PROCESS AND REACTOR FOR CONTINUOUS CHARCOAL PRODUCTION

Abstract

Continuous charcoal production system in a vertical reactor with a concentric charging zone (1) and drying zone (2), a carbonization zone (3), a cooling zone (4) and a discharge zone (5), and a method for recovering energy from carbonization gases for the production of this charcoal, comprising the extraction of carbonization gas from the drying zone (2) and subdividing it into recirculating gas and heating gas, with the remaining gas exceeding the energy required to generate electricity; burning the heating gas in a hot gas generator (11); injecting the recirculating gas into a heat recovery unit (9); injecting the heating gas after combustion into the heat recovery unit (9), indirect heating of the recirculating gas; and reinjecting the heated recirculating gas into the carbonization zone (3) of the reactor (R).

Claims

1. A method for recovering energy from carbonization gases for the continuous production of charcoal in a reactor with a vertical structure comprising in sequence: a top charging zone, a drying zone, a carbonization zone, a cooling zone and a discharge zone, the method characterized by comprising the steps of: extracting carbonization gas from the top of the drying zone of the reactor and subdividing it into fractions that comprise at least a recirculating gas mass and a heating gas mass; conducting the combustion of the heating gas mass in a hot gas generator; injecting the recirculating gas mass into a heat recovery unit; injecting the heating gas mass after combustion onto the heat recovery unit, for indirect heating of the recirculating gas mass; and reinjecting the recirculating gas mass heated by the heat recovery unit into the carbonization zone base of the reactor.

2. The method according to claim 1, wherein during the step of extracting and subdividing the carbonization gas from the reactor, the carbonization gas is subdivided into three fractions, whereby the third fraction is a remaining mass that is sent to a thermo-power plant.

3. The method according to claim 1, wherein after combustion and after injection onto the heat recovery unit for indirect heating, the heating gas mass is then used to dry the wood that will be subsequently fed into the charging zone of the reactor.

4. The method according to claim 1, wherein it comprises a step of controlling the temperature of the recirculating gas mass reinjected into the carbonization zone base of the reactor by means of controlling the amount of atmospheric air forced into the hot gas generator.

5. A continuous charcoal production system characterized by comprising: a reactor with a vertical structure comprising in sequence: a top charging zone, a drying zone with at least two outlets for extracting carbonization gas at its top, a carbonization zone, a cooling zone and a discharge zone, and a gas recovery circuit in fluid communication with at least two outlets of the drying zone, wherein the gas recovery circuit comprises: a heat recovery unit within which the recirculating gas mass extracted from the reactor circulates, where this recirculating mass is heated and reinjected into the carbonization zone base; and a hot gas generator that receives and handles the combustion of a heating gas mass extracted from the reactor, discharging heating gas after combustion onto the heat recovery unit for indirect heat exchange with the recirculating gas mass in the heat recovery unit.

6. The system according to claim 5, characterized by comprising a wood dryer, into which the heating gas is fed after combustion and after running through the heat recovery unit.

7. The system according to claim 5, characterized by comprising a pipe in communication with the outlets of the reactor that carries a remaining mass of the carbonization gas extracted from the reactor to a thermo-power plant.

8. The system according to claim 5, wherein it comprises a tubular ring surrounding the carbonization zone base, the ring being in fluid communication with the heat recovery unit, and comprising a plurality of connections distributed regularly around the carbonization zone, establishing fluid communication between the interior of the ring and carbonization zone base, whereby the recirculating gas mass flows from the heat recovery unit to the ring and through the connections to the carbonization zone base.

9. The system according to claim 5, wherein: the charging zone of the reactor has a cross-section smaller than the drying zone and has an extension into the interior of the drying zone, forming an annular space around the extension, and the charging zone is arranged concentrically in relation to the drying zone, wherein the ratio between the diameter of the charging zone and the diameter of the drying zone is between 0.68 and 0.72.

10. The system according to claim 5, wherein the hot gas generator performs full combustion with excess atmospheric air of the heating gas mass extracted from the reactor, before discharging the heating gas onto the heat recovery unit for indirect heat exchange with the recirculating gas mass in the heat recovery unit.

11. The system according to claim 5, wherein it performs the method for recovering energy from carbonization gases for the continuous production of charcoal in a reactor with a vertical structure comprising in sequence, a top charging zone, a drying zone, a carbonization zone, a cooling zone and a discharge zone, the method characterized by comprising the steps of: extracting carbonization gas from the top of the drying zone of the reactor and subdividing it into fractions that comprise at least a recirculating gas mass and a heating gas mass; conducting the combustion of the heating gas mass in a hot gas generator; injecting the recirculating gas mass into a heat recovery unit; injecting the heating gas mass after combustion onto the heat recovery unit, for indirect heating of the recirculating was mass; and reinjecting the recirculating gas mass heated by the heat recovery unit into the carbonization zone base of the reactor.

