Attachment 1 - C108435 Specifications and Operating Capacities of Mechanical Systems.pdf

Attachment 1 – Specifications and Operating Capacities of Mechanical Systems

1. Overview

The CUP at the NIH is capable of generating 800,000 pounds per hour (pph) of saturated steam at 165 pounds per square inch gauge (psig), 60,000 tons of chilled water at 42 degrees Fahrenheit (°F).

Potable water from WSSC is used in the CUP as makeup for the boiler (after water softening and/or reverse osmosis filtering), chilled water and cooling systems.

The boiler pretreatment system at the CUP includes three (3) sodium zeolite softeners (nominal service flowrate: 700 gpm), reverse osmosis system (nominal service flowrate: 580 gpm) and three (3) deaerators (nominal service flowrate: 1,800 gpm, 10 psig).

The CUP consists of five (5) dual-fired (primary-gas/secondary-ultra low sulfur number 2 diesel oil) saturated steam boilers and twelve (12) 5,000 ton chillers associated with twelve (12) cooling towers.

Boiler Identification

Operating Pressure Saturated

(psig)

Nominal Steaming Rate

(kpph)

Maximum Steaming Rate

(kpph)

Target Cycles of Concentration

Boiler 1 165 127.5 150 45

Boiler 2 165 127.5 150 45

Boiler 3 165 127.5 150 45

Boiler 4 165 127.5 150 45

Boiler 5 165 170.0 200 45

The CUP has two (2) liquid discharge streams from the site. The boiler blowdown, softener and condensate polisher regenerant and plant drains are directed to the Washington Suburban Sanitary Commission (WSSC) sewerage line. The cooling tower blowdown is directed to an unnamed tributary of Rock Creek as part of the NIH outfall 001.

2. The CUP Boiler Plant generates steam for most of the campus buildings for heating, building humidity control, equipment sterilization, steam cleaning of animal facilities and lab bench use. The boiler plant uses chemical treatment to provide proper passivation and corrosion control of the boiler feed water, boiler, steam lines and condensate return systems.

The boiler system chemical treatment consists of oxygen scavenger injected into the deaerator storage tank; neutralizing amine is injected into the steam header; and organic polymers for hardness sequestration scale prevention and dispersion of solids. The boiler polymer program is fluorescence traced for concentration monitoring sodium hydroxide are injected into the RO inlet for CO2 removal and RO permeate for pH control. Neutralizing amine demand is calculated based on weekly steam production, condensate pH and its concentration are maintained below FDA prescribed limits.

A. WSSC supplies water to the CUP through the city water lines and the IWS Tank. The existing city water lines serve as a backup water supply in the event the IWS tank cannot provide water to the CUP. Chlorine injection at IWS is required to minimize the microbiological growth in the tank.

B. oiler Pretreatment System: Potable water from WSSC is used in the CUP as makeup for the boiler (after water softening and reverse osmosis filtering). The boiler pretreatment system at the CUP includes three (3) sodium zeolite softeners (nominal service flowrate:

470 gpm), two (2) main Reverse Osmosis (RO) systems, one (1) recovery RO system and three (3) deaerators ((nominal service flowrate: 1,800 gpm, 10 psig). The CUP consists of seven (7) dual-fired (primary-gas/secondary-ultra low sulfur number 2 diesel oil) saturated steam low pressure boilers (165 psi)– two (2) boilers generating 75,000 pph each, four (4) boilers generating 100,000 pph each, one (1) boiler generating 150,000 pph saturated steam.

C. Water Softener Subsystem: The Boiler Plant in Building 11 receives potable water from the WSSC at approximately 60 to 100 psig. Three (3) water softeners remove hardness, copper, and iron from the domestic water. The softened water is then treated by reverse osmosis system to remove dissolved solids, mineral ions and silica. The water is then used in the Boiler and Cogeneration Plants as feedwater makeup and as cooling water for the No.3 Air Compressor intercooler. The condensate polisher uses softened water for backwashing.

D. Reverse Osmosis (RO) Subsystem: Softened water enters the RO system, and the RO system removes almost all mineral ions and sends permeate water to the treated water storage tank. To prevent damage to the boiler and boiler system components (i.e., valves), a limit is set for the concentration of certain minerals in the boiler feedwater.

Conductivity is used as a measure for mineral concentration. When the conductivity set point is reached, an automatic valve opens to blowdown the boiler. By operating the RO system, water, fuel consumption and chemical consumption from the boiler blowdown is reduced. Three chemicals are added to the RO Subsystem. Caustic is fed to the inlet of RO to remove CO2 and at permeate to protect the carbon steel in the CUP boiler plant, a dechlorinator is added to protect the RO membranes from chlorine in the softened water, and an anti-scalant is added to protect the RO membranes from any hardness breakthrough events from the Water Softener Subsystem.

