Title of Invention	AN IMPROVED FLUIDIZED BED THERMIC FLUID HEAT EXCHANGER AND AN IMPROVED METHOD FOR THE RECOVERY OF HEAT IN A THERMIC FLUID FLUIDIZED BED HEAT EXCHANGER
Abstract	An improved fluidized bed thermic fluid heat exchanger comprising fluidized bed column having principally three sections, namely, a first lower most section having means for admission of fluidization air, a second intermediate section, above the said first section having, on a perforated support, a bed of inert solids adopted to.be fluidized by fluidization air when admitted through the said first section,tfhe sad bed has embedded therein heat transfer tubes adopted for passing a first fluid other than a thermic fluid to effect heat exchange with the hot fluidized bed, said second intermediate section having means for feeding required fuel thereto, the said third section being provided at the top of the said column having a set of heat exchanger tubes' for passing thermic fluid there through, in heat exchange relationship with the hot gases evolved from the fluidized bed, the thermic fluid exit end having means for connecting same to an end use section, the top end of the column having means for connecting it to pollution control equiHuient and stack and wherein there is also provided an additional heat exchanger adopted to circulate incoming thermic fluid and the hot intermediate fluid exiting the embedded tube in heat exchange relationship with one another.

Title of Invention

AN IMPROVED FLUIDIZED BED THERMIC FLUID HEAT EXCHANGER AND AN IMPROVED METHOD FOR THE RECOVERY OF HEAT IN A THERMIC FLUID FLUIDIZED BED HEAT EXCHANGER

Abstract

An improved fluidized bed thermic fluid heat exchanger comprising fluidized bed column having principally three sections, namely, a first lower most section having means for admission of fluidization air, a second intermediate section, above the said first section having, on a perforated support, a bed of inert solids adopted to.be fluidized by fluidization air when admitted through the said first section,tfhe sad bed has embedded therein heat transfer tubes adopted for passing a first fluid other than a thermic fluid to effect heat exchange with the hot fluidized bed, said second intermediate section having means for feeding required fuel thereto, the said third section being provided at the top of the said column having a set of heat exchanger tubes' for passing thermic fluid there through, in heat exchange relationship with the hot gases evolved from the fluidized bed, the thermic fluid exit end having means for connecting same to an end use section, the top end of the column having means for connecting it to pollution control equiHuient and stack and wherein there is also provided an additional heat exchanger adopted to circulate incoming thermic fluid and the hot intermediate fluid exiting the embedded tube in heat exchange relationship with one another.

