Field of Invention:
The present invention relates to a bed ash extraction combustor for fluidized bed combustion boilers and systems.
The present invention relates to a bed ash extraction combustor for Fluidized Bed Combustion (FBC) Boilers and Systems. This comprises a non-mechanical sealing device to provide sealing at the discharge end of the ash collection pipe and a transfer pipe to discharge the ash from the sealing device to a suitable cooling device/disposal system.
Background art:
In Fluidized bed Combustion (FBC) boilers and combustors ash/bed material at the operating temperature of 700 to 1100 Deg C is removed from the fluidized bed either continuously or intermittently in order to maintain the bed inventory and particle size distribution. Continuous removal is generally through a pipe located just above the fluidized bed level. The ash removal through such an arrangement results in ingress of air from atmosphere in to the combustor as about minus 5 to minus 10 mm of vacuum is maintained in the combustor. As the material is flowing against a differential pressure to atmosphere, there is reduction in quantity of ash removed. Intermittent systems usually are through a drain pipe connected at the combustor air distributor level. The removal of ash through drain pipes is done usually in batches by opening/closing or regulating a slide gate or a mechanical device. In this method the material suddenly rushes due to the fluid like behavior of the bed and control of the quantity/rate is difficult. Operation of this slide gate is risky for the personal safety and the mechanical device is not reliable due to the requirement to handle high temperature ash.
The difficulties in mechanical conveying and transportation of bed ash are two major problems for the users of FBC Boilers and Systems. Hot ash when directly quenched by water, will lose some of its important characteristics for utilization.
An object of this invention is to overcome the above drawbacks of the existing methods and provide a reliable solution.
gate is not reliable and risky for the operation of the fluidized boilers and systems. The mechanical device is also complex and less reliable due to the need to handle solids at high temperature. This leads to unsafe working condition in the field.
To obviate the above difficulties of this conventional method, ash overflow pipe should be provided with a seal, ash drain pipe should be operated by a reliable and safe means in atmospheric Bubbling/Circulating FBC Boilers and systems.
STATEMENT OF INVENTION
According to this invention there is provided a bed ash extraction combustor for fluidised bed combustion boilers and systems comprising:
- a sealing device to provide a sealing at the discharge end of the ash collection pipe and characterized by
- an ash transfer pipe to transfer the ash from said sealing device to a suitable cooling device and/or disposal system.
Description of the invention
The invention relating to Bed Ash Extraction Combustor for FBC Boilers and Systems is characterised by the following design/construction features.
1. Ash collection pipe
2. Non-mechanical sealing device
3. Air distributor
4. Wind box
5. Ash transfer pipe
The present invention will be described in detail with reference to the accompanying drawings where
Figure 1 shows the bed ash extraction system for ash overflow pipe and Figure 2 shows the bed ash extraction system for ash drain pipe.
Design and construction features are nearly same for both the applications.
The Bed Ash Extraction System of the present invention is provided with an ash collection pipe (1) at the inlet of the non-mechanical sealing device (2). Necessary features in the form of perforated plate (6) has been provided to avoid entry of ash agglomerates from the bed if any, into the sealing device. An air distributor (3) with plurality of air nozzles and a wind box (4) are attached to the sealing device. The ash from the sealing device is transferred through an ash transfer pipe (5) to a suitable cooling device and/or disposal system. The unique of operating parameters of the non-mechanical device as proposed by this invention is given below.
Average ash particle size 0.2 to 2.0 mm
Fluidisation velocity in the device 0.5 to 6 m/s
Operating temperature upto 1200 deg. C
Desired wind box pressure 400 to 3000 mmwc-

WE CLAIMS :-
1. A bed ash extraction combustor for fluidised bed combustion boilers
and systems comprising:
- a sealing device to provide a sealing at the discharge end of the ash collection pipe and characterized by
- an ash transfer pipe to transfer the ash from said sealing device to a suitable cooling device and/or disposal system.

2. A combustor as claimed in claim 1, wherein said sealing device is non-mechanical device.
3. A combustor as claimed in claim 1, wherein an ash collection pipe is positioned at the inlet of the sealing device to receive the ash from the combustor.
4. A combustor as claimed in claim 1, wherein a provision is made in the ash collection pipe to avoid entry of any ash agglomerates from the bed.
5. A combustor as claimed in claim 1, wherein an air distributor with plurality of air nozzles and wind box are provided in said sealing device.
6. A combustor as claimed in claim 1, wherein a provision is made to by pass the said device in case of requirement and continue with the removal through the by pass line provided for operational maintenance of the sealing device.