Methanol flow sheet

Quench Converter. The quench converter (Fig. 7a) was the basis for the initial ICl low pressure methanol flow sheet. A portion of the mixed synthesis and recycle gas bypasses the loop interchanger, which provides the quench fractions for the iatermediate catalyst beds. The remaining feed gas is heated to the inlet temperature of the first bed. Because the beds are adiabatic, the feed gas temperature increases as the exothermic synthesis reactions proceed. The injection of quench gas between the beds serves to cool the reacting mixture and add more reactants prior to entering the next catalyst bed. Quench converters typically contain three to six catalyst beds with a gas distributor in between each bed for injecting the quench gas. A variety of gas mixing and distribution devices are employed which characterize the proprietary converter designs. 

The bill of materials under the picture includes only the important parts that are needed in addition to those already listed on the vapor phase methanol flow sheet in Figure 4.2.1... 

The subject has been reviewed (37,38). Water may be added to the feed to suppress methyl acetate formation, but is probably not when operating on an industrial scale. Water increase methanol conversion, but it is involved in the unavoidable loss of carbon monoxide. A typical methanol carbonylation flow sheet is given in Figure 2. 

The unit has virtually the same flow sheet (see Fig. 2) as that of methanol carbonylation to acetic acid (qv). Any water present in the methyl acetate feed is destroyed by recycle anhydride. Water impairs the catalyst. Carbonylation occurs in a sparged reactor, fitted with baffles to diminish entrainment of the catalyst-rich Hquid. Carbon monoxide is introduced at about 15—18 MPa from centrifugal, multistage compressors. Gaseous dimethyl ether from the reactor is recycled with the CO and occasional injections of methyl iodide and methyl acetate may be introduced. Near the end of the life of a catalyst charge, additional rhodium chloride, with or without a ligand, can be put into the system to increase anhydride production based on net noble metal introduced. The reaction is exothermic, thus no heat need be added and surplus heat can be recovered as low pressure steam. 

Esterifica.tlon. The process flow sheet (Fig. 4) outlines the process and equipment of the esterification step in the manufacture of the lower acryflc esters (methyl, ethyl, or butyl). For typical art, see References 69—74. The part of the flow sheet containing the dotted lines is appropriate only for butyl acrylate, since the lower alcohols, methanol and ethanol, are removed in the wash column. Since the butanol is not removed by a water or dilute caustic wash, it is removed in the a2eotrope column as the butyl acrylate a2eotrope this material is recycled to the reactor. 

Methanol Synthesis. AH commercial methanol processes employ a synthesis loop, and Figure 6 shows a typical example as part of the overall process flow sheet. This configuration overcomes equiUbtium conversion limitations at typical catalyst operating conditions as shown in Figure 1. A recycle system that gives high overall conversions is feasible because product methanol and water can be removed from the loop by condensation. 

The different operating conditions for the methyl and phenyl reactions make it desirable to employ two separate flow sheets to illustrate the production of methyl and phenyl silicones by the direct process. Fig. 2 shows the flow of materials for the production of methyl silicone via the methanol process, and Fig. 3 depicts the production of phenyl silicone from benzene. 

The work reported by Ralph etal. (2003) is a well-rounded, self-contained essay on the DMFC. (See DMFC flow sheet in Figure 6.6.) Moreover, because Ballard/Johnson Matthey did not contribute on fuel cells at the Palm Springs Fuel Cell Seminar in 2002 (see below), Ralph etal. (2003) is the current information source, additional to the patents in the list of references. Note that the methanol-water mixture presents to the fuel electrode its associated methanol vapour pressure. The DMFC does not have an incompressible fuel. The cell needs circulators. It is incomplete. 

To provide an illustration, the flow sheet of the IFP process shown in Fig. 3.12 comprises two possible variants. The simpler corresponds to the direct use of the etherified solution in the gasoline pool, without separating e excess methanol contained. Operations are conducted with two reactors in series the first with an upflow stream and expanded bed with recycle of part of the previously cooled effluent for better control of the temperature rise, and the second with a downflow stream and a fixed bed. The more complex involves the recovery of excess methanol, first by azeotropic distillation in a depentanizer with part of the unconverted hydrocarbons, and then by water washing of this raffinate. The hydrocarbon phase is added to the bottom of the depentanizer. The water/methanol mixture is distilled to recover and recycle the alcohol to the etherification staee. 

