Mitsubishi Heavy Industries Technical Review Vol. 60 No. 3 (September 2023)
1

Development of Ammonia Burner at Coal-fired Boilers
for Decarbonized Society

TAKATOSHI YAMASHITA*1 TAKESHI AMARI*1
YUICHIRO URAKATA*2

KEIGO MATSUMOTO*3TOSHIHIKO MINE*4

AKIMASA TAKAYAMA*5The Japanese government's Green Growth Strategy for carbon neutrality by 2050 presents a"roadmap" for the growth of the fuel ammonia industry. One of the future initiatives is the spreadof ammonia co-firing and the increase in the co-firing rate in coal-fired thermal power plants, andthe shift to ammonia single-fuel firing. Mitsubishi Heavy Industries, Ltd. (MHI) is developing
technologies to enable ammonia co-firing for both circular firing and opposed firing systems ofcoal-fired boilers in order to respond to the efforts of various customers in Japan and overseas touse ammonia fuel toward the goal of carbon neutrality. This report presents the development ofammonia burners.

|1. Introduction
MHI has declared its intention to realize carbon neutrality by 2040 (MISSION NET ZERO),
which includes the promotion of the carbon neutrality of existing infrastructure. In order to achievecarbon neutrality in thermal power generation, which generates a large amount of CO2, it isimportant to reduce CO2 emissions from coal-fired boilers. MHI has been developing technologies
that enable higher co-firing rates of ammonia, which does not emit CO2 when combusted. This
paper presents the development status of ammonia burners applicable to both the circular firing andopposed firing systems.

|2. Concept of ammonia firing
2.1

Approach to higher ammonia co-firing rates

There is a problem that combusting ammonia in a coal-fired thermal power plant generates alarge amount of NOx. Since this NOx generation is sensitive to the air ratio, i.e., the ratio of fuel toair, the setting of the amount of air to be fed from the burner is important. In order to increase theammonia co-firing rate, in addition to controlling NOx, maintaining the combustibility of coal andcontrolling the increase in unburned combustible are required, so the combustion conditions
required for both coal and ammonia need to be maintained at the same time. For this purpose,
combusting coal and ammonia in separate burners (single-fuel firing burners) to co-firing them inthe boiler can easily control the air ratios of each and reduce NOx emissions even at high co-firing
rates. Also, this enables the co-firing rate to be changed as desired by adjusting the number ofburners in operation and the burner load.
In combustion tests in a small burner furnace, installing separate coal and ammonia burners
and setting optimal combustion conditions for each resulted in the suppression of NOx generationand no detection of unburned ammonia at the furnace outlet, even when the co-firing rate wasincreased(1). Based on this, the modification to ammonia co-firing adopted the concept of replacing
the existing burners with ammonia single-fuel firing burners.
*1

Chief Staff Engineer, Engineering Department, Steam Power Maintenance Innovation Business Division, Energy systems,*2

Engineering Department, Steam Power Maintenance Innovation Business Division, Energy systems, Mitsubishi Heavy*3

Deputy Senior Director, Combustion Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.

*4

Chief Staff Researcher, Combustion Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.

*5Combustion Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.

Mitsubishi Heavy Industries, Ltd.
Industries, Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 60 No. 3 (September 2023)
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2.2

Selection of ammonia burner structure design based on combustion simulation

In order to modify an existing burner to be an ammonia single-fuel firing burner, several
burner structure designs were developed based on the assumption that the burner can be switched toan ammonia burner, and a test burner for a combustion test in a 0.5 t/h furnace was selected by
combustion simulation. Figure 1 shows the simulation results of ammonia single-fuel firing
burners. Using a simulation model that improved the prediction accuracy of combustion
performance for coal-ammonia co-firing based on the results of basic tests, predictions for ignition
conditions, NOx, unburned ammonia, etc., were made, and the burner structure to be used for thecombustion test was determined.

Figure 1 Selection of burner modification design based on combustion simulation

The next and subsequent chapters will describe initiatives to verify the performance throughlarge-scale burner combustion tests to determine the burner structure.

|3. Combustion test equipment and combustion test plan
3.1

Combustion test equipment

In order to evaluate combustion stability and exhaust gas performance during coal-ammonia
co-firing and ammonia single-fuel firing, combustion tests are conducted in MHI's 0.5 t/h furnace(Figure 2). This equipment is capable of developing burners for both circular firing and opposedfiring systems. In accordance with the burner arrangement characteristics of the two types shown in
Figure 3, tests are conducted with two-stage coal burners and an oil burner placed between themfor the circular firing system, and with a single ammonia burner for the opposed firing system. Thisequipment can test both ammonia gas-firing and liquid-firing systems to meet the various needs ofour customers. Using this equipment, various exhaust gas concentrations such as NOx, unburnedammonia, nitrous oxide (N2O), etc., which are of concern in ammonia co-firing, as well as flame
temperature and various gas concentrations in the furnace can be obtained from the access port on
the side of the furnace and utilized to improve the accuracy of combustion CFD.

