Distillation: processes – thermolytic – Applying electrical energy directly to material
Patent
1990-05-11
1992-01-28
Woodard, Joye L.
Distillation: processes, thermolytic
Applying electrical energy directly to material
201 25, 201 29, 201 32, 201 35, 423449, 585241, C10B 5300
Patent
active
050841416
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is concerned with the destructive distillation (or pyrolysis) of organic material, and particularly (but not exclusively), the pyrolysis of waste tire material or other similar rubber compounds.
2. Description of the Prior Art
A process of pyrolyzing organic waste by means of microwaves is disclosed in U.S. Pat. No. 3,843,457. In this process organic industrial and household wastes are comminuted and the comminuted solid material is subjected to a microwave discharge in a gas stream at a pressure substantially less than atmospheric for a contact time of the order of one second. The gas stream and the comminuted solid material pass through the microwave zone in parallel, with a view to maximizing interaction between the gas and the solid.
Microwave destruction of waste tire material has also been disclosed in, for example, (examined) Japanese Patent Applications 76/47192-3, 77/26553, 82/3491 and (unexamined) Japanese patent applications 52/3672 and 51/123287. These documents describe laboratory scale processes, in which small quantities of the waste rubber are subjected to microwave discharge so as to completely break the rubber down and produce carbon black and hydrocarbons (gaseous or liquid). These documents give no details as to how the basic idea of microwave pyrolysis could be converted into a commercial process.
A more recent document, U.S. Pat. No. 4,647,443, discloses a process of pyrolyzing of waste tire material which involves subjecting the tire material to radiant heating so as to produce a pyrolyzed char, and then subjecting the char to microwave discharge to remove volatile hydrocarbons from the char, so as to produce carbon black.
The disadvantage of this process is that radiant heating of tire material involves relatively inefficient heat transfer. I have found that, contrary to the teaching of U.S. Pat. No. 4,647,443, it is advantageous to pre-heat tire material (and other organic materials), without pyrolysis thereof, prior to complete pyrolysis by means of microwaves. Microwave-induced pyrolysis has been found to be impaired if tire material (or other organic material) has previously been partly pyrolyzed (this is postulated to be because of the insulating effect of the elemental carbon produced on pyrolysis). It is believed that this may be why the U.S. patent teaches that the pyrolysis should be taken to substantial completion in the radiant heating stage.
I have now found that, in contradistinction to the teaching of U.S. Pat. No. 4,647,443, it is advantageous to completely avoid pyrolysis in a pre-heating stage prior to microwave-induced pyrolysis.
The process according to the invention enables microwave pyrolysis of waste tire material and other rubber compounds, as well as other organic materials, to be operated as a commercial destructive distillation process.
SUMMARY OF THE INVENTION
According to the present invention, therefore, there is provided a process of destructive distillation of organic material, which comprises:
(a) pre-heating said organic material, substantially without pyrolysis of said organic material to elemental carbon, by means of a hot gas stream;
(b) feeding said pre-heated material directly to a microwave discharge zone in an atmosphere of substantially oxygen-free gas which is above atmospheric pressure;
(c) pyrolyzing said pre-heated material in said zone by means of a microwave discharge of sufficient power, and for a sufficient time, to cause substantial fission of carbon-carbon bonds in the organic material, in addition to fission of more polar chemical bonds, so as to produce solid fission products containing elemental carbon, and gaseous by-products;
(d) collecting said solid fission products downstream of said microwave discharge zone; and
(e) recycling at least part of said gaseous by-products to said hot gas stream to effect said pre-heating.
The process according to the invention can be operated as a continuous process, as will be explained hereinafter.
DESCRIPTION OF
REFERENCES:
patent: 3449213 (1969-06-01), Knapp et al.
patent: 3843457 (1974-10-01), Grannen et al.
patent: 4118282 (1978-10-01), Wallace
patent: 4376034 (1983-03-01), Wall
patent: 4647443 (1987-03-01), Apffel
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