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US-12624302-B2 - Method and reactor for processing a gas

US12624302B2US 12624302 B2US12624302 B2US 12624302B2US-12624302-B2

Abstract

A plasma processing method for a gas includes: supplying a gas inside a cavity for plasma processing, supplying microwaves having a predetermined frequency and power in order to generate a plasma of the gas, and propagating the microwaves in the gas by a waveguide which communicates directly with the cavity so as to provide a plasma cracking processing operation for the gas inside the cavity.

Inventors

  • Shahram ROSHANPOUR
  • Anton DANILENKO

Assignees

  • RONDA HIGH TECH S.R.L.

Dates

Publication Date
20260512
Application Date
20210719
Priority Date
20200717

Claims (18)

  1. 1 . A plasma processing method for a gas, the method comprising: supplying a gas inside a cavity for plasma processing, supplying microwaves having a predetermined frequency and power in order to generate a plasma of the gas, propagating the microwaves in the gas by means of a waveguide which communicates directly with the cavity so as to provide a plasma cracking processing operation for the gas inside the cavity, the internal volume with respect to the cavity and the waveguide not having any discontinuities, receiving the gas and the microwaves from the waveguide in a processing pipe of the cavity, conveying the gas and the microwaves inside an electromagnetic resonator which is arranged along the processing pipe, the electromagnetic resonator being in the form of a widening of the processing pipe and concentrating the microwaves so as to generate a plasma of the gas inside the electromagnetic resonator, wherein the electromagnetic resonator is arranged along the processing pipe downstream of the waveguide in relation to a direction of flow of the gas and propagation of the microwaves by the waveguide towards the processing pipe.
  2. 2 . The method according to claim 1 , further comprising receiving the gas and the microwaves in the electromagnetic resonator only after the gas and the microwaves have been discharged from the waveguide.
  3. 3 . The method according to claim 1 , wherein the microwaves propagate from the waveguide to the cavity through the gas without encountering any obstacle.
  4. 4 . The method according to claim 1 , wherein the generation of the plasma inside the cavity is fed by the gas without adding any additional gas being introduced into the cavity intended to sustain the generation of the plasma inside the cavity, and wherein the gas comprises a pyrolysis gas.
  5. 5 . The method according to claim 1 , wherein the plasma cracking is carried out at atmospheric pressure.
  6. 6 . A plasma-chemical reactor for carrying out the plasma processing method for a gas according to claim 1 , the plasma-chemical reactor comprising a plasma processing cavity which is configured to receive the gas inside the cavity, an electromagnetic wave source which is configured to supply microwaves having a predetermined frequency and power in order to generate a plasma of the gas inside the cavity, a waveguide which communicates directly with the cavity, the internal volume with respect to the cavity and the waveguide not having discontinuities, the waveguide being configured to receive the microwaves from the electromagnetic wave source and to propagate the microwaves in a guided manner in the cavity through the gas so as to provide a plasma cracking processing operation for the gas inside the cavity, the cavity comprising an inlet pipe which is configured to convey the gas towards the waveguide and a processing pipe which is configured to receive the gas and the microwaves from the waveguide so as to provide the plasma cracking processing operation for the gas inside the processing pipe and an electromagnetic resonator which is arranged along the processing pipe, the electromagnetic resonator being configured to receive the gas and the microwaves along the processing pipe and to concentrate the microwaves inside the electromagnetic resonator so as to generate a plasma of the gas passing through the electromagnetic resonator, the electromagnetic resonator being in the form of a widening of the processing pipe, wherein the electromagnetic resonator is arranged along the processing pipe downstream of the waveguide in relation to a direction of flow of the gas and propagation of the microwaves by the waveguide towards the processing pipe.
  7. 7 . The plasma-chemical reactor according to claim 6 , wherein the electromagnetic resonator along the processing pipe is spaced apart from the waveguide by a first distance and the processing pipe has a first diameter, the first distance being greater than the first diameter, and being between two and ten times the first diameter.
  8. 8 . The plasma-chemical reactor according to claim 7 , wherein the electromagnetic resonator extends along the longitudinal extent of the processing pipe over a second distance which is less than the first distance, the first distance being between two and ten times the second distance.
  9. 9 . The plasma-chemical reactor according to claim 6 , wherein the waveguide has a hollow linear structure which extends along a first axis, the hollow linear structure of the waveguide having a rectangular cross-section.
  10. 10 . The plasma-chemical reactor according to claim 6 , wherein the waveguide has a hollow linear structure which extends along a first axis and the cavity and/or the inlet pipe and/or the processing pipe have a hollow linear structure which extends along a second axis, the second axis being perpendicular to the first axis.
  11. 11 . The plasma-chemical reactor according to claim 10 , wherein the hollow linear structure of the cavity and/or the inlet pipe and/or the processing pipe having has a circular cross-section.
  12. 12 . The plasma-chemical reactor according to claim 10 , wherein the linear structure of the waveguide extends along the first axis over a first length and along the second axis over a second length, the first length being from three to ten times the second length.
  13. 13 . The plasma-chemical reactor according to claim 12 , wherein the first length is from six to seven times the second length.
  14. 14 . The plasma-chemical reactor according to claim 12 , wherein the cross-section of the waveguide extends in a direction perpendicular to the plane defined by the first axis and the second axis over a third length, the second length being from one to two thirds of the third length.
  15. 15 . The plasma-chemical reactor according to claim 6 , wherein the electromagnetic resonator has a hollow cylindrical structure which extends along the second axis of the processing pipe, the hollow cylindrical structure having a cross-section greater than a cross-section of the processing pipe, and wherein the processing pipe has a first diameter, and the electromagnetic resonator has a second diameter greater than the first diameter.
  16. 16 . The plasma-chemical reactor according to claim 6 , wherein the electromagnetic resonator has a second diameter and extends along the longitudinal extent of the processing pipe over a second distance less than or approximately equal to the second diameter.
  17. 17 . The plasma-chemical reactor according to claim 6 , wherein the electromagnetic resonator does not have moving parts.
  18. 18 . An installation for pyrolysis and/or gasification of biomass, comprising a pyrolyzer and/or gasifier which is configured to supply a pyrolysis gas which is generated by the pyrolysis and/or gasification of the biomass and furthermore the reactor according to claim 6 , wherein the reactor is configured to receive the pyrolysis gas and to provide a plasma cracking processing operation for the pyrolysis gas.

