Nowadays the bulk liquid storage sector encounters several environmentally related challenges. One of them is regarding gas venting emissions.
The tank storage sector has to obtain a specialized solution tailored to each situation in order to eliminate the gas venting emissions generated, regardless of the tank content, the characteristics of the tank or the type of loss produced (permanent or working).
The importance of gas venting
Gas venting consists of discharging unburned gases into the atmosphere, often carried out in order to maintain safe conditions during the different phases of the treatment process. During venting operations methane, carbon dioxide, Volatile Organic Compounds (VOC), sulphur compounds and gas impurities are released.
During storage (the so-called tank breathing), product loading and unloading, transport, cleaning and inerting of the tanks, pollutant emissions are emitted into the atmosphere and must be eliminated.
These emissions are mostly emissions of volatile organic compounds (VOC). To eliminate VOCs, the most commonly used and most effective technology is RTO (Regenerative Thermal Oxidation) equipment.
The environmental impact of hydrocarbon venting
The flared and vented gas contain some pollutants that have proven to be toxic to people and the environment. Flaring and venting present different threats, such as: while flaring burns the associated gas and therefore creates carbon dioxide, venting releases the natural gas, which is predominantly methane, into the environment.
The technology solution
Within the tank storage sector, installing a combination of Regenerative Thermal Oxidation (RTO) equipment together with Vapour Recovery Units (VRU) not only fulfils the objective of eliminating Volatile Organic Compounds and the emissions associated, but it also provides hydrocarbon vapour recovery, which is translated into recovering product, and therefore, money.
Let’s see those technologies more in detail:
- About RTO technology
An RTO is a piece of equipment designed to eliminate Volatile Organic Compounds (VOCs). Essentially, it is formed of three towers with ceramic beds, where energy is recovered, and a combustion chamber in which the temperature is kept constant in order to enable oxidation. The organic compounds it eliminates consist primarily of carbon and hydrogen: consequently, when they react with oxygen they form carbon dioxide and water. The combustion chamber incorporates a burner that normally uses natural gas to raise the temperature inside the chamber, although other fuels (fuel oil, diesel oil, etc.) can also be used.
In a Regenerative Thermal Oxidation (RTO) system, the polluted air to be treated is sucked in by the main fan, which is usually located upstream of the oxidiser, although for processes with high concentrations of suspended particles the fan is usually located downstream of the oxidiser.
The fan then pushes the air to be treated through the first ceramic tower. In this first tower, the air is heated along with the ceramic media. When the air has passed through the ceramic bed, it reaches the combustion chamber, where the oxidation takes place. For gases without halogenated compounds, the temperature is usually around 800 ºC – 900 ºC; however, for gases that contain halogenated compounds, the temperature needs to be around 1100 ºC in order to ensure full oxidation. In each instance, the temperature will depend on the compounds that are to be treated.
At the same time, as air to be treated enters the first chamber, the now-oxidised air is passed through the second ceramic tower, in order to transfer its heat to the ceramic media. This cools the gas and heats the ceramic bed. After passing through the second tower, the air – now free from pollutants – is sent up the flue.
The third ceramic tower is used to recirculate the purged elements, as all of the air must be oxidised during the valve sequencing.
The sequencing procedure is repeated periodically, every 45-90 seconds, in order to make sure each tower is operating in the same way.
Systems with three ceramic towers are the most common, although you can find RTOs with two towers and even some that have five towers.
- About VRU technology
Vapour Recovery Units are equipment that collect vapours from storage and loading facilities, re-liquefy them and return them in the form of liquid hydrocarbons to storage tanks.
Methods to recover vapours include absorption, condensation, adsorption, and simple cooling.
Fuels contains Volatile Organic Compounds (VOCs) that evaporate easily.
Evaporated vapours, in addition to their effects on human health, are harmful for the environment and represent a significant loss of sales.
Approximately, 0.2% of the contents of a tank of gasoline will evaporate:
Tank truck 40m3 volume
40m 3 = 40,000 litres of gasoline
80 litres of gasoline
Several studies reveal that the investment recovery time is in the range of 1 to 5 years, depending on the operation volume.
The advantages of recovering vapours are:
- Increasing safety and mitigate health risk.
- Recovering valuable resources.
- Eliminating emissions of hazardous substances.
Koole Terminals success story, an example of what Tecam can do for you
Koole Tankstore Minerals is an international hydrocarbon storage company with a total storage capacity of over 3,500,000 cubic meters. For its facilities in the port of Rotterdam, the Netherlands, Tecam was awarded a project to eliminate the emissions of Volatile Organic Compounds (VOCs) generated during gas venting.
Tecam proposed a custom-made solution based on Regenerative Thermal Oxidation (RTO) technology that managed to reduce its VOC emissions by 99.9%.
Get to know the details of this success story, with which Tecam won the Tank Storage Awards 2020 in the “Environmental Performance” category: https://www.tecamgroup.com/wp-content/uploads/2020/02/Tecam_Case-Study_vent-gas-treatment-for-Koole-Terminals.pdf
Contact us today to learn how we can help you with your gas venting challenges at your tank farm. We are experts in the field.