Process and plant for producing crotonic acid

Abstract

A process and plant are described for obtaining crotonic acid starting from a biomass containing PHAs, comprising the steps of: introducing an amount of said biomass inside a thermal reactor (105) placed under vacuum; heating the amount of biomass inside the thermal reactor (105) to a preset heating temperature, so that at least a part of said amount of biomass passes to the gas state; conveying the gas obtained in the thermal reactor (105) to a condensation apparatus, inside which said gas is cooled, so as to ob-tain a final condensed liquid and a final residual gas, said condensation apparatus com-prising at least one condenser or at least a plurality of condensers (200, 300, 400) placed under vacuum and in gaseous communication with each other according to a se-ries arrangement; evacuating the final residual gas and withdrawing the final condensed liquid from the condensation apparatus.

Description

[0001] PROCESS AND PLANT FOR PRODUCING CROTONIC ACID

[0002] Technical field

[0003] The present invention relates to a process and a plant for producing crotonic acid starting from a biomass containing polyhydroxyalkanoates, hereinafter also referred to with the acronym PHA, which they are commonly called.

[0004] State of the art

[0005] Crotonic acid (IUPAC name: (2E)-but-2-enoic acid) is an unsaturated aliphatic carboxylic acid of formula CH3-CH=CH-COOH

[0006] At room temperature it appears as a white crystalline solid or a viscous liquid. It has a pungent odour similar to that of butyric acid and is soluble in water and many organic solvents, such as ethanol and ether.

[0007] Crotonic acid is used in several fields. For example, it can be used to produce crotonic esters, as an intermediate for other chemicals and / or for producing polymers and resins. It can be used as a precursor to synthesise drugs and bioactive compounds. Some derivatives of crotonic acid can be used as active ingredients in cosmetic formulations.

[0008] Presently, crotonic acid can be produced through several synthetic routes. The two main industrial methods are: dehydrogenation of butyric (butanoic) acid and the selective oxidation of crotonaldehyde (2-butenal).

[0009] The butyric acid dehydrogenation process consists of removing two hydrogen atoms from the butyric acid chain, creating a double bond between the second and third carbon atoms. The reaction is catalysed using metal oxides or specific catalysts for dehydrogenation. This synthesis requires high temperature conditions and sometimes high pressures. The crotonaldehyde elective oxidation process consists of the oxidation of crotonaldehyde in the presence of an oxidising agent, such as molecular oxygen or compounds such as KMnO4 or K2Cr2O?. This method is advantageous because crotonaldehyde is readily available and the oxidation is controllable.

[0010] Alternative methods for producing crotonic acid are hydrocarboxylation of propylene (propene), in which propylene is used as a starting substrate, converting it into crotonic acid through processes catalysed by transition metals, and biosynthesis, in which crotonic acid is produced through biological processes using certain bacterial strains or enzymes.

[0011] It is also known that crotonic acid is generated as one of the main decomposition products resulting from the thermal degradation of polyhydroxyalkanoates (PHAs). Polyhydroxyalkanoates (PHAs) are biodegradable, biocompatible polyesters which are stored as granules in the cell cytoplasm of certain types of microorganisms when the latter are subjected to stress conditions caused, for example, by the limitation of a nutrient, dissolved oxygen or the presence of an electron donor / acceptor (Anderson and Dawes 1990; Majone et al. 1996; Satoh et al. 1998; Gujer et al. 1999).

[0012] Microorganisms capable of storing PHAs are often found in the biomass (e.g., consisting of bacteria, protozoa, amoebae, rotifers and other microorganisms) contained in activated sludge which is used in wastewater treatment to remove organic impurities and pollutants. In fact, several research groups have demonstrated that under certain conditions, viz., where there are very wide fluctuations in nutrient (substrate) availability, the bacterial communities in the activated sludge present in civil and industrial sewage treatment plants tend to utilise (and accumulate) large amounts of PHA as an energy reserve to survive "feast&famine" (F&F) regimes.

[0013] Therefore, by subjecting these bacterial communities to several "feast&famine" (F&F) cycles, it is possible to carry out a biological selection of microorganisms, where those which are actually able to accumulate PHAs survive, e.g., prokaryotes of the genera Azoarcus sp., Amaricoccus sp., Tahuera sp., Rhodobacter sp., Alcaligenes sp., Pseudomonas sp., while microorganisms which cannot do so succumb.

[0014] The selected microbial communities can then be further fed with nutrients, e.g., nitrogen and phosphorous, and / or an easily degradable substrate containing a carbonaceous source, e.g., volatile fatty acids, commonly referred to as VFAs, in order to induce the growth and multiplication of the selected organisms and thus the accumulation of PHAs. It is thereby possible to obtain a biomass containing a high mass concentration of PHAs. Such a process was recently developed by the same applicants and is described in a corresponding Italian patent application No. 102024000006835.

[0015] Disclosure of the invention

[0016] In light of the above, an aim of the present invention is to provide a process and a plant which allows crotonic acid to be produced industrially and efficiently starting from a biomass containing PHAs, e.g., from a biomass of the type outlined above.

[0017] Another aim of the present invention is that of achieving the aforesaid objective within the context of a simple, rational and relatively cheap solution.

[0018] These and other aims are achieved by the features of the invention reported in the independent claims. The dependent claims outline preferred and / or particularly advantageous aspects of the invention but not strictly necessary for implementing it.

[0019] In particular, an embodiment of the present invention provides a process for obtaining crotonic acid starting from a biomass containing PHAs, wherein said biomass preferably but not necessarily contains an amount by weight of PHAs comprised between 20% and 80% (extremes included) of the total weight of the bacteria present in the same biomass, and / or wherein said biomass is preferably but not necessarily found in a dried state (an- hydrous / dehydrated / dry) and / or in the form of flakes.

[0020] According to the invention, the process comprises the steps of:

[0021] - introducing an amount of said biomass inside a thermal reactor placed under vacuum, viz., at an absolute pressure lower than atmospheric pressure,

[0022] - heating the amount of biomass inside the thermal reactor to a preset heating temperature, e.g., comprised between 190°C and 280°C (extremes included), so that at least a part of said amount of biomass passes to the gas state, e.g., by sublimation and / or evaporation (possibly following a previous melting) of all or at least some of the substances contained therein, preferably without combustion or as part of a pyrolytic (or thermolysis) process,

[0023] - conveying the gas obtained in the thermal reactor to a condensation apparatus, within which said gas is made to cool, so as to obtain a final condensed liquid and a final residual gas, said condensation apparatus comprising at least one condenser placed under vacuum or at least a plurality of (at least two) condensers placed under vacuum and in gaseous communication with each other according to a series arrangement,

[0024] - evacuating the final residual gas and withdrawing the final condensed liquid from the condensation apparatus, e.g., from the condenser or from a last condenser of the plurality of condensers placed in series (with respect to the direction in which said series of condensers is crossed by the gas).

[0025] Thanks to this process, which can be defined as a "thermolytic distillation" process of the biomass containing PHAs, as it is obtained by combining a thermal process - e.g., pyrolysis (or thermolysis) - adapted to thermally break down the PHAs contained in the starting biomass, and a gas distillation process obtained from such a thermal process, adapted to separate the components thereof, the final condensed liquid will consist of crotonic acid or at least a liquid mixture containing crotonic acid, e.g., in an amount by weight greater than the weight of each of the other components of the mixture, preferably greater than at least 50% of the total weight of the mixture, more preferably greater than 90% of the total weight of the mixture, and can therefore represent the final product of the process. The final residual gas can instead be treated as a waste substance and disposed of appropriately.

