Cold junction problem
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There was originally a small ammonia synthesis plant that used 600-type heat exchangers; the internal components of these heat exchangers have been replaced, resulting in improved heat exchange efficiency. However, the ammonia content at the inlet increased by nearly 0.5, while all other process parameters remained unchanged. The three-stage centrifugal separation structure used at the bottom of the cold exchanger is, arguably, better than the previous multi-layer concentric sleeve structure. However, the actual performance is not very good; I would like to modify this separation structure and am wondering if there are any successful experiences in this regard. The cold exchange is the secondary ammonia fraction; water cooling leads to the cold exchange, which in turn leads to the primary ammonia fraction, and then ammonia cooling results in separation at the lower section.
It is recommended to use a combined system: install a wire mesh demister on top of the swirl plate to provide additional protection. It is also possible that the circulation rate does not match the designed flow velocity of the swirl plate. However, the efficiency of the swirl plate in separating small droplets is still somewhat unsatisfactory.
The key is to determine whether the gas flow velocity in the separation section under cold conditions has increased compared to before； With the sleeve-type separation structure, the gas flows radially, and the flow velocity may not be high; once a swirl plate structure is used, the gas flows axially, and the flow velocity can be higher than before ； In gas-liquid separation equipment, the gas flow rate has a significant impact on the separation efficiency. Generally, as long as the gas flow rate is maintained at 0.15 m/s, the separation effect can still be ensured even without any separation structures ； Cyclone plates can separate larger droplets, while screens can gather smaller droplets; these two methods improve the separation efficiency of the equipment. Our cold exchanger utilizes a structure that combines cyclone plates and screens, and it works very well.
Personally, I think it should be considered from two aspects: one is whether the entire system is overloaded, and the other is likely a temperature control issue.