FORM 2
THE PATENT ACT, 1970,
(39 OF 1970)
&
THE PATENTS RULE, 2003
COMPLETE SPECIFICATION
(SEE SECTION 10; RULE 13)
"FULLY AUTOMATIC, SOLID FUEL FIRED, NATURAL CIRCULATION TYPE, THERMAL OIL VAPORIZER"
TRANSPARENT ENERGY SYSTEMS PRIVATE LIMITED
AN INDIAN NATIONAL
"PUSHPA HEIGHTS", 1ST FLOOR,
BIBWEWADI CORNER, PUNE-SATARA ROAD,
PUNE-411037,
MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES AND ASCERTAINS THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE
PERFORMED

FIELD OF THE INVENTION:-
The Present invention relates to fully automatic, solid fuel fired, natural circulation type, thermal oil heater / vaporizer.
PRIOR ART:-
Conventionally, the solid fuel fired thermal oil heaters are coil type with forced circulation of thermal oil inside the heater tubes (typically tubes are in single or double helical shaped coils or it can be vertically arranged tubes with multiple passes), with the help of centrifugal type oil circulation pumps. The thermal oil from expansion tank is supplied to thermal oil heater coil through an oil circulation pump. The solid fuels like, petcoke, coal, bio mass briquettes, bagasse, Rice Husk, etc. are burned inside the helical coil of thermal oil heater. The fuel combustion equipment like fixed grate or dumping grate or travelling grate or water cooled oscillating grate are used for combustion of fuel inside the helical coil of thermal oil heater. The heat is released after fuel combustion inside the thermal oil heater coil.
The thermal oil from expansion tank, through oil circulation pumps enters at inlet of the coil (in a single tube or multiple tubes of the helical coil). While circulating through the heater coil inside tubes, thermal oil absorbs the heat released in the furnace, by combustion of fuel. The temperature of thermal oil increases in the coil, and thermal oil (in liquid phase) at higher temperature is delivered at the other end (outlet) of helical coil of the thermal oil heater. Typically, the temperature difference between inlet and outlet oil temperature is 30-40 Deg C. As the temperature difference between inlet and outlet temperature are in the said range, the thermal oil flow rates goes on increasing with the heater thermal output capacity. Massive flow rates are required for high capacity heaters. Depending on thermal output capacity of the heater, the oil flow rate inside tubes, tube size, numbers of parallel passes in the helical coil are designed. The higher temperature thermal oil from heater outlet is supplied to various industrial process heating applications. The thermal oil delivers heat in the process heating application and then it is returned back to expansion tank at lower temperature (typically, 30-40 Deg C lower than the heater outlet temperature).

Conventionally the phase of thermal oil, at heater inlet and outlet is liquid only.
Taking into consideration the conventional solid fuel fired, coil type, forced circulation type, thermal oil heaters, following are the disadvantages-
1. The conventional thermal oil heaters are forced circulation type; hence an oil circulation pump is required. This pump becomes critical for continuous operation of the thermal oil heater. Hence, the operation of heater is dependent on reliable & continuous operation of the pump.
2. The oil circulation pump handles massive thermal oil flow rate. To handle such massive oil flow rate high capacity pumps are required or multiple pumps are required in parallel operation. Accordingly, stand by pumps are required to ensure operation of heater in case of failure of any pump.
It increases the initial investment / capital cost and maintenance cost for the thermal oil heater.
3. The massive oil flow rates are circulated inside helical tube coils. The pressure drop of oil circulation across the heater coil is higher, typically 4-5 kg/cm2. This requires higher head (pressure) of the oil circulation pump. The massive oil flow and higher pump head requires huge power for circulation of oil inside the heater. The power requirement is higher, resulting in higher operating cost.
4. Conventionally, the solid fuel fired thermal oil heaters deliver the thermal oil in liquid phase only. Hence only sensible, heat (liquid enthalpy) can be used for conveying heat from the heater. Hence, as heater capacity goes higher, the higher oil circulation flow rates are required.
This results in higher operating cost of the heater, for circulation of oil inside multiple tubes through oil circulation pump.