[0026] According to an aspect of the invention, the condensation apparatus can comprise at least a first condenser placed under vacuum, inside which the gas obtained in the thermal reactor is conveyed and cooled to a first condensation temperature below the heating temperature, for example comprised between 160°C and 200°C (extremes included), so as to obtain a first condensed liquid and a first residual gas.

[0027] If the condensation apparatus comprises only one condenser, the first condensed liquid can represent (constitute) the aforementioned final condensed liquid and the first residual gas can represent (constitute) the aforementioned final residual gas.

[0028] More preferably, however, the first condensed liquid and the first residual gas are intermediate products in the context of a process involving the use of a condensation apparatus provided with a plurality of condensers under vacuum arranged in series.

[0029] In both cases, however, an aspect of the invention envisages that the process can comprise the further steps of:

[0030] - connecting a transportable receptacle to an outlet nozzle of the first condenser,

[0031] - placing said transportable receptacle under vacuum,

[0032] - opening the outlet nozzle of the first condenser so that the first condensed liquid flows out into the transportable receptacle,

[0033] - closing the outlet nozzle of said first condenser, and

[0034] - separating the transportable receptacle from the respective outlet nozzle.

[0035] It is thereby advantageously possible to distance the first condensed liquid from the crotonic acid production apparatuses, e.g., to be managed as an end product or to be disposed of appropriately.

[0036] According to another aspect of the invention, the condensation apparatus can comprise, as anticipated, at least a second condenser placed under vacuum, inside which the first residual gas obtained in the first condenser is conveyed and cooled to a second condensation temperature lower than the first condensation temperature, for example comprised between 130°C and 170°C (extremes included), so as to obtain a second condensed liquid and a second residual gas.

[0037] If the condensation apparatus comprises only two condensers arranged in series, the second condensed liquid can represent (constitute) the aforementioned final condensed liquid and the second residual gas can represent (constitute) the aforementioned final residual gas.

[0038] If, however, the condensation apparatus comprises more than two condensers arranged in series, the second condensed liquid and the second residual gas can be intermediate products of the process.

[0039] In both cases, however, an aspect of the invention envisages that the process can comprise the further steps of:

[0040] - connecting a transportable receptacle to an outlet nozzle of the second condenser,

[0041] - placing said transportable receptacle under vacuum,

[0042] - opening the outlet nozzle of the second condenser so that the second condensed liquid flows out into the transportable receptacle,

[0043] - closing the outlet nozzle of said second condenser, and

[0044] - separating the transportable receptacle from the respective outlet nozzle.

[0045] It is thereby advantageously possible to distance the second condensed liquid from the crotonic acid production apparatuses, e.g., to be managed as an end product or to be disposed of appropriately.

[0046] According to another aspect of the invention, the condensation apparatus can comprise a third condenser placed under vacuum, inside which the second residual gas obtained in the second condenser is conveyed and cooled to a third condensation temperature lower than the second condensation temperature, for example comprised between 100°C and 140°C (extremes included), so as to obtain a third condensed liquid and a third residual gas.

[0047] If the condensation apparatus comprises only three condensers arranged in series, the third condensed liquid can represent (constitute) the aforementioned final condensed liquid and the second residual gas can represent (constitute) the aforementioned final residual gas.

[0048] If, however, the condensation apparatus comprises more than three condensers arranged in series, the third condensed liquid and the third residual gas can also be intermediate products of the process.

[0049] In general, the condensation apparatus can comprise any number of condensers arranged in series (e.g., two, three or more than three), starting with a first condenser in gaseous communication with the thermal reactor, up to a last condenser in the series, inside which an n-th condensed liquid and an n-th residual gas are obtained, representing (constituting) the final condensed liquid and the final residual gas, respectively.

[0050] Correspondingly, to withdraw the condensed liquid from each of these condensers, the method can envisage connecting a transportable receptacle to an outlet nozzle of each thereof, placing said transportable receptacle under vacuum, opening the outlet nozzle of each condenser so that the respective condensed liquid flows into the transportable receptacle, closing the outlet nozzle of each condenser, and separating each transportable receptacle from the respective outlet nozzle.

[0051] According to an aspect of the invention, the process can include performing, one or more times, a redistillation cycle of the final condensed liquid comprising the steps of:

[0052] - collecting the final condensed liquid in a storage vessel placed under vacuum,

[0053] - heating the final condensed liquid inside the storage vessel so as to cause the evaporation thereof,

[0054] - conveying the obtained vapour into the storage vessel inside the condensation apparatus (e.g., in the only condenser or in the first condenser of the series), inside which the vapour is cooled (in a manner similar to the above), so as to obtain a final condensed liquid and a final residual gas.

[0055] For example, the vapour obtained in the storage vessel can be conveyed inside the first condenser placed under vacuum, inside which the vapour is cooled to the first condensation temperature, so that a first condensed liquid and a first residual gas are re-ob- tained.

[0056] The first residual gas can be conveyed to the second condenser placed under vacuum, inside which the first residual gas is cooled to the second condensation temperature, so that a second condensed liquid and a second residual gas are re-obtained.

[0057] The second residual gas can then possibly be conveyed into the third condenser placed under vacuum, inside which the second residual gas is cooled to the third condensation temperature, so that a third condensed liquid and a third residual gas are re-obtained.

[0058] And so on, if there are more than three condensers, until the final condensed liquid and the final residual gas are re-obtained.

[0059] Thanks to this solution, it is advantageously possible to increase the purity of the third condensed liquid, viz., the concentration of crotonic acid in the third condensed liquid, e.g., by reaching values exceeding 95% by weight of the total weight of the third condensed liquid.

[0060] During the execution of each redistillation cycle of the third condensed liquid, it may be preferable (although not necessary) to prevent gaseous communication between the thermal reactor and the condensation apparatus, e.g., by closing a suitable valve.

[0061] Of course, the possibility of performing these redistillation cycles automatically by means of the storage vessel remains an option, and it is not excluded that in some embodiments this can be omitted and possibly replaced with manual recirculation.

[0062] Another aspect of the invention envisages that, after completing said one or more redistillation cycles of the third condensed liquid, the process can comprise the further steps of:

[0063] - connecting a transportable receptacle to an outlet nozzle of the storage vessel,

[0064] - placing said transportable receptacle under vacuum,

[0065] - opening the outlet nozzle of the storage vessel so as to collect the third condensed liquid in the transportable receptacle,

[0066] - closing the outlet nozzle of the storage vessel, and

[0067] - separating the transportable receptacle from the outlet nozzle of the storage vessel.

[0068] It is thereby advantageously possible to remove the third concentrated liquid (viz., crotonic acid) from the production apparatuses, e.g., to be marketed or used.

[0069] Of course, if no redistillation cycle is to be performed, the condensed liquid could be collected, e.g., in a similar manner, from an outlet nozzle obtained directly in the last condenser of the series, as mentioned above.

[0070] According to another aspect of the invention, the vacuum pressure in the thermal reactor, viz., the absolute pressure therein, can be comprised between 150 mbar and 900 mbar (extremes included).

[0071] It is thereby advantageously possible to both significantly lower the sublimation and / or evaporation temperature of the substances contained in the biomass, favouring the transformation thereof into gas, and to improve the anoxia conditions inside the thermal reactor and thus reduce the risk of triggering combustion. Another aspect of the invention envisages that the thermal reactor and the condensation apparatus can be brought under vacuum by means of a vacuum pump placed in gaseous communication with the condenser or with a last condenser of the plurality of condensers arranged in series (with respect to the direction with which said series of condensers is crossed by the gas).

