FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13)
IMPROVED LOOP SEAL FOR A FLUIDIZED BED REACTOR
THERMAX LIMITED
an Indian Company
of D-13, MIDC Industrial Area,
R.D. Aga Road, Chinchwad,
Pune - 411 019, Maharashtra, India
Inventors:
GUPTA DEVKUMAR MITRA CHAITANYA
The following specification particularly describes the invention and the manner in which it is to be
performed.

FIELD OF DISCLOSURE
The present disclosure relates to a fluidized bed reactor. In particular, the present disclosure relates to an improved Seal for recycling solids in a fluidized bed reactor.
BACKGROUND
Fluidized bed reactors have been commonly used for gasification of solid carbon fuels such as coal, char, charcoal, wood, peat, and the like, with steam and air or oxygen, to produce useful synthesis gas (syngas). These fluidized bed reactors primarily comprise a furnace section in which air is supplied through a bed of particulate solid fuel, an inert matter and a sorbent for the oxides of sulfur generated during the combustion, to fluidize the bed and promote combustion of the fuel at a relatively low temperature. The fluidized bed is typically classified into bubbling fluidized bed and circulating fluidized bed. In the bubbling fluidized bed, the bed of the particulate material has a relatively high density and a discrete upper surface. In the circulating fluidized bed the fluidized bed density is below that of a typical bubbling fluidized bed and the fluidizing air velocity is greater than or equal to the bubbling bed, and the flue gases passing through the bed entrain a substantial amount of the particulate matter. The circulating fluidized beds are typically preferred as they provide minimum temperature variations and thereby stabilize the sulfur emissions. However, in the circulating fluidized beds high internal and external solids recycling occurs. The external solids recycling is achieved by separating the solids from the flue gases and returning the solids back to the furnace. This recycling results in increase in the process efficiency.
In such circulating fluidized bed arrangements, a loop seal is provided between the separator and the furnace for externally recirculating the solids back to the dense bed section of the fluidized bed. The loop seal also prevents backflow of

the flue gases. A conventional loop seal is illustrated in the FIGURE 1 of the accompanying drawings. The conventional loop seal, illustrated by the numeral 10 in the FIG. 1, comprises two sections, a first section 18 for receiving the particulate matter 12 through a recycle pipe 14 and a second section 22 for recycling the particulate matter 12 to the fluidized bed through a discharge pipe 24. The first section 18 and the second section 22 are separated by a partition 20 having an opening 26 at the operative bottom for the particulate matter 12 to traverse from the first section 18 to the second section 22. A plenum 16 and a distributor plate 28 are provided at the operative bottom of the first section 18 and the second section 22 to fluidize the matter 12. The particulate matter 12 is recycled to the furnace section of the reactor through the discharge pipe 24 provided above the distributor plate 28.
Several efforts have been made in the past to provide improvements in the loop seals for circulating fluidized bed reactors. JP Patent No. 4076460 discloses the use of a L-valve type loop seal for the circulation fluidized bed incinerator. The L-valve type loop seal is formed in a L-shape ranging from a hollow rising portion of the bottom of a downcomer to a horizontal pipe connected thereto for temporarily storing fluid medium moving down from a cyclone into the downcomer to seal a fluid layer in a riser from the cyclone. The L-valve type loop seal provides a tube diameter adjustment device for expansively changing the inner diameter of the horizontal pipe in the vertical direction.
US Patent No. 5735682 discloses a loop seal valve is in the form of three ducts which connect an outlet of the separator to the furnace for recycling the separated particulate matter back to the furnace. One of the ducts extends vertically from the separator and another duct extends horizontally from the latter duct and connects this latter duct to an angled duct which registers with an