NEED OF THE PRESENT 1NVENTION:-
It is object of the present invention to provide a "Natural circulation type, thermal oil vaporizer", wherein the circulation of oil inside the heater tubes is by natural circulation and the vapors of thermal oil vapors are delivered at heater outlet. The natural circulation of thermal oil inside the heater tubes eliminates the requirement of oil circulation pump during continuous operation.
It is also the object of the present invention to provide the Natural circulation type, thermal oil vaporizer, which overcomes all the disadvantages and shortfalls of the prior art.
SUMMARY OF THE INVENTION:-
According to the thermal oil vaporizerheater of present invention i.e. fully automatic, solid fuel fired, natural circulation type, thermal oil heateroii vaporizer; there is a membrane wall type furnace, convective heat exchanger in flue gas path and a liquid-vapor separation drum. The liquid-vapor separation drum is connected to membrane wall type furnace, convective heat exchanger in flue gas path and membrane wall type casing of the convective heat exchanger with multiple numbers of down comers and risers. The liquid-vapor separation drum is placed at sufficient height to overcome various pressure losses in the heater tubes.
The thermal oil from liquid-vapor separation drum goes to the bottom header of furnace by gravity through multiple down comers and it absorbs the heat in vertical tubes of the membrane wall type furnace. As oil is heated in the furnace tubes, the density of hot oil becomes lower and it rises up in the vertical tubes. As, hot oil rises up due to density difference, its space inside tubes is occupied by lower temperature oil coming from liquid-vapor drum in bottom the furnace header, which has higher density. In the similar way, oil is naturally circulated in the furnace, convective heat exchanger and its membrane wall type casing. As oil gets heated further, it reaches the saturation temperature of oil at the operating pressure of the heater. On further heating, the vapors are generated and vapors are released from liquid in the liquid-vapor separation drum. As vapors are released in the liquid-vapor separation drum,

the inside pressure in drum increases. The pressure in liquid-vapor separation drum is maintained such that the corresponding saturation temperature of oil vapors is as per process requirement.
As the circulation of oil in the thermal oil heateroil vaporizer is governed by density difference of oil and vapors, it is called natural circulation. As oil is circulated inside tubes by density difference only, there is no requirement of large oil circulation pumps for continuous operation of the thermal oil heateroil vaporizer.
The present invention eliminates initial investment of multiple large pumps and subsequent operating, maintenance cost of these pumps. Also, it eliminates the dependency on reliable and continuous operation of pump for continuous operation of thermal oil heateroil vaporizer.
The oil vapors from liquid-vapor separation drum are supplied to the process. The vapors deliver the heat in process side heat exchanger and get condensed. The condensed vapors i.e. condensate from various process side heat exchangers is returned back to a condensate collection tank. The condensate collected in this tank is returned back to the liquid-vapor separation tank.
STATEMENT OF INVENTION:-
The proposed invention comprises a membrane wall type furnace having tubes linearly arranged at certain pitch in a vertical alignment with the bottom ends connected to bottom headers of the furnace and the top end connected to riser headers at the top of furnace; the said membrane wall furnace provided with leak-proof volume for combustion of fuel in the thermal oil heateroil vaporizer by welding a steel flat in the gap between the said consecutive tubes continuously on the said tubes; a fuel hopper provided to feed the solid fuel inside membrane wall furnace, through a feeder to feed fuel on water cooled oscillating grate installed inside the said furnace; a liquid-vapor separation drum, holding the thermal oil at height and also to allows oil-vapors to separate from the liquid oil, having multiple vertical down comers connected to the said bottom headers of the said membrane wall type furnace to carry the thermal oil to bottom header of the said furnace by gravity and

