Methanol synthesis operation

I’m not sure what type of tower you have; if it’s a quench tower, the key is to adjust the temperature of the synthesis tower, that is, to regulate the flow rate. If it’s from Luchi, it’s necessary to control the pressure in the drum as well as the temperature at the outlet of the synthesis tower; nothing else is particularly important

How should David’s techniques at KS Kassel be applied?

You will gradually discover it through your own actions

First, it is necessary to thoroughly understand the production principles and the performance structure of the equipment. Secondly, strengthen practice and be diligent in summarizing.

The main thing is to control the temperature of the catalyst bed. And your circulation volume

First is the temperature of the catalyst; large fluctuations in temperature must be avoided； Second, strictly control the sulfur content in the fresh gas to ensure it does not exceed the specified limits ； Third, control the circulation gas volume to keep the content of polyform gas in the gas entering the tower within the specified process parameters ； Fourth is to control the outlet temperature of the methanol water cooler, etc.

The main task in synthesis is to control the temperature, as everyone knows. But the question is how to achieve proper temperature control, which requires careful observation, early detection of issues, and timely adjustments. With a constant flow rate, changes in the composition of the gas or in the temperature of the incoming gas can all affect the temperature. Therefore, to do this job well, one must not only be familiar with their own responsibilities but also have some understanding of the previous stages in the process; this helps to perform one’s duties more effectively. It’s important to work together, reminding each other of any problems and helping one another. Chemical production is a collective effort – only when everyone works together can stable and high yields be achieved.

It needs to be determined based on the type of tower. In the case of cold-stirring type synthesis towers, it is mainly achieved by adjusting the cold-stirring effect, the circulation rate, and the gas composition, as well as by enhancing communication with the conversion process; adjustments should be made in advance and frequently, with fine-tuning carried out regularly. In the shell-and-tube type, attention is mainly paid to controlling the drum pressure, as well as to the gas composition, circulation volume, drum liquid level, and chemical dosing system. On-site personnel must operate the circulator properly and conduct regular inspections, while also keeping an eye on the alcohol level

When carrying out methanol synthesis, it is important to select the appropriate process conditions: 1. Operating pressure: Currently, base-metal catalysts are widely used; copper-based catalysts have a lower activation temperature, usually ranging from 230 to 290 degrees, and can operate at different pressures. In facilities of larger scale, medium-pressure processes are preferred, as the equipment and pipelines required for such processes are larger in size. 2 Operating temperature: The temperature of the methanol synthesis catalyst bed is primarily determined by the active temperature of the catalyst. Generally, the active temperature for copper-based catalysts lies between 200 and 290 degrees. In actual production, it is more appropriate to maintain the operating temperature between 250 and 270 degrees. At the beginning of catalyst use, the reaction temperature is kept at a lower level to prevent catalyst aging; as the catalyst is used for a longer period, the reaction temperature can be increased appropriately, with the aim of maintaining it at the optimal level based on practical operational experience. 3 Composition of syngas: For the hydrogen-to-carbon ratio in the raw gas used for methanol synthesis, it is required to be maintained between 2.05 and 2.15, with a certain amount of carbon dioxide present. The designed level of carbon dioxide in our facility is around 3.42%, which helps to maintain the temperature of the bed layer effectively. 4 Space velocity and its role in the systemic circulation: The conversion rate of syngas when it passes through the catalyst bed is low; therefore, it is necessary to recycle the feed gas. By controlling the space velocity appropriately, energy consumption can be reduced effectively, and the gas components in the syngas can also be properly controlled.

But what process are you using, and what are the raw materials employed in the synthesis? After reading the comments from everyone above, I’m not very satisfied. What if carbon monoxide and hydrogen are used as raw materials to produce methanol, or carbon dioxide and hydrogen?

I have operated isothermal towers, homogenization towers, and constant-temperature towers. The temperature of the synthesis catalyst is controlled primarily using parameters such as gas flow rate, gas composition, circulation volume, and pressure in the synthesis tower; the catalyst temperature is adjusted based on the catalyst’s activity.