Full Text	THE PATENT ACT, 1970 COMPLETE SPECIFICATION (SECTION-10) TITLE "AN IMPROVED FLUIDIZED BED THERMIC FLUID HEAT EXCHANGER AND AN IMPROVED METHOD FOR THE RECOVERY OF HEAT IN A THERMIC FLUID FLUIDIZED BED HEAT EXCHANGER" APPLICANT THERMAX LIMITED, HAVING REGISTERED OFFICE AT D-13, MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE-411 019, MAHARASHTRA, INDIA, AN INDIAN COMPANY GRANTED The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed. INTRODUCTION TO THE FIELD OF THE INVENTION This invention relates to Improved Fluidized Bed Thermic Fluid Heater (FBTH). PRIOR ART AND DRAWBACKS FBTH is already known in the art and is used widely for various end uses of the Thermic Fluid. In the existing FBTH, conventional solid fuel is burnt in the fluidized bed and the heat generated is used to heat Thermic Fluid in a separate Heat exchanger System, namely in a Tubular Heat exchanger, by Indirect Heat Exchange. In this conventional FBTH, required Thermic Fluid is passed through a set of tubes provided at the top end of the body of the FBTH, in the space (free board) through which the hot gases pass. Because of the high risk involved, the Thermic Fluid circulating tubes can not be introduced into the mbed heat exchanger tubes embedded in the Fluidized Bed and therefore in the existing FBTH the full potential of the Fluidized Bed system is untapped. SCOPE FOR IMPROVEMENTS Studies have indicated that if the untapped potential of a FBTH can be realized, it will result in the following advantages : 1. Increase in efficiency 2. Reduction in electric power consumption 3. Reduction in degradation of thermic fluid 4. Reduction in the size of pollution control equipment No concrete and practical suggestion has so far been made for realizing the above stated advantages in FBTH. OBJECTS OF THE INVENTION It is therefore a principle object of this invention to propose improvements to the existing FBTH for realizing all the potentials untapped so far. It is another object of this invention to propose use of embedded Heat Exchanger tubes in a FBTH which has never been considered feasible. It is a further object of the invention to propose such an improved FBTH wherein greater amount of heat can be recovered at the site of the fluidized bed itself than hitherto possible. It is a still further object of this invention to propose such an improved FBTH in which the usual pollution problem can be effectively controlled. It is an additional object of this invention to propose such a FBTH wherein the thermic fluid is pre-heated before being admitted into the FBTH. A still further object of this invention to propose such an improved FBTH wherein not only the rate of heat transfer is enhanced but also the heat economy is significantly improved compared to conventional FBTH. These and other objects of this invention will be more clear from the ensuing paragraphs : BRIEF STATEMENT OF THE INVENTION Thus, according to this invention there is provided an improved fluidized bed thermic fluid heat exchanger comprising fluidized bed column having principally three sections, namely, a first lower most section having means for admission of fluidzation air, a second intermediate section, above the said first section having, on a perforated support, a bed of inert solids adopted to be fluidized by fluidization air when admitted through the said first section, the said bed having embedded therein heat transfer tubes adopted for passing a first fluid other than a thermic fluid to effect heat exc hange with the hot fluidized bed, said second intermediate section having .means for feeding required fuel thereto,jihe said third section being provided at the top of the said column having a set of heat exchanger tubes for passing thermic fluid there through, in heat exchange relationship with the hot gases evolved from the fluidized bed, the thermic fluid exit end having means for connecting same to an end use section, the top end of the column having means for connecting it to pollution control equipment and stack and wherein there is also provided an additional heat exchanger adopted to circulate incoming thermic fluid and the hot intermediate fluid exiting the embedded tube in heat exchange relationship with one another. The embedded tube is in the form of straight tubes, coils etc extending substantially to the whole area of the fluidized bed and the heat exchanger provided at the top of the column is separated and spaced apart from the fluidized bed. It is to be noted that the additional heat exchanger is provided with inlet means for admitting thermic fluid exiting the said third section at the top of the column with or without replenishment. Preferably, the additional heat exchanger is provided(additipnal heat . Cexchang'ef isyprovided loutside the said column, with inlet means for admitting thermic fluid exiting the said third section at the top of the column with or without replenishment In this heat exchanger, the said thermic fluid exiting the additional heat exchanger is connected to said end user section directly and the inlet end of the thermic fluid at the additional heat exchanger is connected to the outlet end of thermic fluid tube in the third section of the said column, the inlet end of the thermic fluid at this section being connected to the thermic fluid return means from the end user section. In this construction the inlet end of the thermic fluid in the third section of the said column is provided, if required, with a diversions means for diverting a part of the returned thermic fluid to the inlet end of the thermic fluid tube in the additional heat exchanger in which case the outlet end of the thermic fluid tube in the third section of the said column is connected to the outlet means of the thermic fluid exiting the additional heat exchanger. The inlet means for admitting the thermic fluid is directly connected to the end user section for receiving returned thermic fluid and the inlet means for the thermic fluid is provided if required with diversion means for diverting a part of the thermic fluid to the third section in the said column, in which instance the thermic fluid outlet means at the additional heat exchanger is connected to the outlet means at the thermic fluid tube in the said third section of the said column. The additional heat exchanger is provided with inlet means for admitting the hot fluid exiting the embedded tube in the fluidized bed and is also provided with means for returning the heat depleted fluid to the inlet of the embedded tube. According to another aspect of the invention, there is also provided an improved method for the recovery of heat in a thermic fluid fluidized bed heat exchanger wherein a thermic fluid admitted at the top section of the heat exchanger is heated by the flue gasses passing from the fluidized bed characterized in that a part of the heat generated by the burning of the fuel m the fluidized bed is recovered at the fluidized bed section itself by means of a fluid other than the thermic fluid and wherein such heat partly recovered is used to heat the thermic fluid recovered in the fluidized bed heat exchanger and the heating of the thermic fluid by other fluid exiting the embedded tubes is