WO2015199561A1

WO2015199561A1 - Process for recycling waste thermal insulation materials

Info

Publication number: WO2015199561A1
Application number: PCT/PL2014/000116
Authority: WO
Inventors: Izabella Bogacka; Stanisław LEWANDOWSKI; Bartosz SZCZYTOWSKI
Original assignee: Laboratorium Czystych Technologii Acren Sp. Z O.O.
Priority date: 2014-06-25
Filing date: 2014-10-24
Publication date: 2015-12-30
Also published as: PL231669B1; PL408661A1

Abstract

A process for the recycling of waste thermal insulation materials comprising dissolution of the selected wastes in an organic solvent, separation of insoluble impurities, and the subsequent addition of a non-solvent, and separation of the precipitated raw material consists in that an aqueous solution of an alkaline agent in an amount of 0.1 %-2.0% by weight relative to the amount of wastes as per the pure alkaline agent is added to the solution of the selected wastes in the solvent after separation of impurities, the mixture is heated at its boiling point for several hours with optional stirring, and, subsequently, the heating is turned off, and the organic and aqueous phases are separated once they form. The organic phase is neutralised, and then water is added while heating and distilling the residues of the solvent until its removal after optional preliminary removal of a portion of the solvent by distillation, and the resulting suspension of the raw material in water is cooled and separated.

Description

Process for recycling waste thermal insulation materials

The present invention relates to a process for recycling thermal insulation materials, particularly polystyrene, from municipal waste, which allows for their secondary application.

Polystyrene is one of the oldest plastics. Originally, it was used solely to manufacture hard, durable elements. Once the process for its foaming was developed, its use rapidly grew. Currently, it is applied practically in all branches of industry, from construction to the food industry. It is used for the manufacture of hard objects, foam insulation, foam packaging, plates and cups.

Polystyrene wastes may have various origins. Production waste does not pose significant problems for their subsequent application. This waste, such as factory rejects, can easily be granulated and re-used. Other types of waste are, segregated as early as at the stage of collection, large waste in the form of products such as transport protective fittings, used e.g. to protect furniture, refrigerators, television sets. This waste causes practically no technical difficulties in their re-use either.

The most difficult polystyrene waste is municipal waste. This waste is in contact with the contents of the landfill and also contains its own impurities. Particularly, food trays or cups, especially those applied for fish, are characterised by a very unpleasant smell. The amount of this type of waste polystyrene is very large, and this waste is practically unsuitable for re-use, because of its unpleasant smell. Polystyrene obtained from municipal waste is not further segregated for its initial application, which means that potentially clean waste is mixed with waste with an unpleasant smell.

There are several methods aimed at the recovery of polystyrene from waste, including municipal waste. These methods are based on a general principle that comprises dissolution of polystyrene in a solvent, the addition of a second reagent, being a liquid which does not dissolve polystyrene for its precipitation, and the subsequent isolation and drying of the separated granules. The raw material obtained in this way may be re-used.

The description of CN 103224646 discloses a process that comprises the crushing of polystyrene, addition of a solvent, filtration, addition of a precipitating agent, filtration of the obtained granules, fractionation and separation of components in a mixture of the solvent and the precipitating substance.

The description of JP2002363333 discloses a process for dissolution of polystyrene in an organic solvent, the addition of water and a suspending agent. The recovery of polystyrene is carried out by evaporation and removal of the solvent.

The description of EP 907462 discloses a process comprising the following steps: reduction of the volume of foamed polystyrene by means of dissolution in a solvent, separation of insoluble components, precipitation of polystyrene from the solution, using a non-solvent, separation, washing and drying of the precipitated polystyrene, fractionation of the components of the mother liquor applied in precipitation and rinse by distillation, recovery of the solvent from the head of the distillation column and its return and recovery of the non-solvent from the bottom of the distillation column. The non-solvent is butanol, selected from n-butanol, isobutanol or sec-butanol, while the solvent is dimethyl carbonate, alone or in a mixture, containing up to 25% by weight of the said butanol.

