ES2224863B1 - PROCEDURE FOR THE USE OF DISPOSAL PLASTICS AS A CARBON NUTRITIVE SOURCE OF INDUSTRIAL BIOTECHNOLOGICAL INTEREST MICROORGANISMS. - Google Patents

Abstract

Procedure for the use of waste plastics as a carbonated nutrient source of microorganisms of industrial biotechnological interest. The present invention relates to a process that includes the pyrolytic treatment of plastic waste polymers and the use of the resulting products as a source of cheap carbon in the cultivation of microorganisms of industrial interest. In particular, the present invention is very useful for converting polyethylene film from agricultural greenhouses, degraded by the sun, into saturated and unsaturated linear liquid hydrocarbons and their transformation into commercial, primary and secondary microbial metabolites.

Description

Procedure for the use of plastics of waste as a carbonated nutritional source of microorganisms from industrial biotechnological interest.

Object of the invention

The present invention relates to a procedure that includes pyrolytic polymer treatment waste plastics and the use of the resulting products as a source of cheap carbon in the cultivation of microorganisms of industrial interest In particular, the present invention is of great utility to convert polyethylene film from agricultural greenhouses, degraded by the sun, in hydrocarbons saturated and unsaturated linear liquids and their transformation into microbial, primary and secondary metabolites, for application commercial.

State of the art

Plastics obtained in the industry petrochemicals contribute significantly to pollution environmental, not only from land areas but also from Waters and atmosphere. As an example, you can cite the very serious problem of waste disposal industrial mixtures of thermoplastic materials with a high Polyvinyl chloride content. They are currently incinerating thousands of tons and, as a consequence, polluting the atmosphere with carcinogenic hydrocarbons, hydrochloric acid (approximately 60% of those amounts), halogenated derivatives and, quite possibly, with dioxins, highly dangerous substances whose lethal doses in laboratory animals are 500 times that of strychnine and more than 100,000 that of sodium cyanide. Is embryotoxic, teratogenic and suspected to cause cancer in the humans. Very recently, October 2002, the Court of Justice of the European Communities, the highest legal body of the Union European, issued an opinion censoring the incineration of plastics There are currently no solutions to these facts, since recycling processes do not seem to be a global alternative to this problem

A small proportion of plastics petrochemicals are being recycled, through processes of regeneration that allow its subsequent use as polymers of lower quality. However, it does not appear that this recycling is capable of absorbing, in the future, all plastic waste urban, industrial and those from the "plasticultivo", fundamentally for three reasons:

a) Not only urban waste, but also many of the industrialists are usually mixtures of different polymers, with the consequent difficulty of separation and classification.

b) The agricultural film, submitted for one or two campaigns to the intense action of UV radiation, ends crystallizing and losing, therefore, its properties plastic.

c) The recycling process turns out to be laborious and complex, especially under the premise of producing low materials quality.

An application, certainly different from those mentioned above, consists of transforming plastics into chemical products that can be used at other industrial levels. Thus, there are currently industrial processes in which waste plastics are used to generate combustible oils that are used " in situ " to produce energy.

Devices are known in the art for the pyrolysis of polymers, in which the plastic is introduced in externally heated rotary kilns. A problem with these furnaces is the sealing of the hot rotary cylinder and the tank of carbon in the walls, which make it less and less conductive heat, with the problems that entails.

Vertical reactors have also been used externally heated with high pressure steam or eutectic of molten salts (potassium nitrate / sodium nitrate / sodium nitrite) using mechanical pumps for handling. The first method it presents among others the inconvenience of high pressures and the second, in addition to the corrosion problems of the pump, the mismatch in phase changes (liquid and solid) in the starts and stops of the process, the very serious risk of explosions if they accidentally contacted the eutectic and hydrocarbon reaction mass, both at high temperatures

Equally known are fluid beds for thermoplastic pyrolysis at high temperatures. These have the inconvenience of the high heat requirement, difficulty in separation of impurities that accompany the thermoplastic as well such as the removal of coal produced in the process.

Tubular reactors and extruders that present even greater inconveniences than above regarding the separation of impurities, deposits of coal, moving parts at high temperatures, etc.

