lunes, 8 de octubre de 2012

Dangerous Goods Classification

Classifying goods for transport is not the same as establishing its customs clearance number, as they have different purposes. This concept is still deeply rooted in most people involved in foreign trade transactions.

Customs regulations have almost no relationship with safety conditions in the transport of dangerous goods. And one of the most important issues to determine such safety conditions is the allocation of a UN number and a proper shipping name, as well as the determination of the relevant type of risk and, if applicable, the packaging group (which indicates how dangerous the relevant goods may be). This is classification for transport. A mistake in the classification for transport may entail mistakes in the determination of conditions for transport and, obviously, it may also have very serious consequences if those conditions trigger an accident.

A UN Number and a proper shipping name are not good for customs clearance. Similarly, a clearance customs number is not enough to determine if certain goods are dangerous for transport.

The main responsible for classifying a product for transport is the shipper, who defines if the goods are dangerous or not for transport. If the goods to be transported are dangerous, shipper must prepare and sign a Shipper's Declaration stating that the contents of the shipment have been duly classified, packaged, marked and labeled, and that all requirements under transport regulations have been met.

In fact, a customs officer or agent may represent the Shipper and act as such when the goods are sent and he/she may sign the Declaration, with the same effects stated above. In fact, this situation is expressly contemplated in the Dangerous Goods Regulations of the International Air Transport Association (IATA), which further states that the individual signing on behalf of the shipper must be duly trained regarding this issue. Thus, IATA implemented training through well-known schools or IATA Schools, which are endorsed by such institution.

Meanwhile, regarding sea transport, training of land staff is mandatory since January 2010, though there is no certification system for courses on sea transport of dangerous goods. This new requirement was imposed by the International Maritime Organization after the fire in vessel Hyundai Fortune in March 2006, allegedly due to dangerous cargo not declared, i.e., cargo classified as not dangerous by shipper.

We always highlight the importance of a proper classification of goods for their transport.

Customs clearance will be correct if a customs clearance number is assigned which truly reflects the goods to be exported. However, this does not ensure that the goods will be safe for transportation, even less, in the case of dangerous goods.
Translated by Camila Rufino, accredited translator

domingo, 20 de mayo de 2012

Hydrofluoric Acid Alkylation

 In the past, it was thought that almost no chemical compound caused alkanes to react. These hydrocarbons were even called paraffins, from “parum affinis” or “little affinity.”

Thereafter, it was discovered that, in fact, their reactivity depends on the reagents used. When in contact with an alkene (which is also a hydrocarbon, but which may be called “olefin,” with carbon-to-carbon double bonds, unlike alkanes, which have simple bonds), an interesting addition reaction of the alkane to the alkene, a combination of two molecules to create a single one, may occur.

Addition reactions need multiple bond molecules, such as alkenes (C=C double bonds). This allows for the formation of a stable carbocation, an essential step for the reaction to develop. In this case, the carbocation is the alkene to which a proton contributed by a strong acid is transferred. Protons are electron deficient and they have affinity to those electrons of one of the two C=C bonds, specifically, the π bond electrons, which bond is the most labile one. Thus, one of the double bond carbons losses the π electrons to the incoming proton, which results in a positive charge density of the double bond carbons due to the resulting electronic deficiency and in the formation of an electron-avid carbocation.
Thereafter, the carbocation will attack the double bond of another olefin and will take the relevant π bond electrons, thus, creating a bigger carbocation out of which used to be two olefins. This second carbocation will take a hydrogen atom from another alkane together with its electron pair (i.e., with negative charge, a hydride ion), thus neutralizing the positive charge density and ending its reaction. However, this step results in the formation of a new carbocation that will repeat the process (1).
In brief, olefins behave as a weak base that may accept a proton by giving electrons from the π orbitals originally used in the double C=C bond, which finally breaks.
All this leads us to a specific addition reaction between hydrocarbons: alkylation.

From Theory to Practice

In practice, it is important to make a paraffin, such as isobutane, react with a light olefin, such as propylene or butylene. However, they are not the only characters of this story. We stated above that the carbocation was the essential intermediary in the alkylation reaction, and that this reaction is caused by the presence of a strong acid which allows for the formation of that carbocation by giving it positively charged protons which seek to attract the alkene double bond electrons.

The strong acids generally used to cause the reaction are sulfuric acid and hydrofluoric acid.

This reaction has been applied to several industrial processes. One of the most valuable applications has been in refineries, for the manufacturing of high-octane hydrocarbons based on low molecular weight olefins and paraffins. In specialized literature these hydrocarbons are called “alkylates,” which are added to fuel for octane enhancement.

Alkylate production was first developed during the Second World War in 1940, searching for high-octane airplane fuels and petrochemical charges to manufacture explosives and synthetic rubber (2). That same year, not only alkylation was developed, but also paraffins that would become part of the reaction were manufactured. This process was called isomerization.

On the other hand, olefins do not result from isomerization, but from a previous catalytic cracking unit. It may be concluded that the purposes of alkylation and catalytic cracking are opposite: while catalytic cracking aims at reducing the size of long hydrocarbons, some olefins produced in this process, such as propylene and butadiene, are used in alkylation and added to isobutane (a paraffin or alkane) to form an alkylate, a larger branched hydrocarbon.

Alkylates have a high research octane number (RON) ranging between 92 and 96, which gives them value as antiknock additives for gasoline. They also have low steam pressure and they do not generate byproducts such as olefins or alkenes or aromatic substances (such as benzene). Due to these features and the fact that light olefins and isobutene come from light cuts of hydrocarbons and do not have a significant commercial value, the alkylation process is necessary to increase the size of hydrocarbons in refineries that have a catalytic cracking unit to reduce it.

Only Flammability Hazard?

Certainly, upon evaluating the hazads inherent in alkylate production, the flammability hazards will be taken into account due to the great amount of hydrocarbons involved in the process. A typical situation would be a fire in a fuel deposit or an alkylate deposit. However, it is important to consider hazards not related to flammability.

We have already highlighted that the hydrocarbon alkylation reaction implies the use of a strong acid able to give away protons to break the alkene or olefin double bond so as to then allow an alkane enter in its structure.  Sulfuric acid and hydrofluoric acid are good for this purpose.

The first hazard to be taken into account with many acids is corrosivity, which entails an action that may destroy not only human tissue, but also materials, for instance pipes or tanks. Corrosive action on the facilities may cause the release of those substances.

This aspect may be controlled using tools such as corrosion rate prediction (such rates closely depend on the process temperatures) and periodic audits (10).

Any corrosive substance may kill an individual when in contact with him/her if such contact is significant. However, a corrosive substance is not the same as a toxic substance.

Corrosivity refers to the capacity of a substance to cause an irreversible damage to skin, such as a visible necrosis, from the epidermis to the dermis, after an application of up to 4 hours. A skin corrosion reaction shows injuries to the skin, bleeding, bleeding sores and after a 14-day observation period, complete areas of alopecia and scars (4).

On the other hand, the acute toxicity of a product refers to the adverse effects experienced after the oral or skin administration of a single dose of the substance, or as a result of inhalation throughout 4 hours (4). In the case of acute toxicity, the adverse effect to be observed is the death of the affected individual. Therefore, the acute toxicity values are usually stated as Lethal Dose 50 (LD50) when the toxic substance enters the body orally or through the skin, or Lethal Concentration 50; (LC50) when the toxic substance enters by inhalation.
Hydrofluoric acid involves both types of hazards: corrosivity, thus, being able to destroy the skin and some materials, and toxicity, being able to cause the death of an individual with a very low dose.