[0072] Thanks to this solution, a single vacuum pump is advantageously able to place and maintain all these devices under vacuum, reducing the process implementation costs.

[0073] Furthermore, thereby, at least due to the effect of pressure drops, the vacuum pressure, viz., the absolute pressure, in the thermal reactor will be (at least slightly) greater than that in the condensation apparatus, which will also be decreasing from a first to a last condenser of the plurality of condensers in series (if present).

[0074] Therefore, the conveyance of gas from the thermal reactor to the condensation apparatus, as well as the conveyance of gas between the possible various condensers in series, can occur as a natural consequence of the aforesaid pressure differences, viz., following the suction effect generated by the vacuum pump connected to the condenser or the last condenser in the series.

[0075] This same suction effect can also allow the evacuation and venting of the final residual gas from the condensation apparatus.

[0076] It is however preferable that the pressure difference between the thermal reactor and the condenser or the last condenser in the series is not excessively high, e.g., less than or equal to 300 mbar.

[0077] According to another aspect of the invention, the introduction of the amount of biomass in the thermal reactor can envisage the steps of:

[0078] - preliminarily loading the amount of biomass into a loading vessel,

[0079] - placing said loading vessel under vacuum, and

[0080] - then transferring the amount of biomass from the loading vessel to the thermal reactor.

[0081] Thanks to this solution, it is advantageously possible to introduce biomass into the thermal reactor when the latter is already under vacuum conditions and, therefore, e.g., progressively.

[0082] According to a further aspect of the invention, the process can envisage, during the heating step, advancing the amount of biomass introduced into the thermal reactor by rotatably driving a screw body installed therein.

[0083] Thereby, both a re-stirring of the biomass is obtained, which favours the release of gas, and a progressive conveyance of the biomass itself, e.g., from an inlet zone towards an outlet zone of the thermal reactor, where a residual part of the amount of biomass, viz., that which has not passed to the gas state at the end of heating, can accumulate to be collected, for example.

[0084] In particular, an aspect of the invention envisages that the residual part of the amount of biomass can be transferred from the thermal reactor to a collection vessel placed under vacuum.

[0085] In this context, another aspect of the invention envisages that, after the heating step is complete, the process can comprise the further steps of:

[0086] - connecting a transportable receptacle to an outlet nozzle of the collection vessel,

[0087] - placing said transportable receptacle under vacuum,

[0088] - opening the outlet nozzle of the collection vessel so as to collect the residual part of said amount of biomass in the transportable receptacle,

[0089] - closing the outlet nozzle of the collection vessel, and

[0090] - separating the transportable receptacle from the outlet nozzle of the collection vessel.

[0091] It is thereby advantageously possible to distance the residual part of the biomass from the crotonic acid production apparatuses, e.g., to be disposed of appropriately.

[0092] Of course, if the screw body and / or collection vessel are not envisaged, the residual part of the biomass could be collected, e.g., in a similar manner, by an outlet nozzle directly obtained in the thermal reactor.

[0093] According to another aspect of the invention, the final residual gas evacuated from the condensation apparatus can be bubbled in water, viz., made to flow out into a mass of water.

[0094] Thanks to this solution, the final residual gas is advantageously cooled and purified of some of the substances contained therein, which can dissolve and / or mix with water, thus being more easily treatable and / or disposable.

[0095] Another embodiment of the present invention provides a plant for producing crotonic acid starting from a biomass containing PHAs, comprising:

[0096] - a thermal reactor adapted to receive an amount of said biomass and provided with thermoregulation means for heating the amount of biomass to a preset heating temperature, so that at least a part of said amount of biomass passes to the gas state,

[0097] - a condensation apparatus in gaseous communication with the thermal reactor and comprising one or more condensers individually provided with thermoregulation means for cooling the gas so as to obtain a final condensed liquid and a final residual gas, and

[0098] - suction means for putting the thermal reactor and condenser(s) of the condensation apparatus under vacuum.

[0099] Thanks to this plant, it is advantageously possible to implement the crotonic acid production method outlined above, achieving the related benefits.

[0100] It should be specified that the thermoregulation means of the plant can be of the electrical type, e.g., Joule effect (e.g., resistors), electromagnetic induction, electromagnetic wave radiation (e.g., microwaves) or others, or they can be thermoregulation means of any other type, e.g., but not limited to heat exchangers operating with liquid and / or gaseous carrier fluids.

[0101] All the illustrative and preferred features outlined above with reference to the process are thus understood to be equally applicable to this plant as well .

[0102] In particular, an aspect of the invention envisages that the condensation apparatus can comprise at least a first condenser in gaseous communication with the thermal reactor and provided with thermoregulation means for cooling the gas to a first condensation temperature below the heating temperature, so as to obtain a first condensed liquid and a first residual gas.

[0103] The condensation apparatus can thus comprise a transportable receptacle adapted to be connected to an outlet nozzle of the first condenser, which outlet nozzle is openable to allow said transportable receptacle to collect the condensed liquid, suction means being provided for putting the transportable receptacle under vacuum after the connection to the outlet nozzle of the first condenser and before opening the same.

[0104] Another aspect of the invention envisages that the condensation apparatus can comprise a second condenser in gaseous communication with the first condenser and provided with thermoregulation means for cooling the first residual gas to a second condensation temperature below the first condensation temperature, so as to obtain a second condensed liquid and a second residual gas.

[0105] The condensation apparatus can thus comprise an individually transportable receptacle adapted to be connected to an outlet nozzle of the second condenser, which outlet nozzle is openable to allow said transportable receptacle to collect the condensed liquid, suction means being provided to put the transportable receptacle under vacuum after connection to the outlet nozzle of the second condenser and before opening the same.

[0106] A further aspect of the invention envisages that the condensation apparatus can also comprise a third condenser in gaseous communication with the second condenser and provided with thermoregulation means for cooling the second residual gas to a third condensation temperature below the second condensation temperature, so as to obtain a third condensed liquid and a third residual gas.

[0107] In general, the condensation apparatus can comprise any number of condensers arranged in series (e.g., two, three or more than three), starting with a first condenser in gaseous communication with the thermal reactor, up to a last condenser in the series, inside which an n-th condensed liquid and an n-th residual gas are obtained, representing the final condensed liquid and the final residual gas, respectively.

[0108] According to another aspect of the invention, the suction means can comprise a vacuum pump placed in gaseous communication with the condenser or with a last condenser of the plurality of condensers in series of the condensation apparatus.

[0109] Another aspect of the invention envisages that the plant can comprise a storage vessel adapted to receive the final condensed liquid from the condensation apparatus and provided with thermoregulation means for heating the final condensed liquid inside the storage vessel so as to cause the evaporation thereof, the condenser or the first condenser of the plurality of condensers of the condensation apparatus being in gaseous communication with said storage vessel to receive the vapour obtained from said evaporation.

[0110] This aspect of the plant allows to carry out one or more redistillation cycles of the final condensed liquid as explained above in relation to the process.

[0111] As anticipated, the presence of the storage vessel remains an option regardless, and it is not excluded that some embodiments can lack the storage vessel.

[0112] According to an aspect of the invention, the apparatus can comprise a transportable receptacle adapted to be connected to an outlet nozzle of the storage vessel, which outlet nozzle is openable to allow said transportable receptacle to collect the final condensed liquid, suction means being provided to put the transportable receptacle under vacuum after connection to the outlet nozzle of the storage vessel and before opening the same. According to a further aspect of the invention, the plant can comprise a loading vessel adapted to receive the amount of biomass and provided with a transfer duct, which transfer duct is openable to allow the amount of biomass to pass from the loading vessel to the thermal reactor, suction means being provided for putting the loading vessel under vacuum before opening the transfer duct.

