Użycie paliwa zawierającego algi Chlorella vulgaris w silniku diesla

A.H. Scragg∗, J. Morrison, S.W. Shales

Abstract

Istnieje potrzeba zrównoważenia paliw do silników diesla oraz faktu aby paliwa zawierające dodatki funkcjonowały jako pełne paliwo w silnikach diesla. Niektóre mikroalgi jak Chlorella vulgaris są jednokomórkowe o rozmiarach 5-10 µm, które są odpowiednie (właściwe) do łączenia (wiązania) w paliwach emulsyjnych. Emulsja składająca się z transestryfikowanego oleju rzepakowego, surfaktantu oraz zawiesiny C.vulgaris była używana jako paliwo w jednocylindrowym niezmodyfikowanym silniku diesla. Ustalone zostało zużycie oraz emisja omawianego paliwa i chociaż emisja tlenku węgla była wyższa to emisja NOx była znacznie niższa niż w przypadku standardowego paliwa.

Wprowadzenie:

The need to develop alternative fuels to those derived

from fossil fuels is clear-cut. Not only are fossil fuels limited

resources but also burning them produces carbon dioxide,

which is one of the causes of global warming [1-4].

There are a number of alternative sources of energy such

as hydroelectric, nuclear, wave, and wind power and biological

material. The advantages of biological sources of energy

are that they are renewable, biodegradable, produce fewer

emissions and do not contribute to the increase in carbon

dioxide in the atmosphere [5]. Biological materials can produce

energy by the burning of biomass (wood and grasses)

[6], the production of biogas (methane), the generation of

hydrogen [7,8], the production of ethanol by fermentation

[9], and the use of plant-derived oils [10-12].

One of the most important energy sources are the liquid

fuels such as petrol and diesel. Diesel engines are used extensively

for transport, the powering of equipment and the generation

of electricity [13] and the USA uses over 50 billion

gallons of diesel annually [14]. Alternatives to diesel should

be liquid, compatible with the engines used at present, economically

competitive, and available in sufficient quantities.

Incidentally the engine designed by Diesel ran for the first

time in 1893 and two of the fuels proposed for this engine

were a plant-derived oil (peanut oil) [15] and pulverized

coal [10,16,17]. Plant-derived oils have been used as substitutes

for diesel when supplies were limited but the oils have

proved too viscous for prolonged use [16,18,19]. Therefore,

plant oils have to be modified before use, mainly to reduce

their viscosity and four methods have been used to achieve

this; blending with diesel, the formation of microemulsions

of oil, diesel, water and a surfactant [14,19], pyrolysis and

transesterification. Transesterification breaks down plant oils

to their constituent fatty acids which reduces their viscosity

considerably [18] and the product is known as biodiesel.

Microalgae have been used for food and chemical production

for some time [20,21] and more recently microalgae

have been proposed as an energy source. Microalgae can

be used in a number of ways for the production of energy.

Microalgae can be digested to produce methane [22], they

will produce hydrogen photosynthetically [8], and some algae

accumulate oils that can be cracked to form a liquid

fuel [23,24]. The advantages of microalgae are that they can

grow photosynthetically so that no carbon source is required

for growth and any carbon dioxide released on combustion

will have been previously fixed so that the energy supply

will be carbon dioxide neutral.

Diesel engines will also run on pulverized coal but the

particle size has to be in the range of 5-8_m to combust

properly [25]. A biomass slurry fuel has been proposed

with radiata pine particles of 30-70 _m in size [26]. Some

microalgae such as the Chlorella species are unicellular

with a cell size in the range of 3-10_m which is ideal for

combustion in a diesel engine. Here we describe the production

of a liquid fuel consisting of an emulsion of biodiesel

2. Materiał I metody

2.1. Hodowla oraz warunki hodowli

Chlorella vulgaris Beijeernick (CCAP 211/11B) otrzymywana jest z Culture Collection of Algae and Protozoa, w Ambleside, Combria, UK. Algi wzrastały I utrzymywane były w Bolds Basic medium [27]. pH nastawiane (regulowane) na 6, przed autoklawowaniem (obróbką w autoklawie) w temp. 120C przez 20 min. Hodowla była utrzymywana w 25C w kolbach o pojemności 250 ml zawierających 100 ml hodowli pod działaniem świtła o intensywności 76 µmol m-2 s-1w cyklu 16 h naświetlaniai 8h ciemności, mieszane z prędkością 60 rpm (obrotów na minutę) z mieszadłem orbitalnym. Wzrost hodowli został określony poprzez pomiar gęstości optycznej (absorbancji, wartości absorpcji) o wartości 500 nm. Hodowla większych ilości alg C.vulgaris miała miejsce w pompowanych cylindrycznych fotobioreaktorach230-1, które zostały opisane wcześniej.

2.2. Produkcja biodiesla

The conversion of rapeseed oil was carried out under acid

conditions in batches of 20 l. The reaction mixture contained

3 l rapeseed oil, 2 l l 5M HCl and 15 l ethanol and was

heated at 85 ◦C for 3-4 h. At the end of the reaction the

excess ethanol was removed by distillation. The remaining

mixtures separated into two layers, the top layer the ethyl

ester and the lower layer glycerol, which was removed from

the base of the reaction vessel.

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