Analysis of ammonia synthesis catalyst poisoning in the dihydric alcohol production process
Thread Content
The last edit to this post was made by chenfeng8638 on 2015-7-7 at 10:34. The ammonia gas purification process used in this facility relies on a non-isobaric alcohol alkylation method; pressure swing adsorption is employed to raise the pressure of the gas to 12 MP before it enters the medium-pressure alcohol system (at a temperature of 235–240 degrees). From there, the gas is further pressurized and sent to the high-pressure alcohol system (with a pressure of 25 MPa and a temperature below 240 degrees). The high-pressure alkylation system requires that the concentration of CO and CO2 at the inlet be less than 300 ppm, while at the outlet, the concentration of these gases should be less than 5 ppm (this has been confirmed repeatedly). After alkylation, the gas undergoes cooling with ammonia and is then passed through a water separator before entering the ammonia synthesis system. Occasionally, there are slight fluctuations in the CO concentration in the medium-pressure alcohol stage (ranging from 1.6% to 2.0%), while the concentration of these gases at the alkylation outlet remains unchanged. Poisoning of the synthesis catalyst can occur, leading to increased pressure, decreased temperature, and reduced flow rate. Oil poisoning can basically be ruled out, as the synthetic cycle machines use oil-free lubrication. I would like to explore whether there might be a third type of toxin that could cause poisoning of the synthetic catalysts used in hydroxyl alcohol production – such as unsaturated hydrocarbons or ethers. If so, are there any indicators for these substances? Want to learn about the experiences and approaches of peers in this area?
The poster must have allowed untreated gas to be directly fed into the ammonia synthesis process via circuits and other pipes
1. “The high-pressure alkylation system (the concentration of CO + CO2 at the high-pressure alkylation inlet is less than 300 ppm); the concentration of trace amounts of CO + CO2 at the high-pressure alkylation outlet is less than 5 ppm (this has been confirmed repeatedly). After alkylation, there is ammonia cooling and a water separator, after which the mixture enters the ammonia synthesis system,...” It is recommended to check the high-pressure alkylation pipeline circuits, as there is a possibility of contamination entering the ammonia synthesis process. 2. Additionally, consider the issues related to ammonia synthesis itself, such as ammonia cooling and the control of ammonia liquid levels, to determine whether there is any potential for temporary poisoning.
It is not clear whether a circulation pump is in use for the dual-methyl system, and what the degree of opening of the circulation pump’s circuit is. Due to pipeline configuration issues, the pressure may increase slightly as the auxiliary valve of the circulation pump (the circuit) is fully open; moreover, since the sampling point is located closer to the source, an accurate reading cannot be obtained
I’m curious about the performance of your ammonia and alcohol co-production process I was wondering what the current competitiveness is like?
The alkylation tower uses the reaction heat from the ammonia synthesis tower as a heat source. When the operating pressure in the alkylation unit is at the same level as that designed for the ammonia synthesis tower, the pressure in the alkylation system is higher than that in the subsequent ammonia synthesis system; this can lead to leakage of the material entering the alkylation unit into the circulation gas of the ammonia synthesis process. The problem mainly occurs in the exchangers outside the tower, as one side of the tubes in these exchangers is in contact with the circulation gas while the other side is in contact with the gas after secondary alcohol treatment, and the pressures on these two sides differ. As a result, if there is a leak in the sealing gaskets or in the tubes themselves, a slight increase in the concentration of ammonia in the circulation gas at the entrance of the ammonia tower may occur. Under normal conditions, the CO concentration at the entrance of the alkylation unit is relatively low, and the amount of leakage is not sufficient to affect ammonia synthesis. However, when there are fluctuations at the entrance of the alkylation unit and the CO concentration rises to a certain level, significant fluctuations occur in the reaction process within the ammonia synthesis tower.
Agree with the opinion above; focus on checking for leaks in the alkylation heat exchanger