WO1995003374A1

WO1995003374A1 - Process for upgrading fuels by irradiation with electrons

Info

Publication number: WO1995003374A1
Application number: PCT/IT1994/000120
Authority: WO
Inventors: Marco Maltagliati; Paolo Puccetti
Original assignee: Pancani, Giuseppe
Priority date: 1993-07-23
Filing date: 1994-07-21
Publication date: 1995-02-02
Also published as: AU7275094A; IT1262524B; CN1127518A; EP0710269A1; ITFI930140A0; ITFI930140A1; BR9407146A

Abstract

A process and a plant for the improvement of the chemical-physical and technological properties of fuels, in particular bio-fuels and pyrolysis oils obtained from biomass or industrial or municipal wastes is suggested. The fuel obtained by thermochemical convertion processes in a reactor (1) is subjected to an electron irradiation or electron stimulation activation process by means of electrostatic accelerator (10) or other equivalent means, such as silent dielectric discharge or pulsed streamer corona discharges. This plasma-chemical treatment induces complex chemical reducing/oxidising mechanisms in the fuel under treatment with improvement of its characteristics.

Description

DESCRIPTION

PROCESS FOR UPGRADING FUELS BY IRRADIATION WITH ELECTRONS

Technical Field

The present invention relates to an innovative process for the improvement of the characteristics of fuels, in particular oils obtained by thermochemical conversion (pyrolysis, liquefaction, catalytic etc.) of biomasses resources and/or industrial-urban wastes. The invention also relates to a plant for carrying out said process.

Background Art

It is well known that biomass is an high-value source of carbon and it is also the only renewable source of energy able to produce liquid fuels. Ligno-cellulosic resources, as well as several industrial-urban wastes, can be converted into fuels by different proces¬ ses. Among these ones, the thermochemical flash fast pyrolysis conversion process is very attractive for its capacity of fast conversion rate. In this way, large volume of organic-indu¬ strial wastes and of biomass resources can be converted into fuels (pyroiysis-oiis) of high specific weigh (about 0.6 TOE/m3) reducing thus the handling, transport, storage pro¬ blems of solid biomass.

The pyrolitic-oil (called also "bio-crude oil" if derived from biomasses) is obtained by fast thermochemical decomposition of biomasses (or wastes) at about 500°C in complete or partial absence of oxygen (in general: heating rate 500° C/sec + 2.500° C/sec). Its com¬ position is constituted by a mixture of more than 200 compounds as a result of a complex overlapping of mass transfer, evaporation, secondary chemical reaction processes. The nature, the dimensions of the biomass waste particles influence the quality of the final pro¬ duct The fast quenching (cooling) of the evaporated biomass oblige the liquid products to condensate before further secondary reactions take place.

The pyrolysis process (no yet completely clarified) is very complex but in agreement with the more recognised theory it seems that the primary vapours produced present cha¬ racteristics, which are most influenced by the heating-rate of biomasses waste particles. Afterwards these primary vapours undergo a degradation towards secondary products (gases and tars) if they remain at high temperature for more than some seconds, because then various secondary reactions take place. Infact the characteristics and percentage of the secondary products obtained are function of the temperature level and of the resi¬ dence time at high temperature. The percentage of the liquid portion (obtained by pyroly¬ sis) is influenced mainly by the speed of reaction (rate of particle heating) at parity of max. temperature, while an increase of the max temperature level, produces a percentual re¬ duction of the liquid portion and increase of the gas production as shown in the following Table 1.

Table 1

The typical conditions to obtain max. production of iiquid are summarised in the following Table 2.

Table 2

Parameters to obtain max. production of liαuid from biomass-wastes bv flash- pyrolysis:

Parameter Value

Temperature 475-535°C

Vapour residence time 0,4-0,7 sec.

Biomass particle size < 2 mm for wood

% Liquid production (weight) 80% (max) Typical characteristics (chemical-physical) of flash pyrolysis oils (bio-crude oils) from biomass are shown in Table 3.

Table ?

TYPICAL BIO-OIL ANALYSIS

Elemental analysis % wt (wet basis)

c 61.90

H 6.00

N 1.05

S 0.03

O (by difference) 31.12

H/C ratio 0.10

O/C ratio 0.50

Moisture %wt 25

Ash %wt 1.50

Char content % wt 9.20

Viscosity, cp at70°C 55

HHV, MJ/kg 26.3

Specific gravity (15°C)gr/cπ.3 1.195

Pyrolysis-oils derived from biomasses or organic wastes is composed mostly of a mixture of oxygenated hydrocarbons with high percentage of water deriving from the origi¬ nal amount of humidity in the raw-material and also from the conversion process. Solid char may also be present All this make, pyrolysis-oils relatively chemically and physically unstable, although it may be readily burned.

Some problems have been reported in the use, particularly in storage, where phase separation, high oxygen and water contents make it incompatible with conventional fuels, although it may be used in a similar way.

Some conversion or upgrading for oxygen and water removal and stabilisation is necessary to obtain a product that is fully compatible with conventional fuels. Main characteristics and problems of pyrolysis-oil (bio-crude oil) are enumerated here below.