Burns with hydrofluoric acid are more serious than those caused by sulfuric acid, and they may not be immediately visible or painful, as the first symptoms may appear 8 hours after the exposure. Hydrofluoric acid penetrates the skin quickly destroying all deep tissues, including bones.

Hydrofluoric acid may also cause serious burns in the eyes and the respiratory tract, given that it is extremely volatile and, in the event of a leakage, as gas is denser than air, it remains at a low- height level, and it is incompatible with many compounds, such as glass, rubber, leather, ammonia, ethylenediamine, calcium oxychloride, etc. In contact with metals, it may release hydrogen, an extremely flammable gas, and in contact with water, it may generate a strong exothermic reaction (5), though a water supply system may be used to respond to a leakage as both substances are miscible.

Accidents involving hydrofluoric acid (HF) leakages at a large scale are not very common.  In the accident occurred on July 19, 2009 at CITGO's refinery in Texas, USA, there was a HF release due to a previous loss of flammable gaseous hydrocarbon, which accumulated in areas where there was hydrofluoric acid and caused a fire which affected the pipes that contained the acid and released it.  In total, 21 tons of HF were released, 2 of which evaporated in the atmosphere, and could not be recovered, though the facilities had a water mitigation system (11).

Some Comparisons

It is reasonable to think that, compared with an alkylation process with sulfuric acid, the process that uses hydrofluoric acid has more safety and environmental disadvantages.

We have already discussed that hydrofluoric acid may cause burns that are more serious than those caused by sulfuric acid. However, it is also important to consider that the former is much more volatile and that its vapors are corrosive to the respiratory tract (5). More precautions should be taken in the case of hydrofluoric acid leakages, considering the volatility of such substance. This factor is very important when evaluating the impact of a possible accident with leakage in a populated area. 
One of the main reasons why this process has been so successful during the last 50 years has been the economic reason. Processes involving hydrofluoric acid (HF) have the following advantages(5)(9):
  • Units with HF do not require such a strict temperature control as sulfuric acid, which requires a strict control as it involves an exothermic reaction.
  • The capacity of the HF to catalyze the alkylation reaction is larger than that of the sulfuric acid.  
  • Hydrofluoric acid is more expensive than sulfuric acid, but it may be used in much smaller amounts. In fact, HF consumption may be about 100 times less.
  • HF may be regenerated at the user's facilities without any need to transport it to third parties' facilities, which is not the case in processes involving sulfuric acid.
In Argentina, for instance, alkylation units with hydrofluoric acid are used at the refineries of Shell CAPSA (Dock Sud) and Repsol-YPF (La Plata).

On the other hand, two factors considerably favored the use and production of alkylates during the last ten years:
  • The recent prohibition to use the most popular antiknock additive, methyl t-butyl ether (MTBE) in most of the States of the USA in the last 20 years, as a result of the 1990 Clean Air Act Amendments (CAAA90) in that country (6).
  • The most used substitute for the MTBE has been ethanol, but when ethanol is mixed with gasoline, the mixture is more volatile (i.e., it has more Reid Vapor Pressure, an indirect measure of the actual vapor pressure of the mixture) which makes it increasingly difficult to comply with the emission standards issued by the authorities in the different countries, where there is a significant trend to reduce the RVP value in commercial gasoline (7).
 Alkylates do not have such complications and have had no obstacle to gain their market share. Meanwhile, the alkylation technology is still searching for an increasingly safer production.
(1)    Química Orgánica (Organic Chemistry) - Chapter 3.18. Robert Morrison and Robert Boyd.  Addison – Wesley Iberoamericana. 5th ed. 1990.

(2)    Encyclopedia of Occupational Health and Safety. Chapter 78 – Chemical Industries/Oil and Natural Gas – Oil Refinery Process. International Labour Organization, 4th ed. 1998. Editor-in-Chief: Jeanne Mager Stellman, PhD. Chapter Director: Richard Graus, PE, CSP.
(3)    Energy and Environmental Profile of the US Petroleum Refining Industry – US Department of Energy – Office of Industrial Technologies. 1998.

(4)    Globally Harmonized System of Classification and Labeling of Chemicals (GHS). Third Revised Edition – Part 3: Health Hazards. United Nations, 2009.
(5)    Material Safety Sheet of Hydrofluoric Acid, prepared by Mallinkrodt Baker Inc, USA.

(6)    Status and Impact of State MTBE Bans. US Energy Information Administration.

(7)    Determination of Environmental Contamination due to the Evaporation Percentage of Colombian Gasoline – Final Report.  Corporación para el Desarrollo Industrial de la Biotecnología y Producción Limpia – CORPODIB. March 2004.


(9)    Advances in Hydrofluoric (HF) Acid Catalyzed Alkylation. J. Frank Himes, Robert L. Mehlberg PhD-ChE, Franz-Marcus Nowak. UOP, LLC. Document presented in 2003 at the annual meeting of the National Petrochemical & Refiners Association, USA.
(10)The American Petroleum Institute (API), in its Recommended Practice 751, Safe Operation of Hydrofluoric Acid Alkylation Units, recommends that these safety audits be performed on a quarterly basis.
(11)“Urgent Recommendation" of the US Chemical Safety Board (CSB) to CITGO, issued on December 9, 2009. The investigation of this accident is still open, although, for the time being, the investigation agency has recommended the performance of an audit plan according to API Rule RP 751, and the enhancement of the spill response system with water, given that the estimated capacity to absorb the spilled product was of about 90 %.

Article translated by Camila Rufino, accredited translator.

miércoles, 29 de febrero de 2012

The Andrews’s Critical Point

Thomas Andrews was born in Belfast, Northern Ireland, on December 19th, 1813. He was a chemist; physicist and physician who studied phase transitions in the 1860's.

Andrews studied chemistry and physics in Great Britain and Paris. In 1835 he received his medical degree at the University of Edinburgh. After developing his career in medicine in Belfast and teaching in chemistry at Belfast Royal Academy for ten years, in 1845 he was Vice President of Northern College in that city, contributing to its reorganization and creating the Queens College in 1849, where he was professor of chemistry until the end of his career in 1879 at age 66 (1).
In 1869, he discovered the necessary conditions for the liquefaction of gases by studying the relationship between the pressure, temperature and volume of carbon dioxide, by measuring the pressures at different volumes at constant temperature. When repeating these measurements at different temperatures he plotted the isotherms for carbon dioxide (2) and established the critical constants, which then enabled the development of liquefaction techniques for gasses which until that moment could not be taken to the liquid state. Oxygen, hydrogen, nitrogen and helium were in this group, the so called “stable gases”, during mid-nineteenth century.

The critical constants are the critical temperature, the critical pressure and the critical volume (some authors as D. Fernandez and Fernandez Prini (3) prefer to refer to the critical density, which is inversely proportional to the critical volume). Considering the isotherm corresponding to the critical temperature, critical pressure and critical volume converge at the critical point.

By increasing the pressure (and decreasing the volume) in a system containing carbon dioxide at a constant temperature which is lower than the critical temperature, Andrews noted that to a certain volume, the gas phase abruptly starts to coexist with a liquid phase. This occurs during a range of volumes, with constant pressure throughout the transition phase. This pressure is the vapor pressure of the liquid.
At the critical point, the properties of liquid and gas phases are indistinguishable. It cannot be stated that there is a liquid phase and a gaseous phase.
At temperatures above the critical temperature, Andrews observed a behavior consistent with Boyle's law, which is valid for ideal gases: P1V1 = P2V2, temperature and number of moles of gas constant. He found that at temperatures higher than the critical temperature it is impossible to liquefy a gas.

