Isothermal Refining by Organic Solvent Nanofiltration - ISOREF

Crude oil refining is (after chemicals production) the second most energy intensive industry in advanced economies. For example, refining consumes 6% of the total energy used in the US. Current refinery technology is based on distillation for separation of the crude oil into fractions with varying molecular weights, followed by further reactions on some of these fractions (reforming, hydrotreating, cracking etc), which must then be further distilled. Distillation involves converting a large fraction of a liquid feed into a gas by boiling, so that compounds present in the feed can be separated by means of differences in their boiling points. In refining, distillation typically account for more than half of all the energy consumed, since the phase change on boiling requires significant energy input.

One way of avoiding this large energy consumption would be to carry out fractionation in the liquid phase via a membrane. If a mixture of hydrocarbons is pressed by pressure against a membrane, and the membrane is permeable to only some of the materials, then we can separate the molecules that pass through the membrane from those that do not. This avoids the large energy injections of evaporation or distillation. Theoretical calculations show that the energy required for concentrating a mixture by membrane separation is less than 5% of the energy associated with distillation.

Not surprisingly, people have been interested in using membranes to separate and concentrate liquids for some time. The majority of membrane separations to date are water based. A major success is in the area of desalination, where membranes are used to separate fresh water out of seawater. Membranes are not generally used for molecular separations in organic systems, because until recently there were few membranes stable in organic liquids. This has changed recently - research at Imperial College has developed membranes that are stable in most organic systems. These have been commercialised through an Imperial spin out company, Membrane Extraction Technology (MET) which was acquired by Evonik Industries on 1 March 2010. Evonik MET has made a substantial investment in a large scale membrane manufacturing facility in West London, delivering on the UK Government's vision for Manufacturing the Future.

In many cases the required separation cannot be achieved in a single pass through a membrane, because the membrane does not discriminate highly enough between the different molecules that are present. In these cases, to achieve the required separation, the liquid can be processed through membranes multiple times. This arrangement of membranes is known as a membrane cascade.

Given the advances that have been made in the development of membranes for organic systems and their application in membrane cascades, this project will research the use of membranes for refining crude oil. Membranes do not require boiling and condensation, and so can be operated at a single temperature. This will reduce the needs for heating and cooling, and so the associated heat losses. Thus we expect that isothermal refining with organic solvent nanofiltration membranes will significantly reduce the energy requirements for manufacturing fuels and lube products from crude oil.

The project will work with a synthetic clean crude, made up to simulate the key hydrocarbon components of a real material. Experimental and simulation work will be used to design a membrane cascade to separate the synthetic crude; this cascade design will then be assembled and operated to prove the concept. Further simulations will then estimate what energy savings would result if isothermal refining were employed with a real crude. The project will work closely with partner Shell Gobal Solutions, who are a major company in oil refining and refinery technology.

The economic benefits of the research proposed are (i) the business around licensing the technology developed to refinery operators globally, production of the required membranes, and installation of the capital plant, and; (ii) energy savings by the refinery operator through using isothermal refining.

The separations research group at Imperial College has a strong demonstrated record in the commercialisation of membranes derived from its research. Evonik MET, based in West London, is the only dedicated manufacturing facility for organic solvent nanofiltration membranes in the world. The fundamental processes they use were developed at Imperial College with EPSRC research funding. Therefore the group has experience in the development of manufacturing processes and commercialisation of research.

If the proposal is successful, it will be the first step in a revolutionary new technology for crude oil refining. We estimate that distillation consumes some 300 MJ per barrel of crude, and that isothermal refining might reduce this by at least 150 MJ per barrel. A barrel contains around 6400 MJ and is worth around US$100 or £60; so our savings of 150MJ correspond to about 2% of a barrel or £1.20 per barrel. Global oil production is around 75 million barrels per day, or 27 billion barrels per year. Therefore potential impact is over £32 billion per annum. Realistically, technology penetration is unlikely to reach past 1% of oil refined in the next 10 years, and so a more realistic figure for savings is around £320 million per annum by 2024.

These economic benefits have parallel social benefits. The manufacture of the capital assets and membranes isothermal refining would require, creates high level and knowledge intensive employment, and improves the national accounts through exports achieved. The reduction in energy consumption has environmental benefits, reducing carbon dioxide emissions and making more efficient use of the finite resource which crude represents.