Integrated reactor system and process for simultaneously producing a mixture of hydrocarbons from a carbonaceous feedstock and recovering heat

Abstract

A process for simultaneously producing a mixture of hydrocarbons and / or syngas from a carbonaceous feedstock and recovering heat, the process comprising the steps of providing a gaseous stream comprising steam via at least one gas inlet to a bottom section of a fluidized bed reactor; contacting said gaseous stream comprising steam with a solid bed material thereby transferring heat from said gaseous stream to said bed material such that a heated bed material is obtained; feeding a carbonaceous feedstock into said fluidized bed reactor; contacting said carbonaceous feedstock with said gaseous stream comprising steam and said heated bed material at a temperature in the range of from 400 to 1000 °C thereby forming a mixture of hydrocarbons and / or syngas, withdrawing a product mixture comprising said mixture of hydrocarbons and / or syngas from said fluidized bed reactor; and recovering heat for district heating from the process. An integrated reactor system for gasifying a carbonaceous feedstock and recovering heat, comprising at least one fluidized bed reactor and at least one heat exchanger, wherein said fluidized bed reactor comprises at least one first fluid outlet being fluidly connected to at least one fluid inlet of said at least one heat exchanger, and wherein said at least one heat exchanger is part of or connected to a district heating system. Use of a carbonaceous feedstock for simultaneously producing hydrocarbons and / or syngas, and recovering heat and / or generating electricity..

Description

[0001] INTEGRATED REACTOR SYSTEM AND PROCESS FOR SIMULTANEOUSLY PRODUCING A MIXTURE OF HYDROCARBONS FROM A CARBONACEOUS FEEDSTOCK AND RECOVERING HEAT

[0002] Field of the invention

[0003] The present invention relates to the field of chemical recycling and / or pyrolysis of carbonaceous feedstock, in particular plastic waste, and heat recovery.

[0004] Background

[0005] The production of hydrocarbons, in particular monomers such as ethylene and propylene for polymer synthesis, via chemical recycling of plastic waste is gaining more and more importance in view of global developments. Simultaneously, the use of waste incinerators for district heating continues to be popular in many countries, for example Finland and Sweden.

[0006] Since both of the above applications rely on plastic waste as a feedstock, a shortage of suitable feedstock, viz. plastic waste, may result.

[0007] Commercial scale pyrolysis processes are under development, but thus far require stringent specifications on waste feedstock composition. This poses limitations on the availability of the feed streams. The resulting sorting of fractions also means that residue fractions lose value and it thus becomes increasingly difficult to improve the circularity of the global material system.

[0008] FI127753B describes a method to extract valuable chemicals from fluidized bed combined heat and power plants by adding staged gasification reactors to the particle circulation loop.

[0009] Similar to the method know from the prior art, it has now been considered to extract valuable chemicals by means of an indirect gasification method through thermal sorting of mixed waste. The biogenic fraction of a mixed waste stream typically converts to energy at given conditions, whereas the synthetic / polymeric fraction converts to chemicals.

[0010] Indirect gasification provides conditions for a high temperature pyrolysis with limited formation of carbon oxides. Instead of supplying heat through direct oxidation of a fraction of the feed, heat is added to the process by means of a heated solid medium transferring between the reactor and the regenerator. Thus, the recovery of smaller fractions of monomers or other high value chemicals deriving of lower quality feed and a at lower energy cost through economies of scale may be expected when combining said lower quality feed with waste streams that provide greater fractions of monomers or other high value chemicals. As a bonus, the technology is believed to provide a low temperature stream of steam that can be used for district heating.

[0011] Object of the invention

[0012] It is an objection of the present invention to overcome the shortage of plastic waste available for chemical recycling and / or pyrolysis resulting from its use in concurring applications. In particular, the invention aims at satisfying the material needs of plastic waste to be used in both chemical recycling and district heating.

