Alternative fuel resources
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The illustration shows a form of the supply/demand curve which attempts to take into account all of these influences. We are fairly certain to be within sight of the end of growth in oil production. In an exercise carried out by the 1 977 World Energy Conference, the consensus estimate of the world's ultimately recoverable reserves of crude wag around two million million barrels. About three quarters of this crude is thought to lie outside communist areas. If this were developed at the fastest technically feasible rate, production would peak in the 1990's and then gradually start to decline.
Exporting countries will undoubtedly choose to develop their reserves at a slower rate. Saudi Arabia recently fixed its base level at 8.5 million barrels per day, compared with past production levels in excess of 10 million barrels per day, with a peak of over 13 million barrels per day. The country has adequate foreign exchange from serve their resources. Others, like Iran, can become disenchanted with some of the effects of oil wealth. All this amounts to a very unstable and unpredictable supply situation conditoned not by technicalities but by the geopolitical forces and economic considerations that influence producer logic.
It must therefore be assumed that production levels somewhat lower than the technical ceiling will be acceptable to the producer countries. Two views can be developed from this demand for oil, even under a low growth scenario, is likely to be constrained by available supply within the next ten to twenty years.
In essence, oil supplies will be accident prone from now on. The events of 1973 and 1979 will not be the last.
Critics think that this picture is too pessimistic and that far more oil may be found than we assume. It is certinaly true that there are vast reserves of unconventional oil in tar sands and oil shale. But the technical and environmental problem; associated with most of these pioneering extraction project; are considerable and their role ir the world's energy supply con. text — at least during this cen. tury — has been greatly exag. gerated. Undoubtedly furthet discoveries of conventional oi will be made and recovery frorr existing reserves will also be improved.
Another factor is the lonc lead times required to brinc, these new supplies onstream The .Alaskan and North SeE fields have taken ten years tc find and raise to their present production levels. The next oi province might lie in even more difficult operating regions, taking commensurately longel to develop. So, even if there is s lot more oil than the experts predict, it will merely push the production plateau further to the right and into the next century.
This is all very well for those energy consuming applications where alternative fuels can be used. Unfortunately the autc engine and diesel engine require liquid or gaseous fuels ol appropriate quality. In addition the fuel must contain sufficien1 energy to provide adequate range from a modestly sized vehicle storage tank. Air transport demands over more stringent fuel properties and much of the chemical industry is dependent upon oil as a feedstock. The message is clear — oil must be conserved for those applications where no ready substitute is available and the heavy fuels currently burnt in static plant should be transformed into lighter transport grades.
The conversion of a greater proportion of crude oil into automotive fuels is expensive in terms of the consumption of both money and refinery fuel. Fortunately, these effects are relatively simple to quantify and will be described later. However, what is not so simple is the -market which the oil industry has to satisfy. The investment in boiler and process plant is such that its rapid conversion to fuels other than oil is just not practicable. Demand for heavy boiler fuel will inevitably decrease but the oil industry has a responsibility to service the existing infrastructure in balance with the increasing requirement for 'oil specific' transport fuels. As a consequence a philosophy of hydrocarbon saving based on optimum use is applied arid is worthy of our consideration. In any optimization projramme one is aiming at maxinum added value between :rude oil input and product outwt, taking into account the leed to match market requirenents with the effect of crude liet on refinery efficiency. It is )ointless to produce more high ralue products, say gasolines, han the market can absorb. It is )lso pointless to manufacture )roducts of too high a specificaion for the requirements of the narket, for instance selling as uel oil a product which ipproaches a diesel fuel specification. This 'giving away' of quality is, of course, inconsistent with a maximum added value concept.
The question of quality give away goes deeper than this basic example. Significant hydrocarbon savings are feasible if it can be demonstrated that engines are more tolerant of fuel quality than has previously been supposed. A delicate balance between environmental considerations and oil conservation has to be struck but if, for example, diesel engines could operate satisfactorily on 45 cetane fuel, availability would be increased. It is for this reason that the oil industry continuously questions the relevance of specification limits. For example, the current British Standards for oil products were produced in 1970 and, although there have been subsequent amendments, the specification limits still tend to reflect the pre-1973 era of abundant oil supplies. Future specifications will need to reflect future oil product availability. This does not necessarily mean a lowering of standards, it simply requires a more realistic approach from all concerned. The need fof close co-operation between the oil industry, consumer bodies, motor manufacturers and government has therefore never been greater.
