FORM - 2
THE PATENTS ACT, 1970
(39 OF 1970)
COMPLETE SPECIFICATION
(See Section 10)
TITLE OF INVENTION
"Air Assisted Solid Injecting Device"
(a) Thermax Limited (b) having administrative office at D-1, MIDC, Chinchwad, Pune411 019 India
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

Field of Invention
The present invention relates to an air assisted solid injecting device for combustion system in particular fluid bed system.
Background of the Invention
In a combustion system, solid air mixture is supplied to the combustion chamber. It is necessary to convey appropriate quantity of solid against the combustion chamber pressure for an effective combustion, with aid of air. The solid air mixing system generally comprises of a converging section, solid air mixing section, diverging section and solid supply nozzle. Air pressure in the mixing chamber plays important role in solid suction and appropriate transport of the solid against said back pressure. Along with other parameters, ratios of the diameters of the converging, diverging conduit governs the pressure in the chamber. The solid may be selected from a combustible substance, but not limited to it.
US patent 6,402, 068 discloses eductor-mixer system designed to continuously mix a solute such as paint pigments, fire retardants, liquids and gels, (e.g., a powder, particulate, or other pressure transportable or fluidizable material, a liquid or a gas) and a solvent or working fluid (e.g., a liquid or in some instances a gas) to form a dispersion, slurry, or solution. The pressurized working fluid is discharged through a cylindrical annular nozzle as a translational high speed jet flowing longitudinally past a end of a solute inlet tube into a tubular discharge passage having a uniform inner diameter greater than the outer diameter of the annular nozzle, for generating a vacuum thereby to positively draw a pressure transportable material such as a granular, powdered, or other particulate solid, or a liquid or a gas, through the solute inlet tube and into the tubular discharge passage for mixing with the working fluid to form a dispersion.
Conventional devices reported in the literature suffer from the following
drawbacks:
Substantially high pressure drop across the device leading to higher pumping power
2

> Substantially lower suction pressure for a desired combustion chamber pressure.
> Increased excess air supply which results reduced efficiency
> Choking problems
> Problems of wearing out of the mixing section walls
> Inadequate access to the converging, diverging and mixing sections individually.
To reduce pumping power it is desirable to reduce pressure drop without compromising on the air-solid flow rate across this device.
Necessity has constantly been felt to develop a device that can produce substantially increased suction pressure at the mixing section and reduced terminal pressure drop obviating chocking and maintenance problems.
The present invention addresses drawbacks of the prior art.
Summary of the Invention
The main object of the invention is to provide an air assisted sized solid injecting device for fluid bed combustion system.
Another object of the invention is to supply appropriate quantity of solid against combustion chamber back pressure.
Another object of the invention is to substantially increase suction pressure at the air-solid mixing section of the said device.
Yet another object of the invention is to substantially reduce transport / conveying air quantity.
Yet another object of the invention is to reduce terminal pressure drop substantially.
3

Another object of the invention is to substantially reduce wearing out of the mixing section walls.
Yet another object of the invention is to reduce transport/conveying air to the combustion system.
Another object of the invention is to improve maintainability and accessibility of the device
Yet another object of the invention is to obviate chocking of the solid flow.
Yet another object of the invention is to provide solid injecting device for sized solids up to 15 mm size.
Thus in accordance with this invention the device comprises of:
a converging portion provided with a reducing cross section passage in the
direction of the air flow with bigger diameter end as inlet to air;
an insert provided with contoured passage, smaller and bigger diameter end; a
diverging conduit with bigger diameter end as outlet to air-solid mixture; online
cleaning provision;
air-solid mixing section adapted to fit a part of the said converging portion and
said contoured insert; solid inlet provision on the said air-solid mixing section;
wherein the said converging portion, air-solid mixing section, insert and the
diverging conduit are coaxially connected such that:
smaller diameter end of the said converging portion extends in the air-solid mixing
section; the said insert is fitted in the said air-solid mixing section
wherein
smaller diameter end of the said insert and the smaller diameter end of the
diverging conduit are connected, bigger diameter end of the said diverging conduit
is the outlet to air-solid mixture.
4

