38 Measurement and Testing
Monitor Maximises Combustion Efficiency in Ethylene Furnaces
Laser Hygrometer Provides Fast, Precise Moisture Measurement
The new Aurora Trace moisture analyser from GE Measurement & Control (USA), uses high definition laser absorption spectroscopy (HDLAS) to provide fast and accurate measurement of the moisture content of gases in the 0-10 parts per million (PPMV) range. It incorporates technology which ensures that its resolution is significantly higher than existing laser absorption equipment, while its sensitivity, or its ability to detect minute amounts of moisture, is increased by a factor of 30. In addition, the response time of the new instrument is the fastest of any currently available system. Typical applications for the new Aurora Trace include moisture measurement in the dry feed gas for the LNG liquefaction processes as well as a range of applications in the petrochemical sector where water-detection is process-critical.
The SERVOTOUGH LaserSP TDLS gas analyser from Servomex (UK), the global specialist in gas analysis, delivers the optimum combustion control solution for ethylene cracker furnaces.
The key to combustion efficiency is minimising excessive air in the combustion chamber, a process which requires fast speed of response when monitoring the flue oxygen concentration at close to the optimum level and for the detection of carbon monoxide in the flue gas. The LaserSP, a high performance combustion monitor which utilises the latest tuneable diode laser (TDLS) technology, combines a response time of less than two seconds with an in-situ measurement location that eliminates any sample system delays.
The ability to measure these gases at up to 1500°C allows the LaserSP to be located close to the furnace burner, delivering the fastest possible speed of response. Additionally, the TDLS analysis technique offers a representative path-averaged measurement of process gas concentrations with a sensitivity that enables it to highlight faults: for example problems with a single burner jet can be detected by the LaserSP, even in furnaces where more than 100 burners may be present.
When utilised for a typical measurement of 0-10% O2 and 0- 1000ppm CO respectively, the LaserSP delivers a flue gas
analysis solution that enables optimisation of the combustion control process, improving process efficiency by lowering fuel consumption and reducing carbon dioxide emissions. Offering highly stable performance and minimum sample conditioning requirements with no moving parts and consumables, the LaserSP also minimises maintenance costs. With the accurate and reliable measurement delivered through a rugged and reliable Servomex design, the LaserSP is the best solution for in-situ measurements in the extreme and harsh environments of an ethylene furnace.
Servomex’s advanced technology also enables additional cost and process control benefits. In traditional TDLS in-situ
installations, it is common practise to flow a dry N2 purge gas over the windows of analysers to protect the optics. Instrument air is not used as the oxygen content would
interfere with the O2 combustion chamber measurement. The infra-red scan range of the LaserSP enables the inclusion of additional absorption lines which only appear at greater than 600°C. By using one of these “hot lines” to monitor the
process O2, it is possible to use instrument air as the window purge gas without any interference to the measurement. The
standard “cold” O2 absorption line is also monitored and the signal utilised for the purpose of checking the LaserSP’s response to a test gas, and to provide an alarm in the event of an interruption of the flow of window purge gas. The LaserSP monitor with air purge typically saves $5000pa (Euro4000pa) compared to a traditional TDL with nitrogen purge.
The thermally induced flexing of furnace walls can cause measurement failure for basic TDL technologies, due to the movement of the wall on which the analyser is mounted resulting in the laser “target” moving. The SERVOTOUGH LaserSP enables the laser transmitter optics to diverge the laser beam, ensuring the receiver remains unaffected by thermal movements of the process. This “receiver overfilling” technique is only made possible as a result of the LaserSP’s advanced second harmonic (2f) wavelength modulated signal (WMS) processing, which operates at a 200kHz carrier signal frequency, providing an order of magnitude improvement in signal to noise ration compared to traditional TDL.
“From reduced emissions and lower fuel costs to vastly improved response and reliability, the advanced technology of the SERVOTOUGH LaserSP delivers ethylene manufacturers overwhelming cost, process and safety benefits”, says Roger Highton, Product Business Manager, Servomex.
