Reasons for the poor heat exchange efficiency in cold exchange
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Our company’s ammonia synthesis plant has been in operation for about half a year, and the temperature at the exit of the cold exchanger has increased from 15°C to 30°C. This has had a significant impact on the load of the ice machines as well as on the concentration of ammonia at the inlet. What are the possible reasons for this phenomenon?
In my opinion, the factors that affect the heat exchange efficiency in cold exchangers are as follows: 1. An excessive amount of gas in the circulation stream adheres to the tube walls of the exchanger, reducing its heat exchange efficiency. 2. A high concentration of CO2 in the make-up gas reacts with NH3 in the circulation stream, resulting in the formation of carbonate crystals that block the pipes. 3. Leaks in the tubes of the heat exchange section of the cold exchanger
Additional handling suggestions: 1. Conduct a hot wash during maintenance. 2. Lift out the heat exchange tubes to check for leaks.
1. The raw gas CO2 level is too high, resulting in carbon ammonium crystal buildup and blockages. 2. The gas entering the tower is relatively dirty, causing scaling and blockage in the tubes ； Treatment: Perform a complete process measurement before stopping the machine, especially the pressure difference during cold transfer in and out ； System shutdown for steaming and hot washing.
First, you need to clarify the phenomena – which indicators have changed, such as the circulation flow rate, the ammonia concentrations at the inlet and outlet of the tower, whether there is any oil leakage, etc. Without these data, it would be too speculative to give you an answer; I suggest you be more specific.
We are a 1600 ammonia tower; currently, we produce 120 tons of ammonia per shift, which is still a relatively small amount. Pressure difference for cold air inlet and outlet: 20.3→18.4 MPa. Inlet temperature of cold air: --5.3 °C; Outlet temperature: 16.3 °C. Inlet temperature of hot air: 38.1 °C; Outlet temperature: 28.5 °C℃
It might be due to high levels of CO2 in the feed gas, which causes ammonium carbonate crystals to form and cause blockages; moreover, the gas entering the tower is dirty, leading to scaling and blockages in the heat exchange tubes It’s best to stop the car and deal with it~~~~
Reasons for the poor heat exchange effect in cold conditions: Q=cm(t-t); a poor effect means it is not as good as before, but the difference isn’t very significant yet. 1. First, use a flow meter to check whether there is any change in the flow rate, which can be seen from the water usage records. 2. Check if there are any significant changes in the amount of heat generated, as well as any waste of heat. 3 Scaling phenomenon. 4 Assessment of the condition of the heat exchanger.