The process has been demonstrated on a pilot scale by Lurgi and Statoil. Sufficient propylene has been produced to make polypropylene resin product by Borealis. This process appears to use an oxide doped ZSM-5 zeolite catalyst in fixed bed reactors. The oxide doping promotes the methanol conversion to olefins. All olefins, other than propylene, are recycled to extinction or purged as fuel gas or produced as naphtha. The flow sheet is illustrated in the Figure 11.8. 

When comparing the competing processes for making hydrocarbons from synthesis gas - the Fischer Tropsch CO hydrogenation and the MTG conversion -the process flow sheets show as the main difference the additional step of methanol synthesis for the MTG route. However, product selectivity is basically different for both the conversions. And from this point of view the one or the other route can be the more favourable option as fitting best the particular demand pattern. Selectivity differences fundamentally result from the different kinds of chemistry which are involved Hydrogenation on special metal type catalysts in case of the Fischer Tropsch reaction and a conversion via car-benium ion intermediates on acidic sites, which is additionally constrained by shape selectivity in case of the MTG process. 

Flow sheet of the Lurgi low pressure methanol synthesis process. 

Fig. 10-9. Flow sheet for the synthesis of methanol from carbon monoxide and hydrogen.

Continuous methanolysis is adopted for the deacetylation process. Figure 4.6 shows a schematic flow sheet of deacetylation. The first step of the process is the mixing of a concentrated methanol solution of polyvinyl acetate with a methanol solution of alkali. 

In the expansion vessel DA of a Rectisol plant (installation for physical gas cleaning), whose flow sheet is shown in Fig. 9.49, CO2 is separated from methanol saturated with CO2 by lowering the pressure. The separated CO2 is fed into the vessel FA. The methanol, which is again saturated because pressure is lower (this implies, of course, a CO2 content lower than initially) is discharged in a controlled way from DA. The control maintains a fllUng level of about 40 % in the vessel... 

Figure 15.2 shows the flow sheet of the FP-FC system. The fuel forthe system is an aqueous solution of methanol at the molar ratio of methanol to water of 1 2 for the standard case. The fuel is evaporated in the vaporizer (VAP) at 150°C. In the reformer, the vaporized methanol and water react at 250 °C to form a hydrogen-rich gas, which contains also some CO2 and CO. The steam reformer is modeled as a Gibbs reactor assuming chemical equilibrium between the species at the outlet of the reactor. At the reforming temperature of 250 °C, the equilibrium conversion of methanol is almost 100%. The selectivity of methanol to CO2 is about 97% and to CO about 3%. In the mixer (MIX), the hydrogen-rich gas from the reformer is mixed with a small quantity of air, which is needed for the oxidation of CO present in the product gas from the reformer. The selective CO oxidation takes place in the COS reactor at 150 °C. The COS reactor is modeled as a stoichiometric reactor where 50% of the supplied O2 from the air is used for complete oxidation of CO and the remaining 50% of O2 reacts with H2. 

The paper by Tonkovich et al. cited above deals with methanol production, tailored to an FPSO vessel, and employing plants similar to those designed by Heatric Ltd. One of the principal differences between the plant described earlier and the methanol unit is the need to carry out distillation and compression processes, the flow sheet being shown in Figure 9.11. 

Figure 9.1 I Integrated methanol production flow sheet - a simulation was carried out based on a 1000 tonne/day output.

Fig. 15 gives a simplified flow sheet of the BASF plant [534, 1007]. The plant has a present capacity of 40,000 tons [1006]. Some years ago up to 70% of the starting methanol was replaced by dimethyl ether, which is obtained as a by-product in the methanol synthesis. Another plant with a capacity of 30,000 tons/year is operated by The Borden Chemical Co. in Geismar (U. S.A.) under license from BASF [1007, 1008]. 

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