US20090235849A1

US20090235849A1 - Process for eliminating organic matter and for generating energy

Info

Publication number: US20090235849A1
Application number: US12/279,929
Authority: US
Inventors: Stephane Barbati; Maurice Ambrosio; Virginie Fontanier
Original assignee: Universite de Provence Aix Marseille I
Current assignee: Aix Marseille Universite
Priority date: 2006-02-20
Filing date: 2007-02-16
Publication date: 2009-09-24
Also published as: WO2007096506A1; EP1986964A1; EP1986964B1; FR2897674A1; FR2897674B1

Abstract

Process for destroying organic matter, in which said organic matter in ground form is introduced into a reactor and subjected to flameless combustion at a temperature of 240 to 400° C. under a pressure of 100 to 300 bar, in the presence of an oxygen-containing oxidizer for at least 20 minutes, while stirring the medium, and process for generating energy, in which the energy generated by the combustion is furthermore recovered.

Description

The subject of the present invention is a novel process for the disposal of organic matter and production of energy
In present-day society, the disposal of waste and in particular of organic matter especially of animal origin is becoming increasingly important.
Moreover, the appearance of certain disease factors such as prions necessitate a radical destruction of much organic matter.
The waste to de disposed of can be solid, or non-solid.
It is already known, for example, to dispose of some waste by pyrolysis, i.e. by combustion at high temperature in a furnace.
As regards more particularly, for example, animal carcasses, the raw product is firstly converted into a solid waste called animal meal, which is then destroyed by incineration, i.e. by combustion with a flame at a temperature above 850° C.
But incineration produces dioxins, and it must be carried out on meal which produces dusts which may be toxic.
It would therefore be desirable to find an effective technique for the disposal of organic matter, making it possible to work directly on the raw product, not producing toxins and making it possible to avoid the formation of potentially toxic dusts.
It would be also be desirable to find a process which does not require energy and which even, if possible, produces energy rather than consuming it.
After a lengthy search, the applicants have found a satisfactory process.
This process is essentially based on a low-temperature combustion without flame at a relatively low temperature, and under pressure, in the presence of a fuel such as air.
For this reason, the subject of the present application is a process for the destruction of organic matter, in which the said matter is introduced in ground form into a reactor and subjected to combustion without flame at a temperature of 240 to 400° C., under a pressure of 100 to 300 bars, in the presence of an oxygenated fuel, for at least 20 minutes, while stirring the medium.
By “organic matter” is meant carbon-containing matter originating from animal or vegetable entities, whether living or not. More specifically, it is matter capable of decomposing. This concept must not be confused with that of “organic compound”, a family to which, in particular, plastics and polymers belong and, more particularly, PCBs (polychlorinated biphenyls), also called, in particular in Quebec, BPCs (Biphenyles PolyChlorés) as well as polychloroterphenyls, monomethyl tetrachlorodiphenylmethane, monomethyl dichlorodiphenylmethane and monomethyl dibromodiphenylmethane which are treated in the same way as them.
According to the present invention, the treated organic matter need not be in solid form. It can clearly be in a form capable of being ground (i.e. chopped in the case of meat or fish for example).
Under preferred conditions of implementation of the invention, raw products are processed. In particular they are not trimmed.
As organic matter, there may be mentioned that of animal origin (including human) in particular animal by-products including poultry breeding and fishery by-products and animal waste.
There may be mentioned in particular organic matter of animal origin such as that from bovines, porcines, caprines, poultry, equids, rodents such as rabbits and hares. There may also be mentioned in particular waste leaving animal abattoirs or quartering plants, for example carcasses of cattle, poultry, pigs, sheep, and animal fats originating from the preparation of meats. Liquid manures and fishery waste may also be mentioned.
