Process for producing fuel

Abstract

A fuel is produced from bitumen by precipitating a substantial portion of asphaltenes from bitumen by contacting the bitumen with a lower alkane solvent. Suitable burners include a fluidized bed boiler, a circulating fluidized bed boiler and a pitch boiler which utilize either pre-combustion sulfur sorbents or post-combustion flue gas desulfurization. The sulfur in emissions can be used to produce sulfuric acid. The process uses a low cost fuel, generates steam, power and sulfuric acid and meets all emission requirements for SO2, NOx and PM.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims priority on U.S. Provisional Application 60 / 599,575 filed Aug. 9, 2004.FIELD OF THE INVENTION [0002] This invention relates to a process for producing fuel from bitumen. [0003] More specifically, the invention relates to an integrated process in which heavy oil or bitumen produced from both “in situ” or surface oil sands mines is solvent de-asphalted to yield a de-asphalted oil and an asphaltene fraction, which is used as fuel in a boiler to replace expensive natural gas, reduce energy costs and reduce or obviate the need for diluents to make the de-asphalted oil pipelinable. In particular the invention will substantially reduce energy and diluent costs and improve the economics of producing bitumen. In addition, produced de-asphalted oil will be of higher quality, lower viscosity, reduce sulphur, nitrogen, Conradson carbon, nickel and vanadium. BACKGROUND OF THE INVENTION [0004] Since Canadian conventional oil pr...

AI Technical Summary

Benefits of technology

[0010] The inventor discovered that unprocessed bitumen (from both from oil sands and “in situ”” processes can be efficiently de-asphalted to produce higher quality de-asphalted oil and asphaltenes which can be used as a liquid or solid fuel for producing steam. The bitumen is merely dehydrated and desalted, flashed to remove the gas oil fraction and then de-asphalted. The process is cost effective and produces high quality fuel, that is of higher BTU (British Thermal Unit) content than coal or pet coke with lower amounts of ash than coal. These characteristics make asphaltenes an ideal fuel to be transported in solid form as granules, or in hot liquid form, or as a water slurry or as a water or oil emulsion. Moreover, fluidized bed boiler, BFD (bubbling fluidized bed), CFB circulating fluidized bed or OTSG (once through boiler, CFB boilers) or OTSG boiler with FGD (flue gas de-sulfuration) units burn asphaltenes in a clean manner and generate much less emissions than coal. Alternatively the boilers can be used either with a sulfuric acid plant or preferably with a SNOX™ or WSA™ unit for cleaning emissions of SO2, NOx and PM while producing commercial grade, sulfuric acid. Removing SO2, NOx and PM in the gas phase after combustion has additional benefits: reduced needs for sulfur sorbents, reduced production of ashes and gypsum, improved thermal efficiency of boiler. In addition the removal of polluants allows for the production of sulfuric acid of commercial grade; the most common and basic chemical.

[0011] Moreover, the process is fully integrated and can be used on site without the need for additional processing units. Since the process uses raw, unprocessed bitumen, it significantly decreases costs by reducing the amount of pretreatment with organic solvents. The process of the present invention significantly improves oil quality, and significantly lowers oil viscosity thereby permitting easier pumpability of the oil through standard pipelines. Organic and inorganic contaminants are reduced in the oil which improves the value of the de-asphalted oil.

[0019] Alternatively, the CFB boiler can operate without the addition of limestone or lime sorbent. Instead of producing gypsum a sulfuric acid plant or SNOX® or other process know to the art to remove sulfur can be used for the back end. The benefits will be reduced cost for limestone, higher thermal efficiency and better emissions, since 95-98% of both SO2 and NOx will be removed. Prior processes failed to include the production of sulfuric acid as an efficient way to meet emissions requirement for SO2, NOx and PM. The use of a sulfuric acid plant at the back end allows for higher thermal efficiency of the boiler, reduced need for limestone and reduced production of gypsum. In northern Alberta transportation costs are high, the use of limestone is expensive and production of gypsum increase costs. The production of marketable sulfuric acid disposes of sulfur in the most economical and permanent manner. No stockpiles of sulfur or gypsum will be created as a result of this invention. The use of a sulfuric acid plant makes it possible to remove SO2 NOX and PM without using water. The added benefit of not using limestone and making sulfuric acid instead of gypsum makes the water chemistry much simpler, because the pH of water is not affected by limestone and other contaminants. The resulting ash from the sulfuric acid process is water free and totally inert so that they can be disposed of safely.

Problems solved by technology

As conventional oil deposits dwindle, upgradable fuel derived therefrom has become increasingly more expensive to produce.

The search for inexpensive fuel sources is an on-going problem.

Extracting bitumen from oil sands and other deposits is difficult and requires hot water or steam injection to liquefy the high viscosity bitumen for transport to a surface processing plant.

The processes described in the prior art suffer from a number of important drawbacks.

The processes are complex, involving multiple separate steps, which are not fully integrated.

Moreover, the processes involve pre-treating the bitumen which may be expensive, requiring many reagents and diluents, specialized equipment and prior manipulation of the crude bitumen.

None of the processes offers an affordable solution to the reduction of production costs of heavy oil producers who rely on expensive fuel such as natural gas to generate the high pressure steam needed to extract the low viscosity bitumen found in different places such as in the Athabasca region of Alberta, Canada.

Existing processes do not meet the need for reduced fuel and diluent dependency in the production of a partially upgraded bitumen stream and a precipate of asphaltenes.