Why at lower temperatures the behavior of the gas deviates from Boyle's law? Because when the temperature drops, interactions between gas molecules, especially the attraction, starts to be more important, depending on the distance between them, and showing a real gas behavior.
By increasing the system pressure (T always constant and less than the critical T), the molecules come to be at a distance in which the intermolecular attraction force is maximum, joining each otherand forming the liquid phase. If the pressure increases further, then the repulsive intermolecular forces start to prevail.

These studies have been the background to Johannes van der Waals in 1873, who proposed the equation of state for real gases in his doctoral thesis ("Over the Continuïteit van den Gas - in Vloeistoftoestand" or "On the Continuity of liquid-gas state")
Considering the isotherms obtained empirically by Andrews, van der Waals tried to find an explanation for the experiments that revealed the existence of "critical temperatures" of the gases. He could finally establish a relationship between pressure, volume and temperature of gases and liquids taking into account the molecular volume and intermolecular attractive forces, the "Van der Waals forces" (4).

Indeed, the "new" equation of state, which took into account the repulsive and attractive forces between molecules, were consistent with the isotherms observed by Andrews.
P=RT/(Vm-b) – aVm2

Where P is pressure, R is the constant of gases (8.3144 J/Kmol), T is the temperature in Kelvin, Vm is the molar volume of gas. a and b are the Van der Waals constants: a, related to the attractive forces, and b related to the molecular volume, and hence the repulsive forces imposed at high pressures. At very high temperatures, the components of the equation for these constants (or rather the corresponding intermolecular forces) become negligible compared to the component dominated by T, leaving as a result the old equation of state for ideal gases, and assuming that also are negligible interactions between molecules.


Without going into detail on the limitations of the equation of state for real gases formulated by van der Waals, we can say that his studies made it possible to calculate the conditions for the liquefaction of gases, which opened the door to modern techniques of cooling (5).

The critical point and the hazardous substances
Almost one hundred and forty years after the experiments of Andrews, the critical point remains.

At a first sight, the critical constants don’t seem to have much importance in the world of hazardous substances. Is it important for safety to know at what temperature a gas can be liquefied if it is compressed?
I have never seen a product safety sheet (MSDS) containing the critical constants of a liquid or gas. These parameters are not even mentioned in any regulation relating to MSDS authoring. Taking this into account we can assume that in fact the critical point is not so important after all.

Wrong. The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) establishes the criteria for classification of gases under pressure according to the critical temperature. It identifies four groups of gases:

Compressed gases: those with critical temperature less than or equal to -50 °C.
Liquefied gases: at high pressure, those with critical temperature between -50 °C to 65 °C, and low pressure, those having a critical temperature higher than 65 °C.
Refrigerated liquefied gases: partially liquefied gases when they are at low temperatures.
·      Dissolved gases in a liquid phase.

The critical temperature defines the type of gas, if it is compressed or liquefied, at high or low pressure. In the definition of this temperature, the GHS only refers to pure gases (6).
However, it is necessary to note that GHS states these groups are only valid for gases under pressure, with risks of explosion by heating or cryogenic burns or injuries. GHS consider these gases in Chapter 2.5, separately from gases presenting other hazards, such as oxidizing gases (GHS Chapter 2.4), gases which are flammable and chemically unstable (GHS Chapter 2.2), and toxic gases (GHS Chapter 3.1) thus the concept of critical temperature is limited only to the pressurized gases.

At the end of Chapter 2.5, the GHS contains an informative paragraph regarding the classification of gases under pressure (GHS Chapter 2.5, paragraph According to this paragraph, It is necessary to know three characteristics of the substance in order to classify it as a gas:

• The vapor pressure at 50 °C.
• The physical state at 20 ° C at standard pressure.

The critical temperature.

The GHS does not indicate further details on these parameters, or why they should be considered, or what vapor pressure is at 50 °C, or what does it mean with “physical state at 20 ° C and standard pressure”. Regarding the latter, I suppose I would have to be completely gaseous. But perhaps it could include both gaseous and liquid phases present in the system in equilibrium, so as to consider the substance as a gas for the purposes of classification risk according to the GHS.
GHS only indicates that the information can be found in the literature, calculated or determined by tests. For pure gases, it indicates that the majority are classified on the Recommendations on the Transport of Dangerous Goods of the United Nations. This is true. Almost all pure gases are identified in the list of dangerous goods of Chapter 3 of the Recommendations, with a UN number assigned along with a proper shipping name and the risk class.
What happens with gas mixtures? The GHS is not conclusive on this issue, and it indicates that "most of mixtures require additional calculations that can be very complex." This statement is special for the determination of the critical temperature.

To take one example, which may not have much to do with "gases under pressure" referred to the GHS, but can illustrate the complexity of the issue, F. Escobar suggests a procedure for determining the critical properties of hydrocarbon mixtures (7). The critical temperature of each component is taken and then they are multiplied by the corresponding volume fraction. The sum of all is the critical temperature of the mixture. This procedure would only be valid when the components are hydrocarbons lighter than heptanes.

Trying to find an answer for the other two aspects mentioned in the GHS (vapor pressure at 50 °C, and physical state at 20 °C and standard pressure), this can be found in the UN Recommendations, or Orange Book.
The Orange Book of the United Nations provides the same four categories of gases according to their physical state, but unlike the GHS, this classification is valid for all gases, regardless of the risk involved. On the other hand, although there is no definition of the critical temperature, there is a definition of "gas".

For the Orange Book, gases are substances with a vapor pressure exceeding 300 kPa at 50 °C, or gases which are completely gaseous at standard pressure of 101.3 kPa. Even though these concepts are applicable to all gases according the UN Recommendations for the Transport of Dangerous Goods, they are consistent with the GHS indications valid only for the "gases under pressure".

Once we know whether a substance can be defined as a gas or liquid (a typical case where the situation is not so obvious could be a mixture of light hydrocarbons), if it is a gas, then the critical temperature may help making the classification according to their physical state.
If we consider the Orange Book, the categories will define the conditions of transport, for instance, Packing Instruction P200.

The first impression when I studied the critical parameters when I began my studies was that these concepts are of little practical application. Then I realized that the legacy of Andrews was much more important than I imagined. His contribution to the history of science, which enabled the subsequent liquefaction of stable gases, which led to the studies of Van der Waals and his equation of state and deserved Nobel Prize, and which enabled the development of applications such as refrigeration or exploitation of hydrocarbons, also left consequences in the world of chemical safety.

(1) "Thomas Andrews." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. 18 Feb. 2012.

(2) Elements of Physical Chemistry, Samuel Glasstone, Surgical Medical Publishing, New York, 1946.

(3) "Fluídos supercríticos", Diego Fernandez and Roberto Fernandez Prini, Science Today, Volume 8, No. 43, November-December 1997.

(4) "J. D. van der Waals - Biography". February 2012

(5) "Nobel Prize in Physics 1910 - Presentation Speech". 20 Jan 2012

(6) "Critical temperature is the temperature above which a pure gas can be liquefied, regardless of the degree of compression," according Chapter 2.5 "Gas Pressure", GHS United Nations, Edition 4th, 2011.
(7) " Fundamentos de Ingeniería de Yacimientos ", Freddy Humberto Escobar Macualo, PhD, Surcolombiana University Editorial, First Edition.

(8) Recommendations on the Transport of Dangerous Goods, United Nations, Edition 17th.

lunes, 27 de febrero de 2012

El Punto Crítico de Andrews

Thomas Andrews nació en Belfast, Irlanda del Norte, el 19 de diciembre de 1813. Fue un químico, físico y médico que estudió las transiciones de fase en la década de 1860.

