1 Foreign methanol process technology
Currently, 92% of the methanol produced abroad uses natural gas as raw material and 2.3% uses coal as raw material. Therefore, the methanol production of foreign companies The technologies are all focused 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), OPSO E, U hde, Lu 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 Characteristics of DAV Y methanol technology
The advantage of DAV Y low-pressure methanol synthesis technology lies in its excellent low-pressure methanol synthesis catalyst, synthesis pressure: 5. 0～10M Pa, The synthesis pressure of large-scale methanol production equipment is 8 to 10 MPa. 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 distillation uses two towers, sometimes three towers are used for distillation, and the steam system settings are considered together. Steam system: divided into three levels: high pressure 10.
5M Pa, medium pressure 2. 8M Pa, and low pressure 0. 45M Pa. The waste heat generated by the conversion and the waste heat of the reformer flue gas are used to generate 10.5MPa, 510℃ high-pressure superheated steam. The high-pressure superheated steam is used to drive the steam turbine of the synthetic compressor, and the medium-pressure steam is extracted for use in the device.
1. 2 Lürgi methanol technology
Lürgi 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 tube, boiler water between the tubes, and saturated medium-pressure steam of 3. 5
～4. 0MPa 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 will be 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 synthetic ammonia and methanol industries. Its methanol technical characteristics are mainly reflected in Methanol synthesis includes: methanol synthesis tower adopts BWR synthesis tower (tube by-product steam), or uses CMD multi-bed adiabatic synthesis tower. Its 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℃. 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 of the synthesis tower
dropped slightly to 0. 1M Pa. < /p>
Move steam.
1. 5 Characteristics of Mitsubishi Heavy Industries’ methanol technology
Mitsubishi methanol technology is similar to the I.C.I process, and its characteristics are:
Using super methanol with a unique structure Synthesis Tower. The synthesis pressure is related to the capacity of the methanol
unit. The methanol unit with a daily output of 2,000 tons has a synthesis pressure of approximately 8. 0MPa.
The characteristics of the super methanol synthesis tower are: the use of double sleeves, uniform catalyst temperature
, high single-pass conversion rate, and the highest concentration at the outlet of the synthesis tower
14%vol. By-product 3. 5 ~ 4. 0M Pa medium pressure steam synthesis tower, the outlet concentration can reach 8 ~ 10%vol, the synthesis system circulation volume is larger than that of traditional technology
The technique is greatly reduced, and the consumption of supplementary energy is minimal.
Use 2 or 3 towers for distillation, depending on the steam system settings.
1. 6 Wood Company’s methanol technology features
Using I.C.I low-pressure synthesis process and catalyst, the synthesis pressure of the daily 2000 methanol unit is 8. 0M Pa.
Synthesis tower: Wood Company uses an improved air-cooled quenched diamond-shaped reactor
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 be up to
Up to 1200M TPD. Equipment investment is high.
Cold tube type synthesis tower: axial, cold tube indirect heat exchange, single tower production
The maximum capacity can reach 2000M TPD. Equipment investment is low. 2
tower, 3-tower distillation or 4-tower rectification can be used. The comparison is as follows: 2-tower rectification, methanol recovery rate is 98. 5%, tons of methanol It consumes 1.2 tons of low-pressure steam. 3 towers
distillation, the methanol recovery rate is 99%, and one ton of methanol consumes 0. 47 tons of low-pressure steam
steam. 4-column distillation, with a methanol recovery tower, the methanol recovery rate is 99. 5%, and 0. 45 tons of low-pressure steam is consumed per ton of methanol.
1. 7 Characteristics of Linde’s methanol technology
Using I.C.I low-pressure synthesis process and catalyst.
A spiral-tube isothermal synthesis tower using by-product steam is used. Inside the tube is
boiler water. The medium-pressure steam pressure is 3. 5 ~ 4. 0MPa, and the gas resistance is reduced
p>
Low.
The rest is similar to IC I low pressure methanol.
2 Domestic methanol process technology
my country is a coal-rich country, and natural gas and coal are mostly used as raw materials for methanol. Production is currently almost evenly divided. There are two production processes: single production of methanol and co-production of methanol. In addition to co-producing methanol in the ammonia synthesis unit
, chemical plant exhaust gas or combined with city gas can also be used to co-produce methanol.
2. 1 Domestic methanol gas production technology
my country's methanol synthesis technology using natural gas as raw material mainly includes: first-stage steam reforming process and China Chengda The company's two-stage pure oxygen conversion process
. The main technologies for methanol synthesis in my country using coal as raw material include: fixed bed gasification (including Lürgi furnace, Ende furnace and intermittent gasification furnace), fluidized bed gasification (ash fusion polygasification), entrained bed gasification furnace, Texaco coal water slurry gasification and Shell pulverized coal gasification introduced in recent years, among which Texaco
's gasification It was introduced earlier, has more experience in use, has a high localization rate and saves investment
. No experience with Shell vaporization yet.
2. 2 Domestic gas purification technology
The desulfurization and decarbonization purification of methanol crude gas is the same as that of synthetic ammonia,
it just does not require liquid nitrogen washing. The main domestic purification technologies include low-temperature methanol washing, MDEA, and NHD. For small and medium-sized plants, there are also ADA,
PDS for desulfurization, and hot potassium alkali, PC, and MDEA technologies for decarburization. .
2. 3 Synthetic methanol and distillation technology
my country has developed low-pressure methanol synthesis and distillation technology since 1986, and it is currently widely used in the country The shell-and-tube by-product steam synthesis tower and
two-tower distillation originated from this development, and later the "U"-shaped cold tube combination
tower and distillation were popularized. It has also developed from two towers to three towers, and can produce not only GB338-
2004 high-quality refined methanol, but also American O-M-232K
AA grade refined methanol, containing alcohol. Breakthrough progress has been made in the treatment process of sewage. The sewage can be recycled after treatment. Therefore, the methanol plant achieves the discharge of alcohol-free sewage during normal production.
In recent years, methanol technology has developed rapidly, and the main trends are:
① The raw materials produced have shifted to natural gas and hydrocarbon processing tail gas. Calculated from the actual situation of methanol production, the investment of using natural gas as raw material can be reduced by 50% compared with using solid material as raw material; using acetylene tail gas is more economical
< p>The effect is more significant. Currently, the raw materials for methanol production in the world are mainly natural gas, accounting for about 90%, and coal as the raw material, accounting for only 2%. In recent years, the proportion of methanol produced from coal as raw material has gradually increased in China, which is related to China's energy structure.②The production scale is large-scale, with the maximum scale of a single series reaching 2.25 million tons/year, that is, the daily output of a single series is 7,500 metric tons. After the scale is expanded, the investment and cost per unit product can be reduced
.
③ Fully recover the heat of the system. Generate economical pressure steam to drive compressors, boiler feed water pumps, and circulating water pump turbines to achieve comprehensive utilization of heat energy.
④ Use a new methanol synthesis tower that produces medium-pressure steam as a by-product to reduce
energy consumption.
⑤Adopt energy-saving technologies, such as hydrogen recovery technology, pre-conversion, process
Condensate saturation technology, combustion air preheating technology, etc., to reduce methanol consumption
Consumption.