JP2004141871A - Method and plant for microwave treatment of solid residue from pyrolysis of organic-containing feed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for microwave treatment of solid residue resulting from pyrolysis of a feed containing organic substances, and a plant therefor. <P>SOLUTION: The method for treating a feed containing at least 5% organic substances comprises the stages of: (a) thermally decomposing the feed by pyrolysis under such a condition that enable the formation of carbon-containing solid residue and a gas phase, (b) separating the gas phase from the carbon-containing solid residue, and (c) treating the carbon-containing solid residue by microwave radiation in the presence of an oxidizing agent. The plant can implement the method. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a method and a plant for the microwave treatment of solid residues from the pyrolysis of organic-containing feeds.

More specifically, the present invention provides an at least partially chemically inert, which can be disposed of in the environment without any danger, or can be used as a material for road construction or construction and civil engineering applications. And a method and plant that can provide the final residue.

The invention finds application, inter alia, in the treatment of domestic or industrial waste, industrial or sewage sludge, biomass, and more generally any feed containing at least 5% organic matter.

The flammable gas is obtained by pyrolysis of a feed such as pyrolysis (also referred to as thermolysis) by the well-known method described in European Patent Applications 0,692,677 and 1,077,248. Can be produced from a solid feed containing the organic fraction.

This operation can advantageously upgrade feeds containing at least partially organic matter, such as biomass, industrial or household waste, industrial or sewage sludge.

Pyrolysis is the operation of thermally decomposing a feed, which takes place in the absence of air and thus oxygen. Pyrolysis has a moderate to high quality heating value that can be improved, most often used as fuel for known energy generators such as boilers, engines, turbines, etc., and is also referred to as solid residue or coke. This results in the production of gases used for the production of rich solids.

固 相 This solid phase, usually a low quality fuel, is burned in a conventional burner, and the ash from the combustion is cooled and discarded.

However, this solution has many disadvantages in its implementation. That is, high energy costs are required at the same time as expensive equipment. This is especially true when the calorific value of the coke is low, that is, when its ash content is high, about 40%, and more specifically about 60%.

Improving the quality of the solid phase is therefore a recurring problem due to the practice of waste pyrolysis.

解決 Several solutions for treating this solid phase have been proposed.

EP 1,077,248 proposes a combustion means for releasing the heat for heating the pyrolysis oven on a solid residue obtained from the pyrolysis feed with a low heating value. .

Another solution is proposed in U.S. Patent No. 6,398,921. The solid and gas phases obtained by the pyrolysis method are subjected to the action of microwave irradiation in the absence of an oxygen source, so that a part of the solid phase is gasified. However, implementing such a method does not convert all the coke and requires a normal final combustion stage to burn the residual coke and render the combustion ash inert by melting and solidification. This results in additional costs and increased plant complexity.

The present invention relates to a method aimed at overcoming the above problems in a simple, efficient and inexpensive manner.

Specifically, the present invention provides:
a) pyrolyzing the feed by pyrolysis under conditions that result in the formation of a carbon-containing solid residue and a gas phase;
b) separating the gas phase and the carbon-containing solid residue;
c) treating said carbon-containing solid residue by microwave radiation in the presence of an oxidizing agent.

More specifically, the oxidizing agent can be air, oxygen, high oxygen concentration air or steam.

Most of the carbon present in the carbon-containing solid residue is oxidized to carbon monoxide or carbon dioxide, and at least some, or even most, of the resulting mineral solid residue is non-leaching, more often melt-solidified The treatment is carried out under the conditions that result in the prescribed form.

For "most carbon present", it is believed that at least 70%, preferably 90%, most preferably at least 95%, and even 99% of the carbon-containing material is oxidized.

For "at least a portion of the solid residue", it is believed that at least 30% and preferably at least 50% of the solid is in a non-leaching form.

It has been confirmed by the applicant that the high temperature carbon-containing solid residue obtained from the pyrolysis (ie pyrolysis) is very reactive to microwave radiation and a synergistic effect is observed between the two stages of the process. Was. Combining the pyrolysis step of producing a carbon-containing solid residue with the step of subjecting the hot solid residue to microwave radiation reaches a high temperature and, with low energy consumption, renders the residue at least partially inert, and even melts. It can also be solidified. Furthermore, the electrical energy consumed to generate the microwaves is transferred directly to the carbon-containing solid residue without any thermal inertia, for example for the preparation operation of the melt-solidification oven. This results in good overall energy efficiency.

In most cases, the pyrolysis is carried out in a temperature range from about 300 to 800 ° C., for example, such that under the action of microwave radiation during step c) the temperature of the solid residue is between 600 and 1400 ° C. The microwave treatment is performed on the high-temperature solid residue under suitable conditions.

The process of the present invention may also include, prior to the treatment of step c), a step of chemical and / or physical modification, sorting, gravity separation, eg washing with water, grinding or forming of the carbon-containing residue. .

Furthermore, water can be injected before or during the processing step c) without departing from the scope of the invention.