1) water content (16-60%) is important and has several effects:

- It lowers the heating value of the oil;

- It affects the acidity of the oil;

- It reduce the viscosity of the oil;

- It influence both chemical and physical stability;

- It influence subsequent up-grading processes;

- It is difficult to remove this water from the oil by heat because at 100°C deleterious chan¬ ges in the liquid occurs; drying at lower temperature is not successful because it seems that the water is chemically combined with the organic components;

2) particulates levels may be high from char and ash carry-over (up to 15% by weight);

3) oxygen content is very high and up to 40% (dry wt);

4) acidity the low PH value is due to the acid contents (acetic acid, formic acid etc.);

5) polymerisation is a deleterious process on pyrolysis, which can be caused by temperature above-around 100°C and/or exposure to air (oxidation), with negative effect on viscosity, phase-separation, deposition of bitumen like substances; exposure to air alone also causes deterioration but a slower rate than that obtained by a temperature in¬ crease;

6) compatibility with conventional fuels; pyrolysis-oil is compatible but immiscible with conventional fuels; some up-grading is thus needed to obtain a product wholly com¬ patible and assimilable into a conventional fuel infrastructure.

Up-grading technology of pyrolysis-oils is actually based on orthodox hydrotreating technology to produce successively lower-oxygen content hydrocarbons, or on the evol¬ ving zeolite technology to produce high quality hydrocarbon fuels or aromatic chemicals directly, as shown below:

hydrotreaϋng

Cz bO + 1.5H2 2(CH₂)n + HΛ bio-oil hydrogen gasoline etc. water

zeolites

bio-oil gasoline, etc. carbon dioxide

Conceptual chemistry of bio-oil up-grading processes: hydrotreating is based on technology that is established in the petroleum industry and is in principle readily adaptable to pyrolysis-oils. The product ^'ts a low-grade gasoline that would require orthodox refining and blending to give a marketable product zeolite based synthesis has been extensively demonstrated for alcohol feeds, and a commercial plant is currently operating in New Zealand. A significant feature is the high yield of aromatic which give a premium-value gasoline product and from which benzene, xylene an or toluene could be recovered.

Disclosure of the Invention

Main object of the present invention is to offer an alternative process to avoid or re¬ duce many of the drawbaks described previously, to improve the quality of the products and the economy of the pyrolysis and of the up-grading conversion processes for industrial biomasses resources and/or for industrial urban wastes. In particular

- reducing the oxygen content of the oil;

- reducing the acidity content of the oils;

- reducing the polymerisation characteristics of the oils;

- improving its chemical, and physical, technical characteristics and stability;

- improving the compatibility of pyrolysis oils and their miscibiiity with conventional fuels;

- breaking the large molecules chains;

- improving the heating value of the oils;

- reducing the viscosity of oils;

- removing or reducing the chemically bonded water of the oils (drying at low tem¬ perature);

- increasing the productions of wanted chemicals compounds;

- reducing the cost of up-grading and refining of the oils;

- replacing or reducing the amount of the catalysts normally needed for the up¬ grading of the pyrolysis-oils; - removing or reducing (eventually) some micro-pollutants like vanadium, calcium, lithium, sodium, potassium, sulphur, nitrogen, chlorine, nickel, carbon , ashes, etc.;

- permitting the utilisation of low-cost "hydrogen-carbon" donors like: methane, et¬ hane, butane, propane, ethanol, methanol, etc..

The present invention is able to offer important perspectives for the production of suitable fuels especially for power generation technologies.

In summary, because the hydrotreating processes and the zeolites processes have not found yet a practical application, mainly for the high investment and processing costs, the main scope of the present invention is to supply an economical alternative process for improving the characteristics of fuels, in particular those derived from pyrolysis of biomas¬ ses and industrial-municipal wastes.

A particular objet of the present invention is also to supply a process, as illustrated previously, able to reduce the water content, the oxygen content of pyrolysis oil derived from biomasses and or industrial-municipal wastes so to improve their quality, like: The heating value, their stability and compatibility with conventional fuels.

A further object of the present invention is to supply a process, as described before able to implement the "gas-cleaning" (char-tars craking, suspend particles and micro-pollu¬ tants abattement) after gasification of biomass, industrial municipal wastes, conventional fuels.

A further object of the present invention is to supply a process able to be easily in¬ tegrated with the thermochemical conversion process itself (like pyrolysis of biomass and/or industrial-municipal wastes) with a limited supplementary investment and operating costs.

A further object of the present invention is to supply a process as described before able to convert the residues and tars from refineries into good fuels. The process, object of this invention, is also applicable for the treatment and improvement of bituminous schistes, and its derived fuels.

Another objet of the present invention is the supply of a process, as mentioned before ward, able to reduce or eliminate the amount of micro pollutants (vanadium, cal¬ cium, lithium, sodium, chlorine, nitrogen, potassium, sulphur, chat, tar, ashes, suspended carbon, etc.) present in the fuels.

Furthermore, objet of the present invention is to supply an improved thermochemi¬ cal flash-pyrolysis plant with an "electrons stimulated up-grading process" integrated with the main conversion process, and able to produce fuels with improved physical-chemical- technological characteristics, in comparison with those obtained in usual flash pyrolysis plants, liquefaction plants, gasification plants, thermochemical catalytic conversion plants.

