FORM - 2
THE PATENTS ACT, 1970
(39 OF 1970)
AND
THE PATENT RULE, 2003
COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)
"DESIGN OF A WATER COOLED SCREENING ARRANGEMENT FOR PARTICULATE CAPTURE IN WASTE HEAT RECOVERY SYSTEM-TRANSPARENT ENERGY SYSTEMS PRIVATE LIMITED AN INDIAN COMPANY, "PUSHPA HEIGHTS", 1ST FLOOR, BIBWEWADI CORNER, PUNE SATARA ROAD, PUNE- 411 037, MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF INVENTION
The present invention relates to the design of a screening arrangement for waste heat recovery system. More particularly present invention relates to a screening arrangement for waste heat recovery system on hot, dust and corrosive exhaust gases liberated from Glass Melting Furnace facilitating continuous operation of the system
PRIOR ART
Glass industry is an extremely energy intensive industry utilizing various fossil fuels such as natural gas, pet-coke, furnace oil, coal, etc. A valved periodic flow regenerator is used to recover heat from the melting tank exhaust gases. This regenerator consists of an array of bricks stacked in an "open checkerwork" pattern, through which the exhaust gases and combustion air are alternately passed. The cycle is changed at approximately 20 min intervals. The exhaust gas inlet temperature is approximately 14300TC and the outlet temperature ranges from 815 to 430°C, depending on the number of passes in the "brick checkers" regenerator, Typically used brick checker designs have gas outlet temperatures of 540-650°c, which yield air preheat temperatures approximately 1100X, and operate at a thermal effectiveness of 75-80%. Although there is considerable potential for additional heat recovery, glass manufacturers do not employ secondary heat recovery equipment downstream from the checkers regenerator. The industrial survey has shown that the gas-side fouling is the key barrier that inhibits use of secondary heat recovery Equipment. The recovered heat

can be used for driving steam based or Organic Rankine cycle power plant or for generation of steam or hot thermal oil for process use.
The research papers explain the mechanism of fouling as under.
The reaction of the volatile elements, and their subsequent condensation and solidification yield a slag or particulates that solidify at 884°C. The fine, solid particulates are the main source of fouling in a heat exchanger downstream from the regenerator. A "hot end" corrosion reaction may result from the reaction of K2S04 or Na2S04 with SO3. The reaction products are corrosive liquid pyrosulphates (K2S2O7 or Na2S207); these pyrosulphates solidify at 407 and 401°C, respectively. The liquid pyrosulphates will tend to entrap the Na2S04 particulates. As the surface temperature is lowered, the deposit dries to form a hard scale, which is quite difficult to remove by air lancing. But, it is water soluble and can be removed by water washing.
A "cold end" corrosion reaction will occur if the H2S04 formed by reaction of S03 and H20 vapor condenses. The dewpoint of the H2S04 depends on the S03 concentration. It is also possible for the condensed acid to react with Na2S04 to form Na2S07. And, if the water vapor also condenses, NaHS04 will be formed. These condensates form a "sticky" surface which entraps the Na2S04 particulates. The resulting deposit may be removed by steam or water wash.

The addition of MgO to the flue gases consumes the excess S03 forming MgS04. This further prevents formation of "sticky" condensates so that the surface fouling problem is greatly alleviated. The resultant deposits are dry, soft and can be removed by air lancing or steam soot blowers.
Further, the character of the foulant was dependent on the tube surface temperature, as given below
1. 465°C gas temperature without heat transfer: the deposit consisted of a very thin coating of fine powder, which was easily removed
2. 404-500°C gas temperatures, with 260°C tube temperature: around 3.2 mm thick dense powder deposit. An air lance removed "most of the deposit".
3. 343-460°C gas temperature, with 149°C tube temperature; the tube surface was coated with a 0.12-0.25 mm thick hard scale. On top of this was around 6 mm thick layer of soft yellow powder. The air lance removed only the outer soft layer. The hard scale was removable with a water wash.
LIMITATIONS OF PRIOR ART
The description of prior art clearly indicates following disadvantages of the prior art.
The gases exhausted by glass furnaces comprise of sticky dust particulates which have a tendency to cause fouling of heat exchangers. This limits the use of waste heat recovery systems on the exhaust gases from glass furnaces.

