FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules, 2003
Complete Specification
(See section 10 and rule 13)
A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat
Mahindra and Mahindra Ltd.
An Indian company registered under the Indian Companies Act, 1956.Mahindra Towers, R.K. Kurne Chowk, Worli, Mumbai - 400 018,Maharashtra, India
The following specification particularly describes the invention and the manner in which it is to be performed.
Field of Invention:
Present invention relates recovering heat from oven exhaust gases & using it to heat up any other process in the paint shops used in industrial units such as those used for manufacture of automotives, white goods, other household or industrial appliances that require painting, or indeed ceramic industry. The scope of the invention is to use the waste heat, extracted from the oven exhaust for the process heating.
Background of Invention:
Paint shops conventionally use indirectly fired ovens to bake paints. The incinerators burn completely the exhaust gases with volatile organic contents (VOC). These exhaust gases in turn heat up the various heat-up zones in the oven, before they are finally let-off to the atmosphere. They temperature of gases which are exhausted in to the atmosphere ranges from 180 Deg C to 220 Deg C.
On the other hand, the pretreatment process heating in the paint shops is conventionally achieved through a hot water generator, which is energized by

liquefied petroleum gas (LPG), High Speed Diesel (HSD), or even by Electricity. This incurs a huge cost & adds to C02 emissions. The need was to have a consistent source of heating which would reduce the cost & environmental impacts.
There have been no known instances of heat recovery from the oven in automotive industry. In one of the recovery systems for heat from ovens - used by a commercial bakery - the recovery from oven exhaust is achieved by direct contact of water with the oven & used the resulting heated water, in turn, to preheat the makeup water for a boiler. The amount of make up water in the heating processes used in automotive industry, for example, is extremely small as the system losses are small. The scope of application of this system is therefore very limited.
In our invention we use the oven exhaust heat to indirectly heat up a water circuit which continuously heats up the paint shop process (Pretreatment), We are not merely heating make up water. Besides we use indirect heating of water circuit through heat exchanger, due to which there are no evaporation losses.
In another invention by Ford India the oven exhaust heat is used to preheat the oven fresh air. Once again, the application of this process is quite limited, and it

cannot be used towards the processes which typically used in industrial paint shops.
In yet another invention, initiated by Coke, a process is described to use the oven exhaust to oxidize the volatiles within the ovens; the fuel used for the ovens is coal where the oven exhausts oxidize the volatiles within the ovens. The heat from oven exhaust continues to get wasted to a large extent.
There is therefore a need to harness this energy by recovering it and using it towards industrial processes.
Objects of the invention:
Accordingly the one of the objects of the present invention is to recover the exhaust oven heat.
Another object of the present invention is to use the recovered heat towards the industrial processes.
Yet another object of the invention is to provide a consistent source of heating in the form of heat recovered from the industrial ovens which would reduce the operational costs and the adverse environmental impact.

Summary of the invention:
A system is proposed that would harness heat otherwise rejected to the atmosphere from industrial processes involving ovens and recycle it back into another industrial processes. The system uses at least one heat exchanger, preferably a number of heat exchangers, which recover the heat from the hot exhaust gases of the ovens that are used for downstream baking operations of an industrial process and provide the recovered heat to pretreatment operations that typically take place at the upstream end of industrial processes. The heat exchanger used for recovering heat from the hot exhaust gases preferably work on gas to liquid heat exchange principle. The heat exchangers used to transfer the recovered heat preferably work on a liquid to liquid heat transfer principle.
List of Figures:
Figure 1 shows the conventional method of disposing oven hot exhaust gases Figure 2 shows the conventional industrial processes using a hot water generator and a heat exchanger
Figure 3 shows an embodiment of the system of the present invention Figure 3A shows another embodiment of the system of the present invention Figure 3B shows yet another embodiment of the system of the present invention Figures 4 and 4A shows the paint shop outline layout for the examples of the invention