[0013] Summary of the invention

[0014] It has surprisingly been found that the above-mentioned object can be achieved by a process for simultaneously producing a mixture of hydrocarbons and / or syngas from a carbonaceous feedstock and recovering heat, the process comprising the steps of providing a gaseous stream comprising steam via at least one gas inlet to a bottom section of a fluidized bed reactor; contacting said gaseous stream comprising steam with a solid bed material thereby transferring heat from said gaseous stream to said bed material such that a heated bed material is obtained; feeding a carbonaceous feedstock into said fluidized bed reactor; contacting said carbonaceous feedstock with said gaseous stream comprising steam and said heated bed material at a temperature in the range of from 400 to 1000 °C thereby forming a mixture of hydrocarbons and / or syngas, withdrawing a product mixture comprising said mixture of hydrocarbons and / or syngas from said fluidized bed reactor; and recovering heat for district heating from the process.

[0015] Brief description of the figures

[0016] Figure 1 : Schematics of the experimental set-up used at industrial scale.

[0017] Detailed description of the invention

[0018] As already outlined above, the present invention relates to a process for simultaneously producing a mixture of hydrocarbons and / or syngas from a carbonaceous feedstock and recovering heat, the process comprising the steps of providing a gaseous stream comprising steam via at least one gas inlet to a bottom section of a fluidized bed reactor; contacting said gaseous stream comprising steam with a solid bed material thereby transferring heat from said gaseous stream to said bed material such that a heated bed material is obtained; feeding a carbonaceous feedstock into said fluidized bed reactor; contacting said carbonaceous feedstock with said gaseous stream comprising steam and said heated bed material at a temperature in the range of from 400 to 1000 °C thereby forming a mixture of hydrocarbons and / or syngas, withdrawing a product mixture comprising said mixture of hydrocarbons and / or syngas from said fluidized bed reactor; and recovering heat for district heating from the process.

[0019] Said step of recovering heat may comprise recovering heat from at least one of said gaseous stream comprising steam and / or the solid bed material; from said product mixture of hydrocarbons and / or syngas; and / or from the reactor sides / shell via suitable integrated heat exchangers.

[0020] Preferably, said step of recovering heat comprises transferring at least part of said gaseous stream comprising steam to a heat exchanger. Preferably, the process is a continuous process.

[0021] The type of carbonaceous feedstock is not particularly limited and may be selected, for example, from mixed (solid) waste, mixed plastic waste, polyolefins, a plastic waste derived pyrolysis oil of aliphatic character with a high degree of unsaturated substances, vegetable oil, animal fat, a reject fraction of mechanical recycling, a reject fraction of paper recycling, (pre-) sorted plastic waste, oils and waxes of synthetic or biogenic origin and biomass.

[0022] According to a preferred embodiment, said carbonaceous feedstock used in the process of the present invention is a mixed feedstock comprising at least one of oils and waxes of synthetic or biogenic origin, sorted plastic waste, biomass and mixed plastic waste (MPW). Importantly, the DFB system can operate on a variety of plastic wastes, including but not limited to PE, PP, PS, PU and MPW.

[0023] Preferably, at least part of said carbonaceous feedstock is in a liquid state at ambient temperature and pressure.

[0024] Preferably, said carbonaceous feedstock comprises one or more fluid pyrolysis products, more preferably one or more fluid pyrolysis products obtained from plastic waste that has not been subject to hydrotreatment operations.

[0025] Moreover, said step d) is preferably carried out at a temperature in a range of from 400 to 800°C, preferably from 400 to 600°C.

[0026] Without wanting to be bound to theory, it is generally assumed that a temperature in a range of from 400 to 600°C in step d) will lead to the production of a mixture of condensed, that is predominantly liquid, hydrocarbons; a temperature in a range of from 600 to 800°C in step d) will lead to the production of a mixture of gaseous hydrocarbons; and a temperature in a range of from 800 to 1000°C will lead to the production of syngas. In case syngas is the main component obtained from the process, subsequent process steps may be required in order to arrive at a final product mixture comprising condensed and / or gaseous hydrocarbons. However, such subsequent process steps and relevant parameters are well known in the art. Optionally, the process as described herein may further be characterized in that said step a) comprises providing a gaseous stream comprising a mixture of hydrogen, oxygen and steam via at least one gas inlet to a bottom section of a fluidized bed reactor and allowing at least part of the oxygen and hydrogen comprised in said gaseous stream to react at the bottom section of said fluidized bed reactor to produce a superheated stream of steam and said step b) comprises contacting said superheated stream of steam with a solid bed material thereby transferring heat from said superheated stream of steam to said bed material such that a gaseous stream comprising steam and a heated bed material are obtained.

