WO2019030689A1

WO2019030689A1 - Fast pyrolytic process with low environmental impact based on controlled reforming of produced syngas

Info

Publication number: WO2019030689A1
Application number: PCT/IB2018/055966
Authority: WO
Inventors: Biagio BIANCHI; Giuseppe Marchionni
Original assignee: Universita' Degli Studi Di Bari Aldo Moro; Marchionni Srl
Priority date: 2017-08-09
Filing date: 2018-08-08
Publication date: 2019-02-14
Also published as: IT201700092370A1

Abstract

The invention relates to a process for the pyrolytic treatment of micronizable materials, comprising the following steps: - low-temperature pyrolytic treatment of a flux of micronized material; - controlled reforming of the syngas against the micronized material by means of the application of energy coming from renewable or recovered sources.

Description

"Fast pyro lytic process with low environmental impact based on controlled reforming of produced syngas"

FIELD OF THE INVENTION

Object of the present invention is a fast pyroiytic process with low environmental impact.

In particular, the invention consists in a pyroiytic process based on the controlled reforming of the syngas produced.

KNOWN PRIOR ART

In the traditional industrial pyroiytic systems the heating is performed by burning part of the material, with a strongly exothermic process, during which temperatures above 1000 °C are reached; like that:

- an initial gasification process which involves the formation of toxic compounds is established;

- in the system a flux of hot inert gas, generally N₂, is established, which tends to dilute the syngas and reduce its calorific value;

- dioxin, which is formed in the conditions of presence of oxygen-chlorine and temperatures of 600- 1400 °C, is produced.

Therefore it is a purpose of the present invention to implement a pyroiytic treatment that takes place at temperatures lower than those mentioned above and has iow environmental impact, both for the use of energy mostly being renewable or recovered energy, and for the elimination of the steps that would involve the production of dioxin.

Interest in the proposed process is very high because it can be applied to all organic- matrix waste, even the most polluting ones and more difficult to degrade, and has real potential for industrial scale-up.

Other purposes and advantages of the invention will be evident from the following description.

BRIEF SUMMARY OF THE INVENTION

The main advantages are obtained by a process for the pyroiytic treatment of micronizable materials; it comprises the fo llowing steps:

- low-temperature pyro lyt ic treatment on a flux of micronized material;

- controlled reforming of the flux of pyrolyzed syngas by means of the application of renewable and recycl ing heat sources.

An advantage of such implementation is that, just because it is about micronized material, it allows a pyrolysis that takes place at low temperatures, not above 450 - 500 °C and in very short times.

In the process of the invention, the step of low-temperature pyro lytic treatment of the flux of micronized material is preceded by a dehydration step with superheated steam of the material to be treated and by a micronization step of the material to be treated. A further advantage is the wide applicability of such process.

In fact it is applicable to micronizable matrices such as:

• wet waste fraction;

• sewage sludge;

· waste from the food industry;

• wood;

• organic materials or waste having a calorific value lower higher than 3000 kcal/kg in the dry state.

For the plastic materials and rubbers, the micronization can be energetically unfavorable if it takes place at room temperature, but if such materials undergo a cryogenic pretreatmeiit targeted to modify the crystalline structure of the material, this can be made fragi le, micronizable and usable in the process of the invention. In the proposed application, the step of low-temperature pyro lyt ic treatment of the flux of micronized material takes place at a temperature of 450-500 °C, which is reached in times shorter than 1 s.

An advantage of this implementation is the absence of the risk of air pollution by d ioxin: the pyro lysis in the present invention takes place at temperatures lower than 500 °C and in the absence of oxygen; these two conditions make the formation of dioxin unfavorable, from the thermodynamic point of view. For such reason, the pyrolysis can also be made against organic chlorides. It is emphasized that in the present process the absence of d ioxin can be ensured because, unlike traditional pyrolysis that burns in a preliminary phase part of materials by injecting air and thus oxygen into the system, in the present process no pre-combustion is carried out, as the heating of the reactor takes place with heat recovery inside the system, integration with solar energy and integration with thermal energy coming from the combustion of the tar and char and, possibly, the syngas; hence fuels obtained from the process itself.