The description of Polish PL 214369 discloses a process for recycling foamed polystyrene by dissolution in an organic solvent and enrichment with auxiliary agents. The waste polystyrene is dissolved in an organic solvent, in particular in an excess of methylene chloride DCM, and then in a known process, the solvent is evaporated at elevated temperature and, after condensation, returned to the process, while the thermally plasticised polystyrene is enriched with auxiliary agents and directed to the extruder or pump, where it is extruded in the form of granules and/or micro-granules.

The abovementioned methods are based on dissolution of polystyrene and its subsequent precipitation by another non-solvent or by cooling. These methods are fully efficient, but they are suitable only for clean waste. They can also be applied to polystyrene separated from municipal waste; however, polystyrene obtained in this way is not suitable for the production of items intended for long-term use. The items made of this may start to produce an unpleasant smell even after several years. This is associated with impurities that adhere to the polystyrene during storage and then become a component of the item. It was found that 0.1 % by weight of the contents of the packaging of fish, relative to the total weight of the processed waste, causes a release of an unpleasant smell out of the obtained secondary products. The items that are subjected to different kinds of pressures, frictions or mechanical damage during their use are vulnerable to cracking and destruction of their uniform structure. The damaged, or even cracked, structure releases an unpleasant smell from the odorous compounds enclosed within the granules of polystyrene produced in the course of its recovery. Therefore, material of such an origin is mostly used as a component of alternative fuels.

Attempts to liberate the polymer from its annoying smell have been made for a long time now; however, so far they have not led to its removal, but only mask the smell for some time, and after several months, the products once again began to release an odour. The most probable problem seems to be occlusion. Previous methods involving dissolution of polystyrene waste and subsequent precipitation from the solution once the impurities were separated led to the obtaining of only apparently pure granules. During rapid precipitation, a part of the odorous compounds remained in the closing structures of polystyrene, and after some time, an unpleasant odour once again began to be released.

The invention relates to a process for recycling waste thermal insulation materials, particularly polystyrene from municipal waste, liberated from malodorous substances.

A process for recovery of polystyrene from municipal waste comprising dissolution of the selected waste polystyrene in an organic solvent, separation of insoluble impurities, and the subsequent addition of a non-solvent, and separation of the precipitated polystyrene consists in that an aqueous solution of an alkaline agent in an amount of 0.1 %-2.0% by weight relative to the amount of polystyrene as per pure the alkaline agent is added to the solution of polystyrene in the solvent after separation of impurities, the mixture is heated at its boiling point for several hours with optional stirring, and, subsequently, the heating is turned off and the organic and aqueous phases are separated once they form, the organic phase is neutralised, and water is added while heating and distilling the residues of the solvent until its removal after optional preliminary removal of a portion of the solvent by distillation, and the resulting suspension of the raw material in water is cooled and separated. A solution of polystyrene in a solvent, after the separation of impurities and before the addition of an aqueous solution of an alkaline agent, is preferably heated to a temperature of 35°C-^0°C.

The alkaline agent is preferably sodium hydroxide or sodium carbonate.

The organic phase can be rinsed with water several times after separation from the aqueous phase.

Carbon dioxide or organic carboxylic acids, especially oxalic acid or citric acid, are preferably used to neutralise the organic phase.

Additionally, cation-exchange resins can be used to neutralise the organic phase.

The resulting material is optionally dried or stored in a warehouse to dry itself.

The subject of the invention is presented in the illustration, in which Fig. 1 presents a diagram of an installation in which both the alkalisation and neutralisation steps are conducted in one apparatus, and Fig. 2 presents a diagram of an installation in which the neutralisation is carried out using a cation-exchange resin. Example 1

The aparatus shown in Fig. 1 was used.