[0027] Preferably, the process described herein further comprises a step g) of recovering heat in said heat exchanger.

[0028] The present invention is further directed to an integrated reactor system for gasifying a carbonaceous feedstock and recovering heat, comprising at least one fluidized bed reactor and at least one heat exchanger, wherein said fluidized bed reactor comprises at least one first fluid outlet being fluidly connected to at least one fluid inlet of said at least one heat exchanger, and wherein said at least one heat exchanger is part of or connected to a district heating system.

[0029] Preferably, said at least one fluidized bed reactor further comprises at least one second fluid outlet for recovering hydrocarbons. More preferably, said at least one second fluid outlet for recovering hydrocarbons is fluidly connected to a steam cracker or, alternatively, to a polymerization reactor.

[0030] Preferably, said at least one fluidized bed reactor is a dual fluidized bed reactor.

[0031] The type of heat exchanger to be used is not particularly limited.

[0032] Said at least one heat exchanger may be integrated in the reactor.

[0033] For example, a direct contact heat exchanger in the form of a jacketed reactor design may be employed. In such a configuration, the outer wall of the reactor can be designed as a jacket though which a heat transfer fluid circulates. Another possibility is to extract heat by utilizing high-temperature process gas outlets, which can be done, for example, by using shell and tube based and / or double pipe and / or tube in tube heat exchangers. In such a configuration, the working fluid exchanges heat with the high-temperature process gas (such as a gaseous stream comprising steam and / or a (gaseous) product mixture of hydrocarbons and / or syngas) by thermal contact which is placed within the shell or pipe or a tube acting as a conductive barrier.

[0034] Moreover, it is also possible to recover heat from the (solid) bed material, either in the reactor itself or by adding an additional particle cooler.

[0035] Three possible solutions to overcome the above mentioned problem of limited feedstock availability are envisaged:

[0036] (I) The aforementioned indirect gasification process can be used where there is a localized demand for certain high value chemical such as, for example, ethylene and propylene to produce the intermediates combined with district heating to the local public market. Preferably, in such embodiments, that is in case the DBF system(s) is / are integrated within a petrochemical complex, the operation conditions of the one or more DFB system(s) is / are adapted to produce valuable chemicals from C2 fraction onwards to heavy hydrocarbon liquids. Thus, the fluidized bed reactor uses a carbonaceous feedstock, preferably plastic waste, as a feed to produce a mixture of gaseous and liquid hydrocarbons. Depending on the quality of the produced hydrocarbons, one or more fractions - in particular comprising liquid hydrocarbons - are processed by means of an upgrading I purifying section. Upgrading and / or purifying sections may include, for example, a distillation column, a hydrotreatment unit, a hydrocracking unit and / or a liquid wash unit or a combination thereof. After said optional fractionation in said upgrading / purifying section, a gaseous hydrocarbon fraction comprising, for example ethane, propane, butane, ethylene, propylene, butylene or a mixture thereof, can be directed towards a recovery unit. A liquid hydrocarbon fraction may further be transferred to a steam cracker which allows for the production of valuable base chemicals, such as hydrogen, ethylene, propylene, butylene, pentene, etc. prior to the transfer to said recovery unit. Such obtained monomers (in particular ethylene and propylene) may then serve as a resource in polymerization plants.

[0037] (II) Most of the waste incinerators, in particular in Sweden, are soon facing their end of life and, thus, require severe upgrading. Hence, an alternative solution consists of upgrading or replacing outdated waste incinerators by indirect gasification units comprising one or more Dual Fluidized Bed systems (DFB). Following this approach, it is expected that waste incinerators can separate and provide greater fractions of monomers and / or other high value chemicals from waste. The method may be further optimized in order to target shippable products in order to allow for integration with localized chemical production units. In this context, the expression shippable products generally relates to oils and waxes. Preferred examples of shippable products include liquid hydrocarbons.

[0038] Preferably, in such embodiments, the operation conditions of the one or more DFB system(s) is / are adapted to produce shippable products from the carbonaceous feedstock, e.g. plastic waste. The thus obtained shippable products are transferred from the DFB system(s) to a chemicals logistics unit or central hub, from which the shippable products can be transported to a steam cracker. Similar to (I) above, the base chemicals produced in the steam cracker(s) are then separated in a recovery section to provide monomers such as ethylene and propylene for use in subsequent polymerization processes.