The main characteristics of the process object of the present invention is based on the fact that the thermochemical conversion products derived from biomass resources (or industrial-municipal wastes) is submitted to an electron irradiation stimulation by differents methods. Further advantageous features of the method and plant according to the inven¬ tion are set forth in the appended claims. The following techniques may be used:

1) HIGH ENERGY ELECTRONS BOMBARDMENT ( Figure 1, Figure 5) which can penetrate, as small bullets, at molecular and a atomic level, producing a rupture of chemical bonds, stimulation (at large scale) of atoms with consequent production of an anonymous amount of radicals, excited atoms and ions which can group together again as hydrocarbon chains smaller and more homogeneous, with a water and oxygen content negligible or in any case reduced considerably.

The electrons energy must be sufficiently high to transmit to atoms and molecules (striken on their way) the energy needed to break-down the chemical bonds (5-100 e V) of the diatomic H2, C2, CO and of polyatomic molecules constituting the pyrolysis oils, or the ionisation energy of first level (11-14 e V) and second level (25-35 e V) to atoms C,O,H, or the additional energy to neutral gaseous atoms to produce negative ions (0.75-1.47 e V).

The energy of electrons emitted by the accelerator, will depend thus of the dimen¬ sions of the radiation chamber and of the mass flow of the compound (oil) to be irradiated; for practical reasons it will be above the energy absorption level the window (presently about 0.05 Mev) and in general not above 1 Mev. Higher the electrons energy, higher their penetration capacity and larger the activation volume and in general the energy ab¬ sorption dose by the compound to be processed.

For lower electrons energy level, the ionisation process decreases and the molecu¬ lar excitation process increases; this last one produces too the formation of radicals, but with much lower efficiency.

The global result of the compound refining will thus depend, beyound the ambient temperature and pressure, of the choice of four main parameters: energy of electrons, electrons flux, travelling distance of electrons across the compound to be processed, mass flow of the compound and, of course, of the presence of secondary gases vapours, as de¬ scribed here below. Preferably, together the compound to be electrons irradia¬ ted stimulated, an auxiliary substance is added so to be able to supply hydrogen and/or carbon to the pyrolysis oils in order to reduce its oxygen content with production of water and carbon dioxide and to increase the H/O ratio. The secondary substance could also be irradiated/stimulated separately by electrons and then mixed with the pyrolysis oil; ot¬ herwise it could be electron irradiated at the same time with the pyrolysis oils so to optimise the wanted refining process: oxygen and water decrease will produce more energetic and better quality compounds through the establishment of conditions able to favour the wan¬ ted chemical reactions and able to improve the qualities of the final products.

As auxiliary substance methane could be profitably utilised for its wide availability and its low cost. Other hydrocarbons compounds as ethane, propane, butane or alcohol like ethanol, methanol, etc. could also be utilised in a liquid or vapour state. Of course pure hydrogen could also be utilised, but with lower advantages due to the high cost and the safety norms needed.

The chemical-physical-technical characteristics of the final product will depend es¬ sentially of the absorbed energy by the compound to be processed and this one is func¬ tion of the specific energy of the striking electrons, of the electrons flux, of the irradiation time (mass flow) behyond the presence of auxiliary substance. By electrons with energy above 1 Mev and appropriate temperature and pressure complete gasification of the irra¬ diated oil could be obtained. Instead, by opportune adjustment of the energy absorption level and in presence of an opportune auxiliary substance (H and C etc. donor) it will be possible to modify the composition and the characteristics of the final products: for example it is possible to obtain a synthesis gas (H2-CO mixture).

The electrons flux needed for the activation and refining of the compound can be produced by conventional electrostatic accelerator of electrons as, for example, that pro¬ duced by EBARA INTERNATIONAL CORP. JAPAN AND USA as well as by "pulsed co¬ rona effect" or by "silent dielectric discharge" (which will be described afterwards). These are indeed able to produce directly in the compound volume a large number of radicals etc. having sufficient energy to produce (by chemical plasma processing) the wanted re¬ fining result on the compound.

2) SILENT-DISCHARGE-PLASMA fFio. 6), called also dielectric-barrier-discharge, consisting of a multitude of small scale pulse discharges across a thin (in general <1 cm) restricted region (reaction chamber) where the fluid stream flows. The micro-discharges, which are statistically spread in space and time, develop along the surface of insulating dielectric layer (ceramic like: alumina, glass, quarz, etc.) covering one or both cylindrical or planar electrodes (aluminium, tungsten, nickel, etc) and constituting the reaction chamber, under the application of pulsating high voltage (example 30 KV with frequency up to seve¬ ral KHz).

Typically, the rise time of the pulse voltage is around 10-50 nsec and its length of around 20/200 nsec.

These micro-discharges are able to generate a large and substantial quantity of plasma and an extremely reactive medium, able to dissociate, excite, ionise the mass-flow to be processed. The micro-discharges are transient discharges (able to produce a wide spectrum of elementary reactions, like: ionisation, dissociative ionisation, dissociative at¬ tachment, dissociation, metastable fomation, charge transfert, detachement, electron-ion recombination, ion-ion recombination, atom recombination, etc.); due to their short dura¬ tion and the low-ions mobility, electrical energy in this silent discharge process are princi¬ pally coupled into electrons channel (electrons, ions, gas do not equilibrate). So the "electrons are hot" (elettron temperature in general between 1,000°K and 100,000°K) while the "other species are cold ", constituting thus a relatively low-power consumption processing.

