Review of the Fuel and Limestone Handling Systems
of the
Red Hills Generation Facility

Client

Bechtel Corporation
9801 Washingtonian Boulevard
Gaithersburg, Maryland 20878-5356

Completion Date

December, 1998

Project Description

Bechtel engineered a two unit, lignite-fired power plant, known as the Red Hills Generation Facility. This is an atmospheric fluidized bed combustion (AFBC), mine-mouth power plant to be located in Mississippi. Bechtel developed the preliminary concepts for the fuel and limestone handling systems. These included the truck dump, crushing, storage, and reclaim systems. As part of the development, an independent review by Energy Associates of the lignite and limestone system concepts was authorized.

Bechtel engaged Energy Associates to review the basis and arrangement of the lignite handling system. A variety of issues were examined including conveying rates, belt speeds, weighing, dust emission control, redundancy, flow paths, storage, spontaneous combustion, fire protection, area classifications, etc. Lignite processing concerns and quality control including sampling were examined. The design of the in-plant silo hoppers was reviewed including the flow report completed by Jenike & Johanson. A number of alternatives were developed for consideration by Bechtel.

The lignite system consists of a number of elements. In this design, lignite is unloaded from 160 ton, dedicated mine trucks. They dump into a 200 ton receiving hopper, which is discharged by a 1900 tph apron feeder. The lignite is crushed by primary and secondary roll crushers, which are located at the discharge of the apron feeder. From the hopper, the lignite is conveyed to a 40 ton surge bin. A 1900 tph feeder discharges the lignite from the surge bin to a tertiary crusher. An overland conveyor system transports the lignite to two, 20,000 ton Eurosilos. Each Eurosilo is equivalent to approximately a two-day storage capacity, at the maximum plant burn rate of 420 tph. Each Eurosilo is equipped with two, 1900 tph discharge feeders. They feed a redundant reclaim system, one feeder from each Eurosilo discharges to each conveyor. The reclaim conveyors are rated at 1500 tph. The plant silos are filled via traveling trippers.

The system is equipped with magnetic separators, to remove tramp iron. One is located on the receiving transfer conveyor, ahead of the tertiary crusher. A set of magnetic separators is also located on the reclaim conveyors. The fuel system is equipped with dust collectors at the surge bin, Eurosilos, and plant silos. Belt scales are located on the reclaim system.

For the limestone system, Energy Associates conducted a dryer survey to examine technology options. These included rotary, fluidized bed, vibrating fluidized bed, and flash dryers. Manufacturers and users were contacted for technical details and operating experience. Results were reported to Bechtel in an industry survey report, as an assist to selecting the most appropriate drying technology for the plant.