Claims:
1. A method comprising:
receiving (301) a sample (113) of a waste gases mixture (102) in a Raman-cum-absorption spectroscopy sensing device disposed at an entry location of a flaring device;
determining (302) a plurality of crude concentrations of a plurality of constituent gases potentially present in the sample of the waste gases mixture based on a plurality of outputs of the Raman-cum-absorption spectroscopy sensing device;
selecting (304) a subset of the plurality of constituent gases present in the sample based on the plurality of crude concentrations;
determining (306) a plurality of refined wavelengths of a plurality of refined light beams for the Raman-cum-absorption spectroscopy sensing device, based on the selected subset of the plurality of constituent gases present in the sample;
determining (308) a plurality of refined concentrations of the selected subset of the plurality of constituent gases based on the plurality of refined light beams characterized by the determined plurality of refined wavelengths, using the Raman-cum-absorption spectroscopy sensing device;
determining (310) an amount of steam or air to be mixed in the waste gases mixture before combustion, based on the plurality of refined concentrations; and
generating (312) a plurality of feedforward control signals to control a valve configured to feed the determined amount of steam or air to mix the determined amount of steam or air to the waste gases mixture to achieve a desired combustion efficiency of the waste gases mixture.

2. The method of claim 1, wherein determining the plurality of crude concentrations of the plurality of constituent gases comprises determining the plurality of crude concentrations using a combination of a Raman spectroscopy based technique and an absorption spectroscopy based technique.

3. The method of claim 2, wherein determining the plurality of crude concentrations comprises determining (400) the plurality of crude concentrations of at least one of an inert constituent gas, hydrogen, and a hydrocarbon constituent gas using the Raman spectroscopy based technique and determining (500) the plurality of crude concentrations of the hydrocarbon constituent gas using the absorption spectroscopy based technique.

4. The method of claim 2, wherein determining (400) the plurality of crude concentrations of the plurality of constituent gases, using the Raman spectroscopy based technique comprises:
receiving a crude Raman spectrum corresponding to the plurality of constituent gases potentially present in the sample;
receiving (404) a reference Raman spectrum corresponding to the plurality of constituent gases potentially present in the sample; and
determining (406) the crude concentrations of the plurality of constituent gases potentially present in the sample based on the reference Raman spectrum and the crude Raman spectrum.

5. The method of claim 4, wherein receiving the reference Raman spectrum comprises selecting the reference Raman spectrum from a plurality of reference Raman spectrums based on a temperature and a pressure of the sample inside the Raman-cum-absorption spectroscopy sensing device.

6. The method of claim 4, further comprising generating the crude Raman spectrum by:
generating transmitted crude Raman light beams by illuminating the sample using a plurality of crude Raman light beams characterized by a crude Raman wavelength range corresponding to the plurality of constituent gases potentially present in the sample; and
generating the crude Raman spectrum based on the transmitted crude Raman light beams.

7. The method of claim 4, further comprising determining a current Raman spectrum baseline (602) based on the reference Raman spectrum and the crude Raman spectrum.

8. The method of claim 7, wherein determining the plurality of refined concentrations of the selected subset of the plurality of constituent gases comprises determining the plurality of refined concentrations using a combination of the Raman spectroscopy based technique and the absorption spectroscopy based technique.

9. The method of claim 8, wherein determining the plurality of refined concentrations of the subset of the plurality of constituent gases using the Raman spectroscopy based technique comprises:
determining (606) an updated Raman spectrum baseline based on the current Raman spectrum baseline and a previous Raman spectrum baseline;
receiving (608) the reference Raman spectrum corresponding to the plurality of constituent gases potentially present in the sample;
receiving (610) a refined Raman spectrum generated by irradiating the sample using a plurality of refined Raman light beams characterized by refined Raman wavelengths, wherein the plurality of refined light beams comprises the plurality of refined Raman light beams and the plurality of refined wavelengths comprises the refined Raman wavelengths; and
determining (612) the plurality of refined concentrations of the subset of the plurality of constituent gases based on the refined Raman spectrum, the reference Raman spectrum, and the updated Raman spectrum baseline.

10. The method of claim 2, wherein determining the plurality of crude concentration of the plurality of constituent gases using the absorption spectroscopy technique comprises:
receiving a crude absorption spectrum generated by irradiating the sample using a plurality of crude absorption light beams characterized by a plurality of crude absorption wavelengths corresponding to the constituent gases irrespective of a presence or an absence of one or more of the constituent gases in the sample;
receive (504) an intensity and a path length of the plurality of crude absorption light beams; and
determining (506) the plurality of crude concentrations of the plurality of constituent gases based on the crude absorption spectrum, the intensity, and the path length of the plurality of crude absorption light beams. .

11. The method of claim 1, wherein determining the plurality of refined wavelengths of the plurality of refined light beams comprises solving an optimization function subject to satisfying a plurality of constraints.

12. The method of claim 11, wherein the optimization function comprises a local optimization function.

13. The method of claim 11, wherein the plurality of constraints comprises a check to determine that a refined wavelength range of the plurality of refined light beams is less than or equal to a differential wavelength determined based on a grating of the Raman-cum-absorption spectroscopy sensing device.

14. The method of claim 13, wherein the plurality of constraints comprises a check to determine that a maximum refined wavelength of the refined wavelength range is less than or equal to a maximum crude wavelength of a crude wavelength range, and a minimum refined wavelength of the refined wavelength range is greater than or equal to a minimum crude wavelength of the crude wavelength range.

