Method and apparatus to improve the energy efficiency of thermal conversion processes of biomasses, wastes and / or waste derived fuel into syngas and his subsequent conversion in other chemicals

Abstract

A method and apparatus for improving the efficiency of thermal conversion processes of waste characterized in the fact that, in order to obtain a reduction of the CO2 emissions and also the water and power consumption, by starting from a gasification of biomasses, wastes and / or waste derived fuel with oxygen at high temperature (above 1100°C) to obtain a raw syngas and subsequent conversion of said syngas into chemical products, said method foresees the use of a cooling and separation step of the raw syngas performed by an all-radiant membrane, preferably metallic, tube wall boiler type wherein the raw syngas, outcoming from gasification, is partially cooled down from at least 1100°C to not less than 700°C, and also at the same time in the same step, the coarse particle is separated from the gas stream through a routing of the stream inside the same boiler, wherein the recovered heat is used for steam production and wherein said all-radiant membrane tube wall boiler perform both the operation of cooling and separation, wherein the use of said all-radiant membrane tube wall boiler type allows both a saving of water consumption in the deep polishing steps and also a reduction of C02 emissions, and wherein the steam produced in said all-radiant membrane tube wall boiler type is used for any eventually step of syngas conversion according to the specific chemical production, allowing a reduction of power, natural gas consumption and an optimization of the overall conversion process.

Description

METHOD AND APPARATUS TO IMPROVE THE ENERGY EFFICIENCY OF THERMAL CONVERSION PROCESSES OF BIOMASSES, WASTES AND / OR WASTE DERIVED FUEL INTO SYNGAS AND HIS SUBSEQUENT CONVERSION IN OTHER CHEMICALSDESCRIPTIONSummary

[0001] The present invention relates to a method and apparatus to improve the energy efficiency of the conversion processes of biomasses, wastes and / or waste derived fuel into syngas, where such syngas is further converted into chemicals as methane, methanol or DME, ethanol / ethylene, ammonia / urea or sustainable aviation fuel (SAF) .Technical field

[0002] The present invention falls within the chemical sector, precisely in the field concerning the conversion of biomasses, waste materials, preferable industrial or municipal wastes into chemicals; more specifically the present invention discloses a method and an apparatus for the improvement of the overall energy efficiency of the conversion process.Background art

[0003] New ideas are emerging to use wastes or what is left from conventional recycle process as a new source for chemicals production (e.g. "Waste as a source of carbon for methanoL production" for methanol production[https : / / doi . org / 10.1016 / b978-0-444-63903- 5.00004-2] or "Waste- to-chemicaLs for a circuLar economy: the case of urea production” for Waste to urea [ChemSusChem 10.1002 / CSSC.201601555] ) .

[0004] The production of a clean syngas from wastes by high temperature conversion with oxygen is following into such a model of circular economy, as disclosed, for example in patentsEP 3775108 Bl or EP 3433341 Bl.

[0005] Circular economy approach is intended to save resources, mainly hydrocarbons, and minimize emissions and pollution, and thus consequently protect the environment also in terms of C02emissions.

[0006] High temperature conversion greater than 1100 / 1300°C, ensures that there are no unconverted hydrocarbon molecules, so- called tar, in the gasification outcoming syngas.

[0007] Most of prior art gasification reactors, such the one disclosed in EP 3775108 Bl or EP 3433341 Bl, using biomasses, wastes or waste derived fuel as feedstocks and based on oxygen are usually followed by a water quench in order to cool down the syngas to 80 / 90°C before any further treatment.

[0008] Quench cool down is also aimed to the removal of the following contaminants / components :• Metallic materials such as iron, lead, chromium, copper and others;• Chlorine compounds mainly present as HC1;• Nitrogen compounds mainly present as HCN and NH3;• Sulphur compounds present as H2S, COS and CS2where the ratio of H2S / C0S is normally 10 / 1 but it may be as 2 to 1;• Particulate compounds mainly present as carbon particles, oxides, or even metallic form.

[0009] This layout will avoid reformation of noxious compounds as dioxins, furans etc, avoid corrosion problems and / or fouling, but conversely it does not allow to recover the sensible heat of syngas which is transferred to the cooling water; also said architecture allows the transfer of all the particulate into a liquid stream leaving the bottom of quencher.