[0113] Another aspect of the invention envisages that the thermal reactor can receive a rotating screw body configured to advance the amount of biomass in the thermal reactor itself.

[0114] In practice, the thermal reactor can be considered a heating screw conveyor.

[0115] According to another aspect of the invention, the plant can comprise a collection vessel adapted to receive a residual part of the amount of biomass contained in the thermal reactor, viz., that which has not passed to the gas state at the end of heating.

[0116] A further aspect of the invention envisages that the plant can comprise a transportable receptacle adapted to be connected to an outlet nozzle of the collection vessel, which outlet nozzle is openable to allow said transportable receptacle to collect the residual part of said amount of biomass, suction means being provided for putting the transportable receptacle under vacuum after connection to the outlet nozzle of the collection vessel and before opening the same.

[0117] According to another aspect of the invention, the apparatus can comprise a vat adapted to contain a mass of water and at least one nozzle in gaseous communication with the condenser or with a final condenser of the plurality of condensers of the condensation apparatus and adapted to bubble the final residual gas in the mass of water contained in the vat.

[0118] Brief description of the drawings

[0119] Further features and advantages of the invention will be more apparent after reading the following description provided by way of a non-limiting example, with the aid of the accompanying drawings.

[0120] Figure 1 is a schematic representation of a plant according to an embodiment of the present invention.

[0121] Figures 2 to 15 are the schematic representation of Figure 1 in as many operating steps during its operation. Detailed description

[0122] Referring to the illustrative but not limiting figures mentioned above, a plant 100 and a process for producing crotonic acid starting from a biomass containing PHAs, viz., a mass of microorganisms containing PHAs, is described below.

[0123] Crotonic acid and PHA and how a biomass containing the latter can be obtained has already been explained in the preamble of this document, to which reference is made for any further clarifications, it being understood that the explanations given in that context are also understood an integral part of this detailed description.

[0124] The biomass containing PHAs, which is used in the plant 100 and in the process described herein, preferably (but not necessarily) contains between 20% and 80% by weight of PHAs (extremes included) of the total weight of bacteria present in the same biomass. Regardless, such biomass containing PHAs is preferably (but not necessarily) found in a dried (anhydrous / dehydrated / dry) state and / or in the form of flakes.

[0125] If the biomass containing PHAs is in liquid or semi-liquid form, viz., in the form of a more or less concentrated solution of microorganisms containing PHAs, the process could envisage an initial drying step of the biomass and the plant 100 could correspondingly comprise a drying device (not shown) adapted to receive the liquid biomass, dry it and release the dried biomass to the devices of the plant 100 which will be described below.

[0126] For the sake of simplicity, in the following, the biomass containing PHAs will simply be referred to as "biomass".

[0127] The plant 100 comprises a thermal reactor 105, viz., a device comprising a casing 110, the internal volume of which is adapted to contain an amount of said biomass, and thermoregulation means, referred to overall as 115, in this case heating means, which are adapted to heat the amount of biomass inside the casing 110.

[0128] The thermoregulation means 115 can be electrical, e.g., Joule effect (e.g., resistors), electromagnetic induction, electromagnetic wave radiation (e.g., microwaves) or others, or they can be of any other type, e.g., but not limited to heat exchangers operating with liquid and / or gaseous carrier fluids.

[0129] The thermal reactor 105 can further comprise a screw body 120, which is installed in the inner volume and is adapted to rotate about the axis thereof, so as to stir and advance the amount of biomass from an inlet zone towards an outlet zone of the casing 110.

[0130] For example, the casing 110 can be cylindrical in shape and the screw body 120 can be oriented with axis parallel to or coincident with the axis of such a casing 110.

[0131] In practice, the thermal reactor 105 can be shaped like a screw conveyor provided with the thermoregulation means 115 for heating the amount of biomass during conveyance. The driving of the screw body 120 in rotation can be delegated to a motor 125, preferably an electric motor, which can be installed outside the casing 110.

[0132] The plant 100 can further comprise a loading vessel 130 for the amount of biomass, which is in communication with the thermal reactor 105, e.g., at the inlet zone, through a transfer duct 135.

[0133] A shut-off valve 140, preferably of an electrically controllable type, which is adapted to selectively open and close this transfer duct 135, can be associated with said transfer duct 135, preventing and respectively allowing a passage of biomass from the loading vessel 130 to the thermal reactor 105.

[0134] The outflow of biomass through the transfer duct 135 can be driven or facilitated by an extractor 145, e.g., of the vane impeller type, which can be driven by a respective motor, preferably electric, installed externally.

[0135] The loading vessel 130 can also be provided with an access nozzle 150 for introducing biomass, which can be opened and closed by a respective shut-off valve 155, preferably of an electrically controllable type.

[0136] The access nozzle 150 can in turn be placed on the bottom of a hopper 160 adapted to receive the biomass, so that when the access nozzle 150 is opened, part of the biomass contained in hopper 160 passes into the loading vessel 130.

[0137] The loading vessel 130 can furthermore be in gaseous communication with the thermal reactor 105 by means of a secondary duct 530, which is intercepted by a shut-off valve 535, preferably of the electrically controllable type, which is selectively adapted to open and close the aforesaid gaseous communication.

[0138] Irrespective of what has been described so far, the plant 100 can also comprise a collection vessel 165, which is in communication with the thermal reactor 105, e.g., at the outlet zone, through a transfer duct 170.

[0139] A shut-off valve 175, preferably of an electrically controllable type, can be associated with this transfer duct 170, which is adapted to selectively open and close said transfer duct 170, preventing and respectively allowing a passage of biomass from the thermal reactor 105 to the collection vessel 165. The outflow of the biomass through the transfer duct 170 can be driven or facilitated directly by the screw body 120 (if present) placed inside the thermal reactor 105.

[0140] The collection vessel 165 can also be provided with an outlet nozzle 180 for discharging the biomass, which can be opened and closed by a respective shut-off valve 185, preferably of an electrically controllable type.

[0141] The collection vessel 165 can be associated with thermoregulation means, referred to overall as 190, in this case heating means, which are adapted to heat the biomass therein. The thermoregulation means 190 can be electrical, e.g., Joule effect (e.g., resistors), electromagnetic induction, electromagnetic wave radiation (e.g., microwaves) or others, or they can be of any other type, e.g., but not limited to heat exchangers operating with liquid and / or gaseous carrier fluids.

[0142] Irrespective of what has been described so far, the plant 100 comprises a condensation apparatus.

[0143] This condensation apparatus can comprise a single condenser or, more preferably, a plurality of (at least two) condensers which are in gaseous communication with each other according to a series arrangement.

[0144] In the example illustrated herein, the condensation apparatus comprises three condensers, of which a first condenser 200, a second condenser 300 and a third condenser 400. As mentioned above, however, it cannot be excluded out that the condensation apparatus can comprise only two condensers or a number of condensers greater than three.

[0145] As far as at least general constructional aspects are concerned, the three condensers 200, 300 and 400 can be the same, therefore in the following only the first condenser 200 will be described, it being understood that everything detailed will also correspond to the description of the second condenser 300 and the third condenser 400 (or any other condenser in the condensation apparatus).

