THERMOLYSIS SYSTEM AND METHOD FOR OBTAINING RECOVERED CARBON BLACK AND FUEL FROM DISUSED TIRES

Abstract

The invention relates to a thermolysis system and method for obtaining recovered carbon black and fuel from disused tires, which includes a thermolysis reactor and a flash vessel acting jointly to refine fuel without the need for post-treatment to clean same. During thermolysis, condensers are cleaned without needing to cut the flow or deviate the gas stream, since the deposits formed inside tubes of a heat exchange system are cleaned using a part of the fuel obtained. The carbon black obtained is comparable to existing semi-reinforcing carbon blacks. The obtained fuel has a high content of aromatic compounds, and its carbon content is reduced to 3% by weight, up to 0.8% by weight, with respect to fuels obtained in pyrolytic processes, without requiring post-treatment such as distillation processes or catalytic treatment.

Claims

1. A thermolysis process to obtain recovered carbon black and fuel from disused tires, comprising the steps of: a) crushing the disused tires (rubber) to a size between 0.1″ to 4″ (0.25 cm to 10.16 cm) to obtain crushed material; b) feeding the crushed material to a rotating horizontal cylindrical thermolysis reactor, which is surrounded by an outer chamber; c) closing the reactor and feeding an inert gas to the reactor in order to generate an oxygen-free atmosphere; d) indirectly heating the reactor with gases from a combustion chamber by directing the gases to the outer chamber; e) increasing the temperature gradually from room temperature and keeping it in a range between 250° C. and 350° C. for a period of 1 to 4 hours, gasifying the water, all of the lighter hydrocarbons and some of the heavier hydrocarbons; f) increasing the temperature again to more than 450° C. for a period of 2 to 4 hours, achieving the gasification of the heavier hydrocarbons that are still in liquid state; g) obtaining from the reactor and outer chamber, a gaseous stream of hydrocarbons, combustion gases and recovered carbon black; h) cooling the recovered carbon black inside the reactor and extracting residual hydrocarbons from the recovered carbon black by stripping with the inert gas and extracting the recovered carbon black from the reactor; i) taking the gaseous stream of hydrocarbons to a flash distillation container, where part of the stream remains in a gaseous phase to form a gaseous stream and the other goes to a liquid state; j) passing the gaseous stream from the flash container towards a system of heat exchangers, where a part of the gaseous stream is condensed to form a condensate and another part is kept in a gaseous state, finally obtaining a two-phase current at the end of the passage through the system of heat exchangers; k) taking the two-phase current that leaves the system of heat exchangers to a phase separation tank where a separation of the condensate occurs due to the effect of the phase difference of the two-phase current, producing a gas phase current and a liquid phase current; l) directing the gas phase current towards a battery of water seals, which produces a fuel supply that feeds the combustion chamber to generate the necessary heat in the process making it energetically self-sustaining; m) directing the liquid phase current towards a filtering system to obtain a filtered fuel stream that is stored for marketing in a final storage tank, where a part of this filtered fuel stream remains in a lung container; and n) using the part of the filtered fuel from the lung container to co-currently clean the system of heat exchangers.

2. The process according to claim 1, wherein in step c) the inert gas is nitrogen gas, and in this step an oxygen-free atmosphere of between 99.0% and 99.9% is generated and a pressure inside the reactor of between 10 and 200 mbar (1 and 20 kPa) is maintained.

3. The process according to claim 1, wherein in step i) where a part of the gaseous stream of hydrocarbons remains in the gaseous phase and another goes to the liquid state due to a design of the flash container and the pressure changes inside it.

4. The process according to claim 1, wherein prior to and during step a) there is an extraction of metals.

5. The process according to claim 4, wherein the extraction of metals is carried out by means of a magnetic separator.

6. The process according to claim 1, wherein in step e) there is a heat transfer from the external chamber to the reactor, which regulates the fuel supply to the combustion chamber through a control loop that takes the temperature signal inside the reactor, to avoid violent sublimation of the rubber and prevent the increase of excessive gas flows that carry carbonaceous material.

