Integrated approach to assessment of impact of beyond-design modes on operation of steam supply systems

Abstract

The object of the study are the steam networks of Smolensk. The purpose of the article is to determine the influence of beyond-design modes on the functioning of the entire steam supply system. Beyond-design modes of industrial steam supply pose a serious problem for all elements of the system: they make it difficult to fully load the turbines, lead to high excess losses of heat and coolant, and also lead to disruption in technological processes. Analysis of statistical data on reduction of industrial steam extraction has been carried out, archived data on heat supply and consumption have been processed and analyzed over the period from 2007 to 2017. A methodological error is found in the accounting of thermal energy and coolant by variable pressure drop flowmeters designed to handle superheated and dry steam. Calculation of heat network quality indicators is carried out, maximum permissible lengths of steam pipeline sections are determined, enabling to transport superheated steam to consumer regardless of the load reduction. The influence of the extent of wear of insulation and the diameter of the pipeline on the change in the aggregate state of the coolant has been analyzed, and the maximum load for steam networks has been found as being 30% of the designed one. It has been established that, with industrial extraction decreased, the CHPP is forced to disengage the turbine from operation, since a load drop of more than 50% brings the turbine to the condensation mode and reduces the technical and economic performance of the CHPP to the threshold permissible values. The obtained results enable to draw a conclusion that such a problem as beyond-design modes, especially in steam supply systems, requires an integrated approach, since the influence on an individual element in isolation from the system leads to a change in the performance of the remaining elements.