WO2009093122A2

WO2009093122A2 - Fluidised-bed combustion chamber with an anti-agglomerating system

Info

Publication number: WO2009093122A2
Application number: PCT/IB2009/000096
Authority: WO
Inventors: Tullio Caselli; Ibrahim Gulyurtlu
Original assignee: Shap Corp S.R.L.
Priority date: 2008-01-22
Filing date: 2009-01-21
Publication date: 2009-07-30
Also published as: ITBO20080038A1; WO2009093122A3

Abstract

A f luidised-bed combustion chamber comprising a bed, the features of which avoid the phenomenon of agglomeration in the presence of combustibles with a high amount of alkaline metals. The bed is made with siliceous sand held in suspension by an ascending air current and comprising from 20 to 35 weight % of A12O3 and from 50 to 60 weight % of SiO2.

Description

FLUIDISED-BED COMBUSTION CHAMBER WITH AN ANTI- AGGLOMERATING SYSTEM

TECHNICAL FIELD The present invention relates to a fluidised-bed combustion chamber with an anti-agglomerating system.

BACKGROUND ART

A fluidised-bed combustion chamber substantially consists of a combustion chamber which contains a certain amount of inert material, normally sand, held in suspension by an ascending air current that also serves as carburant and is fed through a distribution grid placed on the bottom. The sand which is used for this purpose is usually of the river siliceous type, non- triturated and dry, and has an average granule size of 0.32 mm.

The motion of the sand bed ensures an appropriate comburent-combustible contact, as well as ensuring a considerable temperature and mixing uniformity which contribute^~ to- ensure- a—constant—and—compl-ete-combusti-on-.--

Furthermore, in the fluidised-bed combustion chamber, an optimal combustion of the effluents is ensured by the free space above the bed in which the combustion of gases generated during the process takes place. These combustion features ensure low emissions and thus a low environmental impact. For these reasons, the use of the fluidised-bed combustion chamber has aroused a considerable interest both for waste disposal and for cutting down pollutants in the exhaust fumes of other machineries .

Very often the material used as a combustible contains a high amount of alkaline metals (Na, K) , for instance vegetal combustibles. It has experimentally- been shown that the sand commonly used with this kind of combustibles tends to agglomerate, thus compromising the benefits deriving from the fluid bed.

DISCLOSURE OF INVENTION It is an object of the present invention to provide a fluidised-bed combustion chamber the technical features of which are such as to avoid the drawbacks of the known art .

It is an object of the present invention to provide a fluidised-bed combustion chamber comprising siliceous sand held in suspension by an ascending air current as a bed; said fluidised-bed combustion chamber being characterised in that said siliceous sand comprises from

20 to 35% by weight of Al₂O₃ and from 50 to 60% by weight of SiO₂.

BEST MODE FOR CARRYING OUT THE INVENTION According to a preferred embodiment of the present invention the siliceous sand comprises from 5 to 15% by weight of Fe₂O₃, from 2 to 5% by weight of CaO. According to still another preferred embodiment of the present invention the siliceous sand has the following composition in weight %: 58.7% SiO₂, 27.9% Al₂O₃, 9.6% Fe₂O₃, 2.8% CaO. The following example is given by way of non- limitative illustration for a better understanding of the invention.

The siliceous sand which is the object of the present invention and, by comparison, a currently used siliceous sand have been tested for their tendency to agglomerate in the presence of vegetal combustibles.

Table I respectively shows the compositions in weight % of the siliceous sand which is the object of the present invention (sand A) and of the compared siliceous sand (sand B) .

Table I

Sand A (object of the invention) and sand B (comparison) have been tested for their tendency to agglomerate when used with combustibles. In particular, the tendency to agglomerate has been evaluated as a function of the measurements of the agglomeration starting temperature and of the agglomeration time. Table II shows the experimental results obtained as a function of the combustible used. Table II

As is apparent from the results of Table II, the sand which is the object of the present invention, when used with vegetal combustibles, ensures higher agglomeration starting temperatures and higher agglomeration times than those obtained with the known art sand.

This behaviour of the sand which is the object of the present invention ensures that no agglomeration phenomena typical of the known art occur during normal operation of the fluidised-bed combustion chamber with vegetal combustibles .

Claims

1. A fluidised-bed combustion chamber comprising siliceous sand held in suspension by an ascending air current as a bed; said fluidised-bed combustion chamber being characterised in that said siliceous sand comprises from 20 to 35 weight % of AI₂O3 and from 50 to 60 weight % of SiO₂-

2. The fluidised-bed combustion chamber according to claim 1, characterised in that the siliceous sand comprises from 5 to 15 weight % of Fe₂O₃, from 2 to 5 weight % of CaO.

3. The fluidised-bed combustion chamber according to claim 2, characterised in that the siliceous sand has the following composition in weight percentages: 58.7% SiO₂, 27.9% Al₂O₃, 9.6% Fe₂O₃, 2.8% CaO.

4. A siliceous sand to be used in a fluidised-bed combustion chamber characterised in that it comprises from 20 to 35 weight % of Al₂O₃ and from 50 to 60 weight % of SiO₂.

5. The siliceous sand to be used in a fluidised-bed combustion chamber according to claim 4, characterised in that it comprises from 5 to 15 weight % of Fe₂O₃, from 2 to 5 weight % of CaO.

6. The siliceous sand to be used in a fluidised-bed combustion chamber according to claim 5, characterised in that it comprises from 58.7 weight % of SiO₂, 27.9 weight % of Al₂O₃, 9.6 weight % of Fe₂O₃, 2.8 weight % of CaO.