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I have some information whose source I’ve forgotten; please don’t accuse me of plagiarism – it’s just for sharing among everyone. Sorry about that. In 1997, Lurgi was the first company to introduce the concept of MegaMethanol, which involves production on a million-ton scale. Since then, methanol production technologies with a capacity of over 1 Mt/a per plant have become the focus of research in this industry. Currently, there are more than a dozen methanol plants around the world with an annual production capacity of over 1 Mt, three of which have a capacity exceeding 1.7 Mt/a. Below are several million-ton-scale methanol synthesis technologies with proven application records. 1 Lurgi two-stage isothermal methanol synthesis process 1.1 Introduction to structure and process flow: Considering the high heat generation during the methanol synthesis reaction and the poor heat resistance of existing copper-based catalysts, Lurgi has adopted a tubular reactor. For large-scale methanol production exceeding one million tons, a two-stage isothermal methanol synthesis technology scheme involving “gas-cooled reactors + water-cooled reactors” is adopted. This scheme does not mandate the installation of a guard bed. The process flow is shown in Figures 1 and 2. In water-cooled reactors, the reaction heat is removed by generating secondary medium-pressure steam, while in air-cooled reactors, the reaction heat is removed through counterflow heat exchange with fresh syngas, thereby achieving heat coupling. In the air-cooled reactor, the fresh gas flowing inside the tubes (at around 125°C) exchanges heat in counterflow with the catalyst outside the tubes, being heated to 250°C before proceeding to the water-cooled reactor for the methanol synthesis reaction, which takes place at a temperature of 265°C; thereafter, it returns to react outside the tubes of the air-cooled reactor. In Lurgi’s two-stage isothermal methanol synthesis process, most of the catalyst is installed in a gas-cooled reactor. Figure 1: Lurgi methanol synthesis process. Figure 2: Schematic diagram of the reactor. 1.2 Main features: (1) Water-cooled reactor. The reaction is easily and accurately controlled; it operates under approximately isothermal conditions. It features a high methanol yield (the catalyst’s methanol yield is 1.2 kg/L), high energy efficiency, and high reliability. The heat generated by the reaction produces high-pressure steam. (2) Air-cooled reactor. An optimized reaction pathway (high equilibrium driving force, high conversion rate); no risk of catalyst poisoning, and no reactor feed preheater is required. (3) High single-series production capacity. (4) Low investment cost. (5) The recycle ratio is 1.5. The methanol content at the reactor outlet can reach 17% (mole fraction). 1.3 Performance: Lurgi introduced the concept of megaton-scale methanol in 1997, and in the same year it signed a contract with TITAN in Trinidad for a methanol plant with a capacity of 2500 t/d. In 2000, a 5,000 t/d methanol plant was contracted with ATLAS in Trinidad, and it came online in June 2004. Separately in 2000 and 2004, contracts were signed with Iran’s **National Petrochemical Company (NPC) for methanol plants each with a capacity of 5,000 t/d. In 2004, a contract was signed with QAFAC in Qatar for a 6,750 t/d methanol plant. In 2005, contracts were signed with PETRONAS in Malaysia and China Datang International for a 5,000 t/d methanol plant each. In 2006, contracts were signed with Shenhua Ningmei for 5,000 t/d methanol plants. 1.4 Main drawbacks: High consumption of cooling water; low amount of by-product steam ； The equipment is large, and its transportation is restricted ； The equipment resistance is too high ； Large temperature difference between water cooling and air cooling ； Special materials such as dual-phase steel are required. 2 Davy (ICI) radial-flow steam-assisted methanol synthesis technology 2.1 Davy’s early large-scale methanol production technologies When it comes to Davy’s methanol synthesis technology, people usually think of its multi-stage refrigerated methanol synthesis towers. These towers utilize fixed-bed reactors and are of the 4-stage refrigerated adiabatic axial-flow type; a diamond-shaped distribution system is used between the stages to inject refrigerant gas in order to lower the temperature and thus regulate the temperature inside the synthesis towers. Due to the simple structure of this type of tower, it is also suitable for large-scale applications; among the early large-scale methanol plants in the world, those that used multi-stage cold-quench methanol synthesis towers were the most common. However, it also has the following obvious problems: (1) It is unable to recover the high-grade heat energy generated during methanol synthesis, and the volume of gas circulating in the synthesis loop is large ； (2) There is backmixing between catalyst sections, resulting in a low methanol content at the outlet of the synthesis tower ； (3) The space-time yield of the catalyst is not high, and a large amount of gas is used. Therefore, large-scale devices are now rarely used. 2.2 Davy radial-flow steam-upward methanol synthesis technology 2.2.1 Introduction to structure and process In recent years, DAVY Company has developed radial-flow steam-upward methanol synthesizers specifically for methanol plants with production capacities of millions of tons. The main feature of these reactors is that the catalyst is placed on the shell side, while the feed gas enters through the central tube and flows radially from the center outward. This process requires a protection bed to be installed before the reactor to further purify the syngas. Figure 3 shows a schematic diagram of the process currently designed by Davy for large-scale methanol plants, while Figure 4 depicts a schematic diagram of a radial-flow steam-rise type large-scale methanol synthesizer. Figure 3: Schematic diagram of the process in Davy’s large-scale methanol plant. Figure 4: Davy’s large-scale methanol synthesis tower. 2.2.2 Main features: (1) Adoption of gas radial flow, steam upward flow, and a series/parallel configuration of synthesizers. (2) The gas passes through the catalyst bed radially from inside to outside, with a small pressure drop. (3) The boiler feedwater enters from the bottom of the reactor and flows upward through a vertically arranged tube bundle; this generates medium-pressure steam that carries away the heat of reaction. By controlling the steam pressure, the temperature of the catalyst bed can be regulated, resulting in a temperature distribution that is nearly isothermal. (4) Convert CO + H2 into methanol as efficiently as possible; the conversion rate can reach 98.5%. (5) There is no need to use precious metals; the requirements for materials are relatively low, resulting in low costs for synthesizers. 2.2.3 Performance The methanol plant with a daily production capacity of 5,400 tons, constructed by DAVY in Trinidad, consists of two steam-reforming reactors connected in series/parallel. It was put into operation in October 2005. In December 2006, Baotou Shenhua Coal Chemical Co., Ltd. signed a technology introduction contract for 5,500 t/d methanol production with DAVY Company, utilizing two synthesis towers connected in a series-parallel configuration. The 3,600 t/d methanol plant of EMethanex in Egypt and the 4,430 t/d methanol plant of Kharg Petrochemicals in Iran also utilize Davy technology. 2.2.4 Main shortcomings: The concentration of methanol exported needs to be increased further in order to reduce the circulation volume and thus lower the energy consumption associated with compression during circulation ； The gas flows outward in a diverging pattern, with the flow speeds varying by several times, making it difficult to ensure a uniform distribution ； The by-product steam has a pressure of 2.2 MPa and a temperature of about 220°C; its usability is poor. 3 Topsφe’s adiabatic shell-and-tube methanol synthesis technology 3.1 Introduction to structure and process Denmark’s Topsφe company utilizes several adiabatic shell-and-tube synthesis reactors connected in series and parallel; the catalyst is placed in the tube side, while boiling water is used in the shell side, to develop a methanol production process with a capacity of millions of tons per year. This process requires a protection bed to be installed before the reactor in order to further purify the syngas, reducing the total sulfur content in it to less than 5×10‑9. 3.2 Main Features (1) The company’s proprietary RM101 copper-based catalyst is required; this type of catalyst boasts advantages such as high activity, high strength, small particle size, high selectivity, and low usage amount. (2) The recycle ratio is 1.5–2.5, with a high one-pass conversion rate (typically 50%–60%), and the methanol content at the reactor outlet can reach 13.86% (mole fraction). (3) High carbon conversion rate. Methanol plants that use coal as a raw material can typically convert 95% to 96% of the carbon in the feed gas into methanol. (4) The pressure drop in the synthesis tower is usually below 0.2 MPa, and the net energy consumption per ton of methanol is approximately 22.15 GJ (taking feed gas, turbine steam, and steam output into account). (5) Good heat recovery. 3.3 Performance: The 2,500 t/d methanol plant in Norway employs a three-series TopsΦe process. Large methanol projects that adopted the Topse technology in 2006–2007 include: a gas-based methanol plant in Saudi Arabia with a capacity of 5,000 metric tons per day (expected to be commissioned in 2009), and a gas-based methanol plant in Nigeria with a capacity of 10,000 metric tons per day (expected to be commissioned in 2010). 3.4 Shortcomings: It is basically similar to Lurgi’s traditional design; there are no significant innovations in terms of structure ； Special materials need to be used ； Large number of devices ； The investment is relatively large. 4 Casale’s IMC inter-plate heat exchange methanol synthesis technology
4.1 Introduction to the structure and process
Casale has developed an IMC inter-plate heat exchange reactor in which heat exchange plates are arranged radially and in concentric sectors. These plates serve as cooling heat exchange elements embedded within the catalyst bed. Boiler feedwater flows through these plates, generating medium-pressure saturated steam, thereby removing the reaction heat from the catalyst bed. The heat exchange plates are supported at the bottom of the bed, while the catalyst is supported by the underlying bed of inert medium. The central pipe serves as a passageway at the lower part of the synthesis reactor, allowing the catalyst to be discharged through the bottom discharge port. Figures 5 and 6 are schematic diagrams of Casale’s plate-type heat-exchange methanol synthesis tower. Figure 5: Schematic diagram of the Casale methanol synthesis tower. Figure 6: Schematic diagram of the structure of the Casale plate-type heat-exchange methanol synthesis tower. 4.2 Main features: (1) Large heat exchange area of the internal components. (2) The alcohol purity is high, reaching 10%. (3) The gas can flow co-currently or counter-currently, axially or radially, with low pressure drop. (4) High catalyst loading factor, high utilization of high-pressure space, and high production intensity. (5) Domestic catalysts are used, but they must be approved by Casale testing and come with performance guarantees; this is the biggest difference compared to the technologies of foreign companies such as Lurgi, Davy, and TopsΦe. 4.3 Performance: In November 2002, Casale carried out an on-site renovation of a 320 MTD methanol plant at the Nevinnomyssk Azot company in Russia using an IMC inter-panel heat exchange design, resulting in a 33% increase in production. China’s Shanghai Coking Co., Ltd.’s 450 kt/a methanol plant, Xinneng Energy Co., Ltd.’s 600 kt/a methanol plant, and Shandong Jiutai Energy (Inner Mongolia) Co., Ltd.’s 1 Mt/a methanol plant have also adopted Casale’s IMC plate-type heat-exchange methanol synthesis technology. Utilizing the IMC plate-type isothermal methanol synthesis reactor, the largest methanol project undertaken by Casale is the 7,000 t/d natural gas-to-methanol project in Iran, which is currently in the project design phase. 4.4 Disadvantages: Difficult to load the catalyst ； Forced circulation is used, which places high demands on the forced circulation pump ； Methanol synthesizers have a complex structure, require high-quality materials, are difficult to manufacture, and involve substantial investment ； When the methanol synthesis pressure is relatively high (e.g., greater than 8 MPa), the structural reliability and process feasibility require verification through practice. 5 MHI/MGC shell-coil cold-tube composite SPC methanol synthesis technology 5.1 Structure and brief introduction This technology is a SPC (Superconverter) methanol synthesizer jointly developed by Japan’s Mitsubishi Heavy Industries (MHI) and Mitsubishi Gas (MGC); it functions as a vertical, simple double-tube heat exchanger. The catalyst is placed between the inner tube and the outer tube, while boiling water circulates between the tubes. The feed gas enters the inner tube from below; the heated gas then passes through the catalyst bed. The reaction gas is cooled by both the boiling water on the outside and the gas inside, thereby bringing the operating temperature closer to the optimal level. The air currents flowing along the inner and outer tubes are in opposite directions; the inlet temperature of the syngas to the catalyst layer is the highest, and it gradually decreases as it moves toward the outlet. Such a temperature distribution ensures an optimal reaction rate; that is, a high conversion rate can be achieved while reducing the amount of catalyst used. The SPC methanol synthesizer can also be used for methanol production on a million-ton scale, and its structure is shown in Figure 7. Figure 7 Schematic diagram of the SPC methanol synthesizer. 5.2 Main features: (1) Compared to Lurgi tubular reactors, the SPC methanol reactor has a lower recycle ratio and higher single-pass conversion rate. At an space velocity of 5000 h⁻¹ and a pressure of 8.0 MPa, an outlet methanol concentration of 14% can be achieved. (2) The synthesizer acts as a preheater to warm the inlet gas; the fresh syngas is preheated within the reactor, thereby eliminating the need for a heat exchanger. (3) Good energy recovery: 1 t of methanol can produce 1 t of steam at 4.0 MPa as a by-product. Reportedly, the energy consumption per ton of methanol when using this reactor can be reduced to 29 kJ/t. (4) Good process stability. 