Oil and gas production handbook An introduction to oil and gas production

Figure 22. Claus process (
Source: Wikipedia
) 
 
The Claus process is the most common with the overall reaction: 

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85 
 
 
2 H
2
S + O
2
 
→ S
2
 + 2 H
2
O 
 
The reactor runs at 1,000° C and 0.15 MPa, with three steps: one thermal 
and two catalytic to improve yield. 
 
 
Using these processes, a modern refinery can raise the basic gasoline yield 
depending on crude quality from 10-40% to around to 70%. 
6.4 Blending and distribution 
After the refining processes, the various fractions are stored in intermediate 
tanks, then blended into marketable products for loading onto railcars, trucks 
or ships, and distribution to gas stations or industries.  
 
Each product is blended to a specification of up to 25 parameters such as 
octane rating, energy content, volatility and sulfur content. The task is to 
achieve the specification (and not exceed, where applicable) with the 
minimum amount of over-spec “giveaway.” The blending quality is managed 
with infrared or chromatograph type process analyzers. These can 
determine the precise fractions of a sample by molecule type.  
 
The standard specification gasoline is therefore standard from company to 
company in the individual markets, ensuring compatibility with vehicle 
manufacturer requirements. Also, the terminal operator may be an 
independent third party or run as co-distribution, so that a terminal in one 

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region distributes for several companies based on the same products in the 
same tanks. 
 
Each company 
then seeks to 
differentiate its 
product by adding 
small quantities of 
unique 
additives 
that are marketed 
to increase engine 
performance, 
lifetime, clean 
combustion and so 
forth. These 
additives are 
added as the 
product is 
dispensed to trucks 
for delivery to that brand gasoline station. 
 
A main task is to ensure the balance of incoming and outgoing products and 
consolidate with stored volumes. These have to be compensated for 
temperature, water content (water may be absorbed from air humidity and 
released at low temperatures as bottom slop in tanks) and vapor loss. Vapor 
or volatile organic compounds (VOCs), form above the product in fixed roof 
tanks and when filling up compartments in cars or vessels. VOC loss can be 
significant for high volatility products like gasoline, and must be recovered 
and/or handled to reduce emissions and explosive hazard. 
 
The terminal management system tracks batches of product received or 
dispensed, as well as those eventually received by gasoline stations, airports 
or other consumers and consolidates with stored volumes. Each operation 
should be validated against orders, bills of lading and positive identification 
of trucks, vessels and their operators. In countries where this process is not 
well managed, losses of product due to theft and other factors can be as 
high as 15% or more in the distribution operations.  
 
Eventually the main goal is to ensure that orders are met, and stakeholders 
pay or get paid in the form of VAT, taxes, product, delivery charges, etc. 
 

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7 Petrochemical 
Petrochemicals are chemicals made from petroleum or natural gas. Primary 
petrochemicals are divided into three groups, depending on their chemical 
structure: 
 
Olefins include ethylene, propylene, and butadiene. Ethylene and propylene 
are important sources of industrial chemicals and plastics products. 
Butadiene is used in making synthetic rubber. Olefins are produced by 
cracking.