Some of this matter may be in the form of cadavers or carcasses. It may also comprise animal parts such as the blood, feet, head, horns, muzzle, tonsils/pharyngeal lymphatic ring, penis, tail, lungs, kidneys, oesophagus, liver, heart, diaphragm, spleen, forestomachs, stomach, testicles, trachea, larynx, extralobular bronchi, biliary vesicle, bile, fat, intestine, mesentery, anus, female genitalia, udders, foetuses, spinal cord and dura mater, vertebral column, sacrum, tendons, ligaments, nervous tissue, lymphatic tissue, blood vessels, meat not intended to be used as food. It can also comprise metabolic waste.
There may also be mentioned waste of any kind originating from the pharmaceutical industry or hospitals or veterinary hospitals for example such as dirty cottons, linen or compresses, anatomical waste of human or animal origin such as those mentioned above.
There may also be mentioned in particular organic matter suspended or dissolved in waste (also called residual) or washing water. Domestic waste water consists of effluent flushed from toilets, household water drained from kitchens and bathrooms. The waste present in this dirty water is constituted by degradable organic matter and mineral matter. These substances are dissolved or suspended. For the record, waste water systems discharge into treatment plants where the water is processed and where most of the organic matter is in the form of sludges.
Primary sludges, deposits recovered by simple decantation of waste water and displaying high concentrations of mineral matter (sand, soil etc.) but also organic matter, can be treated just as well as physico-chemical sludges, sludges which resemble primary sludges but to which a reagent has been added (salts of iron, aluminium, or other flocculating agents) in order to agglomerate the fine particles and improve the decantation, as biological sludges, also called secondary sludges, and originate from a biological purification of the water (activated sludges, bacterial beds etc.). There may also be mentioned the mixed sludges constituted by a mixture of primary and biological sludges and extended aeration sludges obtained without primary decantation with intensively aerated pollutants.
There may also be mentioned animal by-products not intended for human consumption in categories 1 2 and 3 according to the regulation of 3 Oct. 2002 setting out in France the health rules applicable to animal by-products not intended for human consumption.
Under preferred conditions of implementation of the invention, the waste is used in the process in reduced form.
By “reduced form” is meant that the pieces of organic matter or containing organic matter are small in size. They are present for example in the form of a pasty slurry. The grain size of at least advantageously 50%, preferably 80%, in particular 90% of the pieces is advantageously less than 20 mm, preferably less than 15 mm, in particular less than 10 mm, quite particularly less than 5 mm (evaluation by screening).
It is advantageous to work on a slurry of the organic matter that it is wished to treat.
The state of the products (solid, slurry, etc.) is indicated in a standard fashion for normal conditions of temperature and pressure.
The process of the invention can be implemented between 240 and 400° C., preferably between 250 and 350° C., particularly between 280 and 320° C.
The process of the invention is implemented under a pressure of 100 to 300 bars, preferably between 150 and 250 bars, preferably between 180 and 230 bars, particularly approximately 200 bars.
Oxygenated compounds may be mentioned as fuel.
Under preferred conditions of implementation of the invention, oxygen is used, in particular in the form of air optionally mixed with one or more other gases.
Under further other preferred conditions of implementation, oxygenated compounds originating from industrial waste or by-products, such as for example nitrogen (II) oxide, are used.
It is advantageous to work in the presence of an excess of fuel.
To this end, the chemical oxygen demand (COD) of the organic matter it is wished to treat can be determined beforehand. For the record, the COD expresses the quantity of oxygen necessary to oxidize the organic matter (biodegradable or not) using an oxidant, potassium bichromate.
Under further other preferred conditions of implementation of the invention, operations take place in the presence of a catalyst, in particular based on Cu, Pt, Pd, Ru, Rh, Ti, in particular on different supports such as oxides of aluminium, cerium or silicon.
The catalyst will be for example a metallic oxide, such as the oxide of selenium, rhenium or hafnium, or those mentioned in the examples.
The catalyst can be for example used at a rate of approximately 2 g/L.
