Page 103 - Synthetic Fuels Handbook

90 CHAPTER THREE

include hydrogen consumption that may be 20 to 100 percent higher than that for fixed bed
resid desulfurization process, and loss of liquid and hydrogen to high gas yields. The distil-
late products require further hydrotreating and conversion to produce transportation fuels.
Thus, the options for refiners processing heavy high sulfur will be a combination of
upgrading schemes and by-product utilization. Other heavy oil upgrading options include:
(a) deep cut vacuum distillation, (b) solvent deasphalting prior to conversion, and (c) hydro-
genation prior to conversion.
For the present, using a schematic refinery operation (Fig. 3.1), new processes for the
conversion of residua and heavy oils will probably be used in concert with visbreaking
with some degree of hydroprocessing as a primary conversion step. Other processes may
replace or augment the deasphalting units in many refineries. Depending on the properties,
an option for heavy oil, like tar sand bitumen, is to subject the feedstock to either delayed
coking or fluid coking as the primary upgrading step with some prior distillation or top-
ping (Speight, 2007). After primary upgrading, the product streams are hydrotreated and
combined to form a synthetic crude oil that is shipped to a conventional refinery for further
processing to liquid fuels.
The product qualities resulting from the various heavy oil upgrading technologies are
quite variable and are strongly dependent on feed type, process type, and processing condi-
tions. However, producing fuels of acceptable properties is possible (in all cases) with exist-
ing petroleum processing technology, although the economics vary with a given refinery.
However, there is not one single heavy-oil-upgrading solution that will fit all refineries.
Heavy feedstock properties, existing refinery configuration, and desired product slate all
can have a significant effect on the final configuration. Furthermore, a proper evaluation
however is not a simple undertaking for an existing refinery. The evaluation starts with an
accurate understanding of the nature of the feedstock; along with corresponding conversion
chemistry need to be assessed. Once the options have been defined, development of the
optimal configuration for refining the incoming feedstocks can be designed.

3.5 PETROLEUM PRODUCTS AND FUELS

Petroleum products and fuels, in contrast to petrochemicals, are bulk fractions that are
derived from petroleum and have commercial value as a bulk product (Speight, 2007).
In the strictest sense, petrochemicals are also petroleum products but they are individual
chemicals that are used as the basic building blocks of the chemical industry.
The constant demand for fuels is the main driving force behind the petroleum industry.
Other products, such as lubricating oils, waxes, and asphalt, have also added to the popularity
of petroleum as a national resource. Indeed, fuel products derived from petroleum supply more
than half of the world’s total supply of energy. Gasoline, kerosene, and diesel oil provide fuel
for automobiles, tractors, trucks, aircraft, and ships. Fuel oil and natural gas are used to heat
homes and commercial buildings, as well as to generate electricity. Petroleum products are the
basic materials used for the manufacture of synthetic fibers for clothing and in plastics, paints,
fertilizers, insecticides, soaps, and synthetic rubber. The uses of petroleum as a source of raw
material in manufacturing are central to the functioning of modern industry.

3.5.1 Gaseous Fuels
Natural Gas. Natural gas, which is predominantly methane, occurs in underground res-
ervoirs separately or in association with crude oil (Speight, 2007). The principal types
of gaseous fuels are oil (distillation) gas, reformed natural gas, and reformed propane or
liquefied petroleum gas (LPG).