opening in the fixrnace wall. The last duct is angled downwardly to provide an increased throughput when compared to standard loop seal devices.
US Application No. 20120138861 discloses a loop seal for a fluidized bed reactor comprising a vertical downcomer segment connected to a tube for receiving solid particles from the tube, a horizontal segment downstream of the downcomer, a riser segment downstream of the horizontal segment, and a downwardly inclined segment downstream of the riser, whereby the solids are entrained to the fluidized bed reactor. An eductor is added to the angled leg to induce the underflow gas from the cyclone.
Problems associated with the known devices for recycling solids in a fluidized bed reactor, include: difficulty in controlling the solid discharge rate,, need for a separate plenum for the receiving and discharging sections, and the sealing issues between the fluidized bed and the loop seal device.
OBJECTS
Some of the objects of the present disclosure, which the preferred embodiment herein satisfies, are as follows:
It is an object of the present disclosure to overcome the above listed drawbacks of the known devices for recycling solids in a fluidized bed reactor. Accordingly, an object of the present disclosure is to provide a seal for a circulating fluidized bed reactor which is adapted to control the solid discharge rate, eliminate the need for a separate plenum for the receiving and discharging sections, and overcomes the sealing issues in the fluidized bed reactor. Further, the seal provides ease for small-scale operations for laying refractory.

It is another object of the present disclosure to provide a seal which is easy-to- construct, easy-to-maintain and economical.
These objects and other advantages of the present disclosure will be more apparent from the following description.
SUMMARY
In accordance with the present disclosure, there is provided an apparatus for recycling solids in a fluidized bed reactor, said apparatus comprising:
a chamber;
a recycle pipe for receiving solid particulate matter separated from gases generated in the fluidized bed reactor;
a loop pipe operatively connected to said recycle pipe and extending vertically into said chamber;
a plenum located at the operative bottom of said chamber for receiving a fluid to fluidize the solid particulate matter in said chamber;
a distributor plate having a plurality of openings provided between said plenum and said chamber for distributing fluid in said chamber;
a discharge outlet provided on an operative side wall of said chamber for discharging solid particulate matter from said chamber;
a discharge nozzle operatively connecting said discharge outlet to the fluidized bed reactor provided for recycling solid particulate matter;
wherein,
said loop pipe is positioned eccentrically and spaced apart from said discharge outlet;
said recycle pipe and said loop pipe are adapted to hold at least a portion of the solid particulate matter therein and convey the solid particulate matter to a discharge section of the chamber defined between said loop pipe and said discharge outlet; and

said plurality of openings are unevenly distributed on said distributor plate such that the density of the openings proximal to said discharge outlet operatively below said discharge section is greater than the density of the openings operatively below said loop pipe.
Typically, in accordance with the present disclosure, said discharge nozzle is provided at an angle (0) not greater than 30 ° with the operative vertical axis. Preferably, said discharge nozzle has a rectangular cross-section.
In accordance with the present disclosure, the ratio of the diameter of said chamber and the diameter of said loop pipe is in the range of 1.5 - 3.
Typically, in accordance with the present disclosure, the distance between outlet of said loop pipe in said chamber and said distributor plate is in the range of 40 mm to 100 mm.
Preferably, in accordance with the present disclosure, said recycle pipe and said loop pipe are connected by means of a flange.
In accordance with the present disclosure, there is provided a method for recycling solids in a fluidized bed reactor, said method comprising the following steps:
receiving solid particulate matter separated from syngas/flue gases generated in the fluidized bed reactor in a recycle pipe;
conveying the solid particulate matter through a loop pipe extending vertically in a chamber;
fluidizing the solid particulate matter in said chamber by means of a fluid received through a plenum via a distributor plate having a plurality of openings;

recycling the solid particulate matter to the fluidized bed reactor through a discharge outlet provided at the operative side wall of said chamber; wherein,
said loop pipe being positioned eccentrically and spaced apart from said discharge outlet;
said recycle pipe and said loop pipe being adapted to hold at least a portion of solid particulate matter therein and convey solid particulate matter to the chamber defined between said loop pipe and said discharge outlet; and
said plurality of openings being unevenly distributed on said distributor plate such that the density of the openings proximal to said discharge outlet operatively below said discharge section being greater than the density of the openings operatively below said loop pipe.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The disclosure will now be described with the help of the accompanying drawings, in which,
FIGURE 1 illustrates a conventional loop seal for a circulating fluidized bed reactor; and
FIGURE 2 illustrates a loop seal for recycling solids in a fluidized bed reactor in accordance with the present disclosure.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The disclosure will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.