It can in particular be used at a pH of approximately 12.
Under further other preferred conditions, a zeolite will be used.
The reaction time depends on the quantity of organic matter introduced at the start. The reaction time can vary between 20 min. and 120 min. for carbon concentrations comprised between 5 g and 40 g per litre, advantageously 20 to 120 min, preferably 60 to 100 min, quite particularly 75 to 90 min.
As the process of the invention is autothermal, the initial heating can be discontinued as soon as the set temperature is reached.
Under other preferred conditions of implementation of the invention, one or more input effluents are heated, for example, the fuel or the supplementary organic matter to be treated in the case of semi-continuous, or continuous, implementation using the energy produced by the implementation of the process.
Under further preferred conditions of implementation of the invention, the heat energy produced by the reaction is removed using an aqueous fluid in particular, such as using industrial effluents, and more particularly using effluents from slaughterhouses for on-site treatment of the raw animal matter.
The stirring system can be a standard bladed system. Under preferred conditions of implementation, the fuel, preferably air, performs or in particular contributes to the stirring of the treated organic matter.
In order to do this, it is advantageously injected under pressure within the organic matter.
The process of the invention can be implemented non-continuously, semi-continuously, or continuously. The reactor will be suited to the form of implementation of the process. This is generally any suitable enclosure capable of withstanding high temperature and pressure.
At the end of the implementation of the process, an aqueous suspension containing essentially minerals is obtained.
The latter can, depending on its composition, be retreated or discarded directly into the natural environment or transferred to a treatment plant.
The mineral phase is a final waste.
The process of the invention has remarkable qualities. It allows the effective destruction of the treated organic matter, in particular proteins, and quite particularly prions.
II allows this organic matter to be converted essentially into minerals, water and carbon dioxide.
The process also offers the advantage of being autothermal. When the combustion is started, it is no longer necessary to supply additional energy.
Excess energy is actually obtained, which for example allows the heating of the input effluents for example the fuel or additional organic matter to be treated. The effluents are preferably brought to the reaction temperature.
The quantity of water necessary to remove the heat energy produced by the reaction can be provided by industrial effluents, and more particularly effluents from slaughterhouses for on-site treatment of the raw animal matter. This produced energy can also be used to supplement a district heating system.
The process allows operation not only on animal meal, as is the case with incinerators, but also on raw products.
The invention can be implemented simply in a reactor capable of withstanding the above pressures, for example by using a reactor fitted with a heating system, a system for introducing fuel, a system for introducing organic matter, a stirring system, a gas-evacuation system, a bottom outlet for the mineral matter, and preferably water and bath probes.
The above properties are illustrated below in the experimental part. They justify the use of the processes described above in the production of energy.
For this reason a subject of the present application is also a process for the production of energy in which organic matter is introduced in ground form into a reactor and subjected to combustion without flame at a temperature of 240 to 400° C., under a pressure of 100 to 300 bars, in the presence of an oxygenated fuel, for at least 20 minutes, while stirring the medium and the energy produced by the combustion is recovered.
The recovery of the energy produced by the combustion can be achieved in particular by the use of one or more heat exchangers, in particular exchangers with brazed plates and fins.
The energy thus produced and recovered for example in the form of hot liquid, for example hot water, can be used in a standard fashion.
The preferred conditions of implementation of the processes described above for the destruction of organic matter also apply to the other subjects of the invention mentioned above, in particular to the processes for the production of energy.

