactor, to an upper part of this reactor, and each reactor is further adapted to feed the material that has been treated in this reactor, from its lower part to the conveyor which is subsequent to the reactor, wherein

the feeding of the material to be processed into each reactor, and the transportation of it from each reactor to the subsequent one is arranged in a gas-tight manner in such a way that the gases generated in each reactor do not come into contact with the contents of other reactors or the gases that are generated in other reactors,

wherein there is a gas-tight rotary valve between consecutive reactors, in such a way that each reactor and the subsequent conveyor form a discrete gas-tight space,

and to each reactor is connected two or more consecutive condensation units, in order to process the gases that are generated in this reactor, in such a way that the condensation temperature is arranged to be stepwise descending. According to a preferred embodiment, the condensation units are condensation heat exchangers.

The present invention also relates to the use of the apparatus for producing carbon. In addition, the present invention relates to the use of the apparatus for fractionating organic material into desired gas and liquid fractions.

Furthermore, the present invention relates to the use of the apparatus for slow stepwise pyrolysis of organic material.

According to a preferred embodiment, the gases generated in the pyrolysis are separately collected from each reactor and condensed in two or more stages in such a way that the temperature is stepwise lowered. Description of the drawings

Figure 1 shows the first two consecutive reactors of the apparatus which are in series, after which the reactor line can continue in a corresponding way.

Figure 2 shows the first two condensation units of the condensation line, which condensate the gas coming from the reactor. After these two condensation units, the condensation line can continue in a corresponding way.

Detailed description of the present invention

In the following, the present invention is described in more detail with reference to the accompanying drawings.

According to the present invention, the reactors of the apparatus are in a vertical position in such a way that the solid feed is brought into the upper end of the reactor. In each reactor, the feed is transported from above downwards and the gases generated in the reaction rise. From the bottom part of the reactor, the solid matter moves to the upper part of the next reactor by a conveyor. Gases from each reactor are collected from the upper part of the reactor into the condensation unit, which may be one or more in series for each reactor.

When the process apparatus is started, it is empty (i.e. full of air), and the temperature inside the apparatus is the same as the ambient temperature. The first conveyor 1 transfers the raw material into the reactor 4 until this is full. After that, the conveyor 1 is stopped, and the gas-tight and cutting rotary valve 2 is shut. The burner 7 starts and leads the combustion gases 14 generated in it into the combustion gas space 5, which is between the reactor 4 and its outer jacket, from which space the combustion gases 14 are removed in a controlled way along the flue pipe 13 to a desired place to be heated (not shown) or ex- hausted into the outside air. The combustion gases 14 generated in the burner heat the inner part of the reactor 4 until the temperature predetermined in the control logic is reached. After that, the temperature is maintained constant as long as the process is run. When the raw material has been in the reactor 4 for a time specified in the control logic, the conveyor 15 transfers it to the reactor 17, through the gas-tight rotary valve 16. When the reactor 17 is filled, the gas-tight rotary valve 16 is shut. After that, the emptied reactor 4 is filled as described above. The temperature of the reactor 17 is raised to a level that is predetermined in the control logic, by using the hot combustion gases 36 generated in the burner 23, which combustion gases are led from the burner 23 to the space between the outer jacket 19 and the inner part 17 of the reactor 17, and from there out along the flue pipe 35, either to the outside air or to a certain part of the process (not shown), in order to generate heat. When the feed has been in the reactor 17 for a holding time predetermined in the logic, it will be transferred along the gas-tight conveyor 27, through the gas-tight rotary valve 28 to the following reactor (not shown). After that, the solid matter in the reactor 4 is transferred to the reactor 17, after it has been in the reactor 4 for a specified period of time. After that, the reactor 4 is filled with new raw material.

The process is continued as described above until the last reactor is full, and after its hold- ing time has expired, periodic operation of the process starts as follows. An amount of final carbon is removed from the last reactor that corresponds to the amount of the contents of the gas-tight rotary valve and, after that, the same amount of solid matter generated from the previous reactor, is added into the reactor. The operation will be continued until partial emptying and filling of the first reactor 4 have been carried out. The process continues as described above until it is stopped in such a way that the first reactor 4 is no longer provided with new raw material. As the reactors are emptied, their burners also stop functioning and the reactors cool off to ambient temperature.