15. A method comprising:
receiving (301) a sample of a waste gases mixture in a Raman-cum-absorption spectroscopy sensing device disposed at an entry location of a flaring device;
determining (302) a plurality of crude concentrations of a plurality of constituent gases potentially present in the sample based on a plurality of outputs of the Raman-cum-absorption spectroscopy sensing device;
determining a plurality of refined wavelengths of a plurality of refined light beams for the Raman-cum-absorption spectroscopy sensing device, based on the plurality of crude concentrations;
determining (308) a plurality of refined concentrations of a subset of the plurality of constituent gases certainly present in the waste gases mixture, based on the plurality of refined light beams characterized by the determined plurality of refined wavelengths, using the Raman-cum-absorption spectroscopy sensing device;
determining (310) an amount of steam or air to be mixed in the waste gases mixture before combustion based on the plurality of refined concentrations; and
generating (312) a plurality of feedforward control signals to control a valve configured to feed the determined amount of steam or air to mix the determined amount of steam or air to the waste gases mixture to achieve a desired combustion efficiency of the waste gases mixture.

16. The method of claim 15, wherein determining the plurality of refined wavelengths of the plurality of refined light beams comprises solving an optimization function subject to satisfaction of a plurality of constraints.

17. A system comprising:
a Raman-cum-absorption spectroscopy sensing device (108) disposed at an entry location (110) of a flaring device (106), wherein the Raman-cum-absorption spectroscopy sensing device (108) is configured to receive a sample (113) of a waste gases mixture (102);
a processing subsystem (116) operationally coupled to the Raman-cum-absorption spectroscopy sensing device (108) and configured to:
determine (302) a plurality of crude concentrations of a plurality of constituent gases potentially present in the sample of the waste gases mixture based on a plurality of outputs of the Raman-cum-absorption spectroscopy sensing device;
select (304) a subset of the plurality of constituent gases present in the sample based on the plurality of crude concentrations;
determine (306) a plurality of refined wavelengths of a plurality of refined light beams for the Raman-cum-absorption spectroscopy sensing device, based on the selected subset of the plurality of constituent gases certainly present in the sample;
determine (308) a plurality of refined concentrations of the selected subset of the plurality of constituent gases based on the plurality of refined light beams characterized by the determined plurality of refined wavelengths, using the Raman-cum-absorption spectroscopy sensing device;
determine (310) an amount of steam or air to be mixed in the waste gases mixture before combustion based on the plurality of refined concentrations; and
generate (312) a plurality of feedforward control signals to control a valve configured to feed the determined amount of steam or air to mix the determined amount of steam or air to the waste gases mixture to achieve a desired combustion efficiency of the waste gases mixture.

18. The system of claim 17, wherein the Raman-cum-absorption spectroscopy sensing device (108) comprises:
an integrating sphere (200) configured to be filled with the sample (113);
an absorption light source (206) operationally coupled to the integrating sphere and configured to emit a plurality of crude absorption light beams and a plurality of refined absorption light beams, wherein the plurality of crude absorption light beams is characterized by a crude absorption wavelength range and the plurality of refined absorption light beams is characterized by a plurality of refined absorption wavelengths; and
a Raman light source (204) operationally coupled to the integrating sphere and configured to emit a plurality of crude Raman light beams and a plurality of refined Raman light beams, wherein the plurality of crude Raman light beams is characterized by a crude Raman wavelength range and the plurality of refined Raman light beams is characterized by a plurality of refined Raman wavelengths,
wherein the plurality of refined light beams comprises the plurality of refined Raman light beams and the plurality of refined absorption light beams.

19. The system of claim 18, wherein the Raman-cum-absorption spectroscopy sensing device (108) further comprises:
a first fiber optic cable (212) that couples the integrating sphere (200) to the Raman light source (204) and configured to transmit the plurality of crude Raman light beams and the plurality of refined Raman light beams into the integrating sphere resulting in generation of a plurality of transmitted Raman light beams;
a second fiber optic cable (216) that couples the integrating sphere (200) to the absorption light source (206) and configured to transmit the plurality of crude absorption light beams and the plurality of refined absorption light beams into the integrating sphere (200) resulting in generation of a plurality of transmitted absorption light beams;
an absorption detector (226) coupled to the integrating sphere via a third fiber optic cable (228) and configured to generate an absorption spectrum based on the plurality of transmitted absorption light beams; and
a Raman detector (220) coupled to the integrating sphere (200) via a fourth fiber optic cable (222) and configured to generate a Raman spectrum based on the plurality of transmitted Raman light beams.

