# Presentation: 707398

## Biodiesel Properties of Concern

*C.R. Krishna, Brookhaven National Lab*
*John Batey, Energy Research Center Inc*
*BIODIESEL WORKSHOP 2008*
*May 2, 2008*

## Biodiesel properties of Concern

- Currently there is a fuel standard for biodiesel
- ASTM D 6751 which is undergoing some changes
- The standard applies irrespective of the source material, that is the starting oil or fat
- At present, most biodiesel in the U S is made from soy oil
- We have found that there are differences in two properties between biodiesels made from different source materials
- These properties are not presently specified in the standard
- They are important to the use of biodiesel in heating
- The two  relate to cold flow and flame Sensing in Boilers

## Biodiesel properties of Concern-Cold Flow

- Cold Flow Properties
- Usually defined by cloud point or pour point
- Temperature at which some of the components in the fuel start to freeze or when it cannot be poured
- Typical cloud point temperature for heating oil is well below 00 C or 320 F
- The cloud point temperature for biodiesel made to ASTM 6751 depends on the source material and can be well above 320 F

## Biodiesel properties of Concern

## Biodiesel properties of Concern

## Biodiesel properties of Concern

## Biodiesel properties of Concern-Cold Flow

- Conclusions from Cold Flow Properties of different biodiesels
- The source material affects strongly the cloud points
- Even small amounts in blends can affect transport, storage and use in boilers
- Hence, it may not be enough to specify just ASTM 6751 for buying biodiesel blends
- We acknowledge the help of summer students, Christopher Brown and Kaitlin Thomassen in making measurements
- See Publication in Ind. Eng. Chem. Res. 2007, 46, 8846-8851 for details

## Biodiesel properties of Concern  - Flame Sensing

-     Project to evaluate how different biodiesels and their blends with heating oil impact the cad cell system operation
- The cad cell senses the presence or absence of flame
- Based on this, the control system keeps the burner on or turns it off
- It had been observed that oil burners firing biodiesel may shut off even when the flame was stable and this was traced to the cad cell control system
- Phase I tests found high cad cell resistance for higher percentages of Biodiesel in #2 oil and for higher  excess burner air settings.
- Phase II test found cad cell resistance varies with burner manufacturer
- Project was funded by the National Biodiesel Board

##  Biodiesel properties of Concern – Cad cells

## Biodiesel properties of Concern – Cad cells

- _Key Points_:
-  The cad cell resistance at high burner excess air varies
-    with the type of biofuel used.
-   Conventional oil burner cad cells that sense the
-    presence of a flame cannot be used for high blends
-    ratios of many biofuels.
-   Soy biofuels produce the highest resistances, followed
-    by Canola Oil, Tallow3 and Soy/ Tallow blends, and
-    Yellow Grease.
-  These finding are also important because they can be
-   used as a new test method for identifying the type of
-   biofuel being used.

## Biodiesel properties of Concern

- Biodiesels made to ASTM 6751 from different sources were tested
- Two different burners in two residential boilers were tested
- The resistance of the cad cell is used by the control
- Resistance higher than set value triggers burner shut   down
- Cad Cell resistances while the flame is present of 1500 to 1600 Ohms is usually desired
- So, cad cell resistance was measured during burner operation on different blends and varying burner excess air settings

## Changes in Cad Cell Resistance with Burner Excess Air

**Changes in Cad Cell Resistance with Burner Excess Air**

## Biodiesel properties of Concern

## Conclusions  -  Flame Sensing and Control

- A new field test can be developed using cad cell output to determine the type of biofuel in a sample
- The Cad Cell resistance varies with the type of biofuel used, its blend ratio in heating oil, and the excess air setting of the burner
- Soy-based biodiesel percentages may be limited to low blend ratios and low excess air settings, or alternate flame sensing devices may be needed
- Burner design has an important impact on cad cell resistances and compatibility of conventional cad cell flame sensors with biodiesel blends
- More research is needed to fully develop these relationships and determine solutions for the use biofuel blends.