[0010] It will maximize however the on-stream time of the plant.

[0011] Some other gasification reactors, such the one disclosed in WO 2014 / 126916 Al, have a syngas cooler where the syngas is cooled down to 300-400°C in order to produce steam by radiation and convective modes .

[0012] This architecture will allow to maximize the heat recovery, but it will face both metal dusting due to the high CO concentration which is going to be quite dangerous at temperature lower than 700°C, and chemical attach due to the presence of HC1 and H2S and also fouling of the cooler where the heat is transferred by convection mode, not to mention the possibility to produce dioxins if the residence time are not short enough.

[0013] Such arrangement will have as one may expect a quite reduced on-stream time.

[0014] In view of all above, it is evident the need for a method and an apparatus which will allow to recover the sensible heat of syngas in order to produce steam, thus increasing the overall energy efficiency of the process by maintaining the onstream time of the water quenching architecture.

[0015] Another object of this invention is to minimize liquid emissions associated with waste disposal .

[0016] Yet another object of this invention is to provide a cost-effective method to make chemicals by minimizing natural gas and cooling water consumptions .

[0017] These and other results are achieved according to the present invention by coupling the high temperature conversion (higher than 1100°C) of biomasses and / or wastes with oxygen and a radiant syngas cooler.Technical problem

[0018] Thus the technical problem solved by the present invention is both the thermal recovery of heat by means ofcooling down a syngas mixture outcoming from a syngas reactor operating at high temperature and, at the same time, the removal of coarse particle from said syngas stream in order to avoid corrosion problem and in order to increase the efficiency of thermal conversion process .Solution to problem

[0019] According to the present invention the solution is a peculiar all-radiating boiler which performs, at the same time, the cooling of the syngas and the separation of coarse particle in order to increase the efficiency of thermal conversion processes and then reducing the C02emissions .

[0020] The terms "comprises / comprising" , where used in this description, are taken to specify the presence or addition of one or more other features, integers, steps, components, or group thereof .

[0021] Subject-matter of the invention is defined in the appended claims .Brief description of the drawings

[0022] The following appended figures and tables illustrate only some preferred embodiments of the present invention; therefore they shall not be considered limiting of its scope, indeed the invention may admit other equally effective embodiments .

[0023] These and other aspects, features and advantages of which embodiments of the invention are capable of, will be clear and explained from the following description of the present invention, reference being made to the accompanying drawings / tables in which:

[0024] Figure 1 is a schematic representation of the syngas radiant boiler and subsequent purification steps according to the present invention;

[0025] Figure 2 is a schematic representation of the heat exchange in a radiant section boiler: syngas is flowing into a sort of empty box where heat is mainly exchanged by irradiation with the water-cooled walls;

[0026] Figure 3 is representing a typical detail of insulation and cladding of a membrane tube radiant boiler;

[0027] Figure 4 is a schematic representation of a membranetube radiant boiler (A) shaped as a cyclone.Detailed description of the invention

[0028] Specific embodiments of the invention are described with reference to the accompanying drawings; this invention may, however, be embodied in many different forms and should not be constructed as limited to the embodiments set for herein.

[0029] Rather, these embodiments are provided so that disclosure will be thorough and complete, and will fully convey the scope of the invention - as defined in the claims - to those skilled in the art.

[0030] In the following description the term radiant boiler means that the heat exchanged in it is mainly by irradiation, being the syngas at high temperature and flowing low-moderate velocity.

[0031] The present invention relates to a method and an apparatus in which an all-radiant steam drum boiler type is used in order to increase the efficiency of the thermal conversion processes of biomasses, wastes and / or waste derived fuel into syngas and the subsequent conversion of said syngas in products such as methane, methanol or DME, ethanol, ammonia / urea, sustainable aviation fuel (SAF) and other chemicals in order to increase the efficiency of said thermal conversion processes and also reducing the C02emissions .