Reader Reply Card No 128
Laser absorption spectroscopy is now an accepted moisture measurement technique in the gas sector but Aurora Trace brings new levels of accuracy and reliability. As Ken Soleyn, Product Manager at GE, explains, “As with all Laser Absorption moisture instruments, the new high definition technique scans a laser diode across a narrow frequency band and at certain frequencies the loss of laser intensity is directly proportional to the water concentration in the sample, as water absorbs the photonic energy. However, HDLAS incorporates two fundamental innovations to increase resolution and sensitivity. First of all, it incorporates a finesse cell to bounce the laser beam back and forth between two specially curved mirrors. This essentially increases the path length of the laser beam so that it encounters more water molecules in its passage through the gas. As a result, HDLAS offers thirty times the sensitivity of existing laser absorption technology. The second innovation is the application of vacuum in the measurement cell. This decreases the interactions between the water and carrier gas molecules, which can affect absorption, so that resolution is significantly increased by a factor of five and signal-noise ratio is improved.”
Aurora Trace is completely non-contact, as only the laser light and wetted parts come into contact with the process gas. It is designed to monitor continuously, without maintenance, for more than five years and has no need for field calibration or zero gas baselining. In addition to the measurement of moisture concentration, dew/frost point, temperature and pressure “instrument health” parameters are also continuously monitored to assure measurement integrity. An optional verification system is also available.
Aurora Trace is designed for use in hazardous environments and magnetic induction buttons enable it to be programmed remotely by a magnetic stylus. Consequently, a “hot permit” is not required for programming in a hazardous area, further reducing maintenance costs and simplifying operation. Aurora Trace data is transmitted as three programmable 4-20 MA signals or digitally via RS-232/485 with Modbus RTU. Ethernet and Foundation Fieldbus are also available.
Reader Reply Card No 125
Computer Controlled-Combined Distillation System According to ASTM D-2892 and ASTM D-5236
The i-Fischer (Germany) DIST D-2892/5236 CC / FISCHER AUTODEST 800/860 AC is a fully computer controlled unit of turn-key design, and ready for use after installation and commissioning.
This unit is fully housed and equipped with doors in the front and rear to satisfy safety requirements and to facilitate service aspects.
The automatic fraction collector (in the system section TBP: with 20 receivers) includes a built-in internal balance for the determination of the fraction weight, while the separate volume follower system is used for discharging the fractions into the final receivers and the determination of the fraction volume as well as for the direct distillation rate control.
The automatic fraction collector (in the system section Potstill: with 12 receivers) includes a built-in internal balance, which is used for the simultaneous determination of the fraction weight and for the direct distillation rate control.
Reader Reply Card No 126
Liquid Hydrocarbon Identification in Transportation Operation
Chemical plants and refineries receive or deliver many different liquid hydrocarbons, including Natural Gas Liquids (NGLs) which are transported via pipeline, railcar, tanker trucks and/or ship. Many of these products are very similar in properties and appearance. Therefore, proper identification and interface detection of these hydrocarbons at transport locations, handling multiple products, is important to ensure good quality assurance. Combining an interface detection device with automatic controls can minimise transmix of products, reduce waste, reduce the filling/ unloading times, decrease safety risks, reduce sampling and minimise operator errors.
Having operated globally for over 30 years, K-Patents (Finland), specialising in in-line liquid concentration measurement instruments for industrial users and OEMs in the chemical, oil and petrochemical, pulp and paper, food, semiconductor and pharmaceutical industries, can provide an instrument for accurate liquid hydrocarbon identification in transportation operation.
Based on the Refractive index technology K-Patents’ refractometer is a reliable instrument for identifying liquid hydrocarbon products since each hydrocarbon has a different and distinct refractive index. This refractive index is a property inherent to the hydrocarbon, and can be used to “fingerprint” the product for identification. This “fingerprint” can be applied to a scale to achieve the proper controls.
Two typical products that require proper interface detection are n-butane and iso-butane. These are the two structural isomers of butane meaning they have the same molecular formula but different arrangement of the chemical structural. Since they are isomers, the chemical properties of these products are very similar, in particular, the density. However, the difference in refractive index is wide enough to accurately and reliably distinguish between these two products. K-Patents can provide an accurate and repeatable refractive index measurement to +/-0.0002. Often, this refractive index number is applied to the Brix scale so that whole number values can be monitored.
K-Patents Process refractometer is typically installed in main supply line and the inlet of the product storage. This provides adequate timing for interface detection and double assurance of the hydrocarbon product being delivered to the right storage.
Due to the refractometer digital sensing technology small amounts of entrained air or gases will not affect the measurement. Normal wetted parts are stainless steel 316L with other options available on request. Appropriate hazardous and intrinsic safety approvals are available if required.
Reader Reply Card No 127
APRIL / MAY 2013 •
WWW.PETRO-ONLINE.COM
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
