THE PATENT ACT, 1970
COMPLETE
SPECIFICATION
(SECTION-10)
TITLE 'Exhaust Gas Steam Generator for Low Speed Diesel Engines"
APPLICANTS
M/S. THERMAX LTD.,
D-13, MIDC Industrial Area, Chinchwad, Pune-411 019
Maharashtra, an Indian Company.
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.

EXHAUST GAS STEAM GENERATOR FOR LOW SPEED DIESEL ENGINES
INTRODUCTION TO THE FIELD OF INVENTION
This invention relates to a novel exhausts gas stem generator for Low Speed Diesel Engines.
More particularly, this invention relates to the development of an exhaust gas steam generator in which water hold up does not exceeds 22.75 litres.
PRIOR ART:
It is already known in the prior art to generate steam, using heat in the low speed Diesel Engine exhaust. And in these conventional exhaust gas boilers (EGB), it is known to generate steam by exchange of heat from hot exhaust Gases of diesel engine to the water/steam with pool boiling as steam generating phenomena.

In this process the heat surface transfer coefficient ranges from 15 to 50 Kcal/h.m.20 C. Therefore, large surface are is required Hence the water hold up invariably exceeds 22.75 litres.

DRAWBACKS OF THE PRIOR ART.

• The main limitation of the prior art is that the water hold-up of the pressure part exceeds
22.75 litres bringing this unit under purview of Indian Boiler regulations (IBR).
• Higher manufacturing and erection time.
• Higher capital cost.
• Higher operating cost.
• Increased footprint of the equipment hence higher space requirement.
• Less availability due to annual inspection/maintenance requirements.
OBJECTS OF THE INVENTION
It is, therefore, a primary object of the invention to propose improved exhaust gas stem generator for low speed diesel engines.
It is another object to propose such a stem generator due to which the heat transfer coefficient will be higher than possibly so far in this field.
It is further object of the invention to propose such a stem generator wherein the water hold up will come down considerably |to limits less than the proposed by Indian Boiler Regulations (IBR) so that this generator does not come under the purview of IBR.
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The further object of this invention is to propose an improved method of generating steam keeping the water hold up to limits lower than the required by IBR.
It is a still further object of this invention is to propose such a method wherein heat of the exhaust gas of a diesel engine is profitably used as a medium.
Yet another object of this invention is to propose such a method of generation of steam using the hea of exhaust gas of low speed diesel engines so as to achieve higher heat transfer coefficient.
These and other objects of this invention will be more clear from the following paragraphs: -
BRIEF STATEMENT OF THE INVENTION
According to this invention there is provided an improved method for generating steam from exhaust gas of low speed diesel] engines, which comprises passing hot exhaust gas through an enclosure/shell, housing therein a plurality of heat exchangers, each set heat exchanger having a water tube for passing water, all the water tubes being inter-connected in series, the water tube of the heat exchanger from which the hot water leaves the exchangers being connected to a steam separator thereby to separate steam and the water, the recovered water being re-circulated to the water tube in the shell side from which the heat depleted gases leave the shell while the steam is
recovered in a conversional manner.
The other important features are the following.
(a) The inlet hot exhaust gas are admitted to the enclosure so as to be in direct contact with the heat exchangers within which is located the water tube leaving the steam.
(b) The exhaust gas from the diesel engine devoid of the heat leave the system after contacting the heat exchanger within which is housed the inlet of the first water tube.
(c) There is provided an intermediate fluid material, which absorbs the heat quickly from the exhaust gas surrounding the heat exchanger and transfers the same quickly to the water passing through the water tube, thereby ensuring minimum heat loss and maximum heat recovery from the hot exhaust gas.
According to another aspect of the invention there is provided an improved exhaust gas steam generator for low speed diesel engines, which comprises:
(a) An enclosure or a shell for passing hot gas of the diesel engine across a plurality of heat exchangers housed within the said shell,
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(b) Each set heat exchanger being disposed preferably vertically across the path of the hot exhaust gas from the diesel engine.
(c) Each set heat exchanger having a water tube housed within the same to its entire length.
(d) All the water tubes being connected in series with one another so as to provide continuous passage for the water,
