Method to improve the energy efficiency of carbon conversion processes relevant to syngas produced by biomasses, wastes and / or waste derived fuel into syngas and its subsequent conversion in methanol and methanol derived chemicals

Abstract

A method to improve the overall efficiency of carbon conversion within a gasification process of biomasses, wastes and / or waste derived fuel into syngas, where the produced syngas is further converted into chemicals characterized by the fact that a stream of pure C02 (equal to 5-20% of the produced C02 stream) is injected in the feeding system and, thus, in the gasification section wherein said biomasses and / or waste materials, preferably industrial or municipal wastes, are converted in a C0 / H2 rich mixture, or raw syngas, by means of gasification with oxygen at high temperature and at almost atmospheric pressure (0, 1-0, 5 barg) and wherein such pure carbon dioxide (C02 ) stream avoids any backflow from the conversion reactor to the feeding system and also the amount of carbon dioxide (C02 ) recycled to the gasificator reactor, is both one of the syngas components and also a reactant in the subsequent conversion of syngas in methanol or in methanol derived chemicals such as DME or SAF.

Description

"METHOD TO IMPROVE THE ENERGY EFFICIENCY OF CARBON CONVERSION PROCESSES RELEVANT TO SYNGAS PRODUCED BY BIOMASSES, WASTES AND / OR WASTE DERIVED FUEL INTO SYNGAS AND ITS SUBSEQUENT CONVERSION IN METHANOL AND METHANOL DERIVED CHEMICALS”DESCRIPTIONSummary

[0001] The present invention relates to a method to improve the overall efficiency of carbon conversion process of biomasses, wastes and / or waste derived fuel into syngas, where such syngas is further converted into chemicals as methanol or methanol derived chemicals such as dimethyl ether (DME) or sustainable aviation fuel (SAF) .Technical field

[0002] Generally, the present invention relates to the conversion of biomasses, waste materials such as, preferably, industrial or municipal wastes, into chemicals .

[0003] More specifically the present invention discloses how to improve the overall energy efficiency of the carbon conversion process .Background art

[0004] 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] .

[0005] Most of the well-known gasification reactors converting biomasses, wastes or waste derived fuel as feedstocks, and using oxygen for conversion, for example patents EP 3775108 Bl or EP 3433341 Bl, usually foresee a nitrogen (N2) stream in the waste feeding system in order toprevent the backflowing of the raw syngas produced into the gasifier.

[0006] The flow required to avoid said backflow is such that the nitrogen (N2) content in the syngas outcoming from the gasification reactor is in the range between 3-6%vol .

[0007] The presence of said nitrogen, together with associated argon, decreases the partial pressure of the reactants and, when the syngas outcoming from the gasification reactor is further converted into chemicals as methanol or Fischer-Tropsch (FT) products, said presence of nitrogen reduces the specific conversion, thus it is strongly felt the need of a purge unit in order to avoid the build-up of nitrogen and argon where a process recycle is present.

[0008] The purge gas composition usually comprises nitrogen and argon (N2,Ar) and also carbon monoxide (CO), carbon dioxide (C02) and hydrogen (H2) ; particularly the hydrogen (H2) can be partially recovered and recycled, but an amount of said hydrogen (H2), together with carbon monoxide (CO) and the carbon dioxide (C02) , leaving the system with the purge gas shall be disposed, thus reducing the overall carbon conversion and re-use.Technical problem

[0009] In view of all above, it is evident the need for a method which allows to increase the overall energy efficiency of the carbon conversion process into methanol or methanol derived chemicals .

[0010] Another object of this invention is to avoid the use of nitrogen (N2) associated with waste conversion.

[0011] Yet another object of this invention is to provide a cost-effective method to increase the carbon conversion rate.

[0012] Yet another object of this invention is to minimize the C02foot print of the plant .Solution to problem

[0013] According to one aspect of the invention it is provided a process for producing methanol and methanol derived chemicals by starting from a C0 / H2rich mixture (or syngas) resulting from gasification of biomasses and / or waste materials, preferably industrial or municipal wastes, wherein a stream of recovered C02is recycled in the gasification step in order to avoid any backflow from the gasification conversion reactor to the feeding system; the produced syngas is subsequently converted into methanol or methanol derived chemicals.

[0014] According to the present invention the amount of C02recycled to the gasificator reactor is both one of the syngas components and also a reactant in the subsequent conversion of syngas into chemicals.

[0015] The terms "comprises / comprising", where used in this specification, are taken to specify the presence or addition of one or more other features, integers, steps, components, or group thereof .

