In ISPT’s Gas Separation & Treatment cluster, several projects were successfully concluded earlier this year. The projects focused on determining the technical and economical feasibility of innovative technologies to remove acid components (CO2 and H2S) from natural gas and biogas. These new technologies could lead to significant savings in energy consumption.
A large percentage of the remaining natural gas reserves contains contaminating acid components such as H2S and CO2, and biogas typically contains a large amount of CO2. To turn these “sour” gases into pipeline-quality gas, they first need to be purified. The most common way to remove acid components from gas is by means of amine stripping. In this process, a solvent is used containing amines, which are able to bind with CO2 and H2S. To subsequently remove the contaminants from the solvent (in the regeneration process), the solvent needs to be heated. This is a very energy-consuming process. The project partners therefore focused on two new technologies that would make the gas purification process more energy effective: pressure-assisted stripping and immobilised amines.
Pressure-assisted stripping (PAS)
Pressure-assisted stripping (PAS) uses the same technology as traditional amine stripping, but a solvent regeneration step at elevated pressure is added to reduce water evaporation in this part of the process. “Back in 2013, our company filed a patent for PAS, with the aim of reducing the regeneration energy of acid gas-loaded solvents,” says Martijn Oversteegen of Procede Gas Treating. “We discovered that we can lower energy consumption by first regenerating loaded solvent at high pressure. Subsequently, leaner solvent, which contains less CO2, can be regenerated at lower pressure. The objective of the project was to evaluate the potential of PAS for several industrial gases. The efficiency of PAS was demonstrated successfully for various feed gases and gas specifications. Simulations have proven that PAS lowers the required regeneration heat by up to 28% and that it is particularly beneficial for applications where CO2 is required at high pressure. We’re now working on a pilot unit for the experimental validation of PAS for selected cases.”
Immobilised amines
A highly innovative technology for removing acid components from gas makes use of a solid carrier material for the amines instead of water. “A solid carrier immobilises the amines, enabling process intensification, and the absence of an aqueous solvent means that no energy is wasted on evaporation of water,” explains Peter Hauwert of Frames Oil & Gas Processing. “The effect of this is that both energy use and the size of the reactors can be reduced.” Between June 2013 and March 2016, ECN and the University of Twente performed experiments to determine the capacity, kinetics and stability of the solid sorbents, as well as process studies to test the optimum conditions and reactor design. This was combined with system studies into energy integration and a technical-economic analysis. “This integrated approach has shown that the immobilised amines application is technically feasible, and will indeed result in savings in terms of both reactor size and energy consumption,” says Peter. “A follow-up study has now been started, and we hope we will be able to generate a proof of concept in the next few years.”
System studies
Project partner ECN carried out system studies related to the two technologies. “In our technical-economic evaluation, we used conventional amine stripping as a reference,” says Jan Wilco Dijkstra of ECN. “We had to bear in mind that the two technologies are at a different stage of development, with the PAS technology being far more mature than immobilised amines, which is still in a very early development phase. Nevertheless, making the comparisons was still useful, as you gain better insight into the aspects that are most important for the applications. We not only considered the removal phase of CO2 and H2S, but also the entire system of gas production, including drying for instance, and, in the case of biogas, fermentation and compression. We particularly focused on options for heat integration at the various stages. All in all, it was a fruitful exercise, in which we worked very well with all partners involved. The results were also positive. We now have better insight into the specific cases that would benefit from PAS, and we learned that the utilization of immobilised amines had an unexpected benefit for biogas treatment, as you can make good use of residual heat in the fermentation process. Overall, we’ve calculated that the two technologies could lead to potential savings in energy consumption of 20%. This is a significant reduction, which can have a truly positive impact on the gas industry as a whole.”
About the Gas Separation & Treatment Cluster
Removal of contaminations is an important issue in the production of pipeline quality gas. The projects in this cluster focus on reducing energy usage and emission of gases with a calorific value to enable the maximum utilisation of renewable gas and stranded natural gas fields. The projects described above started in 2013 and ran until early 2016. They were coordinated by ISPT. The industrial partners were Shell, Procede and Frames, while ECN and the University of Twente served as research partners.
About ISPT
The Institute for Sustainable Process Technology unites industry, universities, research organizations and SMEs in order to accelerate innovation and ultimately transform process technology into a green, clean, efficient endeavour. In addition to developing knowledge, the Institute fosters the demonstration and application of new technologies. For more information, take a look around on this website.