SAFETY
Safety Characteristics of Ethanol /
Automotive Petrol Mixtures
By E. BRANDES, D.-H. FROBESE and M. MITU*
ntroduction
Due to the promotion of renewable energy
sources, the demand for ethanol/automotive petrols is steadily increasing, whereby
the ethanol is produced from biomass. As
these ethanol/automotive petrols are flammable liquids, an explosion safety concept is
needed for their transport, use and storage as
well as for the operation of petrol stations.
However, as the safety characteristics of ethanol and automative petrol (which are the
basis of such concepts) clearly differ from
each other (see Table 1), the explosion safety
concepts do not necessarily have to be identical.
In Germany, the operation of petrol stations
[1] requires the knowledge of the following
safety characteristics:
– upper explosion point (UEP)
– maximum experimental safe gap (MESG)
– auto ignition temperature (AIT).
The transport classification into hazardous
classes, packing groups and the protection
of the tanks [2, 3] requires the knowledge of
the following safety characteristics:
– flash point (FP)
– maximum experimental safe gap (MESG)
– vapour pressure (p) at 50 °C and
– initial boiling point.
I
* Elisabeth Brandes, Dirk-Hans Frobese, PhysikalischTechnische Bundesanstalt (PTB), Braunschweig, Germany
(E-mail: [email protected]); Maria Mitu, Bukarest.
0179-3187/06/IV
© 2006 URBAN-VERLAG Hamburg/Wien GmbH
Table 2
Table 1
Safety characteristic data of ethanol and automotive petrol
Safety
characteristic
Ethanol
Automotive petrol
Fp
12 °C [6]
approx. – 40°C
Tz
400 °C [6]
280 °C–350°C
Temperature class
T2 [6]
T3–T2
LEL
3.1 vol% (59 g/m³)
(at 20 °C) [6]
0.6 Vol% –0.8 vol% (33 g/m³ to 36g/m³)
(at 20 °C)
UEL
27.7 vol% (532 g/m³)
(at 100 °C) [6]
7.0 Vol% –8.6 vol% (280 g/m³ to 330 g/m³)
(at 100 °C)
MESG
0.89 mm (at 30 °C) [6]
Explosion group
IIB (IIB1) [6]
IIA
UEP
44.0 °C [6]
(also in the case of very
low filling amounts)
< –4 °C
(also in the case of very low filling amounts)
p (at 37.8 °C)
15.9 kPa
45 kPa – 90 kPa [14]
commercially available:
summer petrol (ROZ95): 58 kPa – 60 kPa
winter petrol (ROZ95): 85 kPa – 90 kPa
For the classification according to the EC
Directives [4, 5] and for the material safety
data sheet knowledge of the following safety
characteristics is required:
– flash point (FP)
– lower explosion limit (LEL)
– upper explosion limit (UEL)
– auto ignition temperature (AIT)
– vapour pressure (p) at 20 °C and
– initial boiling point.
Auto ignition temperatures of exemplary mixtures of ethanol/
automotive petrol mixtures
Table 3
nvestigated Mixtures and
Determinations Carried Out
For exemplary mixtures of ethanol/automotive petrol mixtures which were prepared
by mixing respective amounts of volumes
(uncertainty of measurement 0.1 vol% absolute), the following safety characteristic data
were determined:
– auto ignition temperature (AIT)
– lower explosion limit (LEL)
I
LEL and UEL of exemplary mixtures of ethanol/automotive petrol
mixtures
Product
AIT
in °C
Temperature
class
Petrol ROZ 95 winter
320
T2
Petrol ROZ 95 summer
325
T2
Petrol ROZ 95 summer
0.7
33
7.6
280
E50 ROZ 95 summer
390
T2
E50 ROZ 95 summer
1.3
36
14.0
380
E60 ROZ 95 summer
395
T2
E60 ROZ 95 summer
1.5
40
15.8
420
E85 ROZ 95 summer
2.2
48
25.5
555
E75 ROZ 95 summer
390
E85 ROZ 95 summer
Ethanol
OIL GAS European Magazine 4/2006
400 [6]
T2
Product
Petrol ROZ 95 winter
LEL
(at 20 °C)
vol %
g/m³
0.8
32
UEL
(at 100 °C)
vol %
g/m³
8.1
310
E50 ROZ 95 winter
1.5
38
17.2
380
T2
E85 ROZ 95 winter
2.1
46
25.2
545
T2
Ethanol
