FIELD OF INVENTION:
The invention is relevant to bed material transfer lines in CFBC Boilers (Circulating Fluidised Bed Combustion Boilers). More particularly, the present invention is relevant to the refractory lining to be carried out in bed material mixing nozzle cum transfer line connected to the combustion chamber in CFBC Boilers.
BACKGROUND OF THE INVENTION:
Bed material made from crushed refractory is used as circulating medium in a CFBC boiler. The bed material is stored in bunkers and then transferred to combustion chamber through transfer lines. Usually the transfer lines are provided with adequate slope to aid gravity flow of bed material. The existing art (Figure 1 and 2) includes an assembly which consists of mixing nozzle chamber (01), mixing nozzle transition pipe (02) and air inlet pipe (03) for air assisted flow of bed material. The assembly is joined with straight pipe (04) and directed to combustor seal box (06) with provision of expansion joint (05).
The bed material used for circulating in a CFBC boiler is made from crushed refractory grog. This is highly erosive in nature. The bed material is stored in bunker and is fed into combustor chamber in required quantity during operation. As per the existing art (figure 1 and 2), bed material from bunker falls vertically downwards on the mixing nozzle chamber (01). with the help of supply air through air inlet pipe (03), the fallen bed material is forced into the mixing nozzle transition pipe (02) and then routed to the combustor chamber through the straight pipe (04) connected to seal box (06) with expansion joint (05). During the course of operation, mixing nozzle chamber (01), mixing nozzle transition pipe (02) and straight pipe (04) were severely eroded leading to creation of holes causing leakage of bed material within short span of operation.

As a result, the supply of bed material into combustion chamber is cut off causing interruptions in smooth operation of boiler. Hence there is a need to find out a method of feeding system for bed material so that interruptions due to leakage of bed material can be avoided.
OBJECTS OF THE INVENTION:
An object of the present invention is to provide an assembly of wear resistant bed material system of CFBC boilers, which can prevent erosion of duct due to bed material flow by providing a refractory lining held in position using anchors.
Another object of the present invention is to provide an assembly of wear resistant bed material system which enable transfer of bed material from bunker to combustion chamber without any damage of any structural equipments such as mixing nozzle chamber, mixing nozzle transition pipe and straight pipe.
Yet another object of the present invention is to provide an assembly of wear resistant bed material system which has longer durability compared to that without refractory lined ones.
A further object of the present invention is to provide an assembly of wear resistant bed material system which enable uninterrupted feeding of bed material from bunker to combustion chamber and hence facilitate smooth operation of CFBC boiler.
SUMMARY OF THE INVENTION:
An assembly of wear resistant bed material system of CFBC boilers comprises bed material mixing nozzles made of duct plate assemblies; and a refractory lining inside the said nozzle supported by anchors welded on the duct plate to prevent the erosion of duct plate due to bed material flow.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates an existing art of Bed material mixing nozzle cum transfer lines.Figure 2 illustrates an existing art of straight pipe (04) connected to combustor seal box (06) with a provision of expansion joint (05).
Figure 3 illustrates a present art of Bed material Mixing Nozzle cum transfer lines.
Figure 4 illustrates a present art of refractory lined straight pipe (04) connected to combustor seal box (06) with a provision of expansion joint (05).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
The subject matter of the present invention discloses a refractory lining (08) in the mixing nozzles supported by anchors (07) welded to the duct plate in circulating fluidized bed combustion (CFBC) boilers to prevent erosion of duct plate due to bed material flow.
According to an implementation of present subject matter, an assembly is provided in the bed material mixing nozzles cum transfer lines associated with bed material feeding system of Circulating Fluidised Bed Combustion (CFBC) boilers, aimed to prevent erosion of duct plate due to bed material flow. The present art on providing wear resistant bed material mixing nozzles cum transfer lines mainly comprising of lining the inner of duct assemblies with refractory lining (08) held in position using anchors (07) welded to the duct plate or pipeline.

