NEX XT Total Sulfur Process Analyzer

Advanced X-ray Transmission / Absorption (XRT/XRA) Total Sulfur Gauge for Crude Oil, Marine Bunker Fuel and Blending Operations

Rigaku's NEX XT is the next generation process gauge for high-level total sulfur measurement (0.02% to 6% S) of crude, bunker fuel, fuel oils, and other highly viscous hydrocarbons, including residuums.

On-Line total sulfur gauge

This versatile, compact and robust X-ray Transmission / Absorption (XRT / XRA) process gauge is specifically optimized for the total sulfur analysis needs of refineries, pipelines, blending operations, bunkering terminals and other storage facilities. Applications for the NEX XT include bunker fuel blending to meet MARPOL Annex VI sulfur restrictions, interface detection of different grade fuels delivered via pipelines, refinery feedstock blending and monitoring, and the quality monitoring of crude at remote collection and storage facilities.

Measure sulfur (S) from 200 ppm to 6 wt%

  • Compact design with no routine maintenance
  • Up to 1480 psig and 200°C
  • User adjustable data update frequency
  • Reduced standards requirements
  • No sample condition or recovery system
  • No radioisotopes



XRT Applications

Pipelines, Upgrading Facilities and Refineries

This versatile, compact and robust X-Ray Transmission (XRT) process gauge was specifically optimized for the total sulfur analysis needs of refineries, pipelines, blending operations, heavy oil upgrading, bunkering terminals and other storage facilities.

Applications include bunker fuel blending to meet MARPOL Annex VI sulfur restrictions, interface detection of different grade fuels delivered via pipelines, refinery feedstock blending and monitoring, and the quality monitoring of crude at remote collection and storage facilities.

MARPOL Regulations

IMO ship pollution rules are contained in the "International Convention on the Prevention of Pollution from Ships", known as MARPOL 73/78. On 27 September 1997, the MARPOL Convention was amended by the "1997 Protocol," which includes Annex VI titled "Regulations for the Prevention of Air Pollution from Ships". MARPOL Annex VI sets limits on NOx and SOx emissions from ship exhausts and prohibits deliberate emissions of ozone depleting substances. The Rigaku NEX XT is the perfect tool to assay marine bunker fuels for blending to meet emissions regulation compliance.

3rd Generation Technology

The new Rigaku NEX XT system is faster, more sensitive and far more compact than competitive systems and provides continuous, reliable detection of sulfur at pressures up to 1480 psig and 200ºC. Rigaku NEX XT can operate as a stand-alone analyzer or provide real time closed loop control when tied into a blending or plant wide automation system.

Among its other key features are a simplified user interface, reduced standards requirement, automatic density compensation, automatic water compensation, password protection, and standard platform for communicating sulfur, density, and water content to a plant-wide DCS. Due to its unique design and robust construction, sample conditioning and recovery systems are typically not required.

X-ray Transmission (XRT) gauging has long been an accepted technique for the measurement of total sulfur (S) in heavy hydrocarbon process streams. Whether used for pipeline switching, crude oil blending or to assay or blend marine and bunker fuels, the Rigaku NEX XT XRT process analyzer is well suited to rigorous process environments, with pressures up to 1480 psig and temperature up to 200°C. X-ray transmission gauging involves measuring the attenuation of a monochromatic X-ray beam at a specific energy (21 keV) that is specific to sulfur (S). In practice, a process stream passes through a flowcell where sulfur (S), in the hydrocarbon matrix, absorbs X-rays transmitted between an X-ray source and detector. The recorded X-ray intensity is inversely proportional to the sulfur concentration, thus the highest sulfur levels transmit the least X-rays.

XRT / XRA Technique

X-ray transmission gauging involves measuring the attenuation of a monochromatic X-ray beam at a specific energy (21 keV) that is specific to sulfur (S). In practice, a process stream passes through a flowcell where sulfur (S), in the hydrocarbon matrix, absorbs X-rays transmitted between an X-ray source and detector (see schematic at left). The recorded X-ray intensity is inversely proportional to the sulfur concentration, thus the highest sulfur levels transmit the least X-rays.

X-ray Transmission Gauging

Transmission of X-rays through the flowcell is given by the following equation:

T=I/Io=exp-dt[μm(1-Cs)+ μsCs]

where:

  I = measured X-ray intensity (after flowcell, in photons/sec) 
  Io = initial X-ray intensity (before flowcell, in photons/sec) 
  d = density of the hydrocarbon stream 
  t = thickness of the flowcell path (in cm) 
  μm = molar absorptivity for the hydrocarbon matrix @ 21 keV (cm2/gm) 
  μs = molar absorptivity for sulfur @ 21 keV (cm2/gm) 
  Cs = weight fraction of sulfur (% wt/wt)

Element Molar Absorptivity @ 21 keV
H 0.37
C 0.41
O 0.79
S 5.82


As illustrated in the table, 21 keV is chosen as the energy of X-rays employed in the measurement because: 1) the molar absorptivities of C and H are almost identical and 2) the absorption due to sulfur is 14X larger than the CxHy matrix and 7X larger than oxygen. Thus the method is insensitive to changes in the C:H ratio and is primarily sensitive to only the sulfur content.

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Petro Industry News - Dirty Bomb Article
NEX XT Specifications

  • 0.02 - 6%
Process Conditions
  • Stream pressures to 100 bar (1480 psig)
  • Stream temperatures to 200ºC (392ºF)
  • Flow rates up to 200 l/m (53 gal/m)
Ambient Conditions
  • 0 - 43ºC (32 - 110ºF)
Communications
  • Sulfur results: 4 - 20 mA output
  • Density results: 4 - 20 mA output
  • General warning: dry contact
  • General alarm: dry contact
  • PROFINET or MODBUS 485
Required Inputs
  • 4 - 20 mA raw density
    • precision of ±0.0001 or better
Optional Inputs
  • 4 - 20 mA process temperature
    • for density corrected to 15ºC / 59ºF
  • 4 - 20 mA water concentration
    • if water correction is desired
  • 4 - 20 mA flow
    • for loss of flow warning
  • 4 - 20 mA remote calibration selection
Process Connection
  • Two 1 inch 600 # ANSI flanges
Area Classifications
  • Class 1 Div 1
  • Class 1 Div 2
  • ATEX zone 1 (pending)
  • ATEX zone 2
Air Supply
  • Purge
    • 4.1 - 8.3 bar (60 - 120 psig) air pressure
    • 115 - 225 l/m (4 - 8 scfm) rapid exchange
  • Leakage compensation (application specific)
    • 710 - 990 l/m (25 - 35 scfm) dry oil free air
    • 6.9 - 8.3 bar (100 - 120 psig) air pressure
Power Requirements
  • 115/230 Volts 2.8/1.4 Amps 47 - 63 Hz
    • Dedicated supply

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