3) PULSE CORONA DISCHARGE INDUCED (Fig. 7) plasma chemical is a pro¬ cess based essentially on the same physical mechanism of the "silent-discharge" (formation of highly non equilibrium cold plasma in a medium-gas, vapour... under ordinary temperature and pressure). The high-voltage nanosec pulse streamer corona generates the plasma in the fluid gap between the corona and the counter electrodes (cylinder or plate) which will constitutes the reaction-section.

The CORONA is a partial discharge that occurs when a high-voltage is put on cur¬ ved-electrodes (it is called positive-corona when the most curved electrode is positive). The discharge consists of current bursts in the gas called streamers (straight pats). Using high-voltage pulses instead of DC, higher power input into the discharge can follows.

The streamer structure and characteristics depends on the pulse-iise-time (discharge starts or not at the full pulse voltage) and on the repetition rate.

The corona discharge arises in several chases. Reference being made to the posi¬ tive corona as an exemple. The phases may be summarized as follows (see Fig. A): a) a free charge carrier (usually an electron) is accellerated in the high field of the curved electrode and ionizes gas molecules, this is called an avalanche (time scale <1 ns); b) the electrons drift towards the anode leaving behind a cloud of positive ions, called the streamer head (time scale~10 ns); c) photoionization creates electrons outside the streamer head, leading to new avalanches. This displaces the streamer head (along the electric field lines), leaving behind the streamer path (time scale~100 ns).

Generally, the following elementary chemical reactions are thus in general produ¬ ced:

1) the corona produces high energy electrons: about 3-15 e V (1e V=1.6x10-¹⁹ J); time-scale: nano seconds;

2) the electrons dissociate the molecules; time-scale: microseconds;

3) further reactions and formation of compounds; time scale: milliseconds/seconds.

This electron energy is good enough to initiate the wanted chemical reactions (up¬ grading) through a very complex mechanism of electrons diffusion, negative and positive ions formation, ionisation, attachment, electron-ion/ion-ion recombination, excitation, ab¬ sorption, radicals formation, etc..

The produced free-electrons under the influence of the electric field are accelerated during their travelling and start to produce "inelastic collisions" producing on atoms or par- ticules ionisation, dissociation, excitation effects with significant transfer of energy from the electrons to the target-species. For example:

- electron attachment by electronegatives gases to form negative ions;

- dissociation of big molecule (like pyrolysis-oil) into smaller fragments, including formation of free radicals (useful for breaking the long molecules of the pyrolysis oils);

- excitation of molecules (oxygen molecules are the easiest to excite: 1st exci¬ tation: 1 e V / 2nd excitation: 1.63 e V / 3rd excitation: 4.25 e V / 4th excitation: 6 e V).

Thus with electron energy greater than 7 e V we shall get dissociation of the oxygen molecules to one atom in the ground-state and one in the first excitation-state) useful for example to reduce the oxygen content of the pyrolysis oils.

The energy of electrons to break a C-H bond is about 5 e V.

The energy of electrons to break a C-C bond is about 6 e V. Methane does not have any C-C bonds.

In general the corona steamers start dose to the wire, some of which do not cross the whole gap, some cross the whole gap becoming broader and more diffuse. Their density increases with the higher voltage and shortest rise time. The up-grading conver¬ sion effidency object of the present invention depends of the:

- pulse energy imput'

- pulse rise time. For the up-grading process of the present invention, to improve the energy effi¬ ciency, the high voltage supply will be adjusted to obtain the propagation of streamers energetically stable ("stability field"); In air this is about δKV/cm.bar.

In comparison with other known biomass derived pyroiitic oils up-grading methods, like the hydro-treatment and the zeolite-treatment the process following the present in¬ vention offer also the great advantage to be completely and easily integrated, inside the conventional thermochemical conversion reactors, with limited investments, as will be de¬ scribed hereinafter.

Brief Description of the Drawings

Several embodiment of the present invention are shown in the annexed drawings, shown as examples and not as a limitation of possibilities:

Figure 1 shows a first sketch of a thermochemical plant for the conversion of bio¬ mass into bio-fuels integrated with the up-grading processing, following the present inven¬ tion;

Figure 2, 3 and 4 show different sketches (solutions) for the same conversion plant

Figure 5 shows a sketch of a thermochemical conversion reactor for biomasses with an integrated up-grading (refining) process by electrons beam radiation utilised in the plant of Figure 1;

Figure 6, 7 and 8 show modified embodiments of the reactor, utilising the pulse co¬ rona or the dielectric barrier discharge.

Best mode for Carrying Out the Invention

Referring to Figure 1, a typical thermochemical conversion fast pyrolysis plant for biomass is composed of a main fluidised drculating bed reactor 1 where very small parti¬ cles of biomass are injected, (together high temperature pre-heated sand powder), through a lower duct 2. As a consequence of the rapid heat exchange from the sand to the biomass, this last vaporises. As fluidising gas, "methane" or other H-C donors could eventually be utilised to carry out simultaneously through electron irradiationfetimulation the up-grading treatment The methane excess could be duly recycled. These vapours gas are transferred through an upper duct 3 to a cyclone 4 for re¬ moval of the sand, charcoal .particulate. Through the pipe 5 connected to the upper zone of the cyclone 4 the vapours are sent to a condenser 6, generally of pipes-bundle type, where the oil vapours are cooled rapidly, condensed and separated by the non conden¬ sable gases (collected through a pipe 7 in a storage tank not shown). The condensed li¬ quid phase collected at the bottom of the condenser is stored through the pipe 8 into a container (not shown) for eventual further refining and storage. Of course the fast-flash py¬ rolysis reactor could also be of different concept like, for example: "the entrained flow reac- tor", the "multiple hearth-reactor", the "vortex reactor" or the "ablative-reactor" etc.. The different type of flash-pyroiysis reactors will require consequently an adjustment adaptation of the plasma reactor (silent discharge-pulse corona-electron beam) characteristics and drawing.