[0016] Subject-matter of the invention is defined in the appended claims.Brief description of the drawings

[0017] 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.

[0018] The following appended figures and tables illustrate only examples of some preferred embodiments of the present invention; therefore, they shall not to be considered limiting of its scope, indeed the invention may admit to other equally effective embodiments.

[0019] Reference being made to the accompanyingdrawings / tables in which :Figure 1 is a schematic block diagram of a typical (well-known) methanol process block diagram with N2injection;Figure 2 is a schematic block diagram of the present invention for methanol production without N2injection.Detailed description of the invention

[0020] The present invention relates to a method to improve the overall efficiency of the carbon conversion in a gasification process of biomasses, wastes and / or waste derived fuel with oxygen at high temperature in order to obtain a raw syngas, wherein such raw syngas is further converted in methanol or methanol derived chemicals such as dimethyl ether (DME) or sustainable aviation fuels (SAF) .

[0021] Rather, this embodiment is 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 .

[0022] According to the present invention the embodiment comprises the following steps :• Gasification (A) of waste with oxygen at high temperature in order to obtain a raw syngas where the waste feeding system is pressurized with C02;• Purification and / or conditioning (B) of the raw syngas previously obtained;« Removal of carbon dioxide (C) from the raw syngas where an amount of such recovered C02is recycled back to the waste feeding system;• Conversion of the purified syngas in methanol (D), with production of purge gas as byproduct;• Treatment of the purge gas (E) with recovery of hydrogen (H2) .

[0023] According to the present invention an amount of the stream of recovered pure carbon dioxide (C02), in the range of 5-20% of the removed C02, is recycled back by injection in the feeding system and, thus, in the gasification section wherein biomasses and / or waste materials, preferably industrial or municipal wastes, are converted in a C0 / H2rich mixture (syngas) by means of gasification with oxygen at high temperature and at almost atmospheric pressure, ranging from 0, 1-0, 5 barg.

[0024] Said pure carbon dioxide (C02) stream, which depends on the volume of the waste feeding system, is such to avoid any backflow from the conversion reactor to the feeding system and also the amount of carbon dioxide (C02) recycled to the gasificator reactor is both one of the syngas components and also a reactant in the subsequent conversion of syngas into chemicals .

[0025] Thus the C02flow is able to create a positive pressure high enough to prevent the backflow of syngas from the gasifier.

[0026] Furthermore the use of a carbon dioxide (C02) recycle stream instead of a nitrogen (N2) stream allows for a decrease of the volumetric flow required for the methanol synthesis and the consequent recirculation flow; moreover the presence of such amount of carbon dioxide (C02) instead of a bigger amount of nitrogen (N2) involves in an increase of the partial pressure of the syngas components such as carbon monoxide (CO) , carbon dioxide (C02) and hydrogen (H2) reducing the specific volume of catalyst per unit of product .

[0027] According to the present invention the recovery of carbon dioxide (C02) is performed downstream the gasification reactor, thus the C02removal unit is placed downstream the gasification unit in the best position according to the specificsyngas subsequent conversion.

[0028] In the light of the above considerations said recycle of recovered carbon dioxide (C02) involves in a reduction in energy consumption with an overall optimization among the known process j less Kwh per ton of methanol produced .

[0029] Moreover the recycle of carbon dioxide (C02) as inertizing medium in the gasification section allows to decrease the off gas stream leaving the plant in the range of 75-90%.Feedstock

[0030] In the following table 1 it is shown a composition of a typical feedstock (percentage by weight ), consisting of refuse derived fuel (RDF), routed to the gasification step.TabLe 1Comparison for MethanoL production

[0031] As shown in Figure 1, in the known biomass and / or waste gasification process an amount of nitrogen (N2) is injected into the feeding system in order to create a positive pressure high enough to prevent the backflow of syngas from the gasifier (Figure 1, block A) .

[0032] The amount of N2is strictly related to the geometryof the feeding system and to the feedstock rate; the concentration of N2in the produced syngas is usually in the range between 3-6%vol.

[0033] Data shown on the following tables 2,3, 4 and 5 have been elaborated for treating 200,000 ton per year of RDF producing methanol, which represent one of the potential applications of the invention.

[0034] In the following table 2 it is shown a typical composition and flow of a syngas outcoming from a gasification reactor in which a feedstock such the one above disclosed (table 1) is converted with oxygen at high temperature thus obtaining a raw syngas; syngas composition and flow conditions are presented both for base case with nitrogen (N2) presence and also for C02injection into the feeding system.TabLe 2

[0035] As it can be seen from table 2 in the base case the concentration on dry basis of the single nitrogen (N2) is around 5%mol; by considering the other inerts, as methane and argon, the overall inert concentration rises up over 6%mol.

