WO1990011144A1

WO1990011144A1 - Elimination of and beneficial use of harmful wastes

Info

Publication number: WO1990011144A1
Application number: PCT/SE1990/000090
Authority: WO
Inventors: Bengt Ahling
Original assignee: Cementa Ab
Priority date: 1989-03-22
Filing date: 1990-02-13
Publication date: 1990-10-04
Also published as: SE8901022D0; AU5351290A; SE8901022L

Abstract

Environmentally harmful waste is hard to handle and the capacity for an economical handling is not sufficient. According to the invention such waste can now be worked up to a full worth fuel which can replace conventional fuels, which can be stored and has a specific composition and which gives little harmful air pollution, and a solid residue which can be deposited cheap and safe. According to the invention the waste is fractionated in centrifuges or cyclones (5, 10) into a solid part, in which the main part of the heavy metals in the waste are enriched and a liquid part containing oils, solvents and dissolved substances. The solid part containing plastics, pigments, insoluble oil residues, organometallic compounds, etc. is mixed, after drying (12) and optional grinding with other wastes, such as Cefyll R with which it can form a very sparingly soluble, monolithic compound and be deposited. The liquid part is used as a fuel.

Description

ELE INATION OF AND BENEFICIAL USE OF HAHMI-UL WASTES.

The present invention relates to a product of mixtures of diffe¬ rent types of harmful, liquid and/or semi-solid wastes consis- ting of a liquid combustible mixture of different liquids con¬ taining dissolved organic substances and a solid residue, and a method of manufacturing the product-.

The invention implies a riddance of environmentally harmful waste with no environmentally harmful or health hazarous sub¬ stances escaping out into the surroundings and with a reuse which to a large extent is independant of the original composi¬ tion of the starting materials, which is economically self- supporting and which does not nessecitate any sofisticated intermediate treatments, such that the products and residues emanating from the process can be further used in a harmless and safe way.

In view of the increasing environmental consciousness, the large and increasing amounts of waste, the knowledge of the serious injuries which can be caused by wastes and the difficulties which exist in getting rid of the wastes, much work have been put into the effort of reducing the amounts of waste and the risks with harmful wastes.

The Swedish institution Naturvardsverket has in an investigation entitled "Avfallet, Miljδn; Naturvardsverket 1988" estimated the amount of wastes in Sweden to about 52 million tons, whereof about 20 million tons can be re-used. The scope of the term "waste" is very unclear, but with the definition "material being in wrong place" the net amount of waste can be estimated to about 32 million tons a year, and it can be drastically reduced with a better care-taking for re-use and/or altering of manufac¬ turing processes and raw materials.

From household garbage, estimated to 2.5 million tons/year, pa¬ per, glass, aluminium cans etc. are collected and re-used and further large amounts are composted, fibre from the cellulose

CTED industry is re-used, being fed back into the production and rind is used as a fuel.

Mercury batteries are replaced by other less dangerous batte- ries; freons are replaced by other substances; the use of cad¬ mium is minimized; the concentration of lead in gasoline is re¬ duced successively to nil; catalysts are used to purify the ex¬ hausts from cars; paints and lacquers are based on water instead of on solvents, etc.

The industrial wastes are often harmful to the environment and must be made harmless in some way in order not to poison the atmosphere, water or earth on deposition or combustion, and the present invention relates to the re-use and riddance of part of the very large amounts of such harmful and hard-to-treat wastes .

Naturvardsverket has in their general advice "Allmanna rad, page 857, Naturvardsverket 1987" mentioned those wastes presently being regarded as the most dangerous wastes, and those of the listed main groups being the object of the present invention are oil waste, solvent waste, paint or lacquer waste and glue waste, that is waste consisting of a mixture of liquid and solid or semi-solid substances and which might contain harmful substances from the other main groups, such as e.g. cadmium, heavy metals, etc. Such wastes are produced in large amounts, in the order of 500,000 tons a year and the riddance thereof is both difficult and expensive.

The ordinary methods of getting rid of waste with a possible re- use of part of the waste and combustion and/or depositing the rest can not be performed without certain measures or pretreat- ments being performed. Thus, the waste can not be deposited in its prevailing form and a combustion demands special plants in order not to produce poisonous flue gases and poisonous dust .

