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Zawartość zarchiwizowana w dniu 2022-12-27

REVAMPING OF A PLANT PRODUCING METHANOL TO A PLANT PRODUCING METHANOL AND HIGHER ALCOHOL

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The joint production of higher alcohols with methanol in a typical 30/70 ratio obtained from syngas via direct synthesis. The blend has the composition required to avoid phase separation when blended with gasoline. The project demonstrates that :
1. energy can be saved in a refinery by blending MAS into gasoline up to ECC limits
2. products are of a higher purity
3. life of catalyst, reliability and ease of operation are increased.
Plant operation, to ascertain production capacity under reaction isothermal conditions, was mainly aimed at experimenting with both catalyst and process performances on an industrial scale, after laboratory test on a reduced scale, had been carried out. Of the three plant sections, only the product synthesis synthesis and the distillation section were submitted to experimentation.
Testing included the following:
- running the plant with temperatures at catalytic bed outlet +/- 10% lower than normal;
- to check the effect on production, by variation of H2/CO in reactor inlet gas;
- to check reaction when different CO2 percentages were fed to the reactor;
- to check possible kinetic effect of methanol on formation of alcohols having a higher molecular weight;
- as far as the distillation section is concerned, different condenser temperatures, reflux flow rates and feed tray positions were tested for all three cycle columns, to reduce steam consumption;
- a test was also made on neutralisation of the product containing an amount of organic acids as raw material.
All experimental work on the plant was carried out concurrently with laboratory analyses, revision of well known analytical methods, development of new analytical methods and experimental data processing. Accurate knowledge was gained of the composition of all the streams in the plant, even for components present in ppm. Other steps led to verification of a kinetic equation, based on laboratory data for the design and optimization of the synthesis reactor. Additionally, by processing the data gathered from the Pisticci plant, it was possible to implement tha basic design of a typical plant for production of methanol and higher alcohols.
In the light of results obtained throughout the plant running period, experimentation on methanol and higher alcohol production has been successful, in terms of both catalyst performance, durability and plant consumption.

Having collected all the data required for thedesign of an industrial plant, it is now possible to commercialise this technology.
The project envisages modification of an existing methanol plant to obtain the simultaneous production of methanol and higher alcohols.
The innovatory aspect of the process lies in securing the economic advantage conferred by the simultaneous industrial scale production of a methanol-higher alcohol blend suitable for use as an additive to gasoline. Although similar products are available, these result from the blending of separately produced alcohols.
The demonstration plant is subdivided into three sections:
- synthesis gas preparation unit;
- raw product synthesis section;
- distillation section.
Plant operation, to ascertain production capacity under reaction isothermal conditions, was mainly aimed at experimenting with both catalyst and process performances on an industrial scale, after laboratory testing on a reduced scale had been carried out. Synthesis gas is obtained from steam reforming of natural gas: after desulphurization, natural gas is mixed with steam and carbon dioxide and then fed into the steam reforming furnace. Carbon dioxide serves to reduce the H2/CO ratio to an optimal value for MAS synthesis.
Synthesis gas from the furnace is cooled to ambient temperature then sent to a carbon dioxide washing unit. Part of the heat is recovered, producing low pressure steam. Synthesis gas from the gas preparation section (hydrogen and carbon monoxide) is compressed to synthesis pressure, ranging from 50 to 150 atmospheres. Make-up gas joins recycle gas, and preheated by reactor gas synthesis gas is fed to the reactor. Reactions are exothermic and the reaction heat disposed of, preventing catalyst temperature from rising.
The reaction system is very similar to the systems adopted for methanol production, the difference between the two being mainly in the catalyst. In the MAS process, the catalyst uses a different formula, and reaction temperature required to promote the formation of higher alcohols, is higher.

The distillation stage is important, because the use that MAS is intended for, requires a very low water content. Raw MAS is preheated and fed to a rectifying column at the top of which, methanol, ethanol and small quantities of light products are extracted. Heavier products, alcohols and water come out at the bottom of the column, cooled and sent to a phase separator where two liquid phases settle: an organic light phase and an aqueous heavy phase. The organic phase (higher alcohols) in leaving the bottom of the column is mixed with the top product of the rectifying column producting an anhydrous product. Azeotropic vapour consisting of higher alcohols-water-cyclohexane, is extracted from the top of the azeotropic column, condensed and sent to the separator. The light, organic phase containing cyclohexane is sent to the column, the heavier aqueous phase to feed tray or separator. This dehydration scheme gives a product containing less than 1,000 ppm water.

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SNAMPROGETTI SPA
Wkład UE
Brak danych
Adres
Viale Alcide De Gasperi 16
20097 SAN DONATO MILANESE
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