(e) The water tube at the lower end of the last heat exchanger adjacent to the exit point of the gas in the shell being connected to a fed water tank through a pump for feeding water thereto.
(f) The end of the water tube at the top of the first of the said heat exchanger adjacent to the inlet end of the shell for the hot gas being connected to a stem separator through conventional arrangements.
(g) Said steam separator having conventional means for separating water from the steam,
(h) There being provided an outlet for the steam in the steam separator and an outlet for the separated water connecting the steam separator with a feed water tank,
(i) The shell having a number of identical finned heat exchangers positioned equal distance from one another.
(j) The water tubes', being disposed along the verticle axis of each heat exchanger, preferably at the central axis, so as to leave an angular space around the tube and within the heat exchanger, said angular space being provided with an intermediate heat exchanger material preferably the intermediate heat exchanger having such characteristics which will absorb the heat from the hot gas as quickly as possibly and transfer to the water in the tube as quickly as possible thereby assuring less heat loss and more heat recovery.
The water holds up in this new design has been found out to be 22.0 litres.
The heat transfer coefficient varies from 25 K Cal/hr m 2°C to 45 K Cal/hr m 2° C.
Though we have described a finned heat exchanger within the shell it is possible to employ equally
suited other heat exchangers.
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Most efficient results have been achieved by disposing a plurality of the heat exchangers in the verticle manner parallel to one another; it has not out side the scope of the invention to suitably alter the construction by angularly disposing the heat exchanger, parallel to one another to a limited extent.
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BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In figure 1 of the accompanying drawings, we have disclosed schematically the improved exhaust gas steam generator for Low Speed Diesel Engines.
DETAILED DESCRIPTION OF THE DRAWINGS.
It will be clear from the drawings that numeral (1) shows the normal known shell/duct, capable of enclosing specially designed heat exchangers (2). The hot exhaust gases are made to pass through
shell/duct (1) sweeping over the heat exchangers (2). The hot exhaust gases then exchange heat in
the heat exchangers (2), which are integral with the shell/duct (1). The intermediate material (7) inside
the heat exchangers gets heated in the heat exchangers (2). The intermediate material is in heat
transfer contact with water tubes (3) within where it rejects heat to the water thus generating steam.
The steam is then taken to separator (4) and the separated water is taken back into feed water tank
(5). The hot water in the feed water tank is pumped back into the heat exchangers (2) using pump (6).
This heat exchanger (2) can be a single unit or several modular units connected to a Diesel Engine
Exhaust.
The nature of interim material used in heat exchanger is solid materials made up of either Cu/ Al / MS / SS. The heat exchanger is of finned tube type.
Further details of the heat exchanger 2 are given below and are shown in figure 2.
EXPERIMENTAL VERIFICATION AND ADVANTAGES.
We have carried out a number of experimental studies and have found a number of advantages, the
important of which are narrated below.
There is;
a) Low capital cost,
b) Low operating cost,
c) Compact-less foot print and hence less space requirement,
d) Comparable pressure drops with regards to prior art
e) Out of the purview of Indian Boiler Regulations Act resulting in lower manufacturing/operational cost and
f) Provides accessibility for fire side cleaning.
It is further been found that the gas side heat transfer area is independent of water side heat transfer area, which is a big achievement and advantage.
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WE Claim
1) An improved method for generating steam from exhaust gas of low speed diesel engines, which comprises passing 'hot exhaust gas through an enclosure/shell, housing therein a plurality of heat exchangers, each set heat exchanger having a water tube for passing water, all the water tubes being inter-connected in series, the water tube of the heat exchanger from which the hot water leaves the exchangers being connected to a steam separator thereby to separate steam and the water, the recovered water being re-circulated to the water tube in the shell side from which the heat depleted gases leave the shell while the steam is recovered is in a conversional manner.
2) An improved method for generating steam from exhaust gas of low speed diesel engines as