Lately, procedures have been described in those that supply the heat needed for pyrolysis by doing use of supercritical water (EP-0814143) or sand hot (EP-0823469). Both processes present serious difficulties, such as high work pressures or use of hot sand in motion, with abrasion problems, transport, heating, maintenance of the inert atmosphere, etc.

The idea of using molten lead is known for the thermal conversion of polymers, introducing pieces of the solid polymer in a bath of molten lead. US patents 4925532, US 5085738 and WO 96/00268 describe apparatus for processes of pyrolysis on a molten metal bath. However all these  processes have too many operational problems to be commercially viable. Such problems include difficulty in separation and isolation of polyvinylchloride, which would produce HCl during the process in the molten lead bath, in the maintenance of the inert atmosphere during the introduction of polymer in said bath, which would cause lead to lead to the corresponding oxides that in turn would have to be removed and, in as regards WO 96/00268, in addition, little effectiveness in the heat exchange process between the metal molten and thermoplastic, due to the small surface of heating as a result of inefficient mixing between both materials To date none of the processes described In bibliography it has reached commercial importance. I only know they have built pilot plants, because the known methods, taking into account current oil prices, they are not economically profitable

Moreover, since ancient times and today microorganisms are used to produce products industrially commercial, from mineral nutrients and carbohydrates such as carbonated raw material in the culture broth. But the Carbohydrates are relatively expensive and in many cases higher price than products produced through the process of fermentation. That's why we thought of another source cheaper carbon.

There is considerable documentation about use of oil or any of its hydrocarbon fractions as a substrate in the fermentation of microorganisms and, in fact, several commercial plants in the world that produced thousand tons per year of unicellular proteins used in feeding. But a few years ago those facilities fell into disuse for several reasons: some as a result of the high price reached by oil and others because not all hydrocarbons contained therein are metabolized by microorganisms with equal ease. Thus, the linear ones are more easily attacked than branched or cyclic. A third reason, also of great importance, was the danger of toxicity in the use of these unicellular proteins as products food because they could carry toxic substances from the remains of aromatic hydrocarbons from of the substrate, so a laborious process of purification.

Technical problem raised

There is no background on the use of substrates from the degradation of plastics not Biodegradable for microorganism culture.

Almost exclusively linear hydrocarbons, saturated and unsaturated, coming from the degradation of the most plastics (excluding those containing rings aromatics such as polystyrene, for example) can be a important source for its use as a raw material cheap carbonate for the industrial cultivation of microorganisms of high biotechnological interest (in the production of phytohormones, vitamins, antibiotics, unsaturated fats, proteins, amino acids, etc.)

This way two serious ones are solved problems: one of an economic nature and the other of a kind ecological.

Explanation of the invention.

In view of the technical problem raised, the The present invention aims at:

1) Remove plastic waste from the environment environment, giving it a nobler utility than its combustion.

2) Establish a procedure to convert the solid waste plastic material in a liquid reducing the problems arising from high pressures, partial carbonization what happens when supplying heat to the polymer, avoid products abrasive, corrosive or oxidizing as the indicated salts previously, as well as the use of moving parts at high temperatures

3) Select the appropriate microorganisms capable of metabolizing the hydrocarbons resulting from the process and establish the ideal conditions for this to take place. From this way biomass would be obtained from liquid hydrocarbons from sources other than oil, which differ of them in that they are linear in their totality, absent of products aromatic and high olefin content and, of course, of lowest price.

It is therefore the object of this invention a procedure for the use of plastics of waste as a carbonated nutritional source of microorganisms from industrial biotechnological interest that includes the following stages:

- manual removal of impurities from plastic of waste.

- crushing of waste plastic

- removal of moisture and fine minerals of waste plastic

- fusion of waste plastic to a temperature between 250ºC and 350ºC

- pyrolysis of molten plastic to a temperature between 400 and 550 ° C, using metal molten, in particular liquid lead, at a temperature comprised between 500 and 600 ° C as heat transfer fluid

- two-stage condensation of the vapors from the previous stage using the condensed oil for the cultivation of microorganisms, in particular bacteria, fungi and yeasts capable of metabolizing hydrocarbons.