In the step of low-temperature pyrolytic treatment of the flux of micronized material, a mixture of syngas and superheated steam, the latter coming from the heat ing/re forming step, is used to make a rapid pyrolysis. An advantage is coming from the fact that this solution al lows a system yie ld higher than the current systems, significantly higher for three reasons:

- the production of syngas al lows an internal combustion engine to be fed having a thermodynamic yield up to 42%, significantly higher than the yield that would be obtained by burning the so lid-state material in a Rankine cycle system, which would correspond to a maximum yield of 28% (value referring to large plants);

- the studied pyrolytic system leads to a net increase of hydrogen in the system, through the induction of the processes of control led reforming, therefore it clears the way for recovering hydrogen from the syngas by using it in fuel cel ls that would further integrate energy recovery with no environmental impact and a thermodynamic yield up to 60%;

- the studied process determines a clear prevalence of endothermic reactions, which results in increase of system enthalpy; substant ial ly, there is an accumulation of chemical energy by using waste thermal energy (combustion ftimes, latent and sensible heat of the superheated steam, etc.); the result is that the mass unit of the input material is converted into syngas with a higher calorific value: up to 20%.

The step of controlled reforming o f the syngas takes place also by photocatalysis. This generates an increase of the process kinet ics also because the UV energy, which affects the bonding energy, is supplemented by energy provided by microwaves that acts on the kinetic energy o f the mo lecules; the reforming processes in the throat of the ejector also allow an increase of the hydrogen fraction in the syngas to be obtained.

Furthermore, the renewable or recovered heat sources used in the step of reforming of the flux of pyrolyzed syngas comprise energy coming from UV rays and/or microwaves (MW).

The pyrolysis takes place in a reactor subdivided into: an inlet section, wherein a low-temperature pyrolytic treatment of a flux of micronized material takes place, and a reforming/heating section; in the latter superheated steam is acting predominantly, which increases the water content in the gaseous phase and raises the overall temperature of the system (by means of the application of renewable or recovered heat sources), and a controlled reforming takes place in the flux of pyrolyzed syngas. Further characteristics of the invention can be deduced from the dependent claims. BRIEF DESCRIPTION OF THE FIGURES

The advantages of the invention are evident from the reading of the figures shown in the attached tables:

• figure 1 is a generic plant layout of the technology;

• figure 2 is a generic layout of the temperature flows, and thus of the thermal energy, with particular reference to the inlet section and the heating/reforming section of the pyrolytic reactor;

· figure 3 is a more in-depth plant layout of the technology;

• figure 4 is a more in-depth plant layout of the temperature flows and thus of the thermal energy, with particular reference to the inlet section and the reactor section wherein the controlled reforming of the syngas (throat of the ejector) takes place.

DETAILED DESCRIPTION OF THE INVENTION

With reference to figures I and 3, a plant lay-out, respectively generic and in-depth, of the technology, is highlighted. The process operates on a flux of previously dehydrated and micronized material, for example a wet biomass 10, all within a system denoted with numerical references 100 as a whole, in fig. 1 , and 100' in fig. 3. Such wet biomass 1 0 enters a dehydrator 20 and is transformed into dry biomass 30 by using thermal energy supplied by superheated steam and by combustion fumes of a GE engine fed by syngas, and subsequently treated by a micronizer 40, to create a micronized biomass.

The micronized biomass is fed to a pyrolytic reactor 50 that, in turn, is subdivided in an inlet section 55 and in a next reforming/heating section 57 (in the flux direction of micronized material).

The fast (flash) pyrolysis is made with an instantaneous impact of the micronized material and a mixture of steam and syngas coming from the heating/reforming section, so that it reaches the working temperature (450-500 °C) in a very short time, in the order ef fractions of a second. The pyrolytic reactor 50 is a plug-flow reactor and is equipped with external interstice. In the interstice of the pyrolysis section of the reactor, combustion fumes at 520-550 °C coming from an engine 60 fed with syngas, circulate, which release thermal energy and maintain the temperature inside the system at 450-500 °C. In the interstice of the next section of the reactor, combustion fumes at 800 °C exiting the steam superheater 70 and coming from a burner 125 (T = 850 °C) fed with char and tar, which are possibly integrated with syngas, circulate. The step of preheating the input material, up to 450-500 °C, if carried out in long times, could make secondary reactions prevail, with a strong environmental impact, with the production of toxic gases and carbon polymers (char). The reaction takes place in a fixed reactor 50 (plug flow) crossed by a flux of micronized biomass.

