Ukai 4: milestone coal upgrade project

2 April 2018



Despite setbacks, not least the catastrophic explosion/fire at NTPC’s recently commissioned Feroze Gandhi Unchahar plant, unit 6, on 1 November, coal is likely to remain a mainstay of power generation in India for the foreseeable future. There is therefore considerable interest in the potential for upgrading the existing fleet, which includes a large number of ageing and inefficient plants.


Despite setbacks, not least the catastrophic explosion/fire at NTPC’s recently commissioned Feroze Gandhi Unchahar plant, unit 6, on 1 November, coal is likely to remain a mainstay of power generation in India for the foreseeable future. There is therefore considerable interest in the potential for upgrading the existing fleet, which includes a large number of ageing and inefficient plants.

A recent project carried out by GE in consortium with NGSL (a joint venture of GE and NTPC) demonstrates what can be achieved. It has seen restoration of the original nameplate output of a nearly-40-year-old BHEL-supplied LMZ turbine at unit 4 of the Ukai power plant in the state of Gujarat. The plant had been operating at about 170 MW, and is now back up to 200MW. In addition the heat rate has been improved by 14.5%, from 2270 kCal/kWh to 1941 kCal/kWh, with an increase in overall power plant efficiency of 5.5 percentage points, reducing coal consumption by over 140 000 t/y and CO2 emissions by 180 000 t/y.

The backfit, which employs GE’s Advanced Steam Path technology (part of what the company calls its Fleet360* portfolio), entailed a complete shaftline replacement in the 200 MW unit, believed to be a first-of-a-kind for a BHEL supplied steam turbine, and is expected to add up to 25 years to the life of the plant, which is owned and operated by Gujarat State Electricity Corporation Limited (GSECL).

The ASP modernisation featured HP and IP full module upgrades and an inner block upgrade for the LP section, basically a complete redesign of the steam path and replacement of the steam turbine internals, leaving just the outer casing intact. Essentially, state of the art technology has been fitted into the small envelope of a 200 MW steam turbine. “That’s the hard part”, says Ashok Ganesan, general manager, GE steam plant product line.

The scope also included improvements to auxiliaries, foundation modifications and upgrades to control and governor systems. But the steam conditions (live steam pressure of 130 kg/cm2, live and reheat steam temperature of 535°C) have remained unchanged, the request from GSECL being to restore steam turbine nameplate power rating. The ASP backfit also improves flexibility, rendering the turbine capable of operating in constant pressure mode as well as variable pressure mode during part load and start up operation.

GE sees the Ukai upgrade as a milestone project for its Powering Efficiency Center of Excellence (COE) initiative, which “aims to slash global CO2 emissions from the world’s fleet of existing coal plants through a total plant hardware and software solution approach.” GE’s involvement in coal plant upgrade derives from its acquisition of Alstom’s power business back in 2015. Ashok Ganesan believes that global carbon dioxide emissions could be reduced by around 11% “if all we did was to bring our technology to bear on the current coal fleet”, and he regards the Ukai project as a “proof point” showing what can be delivered in practice.

In India ageing 200 MW units, supplied by BHEL as well as other vendors, account for a significant amount of generating capacity, and present a sizeable opportunity for backfitting projects.

As well as the GSECL project at Ukai, described above, GE has been working on the modernisation of three 200 MW Ansaldo steam turbines at the Ramagundam station in India. These are also being fitted with ASP technology, increasing turbine output and increasing efficiency and flexibility.

Ashok Ganesan points out that backfitting doesn’t have to be confined to elderly 200 MW units, it is also worth considering for much younger and larger plants, eg, 500-600 MW units, five to seven years old, employing ten year old technology. That is because the pace of change in turbine steam path design has been so great it makes such retrofits economically worthwhile, he believes. 

Ukai Ukai 4 steam turbine before upgrade
Ukai Ukai 4 steam turbine after upgrade
Ukai Scope of the Ukai 4 upgrade included complete shaft line replacement, shown in blue. Original design data for the Ukai unit 4 turbine: type, K200(210)-130-3; no of stages HP/IP/LP, 11/11//2x4; design heat rate, 2062 kCal/kWh; LSB length 765 mm


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