Title of Invention	A SHUTTING DOWN DEVICE FOR PRESSURIZED FLUIDIZED BED GASIFIER
Abstract	A shutting down device for a pressurized fluidized bed gasifier, the gasifier operating at a bed temperature between 900° to 1100°C; and being in a state of shutting down by cutting-off supply of feed coal followed by stoppage of the flow of air and steam, the device comprising a liquid nitrogen storage vessel (01) accommodating pressurized liquid nitrogen and a plurality of vaporized coils (02) connected to the storage vessel (01) via piping circuit including control valves, the vaporizer coils (02) converting the liquid nitrogen in gaseous form by vaporization and a plurality of nitrogen gas holders (03) receiving nitrogen gas from the vaporizer coils (02) and holding the nitrogen gas at ambient temperature by maintaining a reduced pressure characterised in that an auto pressure regulating valve (04) is connected to the nitrogen gas holders (03) which is set to adjust the pressure of nitrogen gas higher than that maintained in that gasifier (07) and in that a piping circuit (05) with a non-return valve (06) is flowably connected to the nitrogen gas holders (03) to allow pressurized nitrogen gas at ambient temperature to be delivered to the gasifier (07).

Title of Invention

A SHUTTING DOWN DEVICE FOR PRESSURIZED FLUIDIZED BED GASIFIER

Abstract

A shutting down device for a pressurized fluidized bed gasifier, the gasifier operating at a bed temperature between 900° to 1100°C; and being in a state of shutting down by cutting-off supply of feed coal followed by stoppage of the flow of air and steam, the device comprising a liquid nitrogen storage vessel (01) accommodating pressurized liquid nitrogen and a plurality of vaporized coils (02) connected to the storage vessel (01) via piping circuit including control valves, the vaporizer coils (02) converting the liquid nitrogen in gaseous form by vaporization and a plurality of nitrogen gas holders (03) receiving nitrogen gas from the vaporizer coils (02) and holding the nitrogen gas at ambient temperature by maintaining a reduced pressure characterised in that an auto pressure regulating valve (04) is connected to the nitrogen gas holders (03) which is set to adjust the pressure of nitrogen gas higher than that maintained in that gasifier (07) and in that a piping circuit (05) with a non-return valve (06) is flowably connected to the nitrogen gas holders (03) to allow pressurized nitrogen gas at ambient temperature to be delivered to the gasifier (07).