[0146] Hence, the first condenser 200 generally comprises a casing 205, which defines an inner volume and is provided, preferably but not necessarily at a top zone thereof, with at least one inlet nozzle 210 adapted to allow the entry (into the inner volume) of a gas to be condensed.

[0147] The first condenser 200 further comprises thermoregulation means, referred to overall as 215, in this case cooling means, which are adapted to cool the gas inside the casing 205. It should be noted, however, that since the gas to be condensed can have a very high temperature, the thermoregulation means 215 can cool the gas, bringing it to lower but still rather high absolute temperatures.

[0148] The thermoregulation means 215 can be electrical, e.g., Joule effect (e.g., resistors), electromagnetic induction, electromagnetic wave radiation (e.g., microwaves) or others, or they can be of any other type, e.g., but not limited to heat exchangers operating with liquid and / or gaseous carrier fluids.

[0149] In any case, the cooling causes at least part of the substances contained in the gas to be condensed to condense inside the first condenser 200, thus obtaining (from said gas) a condensed liquid and a residual gas.

[0150] The condensed liquid generally collects on a bottom of the casing 205, viz., of its inner volume, while the residual gas can be made to flow out through at least one evacuation port 220, which is arranged in the casing 205, preferably but not necessarily at an upper zone.

[0151] The casing 205 can also be provided, preferably but not necessarily at the bottom, with an outlet nozzle 225 for draining the condensed liquid, to which can be associated a shutoff valve 230, preferably of electrically controllable type, adapted to selectively open and close said outlet nozzle 225.

[0152] In order to improve condensation efficiency, the inner volume of the casing 205 can be divided into two chambers, of which a first chamber 235, preferably located at the upper zone, which is in direct communication with the inlet port 210, and a second chamber 240, preferably located at a lower zone, which is in direct communication with the evacuation port 220 and inside which the condensed liquid collects.

[0153] These two chambers are connected to each other by a tube bundle 245, preferably consisting of vertically oriented tubes, inside which all the gas to be condensed is forced to pass in order to flow from the inlet port 210 towards the evacuation port 220.

[0154] In the example shown, the tubes of the tube bundle 245 are made in the form of ducts drilled in a solid body (possibly formed by several assembled parts) occupying an entire portion of the inner volume of the casing 205, separating the first chamber 235 from the second chamber 240.

[0155] The thermoregulation means 215 can therefore be adapted to regulate (only or also) the temperature of this solid body, so as to cool the gas to be condensed flowing inside the ducts. However, it is not excluded that, in other embodiments, the tube bundle 245 can be formed by actual tubes interposed between two separation flanges, which can be adapted to separate the first chamber 235 from the second chamber 240 and, for example, also to define an intermediate chamber housing the tubes and in which a carrier fluid (e.g., vapour) can be circulated, which, lapping the tubes themselves externally, is able to cool the gas to be condensed flowing therein.

[0156] In both cases, the communication between the second (lower) chamber 240 and the evacuation port 220 can occur through a connecting duct, at least a portion of which can coincide with one of the tubes of the tube bundle 245.

[0157] The three condensers 200, 300 and 400 can be in gaseous communication with the thermal reactor 105 according to a series arrangement, viz., so that a gas exiting from the inner volume of the thermal reactor 105 is forced to pass through the first condenser 200, the second condenser 300 and the third condenser 400 in sequence.

[0158] In other words, the first condenser 200 can be in direct gaseous communication with the thermal reactor 105, while the second condenser 300 can be in gaseous communication with the thermal reactor 105 through the first condenser 200, and the third condenser 400 can be in gaseous communication with the thermal reactor 105 through the first condenser 200 and the second condenser 300.

[0159] For example, the casing 110 of the thermal reactor 105 can be provided with at least one venting port 195 adapted to allow gas to exit from the inner volume.

[0160] By means of a first duct 500, this venting port 195 can be connected to the inlet port 210 of the first condenser 200, whose evacuation port 220 can be connected to the inlet port 210 of the second condenser 300 by means of a second duct 505, and finally the evacuation port 220 of the second condenser 300 can be connected to the inlet port 210 of the third condenser 400 by a third duct 510.

[0161] Similar connections could also be envisaged with a different number of condensers.

[0162] A shut-off valve 515, preferably of the electrically controllable type, can be provided in the plant 100 to selectively prevent and allow gaseous communication between the thermal reactor 105 and the first condenser 200.

[0163] For example, said shut-off valve 515 can be placed to intercept the first duct 500.

[0164] The plant 100 further comprises suction means 600 for putting at least the thermal reactor 105 and all the condensers of the condensation apparatus under vacuum, for example the first condenser 200, the second condenser 300 and the third condenser 400.

[0165] For example, these suction means 600 can comprise at least one vacuum pump 605, which is placed in gaseous communication with the last condenser of the plurality of condensers, in this case with the third condenser 400.

[0166] In particular, by means of a fourth duct 520, the evacuation port 220 of the third condenser 400 can be connected with a suction port of said vacuum pump 605.

[0167] The vacuum pump 605 can be a liquid ring pump or any other type of pump (e.g., piston, diaphragm, diffusion, etc.) capable of sucking air and / or gas from the thermal reactor 105 and, for example, from the first condenser 200, the second condenser 300 and the third condenser 400, so as to create a vacuum condition therein, viz., an absolute pressure below atmospheric pressure.

[0168] A motor 610, preferably an electric motor, can drive the vacuum pump 605.

[0169] The same suction means 600 or, more preferably other suction means 615, e.g., another vacuum pump of any type, can be in gaseous communication with the loading vessel 130, preferably by means of a shut-off valve 620 (preferably electrically controllable) adapted to selectively open and close said communication, so that air and / or gas can also be sucked from the loading vessel 130 and thus create, also therein, a vacuum condition.

[0170] The plant 100 can further comprise a vat 700 adapted to contain a mass of water and at least one nozzle 705, in gaseous communication with the last condenser of the series of condensers forming the condensation apparatus, in this case the third condenser 400, for example with the evacuation port 220 of the latter, which is capable adapted to make the residual gas obtained in the third condenser 400 flow out inside the vat 700, preferably by bubbling it in the mass of water contained therein.

[0171] For example, the nozzle 705 can be connected with a delivery port of the vacuum pump 605.

[0172] Irrespective of what has been described so far, the plant 100 can comprise a storage vessel 800, which is in communication with the last condenser of the series of condensers forming the condensation apparatus, in this case with the third condenser 400, for example through the outlet nozzle 225 of the latter and the relative shut-off valve 230, so that it can receive the condensed liquid accumulating therein.

[0173] The outflow of the condensed liquid preferably occurs by gravity, but it is not excluded that appropriate pumping systems can be used in other embodiments. The storage vessel 800 can in turn be provided with an outlet nozzle 805 for draining the condensed liquid, to which a further shut-off valve 810 can be associated, preferably of the electrically controllable type, adapted to selectively open and close said outlet nozzle 805.

[0174] The storage vessel 800 can be associated with thermoregulation means, referred to overall as 815, in this case heating means, which are adapted to heat the condensed liquid accumulated therein, so as to cause the evaporation thereof.

[0175] The thermoregulation means 815 can be electrical, e.g., Joule effect (e.g., resistors), electromagnetic induction, electromagnetic wave radiation (e.g., microwaves) or others, or they can be of any other type, e.g., but not limited to heat exchangers operating with liquid and / or gaseous carrier fluids.

[0176] The storage vessel 800 can be in gaseous communication with the first condenser 200 of the series of condensers forming the condensation apparatus, so that the latter can receive the vapours obtained inside the storage vessel 800.