Claimed in Claim1, wherein the inlet hot exhaust gas are admitted to the enclosure so as to be in

direct contact with the heat exchangers within which is located the water tube leaving the system.
3) An improved method for generating steam from exhaust gas of low speed diesel engines, as claimed in Claim 2, wherein, the exhaust gas from the diesel engine devoid of the heat leave the system after contacting the heat exchanger within which is housed the inlet of the first water tube.
4) An improved method for generating steam from exhaust gas of low speed diesel engines as claimed in claims 1 to 3, wherein there is provided an intermediate fluid material, which absorbs the heat quickly from the exhaust gas surrounding the heat exchanger and transfers the same quickly to the water) passing through the water tube, thereby ensuring minimum heat loss and maximum heat recovery from the hot exhaust gas.
5) An improved exhaust gas stem generator for low speed diesel engines which comprises:

a) An enclosure or a shell for passing hot gas of the diesel engine across a plurality of heat exchangers housed within the said shell,
b) Each set heat exchanger being disposed preferably vertically across the path of the hot exhaust gas from the diesel engine.
c) Each set heat exchanger having a water tube housed within the same to its entire length. All the water tubes being connected in series with one another so as to provide continuous passage for the water, the water tube at the lower end of the last heat exchanger adjacent to the exit point of the gas in the shell being connected to a feed water tank through a pump for feeding water thereto.
d) The end of the water tube at the top of the first of the said heat exchanger adjacent tc the inlet end of the shell for the hot gas being connected to a stem separator through conventional arrangements.
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e) Said steam separator having conventional means for separating water from the steam, here being provided an outlet for the steam in the steam separator and an outlet for the steam in the stem separator and an outlet for the separated water connecting the steam separator with a feed water tank.
f) The shell having a number of identical finned heat exchangers positioned equal-distance from one another.
g) The water tubes being disposed along the verticle axis of each heat exchanger,
preferably at the central axis, so as to leave an angular space around the tube and
within the heat exchanger, said angular space being provided with an intermediate
heat exchanger material preferably.
h) The intermediate heat exchange material provided within the heat exchanger having such characteristics which will absorb the heat from the hot gas as quickly as possible and transfer to the water in the tube as quickly as possible thereby assuring less heat loss and more heat recovery.
(6) An improved method for generating steam from exhaust gas of low speed diesel engines
substantially as herein described.
(7) An improved exhaust gas steam generator for low speed diesel engines substantially as herein
described with reference to the accompanying drawings.

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Abstract Of The Invention
Title: NEW EXHAUST GAS STEAM GENERATOR FOR LOW SPEED DIESEL ENGINES
There is proposed an improved exhaust gas stem generator for low speed diesel engines which comprises:
1. an enclosure or a shell for passing hot gas of the diesel engine across a plurality of heat exchangers housed within the said shell,
2. each set heat exchanger being disposed preferably vertically across the path of the exhaust gas from the diesel engine.
3. each set heat exchanger having a water tube housed within the same to its entire length.
4. all the water tubes being connected in series with one another so as to provide continuous
passage for the water,
5. the water tube at the lower end of the last heat exchanger adjacent to the exit point of the gas in the shell being connected to a feed water tank through a pump for feeding water thereto.
6. the end of the water tube at the top of the first of the first of the said heat exchanger adjacent to the inlet end of the shell for the hot gas being connected to a steam separator through conventional arrangements.
7. said steam separator having conventional means for separating water from the steam,
8. there being provided an outlet for the steam in the steam separator and an outlet for the separated water connecting the steam separator with a feed water tank.
9. the shell having a number of identical finned heat exchangers positioned equal-distance from one another.
10. the water tubes being disposed along the verticle axis of each heat exchanger, preferably at the central axis, so as to leave an angular space around the tube and within the heat exchanger, said angular space being provided with an intermediate heat exchanger material
preferably,
11. the intermediate heat exchange material provided within the heat exchanger having such
characteristics which will absorb the heat from the hot gas as quickly as possible and transfer
to the water in the; tube as quickly as possible thereby assuring less heat loss and more heat
recovery.
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