Full Text	FIELD OF THE INVENTION This invention relates to fluidized bed gasifiers, in particular pressurized Fluidized bed gasifiers, and more particularly to a shutting down device adaptable to pressurized fluidized bed gasifiers. BACKGROUND OF THE INVENTION Fluidized Bed Gasifiers are adopted to generate Syngas from coal for use in power, process and chemical applications. In a fluidized bed gasifier, the bed of inert material with coal is fluidized by air and steam mixture is admitted from the bottom of the bed through an air distributor. During normal operation, a temperature of 900 to 1100 ° C is maintained in the Fluidized Bed by partial combustion of coal. In steady operating conditions, the coal and the unburnt char constitute about 5 - 25% of the inventory in the fluidized bed. The balance is inert material like coal ash. In an emergency condition leading to instant shut-down of the gasifier, an inventory of coal and unburnt char particles at high temperature in the bed poses a safety problem. Presently steam is used to inhibit any combustion that may continue rising the bed temperature even after the shut down. However, such a system needs to ensure availability of steam for this purpose, irrespective of the conditions prevailing. Besides, the steam condenses leading to heavy fouling of the down stream devices like Heat Exchanger and Gas Pipes and makes the ash sticky and difficult to remove and handle. It further affects the surfaces of refractory lining provided on inside of the gasifier. OBJECTS OF THE INVENTION It is therefore, an object of the invention to propose a shutting down device which ensures a safe shut down of pressurized fluidized bed gasifiers maintaining higher carbon inventory. Another object of the invention is to propose a shutting down device which is capable of creating an atmosphere of inert nitrogen inside the refractory lined gasifier throughout the shut down period for protecting the refractory lining thus ensuring better and longer life of the refractory. A further object of the invention is to propose a shutting down device which is capable of cooling the bed slowly and steadily with nitrogen. A still further object of the invention is to propose a shutting down device which substantially eliminates fouling of down stream equipment of the pressurized fluidized bed gasifier system. Yet another object of the invention is to propose a shutting down device which ensures easy removal of bed ash by disallowing the bed ash to become sticky. SUMMARY OF THE INVENTION Accordingly, there is provided a shutting down device adaptable to pressurized fluidized bed gasifier, the gasifier operating at a bed temperature between 900° to 1100°C; and being in a state of shutting down by cutting-off supply of feed Coal followed by stoppage of the flow of air and steam, the device comprising; a liquid nitrogen storage vessel accommodating pressurized liquid nitrogen, a plurality of vaporizer coils connected to the storage vessel via piping circuit including control valves, the vaporizer coils converting the liquid nitrogen in gaseous form by vaporization; a plurality of nitrogen gas holders receiving nitrogen gas from the vaporizer coils and holding the nitrogen gas at ambient temperature by maintaining a reduced pressure; and an auto pressure regulating valve connected to the nitrogen gas holders which is set to adjust the pressure of nitrogen gas higher than that maintained in the gasifier, the pressurized nitrogen gas at ambient temperature being admitted to the gasifier via a piping circuit provided with a non-return valve. The device according to the invention consists of a storage for liquid nitrogen, vaporizer coils, gas holders for nitrogen gas, a pressure regulating valve and piping with a non return valve which is capable of admitting controlled quantity of pressurized nitrogen gas at ambient temperature in a safe manner into the bed of the pressurized fluidized bed gasifier to bring down the temperature of the bed as and when needed. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING Figure 1- shows a shutting down device adaptable to pressurized fluidized bed gasifiers. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The device for Shutting Down of a Fluidized Bed Gasifier (07) comprises, a Liquid Nitrogen Storage Vessel (01); Vaporizer coils (02) to convert liquid nitrogen into gaseous form; Nitrogen Gas Holders (03) to hold nitrogen gas at pressures in the range of 5 to 12 Kg/cm2 and at ambient temperature; an Auto Pressure Regulating Valve (04) to control the pressure of nitrogen gas at the required level before admitting into the Fluidized Bed Gasifier, (07); and interconnecting piping circuit (05); and a non return valve (06). During any planned or emergency shut down of a gasifier operating with supply of a mixture of air and steam through the distributor and having coal above the distributor, at a steady state with the bed temperature of the order of 900 to 1100 ° C, the flow of feed coal is cut off first, followed by stoppage of air and steam and simultaneously nitrogen gas is admitted to reduce the bed temperature to a safe value depending on the nature of fuel being used for gasification. Prior to the admission of nitrogen, the pressure of nitrogen gas is adjusted by setting the pressure regulating valve (04), to a pressure greater than that of the gasifier (07) and the pressure of nitrogen in the gas holders (03) is also correspondingly maintained by vaporization of liquid nitrogen from the storage vessel (01) through the vaporizer coils (02). Once bed temperature is reduced to the required level, the nitrogen gas flow is cut off and air is again admitted for further cooling of the bed. When the bed temperature reaches much below the ignition range of the fuel, the air supply is also cut off. Now the gasifier is safely shut down although having high carbon inventory in the bed. The use of nitrogen is also economized in this method and only the required quantity of nitrogen is consumed . The device is capable of cooling the bed uniformly. Further, the device reduces the formation of carbon monoxide and hydrogen during the shut down of the gasifier including reducing the carbon monoxide entrapment in the sub systems of the pressurized bed system. The device is also capable of reducing or eliminating fouling of heat transfer surfaces and other areas. The device reduces or eliminates steam condensation and the consequential effects like corrosion, non sticky bottom ash handling. WE CLAIM 1. A shutting down device for a pressurized fluidized bed gasifier, th egasifier operating at a bed temperature between 900° to 1100°C; and being in a state of shutting down by cutting-off supply of feed coal followed by stoppage of the flow of air and steam, the device comprising: - a liquid nitrogen storage vessel (01) accommodating pressurized liquid nitrogen; - a plurality of vaporized coils (02) connected to the storage vessel (01) through piping circuit having control valves, the vaporizer coils (02) converting the liquid nitrogen in gaseous form by vaporization; and - a plurality of nitrogen gas holders (03) receiving nitrogen gas from the vaporizer coils (02) and holding the nitrogen gas at ambient temperature by maintaining a reduced pressure. Characterized in that an auto pressure regulating valve (04) is connected to the nitrogen gas holders (03) which is set to adjust the pressure of nitrogen gas higher than that maintained in that gasifier (07) and in that a piping circuit (05) with a non-return valve (06) is flowably connected to the nitrogen gas holders (03) to allow pressurized nitrogen gas at ambient temperature to be delivered to the gasifier (07). 2. A shutting down device for a pressurized fluidized bed gasifier, as substantially described herein with reference to the accompanying drawings. A shutting down device for a pressurized fluidized bed gasifier, the gasifier operating at a bed temperature between 900° to 1100°C; and being in a state of shutting down by cutting-off supply of feed coal followed by stoppage of the flow of air and steam, the device comprising a liquid nitrogen storage vessel (01) accommodating pressurized liquid nitrogen and a plurality of vaporized coils (02) connected to the storage vessel (01) via piping circuit including control valves, the vaporizer coils (02) converting the liquid nitrogen in gaseous form by vaporization and a plurality of nitrogen gas holders (03) receiving nitrogen gas from the vaporizer coils (02) and holding the nitrogen gas at ambient temperature by maintaining a reduced pressure characterised in that an auto pressure regulating valve (04) is connected to the nitrogen gas holders (03) which is set to adjust the pressure of nitrogen gas higher than that maintained in that gasifier (07) and in that a piping circuit (05) with a non-return valve (06) is flowably connected to the nitrogen gas holders (03) to allow pressurized nitrogen gas at ambient temperature to be delivered to the gasifier (07).

