PTQ Q3 2025 Issue

Engineering the next step in absorber efficiency and capacity

Enhancing contactor column hydraulics and mass transfer in gas processing to enable smaller absorbers, higher throughput, reduced costs, and better contaminant handling

Anh Do Thi Viet, Ton Schlief, and Karl Stephenne Shell Catalysts & Technologies

S hell’s Turbo Technologies (STT) solution is designed to enhance contactor column hydraulics and mass trans- fer in acid gas removal units (AGRU) and triethylene glycol (TEG) dehydration applications. STT can substantially reduce costs and energy consumption by eliminating the need for new equipment and solvents while improving con- taminant removal and enhancing processing capacity. Operators of AGRUs and TEG dehydration plants face growing challenges as the oil and gas industry contends with more contaminated resources, stricter product spec- ifications, and increasing pressure to maximise efficiency while minimising costs. In greenfield projects, one of the biggest constraints is the high capital expenditure (Capex) of the high-pressure absorption column, which can account for up to 40% of total project costs (see Figure 1 ). The abil- ity to increase mass transfer rates and throughput without expanding equipment size is crucial to keeping costs down while ensuring compliance with product specifications. In existing plants, operators are increasingly facing capacity constraints from rising feed gas contamination levels. Many facilities have already upgraded to the latest- generation structured packing or high-capacity trays. However, absorbers remain a critical bottleneck, restricting their ability to process higher concentrations of contaminants without compromising product quality.

Expanding capacity by adding processing trains is both expensive and complicated. Concerns about operational dis - ruptions and high upgrade costs often deter investment, even as regulatory limits on contaminants such as hydrogen sul- phide (H 2S) and carbon dioxide (CO2 ) become more stringent. Overcoming AGRU constraints Against the backdrop of these bespoke challenges, STT enhances mass transfer efficiency and column hydraulics, allowing operators to debottleneck absorbers, increase throughput, and process higher contaminant loads – without major infrastructure expansions. For greenfield projects, STT enables smaller, more cost-ef - fective absorbers by maximising gas-liquid contact and sep - aration efficiency, reducing the contactor column Capex by up to 50%. In brownfield applications, it provides a simple, retrofit-friendly solution, helping operators increase column capacity by up to 50% and defer costly additional trains. The key innovation lies in the seamless integration of the dedi - cated contacting and separation zones within a single tray package (see Figure 2a ). In the contacting zone, natural gas and solvent are thor - oughly mixed for effective contaminant absorption. Liquid enters through ports at the base of the tray (see Figure 2b ), while gas flows from the tray below into the contacting box

100

Liquid

70-bar column 20-bar column

Gas

Figure 2 STT tray assembly ready to fit in a column (a) and a schematic diagram of the gas and liquid flows (b): (1) liquid entering the contacting box; (2) absorption of contaminants (co-current upward flow); (3) swirl tube (gas-liquid separa - tion); (4) upward gas flow; (5) downward liquid flow

Absorption column diameter (m)

Figure 1 The relationship between the cost and diameter of an absorption column at high and low pressure

PTQ Q3 2025