carried out by indirect heat exchange relationship in an additional heat exchanger. In one aspect, the thermic fluid returned from the end user section is fully directly used in the additional heat exchanger and the pre-heated thermic fluid is further heated in the fluidized bed heat exchanger. In another aspect, a part of the thermic fluid returned from the end user is used in the said additional heat exchanger while another part of the returned thermic fluid is used in the fluidized bed heat exchanger and the heated thermic fluid from the additional heat exchanger and the fluidized bed heat exchanger are used together for end user section. In yet another aspect, all the thermic fluid returned from the end user section is used in the fluidized bed heat exchanger to pre-heat the same and the said pre-heated thermic fluid is then used in the said additional heat exchanger for recovering additional heat from the hot liquid taken from the embedded tubes. In a further aspect, a part of the thermic fluid returned from the end user section is used in the fluidized bed heat exchanger for preheating the same, while the other part of the thermic fluid is used in the said additional heat exchanger, in heat exchange relationship with the hot fluid stream exiting the fluidized bed heat exchanger and the two exiting heated thermic fluid streams are mixed together before being sent to the end user. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be more fully described with reference to the accompanying drawings which are only schematic representation of the improved FBTH. In the accompanying drawings Figure 1 shows a conventional FBTH. Figures 2 & 3 show one embodiment of the improved FBTH according to the invention. Figure 4 shows a second embodiment of the FBTH according to the invention. Figure 5 shows a third embodiment of the improved FBTH according to the invention. Figure 6 shows a further embodiment of the improved FBTH according to the invention. DETAILED DESCRIPTION OF THE DRAWINGS Referring now to Figure 1, it will be observed that in the conventional FBTH-1, necessary air is supplied by fan-3 and the air travels upwards through a hot fluidized bed-2. The fluidized bed is made of inert solids which can be selected from silica sand, refractory grog etc of suitable particle sizes. The necessary fuel can be selected from coal / rice husk / lignite and other agrowaste fuels and the fuel is fed into the bed by any known standard fuel feeding system with all accessories and is not shown in the figure. The space above the fluidized bed is provided with heat exchange tubes-4 through which the thermic fluid to be heated is pumped by pump-5. In a conventional heat exchange between the hot gases and thermic fluid, heat recovery rate is limited and hence for a fixed amount of heat to be recovered, the whole system becomes large and is not economical. Referring now to Figure-2, it will be noticed that there is an inbed heat exchanger 6 embedded in the fluidized bed-2 itself. This heat exchanger is provided with independent heat recovering.fluid other than thermic fluid from an independent source. This fluid is called intermediate fluid, and extracts substantial amount of heat from the fluidized bed and is heated to a temperature depending upon the type of the fluid and conditions of the circulation. This intermediate fluid can be selected from water / air As will be observed from the Figure-2, there is also provided a second heat exchanger-7 external to the fluidized bed heat exchanger which contains the thermic fluid. The heated fluid coming from a fluidized bed-2 is in a hot condition and exchanges heat to the thermic fluid held in the heat exchanger-7 and thus heats the thermic fluid. Depleted of its heat, the intermediate fluid is then returned to the embedded inbed heat exchanger tubes for heat absorption. It will also be observed that in the second heat exchanger-7, there is provision for heating up the thermic fluid which is then used for further processing or end uses. The preheated thermic fluid-8 leaving the heat exchanger-7, is then introduced into the conventional heat exchanger tubes, provided at the top end of the body of the FBTH. The heated thermic fluid is sent for the end uses. In both figures f&2, the exhaust gases leaving the FBTH is subjected to usual pollution control in the pollution control equipment. Additional heat can be recovered in an air pre-heated .APH. In both the instances the flue gas can be exhausted into the stack or further heat can be recovered from it by pre-heating combustion / fluidizing air in any known air preheater APH. Figure-3 is a replica of Figure-2 only shown in a different manner. In this Figure the thermic fluid is first admitted to the heat exchanger-7, preheated and then admitted to the FBTH, from where it picks up additional heat and then sent for end1 uses. It will thus be observed from Figure-3, that pre-heated air is blown into FBTH. The intermediate fluid is passed through the imbedded heat exchanger as in Figure-2, which is heated and passes through the heat exchanger-7 as in Figure-2. Thermic Fluid to be heated is pumped through the heat exchanger-7 again as in Figure-2 and the pre-heated thermic fluid is sent to the convention bank at the top of the FBTH as in Figure-2 and the heated thermic fluid is sent to end uses. The air stream or the flue gas is treated in the same manner as in Figure-2. Figure-4 is the same as Figure-3 excepting for the reverse flow of the thermic fluid, first through the convection bank and then through heat exchanger-7. Thus in Figure-4 the thermic fluid is pre-heated in the convection bank picking up heat from the flue gases and then further heated in the exchanger-7 picking up heat from the heated intermediate fluid and the thus heated thermic fluid is sent for end uses. The heat depleted intermediate fluid is returned to the imbedded tubular arrangement for picking up heat from the fluidized bed. The flue gases exiting the convention bank is used to preheat incoming air in an air pre-heater and then sent to the stack. Figure-5 is a slight modification of Figure-3 in that there is no change in the treatment of the flue gases. However there is a slight modification in the treatment of the intermediate fluid. Compared to Figure-3, in Figure-5, the incoming thermic fluid is split into two streams S1 and S. While stream S1 exchanges heat in the heat exchanger-7 with the hot intermediate fluid, it does not pass through the convection bank as in Figure-3. The stream S2 is instead passed through the convection bank. The outgoing stream S1 and S are combined for end use. Figure-6 is reverse of Figure-5 and is similar to Figure-4 in that there is no change in the treatment of the flue gases but there is a modification in the treatment of the thermic fluid. The incoming thermic fluid is divided into two streams S1 and S* and stream S1 is passed through heat exchanger-7 and the stream S* is passed through the convection bank. Both the out-coming streams are combined for end use. ADVANTAGES OF THE INVENTION AND REALISATION OF OBJECT OF THE INVENTION It will thus be observed that the improved FBTH has flexibility in operation in addition to being more