Description of the Invention
Features and advantages of this invention will become apparent in the following
detailed description and the preferred embodiments with reference to the accompanying drawings.
Figure 1: Schematic of the air-solid mixing device (Sheet 1)
The air-solid mixing device comprises of a converging portion / section 10, a air-solid mixing section/ chamber 11, solid supply pipe 12, contoured insert 13 and diverging portion 14 joined coaxially with each other. The bigger diameter end 1 having diameter d1 of the converging portion is the inlet to working fluid that is air. A portion of 10 that is the smaller diameter end 2 having diameter d2 of the said converging portion 10 extends in the air-solid mixing chamber 11. The solid supply pipe 12 is positioned above the air-solid mixing chamber 11. The insert is joined / fitted/ disposed into the mixing chamber 11 and the diverging section 14 such that the bigger end of the insert 15 is towards 11 and the smaller is joined to the smaller end of the diverging conduit 14. The minimum diameter of the said contoured insert is d4. The insert is provided with a profiled passage, this is indicated in the Figure 1 with 16 and 17 as contoured walls of the passage in the cross section of the passage. The passage has minimum cross sectional diameter formed by the said contoured walls. The bigger end 4 of the diverging conduit 14 is the outlet for air-solid mixture. Online cleaning provision 18 is provided at the bottom of the said mixing chamber 11.
Working fluid that is air enters the bigger diameter end 1 of the said converging portion 10, velocity of air increases and pressure reduces as it passes through the converging portion, the pressure, hereinafter called as suction pressure reaches minimum in the air-solid mixing chamber 11 wherein velocity reaches to its maximum. The walls of the insert are prone to severe ware because of the impingement of high velocity air-solid mixture. Since converging portion, mixing chamber, insert and the diverging conduit are joined to each other and not integral parts, it is possible to replace any of the part easily. Further, only the insert can
be made of ware resistant special material.
In one of the embodiments, solid is a combustible substance, fuel etc.
5

We claim:
1. An air assisted solid injecting device for fluid bed combustion system
comprising:
a converging portion provided with a reducing cross section passage in the
direction of the air flow with bigger diameter end as inlet to air;
an insert provided with contoured passage, smaller and bigger diameter
end; a diverging conduit with bigger diameter end as outlet to air-solid
mixture; online cleaning provision;
air-solid mixing section adapted to fit a part of the said converging portion
and said contoured insert; solid inlet provision on the said air-solid mixing
section;
wherein the said converging portion, air-solid mixing section, insert and the
diverging conduit are coaxially connected such that:
smaller diameter end of the said converging portion extends in the air-solid
mixing section; the said insert is fitted in the said air-solid mixing section
wherein
smaller diameter end of the said insert and the smaller diameter end of the
diverging conduit are connected, bigger diameter end of the said diverging
conduit is the outlet to air-solid mixture.
2. An air assisted solid injecting device for fluid bed combustion system as claimed in claims 1-2 wherein the passage walls of the said insert are contoured.
3. An air assisted solid injecting device for fluid bed combustion system as claimed in claim 1 wherein the insert is made of special wear resistant material such as alloy steel.
4. An air assisted solid injecting device for bed fluid bed combustion system as claimed in claims 1-3 wherein ratio of the small end diameter of the said converging portion to the minimum cross sectional diameter of the said contoured insert is in the range of 1.35 to 1.65.
6

5. An air assisted solid injecting device for fluid bed combustion system as claimed in claims 1-3 wherein the distance between the said small end diameter of the converging portion and minimum diameter of the said contoured insert is 3 to 6 times the small end diameter of the converging portion.
6. An air assisted solid injecting device for fluid bed combustion system as claimed in claims 1-5 wherein the said converging portion, air-solid mixing section and the said diverging conduit are bolted /flanged together.
7. An air assisted solid injecting device for fluid bed combustion system as claimed in claims 1-6 wherein the said converging portion, air-solid mixing section and the said diverging conduit are flanged together.
8. An air assisted solid injecting device for fluid bed combustion system as claimed in claims 1-7 wherein the said converging portion is provided with two parts wherein first part with a bigger end diameter is bolted to the said air-solid mixing section and the second part with a smaller diameter end is disposed / fitted in the said provision provided in the said air-solid mixing section.
9. An air assisted solid injecting device for fluid bed combustion system as claimed in claim 1 wherein solid is a sized fuel.
Date: 4/09/2006
Applicant
Thermax Limited
7

Abstract
In a combustion system, solid air mixture is supplied to the combustion chamber. It is necessary to convey appropriate quantity of solid against the combustion chamber pressure for an effective combustion, with aid of air. In the solid air mixing system, mixing wall sections often encounter the problem of wearing out. Further, in the conventional devices there is inadequate access to the converging, diverging and mixing sections individually. Necessity has constantly been felt to develop a device that can produce substantially increased suction pressure at the mixing section and reduced terminal pressure drop obviating chocking and maintenance problems so as to reduce pumping power. The synergistic combination of converging section, mixing section, insert, diverging section of the device of the present invention facilitates easy access to the mixing section and overcomes the problems of its wearing out. Further, it substantially reduces chocking problems.