FIELD OF THE INVENTION
The pre~ent invention relates to the process of enriching a low calorific value fuel
with high calorific value in a furnace of high pressure boiler plant. The invention
further relates to a system for enriching a low-calorofic fuel producer gas with a
liquid petroleum gas before supplying to the furnace burners.
BACKGROUND OF THE INVENTION
The furnaces in high pressure boiler plant (HPBP) operate on low calorific fuel
Producer gas (PG). The Heat treatment cycles are carried out in these furnaces.
Due to the deficit of the producer gas (PG) in the gas plant, a minimum quantity
of heat required to carry out the heat treatment cycles is not fulfilled. The
enthalpy balance of the furnace is not allayed by the supplied quantity of PG.
The set temperature is attained tardily due to the low calorific value of PG.
Therefore in order to compensate the shortfall of PG, it is necessary to
supplement the PG with High calorific fuel Liquefied Petroleum Gas (LPG) to
satiate the net heat balance.
Due to deficit -of PGin gas plant, the minimum quantity of heat required to carry
out the heat treatment cycles is not fulfilled. The shortfall of PG as stated
hereinabove is compensated by supplementing LPG.Since the properties of both
the gases are different, a correspondingly configured venturi/nozzle is prOVided
to achieve the required pressure at burner inlet. The venturi arrangement is
designed and manufactured based on Bernoulli's theorem and law of
conservation so as to maintain a transient flow of the mixed gas and uniform
pressure at burner inlet.
3
OBJECTS OFTHE INVENTION
It is therefore, an object of this i,:,ventionto propose a system for supplementing
a low calorific fuel with high calorific fuel in the furnace of HPBP.
Another object of the invention is to propose a system for supplementing a low
calorific fuel with high calorific fuel in the furnace of HPBP, which allows
achieving a required quantity of heat.
A still another object of the invention is to propose a system for supplementing a
low calorific fuel with high calorific fuel in the furnace of HPBP,which enables
attainment of the set temperature faster than the known method :
Yet another object of the invention is to propose a system for supplementing a
low calorific fuel with high calorific fuel in the furnace of HPBP, which
substantially reduces the heat treatment cycle.
A further object of the invention is to propose a process for, enriching lowcalorofic
fuel producer gas (PG) with a liquid petroleum gas before supplying to
the furnace burners.
SUMMARY OF THE INVENTION
Accordingly, there is provided a system for supplementing a low~calorific fuel
with a high calorific fuel in a furnace, the furnace operating with the low-calorific
fuel producer gas (PG), and is occasionally supplemented with the high calorific
fuel (LPG) when the residual PG is inadequate to complete a heat treatment
cycle, the sys tern comprising: a gas train device connected at a first end to a
4
LPG supply source, a second end of the device being attached to a venturi
apparatus for supplying regulated quantity of LPG to burners of the furnace
when deficit of PG in the furnace is determined; and a venturi apparatus
operably connected to the burners of the furnace for supply of regulated quantity
of LPG,wherein determination of the inlet and outlet of the venturi apparatus
including differential pressure of the PG/LPGis based on calorific value, specific
gravity, and density of PG, LPG, and mixed gas including total replenishment
quantity of PG and the mixed gas, and wherein venturi sizing is determined
based on desired suction, velocity pressure, static pressure, diameter, and total
pressure at several locations of the apparatus including density of the LPG
observed at different stages.
According to the invention a venturi arrangement is configured based on the
technical parameters for example, the pressure head, velocity head, static head
and calorific values of both gases. By considering dynamic pressure and
piezometric head of PG, the dimensions of venturi's inlet, outlet and the
differential pressure is derived. Depending on volume of the PG, the volume of
LPGis regulated by enthalpy balance. Prior to impregnation LPGinto PG,the LPG
pressure is regulated and safety precautions assured. This is achieved by a
suitable gas train device consisting of a safety relief valve, a solenoid valve,
pressure' gauges and pressure regulators. When the furnace is deficit with
minimal amount of PG, it is supplemented by LPGdepending on the enthalpy
balance.
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BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 Shows a system for supplementing a low-calorific fuel with high
calorific fuel a furnace according to the invention.
Figure 2 Shows a gas train device of the system of Figure 1.
Figure 3 Shows a process flow chart for enriching a low calorific value fuel
with high calorific value fuel in a furnace using the system of figure
1.
DETAIL DESCRIPTION OF THE INVENTION
As shown in figure 2, a gas train device forming a part of the inventive system of
figure 1, is releasably connected through a first end to a LPGsupply source when
the quantum of PG in the furnace in below a threshold value, the device is
activated to supplement the deficit PG by supplying LPG.The supply of LPGto
the furnace from the device is regulated and controlled by an apparatus
constituting a venturi/nozzle apparatus. The device comprising a ball valve (1)
which can be activated/de-activated depending upon the state of supply/nonsupply
of LPGof supplement the PG.The impurities in the supplied LPGthrough
the ball valve is filtered via a gas filter (2). A pressure gauge (3) is provided to
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indicatethe inputted pressure of the LPG.A safety shut-off valve (4) acquiring
signalsthrough an impulse line (12) and automatically closes the LPGsupply in
the even a gas-leakage is sensed. A main solenoid valve (8) providing signals to
a pressure regulator (5) and to the safety release valve (6) based on the
requirement of output pressure of LPG.The pressure regulator (5) regulates the
input pressure based on the output pressure of LPG signaled by the main
solenoid valve (8). The safety-relief valve (6) opens the release of LPGbetween
the main solenoid valve (8) and the safety shutt-off valve (4). The impulse line
(12) provides pressure input to the safety shutt-off valve (4). The pressure
regulator (5) is controlled based on an output pressure indicated by an output
pressure,gauge (7) one each high and low pressure switches (9,10) is electrical
activated on attaining the set pressure to required inputs.