Proceeding along the axis of the reactor 50, in the section following immediately after the inlet one, the "pyrolytic" process is completed, with a steady state.

The solar energy, concentrated by a paraboloid 80, is split into two fractions at 1R and UV wavelengths: the IR fraction is used in a superheater 70, whereas the UV fraction and the microwaves (MW) generated in a magnetron 90 supplied with the electric power produced by a generator 1 10 connected to the internal combustion engine 60 which, in turn, is fed by purified syngas, are used in the high reactivity areas: firstly the heating/reforming area, with particular reference to the throat 140 of the ejector.

The process is continuous: the biomasses are dehydrated by a heat exchange that takes place at the beginning with combustion ftimes coming from the double jacket of the reactor and, subsequently, with superheated steam, and also they are micron ized prior to the input in the reactor 50.

In the thermal dissociation of the material, intermediate stages of "activated" complexes evolving to the final products, are generated. These intermediate stages influence the reaction rate and the process direction. In this working hypothesis, the contribution of external energy to the system, provided by UV and MV, intervenes on the activated complex, accelerating the reactions and bringing the system to final products having different composition than that they should have for the action of the thermal energy only.

Two energy forms have been considered:

- energy from UV rays, acting on the chemical bonding energy;

- energy from microwaves (MW), which modifies the internal energy of the molecules or activated complexes; this share acts selectively, with absorption by polar molecules (e.g. water): this phenomenon determines transitory states in the system, wherein some molecules have a considerably higher energy than that they would have in the steady state, and this condition determines an increase in temperature and reaction rate, mainly against polar chemical species or chemical species in the transition state (activated complexes).

in the plant two areas are identified, wherein there can be chemical species in the transition state and active polar molecules: micronized inlet and throat of the ejector; in the latter area, energy is directed from UV and MW sources. In the inlet area 55 to the pyrolytic reactor 50, the complex molecules (proteins, polysaccharides, etc.) dissociate due to the effect of the fast heating, whereas in the heating/reforming section 57 of the pyrolytic reactor a strong turbulence and a considerable thermal gradient are created; this leads to a molecular rearrangement of the chemical species coming from the pyrolytic cleavage that, in particular, occurs in the throat 140 of the ejector. The thermal energy needed to the realization of the process is provided almost exclusively from renewable or recovered sources, in particular:

- solar paraboloid with apparatus that breaks down the l ight energy into UV and IR;

- sensible heat of the syngas and steam, possibly mixed;

- mechanic energy of an internal combustion engine fed with syngas;

- thermal energy from the combustion of the char and tar, possibly integrated with syngas;

- thermal energy of the combustion fumes of an internal combustion engine fed with syngas and of a burner fed with char and tar;

- electric power from cogeneration for the integrative production of UV and MW.

From figures 2 and 4, wherein a generic and in-depth lay-out is depicted, respectively, of the fluxes of mass and energy in the pyrolytic reactor, the following is apparent.

The fixed pyrolytic reactor 50 (plug flow) has two stages obtained in two sections. The first section is the inlet/pyrolysis section 55 wherein the reactor is crossed by a flux of micronized matter and in the double jacket the combustion fumes of the syngas engine 60 circulate; in the immediately following section, in double jacket of the reactor, fumes coming from the superheater of the steam 70 circulate and, in this area, the "pyrolytic" process is completed, with a steady state. The recirculation of the mixture consisting of syngas and superheated steam coming from the heating/reforming section 57 is directed in the inlet/pyrolysis area of the micronized material, to make a rapid heating.

