Separação de finos de coque por hidrociclonagem

Abstract

In the delayed coking process, a thermal cracking process of residues results in the formation of a solid final product called petroleum coke (or petcoke), which is removed through cuts caused by high-pressure water jets. These cuts produce a wide range of solids, ranging from fine particles to stones. The petcoke is separated from the water for sale, and the rest of the water with solid residues, the petcoke fines, is clarified and reused in the refinery. This separation process usually happens by sedimentation with a relatively high residence time. In cases where the capacity of the units is increased, this process is no longer efficient, causing an increase in the concentration of petcoke fines in the clarified water, and, consequently, generating erosion and corrosion problems. Thus, it is necessary to analyze alternatives for the separation process, and the study of the application of hydrocyclones stands out, since they are simple, easy-to-operate and robust equipments, being widely used in industry. That said, this work aimed to study hydrocycloning as a physical process for separating petcoke fines from water. For this, petroleum coke was characterized and two non-conventional hydrocyclones were developed to carry out this separation: the hydrocyclones had two conical sections, and in one of them there was a feed ramp with an 11º inclination. The performance of these two equipments together with a third smaller conventional hydrocyclone was evaluated experimentally. A factorial experimental design (32) was performed for each hydrocyclone, and from the results, empirical mathematical models were developed, capable of describing the equipment capacity, the total efficiency and the split ratio as a function of the solids concentration of the fed suspension. and the pressure drop in the equipment. It was found that the proposed non-conventional hydrocyclones had higher capacities, split ratios and separation efficiencies than the conventional mini-hydrocyclone. The average efficiencies obtained by the two hydrocyclones were above 92%, while the efficiency in the mini-hydrocyclone was at most 89%. Relating the two proposed equipments, it was verified that the presence of the feed ramp promoted a reduction in the pressure drop and a slight increase in the total separation efficiency. Comparing the results obtained with data on the separation of petcoke fines by sedimentation, provided by the refinery, it was found in this study that at low concentrations the proposed hydrocyclones are viable alternatives to clarify the water, with the advantage of greater suspension processing capacity.