List of parts:
System of heat exchange (1) First main collector pipe (6),
Oven (2), First secondary collector pipe (6A)
Oven hot exhaust gases (2A), Second secondary collector pipe (6B)
Oven cool exhaust gases (2B) Third secondary collector pipe (6C)
Heat recovery unit (HRU) (3) Fourth secondary collector pipe (6D)
Heat exchanger (3A) Second main collector pipe (6E)
First heat exchanger (4), First main return pipe (7),
Second heat exchanger (4A) First secondary return pipe (7A)
First loop (5), Second secondary return pipe (7B)
Second loop (5A), Third secondary return pipe (7C)
Third loop (5B), Fourth secondary return pipe (7D)
Fourth loop (5C), Second main return pipe (7E)
Fifth loop (5D), Pretreatment tank (8)
Hot water generator (9)
Definitions:
Heat exchanger (HE): A heat exchanger is used for the purpose of transferring
heat from one source or medium to the other.
First heat exchanger: The heat exchanger(s) between the HWG and the pretreatment tanks

Second heat exchanger: The heat exchanger between system of HRUs and the hot water generator (HWG)
Collector pipes (main and secondary): The pipes carrying fluids heated after heat exchange shown as long dashed lines in Figure 3, 3A, and 3B, Main pipes are shown with thick lines and secondary with thin lines
Return pipes (main and secondary): The pipes carrying cooled fluids shown as short dashed lines in Figure 3, 3A, and 3B. Main pipes are shown with thick lines and secondary with thin lines
Heat recovery unit (HRU): Heat recovery unit is in fact a heat exchanger itself, except it is closest to the primary source of heat - the oven
Hot water generator (or a heat generator): Equipment used to heat fluids to temperatures required in the start up phase of the pretreatment process.
Close loop: A loop where the fluids contained within the loop are not exposed to atmosphere; typically a network of pipes.
Open loop: A loop in which the fluids are exposed to atmosphere; typically a loop where fluids are transported through a pipe network, however, the loop also contains open containers such as tanks containing the chemicals in the loop. The

purpose of open loops is to allow its chemicals to be used in chemical baths in which articles of manufacture are dipped.
Detailed description of the invention:
The industrial processes such as those deployed in paint shops of automobile manufacturing plants typically involve pretreatment process of parts to be painted. The pretreatment processes use chemicals that are heated. The heat provided varies from application to application and on the chemicals used. The paint process also involves baking operations that involve use of ovens which typically operate at substantially higher temperatures than those required for pretreatment steps.
The conventional process of releasing oven exhaust gases is shown in Figure 1. The exhaust gases from the oven directly go to the atmosphere at a very high temperature, typically around 200 °C (ranging from 180 °C to 219 °C) depending on the fuels used for heating and the type of the process for which the ovens are used.
Conventional processes requiring heating typically use hot water generated through a hot water generator and a heat exchanger that provides the heat to the process or the application that requires it. A typical conventional system used for this purpose is shown in Figure 2. It shows a hot water generator (HWG) which is

used to heat up the pretreatment process tanks using a heat exchanger as a intermediate device for heat transfer. The hot water generators are typically fired with LPG but HSD or electric energy source is also known to be used.
In the conventional industrial processes that use heating as a step of the overall process, the two systems, namely the oven and the pretreatment process tanks are operated independently of each other.
The proposed invention discloses a system whereby the heat contained in the exhaust gases of the oven is recovered and provided to the pretreatment stage.
Depending on the nature of the chemicals used in the process and their heat (or temperature) requirement, the heat may be transferred in a single step or through a cascade that involves stepwise heat reduction starting from close to source (the oven) to the pretreatment process tank.
Figure 3 shows the simplest embodiment of the present invention which is useful in the case of pretreatment processes that use chemicals which typically require heating close to the temperature of oven hot exhaust gases (2A). However, it may be used in cases of chemicals that require lower temperatures by controlling the amount of heat recovered. It shows a system of ovens (2) from which a system of heat recovery units (HRU) (3) recovers heat in the form of fluids which are heated by hot exhaust gases (2A) of the oven (2) and transfers the recovered heat in the

form of heated fluids through a first loop (5) to the pretreatment process tanks (8). The first loop comprises a first main collector (6) which collects heated fluids from each of the HRU (3) through a set of first secondary collectors (6A) as required. The first main collector (6) passes through an optional heat generator (9) which provides additional heat to the fluid in the first main collector (6) during the start up phase of the pretreatment process. The optional heat generator (9) serves as a back up in case the heat recovery mechanism fails. It also provided additional heat that may be required during the start up phase of a pretreatment process. The first main collector (6), through a set of second secondary collectors (6B) provides heat to the chemicals in pretreatment process tanks (8). The chemicals in the pretreatment process tanks are transported back to the HRUs. This is achieved through a system of second secondary return pipes (7B) which returns chemicals to the first main return pipe (7), which in turn returns the cooled chemicals to HURs (3) through first secondary pipes (7A).
As indicated in Figure 3, the loop formed by the various secondary collectors and the main collector and the various secondary returns and main return together with the pretreatment process tanks is termed as first loop. It is evident that the first loop is an open loop and contains chemicals that are used in the pretreatment process.
An HRU (3) is essentially a shell & tube type heat exchanger through which the oven exhaust hot gases (2A), which are normally let off in to the atmosphere at a