The next section is the heating/reforming section 57. In this section, predominantly reforming reactions occur: a boosted formation of hydrogen is obtained with reactions between steam and pyroiyzed material coming from the inlet section that is in a simpler molecular state (carbon, carbon oxide, methane, etc.). In this section a strong turbulence and an increase in temperature are generated; by using steam coming from the superheater 70 as the working medium of an ejector 130, wherein the steam, from the dehydration section of the biomass (possibly integrated by boiler steam), is superheated to the pressure of 2 atm and the temperature of 850 °C; IR energy and the energy released by the combustion fumes of a burner fed with char and tar and, possibly, with syngas, act in the superheater 70. In the ejector 130 a share of syngas is sucked (T=600 °C) at the outlet of the section following immediately after the inlet/pyrolysis one : a mixture of steam and syngas at about 750 °C, which is direct ly input in the inlet/pyrolysis section 55 of the reactor, in which it meets the micronized material, is obtained.

At the molecular level, in the heating/reforming section 57 a photocatalytic effect is induced that is adding to the action of the temperature: such effect is produced by UV and MW in a field of the throat 140 of the ejector.

In the heating/reforming section a fluid bed based on mineral and metal particles can also be made: the fluid dynamics of the system must be such that in the final area of the reactor the solid materials are separated, which must stay in the heat ing section, whereas in the inlet section must only pass the gaseous heating flux, i.e. the mixture syngas + steam obtained with the ejector.

In conclusion, in the inlet section 55 pyrolytic cleavage reactions from the starting micronized material take place; in the heating/reforming section 57, instead, reforming reactions under control led conditions take place, with modification of the molecules formed in the inlet section. This process brings to an increase of the H₂ content in the syngas.

As previously mentioned, one of the energy sources is consisting of a paraboloid 80, which spl its the sunlight and uses the I R band to superheat (superheater 70) the steam represent ing the heat engine of the system (exchange fluid in the dehydrator 20 and working medium in the ejector 130 in the heating/reforming area 57 of the pyrolyt ic reactor 50). The thermal energy is obtained by a burner 125 fed with char and tar and, possibly, with syngas.

Further developments of the invention provide for studying a low-cost cryogenic technique for the plast ic materials: when brought to temperatures of - 160°c with liquid nitrogen they are becoming fragile and friable. Small-scale tests shown that temperatures of -50 °C are sufficient. In this way, also said materials will be able to be used in the described process. Summarizing: the most relevant innovative aspects of the technology are the following:

- fast pyro lysis;

- more boosted gasification with char and tar reduction;

- continuous process;

- execution of the reforming reactions under controlled conditions of space and time;

- increase of the process kinet ics also through the induction of photocatalysis (UV and M W energies);

- increase of the hydrogen fraction in the syngas through the induction of the reforming processes in the heating area;

- increase of the calorific value of the syngas;

- increase of the energy given back per unit of input energy (Ho/Hi > ] ); it can be affirmed that the enthalpy of the syngas (Ho) is equal to, or greater than, the inlet enthalpy (H i), as the endothermic reactions act ivated in the system (e.g. : CO+H₂0 = CO2+H2) store thermal energy outside the system in the form of chemical energy. Thus the process also has the fo llowing characteristics of uniqueness.

It allows the waste treatment with energy recovery systems and low thermal pol lution: the recovery of the thermal energy for the process, in fact, al lows combustion fumes to be discharged at lower temperatures.

The process also has a low environmental impact: with respect to the combustion, there is a very low pollut ion by gas and fine particles; in fact, whereas the combustion burns the solid-state matter, in the pyrolysis the final combustion takes place on the syngas. It is known that the combustion of sol ids or liquids, with respect to gases, causes an increase of the fine powders, NO*, etc.

The invention, as it is defined, is of considerable commercial interest for compan ies that produce industrial pyrolysis and gasification plants. Public Authorities for waste management and waste water purificat ion having, respectively, organic fract ion and sludge to be disposed of, can also be particularly interested. An industrial plant would require considerable investments but lower than those made with different techno logies and certainly profitable, Obviously, modifications or improvements may be added to the invention as described as a result of contingent or particular motivations, but without deviating from the scope of the invention claimed hereunder.

