Waste processing

Abstract

The present invention relates generally to the field of waste processing. The method comprises separating waste into at least two parts, comprising: (i) mainly food waste (fines) and (ii) mainly paper and other recyclable material (overs). The overs are pulped and washed to obtain a cellulose-rich biomass and the fines are optionally processed separately to recover a cellulose-rich biomass and the cellulose-rich biomass from both the fines and the overs may be combined.

Claims

1. A method for processing Municipal Solid Waste (MSW), comprising the steps of: a) separating said waste into at least two parts, comprising: (i) fines comprising mainly food waste and (ii) overs comprising mainly paper and other recyclable material; b) pulping said overs; and c) washing said pulped overs to obtain a first cellulose-rich biomass; and d) processing said fines by thermomechanical pulping followed by density separation to obtain a second cellulose-rich biomass, wherein said first and second cellulose-rich biomass combined comprises less than about 10% ash and a glucan:xylan ratio of between about 5-8:1.

2. The method according to claim 1, wherein said separating is effected by at least one screen or trommel.

3. The method according to claim 2, wherein said trommel has a screen size of between about 300-500 mm.

4. The method according to claim 2, wherein said trommel has a screen size of between about 50-150 mm.

5. The method according to claim 1, wherein the separated fines have a diameter of less than about 200 mm.

6. The method according to claim 1, wherein following said pulping step b), at least a part of the pulped material is shredded.

7. The method according to claim 6, wherein said shredded material is re-pulped.

8. The method according to claim 1, wherein said pulping step b) results in obtaining at least three parts, comprising: (i) a pulp; (ii) other recyclables, and (iii) dirty wash water.

9. The method according to claim 8, wherein said other recyclables are removed from said pulped material before washing step c), wherein said other recyclables comprise plastic film and recyclable materials.

10. The method according to claim 1, wherein said washing step c) includes the use of at least one agent selected from the group consisting of surfactants, enzymes, catalysts, and additives.

11. The method according to claim 1, wherein said washing step c) further generates wash water which is optionally processed through biological treatment and recycled back into the main process and/or used for biogas production.

12. The method according to claim 1, wherein said fines are thermo-mechanically treated to allow breakdown of organic matter without the substantial shrinking of any plastics materials.

13. The method according to claim 12, wherein said thermo-mechanically treated fines undergo density separation to enable separation of (i) heavy particulate material; (ii) light particulate material; and (iii) organic matter.

14. The method according to claim 12, wherein said processing of said fines results in an organic-rich wash water.

15. The method according to claim 14, wherein said light particulate matter is fed back into washing step c).

Description

FIGURES

(1) The present invention will now be described by way of example only and with reference to the accompanying illustrative drawing in which FIG. 1 shows a process according to the present invention for the processing of MSW, which may comprise any of the following: paper, cardboard, plastics, metals, glass, batteries, appliances, textiles, rubber, wood, garden and food waste.

(2) The incoming MSW is shown to undergo an optional (shown with dashed lines) PRE-SORTING step in which any hazardous items or items unsuitable for processing, such as items too large for downstream processing, masonry, furniture, electrical appliances, textiles, carpets and dead animals are removed (REJECTS).

(3) Following optional PRE-SORTING, the MSW undergoes PRIMARY SORTING, which involves passing the MSW through at least one trommel or other screen (not shown) which separates the material into FINES (comprising mainly food waste with other minor components, such as glass, grit, plastics and paper) and OVERS (comprising mainly plastics, metal, paper and cardboard). The trommel(s) or screen(s) allows for separation of material to allow fines with a diameter of less than about 200 mm to be obtained.

(4) The OVERS then undergo an optional (again shown with dashed lines) TEXTILE REMOVAL step. Any TEXTILES recovered are recycled separately.

(5) The substantially textile-free OVERS are then shown to undergo HYDRO-MECHANICAL PULPING with the addition of water (W). The HYDRO-MECHANICAL PULPING may be carried out in a drum pulper (not shown). The pulped material then undergoes a SECONDARY SORTING step, during which plastic film (FILMS), plastic and metal containers (RIGIDS) are removed. The FILMS may be removed by passing the pulped overs through a vacuum drum separator (not shown) or the like which lifts and removes the light-weight FILMS, leaving behind the heavier containers (RIGIDS). The FILMS may alternatively be removed on a moving belt with the aid of a vacuum device (not shown). The RIGIDS may be sorted using an automated optical sorting device (not shown), which can separate rigid containers according to polymer type. Overband magnets may be used for the separation and recovery of steel and other ferrous containers and eddy current separators may be used for the separation and recovery of aluminium or other non-ferrous containers. The recovered FILMS and RIGIDS may then be baled for further recycling or reuse. Any un-pulped paper or cardboard found amongst the recyclable material at this stage may be manually or automatically picked out and reintroduced to THERMO-MECHANICAL PULPING.

