Method and Installation for the Production of Pellets from Biomass in a Pelletizing Press for Use as Fuel in Furnaces

Abstract

A method and an installation for producing pellets from prepared biomass in a pelleting press for use as fuel in fireplaces. The biomass is made of fibers, shavings or chippings containing cellulose and / or lignocellulose, with or without a binding agent and / or additives, and after being prepared is stored in a biomass bunker. The method includes: biomass discharged from the biomass bunker into a scatter device, a mat made of the biomass having a substantially uniform weight per unit area formed by the scatter device on a molding belt, the mat produced on the molding belt examined by an examining device for defective spots and / or foreign substances, and the mat supplied to a pelleting press. At least parts of the mat or a section of the mat include defective regions and / or foreign substances separated from the method upstream of the pelleting press.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS[0001]Germany Priority Application DE 10 2009 016 470.7, filed Apr. 13, 2009 including the specification, drawings, claims and abstract, is incorporated herein by reference in its entirety.BACKGROUND[0002]1. Field of Embodiments[0003]The embodiments relate generally to a method for producing pellets from prepared biomass in a pelleting press for use as fuel in fireplaces or furnaces. The embodiments further relate to an installation for producing pellets from prepared biomass in a pelleting press for use as fuel in fireplaces or furnaces.[0004]2. Description of Related Art[0005]The production of pellets, also referred to as briquettes or granulates, from fine material or compacted and / or molten material has long been known. Compactors compact material between two rollers, either one or both being formed as a die, and mold the same to form briquettes for use as fuel. Pelletizing by means of extruders and punched disks, optionally with cut...

AI Technical Summary

Benefits of technology

[0016]The object underlying the disclosed embodiments is to provide a method for the production of pellets from biomass, particularly in major industrial production, in which the biomass can be easily but effectively examined, following its preparation, for foreign substances such as stones, sand, inhomogeneities, excessive density or the like upstream of a pelleting press in order to enable a timely separation of the foreign substances before the supply of biomass to a pelleting press and in order to prevent damage to the dies and / or the pan-grinder rollers of a pelleting press. At the same time, the shutdown caused by the required separation process ought to be as short as possible and enable the orderly and uniform supply of biomass to a pelleting press.

[0018]It has proven to be particularly advantageous that small bodies having a size of 1 mm3 and a higher density relative to the biomass can be detected safely with the aid of a radiography device, preferably a gamma emitter or an X-ray tube assembly. The radiography device preferably disintegrates the weight per unit area of the mat scattered on the molding belt and determines the weight per unit area in the smallest possible grid, for example, of 1 mm2, while the continuously scattered mat passes through the radiography device. The density of usable wood (which is not present in the form of bulk material or prepared biomass) is approximately 400 to 800 kg / m3 and common foreign substances such as sand have a density of more than 1.5×103 kg / m3. If the regular weight per unit area of a scattered and loose mat (containing a lot of air) on a molding belt is, for example, 2 kg / m2 with a mat height of 13 mm and a theoretical bulk density of 155 kg / m3 of biomass, then a foreign substance of a size of 1 mm3 and a density of 2×103 kg / m3 within the mat would significantly increase the weight per unit area in a measuring field of a square millimeter such that this increase is clearly measurable by radiography devices.

Problems solved by technology

Usually, the metering devices used are metering screw conveyors that are, however, not suitable for simultaneously loading several pelleting presses with a constant flow of materials.

However, clusters of material pose problems in the constant supply to pelleting presses since the former are discharged from the conveyor in lumps in extreme cases.

They can even result in problems at the inlet of pelleting presses and a reduction of the maximum throughput per hour if the pelleting presses can no longer comminute the clusters of material or can do so only with great difficulty, and these clusters can block the inlet of the pelleting press on account of their size and can obstruct or even prevent the inflow of biomass into the press gap.

At the same time, the conveyance of lumpy biomass results in a non-uniform loading of the pelleting press which manifests itself, depending on the type of the pelleting press, in increased wear or energy input if irregular driving or compacting forces have to be powered or if locking devices or bearings on shafts are loaded excessively.

The separation of the biomass in the biomass bunker or during its metering to the pelleting press poses an additional problem.

The conveyance of the biomass results in the problem of so-called lumps of uniform material, for example, dust lumps being formed in addition to coarse lumps of biomass.

The problem confronted in major industrial production planning is that in the case of an enlargement of a two-roller press or a pan-grinder press, the supplying metering screw conveyor would have to be larger by an extremely large factor in order to enable proper loading, or several metering screw conveyors would have to be set up parallel to each other for a large pelleting press.

In both solutions, the probability of failure increases significantly and there arise high procurement costs for installation engineering, particularly the control and feedback control systems.

Even if only one metering system fails, the entire installation has to be switched off since portions of the pelleting press would otherwise operate in the absence of material, thereby causing increased wear.

However, the disadvantage of a multi-stage gravity separation or other separation processes is that they do not have 100% efficiency, but instead grains of sand or other high-density materials repeatedly remain in the biomass during major industrial use and high throughput of biomass per hour (more than 15 tons / hour).

It is also possible for foreign substances to enter into the plant components after the separation process, that is to say, during or after the storage of the biomass in the biomass bunker, as a result of abrasion or wear of plant components in the production process, which foreign substances can result in damaging the pelleting presses.

Even a coarse grain of sand in biomass being pressed by a roller press or an annular die comprising associated pan-grinder rollers can damage the press molds.

If the borehole of an annular die or a surface die of a roller press suffers from even slight damage, this results in the serial production of pellets that are slightly elevated.

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