Process for producing steam and/or power from oil residues with high sulfur content

Abstract

Power is produced using fuel, preferably with a sulfur content larger than 1% wt, from raw and / or preprocessed oil residues which are burned alone, i.e. without any addition of sorbents, diluents or the like, with a CFB boiler, a pitch boiler or a downshot boiler to generate high pressure steam and / or power and residual emissions. Residual emissions are cleaned to simultaneously remove PM, NOx and SO2 therefrom. The sulfur in emissions can be used to produce sulfuric acid. The process uses a low cost fuel, generates steam, and / or power and sulfuric acid and meets all emission requirements for PM, NOx and SO2.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application is a Continuation-In-Part (C.I.P.) of U.S. patent application Ser. No. 12 / 078,972 filed on Apr. 9, 2008, now abandoned, which was a Continuation-In-Part (C.I.P.) of U.S. patent application Ser. No. 11 / 199,127 filed on Aug. 9, 2005, now abandoned, and which claimed priority on U.S. Provisional Application for Patent Ser. No. 60 / 599,575 filed on Aug. 9, 2004, all of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]This invention relates to a clean process for producing steam and / or power from raw and / or preprocessed oil residues with relatively high sulfur content, generally more than 1% wt.[0003]More specifically, the invention relates to an integrated process in which raw and / or preprocessed oil residues are burned alone, without any addition of sorbents or the like, as fuel to generate steam and / or power, as well as residual emissions that are cleaned by simultaneously removing PM (particulat...

AI Technical Summary

Benefits of technology

[0011]More specifically, the invention may relate 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 (DAO) 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 diluents costs and improve the economics of producing bitumen. In addition, produced de-asphalted oil will be of higher quality, lower viscosity, reduced sulfur, nitrogen, Conradson carbon, nickel and vanadium.

[0012]The inventor found that any raw and / or preprocessed oil residues such as, but not limited to, 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 (and / or power) in a clean, or ‘green’, way. The bitumen, typically from parafinic process or naphta-based process, 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 (petroleum) 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 / oily slurry or as a water or oil emulsion. Moreover, fluidized bed boiler, BFD (bubbling fluidized bed), CFB circulating fluidized bed or OTSG (once through steam generating) CFB boilers or OTSG boiler with FGD (flue gas desulfurization) units burn asphaltenes in a clean manner and generate much less emissions than coal. Nonetheless, when high efficiency burning of 99% and more of the carbons with high sulfur content oil residue fuel is considered, only CFB boilers (because of circulation), pitch boilers and downshot boilers (for petcoke) are suitable to burn alone the fuel. Moreover, the boiler(s) is used with a residual emissions cleaning unit such as a sulfuric acid plant (such as a WSA™ process) or preferably with a SNOX™ unit for simultaneously cleaning emissions of SO2, NOx and PM while producing commercial grade sulfuric acid. Removing PM, NOx and SO2 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 pollutants allows for the production of sulfuric acid (H2SO4) of commercial grade; the most common and basic chemical.

[0013]Moreover, the process is fully integrated and can be used on site without the need for additional processing units. Since the process uses raw, or preprocessed oil residues, 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.

[0015]Typically, the oil residues have a sulfur content larger than 1% wt (more than 1% wt being high sulfur content as defined by US Environmental Protection Agency (EPA)), and preferably larger than 3% wt, and wherein cleaning improves an efficiency of the burning of the oil residues, said sulfur content of said oil residues increasing the thermal efficiency of the burning process because of an exothermic chemical reaction in the production of the gaseous sulfuric acid.

[0021]Typically, instead of producing gypsum as in conventional CFB boiler using limestone or lime sorbents, the residual emissions are processed through a sulfuric acid plant or sulfuric acid and denox unit or the like process to remove sulfur from the back end. The benefits are reduced cost for limestone, higher thermal efficiency and better emissions, since 95-98% of both SO2 and NOx are 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, no or reduced need for limestone and consequent 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 and denox plant makes it possible to remove PM, NOx and SO2 without generating liquid waste materials such as waste water. In fact, 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 remote places such as in the Athabasca region of Alberta, Canada.

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

Finally, prior art was not addressing the need of reducing air emissions, greenhouse gas emissions and the need to improve efficiency of the process and reduce waste.

This system deals mainly with flue gas desulfurization (FGD) scrubbers which are known to efficiently remove SO2, as long as the sulfur content is less than 1% wt (the efficiency dramatically reduces above 1% wt sulfur content because of produced ashes that foul the scrubbers and catalysts, to drastically increase the operation cost), notwithstanding the amount of volume to be treated.

Furthermore, the SO3 and metal oxide (of Nickel and Vanadium) dusts created by the burning of petcoke produce severe environmental and operational problems in traditional FGD plants.

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