7. The process according to claim 6, wherein a system of temperature sensors is provided in the reactor that delivers a signal to a control loop system, with which, through a set temperature, the quantity of fuel supply that is used in the combustion chamber can be regulated and therefore, the quantity of gases that is fed to the outer chamber of the reactor.

8. The process according to claim 1, wherein in step e) a liquid bed is maintained where the liquid phase/vapor phase is in equilibrium within the reactor.

9. The process according to claim 1, wherein the thermolysis inside the reactor ends when the gas generation ends, after the second temperature increase in step f), which is monitored through a sensor flow.

10. The process according to claim 1, wherein the maximum residence time of the crushed material in the reactor is 12 hours.

11. The process according to claim 1, wherein the combustion chamber works with gaseous or liquid fuels, generating the thermal energy necessary to achieve the operating conditions of the reactor using the combustion gases as a source of heat for the reactor.

12. The process according to claim 1, wherein the gases that are generated in the combustion chamber pass through the outer chamber of the reactor providing the necessary heat to carry out the thermolysis of the crushed material.

13. The process according to claim 1, wherein the combustion gases that come out of the outer chamber are mixed with fresh air in a centrifugal blower to generate a stream of fresh combustion gases, where part of this stream of fresh combustion gases is recirculated to the combustion chamber in order to improve energy efficiency and ensure complete combustion of the gases, with this wherein the fresh air has been preheated by the combustion gases that left the outer chamber of the reactor, and the remaining part of the stream of fresh combustion gases is released into the atmosphere.

14. The process according to claim 1, wherein the flash distillation container has a vertical cylindrical design such that its upper part, where the gas phase is located, is of greater volume in relation to its lower part, where the liquid phase accumulates, which allows the return to the reactor of the liquid state separated by the effect of the pressure change in the flash container, preventing the drag of carbonaceous material in the gaseous stream that remains in the gaseous state, due to the reduction in the speed of this flow, with which the heavy hydrocarbons present in the liquid state are reprocessed since the design has an overflow, which allows the hydrocarbons in phase liquid state to return to the reactor, reducing the carbonaceous residues in the final fuel in addition to reducing the particulate material that is deposited inside tubes of the heat exchangers system.

15. The process according to claim 1, wherein the gas phase current from the phase separation tank passes through the battery of water seals of step 1) consisting of a series of vertical containers with water, which act as a safety system to avoid ignition of the gas.

16. The process according to claim 15, wherein one of these vertical containers of the battery of water seals contains a solution of calcium hydroxide or caustic soda, reducing the sulfur content of the gas phase current.

17. The process according to claim 1, wherein the cleaning of the system of heat exchangers is carried out due to the action of the part of the filtered fuel from the lung container that is recirculated to produce recirculated fuel, wherein the system of heat exchangers comprises at least two tube and shell exchangers in series or in parallel.

18. The process according to claim 17, wherein to achieve the cleaning of the interior of the tubes, without stopping the operation/process, the following steps are carried out in the system of heat exchangers which is used in step j): j.1) introducing the recirculated fuel co-currently to the gaseous stream from the flash container to the interior of the tubes, where the recirculated fuel enters the interior of some heads in the tubes through injectors oriented in a direction co-current with the flow of the gaseous stream; j.2) introducing a stream of cooling water from a cooling circuit to the shell; and j.3) cleaning the inside of the tubes with the high pressure with which the recirculated fuel is injected and its dissolving capacity, dragging the material deposited into the tubes.

19. The process according to claim 18, wherein the number of injectors will be one for every 4 tubes for a correct cleaning of the interior of the tubes of the heat exchangers.

20. The process according to claim 18, wherein the recirculated fuel is automatically activated when efficiency in heat exchange is lost, which occurs when the difference is reduced between the temperatures of the inlet and outlet of the cooling water stream that passes through the shells of the heat exchangers, where the cooling water stream is directed to the refrigeration cooling circuit to return to the system of heat exchangers, where a verification is carried out through sensors.

