International Journal of Engineering Business

and Social Science

Vol. 1 No. 05, June 2023, pages: 387-400

e-ISSN: 2980-4108, p-ISSN: 2980-4272

https://ijebss.ph/index.php/ijebss

387

Analysis of Rice Husk Pellet Combustion Test for Co-Firing in

Pulverizer Coal (PC) Boilers

Ubaedi Susanto

, Adi Surjosatyo

1,2

Universitas Indonesia

Email: Ubaedi.su[email protected]

Keywords

Abstract

co-firing, rice husk pellet,

operation parameters,

emission

The increase in population has driven increased demand for energy, especially for

transportation and electricity. Meanwhile, fossil energy production continues to decline,

forcing the government to import petroleum to meet domestic needs. In order to

anticipate the increasingly limited national fossil energy reserves and the increasing

public energy needs, the government is promoting the use of renewable energy. One of

the efforts is by co-firing biomass in coal-fired power plants. At PLTU Indramayu, the

selected biomass is rice husk which has undergone pelletization treatment, compaction,

and heating, to obtain biomass with a high density and calorific value better than the

physical form of rice husk. Coal as fuel in PLTU Indramayu has an average calorific

value of 4200 kCal/kg, while rice husk pellets have an average calorific value of 3400

kCal/kg. Combustion tests for co-firing need to be carried out to determine the operating

performance of generating unit equipment. Co-firing tests in this study were still limited

to a composition of 1% biomass and 3% biomass which required a total of 43.2 tonnes

of rice husk pellets and 3196.8 tonnes of coal. Before the boiler combustion test,

computational fluid dynamics (CFD) numerical simulations were also carried out to get

an initial description. The results of the simulation and fuel tests show that the operating

parameters are in normal limits. Types of equipment also show good and normal

performance. Likewise, the resulting emissions support the achievement of the quality

standards required in the Minister of Environment Regulation No. 15/2019. Even so,

tests still need to be carried out with a higher percentage of biomass composition in order

to generate electricity from greater green energy and reduce the use of coal as fuel.

for possible open-access publication

under the terms and conditions of the Creative Commons Attribution (CC BY SA)

license (https://creativecommons.org/licenses/by-sa/4.0/).

1. Introduction

Indonesia as an agricultural country has considerable potential for biomass. Data from the Ministry of Energy

and Mineral Resources through the Directorate of Bioenergy, the potential for biomass as a source of power generation

reaches 32,773 MW. There are several types of biomass sources that can be used as an energy source. The sources are

oil palm, sugar cane, rubber, coconut, rice, corn, cassava, wood, livestock, and urban waste (Statistics, 2020). The parts

of palm oil that can be used are the flesh and seeds. It can be converted to biodiesel oil. Coir and shells can be used as

co-firing fuel in coal-fired power plants (Korea, 2014) . Likewise, rice husks, bagasse, rubber tree trunks, coconut

388 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

shells and coir, corn cobs, cassava stems, and all types of wood can be used as fuel for Biomass Power Plants (PLTBm)

or can also be used for cofiring in coal-fired power plants. (PLTU) [D.S. Primadita et al., 2020]

As fuel in a biomass power plant or co-firing PLTU, the potential of the biomass must be selected according

to the technical specifications of the generating machine and the potential of the biomass around the generating unit.

The area around the generating unit needs to be identified for the large potential of the existing biomass as part of the

guarantee for the continued operation of the PLTBm or fuel cofiring at the PLTU (Madanayake et al., 2017). The

potential for rice husk-type biomass is quite large in Java and the biggest in West Java. Rice husk, which is currently

a burden of waste in the agricultural sector, can be used as a biomass fuel. Its energy content is good enough to be used

as a fuel mixture/co-firing in coal-fired power plants (Agbor et al., 2014). Based on observations of farmers, rice husks

can be produced by approximately 20% of milled dry unhusked rice. This means that the utilization of rice husk as

fuel in the electricity sector is quite large considering that West Java is a national rice-granary area.

Rice production in West Java province in 2022 is 9,432,277.12 tons (BPS, 2022). In the areas closest to PLTU

Indramayu, namely Indramayu Regency, Subang Regency, Majalengka Regency and Sumedang Regency produced a

total of 3,385,286.78 tons of rice in 2022. PLTU Indramayu has carried out cofiring of biomass with saw dust but the

feed stock in the area around PLTU Indramayu is very limited. Using rice husk as an alternative fuel will increase the

percentage of cofiring at the Indramayu PLTU and of course it can help achieve the Green Energy performance target.

Pelletization is a densification technology, namely the process of compacting residues into products that have a higher

density than the original raw material (Arai et al., 2015). The densification process in pellet production has several

advantages, including increasing the total calorific value per unit volume, facilitating transportation and storage of the

final product, having uniform shape and quality and being able to substitute forest wood thereby reducing forest

logging activities (Hiloidhari et al., 2014). The process of making pellets consists of several stages, namely: raw

material pre-treatment, drying, size reduction, pelleting, cooling, and silage [Fantozzi S. et al. al., 2009].

With rice husk pellets, technically operational in the boiler is expected to obtain higher biomass calories close

to the coal calories required in burning boilers at PLTU Indramayu. With rice husk pellets that have a higher density,

you can increase the calories. However, prior to cofiring the coal power plant, rice husk pellets still need to be

technically analyzed by focusing on the formulation of the problem. What are the specifications/properties of rice husk

pellets that can be used as cofiring fuel for coal power plants How does the operational performance of the cofiring

coal power plant boiler with rice husk pellets simulated using Computational Fluid Dynamics (CFD) (ISO, 2014). How

does the operational performance of the PLTU Indramayu boiler when the cofiring test is carried out with rice husk

pellets (Pode, 2016). The purpose of this study was to obtain data on specifications for rice husk pellets that are suitable

for use as a cofiring mixture for coal-fired power plants using the fuel test method. Obtain operational parameter data

for cofiring biomass with rice husk pellets from Computational Fluid Dynamics (CFD) simulations. Obtain operational

parameter data for cofiring biomass with rice husk pellets resulting from trials of combustion in a boiler (Tsuchiya &

Yoshida, 2017).