20. The system of claim 19, wherein the processing subsystem (116) is configured to determine the plurality of crude concentrations of the plurality of constituent gases, using a Raman spectroscopy based technique by:
receiving a crude Raman spectrum corresponding to the plurality of constituent gases potentially present in the sample;
receiving a reference Raman spectrum corresponding to the plurality of constituent gases potentially present in the sample; and
determining the crude concentrations of the plurality of constituent gases potentially present in the sample based on the reference Raman spectrum and the crude Raman spectrum.
, Description:BACKGROUND
[0001] Embodiments of the present invention generally relate to flaring of waste gases
and more specifically to a flare management system and an associated method thereof.
[0002] Operation of an industrial plant, particularly chemical plants results in generation
of waste gases. Such waste gases are required to be disposed such that disposition does not lead
to environmental pollution beyond a permissible statutory limit. Generally waste gases are a
mixture of a plurality of combustible and non-combustible constituent gases. The waste gases
are typically flared/combusted in a flaring device due to the presence of the combustible
constituent gases in the waste gases. Combustion of the waste gases prevents unwanted
emissions to be released to the atmosphere and further eliminates pressure buildup in processing
units during emergency conditions. However, the combustibility of waste gases may be too low
for an efficient combustion in an environmentally acceptable manner. For example, a low
British Thermal Units (BTU) content of waste gases may result in poor combustion. Incomplete
or poor combustion of the waste gases may result in emission of dark smoke from the flaring
device. Additionally, poor combustion may lead to emission of unacceptable amounts of
hydrocarbons into the atmosphere resulting in environmental pollution.
[0003] Various proposals have been made for monitoring and controlling pollution
created by smoke generated due to combustion of waste gases. For example, one proposal is to
monitor a smoke plume coming out of a flaring device. A source and a detector are located
remotely from the smoke plume for monitoring the smoke plume. The source illuminates the
smoke plume and the detector receives radiation reflected/scattered by the smoke plume. The
radiation is analyzed to determine a composition of the smoke plume. A composition of waste
gases to be burnt in future is varied by addition of air and steam based on the composition of the
smoke plume. However, this method is ineffective due to continuous variation in the
composition of the waste gases. Furthermore, such a method is a feed backward control where a
composition of the future waste gases is varied based on the composition of smoke plume.
[0004] Accordingly, an enhanced flare management system and an associated method are
desirable.
BRIEF DESCRIPTION
[0005] In accordance with one embodiment, a method is presented. The method includes
receiving a sample of a waste gases mixture in a Raman-cum-absorption spectroscopy sensing
device disposed at an entry location of a flaring device, determining a plurality of crude
concentrations of a plurality of constituent gases potentially present in the sample of the waste
gases mixture based on a plurality of outputs of the Raman-cum-absorption spectroscopy sensing
device, selecting a subset of the plurality of constituent gases present in the sample based on the
plurality of crude concentrations, determining a plurality of refined wavelengths of a plurality of
refined light beams for the Raman-cum-absorption spectroscopy sensing device, based on the
selected subset of the plurality of constituent gases present in the sample, determining a plurality
of refined concentrations of the selected subset of the plurality of constituent gases based on the
plurality of refined light beams characterized by the determined plurality of refined wavelengths,
using the Raman-cum-absorption spectroscopy sensing device, determining an amount of steam
or air to be mixed in the waste gases mixture before combustion, based on the plurality of refined
concentrations, and generating a plurality of feedforward control signals to control a valve
configured to feed the determined amount of steam or air to mix the determined amount of steam
or air to the waste gases mixture to achieve a desired combustion efficiency of the waste gases
mixture.
[0006] In accordance with another embodiment, a method is presented. The method
includes receiving a sample of a waste gases mixture in a Raman-cum-absorption spectroscopy
sensing device disposed at an entry location of a flaring device, determining a plurality of crude
concentrations of a plurality of constituent gases potentially present in the sample based on a
plurality of outputs of the Raman-cum-absorption spectroscopy sensing device, determining a
plurality of refined wavelengths of a plurality of refined light beams for the Raman-cumabsorption
spectroscopy sensing device, based on the plurality of crude concentrations,
determining a plurality of refined concentrations of a subset of the plurality of constituent gases
certainly present in the waste gases mixture, based on the plurality of refined light beams
characterized by the determined plurality of refined wavelengths, using the Raman-cumabsorption
spectroscopy sensing device, determining an amount of steam or air to be mixed in
the waste gases mixture before combustion based on the plurality of refined concentrations, and
generating a plurality of feedforward control signals to control a valve configured to feed the
determined amount of steam or air to mix the determined amount of steam or air to the waste
gases mixture to achieve a desired combustion efficiency of the waste gases mixture.
[0007] In accordance with still another embodiment, a system is presented. The system
includes a Raman-cum-absorption spectroscopy sensing device disposed at an entry location of a
flaring device, wherein the Raman-cum-absorption spectroscopy sensing device is configured to
receive a sample of a waste gases mixture, and a processing subsystem operationally coupled to
the Raman-cum-absorption spectroscopy sensing device. The processing subsystem is
configured to determine a plurality of crude concentrations of a plurality of constituent gases
potentially present in the sample of the waste gases mixture based on a plurality of outputs of the
Raman-cum-absorption spectroscopy sensing device, select a subset of the plurality of
constituent gases present in the sample based on the plurality of crude concentrations, determine
a plurality of refined wavelengths of a plurality of refined light beams for the Raman-cumabsorption
spectroscopy sensing device, based on the selected subset of the plurality of
constituent gases certainly present in the sample, determine a plurality of refined concentrations
of the selected subset of the plurality of constituent gases based on the plurality of refined light
beams characterized by the determined plurality of refined wavelengths, using the Raman-cumabsorption
spectroscopy sensing device, determine an amount of steam or air to be mixed in
the waste gases mixture before combustion based on the plurality of refined concentrations, and
generate a plurality of feedforward control signals to control a valve configured to feed the
determined amount of steam or air to mix the determined amount of steam or air to the waste
gases mixture to achieve a desired combustion efficiency of the waste gases mixture.
DRAWINGS
[0008] These and other features and aspects of embodiments of the present invention will
become better understood when the following detailed description is read with reference to the
accompanying drawings in which like characters represent like parts throughout the drawings,
wherein:
[0009] Fig. 1 is a block diagrammatic illustration of a system for obtaining a desired
combustion efficiency of a waste gases mixture in accordance with certain embodiments of the
present invention;
[0010] Fig. 2 is a diagrammatic illustration of the Raman-cum-absorption spectroscopy
sensing device in accordance with the embodiment of FIG. 1;