Oil is rapildy becoming too valuable to be burnt as an under-boiler fuel for electricity generation, or in any other application where alternatives like nuclear power and coal can equally well be used. About 50% (by weight) of a typical crude oil consists of a residual heavy oil fraction. Instead of using this residue as a fuel oil component it can be converted by cracking into lighter destillate fractions from which transport fuels and petrochemicals can be manufactured. The residue can also be refined to other products such as lubricants, bitumen and wax. Conversion of residue is not a new technique — it has been employed in the United States since the early 1920's simply because fuel oil represents only 14% of their total requirements. Over the last few years, however, the drop in the demand for fuel oil has accelerated in most parts of the world — the barrel is getting 'whiter.
Before going to consider the implications for conventional automotive fuels and to exam ine the alternatives, it might be appropriate to define what we mean by 'the future.' Our planners think of the future in terms of three periods: short term (4-5 years), medium term (5-15 years) and long term (15 plus years). It seems almost certain that the internal combustion engine will continue as the principal power plant for road transport for at least the next two decades and that gasoline and diesel fuel will remain as its principal fuels. Nevertheless, many engine improvements, modifications or varients de signed to reduce fuel consumption and emissions can be ex pected. Some of these innova tions may well assist in the development of more fuel tolerant engines and the oil industry must be aware of these advances if the consumer is to ultimately benefit.
The graph depicts present and potential alternative fuels. It would be unwise to precisely catorise the alternatives on a time scale because political and technical considerations influence the fate of alternative fuels as much as they impact on the oil supply scene. However, in the short to medium term gasoline and diesel fuels, albeit via the conversion route, will continue to dominate, Liquified .Petroleum Gas, Gasoline/ Alcohol blends (Gasohol) and Alcohols may also pay a part. Looking to the medium and long term future synthetic hydrocarbons and hydrogen may become more viable propositions..
Like gasoline the yields of diesel fuel can be improved by secondary processing of the crude residue. Again, cracking will affect fuel characteristics as the breaking down of the heavier molecules produces different hydrocarbon species. Variation in crude diet will also have ab influence as diesel fuel contains higher proportion of straight run distillate than motor gasoline. Distillation is the basic refinery process which, unlike cracking, separates hydrocarbons by the physical differences in their boiling ranges. As a consequence the quality of 'straight run' distillates is very much crude dependant and diesel fuel, which is typically blended from fewer components than mostor spirit, will reflect more closely the characteristics of the crude feed.
Until recently diesel fuels have generally been blended. from straight run distillate fraction of paraffinic origin which provide good ignition quality. However, supply uncertainities mean that increased quantities of naphthenic crude may be processed and this, coupled with cracking, could lower cetane numbers. The effect of cracking is besf demonstrated by the American market where gasoline dominates the demand barrel. In the United States 45 Cetane fuel is not uncommon and numbers as low as 35 have been recorded. The U.K. and Western Europe are not so influenced by the motor spirit sector so that, whilst some
reduction in cetane number is desirable, the extremes of 35. are unlikely to be reached. The! oil industry has in mind a figure in the region of 46-47 rather than the current British Standard limit of 50 minimum.
This would align more closely with our EEC partners but, because ignition quality affects combustion noise and cold starting performance, further liaison with engine manufacturers is essential.
Other characteristics of diesel fuel may also be affected but suitable refinery corrective. treatment, at a cost, can be applied. The changes outlined above will be gradual and can only be introduced if engines are capable of utilising the fuel within the confines of environmental legislation. The need for continued discussions between the oil industry, motor manufacturers, vehicle operators and government cannot be over emphasised.
Liquified Petroleum Gas has
been used as a fuel for cars on a modest scale in several countries for a number of year. It is undoubtedly an excellent otto engine fuel, providing high octane quality and exceptionally smooth driveability. However, its principal attraction has been economic, in that it generally bears a lower tax than other automotive fuels, Traditionally, LPG has been derived from refinery processes but in the near future this situation will change radically. Massive investments are being made in gas gathering schemes to 'strip' the large amounts of associated gas which was gathering schemes to 'strip' the large amounts of associated gas which was previously flared at the oil well-head. LPG can be cryrogenically separated from these natural gas liquids and the graph on page 54 depicts the impressive increase in availability that can be expected within the next ten years.