The fusion of the plastic takes place taking advantage of the heat of the exhaust gases from the heating of molten metal used in the pyrolysis stage and the gases from said melting stage are cooled, washing the incondensables in countercurrent to retain the hydrochloric acid and gaseous hydrocarbons that are used as fuel.

Condensation is carried out in two stages:

- condensation of all knitted compounds boiling above 350ºC and condensate recycling at pyrolysis reactor.

- condensation to room temperature gases from the initial stage using the gases untreatable after washing as a fuel of the process pyrolysis

In general, the compounds resulting from apply any cracking process to waste plastics it they can use for the cultivation of microorganisms, in particular bacteria, fungi and yeasts capable of metabolizing hydrocarbons

To do this, microorganisms capable of metabolize hydrocarbons are grown in a medium with the compounds resulting from pyrolysis or cracking of plastics of waste until they reach an adequate development, according to will detail later in this report.

Brief description of the figures

Figure 1 is a schematic representation of an installation to obtain liquid hydrocarbons from thermoplastic materials

Figure 2 represents the reactor 8 where Pyrolysis takes place.

Detailed description of the invention

It is mandatory that it be concretized in detail in this section the present invention, however it should be understood that this can be done in different ways in terms of materials, dimensions, shapes or relative positions of the components described herein, so the scope of the invention does not should be limited to what is going to be specified, since this explanation It should be taken as an example. The invention will be described by making Reference to the figures.

Figure 1 shows a representation schematic of an installation to obtain hydrocarbons from of waste plastics. The waste plastic coming fundamentally of agricultural greenhouses, 1, is constituted in 85% of polyethylene film being the remaining 15% of composition varied (wire, sand, dust, etc.). During the stage of Breaker feed, 2, manually remove the larger impurities and pneumatic air transport hot is taken to storage tank 4, through the Cyclone 3, removing moisture and some of the finest minerals in This process. This material is introduced through the valve doser 5 in the feeding system 6 which can be a endless thyme, piston press or any other device analogous. Through this system the material enters the vessel 7 and melts at 250-350 ° C, heating externally with the exhaust gases from the furnace heating of liquid lead used as an agent of heat transfer in the pyrolysis reactor 8. In this way PVC is also broken down that may occasionally accompany the polyethylene. The gases from this operation are cooled with the condenser 9 bringing the liquid to the tank 16 and the incondensables are washed in countercurrent with water or solution of sodium hydroxide in towers 12, to retain the acid hydrochloric in tank 14 and gaseous hydrocarbons in the tank 15, which will be used as fuel in the home 17.

By gravity, or with the help of a pump mechanically, molten plastic is carried along with fines not pyrolyzables remaining to the pyrolysis reactor 8. This consists of a tank that in the example we have considered cylindrical (figure 2), filled to the level V of the liquid to be pyrolyzed. On the part upper molten plastic heated to 250-350 ° C from container 7. In this reactor the plastic is pyrolyzed at 400-550 ° C, heating with molten metal, particularly liquid lead, which circulates through an inner or outer coil or through a shirt that wraps around the reactor. The metal is recirculated towards the boiler 18 for heating. This transfer could take carried out with the help of a mechanical pump although it is much better still do it by means of an electromagnetic induction pump, a lot greater durability and lower maintenance cost, due to the absence of moving parts, joints, etc., subjected to such high temperatures The use of this pumping system is possible here with help of a variable magnetic field due to conductivity electric of the liquid to be pumped.

The reactor 8 (see figure 2) is provided with a agitator and solidarity to its vertical axis a system of scraping to separate particles that can be deposited in walls. In the example that illustrates this invention it has been considered an anchor stirrer and chains 22 that scratch said walls during the turn.

The condensation of the vapors from the Pyrolysis is carried out in two stages. In the first one it condenses in heat exchanger 10 everything that boils above 350 ° C and recycled to reactor 8. The second condenser 11 cools to ambient temperature the gases that leave the condenser 10. The condensed liquid is carried to tank 16 and the non-condensable gases, after washing, they are taken to the tank 15 to be used as a fuel for the pyrolysis process.

Actuating valve 19 eliminates periodically the non-pyrolyzable impurities that are deposited in the bottom of the reactor and recover to recirculate to the reactor the high molecular weight hydrocarbons that can accompany the solids, for example by a hydrocyclone or by any of known separation procedures liquid-solid, 20. Thus, it is not necessary to wash previously plastics to remove adhering dust.