[0011] Fig. 3 is a flow chart illustrating a method for obtaining a desired combustion
efficiency of a waste gases mixture in accordance with certain embodiments of the present
invention;
[0012] Fig. 4 is a flow chart illustrating a method for determining crude concentrations of
constituent gases using a Raman spectroscopy based technique in accordance with certain
embodiments of the present invention;
[0013] Fig. 5 is a flow chart illustrating a method for determining crude concentrations of
constituent gases using an absorption spectroscopy based technique in accordance with certain
embodiments of the present invention;
[0014] Fig. 6 is a flow chart illustrating a method for determining refined concentrations
of a subset of constituent gases using a Raman spectroscopy based technique in accordance with
certain embodiments of the present invention; and
[0015] Fig. 7 is a flow chart illustrating a method for determining refined concentrations
of an identified subset of constituent gases using a absorption spectroscopy based technique in
accordance with certain embodiments of the present invention.
DETAILED DESCRIPTION
[0016] Unless defined otherwise, technical and scientific terms used herein have the
same meaning as is commonly understood by one of ordinary skill in the art to which this
disclosure belongs. The terms “a” and “an” do not denote a limitation of quantity but rather
denote the presence of at least one of the referenced items. The term “or” is meant to be
inclusive and mean one, some, or all of the listed items. The use of “including,” “comprising” or
“having” and variations thereof herein are meant to encompass the items listed thereafter and
equivalents thereof as well as additional items. The terms “control system” or “controller” may
include either a single component or a plurality of components, which are either active and/or
passive and are connected or otherwise coupled together to provide the described function or
functions.
[0017] Fig. 1 is a diagrammatic illustration of a system 100 for obtaining a desired
combustion efficiency of waste gases mixture 102 in accordance with certain embodiments of
the present invention. The system 100 includes an industrial unit 104 that produces the waste
gases mixture 102. The industrial unit 104, for example, may be a chemical plant, a power plant,
a refinery, an oil or gas production site, a gas processing plant, or the like. For example, the
industrial unit 104 may release the waste gases mixture 102. Typically, the waste gases mixture
102 is combusted in a flaring device 106 resulting in generation of smoke. Generally, the
composition of the waste gases mixture 102 varies leading to variation in combustibility. The
variation of the combustibility of the waste gases mixture 102 may lead to pollution.
[0018] The system 100 includes a Raman-cum-absorption spectroscopy sensing device
108 disposed at an entry/upstream location 110 of the flaring device 106. The Raman-cumabsorption
spectroscopy sensing device 108 is configured to analyze the waste gases mixture 102
in real-time with respect to a time of arrival of a sample 113 of the waste gases mixture 102 in
the Raman-cum-absorption spectroscopy sensing device 108. The Raman-cum-absorption
spectroscopy sensing device 108 operates using a combination of Raman spectroscopy based
technique and an absorption spectroscopy based technique. The Raman spectroscopy based
technique is used to determine concentrations (crude or refined concentrations) of inert
constituent gases, hydrogen, and hydrocarbon constituent gases in the waste gases mixture 102.
Further, the absorption spectroscopy based technique is used to determine concentrations (crude
or refined concentrations) of hydrocarbon constituent gases in the waste gases mixture 102. The
Raman-cum-absorption spectroscopy sensing device 108 (hereinafter referred to as the sensing
device 108) is explained in greater detail with reference to Fig. 2. The redundancy in
concentration measurements of the hydrocarbon constituent gases may be used to improve
measurement accuracy of the concentration measurements. Additionally, one of the absorption
spectroscopy based technique and the Raman spectroscopy based technique may compensate for
inaccuracies in concentration measurements caused due to high interference observed in Raman
spectrum or absorption spectrum generated using the Raman spectroscopy based technique and
the absorption spectroscopy based technique respectively.
[0019] The industrial unit 104 is coupled to the flaring device 106 via a pipe 112 or a
similar component. The industrial unit 104 transfers the waste gases mixture 102 to the flaring
device 106 via the pipe 112. The sensing device 108 is operatively coupled to the pipe 112.
When the waste gases mixture 102 passes through the pipe 112, a small portion 113 (referred to
as the sample 113) of the waste gases mixture 102 enters the sensing device 108.
[0020] The system 100 further includes a processing subsystem 116 operationally
coupled to the sensing device 108 and a data repository 117. Although the processing subsystem
116 is located outside the sensing device 108, in certain embodiments, the processing subsystem
116 may be located inside the sensing device 108. In one embodiment, the processing subsystem
116 may be an integrated chip, a chip on package, or the like. In one embodiment, when the
sample 113 enters the sensing device 108, the processing subsystem 116 generates primary input
and control signals 114 and transmits the input and control signals 114 to the sensing device 108.
The primary input and control signals 114, for example, may include a mandate to initiate
primary analysis of the sample 113. The primary input and control signals 114, for example,
may further include characteristics of a plurality of crude light beams to be used by the sensing
device 108. The crude light beams, for example, include crude Raman light beams and crude
absorption light beams. The characteristics of the light beams, for example, may include
wavelengths (hereinafter referred to as “crude wavelength range”) of the crude light beams, an
intensity of the light beams, or the like. As used herein, the term “crude wavelength range”
refers to wavelengths corresponding to constituent gases potentially present in the waste gases
mixture 102. The crude wavelength range is used without any data regarding a presence or an
absence of one or more of the constituent gases.
[0021] The processing subsystem 116 generates the primary input and control signals
114 assuming that all constituent gases known to be generally present in waste gases mixtures
102 are potentially present in the sample 113. Accordingly, the processing subsystem 116
generates the primary input and control signals 114 to use the crude wavelength range
corresponding to all the constituent gases known to be potentially present in waste gases
mixtures 102. Particularly, the processing subsystem 116 commands the sensing device 108 to
use the crude wavelength range corresponding to all the constituent gases regardless of a
presence or an absence of one or more of the constituent gases in the sample 113. In other
words, the processing subsystem 116 commands the sensing device 108 to use the crude
wavelength range corresponding to all the constituent gases based on a presumption that each of
the constituent gases known to be potentially present in waste gases mixtures 102 is present in
the waste gases mixture 102.
[0022] The crude wavelength range, for example, may include a crude Raman
wavelength range and a crude absorption wavelength range. The crude Raman wavelength range
corresponds to at least one of the inert constituent gases, hydrogen and hydrocarbon constituent
gases. The crude absorption wavelength range corresponds to the hydrocarbon constituent gases.
[0023] Subsequent to the transmission of the primary input and control signals 114 to the
sensing device 108, the sensing device 108 executes a combination of the Raman spectroscopy
based technique and the absorption spectroscopy based technique. Particularly, the sensing
device 108 irradiates the sample 113 using the crude Raman light beams characterized by the
crude Raman wavelength range and the crude absorption light beams characterized by the crude