The potential contribution of
this trade will be relatively small in world terms. Total projected LPG export availability in the mid 1980's is equivalent to a little over one million barrels of oil a day, or about 2% of predicted oil production. Then there is the problem of bringing supplies from the main producing areas to the major markets and the creation of suitable market outlets. LPG export and import facilities require specialised transport, storage and han
dling, with the inevitable consequence that it is likely to remain a relatively expensive form of energy. An import facility is being constructed in Rotterdam but the chances of a U.K. terminal being built are pretty remote for the forseeable future.
The other major dilemma facing the oil industry is just who will be the 'right' customer for this premium priced product? LPG is free from sulphur and most other contaminants and can therefore be used in ,many high-value markets. With the threat of uncomfortably restricted availability for oil it seems likely that a number of users will compete for such a top quality fuel. Unfortunately high distribution costs and stringent safety regulations may well perdude thethe development of anything but a very limited automotive LPG network. Despite these misgivings there could well be a significant increase in some parts of the world.
As far as the U.K. is concerned it seems likely that the availability of LPG will continue to be linked to refinery production. Codes of practice for the storage and handling of LPG will limit the development of a filling station network so we therefore see the future in terms of 'dedicated' LPG vehicle for distribution fleets, taxis etc and, possibly, public service vehicles.
The dedicated vehicle, optimised for LPG use, is unquestionably more fuel efficient than a converted spark ignition engine. LPG has inherently higher octane quality than premium gasoline so that the dual fuel vehicle is 'losing out' in terms of compression ratio and ignition timing. LPG is delivered to the manifold as a vapour which enhances mixture distribution so that leaner fuel/air ratios can be employed. Unfortunately the hot spot, essential for motor spirit vapourization, reduces the volumeric efficiency for LGP when compared with a 'cold' manifold. A further complication lies in the conversion itself. The introduction of an LPG feed to the conventional carb carburettor/ induction system can upset carburettor metering so that, when the engine is running on petrol, some loss of fuel economy may accrue.
No mention has been made of the concept of a wide cut fuel which is basically a mixture of anything between naphtha (gasoline with no antiknock quality) and gas oil. It would also include butane and the other light components which the Otto engine burns so well. At first glance the proposition seems to offer real hydrocarbon savings in that octane upgrading would be avoided and an engine approaching diesel efficiency would be utilised. We have serious misgivings as to the real benefits this concept will offer and, whilst it would be remiss to ignore the idea, the following thoughts will indicate why wide cut fuels have been omitted from our plans.
It is true that distillation costs could be reduced if the wide cut fuel philosophy was introduced. However, the cost of separating crude into fractions is relatively small when compared to the cost of upgrading the gasoline range to high octane quality. Most of the economic advantage from a low octane requirement stratified charge engine would be gained by designing it to run on a normal cut gasoline whose octane level was optimised on the integrated car/refinery system. To further develop the engine to operate on the gas oil fraction of a wide cut fuel would only save marginal distillation costs.
Approaching the wide cut fuel concept from the diesel engine viewpoint presents a different picture. The lower cetane number of a wide cut grade could probaly be accommodated and the cost of octane upgrading would undoubtedly be saved. Regretably a number of difficulties still remain — octane upgrading would still be required for the existing otto engine stock and, once this stock had diminished, less' hydrogen (a by-product of octane-upgrading reforming processes) would be available for desulphurization. Kerosene would still be required for aviation and conventional diesel diesel for conventional compression ignition engines. A further point, which applies to either stratified charge or diesel engines, is that wide cut fuel would be more hazardous to store either gasoline or derv.
Turning to less conventional fuels we are looking at medium to long term options. Like most generalisations such a statement requires qualification for, as far as alcohols are concerned, both gasoline/alcohol are concerned, both alcohol fuels are already in limited use.
In the early 1920's Ricardo Engineering undertook a comprehensive study of alcohol fuels. Even at that time there was concern about the future availability of gasoline, and Ricardo's work was part of the effort to ensure that there would be no shortage. Alcohols are attractive because of their high octane quality. Indeed, had the anti-knock performance of tetra ethyl lead not been discovered in 1922, alcohols might have been more widely used as high octane fuel today.