Following the present invention, the first type of reactor 1 is provided of one or two electrostatic accelerators 9 (located laterally, at opposite sides, and at different vertical axial level) with the electrons emission filaments located internally as generically shown with 10. Several electrons beams could be utilised in case of large and complex reactors.

The electrons beams produced will irradiate and strike the mass of produced va¬ pours gases by pyrolysis of biomass, produdng the above described volumetric activation, ionisation, radicals formation. By a lateral duct, or from the bottom an auxiliary substance rich in hydrogen (and eventually in carbon), preferably methane, is introduced into the re¬ actor 1 to obtain a good mixing with the biomass vapours preferably immediately before the main electron irradiated zone of the reactor.

This auxiliary substance could be equally submitted to electrons irradiation by one two electrostatic accelerators or by equivalent system (pulsed corona, silent dielectric discharge...) 12 located long the duct In this way the auxiliary compound (rich in radicals, atoms, ions) will be mixed with oil vapours an will produce the wanted chemical reactions.

In addition or in alternative the auxiliary substance can be mixed with the oil va¬ pours without previous pre-activation. In this case, the linear accelerators 9 (or equivalent systems like: the pulsed corona discharge, the silent dielectric discharge etc.) will provide the activation and the refining of the vapour mass of the oil.

The electron processed vapours will cross the cyclone 4 will arrive to the conden¬ ser 6, from where they are collected and sent to the storage tank after phase separation.

Known the reactor 1 cross section, the oil vapour and auxiliary substance mass flow, the time of exposition of vapours gases to the electron gun radiation can be determi- nated as well as the accelerators power and the electrons energy in such way that the energy absorbed dose by the vapours/gases will be of the order of 1-2 rad (about 1-2X10⁴ Joule/mole) following the required final product characteristics. Similar calculation can be carried out in case other activation systems (pulse corona discharge-silent dielectric di¬ scharge...) are chosen.

The amount of the secondary compound to be feeded to the reactor 1, for the re¬ fining process, is from 2% to 10% (in weight) of the oil to be processed with optimal average value around 5%, it is dear that such percentage will depend of the biomass type, the pyrolysis process, the type of the auxiliary substance adopted, the quality of the final product wanted (more or less refining-deoxygenated, etc.).

Following the first implementation solution of the invention illustrated in Figure 2, the vapours electrons irradiation section is situated on the duct connecting the reactor 1 to the cyclone 4. One or two electrostatic accelerators for electrons 9 at opposite sites and staggered are locate radially around the duct 3. The injection of the auxiliary substance, eventually actived by secondary electrons accelerators 12, is carried out upstream of the accelerators 9 through the duct 11. The activation process can also be implemented with other methods replacing the electrons accelerators by a pulse corona discharge or a pulse dielectric silent discharge.

In the Figure 3 another variant of the invention, similar to that illustrated in Figure 2, but with the irradiation section and the corresponding auxiliary substance injection duct lo¬ cated on the vapours connecting duct between the cydone 4 and the condenser 6. in another possible drawing variant of the invention illustrated in Figure 4, the elec¬ trons irradiation section is situated downstream the condenser 6, directly in the liquid phase of the product to be processed. The one or two electrons accelerators 9 are located at opposite sides of a container 13 feeded by the condensed product through the dechar- ging duct 8 of the condenser 6. The auxiliary substance is injected into the container 13 through the duct 11 provided with secondary electron accderators 12 or a pulse corona discharge or pulse dielectric silent discharge system. The liquid substance (oil), to be up¬ graded, could be also injected into the reaction up-grading section utilising an high pres¬ sure methane operated injector, so that a good mixture of small oil droplets and methane gas will be obtained facilitating thus the wanted up-grading reaction treatment of the liquid (ex-oil).

For the activation of the auxiliary substance only one electrons accelerators could be sufficient, although two of them are preferable to obtain an higher homogeneity of ra- diation. In alternative, silent-discharge-piasma or puise-corona-discharge systems will be utilised.

The configuration shown in Figure 1, Figure 6, Figure 7, Figure 8 are the preferred one, because are able to avoid or to reduce, on the starting, the ddeterious secondary re¬ actions offering thus a better global result of the refining processing and of the chemical- physical-technological characteristics of the pyrolysis oils instantaneously at the moment of its production by the hdp (presence) of a deoxygenating auxiliary substance (for example methane as hydrogen-carbon donor). The configurations shown in Figure 2 and 3 are presented for supplementary processing and refining stages of the pyrolysis oil vapours and in any case when limited irradiation energy absorption level by the vapours is required, i.e. for partial deoxygenating or bonded water reduction.

