Cleaning method for unconverted oil heat exchanger of residual oil hydrocracker of fluidized bed

Abstract

The invention relates to a cleaning method for an unconverted oil heat exchanger of a residual oil hydrocracker of a fluidized bed, and belongs to the field of oil refining. The cleaning method comprises the steps that heavy aromatics are heated to range from 130 DEG C to 150 DEG C, the heated heavy aromatics enter a spiral plate heat exchanger, and the flow of the heavy aromatics is larger than 80 t / h. The advantage that heavy aromatics have good dissolution and pulverization functions on coke blocks in the heat exchanger is utilized, cleaning can be achieved without dismounting a body largecover, and the cleaning cost is greatly saved.

Description

Technical field [0001] The invention relates to a method for cleaning an unconverted oil heat exchanger of a fluidized bed residue hydrocracking unit, which belongs to the field of oil refining. Background technique [0002] In recent years, with the intensification of the trend of heavy and inferior crude oil, the market's increasing demand for light oil products and the increasingly stringent environmental regulations, the efficient conversion and clean utilization of heavy oil, especially residual oil, has become the focus of the world's oil refining industry. hot spot. The fluidized bed residue hydrogenation process is increasingly recognized by major refineries for its advantages such as a wide range of processing raw materials, small reactor pressure drop, and good heat and mass transfer effects. However, due to the characteristics of poor raw material properties, high operating temperature and high conversion rate, a series of problems such as coking and clogging will occ...

AI Technical Summary

Problems solved by technology

However, due to the characteristics of poor raw material properties, high operating temperature, and high conversion rate, a series of problems such as coking and blockage will occur during operation.

Among them, the coking blockage of the unconverted oil external delivery heat exchanger has become one of the main problems restricting the long-term stable operation of the fluidized bed residual oil hydrogenation unit.

The residual oil is a colloidal system composed of a dispersed phase and a continuous phase. The vacuum residual oil exists in the form of saturated hydrocarbons, aromatic hydrocarbons, colloids and asphaltenes. Normally, there will be no asphaltene precipitation and deposition, but after passing through the ebullating bed After the reaction in the reactor, the stable colloidal system was destroyed, resulting in the precipitation and deposition of asphaltenes in the unconverted oil

The asphaltene in the unconverted oil will adhere to the inner wall of the heat exchanger after being precipitated, and gradually condense into coke at high temperature, resulting in a great decrease in the heat exchange efficiency and flow capacity of the heat exchanger

The unconverted oil heat exchanger generally exchanges heat with the raw material residual oil. After the heat exchange efficiency decreases, on the one hand, it will cause the raw material residual oil to enter the high exchange and the temperature of the heating furnace will drop, resulting in an increase in gas consumption; on the other hand, it will lead to unconverted oil. The temperature of the oil outlet device increases, which affects the safety of downstream devices or tank farms

In addition, after the flow capacity of the unconverted oil heat exchanger decreases, the external delivery will not be smooth, resulting in an increase in the liquid level at the bottom of the decompression tower, and in severe cases, it will lead to a decrease in reaction volume

[0003] The unconverted oil heat exchanger at the bottom of the vacuum tower of the ebullated bed residue hydrocracking unit in foreign countries generally uses a common shell-and-tube heat exchanger. The heater needs to be pulled out for high pressure water gun cleaning and chemical cleaning