Fluidized bed coking with fuel gas production

Abstract

A Flexicoking™ unit which retains the capability of converting heavy oil feeds to lower boiling liquid hydrocarbon products while making a fuel gas from rejected coke to provide only a minimal coke yield. The heater section of the conventional three section unit (reactor, heater, gasifier) is eliminated and all or a portion of the cold coke from the reactor is passed directly to the gasifier which is modified by the installation of separators to remove coke particles from the product gas which is taken out of the gasifier for ultization. In one embodiment, a portion of cold coke is transferred directly from the reactor to the gasifier, and another portion of cold coke is combined with hot, partly gasified coke particles transferred directly from the gasifier to the reactor. The hot coke from the gasifier is passed directly to the coking zone of the reactor to supply heat to support the endothermic cracking reactions and supply seed nuclei for the formation of coke in the reactor. Coke is withdrawn from the gasifier to remove excess coke and to purge the system of metals and ash.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of and claims priority to U.S. application Ser. No. 14 / 729,101, filed Jun. 3, 2015, and U.S. Provisional Application Ser. No. 62 / 014,762 filed Jun. 20, 2014, the contents of all of which are herein incorporated by reference in their entirety.FIELD OF THE INVENTION[0002]This invention relates to a fluid coking process in which a heavy oil feed is subjected to thermal cracking (coking) in a fluidized bed reactor with the coke product being converted by gasification to form a fuel gas.BACKGROUND OF THE INVENTION[0003]Heavy petroleum oils and residual fractions derived from them are characterized by a combination of properties which may be summarized as high initial boiling point, high molecular weight and low hydrogen content relative to lower boiling fractions such as naphtha, gasoline, and distillates; frequently these heavy oils and high boiling fractions exhibit high density (low API gravity), h...

AI Technical Summary

Benefits of technology

The new Flexicoking unit is a modified version of a conventional three section unit that can convert heavy oil feeds to lower boiling liquid hydrocarbon products with minimal coke yield while being constructed with lower capital expenditure. The new unit eliminates the heater and uses a modified gasifier with internal or external cyclones to separate coke particles from the product gas. Both cold and hot coke are combined to supply heat for the cracking reactions and form coke in the reactor. The coke is withdrawn to remove excess coke and purge the system of metals and ash. Technical effects of this patent include improved efficiency and cost-effectiveness of heavy oil conversion and removal of excess coke from the system.

Problems solved by technology

Carbon rejection processes generally operate at moderate to high temperatures and low pressures and suffer from a lower liquid yield of transportation fuels than hydrogen addition processes, because a large fraction of the feedstock is rejected as solid coke; light gases are also formed as by-products in the thermal cracking reactions and, being of high H / C ratio tend to degrade the quantity of the more valuable liquid products.

The liquids are generally of poor quality and must normally be hydrotreated before they can be used as feeds for catalytic processes to make transportation fuels.

Images