absorption wavelength range resulting in generation of a crude Raman spectrum and a crude
absorption spectrum. The irradiation of the sample 113 by the crude Raman light beams
characterized by the crude Raman wavelength range results in generation of the crude Raman
spectrum. Similarly, the irradiation of the sample 113 by the crude absorption light beams
characterized by the crude absorption wavelength range results in generation of crude absorption
spectrum. As used herein, the term “crude Raman spectrum” refers to Raman signals generated
by irradiating the sample 113 of the waste gases mixture 102 by a light beam characterized by a
crude wavelength range including Raman wavelengths corresponding to each of the constituent
gases irrespective of a presence, an absence and concentrations of one or more of the constituent
gases in the waste gases mixture 102. As used herein, the term “crude absorption spectrum”
refers to absorption signals generated by irradiating the sample 113 of the waste gases mixture
102 by a light beam characterized by a crude wavelength range including absorption
wavelengths corresponding to the constituent gases irrespective of a presence, an absence and
concentrations of one or more of the constituent gases in the waste gases mixture 102. The
generation of the crude Raman spectrum and the crude absorption spectrum is explained in
greater detail with reference to Fig. 2. The crude Raman spectrum and the crude absorption
spectrum shall hereinafter be collectively referred to as outputs 118.
[0024] Further, the sensing device 108 transmits the outputs 118 to the processing
subsystem 116. The processing subsystem 116 determines crude concentrations of the
constituent gases potentially present in the waste gases mixture 102 based on the outputs 118.
As used herein, the term “crude concentrations of constituent gases” refers to concentrations of
constituent gases potentially present in a waste gases mixture 102. The crude concentrations of
constituent gases is determined based on at least one of the crude Raman spectrum and the crude
absorption spectrum.
[0025] In one embodiment, the processing subsystem 116 determines the crude
concentrations of the constituent gases using a Raman spectroscopy based technique. For
example, the processing subsystem 116 determines the crude concentrations of the inert
constituent gases, hydrogen, and hydrocarbon constituent gases based on the crude Raman
spectrum generated using the Raman spectroscopy based technique. Particularly, the crude
concentrations of the inert constituent gases, hydrogen, and hydrocarbon constituent gases are
determined based on a reference Raman spectrum and the crude Raman spectrum. As used
herein, the term “reference Raman spectrum” refers to a signature of Raman measurement that
maps signal amplitude to emission wavelength at unit concentration at specified temperatures
and pressures. The processing subsystem 116 receives the reference Raman spectrum from the
data repository 117. Particularly, the processing subsystem 116 selects the reference Raman
spectrum from a plurality of reference Raman spectrums stored in the data repository 117 based
on a temperature and a pressure of the sample 113. The processing subsystem 116, for example,
may receive the temperature and the pressure of the sample 113 from the sensing device 108.
[0026] Additionally, the processing subsystem 116 is configured to determine a current
Raman spectrum baseline based on the reference Raman spectrum and the crude Raman
spectrum. As used herein, the term “Raman spectrum baseline” refers to a value that is used to
correct errors in concentrations of constituent gases introduced due to drift in the one or more
components of the system 100. In one embodiment, the crude concentrations of the constituent
gases (for example: the inert constituent gases, hydrogen, and hydrocarbon constituent gases)
and the current Raman spectrum baseline is determined by solving equations represented by
equation (1):
S=
= +
n
i
i i S j c u j B j t
1
( ) ( ) ( , ) (1)
wherein j? [,
], S ( j) is representative of a crude Raman spectrum corresponding to
crude Raman wavelength range j, ci is representative of crude concentrations of constituent gases
i, ui(j) is representative of reference Raman spectrum, and B(j, t) is representative of a current
Raman spectrum baseline.
[0027] In another embodiment, the processing subsystem 116 determines the crude
concentrations of the constituent gases using absorption spectroscopy technique. For example,
the processing subsystem 116 determines the crude concentrations of constituent gases (for
example: the hydrocarbon constituent gases) using Beer Lambert Law represented by the
following equation (2):
I = I e-aCL 0 (2)
wherein I is an intensity the transmitted absorption light beams of the crude absorption spectrum,
I0 is an intensity of the crude absorption light beams irradiated by the sensing device 108, C is
crude concentration of constituent gases, L is a path length of the crude absorption light beams
inside the sensing device 108, and a is an absorbance coefficient that is a function of the
atmospheric temperature.
[0028] Subsequently, the processing subsystem 116 determines a subset of the
constituent gases certainly present in the sample 113 of the waste gases mixture 102. For
example, the processing subsystem 116 identifies the subset of the constituent gases certainly
present in the sample 113 if the crude concentrations of the identified subset of the constituent
gases are greater than a determined concentration threshold. For example, the processing
subsystem 116 may identify three constituent gases as being certainly present in the waste gases
mixture 102 from 5 constituent gases potentially present in the waste gases mixture 102, if crude
concentrations of the 3 constituent gases are greater than the determined concentration threshold.
[0029] Further, the processing subsystem 116 determines refined wavelengths of refined
light beams for use in the sensing device 108. As used herein, the term “refined light beams”
refers to light beams that are characterized by the refined wavelengths corresponding to the
identified subset of gases certainly present in the waste gases mixture 102. As used herein, the
term “refined wavelengths” refers to at least one of absorption wavelengths and Raman
wavelengths corresponding to the identified subset of constituent gases, such that usage of the
absorption wavelengths while executing the absorption spectroscopy based technique and usage
of the Raman wavelengths while executing the Raman spectroscopy based technique achieves
maximum possible intensity of Raman/absorption signal and minimum interference between two
constituent gases. As used herein, the term “certainly present” refers to presence of constituent
gases in waste gases mixture 102 if a concentration of the constituent gases is greater than a
determined concentration threshold.
[0030] The processing subsystem 116 determines the refined wavelengths of the refined
light beams based on the determined subset of the constituent gases certainly present in the
sample 113. In another embodiment, the processing subsystem 116 determines the refined
wavelengths of the refined light beams based on the crude concentrations of the constituent
gases. The refined wavelengths of the refined light beams correspond to the identified subset of
the constituent gases certainly present in the sample 113. The refined wavelengths
corresponding to the subset of the constituent gases, for example, may be a subset of the crude
wavelength range that contribute towards accurate refined concentration measurements of the
subset of the constituent gases. The refined wavelengths, for example, include at least one of
refined Raman wavelengths and refined absorption wavelengths. The refined Raman
wavelengths correspond to at least one of the inert constituent gases, hydrogen, and hydrocarbon
constituent gases. The refined absorption wavelengths correspond to the hydrocarbon
constituent gases. The refined wavelengths, for example, is determined by solving an
optimization function subject to satisfying one or more constraints. For example, the
optimization function is represented as follows:
argmax,