Andrews llevó a cabo sus estudios de química y física en Gran Bretania y en París. En 1835 recibió su título de Médico en la Universidad de Edimburgo. Luego de comenzar su carrera profesional en medicina en Belfast y de ejercer la docencia en química en la Academia Real de Belfast durante diez años, en 1845 fue Vicepresidente del Northern College de esa ciudad, contribuyendo a su reorganización y dando forma al Queens College en 1849, donde fue profesor de química hasta el final de su carrera en 1879, a los 66 años (1).

En 1869 descubrió las condiciones indispensables para la licuefacción de los gases estudiando la relación entre la presión, la temperatura y el volumen del dióxido de carbono, midiendo los las presiones a distintos volúmenes a temperatura constante. Al repetir estas mediciones a distintas temperaturas logró graficar las isotermas para el dióxido de carbono (2) y estableció las constantes críticas, que posibilitaron el desarrollo de técnicas de licuefacción de gases que hasta entonces era imposible llevar al estado líquido (a mediados del siglo XIX estos gases eran llamados “gases estables”). El oxigeno, el hidrógeno, el nitrógeno y el hélio se encontraban en este grupo.

Las constantes críticas son la temperatura crítica, la presión crítica y el volumen crítico (algunos autores como Fernandez Prini y D. Fernandez (3) prefieren referirse a la densidad crítica, siendo esta inversamente proporcional al volumen crítico). Teniendo en cuenta la isoterma correspondiente a la temperatura crítica, la presión crítica y el volumen crítico confluyen en el punto crítico.

Al aumentar la presión (y disminuir el volumen) en un sistema conteniendo dióxido de carbono a temperatura constante, siendo esta menor que la temperatura crítica, Andrews observó que a un dado volumen la fase gaseosa comienza abruptamente a coexistir con una fase líquida. Esto ocurre durante un rango de volúmenes permaneciendo la presión constante durante toda la transición de fases. Esta presión no es otra que la presión de vapor del líquido.

En el punto crítico, las propiedades de las fases líquida y gaseosa se hacen indistinguibles. No se puede decir que hay una fase líquida y una fase gaseosa.

A temperaturas superiores a la temperatura crítica, Andrews observó un comportamiento acorde con la ley de Boyle, que es válida para gases ideales:
P1V1= P2V2 a temperatura y cantidad de moles de gas constantes. Comprobó que a temperaturas mayores que la temperatura crítica es imposible licuar un gas.

¿Por qué a menores temperaturas el comportamiento del gas se aparta de la ley de Boyle? Porque cuando baja la temperatura, comienzan a ser más importantes las interacciones entre las moléculas de gas, especialmente la atracción, dependiendo de la distancia entre ellas, y mostrando un comportamiento de gases reales.

Al aumentar la presión del sistema (siempre a T constante y menor que la T crítica), las moléculas llegan a estar a una distancia en la que la fuerza de atracción intermolecular es máxima, cohesionando entre sí y formando la fase líquida. Si la presión aumenta un poco más, las fuerzas de interacción que comienzan a prevalecer entre las moléculas son las fuerzas repulsivas.

Estos estudios sirvieron como antecedentes para que Johannes van der Waals planteara en 1873 la ecuación de estado para gases reales en su tesis de doctorado (“Over de Continuïteit van den Gas - en Vloeistoftoestand”, o “Sobre la Continuidad del estado líquido-gaseoso”).

Teniendo en cuenta las isotermas obtenidas empíricamente por Andrews, van der Waals trató de encontrar una explicación a los experimentos que revelaban la existencia de “temperaturas críticas” de los gases. Finalmente pudo establecer una relación entre la presión, el volumen y la temperatura de los gases y de los líquidos teniendo en cuenta los volúmenes moleculares y las fuerzas de atracción intermoleculares, luego llamadas “fuerzas de van der Waals” (4).

Efectivamente, la “nueva” ecuación de estado, que tenía en cuenta a las fuerzas repulsivas y atractivas entre las moléculas, pudo ser coherente con las isotermas observadas por Andrews.

P=RT/(Vm-b) – aVm2
Donde P es la presión, R es la constante de los gases (8,3144 J/Kmol), T es la Temperatura en grados Kelvin, Vm es el volumen molar del gas. a y b son las constantes de van der Waals: a, relacionada con las fuerzas atractivas; y b relacionada con el volumen molecular, y por lo tanto con las fuerzas de repulsión que se imponen a altas presiones. Notar que a muy altas temperaturas, los componentes de la ecuación correspondientes a estas constantes (o mejor dicho los correspondientes a las fuerzas intermoleculares) se vuelven despreciables frente al componente dominado por T, quedando como resultado la antigua ecuación de estado para gases ideales, y asumiendo que también son despreciables las interacciones entre las moléculas.

PVm  =  RT
Sin entrar en detalle en las limitaciones de la ecuación de estado para los gases reales formulada por van der Waals, se puede afirmar que sus estudios posibilitaron calcular las condiciones para la licuefacción de gases, lo que abrió la puerta a las técnicas modernas de refrigeración (5).

El punto crítico y las sustancias peligrosas

Casi ciento cuarenta años después de los experimentos de Andrews, el punto crítico sigue vigente.

En principio las constantes críticas no parecen tener mucha importancia en el mundo de las sustancias peligrosas. ¿Es importante para la seguridad saber a qué temperatura un gas puede ser licuado si se lo comprime?

No he visto nunca una hoja de seguridad de producto (MSDS) conteniendo las constantes críticas de una sustancia líquida o gaseosa. Estos parámetros ni siquiera son mencionados en las normas relacionadas con la elaboración de las MSDS. Teniendo en cuenta este detalle podemos suponer que en realidad el punto crítico no es tan importante después de todo.

Error. El Sistema Globalmente Armonizado para la Clasificación y el Etiquetado de Productos Químicos (SGA, o GHS en inglés) establece los criterios de clasificación de los gases a presión en función de la temperatura crítica. Indica cuatro grupos de gases:

• Los gases comprimidos, aquellos con temperatura crítica menor o igual a -50ºC.
• Los gases licuados: a alta presión, los que tienen temperatura crítica entre -50ºC y 65ºC; y a baja presión, aquellos cuya temperatura crítica es mayor que 65ºC.
• Gases licuados refrigerados: son gases que se encuentran parcialmente licuados cuando se encuentran a bajas temperaturas
• Gases disueltos en una fase lìquida.

Claramente, la temperatura crítica define qué tipo de gas tenemos, si es comprimido o si es licuado, a alta o baja presión. En la definición de esta temperatura, el GHS solamente se refiere a los gases puros (6).

Sin embargo, es necesario tener en cuenta que para el GHS estos grupos son solamente válidos para los gases a presión, que implican riesgos de explosiones por calentamiento o por quemaduras o lesiones criogénicas. El GHS los considera en el Capítulo 2.5, por separado de los gases que presentan otros riesgos, como los comburentes (GHS Capítulo 2.4), los inflamables y los que son químicamente inestables (GHS Capítulo 2.2), y los tóxicos (GHS Capítulo 3.1), de este modo el concepto de temperatura crítica queda encerrado solamente en los gases a presión.

Al final del Capítulo 2.5, el GHS contiene un párrafo informativo referente a la clasificación de los gases (GHS, Capítulo 2.5, Párrafo De acuerdo a este párrafo, es necesario conocer tres características de la sustancia para clasificarla como gas:

• La presión de vapor a 50ºC.
• El estado físico a 20ºC a presión estándar.
• La temperatura crítica.

El GHS no indica mayores precisiones respecto a estos parámetros, ni por qué deberían ser considerados, ni qué presión de vapor tomar a 50ºC, ni cómo tiene que ser el estado físico a 20ºC y presión estándar. Respecto a este último aspecto, supongo que tendría que ser completamente gaseoso. Pero  tal vez podría referirse a que esté presente la fase gaseosa junto con el líquido, o sea, que a esa presión y temperatura las dos fases se encuentren en equilibrio, como para considerar a la sustancia como un gas a los efectos de su clasificación de riesgos según el GHS.