Description

FIELD OF THE INVENTION The invention relates to a method, a reactor and an installation for processing a gas of the type suitable for example, for cracking a pyrolysis gas from the thermal destruction of biomass or refuse. BACKGROUND It is known to use the pyrolysis process for thermochemically decomposing biomass (that is to say, organic materials) by means of the application of heat (normally in the temperature range from 150 to 1000° C.) and substantially without any oxidizing agent (normally oxygen). In practice, while heating the material in the presence of oxygen there is carried out a combustion which generates heat and which produces oxidized gaseous compounds, but by carrying out the same heating under conditions without oxygen, the material is subjected to the splitting of the original chemical bonds with simpler molecules being formed. The products of pyrolysis are solid residues of coke, liquids and gas. In accordance with the parameters of the process, such as, for example, final temperature, pressure and presence of catalysts, the ratio of the components at the outlet in a different aggregation state may vary significantly. There exist different types of pyrolysis which differ under process conditions and which are intended to obtain specific products. Among the main pyrolytic processes carried out on a large scale, industrial cracking and thermal processing of refuse stand out. It will be appreciated that the pyrolysis gas generated during the gasification of the biomass is currently considered to be an alternative source of energy gas which is economically advantageous with respect to natural gas for chemical synthesis and as a fuel for generating thermal energy. However, it must be observed that the direct use of the pyrolysis gas is complicated by the presence of aromatic substances in the composition thereof. To this end, the development of cracking processes for the pyrolysis gas which are effective and economically feasible is of particular importance. Therefore, there is perceived the need for a system for processing pyrolysis gas which allows cracking of the pyrolysis gas and the dissociation of the tarry substances in order to convert the crude gas into an ecological fuel in an economic manner. Furthermore, there is perceived the need for a conversion system for the tarry substances into a gaseous state while maintaining the energy value of the gas. Furthermore, not only the pyrolysis gas but also the exhaust gas generally contains tarry agents which must be destroyed so as to ensure that the emissions of the exhaust gas are safe for humans and for the environment. There are known three main systems for removing the tarry substances from the gas. The first system involves physical removal during the washing of the gas with solvents. In this system, the criterion of purity for the tarry substances remaining in the gas is the dew-point. The second system is the destruction at high temperature. Generally, the tarry substances are subjected to cracking during the injection of oxygen. Disadvantageously, however, the destruction of the hydrocarbons is also brought about during the injection of oxygen. The third system is the catalytic conversion of the tarry substances which is usually carried out using catalysts based on nickel for the crude gas immediately after the gas has been produced at high temperatures (from 400 to 900° C.). However, the main disadvantage of the prior art of the catalytic conversion systems for the pyrolysis gas for producing gaseous fuels is the high cost of the final product. Various attempts have been made to solve the problem of providing an effective and ecological system for processing pyrolysis gas or exhaust gas. The problem has evident difficulties, furthermore as a result of the need to limit the energy costs and operating costs of the processing and to reduce the number of additional components which contribute to increasing the costs and the complexity of the system for processing the gas. It may be noted that, in this context, the term “cracking” is intended to be understood to mean a chemical process for dissociating hydrocarbon compounds via which light hydrocarbons are obtained by splitting the heavy hydrocarbon molecules. It will be appreciated that the hydrocarbons comprise, for example, paraffinic, naphthenic or aromatic hydrocarbons. It may further be noted that the term “tarry substances” (or tars) is intended to be understood to mean organic compounds having a high molecular mass and low level of oxidation, such as, for example, heavy molecules of paraffinic hydrocarbons. Some examples of systems for processing a gas are described in Jamróz P. et al.: “Microwave plasma application in decomposition and steam reforming of model tar compounds”, FUEL PROCESSING TECHNOLOGY, vol. 169, pages 1-14, 19 Sep. 2017, or in Eliott Rodrigo Monteiro et al.: “Tar Reforming under Microwave Plasma Torch”, ENERGY & FUELS, vol. 27, no. 2, pages 1174-1181, 21 Feb.