[0032] With reference to figure 1, the method according tothe present invention is thus applicable in thermal conversion processes such as gasification of waste with pure oxygen at high temperature (above 1100°C) to obtain a high temperature raw syngas 100 , and comprises the following steps:• a cooling and separation step A of the raw syngas 100 performed by an all-radiant membrane tube wall boiler type, wherein the raw syngas is partially cooled down from at least 1100° to not less than 700°C, and also at the same time in the same step, the coarse particle 112 is separated from the gas stream and wherein the recovered heat is used for steam production 138 by boiler feed water 136;• a series of purification steps of the syngas stream 102 outcoming from said all-radiant membrane tube wall boiler type A wherein all the metallic materials such as iron, lead, chromium, copper and others, chlorine compounds mainly present as HC1, nitrogen compounds mainly present as HCN and NH3, sulphur compounds present as H2S, COS and CS2and also the remaining amount of particulate compounds still present in the stream, are removed, said deep purification steps comprising the following: o a quenching step B of the syngas 102 in order to separate the particle not removed in the above cooling and separation step A thus producing a quenched syngas stream 104 and a liquid waste stream 118, said quenching step B being followed by o an acidic scrubbing step C wherein the syngas stream 104 outcoming from said quenching step B is treated by an acidic washing thus producing a syngas stream 106 and a liquid waste 116, said acidic scrubbing step C being followed by o a basic scrubbing step D wherein the syngas stream 106 istreated by basic washing thus producing a syngas stream 108 and a liquid waste 114, said basic scrubbing step D being followed by o a wet electrostatic precipitation (WESP) step E wherein the syngas stream 108 outcoming from said basic scrubbing step D is further treated in order to remove the particle still eventually present in the syngas, thus producing a deep polished syngas stream 110;• a water effluent treatment F of the liquid waste streams outcoming both from the quenching step B (stream 118), the acidic scrubbing step C (stream 116) and also basic scrubbing step D (stream 114) .

[0033] According to the present invention, the all radiant steam drum boiler is a preferably metallic membrane-wall box type wherein the syngas inlet and outlet sections are not placed on the same axe in order to obtain that the design of said membrane-wall box is such to avoid fouling and minimize the pressure drop and not impacting the on-stream time of the plant.

[0034] According to the present invention, said pressure drop is comprised between 100 - 500 mmWC (millimeters of water column equivalent to 9.8 - 49 mbar) .

[0035] Optionally on the heat exchanger surfaces a refractory lining could be installed, extension of it and its thickness will depend on the required cooling duty, meanwhile insulation and cladding are going to be installed on the external section.

[0036] Moreover a plurality of boilers, such the one according to the present invention, will be inserted into each plant, one for each line, where the number lines will depend on the plant capacity.

[0037] According to one aspect of the invention themembrane-wall radiant syngas boiler is provided at the outlet of the conversion reactor used for producing a CO / H2rich mixture, said radiant syngas boiler being aimed both for cooling down the temperature from at least 1100°C, more preferably 1300°C, to 700°C, more preferably 750°C and also for removing a substantial amount of the coarse particulate 112 eventually present in the syngas; advantageously, according to the composition of said solid coarse particle, the stream 112 can be sent to specific treatment or recycled to the gasification step.

[0038] Said membrane-wall radiant syngas boiler is thus provided with a steam drum in order to perform the steam production (stream 138) by boiler feed water (stream 136) .

[0039] Optionally at the bottom of said membrane-wall boiler, a particulate lock hopper can be installed followed by a particulate storage bin, in order to collect the coarse particle (stream 112) .

[0040] The metallic membrane-wall of radiant syngas boiler type is fundamental for the cooling of the syngas outcoming from such kind of conversion process performed with gasification at high temperature of biomass and / or wastes with oxygen due to the high temperature of the syngas outcoming from the gasification step; indeed the outlet syngas temperature (upper than 1100°C) together with the design of the membrane-wall boiler allows the recovery of the heat only by radiation, thus avoiding any convective exchange with all the related problems .

[0041] Such a boiler will produce the steam which can be used in the subsequent syngas conversion steps; for instance said steam can be used by the water gas shift reactor, if present, as the case of methanol production, or in the reboiler section for the ethanol distillation or more generally where steam will be required, sensibly reducing the duty of theauxiliary boiler.

