ACC Operations and Maintenance budget

[dpwatson]

Our company is looking to potentially build a new Combined Cycle 1×1 Large frame site and utilize a ACC instead of a wet system. This will be our first experience with a ACC and I am looking to build some information on potential budgetary cost impacts due to the ACC. I would like to included chemical, cleaning, motor/fan maintenance, and any other potential cost impacts we would need to capture. Any information is appreciated.

[tstafford17]

Geographic location can have some impact to the performance and maintenance of your ACC. I’ve had them (Forced draft) in California with a mostly dry climate and also in Mississippi in a fairly humid climate and I’m currently involved in an Induced Draft design and implementation in SE Louisiana (not yet constructed). Below are some generalities I’ve observed from 20+ year old vintage ACCs:
• Consider running a slightly higher PH in the HRSG (we ran 9.8-10.0) than you would for wet systems. The OEM can confirm or suggest other parameters.
• Determine/decide if you need Anodamine or not…this can be quite expensive and likely your biggest chemical expense. Other than that, the chemical costs should be less than a cooling tower.
• You can clean the ACC in house or pay a contractor to do it (experience vs. cost thing). You may want to clean more than once a year depending on environmental conditions (tree pollen, agricultural dust, etc.).
• Motor, gearbox, fan blades, and shrouds should be given consideration. For older generation fan cells you really need to stay ahead of the maintenance…gear boxes especially. I’ve had a few different manufacturers with various results, but the technology and performance has improved as we replaced units so I’m hesitant to suggest one over the other. For material handling, consider access to all components of the cell, this can be expensive and problematic if you have to scaffold up to individual cells for repair/replacement of components. Look into OEM design to see if the proper means of access is there.
• Soft starts or VFD would be helpful…I’ve never had either, but would’ve liked it.
• Plan to do in depth helium (or other) testing for air-in-leakage at least once per year (or as needed) in addition to everyday monitoring…A-I-L is a killer for ACCs and especially “painful” in the summer. Hopefully, your design has vacuum pumps in addition to SJAE, this can help for “air pockets” in the condenser and bring down vacuum as you’re starting up.

With many years of experiencing both ACCs and conventional cooling towers I prefer ACCs regardless of region, but you must stay ahead of the maintenance and if you are in a dry climate with water restrictions they’re even more impactful.

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