The Davy Process Technology–Johnson Matthey process is a low-pressure methanol process. The process produces methanol from natural or associated gas via a reforming step or from syngas generated by the gasification of coal, coke or biomass. The reforming step, also available from this licensor, may be conventional steam reforming (SMR), compact reforming, autothermal reforming (ATR), combined reforming (SMR + ATR) or gas-heated reforming (GHR + ATR). The reforming or gasification step is followed by compression, methanol synthesis and distillation (one, two or three column designs) Capacities up to 7,000 metric tpd, are practical in a single stream and flowsheet options exist for installation of the process offshore on FPSO vessels.
The following description is based on the SMR option. Gas feedstock is compressed (if required), desulfurized (1) and sent to the optional saturator (2) where most of the process steam is generated. The saturator is used where maximum water recovery is important and it also has the benefit of recycling some byproducts. Further process steam is added, and the mixture is preheated and sent to the optional pre-reformer (3), using the Catalytic-Rich-Gas (CRG) process. Steam raised in the methanol converter is added, along with available carbon dioxide (CO2), and the partially reformed mixture is preheated and sent to the reformer (4). High-grade heat in the reformed gas is recovered as high-pressure steam (5), boiler feedwater preheat, and for reboil heat in the distillation system (6). The high-pressure steam is used to drive the main compressors in the plant. After final cooling, the synthesis gas is compressed (7) and sent to the synthesis loop. The loop can operate at pressures between 50 bar to 100 bar. The converter design does impact the loop pressure, with radial-flow designs enabling low loop pressure even at the largest plant size. Low loop pressure reduces the total energy requirements for the process. The synthesis loop comprises a circulator (8) and the converter operates around 200°C to 270°C, depending on the converter type.
Reaction heat from the loop is recovered as steam and saturator water, and is used directly as process steam for the reformer. A purge is taken from the synthesis loop to remove inerts (nitrogen, methane), as well as surplus hydrogen associated with non-stoichiometric operation. Also, the purge is used as fuel for the reformer.
Crude methanol from the separator contains water, as well as traces of ethanol and other compounds. These impurities are removed in a two-column distillation system (6). The first column removes light ends such as ethers, esters, acetone and dissolved noncondensable gases. The second column removes water, higher alcohols and similar organic heavy ends.
Licensor: Davy Process Technology with Johnson Matthey Catalysts, both subsidiaries of Johnson Matthey Plc.