Peak Load Regulating Capability and Economic Benefit Analysis of Industrial Heating Steam System Upgrading for Cogeneration Units

Abstract

With the increasing pressure of the strengthening the peak load regulating capability for the cogeneration units in North China, very few attention has been paid to the flexibility upgrading schemes of the industrial heating steam supply for the existing cogeneration units. Typical configuration of the industrial heating steam system from the reheat steam source is introduced, which will cause close coupling of the heating supply and power output and seriously influence the peak load regulating capability of the cogeneration unit. One flexibility upgrading scheme is suggested which takes the main steam as the high pressure industrial heating steam source and detailed information including the advantages and disadvantages of the system is described. Model-based software code is used for the performance simulation of one 350MW supercritical cogeneration unit under different industrial heating steam modes, and the peak load regulating performance improvement attained using the proposed scheme is compared in detail. It is shown that with the same HP turbine exhaust temperature set limit, the minimum power output of the cogeneration unit under normal single-stage industrial steam flow conditions can be decreased around 137MW, while the minimum power output of the cogeneration unit can be decreased around 50MW and 124MW in different scenarios using the proposed scheme under double-stage industrial steam flow conditions. In spite of the lower minimum power output improvement in peak load regulating under same heating steam flow condition, poorer heat rate and less profitable total economic benefit of the cogeneration unit are expected in upgrading scheme than in original scheme. The minimum peak load regulating marginal cost is calculated, which can be taken as a price bidding reference in the future power ancillary service market for compensating the economic benefit loss incurred by the adoption of the proposed flexibility upgrading scheme.