(95c) Advanced Control Implementation By Dynamic Matrix Control Pyrolysis Gasoline Hydrogenation Units in Braskem Plant

Authors: Ribeiro, Pleycienne Trajano; Reis, Ivã das Neves; Paim, Anderson; Ribeiro, Joana Arnaldo; Amaral, Francisco Franco.

E-mail:pleycienne.ribeiro@braskem.com; iva.reis@braskem.com; anderson.paim@braskem.com; joana.ribeiro@braskem.com; francisco.amaral@braskem.com

Advanced controllers based models are being increasingly employed in industrial units, especially in the petrochemical sector due to the advancement of technologies that facilitate the development and the application of these controllers. This type of application provides adaptability and robustness in the operability of the unit, and provide models capable of driving the process for optimum operating conditions.

All phases leading to the development of an advanced control necessarily undergo a comprehensive review of the basic regulatory control, instrumentation, process limits and operational restrictions

Thus, this study aims to describe the process of deploying an advanced process control based on dynamic array in a Pyrolysis Gasoline Hydrogenation (PGH) unit located in basic petrochemicals complex at Braskem, in Camaçari, Bahia. Control strategies have been developed with the objectives to stabilize the variations of the unit feed flow, to avoid instabilities, minimize the consumption of energy and maximize the production of streams with higher added value.

The PGH units has high flow rates, high energy consumption and has the function of di-hydrogenated gasoline pyrolysis produced in naphtha crackers, for the production of BTX (benzene, toluene and xylenes) and other byproducts. In this unit configuration, the first equipment is a depentanizer column that has the function of recovering raw C5 of the heavy pygas. This stream is sent to the isoprene production unit, which also produces piperylenes, DCPD and C5 raffinate. In sequence, there is a column that removes the C10+ compounds from the Pygas . This stream is sent to the unit fuel oil pool, and is burned in others boilers and furnaces of the complex. Subsequently occurs and the selective catalytic hydrogenation of diolefins, olefins and sulfur compounds in two reactors. After the reactors, the lights compounds and the hydrogen sulfide are removed in a striper colmun and the last main equipment is a deoctanizer column, where occurs the separation between dihydrogenated C9 stream and C6-C8 stream. The first stream is directed to automotive gasoline production and the second one is sent to the aromatics extraction units for benzene, toluene and xylenes production.

The developed control strategy provided a reduction in the unit's energy consumption by 10.0%, and also improved the recovery from the main products streams, without compromising its specifications as follows: increase of raw C5 stream by decreasing the C5 content in the depentanizer bottom stream and also decreasing the C6 content in the raw C5 stream; lower of production of fuel oil by increasing the production of automotive gasoline and a higher C6-C8 production by lowering the Aromatics C8 content in the automotive gasoline stream and promoted a gain of US$ 2,109,000.00 per year. The results of the new advanced process control proved the effectiveness of this type of implementation in industrial units, resulting in measurable financial gains and providing qualitative gains in the form of unit operation.