Mitsubishi Heavy Industries Technical Review Vol. 54 No. 3 (September 2017)46

Introduction of Taiwan Power Company’s
Linkou Power Plant Units 1 and 2- Steam Temperature Control Improvement of Ultra-Supercritical Sliding
Pressure One-through Coal-fired Boiler and Combustion Tuning by AI -YASUHIRO TAKEI*1

KAZUHIRO DOMOTO*2

TAKASHI TSUTSUBA*3

HISASHI SANDA*4

KOICHI TAKEI*5

KAZUTAKA OBARA*6

Taiwan Power Company (TPC) Linkou Power Plant Units 1 and 2 are high-efficiency
600°C-class coal-fired ultra-supercritical pressure power generation units that were renewed fromthe existing units. They have commenced commercial operation as a stable power source inTaiwan, where the power demand has been increasing year after year. Units 1 and 2 adopt steam
temperature control, which further improves the stability of the boiler outlet steam temperature andfacilitates tuning. Furthermore, a new system featuring Artificial Intelligence (AI) is underdevelopment for the purpose of performing automatic combustion tuning of the boiler. The newsystem is utilized in Unit 2 and confirmed availability. MHPS is making further improvement in its
precision, as well as further advancement of the AI performance.

|1. Introduction
The construction of the boiler steel structure of TPC Linkou Power Plant Unit 1 started inFebruary 2013 and commercial operation started in October 2016. The construction of the boiler
steel structure of Unit 2 started in January 2014 and commercial operation began in March 2017.
Mitsubishi Hitachi Power Systems (MHPS) was engaged in the design, manufacture and supply ofthe mechanical equipment including the turbine and boiler, providing a coal-fired ultra-supercriticalpressure power generation plant with the world’s best plant efficiency and reliability achieved by
the company’s collective strengths, including plant engineering and advanced main mechanicalequipment technologies. This article features the boiler technologies and boiler combustion tuning
by AI.

|2. Project overview
In order to contribute to the stable supply of power in Taiwan, MHPS has been proceedingwith a project to renew the existing subcritical pressure power plant with a high-efficiency
600°C-class coal-fired ultra-supercritical pressure power generation plant in the TPC Linkou PowerPlant. The power plant output is 800MW×3 units. In order to utilize coal cleanly with highefficiency, ultra-supercritical (USC) pressure steam conditions were applied, each unit installed aselective catalytic reduction (SCR) system, particulate removal system, and flue gas desulfurization
system were installed in each unit in consideration of environmental protection. The order for thisproject was jointly accepted by Taiwanese EPC firm CTCI and Mitsubishi Corporation, for which
MHPS is in charge of the design, manufacturing and supply of the main mechanical equipment
including the turbine and boiler. Units 1 and 2 have already commenced commercial operation. Asfor Unit 3, the boiler steel structure construction was completed in August 2016 and is scheduled tobegin commercial operation in 2019.
*1 Deputy General Manager, Boiler Business Strategy Planning Department, Boiler Technology Integration Division, Mitsubishi Hitachi Power Systems, Ltd.
*2 Manager, Boiler Technology Development Department, Boiler Technology Integration Division, Mitsubishi Hitachi Power Systems, Ltd.
*3 Manager, Boiler Technology Development Department, Boiler Technology Integration Division, Mitsubishi Hitachi Power Systems, Ltd.
*4 Instrument & Control Department, Plant Engineering Division, Mitsubishi Hitachi Power Systems, Ltd.
*5 Boiler Business Strategy Planning Department, Boiler Technology Integration Division, Mitsubishi Hitachi Power Systems, Ltd.
*6 Boiler Technology Development Department, Boiler Technology Integration Division, Mitsubishi Hitachi Power Systems, Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 54 No. 3 (September 2017)47|3. Boiler overview
Table 1 shows the boiler overview of the Linkou Power Plant. Because the project is arenewal of the existing power plant, the construction space is limited and the design was made inconsideration of boiler size and other equipment arrangement. Highly-reliable materials mostsuitable for the steam temperature of 600°C were applied in the boiler heated and non-heatedpressure parts. The performance coal is a mixture of bituminous coal and subbituminous coal. The
furnace size and specifications of its auxiliaries are designed to be able to burn coal with a total
moisture level of 20%.
Table 1 Overview of boilers
Linkou Power Plant
Unit 2
Unit 3800MW
Ultra-Supercritical Sliding Pressure
One-through Boiler Radiant Reheat Type2,404 ton/h (@BMCR)
25.38MPa/604℃/602℃
Performance Coal＝Blending of Bituminous coal and Subbituminous coalOct, 2016
Mar, 2017（2019）Unit 1Output（per 1 Unit）
Boiler Type
Main Steam Flow
Boiler Outlet Steam Condition
Coal
Commercial Operation Date

The pulverizer has a capacity equivalent to the largest existing size, and Xwin® technology isapplied for the roller and table liner materials. Figure 1 presents the Xwin® technology. WithXwin®, highly wear-resistant special ceramics are embedded on the grinding surfaces of thehigh-chrome cast iron roller and table liner, improving the wear resistance immensely. After 1,000to 2,000 hours of use, the Xwin® layer appears on the surfaces of the roller and table liner where
dimples of several millimeters occur, trapping more coal therein, which leads to the reduction ofslip vibration. Xwin® is applicable not only to new pulverizrs, but also when replacing the rollers ortables in existing pulverizers.