((
(

(3)
[0031] For example, the optimization function is a local optimization function that picks
within a predetermined existing library of scaled reference spectra for regions of refined
wavelength such that constituent gas’s spectral signature is strongest within the wavelength
regions included in the library while simultaneously minimizing the interference from other
constituent gases. The Raman spectral signature of each constituent gas is governed by physics,
unique, and not system dependent. The result from the optimization function only varies due to
changing stream compositions. Hence, for any system using the same optimization function for
the same mixture of gases, the result from the optimizer will be the same.
[0032] The constraints are represented by the following relationships (4) to (6). It should
be noted herein that the constraints (4)-(6) are represented as an exemplary embodiment and a
subset or other additional constraints may be imposed based on the optimization function.
l -l £Dl 2 1 (4)
2 max l £ l (5)
1 min l ³l (6)
wherein min l to max l is representative of a crude wavelength range, 1 l to 2
l is a representative of a
refined wavelength range or refined wavelengths, and Dl is representative of differential
wavelength determined based on a grating of the sensing device 108. As indicated in equation
(4), a check is performed to determine whether the refined wavelength range of the plurality of
refined light beams is less than or equal to the differential wavelength determined based on a
grating of the sensing device 108. As indicated in equation (5), a check is performed to
determine whether the maximum refined wavelength of the refined wavelength range is less than
or equal to a maximum crude wavelength of a crude wavelength range. Furthermore, as
indicated in equation (6), a check is performed to determine whether a minimum refined
wavelength of the refined wavelength range is greater than or equal to a minimum crude
wavelength of the crude wavelength range.
[0033] Subsequent to the determination of the refined wavelengths, the processing
subsystem 116 determines refined concentrations of the subset of the constituent gases based on
the refined light beams and the refined wavelengths of the refined light beams. Determination of
the refined concentrations of the subset of the constituent gases based on the refined light beams
characterized by the refined wavelengths is explained in greater detail with reference to Fig. 6.
[0034] Furthermore, the processing subsystem 116 is configured to determine an amount
of steam or air to be mixed in the waste gases mixture 102 before combustion based on the
determined refined concentrations of the subset of the constituent gases. The processing
subsystem 116, for example, may determine the amount of steam or air to be mixed in the waste
gases mixture 102 based on a look up table or a model.
[0035] Subsequently, the processing subsystem 116 generates feedforward control
signals 124 to control a valve 122. Additionally, the processing subsystem 116 transmits the
feedforward control signals 124 to the valve 122. The transmission of the feedforward control
signals 124 enables the valve 122 to feed the determined amount of steam or air to mix the
determined amount of steam or air in the waste gases mixture 102 before combustion of the
waste gases mixture 102. Subsequent to mixing of the steam or air in the waste gases mixture
102, the mixture (hereinafter referred to as “altered waste gases mixture”) including the steam/air
and the waste gases mixture 102 is combusted within the flaring device 106.
[0036] The mixing of the determined amount of steam or air into the waste gases mixture
102 changes the composition and increases the combustion efficiency of the waste gases mixture
102. For example, about 90% to about 98% combustion efficiency can be achieved by
accurately determining the refined concentrations of the identified subset of constituent gases
certainly present in the waste gases mixture 102 and then adding optimal amount of steam or air
to the waste gases mixture 102. The composition of the waste gases mixture 102 is optimally
altered before combustion so that emissions from the flaring device 106 can be proactively and
efficiently controlled. Additionally, usage of the sensing device 108 enables real-time
concentration measurements of the subset of constituent gases and automated, real-time
alteration of the composition of the waste gases mixture 102.
[0037] Fig. 2 is a diagrammatic illustration of the Raman-cum-absorption spectroscopy
sensing device 108 in accordance with the embodiment of FIG. 1. In the illustrated embodiment,
the sensing device 108 includes an integrating sphere 200. The integrating sphere 200 is
configured to be filled with the sample 113 of the waste gases mixture 102 for analysis. The
sensing device 108 includes a sealable inlet port 202 that enables entry of the sample 113 into the
integrating sphere 200.
[0038] Furthermore, the sensing device 108 includes light sources 204, 206 configured to
emit light beams 208, 210. The light source 204 is a Raman light source and the light source 206
is an absorption light source. The light sources 204, 206, for example, may include a coherent
source, an incoherent source, a visible light source, an infrared source, or the like. The coherent
source may include a tunable laser source, a diode laser, a laser, a distributed feedback laser
source, a Quantum cascade laser source, or the like. One example of an incoherent source is a
Light Emitting Diode (LED).
[0039] Particularly, the Raman light source 204 and the absorption light source 206 are
operationally coupled to the processing subsystem 116. The Raman light source 204 and the
absorption light source 206 are configured to emit the light beams 208, 210 on receipt of the
input and control signals 114 from the processing subsystem 116.
[0040] The Raman light source 204 is coupled to the integrating sphere 200 via a first
fiber optic cable 212. The first fiber optic cable 212 is configured to transmit the Raman light
beams 208 from the Raman light source 204 into the integrating sphere 200. The Raman light
beams 208 include the crude Raman light beams and the refined Raman light beams. The
transmission of the Raman light beams 208 into the integrating sphere 200, filled with the sample
113, scatters the Raman light beams 208 inside the integrating sphere 200. The scattering of the
Raman light beams 208 results in generation of transmitted Raman light beams 214. The
transmitted Raman light beams 214, for example, include transmitted crude Raman light beams
or transmitted refined Raman light beams. If the Raman light beams 208 are crude Raman light
beams characterized by a crude Raman wavelength range, then the transmitted crude Raman
light beams 214 are generated. Similarly, if the Raman light beams 208 are refined Raman light