FIG. 1 describes a type of apparatus and assembly that can be used to implement the invention, used for the realization of the following examples which illustrate the present application.

EXAMPLE 1

Treatment of a batch of raw animal matter

A batch (batch system) of 20 grams of substrate is introduced into a hot oxidation treatment reactor, and hermetically sealed.
The hot oxidation treatment reactor used is an autoclave with an working capacity of 450 mL formed from a stainless steel crucible and a cover made of Hastelloy C276, operating sub-critically. The apparatus is designed to withstand a maximum temperature of 400° C. and a maximum pressure of 30 MPa. The reactor is heated by an electric furnace with an output of 4500W, placed around the autoclave. The system is also fitted with a mechanical stirrer and a manometer. The safety of the whole is ensured by a solenoid valve and a bursting disk. The reactor also has two liquid and gaseous feed/offtake lines.
The treated substrate is constituted by 20 g of raw animal matter (8 g dry weight), not trimmed, in the form of a brown pasty slurry with a characteristic odour and a grain size of less than 5 mm.
The composition of the samples that is given below was determined relative to the dry matter.
Average composition of the raw animal matter:


	Elements (%)

DM (%)	TOC (%)	C	H	N	S	Cl	P

35-40%	60	56	8.7	5.3	0.48	0.37	1.83

DM = Dry Matter
TOC = Total Organic Carbon

Mechanical stirring is maintained continuously at 500 rpm. The furnace is then started and the thermostat adjusted so as to reach a temperature of 280° C. inside the reactor.
At the set temperature, air is injected and the pressure is set at 200 bars. The thermostat stops. A continuous flow of air is provided by means of a microleak at the outlet of the reactor. This is allowed to react for 60 min.
The heat energy produced by the reaction is removed using water.
The optimum hydrothermal oxidation reaction produces a liquid effluent. This effluent contains 1.6 g/L of TOC (including 0.8 g of acetic acid) and 1.6 g/L of ammonia. The destruction of the organic matter represents a reduction of more than 99%.
At end of the reaction, the solid phase contains approximately 400 mg of inert mineral matter, which represents a 95% reduction of the dry matter. This solid phase contains a negligible quantity of organic matter.
The gaseous effluents produced are separated and collected using a condenser then trapped in an acid (HCl) then a basic (NaOH) solution.

EXAMPLE 2

Treatment of Raw Animal Matter

The procedure is as given above in Example 1, but adding 2 g/L platinum catalyst on alumina at pH 12. The TOC value of the output effluent is not more than 60 mg/L.

EXAMPLE 3

Treatment of Raw Animal Matter

The procedure is as given above in Example 1, but adding 2 g/L platinum catalyst on alumina at pH 12. The value of the concentration of ammonia is not more than 32 mg/L.
For the three examples, it was not possible to detect the presence of proteins in the final medium by the determination technique used. The process of the invention is therefore effective in disposing in particular of prions, both in organic matter and in animal meal.

Claims

1. A process for the destruction of organic matter, in which the said matter is introduced in ground form into a reactor and subjected to combustion without flame at a temperature of 240 to 400° C., under a pressure of 100 to 300 bars, in the presence of an oxygenated fuel, for at least 20 minutes, while stirring the medium.

2. A process according to claim 1, characterized in that the organic matter is of animal origin.

3. A process according to claim 1, characterized in that the organic matter is an organic matter originating from cells suspended or dissolved in waste water (residual water).

4. A process according to claim 1, characterized in that the grain size of at least 50% of the pieces of the organic matter is less than 20 mm.

5. A process according to claim 1, characterized in that it is implemented between 250 and 350° C.

6. A process according to claim 1, characterized in that it is implemented between 150 and 250 bars.

7. A process according to claim 1, characterized in that the oxygenated fuel comprises air.

8. A process according to claim 1, characterized in that it is implemented in the presence of an excess of fuel.

9. A process according to claim 1, characterized in that it is implemented in the presence of a catalyst, for example based on Cu, Pt, Pd, Ru, Rh, Ti.

10. A process according to claim 1, characterized in that one or more input effluents are heated, for example the fuel or the supplementary organic matter to be treated in the case of semi-continuous, or continuous, using the energy produced by the implementation of the process.

11. A process according to claim 1, characterized in that the fuel is injected under pressure within the organic matter in order to stir it.

12. A process for the production of energy in which an organic matter is introduced in ground form into a reactor, subjected to combustion without flame as defined in one of claims 1 to 11 and the energy produced by the combustion is recovered.