21. A thermolysis system for obtaining recovered carbon black and fuel from disused tires, comprising: i. a rotating horizontal cylindrical thermolysis reactor, which is surrounded by an outer chamber, where the reactor receives crushed material to be treated, obtaining from the reactor and outer chamber, a gaseous stream of hydrocarbons, combustion gases and recovered carbon black; ii. a combustion chamber, which indirectly heats the reactor with gases that are directed to the outer chamber; iii. a flash distillation container, which receives the gaseous stream of hydrocarbons from the reactor, where a part of the gaseous stream of hydrocarbons is kept in a gas phase and another goes to a liquid state; iv. a system of heat exchangers that receives the gaseous phase from the flash container, where a part of the gaseous stream is condensed to form a condensate and another part is kept in a gaseous state, obtaining finally a two-phase current at the end of the passage through the system of heat exchangers; v. a phase separation tank that receives the two-phase current that leaves the system of heat exchangers, where a separation of the condensate with the gas occurs due to the difference in phases of the two-phase current, producing a gas phase current and a liquid phase current; vi. a battery of water seals that receives the gas phase current, generating a fuel supply that then feeds the combustion chamber to generate the necessary heat in the process and make it energetically self-sustaining; vii. a filtering system that receives the liquid phase current to obtain a filtered fuel stream; viii. a lung container that stores a part of the filtered fuel stream; and ix. a storage tank for storing the rest of the filtered fuel stream for marketing.

22. The system according to claim 21, further comprising a cooling circuit, which keeps process water that circulates through the system of heat exchangers cold.

23. The system according to claim 21, wherein the flash distillation container has a vertical cylindrical design such that its upper part, where the gas phase is located, is of greater volume in relation to its lower part, where the liquid phase accumulates, which allows the return to the reactor of the liquid state separated by the effect of the pressure change in the flash container, preventing the drag of carbonaceous material in the gaseous stream that remains in the gaseous state, due to the speed reduction of this flow, with which the heavy hydrocarbons present in the liquid state are reprocessed since the design has an overflow, which allows the hydrocarbons in liquid state to return to the reactor, reducing the carbonaceous residues in the final fuel in addition to reducing the particulate material that is deposited inside the tubes of the system of heat exchangers.

24. The system according to claim 21, wherein the battery water seals consist of a series of vertical containers with water through which the gas phase current passes, acting as a safety system to prevent the ignition of the gas.

25. The system according to claim 21, wherein the system of heat exchangers comprises at least two tube and shell heat exchangers in series or in parallel.

26. The system according to claim 21, wherein the system has various sensors, where the reactor has a temperature sensor system that delivers a signal to a process control loop system, with which through a set temperature regulates the amount of fuel supply that is used in the combustion chamber and thus the amount of gases that is fed to the outer chamber of the reactor; furthermore, the reactor has a flow sensor to monitor the completion of thermolysis inside the reactor by recording when the gas generation is completed.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0019] FIG. 1: Flow diagram of the process of the invention where each of the components of the system of the invention are identified, together with the flow currents involved.

[0020] FIG. 2: Explanation of the condensation system with 2 heat exchangers in series, where the use of part of the produced fuel that is being recirculated from the buffer tank for temporary fuel storage is indicated.

DESCRIPTION OF THE INVENTION

[0021] The process of the invention will be explained through the flow diagram of FIG. 1, identifying each of the streams involved in the process and each of the components of the system of the invention.