3.1 [6]
59 [6]
27.7 [6]
532 [6]
OG 199
SAFETY
Table 4
Maximum experimental safe gaps at 50 °C for the vapour phase composition at 50 °C
of E50 ROZ 95 summer and E85 ROZ 95 summer
Product
Volume amount
ethanol
liquid phase
Volume amount
ethanol
vapour phase
0
0
E50 ROZ 95
summer
0.5
0.127
E85 ROZ 95
summer
0.85
1
ROZ 95
(summer quality)
Ethanol
Table 5
MESG
in mm
Explosion group
explosionFlame
proof
arresters
equipment
IIA
IIA
0.94
IIA
IIA
0.35
0.92
IIA
IIA
1
0.89 [6]
IIB
IIB1 [13]
ROZ 95 winter
UEP in °C
20%
–26.5
10%
–25.0
3%
1%
–22.0
–17.0
ROZ 95 summer
–13.5
–13.0
–11.0
–9.5
ROZ 95 summer 2
–13.5
–13.0
–12.0
–11.0
E50 ROZ 95 winter
–24.0
–20.0
–9.0
E50 ROZ 95 summer
–11.0
–10.0
–9.0
E60 ROZ 95 summer
–9.5
–9.0
–8.0
E65 ROZ 95 winter
–17.0
–15.5
–11.5
Ethanol
OG 200
–2.0
–6
3.5
44.0
– upper explosion limit (UEL)
– flash point (FP)
– maximum experimental safe gap (MESG)
– upper explosion point (UEP) as well as
– vapour pressure.
Fig. 1
–4.5
–3.0
–3.5
E85 ROZ 95 winter
E85 ROZ 95 summer
–5.0
–1.0
2
4.5
44.0
7.0
17
8.5
44.0
18.0
44.0
The automotive petrols used for this purpose
were unleaded petrols super grade (Eurosuper ROZ 95) which are commercially
available and have a Reid vapour pressure
between 580 mbar and 595 mbar for the
Dependence of the UEP on the filling amount of ethanol ROZ 95
mixtures
Flashpoints
The flashpoint was determined according to
EN ISO 3679 [11]. Up to an ethanol volume
amount of 95%, it lies below – 20 °C. If the
ethanol volume amount exceeds 98 %, it
lies, however, only between 0 °C and 12 °C.
–5.5
E70 ROZ 95 winter
E75 ROZ 95 summer
Auto ignition temperatures
The auto ignition temperatures were determined according to DIN 51794 [8] (= IEC
60079-4). From the values thus determined,
the temperature class was derived according
to EN 60079-0 [9] (Table 2).
Explosion limits
The lower and upper explosion limits were
determined according to EN 1839 [10]
method T (Table 3).
Upper explosion points of exemplary ethanol ROZ 95 mixtures
Product
Fill amount
summer quality (EN 228 [7]: climate zone
A) and 870 mbar to 900 mbar for the winter
quality (EN 228 [7]: climate zone E).
In the following E.. ROZ95 -- (e. g. E50
ROZ 95 winter) indicates the volume amount
of ethanol in the product (..) and the petrol
quality (--).
Fig.2
Maximum experimental safe gaps
The transport regulations refer in some aspects to 50 °C. Therefore, the maximum experimental safe gap was determined for the
vapour phase composition at 50 °C for the
mixtures E50 ROZ 95 summer und E85
ROZ 95 summer, the determination was carried out according to IEC 60079-1-1 [12]
(Table 4).
As the maximum experimental safe gap decreases with increasing temperature, this
value is on the safe side also for lower temperatures.
Dependence of the UEPs on the ethanol content of the investigated
ethanol ROZ 95 mixtures investigated
OIL GAS European Magazine 4/2006
SAFETY
Table 6
Reid vapour pressures and interpolated vapour pressures
Automotive petrol
Reid vapour
pressure
in mbar
Interpolated vapour
pressure at 37.8 °C
in mbar
599 [14]
580
ROZ 95 summer
ROZ 95 winter
887 [14]
Upper explosion points
As so far, no standardized European method
exists to determine the upper explosion
point, it was determined by means of PTB’s
own static method. Usually, the explosion
points of mixtures show a dependence on the
ratio liquid phase to vapour phase. The upper explosion point increases with decreasing fill amount. Therefore, the UEP was determined for the fill amounts 20%, 10%, 3%
and 1% (Table 5, Figs. 1 and 2).