Full Text

FIELD OF THE INVENTION
This invention relates to fluidized bed gasifiers, in particular pressurized Fluidized
bed gasifiers, and more particularly to a shutting down device adaptable to
pressurized fluidized bed gasifiers.
BACKGROUND OF THE INVENTION
Fluidized Bed Gasifiers are adopted to generate Syngas from coal for use in power,
process and chemical applications. In a fluidized bed gasifier, the bed of inert
material with coal is fluidized by air and steam mixture is admitted from the bottom
of the bed through an air distributor. During normal operation, a temperature of 900
to 1100 ° C is maintained in the Fluidized Bed by partial combustion of coal. In
steady operating conditions, the coal and the unburnt char constitute about 5 -
25% of the inventory in the fluidized bed. The balance is inert material like coal ash.
In an emergency condition leading to instant shut-down of the gasifier, an inventory
of coal and unburnt char particles at high temperature in the bed poses a safety
problem.
Presently steam is used to inhibit any combustion that may continue rising the bed
temperature even after the shut down. However, such a system needs to ensure
availability of steam for this purpose, irrespective of the conditions prevailing.
Besides, the steam condenses leading to heavy fouling of the down stream devices
like Heat Exchanger and Gas Pipes and makes the ash sticky and difficult to remove
and handle. It further affects the surfaces of refractory lining provided on inside of
the gasifier.
OBJECTS OF THE INVENTION
It is therefore, an object of the invention to propose a shutting down device
which ensures a safe shut down of pressurized fluidized bed gasifiers maintaining
higher carbon inventory.
Another object of the invention is to propose a shutting down device which is
capable of creating an atmosphere of inert nitrogen inside the refractory lined
gasifier throughout the shut down period for protecting the refractory lining thus
ensuring better and longer life of the refractory.
A further object of the invention is to propose a shutting down device which is
capable of cooling the bed slowly and steadily with nitrogen.
A still further object of the invention is to propose a shutting down device which
substantially eliminates fouling of down stream equipment of the pressurized
fluidized bed gasifier system.
Yet another object of the invention is to propose a shutting down device which
ensures easy removal of bed ash by disallowing the bed ash to become sticky.
SUMMARY OF THE INVENTION
Accordingly, there is provided a shutting down device adaptable to pressurized
fluidized bed gasifier, the gasifier operating at a bed temperature between 900°
to 1100°C; and being in a state of shutting down by cutting-off supply of feed
Coal followed by stoppage of the flow of air and steam, the device comprising; a
liquid nitrogen storage vessel accommodating pressurized liquid nitrogen, a
plurality of vaporizer coils connected to the storage vessel via piping circuit
including control valves, the vaporizer coils converting the liquid nitrogen in
gaseous form by vaporization; a plurality of nitrogen gas holders receiving
nitrogen gas from the vaporizer coils and holding the nitrogen gas at ambient
temperature by maintaining a reduced pressure; and an auto pressure regulating
valve connected to the nitrogen gas holders which is set to adjust the pressure
of nitrogen gas higher than that maintained in the gasifier, the pressurized
nitrogen gas at ambient temperature being admitted to the gasifier via a piping
circuit provided with a non-return valve.
The device according to the invention consists of a storage for liquid nitrogen,
vaporizer coils, gas holders for nitrogen gas, a pressure regulating valve and
piping with a non return valve which is capable of admitting controlled quantity
of pressurized nitrogen gas at ambient temperature in a safe manner into the
bed of the pressurized fluidized bed gasifier to bring down the temperature of
the bed as and when needed.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1- shows a shutting down device adaptable to pressurized fluidized bed
gasifiers.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The device for Shutting Down of a Fluidized Bed Gasifier (07) comprises, a Liquid
Nitrogen Storage Vessel (01); Vaporizer coils (02) to convert liquid nitrogen into
gaseous form; Nitrogen Gas Holders (03) to hold nitrogen gas at pressures in the
range of 5 to 12 Kg/cm2 and at ambient temperature; an Auto Pressure Regulating
Valve (04) to control the pressure of nitrogen gas at the required level before
admitting into the Fluidized Bed Gasifier, (07); and interconnecting piping circuit
(05); and a non return valve (06).
During any planned or emergency shut down of a gasifier operating with supply
of a mixture of air and steam through the distributor and having coal above
the distributor, at a steady state with the bed temperature of the order of 900 to
1100 ° C, the flow of feed coal is cut off first, followed by stoppage of air and
steam and simultaneously nitrogen gas is admitted to reduce the bed
temperature to a safe value depending on the nature of fuel being used for
gasification. Prior to the admission of nitrogen, the pressure of nitrogen gas is
adjusted by setting the pressure regulating valve (04), to a pressure greater
than that of the gasifier (07) and the pressure of nitrogen in the gas holders (03)
is also correspondingly maintained by vaporization of liquid nitrogen from the
storage vessel (01) through the vaporizer coils (02).
Once bed temperature is reduced to the required level, the nitrogen gas flow is
cut off and air is again admitted for further cooling of the bed. When the bed
temperature reaches much below the ignition range of the fuel, the air supply is
also cut off. Now the gasifier is safely shut down although having high carbon
inventory in the bed. The use of nitrogen is also economized in this method and
only the required quantity of nitrogen is consumed .
The device is capable of cooling the bed uniformly. Further, the device reduces
the formation of carbon monoxide and hydrogen during the shut down of the
gasifier including reducing the carbon monoxide entrapment in the sub systems of
the pressurized bed system. The device is also capable of reducing or eliminating
fouling of heat transfer surfaces and other areas. The device reduces or
eliminates steam condensation and the consequential effects like corrosion,
non sticky bottom ash handling.
WE CLAIM
1. A shutting down device for a pressurized fluidized bed gasifier, th egasifier
operating at a bed temperature between 900° to 1100°C; and being in a
state of shutting down by cutting-off supply of feed coal followed by
stoppage of the flow of air and steam, the device comprising:
- a liquid nitrogen storage vessel (01) accommodating pressurized liquid
nitrogen;
- a plurality of vaporized coils (02) connected to the storage vessel (01)
through piping circuit having control valves, the vaporizer coils (02)
converting the liquid nitrogen in gaseous form by vaporization; and
- a plurality of nitrogen gas holders (03) receiving nitrogen gas from the
vaporizer coils (02) and holding the nitrogen gas at ambient temperature
by maintaining a reduced pressure.
Characterized in that an auto pressure regulating valve (04) is connected
to the nitrogen gas holders (03) which is set to adjust the pressure of
nitrogen gas higher than that maintained in that gasifier (07) and in that a
piping circuit (05) with a non-return valve (06) is flowably connected to
the nitrogen gas holders (03) to allow pressurized nitrogen gas at ambient
temperature to be delivered to the gasifier (07).
2. A shutting down device for a pressurized fluidized bed gasifier, as
substantially described herein with reference to the accompanying
drawings.