economical. in the following table we have given the improvements / advantages in the invention over conventional FBTH PARAMETERS IMPROVED FBTH Efficiency increase About 3 - 4% Reduction in Power Consumption By 30% Increase in life of Thermic Fluid About 50% Reduction in size of Pollution Control Equipment By 10-15% WE CLAIM : 1. An improved fluidized bed thermic fluid heat exchanger comprising fluidized bed column having principally three sections, namely, a first lower most section having means for admission of fluidization air, a second intermediate section, above the said first section having, on a perforated support, a bed of inert solids adopted to.be fluidized by fluidization air when admitted through the said first section,tfhe sad bed has embedded therein heat transfer tubes adopted for passing a first fluid other than a thermic fluid to effect heat exchange with the hot fluidized bed, said second intermediate section having means for feeding required fuel thereto, the said third section being provided at the top of the said column having a set of heat exchanger tubes' for passing thermic fluid there through, in heat exchange relationship with the hot gases evolved from the fluidized bed, the thermic fluid exit end having means for connecting same to an end use section, the top end of the column having means for connecting it to pollution control equiHuient and stack and wherein there is also provided an additional heat exchanger adopted to circulate incoming thermic fluid and the hot intermediate fluid exiting the embedded tube in heat exchange relationship with one another. 2. An improved fluidized bed thermic fluid heat exchanger as claimed in Claim 1, wherein said embedded tube is in the form of straight tubes, coils extending substantially to the whole area of the fluidized bed. 3. An improved fluidized bed thermic fluid heat exchanger as claimed in Claim 1 or 2 wherein the heat exchanger provided at the top of the column is separated and spaced apart from the fluidized bed. 4. An improved fluidized bed thermic fluid heat exchanger as claimed in. any of the Claims 1 to 3 wherein the said'additional heat exchanger is r provided, with inlet means for admitting thermic fluid exiting the said third section at the top of the column with or without replenishment. 5. An improved fluidized bed thermic fluid heat exchanger as claimed in any of the Claims 1 to 3 wherein the said additional heat exchanger provided additional heat exchanger is provided outside the said column, with inteli means for admitting thermic fluid exiting the said third section at the top of the column with or without replenishment. 6. An improved fluidized bed thermic fluid exchanger as claimed in claim-1 wherein the said thermic fluid exiting the additional heat exchanger is connected to said end user section directly and the inlet end of the thermic fluid at the additional heat exchanger is connected to the outlet end of thermic fluid tube in the third section of the said column, the inlet end of the thermic fluid at this section being connected to the thermic fluid return means from the end user section. 7. An improved fluidized bed thermic fluid exchanger as claimed in claim-6 wherein the inlet end of the thermic fluid in the third section of the said column is provided, if required, with a diversions means for diverting a part of the returned thermic fluid to the inlet end of the thermic fluid tube in the additional heat exchanger in which case the outlet end of the thermic fluid tube in the third section of the said column is connected to the outlet means of the thermic fluid exiting the additional heat exchanger. 8. An improved ftuidized bed thermic fluid exchanger as claimed in claim-4 wherein the said inlet means for admitting the thermic fluid is directly connected to the end user section for receiving returned thermic fluid. 9. An improved fluidized bed thermic fluid exchanger as claimed in claim-8 wherein the inlet means for the thermic fluid is provided if required with diversion means for diverting a part of the thermic fluid to the third section in the said column, in which instance the thermic fluid outlet means at the additional heat exchanger is connected to the outlet means at the thermic fluid tube in the said third section of the said column. 10. An improved fluidized bed thermic fluid exchanger as claimed in claim-4 wherein the said additional heat exchanger is provided with inlet means for admitting the hot fluid exiting the embedded tube in the fluidized bed and is also provided with means for returning the heat depleted fluid to the inlet of the embedded tube. 11. An improved fluidized bed thermic fluid exchanger substantially as herein described with reference to Figures2 to 6 of the accompanying drawings. 2. An improved Wfesd for the recovery of heat in a thermic fluid exchanger wherein a thermic fluid admitted at the top section ol the heat exchanger is heated by the flue gasses passing'from the fluidized bed characterized in that a part of the heat generated by the burning of the fuel in the fluidized bed is recovered at the fluidized bed section itself by means of a fluid other thanJthethermic fluid and wherein such heat partly recovered is used to heat the thermic fluid recovered in the fluidized bed heat exchanger. 13. A process as claimed in claim-12 wherein said heating of the thermic fluid by other fluid exiting the embedded tubes is carried out by indirect heat exchange relationship in an additional heat exchanger. 14. A process as claimed in claims 12 & 13 wherein the thermic fluid returned from the end user section is fully directly used in the additional heat exchanger and the pre-heated thermic fluid is further heated in the fluidized bed heat exchanger. 15. A process as claimed in claims 12 & 13 wherein a part of the thermic fluid returned from the end user is used in the said additional heat exchanger while another part of the returned thermic fluid is used in the fluidized bed heat exchanger and the heated thermic fluid from the additional heat exchanger and the fluidized bed heat exchanger are used together for end user section. 16. A process as claimed in claims 12 & 13 wherein all the thermic fluic returned from the end user section is used in the fluidized bed heat exchanger to pre-heat the same and the said pre-heated thermic fluid is then used in the said additional heat exchanger for recovering additional heat from the hot liquid taken from the embedded tubes. 17. A process as claimed in claims 12 & 13 wherein a part of the thermic fluid returned from the end user section is used in the fluidized bed heat exchanger for preheating the same, while the other part of the thermic fluid is used in the said additional heat exchanger, in heat exchange relationship with the hot fluid stream exiting the fluidized bed heat exchanger and the two exiting heated thermic fluid streams are mixed together before being sent to the end user. 18. An improved process'ror recovering heat in a thermic fluid heat exchanger substantially as herein described with reference to the Figures 2 to 6 of the accompanying drawings. Dated this 3rd Day of May 2000. (K.RAJAGOPALAN ) of RAJAGOPALAN AND ASSOCIATES AGENT FOR APPLICANT.

