A METHANOL SYNTHESIS PROCESS LAYOUT FOR LARGE PRODUCTION CAPACITY

Abstract

A process layout for large scale methanol synthesis comprises one or more boiling water reactors and one or more radial flow reactors in series, the boiling water reactor(s) being fed with approximately fresh make-up syngas. The methanol synthesis loop comprises a make-up gas compressor K1, a recycle gas compressor K2, two or more boiling water converters for methanol synthesis (A1, A2, . . . ), a radial flow converter (B) for methanol synthesis, a steam drum (V1), a high pressure separator (V2), a low pressure separator (V3), feed effluent heat exchangers (E1 and E2), a wash column (C), an air cooler (E3) and a water cooler (E4).

Claims

1. A process layout for methanol synthesis, comprising one or more boiling water reactors and one or more radial flow reactors in series, wherein the boiling water reactor(s) is/are fed with approximately fresh make-up syngas.

2. A process layout for a methanol synthesis loop comprising a make-up gas compressor K1, a recycle gas compressor K2, two or more boiling water converters for methanol synthesis, a radial flow converter for methanol synthesis, a steam drum, a high pressure separator, a low pressure separator, feed effluent heat exchangers, a wash column, an air cooler and a water cooler.

3. A process layout for a methanol synthesis loop according to claim 2, wherein the purge gas is split from the effluent product gas as wet gas (including methanol) and washed with water to recover methanol at approximately the synthesis loop pressure.

4. A process layout for a methanol synthesis loop according to claim 2, wherein the radial flow reactor temperature is controlled by adjusting the purge gas and hence the level of inert gas in the reactor inlet.

5. A process layout for a methanol synthesis loop according to claim 2, wherein the radial flow reactor has a structure, which requires no cooling device.

6. A process layout for a methanol synthesis loop according to claim 2, wherein only one train of cooling equipment is used.

Description

EXAMPLE

[0038] A natural gas (NG) based methanol synthesis loop according to the invention with a capacity of 5000 MTPD methanol is used. A front-end stand-alone ATR gives a flow of hydrogen enriched (from the hydrogen recovery unit from purge gas) make-up gas (MUG) of 510.000 Nm.sup.3/h with the following composition: 69% H.sub.2, 21% CO, 8.5% CO.sub.2, 1% CH.sub.4 and 0.5% N.sub.2.

[0039] The total volume of methanol catalyst is 174 m.sup.3, more specifically split into 108 m.sup.3 in the two BWCs and 66 m.sup.3 in the RFC. The two BWCs include 11000 tubes in total, each with an inner diameter of 40.3 mm, an outer diameter of 44.5 mm and a length of 7.7 m. In the RFC, the inner diameter of the center tube is 1.0 m, the shell diameter is 3.6 m and the bed height is 7 m.

[0040] A synthesis loop operating pressure of 80 kg/cm.sup.2 is kept constant from the start-of-run (SOR) to the end-of-run (EOR). The BWT (boiling water temperature) is varied from 225? C. to 260? C. from SOR to EOR.

[0041] The catalyst activity loss is assumed to be 60% for the RFC and 65% for the BWCs over an operation time of 4 years.

[0042] At the end-of-run (EOR), i.e. after an operation time of 4 years, the stream composition results (in mole %) shown in the following Table 1 were calculated (the stream numbers (S. no) refer to the FIG.):

TABLE-US-00001 TABLE 1 Stream compositions after 4 years of operation S. no H.sub.2 CO CO.sub.2 N.sub.2 CH.sub.4 MeOH H.sub.2O 1 69.0 21 8.5 0.5 1 0 0 3 66.9 11.3 5.8 5.5 10.2 0.25 0.02 4 61.4 6.9 5.6 6.3 11.6 7.2 1 10 65.7 5.6 4.1 8.6 15.6 0.4 0.03 13 63.5 4.8 3.4 8.9 16.1 2.3 0.9 18 65.1 4.9 3.5 9.2 16.6 0 0.7

[0043] The product stream 15 from the low pressure separator V3 consisted of 85.7 weight percent crude methanol (corresponding to 5009 MTPD pure methanol). The stream 15 contained 1120 ppmw ethanol and 9 ppm methyl ethyl ketone.

[0044] The flow (f) of the individual streams (S) is indicated in Table 2.

TABLE-US-00002 TABLE 2 Flow of individual streams* 1 2 3 4 6 10 12 13 14 18 510 867 1377 1210 3315 4335 3468 3342 3 26 *Upper row: Stream no., lower row: Flow (?1000 Nm.sup.3/h)

[0045] The power and duty of respectively compressors and heat exchangers used in this production unit are listed as follows:

[0046] Compressors

[0047] K1: 39.7 MWe K2: 12.5 MWe (both 65% efficiency)

[0048] Heat exchangers

[0049] E1: 75 MW E2: 256 MW E3: 143 MW E4: 50 MW

[0050] The synthesis loop carbon efficiency drops slightly from 98.6% at SOR to 97% at EOR (after 4 years of operation). The pressure drop of the catalyst beds in RFC and BWCs increase from 0.1 and 0.9 bar to 0.3 and 1.8 bar, respectively.