Page 36 - Energize March 2021

TECHNICAL

Design modifications at Medupi and

Kusile: progress and problems

by Chris Yelland, EE Business Intelligence

Much has been written about the cost and time overruns at Eskom’s flagship new-build mega-projects
– the Medupi and Kusile coal-fired power stations in South Africa. This article focuses on the boiler plant
design defects and the status of rectification work currently in progress.

he Medupi and Kusile projects The planned modifications required on each of the twelve units at Medupi and Kusile include:
involve the construction of two - Mills: Eleven modifications were agreed to be implemented – initially in a matrix across
T4800 MW, coal-fired, direct dry- the five mills of Medupi Unit 3 to determine the performance of the modifications and
cooled power stations. The Medupi their interdependencies.
site is close to Eskom’s Matimba - Pulse jet fabric filter (PJFF) plant: The modifications include redirecting the flue gas inlet
power station in the Lephalale district to the bag filter and equipment changes to the pulsing systems used for cleaning the
of Limpopo Province. The Kusile site fabric filter bags during operation. A new set of fabric filter bags are also to be installed
is close to Eskom’s existing Kendal after the modification.
power station in the Nkangala District of - Gas air heater (GAH): Modifications to the gas air heaters include internal erosion
Mpumalanga Province. protection and modifications to the pin rack driving the rotation of the gas air heaters.
An article in Engineering News on - Hot air duct erosion: Solutions for erosion protection in the various hot air ducts include
1 February 2019 summarised a number fitting of ceramic tiles and combinations of ceramic tiles and wear resistant metal plates in
of technical defects identified by Eskom the hot air ducts.
at Medupi and Kusile that were causing
serious underperformance at the power The first unit of the six units at Medupi to be reworked was Unit 3 during a 10-week shut down
stations. The generation units handed from the last week in January 2020 to the first week in April 2020. Although Unit 3 at Medupi
over for commercial service were was intended as a “proof of concept”, work on the design modifications of further units at
unable to operate at full load and were Medupi commenced even before performance testing of the modifications on Unit 3 was
experiencing frequent planned and completed, as shown in Figure 1.
unplanned outages. One of the five mills on Medupi Unit 3 was used as the reference mill without any
Thereafter, an open letter written modifications, and one mill as the reference mill for all the modifications. Modifications on the
by Mr Alex Ham, a former Eskom Chief
Engineer: Power Station Design, and later,
Director of Technology, who had worked
for the utility for 30 years, was published
by EE Publishers on 12 May 2019. The
letter spelled out the background to the
boiler and mill problems at Medupi and
Kusile in further detail.
In order to rectify these defects,
Eskom and the boiler works contractor,
Mitsubishi Hitachi Power Systems Africa
(MHPSA) are now undertaking significant
rework of all twelve units at Medupi
and Kusile. This requires that each unit
be shut down for about 75 days, in
sequence, to conduct the necessary
rework, with the associated costs shared
50/50 between Eskom and MHPSA,
pending resolution of the contractual
matters between them. Figure 1: Timelines for rollout of contractor boiler plant technical solutions. (Source: Eskom)

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