Daily Question for the Methanol Section, April 14: Two Approaches to Large-Scale Methanol Synthesis Technology

The Casari synthesis involves external heat exchange and multiple stages of synthesis. As for the yield issue, in my opinion: when the product from one stage is fed into the next stage, and the product from the second stage is fed into the third stage, the average yield will not be higher than that of synthesis using a single tower. As for the manufacturer’s descriptions, they are all based on professional catalysts from abroad; if domestic catalysts are used, it is likely that they won’t be able to exhibit any activity at all, and they will struggle even with the process of heating and reducing the catalyst. As for the combination of two Ruqi towers in large-scale synthesis, it is also difficult to control the heating and reduction processes. When a water-cooled tower is connected to an air-cooled tower, the catalyst used can be C-79/GL from Südchemie in Germany; this is a catalyst designed for high-temperature calcination, and its catalytic structure is already well-defined. The reduction conditions differ between the two towers, and I have not heard of any specific applications for this setup yet. The syntheses developed by Luchi and David are both designed for natural gas methanol; their primary synthesis capacity is limited, and it remains to be determined whether gas-cooled synthesis towers can be adapted for large-scale synthesis using coal gas. Speaking of yield issues, setting aside factors such as catalysts, gas conditions, operational skills, and synthesis processes, my personal ranking is as follows: the David water-cooled synthesis tower comes first, as it is a radial tower with short flow paths, which naturally results in a higher yield. The Ruchi water-cooled tower of the second type, an axial tower, has long flow channels; it offers high heat exchange capacity and efficiency. The catalyst provides optimal reaction conditions, resulting in a high average yield. Additionally, the catalyst has a long service life, and a large amount of alcohol can be produced per ton of catalyst used. The fatal flaw is the too low loading factor. Casari comes in third, with a radial tower and several mixed-flow sections; although the total catalyst flow path is short, the yield is not necessarily higher than that of Luchi’s axial tower. David air-cooled tower type 4: radial tower, which belongs to the category of low-intensity reactors. The bed temperature is relatively reasonable, and the yield is also high; its advantage lies in its large capacity for catalyst loading. Lurgi air cooling tower 5: It must be used as a second tower in conjunction with the Lurgi synthesis process. A special catalyst must be used.

I’m not familiar with Casali, but currently in China, Luchita is the more common one

The heat exchange method of Ruchi’s water-cooled tower is lagging behind that of the Cassali process. The removal of the heat of synthesis reaction relies mainly on the enthalpy of vaporization of saturated water; in a Ruchita-type natural circulation system, the steam generated by heat exchange pushes aside the surrounding saturated water, preventing it from coming into contact with the heat exchange plates. In the Casali process, which is of forced circulation type, the steam generated is removed quickly; as a result, its heat exchange efficiency is inferior to that of the Casali process.

The advanced concept for methanol synthesis is that, regardless of capacity, as long as the transportation conditions permit, one reactor should be used if it is possible, rather than two reactors； If one synthesis circuit is sufficient, never use two ； Unless its technology is not advanced enough, a single synthesis tower or a single synthesis loop cannot do it. Then, considering the same catalyst loading and the same pressure drop, it is better to have a smaller diameter for the synthesis tower. The above reflects the comprehensive factors of investment and energy consumption taken into account for the users. Using the above standards to evaluate so-called advanced technologies, it goes without saying which ones are superior and which ones are inferior – it’s clear at a glance.

We use two of them in our David water-cooled synthesis tower; the main issue is that transportation isn’t allowed. We haven’t started using it yet, so we don’t know how effective it will be

Based on the owner’s estimates regarding the scale of methanol production, if it is below 3000 MTPD for coal-based methanol production, a single methanol synthesis tower will suffice; the transportation diameter will not exceed the specified limit of 4500 mm in terms of both height and diameter. After taking into account factors such as the clearance from the ground, the thickness of the tank car, the length of the pipe outlets, and the wall thickness, the internal diameter should be between 3800 and 4000 mm. If such a production capacity cannot be achieved with this diameter, then it’s another issue.

I’m not very familiar with Casali in terms of synthesis, but currently in China, Luchita is still the most commonly used! After all, the synthesis tower is a very important reactor in the system!

I’m afraid to ask, but what kind of catalyst is used in air-cooled and water-cooled synthesis towers? Is the domestic C301 okay? Thank you!

As for Casali, I was the person in charge of overseeing the entire process for Casali’s largest single synthesis tower in China, from installation to its commissioning, so I should have considerable authority and accuracy in my views. I once posted a thread titled “Summary of the Advantages and Disadvantages of the Casali Synthesis Tower.” If you’re interested, you can take a look at it at http://bbs.hcbbs.com/forum.php?mod=viewthread&tid=88320. Some of the content of that thread is as follows: I’ve been in contact with Luch’s isothermal synthesis tower, Linda’s homothermal synthesis tower, and the three-tube cold shock tower; later on, I worked with the Casali synthesis tower for 2 years. Overall, it seems that foreigners are more meticulous in what they do compared to those in China, and they handle details better. But foreigners are also human; they make mistakes too, so one shouldn’t follow them blindly. 1. Judging from the packaging of the tower internals, the overall quality is very high; the wooden planks of the packaging boxes are polished. Spare parts are fully prepared. The staff are also very dedicated in their work, but with foreigners present in the office building, they often swear, which is not a good environment. Those goods are provided as a service, at 1,000 euros per person per day. Thanks to TNN, back then I didn’t spend even a day in the human world for two months. There are also two pretty Chinese girls acting as translators; the cost to entertain each of them per day is 150 yuan, while it only costs 20 yuan per day to buy meat and other foods for him in the cafeteria. 2. During the operation while the vehicle was in use, the engineers from Casali monitored the process throughout, showing great responsibility. After the operation, the gas composition data originally provided by Casali was largely overturned; to stabilize the temperature, a large amount of inert components were added. But even so, the cycle ratio is only around 3. The circulation ratio is very small. The compressor is similar to some of those used in my 100,000-ton unit before. The steam consumption is only 13 tons more than 100,000 tons. However, its energy consumption is very low. 100,000 tons, but the designed fresh gas volume is 40,000 tons; the rated steam input for the cycle unit is 3.92/450, which equals 32 tons. For my project, the fresh gas volume is 285,000 tons, with a rated input of 2.5/385, i.e., 45 tons. Fresh gas: 285,000; Recycled gas: 570,000. Very low. . . .

Cassali has no strict requirements regarding catalysts; it is only necessary to take samples of the catalyst performance for testing in order to ensure proper evaluation of its performance. It seems Ruqi doesn’t have it either; in 2006, when training the Ruqi reactor, C302 was used. In 2010, for operating the Cassali reactor, XNC-98 was utilized. David has requirements regarding catalysts, and it is sold in conjunction with Sinopec products. Topsoe also seems to have it. I haven’t seen the specific situation regarding Topso, so I can’t make a judgment. Based on on-site inspections and hands-on operations carried out by Luchi, Guochang, Hangzhou Linda, Casali, and David, capacity issues can be ruled out. Luqi and Guochang’s moves are the easiest, while Linda’s moves are the hardest. Casale has relatively the lowest energy consumption. David’s power consumption is much higher than that of Casali; the Jiutai compressor with a capacity of 1 million tons has a rated power of 7,779 KW for its compression and circulation sections. The Shenhua Baotou compressor, with a capacity of 1.8 million tons, has a compression and circulation section power output of over 20,000 KW. Luchi has the highest pressure of by-product steam; I heard it can reach 4MPA, and I have seen it reach 3.2MPA. Cassali’s steam pressure is between 2.7 and 3.2MPA, with actual operation at 2.7MPA. David’s is 1.9MPA, while Linda’s is 0.7MPA. It is relatively difficult to build large-scale synthetic towers that consist of a single unit; I’ve heard that there are units with a capacity of 1.2 million tons per tower, but I haven’t come across any information or reports on this. The most common configurations are those with 600,000 tons per tower, or two towers operating in parallel with a capacity of 300,000 tons each. It is mainly due to transportation restrictions; CNOOC Fudao Chemical’s 600,000-ton per tower Ruqi plant relies on sea transport for its shipments. As of now, it is known that in terms of operating temperature, Casali has the highest value, followed by David. Both Casali and David have areas where heat exchange does not occur, with temperatures reaching 300°C in those areas. However, at present, David’s equipment is being used in many new large-scale projects in China: Shenhua Baotou’s olefin project involving 1.8 million tons of methanol, Ningxia Baofeng’s 1.8 million tons of methanol project, Yanchang Olefins’ project (with uncertain capacity), and Shaanxi Coal’s Pucheng Clean Energy project involving 1.8 million tons – all of these projects use David’s equipment (all of them feature double towers). Fujdao Chemical’s 800,000-ton project was launched earlier, so it’s not worth mentioning here. Casali’s largest project seems to be Jutai Energy’s 1-million-ton project using a single tower

David’s project at Baotou Shenhua involves axial towers; Fudi Island Chemical uses radial towers, while Casali Eni employs axial towers. All the others use either axial or radial towers. Lurgi generally uses axial towers, and Linda also uses axial towers. In terms of trial use, the capacity exceeds 1 million tons; personally, I think Kassali is the most practical option, followed by David’s. If Ruchi can overcome the transportation issues, it would be better than David’s as well. But it seems that for capacities over 600,000 tons (not including 600,000 tons), only David’s and Kassali’s options are available