PhD project: ZEBrA

The ongoing research project ZEBrA – “Zero-Emission Breathing Application for Storage Tanks” aims to stop emissions generated by liquid storage tanks through tank breathing. Those tanks are usually operated under atmospheric pressure because they exhibit only very weak pressure resistance characteristics. Tank breathing is triggered by heat input, cooling by e.g. rain or filling and emptying processes. Nowadays, pressure changes are equalized by means of pressure/vacuum relief valves. These vents enable a tank to “breathe”: air can be drawn inside the tank in case of vacuum, and gas can be discharged in case of overpressure.

Trank breathing phenomena

When talking about the topic of climate change, the release of hazardous components into the atmosphere plays a key role. Greenhouse gases and other air pollutants affect natural systems and lead to an increase of the annual mean temperature. Significant quantities of air pollutants are not only released during the combustion of mineral oil products in engines, but also during processing and distribution steps of those mineral oils. As an example: In Germany, in the energy sector alone, about 50.000t of volatile organic compounds (VOC) are emitted into the environment during storage and refining1. Directive 1999/81/EC is applied as the definition of a VOC. This Directive declares that any organic compound having a vapour pressure of 0.01 kPa or more at 293.15K or having a corresponding volatility under the relevant conditions of use can be considered as a VOC. Apart from mineral oil and products, there are also plenty of other liquid substances in remarkable amounts stored in fixed roof tanks, e.g. of the chemical industry, food industry, pharmaceuticals as well as liquified gases. Hence, emissions from storage tanks play a crucial role concerning the key environmental challenge climate change.

In the first stage of the project, an extensive literature review has been conducted to get an overview of common tank designs and emission reduction measures in use today. Also the impact of the emission problem will be evaluated. A structural analysis of influencing aspects concerning emissions through liquid storage have led to a variety of different solution approaches that are under investigation right now. The next step is to evaluate the different solutions and then select a series to be tested on a laboratory scale.

(1) Umweltbundesamt: Berichterstattung unter der Klimarahmenkonvention der Vereinten Nationen und dem Kyoto-Protokoll; Nationaler Inventarbericht zum Deutschen Treibhausgasinventar 1990 – 2017 (UNFCCC-Submission); 2019

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