Lurgi methanol synthesis

Fig. 3.11. LURGI Methanol synthesis loop, (a) Recycle compressor, Q>) heat exchanger, (c) reactor (d) collCT/condaiser, (e) separator... 

In this energy chain, coal is gasified to generate synthesis gas. The H2 CO ratio required for an optimum efficiency is adjusted via the CO shift reaction of a part of the carbon monoxide (CO) contained in the synthesis gas. The remaining synthesis gas is converted to liquid hydrocarbons via Fischer-Tropsch synthesis or via methanol synthesis with a downstream MtSynfuels (trademark by Lurgi) process (see beginning of Section 7.3.4). The liquid hydrocarbon yield amounts to about 0.40 MJ per MJ of hard coal, which is of the same order of magnitude as in the case of BTL ( 0.40 MJ/MJ) to calculate the thermal process efficiency, the electricity export must also be taken into account (see Table 7.12). 

The preconverted gas is routed to the shell side of the gas-cooled methanol reactor, which is filled with catalyst. The final conversion to methanol is achieved at reduced temperatures along the optimum reaction route. The reactor outlet gas is cooled to about 40°C to separate methanol and water from the gases by preheating BFW and recycle gas. Condensed raw methanol is separated from the unreacted gas and routed to the distillation unit. The major portion of the gas is recycled back to the synthesis reactors to achieve a high overall conversion. The excellent performance of the Lurgi combined converter (LCC) methanol synthesis reduces the recycle ratio to about 2. A small portion of the recycle gas is withdrawn as purge gas to lessen inerts accumulation in the loop. 

Flow sheet of the Lurgi low pressure methanol synthesis process. 

Fig. 7-1 Chemical processing flow chart of the Lurgi low-pressure methanol synthesis, from [38]... 

A side stream of gas is bypassed around the shift unit to achieve the correct Hj CO ratio for the methanol synthesis process. Methanol synthesis itself operates at about 80 bar using the Lurgi Low Pressure Methanol Process followed by a distillation step to achieve the required product quality specification. 

The first copper catalysts suitable for methanol synthesis on a commercial scale were developed at the end of the 60s by ICI in Billingham [3.14] and LURGI in Frankfurt [3.15]. According to the first relevant patents owned by the two companies, these catalysts had the following composition ... 

The LURGI Octamix Process developed in the years 1978 to 1983 also applies a synthesis loop highly similar to that for the LURGI low-pressure methanol process. As in the case of this process, the tubular reactor is also used to produce fuel methanol. A modified variant of the LURGI methanol catalyst is used operating optimally at a temperature range between 260 and 290° C and at pressures below l(X)bar. 

There are several commercial gas-solid catalysed reactions in which heat transfer plays a significant, if not dominant, role in limiting the reactor productivity, lowering the process selectivity and reducing the life of the catalyst. Among these include the oxidation of ethylene, benzene, C hydrocarbons and methanol, the ammoxidation of propylene, methanol synthesis (Lurgi), the hydrochlorination of methanol and steam reforming of natural gas and naphtha. 

Figure 4.9 Overall heat transfer coefficient (a) and heat transfer parameters (b) of a highly conductive structured catalyst in methanol synthesis as a function of the syngas stoichiometric number in the fresh feed stream (Mp). (Squares) Commercial Lurgi multitubular packed-bed reactor (PB) (circles) copper honeycomb monoliths (HM) (triangles) open-cell foams (OF). In Figure 4.9b, the radial effective thermal conductivity is plotted with solid symbols and the wall heat transfer coefficient, h, with empty ones. Reprinted from Montebelli etal. [162], with permission from Elsevier.

Figure 10.9. Lurgi reactor for a low-pressure methanol synthesis plant. Reproduced with permission from Lurgi Aktiengesellschraft.

Lurgi 01 Gas Chemie GmbH Methanol Natural gas, naphtha, vacuum residue, natural gas Oxygen-operated syngas generation, two-step isothermal synthesis with maximum yield and very large single-train capacity 40 2000... 

The processes listed in Table 9.4 that are reported to be used commercially to supply synthesis gas for methanol production are the Lurgi process, the... 

Rectisol is licensed by the two companies that developed it, Lurgi and Linde. It uses cold methanol as a solvent and can remove total sulfur down to below 100 ppb. It will also remove other impurities present in synthesis gas such as cyanides and carbonyls. Although not cheap, the gas purity achievable with this process makes it a prime candidate for applications processing syngas to chemicals such as ammonia or methanol. 

The high pressure of the process was required because of the poor activity of the catalyst, but this problem was alleviated by the introduction of better catalysts by ICI and Lurgi in the 1960s and 1970s [148]. The current process for the synthesis of methanol, as operated by ICI in England [148], requires a CO/CO2/H2 feed mixture and a pressure of between 50 and 100 bar, which may or may not be supercritical, depending on the composition and pressure. 

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