OCR Text |
Show 7 The furnace limestone injection process facilitates the cost-effective use of a dry scrubber for downstream S02 removal by: 1) permitting the use of limestone as the sorbent (as opposed to the more expensive lime used in most dry scrubbing processes), and 2) by reducing the inlet S02 concentration to the dry scrubber through the in-furnace removal of S02. This latter fact permits the LIDS process to be applied to units firing high-sulfur coals by lessening the amount of calcium needed in the dry scrubber, thereby reducing the heat needed to evaporate the water contained in the sorbent slurry fed to the dry scrubber. The remainder of this technical paper covers highlights of the LI DS development work performed in support of the S&W LESS during Phase I of the project. LIDS PILOT -SCALE FEASIBILITY TESTING The feasibility of achieving the project S02 removal goal with a fully-integrated LIDS process under cost-effective operating conditions needed to be demonstrated. While previous data from a variety of sources were used to predict success, it was nevertheless essential to demonstrate this capability early in the project. The primary objective of the LIDS feasibility testing was to show the fully-integrated LIDS process capability of 97% S02 removal. In the furnace limestone injection process, calcination of the limestone must occur under ideal conditions - injection temperature, time/temperature history, etc. - in order to yield a highly reactive sorbent for optimum S02 capture in the boiler furnace and convection pass, and for optimal performance of the downstream dry scrubbing and fabric filter S02 removal processes. In the dry scrubber, the S02 removal efficiency is maximized by increasing the amount of sorbent in the slurry and by operation near the flue gas saturation temperature. The baghouse represents the final S02 removal stage for the LIDS system. Therefore, baghouse performance is critical to the overall S02 removal in LIDS. Key factors for the bag house performance include the approach to saturation temperature, calcium stoichiometry, sorbent characteristics, and baghouse differential pressure (thickness of the filter cake). All ofthese things are examples of the process integration that needed to be accomplished during the fully integrated LIDS feasibility demonstration. Small Boiler Simulator (SBS) and LIDS Pilot Facility The facility used forthe LIDS pilot-scale testing is shown in Figure 5. It is made up of a combustion furnace called the small boiler simulator (SSS) and the LIDS pilot facility. The test unit is located at B&W's Research and Development Division located in Alliance, Ohio. The main components of the SSS facility consist of the coal preparation and feeding system, SBS furnace, and gas monitoring system. Equipment specific to the LIDS facility includes the LIDS dry scrubber, slaker, baghouse, limestone feeder and injectors, a slurry and atomization system, and additional gas analyzers. |