Modular Methanol Plants
Pyramid E&C offers cost-effective, small-scale modular methanol plants capable of producing 150 TPD of fuel or chemical grade Methanol using 6-7 MMSCFD of natural gas. The process scheme consists of a methane steam reformer and a high-temperature secondary reformer with a boiling-water methanol reactor to produce crude methanol. The process comprises of following steps:
(1) Gas Treatment and Compression
(3) Methanol Synthesis
(4) Methanol Purification
1. Gas Treatment and Compression
If battery limit pressure is low, the feed gas will need compression. Natural gas is pre-treated to remove liquids, water and acid gases. Hydrogenation and sulfur removal beds are used to remove traces of sulfur prior to reforming. The gas 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 offers several advantages compared to conventional steam reforming indicated below:
- CO, CO2 and H2 produced are in stoichiometric ratio, thus minimizing feed consumption.
- Syngas generation pressure is relatively high, thereby reducing the energy requirement for make-up gas compression.
- Steam Reformer load is substantially reduced, resulting into a compact reformer and lower fuel consumption which further reduces the size of associated equipment.
3. Methanol Synthesis
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 happens under low temperature and high-pressure conditions. The design offers effective heat removal system to equilibrate the synthesis reaction at low temperature thus ensuring high conversion per pass.
4. Methanol Purification
The distillation section is a single column unit if used for production of Fuel-grade methanol (blending component for gasoline). The section can be expanded to two or three columns unit to produce grade AA methanol (typical chemical grade) and optimize the energy requirements.