Figure 2

Appearance of 0.5 t/h furnaceMitsubishi Heavy Industries Technical Review Vol. 60 No. 3 (September 2023)
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Figure 3 Concept of single-fuel firing burner placement for circular and opposed firing
system boilers

3.2

Ammonia supply and storage equipment

This section describes the ammonia supply equipment installed under a projectcommissioned by the New Energy and Industrial Technology Development Organization (NEDO)
for ammonia co-firing and single-fuel firing tests. Figure 4 shows the appearance of the equipment.
The equipment consists mainly of a liquefied ammonia tank, a receiving compressor, a liquid-phasepump, a vaporizer, and an ammonia detoxification tank for purging the system. The ammonia in thetank is saturated at normal temperature and can be supplied in the liquid phase to the test burner bypressurizing with the liquid-phase pump. The vaporizer enables an ammonia supply in the vapor
phase as well. The capacity of the ammonia tank is 40 tons, which was selected to allow continuous
testing for more than 24 hours in a 0.5 t/h furnace and up to about 8 hours in a 4 t/h furnace.

Figure 43.3

Appearance of ammonia supply equipment

Combustion test plan

We have started combustion tests with this 0.5 t/h furnace, and are evaluating concepts andnarrow down burner shapes for both circular and opposed firing ammonia burners. Based on this,we will select the basic structure of the burner, aiming for stable ignition and the equivalent levelsof NOx and unburned combustible in ash as those in the case of coal single-fuel firing.
After that, we plan to conduct final confirmation tests of the combustion stability and exhaustgas performance in a 4 t/h furnace, which is capable of conducting burner combustion tests withfull-scale burner equivalent to actual equipment.

|4. Schedule for practical application
With the aim of increasing the ammonia co-firing rate, this development is conducted indeveloping and demonstrating a technology to increase the ammonia co-firing rate at coal-fired
boilers under the Green Innovation Fund program "Fuel Ammonia Supply Chain Establishment"

Mitsubishi Heavy Industries Technical Review Vol. 60 No. 3 (September 2023)
4(2)project of NEDO . As shown in Figure 5, we plan to develop an ammonia single-fuel firing
burner by fiscal 2024 through combustion tests with using full-scale burner equivalent to actualequipment. In addition, we are working with JERA Co., Inc. on a basic plan and feasibility study
for an actual-equipment demonstration of an ammonia co-firing boiler, aiming to verify ammonia
co-firing at the co-firing rate of more than 50% in two units, one with a circular firing system andthe other with an opposed firing system, through demonstrative operation using the actualequipment.

Figure 5

Schedule for practical application|5. Conclusion
This report describes the development status of an ammonia burner, which is being
implemented for the carbon neutralization of coal-fired boilers and is intended for modifying
existing boilers. We are developing an ammonia single-fuel firing burner to achieve a highco-firing rate, and presented an outline of a 0.5 t/h furnace combustion test facility. We havealready started the test and will select the basic burner structure after confirming theabovementioned concepts for the burner regarding the achievement of ignition stability, NOx, andin-ash unburned fuel levels equivalent to those of a coal-fired burner. After that, we plan to conduct
final confirmation of combustion stability and exhaust gas performance in a 4 t/h furnace, which iscapable of conducting burner combustion tests on a scale equivalent to that of the actual plant. We
also presented our initiatives toward future practical application.
This development is being conducted under "JPNP21020 Green Innovation Fund Project /Fuel Ammonia Supply Chain Establishment / Ammonia high-ratio co-firing and single-fuel firing
for thermal power generation / High-ratio co-firing and single-fuel firing needed for ammonia
power generation/, Development and demonstration of high-ratio ammonia co-firing technology(including single-fuel firing technology) in coal-fired boilers / Demonstration project of high-ratio
ammonia co-firing in the commercial coal-fired power plants utilizing ammonia single-fuelburners" of the New Energy and Industrial Technology Development Organization (NEDO).

References(1)(2)

Takatoshi Yamashita et. al, Development of Ammonia Co-firing Technology for Coal-fired Boilers toward
Decarbonized Society, Mitsubishi Heavy Industries Technical Review Vol.59 No.4 (2022)
JERA and MHI Start a Demonstration Project to Develop Technology to Increase the Ammonia Co-firing
Rate at Coal-fired Boilers (2022), PRESS INFORMATION, Mitsubishi Heavy Industries, Ltd.,
https://www.mhi.com/news/22010702.html