high temperature, are passed through. In the description and the claims that follow the term heat recovery unit (HRU) may be replaced by heat exchanger to facilitate clarity. A HRU (3) may serve one or more ovens (2). The HRU (3) is designed so that the oven hot exhaust gases (2A) heat the fluids passing through the first loop (5) are heated to a required level depending on the chemicals that are used in the pretreatment process.
The gases which are cooled after transferring heat in the HRU are termed as oven exhaust cool gases (2B), and are at a lower temperature than the oven exhaust hot gases (2A). In the system of the present invention the oven exhaust cool gases (2B) are released to the atmosphere. The heated liquid in the first loop (5) is thus at a temperature lower than that of the oven exhaust hot gases and at a temperature at or slightly higher than that of the oven exhaust cool gases (110 °C),
In a further embodiment of the invention, as shown in Figure 3 A, a set of first heat exchangers (4) are introduced in the system of heat exchange (1) which was disclosed in the earlier embodiment. Here the heat recovery units (3) perform the same role as that in the previous embodiment, that is to recover the heat and transfer it further down the system. The first heat exchangers (4) are of a plate type and used to transfer heat using a liquid to liquid principle of heat transfer. A second loop (5A) is used to transfer recovered heat to the set of first heat exchangers (4).

The second loop comprises a first main collector (6) which passes through the hot water generator (9). It further comprises a set of first secondary collectors (6A) which feed heated water from the HRUs to the first main collector (6) and subsequently to the set of first heat exchangers (4) through a set of third secondary collector pipes (6C). Furthermore, a set of third secondary return pipes (7C) returns the water that is cooled down after heat transfer to a main return pipe (7) and subsequently back to the system of the HRUs (3) through appropriate arrangement of first secondary return pipes (7A). The second loop thus described is a closed loop that carries a fluid, preferably water, for heat transfer. However, any other suitable fluid or gas or a mixture thereof may be used.
One first heat exchangers (4) is provided corresponding to each of the pretreatment process tanks that require heating, however, it is also possible to design the system so as to connect a single first heat exchanger to more than one pretreatment process tanks or vice versa. The second loop (5A) is a closed loop carrying fluid, preferably water. Heat is transferred from first heat exchangers (4) to the corresponding pretreatment process tanks (8) using a third loop (5B), which is an open loop,
The third loop (5B), which is an open loop, comprises a set of fourth secondary collector pipes (6D) arriving from a first heat exchanger (4) which open into corresponding pretreatment tanks (8) containing chemical that requires heating. A fourth secondary return pipe (7D) that leads from the pretreatment tank (8) is run

back to the corresponding first heat exchanger (4), thus forming a loop. The third loop (5B) is thus partially open (the pretreatment tank) and partially close (the secondary pipes). In the embodiment illustrated in Figure 3A, there is a third loop (5B) formed between each first heat exchanger (4) and a corresponding pretreatment tank (8). The chemical contained within the third loop is maintained at around 55 to 60 °C.
A hot water generator (9) is optionally provided to serve the same purposes as the previous embodiment.
In a still further embodiment, yet another system of heat exchange is illustrated (see Figure 3B). It is an example of a process where the temperatures of chemicals used in the pretreatment process is required to be much lower than that of the oven hot exhaust gases. This is achieved by gradually reducing the temperature of the recovered heat progressively down the heat recovery and transfer system in a cascading manner.
It shows a number of ovens (2) that are typically used for the purposes of heating or baking operations in industrial processes used in manufacturing industry. The number of heat recovery units (HRU) (3) which are provided depends on the location and type of the ovens. Any one HRU (3) may serve one or more ovens (2), or vice versa. The system of this embodiment comprises a set of HRUs, at least one second heat exchanger (4A), a set of first heat exchangers (4), and a set

