Oil – to – Fuel – Next Step towards GREEN EVOLUTION

Typical oil extraction from 100 kg. Of oil seeds

Castor Seed 50 kg
Copra 62 kg
Cotton Seed 13 kg
Groundnut Kernel 42 kg
Mustard 35 kg
Palm Kernal 36 kg
Palm Fruit 20 kg
Rapeseed 37 kg
Sesame 50 kg
Soyabean 14 kg
Sunflower 32 kg

Oil from algae

Algae yield is not included in the yield tables because, in spite of all the hype about yields of 20,000 gallons of oil per acre and even 100,000 gallons per acre and so on, biodiesel from algae is still something of the future, not of the present.

As of end-2008, there is no such thing as biodiesel from algae apart from a few laboratory samples. There are some hopeful signs, but technical obstacles remain, pilot projects are not yet feasible for production purposes, and the claims made for high yields have never been demonstrated and remain theoretical.

No doubt that will change, but it’s been “just around the corner” for years. When it does emerge, it’s very likely to be in the form of high-tech industrial-scale solutions, not for backyarders or farms or villages.

There’s a lot of confusion about biodiesel from algae.

Yet many people believe that making biodiesel from algae is an existing option for them now, a tried-and-trusted, ready-to-use technology.

Oil or biodiesel from algae is not a do-able option, there are no tried-and-trusted methods, and it is not a ready-to-use technology.

But that’s not the impression you get from the large amount of sheer hype flying around about algal biodiesel.

Dr John Benemann, the scientist who literally wrote the book on biodiesel from algae, has called some of the claims being made for the technology and yields “bizarre” and “totally absurd”.  The ASP was the U.S. Dept of Energy Aquatic Species Program, which ran for 18 years and cost $100 million.

Dr Benemann was the Principal Investigator and the main author of the ASP Close-Out Report, the book that sparked all the interest in biodiesel from algae.

The Brussels-based biofuels and bioenergy network Biopactpublished a detailed 13,000-word critique of algal biofuels developments in January 2007, “An in-depth look at biofuels from algae”, in order to “temper some of the unfounded and unsubstantiated enthusiasm surrounding algae”.

The Biopact report says:

“Sadly, after decades of development, none of those projects have ever demonstrated the technology on a large scale, let alone over long periods of time. This is why it is time to have a look at the possible reasons as to why algae biofuels are being talked about, but don’t seem to get off the ground. …

“The claims that algae yield ‘enormous’ amounts of useable biomass have never been demonstrated or substantiated. Algae production in photo bioreactors has never left the laboratory or pilot phase and no energy balance and greenhouse gas balance analyses exist for biofuels obtained from such systems.”

Dr. Krassen Dimitrov of the Australian Institute for Bioengineering and Nanotechnology (AIBN, University of Queensland), who made an in-depth analysis of algae-to-biofuels concepts, concludes that a biodiesel-from-algae plant using the much-hyped industrial photo bioreactor approach and operating at maximum efficiency is not economically feasible at fuel prices below US$800 per barrel.

Oils and esters characteristics

Oils and esters characteristics
Type of Oil	Melting Range deg C			Iodine number	Cetane number
	Oil / Fat	Methyl Ester	Ethyl Ester
Rapeseed oil, h. eruc.	5	0	-2	97 to 105	55
Rapeseed oil, i. eruc.	-5	-10	-12	110 to 115	58
Sunflower oil	-18	-12	-14	125 to 135	52
Olive oil	-12	-6	-8	77 to 94	60
Soybean oil	-12	-10	-12	125 to 140	53
Cotton seed oil	0	-5	-8	100 to 115	55
Corn oil	-5	-10	-12	115 to 124	53
Coconut oil	20 to 24	-9	-6	8 to 10	70
Palm kernel oil	20 to 26	-8	-8	12 to 18	70
Palm oil	30 to 38	14	10	44 to 58	65
Palm oleine	20 to 25	5	3	85 to 95	65
Palm stearine	35 to 40	21	18	20 to 45	85
Tallow	35 to 40	16	12	50 to 60	75
Lard	32 to 36	14	10	60 to 70	65

Iodine Values

Chemically, vegetable and animal oils and fats are triglycerides, glycerol bound to three fatty acids. Animal fat such as tallow or lard is saturated, meaning that in the fatty acid portion, all the carbon atoms are bound to two hydrogen atoms, and there are no double bonds. This allows the chains of fatty acids to be straighter and more pliable so they harden at higher temperatures (that’s why lard is a solid).

As you increase the number of double bonds in a fatty acid, you reduce that ability for oils to gain a conformation that would make them solid, so they remain liquid. To picture it, imagine that you put a bunch of strings in a line. Now tie knots in various places on the strings and see how they don’t fit together tightly.

To test a vegetable oil to see how many double bonds it has (how unsaturated it is) iodine is introduced to the oil. The iodine will attach itself over a double bond to make a single bond where an iodine atom is now attached to each carbon atom in that double bond. Higher iodine numbers do not refer to the amount of iodine in the oil, but rather the amount of iodine needed to “saturate” the oil, or break all the double bonds. Oils for the most part contain only trace amounts of iodine naturally.

How does this translate to biodiesel? When the fatty acid chains are broken from the glycerol and then re-esterified to methyl or ethyl groups, those fatty acids still have their double bonds. That means that the more double bonds, the lower the cloud point because they resist solidifying at lower temperatures. So, for instance, if you use lard or tallow, the biodiesel will solidify at a higher temperature because the fat it was formed from also solidified at a higher temperature.

