Synthetic Oil

The inclusion of other aggregates which have been tested and added for various road systems includes sulfur, shredded discarded tires, limestone (<200 mesh), and crushed concrete. Other applications of bitumen are in roofing, flooring, and as an anticorrosion coating on surfaces exposed to corrosive atmosphere, aggressive soils, and chemicals. The main advantage of bitumen, in many of its applications, is that it is cheaper than alternative materials. The world production of bitumen in 1993 was about 17 Mt.

The reserves of oil are limited, and its uses as a fuel for its heat value may eventually become a luxury which few will be able to afford. The petrochemical industry supplies the plastics and resins we use daily, the synthetic fiber for our clothes, and the detergents for our soaps and washings, as well as the chemicals and solvents for industrial use. World petrochemicals amount to about 1/7 of total steel production and about seven times the aluminum produced by weight.

or natural gas or other hydrocarbon blends by steam reforming

CH4þH2O!COþ3H2 DH⁰¼206:1 kJ=mol (3.2) Fig. 3.6 Simplified block diagram of the EDS process

Table 3.6 EDS products and their disposition

Stream Disposition Yield (% of liquids)

C₄-177C naphtha Motor gasoline 40–80

Chemicals

177–204C distillate Jet fuel 10–30

Turbine fuel

204–399C solvent Home heating oil

Fuel oil blendstock

399–538C vacuum gas oil, coker gas oil Fuel oil blendstock 10–30

Scrubber liquids Fuel oil blendstock

Table 3.5 Some potential donor components in solvent

Compound Structure Compound Structure

Tetralin Tetrahydrophenanthrene

Tetrahydroaccnaphthene Octahydrophenanthrene

Hexahydrofluorene Hexahydrophyrene

50 3 Crude Oil

Fig.3.7TheSRC-IIprocess

The syngas is then balanced for a preferred H₂/CO ratio of 2 since the reaction is

2H2þCO!ðCH2ÞxþH2O (3.3)

The reaction occurs on various catalysts such as iron oxide which is the most commonly used material. Some oxygenated compounds such as alcohols and acids (1%) are also formed.

The Fischer–Tropsch process involves the following steps:

1. Manufacture of syngas

2. Gas purification—removal of S, H₂O, etc.,—and H/C balance 3. Synthesis of oil on fresh catalyst

4. Condensation of liquids and removal of light fractions (gasoline) 5. Distillation of remaining products: 35% gas–oil and 30% paraffins

The gasoline is primarily straight chain hydrocarbons of low octane rating and must therefore be reformulated for use.

The only commercial plant converting coal into oil is in South Africa and known as the Sasol I and II. Sasol I was built in 1956 and produced 10,000 bbl/day of synthetic crude oil using fixed bed (with precipitated iron catalyst) and fluidized bed (with powdered iron catalyst) reactors. A typical gasifier is shown in Fig.3.8.

The construction of Sasol II plant was started in 1976 and completed in 1980; it costs $310⁹and produced 40,000 bbl/day oil from 36 gasifiers, each of which processed 1,200 t/day of coal. The third plant, Sasol III, was designed to be the most advanced conversion plant in the world; it costs

$5.510⁹and is set to produce slightly more than Sasol II. Total synthetic crude oil production Fig. 3.8 A Lurgi dry-ash gasifier

52 3 Crude Oil

was expected to be 120,000 bbl/day and represented over half of the country’s needs. A simplified flow sheet of Sasol II and III is shown in Fig.3.9. A photograph of Sasol II is shown in Fig.3.10.

It should be noted that the production cost of the synthetic crude oil is higher than the world price for wellhead crude, but the value of independence cannot be assigned a simple price.

Exercises

1. The populations of the USA, Canada, and Japan in 2006 were approximately 313, 34, and 126 M, respectively. Calculate the annual per capita oil consumption for each country (see Table3.2) and comment on the differences.

2. Calculate the time required to exhaust the world’s oil reserves if the 6 billion people on earth all consume oil at the rate of 28 bbl each per year.

3. Explain the shape of the theoretical depletion curve of world oil reserves (Fig.3.11).

4. Discuss the problems associated with the use of waste glass as an aggregate in asphalt for roads.

5. Write the reaction for the syngas production from ethane.

Fig. 3.9 Sasol Synthol process: simplified flowsheet for Sasol II

6. The reaction CO + H₂O!H₂+ CO₂is called the water-shift reaction and is often used in the Fischer–Tropsch process. Explain why this reaction is used in this process.

7. Why is the direct liquefaction of coal with hydrogen to form oil a more sensible process than the production of crude oil via the Fischer–Tropsch process for the production of synthetic fuel?

8. Estimate the standard heat of reaction for reaction3.3.

Fig. 3.10 General view of Sasol II at Secunda in the Eastern Transvaal

Fig. 3.11 World consumption of oil and theoretical depletion curve for world oil reserves

54 3 Crude Oil

Chapter 4 Liquid Fuels

Dalam dokumen Applied Chemistry: A Textbook for Engineers and Technologists: Second Edition (Halaman 72-79)

Further Reading

Chapter 4

Liquid Fuels