multiple riser tubes connected to the said riser headers; one or more convective heat exchanger, placed above the said membrane wall type furnace , consisting of multiple tube assembly having an inlet header connected to the said multiple down comers and outlet header connected to the said multiple risers; a sealed casing formed to the said convective heat exchanger has membrane wall type construction, similar to the said furnace consisting of vertical tubes linearly arranged at certain pitch and the gap between tubes is sealed with a flat having bottom casing header connected to said multiple down comers and riser casing header connected to the said multiple risers; a chimney fixed above the said casing; a controlled out let provided to the said drum for taking out the heated liquid/vapor oil to a vapor header connected to the industrial process application; and means provided for recirculation of the out put of said heated liquid/vapor oil after using at industrial application.
Further, oil vaporizer is a solid fuel fired, thermal oil vaporizer. The solid fuel fired thermal oil, the circulation of thermal oil inside tubes of heater is under natural circulation due to the density difference of the heating fluids.
BRIEF DESCRIPTION OF THE SCHEMATIC DRAWING:-
The present invention is described with the accompanying Figures 1, and 2.
Figure 1 describes the flow diagram of fully automatic, natural circulation type, thermal oil heateroil vaporizer for thermal oil and vapor circuit, Air and flue gas circuit.
Figure 2 describes the line diagram of fully automatic, natural circulation type, thermal oil heateroil vaporizer.
Figure 3A, 3B and 3C describe the cross section drawing of the furnace and ash removal arrangement of the thermal oil heateroil vaporizer.

DETAIL DESCRIPTION OF THE SCHEMATIC DRAWING:-
The invention will now be described with reference to the drawings of the accompanying specification and the parts of the figure shown by suitable numeral and referred to appropriately in the following description.
Referring to Figures 1, 2 and 3, the following components can be identified in fully automatic, natural circulation type, thermal oil heateroil vaporizer -
1. Liquid-vapor separation Drum 19. Diverter Valve -1
2. Down Comer of furnace 20. Diverter Valve - 2
3. Bottom Header of furnace 21. Two way damper
4. Membrane wall type furnace 22. Heat recovery equipment
5. Fuel Hopper 23. Diverter Valve - 3
6. Fuel feeder 24. Diverter Valve - 4
7. Water cooled oscillating grate 25. Diverter Valve - 5
8. Riser Header 26. Isolation Dampers
9. Riser tubes of furnace 27. Pressurized Water Tank
10. Convective heat exchanger 28. Grate water circulation
pump
11. Down comer of heatexchanger 29. Combustion air pre-heater
12. Inlet header of heat exchanger 30. Combustion air fan
13. Outlet header of heat exchanger 31. Ash removal screw
conveyors
14. Risers of heat exchanger 32. Cold start up pump
15. Casing of convective heat exchanger 33. Vapor header
16. Chimney 34. Industrial Process
Application
17. Flue gas desulphurization system 35. Condensate Return
Collection tank
18.1.D. Fan 36. Condensate return pump
The liquid-vapor separation drum (marked as item no. 1, in figure 1) holds the thermal oil at height and also allows oil-vapors to separate from the liquid oil. The

liquid-vapor separation drum has multiple, vertical down comers (marked as item no. 2, figure 1) which are connected to the bottom headers (marked as items no. 3, in figure 2) of the membrane wall type furnace (marked as item no. 4, in figure 1) on their other end. The down comers carry the thermal oil from liquid-vapor drum to bottom header of furnace by gravity.
The fully automatic, natural circulation type thermal oil heateroil vaporizer has a membrane wall type furnace. The cross section of membrane type furnace is as shown in figure 3. The membrane type furnace has tubes (marked as "A", in figure 3) linearly arranged at certain pitch. The tubes alignment is vertical. The bottom ends of these tubes are connected to bottom headers of the furnace. The top end of tubes is connected to riser headers at the top of furnace. The gap between consecutive tubes is sealed by a steel flat (marked as "B", in figure 3) welded continuously on the tubes. The membrane wall furnace provided leak-proof volume for combustion of fuel in the thermal oil heateroil vaporizer. The thermal oil gets circulated inside the vertical tubes of membrane wall type furnace.
The fuel hopper (marked as item no. 5, in figure 1) feeds the solid fuel inside membrane wall furnace, through a feeder (marked as item no. 6, in figure 1). The feeder can be rotary feeder or screw feeder or any other type of fuel feeder. The fuel feed inside is combusted on water cooled oscillating grate (marked as item no. 7, in figure 1) which is installed inside the furnace. The heat is released by combustion of fuel inside furnace. The thermal oil in the vertical tubes of membrane wall furnace is heated with this heat released by combustion of fuel. As the thermal oil inside vertical tubes is heated, its density is lowered and it rises up inside the tube due to lower density. The space displaced by lower density oil is filled up by relatively cold oil coming from bottom header of the furnace, which has higher density. Thus, the flow of oil inside tubes is established inside tubes due to density difference between hot oil inside vertical tubes and relatively cold oil coming from bottom header.
Once thermal oil starts circulating inside the tubes due to density difference and fuel combustion is continued further, the thermal oil reaches to the saturated temperature corresponding to operating pressure of the heater. On further heating of the thermal oil in the membrane wall furnace of the heater, the two-phase mixture of thermal oil