of pretreatment process tanks (8) carrying chemicals, and adequate number of loops between the various components of the system.
As in the case of an earlier embodiment, preferably one first heat exchanger (4) is provided corresponding to each of the pretreatment process tanks (8). Furthermore, each first heat exchanger is of a plate type and used to transfer heat using a liquid to liquid principle of heat transfer.
The heat recovered from the oven hot exhaust gases (2A) is transferred to a second heat exchanger (4A) using a fourth loop (5C), which is a closed loop. The fourth loop (5C) is formed by a set of secondary collector pipes (6A) and a main collector (6) which takes heated fluids from the HRUs to the second heat exchanger (4A), and a main return (7) and a set of secondary returns (7A) that return the cooled fluids back to the HRUs (3) for the ongoing heat recovery.
The second heat exchanger (4A) serves to reduce the temperature of the heated fluids through its plate type heat exchange mechanism. The fluids in a fifth loop (5D) are heated by the heat transferred from the second heat exchanger (4A) and taken to the set of first heat exchangers (4). The fifth loop (5D) is a closed loop that comprises a second main collector (6E), a second main return (7E) and a set of third secondary collectors (6C) and third secondary returns (7C). The fluid in the fifth loop (5D) is preferably water.

As in the case of an earlier embodiment, the first heat exchangers (4) provide heat to the chemicals in the pretreatment process tanks through a set of third loops (5B), which are the open type loops as disclosed in an earlier embodiment.
Depending on the plant design a number of first heat exchangers and/or a number of second heat exchangers are used. In the case where more than one first or second heat exchangers is used, adequate piping network is provided for collecting heated fluids and returning cooled fluids to appropriate components using main and secondary or any other type of piping networks.
It has been observed by the inventors that the heat recovered by the HRU is typically sufficient to run the pretreatment tanks (which all together may contain hundreds of cubic meter chemicals) in a steady state in an industrial process such as one used in the paint shop of an automobile manufacturing operation. However it is also well known that, during the start-up of a pretreatment process of a paint shop operation, additional source of heat is required as the temperature required at the start-up is typically higher than that required in steady-state or ongoing operations of the pretreatment tanks. The system of the present invention therefore provides a hot water generator in conjunction with the first heat exchangers so that the hot water generator (HWG) may be used optionally upon requirement. HWG is a shell and tube type heat exchanger which works on an indirect heating principle. It may be any other type of heat generator, for example one that works on electricity.

In the conventional processes, the HWG is placed in a separate loop with the first heat exchanger. However, as a further advantageous feature of the present invention and as shown in Figure 3B, the first heat exchanger, the HWG and the second heat exchanger are provided in a series connection, with the HWG situated over a main collector of an appropriate loop. The inventors have found that this allows the optimum use of the recovered heat while providing the additional heat required during the start up stage without having to resort to plant shutdown.
It is observed that there's a gradual temperature drop between the various heat exchange loops that are described here, namely the gas to water loop, and liquid to liquid loops; something that is suitable to reduce the recovered heat in a cascading manner before it is used in the pretreatment process. It is evident that the temperature of the loop at the upstream end (in our case the gas to liquid heat exchange loop) is the highest. The temperature of the fluids in the subsequent loops are gradually reducing, with the lowest temperatures achieved in the third loop, which is an open loop.
It is however, a substantial benefit that the heat requirement of the entire pretreatment operation which involves hundreds if not thousands of cubic meters of chemicals maintained at 55-60 °C, is met through the heat that would be wasted to the atmosphere in absence of the present invention.

The pipe network may carry any fluids for heat transfer, preferably liquids, more preferably water.
The ovens used in the system of the present invention are fired indirectly. After heating up all the oven zones (along with oven fresh air), the system of the present invention advantageously uses the exhaust heat for pretreatment process heating.
As discussed earlier, the invention by Ford India uses the oven exhaust heat to preheat the oven fresh air and not any other process. In our case we have indirectly fired ovens. The exhaust gases are passed through incinerator (Recuperative thermal oxidizer). In the incinerator all the VOCs in the oven are completely burnt. In the process the exhaust gases achieve a temperature in excess of 690 °C is generated. Now these exhaust gases heats up the besides heating other oven zones it also completely heats up the oven fresh air. After heating up all the oven zones (along with Fresh air) we are heating using the exhaust heat for pretreatment process heating. There is thus a clear difference of scope of the present invention than the process described by Ford.
Also as discussed earlier, another invention, by Coke, uses the oven exhaust to oxidize the volatiles within the ovens. The fuel used for the ovens is coal. As mentioned before, in our case all the ovens have incinerators which are used to burn the volatiles (VOCs) in the exhaust. We further use the exhaust heat for heating pretreatment process, which is our scope of invention & is different than