Alcohols have suddenly caught everyone's attention once again and the reason is simple. Alcohols, in particular methanol and ethanol, could provide practical liquid fuels from natural gas, coal, timber, or growing crops. Alcohol fuels present a number of technical problems which are described later but economic, rather than technical factors, are likely to govern the long term use of such products. If plenty of oil (or thi dollars to buy it) are availabli then alcohol is currently uneco nomic. The conversior efficiency of coal or natural ga: to methanol is only about 50 60%. The production of ethano from crops is even less efficien and consumes almost as mud energy to produce as it eventu ally provides as fuel. But if dol lars or oil are not available ther alcohol may prove very attrac tive indeed. This is especially s( if a country has plenty of its owr coal, natural gas, or land an( sunshine plus a workforce whc are paid in local currency.
Of the two grades men tioned, methanol productior has been closely linked t( chemical industry demand However, current and propose( methanol plant constructior programmes indicate the possibility of a departure frorr this relationship. Thus methano production in excess of chemica market requirements may find use as a gasoline extender. Any estimate of how much methano could be surplus is highly Con jectural due to uncertainity about the number of productior capacity of future plants. How ever, it can be assumed that any excess would be insifficient tc provide more than a 5% volume blend in gasoline in any particu lar area. In the longer term the possible availability of methano is even more uncertain and wil largely depend on the extent tc which any surplus has beer utilised as automotive fuel.
To maintain acceptable vehicle performance witlgasoline/methanol blends, fue volatility limits have to be se. which take account of the ad verse effects that methanol ha: on mixture stoichiorrietry and or the fuel's latent heat of vapori. sation, vapour pressure and dis. -dilation characteristics. Ir general terms, the volatility specifications for conventiona fuels provide effective control 01 the cold starting, driveability and hot fuel handling perfor. mance of alcohol fuels, apart from some extreme situation: where modified limits are needed. From an octane quality standpoint, vehicle anti-knocl performance on methanol/ gasoline blends is similar te conventional gasolines at equa octane numbers.
A significant oil industry con corn over methanol /gasolini blends arises from the poo phase stability of the product ir damp conditions and particu larly at low temperatures. Modifications, at high capital cost, would have to be made to the distribution system to maintain product quality and this applies equally to service stations. Additional development work is clearly required in this area to assess fully the procedures and costs involved in methanol fuel distribution. For the motor manufacturers compatability with fuel system materials is a major problem — many currently used elastomers are not resistant to methanol.
Because methanol increases the fuel's vapour pressure some relaxation of existing regulations governing the transport of dangerous goods may be necessary. From a toxicological viewpoint methanol has a similar rating to gasoline but fire.
fighting regulations are different. Although methanol fuels have been shown to produce lower carbon monoxide emission the aldehyde content of exhaust gases is increased. The overall effect of these changes in emission levels will need to be assessed.
The increasing use of ethanol as an automotive fuel extender in Brazil is receiving consider able publicity. As a result, other countries are becoming inter ested, particularly those which can grow carbonhydrate-type crops such as sugar cane. The implications associated with the blending of ethanol in gasoline are less than with methanol and if ethanol /gasoline blends are handled like conventional gasoline, toxicological problems are unlikely to occur.
Although no systematic studies of the lubrication requirements of alcohol-fuelled engines appear to have been carried out, there is consider able experience of using ethanol/gasoline blends, particularly in Brazil. This experience has been favourable no pro blems having been reported. There is no comparable ex perience with methanol / gasoline blends but information will be available over the next two years from trials now being carried out in West Germany on gasolines containing 15% methanol.
The use of neat ethanol has been investigated by a number of car manufacterers, and agencies in Brazil, and by Ford USA. Their work, so far not widely published, suggests that under fully warmed-up conditions, ethanol does not pose any serious lubrication problems. Under cold conditions, however, there are indications of excessive fuel dilution, corrosion and wear. No analogous studies have been carried out on neat methanol-fuelled engines.
It is clear that the entire lubrication aspect needs further study.
Looking further to the future the more widespread introduction of fuels containing over 85% alcohol will depend upon the successful development of engines which are as acceptable to the user as today's conventional power units. Work is underway, particularly in Germany, and the results so far are promising.