Full Text

THE PATENT ACT, 1970 COMPLETE SPECIFICATION
(SECTION-10)
TITLE
"AN IMPROVED FLUIDIZED BED THERMIC FLUID
HEAT EXCHANGER AND AN IMPROVED METHOD
FOR THE RECOVERY OF HEAT IN A THERMIC FLUID FLUIDIZED BED HEAT EXCHANGER"
APPLICANT
THERMAX LIMITED, HAVING REGISTERED OFFICE AT D-13, MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE-411 019, MAHARASHTRA, INDIA, AN INDIAN COMPANY
GRANTED

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.

INTRODUCTION TO THE FIELD OF THE INVENTION
This invention relates to Improved Fluidized Bed Thermic Fluid Heater
(FBTH).
PRIOR ART AND DRAWBACKS
FBTH is already known in the art and is used widely for various end uses
of the Thermic Fluid.
In the existing FBTH, conventional solid fuel is burnt in the fluidized
bed and the heat generated is used to heat Thermic Fluid in a
separate Heat exchanger System, namely in a Tubular Heat exchanger, by Indirect Heat Exchange. In this conventional FBTH, required Thermic Fluid is passed through a set of tubes provided at the top end of the body of the FBTH, in the space (free board) through which the hot gases pass. Because of the high risk involved, the Thermic Fluid circulating tubes can not be introduced into the mbed heat exchanger tubes embedded in the Fluidized Bed and therefore in the existing FBTH the full potential of the Fluidized Bed system is untapped.
SCOPE FOR IMPROVEMENTS
Studies have indicated that if the untapped potential of a FBTH can be
realized, it will result in the following advantages :
1. Increase in efficiency
2. Reduction in electric power consumption
3. Reduction in degradation of thermic fluid
4. Reduction in the size of pollution control equipment

No concrete and practical suggestion has so far been made for realizing the above stated advantages in FBTH.
OBJECTS OF THE INVENTION
It is therefore a principle object of this invention to propose improvements to the existing FBTH for realizing all the potentials untapped so far.
It is another object of this invention to propose use of embedded Heat Exchanger tubes in a FBTH which has never been considered feasible.
It is a further object of the invention to propose such an improved FBTH wherein greater amount of heat can be recovered at the site of the fluidized bed itself than hitherto possible.
It is a still further object of this invention to propose such an improved FBTH in which the usual pollution problem can be effectively controlled.
It is an additional object of this invention to propose such a FBTH wherein the thermic fluid is pre-heated before being admitted into the FBTH.
A still further object of this invention to propose such an improved FBTH wherein not only the rate of heat transfer is enhanced but also the heat economy is significantly improved compared to conventional FBTH.
These and other objects of this invention will be more clear from the ensuing paragraphs :

BRIEF STATEMENT OF THE INVENTION
Thus, according to this invention there is provided an improved fluidized bed thermic fluid heat exchanger comprising fluidized bed column having principally three sections, namely, a first lower most section having means for admission of fluidzation air, a second intermediate section, above the said first section having, on a perforated support, a bed of inert solids adopted to be fluidized by fluidization air when admitted through the said first section, the said bed having embedded therein heat transfer tubes adopted for passing a first fluid other than a thermic fluid to effect heat exc hange with the hot fluidized bed, said second intermediate section having .means for feeding required fuel
thereto,jihe said third section being provided at the top of the said
column having a set of heat exchanger tubes for passing thermic fluid there through, in heat exchange relationship with the hot gases evolved from the fluidized bed, the thermic fluid exit end having means for connecting same to an end use section, the top end of the column having means for connecting it to pollution control equipment and stack and wherein there is also provided an additional heat exchanger adopted to circulate incoming thermic fluid and the hot intermediate fluid exiting the embedded tube in heat exchange relationship with one another.
The embedded tube is in the form of straight tubes, coils etc extending substantially to the whole area of the fluidized bed and the heat exchanger provided at the top of the column is separated and spaced apart from the fluidized bed.

