biodiesel white paper

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WHITE PAPER

Guide to Instrumentation for

Biodiesel Fuel Production



INTRODUCTION

The gasoline engine was only six years old in 1892, when Rudolf Diesel developed and patented

the first diesel engine as a more efficient power source.

“The diesel engine can be fed with vegetable oil and would help considerably in the development

of agriculture of countries which use it,” Diesel said when he introduced his invention to the world

at the at the 1911 World Exhibition in Paris. But while Diesel did prove that pure vegetable oil can

be an alternative to the petro-based diesel fuel, the viscosity was too high for practical use.

Since that time, both the diesel engine and the biodiesel fuel production process have evolved

considerably to minimize the viscosity problem, while the need for a fossil fuel alternative has

been growing steadily. Biodiesel has become increasingly attractive as a non-toxic, biodegradable

fossil fuel alternative that can be produced from renewal sources. In addition to peanut oil, which

powered the first diesel engine, biodiesel can be produced from oils in soybeans, sunflower seeds,

cotton seeds, rape seeds, palm, and even in some forms of algae. It can also be produced from

used vegetable oils (cooking oils) and certain animal fats.

The remaining hurdle is to get the cost of production low enough that it can also compete with

gasoline, which will come as biodiesel producers improve and automate production operations.

This paper contributes to that by describing the production process from the perspective of themeasuring instruments that will be used to control operations.

Processing out viscosity

The following are among the production methods available to minimize the viscosity of vegetable

oils, making them practical for use in internal combustion engines:

• Transesterification, also known as alcoholysis, which involves heating the oil with a catalyst and

an alcohol to change its chemical structure

• Pyrolysis, also known as thermal cracking, which also involves heating the oil with a catalyst,

but in the absence of air or oxygen.

• Micro-emulsification, which disperses the vegetable oil into a solvent such as methanol,

ethanol, or butanol.

• Blending, which involves mixing vegetable oils with existing diesel fuel

It is also well worth noting that maintaining ideal storage conditions through the entire product

lifecycle is critical to standards compliance, quality, and cost-effectiveness of the biodiesel pro-

duction process.

Transesterification: Batch

Transesterification is the most widely used method for commercial production of biodiesel.

Transesterification, so named because biodiesel is chemically structured as an ester. Figure 1

depicts a typical batch reaction transesterification process. The oil is heated to a designated tem-

perature, at which a catalyst, (often calcium hydroxide or sodium hydroxide) and an alcohol,

often (methanol or ethanol) are mixed in. This results in the chemical reaction in which the

triglyceride molecule from the alcohol neutralizes the free fatty acids and removes the glycerin,

thus producing an alcohol ester. This separates the material into three layers, with the biodiesel

on top, a soapy substance as the middle layer and glycerin on the bottom.

fter some settlement time, the biodiesel must be washed to remove any soap, alcohol or impuri-

ties that may have entered the process. Washing is costly and time consuming, but must be done

so the fuel meets ASTM D 6751 standards for biodiesel fuel. (Newly emerging computer-con-

trolled continuous flow processes, eliminate the need for the washing cycle.



Figure 1: Transesterification process

Extending processing time further is a period of drying to remove the water, and filtering to

remove residual particulates. Additives, such as anti-Nox are added to the biodiesel, before it is

ready for use. The soap and glycerin are drained off and pumped for additional refining for use in

co-products.

Temperature and pressure must be measured during transesterification and there, the relatively

low 66 degrees C (150 degrees F) temperatures and 20psi pressures present minimal measure-

ment challenge. Although there is still a need to measure levels, flow, temperature, pH andassociated pressure.

Transesterification: Continuous process

Continuous process transesterification offers significant opportunities for efficient high volume

production of biodiesel, including eliminating the costly washing and drying phases. A popular

method uses continuous stirred tank reactors (CSTRs) in a series. The flexible process allows

CSTRs with various volumes to be arranged in succession for optimum production. For instance,

CSTR 1 may be a larger volume tank, which allows a longer residence time to achieve a greater

extent of reaction. After the initial product glycerol is decanted, a faster reaction can take place

in CSTR 2, with a 98+ percent completion.

An essential element of the CSTR design is sufficient mixing input to ensure that the compositionthrough the reactor is constant. As such, success is very dependent upon precise consistent meas-

ures of all process variables.

Producing bio fuel through pyrolysis

Pyrolysis is another method of reducing viscosity to make vegetable oils useable in internal com-

bustion engines. In fast pyrolysis, shown in Figure 2, the oils are rapidly heated to 450 - 600

degrees C (842 – 1,112 degrees F) in absence of air. Heavy vibrations produced at this tempera-

ture break molecular bonds separating atoms at random positions, producing organic vapors,

gases, and charcoal. The vapors condense into bio-oil. Typically, 70-75 % by weight of the feed-

stock is converted into oil in this way.