(in liquid phase) and its vapors (in vapor phase) is generated in the vertical tubes of heater. The thermal oil in liquid phase has higher density and its vapor (vapor phase) has lower density. Due to density difference between vapor bubbles and liquid thermal oil, the vapor bubbles rise vertically upward in the vertical tubes of furnace. This movement of vapor bubbles inside tube continues to circulate oil-vapor mixture inside the heater tubes. This two phase mixture rises vertically upward in the heater tubes and it is then delivered in the multiple riser headers (marked as item no. 8, in figure 1). The multiple riser tubes (marked as item no. 9, in figure 1) connect the riser headers and liquid-vapor separation drum. These riser tubes carry the two-phase mixture of thermal oil and its vapors from headers to liquid-vapor separation drum. The oil-vapors get separated in the liquid-vapor drum, from the liquid phase thermal oil. The vapors are at the saturation temperature corresponding to operating pressure of the heater.
As explained above, the density difference is the driving force for circulation of oil inside the heater tubes i.e. natural circulation.
The flue gases generated after combustion of fuel inside membrane wall type furnace are further passed through the convective heat exchanger (marked as item no. 10, in figure 1). The heat from flue gas is recovered in the convective heat exchanger. The convective heat exchanger is also connected with liquid-vapor separation drum with multiple down comers and risers. The down comers (marked as item no. 11, in figure 2) of convective heat exchanger are connected to inlet header (marked as item no. 12, in figure 2) of the convective heat exchanger. The thermal oil from liquid-vapor separation drum comes from down comers and enters in the inlet header of convective heat exchanger by gravity.
The convective heat exchanger is an assembly of multiple tubes, which provide convective heat transfer area along with inlet header and outlet header. This heat exchanger recovers heat from flue gas and heat the thermal oil coming from liquid-vapor separation drum. As thermal oil coming from inlet header is heated inside the convective heat exchanger's tubes, the density of thermal oil is lowered and it rises upward in the tubes. The space displaced by hot thermal oil is occupied by thermal oil coming from liquid-vapor separation drum which is at relatively lower temperature.

Thus, due to density difference, flow of thermal oil takes place in the convective heat exchanger tubes.
Once thermal oil starts circulating inside the tubes due to density difference and heat from flue gas is recovered further, the thermal oil reaches to the saturated temperature corresponding to operating pressure of the heater. On further heating of the thermal oil in heating tubes of the convective heat exchanger, the two-phase mixture of thermal oil (in liquid phase) and its vapors (in vapor phase) is generated in the tubes of convective heat exchanger. The thermal oil in liquid phase has higher density and its vapor (vapor phase) has lower density. Due to density difference between vapor bubbles and liquid thermal oil, the vapor bubbles rise upward in the tubes of convective heat exchanger. This movement of vapor bubbles inside tube continues to circulate oil-vapor mixture inside the convective heat exchanger tubes.
The lower density two-phase mixture of thermal oil and its vapors moving upwards in the tubes is delivered to the outlet header (marked as item no. 13, in figure 2) of convective heat exchanger. The two-phase mixture from outlet header is delivered to liquid-vapor separation drum with the help of multiple risers (marked as item no. 14, in figure 2).
As explained above, the density difference is the driving force for circulation of oil inside the tubes of convective heat exchanger i.e. natural circulation.
The casing of convective heat exchanger (marked as item no. 15, in figure 2) has membrane wall type construction, similar to furnace The vertical tubes linearly arranged at certain pitch and the gap between tubes is sealed with a flat. The membrane wall type casing provides a leak-proof flow passage for flue gas on the heat exchanger tubes. The bottom header of membrane wall casing receives thermal oil in liquid phase through multiple down comers by gravity. The heat from flue gases passing through convective heat exchanger is recovered in the membrane wall type casing. The heat recovered in the casing heats the thermal oil inside the membrane wall tubes and set the natural circulation as explained above for the membrane wall type furnace.

