About 70 million barrels of oil are lost each year due to the evaporation of volatile organic compounds (VOCs) during the loading, storage and transport of crude oil on ships. This is an environmental problem as well as a significant economic cost.
The amount lost represents a value of 3.0-3.5 billion USD per year. In other words: if you are a shipping operator, reducing VOC emissions from maritime sources is a chance to make your business more profitable. For a standard vessel such as an Aframax tanker, the economic loss on a single voyage with a full tank is over $ 40,000.
In the past, this loss of cargo was seen as a necessary evil because prevention was seen as too costly. Fortunately, recent technical breakthroughs have changed that.
From depression to positive pressure
Over the past decade, scientific studies have demonstrated the effectiveness of the concept of saturated vapor pressure (SvP). By simply maintaining high pressure inside the cargo tanks, VOCs are contained in the liquid hydrocarbon phase and cannot evaporate.
As a result of this new idea, tanker loading systems were quickly changed so that vacuum was replaced by positive pressure. In the following years, several tankers were equipped with this new technology. Depending on the exact volatility and composition of crude oil, VOC production has decreased by 70-90%. As a positive side effect, the emissions of other volatile cargoes such as chemicals, LPG (liquefied petroleum gas) and LNG (liquefied natural gas) were similarly reduced by the same technology, while the emissions of H2S and other compounds harmful to the environment have also been made. down.
It is important to avoid pressure fluctuations
The story does not end with the introduction of positive pressure into the tank, as traditional ventilation systems allow considerable fluctuations in pressure. Traditional ventilation systems are self-contained, weight-loaded systems that start ventilation at a preset setting and continue well beyond what is needed and therefore close at a much lower pressure, venting an unnecessarily large amount of VOCs. and inert gas in the atmosphere.
To meet the challenge of tank pressure fluctuations, Bay Valves invented the SuperSat system (Sat is for saturation), which continuously maintains the high tank pressure and thus prevents VOC losses.
Controlling VOC emissions is obviously not the only concern of a crude oil transporter. Safety will always be a top priority. Since high speed valves have long been established as the industry standard for safety due to their ability to react extremely quickly to leaks that do occur, a VOC emission control system can only be successful if it is it is fully integrated with high speed valves with negative pressure drop.
This very fact is the motivation behind the invention of SuperSat – a valve which incorporates the excellent safety properties of the high speed valve with pressure control and therefore effective control of VOC emissions which is associated with the concept of vapor pressure. saturated (Please).
Why VOC Emissions Should Be Reduced
VOCs are a large group of organic compounds. Several light hydrocarbons, such as methane, ethane, and propane, are VOCs. Due to the high vapor pressure, VOCs can easily evaporate. For the petroleum industry, the evaporation of hydrocarbons is equivalent to an economic loss.
VOCs can also cause an oil spill on the deck of a ship, as a high production of VOCs can entrain hydrocarbons in the mixture of inert gas and VOCs.
In addition, VOC emissions can harm the environment and human health. In particular, methane is a powerful greenhouse gas, contributing to climate change. Several other VOCs, including ethane, propane, butane, pentane and hexane, react with NOx to form ground-level ozone which has harmful effects on human health and plants.
A neglected problem
For many years, VOC emissions have received little attention. As noted in a major study by Bhatia and Dinwoodie, University of Plymouth, UK, this could be largely attributed to the attention paid to large-scale oil spills, for example the catastrophic Exxon Valdez accident (Alaska , 1989) and similar events with huge amounts of crude oil leaking. While major spills would attract wide media coverage and subsequently political interest in mitigation, the tiny but constant leaks caused by the evaporation of VOCs would go unnoticed.
In their article “Daily loss in shipping raw oil: Measuring raw oil loss rates in daily North Sea shipping operations” (Energy policy, 2004), Bhatia and Dinwoodie state: “Historically low crude oil prices have generated little interest in losses less than 0.5%, but today the oil majors host loss control services that study how the tonnage used, the type of crude, the various ports of loading and unloading and evaporation during freight operations affect losses.
Tiny losses add to a lot of money
The Bhatia and Dinwoodie study went on to demonstrate how continued VOC leaks would equate to large total losses.
As a result of this study and others, several countries and organizations have started to address the problem. For example, the Norwegian Marine Technology Research Institute (MARINTEK) found that the storage and loading of crude oil on ships was responsible for more than 50% of non-methane VOC emissions in Norway.
The studies then estimated that up to 9 million tonnes of VOCs are emitted each year from the global loading and transport of crude oil, with around 5 million tonnes emitted during actual transport. The figure corresponds to approximately 70 million barrels of light hydrocarbons representing a value of between 3.0 and 3.5 billion USD per year.
Stay ahead of the regulations
As a result of increased attention to VOCs, the International Maritime Organization (IMO) and several countries, regions and cities with ports have adapted or are considering programs to reduce VOC emissions.
This offers oil majors a unique window of opportunity: by investing in controlling VOC emissions, they can save millions of dollars while adapting to future industry environmental standards.
Here, the SuperSat system for VOC control is the obvious choice. As the price is comparable to traditional ventilation systems, there is really no reason not to implement this technology which benefits both the environment and the operator’s bottom line.
At Bay Valves, we are, as always, ready to provide further technical information on SuperSat and VOC control in general, while engaging in discussions on possible applications for specific vessels.
Source: Vannes en baie