[0022] The thermolysis process for obtaining recovered carbon black and fuel from disused tires comprises the following stages: [0023] a) crushing the disused tires until reaching pieces of rubber with a size between 0.1 “to 4” (0, 25 cm to 10.16 cm); [0024] b) feeding the crushed material (A) to a rotating horizontal cylindrical thermolysis reactor (1), which is surrounded by an outer chamber (2); [0025] c) close the reactor (1) and feed the reactor an inert gas (3), preferably gaseous nitrogen, in order to generate an oxygen-free atmosphere (between 99.0% and 99.9%) and maintaining a gauge pressure inside the reactor between 10 and 200 mbar (1 and 20 kPa); [0026] d) indirectly heating the reactor (1) with gases (N) that come from a combustion chamber (4), which are directed to the outer chamber (2); [0027] e) increase the temperature gradually from room temperature and keep it in a range between 250° C. and 350° C. for a period of between 1 to 4 hours, gasifying the water, all the lighter hydrocarbons and part of the heaviest hydrocarbons; [0028] f) increase the temperature again to more than 450° C., achieving the gasification of the heavy hydrocarbon that was still in a liquid state, during a period of between 2 to 4 hours. [0029] g) obtaining from the assembly of reactor (1) and outer chamber (2) a gaseous stream of hydrocarbons (B), combustion gases (0) and recovered carbon black (C); [0030] h) cooling the recovered carbon black (C) inside the reactor (1) and extracting the residual hydrocarbons from the recovered carbon black by stripping with the inert gas (3) and extracting the recovered carbon black (C) from the reactor (1); [0031] i) take the hydrocarbon gaseous current (B) to a Flash distillation container (5), where thanks to the design of the Flash container (5) and due to pressure changes inside it, a part of the current remains in the gaseous phase (D) and another goes to the liquid state (B1); [0032] j) passing the gaseous stream (D) from the Flash container (5) towards a system of heat exchangers (6), where a part of the gaseous stream is condensed and another part is kept in a gaseous state, finally obtaining a stream biphasic (G) at the end of the passage through the heat exchanger system (6); [0033] k) take the two-phase current (G) that leaves the exchanger system (6) to a phase separation tank (11) where a separation of the condensate with the gas occurs due to the effect of the phase difference of the two-phase current (G), producing a gas phase current (I) and a liquid phase current (H); [0034] l) direct the gaseous phase (I) towards a battery of water seals (7), whose current (J) then feeds the combustion chamber (4) to generate the necessary heat in the process and make it energetically self-sustaining; [0035] m) direct the liquid phase (H) towards a filtering system (8) to obtain a filtered fuel stream (K) that is stored for commercialization (M) in a final storage tank (not shown in the figures), where a part of this filtered fuel stream (K) remains in a lung container (9); and [0036] n) use part of the fuel (L) produced and that comes from the buffer container (9) in cleaning (L1, L2 . . . ) in co-current of the interchangers system (6).

[0037] Before the crushing stage and during the crushing stage, there is a metal extraction, with for example a magnetic separator (not shown in FIG. 1).

[0038] In stage e) there is a heat transfer from the external chamber (2) to the reactor (1) where the crushed material (A) is located, which regulates the supply of fuel (J) to the combustion chamber (4) through a control loop that takes the temperature signal inside the reactor, to avoid violent processes of sublimation of the rubber and preventing the increase of excessive gas flows that drag carbonaceous material.

[0039] The reactor (1) has a temperature sensors system that delivers a signal to the control loop system, with which through a set temperature it is possible to regulate the amount of fuel (J) that is used in the combustion chamber (4) and therefore the amount of combustion gases (N) that is fed to the outer chamber (2) of the reactor (1).

[0040] Furthermore, in stage e) a liquid bed is maintained in which the liquid/vapor phase is in equilibrium within the reactor (1).

[0041] Thermolysis inside the reactor (1) ends when there is no longer gas generation, after the second temperature increase in stage f), which is monitored through a gas flow sensor. The maximum residence time of the crushed material in the reactor (1) is 12 hours.

[0042] The combustion chamber (4) is capable of working with gaseous or liquid fuel, generating the thermal energy necessary to reach the operating conditions of the reactor (1), using the combustion gases as a heat source for the reactor.

[0043] The Flash distillation vessel (5) has a vertical cylindrical design such that its upper part, where the gas phase is located, is of greater volume in relation to its lower part, where the liquid phase accumulates, this allows the return to the reactor (1) of the liquid phase (B1) separated by the effect of the pressure change in the same Flash container (5). At the same time, the dragging of carbonaceous material in the stream (D) that remains in the gaseous state is prevented, due to the reduction in the speed of this flow, with which the heavy hydrocarbons present in the liquid phase (B1) are reprocessed since this design has an overflow, which allows the hydrocarbons in the liquid phase to return (B1) to the reactor, reducing the carbonaceous residues in the final fuel in addition to reducing the particulate material that is deposited inside the tubes (14) of the heat exchanger system (6).