Solamente se indica que la información puede ser encontrada en la literatura, calculada o determinada por ensayos. Para los gases puros, indica que la mayoría se encuentra clasificada en las Recomendaciones para el Transporte de Mercancías Peligrosas de las Naciones Unidas. Esto es cierto. Casi todos los gases puros se encuentran identificados en el listado de mercancías peligrosas del Capítulo 3 de las Recomendaciones, con un Número de Naciones Unidas asignado junto con un nombre apropiado de expedición y una clase de riesgo.

Qué pasa en tanto con las mezclas de gases? El GHS no es concluyente en este tema, e indica que “la mayoría de estas requieren cálculos adicionales que pueden resultar muy complejos”. Esta afirmación es especial para la determinación de la temperatura crítica.

Para mencionar un ejemplo, que tal vez no tenga que ver con los “gases a presión” a los que se refiere el GHS, pero que puede ilustrar lo complejo del tema, F. Escobar indica un procedimiento para la determinación de las propiedades críticas de mezclas de hidrocarburos (7). Se toma la temperatura crítica de cada componente de la mezcla y se multiplica cada una por su correspondiente fracción volumétrica; la sumatoria de cada una constituye la temperatura crítica de la mezcla. Este procedimiento solamente sería válido cuando los componentes son hidrocarburos más livianos que los heptanos.

Tratando de buscar una respuesta respecto a los otros dos aspectos mencionados en el GHS (presión de vapor a 50ºC y estado físico a 20ºC y presión estándar), esta puede ser encontrada en las Recomendaciones de Naciones Unidas, o Libro Naranja.

El Libro Naranja de las Naciones Unidas establece las mismas cuatro categorías de gases de acuerdo a su estado físico, pero a diferencia del GHS, esta clasificación es válida para todos los gases, independientemente del riesgo que involucren. Por otro lado, si bien no hay una definición de la temperatura crítica, sí hay una definición de lo que son “gases”.

Para el Libro Naranja, gases son sustancias que presentan una presión de vapor superior a 300 kPa a 50ºC, o que son completamente gaseosos a una presión estándar de 101,3 kPa. Si bien aplica para todos los gases, estos conceptos para discriminar a un gas de un líquido son coherentes con las indicaciones que el GHS realiza solamente para los “gases a presión”.

Una vez que sabemos si una sustancia puede ser definida como gas o como líquido (un caso típico donde la situación no es tan obvia podría ser un recipiente conteniendo una mezcla de hidrocarburos livianos), en caso de que sea un gas, la temperatura crítica nos podrá ayudar a realizar la clasificación según su estado físico.

Si nos guiamos por el Libro Naranja, las distintas categorías van a definir las condiciones de transporte, por ejemplo, en las tablas de la Instrucción de Embalaje P200 de dicho Libro.

La primera impresión cuando estudié los parámetros críticos en los inicios de la carrera universitaria fue que estos son conceptos de poca aplicación práctica. Luego me fui dando cuenta de que el legado de Andrews fue mucho más importante que lo que imaginaba. Su contribución a la historia de la ciencia, que posibilitó la posterior licuefacción de gases estables, que derivó en los estudios de van der Waals con su ecuación de Estado y el merecido premio Nobel, y que posibilitó el desarrollo de aplicaciones tales como la frigorífica o la explotación de hidrocarburos, también dejo secuelas en el mundo de la seguridad química.

(1) "Thomas Andrews." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. 18 Feb. 2012. .
(2) Elementos de Fisicoquímica, Samuel Glasstone, Editorial Médico Quirúrgica, Buenos Aires, 1946.
(3) “Fluidos Supercríticos”, Diego Fernandez y Roberto Fernandez Prini, Ciencia Hoy, Volumen 8, nº 43, noviembre-diciembre de 1997.
(4) "J. D. van der Waals - Biography". Feb 2012 (5) "Nobel Prize in Physics 1910 - Presentation Speech". 20 Jan 2012 (6) “Temperatura crítica es aquella por encima de la cual un gas puro no puede ser licuado, independientemente de su grado de compresión”, definición dada en GHS, Naciones Unidas , Edición 4, 2011. Capítulo 2.5 “Gases a Presión”
(7) “Fundamentos de Ingeniería de Yacimientos”, Dr. Freddy Humberto Escobar Macualo, Editorial Universidad Surcolombiana, Primera Edición.
(8) Recomendaciones para el Transporte de Mercancías Peligrosas, Naciones Unidas, Edición 17.

sábado, 12 de febrero de 2011

Lugares de Detención Transitoria para Vehículos con Explosivos

Para la Ley Nacional de Armas y Explosivos de la República Argentina: “Todo vehículo que transporte explosivos debe estar a cargo de dos personas, no debiendo admitirse ninguna otra sobre él.”

Esta Ley también establece que “Durante todo el tiempo que permanezca estacionado, el vehículo estará vigilado, por lo menos, por una persona competente mayor de dieciocho años. Si el estacionamiento fuera para pernoctar y por un lapso mayor de dos horas, se pedirá instrucción a las autoridades policiales del lugar o en su defecto a otras fuerzas públicas de seguridad o las fuerzas armadas, las que fijarán el emplazamiento del vehículo y otras condiciones que consideren necesarias para su mejor custodia”.

“Cuando sea necesario estacionar el vehículo, el lugar de estacionamiento no debe ser usado para otros fines que puedan derivar en accidentes o explosiones.

Los lugares de estacionamiento deberán estar a una distancia razonable de lugares habitados o depósitos que contengan sustancias inflamables”. (1)

En la práctica no existe en la República Argentina una implementación cabal de estos requerimientos. O no es cumplido el requisito de la doble tripulación, o no son cumplidas con las condiciones de seguridad de los lugares de detención. Lo más común es que no se cumpla ninguno de los dos requisitos. También es cierto que el párrafo anterior es tan ambiguo que alguien que transporta materiales explosivos puede terminar preguntándose: ¿Qué otros fines del estacionamiento pueden derivar en accidentes o explosiones? O bien ¿Qué distancia es razonable entre el estacionamiento y los lugares habitados o depósitos que contengan sustancias inflamables?. ¿Y si las otras mercancías almacenadas no son inflamables, sino corrosivas u oxidantes?

Evidentemente esta normativa no ayuda mucho al incremento de las condiciones de seguridad en este aspecto del transporte carretero: ¿Qué se hace con los depósitos transitorios de mercancías peligrosas, y especialmente, de explosivos?

En Argentina no existe una red de lugares de detención de mercancías peligrosas, lo cual contribuye a que el transporte carretero implique detenciones transitorias en lugares inseguros, ya sea por condiciones estructurales que no garantizan la minimización de riesgos de accidentes, o por insuficientes condiciones de protección contra actos de interferencia ilícita. La importancia de esto es acentuada en el caso de tratarse de materiales sensibles para la opinión pública, entre los cuales se encuentran los explosivos.

Tal vez la norma más completa en esta materia es la Disposición 200/2006 del Registro Nacional de Armas (RENAR) de la República Argentina, Anexo IV, pero esta aplica solamente a los “Depósitos Fiscales de Almacenamiento Temporario de Explosivos en Zona Aeroportuaria”. De todas formas, con el fin de determinar las condiciones de seguridad en cualquier otro tipo de instalaciones para detenciones transitorias de vehículos con cargas peligrosas, especialmente con explosivos, podrían ser aplicados los criterios técnicos establecidos en el Anexo IV de la mencionada Disposición.

