Waste to energy by way of hydrothermal decomposition and resource recycling

Abstract

A method and an apparatus for disposing wastes comprising the steps of conducting a hydrothermal decomposition reaction of the wastes, separating the products into a solid fuel and waste water, combusting the solid fuel, scrubbing the combustion gas, generating steam using the heat generated by the combustion, and purifying the waste water, exhibit a high energy-efficiency, while exhibiting a high removal rate of the pollutants generated during the combustion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 61 / 264,001, filed Nov. 24, 2009, and is a continuation of International Application No. PCT / KR2010 / 008237, filed Nov. 22, 2010, both of which are hereby incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to an energy-efficient method for disposing organic wastes such as municipal solid wastes and sewage sludge and an apparatus therefore.BACKGROUND OF THE INVENTION[0003]Organic wastes such as sludge, livestock excreta, food discards, and agricultural wastes have been generally disposed by an anaerobic digestion to recover bio gas such as methane. The anaerobic digestion is useful in that the refined methane gas can be used as an energy resource, but it has the problem that the required long process time causes a high cost and the energy efficiency is low.[0004]Most MSWs (municipal solid wastes) are currently disposed by incinerat...

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Benefits of technology

[0008]Accordingly, it is an object of the present invention to provide a high energy-efficiency, integrated method for disposing wastes containing organic components, and an apparatus therefor.

Problems solved by technology

The anaerobic digestion is useful in that the refined methane gas can be used as an energy resource, but it has the problem that the required long process time causes a high cost and the energy efficiency is low.

The incineration enables the recovery of heat energy, but the process requires expensive fly ash and bottom ash treatment steps.

However, this process has the problem that the resulting solid fuel product contains a considerable amount of chlorine-generating toxic organic chlorine compounds such as dioxin, which must be removed by a treatment process such as SCR (selective catalytic reduction) when such solid fuel is used.

For this reason the waste to energy system is not economically feasible when compared with the conventional incineration process.

The conventional hydrothermal decomposition product is separated into a solid fuel and waste water by centrifugation, followed by treating the waste water in a sewage disposal plant, but such waste water has a BOD value of about 40,000 mg / L and CODcr of about 50,000 mg / L, which may not be effectively treated in the sewage disposal plant.

Also, most conventional processes for treating exhaust gases use a dry scrubber which is generally used in a sulfur removal process, but the exhaust gas generated during the combustion of said solid fuel contains pollutants such as HCl, NOx which are difficult to remove by the dry scrubber.

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