[0044] The combustion gases (N) that are generated in the combustion chamber (4) pass through the outer chamber (2) of the reactor (1) providing the heat necessary to carry out the thermolysis of the crushed rubber material (A).

[0045] The combustion gases (0) exiting the outer chamber (2) are joined with fresh air (P) in a centrifugal blower (13) to generate a stream of fresh combustion gases (Q). Part of this stream (Q) of fresh combustion gases is recirculated (Q1) to the combustion chamber (4) in order to improve energy efficiency and ensure complete combustion of the gases, with this air (P) that has been preheated thanks to the combustion gases (0) that came out of the outer chamber (2) of the reactor (1), the remaining fraction (Q2) is released into the atmosphere (10).

[0046] The water seal battery (7) of stage l) consists of a series of vertical containers with water through which the non-condensed gas (I) passes, acting as a safety system to prevent the gas from igniting.

[0047] One of these vertical containers of the water seal battery (7) contains a solution of calcium hydroxide or caustic soda, which reduces the sulfur content of the gaseous stream (I).

[0048] The heat exchanger system (6) comprises at least two tube (14) and shell (15) exchangers in series (as shown in FIG. 2) or in parallel (not shown).

[0049] In the heat exchanger system (6) that is used in stage j) the following stages are carried out, to achieve the cleaning of the interior of the tubes (14), without the need to stop the operation/process: [0050] j.1) introduce to the gas stream (D) coming from the Flash container (5) in co-current, part of the generated fuel (L1, L2 . . . ) inside the tubes (14), where the recirculation current fuel (L1, L2 . . . ) it enters the Interior of the heads (17) of the tubes (14) through injectors (16) oriented in a direction co-current with the flow of the gas stream; [0051] j.2) introducing the stream of cooling water (F1, F2 . . . ) coming from a cooling circuit (12) to the casing (15); and [0052] j.3) clean the inside of the tubes (14) thanks to the high pressure with which the recirculated fuel (L1, L2 . . . ) is injected and its dissolving capacity, dragging the material deposited into the tubes (14).

[0053] There will be an injector (16) for every 4 tubes (14) to ensure proper cleaning of the interior of these in each heat exchanger.

[0054] The recirculation of the fuel stream (L1, L2 . . . ) is automatically activated when the efficiency of heat exchange is lost, which occurs when the difference between the temperatures of the input and output of the stream is reduced of cooling water (E, E1, E2.) that passes through the casings (15) of the heat exchangers, where said stream of cooling water (E, E1, E2.) is directed to the cooling circuit (12) to return to the heat exchanger system (6). Where said verification is carried out through sensors.

[0055] The system and process of the invention obtains as products a recovered carbon black (C) and a liquid fuel (L) whose main characteristics are described below:

[0056] The recovered carbon black has a quality comparable to the semi-reinforcing carbon blacks currently on the market, thanks to its surface chemistry and its behavior in rubber, depending on the application it can partially or totally replace conventional carbon blacks. such as those used where heat dissipation is required.

[0057] The recovered carbon black obtained can be applied to various rubber elements such as motor vehicle components, shoe soles, hoses; anti-vibration elements; roof covers; conveyors; in addition to black inks for the graphic industry; and for black pigment in the plastics industry.

[0058] One of the main advantages of the recovered carbon black obtained by the invention is that, with respect to conventional carbon black production processes, the emission of CO.sub.2 is considerably reduced. It is estimated that to produce 1 ton of carbon black recovered through the process of the present invention, 130 kg of CO.sub.2 are generated compared to the 2.5 Ton of CO.sub.2 generated by the production process of a conventional carbon black, which equates to a 95% reduction in carbon footprint.