El requerimiento de realizar el transporte de explosivos con un acompañante que vigile la carga no es algo nuevo en el mundo.

En USA la normativa local también establece para algunos materiales explosivos (clases de riesgo 1.1, 1.2 y 1.3) que estos tienen que estar permanentemente custodiados durante el transporte por el chofer u otra persona designada por el transportista a tal efecto. Esta persona adicional, al igual que el chofer, tiene que estar informada de las características de la carga transportada y de las medidas de emergencia correspondientes, además de estar autorizada por el transportista para mover el vehículo en caso de necesidad.

Para la reglamentación norteamericana, un vehículo se encuentra custodiado cuando la persona responsable se encuentra despierta en el vehículo (y no en la cabina para dormir), o bien a un radio de 30 metros pudiendo observar al vehículo en todo momento sin interferencias.

Este requerimiento no siempre debe ser cumplido. Se aplican excepciones cuando las cargas se encuentren en instalaciones de origen, o bien en instalaciones de destino o en instalaciones transitorias determinadas a tal efecto por la autoridad. (2)

Las instalaciones tienen que ser habilitadas por escrito por las autoridades locales, Estatales o Federales, y a los efectos del presente artículo, vamos a referirnos a estas como “refugios”, o “depósitos transitorios” tratando de reflejar el significado del término “safe haven” que figura recurrentemente en la normativa de Estados Unidos.

Aquí hay una similitud con el Reglamento General para el Transporte Carretero de Mercancías Peligrosas de la República Argentina, el cual menciona que “El vehículo que transporta mercancías peligrosas solamente podrá estacionar, para descanso o pernocte de la tripulación, en áreas previamente determinadas por las autoridades competentes y, en caso de inexistencia de las mismas, deberá evitar el estacionamiento en zonas residenciales…”(3). Este requerimiento abarca no solamente al transporte de explosivos sino también todas las mercancías peligrosas, y también se encuentra contemplado en el Decreto 532/09 de la Provincia de Buenos Aires (4)

Si se tienen en cuenta tanto el Reglamento de Transporte Carretero de Mercancías Peligrosas como la Ley de Armas y Explosivos de la República Argentina, surge que es necesario contratar a un chofer adicional, y que además el vehículo tiene que ser resguardado en un refugio aprobado por la autoridad para detenciones transitorias. Para la normativa de USA, puede ser una cosa o la otra. Si existiera un refugio reconocido por la autoridad, no haría falta un acompañante para cuidar la carga y el vehículo, ya que la carga sería controlada de acuerdo con los procedimientos aplicables en la instalación de detención aprobada.

En mi opinión, este último punto de la reglamentación norteamericana es discutible. El empleo de dos choferes no solo es necesario para la atención del vehículo en los lugares de descanso, también es útil para disminuir la probabilidad de accidentes en ruta. Y en caso de que haya un solo chofer, ¿cómo haría en caso de que el refugio habilitado se encuentre a una distancia tal que tenga que manejar más horas que las permitidas?

Los lugares de detención transitorios habilitados pueden ser parte de una solución, pero no lograrían reemplazar al uso de dos choferes para un transporte de mercancías peligrosas, especialmente de materiales explosivos.

Areas determinadas por la Autoridad.

Esa parece ser la consigna: que el vehículo junto con la carga pueda ser resguardado transitoriamente en lugares expresamente aprobados por la Autoridad competente. ¿Pero qué parámetros objetivos y técnicos deberían tomar las Autoridades para aprobar los refugios?

Aún en el hipotético caso de que en Argentina sea implementado un mecanismo de autorización de lugares de detención transitoria, y que a raíz de ello haya numerosos refugios disponibles en el país, esto no garantizaría que las condiciones de seguridad sean adecuadas, ya que no hay una norma estándar argentina que respalde con aspectos técnicos la autorización de dichos lugares.

La Ley Nacional de Armas y Explosivos establece condiciones para instalaciones destinadas al depósito de materiales explosivos, pero no para depósitos transitorios. Se podría simplificar el tema y asumir las mismas condiciones de seguridad, pero no es lo mismo un depósito permanente que una instalación de detención transitoria de un vehículo con la carga. Como fue mencionado en párrafos anteriores, la única norma argentina elaborada para contemplar el depósito transitorio de explosivos aplica solamente en aeropuertos y puertos.

Las Autoridades competentes tienen el derecho de determinar los lugares de detención para los vehículos con mercancías peligrosas, pero carecen de un estándar para llevar a cabo esa determinación, lo cual también podría prestarse a situaciones en las que haya falta de transparencia y/o abuso por parte del personal de dicha autoridad.

Una opción podría ser el seguimiento de estándares internacionales. Otra podría ser el seguimiento de una norma desarrollada por algún Organismo de otro país. Un ejemplo es la NFPA (National Fire Protection Agency, de los Estados Unidos), que dicta y revisa normas respecto a la seguridad contra incendios, usadas en numerosos países como referencia para las respectivas normas locales.

En este caso, podría ser de aplicación la Norma NFPA 498 “Standard for Safe Havens and Interchanging Lots for Vehicles Transporting Explosives”.

Una Norma como la NFPA 498 podría ser una herramienta objetiva para ayudar a las Autoridades competentes a aprobar los lugares de detención transitorios, por lo menos para vehículos que transporten materiales explosivos.

El Departamento de Transporte estadounidense propuso en julio de 2010 incorporar la norma NFPA 498 (5) como estándar para la condiciones de seguridad de los depósitos transitorios, teniendo en cuenta que es una norma estándar comúnmente aceptada en USA, aunque un tanto rigurosa, pero diseñada específicamente para depósitos transitorios de explosivos a ser transportados.

Esta medida no sería tan problemática para los usuarios de los servicios de transporte ni para los transportistas ya que en ese país existen este tipo de depósitos construídos en base a esta Norma, no constituiría una barrera económica desde que ya existe algo armado.

Y, en el fondo, lo que se busca es poder aplicar la dualidad: o dos personas en el vehículo o un lugar de detención apto para albergar vehículos con explosivos que sea reconocido por la Autoridad competente en la materia.

Yo creo que también en Argentina debería ser necesario comenzar a considerar una norma técnica que establezca las condiciones de seguridad que debería cumplir un depósito transitorio. Pero también hay dudas respecto a la posibilidad de cumplirla y hacerla cumplir. Los cambios deberían ser graduales.

Hoy los lugares de detención transitorios no se encuentran, en su mayoría, acondicionados de acuerdo a un estándar que indique las medidas y las condiciones de seguridad que deben cumplirse debido a presencia de carga peligrosa en este tipo de instalaciones. Los depósitos privados no son diseñados ni gestionados como depósitos transitorios, donde prácticamente las operaciones de carga y descarga no son habituales ya que los vehículos se encuentran poco tiempo estacionados en dichas instalaciones.

Muy probablemente la Norma NFPA 498 en Argentina sea imposible de cumplir; arrancar todo desde cero implicaría luchar contra barreras económicas y culturales. No obstante sería interesante alguna iniciativa en el seno del Instituto Argentino de Normalización y Certificación (IRAM), que si bien elabora normas que no son obligatorias, estas suelen ser la antesala de los requerimientos legales cuando estos son establecidos por las correspondientes autoridades.