The present disclosure envisages an apparatus, comprising a submerged-type loop, for recycling solids in a fluidized bed reactor. The apparatus is adapted to control the solid discharge rate, eliminates the need for a separate plenum for the receiving and the discharging sections, and overcomes the positive sealing issues between the fluidized bed and the apparatus. Further, the apparatus provides ease for small-scale operations for laying the refractory. The apparatus is easy to construct and maintain. The apparatus comprises a single chamber in which a loop pipe enters into the chamber; the loop pipe is adapted to hold at least a portion of the solid particulate matter, thereby acting as the receiving section for the apparatus. A fluid, typically air or steam or a steam-air mixture, is received in the chamber through a plenum via a distributor plate. The distributor plate has a plurality of openings which are unevenly distributed on the distributor plate such that density of the openings in the discharging section is greater than the density of the openings in the receiving section.
FIGURE 2 of the accompanying drawings discloses a preferred embodiment of the apparatus of the present disclosure. The apparatus, referred by numeral 100 in the FIG. 2, is a one-chamber 104 seal apparatus which acts both as the receiving chamber and the discharge section. The apparatus 100 can have a rectangular or circular cross-section. A single plenum 101 is provided at the operative lower region of the chamber 104 and a discharge outlet 108 is provided on the operative wall of the chamber 104 for discharging solid particulate matter. The apparatus 100 includes a recycle pipe 102 for receiving solid particulate matter separated from gases generated in the fluidized bed reactor. The recycle pipe 102 is connected to a loop pipe 105 by means of a connecting flange 106. The ratio of the diameter of the chamber 104 and the diameter of the loop pipe 105 is typically in the range of 1.5 - 3. The loop pipe 105 extends vertically in the chamber 104 and is adapted to discharge solid particulate matter in the chamber 104 at an outlet 110.

During operation, the recycle pipe 102 and the loop pipe 105 are adapted to hold at least a portion of the solid particulate matter therein. This eliminates the need for a separate receiving section in the seal apparatus 100. The loop pipe 105 is located eccentrically in the chamber 104, distant from the discharge outlet 108, such that a discharge section 103 is defined between the loop pipe 105 and the discharge outlet 108 for circulation of the solid particulate matter therefrom. The hold-up of the solid particulate matter in the recycle pipe 102, the loop pipe 105 and the discharge section 103 assures positive sealing between the fluidized bed and the apparatus 100. The path of the solid particulate matter in the discharge section 103 is shown by arrow 112 in the FIG. 2.
The plenum 101 is provided at the operative bottom of the chamber 104 for receiving a fluid, typically air, steam or a steam-air mixture, at the point 120, to fluidize the solid particulate matter in the chamber 104. A distributor plate 116 is provided between the plenum 101 and the chamber 104. The distributor plate 116 has a plurality of openings 122. The plurality of openings 122 are unevenly distributed on the distributor plate 116 such that the density of the openings 122 proximal to the discharge outlet 108 operatively below the discharge section 103 is greater than the density of the openings 122 proximal to the loop pipe 105. This can also be achieved by making the size of the apertures larger below the discharge section.
A difference in the density/size of the openings 122 in the receiving section and the discharging section gives the advantage of using a single chamber apparatus. The distance between the outlet 110 of the loop pipe 105 in the chamber 104 and the distributor plate 116 is preferably in the range of 40 mm - 100 mm. The discharge outlet 108 is located at the operative side wall of the chamber 104. The chamber 104 can have a rectangular or circular cross section. A circular cross-section for the chamber 104 is suitable at high pressure. The solid

particulate matter is discharged through the chamber 104 through discharge outlet 108. A discharge nozzle 114 is provided operatively connecting the discharge outlet 108 to the fluidized bed reactor for recycling the solid particulate matter to the fluidized bed reactor. The discharge nozzle 114 preferably has a rectangular cross-section to provide less resistance during solid discharge. The discharge nozzle 114 is provided at an angle (0) 118 not greater than 30 ° with the operative vertical axis to give easy discharge of the solid particulate matter from the discharge section 103.
The distributor plate 116 having different density/size of openings 122 near the discharging section and the receiving section i.e. more holes at the solid discharge than near the loop pipe outlet 110 also eliminates the need for a separate plenum for the discharging section and the receiving section. The fluid entering at the plurality of openings 122 is adapted to keep the solid particulate matter in a fluidized state in the discharge section 103. In the apparatus of the present disclosure one embodiment of the apparatus has the following design parameters: the ratio of the length of the chamber 104 to the diameter of the chamber 104; the ratio of the diameter of the chamber 104 to the diameter of the loop pipe 105; the eccentric location of the loop pipe 105; the area differential between the plurality of openings 122 on the distributor plate 116 at the discharging section and the receiving section; location of the discharge outlet 108; and the distance' between the outlet 110 of the loop pipe 105 in the chamber 104 and the distributor plate 116.
TECHNICAL ADVANTAGES
An apparatus, comprising a submerged-type loop, for recycling solids in a fluidized bed reactor, as described in the present disclosure has several technical advantages including but not limited to the realization of: the submerged-type loop is adapted to control the solid discharge rate, eliminates the need for a