High Iodine Values

The information below refers to straight vegetable oil fuel, but is also useful to show which oils are suitable for making biodiesel and which may not be suitable.

Many vegetable oils and some animal oils are ‘drying’ or ‘semi-drying’ and it is this which makes many oils such as linseed, tung and some fish oils suitable as the base of paints and other coatings. But it is also this property that further restricts their use as fuels.

Drying results from the double bonds (and sometimes triple bonds) in the unsaturated oil molecules being broken by atmospheric oxygen and being converted to peroxides. Cross-linking at this site can then occur and the oil irreversibly polymerizes into a plastic-like solid.

In the high temperatures commonly found in internal combustion engines, the process is accelerated and the engine can quickly become gummed-up with the polymerized oil. With some oils, engine failure can occur in as little as 20 hours.

The traditional measure of the degree of bonds available for this process is given by the ‘Iodine Value’ (IV) and can be determined by adding iodine to the fat or oil. The amount of iodine in grams absorbed per 100 ml of oil is then the IV. The higher the IV, the more unsaturated (the greater the number of double bonds) the oil and the higher is the potential for the oil to polymerize.

While some oils have a low IV and are suitable for use as fuel without any further processing other than extraction and filtering, the majority of vegetable and animal oils have an IV which may cause problems if used as a neat fuel. Generally speaking, an IV of less than about 25 is required if the neat oil is to be used for long term applications in unmodified diesel engines and this limits the types of oil that can be used as fuel. The table below lists various oils and some of their properties.

The IV can be easily reduced by hydrogenation of the oil (reacting the oil with hydrogen), the hydrogen breaking the double bond and converting the fat or oil into a more saturated oil which reduces the tendency of the oil to polymerize. However this process also increases the melting point of the oil and turns the oil into margarine.

As can be seen from the table below, only coconut oil has an IV low enough to be used without any potential problems in an unmodified diesel engine. However, with a melting point of 25 deg C, the use of coconut oil in cooler areas would obviously lead to problems. With IVs of 25-50, the effects on engine life are also generally unaffected if a slightly more active maintenance schedule is maintained such as more frequent lubricating oil changes and exhaust system decoking. Triglycerides in the range of IV 50-100 may result in decreased engine life, and in particular to decreased fuel pump and injector life. However these must be balanced against greatly decreased fuel costs (if using cheap, surplus oil) and it may be found that even with increased maintenance costs this is economically viable.

Oils and their melting points and Iodine Values
Oil	Approx. melting point deg C	Iodine Value
Coconut oil	25	10
Palm kernel oil	24	37
Mutton tallow	42	40
Beef tallow	-	50
Palm oil	35	54
Olive oil	-6	81
Castor oil	-18	85
Peanut oil	3	93
Rapeseed oil	-10	98
Cotton seed oil	-1	105
Sunflower oil	-17	125
Soybean oil	-16	130
Tung oil	-2.5	168
Linseed oil	-24	178
Sardine oil	-	185

REACTIVE DISTILLATION TECHNIQUE

Reactive distillation is a process where we can carry out the chemical reaction in the chemical reactor which is also work as distillation unit. Separation of the product from the reaction mixture does not need a separate distillation step, which saves energy (for heating) and lot of equipments like pumps, heat exchangers, instrumentation etc….

In reactive distillation both chemical conversion and the distillative separation of the product mixture are carried out simultaneously. Through this integrative strategy, chemical equilibrium limitations can be overcome, higher selectivities can be achieved and heat of reaction can be directly used for the reaction.

This technique is especially useful for equilibrium-limited reactions such as esterification and ester hydrolysis reactions. Conversion can be increased far beyond what is expected by the equilibrium due to the continuous removal of reaction products from the reactive zone. This helps reduce capital and investment costs and may be important for sustainable development due to a lower consumption of resources. Reactive Distillation techniques help to increase rate of reaction and efficiency of distillation system. Which can be achieved with minimum equipments and energy consumption thus with lower cost.

The conditions in the reactive column are suboptimal both as a chemical reactor and as a distillation column, since the reactive column combines these.

The separation at the reaction stage leads to complex interactions between vapor-liquid equilibrium, mass transfer rates, diffusion and chemical kinetics, which is a great challenge for design and synthesis of these systems.

Side reactors, where a separate column feeds a reactor and vice versa, is better for some reactions, if the optimal conditions of distillation and reaction differ too much.

Since it is the combination of reaction, distillation and mixing, the design and control of such processes is extremely difficult and at least with the present knowledge and experience, one cannot just rely on thumb rules and gut feelings. Systematic design methods and simulation strategies are being worked out to design a commercial reactive distillation unit for the given application. Complex interaction of reaction and phase equilibrium may lead to non-linear dynamic effects such as multiple steady states, oscillation etc., which are important considerations while operating a reactive distillation column and proper control strategies are required to be devised.

DISTILLATION-AN INTRODUCTION

Distillation is based on the fact that the vapour of a boiling mixture will be richer in the components that have lower boiling points.

Therefore, when this vapour is cooled and condensed, the condensate will contain more volatile components. At the same time, the original mixture will contain more of the less volatile material.

Distillation columns are designed to achieve this separation efficiently.

Although many people have a fair idea what “distillation” means, the important aspects that seem to be missed from the manufacturing point of view are that:

	distillation is the most common separation technique
	it consumes enormous amounts of energy, both in terms of cooling and heating requirements
	it can contribute to more than 50% of plant operating costs

The best way to reduce operating costs of existing units, is to improve their efficiency and operation via process optimisation and control. To achieve this improvement, a thorough understanding of distillation principles and how distillation systems are designed is essential.