E. Conductivity is used as a measure of dissolved minerals in the boiler system. These minerals could damage the boiler if allowed to concentrate above certain limits. The Reverse Osmosis (RO) system generates high purity, low conductivity water that significantly reduces water, fuel consumption, and chemical loss through reducing boiler blowdown frequency. The RO units require membrane cleanings and system disinfections to allow optimal operation and prevent buildup on the membranes. A combination of high pH cleaner, low pH cleaner, and biocide remove scale and microbiological growth on the membranes.

F. CUP Steam and Condensate System: The boilers continuously generate, 165 psig steam for use in the CUP and for distribution to the NIH campus. The condensate collection system receives steam condensate (approximately 60-65% of steam production) and routes the condensate to the Boiler Plant.

G. The condensate return system provides a centralized collection point for receiving condensate. High-pressure and low-pressure condensate from the Boiler Plant, steam turbine and condensate from the campus flows to the Main Condensate Tanks. This blended condensate mixes with water from the treated water storage tank. Six (6) condensate polishers treat the condensate and water from the treated water tank to remove hardness. The polished water flows to the three (3) deaerators. The polisher resin needs to be periodically cleaned to removal iron residual.

H. The steam and condensate lines are treated with a neutralizing amine to minimize corrosion in the condensate return piping and the introduction of these corrosion by-products to the boilers.

I. The CUP injects neutralizing amine into the steam header to prevent carbonic acid erosion of the piping. The FDA sets limits for total amine and by amine type (Cyclohexylamine and DEAE) for clean steam applications around the NIH Campus.

3. The Cogeneration Plant is comprised of one 24 MW Nominal Gas Turbine with Heat Recovery Steam Generator (HRSG) with an unfired capacity on natural gas of 107,000 pph and a duct burner with a fired capacity of 180,000 pph. Provide separate pricing for water treatment services including maintenance and Auxiliary Boiler treatment with boiler polymer and scale inhibitor program or equivalent and annual lay-up and cleaning of the Cogen’s HRSG, two (2) Auxiliary Boilers, gas compressor closed cooling system and the Combustion Turbine Inlet Air Cooling (CTIAC) Cooling System.

4. The NIH Chiller Plant is comprised of twelve (12) 5,000-ton centrifugal refrigeration units, commonly referred to as chillers. The chillers generate a maximum of 60,000 tons of chilled water at 240,000 gallons per minute.

A. Equipment Cooling Water: The Boiler Plant utilizes a closed loop, Equipment Cooling Water system to remove heat from various components that require a separate cooling media such as air compressors, after coolers, induced draft (ID) and forced draft (FD) fan turbine drives and boiler feedwater and main condensate pump turbine drives. The Equipment Cooling Water system uses chilled water as cooling source and Domestic Water (city water) as the coolant (and makeup source) for the equipment, and it is treated with a corrosion inhibitor and non-oxidizing biocide.

B. Chilled Water: The Chiller Plant generates chilled water for most of the campus buildings for both comfort and equipment cooling. The chiller system is a closed loop system, with an eleven million-gallon (11 MMGal) volume. The chilled water system utilizes a halogen stabilized azole corrosion and scale inhibitor with PTSA tracer treatment for corrosion and deposition protection, supplemental azoles for additional copper corrosion control, pH booster, chlorine dioxide as biocide treatment for microbiological control, and blue dye to identify chilled water loss on the NIH Bethesda Campus. A side stream filtration system was installed for a 3 MMGal chilled water loop and has been operational since June 2016.

C. TESS (Thermal Energy Storage System) tank experiences low flow conditions that may cause debris to settle to the bottom of the tank and encourage microbiological growth.

Monitoring bioburden of the TESS and chilled water loop provides actionable information about whether additional water treatment is required. TESS is currently treated as part of the chilled water loop; additional chemicals are to be fed in chilled water to meet the water chemistry requirements in TESS.

D. Condenser Water: Twelve (12) Evaporative Cooling Towers serve twelve (12) nominally-rated 5,000-ton cooling capacity centrifugal chillers. Each tower has a recirculation rate of approximately 15,000 gpm. A phosphonate based anti-scaling corrosion inhibitor is added to recirculating water for scale prevention and control of iron and copper corrosion. Chlorine dioxide is fed continuously and controlled by ORP as biocide treatment for microbiological control. A non-oxidizing biocide is fed three times a week. The cooling tower blowdown is directed to an unnamed tributary of Rock Creek as part of NIH outfall 001, which is subject to a National Pollution Discharge Elimination System Permit. Ferrous chlorine and sodium bisulfite are fed at the CUP blowdown discharge to neutralize biocide byproducts and chlorine.