The configuration shown in Figure 4 is suited to a final refining of the oil in a liquid phase, that is after the pyrolysis oil had been stabilised (to avoid polymerisation degrada¬ tion) so to obtain an high quality product similar to that one obtained in conventional oil re¬ fineries of course other different locations for the dectrons radiations section can be cho¬ sen, depending of specific requirements, which are obvious for a qualified person in this fidd. For another example, the dectrons accderators or silent-discharge-piasma or pulse- corona-discharge systems could be plunged directly into the mass flow of the compound to be treated.

In the Figure 5 an example of typical reactor for biomass pyrolysis is presented with incorporation of an dectrons radiation section. The reactor 100, having a thermal insula¬ tion 101, presents (at the bottom) an inlet duct 102 for the hot sand and the fluidizing gas (eventually methane) and (at the top) an outlet duct 103 for the gases and vapours produ¬ ced by the thermochemical conversion of biomass which is separately feeded through a lateral inlet duct 104 to allow an homogeneous mixing with the hot sand.

A second lateral duct 105 allow, the inlet for the auxiliary substance (for example methane) eventually pre-irradiated and activated by dectrons. The medium-higher zone of the reactor 100, crossed by the vapours produced by the thermochemical conversion of biomass is sdected preferentially for the dectron irradiation or dectron stimulation by si¬ lent-discharge or pulse corona systems. For this scope, in two lateral opposite-side stag¬ gered location, dectrons accderators are situated, presenting emission filaments 107, two window for dectrons 108, with low absorption of energy (for example in titanium) to sepa¬ rate the high-vacuum zone (filament side) from the higher pressure zone (side reactor 100). A special device to keep the dectrons-windows clean is provided, consisting for example of a gasΛtapour system flowing over the window at a temperature higher than the reactor temperature to avoid condensation and deposit formation. The dectrons accdera- tor furthermore is connected with an high-vottage transformer (not shown) and is equipped of a monitoring control and safety systems for the plant and for the operating personnd.

The reactor 100 as wdl as the accderators are located inside a shidded wall 109 for protection against the dectron an X-rays emissions. The shidding is not needed in case of silent-discharge or pulse-corona systems.

Here bdow a practical example, but not as limiting case, of application of the pro¬ cess following the present invention.

In the plant configuration shown in Figure 1 and with a fluidised-drculating-bed fast pyrolysis reactor of a capacity of about 1 t h of dry biomass or industrial-munidpal wastes, the following operating conditions (average) have been sdected:

Temperature about 500°C

Pressure near atmospheric

Residence time about 0.5 sec.

Biomass powder partide size about 2 mm

Biomass water content about 10%

Biomass mass flow/sand mass flow: about 2.2

By thermochemical conversion and in these conditions an instantaneous mass- flow of pyrolysis-oil vapours and gases is obtained. The pyrolysis oil is composed of a very wide mixture (hundreds) of heavy hydrocarbons-oxygenated compounds, acetic-acid, formic-add etc. which, if rapidly cooled (quenched) will supply a fuel-oil having the fol¬ lowing average characteristics:

OH mass efficiency (in weight of dry wood): 75%

Elemental analysis: C 50-60%

O 30-40%

H 6%

N 1%

0.03%

Water content 15-25%

Ashes content 1.5%

Viscosity (at 70°C): 55cp

Lower heating value (about) 5000 Kcal/kg

The oil-fud (as indicated above) presents thus characteristics similar to those of a conventional "bunker-oil" except the heating-value, and S, N content

According to the present invention the produced vapours are dectron activa¬ ted/decomposed in the pyrolysis plant by bombardment with high energy dectrons emitted by an dectrostatic accderators (type EBARA INTERNATIONAL CORP. USA or equiva¬ lent) with a power of about 35 KW and able to produce in the radiation-section zone an dectrons flux having a total useful power of about 20 KW. Alternatively, the up-grading treatment could be obtained by an equivalent silent-discharge or pulse-corona-discharge systems.

As a consequence of the dectrons-radiation the pyrolysis oil-vapours are submitted in a quick sequence to large-molecules break-down, with a final result of a partial total re¬ moval of the oxygen through hydrogenation-carbonisation mechanisms with consequent production of water and carbon dioxide. The hydrocarbons mixture obtained, after an dectrons energy absorption dose max. of about 2 RAD in case of dectron beam irra- diation is similar to a no refined gasoline or/and gasoil and presents the following cha¬ racteristics:

Effidency of oil-treatment 47% in wdght of the pyrolysis oil processed (max)

Oxygen content 0% (max)

Water chemical-bonded 0% (max)

Specific gravity ~1g/cm3 (about)

Heating value (about) 10000 Kcal/Kg

The amount of the methane utilised will be from about 75 to 120 m3Λ of pyrolysis- oil treated, depending from the wanted characteristics for the fud.

In this case, assuming a biomass cost of about 50 ECU/dry ton commerdal py¬ rolysis-oil production cost will be about 185 ECU/T.O.E.

