Evaluation of Algae Biodiesel Production by Transesterification

130 Pages·2012·3.85 MB·English

Project Number CHE-RWT-1208

Evaluation of Algae Biodiesel Production by Transesterification

A Major Qualifying Project Report
Submitted to the Faculty and Staff of
WORCESTER POLYTECHNIC INSTITUTE
For the requirements to achieve the Degree of Bachelor of Science
in Chemical Engineering
by

___________________________________
William Arnold

___________________________________
Kunal Chawla

___________________________________
Michael Haas

Date: March 2, 2012

Approved by:____________________________
Professor Robert W. Thompson
of the Chemical Engineering Department
Arnold, Chawla, Haas
Abstract
With the ever-increasing demand for energy and impending depletion of fossil fuels, it has become
necessary to research sustainable sources of energy. Promising alternatives to conventional fossil fuels
include algae biofuels, particularly algae biodiesel. In an effort to better understand the processing
procedures associated with producing biodiesel, ASPEN Plus software was used to simulate a
transesterification reaction and the following separation steps. Specifically, analyses were conducted by
varying operating parameters to observe how they affect separation throughout the process.

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Acknowledgments
The group would like to thank our professor and advisor, R. W. Thompson, for his support and guidance
throughout the project; our weekly meetings were very insightful. Also, we would like to thank
Worcester Polytechnic Institute for giving us this learning opportunity and experience.
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Table of Contents
Introduction .................................................................................................................................................. 5
Background ................................................................................................................................................... 9
Oil: The Basics ........................................................................................................................................... 9
Increasing U.S. Oil Consumption ............................................................................................................... 9
Hubbert’s Peak ........................................................................................................................................ 11
Benefits of Biodiesel ............................................................................................................................... 13
Introduction to Algae .............................................................................................................................. 14
Chemical Benefits of Algae ..................................................................................................................... 15
Algae Farming ......................................................................................................................................... 16
Algae Farming Designs ............................................................................................................................ 17
Algae Harvesting ..................................................................................................................................... 18
Algae Oil Extraction ................................................................................................................................. 19
Algae to Biodiesel Conversion ................................................................................................................ 21
Anaerobic Digestion ............................................................................................................................ 22
Supercritical Fluids Processing ............................................................................................................ 22
Pyrolysis .............................................................................................................................................. 23
Gasification ......................................................................................................................................... 23
Enzymatic Conversion ......................................................................................................................... 24
Catalytic Cracking ................................................................................................................................ 24
Chemical Transesterification............................................................................................................... 25
Transesterification Catalyst Investigation ............................................................................................... 26
Base-catalyzed Transesterification ..................................................................................................... 26
Acid-catalyzed Transesterification ...................................................................................................... 29
Process Simulation with ASPEN Plus ....................................................................................................... 31
Methodology ............................................................................................................................................... 33
Simulation Basis ...................................................................................................................................... 33
Process Description and Simulation Procedures .................................................................................... 36
Biodiesel-Rich Path ............................................................................................................................. 37
Glycerol Path ....................................................................................................................................... 38
Results and Discussion ................................................................................................................................ 40
Methanol Recovery Evaporator, T-101 ................................................................................................... 40
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Glycerol Path ........................................................................................................................................... 43
First Glycerol Recovery Evaporator, T-102 ......................................................................................... 43
Biodiesel Recovery Evaporator, T-105 ................................................................................................ 45
Biodiesel Path.......................................................................................................................................... 49
Methanol Separation Evaporator, T-103 ............................................................................................ 49
Water Removal Evaporator, T-104 ..................................................................................................... 52
Excess Triolein Removal Evaporator, T-106 ........................................................................................ 53
Conclusion and Recommendations ............................................................................................................ 56
Works Cited ................................................................................................................................................. 58
Appendix A: Extra Figures ........................................................................................................................... 65
Appendix B: T-101 Data .............................................................................................................................. 66
Appendix C: T-102 Data .............................................................................................................................. 87
Appendix D: T-103 Data .............................................................................................................................. 93
Appendix E: T-104 Data ............................................................................................................................. 118
Appendix F: T-105 Data ............................................................................................................................. 120
Appendix G: T-106 Data ............................................................................................................................ 127

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Introduction
Over the past several decades demand for energy has grown, and is projected to continue growing,
drastically around the world. This demand has been met largely by fossil fuels such as coal, oil, and
natural gas. Figure 1 demonstrates the world energy usage and from which it clear that the major
portion of the energy market is fed by fossil fuels. Furthermore, Figure 1 projects an increase in energy
consumption of approximately 40% by the year 2030. This drastic increase in energy demand is not as
severe in the U.S but still presents a major problem.

Figure 1: World Energy Demand (The Energy Groove, 2011)
Although U.S. energy demand is not increasing to the degree that world demand is, the U.S. is not
immune to energy issues. Figure 2 illustrates the steady increase that the US has experienced since 1950
– an increase which shows no sign of slowing. As is the case with the rest of the world, the US feeds
most of its energy needs with fossil fuels. While relatively abundant and inexpensive, these sources are
finite and eventually will become depleted. This is disconcerting, considering the obvious reliance on
fossil fuels. In addition, the combustion of fossil fuels produces large amounts of harmful air pollutants
which accumulate in the atmosphere (Ophardt, 2003). It is for these reasons, among others, that
growing concern has spurred research into alternative fuel sources. One of these particularly intriguing
alternatives is biodiesel.
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Figure 2: U.S. Energy Demand (U.S. Energy Administration, 2010)
Biodiesel is a domestically produced, clean-burning, and renewable substitute for petroleum diesel. In
2010 the United States imported more than 60% of its petroleum, two-thirds of which was used to fuel
vehicles in the form of gasoline and diesel (U.S Department of Energy, 2011). A U.S Department of
Energy study showed that the production and consumption of biodiesel, as opposed to petroleum
diesel, resulted in a 78.5% reduction in carbon dioxide emissions (National Biodiesel Board, 2009). In
addition, biodiesel can be produced from many different sources including plant oil, animal fats, cooking
oil, and algae. Production of biodiesel from algae has been recognized as the most efficient way to make
biofuel. Deriving biodiesel from algae oil has numerous advantages over any other biodiesel production
feedstock since algae have the highest yield per-acre.