[0177] For example, the storage vessel 800 can have a venting port 820, which is connected to the first condenser 200, e.g., with the inlet port 210 thereof, through a fifth duct 525, which can, for example, flow into the first duct 500, downstream of the shut-off valve 515 (if present).

[0178] A shut-off valve 540, preferably of the electrically controllable type, can be arranged on the fifth duct 525 to selectively open and close the gaseous communication between the storage vessel 800 and the first condenser 200.

[0179] Irrespective of what has been described so far, the plant 100 can be provided with one or more transportable (or portable) receptacles, viz., receptacles which are not stably installed in the plant 100 but which can be joined and separated therefrom, e.g., to be transported to other locations and possibly to be returned to the plant 100.

[0180] In particular, these transportable receptacles can include at least one transportable receptacle 900 adapted to be (removably) connected to the outlet nozzle 180 of the collection vessel 165 of the thermal reactor 105, for example by means of a releasable coupling 905.

[0181] Thereby, when the shut-off valve 185 is opened, the transportable receptacle 900 can receive the biomass stored therein from the collection vessel 165, e.g., by gravity.

[0182] Before this occurs, however, it is preferable that the transportable receptacle 900 be placed under vacuum.

[0183] For this reason, at a section comprised between the releasable coupling 905 and the shut-off valve 185, the outlet nozzle 180 can be in gaseous communication with the suction means 600 or, more preferably, with other suction means 625, for example with another vacuum pump of any type.

[0184] By activating these suction means, after the connection of the transportable receptacle 900 but before opening the shut-off valve 185, it is in fact advantageously possible to suck air and / or gas from the transportable vessel 900 and thus create a vacuum condition therein.

[0185] In addition or alternatively, the transportable receptacles can include at least one transportable receptacle 910 adapted to be (removably) connected to the outlet nozzle 805 of the storage vessel 800, for example by means of a releasable coupling 915.

[0186] Thereby, when the shut-off valve 810 is opened, the transportable receptacle 910 can receive from the storage vessel 800, e.g., by gravity, the condensed liquid stored therein. Before this occurs, however, also in this case it is preferable that the transportable vessel 910 be placed under vacuum.

[0187] For this reason, at a section comprised between the releasable coupling 915 and the shut-off valve 810, the outlet nozzle 805 can be in gaseous communication with the suction means 600 or, more preferably, with other suction means 630, for example with another vacuum pump of any type.

[0188] By activating these suction means, after the connection of the transportable receptacle 910 but before opening the shut-off valve 810, it is advantageously possible to suck air and / or gas from the transportable vessel 910 and thus create a vacuum condition therein. In addition or alternatively, the transportable receptacles can include at least one transportable receptacle 920 adapted to be (removably) connected to the outlet nozzle 225 of the first condenser 200, for example by means of a releasable coupling 925.

[0189] Thereby, when the shut-off valve 230 of the first condenser 200 is opened, the transportable receptacle 920 can receive from the first condenser 200 itself, e.g., by gravity, the condensed liquid stored therein.

[0190] Before this occurs, however, also in this case it is preferable that the transportable vessel 920 be placed under vacuum.

[0191] For this reason, at a section comprised between the releasable coupling 925 and the shut-off valve 230, the outlet nozzle 225 of the first condenser 200 can be in gaseous communication with the suction means 600 or, more preferably, with other suction means 635, for example with another vacuum pump of any type.

[0192] By activating these suction means, after the connection of the transportable receptacle 920 but before opening the shut-off valve 230 of the first condenser 200, it is advantageously possible to suck air and / or gas from the transportable vessel 920 and thus create a vacuum condition therein.

[0193] In addition or alternatively, the transportable receptacles can include at least one transportable receptacle 930 adapted to be (removably) connected to the outlet nozzle 225 of the second condenser 300, for example by means of a releasable coupling 935.

[0194] Thereby, when the shut-off valve 230 of the second condenser 300 is opened, the transportable receptacle 930 can receive from the second condenser 300 itself, e.g., by gravity, the condensed liquid stored therein.

[0195] Before this occurs, however, also in this case it is preferable that the transportable vessel 930 be placed under vacuum.

[0196] For this reason, at a section comprised between the releasable coupling 935 and the shut-off valve 230, the outlet nozzle 225 of the second condenser 300 can be in gaseous communication with the suction means 600 or, more preferably, with other suction means 640, for example with another vacuum pump of any type.

[0197] By activating these suction means, after the connection of the transportable receptacle 930 but before opening the shut-off valve 230 of the second condenser 300, it is in fact advantageously possible to suck air and / or gas from the transportable vessel 930 and thus create the vacuum condition therein.

[0198] The operation of the plant 100 can be managed by an electronic control unit (not illustrated) which manages at least the motors, the various valves and the thermoregulation means.

[0199] Operation can include an initial step, in which the thermal reactor 105, the condensers 200, 300 and 400, as well as the collection vessel 165 and storage vessel 800 (if present), are heated and placed under vacuum.

[0200] In this first step, illustrated in Figure 2, the shut-off valve 535, the shut-off valve 140, the shut-off valve 185, the shut-off valve 230 of the first condenser 200, the shut-off valve 230 of the second condenser 300, the shut-off valve 810 of the storage vat 800 and the shut-off valve 540 can be closed, while the shut-off valve 515, the shut-off valve 175 and the shut-off valve 230 of the third condenser 400 can be opened.

[0201] Thereby, the thermal reactor 105, the condensers 200, 300 and 400, the collection vessel 165 and the storage vessel 800 are all in gaseous communication with each other and with the suction means 600, but isolated with respect to the external environment and with respect to the loading vessel 130.

[0202] Therefore, by activating the suction means 600, a vacuum condition (viz., absolute pressure lower than atmospheric pressure) and also substantial anoxia condition, viz., absence or otherwise deficiency of oxygen, is created inside each of these components.

[0203] In particular, the driving of the suction means 600 is preferably controlled so as to reach and subsequently maintain an absolute pressure comprised between 150 mbar and 900 mbar (extremes included) inside the thermal reactor 105.

[0204] The absolute pressure in the condensers 200, 300 and 400, in the collection vessel 165 and in the storage vessel 800 will be comparable to that of the thermal reactor 105 but, due to pressure drops, at least in the condensers 200, 300 and 400, will be at least slightly lower with respect to that of the thermal reactor 105 and generally decreasing from the first condenser 200 to the third condenser 400.

[0205] At the same time, the thermoregulation means 115 of the thermal reactor 105, the thermoregulation means 190 of the collection vessel 165, the thermoregulation means 215 of each of the condensers 200, 300 and 400, and the thermoregulation means 815 of the storage vessel 800 are also activated, so as to bring each of these devices to a corresponding operating temperature, which will be detailed below.

[0206] In a next step, illustrated in Figure 3, an amount of biomass can be introduced inside the loading vessel 130, e.g., by means of the hopper 160.

[0207] Once the introduction of the amount of biomass, the shut-off valve 155 can be closed so as to isolate the loading vessel 130 with respect to the external environment.

[0208] By activating the suction means, for example those indicated with 615 in Figure 3, the loading vessel 130, with the amount of biomass therein, can also be brought into a vacuum condition, preferably up to reaching an absolute pressure equal or close to that of the thermal reactor 105.

[0209] To definitively make the two pressure levels uniform, the shut-off valve 535 can then be opened. Then, as shown in Figure 4, the shut-off valve 140 can be opened and, if necessary, the extractor 145 can be activated, so that the amount of biomass is gradually passed from the loading vessel 130 to the thermal reactor 105.