It consisted of an extractor 1 in the form of a universal steel apparatus with a capacity of 12,000 I, which was equipped with a stirrer, a distillation system 1a and a heating and cooling mantle 1b. A filter 2 equipped with a distillation system isolated with a valve 2a and a heating and cooling mantle 2b was placed under the extractor 1. The bag 2c for the collection of impurities was placed inside the filter 2, under the lid. The lid comprised valves and connectors to administer the solvent and water through a dispenser 8. A drain valve connected to a pump 3, which supplied the reactor 6 with a polystyrene solution through a valve 4, while the valve 5 was closed, was situated in the bottom of the filter 2. The reactor 6 was identical to the extractor 1 and was equipped with a stirrer, a distillation system 6a and a heating and cooling mantle 6b. In the reactor 6, the solution of polystyrene was subjected to an aqueous solution of alkalis, removed by a separatory funnel 9 once used, and then the solvent was removed, and the solution was treated with an aqueous solution of carbon dioxide. The suspension obtained in the reactor 6 was pressed into the separator 7 in the form of a bag filter placed over the tank 7a, in which the aqueous filtrate was collected. After the removal of the whole amount of water that saturated the polystyrene, the pure product was obtained. Insoluble impurities retained in the filter 2 were washed, while the valve connecting it to the extractor 1 was closed, with a pure solvent, which, subsequently, was pressed by the pump 3 through the valve 5, while the valve 4 was closed, to the extractor 1 and used for the next batch of polystyrene.

Procedure

20 tonnes of postconsumer foamed polystyrene containing 93.0% by weight of polystyrene, 6.0% by weight of mechanical impurities, 0.80% by weight of fats and proteins and 0.2% by weight of water were prepared.

Toluene was used as a solvent, a solution of sodium hydroxide was used to alkalise the solution, and carbon dioxide was used as an acid.

In the extractor 1, there were 4,200 kg of toluene remained after washing the filter 2 from the previous batch. 1 ,720.4 kg of foamed polystyrene were additionally loaded, the lid was closed, and the stirrer and then heating were carefully started. When the temperature exceeded 35°C, the heating was switched off, without switching off the stirrer. The filter 2 was prepared for use. The drain valve of the reactor 6 was then closed, the valve 4 was opened, the valve 5 was closed, the drain valves of the extractor 1 and filter 2 were opened, and, subsequently, the pump 3 was switched on. After the filtration was finished, the reactor 6 was loaded with a solution of 6 kg of sodium hydroxide in 200 I of water, and the stirring and heating were switched on. The contents of the reactor were brought to boiling and maintained at this temperature for 2 hours, after which the heating and, subsequently, the stirring were switched off. After half an hour, the lower aqueous phase was removed using the separatory funnel 9, and then washing with 200 kg of pure water by stirring for 15 minutes and setting aside for 30 minutes was performed. The aqueous phase was removed using the separatory funnel 9. The heating and stirring of the reactor 6 were switched on, and the reactor was loaded with 1 ,400 kg of water. In the meantime, with the drain valve of the extractor 1 closed, the filter 2 was rinsed with 4,200 kg of toluene, which was loaded into the extractor 1 using the pump 3, with the valve 4 closed and the valve 5 opened, and, subsequently, the heating of the filter 2 was switched on, while the valve for discharge of solvent vapour to the condensing system was opened. When the temperature of the filter 2 exceeded 120°C, 1 kg of water was introduced to the filter through the dispenser 8, its vapour removed the residues of toluene, and, subsequently, the cooling of the filter 2 was switched on. When the temperature of the water dropped to 35°C, the filter 2 was disassembled, the impurities from the bag 2c placed inside were removed, and then the filter was re-assembled. When the temperature in the reactor 6 exceeded the boiling point, a distillate composed of water, which was returned to the reactor 6 and toluene, which was collected, appeared in the separatory funnel of the distillation system 6a. Upon collection of every 200 kg of toluene, the same amount of water was loaded until 2,000 kg of water was loaded, and afterwards, only toluene was collected until the end of its distillation, which was followed by a collection of 200 kg of water in order to remove the residues of toluene along with the subsequent switching off of the heating and the removal of air from the reactor 6 and replacement with carbon dioxide. Carbon dioxide was fed with the air relief valve open, at a rate of 100-300 l/min. for 30 min., using a tube for loading solutions and rinses. Then the cooling was switched off, the air relief valve was closed, and an overpressure of 0.07 MPa was produced and maintained in the reactor 6. When the temperature in the apparatus dropped to 40°C, the drain valve of the reactor 6 was opened, and the suspension present inside was pressed into the separator 7, the stirring was switched off, and the supply of carbon dioxide was closed. The filtrate, i.e. water from the separator 7, was suitable for re-use in the reactor 6, and the precipitate of polystyrene contained in the bag of the separator 7 was dried. 1 ,600 kg of polystyrene and 103.2 kg of precipitate from the filter 2 were obtained. This precipitate contained mainly papers, polyethylene, polypropylene and sand.