that of Coke's initiative. Now the high temperature exhausts indirectly heat the oven air through heat exchangers.
The piping used between and within the various parts of the invention is insulated as appropriate. The pipe size, type and length is determined depending on the capacity of the plant.
The oven hot exhaust gas temperature for typical industrial operations is between 180 °C to 220 °C. The temperature of oven cool gases is typically 110 °C. The temperature of the fluids in the closed loops nearest to the heat source are first close loop is approximately 110 °C for fluid leaving the HRU and approx. 90 °C for the fluid returning to the HRU. The temperature of fluids coming out of the first heat exchanger into the HWG is approximately 110 °C and that of fluids coming out of the HWG approximately 120 °C during the start-up phase of the pretreatment tanks. The temperature of fluids returning to the first heat exchanger from the second heat exchangers is approximately 70 CC. The temperature of the chemicals in the third loop is approximately 55 to 60 °C.
All the equipment in the system like the ovens, heat recovery units, heat exchangers & hot water generators work in synchronization & are elaborately automated, complete system is controlled by PLC and feedback given to and taken from any equipment enable the operation of the complex system.

Although the above description has disclosed an invention that has a number of loops and a number of types of heat exchangers, it is possible to carry out the heat transfer from the source to the chemical tanks in a fewer number of loops.
Example of the invention:
The invention was deployed in two separate paint shops installations located adjacent to each other (see Figure 4). The first paint shop had overall physical plan dimensions of 330m x 116m. Five ovens of a capacity between 1000 to 1300 KW were deployed. Specifically these were two ovens of 1250 KW capacity, two of 850KW, and one of 1050 KW capacity and located in a linear serial configuration located at a height from floor level of 1 lm were provided. The clear distance between any two ovens was between 30 and 40m.
The second paint shop had plan dimensions of 200M x 50m. Two ovens of a capacity up to 650KW were provided as shown in Figure 4A. These were located at a height from floor of 5.5m and the clear distance between them was approximately 40m.
Each of the ovens or pair of ovens, depending upon their location, was provided with a HRU to recover the exhaust heat. The water heated from each oven is collected together and taken to a second heat exchanger to heat water contained in the close loop connecting these parts (fourth loop in accordance with Figure 3B).

The length of piping involved in the gas to water heat recovery process was approximately 1000m. A pipe size of 150NB was laid through both paint shops for this purpose. The water was circulated through the close water loop at a rate of 95 m3/hr. After the heat recovery from the hot gases the temperature of the hot exhaust gases fell from about 200 °C to 110°C. The temperature of the input water entering the HRU is at 90 °C & was raised to 110 °C as it left the HRU.
At the fourth loop water entered at 110o C & left the second heat exchanger at 90 °C to be circulated back to the HRUs for reheating. The water in the next close loop (termed as the fifth loop in accordance with Figure 3B) as it left the second heat exchanger was found to be at 110 °C. The main collector of the fifth loop was passed through the Hot water generator (HWG) before reaching the set of first heat exchangers. In the present example eight first heat exchangers were provided. The HWG was used to raise the temperature of water reaching the set of first heat exchangers to 120 oC during the start up phase of the pretreatment tanks. Once the process reached a steady state, the HWG was shut down.
The pretreatment chemical temperatures are maintained at 55 to 60 °C. A third open loop was formed between a first heat exchanger and a corresponding pretreatment tank. The water entering the fifth close loop was maintained at 120 °C, during the start up & 110 °C during steady state and the chemicals entering the first heat exchangers was found to be at 55 to 60 °C. An approximately 750m of pipeline constituted the fifth close loop. 185 m3/Hr water flow was maintained

through the fifth loop & the 200NB diameter piping was provided to enable the same.
The pretreatment lines in the two paint shops were stretched over the length of 200m & 70m respectively. The size of the piping used for this purpose was 200NB to carry water at a capacity of 185 m3/Hr and then further distribute it to 8 heat exchangers (5 locations in one paint shop & 3 locations in other paint shop) The 5 heated tanks in first paint shop were of following capacities - 1)13m , 2) 20 m3, 3) 160 m3, 4)160 m3, 5) 267 m3. The three heated tanks in the second paint shop are of following capacities - 1) 15 m3,2) 60 m3,3) 60m3.
The temperature of exhaust cool gases in each case was noted to be approximately 110 °C.
All pipelines were insulated to prevent any heat loss from the system.
The heat recovery was calculated to be of the order of 1.5 Million Kcal for both the paint shops together. This is a significant amount of energy that would have been otherwise wasted.
It is clear from the foregoing discussion that the present invention has the following embodiments.

1. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat, characterized in
that said system comprises
At least one oven, a system for heat exchange made up using a number of heat exchangers, and a system of loops, and a system of pretreatment process tanks containing chemicals, said system of loops connecting the ovens, the heat exchangers and the pretreatment tanks.
2. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat as described in
embodiment 1, wherein
said loops carry fluids as medium of heat transfer, and wherein said system of heat exchangers comprises at least one heat recovery unit, and wherein heat is recovered by said heat recovery unit from the hot exhaust gases of said oven and transferred to the chemicals contained within said pretreatment process tanks through said system of loops,
3. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat as described in
embodiment 2, wherein said system of heat exchange further comprises a
means for hot water generation.

4. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat as described in
embodiments 2 and 3, wherein said fluids are chemicals used in the
pretreatment process chemicals and wherein said system of loops is a first
loop comprising
a first main collector which collects heated chemicals from the heat recovery units through a set of first secondary collectors, and delivers them to the pretreatment process tanks using a set of second secondary collectors
a set of second secondary return pipes that collects chemicals from the pretreatment process tanks and returns them into a first main return pipe, which in turn circulates the chemicals in the respective heat recovery units through a set of first secondary return pipes.
5. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat as described in
embodiments 2 and 3, further wherein a set of first heat exchangers is
provided, wherein said first heat exchangers are connected with the set of
heat recovery units using a second loop and also with the set of
pretreatment process tanks using a set of third loops;
said fluid preferably being water, and wherein

said system of loops comprises a second and a third loop, wherein said
second loop comprises
a first main collector which collects heated water from the heat recovery units through a set of first secondary collectors, and delivers them to a set of first heat exchangers through a set of third secondary collectors
- a set of third secondary return pipes that collects cooled water from
the first heat exchangers and returns them into a first main return
pipe, which in mm circulates the cooled water in the respective
heat recovery units through a set of first secondary return pipes,
and
said third loop comprises
- a set of fourth secondary collector pipes that delivers chemicals
into the pretreatment process tanks, said pretreatment tanks
themselves, and a set of fourth return pipes that deliver chemicals
into said first heat exchangers.
6. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat as described in embodiments 2 and 3, further wherein at least one first heat exchanger and at least one second heat exchanger is provided is provided, wherein said

first heat exchangers are connected with the set of second heat exchangers using a fifth loop and also with the set of pretreatment process tanks using a set of third loops, and wherein the set of second heat exchangers is connected with the set of heat recovery units using a fourth loop, wherein the fourth loop comprises
- a first main collector which collects heated water from the heat recovery units through the set of first secondary collectors, and delivers them to a set of second heat exchangers,
- a first main return pipe, which returns the cooled water from the second heat exchanger to the relevant heat recovery units through a set of first secondary return pipes, and
said fifth loop comprises
a second main collector pipe that delivers heated water into the set of first heat exchangers using a set of third secondary collector pipes
a second main return pipe that received cooled water from the set of first heat exchangers and returns it to the set of second heat exchangers, and
said third loop comprises
- a set of fourth secondary collector pipes that delivers chemicals into the pretreatment process tanks, said pretreatment tanks

themselves, and a set of fourth return pipes that deliver chemicals into said first heat exchangers.
7. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat as described in embodiments 3 to 6, wherein the fluid in first, second, fourth and fifth close loops is selected from a group of fluids comprising gases and liquids, preferably water.
8. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat as described in embodiments 3 to 7, wherein the heat recovery unit operates on a principle of gas to liquid exchange of heat, said first and second heat exchangers operate on a principle of liquid to liquid heat transfer.
9. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat as described in embodiments 3 to 8 wherein said hot water generator is placed in series between said first heat exchanger and second heat exchanger.
10. A system to recover and use recovered heat from industrial ovens as described in embodiments 3 to 9, such that the piping network used to construct the closed water loops is adequately insulated.

