Discussion on Reducing Drag through Cooling in Ammonia Synthesis During Summer
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This post was last edited by ZZJJAA70 on 2009-7-14 at 20:04. The temperature reduction in summer has a direct impact on the production volume of synthetic ammonia; various factors such as gas cooling, the carbonization reaction, and the compression capacity are all crucial. In good factories, the production volume remains unchanged between winter and summer, with only a slight increase in electricity consumption. However, in some poor-performing factories, the difference in production volume can be as much as 20%. Therefore, I believe that synthetic ammonia plants should make full use of cool water towers during summer, and regularly clean any blockages in the water-cooling pipes. We wash these pipes weekly using high-pressure water pumps, while the tubes inside the condensers are cleaned using high-pressure water pumps along with specialized nozzles. The water tanks inside the carbonization towers should be cleaned by professional teams, and it is also necessary to clean these tanks daily using shift gas. As for the ammonia cooler, three aspects need to be addressed: first, ensuring proper insulation of the equipment’s pipelines; second, reducing the pressure in the chiller’s storage tank to enhance its performance; third, lowering the temperature of the mother liquor to improve the absorption of gaseous ammonia. When the pressure of gaseous ammonia is low, less ammonia evaporates from the cooler, resulting in a lower temperature. Of course, specific actions must be taken based on each factory’s process flow... These are just some humble suggestions aimed at sparking further discussion. This post was last edited by jindin312 on 2009-3-10 17:30.]
1. Compress the inlet stream and use lithium bromide refrigerant water to lower its temperature. 2. Evaporative cooling is used to achieve a good cooling effect. 3. Add filters and sand filters to the circulating water to improve heat exchange efficiency. Regularly backwash the filter and sand filter. Replace the filter mesh regularly. 4. Add bactericidal and algaecidal agents to the circulating water regularly, and drain wastewater from the cold water tank periodically. 5. Use high-quality fillers for the circulating water cooling tower to increase evaporation volume.
I hope everyone will participate actively and lend their support
I agree with the views of those mentioned above. The gas ammonia cooler used in our factory utilizes the ammonia vapor evaporated from the synthetic ammonia cooler to cool the incoming gas temperature; in summer, the gas temperature can be reduced to around 19 degrees, resulting in a 10% increase in production. The ammonia-alkali process could serve as a model for this approach.
So, what happens to that ammonia gas generated as a result of heat exchange upstairs? If it goes to the ice maker, then the load on the ice maker increases significantly, and the temperature of the ice maker system also rises in summer. Our company uses gaseous ammonia in the production of compound fertilizers. When the amount of compound fertilizer used is sufficient, the entire system operates well; however, when the amount of compound fertilizer decreases, both the pressure and temperature in the system rise, and the output also drops significantly. Regarding the circulating water, that means turning on all the fans, and sometimes it is also necessary to add more fresh water. Regarding gas cooling, a cooling water tower can be added before the compressor inlet; this tower uses water once to cool the gas and reduce its inlet temperature.
Although temperature fluctuations have little impact on production here, needless to say this is the case in winter. Every summer, the company carries out maintenance work to help the system get through the hot season, involving alkaline cleaning, thorough washing, and maintenance of the more sensitive components. When the external temperature is too high, several key areas where circulating water is used for cooling are appropriately changed to use direct water flow ； The various water coolers are often backwashed with nitrogen, and the results are quite noticeable
Compressor summer operation: 1. Backwash the low-pressure water cooler weekly； 2. The temperature of the fresh gas in the synthesis tower must not exceed 40°C; otherwise, nitrogen backwashing is required for the water coolers in stages 4, 5, and 6. 3. Take advantage of shutdown periods to clean the water jackets of the cylinders from time to time.
Reply to Floor 5: We use the caustic soda synthesis process, where the cooling effect from evaporation in the synthetic ammonia cooler is utilized to lower the temperature of the gas; gaseous ammonia is then extracted for use in caustic soda production. Only 2 gas coolers will be added, with a slight increase in absorption capacity; no other equipment will be installed.
I’ve heard that all the methods mentioned for reducing temperature are quite good, but the quality of the water in our synthesis cycle is too poor, which results in poor cooling effects – the temperature at the outlet of the water coolers remains around 42 degrees. Do any of you have any good suggestions? I would be very grateful if you could offer your advice if possible.