The granulate obtained in this way was crushed, placed in a sealed vessel and shaken several times. These actions were aimed to simulate the conditions of use of items made of recycled polystyrene. It was found that the crushed material does not produce an unpleasant odour.

Example 2. The apparatus and the procedure were as described in Example 1 , wherein .2-dichloroethane was used as the solvent. Alkalisation was performed with an aqueous solution containing 16 g of sodium carbonate, and neutralisation was performed with a solution of oxalic acid, and additionally pressurised air was passed through the reactor 6.

1 ,600 kg of polystyrene and 03.2 kg of precipitate from the filter 2 were obtained.

Example 3. The apparatus illustrated in Fig. 2 was used. As compared to Example 1 , the apparatus was supplemented with two additional apparatuses placed between the reactor 6 and the separator 7. These apparatuses are ion exchange columns 10, containing a cation-exchange resin, which served to press the solution from the reactor 6 to the evaporator 11, in which water was added. The resulting suspension was then pumped to the separator 7, and the procedure described in Example 1 was applied.

Foamed polystyrene containing: 88% by weight of polystyrene, 1% by weight of -fats and proteins, 0.3% by weight of water and 10.7% by weight of insoluble impurities was used as the raw material.

Xylene was used as a solvent, carbon dioxide was replaced with a cation- exchange resin, and nitrogen was additionally passed through the reactor 6.

Procedure

The extractor 1 contained 4,200 kg of xylene, which remained after washing the filter 2 of the previous batch, to which 1 ,720.5 kg of foamed polystyrene were loaded, which was followed by the procedure according to Example 1. The solution in the reactor 6 was treated with sodium hydroxide and then washed with 200 kg of water. Once the washing water was removed in the separatory funnel 9, the obtained solution was pressed through the ion exchange resin 10 to the evaporator 11, in which the solvent was removed and replaced with water using the method described in Example 1. The resulting suspension was cooled and then pumped from the evaporator 11 to the separator 7 using nitrogen. 1 ,514 kg of polystyrene and 84.1 kg of insoluble impurities were obtained.

Claims

1. A process for recycling of waste thermal insulation materials comprising dissolution of the selected wastes in an organic solvent, separation of insoluble impurities, and the subsequent addition of a non-solvent, and separation of the precipitated raw material, characterised in that an aqueous solution of an alkaline agent in an amount of 0.1 %-0.2% by weight relative to the amount of wastes as per the pure alkaline agent is added to the solution of the selected wastes in the solvent, after separation of impurities, the mixture is heated at its boiling point for several hours with optional stirring, and, subsequently, the heating is turned off, and the organic and aqueous phases are separated once they form, the organic phase is neutralised, and water is added while heating and distilling the residues of the solvent until its removal after optional preliminary removal of a portion of the solvent by distillation, and the resulting suspension of the raw material in water is cooled and separated.

2. A process, according to claim 1 , characterised in that the solution of polystyrene in the solvent, after separation of impurities and before the addition of an aqueous solution of an alkaline agent, is heated to a temperature of 35°C-40°C.

3. A process, according to claim 1 , characterised in that the alkaline agent is sodium hydroxide.

4. A process, according to claim 1 , characterised in that the alkaline agent is sodium carbonate.

5. A process, according to claim 1 , characterised in that the organic phase is rinsed several times with water after separation of the aqueous phase.

6. A process, according to claim 1 , characterised in that the organic phase is neutralised with carbon dioxide.

7. A process, according to claim 1 , characterised in that the organic phase is neutralised with organic carboxylic acids.

8. A process, according to claim 7, characterised in that the organic carboxylic acids are oxalic acid or citric acid.

9. A process, according to claim 1 , characterised in that the organic phase is neutralised using a cation-exchange resin.

10. A process, according to claim 1 , characterised in that the resulting raw material is dried.