Vapour pressures
The vapour pressure was determined by
means of PTB’s own static method and corrected with respect to the solved air according to EN 13016-1 [14]. The vapour pressures were determined over a temperature
range from –20 °C to +70 °C. The Reid
vapour pressure was determined by interpolation. The comparison of the interpolated
vapour pressures with the Reid vapour pressures given in the specification (Table 6)
shows that the PTB method is suited.
Table 7 summarizes the interpolated vapour
pressures at 20 °C, 37.8 °C and 50 °C of the
investigated ethanol/automotive petrol mixtures. The values are rounded to 0.5 kPa
(5 mbar).
onsequences for the Explosion
Protection Concepts
Operation of petrol stations
Underground storage tanks: According to
TRbF 40 No. 5.2 paras. 3 and 4 [1], using
flame arresters with underground storage
C
Table 8
Interpolated vapour pressures at 20 °C, 37.8 °C und 50 °C of the
investigated ethanol/automotive petrol mixtures
p20
in kPa
p37.8
in kPa
p50
in kPa
ROZ 95 winter
49.0
87.5
110.0
ROZ 95 summer
33.0
58.0
81.0
E50 ROZ 95 summer
23.0
52.5
79.5
E60 ROZ 95 summer
27.0
52.0
76.0
E75 ROZ 95 summer
tanks is not necesE85 ROZ 95 summer
sary as long as the
ethanol amount in
E50 ROZ 95 winter
the mixture is below
E85 ROZ 95 winter
60 vol%.
Ethanol
If
the
ethanol
amount lies between
60 vol% and 85 vol%, the underground storage tanks have to be provided with flame arresters of type IIA (EN 12874 [13]). If the
ethanol amount is higher than 85 vol%,
flame arresters of type IIB1 are required.
The limiting valve transmitter, the liquid
level indicator, the vapour recovery pump
and the dispensers have to comply with temperature class T2. Usual constructions fulfilling the requirements of temperature class
T3 do not need to be changed as temperature
class T3 equipment covers T2.
If storage tanks for automotive petrols and
storage tanks for ethanol/automotive petrols
are ventilated at petrol stations via a joint
venting line, all tanks of the system have –
according to TRbF 40 No. 3.4.1 paras. 10
and 11 [1] – to be fitted with flame arresters
if the ethanol amount exceeds 60 vol%.
21.5
44.0
62.5
15.0
32.0
47.5
36.0
62.5
90.0
20.0
37.0
53.5
5.8
15.9
29.4
875
The respective vapour composition was determined by gas chromatography.
Table 7
Product
Dispensers: For ethanol amounts up to 85
vol% the vapour recovery system and the respective flame arrester have to comply with
explosion group IIA. For higher amounts of
ethanol equipment certified for explosion
group IIB1 is required.
Ethanol/automotive petrol mixtures with an
ethanol amount ≤ 60 vol% may have a UEP
of – or above – ambient temperature. In that
case, the vapour/air mixture inside the tank
is no longer too rich at ambient temperature.
If it is possible to prevent – by taking suitable measures on the vehicle – a charging of
Comparison of the explosion safety concepts of automotive petrol and mixtures of
automotive petrol and ethanol
Legislation
Alteration compared to automotive petrol
Operation of petrol stations
→ Underground storage tanks
– flame arresters (Germany)
– temperature class
necessary for ethanol amounts of 60 vol% upwards
identical
→ Vapour recovery while refuelling
and filling of the storage tanks
change of the explosion group for ethanol amounts
higher than 85 vol%
Transport
→ Classification, UN-number
UN-number of its own
→ Equipment of the tanks
– flame arresters, pressure resistance
– endurance burning arresting device
identical
additional test according to EN 12874
Use, storage etc.
→ R12 R11
depending on initial boiling point
OIL GAS European Magazine 4/2006
the operator, the hold-open latch of the nozzle can be retained during refuelling.
Classification for transport,
tank equipment
For the classification according to the transport regulations, primarily the initial boiling
point is decisive.
The Sub-Committee of Experts on Dangerous Goods decided at its 29th session to assign to the ethanol/petrol mixtures a UN
number of their own.
To transport ethanol/petrol mixtures having
ethanol amounts up to 85 vol%, the tanks
must be equipped with flame arresters of
type IIA if they are not of an explosion-pressure-shock-resistant design. If the ethanol
amount is higher than 85 vol%, flame arresters of type IIB1 are required.
If the tanks are equipped with endurance
burning arresting devices, these have to fulfil the requirements of EN 12874 [13].