[0210] In this step, the screw body 120 (if present) is placed and kept in rotation, so as to progressively advance the amount of biomass from the inlet zone of the thermal reactor 105, at which the loading vessel 130 is placed, towards the outlet zone, at which the collection vessel 165 is placed.

[0211] Inside the thermal reactor 105, e.g., during the aforesaid advancement, the biomass is heated to a preset heating temperature, e.g., comprised between 190°C and 280°C (extremes included), so that at least a part of said biomass passes to the gas state, e.g., by sublimation and / or evaporation (possibly as a result of a previous melting) of all or at least some of the substances contained therein.

[0212] Thanks to the essentially anoxic conditions, this gas release preferably occurs without combustion, viz., as part of a pyrolytic (or thermolysis) process of the biomass.

[0213] Of course, it is generally not possible for all of the biomass introduced into the thermal reactor 105 to pass into the gaseous state, whereby it is expected that a residual part thereof will always remain (which cannot and / or has not been able to pass into the gas state).

[0214] Thanks to the conveyance carried out by the screw body 120, this residual part will progressively reach the outlet zone of the thermal reactor 105 and collect (e.g., fall) inside the collection vessel 165, as schematically depicted in Figure 5.

[0215] The collection vessel 165 is heated, by the thermoregulation means 190, to substantially the same heating temperature as that at which the thermal reactor 105 is heated, so that the biomass collected therein can eventually continue the pyrolytic process.

[0216] After the entire amount of biomass loaded into the loading vessel 130 has passed into the thermal reactor 105, the shut-off valve 140 can be closed (see Fig.6), while the biomass continues to advance towards the collection vessel 165 until the thermal reactor 105 is completely emptied (see Fig.7).

[0217] It should be noted that this thermal treatment step of the amount of biomass can last, from the moment in which the biomass begins to enter the thermal reactor 105 (see Fig.3) to the moment in which the latter is emptied (see Fig. 7), a time comprised between 100 and 140 minutes, for example about 120 minutes, and / or that the average residence time of the biomass inside the thermal reactor 105, viz., the time taken by each portion of the biomass to pass through the thermal reactor 105 and reach the collection vessel 165, can be comprised between 30 and 50 minutes, for example about 40 minutes.

[0218] As anticipated, during this treatment in the thermal reactor 105, at least a part of the biomass, viz., its constituent substances, passes to the gas state.

[0219] Thanks for example to the suction effect generated by the suction means 600, this gas is conveyed from the thermal reactor 105 inside the first condenser 200.

[0220] It should be noted that, by opening and / or closing the shut-off valve 515, this gas flow towards the first condenser 200 can start after all the biomass has passed through the thermal reactor 105, or at any earlier time.

[0221] By means of the thermoregulation means 215, the gases passing through the first condenser 200 are cooled to a first condensation temperature, which is lower than the heating temperature of the biomass inside the thermal reactor 105.

[0222] For example, the first condensation temperature can be comprised between 160°C and 200°C (extremes included).

[0223] Thereby, at least a part of the substances present in the gas condenses, forming a first condensed liquid which collects at the bottom of the first condenser 200, for example.

[0224] The substances which instead do not condense and remain in a gaseous state form a first residual gas, which is conveyed, e.g., again by the suction action generated by the suction means 600, inside the second condenser 300.

[0225] By means of the thermoregulation means 215, the first residual gas passing through the second condenser 300 is cooled to a second condensation temperature, which is lower than the first condensation temperature in the first condenser 200.

[0226] For example, the second condensation temperature can be comprised between 130°C and 170°C (extremes included).

[0227] Thereby, at least a part of the substances present in the first residual gas condenses, forming a second condensed liquid which collects at the bottom of the second condenser 300, for example.

[0228] The substances which instead do not condense and remain in a gaseous state form a second residual gas, which is conveyed, e.g., again by the suction action generated by the suction means 600, inside the third condenser 400.

[0229] By means of thermoregulation means 215, the second residual gas passing through the third condenser 400 is cooled to a third condensation temperature, which is lower than the second condensation temperature in the second condenser 300.

[0230] For example, the second condensation temperature can be comprised between 100°C and 140°C (extremes included).

[0231] Thereby, at least part of the substances present in the second residual gas condenses, forming a third condensed liquid which collects at the bottom of the third condenser 400, for example, or possibly inside the storage vessel 800 through the shut-off valve 230 (see Fig. 8).

[0232] The substances which instead do not condense and remain in a gaseous state form a third residual gas, in this case a final residual gas, which is evacuated by the third condenser 400, e.g., again as a result of the suction action generated by the suction means 600.

[0233] In particular, the third residual gas can be introduced into the vat 700 and bubbled in the mass of water present therein, so as to cool it and purify it of some of the (potentially polluting) substances contained therein, which can dissolve and / or mix with the water, thus being more easily treatable and / or disposable.

[0234] The third condensed liquid obtained in the third condenser 400 can instead represent a final condensed liquid, viz., the final product of the process.

[0235] Thanks to the various distillation stages, the final condensed liquid will in fact consist of crotonic acid or at least a liquid mixture containing crotonic acid, e.g., in an amount by weight greater than the weight of each of the other components of the mixture, preferably more than at least 50% of the total weight of the mixture, more preferably more than 90% of the total weight of the mixture.

[0236] In order to increase the purity of the final condensed liquid, in this case the third condensed liquid, e.g., to raise the concentration of crotonic acid to values by weight greater than 95% of the total weight of the final condensed liquid, the same can be subjected to one or more redistillation cycles.

[0237] To this end, the possibility is envisaged of closing the shut-off valve 230 of the last (third) condenser 400 and heating the third condensed liquid inside the storage vessel 800 so that it evaporates (see Fig. 9).

[0238] For example, the third condensed liquid can be heated to essentially the same heating temperature at which the biomass inside the thermal reactor 105 is heated. Before or after the start of evaporation, the shut-off valve 540 can be opened, possibly after having closed the shut-off valve 515 (see Fig. 10).

[0239] Thereby, through the fifth duct 525, the vapour of the third condensed liquid is re-con- veyed, again for example by the suction action generated by the suction means 600, into the first condenser 200, where part thereof can condense and give rise to a further amount of the first condensed liquid and a further amount of the first residual gas.

[0240] This further amount of the first residual gas will then be re-conveyed, again for example due to the suction action generated by the suction means 600, into the second condenser 300, where a part thereof can condense and give rise to a further amount of the second condensed liquid and a further amount of the second residual gas.

[0241] This further amount of the second residual gas will finally be re-conveyed, e.g., again due to the suction action generated by the suction means 600, into the third condenser 400, where a part thereof can condense and again give rise to the third condensed liquid, which will, however, be purer than the one initially obtained.

[0242] As long as the evaporation is in progress, the third condensed liquid can collect on the bottom of the third condenser (see Fig. 11 ), while at the end of evaporation, it can be returned to the storage vessel 800 by opening the shut-off valve 230 (see Figs. 12 and 13).

[0243] At this point, the third condensed liquid (or final condensed liquid) can possibly be subjected to a second redistillation cycle, which can occur in the same manner as described for the first, then possibly a third redistillation cycle, and so on until the desired degree of purity is obtained.

[0244] When the third condensed liquid contained in storage vessel 800 has reached the desired degree of purity, it is possible to proceed with a discharge step of the products obtained, pouring them inside transportable vessels 900, 910, 920 and 930.