Dilute AcidEsterification

MethanolRecovery

GlycerinRefining

Transesterification

Refining

BiodieselGlycerin

Crude BiodieselCrude Glycerin

Recycled GreasesVegetable Oils

Methanol + KOH

Basic Technology



Figure 2

Pyrolysis has some very specific advantages. Because it is more of a physical than a chemical conver-

sion, it enables de-coupling of process steps in time, place, and scale. The liquids used in the process

are easier to handle and of more consistent quality than those used in transesterification, and the

process itself produces a clean liquid, which requires no additional washing, drying, or filtering.

Instrumentation requirements for pyrolysis are similar to those for transesterification, including

temperature, pressure, level, flow and pH, although temperature and pressure measurement

requirements will be much more demanding, given the 450 - 600 degrees C (842 – 1,112 degrees)

temperatures and vacuum conditions that the process requires.

Micro-Emulsification techniques

Micro-emulsification, is the third method of controlling viscosity of biodiesel. The process involves

dipping vegetable or other organic oils into solvents such as methanol, ethanol or butanol to dis-

perse micro-emulsions (co-solvency). The micro-emulsion dispersions are transparent,

thermodynamically stable and easily pass through fuel filters. Droplet diameters of micro-emul-

sions range from 100 to 1000 Å. A micro-emulsion can be made of vegetable oils with an ester

and dispersant (co-solvent); or of vegetable oils, an alcohol and a surfactant, and a cetane

improver, with or without diesel fuels. Water (from aqueous ethanol) may also be used for lower-

proof ethanol, thus increasing water tolerance of the micro-emulsions.

Blending biodiesel

Although not necessarily suitable for large scale commercial application, viscosity problems in

biodiesel can be managed through blending. Biodiesel be blended in any amount with petroleum-

based diesel fuels, including Diesel #1, Diesel #2, or JP8. Where B100 is the name for pure

biodiesel, B20 would be a fuel that contains only 20% biodiesel and B10 a fuel that contains only

10% biodiesel. B20 is a standard blend that meets the minimum requirements of the federal EPA

Act clean air criteria. Based on today’s diesel engine performance, B20 also is the highest recom-

mended blend. Beyond a 20% blend has proven to be inefficient in diesel engines. Like any

Flue Gas

Gas

Ash

Sawdust

9

11

Oil

10

87

R2

C1H1

C2

P3 P4

21

4 P1

P26Air

Air

R15

3

9 13



petroleum based diesel fuel, biodiesel needs to blended with additives to keep it from gelling in

extreme cold weather.

TYPICAL MEASUREMENTS IN A BIODIESEL PLANT

Regardless of which production process is used to produce biodiesel, raw materials, agents, prod-

ucts and co-products must be stored, pumped to various locations, and monitored and measured

all the way. The following matrix provides a ready-reference guide to instru-

mentation suitable for biodiesel process measurements.

Typical measurements of bio-diesel production processes

Production Process Invensys Foxboro Solution

Measurement

Pressure Models IAP10, IAP20, IGP10, IGP20, IDP10, IMV25Transmitters

Temperature Model RTT 15, RTT20

Flow Model 83 Vortex, Vortex 84, CFT 50 Mass Flow,

IMT25 / 9300 Magnetic Flowtube, IMV30

Analytical 875 & 870IT pH & Conductivity Analyzers.

Level IMV31 & IDP10 Transmitters, 144LVD & 244LVDBuoyancy Level Transmitter, Centeron WirelessLevel Products

The Invensys Foxboro measurements and instruments product line

With an installed base of field instrumentation in the biodiesel industry, Foxboro offers extensive

expertise to provide on-target measurement solutions. And as the leading supplier of instrumen-

tation for both dry and wet milling plants, Foxboro continues its tradition of Customer Driven

Innovation.

Founded in 1908 in Foxboro, Massachusetts, the company is credited with developing some of

the original devices for making on-line, real-time measurement possible. Hallmark Foxboro inno-

vations include pneumatic transmitters, the MagFlow magnetic flowmeter, pneumatic process gas

chromatographs, and flow through conductivity sensors. Today, the company offers instrumenta-

tion for almost every stage of biodiesel production. These complement systems, software, and

services to boost economic, safety, and environmental performance. The Foxboro measurement

product line includes following product groups:

• Foxboro pressure transmitters — Foxboro pressure transmitters combine field-proven, supe-

rior performance with application versatility, and rugged dependability. Available with a choice

of electronic modules, and mounting configurations – the product line includes the industry’smost extensive offerings of multirange and multivariable instruments, as well as absolute,

gauge, and differential pressure, and low power voltage output.