[0039] The use of localized reactors can promote energy independence and reduce reliance on centralized power generation which may reduce the risk of power outages or disruptions.

[0040] (Ill) The proposed method involves break down of plastic waste into smaller components as elucidated in (I). This entails two scenarios for valorization of smaller components: use as feedstock to steam crackers or, alternatively, use as a feedstock to recovery units post steam crackers. However, both scenarios are believed to allow for a maximization of the availability of plastic waste as a valuable resource for the petrochemical industry.

[0041] The process according to the present invention is preferably carried out in a fluidized bed reactor system (or assembly). According to a particularly preferred embodiment, said fluidized bed reactor system comprises a dual fluidized bed reactor system comprising a reactor / gasifier and a regenerator / combustor wherein heating is provided to a solid bed material which transfers to the reactor / gasifier bed. The reactor may be fed with a single feedstock comprising liquid aliphatic and / or naphthenic hydrocarbons. Alternatively, the reactor can be fed with two or more compositionally different feedstock fractions simultaneously under the provision that at least one feedstock fraction is a feedstock comprising liquid aliphatic and / or naphthenic hydrocarbons.

[0042] Preferably, a fluidized bed reactor system suitable for carrying out the process of the present invention comprises a fluidized bed gasifier, at least one gas analyzer being fluidly connected to a product gas outlet of said fluidized bed gasifier and at least one control unit for adjusting the composition of feedstock; wherein said fluidized bed gasifier comprises at least one, preferably at least two inlets for introducing said mixed carbonaceous feedstock.

[0043] Preferably, said at least one inlet for introducing said mixed carbonaceous feedstock to the fluidized bed reactor assembly comprises an extruder.

[0044] Preferably, said at least one inlet for introducing said mixed carbonaceous feedstock to the fluidized bed reactor assembly is adapted for introducing said mixed carbonaceous feedstock in a liquid state, more preferably as a melt, into said gasifier.

[0045] Optionally, said at least one inlet for introducing said mixed carbonaceous feedstock in a liquid state to the fluidized bed reactor assembly comprises a nozzle for spraying said mixed carbonaceous feedstock into said gasifier.

[0046] According to a particularly preferred embodiment, the fluidized bed reactor assembly comprises a dual fluidized bed reactor comprising a first fluidized bed reactor, serving as a gasifier, and a second fluidized bed reactor, serving as a combustor / regenerator. Said first and said second fluidized bed reactor being fluidly connected to one another.

[0047] The configuration of a dual fluidized bed (DFB) system can be compared to more extensively studied fluid catalytic cracking (FCC) units. In a DFB system, hot fluidized bed material recirculates between two interconnected fluidized beds: a combustor (or regenerator) and a gasifier. The overall reaction on the combustor side is exothermic whereas on the gasifier side the reaction is endothermic. The heat generated on the combustor side is transported by the solid fluidized bed material to the gasifier side to meet its endothermic heat demand. This type of configuration allows production of two separate gas streams: flue gas from the combustor and product gas from the gasifier.

[0048] In a DFB system, a solid bed material is continuously circulated between two interconnected fluidized beds. The solid bed material is completely oxidized in the combustor (in presence of air) and partially reduced in the gasifier (in the presence of hydrocarbon feed). Partially reduced bed material leaves the gasifier along with unconverted solids and enters the combustor. Unconverted solids along with the bed material are oxidized in the combustor.

[0049] Also in a DFB system, the two fluidized beds are preferably interconnected through non mechanical valves called loop seals (LS). Loop seals allow for the transport of bed material between two reactors without exchange of any gases. Usually, these loop seals are fluidized to avoid agglomeration of hot bed material.

[0050] A schematic drawing of an exemplary DFB system is depicted in Figure 1 , wherein said DFB system comprises (1 ) a combustor (or regenerator); (2) fuel feed for the combustor; (3) a cyclone; (4) a particle distributor; (5) a first loop seal to the gasifier; (6) a gasifier; (7) a second loop seal to the combustor; (8) fuel feed for the gasifier. Moreover, a sampling point (X) as well as return points of the second loop seal (crossed circle) are included in Figure 1.