The object of the invention is to take care of mixtures of sol¬ vent, oil, paint and lacquer and glue wastes independent of in which amounts the respective waste are contained in the mixtu- res . Individual waste has earlier being taken care of for reco¬ vering part thereof and riddance of the rest, usually in connec¬ tion with the industry and production where the waste produced, but in the past a recovery of useful components of such mixtures and a safe deposit of the residue in a satisfactory way has not been possible in an economically acceptable way.

At e.g. spray painting processes the solvents may to a certain extent be recovered from lacquer sludge and from ventilation devices, but the solvent can be returned into the production process only if similar lacquers are used all the time. However, generally there are different lacquer types, and a solvent from one type of lacquer can be completely unsuitable for another paint. Use of a recovered solvent mixture therefor demands a separation of the different solvent components and this is in many cases economically very unprofitable.

The same problem exists with oil waste, which may contain sludge and precipitates from heavy oil cisterns, motor oils, lubrica- ting oils, cutting oils, oil-containing chips from metal proces¬ sing, cleaning agents and solvents from washings, collected oil waste from cleaning of shores and releases from ships, etc.

As with paint waste, refining of oil waste is possible provided that a relatively homogenous waste prevails, e.g. spill oil from oil exchanges in motor vehicles and the like, but this is only the case with a very small part of the large amounts of oil waste.

Products or fractions of the greatly varying mixtures of liquid and/or semi-solid substances to which the present invention re¬ lates can only be re-used to a very small extent for production without an extensive and uneconomical work-up and for the rid¬ dance the only possibility has been combustion of it all. How- ever, large amounts of heavy metals might be contained therein, which upon combustion will follow the flue gases and dust out into the atmosphere. If the combustion is not performed under certain, controlled conditions in specialized plants there is also a risk for the formation of poisonous organic compounds at the combustion, for example halogenated dibenzodioxines and dibenzofuranes .

As has been pointed out above prior art technique has been directed towards a certain limited type of waste, but heretofore nobody has succeeded in taking care of and making useful the arbitrary mixtures of liquid and semi-solid, harmful wastes existing in reality, in a cost-effective way.

As an example of such prior art attempts to recover useful com¬ ponents from paint wastes might be mentioned the japaneese pa¬ tent Sho-55-810, according to which lacquer sludge is dried, the volatile constituents are condensed and the solid residue is ground and is used as an additive to cement .

According to EP-A-222 851 paint residues are diluted with up to 50% additional solvent and/or are heated to a viscosity of less than 100 cSt and are then centrifugated in order to separate off the solvent. The residue can then be ground to granules and be added to concrete. In this patent is also given some information about the actual amounts of paint wastes where only the so cal¬ led lacquer sludge from lacquer plants in West Germany is about 150,000 tons a year, to which then are added all the rest of the paint wastes, non-sellable paints, excessive paint residues and so on. The patent also discloses as an example of the approxi¬ mate composition of lacquers, lacquer sludges and other paint residues about 33 % binders such as nitro cellulose, PVCl-PVAc, polyester resin, epoxy resin, 27 % organic solvents, benzen, xylene, carbon tetrachloride, alcohols and esters, etc., 26 % finely ground pigments dispersed in the lacquer, 14 % dyestuffs, fillers such as chalk, caoline, baryte white and so on and dif¬ ferent other auxiliary substances .

The product according to the present invention is characterised in that the combustible liquid mixture is comprised of a mixture of solvents, dissolved resins, softening agents, dyestuffs and other soluble substances and in that the solid residue is com- prised of insoluble pigments, organometallic driers, heavy metal compounds and other insoluble or sparingly soluble substances, miscible with other waste products to insoluble deposits.

The method according to the invention is characterized in that harmful liquid and/or semi-solid waste after removal of coarser material in a continous centrifuge or a cyclone is divided into one liquid fraction with a substantially decreased heavy metal content and a more or less solid fraction, which after drying can be mixed with other solid material to form sparingly soluble masses which can be deposited without any risk of leaching.

The invention thus implies that from the harmful wastes in ques¬ tion are fractionated a liquid product with a specific composi- tion, good storage properties and a substantially lower content of heavy metals than the original waste, preferably for use as a fuel, and a solid product which together with other types of waste products can form an insoluble monolitic compound, which can be deposited without any risk of leaching of heavy metals or other environmentally harmful substances.

