WO2008007204A1

WO2008007204A1 - Modular system and method for separating and recovering fractions from the reject of a pulper

Info

Publication number: WO2008007204A1
Application number: PCT/IB2007/001923
Authority: WO
Inventors: Pietro Italiano
Original assignee: Ecoenergetics S.R.L.
Priority date: 2006-07-11
Filing date: 2007-07-10
Publication date: 2008-01-17
Also published as: ITMI20061338A1; EP2054547A1

Abstract

There is described a modular system for valorizing and recovering waste material from a pulper of the paper industry. The system comprises a grinder, a fine and coarse fraction separator, a soft and hard fraction separator, one or more metal fraction separators, an optional combustion reactor. By means of this system the characteristic components of the waste from the pulper, such as metal, plastic and paper material, are recovered. The process, eco-compatible and economically advantageous, reduces the production of waste and makes the overall paper production cycle more economical.

Description

MODULAR SYSTEM AND METHOD FOR SEPARATING AND RECOVERING FRACTIONS FROM THE REJECT OF A PULPER

FIELD OF THE INVENTION

The present invention relates to the field of treatments to recover raw material and energy from waste materials. There is described a treatment of waste material from a pulper of the paper industry which allows recovery, with advantageous energy balance and in an eco-compatible manner, of the paper, plastic and metal fractions constituting said material, increasing the overall energy efficiency of the paper production process. PRIOR ART

The pulper is a pulper of varied capacity, used in the initial step of the paper production cycle; water and fibrous material are fed therein; thanks to an impeller that moves at high speed, the fibers are separated and hydrated to produce a suspension with variable density; the suspension is then transferred to other plants where it is subjected to further treatments such as refining, the addition of charges, glues and any dyes, felting, pressing and drying, to obtain the final sheet. The pulper is also used to produce recycled paper: in this case water and pulped paper are mixed in appropriate proportions; the suspension then follows the normal paper production chain according to the steps mentioned above. The work of the pulper always generates, as by-product, a certain amount of non- pulpable waste material; when pulped paper is used as raw material, the waste material is constituted by the foreign materials that always come with this product, prevalently plastics, metals, wire, rope, etc., and a noteworthy percentage (approx. 25% of the total waste material) of paper fiber which is retained by said waste. These waste materials can also be present even when starting out from wood fiber.

In common paper production processes, the waste material of the pulper is filtered and separated from the suspension intended to feed paper production; the waste thus separated is no longer usable and is sent for disposal; in accordance with current laws on refuse, this disposal implies an average cost of 90 Euros per ton; considering that a paper mill of average dimensions produces about 90 tons per day of waste from the pulper, the annual cost for disposal thereof amounts to around 3 million Euros, without counting the loss due to paper fiber disposed of along with the waste. SUMMARY

There has now been devised a new treatment method and an industrial process that implements it, wherein the waste from the pulper is no longer treated as refuse to be eliminated, but valorized through an eco-energy process, so as to recover discrete components and/or energy from said material, in an economically advantageous manner, and with a low environmental impact. These objectives are achieved through a modular system, combinable with the paper production plant. This system, in it most general acceptation, comprises the following elements:

(a) grinder

(b) fine and coarse fraction separator

(c) soft and hard fraction separator

(d) metal fraction separator (e) optional combustion reactor

This assembly of elements allows separation of the characteristic components of waste from the pulper, such as metal, plastic and paper. The overall energy cost of the process, lower than the cost of disposing with untreated waste, is further reduced by the possibility of selling/re-utilizing the discrete components recovered, and/or recovering energy through combustion. The modular nature of the system also allows the number of steps to be interchanged and/or reduced according to the quali-quantitative composition of the waste, further increasing the overall energy efficiency of the process.

DESCRIPTION OF THE FIGURES Figure 1: block diagram of the post-pulper modular system forming the object of the invention.

(a) grinder; (b) fine/coarse fraction separator; (c) soft/hard fraction separator; (d¹),

(d") metal fraction separators; (e) combustion reactor.

Figure 2: photograph of industrial prototype: (f): conveyor line for coarse fraction; (g) collection line for paper fraction; (h) collection silo for paper fraction; (i) collection line for plastic fraction; (I) container for plastic fraction.

Figure 3: detail of the fine/coarse fraction separator (b). DETAILED DESCRIPTION OF THE INVENTION