12. A reactor for continuous charcoal production, with a vertical structure comprising in sequence: a top charging zone, a drying zone, a carbonization zone, a cooling zone and a discharge zone, whereby the charging zone has a cross-section smaller than the drying zone and has an extension extending into the interior of the drying zone, forming an annular space around the extension, characterized in that at the top of the drying zone, at least two outlets for extracting gases are arranged in a diametrically opposed manner, and the charging zone is arranged concentrically in relation to the drying zone, and wherein the ratio between the diameter of the charging zone and the diameter of the drying zone is between 0.68 and 0.72.

13. The reactor for continuous charcoal production, according to claim 12, characterized in that it comprises: a lower tubular ring surrounding the base of the cooling zone, in fluid communication with the interior of the cooling zone base; an upper tubular ring surrounding the top of the cooling zone, in fluid communication with the interior of the top of the cooling zone; a heat exchanger with an inlet in fluid communication with the upper ring for extracting carbonization gas at the top of the cooling zone and an outlet in fluid communication with the lower ring, whereby carbonization gas drawn from the cooling zone flows through the heat exchanger to the ring and back to the top of the cooling zone.

14. The recovery of condensable gases resulting from carbonization, condensed in the gas recovery circuit, when the method defined in claim 1 is carried out.

15. Vegetable tar and pyroligneous extract resulting from the condensation of condensable carbonization gases, produced under a controlled thermal profile as defined in claim 1.

16. The recovery of condensable gases from carbonization in a system, according to claim 5.

17. Vegetable tar and pyroligneous extract recovered in the interconnection from the top of the reactor to the heat recovery unit, where the recirculating gas mass passes.

18. Vegetable tar and pyroligneous extract recovered in the interconnection between the top of the reactor and the inlet of the hot gas generator.

19. Vegetable tar and pyroligneous extract recovered in the interconnection between the top of the reactor and the thermal plant.

20. All condensable gases recovered according to claim 14 stored in tanks for storage and then destined for the proposed purpose.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0024] The invention will be described in greater detail below, based on an example of an embodiment illustrated in the Figures. The Figures show:

[0025] FIG. 1A a simplified schematic view of the different zones of a continuous charcoal production reactor, including external equipment and the charging and discharging steps;

[0026] FIG. 1B expanded view of a detail in FIG. 1A of the charging and drying zones;

[0027] FIG. 2 the system for burning the carbonization gases and heating the recirculating mass that provides energy and maintains the heat profile of the reactor;

[0028] FIG. 3 distribution graph comparing the charcoal mesh obtained through the invention in question with the charcoal mesh produced by conventional kilns at the state of the art;

[0029] FIG. 4 graph showing the results of charcoal bed permeability tests, comparing the product obtained through the invention with the previous technique.

DETAILED DESCRIPTION OF THE INVENTION

[0030] As shown in FIG. 1A, in the charcoal production process the wood which is initially wet after felling in the forest 20 is conveyed to a wood chipper 19. The output from this process is conveyed to a dryer 18 and is then carried in a tipper-bucket 21 on rails up to the top of the charging zone 1 of the reactor R of a continuous charcoal production system.

[0031] The carbonization reactor R comprises the charging zone 1 at its top, below which it extends into a drying zone 2, whose diameter is larger than that of the charging zone 1. The following are arrayed under the drying zone 2 in descending sequence: a carbonization zone 3, a cooling zone 4 and a discharge zone 5.

[0032] A detail of FIG. 1A is expanded in FIG. 16. Consequently, FIG. 16 shows that the charging zone 1 extends into a drying zone 2 through an extension 1.

[0033] The charging zone 1 has a diameter that is smaller than the diameter of the drying zone 2, forming a double pipe region with an annular space A around the charging zone extension 1, in the drying zone 2. The diameter of the charging zone 1 is also some 30% smaller than the diameter of the charging zone of reactors at the state of the art. Preferably, the ratio between the diameter of the charging zone DC and the diameter of the drying zone DS is between 0.68 and 0.72. According to a preferred embodiment of the invention, the diameter of the charging zone (DC) is 1.80 m while the diameter of the drying zone (DS) is 2.50 m. As a result, the annular space A has an area that is larger, compared to reactors at the state of the art.