Figure 1 Xwin® technology|4. Improved steam temperature control
The control logic for superheater outlet steam temperature control, which has been improved
based on experience, was applied to Linkou Power Plant Units 1 and 2. Generally speaking, when
the load change rate is increased, the control deviation is also increased during a load change orafter the load is stabilized, and a long time is required for stabilizing the load. In other words, theimprovement of the control deviation and load stabilization through increased controllability is thekey point to improving the load change rate. As shown in Figure 2 which is the existing control
method concept, the water-fuel ratio (fuel) and the 2ry spray mainly control the superheater outlet
steam temperature. Simultaneously, as the 2ry superheater de-superheating ratio (the balance
between the fuel flow and spray flow) is controlled by the 2ry spray. Therefore, the fuel flow
control and 2ry spray control slightly interfere with each other, delaying the stabilization of thesuperheater outlet steam temperature just after the load is reached in some cases.

Mitsubishi Heavy Industries Technical Review Vol. 54 No. 3 (September 2017)48

Figure 2 Conceptual diagram of steam temperature control (conventional)

Figure 3 shows the concept of the control logic which was improved for superheater outlet
steam temperature stability. The 2ry spray focuses on the control of the superheater outlet steam
temperature, while the fuel flow mainly controls the 2ry superheater outlet steam temperature.
Furthermore, the 1ry spray controls the 1ry superheater de-superheating ratio (the balance between
the fuel flow and spray flow). Accordingly, the control logic improves the adaptability to changes
in the furnace heat absorption and 2ry superheater heat absorption, and avoid the mutualinterference between the fuel flow and 2ry spray in the superheater outlet steam temperature
control. Then, the control logic minimalized the time for the superheater outlet temperaturestabilization.
The effect of the improved control logic has been confirmed in simulations. After that, thecontrol logic is applied into Linkou Power Plant, and improvements of stabilization andresponsiveness of the steam temperature were confirmed in the load change tuning test of an actualunit. Furthermore, due to the ease of adjustment, the tuning term has been successfully reduced.

Figure 3 Conceptual diagram of steam temperature control (improved)|5. Combustion control through application of AI
A new system for automatic boiler combustion tuning by AI is under development. AI wasutilized in a combustion tuning test for the Linkou Power Plant Unit 2 boiler, and its effect wasconfirmed. In the conventional combustion tuning test, the operation parameters including theburner windbox dampers opening, burner angle and pulverizer MRS speed are changed in order toadjust the boiler operation condition until the boiler achieves balanced operation condition in terms

Mitsubishi Heavy Industries Technical Review Vol. 54 No. 3 (September 2017)49of the steam temperature characteristics, exhaust gas characteristics (NOx, CO and unburnt carbonin ash), etc. In the combustion tuning test by AI, we built a machine learning model related to thechanges in operating parameters and boiler operation conditions. AI is able to suggest the operation
setting parameters that would achieve a balanced boiler operation. The boiler combustion tuning
test was carried out by setting the conventional operation items and operation items suggested byAI simultaneously. Eventually, the operation parameters suggested by AI were confirmed to bealmost the same as those suggested by an experienced boiler engineer, demonstrating that AI could
determine excellent boiler operating conditions.

|6. Conclusion
Linkou Power Plant Units 1 and 2 have achieved all the predicted and guaranteedperformance targets in terms of the steam temperature, combustion characteristics and exhaust gas
characteristics in the commissioning and performance test, and are currently in stable operation.
Unit 3 is under construction and is scheduled to commence commercial operation in 2019.
We confirmed that the improved steam temperature control method improved the stability
and responsiveness of the superheater outlet steam temperature, and simplified the boiler tuning inan actual unit. The improved steam temperature control method will be applied to future projects toreduce the commissioning term. Furthermore, the effect of applying this improved steam
temperature control method to existing power plants will be verified by simulations in order tocontribute to the further improvement of the power control performance of thermal power plants,
because it is assumed that the utilization of renewable energy will accelerate, and thermal power
plants will be required to achieve more rigorous power control performance.
In addition, MHPS will continue seeking the advancement of combustion tuning by AI, as
well as the application of AI in consideration of systems, their operational status and customer
needs, to existing power plants, in an attempt to support customers achieve better operation.