The present process utilizes, as raw material, the waste material from the pulper, already separated from the aqueous suspension intended to produce paper. This waste material can be recovered from the pulper, stored separately and later treated according to the present invention, or it can be conveyed from the operating pulper and treated directly without intermediate storage. The operating diagram of the modular system of the invention is presented in Figure 1. The first element is constituted by the grinder (a). The object of this element is to reduce the waste from the pulper, normally tangled in the form of plaits of variable dimensions, into a sufficiently comminuted and flowing product. Any mechanical apparatus capable of performing this grinding operation can be utilized as element (a). In a non-limiting embodiment, it is constituted by a pair of co-rotating toothed metal wheels through which the waste from the pulper is fed. The grinding action can take place in a single passage or repeated grinding can take place through cyclical movement of the material through the same pair of wheels, or by providing a series of several pairs of said wheels through which the material is fed. The grinding action can be facilitated with the aid of water jets, vibrations or other systems, in order to promote movement of the material and/or prevent residues from adhering to the surface of these wheels. The material delivered from the grinder is conveyed using suitable means, such as conveyor belts, into the coarse and fine fraction separator (b), also called screen. Any mechanical apparatus capable of performing this function can be used as the element (b). In a non-limiting embodiment, it is constituted by a perforated tubular element rotating about the longitudinal axis thereof. The material coming from (a), is conveyed inside the tubular element appropriately made to rotate. The fine fraction, full of paper fiber, passes through the holes, is collected and, preferably, recycled in the pulper; alternatively, it can be subjected to separate processes to refine and recover the paper fiber. The paper fraction is handled with suitable systems, such as conveyor belts, augers, pneumatic systems, depending on the density and rheological qualities of said fraction. The unprocessed coarse fraction, full of metal material, plastic and larger aggregates of paper fiber does not pass through the holes and proceeds inside the tubular element suitably pushed by the pressure of the incoming material and by the rotational movement of the element (b); upon delivery from (b), it is conveyed by means of appropriate conveyor means into the modular element (c), the soft and hard fraction separator. Any mechanical apparatus capable of performing this separation can be utilized as the element (c). In a non-limiting embodiment, it is constituted by a suitably adapted washing machine. Therein, the material to be separated is treated with a high pressure water recirculation system that carries the soft material in suspension; the hard material is instead retained by suitable filters through which the suspension is fed. The suspension of soft material, full of paper fibers is preferably recycled in the pulper; alternatively, it can be subjected to separate processes to refine and recover the paper fiber. The hard fraction is recovered from the filters and subjected to drying.

In the treatment path described above, there are also provided, at least one collection point for the metal fraction, through suitable metal fraction separators (d). Collection preferably takes place by placing the material on a conveyor belt moving in the range of action of an electromagnet, which attracts and separates the magnetic metals, and of an appropriate electromagnetic field, which repels and separates the non-magnetic metals (obtainable for example by means of the product Eddy Current, Art 901 , soc. Calamit, Cologno Mz.se). The preferred points for this collection are located along the path between the elements (b) and (c), and/or after the element (c). The use of two metal collection points is particularly preferred as it allows more complete separation of this element. The remaining fraction delivered from the cycle a-b-c-d is prevalently constituted by plastic. This fraction can be stored and used as plastic to be recycled, or can be burnt with the aim of recovering energy.

The combustion reactor (e) is chosen from conventional burners suitable for the purpose or, advantageously from the energy and environmental viewpoint, it is constituted by a pyrolyzer, associated with a catalytic oxidation chamber; inside the pyrolyzer, the plastic fraction is heated in an inert gas atmosphere, to a temperature of around 500⁰C; the material vaporizes and is then conveyed by the flow of nitroηen into the oxidation chamber, fed by a flow of air or pure oxygen; vapor combustion takes place through suitable oxidation catalysts, therefore not in the flame phase.

Suitable heat exchangers are associated with the combustion reactor, so as to store the heat generated with the aim of recovering energy. During this treatment, in particular in the step to dry the material delivered from (c), a dust is produced, prevalently constituted by fine plastic material that adheres to the walls of the various collection elements. This material can be recovered, manually or automatically, and then recycled or subjected to combustion as described above for the plastic fraction. The process described here therefore allows complete separation and/or recycling or eco-compatible combustion of the elements constituting the waste from the pulper. The modular nature of the system allows the composition and sequence of the various elements described above to be varied, depending on the quali- quantitative composition of the initial waste product, thereby optimizing the energy balance of the process.

The modular system described above can be produced as a separate plant, or be integrated in the production cycle of a paper mill; in the first case it is fed with the waste from the pulper, previously recovered separately; in the second case feed takes place through suitable ducts that convey the waste material coming from the pulper directly towards the modular system.

The present invention therefore covers the modular system on its own, or integrated within a paper production plant, in particular, but not exclusively, for the production of recycled paper. An example of embodiment has been produced on an industrial scale. Figure 2 shows the modular system as a whole, Figure 3 shows the element (b) in detail.

Claims

1. Modular system for separating and recovering paper, plastic and metal fractions from waste material from a pulper of the paper industry, comprising the following elements: (a) grinder

(b) fine and coarse fraction separator

(c) soft and hard fraction separator and also, subsequent to the grinder (a), at least one metal fraction separator (d), and an optional combustion reactor (e).

2. System according to claim 1 , comprising two metal fraction separators, placed respectively before and after the element (c).

3. System according to claims 1-2, wherein the grinder (a) is constituted by one or more pairs of co-rotating toothed metal wheels through which the waste to be treated is fed.

4. System according to claims 1-3, wherein the element (b) is constituted by a perforated tubular element rotating about the longitudinal axis thereof.

5. System according to claims 1-4, wherein the element (c) is a washing machine provided with filters capable of allowing the soft fraction to pass through and retaining the hard fraction.

6. System according to claims 1-5, connected to the pulper of a paper mill.

7. System according to claims 6, provided with systems suitable to convey the recovered paper fractions in the pulper.

8. System according to claims 1-7, wherein the plastic fractions can be recovered as material to be recycled or subjected to combustion with the aim of recovering energy.

9. System according to claims 1-8, wherein the combustion is performed by means of pyrolysis and catalytic oxidation.

10. Paper production plant comprising, as an extension, the modular system described in claims 1-9.

11. Plant according to claim 10, for producing recycled paper.

12. Method for separating and recovering paper, plastic and metal fractions from waste material from a pulper of the paper industry, characterized by treating said material according to the following steps:

(a) grinding; (b) separation of the fine and coarse fraction;

(c) separation of the hard and soft fraction;

(d) separation of the metal fraction in at least one point subsequent to grinding;

(e) optional combustion.

13. Method according to claim 12, where combustion takes place by means of pyrolysis and catalytic oxidation.