How Process Analyzers are Utilised for Blending Applications -Westech

In order to economically run the processes in modern refineries, the installation of process analyzers is required to continuously provide reliable measurement results within the shortest time. These measurement results represent the actual process status and are the basis for any kind of process control and optimization.

Process analyzers

Process analyzers have been integral part of process control in modern refineries since the early 1970s, and are used not only for final blending, but also upstream in the various process plants. These process analyzers provide status information about the process, communicating the valuable and necessary information that is required by modern process control and process optimization packages.

One of the main reasons for refineries to use process analyzers is to fulfil environmental regulations: for example, the facility may need to reduce sulfur, aromatics or vapor pressure. Additionally, these tools can help the owner/operator respond to market situations within the open market for imported products. Sales may stagnate due to more efficient automobile engines and the market often shifts between product classes and grades, meaning that it is important to have the flexibility to respond to the frequent changing of mixing recipes.

Refineries have identified the rationalization of their processes as a significant contributor to master their challenges, with automated test procedures using process analyzers forming an important part. This allows specific properties of hydrocarbon products to be gathered 24 hours a day; this information can then be integrated into a refinery’s process control optimization level. The main aims are to minimize waste, to maximise process efficiency and guarantee a high product quality.

In the past, the use of process analyzers was limited to a direct process control, for example to check if the actual blend meets the required specifications. However, product blending in contemporary refineries is much more difficult and increasingly complex. This is, on the one hand, due to the fact that the number of quality parameters to be met has significantly increased (e.g. sulfur content, aromatics); on the other hand, economical reasons have forced refineries to have the flexibility to react to changes in the markets.

The behavior of product blending in refineries is rather non-linear, meaning that it is often very difficult or even impossible to reach quality targets within the imposed economical constraints without online adaption of the blend model / recipe during the blend. Process analyzers alone are suitable for providing the necessary status information within the shortest possible time.

The goals for any investment in process control and optimization packages are market success (product qualities adapted to market needs), quality (no out of spec products; consistently high quality) and optimization (flexibility, optimal conformity with applicable standards).

However, only the full integration of instrumentation engineering and the consequent use of process analyzers will make the implementation of such complex process control and process optimization packages possible. The payback from the investment analyzers principally results from higher productivity, reduced giveaway, rapid adaption to market conditions, profit optimal blending, lower manufacturing costs, lower labour costs and lower energy costs.

Blending in tank farms

In some refineries, the products from the different process units, which are each different in their qualities and compositions, are stored in intermediate storage tanks for further use. Depending on the required final product for sales, the specific final blending must be carried out either within storage tanks or directly, by “in line” blending into a pipeline or vessel, for example. A number of quality parameters have to be observed and met to gain approval for commercial sale of the final product. One of these parameters is usually the boiling characteristic of the final product, which has to be carried out according to the ASTM D86 standard.

Refineries established the following procedure in order to minimize or possibly even to resist laboratory analysis during the blending process. Before starting the blending process, a reference measurement is carried out with protofuel. This protofuel is used for the validation and approval of the analyzer results. If the analyzer is validated successfully, then the blending starts. During the complete process, the results of the analyzer are used to monitor and control the blending. At the end of the blending process, the analyzer has to perform a further validation cycle with protofuel. If the validation with protofuel shows results within the given specification, the final product is approved and released for sale.

The precondition for the performance of such a procedure requires the use of appropriate and reliable analyzers, which are compliant to applicable standards. The redesigned Distillation Process Analyzer DPA-4 is the only ASTM D86 compliant process analyzer available in the market. It is fully compliant to the laboratory method as it uses the same apparatus and operates according to the defined procedure, whereby 100 ml sample is evaporated at a given distillation rate of 4 – 5 ml/min. This result in repeatability and reproducibility for optimal process control.

 

The DPA-4 is suitable to determine each distillation point from the initial boiling point to the final boiling point within typical range of 20 °C – 420 °C. New features are implemented to shorten the overall cycle time. This is possible due to the optimization of the heat transfer during the distillation; the reduced time to cool down the analyzer; and the implemented pressurized flushing, which ensures a fast evacuation procedure to get the analyzer ready for the next measuring cycle. The “N₂-stirrer” feature prevents the bumping and super heating of the sample during the distillation. Reduced maintenance efforts are the result of the automatic decoking and fast clearing procedure, which minimizes the risk of plugging. The established standardized design means the analyzer is suitable for installation in hazardous areas.

Conclusion

Process analyzers form an essential component of operations in the modern refinery. They can be used to blend various products from different process units either within storage tanks or directly in line when blending into a pipeline or vessel.

For more information on Westech Industrial’s Bartec Benke product line contact Westech Industrial at 1-800-912-9262 or visit our website

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