Catalysis 2026 Issue

100

120

Base case

Revamp case

Base case

Revamp case

Carbon eciency %

Single pass conversion

Nat gas feed

Nat gas fuel

(Feed + fuel) Nat gas CO2 emissions index

Circulation rate

Purge rate

(Nat gas + ethane) feed

Ethane feed

Note: All the numbers are represented as % of Base Nat Gas Feed Rate

feedwater pumps, and ASU compressor services. Excess medium-pressure steam is used for power generation in an extraction-condensing turbine, and the turbine exhaust flows to the low-pressure header to improve overall energy recovery. Condensate from turbines and from medium- and low-pressure systems is routed to the deaerator to reduce its steam demand. Process condensate is stripped with low-pressure steam, and the off-gases are recovered as SMR fuel to support overall energy efficiency. The combined front-end and synthesis-loop modifica - tions introduce coordinated changes across this integrated steam system. On the front end, the natural gas feed rate decreases while natural gas firing increases, resulting in a lower total natural gas requirement for the revamp case (see Figure 4 ). The SMR experiences a modest increase in firing duty, and auxiliary firing also increases due to lower inter - nal high-pressure steam generation. High- and medium- pressure steam production operates at slightly reduced lev - els, driven primarily by the lower boiler feedwater preheat temperature in the synthesis loop, resulting from reduced circulation rates. Oxygen demand rises slightly; however, the oxygen requirement per unit of methanol shows a small improve - ment. A minor increase in CO₂ emissions is observed, largely reflecting the shift in fuel composition as a greater fraction of purge gas is routed to the PSA for hydrogen recovery. This adjustment helps maintain the target R ratio in the make-up gas. Within the synthesis loop, intermediate condensation significantly increases single-pass conversion and improves carbon efficiency, thereby reducing the required purge rate (see Figure 5 ). A larger share of the reduced purge is directed to the PSA for hydrogen recovery and recycle, supporting the target R ratio but reducing the heat availa - ble from tail gases. The decrease in tail‑gas heat availability is offset by additional natural gas firing. Importantly, these changes do not impose any additional power demand on the make-up gas or recycle compressors. This confirms that the incremental methanol production is not achieved by pushing the existing synthesis loop to higher circulation or compression, but by removing equilib - rium and product build-up constraints that normally define the plant’s maximum achievable rate. Figure 5 Carbon/conversion efficiency and circulation/purge rate

Figure 4 Feed, fuel, and CO₂ emissions

significantly lower methanol and water concentrations. Since only methanol and water are removed, inert levels remain unchanged. The reduction in circulating product shifts the equilibrium in accordance with Le Châtelier’s principle, thereby improving the thermodynamic driving force in the downstream converter. The lower gas flow, combined with reduced methanol concentration and a more favourable temperature pro - file, allows the tube-cooled converter to operate closer to equilibrium, thereby increasing single-pass conversion and reducing overall loop circulation. This allows additional syn - gas conversion beyond what can be achieved by installing a higher-activity or newer catalyst, because the binding limitation being removed is equilibrium and loop circulation rather than intrinsic catalyst kinetics. Simulation results indicate that this intermediate con - densation step provides an additional 4% increase in plant throughput and improved carbon efficiency. When combined with the front-end ethane-blending upgrade, the overall revamp supports a total capacity increase of approximately 5%. Integrated steam system and revamp impacts The plant operates with an integrated steam system that supports all major rotating equipment, including the air separation unit (ASU) main air compressor. High-pressure steam is generated in the ATR waste heat boiler and fur - ther superheated in the SMR convection section. Since this steam generation does not fully meet the demand of all steam-driven equipment, additional high-pressure super - heated steam is supplied from an auxiliary off-site boiler. Medium-pressure steam is produced in the synthesis loop and is also superheated in the SMR convection sec - tion. High-pressure steam drives the syngas compressor, the synthesis loop recycle compressor, and the ASU air compressor. The syngas compressor turbine operates on an extraction cycle, with the extracted steam providing process steam for the steam-to-carbon ratio, ATR burner cooling, and other front-end requirements. Any surplus extraction steam is let down to the medium-pressure header. The medium-pressure header supplies steam to the forced-draft (FD) and induced-draft (ID) fans, boiler

Catalysis 2026