As discussed in prior art, MgO dosing is practiced to modify the properties of sticky particulates in the exhaust gases. This technique proves to be effective only if the mixing of MgO with flue gases is proper. WHR systems are many a times retrofit systems in the running glass melting plants. Therefore, it might be difficult to provide large mixing chambers due to lack of space. Also, MgO is a expensive substance. Therefore continuous dosing of MgO increases the overall operating cost of WHR system.
PRESENT SCENARIO AND NEED FOR INVENTION
As discussed in the prior art, glass industry is extremely energy intensive industry. In absence of a secondary heat recovery system, it would exhaust hot gases in the temperature range of 400 to 600 deg C. Therefore, it necessary to install a waste heat recovery system, for following reasons,
1. Energy recovery resulting in fuel saving
2. Reduction in C02 emissions
3. Prevention of Global Warming
4. Sustainable Development
Also it is necessary that this waste heat recovery system can reliably work on the hot, dusty and corrosive exhaust gases from glass furnace. Therefore, there is a need to develop a system that addresses this problem of fouling without compromising on the heat recovery and without requiring frequent shut downs for clean up.

OBJECT OF THE PRESENT INVENTION
Object of present invention aims at the design of a water cooled screening arrangement for particulate capture in waste heat recovery system on hot, dust and corrosive exhaust gases liberated from Glass Melting Furnace facilitating continuous operation of the waste heat recovery system
It is also object of present invention to design and integrate this screening arrangement with the waste heat recovery system without any reduction in heat recovery
It is also object of present invention to eliminate limitations or drawbacks of the prior art.
It is also the object of the present invention to develop a system that addresses this problem of fouling without compromising on the heat recovery and without requiring frequent shut downs for clean up.
STATEMENT OF THE PRESENT INVENTION
According to this invention, therefore, a design of a water cooled screening arrangement for particulate capture in waste heat recovery system comprising of a waste heat recovery system characterize in that there is provided a screening arrangement, position of which is depending upon the exhaust temperature of the gases of the glass furnace.

According to another preferred embodiment of the present invention, a design of a water cooled screening arrangement for particulate capture in waste heat recovery system, said screening arrangement is installed prior to super heater, if the temperature of gases is in the range of 425 to 500 deg C and on the water side, the water from steam drum is circulated in the screen tubes.
According to one more preferred embodiment of the present invention, a design of a water cooled screening arrangement for particulate capture in waste heat recovery system, said screening arrangement is installed after superheater and prior to evaporator, if the temperature of gases is in the range of 350 to 425 deg C, and on the water side, the water from steam drum is circulated in the screen tubes.
BRIEF DESCRIPTION OF SCHEMATIC DRAWINGS
Fig.1 Process diagram showing details of the system according to the present invention wherein said screening arrangement is installed prior to super heater.
Fig.2 Process diagram showing details of the system according to the present invention wherein, the said screening arrangement is installed after superheater and prior to evaporator
Fig.3 Process diagram showing details of the possible variation in the system according to the present invention wherein the said screening arrangement is installed after superheater and prior to evaporator

DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to the design of screening arrangement for Waste Heat Recovery System on hot, dusty and corrosive exhaust gases from Glass Melting Furnace. More particularly, the present invention relates to the screening arrangement comprising of multiple screens of tubes similar to a tube bank over which the hot, dust and sticky exhaust gas from glass melting furnace passes perpendicular to the tube
gas flow is in horizontal direction. Similarly, the construction of screening tubes would be horizontal in case the gas flow is in vertical direction.
The waste heat recovery system (WHRS) typically comprises of four modules namely, water preheater, economizer, evaporator and superheater to produce high pressure superheated steam. WHRS could also be designed to produce hot thermal oil or steam for process heating.
The WHRS is designed to operate on hot gases exhausted by glass furnace. The prior art discusses the temperature zones in which the various particulates in the condensate deposit over tube surfaces. Therefore, the number of tubes in the WHRB which are under the temperature conditions as indicated in prior art is the number of tubes in a