After recovery of heat from flue gases in thermal oil heateroil vaporizer, the flue gases can be discharged in atmosphere through the chimney (marked as item no. 16, in figure 1) or the flue gases can be further cooled to recover the additional heat. Depending on type of solid fuel the flue gas can be further passed through a Flue gas Desulphurization system (marked as item no. 17, in figure 1), to reduce the S02 emission in the atmosphere. The draughtft in the system can be a natural draughtft or it can be an induced draughtft with the help of I.D. fan (marked as item no. 18, in figure 1).
The "Diverter Valve -1" (marked as item no. 19, in figure 1) has one inlet port and two outlet ports. It allows to divert flue gas either towards "Diverter Valve -2" (marked as item no. 20, in figure 1) or towards "Two way damper" (marked as item no 21, in figure 1). If it is intended to recover further heat from flue gases or it is intended to pass the flue gas from Flue Gas Desulphurization System", the flue gases are diverted towards "Diverter Valve - 2", otherwise flue gases are diverted towards two-way damper and I.D. fan when induced draughtft is intended in the system.
The "Diverter Valve -2" has one inlet port and two outlet ports. It allows diverting flue gases either towards "Heat Recovery Boiler" (marked as item no. 22, in figure 1) or towards "Diverter Valve -3" (marked as item no. 23, in figure 1). If it is intended to recover heat from flue gases the gases are diverted towards "Heat Recovery Boiler", otherwise flue gases are diverted toward "Diverter Valve -3" to bypass the heat recovery boiler.
The "Diverter Valve -3" has two inlet ports and one outlet port. It receives flue gases either from "Heat Recovery Boiler" or "Diverter Valve -2" as explained above. The outlet port of "Diverter valve -3" is connected to inlet port of "Diverter valve -4" (marked as item no. 24, in figure 1).
The "Diverter Valve -4" has one inlet port and two outlet ports. It allows diverting flue gases either towards "Flue Gas Desulphurization System" or towards "Diverter Valve -5" (marked as item no. 25, in figure 1) to bypass the "Flue Gas Desulphurization System".

The "Diverter Valve -5" has two inlet ports and one outlet port. It receives flue gases either from "Flue Gas Desulphurization System" or "Diverter Valve -4" as explained above. The outlet port of "Diverter valve -5" is connected to two way damper.
The two way damper allows either flue gases coming from "Diverter Valve -1" or "Diverter Valve-5" to pass through ID Fan.
Two isolation dampers (marked as item no. 26, in figure 1) are provided at inlet port of "Diverter Valve -1" and outlet port of ID fan respectively. The isolation damper allows isolating the heat recovery system, flue gas desulphurization system, ID Fan and interconnecting diverter valves completely, and operating the thermal oil heateroil vaporizer under the "natural draughtft" of the chimney.
In fully automatic natural circulation type, thermal oil vaporizer fuel combustion takes place on fully automatic water cooled oscillating grate (marked as item no. 7, in figure 1). The grate surface and bed temperature is maintained lower by circulating water inside the grate. The water from pressurized water tank (marked as item no. 27, in figure 1) is circulated in the water cooled oscillating grate with the help of grate water circulation pump (marked as item no. 28, in figure 1). The temperature of circulating water increases while circulating through the water cooled oscillating grate. The heat absorbed by this circulating water is delivered to the combustion air in the combustion air pre-heater (marked as item no. 29, in figure 1). The combustion air pre-heats the air supplied by combustion air blower (marked as item no. 30, in figure 1) and then hot air is supplied to the water cooled oscillating grate for improved combustion of the fuel. The ash generated after combustion of fuel is removed automatically by multiple screw conveyors (marked as item no. 31, in figure 3) provided inside the furnace.
For cold start-up of the thermal oil heateroil vaporizer, a small capacity (small flow rate and pressure) cold start-up pump (marked as item no. 32, in figure 1) is provided which overcomes the friction losses of thermal oil in the heat tubes. Once the thermal oil is sufficiently heated and density difference is generated, this pump can be switched off as further oil circulation is driven by "Natural Circulation"