E. Free Cooling: A Free Cooling system is installed on Cooling Towers 22 and 23 to provide lower-cost cooling when the outdoor air temperature is below approximately 40° F. When the ambient air temperature is below a set temperature, part or all the chilled water can by-pass the chiller and exchange heat in the Free Cooling system.

Chemicals include a corrosion inhibitor for scale prevention and iron and copper corrosion control, chlorine dioxide as biocide treatment for microbiological control and a non-oxidizing biocide. Free cooling system receives the same water treatment program as the rest of the cooling towers. Free cooling requires wet layup when they are not running during spring, summer and fall.

F. Condensing Turbines: Chillers 21, 22, and 23 have the option to operate on steam to generate chilled water during the cooling season. The surface condensers are in series with each chiller’s condenser when they are lined up for operation, which is an additional heat load to the condenser water.

G. The CUP uses chlorine dioxide as an oxidizing biocide to control microbiological growth in the NIH Campus Chilled Water loop, the free cooling system, and the condenser water system (cooling towers). Chlorine Dioxide is generated on site using sodium chlorite, bleach, and sulfuric acid as precursors. Chlorine dioxide serves an oxidizing biocide that is fed into the twelve (12) evaporative cooling towers, the free cooling system, and the chilled water system. The chlorine dioxide concentration after the generator is constantly monitored to ensure enough strength of biocide is produced and injected to the systems.

H. pH Neutralization System: The neutralization system pumps 25 to 30 gallons per day of 25% sodium hydroxide into a major sanitary sewer system line in the CUP and uses boiler blowdown or city water to flush the caustic soda into the sanitary sewer system.

The neutralization system maintains the pH of the overall NIH Bethesda Campus’s sanitary sewer to meet WSSC Discharge Authorization permit limits.

I. Dechlorination System: The Dechlorination System is operated as needed to remove chlorite and total chlorine from the cooling tower blowdown effluent prior to discharge to the unnamed tributary of Rock Creek.

J. Side Stream Filtering: During normal operation of the cooling towers, airborne particles and microorganisms will accumulate in the tower basin. The microorganisms are destroyed through biocide chemical treatment to control algae, bacteria, and fungal slimes. The filtration system captures these particles and decayed microorganisms in a filter by passing a portion of the condenser water flow (side stream filtration) through a filter media. The filter media will eventually reach saturation and require backwashing to rejuvenate the media material. This is determined by differential pressure across the inlet and outlet of the filtration tank. When the pressure exceeds a pre-determined set point, the filtration control system automatically switches valves to initiate the backwash cycle. The waste material from the backwash cycle operation is discharged to the storm drain and some filter media is lost during the backwash. Backwash from the side stream filter may increase bioburden and release toxic bacterial byproducts in the absence of appropriate preventative maintenance. Backwash water is currently combined with cooling tower blowdown and sent to the storm drain. The CUP has a project to re-pipe the backwash water to sanitary sewer.

K. The CUP installed new side stream filters for the Chilled Water system, Free Cooling System and Cooling Towers 17, 18 and 19. A design to replace Chillers 16, 17 and 18 and their cooling towers is currently in progress. A separate design is underway as of September 2019 to remove the old PEP filters for Cooling Towers 20 – 27 and replace them with side stream filters for Cooling Tower groups 2, 3, 4 and 5. The new side stream filters installed are 0.5 microns.

L. The NIH CUP has excess capacity pending the operating season, which requires fewer boilers or chillers to be operated. As a result, boilers or chillers and their associated cooling towers may not require daily operations and can have stagnant water. In addition, boilers and chillers may experience unplanned, scheduled, and forced outages, where water in their system cannot be circulated for an extended period. To minimize downtime corrosion and microbiological growth from equipment downtime, systems must be laid up properly.

5. Provide Chemicals and Recommendations to Maintain Cooling Tower MB Control

A. Provide chemicals for one (1) each hydrogen peroxide cleaning for five (5) Cooling Tower Groups per year.

B. Chlorine dioxide serves as an oxidizing biocide that is fed into the twelve (12) evaporative cooling towers. NIH will perform Hyperhalogenation (shocks) based on ATP as specified in Addenda No. 1. Steam driven chillers were placed in service after the Base Contract Year, they have increased condenser water temperature and require additional biocide.

C. Cooling Tower Wet Lay Up 12 Each.