Methanol production process

The low-pressure method is currently more popular. Increasing the pressure can also raise the rate of the methanol synthesis reaction, resulting in an increase in the amount of methanol produced. However, as pressure increases, energy consumption and equipment strength also increase; therefore, it is necessary to take various factors into account to determine an appropriate operating pressure. Since the active temperature of zinc-chromium catalysts is 620–690 K, a pressure of over 25 MPa is required for methanol synthesis; therefore, the operating pressure for zinc-chromium catalysts is generally set between 25 and 35 MPa ； Since the active temperature of copper-based catalysts is 470–560 K, the pressure required for methanol synthesis is low. With copper-based catalysts, due to their high activity and lower reaction temperatures, the reaction pressure can be reduced to 5 MPa accordingly. Currently, large factories tend to use a pressure of around 15.2 MPa, while medium and small factories use 5 MPa, as this results in lower investment and operating costs.

Over the course of several decades, the synthesis pressure in large-scale methanol plants has evolved, and it now generally falls within the range of 8.0–12.0 MPa. Internationally, there are several well-known companies that hold patents for methanol synthesis processes; this can be found by doing some research.

The low-pressure method is now widely used, but the medium-pressure method is better

Currently, most companies use the low-pressure method, with a pressure range of 5.0–8.0 MPA. This way, the investment is small

Just look at the methanol production process to find out.

The pressure process generally refers to the method of synthesizing methanol using zinc-chromium catalysts at high temperatures and pressures of 300–400°C and 30 MPa. Since the first successful synthesis of methanol using this method in 1923, it has been the standard approach for methanol production around the world for almost 50 years, with only minor differences in design. For example, there are two main types of heat transfer methods within the methanol synthesis tower: the cold-tube continuous heat exchange type and the cold-jet multi-stage heat exchange type. The flow pattern of the reaction gases can be axial or radial, or a combination of both; there are also processes that produce by-product steam and those that do not. In recent years, China has developed a technology for synthesizing methanol using copper-based catalysts at pressures of 25–27 MPa, with a methanol content of about 4% in the outlet gas, and a reaction temperature of 230–290°C. The ICl low-pressure methanol method is a production technique for methanol that was developed by the British company ICL in 1966. This method broke the monopoly of high-pressure methods for methanol synthesis, representing a significant advancement in methanol production technology. It uses copper-based catalyst of type 51-1, with a synthesis pressure of 5 MPa. The synthesis towers used in this method are of the hot-wall multi-stage cold-jet type, featuring a simple structure; each catalyst layer is equipped with a diamond-shaped cold-jet gas distributor to ensure even distribution of cold-jet gas into the catalyst layer, thereby regulating the temperature inside the tower. Other types of low-pressure synthesis towers include those developed by the German company Lurgi, as well as the three-phase methanol synthesis system developed by the American Electric Research Institute. In the 1970s, the Sichuan Vinylon Factory under China’s Light Industry Ministry introduced a low-pressure methanol production facility from the French company Speichim, capable of producing 300 tons per day using acetylene waste gas as raw material (based on British ICI patent technology). In the 1980s, the Second Fertilizer Plant of Qilu Petrochemical Company adopted a low-pressure methanol synthesis unit developed by the German company Lurgi. The medium-pressure method evolved from the low-pressure method. Due to the low operating pressure in the low-pressure method, the equipment required was quite large, which made it difficult to scale up methanol production. Therefore, a medium-pressure methanol synthesis method was developed, with a pressure of around 10 MPa. This method allows for more effective reduction of construction costs and methanol production costs. For example, ICL developed a copper-based catalyst of type 51-2, whose chemical composition and activity are similar to those of the low-pressure catalyst type 51-1, though its crystal structure differs. The manufacturing cost of this catalyst is higher than that of type 51-1. Since this catalyst can maintain its effectiveness at higher pressures, ICL was able to increase the synthesis pressure from 5 MPa to 10 MPa. The synthesis towers used in this method are also of the four-stage cold-jet type, and their process and equipment are similar to those used in the low-pressure method.

Due to advances in synthetic catalysts, the high-pressure method has long been phased out. Since the 1960s and 1970s, the market share of the low-pressure method has been very high. In recent years, the medium-pressure process has shown a trend of gradually becoming the mainstream, and the reason is simple: the methanol synthesis reaction is a reaction that involves volume reduction, and higher pressure allows for a higher conversion rate.

Large-scale methanol plants under construction today generally use the low-pressure process.

The low-pressure method is widely used, while the medium-pressure method represents the trend of development