Getting to Know Chemical Feed Systems - Part 1
A well-developed feed system is an important part of having an effective water treatment program. If a feed system is designed inadequately, chemical control will not meet specifications, operating costs could be expensive, and program results could be lacking. A few costly problems affiliated with poor chemical control include:
- High chemical cost due to overfeeding issues.
- High corrosion pace, equipment replacement, and maintenance (replacing corroded heat exchanger tubes/bundles).
- Risk of severe and far-reaching damage to process equipment from poor control or spillage of acid into cooling towers.
- Erratic product quality, higher steam, and electrical costs from waterside fouling.
- High labor costs due to extra requirements for operator attention.
A considerable investment in a chemical feed system can be justified when compared with the high cost of these control problems. If a chemical system is not properly designed, chemical levels typically are above or below program regulations. Using an appropriate feed system can prevent this situation.
Chemical feed systems can be characterized by the components used, the control scheme employed, the application, or the type of material to be fed (liquid or powder).
Feed System Components
Chemical Storage: Treatment chemicals are typically delivered and stored in one of these three ways: drums, semibulk, and bulk. Choosing which of these three ways depends on several factors. Some of the factors include usage rate, safety requirements, available space, inventory needs, and shipping regulations.
- Bulk Storage: Heavy users may find it beneficial to handle their liquid chemical delivery and storage in bulk. Liquid treatments are delivered by vendor tank trucks or by common carriers. A large tank is placed on the property of the user next to the point of feed. Service agent most often handles the inventory management functions. Treatment can be taken from the storage basins and infused directly to the water system or added to a smaller, secondary feed tank used as a day tank. Day tanks can be used a safegaurd to prevent all of the material from the main storage tank from being discharged into the system and are an easy way to measure daily product usage rates.
- Semibulk Storage: This is appropriate when chemical feed rates are not large enough to justify bulk delivery/storage that can be supplied in reusable shuttle tanks. These tanks normally are constructed to be stacked or placed on top of permanent bases for effortless gravity filling of the base tank.
- Drum Storage: Forty and fifty-five gallon drums were at one time widely used, however, increasing environmental concerns have strongly reduced drum usage. The restriction of drum disposal and drum reclamation have lowered the amount of this delivery and storage method.