Seeking advice: Which process is suitable for the purification of 100,000 tons of synthetic ammonia?

I’ve never heard of pyroalkylation; alcohol alkylation does exist. The alcohol-to-hydrocarbon process involves methanolization followed by hydrocarbonation; hydrocarbonation replaces methanation in the alcohol alkylation step. The products of the CO+CO2 conversion are primarily various hydrocarbons with much higher molecular weights (according to the published analysis results), which can be cooled and separated. The catalyst used is a relatively inexpensive iron-based one ； The alcohol alkylation process involves methanolization followed by methanation; the refined product is inert methane for ammonia synthesis, and the catalyst used is the relatively expensive nickel-based type. Comparison of the two: It is said that hydrocarbonation requires less H2 than methanation. Nickel-based systems have a higher space velocity than the others, making reduction much simpler; however, care is needed as reduction can easily produce the highly toxic Ni(CO)4, which can cause harm. Let’s just say everyone has their strengths.

Methanation is recommended. 100,000 tons of synthetic ammonia is roughly equivalent to one of our production units; methanation requires less investment and is easy to operate (it is integrated into the shift conversion section), so no additional operators are needed. The trace amount in the purified gas is below 10PPM; sometimes it cannot be detected, while the CH4 level is generally around 1.5%. A set of membrane separation devices can be synthesized.

A production scale of 100,000 tons of synthetic ammonia can fully utilize low-pressure ammonia synthesis. A centrifugal compressor is used, driven by a turbine. If used in conjunction with low-pressure ammonia synthesis, methanation is a better option for deep purification. Currently, the well-performing units include the two 1830 models from Shanxi Gaoping Tianji Sinochem, the Shanxi Lanhuatianyue 1830, and the Heilongjiang Heihua 1830 – all of them using methanation + low-pressure ammonia synthesis. If electricity is cheap, high-pressure ammonia synthesis can also be used, as it results in low production costs and low investment requirements. Alcohol hydrocarboxylation and alcohol alkylation have largely replaced copper washing for modification, and can be used. NHD can be used for front-end purification. The three factories I mentioned also use NHD. This post was last edited by tomlhq on 2009-4-19 09:07]

What are the differences between Nanchang’s alcohol hydrocarbonation technology and Anchun’s alcohol alkane technology?

In fact, they are basically the same thing – both are variants of the dual-methyl process. In Anchun, Hunan, it has been nearly seventeen years since the operation of the first dimethylamine production unit at the Hengyang Nitrogen Fertilizer Factory; it truly deserves to be renowned throughout the country. Nanchang and Guochang are lagging behind, especially Guochang, which shows great potential to catch up.

Low-temperature methanol washing is the best option; however, what I’ve seen is copper-based washing, which is quite complicated~~

The fact that you are asking such a question indicates that the new project at your factory falls under the category of energy-saving and emission-reduction initiatives. Depending on the actual circumstances, you can choose from the following options: 1. Low-temperature methanol washing process; 2. Methanation process; 3. Alcohol alkylation process. As for which specific process to select, it depends on your particular conditions. These three processes are suitable for different regions and different types of raw materials, and they should be compared with regard to their economic efficiency. In fact, there is no best process. (Apart from the high energy consumption of the copper washing process) It can be discussed further if necessary.

I am working on low-temperature methanol washing; since I’m just starting out, I haven’t yet designed the methanation and alkoalation processes. But as the person above said, it mainly depends on the type of raw materials and the process costs – there is no absolute good or bad among these three processes!

As mentioned earlier, price is also a factor to consider... Synthetic ammonia doesn’t have any competitive advantage in terms of price, and using copper for purification increases costs, which might be unaffordable