Development of Intensified Continuous Processes: Lessons Learned through Scale up of New H2s Scavengers

The presence of naturally occurring hydrogen sulfide (H₂S) is found in oil and gas reservoirs worldwide. There are several options for the removal of H2S from the production of oil and gas and these options range from fixed assets that scrub H2S to chemical injection at the wellsite. The majority of the non-reversible chemical H2S scavenger market is based on triazine technology derived from the reaction products of formaldehyde and amines (most common monoethyleneamine MEA). In recent past, there has been an active search by all to improve the overall performance of H2S scavengers in oil and gas production.

Major topics that the current technology can be improved upon include: increased consumption of H2S, reduction of nitrogen contamination of crude oil, reduction of scaling issue, elimination deposition of by-products, addressing EHS concerns and minimization of the disposal of products/by-products. Some of the biggest hurdles with new H2S scavengers are the following: ensuring fast kinetic reaction rates, system compatibility, similar molar ratio (i.e., consumption rates), minimal precipitation of scavenger/by-products, large manufacturing scale, large raw material supply and price points that allows for a benefit of change. Ideally, the new product would offer better consumption performance versus the incumbent, reduction in nitrogen content and minimization of deposition.

A product identified over 20 years ago as a potential replacement was 2-Methyl-3-buten-2-ol (MBO). However, MBO has had limited application in field until recently. MBO is a reaction of amine (monoisopropylamine) and formaldehyde which offers some of the same benefits of triazine but improves upon the areas of increasing consumption of H2S per mole of scavenger, reducing nitrogen content in crude oil, reducing the by-product deposition potential and is already produced on large manufacturing scales. Production on a large manufacturing scale is critical for success of any H2S scavenger into the oil and gas market.

The body of work performed here demonstrates Lubrizol’s approach to rapidly scaling H2S scavenger manufacturing production through modular process intensification and conversion of a batch process to a continuous reaction process. The process described herein involves the reaction of formaldehyde with an amine resulting in the formation of water as a by-product of reaction which subsequently needs to be removed to drive conversion to the desired product. Despite the apparent fast reaction rate between formaldehyde and amines, the current batch process has a standard processing time of 18 hours. This long time cycle is due to several factors including: bulk solid paraformaldehyde charging, slow heat up and cool down times, and mass transfer and equilibrium limitations during the reaction and stripping stages of the process. In an effort to debottleneck manufacturing and improve product quality, the project team sought to convert the batch process to a modular continuous process. Initially, a reaction rate and calorimetry study were conducted to elucidate the reaction kinetics and overall heat of reaction. This work became the foundation for continuous reactor train design to maximize heat removal and control the reaction temperature to minimize by-product formation. A subsequent study involved the development of a novel reactive distillation design which enabled a single pass, continuous stripping process. The resultant product is an analytically equivalent product to the batch process.

The project team is currently focusing on scaling the new continuous process in a modular shipping-container-size design for rapid deployment in production. The total process development timeline for this work was less than 10 months and the total time from inception to the deployment of a commercial unit is expected to be less than 24 months.