Biodiesel produced from algae certainly has its benefits, but there are still some major technical
problems that need to be sorted out before it can compete economically within the current energy
market. Further research must be conducted on contamination prevention into open air production
configurations - the envisioned production system of choice due to high production and relatively low
costs. Current research seeking to address this issue includes integrating the open pond system with
closed photobioreactors to provide a more controlled growing environment. For large scale algal culture
to become viable research into the basic biology of microalgae, species selection, genetic manipulation,
and the metabolic switch for carbon sequestration and storage is necessary. It is also necessary to
conduct investigations into the chemistry of biofuels synthesis (Greenwell et al., 2010). Biofuel synthesis
can take several different pathways, each with its own set of benefits and problems.

The conversion technologies for utilizing algae biomass can be separated into two basic categories:
thermochemical and biochemical conversion. The most popular thermochemical conversion processes
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are pyrolysis and gasification. Pyrolysis is the conversion of the biomass to bio-oil and syngas at medium
to high temperatures while gasification involves partial oxidation into a gas mixture that is combustible
at high temperatures. Biochemical conversion of algae biomass includes techniques such as anaerobic
digestion, which involves the breakdown of organic matter to a gas. However, one of the most common
methods to produce biodiesel from algae is a chemical reaction called transesterification.

In order to produce biofuel, one of the possible reactions available is transesterification. The
transesterification reaction involves introducing a triacylglyceride (TAG) from the biomass with an
alcohol (typically methanol) to produce a different alcohol (in this case glycerol) and a fatty acid methyl
ester (FAME) - more commonly known as biodiesel. For the biodiesel production process, this reaction
must also be accompanied by multiple pieces of ancillary equipment. Figure 3 displays a typical process
path for producing biodiesel using transesterification. It is standard to find a series of separation and
purification units after the reactor which removes the biodiesel from the process. Exiting the process are
three major streams consisting of mainly methanol, biodiesel, and glycerol. The biodiesel and glycerol
are sold as products while, if possible, the methanol is recycled back into the system to improve process
efficiency.

Figure 3: Generic Transesterification Process Diagram (Costello and Assoc., 2007)
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The purpose of this study was to investigate biofuel production from microalgae. This entailed a review
of the production, harvest, and oil extraction of microalgae. Also, research was completed on the
various catalysts that can be used for the transesterification reaction. Additionally, research into the
various methods to produce biofuels such as transesterification, supercritical fluid extraction, pyrolysis,
anaerobic digestion, and gasification was conducted. With a focus on transesterification, a process for
biodiesel production from microalgae was created using ASPEN simulation software. From this, process
equipment analyses were conducted, primarily on the evaporators for separation. The analyses included
studying the changes in energy requirements caused by changes in pressure, temperature, feed ratios,
etc.

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Background
In order to fully understand the necessity for biofuels research it was first essential to understand the
rise, and inevitable fall, of oil as the dominant fuel source for transportation services. This decline has
occurred over much of the past century in many countries – beginning with the U.S.
Oil: The Basics
Petroleum, commonly referred to as crude oil, is a naturally occurring liquid consisting of a complex
mixture of hydrocarbons of varying molecular weights. It is found in geologic formations beneath the
Earth’s surface, formed by geological processes millions of years ago. Petroleum is recovered from these
formations through drilling and pumping, in some cases miles beneath the ocean’s surface. After
extraction, the oil travels to a separation facility which uses stages of separation equipment to release
useful products from the oil. The process utilizes operations such as distillation, catalytic cracking,
hydro-treatment, chemical treating, and heat treating to bring out the various usable products (further
details can be gathered from the example oil processing process flow diagram shown in Appendix
A)(OSHA, 2012). Oil processing yields many products including asphalt, chemical reagents,
pharmaceuticals, waxes, and lubricants. However, the most important products to modern society are
the various fuels that are extracted. Oil products consist of refinery gas, ethane, liquid-propane gas
(LPG), aviation gasoline, motor gasoline, jet fuels, kerosene, gas/diesel oil, fuel oil, naphtha, white spirit,
lubricants, bitumen, paraffin waxes, petroleum coke and other oil products (such oil-based products
consist of those obtained by distillation and are typically used outside of the refining industry)
(International Energy Agency, 2012). These fuels drive the machinery, such as the automobile, that allow
modern society to function on a daily basis.
Increasing U.S. Oil Consumption
Demand for oil increased dramatically in the early 20th century with the rise of the automobile industry,
spurred by Henry Ford’s revolutionary assembly line process and the gasoline-powered internal
combustion engine. Henry Ford introduced his assembly line produced Ford Model-T in 1913 (Model-Ts
were being made without an assembly line since 1908). In doing so, he greatly reduced manufacturing
costs which were then passed on to the consumers. Lower purchasing costs allowed many more people
to afford a Model-T and so sales increased dramatically. By 1920 the majority of Americans were driving
one of Ford’s gasoline powered cars (Bak, 2003). Ford’s cheap gasoline powered motor vehicles helped
to usher in the age of the automobile and, inherently, oil.
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