Key points for normal operation control in the methanol unit: (1) Temperature control. The reaction temperature is the main parameter in methanol production; since methanol synthesis is an exothermic reaction, controlling the temperature of the synthesis tower essentially means maintaining its thermal balance. The temperature control of the synthesis tower involves primarily the control of the reaction temperature inside the tower and the temperature of the gas exiting the tower. ①Methods for adjusting the catalyst layer temperature: A. Proactive operation is required; adjust the bypass valves and various branch valves in advance based on fluctuations in CO and CO2 levels, especially when there are significant fluctuations in furnace temperature. B. When the temperature fluctuations are large, regulation of the circulation volume is generally the main approach, with the tower bypass line used for supplementary adjustment. When the temperature fluctuations are small, regulating the flow rate in the synthesis tower’s bypass line is the primary method; adjustments to the valves should be made gradually, without being too drastic or excessive. C. In the event of a sharp drop in tower temperature, and if adjusting the bypass line and circulation rate is not sufficient to maintain the temperature, then, when the CO content behind the tower is not high, it is possible to increase the CO content in the fresh gas, or activate an electric furnace to maintain the furnace temperature. ②To control the temperature of the synthesis tower, the following points must be taken into account: A. Changing the circulation volume has a significant impact on the system resistance; it is necessary to ensure that both the system pressure difference and the tower pressure difference remain within specified limits. B. If the reaction temperature gets out of control, the gas supply should be cut off to protect the catalyst. C. The temperature of the synthesis tower wall and the temperature of the gas exiting the tower must be strictly controlled. (2) Pressure control: Changing the synthesis pressure directly affects the quantity produced; therefore, adjustments must be made carefully and slowly to avoid significant fluctuations in the system or even damage to the internal components of the synthesis tower. If an increase in pressure occurs due to a temperature difference across the furnace, the vent before the tower must be opened immediately; the dispatch team and the compression shutdown system should be notified, and the machine speed should be reduced to ensure that the pressure remains within acceptable limits. When driving, the system outlet valve must be opened wide to prevent pressure buildup in the system if it is opened too small. (3) Control of the recycle gas volume: The amount of recycle gas in the synthesis tower reflects, to some extent, the load and production capacity of the tower. Therefore, the circulation volume should be increased as much as possible under permissible conditions; however, this increase is restricted by the following factors: A. It is limited by the reaction temperature in the synthesis tower. B、Limited by the air inflation volume of the circulation machine. C. Limited by system resistance. D. Limited by the capacity of cooling and separation equipment. (4) Control of gas composition entering the tower: The gas entering the methanol synthesis tower contains CO, CO2, H2, N2, CH4, CH3OH, as well as trace amounts of harmful gases such as H2S. The composition of this inlet gas is controlled by using fresh gas. A. The control of CO content in the fresh gas can be adjusted based on the following factors: (1) The proportion of methanol production in the total ammonia production. Increasing the methanol content raises the CO content in the fresh gas, while increasing the ammonia production reduces the CO content in the fresh gas. (2) The CO+CO2 content in the alcohol-treated gas must be within the specified limits; otherwise, the CO content in the fresh gas must be reduced. (3) H:N ratio of the recycle gas in ammonia synthesis production. B. Control of CH3OH in the gas entering the tower. The CH3OH in the gas entering the tower is brought in by the recycled gas; the high alcohol content in the gas entering the methanol tower affects the equilibrium rate of the synthesis reaction, increases by-products, and lowers the temperature of the catalyst layer. Therefore, it is desirable for the CH3OH content in the gas entering the tower to be as low as possible. The following factors are related to CH3OH in the gas entering the tower: (1) A higher control temperature for water cooling means a higher alcohol content in the gas entering the tower, while a lower control temperature for water cooling corresponds to a lower alcohol content. (2) When starting the cycle machine, the lower the system pressure, the worse the separation of alcohol components, resulting in an increased alcohol content in the feed to the tower. (3) When starting the circulation machine, high levels of alcohol in the liquid phase lead to liquid being carried along, which increases the alcohol content entering the tower; therefore, it is necessary to strictly control the liquid level. (4) Poor alcohol separation due to high water cooling temperatures, design defects in the internal components, or the need for thermal cleaning of these components leads to an increase in the alcohol content entering the tower when the circulation pump is started. C. Prevent small amounts of toxic substances from entering the synthesis tower. The toxic substances in the feed gas are mainly S and other compounds. The poisoning effect of S on catalysts is permanent and cumulative; therefore, strict measures must be taken to prevent harmful substances from entering the synthesis tower. Additionally, imported oil fractions should be discharged promptly to prevent oil substances from entering the synthesis tower and reducing catalyst activity.