[0036] When such syngas is converted into a chemical (block D) the nitrogen (N2), which is non-reactive for the reaction, isseparated from the overall syngas flow and leaves the system as purge gas .

[0037] An higher content of N2in the overall syngas composition correspond to a higher amount of the purge gas flow, where other components such as CO, C02and H2are present together with N2.

[0038] Thus the purge can be considered as a leak of carbon and hydrogen .

[0039] According to the present invention the nitrogen (N2) flow is replaced by a carbon dioxide (C02) flow, where such C02flow is recovered from the C02removal unit (block C), and is partially recycled back into gasification unit (block A) .

[0040] Such C02recycle shifts the syngas composition as shown in table 1, with the nitrogen (N2) and others inerts content dropping down by an order of magnitude, from almost 6%vol to less than l,0%vol.

[0041] In the following table 3 it is shown the heat and material balance for a known conversion process using nitrogen (N2) in order to avoid backflow.

[0042] Table 4 shows the heat and material balance for the process according to the present invention in which carbon dioxide (C02) is used instead of nitrogen (N2) .

[0043] In table 5 it is shown the utilities consumption per ton of methanol for the base case with N2inertization and with C02inertization according to the present invention .

[0044] As it can be seen from tables 3, 4 and 5, the reduction of the flow to the syngas compressor involves in a reduction of the absorbed power of about 9% (390kW out of 4294kW) : this reduction is particularly noticeable considering the pressure profile of the methanol production process .

[0045] At the same time the use of such C02stream willincrease the partial pressure of C0, C02and H2, due to the absence of N2, and the subsequent conversion of syngas into methanol, which in turn will reduce the recycle flow at the entrance of block D and the purge gas flow (107) leaving the system.TabLe 3

[0046] As shown in tables 3 and 4, the reduction of the recycling flow (106) at the entrance of block D is about 3.47%.

[0047] This will result in higher methanol production, stream 105, of about 2,4% in the specific case but it may reach up to 5% under different feedstock composition and H2removal unit, a reduced power absorption between 5-10% and a reduced cooling duty up to 30%, as per tables 3, 4 and 5.

[0048] Similarly the use of carbon dioxide (C02) instead of nitrogen (N2) as inertizing medium in the methanol derived chemicals production implies that a zero or minimal amount of nitrogen (N2) is fed both to the methanol synthesis reactor andalso to the subsequent methanol derived conversion steps, for example Fischer Tropsh reactor; such minimal amount of N2involves in a higher conversion rate of chemicals product, said increase being between 2-5%.TabLe 4TabLe 5

[0049] Moreover said C02recycle allow for an increase of methanol production and consequently in carbon waste conversion up to 95% referred to the synthesis loop.

Claims

CLAIMS1. A method to improve the overall efficiency of carbon conversion within a gasification process of biomasses, wastes and / or waste derived fuel into syngas, where the produced syngas is further converted into chemicals characterized by the fact that a stream of pure C02in the range 5-20% of the recovered C02stream, preferably in the range of 7-15%, recovered downstream the gasification section, is recycled back and injected in the feeding system and, thus, in the gasification section wherein said biomasses and / or waste materials, preferably industrial or municipal wastes, are converted in a C0 / H2rich mixture, or raw syngas, by means of gasification with oxygen at high temperature and at almost atmospheric pressure, in the range of 0, 1-0, 5 barg, wherein such pure carbon dioxide (C02) stream avoids any backflow from the conversion reactor to the feeding system and also the amount of carbon dioxide (C02) recycled to the gasificator reactor, is both one of the syngas components and also a reactant in the subsequent conversion of syngas into chemicals, said recycle of carbon dioxide allowing an increase of capacity for unit of feedstock of up to 5%, a reduction of energy consumption in the overall process among the known process in the range of 5-10% and a decrease the off gas stream leaving the plant in the range of 75-90% and wherein the raw syngas is subsequently converted in methanol or methanol derived chemicals such as dimethyl ether (DME) or sustainable aviation fuels (SAF) .

2. The method according to the preceding claim characterized by the fact that the recycle of such carbon dioxide (C02) stream allows an increase of methanol productionand consequently in the waste carbon conversion up to 95% referred to the synthesis loop.

3. The method according to the preceding claims characterized by the fact that the recycle of such carbon dioxide (C02) stream allows to obtain a reduction of power consumed in the synthesis loop up to 10% for each ton of methanol produced .

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