Claims

CLA IMS I . Process for the pyro lytic treatment of micronizable materials, wherein the process comprises the following steps: low-temperature pyrolytic treatment of a flux of micronized material; - controlled reforming of the syngas generated by the pyrolytic process against the micronized material; reforming that takes place in a confined space and by using renewable energy,

1. e. UV rays obtained from splitting the light waves by solar paraboloid, and recovered energy, i.e. char and tar and possibly syngas are used in a burner to obtain heat with which the steam is overheated;

reforming that takes place in a confined space and by using recovered energy consisting of microwaves generated by a magnetron supplied with the electric power obtained with a generator operating by the combustion of syngas; using microwaves is not only functional to heat the system but also to generate a photocatalytic effect increasing the reforming reaction rate on the polar chemical species of transition.

2. Process according to claim 1 , wherein the step of low-temperature pyrolytic treatment is preceded by a dehydration step with superheated steam of the material to be treated and by a micronization step; in the dehydration step a direct exchange takes place between superheated steam and material to be treated, thus obtaining the elimination of almost ail the air in the system, and creating an atmosphere very favorable to pyrolysis, without the need of any combustion form.

3. Process according to claim 1 , wherein the step of low-temperature pyrolytic treatment of the flux of micronized material takes place at a working temperature of 450-500°C, which temperature is reached in a period shorter than one second, in the absence of oxygen, pre-combustion and without emission of toxic gases.

4. Process according to claim 1 wherein, during the step of low-temperature pyrolytic treatment of the flux of micronized material, syngas and superheated steam both coming from the reforming step are recirculated, thus obtaining the ideal temperature for the fast pyrolysis process, an increase in hydrogen content and in the calorific value of the syngas, and a higher syngas yield.

5. Process according to claim 1 , wherein the controlled reforming step of the syngas material takes place by means of photocatalysis.

6. Process according to claim 1 , wherein renewable or recovered energy is used in the step of controlled reforming of the flux of syngas, the energy consisting of energy coming from UV rays and microwaves (MW),

7. Plant ( 100- 1 00') for the pyrolytic treatment of micronizable materials, wherein the plant comprises a pyrolytic reactor (50) divided in an inlet section (55), in which a low-temperature pyrolytic treatment of a flux of micronized material takes place, and a heating/reforming section (57) in which controlled reforming of the flux of syngas takes place by means of the application of renewable or recovered energy, in a very small space consisting of the throat of a steam-jet ejector, and in very short time.

8. Plant ( 100- 100') according to claim 7, wherein the pyrolytic reactor (50) is a plug flow reactor provided with external interstice in which combustion fumes coming from a gas engine (60) circulate, said fumes being at a temperature between 520 and 550°C are used for indirectly heating the inlet section of the reactor, and fumes coming from a unit (70) producing superheated steam at a temperature of 800 °C, that are used for indirectly heating the section of the reactor following immediately after the inlet one, for completing the pyrolytic process; the superheating unit (70) is fed by combustion fumes of a burner ( 125) fed by char and tar.

9. Plant ( 1 00- 100') according to claim 7 wherein, in the throat of the ejector in which the controlled reforming reactions take place, energy from UV rays is concentrated, which increases the reaction rate by acting on the energetic state of the bonds of the chemical species of the syngas in the presence of steam; such energy is obtained by using a paraboloid (80) designed to concentrate the solar radiation and separate it into two fractions with wavelengths in the infrared (1R) and ultraviolet (UV), wherein the fraction with wavelength in the infrared (1R) is used in the superheater (70), whereas the fraction with wavelength in the ultraviolet (UV) is concentrated in the throat ( 140) of the ejector ( 1 30) for the photocatalysis reactions.

10. Plant ( 100- 100') according to claim 7 wherein, in the throat of the ejector in which the controlled reforming reactions take place, energy from microwaves (MW) is concentrated, which increases the reaction and heating rates, by acting on the kinetic energy of the molecules or activated complexes and it is obtained by a magnetron (90) supplied with the electric power produced by a generator (110) connected to an engine (60) fed with syngas.