[0034] In addition to this increase in the annular space A between the charging zone extension 1 and the drying zone 2, there are at least two carbonization gas extraction outlets 8 in the upper part of the drying zone, opposite each other at 180, in order to divide the flow at the top of the reactor. The association of using at least two outlets 8 with the increased annular space means that the speed of the gas in the reactor is reduced, and the internal flow in the reactor is more uniform. This allows the carbonization gases to be extracted at slower speeds, keeping the same necessary flow rate, substantially reducing the amount of unwanted wood matter carried along, such as sawdust or debris, thus ensuring better distribution and uptake of gases drawn through the extraction outlets 8.

[0035] The vertical axes of the charging zone cylinder 1 and the drying zone cylinder 2 are vertically aligned, whereby charging zone 1 and drying zone 2 are concentric.

[0036] The use of two extraction outlets 8 insurers more homogeneous gas flow control. Together with the homogeneous distribution of the recirculating mass of gases heated in the carbonization zone base as described below, this control endows the reactor with a more accurate heat profile.

[0037] When the reactor R is charged and in operation, new wood is fed into charging zone 1, whereby the drop of the entire contents of the reactor R is controlled through opening the valves in discharge zone 5.

[0038] As a result, charcoal production speed can be controlled through opening and closing these valves, which intervenes in the physical and chemical characteristics of the resulting charcoal. Opening and closing these valves also allows the respective continuity of the charcoal production process.

[0039] While the wood is running through the drying zone 2 of the reactor, it loses its moisture and the pyrolysis phase begins in carbonization zone 3. The wood carbonization temperature is a function of the desired fixed carbon content, whereby a temperature of 400 C. is normally used.

[0040] In the reactor according to the invention, gases are circulated that are drawn from the extraction outlets 8 and fed back on to the carbonization zone base 3, known as recirculation gases or recirculating mass. In addition to these gases, new gases are also formed within the reactor, deriving from carbonization. A method for recovering energy from the carbonization gases is put into operation in order to recirculate these gases in an optimized manner, which will be described here.

[0041] The carbonization temperature in the reactor is attained through the energy contained in the recirculating mass that is reinjected into the reactor through a pipe 10 in a ring 10 in the carbonization zone base 3. However, it is important that this recirculating mass is reheated before injection, which will be explained below.

[0042] FIG. 1A also shows the gas recovery circuit of the continuous charcoal production system according to the invention, where heat energy is recovered from the carbonization gases. Gases extracted from the top of the reactor are divided into three fractions, namely: a heating gas mass that is taken to a hot gas generator 11 through the first pipe 11, the recirculating mass that is taken to the recovery unit 9 through the second pipe 16 and the remaining mass that runs through the third pipe 16 to the thermo-power plant 17. The first pipe 11, the second pipe 16 and the third pipe 16 are in fluid communication with the outlets 8 of the reactor.

[0043] The gas fraction produced during carbonization that is piped to the hot gas generator (HGG)11 is used to provide heat for the process. The combustion of these gases is handled through an excess of atmospheric air forced into the hot gas generator 11 above the stoichiometric condition.

[0044] The remaining fraction or remaining mass of the gases produced during carbonization and not needed to provide energy for the reactor R is carried by pipe 16 to the thermo-power plant 17.

[0045] In turn, the smoke resulting from combustion leave the hot gas generator 11 through a pipe 12 and run to a heat recovery unit 9 where they indirectly heat the recirculating mass of carbonization gases. The recirculating mass is then from the heat recovery unit 9 through the tubular ring 10 onto the carbonization zone base 3 and the heat energy in this mass ensures the final temperature of the carbonization zone and control of the heat profile of the reactor R. As the ring 10 surrounds the carbonization zone base 3, a plurality of connections 10 between the ring and the reactor that are spread around the circumference of the carbonization zone 3, allow fluid communication between the interior of the ring 10 and the carbonization zone base 3. In other words, the circulating mass enters the zone base 3 in a homogeneous manner, which allows a better heat profile in the carbonization zone 3.

[0046] After firing, the mass of heating gases exchanges heat with the recirculating mass in the heat recovery unit 9 and runs through the pipe 14 for secondary use of the remaining heat energy, with this heat energy used to dry wood in the dryer 18. Drying the wood ensures enhanced efficiency for converting wood into charcoal.

[0047] This construction of the gas recovery circuit is fairly simple and energy-efficient, as Bernie takes place without excess air and the heat in these smoke indirectly heats up the recirculating mass, as this recirculating gas mass must effectively be heated prior to injection into the reactor R. The gases forming the recirculating mass are heated in the recovery unit 9 by the smoke or the burned heating gas mass produced in the hot gas generator 11, although with no direct contact between the recirculating mass and the heating gas mass burned in the hot gas generator 11, as will be described below.