1. Decreto 302/83, reglamentario de la Ley Nacional de Armas y Explosivos de la República Argentina Nº 20429, Art 109 y 110

2. 49 CFR Part 397—Transportation of Hazardous Materials; Driving and Parking Rules

3. Reglamento General para el Transporte de Mercancías Peligrosas por Carretera, Decreto 779/95, Artículo 26.

4. Decreto 532/09 de la Provincia de Buenos Aires, Anexo IV, Art. 2

5. Docket No. PHMSA–2005–22987 (HM–238). “Hazardous Materials: Requirements for the Storage of Explosives During Transportation.

viernes, 28 de enero de 2011

Clasificación de mercancías peligrosas

Clasificar una mercancía para el transporte no es lo mismo que determinar su posición arancelaria debido a que ambos persiguen distintos propósitos. Este concepto aún se encuentra arraigado en el común de las personas involucradas en operaciones de comercio exterior.

Las Reglamentaciones aduaneras tienen poco y nada que ver con las condiciones de seguridad en el transporte de mercancías peligrosas. Y uno de los puntos más importantes para determinar dichas condiciones de seguridad es la asignación de un número de Naciones Unidas y de un nombre apropiado de expedición, así como también la determinación de la clase de riesgo pertinente y, si corresponde, el grupo de embalaje (que indica cuán peligrosa puede ser la mercancía). En esto consiste la clasificación para el transporte. Un error en la clasificación para el transporte puede implicar errores en la determinación de las condiciones de transporte, y obviamente también puede tener consecuencias muy graves si estas condiciones desencadenan un accidente.

Un número de Naciones Unidas y un nombre de expedición no sirven para la realización de un despacho de aduanas. De la misma forma, un número de posición arancelaria es insuficiente para poder determinar si una carga es peligrosa para el transporte.

El principal responsable por clasificar un producto para el transporte es el expedidor (el “shipper”). Él define si la carga es peligrosa o no para ese propósito. Y si la mercancía a transportar es peligrosa, el expedidor tiene que elaborar y firmar una Declaración del Expedidor por la cual da fe de que la carga se encuentra adecuadamente clasificada, embalada, marcada y etiquetada, y que cumple todos los aspectos que demandan las reglamentaciones de transporte.

En realidad no está prohibido que un despachante o un agente de cargas pueda representar al Expedidor asumiendo su figura cuando la mercancía es enviada y firmando la Declaración, con todo lo que ello implica según lo visto líneas arriba. De hecho esto se encuentra contemplado expresamente en la Reglamentación de Mercancías Peligrosas de la Asociación Internacional de Transporte Aéreo (IATA), con la aclaración de que la persona que firme en representación del expedidor debe ser debidamente entrenada en el tema. Es así como IATA implementó el entrenamiento a través de escuelas reconocidas, o Escuelas IATA, que cuentan con el aval de dicha institución.

En el transporte marítimo, en tanto, la capacitación al personal de tierra es obligatoria desde enero de 2010, aunque aún no existe un sistema de certificación de cursos de transporte marítimo de mercancías peligrosas. Este nuevo requerimiento fue impuesto por la Organización Marítima Internacional luego del incendio en el buque Hyundai Fortune en marzo de 2006, presuntamente a raíz de una carga peligrosa no declarada. Es decir, clasificada como no peligrosa por el expedidor.

Siempre se vuelve a resaltar la importancia de realizar una adecuada clasificación de las mercancías para su transporte.

El despacho de aduanas será correcto, habiendo sido asignado un número posición arancelaria que refleje fielmente lo que se va a exportar. Sin embargo esto no garantiza que la carga sea segura para el transporte, y menos si se trata de una carga peligrosa.

sábado, 23 de octubre de 2010


Broad Outlook

In the last 25 years, the search for new environmentally-friendly alternative sources of energy, as opposed to other traditional sources, has given rise to two stars which are no longer promises but which have defined the technological path for the XXI century: fuel cells and lithium batteries and cells. This analysis will focus on lithium batteries and cells. The following generalizations should be made to continue with our analysis:

  • Any reference in this article to “batteries” or “cells” will always be understood as “batteries and cells”, but considering that the literature usually refers to “batteries” when there are two or more cells electrically interconnected.

  • “Batteries” will be considered to be “lithium” batteries, including all forms of lithium:
o       Metallic lithium, used in primary non-rechargeable lithium batteries. They are typically used in watches, calculators, etc.

o       Lithium-ion, used in secondary rechargeable lithium batteries. They are used, for instance, in cell phones, portable computers, etc. This type of batteries includes lithium polymer batteries.

During the short existence of lithium batteries, their uses have constantly extended, mainly in portable electronic equipment, given that they provide more energy and have a longer duration, as compared to other types of cells. The increasing demand of these sources of energy required increasingly smaller and more powerful cells. Thus, they could be used for cell phones, digital photographic cameras, portable computers, toys, wheelchairs, medical devices, military devices, etc.

Automobiles could not be an exception. In the latest years, automotive companies have started a fierce race to develop units driven by lithium batteries and hybrid units, propellable both by such batteries and by fuel.

In Argentina, for instance, at the beginning of this year, an agreement was announced between the Australian mining company Orocobre and Toyota Tsusho (1), in which the automotive company Toyota holds a 21.8% interest and which has business links with Sanyo and Panasonic, for the extraction of lithium carbonate in Salar de Olaroz, Province of Jujuy.

To have an idea of the importance of this agreement, the final investment for the project submitted by Orocobre to the Argentine Secretary of Mining amounts to USD 100 million, and contemplates the creation of 160-200 jobs and an annual production of 15,000 tons of lithium carbonate. Currently, the annual production of lithium carbonate in Argentine is of about 10,000 annual tons, which are obtained through the exploitation in Salar del Hombre Muerto, in the Province of Catamarca, by the company Minera del Altiplano (a subsidiary of the American company FMC Corporation). (9)

Specialists estimate that the carbon lithium production of China, one of the three countries which has 97% of the world production (the other two countries are Chile and Argentina), could reach 60,000 tons this year (2). It is, then, understood the great strategic interest on the Salar de Olaroz field.

It is not by chance that the great powers currently dispute this precious metal, now called “white gold” by many authors, through the leading technological companies.

For instance, in the Asian continent: Japan is interested in maintaining its leading position in the production of portable computers, digital cameras, mobile phones and, now, automobiles.

Instead, China prepares to carry out a different lithium revolution: they intend to take the technological lead in the manufacture of vehicles in a post-combustion engine era (the last international economic crisis originated in the United States helped the extinction of the big and heavy combustion engine-driven American cars in favor of medium-sized cars). Thus, they would not have to acquire the expertise developed during the XX century with this type of propeller and they could leverage the large lithium carbonate fields they have (3)(4).

Lithium-based energy sources are becoming prevailing in the world. Consumption is having a wonderful increase year after year in a market that expands more than 20% per year (5). This, in turn, increases transportation.

A “gold” not so noble

Without consumption, there is no transportation. And if there is lithium battery transportation, then, there are specific risks.

In 1998, the UN Committee of Experts on Dangerous Goods (the Committee) started to take into account the progress of lithium technology regarding its application to batteries, and introduced in the Orange Book the concept of “Equivalent Lithium Content” as a measure of batteries' capacity (11). This concept was used to define criteria to exempt certain batteries from transport regulations due to their low capacity. Subsequently, the latest edition of the Orange Book replaced the "Equivalent Lithium Content" with the Watts-hour number, which is easier to calculate and interpret (12).

These batteries have the capacity to generate a great amount of heat and they may even generate a fire if they are damaged, wrongly packaged or poorly manufactured. According to the U.S. Department of Transportation (DOT), approximately 1 out of 10 million of all the primary and secondary lithium batteries have defects which may cause accidents (6). The probability of an accident seems insignificant, microscopic, but the risk will still be important due to the great volume transported and, mainly, due to the catastrophic consequences that a flight loading a single defective battery capable of causing an air accident may have. If it is considered that only during 2008 3300 million cells and batteries have been transported through all transportation means throughout the world (13), the amount of cells and batteries with high probabilities of causing accidents because they are defective is more than interesting. No one would get on a plane if he/she knew that there is a cell o lithium battery in the plane which will be the cause of the plane crash.