[0042] According to the present invention the radiant boiler A is placed downstream of the high temperature waste converter reactor, or gasification reactor, in order to cool down the syngas stream 100 outcoming from said gasification reactor from the temperature between 1300-1100°C to a temperature between 850-700°C as syngas stream 102.

[0043] The boiler feed water (BFW stream 136), used in the membrane-wall all radiant type steam drum boiler, is preheated in the downstream step after said boiler in order to maximize the steam production and minimize the cooling duty of the syngas to the compression section; for example the preheating of said boiler feed water can be performed in the water shift section, if present, or in other section of the plant .

[0044] Boiler' s outlet temperature of syngas is strictly dependant from the syngas composition and in particularly the content of HC1 and carbon particulate; thus the design choices of the membrane-wall boiler in terms of contact surface, hot stream speed, residence time, are made in order to obtain an outlet temperature not less than 700°C.

[0045] According to the present invention, the outlet section of the membrane-wall boiler is connected to the water quencher B which cools down the syngas from the boiler' s outlet temperature (between 850-700°C) to a temperature between 60- 90°C.

[0046] Advantageously the presence of the boiler according to the present invention will reduce the water consumption (stream 122) into quenching and minimize the liquid effluent from the sedimentation tank at the bottom of the quencher section (stream 118) .

[0047] Moreover the quencher section B, in such process ofgasification at high temperature upper than 1100°C, will decrease its operation window from 700 / 850°C to 80 / 90°C instead of from 1100° / 1300°C to 80 / 90°C.

[0048] The water quencher step B is then connected to a scrubbing package comprising an acid scrubbing step C and a basic scrubbing step D; the outlet of said package (stream 108) is connected to a wet electrostatic precipitator E .

[0049] The stream 110 outcoming from said wet electrostatic precipitator E corresponds to the pretreated syngas (stream 110) .

[0050] The peculiar position of the syngas inlet section and the syngas outlet section of the boiler, not in axe, allows a first separation of coarse particle from the syngas stream, due to the change of the flow direction : by considering this, the reduction of the coarse particulate will reduce the load into the final purification steps of the syngas .

[0051] Said pretreated syngas 110 is routed to an atmospheric storage and then said purified syngas can be used for the production of hydrogen, methane, ethanol, ammonia / urea, SAF and other chemicals .

[0052] A first advantage of the syngas cooling method according to the present invention is the simultaneous cooling of the syngas and separation of heavy particles from said syngas .

[0053] A second advantage of the syngas cooling according to the present invention, although said cooling is partial, will result in a reduction of water flow consumption in all the purification steps .

[0054] Reduction of such flows will in turn sensibly reduce the electric power absorption of the pumps associated, thus optimizing the power consumption of the overall process .

[0055] However, the main advantage of the present invention is related to the steam production in the radiant boiler, which is going to reduce the duty of the auxiliary boiler and in particularly of the natural gas flow used there to raise the steam required to carry out the CO conversion step as it appears in the scheme depicted in patent EP 3433341 Bl for instance or for any other steam demand in other waste-to-chemicals schemes .

[0056] The steam produced is said membrane-wall boiler can be used, for example, in the water gas shift section, if present, in order to convert totally or partially the CO in C02according to the water shift reaction:

[0057] Moreover The substantial reduction of natural gas incoming from battery limits implies a sensible reduction of C02emissions for ton of product.

[0058] According to a preferred embodiment of the present invention, but not limiting, the radiant syngas boiler section is shaped as a cyclone; in such a case a substantial fraction of the coarse particulate present in the syngas is removed as a dry solid and not as sludge, thus this particular shape allows an improve of the particle separation inside the radiant syngas boiler. .

[0059] Thus this peculiar shape as a cyclone of the membrane-wall boiler improve the particle separation .Example

[0060] The following is an example of the use of a steam drum boiler according to the present invention, by considering one of the potential applications of the invention such the methanol production; such application is usually performed with three operating lines .

[0061] Typical composition and flow properties of syngasbefore and after the syngas boiler and heat recovered duty are shown in the following Table 1.

[0062] The utilities consumptions before and after the radiant syngas boiler implementation in the process are shown in Table 2.