Finally, all the pipes, pumps, valves, etc. Where products that solidify should circulate at room temperature they are provided with a system of electric or fluid heating, in order to fluidize it at startups. Also the reactor 8 can be heated to this effect by the gases coming from the oven 17, through entry 21.

In the fermentation process they can be used the oils obtained by any of the pyrolysis methods of plastics described in bibliography or, better yet, by the one described in this invention, since in many of the other processes the resulting substances have toxic impurities that could make viable as raw materials in obtaining metabolites for human or animal consumption.

In the present invention can be used species of bacteria, fungi and yeasts capable of metabolizing hydrocarbons

Among the bacteria it has been shown that several species belonging to the genera grow: Pseudomonas, Alcaligenes, Cellulomonas, Brevibacterium, Corynebacterium, Mycobacterium, Streptomyces, Bacillus, Flavobacterium, Sarcina, Achromobacter, Nocardia and Aerobacter .

With regard to yeasts, species of: Candida, Torulopsis, Saccharomyces, Pichia, Hansenula, Oidium, Neurospora and Rhodotorula have been grown.

The growth of fungi belonging to the genera has also been verified: Fusarium, Penicillium, Aspergillus, Talaromyces, Chaetonium, Wardomyces, Gliocladium, Paecilomyces, Trychoderma, Pleurotus, Cladosporium and Mortierella .

The species have been identified according to the relevant keys and are deposited in the University of Buenos Aires (Argentina) and at the Station Experimental Zaidin of the CSIC (Granada).

The present invention, in terms of capacity of using the oil from the pyrolysis of plastics, It is described in more detail with reference to the examples they give below, which, however, do not try to limit The scope of it. In these examples a fraction of oil obtained by the process claimed herein, with the following distillation ASTM 1160:

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one

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and with the following composition:

2

Embodiment of the invention Example 1 Inoculum preparation

It is based on a strain of Rhodotorula mucilaginosa that is necessary to adapt beforehand so that it can assimilate carbon from hydrocarbons as the only carbon source. In this sense, the yeast is grown in an erlenmeyer flask containing 75 mL of the sterile mineral medium to which 0.150 mL of the hydrocarbon mixture from the pyrolysis of the plastic is added and whose composition is indicated above. The culture medium has the following composition: monopotassium phosphate, 7 g / L; magnesium sulfate, 0.2 g / L; sodium chloride, 0.1 g / L; ammonium chloride, 2.5 g / L; tap water (containing trace amounts of mineral elements), 100 mL / L; yeast extract, 1 mg / L and distilled water to complete 1L. It is grown for three days with mechanical stirring at 30 ° C. 5 mL of this culture are taken and added to another erlenmeyer that contains the same amounts as the previous one of mineral medium and hydrocarbons. It remains another three days with agitation. The operation is repeated several times, for example 4 or 5. To an erlenmeyer flask containing 1L of sterilized mineral medium, 2 mL of hydrocarbon mixture is added and seeded with 20 mL of inoculum from the previous culture. Incubate for 36 hours at 30 ° C with mechanical agitation. It is centrifuged at 30 ° C and the collected yeasts constitute the inoculum that we are going to use.

Cultivation of Mucilaginous Rhodotorula

150 mL of culture medium are taken previously mentioned and 1.2 g of the mixture of hydrocarbons from pyrolysis and whose composition we have described above and sterilized at 121 ° C for 15 minutes. It adds yeast inoculum, which is equivalent to 125 mg dry weight, and the suspension is maintained with an air flow with a flow rate capable of maintaining vigorous stirring at 30 ° C, compensating the evaporation with periodic additions of distilled water. After 9 hours 40 mg of surfactant are added, for example Tween 80. The pH is adjusted to 8, centrifuged and the phase solid-paste is washed with water containing 0.25% of the same surfactant, it is centrifuged and the solid part is wash again and centrifuge, with which yeasts are obtained hydrocarbon free. Finally it is washed with pure water at 60 ° C to remove the remains of the surfactant. The product like this obtained weighed 186 mg, after drying at 70 ° C until heavy constant.

