Abnormal fluidization in the external heat exchanger
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Due to production requirements, the external heat exchanger draws a small amount of heat, and the amount of air used for fluidization as pressurized air is very low; the pressure of this pressurized air is about 0.110 Mp higher than the regeneration pressure. Abnormal fluidization in the pneumatically controlled external heat exchanger leads to fluctuations in the steam generation rate and the temperature of the regenerative bed. The temperatures in the upper and middle sections of the external heat exchanger experience little variation, while the temperature in the lower section rises, resulting in reduced heat absorption; there is no significant change in density between the upper and lower parts of the external heat exchanger. I’d like to ask the experts how to adjust the operations?
Control the pressure of the two devices and the bed height, and adjust the pressurizing air gradually.
There is a local dead zone in the external heat exchanger. Pneumatically controlled ones are difficult to adjust when the heat extraction is too low. If the temperature of the dense phase bed in the regenerator is not too high and remains within the specified range, let it go into dead bed mode. :lol
The single-phase back-mixing external heat exchanger used in our equipment allows the gas production volume to be controlled between 6 and 40 tons per hour. When the gas production volume is kept low, below 10 tons per hour, the fluctuations become very significant. Years of practical experience have shown that this problem cannot be resolved; the only solution is to increase the gas production volume.
The several fluidization air supplies for your external heat exchanger should be turned off where necessary, and turned on where they need to be. Now that the heat load has changed, I guess there’s probably no change in the amount of fluidizing air supplied? Take another look at the external heat extraction method, adjust those airflow controls again, and give it a try.
This post was last edited by wt2008 on 2017-6-30 20:09. What was said on the third floor above is correct – gas-controlled external heat exchangers are difficult to adjust when the amount of heat extracted is low, and local dead zones can easily occur. One reason is that when the steam generation rate is low, the balance between the fluidization air and the catalyst becomes unstable, prone to being disrupted ； Second, there is a possibility of local damage to the fluidization air distributor below. However, since gas-controlled external heat exchangers require little fluidization when extracting a small amount of heat, they can recover quickly in the event of fluctuations. The operation is very simple: when the steam generation increases, quickly close the special valve of the external heat exchanger, and then return it to its original state. In this case, there is generally no rapid increase in steam production, so control is relatively easy ； Another scenario is a rapid decline in steam production; this occurs fairly frequently and can easily lead to operational fluctuations. In fact, the operation is very simple as well, allowing for rapid recovery of steam production. The approach is to quickly increase the opening degree of the external heat exchanger special valve by 3-6, or even 3-9 units, when the steam production rate is dropping rapidly; once steam production starts to recover, the valve is then quickly reduced back to its original setting. As for the methods, please use them flexibly.
Aren’t there external heat extraction air and fluidization air? The extraction air can be increased while the fluidization air can be reduced