[0063] The C02emissions in situ for amount (ton) of product before and after the implementation are shown in Table 3.

[0064] Data shown on Tables 1, 2 and 3 have been elaborated for disposing 200000 ton per year of RDF producing 95000 ton per year of methanol .Table 1

[0065] By considering the data on table 1 related to the useof the purified syngas in order to produce methanol, the amount of steam produced by each conversion line with a boiler according to the present invention is about 4, 25 ton / h; if we consider the typical three operating gasification train, the amount of produced steam is equal to 12.75 ton / h . Table 2Table 3

[0066] Said amount corresponds to a half of the added steam required on the CO shift step for the waste-methanol case.

[0067] In other waste-to chemicals applications, the boiler according to the present invention will provide a sensible portion of the required steam.

[0068] As it can be seen from table 1, the membrane-wall boiler is such to both recover the syngas heat, in order to produce steam, and also to allow the separation of particulate from the syngas : indeed the particulate amount in the syngas stream decreases from <20 g / Nm3(before the boiler) to <10 g / Nm3(after the boiler) .

[0069] As it can be seen from table 2, the installation of such membrane-wall boiler allows a decrease both in water consumption (about -12%) and also in power consumption (about - 9.3%) .

[0070] As it can be seen from table 3, the computed C02emitted after the installation of such membrane-wall boiler in the above application of methanol production is about -30%, while the amount (ton) of C02produced for amount (ton) of methanol produced decreases from 2 to 1.88.

Claims

Claims1. A method for improving the efficiency of thermal conversion processes of waste characterized by the fact that, in order to obtain a reduction of the C02emissions and also the water and power consumption, by starting from a gasification of biomasses, wastes and / or waste derived fuel with oxygen at high temperature (above 1100°C) to obtain a raw syngas and subsequent conversion of said syngas into chemical products, said method comprises the following steps :• a cooling and separation step (A) of the raw syngas (110) performed by an all-radiant membrane tube wall boiler type wherein the raw syngas, outcoming from gasification, is partially cooled down from at least 1100°C to not less than 700°C, and also at the same time in the same step, the coarse particle is separated (112) from the gas stream through a routing of the stream inside the same boiler, wherein the recovered heat is used for steam production (138) and wherein said all-radiant membrane tube wall boiler performs both the operation of cooling and separation;• a series of purification steps of the syngas outcoming from said all-radiant membrane tube wall boiler type (102) wherein all the metallic materials such as iron, lead, chromium, copper and others, chlorine compounds mainly present as HC1, nitrogen compounds mainly present as HCN and NH3, sulphur compounds present as H2S, COS and CS2and also the remaining amount of particulate compounds still present in the stream, are removed, said purification steps comprising the following: o a quenching step (B) wherein the syngas outcoming from said cooling and separation step (A) is quenched with water in order to separate the particle not removed inthe above cooling and separation step A, thus producing a quenched syngas stream (104) and a liquid waste stream 118, said quenching step being followed by o an acidic scrubbing step (C) wherein the syngas stream (104) outcoming from said quenching step (B) is treated by an acidic washing thus producing a syngas stream (106) and a liquid waste (116), said step being followed by o a basic scrubbing step (D) wherein the syngas stream (106) outcoming from the acidic scrubbing step (c) is treated by basic washing thus producing a syngas stream (108) and a liquid waste (114), said basic scrubbing step (D) being followed by o a wet electrostatic precipitation (WESP) step (E) wherein the syngas stream (108) outcoming from said basic scrubbing step (D) is further treated in order to remove the particle still eventually present in the syngas, thus producing a deep polished syngas stream (110) ; and• a water effluent treatment (F) of the liquid waste streams (118, 116, 114) respectively outcoming from the quenching step (B), the acidic scrubbing step (C) and the basic scrubbing step (D) ; wherein the use of said all-radiant membrane tube wall boiler type allows both a saving of water consumption in the deep polishing steps and then a reduction of C02emissions, and wherein the steam (138) produced in said all-radiant membrane tube wall boiler type is used for any eventually step of syngas conversion according to the specific chemical production, allowing a reduction of power, natural gas consumption and an optimization of the overall conversion process .