(6) Following SECONDARY SORTING, there is an optional (denoted with dashed lines) SHREDDING step. This involves shredding the un-pulped overs (after recyclate recovery), minus the FILMS and RIGIDS, in a conventional shredder (not shown), and optionally returning the shredding mixture to the pulper so as to maximize recovery of useful products therefrom.

(7) Following SHREDDING or following SECONDARY SORTING, there is a WASHING step for the removal of any food waste, water soluble organic and inorganic contaminants and any other solid debris from the biomass pulp. Conventional surfactants, including bio-derived surfactants, and/or enzymes and/or catalysts and/or additives and/or any other suitable agents may also be used in the washing process to optimize the washing process and to obtain an even cleaner end product.

(8) The WASHING may include conventional equipment for the washing of a biomass pulp, optionally with mechanical dewatering (for example using a filter press or centrifuge), if necessary. Alternatively, the WASHING step may involve washing of pulped overs in a rotating wash trommel or the like, which cleans the material and separates according to size. Alternatively WASHING may comprise washing of the pulped overs in a washing tunnel.

(9) Following WASHING of the OVERS, three main products are obtained: (i) CELLULOSE-BIOMASS, (ii) NON-ORGANIC SOLID, and (iii) ORGANIC-RICH WATER.

(10) The left-hand side of FIG. 1 shows the processing of the FINES which undergo THERMO-MECHANICAL PULPING, with the optional addition of water (W). The pulped FINES then undergo a DENSITY SEPARATION step which results in three main products: (i) WET LIGHTS, (ii) BIOMASS SLURRY and (iii) WET HEAVIES.

(11) FIG. 1 shows the processing of the FINES and the OVERS in one process, however, these may be separately performed.

DEFINITIONS

(12) The following definitions are used throughout the present application. The section captions and headings in this application are for convenience and reference purpose only and should not affect in any way the meaning or interpretation of this application. The technical terms and expressions used within the scope of this application are generally to be given the meaning commonly applied.

(13) Municipal Solid Waste, MSW, Mixed Waste, General Waste, Household Waste, Waste ‘Municipal Solid Waste’ or ‘MSW’ is the typical waste generated by households and commercial establishments, such as offices, schools, warehouses, restaurants, retail establishments, any non-hazardous industrial waste and residues from other waste recycling activities, such as MRF rejects. Typical MSW includes any of the following: paper, cardboard, plastics, metals, glass, batteries, appliances, textiles, rubber, wood, garden and food waste. The terms ‘mixed waste’, ‘general waste’, ‘household waste’, ‘waste’, ‘Municipal Solid Waste’ and ‘MSW’ are all used interchangeably herein to mean any two or more, three or more, four or more, five or more, six or more of the following: paper, cardboard, plastics, metals, batteries, appliances, glass, textiles, rubber, wood, garden and food waste.

(14) Fines

(15) Reference herein to ‘fines’ is taken to mean mainly food waste comprising other minor components, such as glass, grit, plastics and paper.

(16) Overs

(17) Reference herein to ‘overs’ is taken to mean waste comprising mainly plastics, metal, paper and cardboard.

(18) Trommel

(19) Reference herein to a ‘trommel’ is taken to mean a screen used to separate material according to size. Trommels are typically cylindrical, perforated and capable of rotating, allowing undersized material to pass through the perforations.

(20) Hydro-Mechanical, Thermo-mechanical, Hydrothermal,

(21) Reference to ‘hydro-mechanical’, ‘thermo-mechanical’, ‘hydrothermal’ means or apparatus, as used herein, means any force(s) or apparatus or combination of apparatus using water (hydro-) and/or heat (thermo-) and/or mechanical-based action to breakdown waste, fines or overs.

(22) Breakdown, Processing, Pulping

(23) The terms ‘breakdown’, ‘breaking down’, ‘pulpling’, ‘processing’, are all (sometimes depending on the context), used interchangeably herein to mean, for example, in the case of the ‘overs’ any action which results in the disintegration and conversion of waste to at least a biomass pulp.

(24) Biomass Pulp, Pulp, Cellulose Pulp, Cellulose-rich Biomass, Cellulose

(25) The terms ‘biomass pulp’ and ‘pulp’ are used interchangeably herein to mean the resultant product from the breakdown of waste (typically comprising paper, cardboard and plant-based components) to produce a pulp having a paper mâché-type consistency and before the washing step. After the washing step, a ‘cellulose pulp’, ‘cellulose-rich biomass’ or ‘cellulose’ is obtained, which terms are used interchangeably herein to mean the resultant product following washing of the biomass pulp.

(26) Organic, Non-Organic

(27) The term ‘organic’ as referred to herein means any plant or animal-derived material having a carbon basis, but excluding plastics; the term ‘non-organic’ therefore refers to anything which is not organic and includes plastics.