A shutting down device for a pressurized fluidized bed gasifier, the gasifier
operating at a bed temperature between 900° to 1100°C; and being in a state of
shutting down by cutting-off supply of feed coal followed by stoppage of the flow
of air and steam, the device comprising a liquid nitrogen storage vessel (01)
accommodating pressurized liquid nitrogen and a plurality of vaporized coils (02)
connected to the storage vessel (01) via piping circuit including control valves,
the vaporizer coils (02) converting the liquid nitrogen in gaseous form by
vaporization and a plurality of nitrogen gas holders (03) receiving nitrogen gas
from the vaporizer coils (02) and holding the nitrogen gas at ambient
temperature by maintaining a reduced pressure characterised in that an auto
pressure regulating valve (04) is connected to the nitrogen gas holders (03)
which is set to adjust the pressure of nitrogen gas higher than that maintained in
that gasifier (07) and in that a piping circuit (05) with a non-return valve (06) is
flowably connected to the nitrogen gas holders (03) to allow pressurized nitrogen
gas at ambient temperature to be delivered to the gasifier (07).

Documents:

135-KOL-2006-FORM-27-1.pdf

135-KOL-2006-FORM-27.pdf

135-kol-2006-granted-abstract.pdf

135-kol-2006-granted-claims.pdf

135-kol-2006-granted-correspondence.pdf

135-kol-2006-granted-description (complete).pdf

135-kol-2006-granted-drawings.pdf

135-kol-2006-granted-examination report.pdf

135-kol-2006-granted-form 1.pdf

135-kol-2006-granted-form 18.pdf

135-kol-2006-granted-form 2.pdf

135-kol-2006-granted-form 3.pdf

135-kol-2006-granted-gpa.pdf

135-kol-2006-granted-reply to examination report.pdf

135-kol-2006-granted-specification.pdf

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Patent Number

233778

Indian Patent Application Number

135/KOL/2006

PG Journal Number

15/2099

Publication Date

10-Apr-2009

Grant Date

08-Apr-2009

Date of Filing

16-Feb-2006

Name of Patentee

BHARAT HEAVY ELECTRICALS LIMITED

Applicant Address

REGIONAL OPERATIONS DIVISION (ROD), PLOT NO: 9/1, DJBLOCK 3RD FLOOR, KARUNAMOYEE, SALT LAKE CITY, KOLKATA-700091, HAVING ITS REGISTERED OFFICE AT BHEL HOUSE, SIRI FORT, NEW DELHI-110049

Inventors:

#	Inventor's Name	Inventor's Address
1	RAJAMANNAR KANNAN	BHARAT HEAVY ELECTRONICALS LIMITED (A GOVERNMENT OF INDAI UNDERTAKING), HPBP, TIRUCHIRAPALLI-620014
2	TIRUCHI RAJAGOAPAL VAIDNATH	BHARAT HEAVY ELECTRONICALS LIMITED (A GOVERNMENT OF INDAI UNDERTAKING), HPBP, TIRUCHIRAPALLI-620014
3	GAFUR SHAJAHAN	BHARAT HEAVY ELECTRONICALS LIMITED (A GOVERNMENT OF INDAI UNDERTAKING), HPBP, TIRUCHIRAPALLI-620014
4	DHANDAYUDHAM RAMAKRISHNAN	BHARAT HEAVY ELECTRONICALS LIMITED (A GOVERNMENT OF INDAI UNDERTAKING), HPBP, TIRUCHIRAPALLI-620014

PCT International Classification Number

F23C 10/100

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA