Domestic production situation and analysis
1 Foreign methanol process technology At present, the methanol produced abroad with natural gas as raw material accounts for 92%, and the methanol produced with coal as raw material accounts for 2.3%. Therefore, the methanol technology of foreign companies is concentrated on producing methanol from natural gas. The advanced methanol production process technologies widely used in the world mainly include: DAV Y (formerly I. C. I), O PSO E, U hde, L u rgi methanol technology, etc. The consumption and energy consumption of different methanol technologies are not very different. The main difference lies in the type of methanol synthesis tower used as the main equipment. 1. 1 DAV Y methanol technology characteristics The advantage of DAV Y low-pressure methanol synthesis technology lies in its excellent low-pressure methanol synthesis catalyst. The synthesis pressure is: 5. 0~10MPa. The synthesis pressure of large-scale methanol production equipment is 8~10MPa. The types of synthesis towers include: The first type, the quench type synthesis tower, has a large production capacity in a single tower, and the methanol concentration at the outlet is about 4 to 6% vol. The second type is an internal heat exchange cold tube methanol synthesis tower. Recently, a water pipe type synthesis tower has been developed. Most distillations use two towers, and sometimes three towers are used for distillation, which should be considered together with the steam system settings. Steam system: divided into three levels: high pressure 10.5MPa, medium pressure 2.8MPa, and low pressure 0.45MPa. The waste heat generated by the conversion and the waste heat of the reformer flue gas are used to generate high-pressure superheated steam at 10.5MPa and 510℃. The high-pressure superheated steam is used to drive the synthetic compressor steam turbine, and the medium-pressure steam is extracted for use in the device. 1. 2 Lu rgi methanol technology Lu rgi company’s synthesis has its own characteristics, that is, it has its own patent for the synthesis tower. Its characteristic is that the synthesis tower is a tube type, with steam as a by-product, Lurgi synthesis catalyst in the tubes, boiler water between the tubes, and saturated medium-pressure steam of 3.5 to 4.0 MPa as a by-product. Since the diameter of the synthesis tower of large-scale devices such as 2000M TPD is too large, two synthesis towers are often connected in parallel. If the scale is larger, a tubular synthesis tower is used followed by a cold tube or heat pipe synthesis tower, and two series of synthesis towers can also be connected in parallel. The distillation of Lu rgi process adopts three-tower distillation or three-tower distillation followed by a recovery tower. Sometimes two-column distillation is also used. The heat source of the reboiler of the pre-distillation tower and the pressurized distillation tower of the three-tower distillation process comes from the waste heat of the reformed gas. Therefore, distillation consumes very little low-pressure steam. 1. 3 Methanol technical characteristics of TO PSO E TO PSO E is a major patented technology provider and catalyst manufacturer in the ammonia and methanol industries. Its methanol technical characteristics are mainly reflected in methanol synthesis: the methanol synthesis tower adopts BWR synthesis tower ( Tube by-product steam), or use CMD multi-bed adiabatic synthesis tower. The process features are: using an axial insulated bed, heat exchangers between towers, and waste heat used to preheat boiler feed water or circulate hot water in saturated systems. The temperature entering the tower is 220°C. The single-pass conversion rate is high, the catalyst volume is small, the synthesis tower structure is simple, and the single-series production capacity is large. The synthetic pressure is 5. 0 ~ 10. 0 MPa, optimized according to the device capacity. The methanol unit with a daily production capacity of 2,000 tons has a synthetic pressure of approximately 8MPa. Adopt three-tower or four-tower (including recovery tower) process technology. 1. 4 TEC Methanol Technology Characteristics The synthesis process adopts IC I low-pressure methanol technology. Distillation uses Lurgi company's technology. The synthesis uses IC I low-pressure methanol synthesis catalyst. Synthesis tower: Using TEC's MRF-Z synthesis tower (multi-layer radial synthesis tower), the methanol concentration at the outlet can reach 8% vol. The resistance drop of the synthesis tower is small, which is 0. 1M Pa. The waste heat of methanol synthesis is used to generate 3.5-4.0MPa medium-pressure steam. The medium-pressure steam can be used as process steam or used as turbine driving steam after superheating. 1. 5 Characteristics of Mitsubishi Heavy Industries’ methanol technology Mitsubishi’s methanol technology is similar to the I.C.I process. Its characteristics are: the use of a super methanol synthesis tower with a unique structure. The synthesis pressure is related to the methanol unit capacity. The methanol unit with a daily production capacity of 2,000 tons has a synthetic pressure of approximately 8. 0MPa. The characteristics of the super methanol synthesis tower are: it adopts double sleeves, the catalyst temperature is uniform, the single-pass conversion rate is high, and the concentration at the outlet of the synthesis tower can reach up to 14% vol.
The by-product is 3. 5 ~ 4. 0 MPa medium pressure steam synthesis tower. The outlet concentration can reach 8 ~ 10%vol. The circulation volume of the synthesis system is greatly reduced compared with traditional technology, and the supplementary gas consumption is the least. Use 2-column or 3-column distillation, depending on the steam system settings. 1. 6 Wood Company’s methanol technology features I.C.I low-pressure synthesis process and catalyst. The synthesis pressure of the daily 2000 methanol unit is 8. 0MPa. Synthesis tower: Wood Company uses an improved air-cooled shock diamond reactor, isothermal synthesis tower, and cold tube synthesis tower. CA SAL E's ARC synthesis tower (multi-layer axial radial synthesis tower) has a single series production capacity of up to 3000M TPD. Synthetic waste heat recovery method: preheating boiler feed water, low equipment investment. Isothermal synthesis tower: a shell-and-tube synthesis tower that produces medium-pressure steam as a by-product. The medium-pressure steam pressure is 3. 5 ~ 4. 0M Pa. The production capacity of a single tower can reach up to 1200M TPD. Equipment investment is high. Cold tube type synthesis tower: axial, cold tube indirect heat exchange, single tower production capacity up to 2000M TPD. Equipment investment is low. 2-tower, 3-tower rectification or 4-tower rectification can be used. The comparison is as follows: 2-tower rectification, the methanol recovery rate is 98. 5%, and one ton of methanol consumes 1. 2 tons of low-pressure steam. 3-column distillation, the methanol recovery rate is 99%, and 0.47 tons of low-pressure steam is consumed per ton of methanol. 4-column distillation, with a methanol recovery tower, the methanol recovery rate is 99. 5%, and a ton of methanol consumes 0. 45 tons of low-pressure steam. 1. 7 The characteristics of Linde's methanol technology adopts I.C.I low-pressure synthesis process and catalyst. A spiral-tube isothermal synthesis tower using by-product steam is used. Boiler water is in the tube. The medium-pressure steam pressure is 3. 5 ~ 4. 0 MPa, and the gas resistance is reduced. The rest is similar to IC I low pressure methanol.