The vapors from liquid-vapor separation drum are supplied to a vapor header (marked as item no. 33, in figure 1). From the vapor header, the oil vapors are supplied to industrial processes (marked as item no. 34, in figure 1) for heating application. After process heating the oil vapors get condensed and the condensed oil vapors in liquid phase, called as condensate is returned to a central condensate return tank (marked as item no. 35, in figure 1). The condensate from this tank is retuned back to liquid-vapor separation drum by a condensate return pump (marked as item no. 36, in figure 1).
FOLLOWING ADVANTAGES ARE ACHIEVED BY THE PRESENT INVENTION:-
1. Independent of external device -
The circulation of thermal oil inside the heater tubes is achieved by the natural phenomenon of the density difference, i.e. "Natural Circulation". Hence the circulation of thermal oil inside tube is not dependant on reliable operation of external device such as oil circulation pumps.
2. Safety against low flow inside tubes -
In case of forced circulation type thermal oil heaters, if the power supply is suddenly failed, the oil circulation pumps stops and thermal oil inside tubes becomes almost stagnant or moves with very low velocity, but the heat is continued to release by fuel inside the furnace for some time. This may result in cocking (Carbonizing) of thermal oil inside tubes which creates resistance in heat transfer and also reduces life of thermal oil. The layers of cocked thermal oil reduce the heat transfer across heater wall and tube gets overheated. The overheating of tube may lead to bursting of tubes and severe hazardous accident.
In case of natural circulation type, the flow of thermal oil inside tubes is independent of power supply. Even if, power supply is failed the thermal oil continues to circulate by density difference and does not affect the performance of thermal oil heateroil vaporizer.

3. Saving in investment cost for oil circulation pumps -
In Fully Automatic Natural Circulation Type Thermal Oil HeaterOil vaporizers, as there is no requirement of heavy duty oil-circulation pumps for continuous operation of the heater, the initial investment / capital cost of thermal oil heateroil vaporizer is low as compared with forced circulation type heaters.
4. Low operating and maintenance cost -
In Fully Automatic Natural Circulation Type Thermal Oil HeaterOil vaporizers, as there is no requirement of oil-circulation pumps having high flow and head, the operating cost of thermal oil heateroil vaporizer is low as compared with forced circulation type heaters. Also, the maintenance cost of associated with heavy duty pumps is eliminated.
5. Thermal oil in vapor phase -
Conventionally, the solid fuel fired thermal oil heateroil vaporizers deliver the thermal oil in liquid phase only. The present invention can deliver the thermal oil in vapor phase. The vapor phase allows using latent heat capacity of the vapors, which is higher than the sensible heat of same oil in liquid phase at same temperature. As the heat capacity of vapors is higher, the flow rate is lower as compared with oil flow in liquid phase for same heat output of the heater. This reduces overall size of pipelines, valves and mounting and saves the investment cost.
6. Tube wall temperature monitoring -
The tube wall temperature measurement probes are mounted on the heater tubes, which continuously monitor the tube metal temperature, particularly near flame zone. This provides safety interlock to protect tube from overheating and also maintain the thermal oil quality.

VARIATIONS POSSIBLE TO BE COVERED AND PROVIDED WITHIN THE INVENTION OF FULLY AUTOMATIC, WATER TUBE TYPE, THERMAL OIL VAPORIZER
1. The flue gas side draughtfl can be "Natural Draftught" or "Forced Draftught" type.
2. The thermal oil can be also delivered in vapor phase or also in liquid phase. In case of liquid phase, the liquid-vapor separation drum is completely filled with the oil.
3. Tube skin temperature thermocouples may or may not be provided on thermal oil vaporizer tubes, to continuously or intermittently monitor the tube metal temperature.
4. The heat recovery equipment may be a boiler, hot water generator, hot air generator or low temperature thermal oil heateroil vaporizer or any other type of heat exchanger.
5. The flue gas cleaning system may be either flue gas desulphurization system or wet scrubber or any other type of flue gas conditioning system.
6. The heat recovery equipment or flue gas cleaning system may be or may not be provided depending on the application requirement, type of fuel, etc.
7. Pollution control devices like bag filter, multiclone, cyclone separators may or may not be provided.
8. Type of solid fuel combustion equipment can be fully automatic water cooled oscillating grate, or dumping grate or travelling grate or fluidized bed combustor, etc.
9. A single or multiple ash removal screws can be provided for removal of ash outside the furnace.