[0051] Moreover, details regarding a reactor set-up for conventional steam cracking can be found, for example, in Ullmann’s Encyclopedia of Industrial Chemistry (DOI: 10.1002 / 14356007).

[0052] The present invention is further directed to the use of a carbonaceous feedstock for simultaneously producing hydrocarbons and / or syngas and recovering heat and / or generating electricity. Hence, the use of a carbonaceous feedstock may comprise:

[0053] - simultaneously producing hydrocarbons and recovering heat; or

[0054] - simultaneously producing hydrocarbons and generating electricity; or

[0055] - simultaneously producing syngas and recovering heat; or

[0056] - simultaneously producing syngas and generating electricity.

[0057] The type of said carbonaceous feedstock to be used in the process of the invention is not particularly limited and may be selected from: mixed (solid) waste, mixed plastic waste, polyolefins, a plastic waste derived pyrolysis oil of aliphatic character with a high degree of unsaturated substances, vegetable oil, animal fat, a reject fraction of mechanical recycling, a reject fraction of paper recycling, (pre-)sorted plastic waste, oils and waxes of synthetic or biogenic origin and biomass.

[0058] Preferably, said carbonaceous feedstock further meets the requirements set out herein above with regard to the process.

[0059] Preferably, the invention is directed to the use of a carbonaceous feedstock comprising mixed (solid) waste, more preferably mixed plastic waste for simultaneously producing hydrocarbons and recovering heat and / or generating electricity.

[0060] Examples

[0061] DFB Industrial scale experiments The industrial scale experiments were performed in the Chalmers DFB system, which consists of a 12 MWth circulated fluidized bed (CFB) combustor coupled to a 2-4 MWth bubbling fluidized bed (BFB) gasifier. This configuration allows to obtain the heat needed in the gasification side by the recirculation of the bed material that comes from the combustor. To perform the steam gasification experiments, a flow of 150 kg / h of steam was used in the gasifier as fluidization media. In this case, the feeding was done in a continuous way through an extruder that has to functions: (1 ) to melt the feedstock allowing a more steady and homogeneous feeding to the gasifier; and (2) act as sealing preventing air to enter in the gasifier. Steam was also added to the extruder (80 kg / h). The temperature in the gasifier was set at ca. 750 °C during the tests with the different fuels (PE, + PE + PP and MPW). For the PO a different feeding system was used. The liquid feedstock was pumped and fed directly into the gasifier like a spray.

[0062] For a better view of the system, the schematic of the set-up is provided in Figure 1 .

[0063] To quantify the total dry gas produced during the experiments a small flow of helium was added in the gasifier as a tracer gas (35 IN / min), similar to what is done at lab scale. In this case, a raw gas stream is continuously sampled, that is used for both the permanent gases and the condensable hydrocarbons (tars). To analyze the raw gas composition, a slipstream of the dragged raw gas sampled was passed through a hot ceramic filter, cooled down and scrubbed in isopropanol to remove the condensable hydrocarbons. This cold and dry stream was then analyzed in a micro-GC (Varian CP-4900). This micro-GC has two channels and uses Poraplot Q and MS5A columns, with He and Ar as carrier gases, respectively. The micro-GC takes a point-injection (10-30 ms injection time) of the dry and tar-free raw gas every 3 minutes, generating a new chromatogram from each injection. The micro-GC is calibrated every week with five concentration levels that cover the range of the expected concentrations. The species analyzed are: H2, He, CO, CO2, CH4, C2H2, C2H4, C2H6, C3H6, C3H8 and N2.

[0064] The results of the gas composition are the average of the chromatograms taken over a period of stable operation (i.e. , when the gasification temperature and the fuel flow were stable). During this stable measurement the temperature in the gasifier varied in a range of ±3 °C. To measure the tar species, the solid-phase adsorption method was used in the same way that was presented in the previous section. In this case, a set of 4 amines was taken during the stable operation. After eluation, the resulting liquid was analyzed in a BRUKER 430 GC-FID. Each sample was analyzed 3 times, and the results presented are the average of the values obtained in the three- repeat analysis for the 4 different samples.

[0065] The feeding rates to the industrial-scale DFB gasifier were different due to the feedstock variability in terms of density, shape and composition. In Table 1 , these values are indicated.