5.3 Drawbacks: Significant voltage drop ； The equipment structure is relatively complex; each inner tube must be connected to the gas collection pipe using flexible pipes in order to eliminate thermal stress ； The catalyst is installed between the casings, which causes inconvenience in the loading and unloading of the catalyst as well as in the installation and maintenance of the equipment ； The cold-wall effect of catalysts cannot be ignored, requiring the catalyst to have good low-temperature selectivity and activity. Four 800 kt/a methanol plants using SPC technology have been put into operation in Saudi Arabia. 6 MRF Multi-Stage Radial Flow Methanol Synthesis Technology 6.1 Introduction to its structure and characteristics Toyo Engineering Corporation (TEC) of Japan and Mitsui Toatsu Chemicals, Inc. have jointly developed a new type of energy- and cost-saving multi-stage indirectly cooled radial flow methanol synthesis reactor (Multi-Stage Indirect-Cooling Type Radial Flow, abbreviated as MRF). It is said that this reactor can be easily scaled up from the current capacity of 750–850 kt/a to 1.5 Mt/a. The MRF methanol synthesis tower is a vertical cylindrical pressure vessel, consisting of a pressurized shell, a catalyst basket with a central tube, and vertical boiler tubes (cooling tubes) connected to the boiler feedwater vaporization header and the steam collection header. The tubes are arranged in several layers of concentric circles and installed vertically above the catalyst bed. Syngas enters through the central tube and then flows radially through the catalyst layer to undergo reaction. The gas after the reaction collects in the annular space between the catalyst basket and the shell of the synthesis tower, from where it exits at the top. The boiler feedwater enters the cooling tubes from the bottom of the furnace; the steam generated collects in the steam collection main, from where it is then discharged from the top of the tower. The structure of the MRF multi-stage radial flow methanol synthesis tower is similar to that of the Davy radial flow steam-up methanol synthesis tower. 6.2 Main features: (1) Radial gas flow, short flow channels, low space velocity, and low pressure drop. (2) The syngas flows vertically over the surfaces of the boiler tubes; even at low gas flow rates, the heat transfer efficiency between the bed and the cold tubes remains high. (3) High one-way conversion rate and low recycle gas volume. (4) The arrangement of the boiler tubes results in a reaction temperature that is nearly in line with the ideal temperature distribution curve; the reaction proceeds along the optimal temperature profile, leading to a high methanol yield, with the concentration of crude methanol at the outlet of the synthesis tower exceeding 8.5%. (5) The reaction heat is removed promptly and effectively, the bed temperature remains stable, a small amount of catalyst is required, operation takes place under mild conditions, and the catalyst has a long service life. 6.3 Disadvantages: Complex structure, high manufacturing difficulty ； The pressure of the by-product steam is lower than that of the by-product steam in shell-and-tube towers, making it difficult to utilize the steam ； The boiler water is forced to circulate within double tubes; the circulation pump requires significant power, which results in substantial maintenance workload for the pump. Technical requirements and development trends of 7 million-ton methanol synthesis reactors (1) Adoption of low-pressure synthesis technology. (2) Recover reaction heat at a higher potential energy, generating steam as a by-product. (3) The temperature of the catalytic bed is easy to control; temperature adjustment is convenient, rapid, and effective, allowing for flexible regulation. (4) Isothermality is the direction of development; the bed temperature should be as uniform as possible, and the reaction temperature should remain within the optimal range in order to extend the catalyst’s service life. (5) High space-time yield, high catalyst production intensity, low recycle ratio, and high one-pass conversion rate. (6) Good selectivity, high quality of crude methanol, with few side reaction products and impurities. (7) It has strong operational adaptability and can cope with changes in various operating conditions. (8) It has a high volume factor; for a reactor of a given volume, more catalyst can be loaded. (9) The catalyst is easy to load, unload, and reduce. (10) A protection bed is installed before the reactor to further reduce the total sulfur content in the syngas, thereby protecting the methanol catalyst. (11) By using radial or axially radial reactors, the gas distribution in the bed is uniform and the resistance is low. (12) Try to avoid using special and expensive materials in order to reduce the difficulty of manufacturing and assembly and lower production costs.

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I vote hands up in approval! Many posts have great topics, but the response and reply rates are very low, which is a pity. I hope this forum can become more active with more people participating, for the benefit of fans