WE CLAIM:-
1. A fully automatic, solid fuel fired, natural circulation type, thermal oil vaporizer comprises a membrane wall type furnace having tubes linearly arranged at certain pitch in a vertical alignment with the bottom ends connected to bottom headers of the furnace and the top end connected to riser headers at the top of furnace; the said membrane wall furnace provided with leak-proof volume for combustion of fuel in the thermal oil heateroil vaporizer by welding a steel flat in the gap between the said consecutive tubes continuously on the said tubes; a fuel hopper provided to feed the solid fuel inside membrane wall furnace, through a feeder to feed fuel on water cooled oscillating grate installed inside the said furnace; a liquid-vapor separation drum, holding the thermal oil at height and also to allows oil-vapors to separate from the liquid oil, having multiple vertical down comers connected to the said bottom headers of the said membrane wall type furnace to carry the thermal oil to bottom header of the said furnace by gravity and multiple riser tubes connected to the said riser headers; one or more convective heat exchanger, placed above the said membrane wall type furnace , consisting of multiple tube assembly having an inlet header connected to the said multiple down comers and outlet header connected to the said multiple risers; a sealed casing formed to the said convective heat exchanger has membrane wall type construction, similar to the said furnace consisting of vertical tubes linearly arranged at certain pitch and the gap between tubes is sealed with a flat having bottom casing header connected to said multiple down comers and riser casing header connected to the said multiple risers; a chimney fixed above the said casing; a controlled out let provided to the said drum for taking out the heated liquid/vapor oil to a vapor header connected to the industrial process application; and means provided for recirculation of the output of said heated liquid/vapor oil after using at industrial application.
2. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claim 1 wherein the said thermal oil vaporizer is a solid fuel fired, thermal oil vaporizer.

3. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 & 2 wherein in the said proposed solid fuel fired thermal oil vaporizer, the circulation of thermal oil inside tubes of heater is under natural circulation due to the density difference of the heating fluids.
4. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 3 wherein the solid fuel combustion equipment is fully automatic water cooled oscillating grate, or dumping grate or travelling grate or fluidized bed combustor or like.
5. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 4 wherein the said feeder is of rotary feeder or screw feeder or any other type of fuel feeder.
6. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 5 wherein the said water cooled grate receives cooling water from a pressurized tank with a feed pump in circuit and an heat exchanger for pre¬heating combustion air.
7. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 6 wherein automatically operated a single/multiple screw conveyors provided inside the furnace for removing ash generated by the combustion fuel.
8. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 7 wherein the said chimney provided with a further heat recovery system comprising a first diverting valve having one inlet port and two outlets ports connected to chimney pipe through a first isolation damper valve to allow to divert flue gas either towards second diverter valve or towards two way damper; the said second diverter valve has one inlet port and two outlet ports to allow diverting flue gases either towards heat recovery equipment or towards third diverter valve; the said third diverter valve has two inlet ports and one outlet port for receiving flue gases either from heat recovery equipment or the said second diverter valve ; the outlet port of the said third

diverter valve connected to inlet port of the fourth diverter valve; the said fourth diverter valve having one inlet port and two outlet ports to allow diverting flue gases either towards flue gas desulphurization system or towards the fifth diverter valve; the said fifth diverter valve having two inlet ports and one outlet port to receive flue gases either from flue gas cleaning system or the said forth diverter valve; the outlet port of the said fifth diverter valve connected to two way damper with outlet connected to the inlet of id fan; the said id fan outlet pipe provided with a second isolation damper valve protruding inside the chimney pipe and bent upwards to direct flue gas upwards.
9. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 8 wherein the said heat recovery is a heat exchanger/boiler/hot water generator/low temperature thermal oil heateroil vaporizer.
10. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 9 wherein the said flue gas cleaning system is either flue gas desulphurization system or wet scrubber or any other type of flue gas conditioning system.
11. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 10 wherein the said outlet of ID Fan connected to chimney through pollution control devices such as bag filter multi cone cyclone separators.
12. The solid fuel fired thermal oil vaporizerAn oil vaporizer as claimed in claims 1 to 11 wherein the said means for providing recirculation heated liquid/vapor oil comprises a condenser inlet connected to the outlet of industrial process application and outlet of said condenser connected to said drum.