The frequency of the microwave radiation can be in the range of 100 MHz (megahertz) to 100 GHz (gigahertz), preferably 900 to 2500 MHz, and the emission of the microwave radiation can be, for example, a period generally in the range of 0.001 to 1 second. Can be performed in a pulse format having

The electric field density of the microwave radiation can be between ³⁰ and 2000 kilowatts / m3.

According to a possible embodiment of the invention, at least one additive favoring the absorption of microwave radiation or at least one additive capable of adjusting the final composition of the residue from step c) is added to step b). ) Can be added to the solid residue from

The present invention relates to a plant suitable for carrying out the above-mentioned process, aimed at converting a feed containing at least 5% of organic matter, comprising at least an oven intended for the pyrolysis of said feed. A means for separating the gaseous phase and the carbon-containing solid residue from the pyrolysis oven; and an oven connected to the microwave generator for the treatment of said solid residue.

According to an embodiment of the present invention, a plurality of processing ovens are connected to a single microwave generator, and a means for alternately supplying a feed to each of the ovens and performing the processing alternately by microwave radiation is used. be able to.

The process according to the invention or the plant according to the invention is particularly suitable for the treatment of domestic and / or industrial waste, industrial and / or sewage sludge, biomass, agricultural waste and by-products, soils contaminated with hydrocarbons. Application areas are found.

Other advantages, details and features of the invention will become apparent on reading the following description of embodiments, given by way of non-limiting example, with reference to the sole accompanying drawings showing a plant according to the invention. Would be.

The process according to the invention comprises at least 5% of organic substances, such as household and / or industrial waste, industrial and / or sewage sludge, biomass, agricultural waste and by-products, hydrocarbon-contaminated soil. It is preferably for the purpose of processing feeds.

熱 For pyrolysis of the feed, especially pyrolysis or pyrolysis, it is preferred to use a rotary oven 1 because of its ability to process feeds of varying scale and composition.

The present invention can perform a pyrolysis operation, such as, for example, a conveyor belt oven, fluidized bed, fixed bed, moving bed, entrained bed, or rotating bed furnace as described in French Patent No. 2,785,835. It can be applied to any type of oven known to those skilled in the art.

The feed may need to be processed before pyrolysis. This pre-treatment step depends on the nature of the feed (feed type, particle size, moisture), but uses conventional techniques such as crushing, drying, sorting, separation and the like. The purpose of this pretreatment stage is to ensure that the feed can meet the specifications at the entrance of the rotary oven 1. That is,
The maximum particle size of the feed is less than 30 cm, preferably less than 10 cm;
-It can be dried to a controlled feed moisture, for example up to 40% by weight, preferably 20% by weight.

The feed is fed into an oven 1, such as an indirectly heated rotary oven, using a device (shown by arrow C in FIG. 1) that seals the oven from the outside and completely prevents air from flowing into the oven. . The device providing this seal can be an Archimedean screw pump or a device allowing the feed to be introduced in a compact processing unit.

回 転 The rotary oven used for pyrolysis is provided with a rotary enclosure 2. This rotating enclosure 2 is surrounded by an annular space 3 for heating it.

As it travels through the rotating enclosure 2 under the action of heating, the feed releases its residual moisture and is then subjected to pyrolysis, ie pyrolysis, in the absence of any air. By this operation, a gas phase (a raw material gas or a pyrolysis gas) and a solid phase (a carbon-rich solid residue or coke) are formed.

フ ィ ー ド The feed, gas and solid residue obtained from the pyrolysis circulate in this oven in cocurrent. This operation is most often carried out at a temperature in the range from 300 to 800 ° C, preferably from 500 to 700 ° C, and at a pressure near atmospheric pressure. The residence time of the feed in the oven should be long enough to completely decompose the organic material. It is generally in the range from 30 to 180 minutes, more precisely from 45 to 90 minutes. Under such residence time conditions, the production of tars in the gas phase is minimized, given the temperature profile in the rotary oven.

In general, the operating conditions of the pyrolysis operation, especially the final processing temperature and the rate of temperature rise, are such that the flammable gas yield is optimized at the expense of the yield of solid products and tar-like heavy products in the art. Is preferably selected by a technician.

Then, in order to supply energy generating means such as a cogeneration plant (not shown in FIG. 1), European Patent Application Nos. 0,692,677 or 1,077,248 filed by the applicant. The flammable gas (or pyrolysis gas) is treated to improve quality by known techniques such as those described.

炭素 Separate the carbon-containing solid residue from the gas phase by any conventional means 4 known to those skilled in the art, such as a cyclone, to separate the gas phase from the solid phase. The gas phase is discharged through line 5. The solid residue discharged through line 6 is a carbon-rich mixture and most often contains minerals such as silicates or aluminates. The proportion depends, of course, on the composition of the initial feed and the pyrolysis conditions (temperature, residence time).

The high-temperature carbon-containing solid residue from the separation means 4 is subjected to the action of microwave radiation, preferably immediately, in the presence of an oxidizing agent such as air, oxygen, high oxygen concentration air or steam. Exposure to this microwave takes place in a chamber 7 into which a line 6 opens. This oven, in particular a chamber in the form of a rotary oven, is correspondingly adapted, the chamber being connected by a microwave guiding channel 8 to a microwave generator 9 of a well-known type.