Considering the modest increase of investment (about 10% max supplementary in¬ vestment on flash-pyrolysis plant) to be added to that one for the processing-refining equi¬ pment needed and in agreement with the present invention, the expected production cost of this high quality (although not completely refined) fud is of about 240 ECU/TOE, that is very near to full competitiveness with similar conventional fuels produced in crude-oil refi¬ neries, if we compare the investment costs (assuming the same production capacity) of a conventional pyrolysis-oil up-grading treatment plant about 2.2 mil. USA $ (to be added to the investment cost for the fast-pyrolysis plant), with the cost for the supplementary equi¬ pment needed to implement the compound (fud) up-grading processing in agreement with the present invention, that is: about 0.1 mil USA $, one can understand the enoπnous economic advantage that the process of the present invention offers.

By the control of the process conditions and in particular of the amount of the ab¬ sorbed energy by the pyrolysis compounds derived from biomass it is possible to modulate (change) the dectrons irradiation-activation results. For example, operating at iess than 100°C and with low-energy dectrons (lower than 50 e V) it is possible to remove the che¬ mically bonded water, obtaining thus as a result a substantial increase of the heating value of fuel (about 20 %) without provoking the no wanted polymerisation effects on the oil as it happens (on the contrary) during traditional dehydration processing at 100°C.

Increasing instead the amount of energy dose absorbed by vapours/gases up to about 1 2 M.RAD, a complete gasification of the pyrolysis oil can be obtained. This gasifi¬ cation can be obtained at low temperature (about 500°C), avoiding thus the melting of as¬ hes (700-900°C) problems which are found in conventional gasification process creating big operating problems of the plant and also for gas turbine-engine utilisation.

Furthermore we have also to note that the process in agreement with the present invention allows also, together the improvement of the pyrolysis oils characteristics, the removal of noxious emissions for the environment like: NOx, CL, CO, poiy-aromatic com¬ pounds, P.O.C., etc.; and also micro-pollutants like: vanadium, sodium, lithium, potassium caldum, C; iron, copper, ashes, particulate etc.. which are particularly harmful to gas tur¬ bine/engine operation. This can be obtained by the addition of well selected auxiliary sub¬ stances during the dectrons irradiation-activation processing to obtain the abate¬ ment/removal of then non wanted emissions.

Also can be noted that although up to now the processing of biomass thermo¬ chemical derived products in agreement and following the present invention had been es¬ sentially assessed and presented, the processing following the present invention can also profitably be utilised for the treatment of thermochemical conversion product derived from industrial-municipal/wastes (i.e. textile wastes/residues...) as well as for the treatment of crude-oil, refinery residues and wastes, from coal, bituminous schistes, chemical proces¬ sing wastes etc..

The process, object of the present invention, can also be utilised for "gas-cleaning- treatment" in gasification systems of biomass industrial-municipal wastes, conventional fuels etc. for tars-char craking, and abatement of noxious compounds like ashes, particu¬ late, K, Na, Va, P.O.C., etc..

As already mentioned before wards, the production of dectrons and the activation of the product to be treated can be obtained also by alternative methods to the dectrons beams irradiation obtained by dectrostatic accderators, as follows:

- by silent-discharge-piasma (didectric barrier discharge);

- pulsed-streamer-corona-discharge.

The stimolation of the chemical reaction obtained by the trree described methods (dielectric barrier discharge, corona discharge, dectron beam) can be increased by the simultaneous application of a magnetic field in the reaction zone. Figure 6 shows a modified embodiment of a reactor according to the invention, suitable to be used in a plant according to Figures 1 to 4. The reactor, designated 200 as a whole, is based on the pulsed corona discharged method -previously described. The re¬ actor vessel is provided with an insulating wall 201 with an inlet duct 202. 203 is the outiet duct for the processed compounds. The area where the thermochemical reaction takes place is shown at 204. An auxiliary gas or compound inlet duct 206 is also provided. Bio¬ mass is fed through duct 215.

The reactor vessd is provided with an dectrode 205 which is positively biased with respect to the wall 201. Between the thermochemical reaction area and the top of the ves¬ sel an arrangement of cylindrical coaxial dectrodes 207, 208 are provided, which are al¬ ternately connected to the positive dectrode 205 ( trough connecting lines 209) and to the wall 201 of the vessel (through connecting lines 210). The dectrode 205 is supplied with pulsed high voltage. The cylindrical electrodes 207, 208 are covered by a didectric mate¬ rial and define the pulse corona or didectric silent plasma processing zone of the reactor, according to the above described technology, said zone is crossed by the biomass va¬ pours and gases and undergo the pulsed corona discharge up-grading treatment

Figure 7 shows a modified embodiment of the reactor of Figure 6. Similar dements are designated with the same reference number, in this embodiment the cylindrical and coaxial dectrodes 207, 208 are replaced by planar and paralld electrodes, again shown at 207 and 208. The pulsede high voltage supply is shown at 211.

In the embodiment of Figure 8 the electrode arrangement 207, 208 is replaced by a plurality of corona wires 219, connected to the dectrode 205. Each wires 219 is coaxially arranged in a corresponding cylindrical wall 220, connected to the wall 201 of the reactor vessel, i.e. to the negative pole of the high voltage pulsed supply 211. The dectrode 205 is connected to the positive connector of the supply 211 via an dectronic or rotating spark- gap system. A duster of small cylindrical corona plasma reactors is thus obtained. Each cylindrical wall 220 defines a restricted tubolar region where the fluid (gas or vapor) to be processed flows. This region could be filled with didectric ceramic pdlets able to produce free electrons. The above described method can be applied to any kind of (gaseous or li¬ quid) fuels obtained by a thermochemical conversion of a starting products, such as flash- pyrolysis, pyrolysis, gassification, liquefaction.

