KR20160041529A - Method for recycling paper sludges - Google Patents

Abstract

Provided is a recycling method to sort and separate dried paper sludge into fiber and a filler using microwaves. The recycling method of paper sludge comprises: i) dehydrating paper sludge; ii) providing a mixture by sorting the dehydrated paper sludge into high-moisture content sludge and low-moisture content sludge and mutually mixing the two; iii) primarily drying the mixture using the current of a venturi jet stream; iv) secondarily drying the primarily dried mixture using microwaves; v) crushing the secondarily dried mixture; and vi) separating the crushed mixture into fiber and a filler.

Description

[0001] METHOD FOR RECYCLING PAPER SLUDGES [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling papermaking sludge. More particularly, the present invention relates to a method for selectively separating paper sludge dried by microwaves into fibers and fillers for recycling.

In the paper industry, industrial water that is 10 times to 30 times the paper production is used. About 90% of the total used water is converted into wastewater, except for the wastewater which is evaporated in the drying process during the paper manufacturing process, and a large amount of wastewater sludge is generated during the treatment of such wastewater.

In recent years, the sludge generated in the papermaking process is produced by filtration cake having a moisture content of about 80% through concentration, stabilization, mechanical dehydration and drying process similar to general wastewater treatment sludge. The pre-treated sludge is recycled through final treatment such as landfill, incineration, and ocean discharge.

The paper sludge is dried by microwave, then separated by fiber and filler and recycled.

The method of recycling paper sludge according to one embodiment of the present invention comprises the steps of i) dewatering paper sludge, ii) separating the dewatered paper sludge into high moisture sludge and low moisture sludge, ) Drying the mixture by a venturi jet stream, iv) secondarily drying the first dried mixture using microwave, v) crushing the second dried mixture, and vi) And separating the mixture into a fiber and a filler.

Environmental pollution can be reduced by recycling paper sludge. In addition, recycled fibers and fillers can be used for paper manufacturing and other industries, which can generate additional revenue. And the cost of manufacturing paper can be reduced.

1 is a block diagram schematically illustrating a method of recycling paper sludge according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a primary drying step in the method of recycling paper sludge of FIG. 1;

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

FIG. 1 shows a schematic block diagram of a method for recycling paper sludge according to an embodiment of the present invention. The method for recycling paper sludge of FIG. 1 is for illustrative purposes only and the present invention is limited thereto no. Therefore, the method of recycling paper sludge can be modified to other forms.

As shown in FIG. 1, in the method of recycling paper sludge, the process sludge and wastewater treatment sludge are dried to a moisture content of 10% or less using only mechanical energy and electric energy of microwave among wastes discharged from paper mill. After crushing with fine powder, the dried and crushed sludge is sorted and separated by a filler and a fiber in a material separator. Here, the filler can be recycled as a raw material for paper making, and the fiber and other combustible materials can be converted into solid fuel and recycled as an alternative fuel for the paper mill's own incinerator. As a result, it is possible to minimize waste waste from paper mills, increase the recycling rate of waste, and reduce the amount of fossil fuel used for energy used in paper manufacturing.

More specifically, in the dehydration process, the introduced primary sludge is mechanically dewatered and stabilized at a minimum water content. In the mixing process, the dehydrated high-moisture sludge and the low-moisture sludge after drying are mixed at an appropriate ratio. In this case, sticky zones of the sludge during the drying process can be prevented.

In the case of drying the highly adhesive sludge, the above-mentioned adhesion zone is generated by the sludge organic material, and the operation can not be normally performed or the equipment may be seriously damaged. In order to prevent this, the wetting sludge and dry sludge are mixed in the pre-drying stage of the sludge, thereby avoiding the water content region where the adhesion zone occurs.

Next, the paper sludge is dried to a limiting moisture content using a venturi jet air dryer. Then, the paper sludge is dried to an equilibrium moisture content by using a microwave dryer. The microwave dryer is a method for obtaining high drying efficiency compared to the hot air drying, and it can exhibit higher drying efficiency than a general microwave dryer by using the microwave-hot air-fusion drying method combined with the convection drying method. As described above, the entire drying process is divided into primary / secondary drying to minimize energy consumption, and energy can be saved by employing a microwave drying method. In addition, the crusher is used to atomize the dried sludge to an appropriate size to improve the selectivity in the sorting process. Then, the atomized dry sludge is classified into a fiber fraction and a filler fraction by using a sorting machine such as a vibrating screen. About 35% of organic matter (fiber) is solid fuel using most of the solids contained in paper sludge. That is, the fibrous component is molded into a pallet type solid fuel in a molding machine such as a rotary drum molding machine. Finally, the molded SDF (Sludge Drived Fuel) is stored in a silo or storage hopper. And about 60% of inorganic material (filler) is separated and recovered by CaCO ₃ and Clay.

Fig. 2 schematically shows the primary drying step of the method of recycling paper sludge of Fig. The primary drying method of FIG. 2 is only for illustrating the present invention, and the present invention is not limited thereto. Thus, the primary drying process can be modified to other forms.

As shown in Fig. 2, primary drying of paper sludge can save energy during secondary drying. That is, in the primary drying step, when the object to be dried passes through the venturi using a venturi jet air drying method and a high-speed air flow, the particles of the paper sludge are destroyed and moisture is absorbed into the air stream and dried. This method is energy-saving type that does not use a heat source, does not generate air pollutants, and is environment-friendly because odor is not generated.

It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the following claims.

Claims (1)

Dewatering the paper sludge,
Separating the dehydrated paper sludge into a high moisture sludge and a low moisture sludge and mixing them to provide a mixture,
Primary drying the mixture by a venturi jet stream,
Drying the mixture by using a microwave,
Crushing said secondary dried mixture, and
Separating the shredded mixture into a fiber and a filler
Wherein the paper sludge is recycled.

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