Classification according to EU regulations
For classification according to the EU regulations the initial boiling point and the
flashpoint are decisive. If the initial boiling
point is below 35 °C and the flashpoint below 0 °C, the mixtures have to be classified
as R 12 ‘extremely flammable’. If the initial
boiling point is equal to or higher than 35 °C
and the flashpoint is between 0 °C and
21 °C, the mixtures have to be classified as
R 11 ‘highly flammable’. To this classification, also the permitted quantities of the
SEVESO II Directive are bound if the exception for automotive fuels cannot be transferred to ethanol-containing mixtures.
onclusion
Table 8 summarizes the results and alterations concerning mixtures of automotive petrol and ethanol compared to automotive petrol.
C
Literature
[1] TRbF 40 “Tankstellen”. BArbBl. 6/2002, S. 63.
[2] RID: Regulations concerning the international
carriage of dangerous goods by rail
(Internationale Ordnung für die Beförderung
gefährlicher Güter mit der Eisenbahn).
ADR: European Agreement concerning the in-
OG 201
SAFETY
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
ternational carriage of dangerous goods by road
(ADR) and protocol of signature (Europäisches
Übereinkommen über die internationale
Beförderung gefährlicher Güter auf der Straße).
Verordnung über die Beförderung gefährlicher
Güter auf dem Rhein – ADNR –,
Zentralkomission für die Rheinschifffahrt, 2005.
Directive 67/548 EWG including revisions.
Seveso II Directive 96/82/EC.
®
CHEMSAFE Data base for rated safety characteristics, edition 2004, edited by BAM, PTB,
DECHEMA
(http://www.dechema.de/Chemsafe.html).
DIN EN 228, Ausgabe:2004-03 “Automotive fuels – unleaded petrol – requirements and test
methods”
DIN 51794, Ausgabe:2003-05 “Prüfung von
Mineralölkohlenwasserstoffen – Bestimmung
der Zündtemperatur”.
DIN EN 60079-0, Ausgabe:2004-12 “Electrical
apparatus doe explosive gas atmospheres –
Part 0: General requirements”.
DIN EN 1839, Ausgabe:2004-01 “Determination
of explosion limits of gases and vapours”.
DIN EN ISO 3679, Ausgabe:2004-07 “Determination of flash point – Rapid equilibrium closed
cup method”.
IEC 60079-1-1, 2002-07-05 “Electrical apparatus for explosive gas atmospheres – Part 1-1:
Flameproof enclosures d – Method of test for ascertainment of maximum experimental safe
gap”.
[13] DIN EN 12874, Ausgabe:2001-04 “Flame arresters – Performance requirements, test methods
and limits for use”.
[14] DIN EN 13016-1, Ausgabe:2000-12 “Liquid petroleum products – vapour pressure – Determination of air saturated vapour pressure (ASVP)”.
Dirk-Hans Frobese studied
mechanical engineering at TU
Braunschweig. He received his
Ph.D. in 1988. Since 1988 he is
scientist at PTB.
Elisabeth Brandes studied
chemistry at TU Braunschweig
and received her Ph.D. in 1982.
Since 1982 she is scientist at
PTB, the german national metrology institute providing scientific and technical services.
Since 1996 she is heading the
WG “Safety Characteristics”.
Maria Mitu studied chemistry
at Bukarest University. Since
1995 she worked as scientist
at LACECA S.A. – Centrul de
Cercetari pentru Calitatea si
Protectia Mediului, Bukarest
and then as senior scientist at
Institutul de Chimie Fizica
“I.G.Murgulescu” al Academiei Romane, Bukarest
and guest scientist at PTB. She received her Ph.D. in
2003.
Flame Arresters for: - Petrol
- E 85
- D 20
FLAMMER
Flammer - Flame Arresters
Inline and end of line flame arresters
according to EN 12874 and 94/9 EC (ATEX) for:
Petrol Stations
Vapour Recovery Stage IB
Vapour Recovery Stage II
Ethanol-Petrol Blends – E 85
Ethanol-Diesel Blends – D 20
For Storage, Analyse and Transport
of Flammable Vapours and Gases
..
..
..
Flammer GmbH
Strombergstr. 73
D - 74389 Cleebronn
Phone: + 49 (0) 7135 / 96 04 58
Fax:
+ 49 (0) 7135 / 96 04 59
[email protected]
www.flammergmbh.com
ATEX . EN 12874 . Apagallamas . 94/9 EC . Flammensperren . Flame Arresters . Arrête-flammes . Arrestatori
OG 202
OIL GAS European Magazine 4/2006