Lessons Learned with Molten Salt
Salt Blend and Temperature are the starting point
Adequate preheating and heat tracing of salt wetted parts (Valves, Piping, Strainer, Heat exchangers) is required
Pipe routing and piping engineering is not “standard”
Design of equipment must consider experience with salt, i.e. salt creeps, freezes, dissolves graphite, salt has a high density, salt ages when in contact with oxygen, even low impurties and possible insolubles have to be considered (corosion, abrasion)
The entire system should be drainable by gravity
Key Considerations
~ Safety is the most important aspect!
High Reliability of such critical equipment is mandatory to the success of the plant.
Proven field experience, testing programs and highly skilled designers must be used to interface all of the critical components in the Molten Salt System.
The working relationship between the developer and suppliers of the Pumps, Valves, Tanks, Heat Exchangers and Trough/Receiver will be critical in insuring the end user a proven system that is highly reliable.
Pumps require a high degree of coordination between the design, materials of construction and intelligent application
The design and materials of construction must support and strengthen each other because extremely high temperature applications take both of these elements to their limits
No single design is adaptable to all the applications. Molten salt pumps must be designed to meet the individual requirements of the system that they are used in.
Probably the highest risk component in the system at high temperature is the valves. Valve failures are much higher risk than pump failures. Testing of the valves for any molten salt application should be a high priority.
Major challenge is the valve freezing up because of leaks through the seals.
Parts or components in the valve that need to be evaluated:
Type of valve
Type of body and bonnet (Cast, Forged or Wrought)
Sealing options (Bellows, Packing or Combinations)
Sealing faces, stems, heating systems to prevent freezing
Monitoring systems, actuators and materials of construction
Costs Driving Thermal Storage System
Salt Prices
Strong worldwide agricultural demands and demand for explosives for mining
No new production capacity to meet increased demand
Declining value of the USD
Availability will be reduced quickly due to size of TES (120,000 MT/250Mwe)
Price of Materials of Construction
Cost and availability of Carbon Steel and Stainless Steel is difficult to estimate
Equipment suppliers pricing is very high due to high risk factors
Labor
Construction cost will increase due to lack of available crafts and man power
Worldwide projects will reduce the experienced construction companies
Lack of tried and proven systems
We are at minimum 2-3 years away from having proven costs and reliability factors for these systems
Currently the return on investment is too low for troughs with add-on TES