Comparison of decarbonization technologies

Hot potassium alkali solution works too; it’s our proprietary technology

MDEA is good: it causes little corrosion, has mild and simple operating conditions, and low energy consumption. But if desulfurization is done at the same time, methanol washing is required. Generally, methanol washing and air distribution sleeves.

MDEA is good – it causes little corrosion, its operating conditions are mild and simple, and its energy consumption is low. However, during our company’s research, the reports provided were unclear, which led to its rejection; what a pity!

Low-temperature methanol washing requires a high investment and cooling equipment, but it has low operating costs and high purification efficiency. It is generally used more in large-scale devices. Compared to phenol process (thermal potassium alkali method), MDEA (N-methyldiethanolamine) method, and NHD (polyethylene glycol dimethyl ether) method, NHD has the lowest operating costs (when considering steam consumption, electricity usage, and chemical raw material expenses as a whole). If possible, it is advisable to examine several options – look at both NHD and MDEA – so that you can make an informed comparison. It’s still worth conducting preliminary research for a project worth tens of millions! :lol

Who says MDEA causes little corrosion? We use this process, and it was fine in the first few years, but now it’s caused serious problems for us.

I think the low-temperature methanol decarbonization process is preferable, as it is a process specifically designed for removing carbon dioxide and sulfides from feed gas. It consists of an absorption tower, a flash tank, heat exchangers, throttle valves, a stripping tower, along with connected pipelines and various monitoring and control instruments. This method features low costs, small size, light weight, simple operation, safety and reliability, as well as ease of installation and maintenance.

We use benzophenone solution; it tends to crystallize when the temperature drops, which can cause some of the smaller pipes to get blocked

Our company uses large-scale pressure swing adsorption for carbon removal; it can generally be automated, yields excellent results, and problems occur very rarely – it’s really good! ! The decarburized gas can be sent directly for refining! !

Domestically produced MDEA is not suitable; however, the German-made version is acceptable. Lutianhua and Yuntianhua use type 30 modified to type 45 for this purpose. The issue with domestically produced MDEA is its poor formulation, which leads to severe corrosion. The absorption tower in our factory was replaced after just 4 years due to corrosion

Our factory was the first to adopt the German BASF MDEA decarboxylation process; due to the long procurement timeline, we have been using domestically produced MDEA since 2000. Corrosion is minimal with this material, but cavitation occurs. If the corrosion is severe, it may be due to poor management in certain areas.

We use hot potassium alkali. The effect is not very good; affected by the previous process, the solution tends to foam.

Low-temperature methanol washing is a new process! The raw material costs are low, but the equipment investment is high, and a large amount of cooling capacity is required. Hot potassium hydroxide can be used, but it corrodes the equipment; moreover, liquid accumulation occurs, and bubbles in the solution can easily lead to false level readings. Steam regeneration is necessary. The investment for NHD equipment is not high, but the cost of the solution is high, and cooling capacity is also required. The choice depends on the site’s processing processes and equipment, as well as its production capacity. It is recommended that the processing capacity of NHD be around 300,000 tons of urea per year, while the processing capacity of low-temperature methanol washing is much higher than that of NHD

The (DEA) thermal potassium alkali method used by our company suffers from problems such as high solution foaming, numerous impurities, and a dark color. Currently, the Fe3+ content is increasing gradually, leading to intensified corrosion.

Then you need to be careful; check the vanadium pentoxide content to see if the anti-corrosion coating is damaged Don’t end up with holes everywhere before trying to fix it

NHD achieves a high degree of decarburization and purification, making it suitable for ammonia synthesis with high yield； PC has poor decarburization and purification performance, making it suitable for the co-production of ammonia and methanol ； Low-temperature methanol washing offers high purification efficiency and good desulfurization performance, making it suitable for methanol production on a single-unit basis. Other methods are generally not recommended for use nowadays.

Comparison of Comprehensive Operating Costs per Ton of Ammonia Decarburized 1. Raw Material Consumption Two-stage Pressure Swing Adsorption (patented), NHD method, PC method, Modified MDEA method, Modified Thermal Potassium Alkali method ①. Cost of adsorbent consumption (0.17 kg of adsorbent per ton of ammonia; unit price per kg of adsorbent is 7 yuan) 0.17×7=1.2 — — — — ②. Cost of propylene carbonate consumption (0.8 kg of propylene carbonate per ton of ammonia; unit price per kg of propylene carbonate is 7 yuan) — — 0.8×7=5.60 — — ③. Cost of NHD solvent consumption (0.3 kg of NHD solvent per ton of ammonia; unit price per kg of NHD solvent is 16 yuan) — 0.3×16=4.8 — — — ④. Cost of MDEA solvent consumption (0.3 kg of MDEA solvent per ton of ammonia; unit price per kg of MDEA solvent is 16 yuan) — — 0.2×16=3.2 — ⑤. Cost of raw materials such as methyl carbonate — — — — 6.5 Total (yuan): 1.2, 4.8, 5.60, 3.2, 6.50 2. Utility Consumption ①. Cost of circulating water consumption (unit price per ton of circulating water is 0.15 yuan) 2×0.15=0.3, 50×0.15=7.5, 30×0.15=4.5, 40×0.15=6, 50×0.15=7.5 ②. Cost of electricity for decarburization (unit price per kilowatt-hour is 0.25 yuan) 24×0.25=6, 136×0.25=34, 100×0.25=25, 96×0.25=24, 100×0.25=25 ③. Electricity consumption for compressors: — — 40×0.25=10 — — (Since the decarburization pressure for PSA, NHD, Modified MDEA, and Modified Thermal Potassium Alkali methods is 1.7–1.8 MPa, while the decarburization pressure for the PC method is 2.7–2.8 MPa.) Therefore, for carbon-propane decarburization, 27–28% of the CO2 in the reformate gas must undergo the fourth stage of compression, whereas other methods manage to remove 27–28% of the CO2 at a pressure of 1.7–1.8 Mpa. As a result, the power consumption of the compressors used in carbon-propane decarburization is higher than that in other decarburization methods; the additional power consumption per ton of ammonia produced is calculated as follows: (4300 NM3 of reformate gas × 27% CO2 = 1161 NM3 of CO2). The compression work required to raise these 1161 NM3 of CO2 from 1.7 Mpa to 2.8 Mpa is approximately 40 units. ④. Steam consumption — 0.03×40=1.2 — 1.3×40=52 1.8×40=72 ⑤. Average annual maintenance and major repair costs (yuan) 2.0 5.5 6.0 6.00 7.00 ⑥. Increased compressor power consumption due to the return of mixed gas to the gas holder or all high-pressure flash vapor being sent back to the compressor — 6.5 9.8 6.00 3.00 ⑦. Impact on the compressor’s effective pumping capacity resulting from the return of mixed gas to the gas holder or all high-pressure flash vapor being sent back to the compressor (gross profit per ton of ammonia produced calculated at 400 yuan) — 15.2 22.57 14.30 7.10 Subtotal (yuan) 8.3 54.7 77.87 108.3 121.60 Total (yuan) 9.5 59.5 83.47 111.50 128.1