FORM 2
THE PATENT ACT 1970
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION DRYER VAPOUR ENERGY RECOVERY METHOD
2. APPLICANT
(a) NAME: PRAJ INDUSTRIES LIMITED
(b) NATIONALITY: Indian Company
(c) ADDRESS: PRAJ Tower, 274-275, Bhumkar Chowk-
Hinjewadi Road, Hinjewadi, Pune - 411057, INDIA
3. PREAMBLE TO THE DESCRIPTION
The following specification describes the invention and the manner in
which it is to be performed.

4. DESCRIPTION
FIELD OF THE INVENTION
The invention relates to a method of recovery of energy from a dryer vapour stream, further it relates to the recovery of unused energy from said dryer vapour stream for other useful work like heating or evaporation.
BACKGROUND
Dryer vapours are the by-product of many industrial drying processes and contain substantial amount heat energy. They also contain around 30 % to 55 % air by weight due to unavoidable leakages in dryer drums or chambers, along with that it has small particulate matter coming from the drying materials. This presence of air and particulate matter create difficulty in the utilisation of the dryer vapours in the energy recovery and heat integration units. Further the presence of air leads to the substantial increase in the heat transfer area of integrated reboiler/ evaporator requiring high capital investment. Further the particulate matter in the dryer vapour tend to stick to heat transferring surfaces, creating disruption in the process and needs constant cleaning by taking stoppages of the plant. This problem of the presence of air and particulate matter in the dryer vapour, stream and its effective use for

energy recovery and heat integration needs an effective solution, which is disclosed herein with its embodiments.
DESCRIPTION OF THE DRAWING
A particular embodiment of a method in accordance with this invention will now be described with reference to accompanying drawing, in which:
FIGURE 1 is an exemplary plan of the invention showing several features that control method for removing air and a particulate matter present in a dryer vapour stream. The dryer vapour stream is treated with a hot water stream in a direct contact condenser leading to formation of a non-condensable air vapour stream and a first liquid stream containing said particulate matter. Then said first liquid stream is subjected to flashing in a flash tank under negative pressure leading to formation of a second liquid stream containing said particulate matter and a final vapour stream. Said final vapour stream is utilized to recover heat energy. Said second liquid stream is reused as said hot water stream in said liquid condenser and said particulate matter is purged continuously from said second liquid stream before supply to said direct contact condenser. The scheme has several elements that significantly contribute to the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION
In one embodiment of the present invention, as illustrated in FIGURE 1, a dryer vapour stream is a product of an industrial drying process, comprising about 10 % to about 50 % air and about 0.1 % to about 0.5 % particulate matter by weight. The dryer vapour stream is treated with a hot water stream in a direct.contact condenser at a temperature of between about 70 °C to about 99 °C leading to formation of a non-condensable air vapour stream and a first liquid stream containing said particulate matter. Said first liquid stream has a temperature of between about 80 °C to about 99 °C. Then said first liquid stream is subjected to flashing in a flash tank under negative pressure of between about 0.3 bar [absolute] to about 0.95 bar [absolute] leading to formation of a second liquid stream containing said particulate matter and a final vapour stream. The temperature of said second liquid stream and said final vapour stream is between about 75 °C to about 95 °C. Said final vapour stream is utilized to recover heat energy, which is further used in other energy requiring processes. The air vapour stream is removed using an induced draft fan and the final vapour stream is removed under negative pressure developed in the system for this purpose. Said second liquid stream is reused as said hot water stream in said liquid condenser. The particulate matter is purged out continuously from said second liquid stream before supply to said condenser. The make-up water is added to said first liquid stream to cover any loss of water through purging.