It is evident from the foregoing discussion and examples that the present invention recovers significant amount of energy from the ovens used in the industrial processes which would have otherwise been wasted.
While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.

We claim:
1. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat, characterized in that said system comprises
At least one oven, a system for heat exchange made up using a number of heat exchangers, and a system of loops, and a system of pretreatment process tanks containing chemicals, said system of loops connecting the ovens, the heat exchangers and the pretreatment tanks.
2. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat as claimed in claim
1, wherein said loops carry fluids as medium of heat transfer, and wherein said system of heat exchangers comprises at least one heat recovery unit, and wherein heat is recovered by said heat recovery unit from the hot exhaust gases of said oven and transferred to the chemicals contained within said pretreatment process tanks through said system of loops.
3. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat as claimed in claim

2, wherein said system of heat exchange further comprises a means for hot water generation.
4. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat as claimed in claim
2 and 3, wherein said fluids are chemicals used in the pretreatment process
chemicals and wherein said system of loops is a first loop comprising
a. a first main collector which collects heated chemicals from the heat
recovery units through a set of first secondary collectors, and
delivers them to the pretreatment process tanks using a set of
second secondary collectors
b. a set of second secondary return pipes that collects chemicals from
the pretreatment process tanks and returns them into a first main
return pipe, which in turn circulates the chemicals in the respective
heat recovery units through a set of first secondary return pipes.
5. A system for recovering heat from industrial ovens and heating chemicals
in pretreatment process tanks using the recovered heat as claimed in claim
2 and 3, further wherein a set of first heat exchangers is provided, wherein
said first heat exchangers are connected with the set of heat recovery units
using a second loop and also with the set of pretreatment process tanks
using a set of third loops;

said fluid preferably being water, and wherein
said system of loops comprises a second and a third loop, wherein said
second loop comprises
a. a first main collector which collects heated water from the heat
recovery units through a set of first secondary collectors, and
delivers them to a set of first heat exchangers through a set of third
secondary collectors
b. a set of third secondary return pipes that collects cooled water from
the first heat exchangers and returns them into a first main return
pipe, which in turn circulates the cooled water in the respective
heat recovery units through a set of first secondary return pipes,
and said third loop comprises
c. a set of fourth secondary collector pipes that delivers chemicals
into the pretreatment process tanks, said pretreatment tanks
themselves, and a set of fourth return pipes that deliver chemicals
into said first heat exchangers.
6. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat as claimed in claim 2 and 3, further wherein at least one first heat exchanger and at least one second heat exchanger is provided is provided, wherein said first heat

exchangers are connected with the set of second heat exchangers using a fifth loop and also with the set of pretreatment process tanks using a set of third loops, and wherein the set of second heat exchangers is connected with the set of heat recovery units using a fourth loop, wherein said fourth loop comprises
a. a first main collector which collects heated water from the heat
recovery units through the set of first secondary collectors, and
delivers them to a set of second heat exchangers,
b. a first main return pipe, which returns the cooled water from the
second heat exchanger to the relevant heat recovery units through a
set of first secondary return pipes, and
said fifth loop comprises
c. a second main collector pipe that delivers heated water into the set
of first heat exchangers using a set of third secondary collector
pipes
d. a second main return pipe that received cooled water from the set
of first heat exchangers and returns it to the set of second heat
exchangers, and said third loop comprises
e. a set of fourth secondary collector pipes that delivers chemicals
into the pretreatment process tanks, said pretreatment tanks

themselves, and a set of fourth return pipes that deliver chemicals into said first heat exchangers.
7. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat as claimed in claims 3 to 6, wherein the fluid in first, second, fourth and fifth close loops is selected from a group of fluids comprising gases and liquids, preferably water.
8. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat as claimed in claims 3 to 7, wherein the heat recovery unit operates on a principle of gas to liquid exchange of heat, said first and second heat exchangers operate on a principle of liquid to liquid heat transfer.
9. A system for recovering heat from industrial ovens and heating chemicals in pretreatment process tanks using the recovered heat as claimed in claims 3 to 8, wherein said hot water generator is placed in series between said first heat exchanger and second heat exchanger.
10. A system to recover and use recovered heat from industrial ovens as claimed in claims 3 to 9, such that the piping network used to construct the closed water loops is adequately insulated.