Elimination of odour emissions from bitumen production
Eliminating pollution requires extensive research, creative and effective solutions, and a strong partnership. Together, DESOTEC and NYNAS have been able to successfully implement just that.
The Nynas refinery in northern Germany has solved its odour problem by designing an innovative system to treat bitumen vapours, using mobile activated carbon filtration as a starting point.
In this reference case, the experts involved from Nynas explain why they chose a DESOTEC filter and how they were able to develop their individual solution with technical support from DESOTEC.
As Production Manager Plant South Stephan Behrens of Nynas explains, "This project is a success in terms of project development, engineering and implementation together with DESOTEC. "
Nynas is a producer of bitumen and specialty oils headquartered in Stockholm with main refineries in Sweden and Germany. The German refinery is located in Hamburg, divided between sites north and south of the Elbe.
At the northern site, one million tonnes of crude oil are processed annually into naphthenic base oils and bitumen blend components. The distillates and components are then transported to the southern site for further processing, storage and distribution.
Stephan Behrens is head of the production unit at Nynas' South site. Kai Gottschling is the operational contact for this project and Dirk Philipowski is the project manager. The contact person at DESOTEC is sales engineer Tobias Carstens.
The problem: bitumen odours from storage tanks
There are three bitumen storage tanks on the southern site, each with a capacity of 12 000 m³, from which vapours escape from the vents. In addition, vapours are released when trucks are loaded and unloaded and are extracted via a closed system.
Bitumen vapours contain hydrocarbons that have a strong, unpleasant odour. This led to complaints from residents, so in 2017/18 Nynas launched a project to develop a long-term solution, which the company calls the Bitumen Vapour Treatment Unit (BVT).
"When you start a project like this, you don't expect it to be so complex - you have a certain picture in your head. Then it gets more complicated and you have to start changing that picture," says Mr Gottschling.
Nynas conducted initial research for about a year, which the company calls the "preliminary study phase". This involved investigating and comparing all the options on the market. An external company carried out a detailed analysis of the emissions and took accurate measurements.
One potential solution was to install an incinerator. However, a DESOTEC filter proved to be more advantageous for several reasons. Mr Behrens explains: "For this project, we had a very long scouting phase in which we evaluated various technological options. DESOTEC's solution was the best in terms of maintenance activities, cost and reliability." This decision was reinforced by the fact that Nynas' Swedish headquarters had already worked with DESOTEC on a short-term project.
Mr Carstens: "For this project, it was really important to have a good information base. What does the filter have to do, what pollutants and concentrations can be expected and what can we at DESOTEC do? Bringing all this information together was the starting point of the project. "
The solution: Combining all emission sources
Mr Philipowski explains, "After deciding on a solution with DESOTEC, we started to design and build the entire system from scratch. "
The result was the Bitumen Vapour Treatment Unit (BVT), which combines all emissions in one system and feeds them to a single DESOTEC AIRCON HC-XL filter.
Emissions from the storage tanks: The vapours are piped through a specially developed extractor bonnet to a liquid separator to remove the water. They are then fed into a small compressor and then on to a second separator. In the final step, the activated carbon filter separates the vapour emissions. Afterwards, the purified and odourless vapours can be released into the atmosphere.
The flow rate from the storage tanks is about 1000 m³/h and is continuous.
Emissions from truck loading: Each of the four truck lanes is connected to the BVT via a venting system. Here, too, the emissions are directed to a first separator, then to a compressor, then to a second liquid separator and finally to the DESOTEC filter.
About 240 m³/h of exhaust air flows discontinuously from the lorry lanes into the BVT system.
For safety reasons, a carbon monoxide detector (CO detector) is fitted at the outlet of the filter. If CO is detected, this is a potential indicator of a hotspot in the filter bed. If hotspots develop, they are immediately cooled with an automated safety circuit using nitrogen inertisation.
Mr Behrens describes: "The entire process setup is unique in my opinion. During the development of this plant, the Nynas internal process engineering department supported us well. DESOTEC has helped us technically with everything to do with the filter. Whereby we were able to rely on DESOTEC's many years of experience in a wide range of applications. "
The result: No more unpleasant odour
The BVT has now been in operation for two years. Mr Gottschling takes stock: "It is going well - the neighbours have not complained anymore. "
After one year, the filter was changed for the first time: a loading of 65-70 % was detected, of which a significant proportion was water with a very low pH value.
To extend the filter's service life and protect the filter unit from corrosion, the Nynas employees drain it regularly. In addition, the team has now added another element to the BVT: A 12 m³ tank has been equipped with a lamella package to separate the water produced from the exhaust gases even more efficiently before they are passed through the filter. This system is currently in the commissioning phase and the first results are promising.
According to the team, the main lessons learned from the project were the following:
1. Carry out a thorough pre-study phase
Mr Behrens explains: "The preliminary study phase is of enormous importance for project planning and execution, without the risk of costs getting out of hand. This phase lasted more than a year and was carried out in a structured way. It was a new area of activity for us - bitumen vapour treatment is not our core business. But it is an important issue from occupational health and safety and environmental protection point of view. "
"At the end of the preliminary study phase, in which we examined all the technical solutions, we had a relatively clear picture.", Mr Philipowski recalls.
2. Optimise the system to extend the life of the filter bed
Mr Behrens says: "The service life depends very much on the pollutants, including the hydrocarbon and H₂S content. But by regularly testing during operation, we were able to optimise the system and maximise the filter's service life."
3. Good cooperation makes many things easier
"I found the cooperation with DESOTEC to be positive - we had goal-oriented discussions with the technical consultants about aspects such as connections or flanges and how these can be physically implemented in the plant," says Mr Behrens.
"We had good discussions and really quick answers from DESOTEC," adds Mr Philipowski. "From the technical side, everything was good. "
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