Research On Foaming Property Of Heavy Oils In Coking Process

During the delayed coking process, the excessive height of the foaming in the coking drum has long been an serious problem, which affects the safe, stable, long, full-loaded and normal operation of plants in the bad ways. The cold and thermal simulating devices for evaluation of foaming property have been designed and constructed first in order to research the foaming of heavy oils under coking condition. The whole system was then applied in the probing of the antifoaming rule and the developing of inhibition of bubble layer.Non-reaction conditions, including temperature (from ambient temperature to 200℃) and gas flow rate, were tested in cold simulation plants. The thermal simulating device was used for the impact of the amount of feedstock, temperature and gas flow on the bubble layer. The thermal testing was carried out in coking circumstances (550℃maximum).The cold simulating device was then applied in the testing of foaming characterization in the thesis. The samples were several simulating oils (stand for heavy oils). The results showed that the higher the amount of asphaltenes was, the more stable the bubbles were, the stranger foaming property was, when the amounts of resins from samples were close. In addition, the foam was quite stable as long as the ratio of asphaltenes/resins was in a proper range. For that, a considerable height was achieved. It also indicated that he ration was too high or low to be favorable for stability of bubbles. Furthermore, the foaming of simulating oils decreased as the temperature increased while the gas flow had the opposite effect on the foaming height.The last part of thesis was about evaluation of foaming by using thermal simulation device. The foaming property of heavy oils was researched under different coking conditions. It demonstrated that the highest point of foam layer was raised up apparently as the temperature increased. On the whole, however, the composite index of foam layer was on a declining curve and the sum amount of bubbles has also been fallen. So a reasonably rising temperature would help to avert the excessive height of foaming. The feeds blending with cycle oil would have the effect of inhibition of foaming when other reaction conditions remain the same. It was demonstrated that The light cycle oil had better performance than the heavy one regarding the inhibition effect and the rising ration of cycle oil could be benefit for antifoaming, whether the cycle oils was light or heavy.