separate plenum for the receiving and discharging sections, and overcomes the sealing issues between the fluidized bed and the apparatus; the apparatus further assists in small-scale operations for laying the refractory; the apparatus is easy-to-construct, easy-to-maintain and economical.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the invention, unless there is a statement in the specification specific to the contrary.

In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principle of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

WE CLAIM
1. An apparatus (100) for recycling solids in a fluidized bed reactor, said
apparatus (100) comprising:
a chamber (104);
a recycle pipe (102) for receiving solid particulate matter separated from gases generated in the fluidized bed reactor;
a loop pipe (105) operatively connected to said recycle pipe (102) and extending operatively vertically into said chamber (104);
a plenum (101) provided at the operative lower region of said chamber (104) for receiving a fluid to fluidize the solid particulate matter in said chamber (104);
a distributor plate (116) having a plurality of openings (122) provided between said plenum (101) and said chamber (104) for distributing fluid in said chamber (104);
a discharge outlet (108) provided on an operative side wall of said chamber (104) for discharging solid particulate matter from said chamber (104);
a discharge nozzle (114) operatively connecting said discharge outlet (108) to the fluidized bed reactor is provided for recycling solid particulate matter;
wherein,
said loop pipe (105) being positioned eccentrically and spaced apart from said discharge outlet (108);
said recycle pipe (102) and said loop pipe (105) being adapted to hold at least a portion of solid particulate matter therein and convey the solid particulate matter to a discharge section (103) defined between said loop pipe (105) and said discharge outlet (108); and
said plurality of openings (122) are unevenly distributed on said distributor plate (116) such that the density of the openings (122) proximal to said discharge outlet (108) operatively below said discharge section (103) is greater than the density of the openings (122) operatively below said loop pipe (105).

2. The apparatus as claimed in claim 1, wherein said discharge nozzle (114) is provided at an angle (0) not greater than 30 ° with the operative vertical axis.
3. The apparatus as claimed in claim 1, wherein said discharge nozzle (114) has a rectangular cross-section.
4. The apparatus as claimed in claim 1, wherein the ratio of the diameter of said chamber (104) and the diameter of said loop pipe (105) is in the range of 1.5-3.
5. The apparatus as claimed in claim 1, wherein the distance between outlet of said loop pipe (105) in said chamber (104) and said distributor plate (116) is in the range of 40 mm - 100 mm.
6. The apparatus as claimed in claim 1, wherein said recycle pipe (102) and said loop pipe (105) are connected by means of a flange (106).
7. A fluidized bed reactor comprising the apparatus as claimed in claim 1.
8. A method for producing syngas using the fluidized bed reactor as claimed in claim 7.
9. A method for recycling solids in a fluidized bed reactor, said method comprising the following steps:
receiving solid particulate matter separated from syngas/flue gases generated in the fluidized bed reactor in a recycle pipe;
conveying the solid particulate matter through a loop pipe extending vertically in a chamber;

fluidizing the solid particulate matter in said chamber by means of a fluid received through a plenum via a distributor plate having a plurality of openings;
recycling the solid particulate matter to the fluidized bed reactor through a discharge outlet provided at the operative side wall of said chamber; wherein,
said loop pipe being positioned eccentrically, spaced apart from said discharge outlet;
said recycle pipe and said loop pipe being adapted to hold at least a portion of the solid particulate matter therein and convey the solid particulate matter to a discharge section defined between said loop pipe and said discharge outlet; and
said plurality of openings are unevenly distributed on said distributor plate such that the density of the openings proximal to said discharge outlet operatively below said discharge section is greater than the density of the openings operatively below said loop pipe.