beams characterized by refined Raman wavelengths, then the transmitted refined Raman light
beams 214 are generated. As used herein, the term “transmitted crude Raman light beams”
refers to transmitted light beams that are generated due to scattering of Raman light beams
characterized by crude Raman wavelength range corresponding to the constituent gases
potentially present in the sample 113. As used herein, the term “transmitted refined Raman light
beams” refers to transmitted light beams that are generated due to scattering of Raman light
beams characterized by refined wavelengths corresponding to the subset of constituent gases
certainly present in the sample 113.
[0041] The absorption light source 206 is coupled to the integrating sphere 200 via a
second fiber optic cable 216. The second fiber optic cable 216 is configured to transmit the
absorption light beams 210 from the absorption light source 206 into the integrating sphere 200.
The absorption light beams 210 include the crude absorption light beams and the refined
absorption light beams referred to in Fig. 1. The transmission of the absorption light beams 210
into the integrating sphere 200, filled with the sample 113 results in absorption of at least a
portion of the absorption light beams 210 inside the integrating sphere 200. The absorption of at
least a portion of the absorption light beams 210 by the sample 113 results in generation of
transmitted absorption light beams 218.
[0042] The sensing device 108 additionally includes a Raman detector 220 coupled to the
integrating sphere 200 via a third fiber optic cable 222. The third fiber optic cable 222 transmits
the transmitted Raman light beams 214 from the integrating sphere 200 to the Raman detector
220. The Raman detector 220 is configured to generate a Raman spectrum 224 based on the
transmitted Raman light beams 214. The Raman spectrum 224, for example, may include a
crude Raman spectrum and a refined Raman spectrum. For example, if the transmitted crude
Raman light beams 214 are generated, then the Raman spectrum 224 is a crude Raman spectrum.
Similarly, if the transmitted refined Raman light beams 214 are generated, then the Raman
spectrum 224 is a refined Raman spectrum.
[0043] Additionally, the sensing device 108 includes an absorption detector 226 coupled
to the integrating sphere 200 via a fourth fiber optic cable 228. The fourth fiber optic cable 228
transmits the transmitted absorption light beams 218 from the integrating sphere 200 to the
absorption detector 226. The absorption detector 226 is configured to generate an absorption
spectrum 230 based on the transmitted absorption light beams 218. The absorption spectrum
230, for example, includes the crude absorption spectrum and the refined absorption spectrum.
[0044] Fig. 3 is a flow chart illustrating a method 300 for obtaining a desired combustion
efficiency of waste gases mixture in accordance with certain embodiments of the present
invention. At block 301, the sample of the waste gases mixture is transferred to a sensing device.
At block 302, crude concentrations of constituent gases potentially present in the sample of the
waste gases mixture may be determined based on the outputs generated by the sensing device.
As previously noted with reference to Fig. 1, the outputs include the crude Raman spectrum and
the crude absorption spectrum generated by the sensing device. The crude concentrations, for
example, may be determined by the processing subsystem. The crude concentrations may be
determined using a combination of a Raman spectroscopy based technique and an absorption
spectroscopy based technique.
[0045] Subsequently, at block 304 a subset of the constituent gases is selected based on
the crude concentrations of the constituent gases. The subset of the constituent gases is selected
by comparing the crude concentrations to a determined concentration threshold.
[0046] Furthermore, at block 306, refined wavelengths of refined light beams are
determined based on the determined subset of constituent gases. The refined wavelengths
correspond to the selected subset of constituent gases. In an alternative embodiment, the refined
wavelengths of refined light beams may be determined based on the crude concentrations of the
constituent gases. The refined wavelengths, for example, may be determined by solving the
optimization equation shown by equation (3). The refined wavelengths of the refined light
beams, for example, may include refined Raman wavelengths and refined absorption
wavelengths of the refined light beams. Additionally, at block 308, refined concentrations of the
subset of the constituent gases are determined based on the refined light beams characterized by
the refined wavelengths. Subsequently, at block 310, an amount of steam or air to be mixed with
the waste gases mixture is determined based on the refined concentrations. Particularly, the
amount of steam or air to be mixed with the waste gases mixture may be determined based on a
look up table or a model. Furthermore, at block 312, feedforward control signals are generated
to mix the determined amount of steam or air with the waste gases mixture. Proactive mixing of
the determined amount of steam or air with the waste gases mixture enables to attain a desired
combustion efficiency of the waste gases mixture.
[0047] Fig. 4 is a flow chart illustrating a method 400 for determining crude
concentrations of the constituent gases using the Raman spectroscopy based technique in
accordance with certain embodiments of the present invention. Particularly, the method 400
describes block 302 of Fig. 3 in greater detail. At block 402, a crude Raman spectrum is
generated. As previously noted, a crude Raman spectrum is a Raman spectrum that is generated
using a crude Raman wavelength range. The crude Raman spectrum, for example, is generated
by the sensing device. The crude Raman spectrum is generated when Raman light beams are
characterized by the crude Raman wavelength range corresponding to the constituent gases
potentially present in a sample. In one embodiment, the crude Raman spectrum is generated by
the sensing device after receiving the inputs and control signals from a processing subsystem. In
an alternative embodiment, the sensing device automatically initiates generation of the crude
Raman spectrum.
[0048] At block 404, the reference Raman spectrum is obtained. The reference Raman
spectrum, for example, is received by the processing subsystem from the data repository 117.
For example, the processing subsystem may select the reference Raman spectrum from a
plurality of reference Raman spectrums stored in the data repository based on a temperature and
a pressure of the sample inside the sensing device.
[0049] Furthermore, at block 406, the crude concentrations of the constituent gases
potentially present in the waste gases mixture are determined based on the reference Raman
spectrum and the crude Raman spectrum. Additionally at block 406, a current Raman spectrum
