Above: China Resources Power’s Caofeidian site


Performance tests carried out in May 2020 by Siemens and GE at China Resources (CR) Power’s Caofeidian 3 plant (1000 MWe, ultrasupercritical) have demonstrated a unit net efficiency of 46.56% (LHV basis) at full load, with a coal consumption rate of 262.75 g/kWh (among the world’s lowest).

This is a single reheat plant but thanks to implementation of the Feng/Shenergy ‘4E’ portfolio of measures – principally energy-saving innovations throughout the plant, see Modern Power Systems, March 2013, pp 12-14 – the efficiency achieved is markedly higher than that typically reported for “conventional” double reheat plants in China (around 46% (net, LHV) for the best performers), while the capital cost is significantly less – about 85% of that for a conventional double reheat unit.

Caofeidian 3 along with unit 4 (also 1000 MWe, USC) comprise Phase II of the Caofeidian facility (Phase I consisting of two 300 MW units that entered commercial operation in 2009). Caofeidian 3 and 4, with design steam conditions of 29.3 MPa/605°C/623°C, employ Babcock & Wilcox boilers and turbines supplied by Shanghai Steam Turbine Co Ltd.

The steam turbines are the first at a Chinese coal plant to have three LP casings. Other notable features include: 11 stages of recuperation; deep water intake to reduce cooling water temperature; ultra-low back-pressure (3.3 kPa); “deep coupling” of the heat transfer between boiler and turbine; comprehensive optimisation of air preheater; and a range of energy-saving and emissions reducing technologies.

Each unit is equipped with a small Siemens-supplied steam turbine (with Voith couplings) to drive the feedwater pumps. This turbine also drives the generator that provides power for the variable speed drives serving auxiliary equipment, contributing further to energy savings.

Emissions reduction equipment includes an SCR system designed to be very energy-efficient and operate over a wide load range, high efficiency ESP (99.95% dust removal efficiency), and state of the art FGD (desulphurisation efficiency greater than 99.2%). The resulting emissions meet China’s latest requirements, ie, < 10 mg/Nm3 for particulates, < 35 mg/Nm3 for SO2, and < 50 mg/Nm3 for NOx.

The plant also includes an ash storage facility constructed of steel plate rather than an open ash yard.

The range of innovative technologies deployed at Caofeidian 3 and 4 by Weizhong Feng and the Shanghai Shenergy Power Technology team can be seen as an update of those successfully implemented at Waigaoqiao 3, and can be expected to result in an overall efficiency improvement of roughly 1% relative to WGQ 3.

Xuzhou 3 update

As previously reported in Modern Power Systems (November 2019, pp 22-23), Weizhong Feng and Shanghai Shenergy Power Technology have also developed an innovative approach to dramatically improving the efficiency of the extensive fleet of existing 300 MW subcritical coal fired units in China, by raising the steam temperature to 600°C (leaving pressures unchanged) combined with implementation of the 4E suite of energy-efficiency, emissions and performance enhancements.

This concept – the “high temperature subcritical” retrofit – has been demonstrated at Xuzhou 3, also a China Resources power plant, where steam temperatures have been increased to 603°C and the efficiency raised to levels compatible with those achieved by top performing ultrasupercritical plants.

Xuzhou 3 started commercial operation in June 2004, with steam conditions – 16.7 MPa/537°C/537°C – representative of the Chinese 300 MW subcritical coal fired power plant fleet, and an efficiency of 38.6% (net, LHV basis).

Post-retrofit, in August 2019, Xuzhou 3 completed its 168-hour trial operation and was then returned to service. In December 2019, formal performance tests were carried out (by GE and Siemens) as well as low-load certification tests.

Shenergy Power Technology says that post-retrofit, the efficiency of Xuzhou 3 – a remarkable 43.59% (net, LHV basis) at 100% load – “exceeds that of all the supercritical units and a fairly large number of ultrasupercritical units in service in the world” and, in particular, surpasses the efficiency levels of the best performing ultrasupercritical units in Japan and the USA.

Post retrofit, the coal consumption rate of the unit at full load was required to be not more than 287 g/kWh, in line with the Chinese National Energy Administration’s Action plans for energy saving and emissions reduction, upgrading, and retrofitting (2014-2020) – compared with around 318 g/kWh pre-retrofit. The outcome at Xuzhou 3 was much better than this, with the December 2019 test recording 281.8 g/kWh at full load for the retrofitted unit.

The low-load certification tests carried out in December 2019 were witnessed by an independent agency designated by the local grid, and showed that the retrofitted unit could operate in a stable, safe and environment-friendly manner at 19% load for more than 4h, a first in China, and meeting proposed National Energy Administration 2030 requirements for ultra-low (20%) load capabilities “11 years ahead of schedule.”

It is also worth noting that thanks to the technologies implemented by Shenergy Power Technology at Xuzhou 3, the SCR can still operate even below 19% load. Prior to retrofit the limit was 55 % load.

Pingshan Phase II

As readers of Modern Power Systems will appreciate, Weizhong Feng and his Shenergy Power Technology colleagues are of course not content to leave it there and are pressing on with, among other things, implementation of their radical new concept for double reheat, at Pingshan Phase II.

As previously mentioned in Modern Power Systems (eg, October 2013, pp 18-19, December 2018, pp 28-30, and November 2019, pp 22-23), the basic idea is to save money by elevating steam turbine casings to reduce the amount of expensive pipework needed (for main steam, cold and hot first reheat and cold second reheat).

At Pingshan Phase II – 1350 MW, with a design efficiency of over 48.9% (net, LHV) – the LP1, LP2, LP3 + IP2 stages (plus generator) are at a conventional elevation (about 17 m), while the IP1 + HP (driving a second generator) are raised to an elevation of around 85 m.

Covid-19 is estimated to have extended the Pingshan Phase II construction schedule by two months, but the hope is still to get the plant into operation before the end of this year.

The experience with 3LP steam turbine casings at Caofeidian has proved beneficial for Pingshan Phase II.

As noted in Modern Power Systems, November 2019, p 23, there are also plans for a further extension of the elevated steam turbine double reheat concept, with all steam turbine casings elevated and driving a single elevated generator, providing potential for further pipework cost savings and simplified operation, as well as even higher efficiency.

A candidate project was China Resources’ 2 x 660 MW Fuyang Phase II, but it has been decided that this project will now be “conventional” double reheat. However, Shenergy Power Technology believes that other opportunities may emerge to apply its “all-casings-elevated” concept, which has the potential to deliver the world’s most efficient coal fired power plant.