Case Study: Fluoride reduction system for the reduction of fluorides from wastewaters.
| Client:
Major semiconductor fab; Santa Clara, CA.
Industry: Semiconductor Manufacturing. Installation Date: May 2001. Objective: To reduce total fluorides and neutralize rinse waters and concentrated bath dumps from the fab area. Criteria and Limitations: Influent flow varies from 5,000 gpd to 40,000 gpd and can contain up to 2% HF and BOE as fluoride source. Combined plant flow requires a total fluoride level of less than 10 ppm. |
batchTREAT BT125 Duplex Batch pH Adjustment and Fluoride Reduction System |
| Overview:
As with all semiconductor fabs fluorides in the wastewater
is a problem due to the extensive use of Hydrofluoric Acid
(HF) and Buffered Oxides Etches (BOE). Fluorides discharge
levels across the country range from 50ppm to as low
2ppm.
Fluorine, an anion, is unique and behaves much differently than the cations, or heavy metals, that industry is experienced in removing. Ion exchange does not work economically because the very low affinity that anion exchange resins have for fluorides (abv. F-). Membrane technology is normally not economical because of low flux and membrane fouling. Fluoride bearing waste streams are normally high in silica, the bane of crossflow membranes. Fluorides can be precipitated as Calcium Fluoride (CaF2), however, due to the solubility of this salt, and due to the difficulty in separating this salt from solution, this can be very problematic also. |
Solution: Our batchTREAT wastewater treatment systems are very versatile, modular, skid mounted and flexible. In this application the BT125 served as the heart of the treatment system which consisted of several totally automated stages as listed below:
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| The Process: Digital Analysis Corp. has developed a unique process for reducing fluorides in semiconductor fab operations. This process allows for the totally automated reduction in total fluorides. Fluoride levels as low as 2ppm can be reliably attained. |
Conclusion:
The project, as with many wastewater treatment systems, was
constrained by time, space, and money. The use of a standard
packaged system at the center of the treatment process allowed us
to offer the customer a very capable system with a good delivery
time, very competitive price, and minimal installation since the
entire treatment system was fabricated in our shop prior to
shipping.
The system performance has exceeded all specified and published requirements. In the first 2 years of operation there has not been a single discharge contravention and the total plant fluoride has averaged 2ppm. The system has been fully functional 24/7 for the first 2 years with no downtime, other than routine calibrations (weekly) and routine, scheduled maintenance. The influent fluoride levels are routinely in excess of 1,500 ppm.
Description: The
system supplied for this application utilizes our unique process
for reduction and removal of fluoride from semi-conductor
wastewater streams as non-hazardous calcium fluoride (CaF2).
The process we employ is totally automated, requires no operator
intervention (other than periodic maintenance and calibrations),
is safe and can yield total fluoride levels as low as 2 ppm,
depending on configuration.
The system
featured in this case review is a duplex system. Two totally
independent systems operate in parallel with only minimal common
components. One stream can be taken offline for service while the
other continues to operate totally independent of the other
branch.
This package was
totally fabricated in our facility and shipped as several
subsystems, including a catwalk for servicing equipment at higher
elevations. Installation was minimized by the fact that the
entire system was fabricated in our shop prior to shipping.
A Supervisory
Control And Data Acquisition (SCADA)
system is installed that monitors the entire system. All of the
programmable parameters, tuning variables, and setpoints are
available through the SCADA system. All process variables and
system performance are monitored continuously via the SCADA
system. Historical logging will maintain a continuous stream of
data that may span several years.
A remote connection is available via MODEM that allows us to monitor the system from anywhere in the world. We are able to troubleshoot, modify tuning parameters, or conduct training via this phone line connection.
Digital
Analysis Corporation
PO Box 95
716 Visions Drive
Skaneateles, NY 13152
315-685-0760
315-685-0766(fax)
For Product Information : Email : info@digital-analysis.com
For Service & Support :Email : support@digital-analysis.com