Example 2 Inoculum preparation

In a 0.5 L erlenmeyer, 100 mL of a culture medium with the following composition were prepared: dipotassium phosphate, 5 g; diammonium phosphate, 1 g; sodium sulfate, 0.05 g; hydrated magnesium sulfate, 0.04 g; hydrated ferrous sulfate, 0.002 g; hydrated manganous sulfate, 0.002 g; sodium chloride, 0.002 g and water up to 100 mL. The pH is regulated between 7.2 and 7.7; 0.5 g of oil from the pyrolysis are introduced and sterilized at 121 ° C for 15 minutes. It is inoculated with approximately 0.0001 g of Pseudomonas putida . It was grown under stirring at 30 ° C for 48 hours, keeping the pH between 6 and 7.5. After this time, 5 mL of culture is taken and taken to another erlenmeyer that contains the same amounts as the previous one of mineral medium and hydrocarbons, another 48 hours is kept under stirring and the operation is repeated several times (4-5) .

Pseudomonas putida culture

In a 0.5 L erlenmeyer, 100 mL of the previous mineral medium is poured and 2 g of pyrolysis oil is introduced, the pH is regulated between 7.2 and 7.7 and sterilized. It is inoculated with 5 mL of Pseudomonas putida culture prepared above and grown with shaking at 30 ° C for 48 hours. After this time and after successive centrifugation, washing and drying in a manner analogous to that indicated in Example 1, 630 mg of dry biomass are obtained.

Example 3

The same culture medium as in example 1 was used and the inoculum of Penicillium chrysogenum was also adapted in a similar manner. In a 0.5 L erlenmeyer, 10 mL of the medium, 2 g of pyrolysis oil are placed, sterilized and then 5 mL of inoculum is introduced. It was stirred at 30 ° C for 7 days. After working similarly to examples 1 and 2, 581 mg of dry biomass are obtained.

Claims (6)

1. Procedure for the use of waste plastics as a carbonated nutritional source of microorganisms of industrial biotechnological interest that includes the following stages: - manual removal of impurities from plastic of waste. - crushing of waste plastic - removal of moisture and fine minerals of waste plastic - fusion of waste plastic to a temperature between 250ºC and 350ºC - pyrolysis of molten plastic to a temperature between 400 and 550 ° C, using metal molten, in particular liquid lead, at a temperature comprised between 500 and 600 ° C as heat transfer fluid - two-stage condensation of the vapors from the previous stage characterized in that the condensed oil is used for the cultivation of microorganisms, in particular bacteria, fungi and yeasts capable of metabolizing hydrocarbons. 2. Procedure for the use of waste plastics as a carbonated nutrient source of microorganisms of industrial biotechnological interest according to claim 1, characterized in that the fusion of the plastic is carried out taking advantage of the heat of the exhaust gases from the heating of the molten metal used in the pyrolysis stage. 3. Procedure for the use of waste plastics as a carbonated nutrient source of microorganisms of industrial biotechnological interest according to claims 1 and 2, characterized in that the gases from the melting stage are cooled, washing the non-condensables in countercurrent to retain the hydrochloric acid and gaseous hydrocarbons that are used as fuel. 4. Procedure for the use of waste plastics as a carbonated nutritional source of microorganisms of industrial biotechnological interest according to claims 1-3, characterized in that the condensation is carried out in two stages: - condensation of all knitted compounds boiling above 350ºC and condensate recycling at pyrolysis reactor. - condensation to room temperature gases from the initial stage using the gases untreatable after washing as a fuel of the process pyrolysis 5. Procedure for the use of waste plastics as a carbonated nutrient source of microorganisms of industrial biotechnological interest, characterized in that the compounds resulting from applying any cracking process to said waste plastics are used for the cultivation of microorganisms, in particular bacteria, fungi and yeasts capable of metabolizing hydrocarbons. 6. Procedure for the use of waste plastics as a carbonated nutrient source of microorganisms of industrial biotechnological interest according to claims 1-5, characterized in that the microorganisms capable of metabolizing hydrocarbons are grown in a medium with the compounds resulting from the pyrolysis or cracking of waste plastics until they reach proper development.