Studies performed by the U.S. Federal Aviation Administration (FAA) revealed that those materials have a negative impact on transport safety due to the following factors (7) (8):

  1. Their self-ignition temperature could be easily reached if another load in the same decks sets on fire. After that temperature is exceeded, they react more violently than a regular cell or battery.

  1. A fire of lithium batteries, primary batteries, in particular, is harder to fight with the extinguishment methods used in aircraft cargo decks.

  1. In the case of primary batteries, the content of metallic lithium may be released melted during the battery overheating, and it may reach and affect the structures of the cargo compartments of the aircraft.

  1. In the case of secondary or lithium-ion batteries, their overheating causes the release of the flammable liquid mix which contains the electrolytes, due to the increase in the pressure within the device. This entails two consequences:

    • The liquid released will be easily scorched by the flames during a fire.

    • The sudden release of flammable liquid is associated to a pressure pulse generated within the battery during the overheating. If the relief device does not work properly, the pressure pulse pushing the liquid outside may be strong enough so as to cause the battery's explosion. These explosions may also affect the structure of the deck.

So far, the references made to the risks with lithium batteries have only considered a hypothetical fire in a deck with this cargo and, though they do not generate the fire, they may be extremely dangerous. However, we have not taken into account that they may also generate overheating without being induced by any fire or external source.

The most common “natural” cause of that overheating are short circuits in the batteries (6). Once they occur, when temperature increases, they trigger several internal exothermic reactions which favor a higher increase in temperature and, therefore, in pressure. Everything ends with the release of the content and the possibility of an explosion and fire. 

But why a lithium cell may have a short circuit?

The reason may be the contamination of the device during the manufacturing process or due to the cell or battery design problems, which may include physical damages due to hits or perforations, not only manufacturing problems or errors.

These are cases of internal short circuits, but there may also be external short circuits, for instance, because an electrode or a terminal comes into contact with an external metallic object. In these cases, there is also overheating.

Taking into account both internal and external short circuits, the DOT calculated that these were the cause of 72-73 % of the incidents involving lithium cells or batteries between 1991 and 2008 (6).

Certainly, abuses by users may also generate overheating, for instance, during loading and unloading processes or due to the involuntary activation of equipment containing the cells or batteries.

The Last Straw

Most of the incidents accounted had minor consequences, and the personnel involved reacted promptly.

A famous accident which involved lithium cells was the fire of UPS aircraft upon arriving to the airport of Philadelphia, United States, on February 7, 2006. There were no casualties, but action from the airport emergency staff and the support personnel of the airline and of the concerned facilities was necessary. The aircraft was totally destroyed.

The exact cause of the accident could not be identified by the US National Transportation Safety Board (NTSB), given that the evidence necessary to explain it was completely destroyed during the accident. Investigators did not find any evidence of an explosion or a fire with high temperatures sufficient to melt steel components. They did not determine either that the cause was the electrical system, as there were no rests of the electrical system in the most damaged place, and the irregularities in the flight control system were detected by the crew a few minutes after detecting the smell of burning (10).

However, it could be determined that th ere were several electronic devices in the load, which devices contained secondary lithium cells, and that these devices were in the load positions where the fire first originated.

Although investigators could not determine with certainty if the accident was caused by those lithium cells in the equipment, their presence in the scene was additional to all the other incidents caused by lithium cells and registered worldwide. Furthermore, considering the increasing world trend regarding accidents with lithium cells (which increase went hand in hand with that in their manufacturing and use), the UPS aircraft accident was the last straw.

As a result of the investigation, the NTSB recommended the U.S. Department of Transportation (DOT) to remove regulatory exemptions applicable to packaging, marking and labeling of loads of small secondary lithium batteries until completing an analysis of their failure and until the relevant actions to reduce the risks for transporting those materials have been determined. This means that: all lithium cells and batteries should then receive the same treatment for air transport purposes (except extremely small cells, with the approximate size of a button).

This is being implemented by the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) through a new regulation, which will be effective soon (13). Several objections have been voiced against it, including that of the U.S. Portable Rechargeable Battery Association (PRBA), which includes the main cell manufacturers of the world (14). The main argument is the certainty of a significant negative impact for the American economy, as adjusting to the new regulation would imply an approximate cost of USD 1000 million, delays in the import of critical inputs for areas such as medicine, and the loss of jobs due to the relocation of the distribution centers, given the impossibility to import lithium batteries by plane.

As always, economic aspects are a barrier to any measure aiming at safety. The economic aspects may not be ignored at the time of implementing this type of measures.

However, how many resources is it necessary to invest in safety?

On one end we have the loss of jobs, logistic barriers (and, thus, difficulties to supply critical inputs) and loss of competitivity by several companies faced with the energy boom represented by lithium cells. On the other end, there is the possibility of an air catastrophe. In the middle: a defective lithium cell amongst thousand millions of ordinary lithium cells, which causes a short circuit and may generate a fire in the cargo deck of the aircraft.

The dividing line among those two ends is extremely thin.

1.   Toyota participará de la extracción de litio en Jujuy [Toyota will participate in lithium extraction in Juluy], Oliver Galak. La Nación, Argentine, January 21, 2010.
2.Global and China Lithium Carbonate Industry Report, 2008-2010.

3.   Cristina espera que el yuyo la saque del pantanal fiscal [China expects the weed to take it from the fiscal marsh], Jorge Oviedo. La Nación. Argentine. January 24, 2010.

4.   Japan and China fight it out for right to mine lithium under Bond’s battlefield, Leo Lewis. The Times. England. June 15, 2009.

5.   El litio, el nuevo petróleo que promete revolucionar el mundo de los commodities” [Lithium, the new oil which promises to cause a revolution in the world of commodities], Martin Burbridge.

6.      Enterprise Lithium Battery Action Plan. US DOT, PHMSA.

7.      Flammability Assessment of Bulk-Packed, Nonrechargeable Lithium Primary Batteries in Transport Category Aircraft, Harry Webster. Document DOT/FAA/AR-04/26 of the U.S. Department of Transportation (DOT)

8.      Flammability Assessment of Bulk-Packed, Rechargeable Lithium-Ion Cells in Transport Category Aircraft. Harry Webster. Document FAA/AR-06/38 of the US Department of Transportation (DOT)

9.      Los Proyectos Vienen Marchando [Projects come marching]. Emiliano Grasso, Tecnoil magazine, No. 318.

10.  Aircraft Accident Report - Inflight Cargo Fire, United Parcel Service Company Flight 1307, McDonnell Douglas DC-8-71F, N748UP, Philadelphia, Pennsylvania. February 7, 2006. Document NTSB/AAR-07/07/ PB2007-910408 / Notation 7772C of the US National Transportation Safety Board (NTSB).

11.  Recommendations on the Transport of Dangerous Goods, UN Model Regulations. 11th edition, Chapter 3.3, Special Provision 188.

12.  Document ST/SG/AC.10/C.3/2005/13, submitted by the U.S. Portable Rechargeable Battery Association (PRBA) before the US Committee of Experts on the Transport of Dangerous Goods, in April 2005, to amend the 13th edition of the Orange Book.

13.  Document Docket No. PHMSA–2009–0095 (HM–224F), issued by the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) on January 11, 2010.

14.  PRBA Urges PHMSA to Reject Lithium Battery Rulemaking And Adopt Internationally Recognized Transport Regulations. Portable Rechargeable Battery Association, March 16, 2010. 

  Translated by Camila Rufino, Accredited Translator