Modular Methanol Plants
Pyramid E&C offers a cost-effective, small-scale modular methanol production plants. The modular plants are offered with ~200 TPD of chemical grade Methanol. This technology consists of 2-step reforming process which includes a methane steam reformer and a high-temperature secondary reformer (HTCR) with a boiling-water methanol reactor to produce crude methanol.
Methanol production technology using natural gas as feed is divided into following sections:
- Gas Treatment and Compression
- Methanol Synthesis
- Methanol Purification
Gas Treatment and Compression
Feed gas will be compressed, if battery limit pressure is low. Gas will be treated in gas treatment section to remove natural gas liquids, water and acid gases. The treatment requirements will depend on inlet gas quality. Hydrogenator and sulfur removal beds will be used to remove traces of sulfur prior to reforming. The gas (containing hydrogen) from methanol synthesis loop is used for hydrogenation of sulfur compounds.
The two-step reforming process features a combination of tubular reforming (primary reforming) followed by oxygen-fired adiabatic reforming (secondary reforming). This technology can be used for large and small-scale plants and offers several advantages compared to conventional steam reforming indicated below:
- CO, CO2, and H2 produced are in the stoichiometric ratio, thus minimizing feed consumption.
- Syngas generation pressure is relatively higher (about 40 bar) thereby reducing the energy requirement for make-up gas compression (single stage compressor).
- Steam Reformer load is substantially reduced. Consequently, smaller sized reformer and lower quantity of fuel are required which further reduces the required size of associated equipment in the flue gas duct area.
The methanol synthesis step involves conversion of synthesis gas into raw methanol. Raw methanol is a mixture of methanol, small amount of water, dissolved gases and traces of by-products (DME, higher alcohols, other oxygenates and minor amounts of acids and aldehydes). The methanol synthesis catalyst and process are highly selective in nature. The conversion of hydrogen and carbon oxides to methanol is described by the following reactions:
CO2 + 3H2 → CH3OH + H2O
CO + 2H2 → CH3OH
The methanol synthesis is exothermic in nature and maximum conversion is expected under low temperature and high-pressure conditions. A challenge in the design of methanol synthesis process is to remove the heat of reaction efficiently and economically (i.e. at high temperature) and at the same time to equilibrate the synthesis reaction at low temperature thus ensuring high conversion per pass.
The two-column distillation unit represents the low-cost unit and three-column distillation unit is the low-energy system. Two column and three column distillation unit is used to produce grade AA methanol (typical chemical grade) and a single column distillation unit is used for production of Fuel-grade methanol (blending component for gasoline).