Maurice Young was a keynote speaker at the recent 6th IIR conference on Ammonia and CO2 Refrigeration Technologies held between April 16th and 18th at Ohrid, in the Republic of Macedonia.
140 delegates registered for this latest IIR meeting, which represents almost a 40% increase over the previous conferences. Delegates came from about 35 countries including speakers and presenters from 23 countries, mostly from within Europe but also including speakers from the USA, Africa, India, China, New Zealand and Australia.
Summary of presentation:
Ammonia has been considered to be an excellent choice of refrigerant for industrial applications for over 150 years. However, ammonia is toxic and besides it is also flammable and requires careful safety consideration in the design and operation of refrigeration systems, even though it has a good safety record and ignition of ammonia is a very rare occurrence and is virtually unknown in systems which comply with recognised European Standards. In the UK a recent ‘Joint Industry Project’ has sought to provide practical guidance to ensure ammonia refrigeration plants are fully compliant with the Dangerous Substances and Explosive Atmospheres Regulations 2002 as required by EU ATEX Directives. The paper provided an overview of the current legal framework and explains the procedure to be followed in classification of hazardous areas in accordance with IEC EN 60079-10-1. Finally an approach using new software to model potential releases and calculate the hazard range, was described.
About the conference
According to all reports, the concentrations of CO2 and other greenhouse gases (GHGs) in the atmosphere are increasing continuously. There are alarming projections of GHG emissions including HFCs. In Europe, an EU Regulation 842 on F-gases have been introduced which is revised in 2014 with more adopted restrictions, including phase-down of HFCs. More than 110 countries support the proposal for phase-down of HFCs within the Montreal Protocol, but no agreement has been reached so far. In the meantime, new HFC refrigerants (named HFOs) with low GWPs are announced.
In the refrigeration and air-conditioning industry, confusion and uncertainties related to working fluids in many applications are continuing. In addition, there are many groups with diverging interests: chemical companies, manufacturers of equipment, distributors, users, environmental organizations, politicians and the public.
Despite many difficulties, the global trend towards using natural refrigerants is intensifying. There are very positive signals in Europe and some parts in the world where expanding use of ammonia, carbon dioxide and hydrocarbons in various applications is occurring. We will eliminate all uncertainties in the future regarding both Protocols and environmental regulations applying to natural refrigerants.
Of all refrigerants applied today, ammonia and CO2 are the oldest that have been used since the 19th century. The topics of the conference are: design of modern ammonia and new CO2 systems and technological innovations, improving energy efficiency, various applications, technical guidelines and safety regulations. It is very clear: by using more ammonia and CO2 refrigerants, we are employing environmentally friendly technologies.
Anhydrous Ammonia Fertilizer Isn’t Normally Considered An Explosion Risk, So What Happened In West…?
The horrific explosion at a West, Texas fertilizer plant last Wednesday came from a more unlikely source than you might think. The chemical stored there is not generally considered as much of a fire or explosion risk as other nitrogen-based fertilizers. But under certain conditions, what’s been thought of as a safe chemical can turn deadly.
According to reports the fertilizer company had as much as 54,000 pounds (circa 24,500 Kilogrammes) of anhydrous ammonia at its facility. The company noted in an emergency planning report that this kind of fertilizer is not considered an explosion risk in its gaseous form, though it can sometimes explode if kept contained at certain concentrations.
Some news outlets covering the explosion have been conflating anhydrous ammonia with a different kind of fertilizer called ammonium nitrate. But they’re completely different chemicals.
Anhydrous ammonia is made from three parts hydrogen to one part nitrogen. The “anhydrous” part of the name refers to the fact that there’s no water involved in the reaction that makes it. Ammonia was initially produced to make explosives but was repurposed as a fertilizer after World War I. Adding it to soil contributes nitrogen, a vital component needed for plant growth.
As a fertilizer, anhydrous ammonia is stored in tanks as a liquid under pressure — without the added pressure, it would quickly boil into a gas — and transported via pipeline, truck, or rail.
Anhydrous ammonia is considered safer to store in large quantities, because it takes extremely high temperatures to set it off. But it’s not totally harmless. Direct exposure to anhydrous ammonia can be seriously harmful, causing eye and skin irritation, respiratory problems and, at the right concentrations, death.
Leaks of gaseous anhydrous ammonia are also dangerous. Because the vapours hug the ground initially, the chances for humans to be exposed are greater than with other gases.
Ammonium nitrate, a combination of nitrogen, hydrogen and oxygen, is a lot more volatile, prone to combustion and reaction, thanks to the fact that it is a strong oxidant. (Anhydrous ammonia can be converted to ammonium nitrate using nitric acid.)
So what caused the explosion at the West plant…? City University of New York physicist Michio Kaku told CBS News that the water firemen were using to fight a routine fire may have set off a chain reaction of explosions.
“The [US Environmental Protection Agency] regulations say it’s OK to have this amount of material, because nothing’s going to happen, but there’s a rare sequence of events, the right pressure, temperature and right amount of water will set off anhydrous ammonia,” Kaku told CBS.
There’s still the question of what set off the initial fire — whether the company also stored some ammonium nitrate or whether there was some other source of combustion. The next few weeks of investigation may provide answers.
Hazardous Area Classification (HAC) for explosive gas atmospheres is well established, with guidance published in various standards and industry codes of practice. One of these documents, BS EN 60079-10-1:2009 makes use of the concept of a nominal flammable gas cloud volume Vz to determine the level of ventilation and hence the zone. However, it has been shown that the critical formulae given in the standard to estimate Vz have no scientific justification and therefore provides arbitrary results.
Other calculations based on simple well established jet model theory, validated against experimentally validated Computational Fluid Dynamics (CFD) has been shown to provide solutions that are significantly lower (and potentially less onerous and costly) than those resulting from the use of the methodology in the standard BS EN 60079-10-1:2009.
Contact us if you wish to learn more about this alternative methodology.
Quadvent is a mathematical model of a flammable gas jet release that can be used as part of a hazardous area classification exercise under the Dangerous Substances and Explosives Atmospheres Regulations (DSEAR).
It can model releases of flammable gas either in a ventilated enclosure or outdoors.
The model was originally developed by HSL experts in 2011 for calculating the flammable gas cloud volume (Vz) as a scientifically based alternative to the method described in the international standard on area classification IEC EN60079:10-1.
HSL has now developed Quadvent into a software program that is easy to use, quick to run and allows the user to obtain realistic estimates of Vz for a given gas, pressure and hole size and it can take into account the effects of ventilation by specifying the room volume and ventilation rate.
Quadvent also provides estimates of the ventilation rate of naturally ventilated enclosures through a relatively simple model based on the effects of buoyancy and wind driven ventilation.