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Cleaver-Brooks Helps LES Provide Reliable and Cost-Efficient Power

Case Study

  • Company: Salt Valley Generating Station
  • Industry: Utility
  • Location: Lincoln, Neb., metropolitan area
  • Profile: LES’s charter is to provide the most cost-effective energy available for its customers in the Lincoln, Nebraska metropolitan area.
  • Challenge: Pressure differentials can quickly cause icing in the air inlet housing. If any ice were to form, then break free, it could seriously damage the turbine blades and take the unit offline.
  • Solution: LES installed two Cleaver-Brooks Boiler Model NS-L-46, 36,000 PPH Delta Watertube packages operating at 60 psig.
  • Results: Cleaver-Brooks watertube boilers get the plant online efficiently and at full capacity, help ensure that Salt Valley remains at full capacity and eliminate icing and protect the turbine.

Cleaver-Brooks provides critical auxiliary energy production for Lincoln Energy System’s (LES) Salt Valley Generating Station in Lincoln, Neb.

As a public utility, LES’s charter is to provide the most cost-effective energy available for its customers in the Lincoln, metropolitan area. To accomplish this, LES employs three distinct power generating combinations, including the use of its base load coal resources, purchased power and peaking plants. The peaking plants are employed to provide adequate power at the desired cost when this is optimal either for cost reasons or simply because of heightened demand caused by factors such as extreme weather.

LES’s Salt Valley plant is unique in the fact it is the first combined cycle generating plant in the State of Nebraska, consisting of three General Electric LM6000 aeroderivative fuel-fired turbines that can burn either natural gas or #2 diesel fuel, providing maximum flexibility for Salt Valley. These aeroderivative engines are essentially the same engines that have proven themselves for decades in aircraft such as the Boeing 747 and Airbus A300. In its power-generating configuration, the LM6000 is the industry’s most efficient, small-capacity turbine.   

The waste heat from two of the three LM6000 turbines is directed to a Heat Recovery Steam Generator (HRSG) producing steam that is used to drive a Nuovo Pignone (General Electric) steam turbine. In this combined cycle configuration in conjunction with the fuel fired turbine generators, Salt Valley can operate at 175 megawatts and at efficiencies approaching 46%. 

One of the keys to Salt Valley’s efficiency is the temperature of the intake air. At 48 degrees Fahrenheit — the maximum optimal intake air temperature — each LM6000 can generate 45 Megawatts. To achieve this level of efficiency with hot ambient air — say 90 degrees — Salt Valley employs chillers that circulate a 36-degree glycol solution through the combustion turbines’ air inlet housings. This chills warm ambient air (warmer than 48 degrees) down to the optimal 48-degree combustion air temperature. While there is input energy needed for the chilling process, it is nominal compared to the energy output ensured — 10-12 Megawatts per combustion turbine — from optimally efficient combustion.

When ambient air is cool — below 40 degrees — it becomes critical to warm inlet air for the combustion turbines because pressure differentials can quickly cause icing in the air inlet housing. If any ice were to form, then break free, it could seriously damage the turbine blades and take the unit offline.