Figure 1 shows the system of the invention operably connected to the gas train
device. A venture apparatus is attached to an output gas pipe lime (11) of the
device. The inlet, outlet, and the differential pressure detection data are
determined based on the following associated technical parameters, which are
incorporated herein in a non-limiting way for a furnace for example 150 MT
capacity.
Determination of the venturi inlet, venturi outlet, differential pressure.
A. Main Venturi For 150 MT Furnace
Maximum PG Required
Minimum PG Available
Maximum PGTo Be Replenished With LPG
calorific Value Of PG
Spec;ific Gravity Of PG
Density Of PG
Calorific Value Of LPG
Specific Gravity Of LPG
Density Of LPG
Maximum Requirement Of LPG For PG
Replacement
Quantity Of Total Mixed Gas
Calculated Value Of Specific Gravity Of Mixed Gas
Calculated Value Of Density Of Mixed Gas
Calculated Value of CV Of Mixed Gas
B. Venturi Sizing
10000
4000
6000
1350
0.85
1.09905
24000
1.78
2.30154
337.5
4337.5
0.92
1.19
3,112
Desired Draft Or Suction 100 mm WC
2.2727 osi
Velocity At 1
Static Pressure At 1
Density Of LPG At stp, plpg
Density Of LPG At 14 osi, pl
49 fps
9 osi
0.1440 Ibjft3
0.1529 Ibjft3
Nm3jhr
Nm3jhr
Nm3jhr
kcaljNm3
kgjm3
kcaljNm3
kgjm3
Nm3jhr
Nm3jhr
kgjm3
kcaljNm3
15 mjs
400 mmWC
2.30 kgjm3
1.04 factor
Velocity PressureAt 1
Total PressureAt 1
Velocity PressureAt Point 2
Velocity At 2
Diameter At 1
Diameter At 2
Diameter At 3
Velocity PressureAt Point 3
Velocity PressureAt Point 3
Benefits of the invention
5.7490 psf
0.6397 osi
9.7306 osi
12.0033 osi
108 psf
213 fps
0.089 m
0.043 m
0.320 m
13.991 mm WC
314.156 mm WC
28 mmWC
428 mmWC
528 mm WC
65 m/s
338 Nm3jhr 0.094 Nm3js
89 mm 15 m/s
43 mm 65 m/s
15 mjs 4,338 Nm3jhr
i. Cycle time of the Heat treatment cycle is reduced by increased rate of
heating
ii. For both fuel LPGand PG,same burner is used.
iii. Additional Instrumentation parts and gas ignitors were not used.
iv. Complete LPG conversion of furnace is prorogued, while the desired
result is achieved with a minor modification.
v. An innovative method within the available resources was discovered
and the work was completed.
Better Stoichiometric ratio between fuel and air is attained.
Better rate of heating is attained.
Deficit of PGis compensated by LPGwith suitable venturi.
The same methodology can be adopted for other PGfurnaces too.
The total saVingsis calculated around 30 lakhs.
vi. ,
;
vii.
viii.
ix.
x.
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A comparisonbetween the Experimental results obtained through the
inventive svstem/method, and that obtained through the prior art
method/apparatus.
Maximum PGTo Be Replenished with LPG
calorific Value Of PG
Specific Gravity Of PG
Density Of PG
calorifiQValue Of LPG
Density Of LPG
Maximum Requirement Of LPGFor PGReplacement
Quantity Of Total Mixed Gas
Calculated Value Of Specific Gravity Of Mixed Gas
calculated Value Of Density Of Mixed Gas
6000
Nm3/hr
1350
kcal/Nm3
0.85
1.09905 kg/m3
24000
kcal/Nm3
2.30154 kg/m3
337.5
Nm3/hr
4337.5
Nm3/hr
0.92
3,112
Kcal/Nm3
WE CLAIM :
1. A,system for supplementing a low-calorific fuel with a high calorific fuel in
a furnace, the furnace operating with the low-calorific fuel producer gas
(PG), and is occasionally supplemented with the high calorific fuel (LPG)
when the residual PG is inadequate to complete a heat treatment cycle,
the sys tern comprising:
- a gas train device connected at a first end to a LPG supply source, a
second end of the device being attached to a venturi apparatus for
supplying regulated quantity of LPGto burners of the furnace when deficit
of PGin the furnace is determined; and
- a venturi apparatus operably connected to the burners of the furnace for
supply of regulated quantity of LPG, wherein determination of the inlet
and outlet of the venturi apparatus including differential pressure of the
PG/LPGis based on calorific value, specific gravity, and density of PG,
LPG,and mixed gas including total replenishment quantity of PGand the
mixed gas, and wherein venturi sizing is determined based on desired
suction, velocity pressure, static pressure, diameter, and total pressure at
several locations of the apparatus including density of the LPG observed
at different stages.
2. A pr.ocessfor supplementing a low-calorific fuel (PG) with a high calorific fuel
(LPG) in a furnace, comprising the steps of:
- SWitchingthe furnace on and carrying out purging cycle;
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- igniting the furnace with the PGand continuing the step till the furnace
temperature attains a temperature of about 400°C;
- checking adequacy of the PGand continue the furnace operation when PG
is found to be adequate;
- activating the gas train device and operate the venturi apparatus if PGis
inadequate;
- regulate the supply of the LPG including the mixed gas to the furnace
depending on the furnace requirement;
- continuing the regulated supply till the temperature uniformity of the
burners is attained and maintain the regulated supply of the mixed gas
until completion of the heat treatment cycle; and
- sWitchingoff the furnace.