2. The process according to the previous claim characterized in that the deep polished syngas (110) outcoming from said deep purification step is used to produce chemical products such as methane, methanol or DME, ethanol, ammonia / urea sustainable aviation fuel (SAF) and others,3. The process according one or more of the previous claims characterized in that each step can be performed by using multiple trains according to the plant capacity.

4. The process according one or more of the previous claims wherein the raw syngas 100, outcoming from gasification, is partially cooled down from 1300°C to 850-700°C.

5. The process according to one or more of the previous claims wherein the syngas inlet and outlet sections of said allradiant membrane tube wall steam drum boiler are not placed on the same axe, allowing said coarse particle separation due to the change of the flow direction .

6. The process according to claim 5 wherein said position of syngas inlet and outlet section allows to avoid fouling and minimize the pressure drop, which is comprised between 100 - 500 mmWC, thus not impacting the on-stream time of the plant .

7. The process according to one or more of the previous claims wherein a refractory lining is installed on the heat exchanger surfaces, extension of it and its thickness will depend on the required cooling duty, meanwhile insulation and cladding are installed on the external section .

8. The process according to one or more of the previous claims wherein at the bottom of said membrane-wall boiler, a particulate lock hopper is installed followed by a particulate storage been, in order to collect the separated coarse particle.

9. The process according to one or more of the previousclaims wherein the boiler feed water (BFW) used in the membranewall all radiant type steam drum boiler is preheated in the downstream step after said boiler in order to maximize the steam production and minimize the cooling duty of the syngas to the compression section.

10. The process according to one or more of the previous claims wherein the presence of said membrane-wall allows a reduction of operating window of the quencher section from 700 / 850°C to 80 / 90°C thus allowing a water saving.

11. The process according to one or more of the previous claims wherein the membrane-wall all radiant type steam drum boiler is shaped as a cyclone in order to improve the coarse particle separation.

12. A apparatus for improving the efficiency of thermal conversion processes according to claim 1 characterized by the fact that, in order to obtain a reduction of the C02emissions and also the water and power consumption, by starting from a gasification of biomasses, wastes and / or waste derived fuel with oxygen at high temperature (above 1100°C) to obtain a raw syngas and subsequent conversion of syngas into chemical products, said apparatus comprises the following elements :• at least one unit of cooling and separation of the raw syngas (100) performed by at least an all- radiant membrane tube wall boiler type wherein the raw syngas, outcoming from gasification, is partially cooled down from at least 1100°C to not less than 700°C, and also at the same time in the same unit, the coarse particle (112) is separated from the gas stream through a routing of the stream inside the same boiler, wherein the recovered heat is used for steam production (138) and wherein said all-radiant membrane tube wall boiler perform both the operation of cooling andseparation;• a series of purification units of the syngas (102) outcoming from said all- radiant membrane tube wall boiler type wherein all the metallic materials such as iron, lead, chromium, copper and others, chlorine compounds mainly present as HC1, nitrogen compounds mainly present as HCN and NH3, sulphur compounds present as H2S, COS and CS2and also the remaining amount of particulate compounds still present in the stream, are removed, said deep purification comprising the following: o at least one quenching unit followed by o at least one acidic scrubbing unit followed by o at least one basic scrubbing unit followed by o at least one wet electrostatic precipitation (WESP) unit; o at least one water effluent treatment unit of the liquid streams outcoming from the quenching unit, the acidic scrubbing unit and the basic scrubbing column, wherein the use of said all-radiant membrane tube wall boiler type allows both a saving of water consumption in the deep polishing unit and also a reduction of C02emissions, and wherein the steam produced in said all-radiant membrane tube wall boiler type is used for any possible step of syngas conversion according to the specific chemical production, allowing a reduction of power, natural gas consumption and an optimization of the overall conversion process .

13. The apparatus according to claim 12 wherein the syngas inlet and outlet sections of said all-radiant membrane tube wall steam drum boiler are not placed on the same axe, allowing said coarse particle separation due to the change of the flow direction .

14. The apparatus according to claim 13 wherein said position of syngas inlet and outlet section allows to avoid fouling and minimize the pressure drop thus not impacting the on-stream time of the plant .

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