The treatment according to the invention is carried out such that the waste is first coarse filtered in order to remove coar¬ ser contaminants, such as cans, stones, fabrics, twist and other larger objects. The filtered waste is then centrifuged in a decanter centrifuge. In order to get a centrifugable consistenc a thinly liquid waste can be added to a more thickly liquid waste and dilution can also be performed with solvent waste, spirit, liquid product being centrifugated off, fuel oil and so on. With appropriate additions the centrifugation can also be facilitated for example with a flocculation or precipitation. Addition of for example spirit to certain lacquer wastes thus often results in a flocculation which can facilitate the centri fugation conciderably. A decanter centrifug, such as Alfa-Laval ANX which gives a more or less solid residue with up to 80-95 % dryness, and a stream of liquid which is substantially free of heavy metals, which eventually can be further treated in e.g. a separator centrifuge, such as Alfa-Laval BRPX. The liquid product contains the larger part of the liquid sub¬ stances which are contained in the wastes, alcohols, esters, oils etc. , that is the liquid substances which are mentioned in the publication from Naturvardsverket mentioned above, and plas¬ tics and resins, pitch, asphalt and other soluble substances, soluble therein. It can be used as a fuel or an additive to fuel preferably in cement furnaces, blast furnaces, lime sludge fur¬ naces and other furnaces at such high temperature that e.g. halogenated dioxines formed from the comprised organic halocom- pounds are broken down.

The invention will now be more elaboratly described with refe¬ rence to the figure, which illustrates a flow scheme of one example of a separation plant according to the invention. In or¬ der to be used for starting materials of many different kinds alternative or further treatment steps might be added when needed, as well as the design may be simplified in the case only certain types of wastes are to be treated.

One or several wastes are mixed with stirring in the tank 1 and are coarse filtered 2 optionally after dilution or additions from the container 3. The filtered-off coarser components 4 can be dried and be comprised in the solid residues from the plant, be burned or be taken care of in another way and the filtrate is fed to a separator 5. The separator is preferably a decanter centrifug or one or several cyclones for continuous treatment. From the separator comes a continuous liquid stream (fuel) 6 which is fed to a cistern or storage tank 7 or equivalent, and from which one part 8 when needed might be led to the container 3.

The highly viscous part of the waste from 5 has a dry content of up to 80 - 95 % by weight and a composition which depends on the contained material. This part is led to an optional after treat¬ ment step 11. All or part of the fuel 6 can be fed to a separa¬ tor centrifuge 10 for further treatment and separated material 9 can be fed back to the decanter centrif ge or to 11. After the optional after treatment 11 the solid waste is dried in a dryer 12 and is led further through an optional further af¬ ter treatment 13 to a mixer or a storage 1 . In the after treat¬ ment step 11 granulate, slag, ash, sand, sawdust etc. can be added and mixed-in in order to make a sticky mass more easy to handle. Further, one part of Cefyll® or other material can be mixed in in the after-treatment 13, where also a grinding can be performed.

From the dryer 12 one stream 15, 16 of fuel and water is fed to the container 3 or to a distillation step 17. The distillate 18 is fed to the container 3 and the rest 19 is to the largest extent water.

The plant also comprises stirrers, pumps, valves, conveyers, pipe conduits and further ordinary equipment.

After coarse filtering thickly and thinly flowing wastes can be mixed in the tank 1 to a suitable consistency, optionally with dilution from the container 3. Highly viscous and/or semi-solid waste, dried paint and the like can also be diluted/dispersed to a centrifugable consistency in the mixing tank 1.

The fuel 6 produced is sold as light fuel and consists of a mix¬ ture of solvents of different kinds, hydrocarbons, ketones, alcohols, esters, oils, etc. and dissolved substances, plastics, resins, softening agents, dyestuffs, etc. The fuel has a sub¬ stantially reduced content of heavy metals and is free from solid particles and can completely or partly replace other solid or liquid fuels for example in cement furnaces, blast furnaces, lime sludge furnaces and so on.

Certain wastes should be able to be used directly as a fuel, but as no security for a certain composition cannot be given, the risk for process disturbances is quite big, esp. for a sedimen¬ tation and precipitation to take place in tanks and conduits, as well as the risk for environmentally harmfull discharges. The light fuel according to the invention can in contrast thereto be maintained at a certain and guaranteed composition and the ana¬ lytical values from a large number of work-ups has been shown possiboe to be held within the limits below:

T.iσht-. fuel ar.r.nrdinσ to the invention

Density at 15°C 0.80 - 0.95

Viskosity at 20°C 1 - 5 cSt Lowest flow temperature < -15°C

Flash point < -21°C

Cal. heat value > 6000 kcal/kg

Ash 0.6 - 0.8 %

Sediment < 0.5 % Water < 0.5 %

Na < 100 ppm

V < 20 ppm

Zn < 300 ppm Ca < 200 ppm

Cd < 1 ppm

Pb < 100 ppm

Ni < 10 ppm

Cr < 50 ppm PCB < 1 ppm

Cl < 0.5 %

S . < 0.5 %

Br < 0.1 %.