The frequency of the microwave for exposing the carbon-containing residue is preferably in the range of 100 MHz to 100 GHz, more preferably 900 to 2500 MHz. Also, the wavelength range used is in most cases selected by those skilled in the art to favor its absorption by the carbon-containing solid residue, thus accelerating the heating rate. This absorption causes rapid heating of the carbon-containing solid residue, resulting in the oxidation of at least a portion of the carbon present in the residue to carbon monoxide CO and carbon dioxide CO _{2 in} the presence of an oxidizing agent. The effect of this combustion increases the temperature of the solid residue, reaching temperatures in most cases in the range of 600-1400C.

The microwave emission can be carried out either in a continuous manner or in a pulsed form, which may have a period in the range, for example, from 0.001 to 1 second.

The microwave generator 9 is dimensioned and selected by any known technique so that energy sufficient to cause an oxidation reaction can be supplied in a short time, i.e., in a cycle of 1 second to 15 minutes. In any case, depending on the chemical composition of the carbon-containing material, in particular its carbon content, the electric field density is in the range of values on the order of ^{30 to} 2000 kilowatts / m ³ (kilowatts per cubic meter). .

Until an inert solid residue is obtained, ie containing only non-leaching minerals according to the NFX 31210 standard, and generally having a residual carbon content of less than 5%, preferably less than 3%, typically less than 1% Until the process is continued.

It is also advantageous to add at least one known additive to the solid residue obtained from the pyrolysis via the feeding means 10. This additive further enhances the absorption of said wavelengths by the mixture in the rotary oven 7 and / or makes it possible, for example, for water or carbon, to obtain an inert high silica glass frit, such as calcium carbonate, which is finally obtained. The composition of the solid residue can be adjusted later, in particular to improve the residue as a material in the field of construction and civil engineering.

The fumes resulting from the combustion of the carbon-containing residue are discharged from processing oven 7 through line 11 for subsequent processing. This process, conversion to CO ₂ in the CO, can be included for removal of contaminants that might dust and containing.

The inert solid residue is removed from the oven by the withdrawing means 12. Further, a means such as a heat exchanger 13 for recovering energy from a high-temperature inert solid residue can be arranged on the extraction means 12 without departing from the scope of the present invention.

も ち ろ ん Of course, the present invention is not limited to only one embodiment described above.

For example, a plurality of microwave processing ovens provided on a rotating plate are installed, whereby each of the ovens is alternately fed with a feed and then alternately acted upon by a microwave generator. Other embodiments of the invention can be provided. Such a layout in particular offers the advantage of increasing the overall capacity of the plant in a simple and economical way, while at the same time minimizing its space requirements.

FIG. 2 shows a plant according to the invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Rotary oven 2 Rotating enclosure 3 Annular space 4 Separation means 5, 6, 11 Line 7 Chamber 8 Microwave induction channel 9 Microwave generator 10 Supply means 12 Extraction means 13 Energy recovery means, such as a heat exchanger

Claims (11)

A method intended for treating a feed containing at least 5% of an organic substance, comprising:
a) pyrolyzing the feed by pyrolysis under conditions that result in the formation of a carbon-containing solid residue and a gas phase;
b) separating the gas phase and the carbon-containing solid residue;
c) treating said carbon-containing solid residue by microwave radiation in the presence of an oxidizing agent. 2. The method according to claim 1, wherein the microwave treatment is carried out on the hot solid residue under conditions of microwave radiation during step c) such that the temperature of the solid residue is between 600 and 1400C. The described method. 方法 The method according to claim 1 or 2, wherein the step of c) is preceded by a step of chemical and / or physical modification, sorting, gravity separation, washing, grinding or forming of the carbon-containing residue. The method according to any one of claims 1 to 3, wherein water is injected before or during the processing step c). The method according to any one of claims 1 to 4, wherein the frequency of the microwave radiation is in the range of 100 MHz to 100 GHz. The method according to any one of claims 1 to 5, wherein the emission of the microwave radiation is carried out in the form of pulses with a period in the range from 0.001 to 1 second. 7. The method according to claim 1, wherein the electric field density of the microwave radiation ranges from ³⁰ to 2000 kilowatts / m < ³ >. 8. The process according to claim 1, wherein at least one additive which favors absorption of microwave radiation is added to the solid residue from step b). 9. A process according to any one of claims 1 to 8, wherein at least one additive capable of adjusting the composition of the residue from step c) is added to the solid residue from step b). At least an oven (1) intended for pyrolysis of the feed, means (4) for separating the gas phase and the carbon-containing solid residue from the pyrolysis oven, and a microwave generator (9) are connected. An oven (7) intended for the treatment of said solid residue, comprising a feed containing at least 5% organic material for carrying out the method according to any of the preceding claims. A plant intended to be converted. 11. The plant of claim 10, comprising a plurality of processing ovens coupled to a single microwave generator, and means for providing alternate feeds to each of the ovens and for performing alternate processing by microwave radiation. .

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