[0245] In this regard, it should be highlighted that, although in the attached figures the transportable vessels 900, 910, 920 and 930 have always been shown connected to the relative nozzles, it is preferable that all previous steps are carried out in the absence of said transportable vessels 900, 910, 920 and 930 and that they are only connected for the discharge step.

[0246] In any case, after the transportable vessels 900, 910, 920 and 930 have been connected with the relative outlet nozzles 180, 805 and 225, and while the respective shut-off valves 185, 810 and 230 are still closed, it is possible to put the transportable vessels 900, 910, 920 and 930 under vacuum, e.g., by activating the respective suction means 625, 630, 635 and 640.

[0247] When the absolute pressure in each transportable vessel 900, 910, 920 and 930 corresponds to that of the vessels to which they are connected, viz., the collection vessel 165, the storage vessel 800, the first condenser 200 and the second condenser 300 respectively, the shut-off valves 185, 810 and 230 can be opened.

[0248] Thereby (see Fig. 14), the residual biomass collects in the transportable vessel 900, the first condensed liquid in the transportable vessel 920, the second condensed liquid in the transportable vessel 930, and the third condensed liquid in the transportable vessel 910. Finally, the shut-off valves 185, 810 and 230 can be closed again (see Fig. 15) and the transportable vessels 900, 910, 920 and 930 can be detached from the respective nozzles to distance them from the plant 100.

[0249] It should be noted that it is preferable to wait until the temperature of the ducts is below 50°C before detaching the transportable vessels 900, 910, 920 and 930.

[0250] It is then possible to break the vacuum in the loading vessel 130 to start a new process. It should be noted that it is preferable to wait until the temperature inside the loading vessel 130 is below 88°C before proceeding with breaking the vacuum therein.

[0251] Obviously, a person skilled in the art can make numerous modifications of a technical application nature to everything described, without thereby departing from the scope of the invention as claimed below.

Claims

1. CLAIMS1. A process for obtaining crotonic acid starting from a biomass containing PHAs, comprising the steps of:- introducing an amount of said biomass inside a thermal reactor (105) placed under vacuum,- heating the amount of biomass inside the thermal reactor (105) to a preset heating temperature, so that at a least part of said amount of biomass passes to the gas state,- conveying the gas obtained in the thermal reactor (105) to a condensation apparatus, inside which said gas is cooled, so as to obtain a final condensed liquid and a final residual gas, said condensation apparatus comprising at least one condenser or at least a plurality of condensers (200, 300, 400) placed under vacuum and in gaseous communication with each other according to a series arrangement,- evacuating the final residual gas and withdrawing the final condensed liquid from the condensation apparatus, characterized in that, during the heating step, the process comprises the step of advancing the amount of biomass introduced into the thermal reactor (105) by driving a screw body (120) installed therein in rotation.

2. A process according to claim 1 , wherein the condensation apparatus comprises at least a first condenser (200) placed under vacuum, inside which the gas obtained in the thermal reactor (105) is conveyed and cooled to a first condensation temperature below the heating temperature, so as to obtain a first condensed liquid and a first residual gas.

3. A process according to claim 2, comprising the further steps of:- connecting a transportable receptacle (920) to an outlet nozzle (225) of the first condenser (200),- placing said transportable receptacle (920) under vacuum,- opening the outlet nozzle (225) of said first condenser (200) so that the first condensed liquid flows out into the transportable receptacle (920),- closing the outlet nozzle (225) of said first condenser (200), and- separating the transportable receptacle (920) from the respective outlet nozzle (225).

4. A process according to claim 2 or 3, wherein the condensation apparatus comprisesa second condenser (300) placed under vacuum, inside which the first residual gas obtained in the first condenser is conveyed and cooled to a second condensation temperature below the first condensation temperature, so as to obtain a second condensed liquid and a second residual gas.

5. A process according to claim 4, comprising the further steps of:- connecting a transportable receptacle (930) to an outlet nozzle (225) of the second condenser (300),- placing said transportable receptacle (930) under vacuum,- opening the outlet nozzle (225) of said second condenser (300) so that the second condensed liquid flows out into the transportable receptacle (930),- closing the outlet nozzle (225) of the second condenser (300), and- separating the transportable receptacle (930) from the respective outlet nozzle (225).

6. A process according to claim 4 or 5, wherein the condensation apparatus comprises a third condenser (400) placed under vacuum, inside which the second residual gas obtained in the second condenser is conveyed and cooled to a third condensation temperature below the second condensation temperature, so as to obtain a third condensed liquid and a third residual gas.

7. A process according to any one of the preceding claims, wherein a redistillation cycle of the final condensed liquid comprising the steps is performed one or more times, comprising the steps of:- collecting the final condensed liquid in a storage vessel (800) placed under vacuum,- heating the final condensed liquid inside said storage vessel (800) so as to cause the evaporation thereof,- conveying the vapour obtained in the storage vessel (800) inside the condensation apparatus placed under vacuum, inside which the vapour is cooled, so as to obtain a final condensed liquid and a final residual gas.

8. A process according to claim 7, comprising, at the end of said one or more redistillation cycles of the final condensed liquid, the further steps of:- connecting a transportable receptacle (910) to an outlet nozzle (805) of the storage vessel (800),- placing said transportable receptacle (910) under vacuum,- opening the outlet nozzle (805) of the storage vessel (800) so as to collect the third condensed liquid in the transportable receptacle (919),- closing the outlet nozzle (805) of the storage vessel (800), and- separating the transportable receptacle (910) from the outlet nozzle (805) of the storage vessel (800).

9. A process according to any one of the preceding claims, wherein the thermal reactor (105) and the condensation apparatus are brought under vacuum by means of a vacuum pump (605) placed in gaseous communication with the condenser or with a last condenser (400) of the plurality of condensers arranged in series.

10. A process according to any one of the preceding claims, wherein the introduction of the amount of biomass into the thermal reactor (105) includes the steps of:- preliminarily loading the amount of biomass into a loading vessel (130),- placing said loading vessel (130) under vacuum, and- then transferring the amount of biomass from the loading vessel (130) to the thermal reactor (105).

11. A process according to any one of the preceding claims, comprising the step of transferring a residual part of the amount of biomass from the thermal reactor (105) to a collection vessel (165) placed under vacuum.

12. A process according to claim 11 , comprising, at the end of the heating step, the further steps of:- connecting a transportable receptacle (900) to an outlet nozzle (180) of the collection vessel (165),- placing said transportable receptacle (900) under vacuum,- opening the outlet nozzle (180) of the collection vessel (165) so as to collect the residual part of said amount of biomass in the transportable receptacle (900),- closing the outlet nozzle (180) of the collection vessel (165), and- separating the transportable receptacle (900) from the outlet nozzle (180) of the collection vessel (165).

13. A process according to any one of the preceding claims, wherein the final residual gas evacuated from the condensation apparatus is bubbled in water.

14. A plant (100) for producing crotonic acid starting from a biomass containing PHAs,comprising:- a thermal reactor (105) adapted to receive an amount of said biomass and provided with thermoregulation means (115) for heating the amount of biomass to a preset heating temperature, so that at least a part of said amount of biomass passes to the gas state,- a condensation apparatus in gaseous communication with the thermal reactor (105) and comprising one or more condensers (200, 300, 400) individually provided with thermoregulation means (215) for cooling the gas, so as to obtain a final condensed liquid and a final residual gas, and - suction means (600) for putting the thermal reactor (105) and condenser(s) (200,300, 400) of the condensation apparatus under vacuum, characterized in that the thermal reactor (105) accommodates a rotating screw body (120) configured to advance the amount of biomass in the thermal reactor (105) itself.

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