[0059] For its part, the fuel obtained by the invention has the following characteristics:

[0060] It is a fuel with a calorific value that is in the range of traditional fuels such as diesel oil and No. 6 fuel oil. It has low viscosity so it can be used as an additive and improve the performance of more viscous fuels. Its pour point and cold filter plugging point occur at lower temperatures than in traditional fuels, which gives it an operational advantage when using it in places with extreme conditions such as low temperatures in mountain ranges.

[0061] Compared to heavy fuels, fuel has a lower content of sulfur, carbonaceous material, ash, sediment and water, which translates into lower emissions of pollutants.

[0062] The use of this fuel has a neutral fraction of CO.sub.2 emissions, due to the fact that they are obtained from tires that have biomass (natural rubber) in their composition.

[0063] The fuel obtained from the thermolysis process can be used in stationary engines, electric generators, boilers to heat water and generate steam, use as an additive for heavy fuels, and as raw material for the manufacture of other products.

[0064] It is a cleaner liquid fuel, with an aromatics content of more than 90%, compared, for example, with that obtained by U.S. Pat. No. 8,137,508B2 with a maximum of 80% aromatics and with that obtained in the patent application CN 105694942 reaching 60% aromatics. This high content of aromatics in the fuel allows it to act as a solvent for the solid material adhered to the interior of the tubes of the heat exchanger system (6). In addition to the condition of injection under pressure of the fuel in the tubes of the heat exchanger system, the fuel obtained performs the cleaning of the interior of the tubes synergistically due to the high content of aromatics in the fuel.

[0065] In the current state of the art, a brown to black fuel is obtained mainly due to the higher content of carbonaceous material, the fuel obtained by the invention is amber to brown in color, due to the lower content of carbonaceous material.

[0066] In those processes of the state of the art in which the post-treatment of the fuel is considered through distillation and/or the use of catalysts, cleaner fuels are obtained, however, to achieve this, a greater investment in equipment must be made, it is obtained lower yields, additional waste is generated, and operational cost is increased.

[0067] The percentage of carbonaceous residues of the fuel in the invention is between 0.8% and 3% by weight, which is compared to that obtained in the state of the art, but with the application of various post-treatment techniques, such as the use of distillation or catalysts to improve fuel quality, however in the invention there is no post-treatment.

[0068] On the other hand, the invention deals with a thermolysis system for obtaining recovered carbon black and fuel from disused tires that comprises the following components: [0069] i. a rotating horizontal cylindrical thermolysis reactor (1), which is surrounded by an outer chamber (2), where the reactor (1) receives the crushed material (A) to be treated, obtaining from this set (reactor and outer chamber) a gaseous stream of hydrocarbons (B), combustion gases (0) and recovered carbon black (C); [0070] ii. a combustion chamber (4), which indirectly heats the reactor (1) with gases (N) which are directed to the outer chamber (2); [0071] iii. a Flash distillation vessel (5), which receives the hydrocarbon gas stream (B) from the reactor (1), where thanks to the design of the Flash vessel (5) and due to pressure changes inside it, a part of the current remains in the gaseous phase (D) and another becomes liquid (B1); [0072] iv. a system of heat exchangers (6) that receives the gaseous stream (D) from the Flash container (5), where a part of the gaseous stream is condensed and another part is kept in a gaseous state, obtaining finally a two-phase current (G) at the end of the passage through the heat exchanger system (6); [0073] v. a phase separation tank (11) that receives the two-phase current (G) that leaves the exchanger system (6), where a separation of the condensate with the gas occurs due to the difference in phases of the two-phase current (G), producing a current in the gas phase (I) and a current in the liquid phase (H); [0074] vi. a battery of water seals (7) that receives the gas phase (I), generating a current (J) that then feeds the combustion chamber (4) to generate the necessary heat in the process and make it energetically self-sustaining; [0075] vii. a filtering system (8) that receives the liquid phase (H) to obtain a filtered fuel stream (K); and [0076] viii. a lung container (9) that stores a part of the filtered fuel stream (K) of the total fuel that is stored (M) for sale in a final storage tank (not shown in the figures)

[0077] The system also comprises a cooling circuit (12), which keeps the process water that circulates through the heat exchange system (6) cold.