Whilst alcohols are excellent fuels for spark ignition engines their low cetane number poses problems for diesel powered vehicles. Other difficulties also arise and these can be summarised by comparing alcohols with conventional diesel fuel: Despite the foregoing and provided the cost is acceptable to the vehicle buyer, two promising modes of conversion could be developed. The first involves the incorporation of an ignition improver in the fuel. With suitably modified injection systems (to accommodate the problems outlined above) diesel fuel containing up to 80% alcohol have been mooted. However, economic production of an ignition accelerator in sufficient quantities is one prerequisite of this route and additives to enhance the lubrication performance of the fuel would need to be incorporated.
Another appraoch may be to consider dual fuel operation with up to 30% alcohol present. This, however, required further development work in the area of controlling alconoi induction into the intake air stream. Investigations into the possibility of emulsifying alcohols in diesel fuel are also being conducted.
The production of synthetic fuel from coal or natural gas, though requiring slightly more energy and capital investment than methanol, might in the end turn out to be a more practical solution. Recent publicity has been given to the Mobil process for converting methanol into gasoline. This technique, originally developed for use on coal, is currently under consideration in New Zealand where their natural gas can be converted into methanol before processing into synthetic gasoline.
In many parts of the world natural gas, like LPG, may well be required for more traditional gaseous fuel applications. As a consequence, the coal to syn thetic liquid fuel route may well prove more attractive. Coal, in terms of sheer volume of reserves, is the single most important source of fossil energy. The world's total coal reserves have been estimated at 24,900 billion barrels of oil equivalent, but the mineable proportions are lower than for oil. Of these huge known reserves, 48% are situated in the United States, nearly 20% lie in the USSR and about 8% are to be found in Europe.
Coal distillates or 'syncrudes' may be derived either directly from coal or from its gasification and subsequent synthesis. The commercial viability, energy efficiency and quality of the end product are dependant upon the coal used and the processing employed. No single process is, to date, optimum for all coals and the pour point and carbon hydrogen ratio of the syncrude produced is critically dependant upon the level of hydrogenation adopted. Coal is deficient in hydrogen when compared with conventional hydrocarbons and hence hydrogenation is an es sential part of the process. As hydrogenation is increased to maximise distillate yield, conv ersion efficiency declines. A number of more efficient pro cesses are under development but it seems clear that cost competitive synthetic fuel is, for most of us, a long term alternative. The environmental problems associated with vast increases in coal mining would also have to be resolved.
Hydrogen has much to recommend it as a fuel. It is a highly concentrated energy source and it burns to form water. Unfortunately, hydrogen only occurs naturally strongly, combined with other elements and their separation requires a high energy plant. It is generally assumed that this energy will come from 'cheap' nuclear or solar generated electricity which in turn will electroyse water to. produce hydrogen.
Hydrogen gives a clean exhaust, almost free of carbon oxides but containing a fair quantity of nitrogen oxides. It will burn smoothly at very weak mixtures so that emission con centrations are reduced. Much care has to be taken to avoid its dangerous tendency to backfire down the inlet system — a phenomena which is generally associated with its high flame speed and low energy of ignition. This problem can be over come by careful attention to ignition system screening (to avoid induced voltage weak sparks), modified manifold / valve arrangements (to eliminate residual gas effects) and lean mixture control.
If the cost of hydrogen can be reduced then it could have a
future — provided, of course, that a safe, cheap, high capacity method of: storage can be deve-.
loped. Metal hydrides appear to be one of the safest methods of storage and a number of researchers are exploring their potential.
There are many indications of an imbalance between supply and demand for oil in spite of its increased costs. Supplies have become increasingly accident prone but oil is likely to remain with us for many decades to come. During this period an en ergy 'cushion' must be pro duced to protect our society from ftiture energy shortages.
For the immediate future every attempt should be made to direct oil usage towards those applications for which no suitable alternative as yet exists.
There are no dramatic new automotive fuels around the corner. Indeed, there is nothing in sight that has not been known, and in most cases, used, for many years. This situation is lilely to pertain at least to the end of the century. However, the challenge of matching en gines to alternative fuels can only be met by even closer cooperation between the oil industry, motor manufacturer, consumer bodies and government.
The energy cushion can be assisted by diverting demand into oil specific regions and by utilising alternative automotive fuels, taking into account the cost of these alternatives