E
Amine treating
Re nery fuel
Fuel gas
Claus sulphur plant
Sulphur
H S
Other gases
LPG Butanes
Gas processing
Merox treaters
Gas
H S from sour water stripper
Gas
H
Gas
H
Light Naphtha
Hydrotreater
Isomerisation plant
Isomerate
B
Gas
H
Gas
H
Heavy naphtha
A
Hydrotreater
Reformate
Catalytic reformer
Jet fuel
Crude oil
Jet fuel and/ or kerosene
Merox treater
Gas
H
Kerosene
Hydrocracked gasoline
H
Gas
Diesel oil
Hydrotreater
Diesel oil
Diesel oil
Atmospheric
gas oil Heavy vacuum
gas oil
Gas
i-butane
Evacuated non-condensibles
Alkylate
Gas
H
Alkylation
Gas
Butenes, pentenes
Atmospheric bottoms
FCC feed hydrotreater
Light vacuum
H
Gas
FCC gasoline
Hydrotreater
gas oil
Naphtha
Vacuum distillation
Heavy vacuum
FCC gas oil
A
Fuel oil
C
gas oil
Gas
Coker naphtha
Vacuum residuum
(after hydrotreating and reforming)
Coker gas oil
H S to sulphur plant
Asphalt blowing
Asphalt
Air
Sour waters
Petroleum coke
Finished products are shown in blue Sour waters are derived from various distillation tower re ux drums in the re nery The ‘other gases’ entering the gas processing unit includes all the gas streams from the various process units
CO
Natural gas
Steam
Hydrogen synthesis
H
Steam
Stripped water
D
Figure 1 List of measurement points
Moisture and corrosion The measurement of moisture in gases is one of the more complex and difficult applications found in industrial pro - cesses. Moisture, or water traces in combination with other components, can easily become a very corrosive mixture, such as moisture in CO₂ or together with H₂S, affecting stationary sections of process equipment such as pipes, reactors, and vessels. Another important factor is that water traces can negatively influence process yields. Water concentrations may lead to line freezing due to cold weather and other factors. Moisture measurement is different due to the fact that every analyser, especially process analysers, needs to be verified and calibrated. The reading of the instrument can be higher than the concentration expected by the pro- cess engineer. The protocol with every other gas analyser is to connect a bottle with a certified calibration gas to the instrument, verify the reading to be correct, or see that an adjustment is needed. However, this cannot be done with a moisture analyser. Water concentration in the cal (calibrated) gas bottle will vary depending on the pressure and temperature of the bot- tle. It is possible only under laboratory conditions to have a proven water concentration in a background of nitrogen (N₂) or methane (CH₄). The given concentration in a cal gas bottle is only valid at a very limited pressure window and only true and certified at one temperature. That makes the use of such a bottle in the field impossible.
Another critical measurement point is the FCC inlet, where heavy and light VGO is obtained. For optimal FCC operation, it is essential to control the amount of incoming sulphur to stay within design specifications. Measuring sul - phur at the outlet of the FCC unit provides assurance that operations are as intended or helps identify an issue that has developed and should be addressed. Process analyser solution options for sulphur contami- nants include X-ray transmission measurements). These are not the only methods for monitoring sulphur, SO 2, and/or H₂S measurements in refineries, gas plants, chemical pro - duction environments, and even steel mills and coke plants. UV and infrared (IR) technologies are also used to measure these undesired byproducts along production pathways, in the final product, and at emission points. Many plant oper - ational systems are designed based on an expected range of sulphur components and can quickly be damaged or become inefficient if those ranges are exceeded. Purchasing contracts limit the amount of sulphur compo- nents that may be present in the purchased products, and variances can require additional processing or even create purchasing disputes. Finally, the release of H₂S and SO₂ are both highly regulated emissions. H₂S is extremely toxic and lethal to humans, and SO₂ is known to contribute to acid rain development. Measurements of the amount of each of these compounds are required to ensure that emissions stay below specific limits.
20
PTQ Q1 2025
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