Performance optimisation of vertical spindle coal pulverisers

Abstract

Coal pulverisers' performance optimisation is an important process in power generation plants. Pulveriser operation is costly; reliability and availability is key to power generation and cost reduction is achieved by the optimal performance of associated plants. The objective of this dissertation was to investigate the effect of coal feedstock property variation on the vertical spindle coal pulverising mill's performance to facilitate optimal plant performance. Plant design and mill's acceptance test data was analysed to understand the design and subsequent changes over the years of the mill's operation. The mill outputs, pulverised coal fineness and distribution tests were carried out and evaluated from the data measured during plants tests. A mathematical spreadsheet was used to observe mill performance when operating parameters are varied. A mill's heat balance evaluation was done using an Excel spreadsheet to evaluate the mill drying capacity constraint. Coal analysis was done on hard grove grind ability, abrasive indices and calorific value of coal. The effect of low calorific value coal was observed on mill's response to match the boiler energy requirements. Evaluation of the current operating pulveriser data enabled the determination of the areas that need improvement to achieve mill-optimal performance. Coal feed to the mill is important, this was observed to be a limiting constraint on mill capacity when the coal required exceed nominal load requirement