In another embodiment of the present invention, as illustrated in FIGURE 1 dryer vapour stream with particulate matter and air [1] is first received in a direct contact condenser unit [A], where it comes in contact with a hot water stream [4] separating in the process air from [1] as air vapour stream [7] and a first liquid stream [2], which contains most of said particulate matter. Said air vapour stream [7] is removed from said condenser by an induced draft fan [C]. Said first liquid stream [2] is then flashed in a flash tank [B] maintained under negative pressure leading to separation of a final vapour stream [6] from a second liquid stream [4]. Then said final vapour stream [6] is further subjected heat recovery using heat exchangers or evaporators. A waste stream [5] is purged from stream [4] if the amount of particulate matter increases above a set threshold in stream [4]. Said stream [4] is circulated in the system as said hot water stream. Makeup water [3] is added to said stream [2] if amount of water in the stream is below a set threshold for effective operation of the system.
In yet another embodiment of the present invention, about 34255 kg of dryer vapour stream comprising about 18840 kg of water vapour [about 55 % by weight] and about 15415 kg of air [about 45 % by weight] having a temperature of about 89 °C was subjected to a hot water stream at 75 °C, with a recirculation rate of about 650 m3/h, in a direct contact condenser

in an hour long operation. In said condenser, the contact between said dryer vapour stream and said hot water stream led to mass and energy transfer events forming an air vapour stream of about 24835 kg with a temperature of about 82 °C [contenting about 38 % water vapour by weight], which was removed from the system by an induced draft fan. While a first liquid stream of about 74420 kg with a temperature of about 83 °C [heated hot water stream] was directed from the bottom of said condenser to a flash tank operating under a negative pressure of about 0.4 bar [absolute]. A final vapour stream [flash vapours], from said flash tank with a temperature of about 75 °C and amount of about 9575 kg generated in one hour of operation, was taken to energy recovery or heat integration. While said second liquid stream from said flash tank formed said hot water stream directed to said direct contact condenser at a recirculation rate of about 660 m3/h. The particulate matter accumulated in said second liquid stream was removed continuously by purging about 1500 kg of liquid with addition of about 1655 kg of make-up water in one hour operation of the system. This method of energy recovery afforded about 7005 kW of energy from about 13990 kW present in said dryer vapour stream with an efficiency of about 50 % in the one hour of operation of the system as disclosed herein. The system was operated continuous mode affording continuous recovery of useful energy from said dryer vapour stream.

Embodiments provided above give wider utility of the invention without any limitations as to the variations that may be appreciated by a person skilled in the art. A non-limiting summary of various embodiments is given above, which demonstrate the advantageous and novel aspects of method disclosed herein.

5. CLAIMS
WE CLAIM:
1. -A method for recovery of energy from a dryer vapour stream comprising:
(a) contacting safd dryer vapour stream fn a direct contact condenser with a hot water stream forming an air vapour stream and a first liquid stream;
(b) flashing said first liquid stream in a flash tank under negative pressure forming a second liquid stream and a final vapour stream;
(c) utilising said final vapour stream to do useful work or to recover heat energy;
(d) reusing said second liquid stream as said hot water stream in said condenser;
(e) purging said second liquid stream continuously to remove any particulate matter coming from said dryer vapour stream before supply to said condenser as said hot water stream; and
(f) adding make-up water to said first liquid stream to cover any Loss of water through said purging.

2; The method of claim 1, wherein said dryer vapour stream is a product of an industrial drying process.
3. The method of claim 1, wherein said dryer vapour stream comprises about 10 % to about 50% air by weight and about 0.1 % to about 0.5 % particulate matter by weight.
4. The method of claim 1, wherein said direct contact condenser is operated at a temperature of between about 85 °C to about 99 °C.
5. The method of claim 1, wherein said flash tank is operated at a pressure of between about 0.3 bar [absolute] to about 0.95 bar [absolute].
6. The method of claim 1, wherein said dryer vapour stream has a temperature of between about 80 °C to about 99 °C.
7. The method of claim 1, wherein said first liquid stream has a temperature of between about 80 °C to about 95 °C.
8. The method of claim 1, wherein said second liquid stream has a temperature of between about 75 °C to about 95 °C.
9. The method of claim 1, wherein said final vapour stream has a temperature of between about 75 °C to about 95 °C.

10. The method of claim 1, wherein said air vapour stream is removed using an induced draft fan.
11. The method of claim 1, wherein said final vapour stream is removed using negative pressure.
12. A method substantially as described in FIGURE 1.