I. Stabilize the gas generation process and improve the quality of semi-water gas； II. A lithium bromide unit can be installed at the inlet of the first stage of the compressor to reduce the temperature at that inlet ； III. The water coolers at each stage of the compressor should be cleaned regularly to increase its air compression capacity and prevent the compressor from performing unnecessary work ； IV. Strengthen the management of circulating water quality, allocate water supply to each water cooler reasonably, and adjust it to the maximum level possible.
Reading everyone’s discussions makes me feel fulfilled.
The process in our plant involves using lithium bromide units to cool the gas produced during gas generation, while circulating water is used to create cold water for cooling the shift gas and propylene carbonate liquid
Reply to zzJJAA70; we use the double-alkali process. Syngas ammonia is absorbed by the double-base process. The pressure of gaseous ammonia is generally below 0.05 MPa; frost forms in the main pipes for transporting gaseous ammonia from the synthesis stage to the absorption stage, as some liquid ammonia fails to evaporate completely, resulting in a waste of cooling capacity. During the technical upgrade, 2 gas coolers (2 sets of systems) were installed on the syngas ammonia main pipeline; the gas flows inside the tubes while the ammonia flows through the shell side. The heat exchange area can be determined based on the volume of gas, with the load being increased appropriately. It recovers the cold energy while reducing the temperature of the gas.
The method used in our company to cool down ammonia synthesis during summer is as follows: (1) There is a lithium bromide system that can produce cooling water at temperatures as low as 6 to 8 degrees Celsius; this water is used to cool the desulfurized gas flowing into the first stage of the compressor, allowing the temperature of the gas at the inlet to be maintained between 11 and 17 degrees Celsius. As long as the lithium bromide system operates properly, there will be basically no issues with production throughout the summer. (2) With an ice machine unit, gaseous ammonia can be converted into liquid ammonia, which is used for ammonia-based cooling systems and related ammonia-cooling equipment. In summer, it just uses a bit more electricity; there’s no difference from winter. (3) Of course, a cooling tower is essential, as both the lithium bromide system and the chiller system, as well as the shell-and-tube water cooling system, require the cooling water produced by it. As long as these three points are addressed, the ammonia synthesis plant should have no major problems getting through the summer.
Reply to floor 14: What is your factory’s production capacity? Is lithium bromide absorption refrigeration technology suitable for small nitrogen plants with a capacity of around 60,000 tons? http://bbs.hcbbs.com/thread-437152-1-1.html Feel free to participate
Lithium bromide absorption refrigeration technology is widely used in coking plants to cool coke oven gas. In synthetic ammonia plants in the southern regions, where temperatures and water temperatures are high during summer, this lithium bromide absorption refrigeration technology is particularly suitable.
Semicarbon monoxide gas contains a high amount of tar; won’t this cause blockages? You must be angry, right? Last edited by ZZJJAA70 on 2009-4-21 19:12]
Here, in our fixed-bed gas generation system, water is added to the tower after the gas leaves the gas holder; this not only reduces the temperature of the gas as it enters the compressor but also helps remove dust, thereby reducing the load on the electrostatic precipitators. The results are quite noticeable. Last edited by *aoye613 on 2009-4-21 at 20:36.]
Reply to ZZJJAA70: Sorry, I’ve been busy lately and didn’t see your post. Our gas cooler is equipped with inlet and outlet valves. There is a shortcut to the main gas pipeline, controlled by a valve. The bottom of the cooler is equipped with an automatic overflow drain, sealed with water, as well as a manual drain valve. Sometimes, when waste discharge is not carried out in a timely manner, the water at lower temperatures and tar cause blockages, increasing the resistance in the tubes. Just detach the cooler, use gas for a shorter path, and perform hot washing with steam introduced from the bottom. It can be put into production right after hot washing, which is quite convenient.
Our factory has installed lithium bromide refrigeration units on one inlet side, where the inlet temperature can reach around 20 degrees.
This post was last edited by *aoye613 on 2009-5-12 19:52. 9# Da Hai A: I’m not sure if you have urea available. If you do, urea can be used to produce lithium bromide via evaporation using low-grade waste heat, thereby generating cold water to reduce the temperature in processes such as semi-water gas production and decarburization. For more detailed information, please contact me.