It is to be noted that the additional heat exchanger is provided with inlet means for admitting thermic fluid exiting the said third section at the top of the column with or without replenishment.
Preferably, the additional heat exchanger is provided(additipnal heat . Cexchang'ef isyprovided loutside the said column, with inlet means for admitting thermic fluid exiting the said third section at the top of the column with or without replenishment
In this heat exchanger, the said thermic fluid exiting the additional heat exchanger is connected to said end user section directly and the inlet end of the thermic fluid at the additional heat exchanger is connected to the outlet end of thermic fluid tube in the third section of the said column, the inlet end of the thermic fluid at this section being connected to the thermic fluid return means from the end user section.
In this construction the inlet end of the thermic fluid in the third section of the said column is provided, if required, with a diversions means for diverting a part of the returned thermic fluid to the inlet end of the thermic fluid tube in the additional heat exchanger in which case the outlet end of the thermic fluid tube in the third section of the said column is connected to the outlet means of the thermic fluid exiting the additional heat exchanger.
The inlet means for admitting the thermic fluid is directly connected to the end user section for receiving returned thermic fluid and the inlet means for the thermic fluid is provided if required with diversion means for

diverting a part of the thermic fluid to the third section in the said column, in which instance the thermic fluid outlet means at the additional heat exchanger is connected to the outlet means at the thermic fluid tube in the said third section of the said column.
The additional heat exchanger is provided with inlet means for admitting the hot fluid exiting the embedded tube in the fluidized bed and is also provided with means for returning the heat depleted fluid to the inlet of the embedded tube.
According to another aspect of the invention, there is also provided an improved method for the recovery of heat in a thermic fluid fluidized bed heat exchanger wherein a thermic fluid admitted at the top section of the heat exchanger is heated by the flue gasses passing from the fluidized bed characterized in that a part of the heat generated by the burning of the fuel m the fluidized bed is recovered at the fluidized bed section itself by means of a fluid other than the thermic fluid and wherein such heat partly recovered is used to heat the thermic fluid recovered in the fluidized bed heat exchanger and the heating of the thermic fluid by other fluid exiting the embedded tubes is carried out by indirect heat exchange relationship in an additional heat exchanger.
In one aspect, the thermic fluid returned from the end user section is fully directly used in the additional heat exchanger and the pre-heated thermic fluid is further heated in the fluidized bed heat exchanger.
In another aspect, a part of the thermic fluid returned from the end user is

used in the said additional heat exchanger while another part of the returned thermic fluid is used in the fluidized bed heat exchanger and the heated thermic fluid from the additional heat exchanger and the fluidized bed heat exchanger are used together for end user section.
In yet another aspect, all the thermic fluid returned from the end user section is used in the fluidized bed heat exchanger to pre-heat the same and the said pre-heated thermic fluid is then used in the said additional heat exchanger for recovering additional heat from the hot liquid taken from the embedded tubes.
In a further aspect, a part of the thermic fluid returned from the end user section is used in the fluidized bed heat exchanger for preheating the same, while the other part of the thermic fluid is used in the said additional heat exchanger, in heat exchange relationship with the hot fluid stream exiting the fluidized bed heat exchanger and the two exiting heated thermic fluid streams are mixed together before being sent to the end user.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be more fully described with reference to the accompanying drawings which are only schematic representation of the improved FBTH.
In the accompanying drawings Figure 1 shows a conventional FBTH.
Figures 2 & 3 show one embodiment of the improved FBTH according to

the invention.
Figure 4 shows a second embodiment of the FBTH according to the invention.
Figure 5 shows a third embodiment of the improved FBTH according to the invention.
Figure 6 shows a further embodiment of the improved FBTH according to the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to Figure 1, it will be observed that in the conventional FBTH-1, necessary air is supplied by fan-3 and the air travels upwards through a hot fluidized bed-2.
The fluidized bed is made of inert solids which can be selected from silica sand, refractory grog etc of suitable particle sizes.
The necessary fuel can be selected from coal / rice husk / lignite and other agrowaste fuels and the fuel is fed into the bed by any known standard fuel feeding system with all accessories and is not shown in the figure.
The space above the fluidized bed is provided with heat exchange tubes-4 through which the thermic fluid to be heated is pumped by pump-5.

In a conventional heat exchange between the hot gases and thermic fluid, heat recovery rate is limited and hence for a fixed amount of heat to be recovered, the whole system becomes large and is not economical.
Referring now to Figure-2, it will be noticed that there is an inbed heat exchanger 6 embedded in the fluidized bed-2 itself. This heat exchanger is provided with independent heat recovering.fluid other than thermic fluid from an independent source.
This fluid is called intermediate fluid, and extracts substantial amount of heat from the fluidized bed and is heated to a temperature depending upon the type of the fluid and conditions of the circulation.
This intermediate fluid can be selected from water / air
As will be observed from the Figure-2, there is also provided a second heat exchanger-7 external to the fluidized bed heat exchanger which contains the thermic fluid.
The heated fluid coming from a fluidized bed-2 is in a hot condition and exchanges heat to the thermic fluid held in the heat exchanger-7 and thus heats the thermic fluid.
Depleted of its heat, the intermediate fluid is then returned to the embedded inbed heat exchanger tubes for heat absorption.

It will also be observed that in the second heat exchanger-7, there is provision for heating up the thermic fluid which is then used for further processing or end uses.
The preheated thermic fluid-8 leaving the heat exchanger-7, is then introduced into the conventional heat exchanger tubes, provided at the top end of the body of the FBTH. The heated thermic fluid is sent for the end uses.
In both figures f&2, the exhaust gases leaving the FBTH is subjected to usual pollution control in the pollution control equipment. Additional heat can be recovered in an air pre-heated .APH.
In both the instances the flue gas can be exhausted into the stack or further heat can be recovered from it by pre-heating combustion / fluidizing air in any known air preheater APH.
Figure-3 is a replica of Figure-2 only shown in a different manner. In this Figure the thermic fluid is first admitted to the heat exchanger-7, preheated and then admitted to the FBTH, from where it picks up additional heat and then sent for end1 uses.
It will thus be observed from Figure-3, that pre-heated air is blown into FBTH.

