Weekly Update 9_18_08

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8 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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To: Noa

From: Tom

Date: September 1
8
th, 2008

RE:
Berkshire Energy Laboratory

-

Weekly Update

Summary



I’m c
ontinuing work on the
research summary some excerpts from which are below.




Both sludge oils and FT products have too wide a product distribution
to be used as
transportation grade fuels and require varying amounts of secondary processing.



Research in sludge
-
to
-
diesel should be focused on improved controls and reactor designs for
better product selectivity.

Few (one?) production scale reactor desig
ns are available.



Fischer Tropsch
synthesis is

a
more
heavily researched topic most of which is also focused on
improving selectivity. Many opportunities for lab scale research.


Fuel Chemistry

The biomass and sludge conversion processes we’re investigat
ing synthesize fuels across a range of
grades and heating values. On the other hand, the
current
liquid

fossil
-
fuel infrastructure prefers a
much narrower ran
ge, particularly
for

transportation fuels.
Understanding the fundamental
differences between the

two on a molecular level
helps
illuminate some

potential research
opportunities.
The table below is a reference for associating carbon chain length with bio and fossil
fuel constituents.







For example gasoline is blend of straight chain hydrocarbons
in the C
5

to C
12

range with aromatics
and/or iso
-
octane plus impurities

such as sulfur
. Diesel is similar with
hydrocarbons in the range
C
1
3

to C
17

and higher amounts of s
oot. In comparison
current
fischer
-
tropsch
reactors

produces a
broad

distribution o
f hydrocarbons which
are

essentially free of impurities.
The purity is an
obvious benefit however t
o separate the fractions for transportation
and other uses
, the
FT ‘crude’
requires
additional
upgrading in a manner similar to fossil crude
.


The hydrocarb
on

fractions from sludge liquefaction are not as well characterized
in the literature
though we can pull some information from the Bio Petrol documents. They’ve
not yet

provide
d

a
chemical analysis of their diesel
but in the first business plan draft they

summarize the results
saying that the oil is 88% aliphatic (straight) chains in the C
3

to C
29

range.

Even fossil diesel has
trace amounts of low and high carbon number
hydrocarbons, however it seems likely that the
distribution is far too wide for transp
ortation grade. This is further supported by the fact that
they’ve not tested it in diesel engines and that the fuel heating value is only about
85% of the
heating value of #2 Heating Oil
.



Sludge to Diesel

Research

I’m
still
going back through my early

research notes on corporations and organizations involved in
sludge to diesel but it’s a fairly narrow field.
A company called
Castion out of Worcester, Mass has
licensed a sludge
-
to
-
oil technology originally developed by Battelle Laboratories but
seems

to have
altered it to produce a solid fuel.
Another company called Enersludge started up a sludge
-
to
-
oil
plant in 2002 but appears to have gone out of business due to the poor quality of the oil produced.
I’ve also been through some of the academic liter
ature on the RPI website and find very little on
the subject.

It may be stating the obvious to point out that research into improving the fuel grade produced
during hydrothermal liquefaction of the sludge
is warranted. Using the fuel for heating/drying ma
y
still result in a profitable business model but higher grade fuels would improve the economics.

I

was able to
identify
the reactor that Bio
-
Petrol is using (US Patent
US7329395B2
).








Sections 3 and 4 are the heating sections and section 5 is the

cooling section where the carbon
chain growth takes place. As only one possibility, additional controls could be added to that
section to reduce the product distribution

but there are obviously many other possibilities that
could be discovered in the lab
. More likely, it would serve as a jumping off point for new designs.



Wood to Gasoline and Diesel

Research

As indicated above FT synthesis also produces a wide range of hydrocarbons that require post
-
processing to separate the fractions. Fortunately th
ere is quite a bit more research
to draw on
than for sludge liquefaction. The main focus of that research is specifically in the area of improved
product selectivity. The difficulty is that although the process was developed in 1923, there is no
shared a
greement on the exact reaction mechanism (s) which makes modeling difficult. Still a few
things have been learned.

Broadly FT synthesis is carried out at
either
low tempe
rature (200


240C) on cobalt catalysts or
high

temperature (300
-
350C) on either iron

or cobalt catalyst.

The lower temperatures favor the
longer chain hydrocarbons and the
higher temperatures the shorter. T
here is significant cross over

however
. In addition to temperature
,

chain growth is effected by pressure, catalyst type, syngas
qua
lity, degree of catalyst fouling and the reactor design itself.

There are other considerations as
well including undesirable side products (ole
f
ins, alpha olefins) leaving the research opportunities
wide open.

Two completely separate routes for the synthe
sis of gasoline involve methanol which is easily
synthesized from syngas. The Mobil process uses a zeolite catalyst to produce a gasoline blend
directly. The methanol can also be converted to
dimethyl ether (DME) and then to gasoline. I’ll
have more on
these routes next week.