Methanol Synthesis loop

However, not all the hydrogen that is produeed is used in the produetion of methanol. To prevent an exeessive buildup of hydrogen in the reeireulating methanol synthesis loop, a slipstream is drawn off eonsisting of hydrogen and some CO and CO2. It is fed to the boiler as supplemental fuel to the main natural gas fuel supply. The slipstream is at approximately 800 psi pressure and must be redueed to 75 psi before it ean be fed to the boilers. 

In order to prevent any sulfur or other poisons, such as hydrogen cyanide, from reaching the methanol synthesis catalyst, the make-up synthesis gas is passed over an absorbent catalyst and finally cooled for the suction of the synthesis gas circulator in the methanol synthesis loop. 

Unconverted methane present in the refonmng effluent behaves in the successive operations like an inert diluent To prevent its buiid-up in the recycle, which constitutes the methanol synthesis loop", a purge is necessary. 

Sulphur is detrimental to the sjmthesis and trace amounts of sulphur are removed using zine oxide prior to synthesis. After the production of synthesis gas, the methanol sjmthesis requires compression to about lOObar. The methanol synthesis loop con rises a reactor, a separator and recompression of the reeyele gas. A purge gas can be used to produce power supplemented by steam raised in the methanol reactor and the coal gasifier. The crude methanol produced can be upgraded to chemical grade product by distillation. The intermediate methanol is passed into storage. The reaction stoichiometry is ... 

New technologies for methanol synthesis are presently being developed. These new systems, which have been tested in bench or demonstration units, use either low temperature liquid-gas phase or solid-gas phase methanol reaction techniques. However, the suitability for cormvercialization of these new technologies is uncertain due to either questionable economical advantages or insufficient development therefore, this paper will address the conventional methanol synthesis loop. 

Fig. 2 shows the I.C.I. warm-shot methanol synthesis loop. The adiabatic methanol reactor has multiple catalyst beds which cure quenched with warm reactant gas that control the methanol converter s temperature profile and methanol outlet concentration as portrayed in Fig. 3.. In this adiabatic quench redctor methanol loop scheme, the main features are ...

Uhde GmbH Methanol Natural gas, LPG and heavy naphtha Process uses steam-reforming synthesis gas generation and a low-pressure methanol synthesis loop technology 11 NA... 

The synthesis gas, after the customary shift conversion and purification, is delivered at synthesis gas specifications to the compressors for the methanol synthesis loop. This operates as a series of catalytic converters, which have advantages over the systems used conventionally both as to the fiow arrangement and catalyst used in the Wentworth process. Sulfur is removed in the elemental form but the crude methyl fuel retains the higher alcohols and other impurities produced in small amounts (2-3%). They contribute to its value as a fuel. 

Fig. 3.7. Methanol synthesis loop, (a) Recycle compressor (f>) heat exchanger, (c) reactor, (d) cooler/condenser, (e) methanol separator, (/) start-up heater...

A methanol synthesis loop with a stoichiometric feed of CO and H2 is to be designed for a 95% overall conversion of CO. All the methanol formed leaves in the product stream. Not more than 2% of the CO and 0-5% of the H2 emerging from the reactor is to leave in the product stream—the remainder is recycled. Calculate the single pass conversion, the recycle ratio and the composition of the product. 

The main advantage of the indirect routes via syngas is the very high carbon efficiency. As an example, a modem methanol synthesis loop based on natural gas may operate with more than 50% conversion per... 

In both cases only partial conversion can be obtained at realistic conditions, and in order to approach full conversion a recycle system is used. The detailed lay-out is, of course, different in different cases. As illustrations, the lay-out of Haldor Tops0e Low Energy Ammonia Synthesis Loop is shown schematically in Fig. 1 and of a Haldor Tops0e Low Energy Methanol Synthesis Loop in Fig. 2. 

Once the raw has been scrubbed for soot removal, H2s is removed and CO is shifted across a cobalt molybdenum sour gas shift catalyst to adjust the H20/C0/C02 ratio. Finally, excess C02 is removed and the gas may be compressed (if required) and then processed in a conventional methanol synthesis loop. The processing steps as just described yield a syn that is approximately stoichiometric in nature (i 1.0) althou considerably more concentrated in CO than C02. 

Design of the methanol synthesis loop and accompanying distillation train is generally based on the following considerations ... 

Because carbon is the limiting factor, the carbon conversion to methanol, also referred to as carbon efficiency, is an important operating parameter for overall ener efficiency. Carbon efficiency is a measure of how much carbon in the feed is converted to methanol product. There are two commonly used carbon efficiencies, one for the overall plant and one for the methanol synthesis loop. For the overall plant all the carbon-containing components in the process feedstock from the battery limits and the methanol product from the refining column are considered. For a typical plant and natural gas feedstock, an overall carbon efficiency is about 75%. The methanol synthesis loop carbon efficiency for the same plant is about 93%. The synthesis loop carbon efficiency is calculated using only the carbon in the reactive components in the makeup gas (CO and C02). Carbon in the form of methane is not considered because it is inert in the methanol synthesis reaction and is ultimately purged from the loop and burned. The carbon in the product for this calculation is that in the form of methanol in the crude leaving the methanol synthesis loop. 

It is possible to adjust the ratio of hydrogen to caibon oxides by the addition of caibon dioxide to the synthesis gas, either just before the methanol synthesis loop, or directly into the feed for the steam reformer. It is also possible to use a secondary reformer using oxygen rather than air, after the primary reformer. The amount of oxygen used is adjusted to provide the stoichiometric ratio of hydrogen and carbon oxides and, at the same time, reduce the amount of inert methane in synthesis gas. (Table 9.9)... 

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