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• Understanding the increasing use of gasification in the refinery industry 

 
Why has the Oil Refinery Industry been Introducing Gasification?

The refinery industry is a highly competitive global industrial sector where sales are governed largely by price. For individual refineries to survive they must develop and evolve to meet changing quantity and quality requirements for the domestic fuel market, and meet evolving demands for environmental and social benefits.

Some legislation over the past 5 years has placed additional the pressure on refineries to reduce

- Sulphur content in diesel and gasoline
- Sulphur limit in fuel oil.

To stay competitive and meet future market demands the refineries have had to progressively produce lighter, higher-value products that meet EU sulphur-content specifications.

All refining results in the production of a residue known as "barrel bottom" and the cost effective disposal of the refinery residue is a major challenge, which has become more pressing in recent years partly due to waste disposal rules being tightened throughout many nations, over the last 5 years.

Utilizing the barrel bottom material has become more and more vital, both to reduce waste for disposal, thus cutting disposal costs, and to use the potential of this material as a feedstock for producing additional saleable products

The chance for improved profitability has been seen by many refineries to convert barrel bottoms as what have been called "stay-in-business projects" which if successful may also become profitable investments.

So, further upgrading of the refinery bottoms of the barrel has been, and still is, one of the major targets for increasing the light products from the refineryTable 1: Principle upgrading technologies for liquid residue.

Pros and Cons of More traditional Methods Used in Refineries to Improve the Value of Barrel Bottoms

Table 1. below shows the relative merits and disadvantages of the three main previously used methods:

Table 1  

Source: New Refinery Application of Shell Gasification Technology; P Zuideveld, J Wolff: Proceedings of the 7^th European Gasification Conference, IChemE, 25-27 april 2006, Barcelona, Spain 

Discussion of Table 1

All the upgrading technologies, not including gasification, in the table come with substantial downsides:
- Both upgrading technologies, that is thermal conversion and solvent de-asphalting lead to a more viscous residue with accentuated disposal problems
Heavy metals and sulphur in the residue remain untouched by the upgrading technologies in Table 1, and there has been no solution to that coming from those processes

In fact the problem of barrel bottom material is unresolved, unless gasification is considered as difficulties in blending occur when one considers the difficulties in achieving fuel oil quality through this route.
Gasification of these very heavy residues has been shown to be capable of closing gap caused by process deficiencies traditionally experienced by refinery operators, which neither blending nor Thermal conversion/ Solvent De-asphalting could solve. Nor would they ultimately assist much with producing a more neighbour friendly residue to ease disposal problems.

Gasification also wins out as a process, as it is also a flexible process for converting a variety of hydrocarbon feedstocks such as coal, lignite, oil distillates, residues and natural gas into synthesis gas (syngas).

Syngas for those readers that are new to this subject is essentially a mixture of carbon monoxide and hydrogen. A huge benefit of gasification is that environmentally highly damaging species like sulphur compounds can be easily removed.

The syngas produced during gasification may be used for its combustion value, particularly as fuel gas for gas turbines, where in terms of NOx emissions it can favourably compete with natural gas. Apart from this environmental advantage syngas is also of great value in the petrochemical

ndustry, since it can readily be converted into products like ammonia, methanol, oxo-chemicals, and most importantly hydrogen.

The use of gasification in refineries plugs a gap and leads to an integrated solution between the various process units within the refinery. To be effective the gasification solution has to meet the following core targets:

•Cost effective hydrogen production also for meeting future product specification
•Power and steam for the refinery use and export (only balance)
•Production of more high-value products to improve competitiveness
•Elimination of high-sulphur from fuel oil production
•Develop these process solutions in a manner which is integrated within the existing refinery complex
•Be shown to be the most cost-effective solution.
Shell has commented, even 5 years ago, that: “Gasification technology was always a possible driver and plays an important role in [their] project realisations.”

Source: http://gasification4energy.com/Advanced-Thermal-Treatment-Basics

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