In the reactors, due to the heating, different mixtures of gases that depend on the tempera- ture range, are emitted from the raw materials, and these gas mixtures raise the pressure in the reactors. This pressure is used to transfer the gases to the condensation stage.

In the following, the gas and condensing process of the reactor 4 will be described, which process is repeated in all the other reactors of the line in a similar way, the only variable being the temperature range. When the raw material in the reactor 4 is heated using the burner 7, different mixtures of gases begin to be emitted from the raw material, which cause an increase in pressure inside the reactor 4. This pressure transfers gas along the gas tube 6, which starts from the upper part of the reactor 4, to the condensation unit 9. The operating temperature of the condensation unit 9 is controlled by a logic program, by using, for example, an aqueous or vapor stream, which comes to the condensation unit 9 along the tube 12 and exits along the tube 11 to a desired place (not shown) in the preheating of the raw material of the process. If necessary, there may be several sequential con- densation units 9, and in all of them different temperature ranges are used for condensing. In the condensation unit 9, the condensing gases, which are comprised in the gases, are converted into a liquid state, which is then led to the liquid storage tank 10, through the control valve (not shown) that is located between the tank 10 and the condensation unit 9. This valve (not shown) is controlled by the pressure of the reactor 4, keeping the reactor 4 constantly at slightly overpressure. In this way, possible oxygen leaks into the process apparatuses caused by faults (for example a leaky seal) can be prevented.

During the process, the reactor 4 and the subsequent conveyor 15 form a discrete gas-tight space, because the rotary valve 16 prevents mixing of the gases in the reactor 4 and the reactor 17.

According to one embodiment, the temperatures of the reactors increase stepwise in such a way that the temperature of the last reactor is at maximum 350 °C, for example at maximum 320 °C.

According to one embodiment, at least two consecutive reactors, for example three consecutive reactors, are used in such a way that the temperature of the first reactor is at maximum 150 °C, the temperature of the second reactor is at maximum 300 °C, and the temperature of a possible third reactor is at maximum 350 °C.

Figure 2 shows a reactor- specific phased condensation line. The gas generated in the reactor (not shown) is led through the tube 6 to the first condensation unit 9, which in this case is a condensation heat exchanger. In the condensation heat exchanger 9, at a temperature determined in the logic program, and by using the liquid that is led into the tube 12, the condensing components are condensed from the gas, which components are then led to the tank 10. The uncondensed gases are led along the tube 33 to the next condensation heat exchanger 31, the condensing temperature of which is preset by the logic program to be lower than the condensing temperature of the first condensation heat exchanger 9. The condensing components are led into tank 32. The uncondensed gases can be further led to the following condensing units that are similar to those described above, in which case it is possible to condense different components in each unit. The condensing temperature of the subsequent condensation unit is always lower than that of the previous one.

The conveyors used in the apparatus may be, for example steel wires or other suitable conveyors that are able to withstand the high temperatures used in the process.

The material of the reactors is preferably stainless steel or a ceramic mass. These materials are preferred because of the high temperatures used in the process and the acidic components that are emitted from the raw material.

The burners used may be, for example overpressure burners, air atomizing burners or injection burners.

The method according to the present invention makes it possible to generate different gases and liquids, and pure carbon, as end products.

Example

The following example table shows the characteristics of the fractions (carbon and distillate) obtained by laboratory demonstration and using the apparatus according to the present invention. The raw material used was unbarked pine chips. In this example, three reactors are used in such a way that in the first step, the temperature was 145 °C, in the second step, 270 °C and in the last step, 320 °C. The liquids of all the three steps were mixed together to form one mixture for analysis.

The first column of the example table shows the quantity or the element to be investigated in the analysis, the column 98-1 the analysis values derived from the charcoal, the column 55-2 shows the analysis values of the liquids obtained in the present method, and the last column shows the standards of the analysis used.

The distribution in percentage by weight was as follows: charcoal 32, distillates 49, and the uncondensed gases 19. The uncondensed gases were not analyzed.

The analysis shows that the apparatus works as planned, producing high-quality carbon, which is suitable for example to be mixed into coal in dust combustion. In the present in- vention, the yield of liquids will vary depending on the temperatures and condensing temperatures used. The low calorific value of the liquid that was analyzed can be explained by the high water content of the first stages.

dm = of the dry matter