[0066] Table 1 . Different feeding rates for the feedstocks used at industrial scale.

[0067] Industrial fluidized bed systems can be used as a source for providing heat to districts near-by through a process called district heating. In this process, heat generated by the fluidized bed reactor is transferred through a heat exchanger to a heat transfer fluid such as water or steam. The heated fluid is then transported through a network of insulated pipes to nearby buildings or homes, providing space heating and domestic hot water. Alternatively, the recovered heat could be used to produce steam and generate electricity in a combined heat and power system. This is particularly suited for areas with a high demand for heat, such as residential or commercial districts.

[0068] Moreover, the products obtained from chemical recycling in the DFB system contribute to the establishment of a circular economy as they can find use as a valuable resource in petrochemical industry.

[0069] The use of combined heat and power systems with a fluidized bed reactor can result in higher energy efficiency compared to separate generation of steam and electricity. The hot gases and heat generated in the fluidized bed reactor and would - in a conventional setup - be wasted are used to produce steam, which can in turn be used to generate electricity. This results in less fuel being required to generate the same amount of energy.

[0070] A further advantage of a combined fuel / feedstock flow and heat production is that it becomes possible to follow the varying district heating demand and to adjust the balance between cracker feedstock and fuel so that the district heating is unaffected.

Claims

CLAIMS1 . A process for simultaneously producing a mixture of hydrocarbons and / or syngas from a carbonaceous feedstock and recovering heat, the process comprising the steps of: a) providing a gaseous stream comprising steam via at least one gas inlet to a bottom section of a fluidized bed reactor; b) contacting said gaseous stream comprising steam with a solid bed material thereby transferring heat from said gaseous stream to said bed material such that a heated bed material is obtained; c) feeding a carbonaceous feedstock into said fluidized bed reactor; d) contacting said carbonaceous feedstock with said gaseous stream comprising steam and said heated bed material at a temperature in the range of from 400 to 1000 °C thereby forming a mixture of hydrocarbons and / or syngas, e) withdrawing a product mixture comprising said mixture of hydrocarbons and / or syngas from said fluidized bed reactor; and f) recovering heat for district heating from the process.

2. The process according to claim 1 , wherein said step f) comprises transferring at least part of said gaseous stream comprising steam to a heat exchanger.

3. The process according to any one of the preceding claims, wherein the process is a continuous process.

4. The process according to any one of the preceding claims, wherein said carbonaceous feedstock comprises one or more fluid pyrolysis products, preferably one or more fluid pyrolysis products obtained from plastic waste that has not been subject to hydro-treatment operations.

5. The process according to any one of the preceding claims, wherein said step e) is carried out at a temperature in a range of from 400 to 800°C, preferably from 400 to 600°C.

6. The process according to any one of the preceding claims, wherein at least part of said carbonaceous feedstock is in a liquid state at ambient temperature and pressure.

7. The process according to any one of the preceding claims, wherein said carbonaceous feedstock used in step c) is a mixed feedstock comprising at least one of oils and waxes of synthetic or biogenic origin, sorted plastic waste, biomass and mixed plastic waste.

8. An integrated reactor system for gasifying a carbonaceous feedstock and recovering heat, comprising at least one fluidized bed reactor and at least one heat exchanger, wherein said fluidized bed reactor comprises at least one first fluid outlet being fluidly connected to at least one fluid inlet of said at least one heat exchanger, and wherein said at least one heat exchanger is part of or connected to a district heating system.

9. The system according to claim 8, wherein said at least one fluidized bed reactor further comprises at least one second fluid outlet for recovering hydrocarbons.

10. The system according to any one of claims 8 to 9, wherein said at least one fluidized bed reactor is a dual fluidized bed reactor.1 1 . The system according to any one of claims 8 to 10, wherein said at least one second fluid outlet for recovering hydrocarbons is fluidly connected to a steam cracker.

12. The system according to any one of claims 8 to 1 1 , wherein said at least one second fluid outlet for recovering hydrocarbons is fluidly connected to a polymerization reactor.

13. Use of a carbonaceous feedstock for simultaneously- producing hydrocarbons and / or syngas; and- recovering heat for district heating and / or generating electricity.

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