The intermediate fluid is passed through the imbedded heat exchanger as in Figure-2, which is heated and passes through the heat exchanger-7 as in Figure-2. Thermic Fluid to be heated is pumped through the heat exchanger-7 again as in Figure-2 and the pre-heated thermic fluid is sent to the convention bank at the top of the FBTH as in Figure-2 and the heated thermic fluid is sent to end uses.
The air stream or the flue gas is treated in the same manner as in Figure-2.
Figure-4 is the same as Figure-3 excepting for the reverse flow of the thermic fluid, first through the convection bank and then through heat exchanger-7. Thus in Figure-4 the thermic fluid is pre-heated in the convection bank picking up heat from the flue gases and then further heated in the exchanger-7 picking up heat from the heated intermediate fluid and the thus heated thermic fluid is sent for end uses. The heat depleted intermediate fluid is returned to the imbedded tubular arrangement for picking up heat from the fluidized bed. The flue gases exiting the convention bank is used to preheat incoming air in an air pre-heater and then sent to the stack.
Figure-5 is a slight modification of Figure-3 in that there is no change in the treatment of the flue gases. However there is a slight modification in the treatment of the intermediate fluid. Compared to Figure-3, in Figure-5, the incoming thermic fluid is split into two streams S1 and S*. While stream S1 exchanges heat in the heat exchanger-7 with the hot intermediate fluid, it does not pass through the convection bank as in Figure-3. The stream S2 is instead passed through the convection bank.

The outgoing stream S1 and S* are combined for end use.
Figure-6 is reverse of Figure-5 and is similar to Figure-4 in that there is no change in the treatment of the flue gases but there is a modification in the treatment of the thermic fluid. The incoming thermic fluid is divided into two streams S1 and S* and stream S1 is passed through heat exchanger-7 and the stream S* is passed through the convection bank.
Both the out-coming streams are combined for end use.
ADVANTAGES OF THE INVENTION AND REALISATION OF OBJECT OF THE INVENTION
It will thus be observed that the improved FBTH has flexibility in operation in addition to being more economical.
in the following table we have given the improvements / advantages in the invention over conventional FBTH

PARAMETERS IMPROVED FBTH
Efficiency increase About 3 - 4%
Reduction in Power Consumption By 30%
Increase in life of Thermic Fluid About 50%
Reduction in size of Pollution Control Equipment By 10-15%

WE CLAIM :
1. An improved fluidized bed thermic fluid heat exchanger comprising
fluidized bed column having principally three sections, namely, a first
lower most section having means for admission of fluidization air, a
second intermediate section, above the said first section having, on a
perforated support, a bed of inert solids adopted to.be fluidized by
fluidization air when admitted through the said first section,tfhe sad bed has embedded therein heat transfer tubes adopted for passing a first
fluid other than a thermic fluid to effect heat exchange with the hot fluidized bed, said second intermediate section having means for feeding required fuel thereto, the said third section being provided at the top of the said column having a set of heat exchanger tubes' for passing thermic fluid there through, in heat exchange relationship with the hot gases evolved from the fluidized bed, the thermic fluid exit end having means for connecting same to an end use section, the top end of the column having means for connecting it to pollution control equiHuient and stack and wherein there is also provided an additional heat exchanger adopted to circulate incoming thermic fluid and the hot intermediate fluid exiting the embedded tube in heat exchange relationship with one another.
2. An improved fluidized bed thermic fluid heat exchanger as claimed in
Claim 1, wherein said embedded tube is in the form of straight tubes,
coils extending substantially to the whole area of the fluidized bed.

3. An improved fluidized bed thermic fluid heat exchanger as claimed in Claim 1 or 2 wherein the heat exchanger provided at the top of the column is separated and spaced apart from the fluidized bed.
4. An improved fluidized bed thermic fluid heat exchanger as claimed in. any of the Claims 1 to 3 wherein the said'additional heat exchanger is
r
provided, with inlet means for admitting thermic fluid exiting the said third section at the top of the column with or without replenishment.
5. An improved fluidized bed thermic fluid heat exchanger as claimed in
any of the Claims 1 to 3 wherein the said additional heat exchanger
provided additional heat exchanger is provided outside the said column, with inteli means for admitting thermic fluid exiting the said third section at the top of the column with or without replenishment.
6. An improved fluidized bed thermic fluid exchanger as claimed in claim-1 wherein the said thermic fluid exiting the additional heat exchanger is connected to said end user section directly and the inlet end of the thermic fluid at the additional heat exchanger is connected to the outlet end of thermic fluid tube in the third section of the said column, the inlet end of the thermic fluid at this section being connected to the thermic fluid return means from the end user section.
7. An improved fluidized bed thermic fluid exchanger as claimed in claim-6 wherein the inlet end of the thermic fluid in the third section of the said column is provided, if required, with a diversions means for diverting a part of the returned thermic fluid to the inlet end of the thermic fluid tube in the

