O2 measurement in hydrocarbon vapor is used for safety monitoring in vacuum distillation columns in petroleum refining. With conventional paramagnetic oxygen analyzers, O2 concentrations are obtained through an extractive sampling system, which conditions the sample prior to being analyzed. Sample systems cause measurement response time delays, which are very critical in safety systems. Moreover there are many problems related to maintenance and operational costs of sample systems. The process gas to be measured contains high concentration of H2S that leads to quick corrosion of the sample system and analyzer. Another issue when using sampling systems is the sample is not representative of the process after the sample has been conditions and dew point of the sample has been modified, which affects the volume concentration of the sample.
The TDLS8000 Laser Analyzer is the solution to all these problems.
- High-speed response to meet all requirements of safety control
- Continuous monitoring of O2 concentration in-situ
- Eliminates the need for sampling and reduces the maintenance and running costs of the sampling system
The vacuum distillation column is used to distill the residual oil from the atmospheric distillation column. The distillation must be performed at absolute pressures as low as 2 to 15 kPa so as to limit the operating temperature to less than 370 to 380°C and to avoid hydrocarbons cracking processes. The presence of oxygen in the process can be caused by suction and can lead to explosion. Thereby there are rules to control the O2 level in vacuum columns. At level 2 to 5 % O2 the alarm and purging of vapor line by inert gas has to be switched on. That is why high-speed response and high reliability are required for O2 measurements.
- vs Conventional Paramagnetic O2 Analyzer
Conventional Paramagnetic O2 analyzer cannot be used in-line measurement.
The TDLS8000 is capable of directly measuring the O2 concentrations in the vapor line, instead of conventional paramagnetic oxygen analyzers that perform measurements through a sampling system. When using traditional analyzer systems, since the application is for a process working under depression (vacuum), a pump is required. The deeper vacuum the more difficult it is to provide the proper pump. Sometimes it results in seal failure and air leakage and failure measurement results.
- vs Other TDL Analyzers
The shape of O2 absorption spectrum become very sharp under this vacuum condition, which is difficult for other TDL analyzers to measure O2 concentration accurately.
But only TDLS8000 can measure O2 concentration accurately under such vacuum condition by True Peak integration (area) method. For the pressure variation test data, see next page.
/Z: Very low pressure
Note: It is needed the suitable pressure class of the used flanges.
Measuring points of vacuum distillation column
Pressure Variation Test Data
This graph shows O2 measurement on 21%, 4%, 0.8% level under condition which gas pressure change from 1 BarA to 0.2 BarA by TDLS, and shows the measurement done stably and correctly without influence of pressure change.
O2 absorption spectra shape is big changed by pressure change, but the spectrum peak area change to pressure proportionally, so TDLS can compensate pressure influence correctly.
Measurement Value of O2 Concentration under Pressure Change 1 BarA to 0.2 BarA
Chemical plants rely on continuous and batch production processes, each posing different requirements for a control system. A continuous process calls for a robust and stable control system that will not fail and cause the shutdown of a production line, whereas the emphasis with a batch process is on having a control system that allows great flexibility in making adjustments to formulas, procedures, and the like. Both kinds of systems need to be managed in available quality history of product, and to be able to execute non-routine operations. With its extensive product portfolio, experienced systems engineers, and global sales and service network, Yokogawa has a solution for every plant process.
Oil & Gas Downstream
The oil & gas downstream industry has been facing an increasing number of challenges in recent years. These include the changing characteristics of the feedstock to be processed, aging of process facilities and equipment, rising cost of energy, lack of skilled plant operators who can run a refinery safely and efficiently, and the ever-changing requirements from both the market and the customer.
Over the years, Yokogawa has partnered with many downstream companies to provide industrial solutions focused on solving these challenges and problems. Yokogawa's VigilantPlant solutions have helped plant owners to achieve maximum profitability and sustainable safety within their plants.
Petrochemical companies’ needs are extremely diverse. To come out ahead in today’s highly competitive marketplace, producers are striving to improve quality and productivity. Yokogawa provides tailor-made solutions for these needs based on its long and wide-ranging experience in this field.
In the ever changing marketplace, refineries are seen not only as crude processing units but also as profit centers. At the same time, there is a keen awareness of the need for safety at such facilities. A total production solution that encompasses planning, scheduling, management, and control is required to achieve long-term goals for profitability, efficiency, and environmental protection. With years of expertise in the automation field, Yokogawa can bring you affordable total solutions for improved operability and a cleaner world.
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