Decarbonisation Technology - November 2021

Maximise natural gas conversion by recycling >90% of carbon - containing purge stream to reforming feed.

Hydrogen used as primary fuel for reforming. Zero natural gas fuel.

Reduced CO 2 in synthesis gas reduces H consumption in production of methanol.

Amine-based CO removal. Delivery of CO as p roduct s tream .

Barge

CO product

Rail

Feedstock

Natural gas

Methanol product storage

Truck

H fuel

Fuel tail gas ~10%

Recycle tail gas ~90%

Recycle

H separation

Elements added for TrueBlue

Reforming & tail gas recycle

CO removal

Methanol synthesis

Methanol distillation

TruBlue methanol production process with CO 2 capture and removal and hydrogen used as the primary fuel

is in the range of 0.35-0.36 weight CO 2 /weight methanol product. So, for a 2000 tpd conventional methanol plant, the SMR stack gas CO 2 emissions would be in the range of 700-720 tpd (255,500 to 262,800 tpy). TrueBlue Methanol production The BDE TrueBlue Methanol plant design is also SMR based with several significant additions when compared with the conventional plant. First, the SMR front end includes the use of pre-reforming and convection section reheat of pre-reformer effluent to effectively shift a portion of the required reforming reaction duty from the radiant section to the convection section. Second, an amine-based CO 2 removal system is added immediately upstream of the synthesis gas compressor to reduce the proportion of CO 2 feeding to the methanol synthesis reactor. This effectively reduces the quantity of hydrogen consumed in the production of methanol, reducing the amount of reaction water produced, which enables recovery of that hydrogen for use as SMR fuel: CO + 2H 2 ⇔ CH 3 OH + Heat [2 moles of H 2 consumed per mol of CH 3 OH produced] CO 2 + 3H 2 ⇔ CH 3 OH + H 2 O + Heat [3 moles of H 2 consumed per mol of CH 3 OH produced]

Third, purge gas from the methanol synthesis loop is routed to a pressure swing adsorption (PSA) unit to separate out a major portion of the hydrogen remaining in that stream for use as fuel. The tail gas from the PSA unit, containing CH 4 , CO 2 , CO, inert components and unrecovered H 2 , is recompressed to allow recycle of approximately 90% of the tail gas back to the SMR feed stream. Approximately 10% of the PSA tail gas is routed to SMR fuel to limit the accumulation of inerts in the synthesis gas. The recovery of hydrogen as described, along with the small PSA tail gas flow, are enough to supply all the fuel required for the SMR, reducing the natural gas firing of the SMR to zero. The recycle of approximately 90% of the carbon-containing components of the purge achieves more complete conversion of incoming natural gas feed to synthesis gas. These added elements extract CO 2 from the plant as a product stream while reducing the SMR stack gas emissions of CO 2 by 90-93% when compared with a conventional plant. Overall energy consumption of the TrueBlue methanol plant remains in the range of 27.0-28.0 MMBtu of total energy (LHV basis) per short ton of high purity methanol product. Total energy here is based on total natural gas feed with zero natural gas fuel, as well as net electric power import for the methanol plant and associated utility units.