The refractory lined mixing nozzle cum transfer lines ensure that the duct plate is not eroded away easily and thereby giving prolonged life for the assembly.
The material quality and thickness of refractory used for lining (08) is selected based on quality of bed material used, dimensions and shapes of mixing nozzle chamber (01), mixing nozzle transition pipe (02), air inlet pipes (03) and straight pipes (04). The shape, dimensions, pitching and material quality of anchors (07) is selected based on the material quality and thickness of refractory lining (08) and quality of bed material used.
Figure 3 illustrates a mixing nozzles cum transfer lines associated with bed material feeding system of CFBC boilers, wherein a mixing nozzle chamber is provided with a mixing transition pipe (2).
Further, there is provided an air inlet pipe through which air is supplied to force the bed material into the mixing nozzle transition pipe (2) and then routed to the combustor chamber through straight pipe (4).
Figure 3 and 4 also illustrates a refractory lining (8) in the mixing nozzles which is supported by anchors (7).
The anchors (7) are placed onto the duct plate.
From figures 3 and 4, the refractory lining (08) is cast in situ for the designed thickness. The anchors (07) thus selected are welded to the duct plate at the designed pitch to hold the refractory lining (08) in position. The refractory lining (08) thus made withstands the abrasion due to bed material flow (not shown).

The assembly is held on a flat surface and necessary wooden form works (not shown) are made. The form work is held in position by temporary support (not shown). The refractory castable is mixed using refractory mixing machine and then poured into the form works. Then the refractory slurry poured into form works is vibrated using vibrating needles (not shown) to ensure flow of material to complete volume.
Then the casted assembly is kept for natural curing for 24 hours in order to attain sufficient green strength.
After natural curing, dry out of the refractory lined pipes is to be done with the help of external burners. Post dry out, the mixing nozzle chamber (01), mixing nozzle transition pipe (02) and straight pipes (04) with refractory lining (08) are installed in their location of CFBC boiler.
The refractory thus lined prevents erosion of duct plate caused by the bed material. Drying out of refractory is carried out to develop adequate mechanical strength to the refractory by removing any moisture containing in them.
The non-limiting advantages of the present subject matter are as follows:
1. The present art of the arrangement provide a design of mixing nozzle cum transfer line to enable transfer of bed material from bunker to combustion chamber.
2. The refractory lining (08) is held in position by anchors (07) welded from inside of metallic duct lines.
3. The refractory lining (08) takes care of erosion of duct plates by
preventing bed material having direct contact with steel.

4. The refractory lining (08) is present between duct plate and bed material flow and acts as a barrier to prevent any chemical attack by bed material on duct plate.
5. Using this method of transferring bed material to combustion chamber, it is further claimed that the life of refractory lined mixing nozzle cum transfer lines is improved compared to that without refractory lined ones.

6. The material quality and thickness of refractory used for lining (08) is selected based on quality and characteristics of bed material to be transferred, dimensions and shapes of mixing nozzle chamber (01), mixing nozzle transition pipe (02), air inlet pipes (03) and straight pipes (04).
7. The shape, dimensions, pitching and material quality of anchors (07) is selected based on the material quality and thickness of refractory lining (08) and quality and characteristics of bed material to be transferred.

WE CLAIM:
1. An assembly for wear resistant bed material system of CFBC boilers
comprising:
- a mixing nozzles chamber (1), mixing nozzles cum transfer pipe (2), an air inlet pipes (3) for supplying air to the mixing nozzle transition pipe, which is routed to the combustor chamber through the straight pipe (4);
- a refractory lining (8) inside the said nozzle supported by anchors (7) welded on the duct plate to prevent the erosion of duct plate due to bed material flow.

2. The assembly of wear resistant bed material system of CFBC boilers as claimed in claim 1, wherein quality and thickness of said refractory lining is based on quality and characteristics of bed material to be transferred, dimensions and shapes of mixing nozzle chamber (01), mixing nozzle transition pipe (02), air inlet pipes (03) and straight pipes (04).
3. The assembly of wear resistant bed material system of CFBC boilers as claimed in claim 1, wherein said refractory lining is present between duct plate and bed material flow to act as a barrier to prevent any chemical attack.
4. A method of reducing erosion of duct plate in CFBC boilers comprises
- installing a wear resistant bed material mixing nozzles cum
transfer lines to enable transfer of bed material from bunker to
combustion chamber;

- a refractory lining held in position using anchors welded to the duct plate for taking care of erosion of duct plates due to direct contact with steel.
5. The method of reducing erosion of duct plate in CFBC boilers as claimed in claim 4, wherein said refractory lining is held in position by anchored welded from inside of metallic duct lines.