baseline is determined based on the reference Raman spectrum and the crude Raman spectrum.
For example, the crude concentrations of the constituent gases and the current Raman spectrum
baseline are determined by solving equation (1).
[0050] Fig. 5 is a flow chart illustrating a method 500 for determining crude
concentrations of the constituent gases using the absorption spectroscopy based technique in
accordance with certain embodiments of the present invention. At block 502, a crude absorption
spectrum is generated. The crude absorption spectrum, for example, is generated using the
sensing device. For example, the sample in the sensing device is illuminated by crude absorption
light beams corresponding to the constituent gases potentially present in the waste gases mixture.
The crude absorption spectrum, for example, is generated when the absorption light beams are
characterized by the crude absorption wavelength range corresponding to the constituent gases
potentially present in the sample.
[0051] Furthermore, at block 504, an intensity of the crude absorption light beams is
obtained from the sensing device. Additionally, at block 504 a path length of the crude
absorption light beams is received. In one embodiment, the path length of the crude absorption
light beams may be predetermined, and hence may be received from the data repository 117.
[0052] Subsequently at block 506, crude concentrations of the constituent gases are
determined based on the intensity and path length of the crude absorption light beams and an
intensity of crude transmitted absorption light beams of the crude absorption spectrum. The
crude concentrations, for example, are determined using equation (2).
[0053] Fig. 6 is a flow chart illustrating a method 600 for determining refined
concentrations of the subset of the constituent gases using the Raman spectroscopy based
technique in accordance with certain embodiments of the present invention. The method 600
describes block 308 of Fig. 3 in greater detail. Block 602 is representative of a current Raman
spectrum baseline. The current Raman spectrum baseline 602 may be the current Raman
spectrum baseline determined with the crude concentration at block 406 of Fig. 4.
[0054] Furthermore, block 604 is representative of a previous Raman spectrum baseline.
As used herein, the term “previous Raman spectrum baseline” refers to a Raman spectrum
baseline generated in the past with respect to the time of generation of the current Raman
spectrum baseline 602. For example, if the current Raman spectrum baseline is generated at a
time stamp t, then the previous Raman spectrum baseline 604 is generated at a time stamp (t-1).
[0055] At block 606, an updated Raman spectrum baseline is generated based on the
current Raman spectrum baseline 602 and the previous Raman spectrum baseline 604. The
updated Raman spectrum baseline, for example, is a function of the current Raman spectrum
baseline 602 and the previous Raman spectrum baseline 604. The determination of the updated
Raman spectrum baseline, is represented by:
B' ( j, t) = f (B( j, t ), B( j, t -1)) (7)
wherein B'( j, t ) is representative of updated Raman spectrum baseline, B( j, t) is representative
of current Raman spectrum baseline, and B( j, t -1) is representative of previous Raman
spectrum baseline.
[0056] At block 608, a reference Raman spectrum corresponding to the constituent gases
is obtained. As previously noted, the reference Raman spectrum is selected from a plurality of
reference Raman spectrums based on a temperature and pressure of the sample in the sensing
device.
[0057] Subsequently at block 610, a refined Raman spectrum is generated. The refined
Raman spectrum is generated using the sensing device. The refined Raman spectrum, for
example, is generated by illuminating the sample using the refined Raman light beams
characterized by the refined Raman wavelengths.
[0058] At block 612, refined concentrations of the subset of constituent gases is
determined based on the refined Raman spectrum. Particularly, the refined concentrations of the
subset of the constituent gases are determined based on the refined Raman spectrum, the
reference Raman spectrum, and the updated Raman baseline. The refined concentration, for
example, is determined using the following equation (8):
'( ) ( ) '( , )
1
S j c' u j B j t n
Si i i = = + (8)
wherein S'( j) is representative of refined Raman spectrum, '
i c is representative of refined
concentrations of the subset of constituent gases, u ( j) i is representative of reference Raman
spectrum, and B'( j, t) is representative of updated Raman spectrum baseline.
[0059] Fig. 7 is a flow chart illustrating a method 700 for determining refined
concentrations of the identified subset of the constituent gases using the absorption spectroscopy
based technique in accordance with certain embodiments of the present invention. At block 702,
a refined absorption spectrum is generated. The refined absorption spectrum is generated by
irradiating the sample using the refined absorption light beams characterized by the refined
absorption wavelengths. Furthermore, at block 704, an intensity and a path length of the refined
absorption light beams are obtained. The intensity of the refined absorption light beams is
obtained from the sensing device 108. Additionally, the path length of the refined absorption
light beams may be pre-determined and retrieved from the data repository.
[0060] Subsequently, at block 706, refined concentrations of the subset of the constituent
gases are determined. The refined concentrations of the subset of the constituent gases are
determined using the following equation (9):
' '
0 I '= I 'e-aC L (9)
wherein I’ is representative of the intensity the transmitted absorption light beams of the refined
absorption spectrum, I0 is representative of an intensity of the refined absorption light beams
irradiated by the sensing device, C’ is representative of refined concentrations of constituent
gases, L is a path length of the refined absorption light beams inside the sensing device, and a is
representative of an absorbance coefficient that is a function of the atmospheric temperature.
[0061] The exemplary systems and methods discussed herein provide a real-time flare
analysis and control technology to deliver an integrated flare management solution. The sensing
device is sensitive to frequently varying compositions of waste gases mixture. The present
systems and methods proactively provides feed-forward control signals to mix a determined
amount of steam or air in waste gases mixture before combustion to achieve a desired
combustion efficiency.
[0062] While only certain features of the invention have been illustrated and described
herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to
be understood that the appended claims are intended to cover all such modifications and changes
as fall within the true spirit of the invention.