screening arrangement. Which means, the number of rows of tube screens depends on following parameters
1. Gas temperature
2. Temperature of water flowing through the tubes
3. Tube wall temperature
4. S03 percentage in gas.
For example, if the temperature of gas flowing through the system is 482 deg C at inlet & 410 deg C at outlet, the temperature of water flowing through the tubes is 229 deg C, the tube wall temperature is 235 deg C, then the number of screen tube rows required would be 12.
Now, referring to figs.1, 2 and 3, the WHRS comprises of water preheater (6), economizer (5), evaporator module (4) and superheater (3). The treated dematerialized water is supplied to Deaerator tank (7) from where the water is circulated in the water preheater(6). The preheated water (shown by arrows) is supplied to economizer (5) which is further supplied to the steam drum (8). The water from the steam drum (8) circulates in the evaporator (4). According to other embodiments the position of the screening arrangement as per the present invention varies according to the temperature range of the gases coming out from the melting furnace.
Now referring to Fig. 1 The screening arrangement (2) is installed prior to super heater (3), if the temperature of gases is high and in the range of 425 to 500 deg C. On the water side, the water from steam drum (8) is circulated in the screen tubes of the said

screening arrangement (2). The steam from steam drum (8) is supplied to the superheater (3). On the gas side, the gases pass over the said screening arrangement, followed by superheater (3), evaporator (4), economizer (5), and WPH (6). For example, to generate the steam of 27bar pressure and 400 deg C temperature, the minimum temperature of the gas at inlet of superheater has to be 412 deg C. This means, if the temperature of gas at exhaust of glass furnace is 480 deg C. we will have to install the screening arrangement above the superheater, as shown in fig 1. Then the particulates will condense over tubes of screening arrangement and the gas at the exhaust of screening arrangement will be free of particulates. When this screening arrangement is choked due to particulate depositions it will be automatically bypassed with the help of automatic three way diverter valve (1) and the stand by screening arrangement will be taken in line. This will help the WHRS operate continuously without requiring frequent stoppages for cleanup.
Referring to Fig. 2 the screening arrangement (2) according to the present invention is installed after superheater (3) and prior to evaporator (4).If the temperature of gases is lower and in the range of 350 to 425 deg C. On the water side, the water from steam drum (8) is circulated in the screen tubes of the said screening arrangement (2). The steam from steam drum (8) is supplied to the superheater (3). On the gas side, the gases pass over superheater (3), followed by screening arrangement (2), evaporator (4), economizer (5), and WPH (6). For example, to generate the steam of 27bar pressure and 400 deg C temperature, the minimum temperature of the gas at inlet of superheater has to be 412 deg C. This means, if the temperature of gas at exhaust of

glass furnace is 425 deg C. we will have to install the screening arrangement after the superheater, as shown in fig 2. The mechanism of working of screening arrangement in this case is similar to that explained above as in case of fig. 1.
Referring to Fig. 3, which is possible variation of the present invention, the screening arrangement (2) can be installed after superheater (3) and prior to evaporator (4). If the temperature of gases is lower and in the range of 425 to 500 deg C. On the water side, as shown in figure 3, the water from steam drum (8) is circulated in the screen tubes (2). The steam from steam drum is supplied to the superheater (3) which is split in to two parts; primary and secondary superheaters as shown in fig 3. On the gas side, the gases pass over first part of superheater (3), followed by screening arrangement (2), second part of superheater (3), evaporator (4), economizer (5), and WPH (6). For example, to generate the steam of 27bar pressure and 400 deg C temperature, the minimum temperature of the gas at inlet of superheater has to be 412 deg C. This means, if the temperature of gas at exhaust of glass furnace is 480 deg C. we can install the screening arrangement after the superheater, as shown in fig 3. The mechanism of working of screening arrangement in this case is similar to that explained above as in case of Fig. 1 and 2.

ADVANTAGES OF THE PRESENT INVENTION:
1. The present invention related to the design of a waste heat recovery system as described above which can be continuously operated without requiring a complete system shut down
2. The present invention incorporates leak proof, reliable and fully automatic three way diverter valve described in Patent Application Number 591/MUM/2010 which enables automatic diversion of exhaust gases to stand by screen arrangement when the pressure drop across the running screen arrangement rises above the set point. Therefore, it facilitates fully automatic operation of the WHR system.
3. The present invention incorporates one working one stand by type arrangement of evaporator tube screens on which the corrosive dusty particulate from the gases sticks. When the working screen is chocked beyond certain limits, the stand by screen is automatically brought in operation with the help of three way diverter valve. Therefore, with this arrangement, the WHR system can operate on continuous basis without requiring frequent system shut down.
4. The present invention can be advantageously applied in waste heat recovery system having bare tube cross flow type construction due to which this WHR system can be reliably installed on dusty exhaust gases from glass melting industry
5. The present invention relates to a design of screening arrangement for waste heat recovery system designed for exhaust gases from all type of glass furnaces.

6. The present invention relates to a design of a screening arrangement for the waste heat recovery system which facilitates to maintain the pressure drop across the WHR system within permissible limits for the existing natural draft or Induced Draft furnaces of the Glass Industry.
7. The present invention relates to a design of a screening arrangement which could be advantageously designed for waste heat recovery systems all the types such as, natural circulation, forced circulation, with MgO dosing and without MgO dosing.
8. The present invention relates to a design of a screening arrangement which could be used in design of all types of waste heat recovery systems such as boilers and thermic fluid heaters.
9. The heat recovered by the water circulating in the tubes of screening arrangement is circulated back in to the waste heat recovery system therefore, there is no loss of heat and no reduction in heat recovery even after incorporation of screening arrangement in the present invention.
10.All the automatic gas bypass mechanism explained in the detailed description could be made manual as well on case to case basis.

WE CLAIM:-
1. A design of a water cooled screening arrangement for particulate capture in
waste heat recovery system on hot, dust and corrosive exhaust gases liberated
from glass melting furnace and process thereof comprising of a waste heat
recovery system characterize in that there is provided a screening arrangement,
position of which is depending upon the exhaust temperature of the gases of the
glass furnace.
2. A design of a water cooled screening arrangement for particulate capture in waste heat recovery system on hot, dust and corrosive exhaust gases liberated from glass melting furnace and process as claimed in claim 1 above where in said waste heat recovery system comprises of a automatic three way diverter valve (1) for diverting the flue gases from the melting furnace, superheater, evaporator, economizer, water preheater, Deaerator and Steam Drum.
3. A design of a water cooled screening arrangement for particulate capture in waste heat recovery system on hot, dust and corrosive exhaust gases liberated from glass melting furnace and process as claimed in claim 1 and 2 above wherein, the said screening arrangement comprising of multiple screens of tubes similar to a tube bank over which the hot, dust and sticky exhaust gas from glass melting furnace passes perpendicular to the tube axis.

4. A design of a water cooled screening arrangement for particulate capture in waste heat recovery system on hot, dust and corrosive exhaust gases liberated from glass melting furnace and process as claimed in claim 1 to 3 above wherein, said screening arrangement is installed prior to super heater, if the temperature of gases is in the range of 425 to 500 deg C on the water side, the water from steam drum is circulated in the screen tubes.
5. A design of a water cooled screening arrangement for particulate capture in waste heat recovery system on hot, dust and corrosive exhaust gases liberated from glass melting furnace and process as claimed in claim 1, to 4 above wherein, said screening arrangement is installed after superheater and prior to evaporator, if the temperature of gases is in the range of 350 to 425 deg C on the water side, the water from steam drum is circulated in the screen tubes.
6. A design of a water cooled screening arrangement for particulate capture in waste heat recovery system on hot, dust and corrosive exhaust gases liberated from glass melting furnace and process as claimed in claim 1 to 5 above wherein, said screening arrangement is installed between primary & secondary superheaters and prior to evaporator, if the temperature of gases is in the range of 425 to 500 deg C. on the water side, the water from steam drum is circulated in the screen tubes.
7. A design of a water cooled screening arrangement for particulate capture in waste heat recovery system on hot, dust and corrosive exhaust gases liberated from glass melting furnace and process as claimed in claim 1 to 6 above and as

herein described with reference to the drawings of the accompanying specification.