Another important advantage over direct use of non-controllable waste is that the light fuel according to the invention does not give any deposits or sediments in tanks, pipes, valves etc., and therefor the risk of clogging of conduits and nozzles is elimi¬ nated.

The dry solid waste 14 can be deposited after mixing with Cefyll® without risk of leaching of harmful substances . Cefyll® is the object of our patents SE 8401776-3, 8403582-3, 8704111-7, 8405344-6, and is elaborately described in these patents. It is mainly comprised of other waste materials, fly ash, blast fur¬ nace slag and the like with a small addition of Portland cement or lime. Deposited Cefyll® hardens into a solid, impermeable, unsoluble, ageing resistant mass without any tendencies of crack formation. Cracks resulting from outer influences is moreover self healing.

Into Cefyll® can be mixed up to 25 - 80 % by weight of the dry solid waste, whereby a monolitic compound with very low solubi¬ lity is formed, from which no measureable leaching takes place even after a very long time. Similar structures hundreds of years old are well kept without any signs of influence. Organic materials contained therein will be occluded in a constant envi- ronment and even if they are altered in any way they are perma¬ nently encapsulated.

Earlier deposits with embedments in concrete are much more ex¬ pensive and have a tendency of crack formation and thereby agg- ressive substances from the environment can have effect and re¬ sult in leaching.

At deposits on asphalt the ageing of the asphalt will be noti¬ ceable already after som tens of years, whereafter heavy metals can diffuse out into the environment.

Claims

0/11144 -j QC l a i m s

1. Product manufactured from mixtures of different types of environmentally harmful, liquid and/or semi-solid wastes consis- ting of a liquid, combustible mixture of different liquids con¬ taining dissolved, organic substances and a solid residue, cha¬ racterized in that the combustible mixture of liquids is com¬ prised of a mixture of solvents, dissolved resins, softening agents, dyestuffs and other soluble substances and in that the solid residue is comprised of insoluble pigments, organometallic driers, heavy metal compounds, miscible with other waste pro¬ ducts into insoluble deposits.

2. Combustible product according to claim 1, characterized by a content of

Ash 0. ,6-0 .8 w.-% Sediment < 0.5 w.-%

Sodium < 100 ppm Vanadium < 20 ppm

Zink < 300 ppm Calcium < 200 ppm

Cadmium < 1 ppm Lead < 100 ppm

Nickel < 20 ppm Chromium < 50 ppm

PCB < 1 ppm Chlorine < 0.5 w.-%

Sulfur < 0.5 w.-% Bromine < 0.1 w.-%

3. Method of manufacturing a product according to claim 1, characterized in that environmentally harmful liquid and/or semi-solid waste after removal of coarser material (1) is sepa¬ rated in a contiuous centrifuge or a cyclone (5) into a liquid fraction (6) with substantially reduced heavy metal content and a more or less solid fraction which after drying (12) can be blended with other solid material in order to form sparingly so¬ luble masses which might be deposited without any risk of leach¬ ing.

4. Method according to claim 3, characterized in that the waste before the fractionation is diluted with the liquid pro¬ duct and/or coagulants and other fractionating agents.

5. Method according to any of claims 3 or 4, characterized in that all or part of the reject from the fractionation is treated in a second step in a separator centrifuge (10) , from which at least a part of the reject is led back to the first fractionating step and/or to an after-treatment step (13) .

6. Method according to any of the preceeding claims, charac¬ terized in that the rejects from the fractioning after an op¬ tional admixing (11) of solid material for better handling pro- perties are dried (12) and in that the leaving substances after optional distillation (17) before dewatering are used for dilu¬ tion of the starting material.

7. Use of liquid substances consisting of a mixture of sol- vents and dissolved substances substantially free of heavy me¬ tals separated from environmentally harmful waste, as fuel and/or additive to fuel preferably in industrial furnaces, such as cement furnaces, blast furnaces, lime sludge furnaces, etc.