Monitoração eletrônica da incrustação de coque no processamento do petróleo

Abstract

The coke fouling is a serious problem in the oil industry, mainly in equipment operating at high temperatures. This work presents a study to demonstrate the possibility of using the inlay of the coke as a transducer element to form a resistive sensor type, to provide an electrical signal representative of the growth and aging of the local self inlay. In order to demonstrate this, two categories of experiments have been carried out with two heavy oils fractions and two samples of real fouling coke incrustation originated by these oils in the industry. The experiments show good results, but also indicate that the signal combines both oil and incrustations conductivity. The coke produced during the experiment haad non-adherent loose granules that were electrically disconnected between them. It was verified that the signal obtained during the batch controlled thermal cracking shows three distinct regions: at first, the material reacts within a first-order kinetic rate; at the intermediate region, fluid separation happens in two liquid phases and, finally, at the third region, solid coke deposition occurs, though immersed in a high electric resistivity oil, providing a much higher signal than the initial value presented by the oil. However, sucessive thermal cracking on the initial bed of coke showed progressive reductions in the values of the readings, indicating the tendency to be acquired by the aging of coke, to aggregate in a large structure of carbonaceous material with low electrical resistivity. Alternatively, to confirm, was measured the electrical resistance in samples of real inlay using the same conditions employed in the oils. These have showed a resistivity approximately 50 times smaller than the one for the oils. Testing of sucessive oil cracking on these inlays remain practically constant the electric resistance obtained as reading, confirming that the increase in conductivity is due more to the aging and cementation of grains of coke than the growth of the inlay itself. The tests also showed that once the encrustation acquires a resistivity lower than of the oil, the signal becomes more meaningful and representative of the inlay. The signal, if is associated with an appropriate adjustment method, give the rate of growth of the embedded layer that can be used as a control parameter for the industrial process to minimize the problem of fouling by coke.