additional heat exchanger in which case the outlet end of the thermic fluid tube in the third section of the said column is connected to the outlet means of the thermic fluid exiting the additional heat exchanger.
8. An improved ftuidized bed thermic fluid exchanger as claimed in claim-4 wherein the said inlet means for admitting the thermic fluid is directly connected to the end user section for receiving returned thermic fluid.
9. An improved fluidized bed thermic fluid exchanger as claimed in claim-8 wherein the inlet means for the thermic fluid is provided if required with diversion means for diverting a part of the thermic fluid to the third section in the said column, in which instance the thermic fluid outlet means at the additional heat exchanger is connected to the outlet means at the thermic fluid tube in the said third section of the said column.

10. An improved fluidized bed thermic fluid exchanger as claimed in claim-4 wherein the said additional heat exchanger is provided with inlet means for admitting the hot fluid exiting the embedded tube in the fluidized bed and is also provided with means for returning the heat depleted fluid to the inlet of the embedded tube.
11. An improved fluidized bed thermic fluid exchanger substantially as herein described with reference to Figures2 to 6 of the accompanying drawings.
2. An improved Wfesd for the recovery of heat in a thermic fluid

exchanger wherein a thermic fluid admitted at the top section ol the heat exchanger is heated by the flue gasses passing'from the fluidized bed characterized in that a part of the heat generated by the burning of the fuel in the fluidized bed is recovered at the fluidized bed section itself by means of a fluid other thanJthethermic fluid and wherein such heat partly recovered is used to heat the thermic fluid recovered in the fluidized bed heat exchanger.
13. A process as claimed in claim-12 wherein said heating of the thermic fluid by other fluid exiting the embedded tubes is carried out by indirect heat exchange relationship in an additional heat exchanger.
14. A process as claimed in claims 12 & 13 wherein the thermic fluid returned from the end user section is fully directly used in the additional heat exchanger and the pre-heated thermic fluid is further heated in the fluidized bed heat exchanger.
15. A process as claimed in claims 12 & 13 wherein a part of the thermic fluid returned from the end user is used in the said additional heat exchanger while another part of the returned thermic fluid is used in the fluidized bed heat exchanger and the heated thermic fluid from the additional heat exchanger and the fluidized bed heat exchanger are used together for end user section.
16. A process as claimed in claims 12 & 13 wherein all the thermic fluic returned from the end user section is used in the fluidized bed heat

exchanger to pre-heat the same and the said pre-heated thermic fluid
is then used in the said additional heat exchanger for recovering
additional heat from the hot liquid taken from the embedded tubes.
17. A process as claimed in claims 12 & 13 wherein a part of the thermic fluid returned from the end user section is used in the fluidized bed heat exchanger for preheating the same, while the other part of the thermic fluid is used in the said additional heat exchanger, in heat exchange relationship with the hot fluid stream exiting the fluidized bed heat exchanger and the two exiting heated thermic fluid streams are mixed together before being sent to the end user.
18. An improved process'ror recovering heat in a thermic fluid heat exchanger substantially as herein described with reference to the Figures 2 to 6 of the accompanying drawings.
Dated this 3rd Day of May 2000.
(K.RAJAGOPALAN ) of RAJAGOPALAN AND ASSOCIATES AGENT FOR APPLICANT.

Documents:

418-mum-2000-cancelld pages(16-3-2005).pdf

418-mum-2000-claims(granted)-(16-3-2005).doc

418-mum-2000-claims(granted)-(16-3-2005).pdf

418-mum-2000-correspondence(granted)-(5-5-2005).pdf

418-mum-2000-correspondence(ipo)-(12-07-2004).pdf

418-mum-2000-drawing(5-5-2005).pdf

418-mum-2000-form 1(8-5-2000).pdf

418-mum-2000-form 2(granted)-(16-3-2005).doc

418-mum-2000-form 2(granted)-(16-3-2005).pdf

418-mum-2000-form 26(16-3-2005).pdf

418-mum-2000-form 3(16-3-2005).pdf

418-mum-2000-form 5(16-3-2005).pdf

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Patent Number

206970

Indian Patent Application Number

418/MUM/2000

PG Journal Number

43/2008

Publication Date

24-Oct-2008

Grant Date

16-May-2007

Date of Filing

08-May-2000

Name of Patentee

THERMAX LIMITED

Applicant Address

D-13 MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE,

Inventors:

#	Inventor's Name	Inventor's Address
1	BAPAT DILIP WAMAN	C/O. THERMAX LIMITED, D-13 , MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE - 411 019.
2	PHILOMINRAJ CHARLES,	C/O. THERMAX LIMITED, D-13 , MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE - 411 019.
3	AUTADE PRASAD KISAN	C/O. THERMAX LIMITED, D-13 , MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE - 411 019.

PCT International Classification Number

F28F 21/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA