Boiler Efficiency for Reduced Carbon Emission and Cost

by Marcelle P. Villegas - April 01, 2021

A case study at the GNPower coal power plant in Mariveles, Bataan (Photo credit:

GNPower Ltd. Co. (or “GNPower”) is a private limited partnership that was organised and established in 1997 by PMR Holding Corp. as its sole general partner and PMR Limited Co. as limited partner. The company aims to develop, operate and own power generation projects and associated facilities in the Philippines. Through the years, there were changes in the corporate structure and partnerships. By June 2014, the sole general partner of GNPower is GNPower Holdings GP Corporation which is owned by Power Partners, while Power Partners is the sole limited partner.  

With regards to their coal energy project, it started way back in 2005. On that year, the partnership began the development of a coal-fired project. It was their first step in creating an “integrated, multi-fuel electricity generation and fuel handling energy complex”. [1]

Five years later, the GNPower began the construction of a 2x316MW (net) clean pulverized coal-fired power plant located in Mariveles, Bataan, Philippines (“Mariveles Project”). In this project, GNPower and Power Partners own a significant minority position through their ownership of GNPower Mariveles Coal Plant Ltd. Co. (GMCP). GMCP is the special purpose vehicle established to construct, own and operate the Mariveles Project. [1]

In 2013, the coal-fired facility was declared commercially available in the market. It is GNPower’s pioneer project and is the largest greenfield power project that was built in Luzon after the enactment of EPIRA in 2001.

GNPower Mariveles Coal Plant Ltd. Co. is now referred to as GNPower Mariveles Energy Center Ltd. Co.

Coal is considered a baseload energy resource in the Philippines as it is sufficiently cost-effective in providing a consistent supply of power. Currently, there are 28 coal-fired power plants operating throughout the Philippines. [2] One competitive and significant factor in the industry is the plant’s ability to supply adequate power while burning less coal in the process. In relation to this, a study was conducted by a group of experts to determine how cost-efficient is the operation in the Mariveles Coal Plant. What are the possible strategies they can or have implemented to assure boiler efficiency that utilizes less coal? What is the significance of this study with regards to protecting the environment through reduced carbon emission?

“A Study of the Changes in Efficiency of a Coal Fired Boiler Following the Conversion to a Dry Bottom Ash Handling System” is a study done by Artemio Boado (Plant Manager, Mariveles Power Plant), Zhao Peng (Engineering Manager, Qingdao Daneng), Steven Hou (General Manager, Int’l Business of Qingdao Daneng), Wang Yong (Chairman, Qingdao Daneng) and Edgardo B. Cruz (President, Philippine Coal Plant User Group).

The study aims to determine and analyse the boiler efficiency of Unit 2 of Phase 1 of GN Power Mariveles, according to measured data before and after the conversion of the bottom ash system from wet to dry which was implemented in March 2018. [3]

From their report, GN Power Mariveles Phase 1 consists of 2 x 340 MW T-fired sub critical coal fired boilers (Originally 2 x 316MW).  The boilers were supplied by Harbin Boiler Company of China. This has a wet bottom handling system which consisted of a hopper under the boiler, sealing plate, submerged scraper conveyor, cooling water system, silo and discharger. The wet system was later converted to dry system by Qingdao Daneng Environmental Protection Equipment Incorporated Company (or Qingda) utilising their patented DUNOCON conveyor technology. “Both units were converted and commissioned in a standard scheduled 30-day boiler outage with Unit 2 converted in March 2018 and Unit 1 in February 2019. Since commissioning, both units dry bottom ash systems have operated well and without issue.” [3]

“When considering a pulverised coal fired boiler, the application of dry bottom ash handling technology is well proven and has several key advantages over those utilising water for the cooling and transportation of bottom ash. Along with the elimination of water handling and treatment, reduced power consumption, reduced maintenance etc, a significant amount of energy can be returned to the boiler from the reduction of energy losses at the boiler throat, waste heat from the bottom ash and the reduction of unburnt carbon in the bottom ash.” [3]

“However, in order to realise these potential benefits, the dry bottom ash system needs to be carefully designed and operated to ensure that the cooling air quantity and distribution through the conveyor and into the boiler are optimised.” [3]

Boiler efficiency testing standard

For this study, the efficiency of the boiler unit is determined basically by following the testing standard ASME PTC-4.1. (Further calculation methods not considered in ASME PTC-4.1 have been supplemented to compute for the credits specifically due to the adoption of dry bottom ash technology. [3])

There are two ways to compute for the boiler efficiency testing: (1) direct method (2) indirect method.

Direct method is obtained by the ratio of energy gain of working fluid (water or steam) compared to the energy input into the boiler. Here is the formula they used:

Comparative analysis of boiler efficiency

(1) Direct method

Based on Table 1 and Figure 2, that coal consumption has reduced by an average of 2.12% over a boiler load range of 320 MW to 340 MW since the retrofit conversion of Unit 2 to a Dry Bottom Ash System.  Table 2 is the operating data from the owner with the boiler load between 339 and 340 MW which can be used to calculate the boiler efficiency using the ASME PTC4.1 direct method. [3]

(2) Indirect Method

For the Indirect Method, the study explored the various factors in measuring the efficiency of the boiler system. These factors include:

a) dry flue gas heat loss

Dry flue gas heat loss is the main reason of boiler heat loss. Using formula (2), various heat losses are discussed here:

Based on this data, there is no significant change in the flue gas temperature at the inlet of air preheater, and the oxygen content decreases. With the help of the advanced air control DUNOCON system, “the cooling air quantity is controlled quantitatively to the maximum extent”, thus no excess air enters the boiler through dry bottom ash handling system. The other dry system has multiple air doors, but DUNOCON has only one air door on the head of the conveyor which is interlocked with the ash temperature of conveyor outlet. As an effect, “the cooling air quantity has been limited to maximum extent under the premise of ensuring the ash cool down effect”. [3] The DUNOCON also has a special penetration heat transfer design that improves the cooling efficiency and reduces the need for cooling the air. In addition, this helps the unburned carbon at the bottom ash re-burn and recovers its heat.     

In this part of the study, the boiler efficiency is increased by 0.382%.


Other factors under indirect method:

b) heat loss due to evaporation of water formed due to H2 in the coal,

c) heat loss due to H20 in the coal

d) heat loss due to H20 in the air

e) heat loss due to incomplete combustion of combustible gas

“The heat loss due to the incomplete combustion is principally concerned with the losses resulting from incomplete combustion of the gaseous products such as CO, H2 and various other hydrocarbons which can potentially be found in the flue gas of a boiler. Considering Mariveles Unit 2 is a large modern Utility Boiler, then we will assume that the losses through the incomplete combustion of gases is negligible for this study.” [3]

f) heat loss due to Boiler Surface Heat Loss, Radiant Heat Loss, and Convective Heat Loss

“This study assumes that the Boiler Surface Heat Loss and Convective Heat Loss will not be have been affected by the changes to the bottom ash system. However, due to the change from wet system to dry system, the radiant heat at the boiler throat is recovered back to the boiler by the cooling air.”

Based on their calculations, the boiler efficiency is increased by 0.11% because of the radiant heat recovered through the cooling air.

g) heat loss due to unburnt in fly ash

i) heat loss due to bottom ash in the wet system

All the bottom ash is cooled by the water. As a result, there is a loss of all the sensible heat associated with the bottom ash. In comparison, the dry system uses the cooling air to recover the bottom ash sensible heat and reintroduces it to the boiler. In addition, part of the unburned carbon in the ash can burned during the transportation process and the heat will be recovered by cooling air. Also those heat generated improves the boiler efficiency.


Regarding the carbon combustion quantity during the conveying period, the study reported the following test list:

Carbon content in wet ash 4.59%

Carbon content in dry ash 3.5%

This shows that about 1.09% of the carbon in the dry bottom ash reburns and releases heat. Those heat is also brought back to the boiler by the cooling air. The unique penetrating cooling action of the DUNOCON system increases the contact area between the bottom ash and the cooling air, and increases the combustion probability of carbon. Qt=174876 KJ/hr From the formula (16), the boiler efficiency increase R2=0.016%. [3]

To sum up, the efficiency of the boiler is increase by 0.51% after the retrofit in indirect method.

Cost and energy conservation

a) From the table 1, the average coal consumption before and after the retrofit of boiler is 208t/h and 204.45t/h under 330~340MW. Assuming that the annual operating time of 8000h, the annual coal saving is about 28,400t. [3]

b) Comparing this with the wet bottom ash handling system, the dry system has no circulating water system, thus the system is simpler and the operation is fully automatic. Additionally, the power consumption of dry system is lower than wet system.

c) After the retrofit, the daily maintenance work of dry system is almost zero. Compared with the wet system, it saves a lot of labor cost for the power plant.

d) Studies show that for every 1% increase in boiler efficiency, 2% of carbon dioxide emissions can be reduced [5], so the dry system also contributes to the reduction of emissions.

In conclusion, based on the study and analysis, the Unit 2 boiler efficiency of GN Power Mariveles Plant increased about 0.51% after retrofit to DUNOCON dry bottom ash handling system. The reduction of flue gas quantity is the main reason to improve the boiler efficiency. The advanced air control technology of the DUNOCON system is an important key point. “The recovery of radiant heat from the boiler throat and sensible heat from the bottom ash also improves the boiler efficiency. The improvement of boiler efficiency saves about 28,400 t of coal for the power plant every year. And compared with wet system, dry bottom ash handling system is more advanced, safe and stable, and saves a lot of operating costs for the power plant.”


Since the early 1990s, GNPower Ltd. Co. has been excelling in the power industry with their remarkable achievements in the completion of power projects. Their power plant projects had been providing electricity supply services to several Philippine-based customers. Other than developing coal-fired plant in Mariveles, (GNPower Mariveles Energy Center Ltd. Co.), they also have the GNPower Kauswagan Ltd. Co., and the upcoming GNPower Dinginin Ltd. Co. Of note, GNPower is the first Retail Electricity Supplier (RES) to be licensed by the Energy Regulatory Commission. They are also the first to have signed long-term power supply agreements with a group of Contestable Customers since 2006. GNPower also adheres to the mandate of the EPIRA Law of Department of Energy.  



Mr Edgardo B. Cruz of Philippine Coal Plant Users Group and Mr Ariel Punzalan of PMR Group and GNPower Ltd. Co.


[1] Retrieved from the company website of GNPower Ltd. Co. -

[2] Chavez, Leilani (Nov. 5, 2020). Mongabay News. "Philippines declares no new coal plants — but lets approved projects through".

[3] Boado, Artemio, Cruz, Edgardo B., et. al. “A Study of the Changes in Efficiency of a Coal Fired Boiler Following the Conversion to a Dry Bottom Ash Handling System”.

Place your Ad Here!

Place your Ad Here!

Recent Articles


Philippine Resources - May 23, 2023


Photo credit: TVI Resource Development The Board of RTG Mining Inc. is pleased to announce that a comprehensive settlement of all outstanding issues with the Villar Family controlled Sage Capital and TVI Resource Development (Phils.) Inc. (“TVIRD”) has been reached and a binding Memorandum of Agreement signed. On execution of the final documents, expected in the next month, all litigation that RTG had launched will be withdrawn as part of an agreed restructuring of the Mabilo Project. The Villar Family is one of the most prominent families in the Philippines and RTG is pleased to partner with them in the development of the Mabilo Project, which is a significant mining project for the country. The key terms of the agreement for RTG include the following: RTG (through SRM Gold Limited) will retain a 40% interest in Mt. Labo Exploration and Development Corporation (“Mt. Labo”) with the project also developed by Mt. Labo, in line with Philippine regulatory requirements, with Sage Capital (which is owned by TVIRD) holding the remaining 60%; RTG will have a 2% net smelter royalty (“NSR”); RTG’s debt together with interest, currently in the order of US$27M (subject to audit) will be repaid out of the proceeds of Stage 1 of the project, the Direct Shipping Operation subject to customary requirements to address liquidity and ongoing operations of Mt. Labo; Funding arrangements for the project as between the major shareholders of Mt. Labo have been successfully renegotiated, (relieving RTG of a sole funding obligation) and replaced with a pro-rata funding obligation, together with a disproportionate funding obligation of Sage Capital, as set out below; With debt repayments in full and the NSR, RTG will be entitled to approximately 57% of the proceeds of Stage 1, the Direct Shipping Operation; RTG will be entitled to 40% of the operating cashflow of the project, together with the 2% NSR and repayment of its debt, which is currently in the order of US$27M; The first US$5M of expenditure for Mt. Labo (or 12 months of expenditure, whichever occurs the earlier), will be funded pro-rata between the two shareholders (ie RTG will provide 40%) and thereafter, Sage Capital/TVIRD will sole fund the next US$5M of expenditure, with all additional funding thereafter to be provided on a pro-rata basis; All parties are required to act in the best interests of the project and not compete; A shareholders’ agreement will be finalised which will provide typical minority interest protection clauses including reserve matters for voting including annual budgets and appointments of key personnel; Any disputes will be resolved by the Singapore International Arbitration Centre; and On completion of final signed documents, all litigation matters will be withdrawn and settled in full. With the restructuring of the Mabilo Project now agreed, over the balance of this year, the remaining permitting matters and financing plans will be finalised, a review of the 2016 Feasibility Study will be completed, together with finalising the acquisition of surface rights, following which, a commitment to development will be formalised by the Board of Mt. Labo. RTG is pleased with the outcome of the discussions and the co-operative and constructive approach adopted by the Villar Family representatives. RTG believes they can be a strong and positive partner to work with to take the Mabilo Project forward, with both a near term development and future exploration activities to expand the project, which will start to unlock the value of the project for all stakeholders, not only the local communities but for the country as a whole.


Philippine Resources - May 22, 2023

Mining Operational Excellence Through Digital Transformation

Part 1: Mining Operation Challenges and Mine Operations Management Domains 1 & 2. By Mae Ann Cabasag, EM Mining companies encounter numerous challenges throughout their operations. However, initiatives to mitigate these challenges and improve efficiency are often limited. Most of these limitations emanated from a common factor: the challenge of “poor visibility” in mining operations. A viable solution is to adopt digital transformation in mining operations by incorporating available real-time data into an integrated system— capable of ensuring automatic updates and reliable source of information. Through this, mining companies not only understand simulations and plans developed but also anticipate potential outcomes. Various mining industry analysts have found that using non-digital methods in the mining operations can lead to a 27% reduction in production time and 25% increase in data inaccuracy. For a mining company to remain competitive in an industry susceptible to operation challenges, i.e. production processes, workers’ and equipment performances, ore quality and quantity, compliance to regulations, and inter-departmental collaboration, it needs to embrace digital transformation. Dassault Systèmes Mine Operations Management provides transformative digital solution for mining companies to achieve excellence in their operations. Mine Operations Management (MOM) equips mining companies with an integrated system for their mining operations, enabling them to achieve efficient plan and schedule. This system integrates entire operation data into a single repository source of information, known as the “single source of truth”, ensuring complete transparency of the company’s processes from mine to port. By leveraging MOM, we can address the following global mining industry challenges: Maintaining competitiveness amidst market volatility. Eliminating waste materials, poor communication, and error duplication. Improving site productivity and efficiency. Utilizing assets and sharing best practices across the value chain. Ensuring an utmost level of safety. Reducing environmental impacts and achieving sustainable operations. The transformative digital solution, Mine Operations Management, is composed of eight work packages, split across four domains, namely: Data Management, Material Reconciliation, Operational Control, and Assets Performance. These domains help generate valuable insights from integrated operational data for rapid and informed strategic decision-making.  The Data Management consists of Master Data Model and Integration Framework packages essential for material tracking, stockpile management, task and workforce management, machine performance, and asset maintenance. It enables users to manage master data objects such as Site, Material, Location, Equipment, and Operator through manual data entry or third-party source systems.  With this, mining companies can ensure efficient and integrated management of critical data required for seamless operations. Material Reconciliation, on the other hand, consists of Material Tracking and Stockpile Management packages. Material Tracking enables us to track material movements across different stages, i.e. from the least accurate grade estimated in geological model to the most precise information on shipped material quantity and quality, to account for any inaccuracies. While in the Stockpile Management, users not only can calculate daily stockpile balance, add Survey or Sampling data, analyze inventory levels and trends, create graphical representation of the stockpile balances and movements, calibrate stockpile using volumetric survey and sampling, enables comparison of different models, track movement genealogy and review stockpile slices for stockpiles with LIFO and FIFO calculation type but can create a different type of analysis such as actual vs plan vs model. In the upcoming article, we will explore the two remaining domains of Mine Operations Management to where assigning operational tasks, tracking compliance to plan, monitoring equipment down to workers’ performance are feasible in the mining operations. To know more about MOM, mining innovations and solutions, contact Dassault Systèmes Value Solutions Partner: Paramina Earth Technologies Inc. through   References: Make it happen for mine execution excellence: Dassault Systèmes®. MEGATrends. (n.d.).  Dassault Systèmes. (2021, August 12). Digging deeper: The virtual solution for Mining Operational Excellence. Dassault Systèmes. excellence  dassault3ds. (2022, June 16). The mining industry needs to adapt, but how? Dassault Systèmes blog.


Philippine Resources - May 22, 2023

Customer’s First Choice: Sandvik Philippines Delivers 11th and 12th Pantera DP1500i Drills to Filminera Resources Corporation

Sandvik Philippines has successfully commissioned and delivered to loyal customer Filminera Resources Corporation (“Filminera”) their 11th and 12th Pantera DP1500i Top-hammer Surface Drills last 25 January 2023 at the Masbate Gold Project (MGP) located in Masbate Island, Philippines. Photo shows Sandvik Technician Larry Lugnas (second from left) and Service Operations Manager Jorge Cabello (third from left) handing over the drills to MGP representatives. Located 360 km southeast of Manila, the Masbate Mine is operated by Filminera, the Philippine subsidiary of TSX- and NYSE-listed B2Gold with headquarters in Vancouver. In 2022, the mine produced a record-setting 212,728 oz of gold out of 7.93M tonnes of ore milled at an average grade of 1.11 g/t.  B2Gold also operates the Fekola Mine in Mali and the Otjikoto Mine in Namibia. Their projects under development include the Anaconda Area in Mali and the Gramalote JV Project in Colombia. The Masbate Mine started operating in 2008 initially using 4 x Atlas Copco ECM660 Drills owned and operated by the erstwhile mining contractor, Leighton. When the opportunity for re-fleeting came about in 2012, Sandvik succeeded in winning the tender which came packaged with a full maintenance contract for 24,000 service meter hours of five years. Ironically, the said maintenance contract almost led to the cancellation of the order for the first 4 x DP1500i due to a dispute with the rates. Eventually, both Leighton and Sandvik were able to arrive at a mutually acceptable arrangement, and Sandvik ran the service contract for five years without incurring penalties in the availability guarantees. The contract was so profitable, Sandvik even had to share some of the residual profit at the end with Filminera under the pain-and-gain proviso of the contract. The next re-fleeting opportunity came in 2017, with the Masbate Mine. This time, there was no service contract attached to the equipment and Leighton was no longer the mining contractor; the mine has shifted to owner-miner operation. Sandvik managed to secure the repeat order for another batch of 4x DP1500i, banking on the proven performance and reliability of the first four. That brings the total to 8 units. Drill numbers 9 and 10 were ordered in July 2020 and delivered in 2021. Numbers 11 and 12 in the photo above were ordered in January 2022 and are now handed over to the customer. Filminera ordered two more DP1500i’s in November 2022; these machines are now awaiting completion in Tampere, for delivery later this year. That should bring the total to 14 x DP1500i units spread over 11 years for our most loyal Pantera DP1500i customer in the Philippines – Filminera Resources Corporation!

Place your Ad Here!

Place your Ad Here!

Join the Philippines'

Mining, Construction and Industry Community

Be the "First" to get our exclusive Digital Magazine & Newsletter.