[0048] The composition of the recirculating gas mass is similar to that of the carbonization gases in the reactor, namely: oxygen-free. The absence of oxygen in the recirculating mass means that there is no charcoal combustion in the carbonization zone base 3, which allows efficient control of the heat profile, with better charcoal yield and control over the physical and chemical quality of the resulting charcoal.

[0049] FIG. 2 clearly shows that gas from the extraction outlets 8 at the top of the reactor R is subdivided, with one part piped back into the kiln, forming the recirculating mass. However, as mentioned, this recirculating mass must be heated before re-entering the reactor, through the ring 10 on the carbonization zone base 3, in order to reach the ideal carbonization temperature. According to the method for recovering energy from gases addressed by the invention, this heating process is handled through the heat recovery unit 9 that is in fact a heat exchanger 9, in which the smoke or the burned heating gas mass from the generator 11 to not enter into direct contact with the recirculating mass. Control of the recirculating mass temperature is handled through piping excess atmospheric air into the hot gas generator 11. This excess air ensures full combustion of the hot gas in the hot gas generator 11. However, increasing the amount of excess atmospheric air injected into the hot gas generator 11 lowers the temperature of the heating gas mass burned in the hot gas generator 11 piped to the recovery unit 9, which in turn allows carbonization temperature control.

[0050] As the heating gas mass burned in the hot gas generator 11 is used only to heat the recirculating mass through a heat exchanger, namely: recovery unit 9, in other words, not coming into direct contact therewith, it is possible to heat this recirculating mass without causing unwanted clogging of the reactor through the condensation of oils and other components, in contrast to the state of the art.

[0051] FIG. 1A shows cooling zone 4 located below carbonization zone 3. In this 4, the charcoal runs down against the carbonization gases cooled in a heat exchanger 13. Furthermore, the actual carbonization gases are sucked up through an exhaust outlet on tubular ring 15 at the top of cooling zone 4, and then piped to a heat exchanger 13 and reinjected through ring 13 into cooling zone base 4.

[0052] Under cooling zone 4 is discharge zone 5, comprised of two chambers and functioning like a lock-gate, stopping air from entering the furnace during discharge operations. In turn, the resulting charcoal is sent to silo 7 and from there it is used for consumption purposes.

[0053] Proving the efficiency of the system described above, the graph shown in FIG. 3 compares the type of charcoal obtained through the reactor according to the invention with the charcoal obtained from conventional masonry kilns. This graph shows two curves. The more scattered bottom curve with greater variance (more scattered) shows the mesh distribution (in millimeters) of charcoal produced in conventional masonry kilns. The more tightly clustered top curve with less variance (more tightly clustered) shows the normal mesh distribution of the charcoal produced by the reactor addressed by the invention. As the normal curve is more tightly clustered in the center, with less variance, it is clear that the charcoal obtained through the invention offers appreciably greater homogeneity than the charcoal obtained from conventional masonry kilns. This more homogeneous mesh directly impacts charcoal use in the downstream processes where it will be employed, such as better steel production control, for example, with direct implications on the resulting quality.

[0054] Finally, the differential pressure flow rate speed curves in FIG. 4 compare the permeability quality of the charcoal bed obtained through the invention with charcoal from conventional masonry kilns. Permeability is the property through which a bed allows fluid to flow through its particles with greater or lesser ease. Beds with charcoal particles whose dimensions are more homogeneous allow easier throughflow and are more evenly distributed, in other words, they are endowed with greater permeability. The graph in FIG. 4 shows that the lower the differential pressure in other words, the closer the curve is to the abscissa (horizontal or x) axis the better the permeability, as indicated by the arrow in this graph. It is noted that the raw charcoal produced through this invention is endowed with better permeability than raw charcoal and layered charcoal from conventional masonry kilns.

[0055] This invention consequently attains the desired goals of providing a reactor and a system for the continuous production of charcoal, together with a method for recovering energy from carbonization gases with greater energy efficiency, able to produce higher grade charcoal one at the same time eliminating the risk of clogging the equipment. The proposed rules are reached through this invention, due to the fact that the gases are burned completely with excess air, as well as the fact that the heat energy generated through this learning process indirectly heats a recirculating fluid comprised of the carbonization gases. Temperature control of the recirculating mass without coming into contact with smoke and without oxygen allows control of the reactor heat profile, the carbonization yield and the grade of the resulting charcoal. This consequently contributes to a better heat profile with no undesirable halts and operations due to clogging caused by the condensation of pyroligneous vapors.

[0056] Having described an embodiment merely as an example, it must be understood that this invention may be materialized in other ways, with its scope limited only by the following Claims, including characteristics equivalent to those specifically defined herein.