What are some good methods for controlling the temperature of a deaerator? (Premium reply available, winners chosen randomly)
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For a certain sulfur recovery unit with a conventional sulfur recovery design, having an annual capacity of 60,000 tons, the designed consumption of fresh demineralized water is 13 tons per hour, while the reuse of steam condensate at 0.4 Mpa amounts to 10 tons per hour; thus, the boiler water consumption is approximately 23 tons per hour. The normal production load is generally 60%-70% of the designed full load, and the water required for the boiler is only half of the designed amount, around 12 tons per hour. Among this, the condensate water remains a relatively constant value, independent of the processing capacity of the plant. (The device will not reduce the amount of these heat-tracing steams either; otherwise, condensation in the pipes would cause even bigger problems. At this point, a problem arises: the temperature of the deaerator remains above the specified limit. (There are only 2 tons of relatively fresh deionized water available, while there are still 10 tons of condensed water.) According to the current process flow, the only way to reduce the temperature of the hot water and keep it within the specified range is by opening the vent at the bottom of the deaerator. One aspect is the waste of resources, and the appearance of the site is not good either. I wonder if anyone has encountered similar situations in their daily work – how do you deal with such problems?
Will the temperature not drop even if the amount of heating steam is reduced? If nothing else works, consider methods based on the condensed water that enters.
Steam from the deaerator is basically not needed; the heat from the condensate alone is sufficient to meet the temperature requirements of the deaerator. What do you think can be done about the condensed water that enters? Add heat transfer?
Does your condensate go straight into the deaerator, without needing to enter the condensate treatment system?
Are you also working with sulfur-based systems? Is your steam condensate treated before being fed into the deaerator?
Come and watch to learn* a bit. ;P
The excess heat in the condensate can be sent to devices outside the system that need it, such as for water treatment. Then increase the amount of water added to compensate for the loss.
This is indeed a good idea, but the current process does not include any delivery procedure; however, it’s possible to consider this carefully during maintenance!
1. The specific conditions at the site are not clear; therefore, certain assumptions are made to carry out heat balance calculations.
2. Assumptions and known conditions:
2.1. The inlet temperature of fresh water is at the saturated temperature at atmospheric pressure. This assumption is quite conservative for the purposes of these calculations; in reality, the temperature is much lower, requiring more heat.
2.2. The recovered condensate is assumed to be saturated water at 0.4 MPa(A). Again, this assumption is conservative; in fact, the temperature is lower, resulting in less heat available.
2.3. It is assumed that the flow rate of fresh water is 2 tons per hour, while the flow rate of condensate is 10 tons per hour.
3. Calculations:
3.1. The enthalpy value of fresh water is 420 KJ/kg, while that of steam is 2675 KJ/kg. The heat required for vaporization during deoxygenation is 4510 KJ/h.
3.2. The enthalpy value of condensate is 605 KJ/kg, giving a total heat amount of 6050 KJ/h. The heat required for vaporization during deoxygenation is 20700 KJ/h.
4. Discussion:
4.1. If the condensate is in liquid form, even if it’s a saturated liquid, it still does not provide enough heat for the vaporization of both fresh water and condensate, and the shortfall is significant.
4.2. If the condensate is in a mixed phase, its heat content increases significantly. However, it’s not possible to determine the degree of saturation. If there is an excess of heat at the site, it’s likely that the condensate is in a mixed phase.
5. Possible measures:
4.1. In sulfur processing units, appropriate low-temperature heat exchangers should be selected, depending on the actual needs. Until an effective heat exchange process is in place, this heat must be released temporarily; the issue is merely whether the way in which it is released looks good or not. 4.2. Examine the length of the pipes through which the condensate water is supplied by the external equipment; the insulation thickness can be reduced accordingly to help dissipate some of the heat.
2. Assumptions and known conditions:
2.1. The inlet temperature of fresh water is at the saturated temperature at atmospheric pressure. This assumption is quite conservative for the purposes of these calculations; in reality, the temperature is much lower, requiring more heat.
2.2. The recovered condensate is assumed to be saturated water at 0.4 MPa(A). Again, this assumption is conservative; in fact, the temperature is lower, resulting in less heat available.
2.3. It is assumed that the flow rate of fresh water is 2 tons per hour, while the flow rate of condensate is 10 tons per hour.
3. Calculations:
3.1. The enthalpy value of fresh water is 420 KJ/kg, while that of steam is 2675 KJ/kg. The heat required for vaporization during deoxygenation is 4510 KJ/h.
3.2. The enthalpy value of condensate is 605 KJ/kg, giving a total heat amount of 6050 KJ/h. The heat required for vaporization during deoxygenation is 20700 KJ/h.
4. Discussion:
4.1. If the condensate is in liquid form, even if it’s a saturated liquid, it still does not provide enough heat for the vaporization of both fresh water and condensate, and the shortfall is significant.
4.2. If the condensate is in a mixed phase, its heat content increases significantly. However, it’s not possible to determine the degree of saturation. If there is an excess of heat at the site, it’s likely that the condensate is in a mixed phase.
5. Possible measures:
4.1. In sulfur processing units, appropriate low-temperature heat exchangers should be selected, depending on the actual needs. Until an effective heat exchange process is in place, this heat must be released temporarily; the issue is merely whether the way in which it is released looks good or not. 4.2. Examine the length of the pipes through which the condensate water is supplied by the external equipment; the insulation thickness can be reduced accordingly to help dissipate some of the heat.
1. Although the condensate water passes through a flash tank at 0.4 Mpa to have some of its flash vapor recovered and used to supply the pipeline network, there should be a process of secondary flashing as it enters the deaerator. This is because the deaeration vapor available in the plant is hardly used at present; fresh water is heated entirely by the secondary flashing of the condensate water along with the heat it possesses. (Vapor is continuously escaping from the site, which indicates that the incoming water is in a mixed-phase state.) ) 2. The current method is not only unattractive but also wasteful; therefore, it is hoped that this thermal energy can be made better use of in order to save the wasted water. However, adding a heat exchange process means installing new equipment and pipelines, so the likelihood of making such changes is relatively low...