Estimation of capability of changing the boilers TP-14A at Kumertau Termal Power Station to burning B3 grade coal from Verkhne-Sokursky deposit

Abstract

Currently, TP-14A boilers should be changed into burning off-design fuel: grade B3 coal of Verkhne-Sokursky deposit. Its share (by heat) in the fuel balance should be not less than 80%. A test burning of Verkhne-Sokursky coal was carried out, which showed that, in its present form, the boilers and dust-systems are not suitable to operate with this fuel, because their characteristics significantly differs from the project one. It is impossible to maintain the overheating temperature at the required level during operation on only coal; it is difficult to maintain the temperature behind the mills at the level of 200°C. The joint burning the coal with natural gas allows to solve these problems at operation of one or two mills. However, substantial fuel underburning, essential thermal maldistributions on the steam flows, and emissions of NOx above permissible values is observed. Based on the results of test burning and joint calculations of furnace, boiler, and dust-systems, ways to solve these problems were developed. For modeling the furnace process, the Fluent and Sigma Flame software were used. Adapted mathematical models of the boiler and dust-preparing systems were created using the Boiler Designer and Stoker software. It is necessary to reconstruct the boiler plants, which can perform in two stages. In the first stage, the existing burners are replaced by the burners with turning nozzles and two-stage burning is arranged, and the inertial separators and recirculation of the drying agent are installed on the mills. In the second stage, the change to concentric burning is carried out, the heating surface of radiation part of the steam superheater increases, and the preset included hammer part is installed at the mill. It is shown that a positive effect should be obtained already after the first stage of reconstruction. The second stage of reconstruction will require additional expenses, but its implementation will allow to a greater extent to eliminate the disadvantageous in the operation of the equipment.