• Foxboro temperature transmitters — Built for long term stability, Foxboro temperature sen-

sors combine microprocessor-based technology to provide high reliability, maximum flexibility,

and unmatched intelligence. Products support FOUNDATION Fieldbus, 4-20 mA, HART, or

FoxCom Digital Output.

5



• Foxboro flow instrumentation — From vortex and magnetic, to mass flow and digital Coriolis,

Foxboro offers a full range of flow products for the accurate measurement of liquid, gas, or

steam. Designed to meet even the most demanding applications and accommodate diverse

communications protocols, instruments are available in 4-20 mA, HART, FoxCom and FOUNDA-

TION Fieldbus. The product line includes sanitary 3A authorized flow products for food and

beverage, dairy, pharmaceutical, and bio-tech applications.

• Foxboro electrochemical measurement technology — Foxboro electrochemical technologies

assist in analysis or control of pH, ORP, conductivity, resistivity, or dissolved oxygen. The line

includes a broad range of robust, accurate, high quality liquid analytical instrumentation for

industries including pharmaceutical, chemical, food and beverage, pulp and paper, metals, semi-

conductor, power generation, water and wastewater, and more.

• Foxboro level transmitters — Foxboro level transmitters are durable, highly accurate instru-

ments that provide premium performance. The product line includes advanced technologies to

meet the varying demands of biodiesel level measurement, including the ability to detect the

“liquid phase change” between the fuel and discarded materials. Foxboro multivariable technol-

ogy compensates for density changes caused by pressure & temperature variations to provide

accurate level measurement in either open (vented) or closed (pressurized) tanks, while

Foxboro buoyancy level & density transmitters withstand the temperatures involved within theprocess. Foxboro also offers wireless level products that provide a cost effective alternative for

selective applications.

In addition to its products, the following Foxboro offerings support efficient bio-diesel production:

• Next day shipment — In currently running plants, downtime can be expensive. In expansion

or new constructions, staying on plan, on budget requires having parts there when they are

needed. Sometimes long range planning is just not possible and a project could sit on hold

waiting for instrument shipment for a critical part of the facility. To eliminate the process some

instrument manufacturers are guaranteeing next day ship on certain transmitters.

• Training — Foxboro M&I offers Customer designed training classes to supply knowledge in

the areas of installation, configuration, operation, and trouble-shooting for all Products. These

classes can be done on-site or at the factory, whichever meets the Customers’ convenience.

• Customer 24/7 support — - Given the recent expansion of the biodiesel industry, a vendor that

understands the needs of producers as well as the technology can be a significant source of cost

savings in and of itself. Two innovations which would be particularly relevant to biodiesel pro-

ducers are next day shipment of user defined instruments and 24/7 technical support.

CONCLUSION

As the US increasingly seeks domestic fuel alternatives to foreign oil, biodiesel is a very promising

fuel alternative. The biodiesel fuel production process has evolved considerably to minimize theoriginal problems with viscosity. Today, biodiesel is an increasingly attractive, non-toxic, biodegrad-

able fossil fuel alternative that can be produced from a variety of renewable sources. The new

challenge is getting the cost of biodiesel production low enough that it can compete with gasoline,

which will come as biodiesel producers improve and automate production operations.

Process measurements and instrumentation can be very valuable to ensure that product is pro-

duced safely, cost-effectively, and according to ASTM specifications. In addition to a solid

price/performance value with instruments, biodiesel producers need ease of implementation, flex-

ibility, scalability, low maintenance and support. These needs are being met with recent advances



in instrumentation technology. Furthermore, with on going improvements in design and materials,

and methods of delivering technology and support, careful evaluation of instrumentation can

reduce both equipment and operating costs significantly, while improving overall biodiesel pro-

duction efficiency.

RESOURCES AND ACKNOWLEDGEMENTS

National Biodiesel Board

U S Department of Energy

Willie Nelson Biofuels

ATTRA

BTG

As. Ramadha, S Jayaraj, C. Muraleedharan. Use of vegetable oils as I.C. engine fuels—A review. Department of Mechanical Engineering, National Institute of Technology Calicut, Calicut REC P.O. Calicut 673601, India

www.biodieselnow.com

J. Van Gerpen, B. Shanks, and R. Pruszko; D. Clements; G. Knothe. Biodiesel Production Technology. NationalRenewable Energy Laboratory. August 2002-January 2004



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