Drawings and Specifications
for
Nucla's In-Plant Coal Handling System Modification

Client Tri-State Generation & Transmission Association Nucla Plant P.O. Box 698 Nucla, Colorado Completion Date December, 1996

Project Description
Tri-State engaged Energy Associates to prepare drawings and specifications for the turnkey Contractor to design, supply, and installation a new in-plant coal handling system. This assignment was a follow-up to previous plant investigations completed by Energy Associates.

The in-plant coal handling system was part of EPRI's demonstration program for AFBC technology. The Nucla Station originally consisted of three 1959 vintage, 36 (3 x 12) MWe, stoker-fired boilers. In 1988, the stokers were replaced by a new, dual combustor, 110 MWe AFBC boiler. A new 74 MWe topping steam turbine/generator, with extraction to the existing turbines, was installed at that time. The in-plant portion of the conveying system consisted of Stephens-Adamson Redler conveyors and tertiary crushers. The Redler conveyors featured an en-mass conveying design that allows these conveyors to elevate coal at a 66 degree incline. The plant was, however, experiencing wear and other problems with these conveyors. The conveyors were operating 20 hours per day. The plant considered conventional belt conveyors to be more reliable. Belt conveyors are used on the unloading, stacking, and reclaim portions of the coal handling system.

Energy Associates prepared detailed bid drawings and bid specification for awarding a turnkey Contractor project. The in-plant system is critical to operating the plant. The 110 MWe AFBC unit cannot be fueled if the in-plant system is inoperable. As a result, engineering calculations and drawings were completed to illustrate, in detail, the design requirements. This included: conveyor and chute designs (including details of the high-angle conveyor); framing plans for the building addition complete with member sizes and connection details; access for stairs, platforms, doors, windows, etc. This approach was used to ensure that the successful bidder fully understands the requirements for this retrofit project. The potential for construction back-charges, which was experienced by Tri-State on other similar projects which did not use this approach, would be minimized. Most importantly, it helps to define the scope-of-work so the Contractor can anticipate the requirements for completing this modification within the scheduled plant outage. Energy Associates assisted Tri-State with construction reviews and was on-site during the outage period. Illustrated is a portion of the high-angle conveyor inside a the building extension that was added above the bunkers for the original three units and adjacent to the AFBC boiler building.