Starting products may be preferably biomasses, but other products are suitable, such as wastes, fud oils and other as above listed.

Claims

1) Process for the improvements of chemical-physical-technological characteristics of fuels obtained by thermochemical conversion characterized in that said fuels are sub¬ jected to irradiation or activation by dectrons.

2) Process, according to claim 1, wherein said fuels are derived from biomasses, or from industrial-municipal wastes, or from coal, lignite, peat or other fud oils.

3) Process according to claim 1 or 2, wherdn said fuels are subjected to said irra¬ diation in the liquid or vapour state.

4) Process according to one or more of the preceding claims, wherein said fuels are irradiated with electrons having an energy from about 0.055 to 1 Mev.

5) Process according to one or more of the preceding claims, wherdn before the dectrons irradiation, the fuels (liquid or vapour phase) are mixed with an additional secon¬ dary substance able to supply hydrogen and/or carbon (H, C donors).

6) Process according to daim 5 , wherdn this auxiliary substance is irradiated with dectrons before wards bang mixed with the fuels.

7) Process according to daims 5 and 6, where this auxiliary substance supplying Hydrogen is added in the proportion of 2-10% (in wdght) of the fuel to be treated.

8) Process according to one or more of daims 5 to 7 wherein such auxiliary sub¬ stance is methane or ethane or butane or propane or ethanol or methanol.

9) Process according to one or more of daims 5 to 8, wherdn said secondary substance is gaseous and is used as fluidising gas in the reactor itself or to inject (at high pressure) the fud in the dectron reaction section to obtain a good mixture of small oil dro¬ plets with methane (or ethane, butane, propane).

10) Process according to one or more of the preceding claims, wherein the dose of absorbed energy by these (liquid/vapour) fuels is of the order of 1-2 M RAD (about 1- 2x10⁴ Joule/mole).

11) Process according to one or more of the preceding daims, wherdn the dec¬ trons needed for the irradiation of these fuels are generated by an dectrostatic high-vol¬ tage accelerator of electrons.

12) Process, according to one or more of claims 1 to 10, wherdn the dectrons needed for stimulating the chemical reactions and to obtain the up-grading (refining) treatment of fuels are obtained by "pulse corona discharges" (plasma chemical proces¬ sing).

13) Process, according to one or more of daims 1 to 10, wherdn the electrons needed for the stimulation of the chemical reactions and to obtain the up-grading (refining) treatment of the fuels are obtained by "didectric-barrier-discharge stimulation" (silent di¬ scharges plasma-chemical processing). This region could be filled with didectric ceramic pdlets able to produce free dectrons.

14) Plant for carrying out fast pyrolysis of biomass or industrial-munidpal wastes or coal, lignite, peat able to produce fuel-oils with improved chemical, physical, technological characteristics, having a pyrolysis reactor where the thermochemical conversion of bio¬ mass or wastes or coal, lignite, peat happens with production of derived substances in the form of solid, vapours (oil, non condensable gases, particulates) having solid-va¬ pours/gases separators and cooling-quenching apparatus for vapours (oils) condensation, characterised by that an dectron-irradiation or dectrons-stimulation section for the treat¬ ment of the biomass or wastes or coal, lignite, peat thermochemical derived products by dectrons.

15) Plant acording claim 14, wherdn the mentioned dectrons irradiation or dec¬ trons-stimulation section is arranged and integrated in the conversion reactor itself.

16) Plant according to daim 14, wherein the dectrons-irradiation or dectrons-sti¬ mulation section is located on the vapours ducts to the solid vapours separators and/or to the cooling-quenching unit

17) Plant according to daim 14, wherein the dectrons irradiation or dectrons-sti¬ mulation section is located down-stream the oil (fuels) heat cooling condensing system.

18) Plant according to one or more of daims 14 to 17, wherdn an injection system for an auxiliary (hydrogen and/or carbon donor) substance is provided up-stream the dec- trons-irτadiation/dectrons-stimulation section.

19) Plant, according to daims 18, wherdn such auxiliary substance is methane (or propane, ethane, butane) or ethanol or methanol orthdr appropriate mixture.

20) Plant according to daims 18 or 19, wherein means are provided to irradiated said auxiliary substance with dectrons before thdr injection into the electrons-irradiation or dectrons-stimulation section.

21) Plant according to one or more of claims 14 to 20, wherdn said irradiation sec¬ tion includes at least an electrostatic accelerator of electrons. 22) Plant according to daims 21, wherein two accderators are located at opposite sides and at different highness hortogonally to the oil iiquid/vapours-gases mass flow di¬ rection.

23) Plant according to one or more of daims 14 to 20, wherdn dectrons irradia- tion-dectrons stimulation section indudes a system to produce a "pulse corona" induced plasma chemical process.

24) Plant according to one or more of daims 14 to 20, wherein said dectron radia¬ tion-stimulation section includes a system to generate "dielectric-barrier-discharge" able to generate a large and substantial quantity of plasma and an extremely reactive medium.

25) Plant according to one or more of daims 14 to 24, including means for the ge¬ neration of a magnetic field in the dectron irradiation or electron stimulation section, to im¬ prove the up-grading process.