# US 10,309,817 B2 · Method and ultrasound flow measurement unit for the determination of the CO2 emission factor in flare gas plants

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- Number: US 10,309,817 B2
- Document ID: US10309817B2
- Status: Granted
- Kind: B2
- Application number: 14/965,966
- Filed: 2015-12-11
- Published: 2016-06-16
- Granted: 2019-06-04
- Earliest claimed: 2015-12-11
- Assignees: Sick Engineering GmbH
- Applicants: SICK Engineering GmbH
- Inventors: Ekkehard Riedel; Alexander Nerowski
- Web page: https://patentgrep.com/patent/US10309817B2

## CPC

- G01F 15/04: of gases to be measured
- G01F 1/662: {Constructional details}
- G01N 29/024: by measuring propagation velocity or propagation time of acoustic waves
- G01N 33/004: {CO or CO2}
- G01N 2291/02836: Flow rate, liquid level
- Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
- G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## Abstract

The invention relates to an improved and simpler method and to an apparatus for the determination of the CO2 emission factor in flare gas plants comprising the steps: a) measuring the speed of sound in the flare gas; b) detecting known proportions of N2, CO2 and H2O; c1) calculating a maximum speed of sound of the flare gas under the assumption that the hydrocarbon proportion of the flare gas only consists of alkanes having a chain length i; c2) calculating a minimal speed of sound of the flare gas under the assumption that the hydrocarbon proportion of the flare gas only consists of alkanes having a chain length i+1; c3) varying the chain length i for so long until the measured speed of sound lies between the calculated minimal speed of sound and the calculated maximum speed of sound; d) varying the proportions of the alkanes having the chain length i and the chain length i+1 determined in step c) for so long until the speed of sound calculated with these proportions lies within a predefined difference from the measured speed of sound; e) calculating the equivalent chain length; and f) calculating the emission factor.

## Claims

### Claim 1

A method for the determination of the CO2 emission factor in flare gas plants comprising the steps of:
a) using an ultrasound flow measurement unit having an ultrasonic conversion capability for converting transmission and reception of ultrasonic signals and having an evaluation unit configured to determine a speed of sound from the ultrasonic signals to measure the speed of sound (SoSm) in the flare gas and to determine a gas flow via the measured flow speed from the time of flight difference of two ultrasonic signals which have respective components with and against the gas flow, wherein the ultrasound flow measurement unit comprises first and second ultrasonic transducers for respectively generating and receiving the two ultrasonic signals, the first and second ultrasonic transducers being arranged at an angle in a wall of a pipeline through which the flare gas flows, and wherein the two ultrasonic signals are accelerated by the flare gas in a direction of the gas flow and are decelerated by the flare gas in a direction opposite the direction of the gas flow;
b) detecting known proportions (fN2, fH2O, fCO2) of N2, CO2 and H2O;
c1) calculating a maximum speed of sound (SoS(fhigh=0)) of the flare gas as measured by the ultrasound flow measurement unit under the assumption that the hydrocarbon proportion (fCH) of the flare gas only consists of alkanes having a chain length i;
c2) calculating a minimal speed of sound (SoS(flow=0)) of the flare gas under the assumption that the hydrocarbon proportion (fCH) of the flare gas only consists of alkanes having a chain length i+1
c3) varying the chain length i for so long until the measured speed of sound (SoSm) lies between the calculated minimal speed of sound and the calculated maximum speed of sound;
d) varying the proportions (flow and fhigh) of the alkanes having the chain length i and the chain length i+1 determined in steps c1) to c3) for so long until the speed of sound (SoS) calculated with these proportions (flow and fhigh) lies within a predefined difference from the measured speed of sound (SoSm);
e) calculating an equivalent chain length; and
f) calculating an emission factor.

### Claim 2 (depends on 1)

The method in accordance with claim 1, wherein the chain length is determined in iterative steps starting at i=1 in step e).

### Claim 3 (depends on 1)

The method in accordance with claim 1, wherein the proportions are determined in iterative steps in step d).

### Claim 4 (depends on 1)

The method in accordance with claim 1, wherein the step of calculating the speed of sound takes place in accordance with the GERG-2004 XT08 algorithm.

### Claim 5 (depends on 1)

The method in accordance with claim 1, further comprising the steps of: determining a gas flow using an ultrasound flow measurement unit and calculating the CO2 emission using the flow and the emission factor.

### Claim 6 (depends on 5)

The method in accordance with claim 5, further comprising the step of using the measured speed of sound for the calculation of the density of the flare gas.

### Claim 7 (depends on 1)

An ultrasound flow measurement unit for the carrying out of a method in accordance with claim 1, having an input unit for inputting the proportions (fN2, fH2O, fCO2) of N2, CO2 and H2O, having ultrasonic transducers for transmitting and receiving ultrasonic signals, having an evaluation unit which is configured to measure a speed of sound (SoSm) and to carry out the steps a) to h) in accordance with claim 1, and to determine a gas flow via the measured flow speed, wherein the flow speed can be determined from the time of flight difference of two ultrasonic signals which have one component with the flow, on the one hand, and one component against the flow, on the other hand.