2. Materials and Methods

This research begins with a literature study from various literature both from books and research journals.

Then proceed with a survey of the potential of rice husks in Indramayu Regency. In this study, the area of Indramayu

Regency was selected based on the existence of PLTU Indramayu and its large agricultural sector. The data were

obtained from field observations from PLTU Indramayu and farmers in the area around PLTU Indramayu. From

PLTU Indramayu, boiler technical data were obtained as a reference for making CFD modeling, while from the

surrounding farming community, data on rice husk prices and their potential continuity were obtained. The modeling

is made according to the boiler geometry of the Indramayu PLTU, then the parameters of coal and biomass are

included as mixed fuels (Conrad & Prasetyaning, 2014). After completing all the parameters, the CFD modeling is

run to obtain the operating parameters of combustion (combustion).

Computational fluid dynamics (CFD) is a method used to analyze fluid dynamics using a computer. CFD can

be used to analyze many types of fluids, including air, water, and gases. Cofiring tests with a percentage of 3% rice

husk pellet mixture were carried out at PLTU Indramayu 3x330 MW to determine the effect of cofiring on the

reliability and main parameters of PLTU Indramayu and to obtain an overview of cofiring implementation which

includes aspects of operational technical evaluation, evaluation of production costs and environmental evaluation.

The next stage is to analyze the impact of cofiring coal with biomass. The CFD modeling simulation results

can obtain the emission impact of a mixture of coal and biomass fuel. By obtaining the emission data, it can be used

as a reference and the percentage that can minimize the resulting emissions is selected. In the final stages of this

IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 389

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

research, it discusses the operating parameters of the results of the CFD modeling run and the burning test of rice husk

pellets with coal and draws conclusions from this research. Cofiring of biomass with rice husk pellets also has the

potential to cause corrosion in the boiler tube (Mirmohamadsadeghi & Karimi, 2020). To determine the potential for

corrosion and slagging from cofiring results obtained by analyzing the physical properties and chemical content of a

mixture of coal and biomass through laboratory tests (Parinduri & Parinduri, 2020). The required laboratory tests are

Proximate Analysis, Ultimate Analysis, Ash Analysis, Ash Fusion Temperature, and Chlorine Analysis.

3. Results and Discussions

3.1 CFD modeling

In order to use CFD for simulating co-firing of biomass, it is first necessary to determine the geometry of the

combustion system to be studied, as well as the initial conditions of the fluid to be analyzed. Then enter information

about the fuel used, including the composition of the mixture of biomass and fossil fuels, as well as operating conditions

such as temperature and pressure .

This research was conducted at the Indramayu PLTU whose design uses a Puverizer Coal (PC) Boiler. The

modeling carried out in this study consists of four compositions, namely:

a. with 100% coal

b. with 99% coal and 1% rice husk pellets

c. with 97% coal and 3% rice husk pellets

d. with 95% coal and 5% rice husk pellets

Parameters that need to be included in the combustion simulation co-firing This biomass is:

a. mass flowrate for combustion air (primary air & secondary air) that enters coal pulverizer and every coal

burner

b. pressure from the combustion air (primary air & secondary air) that enters coal pulverizer and every coal

burner

c. mass flowrate for the incoming coal pulverizer and every coal piped

d. mass flowrate for husk pellets that go into coal pulverizer and every coal pipe

e. coal particle distribution, coal particle size and mass flowrate for each particle size

f. distribution of husk pellet particles, the particle size of the husk pellets and mass flowrate for each particle

size

g. ultimate analysis and proximate analysis for coal and husk pellets

The greater the composition of the husk pellets based on numerical simulations the impact on the increase in

value COWARD as shown in the graph in Figure 4.5 above. The amount of the increase in value COWARD with the

composition of the husk pellets respectively 1%, 3%, and 5% of the value COWARD coal alone by 15.26%, 15.15%

and 15.15%. This is due to the increase volatile matter in the fuel mixture that enters the combustion chamber comes

from the content volatile matter in husk pellets is much higher than that of coal (Basu, 2018).

390 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

Figure 1. Speed distribution over area boiler nose (a) 100% coal, (b) 99% coal and 1% rice husk pellets, (c)

97% coal and 3% rice husk pellets, (d) 95% coal and 5% rice husk pellets

The fluid flow velocity profile (Figure 4.6) at elevation nose indicates concentration or color with high-

velocity throughout nose tubes bend follow the contours of the physical structure furnace. So that this area suffers from

a high fluid flow velocity and directs the fluid flow in the row-platen superheater tube bundle in front of him.

Figure 2. Graph of the average speed of the simulation results in the area boiler nose

The condition of the average velocity of fluid flow in the Boiler nose area from the results of coal and

composition simulations-firing Rice husk pellets showed an increase with the increase in the ratio of husk pellets used.

The increase in the composition of the 5% husk pellets causes an increase in the average velocity of the boiler nose by

2 m/s. But this is still safe because the maximum speed in the area is still below the maximum limit of 20 m/s, so it

doesn't have a significant erosion impact on tube bundle (platen superheater) and nose tubes.

)

IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 391

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

Figure 3. Distribution of CO gas emissions

on the area back pass, (a) 100% coal, (b) 99% coal and 1% rice husk

pellets, (c) 97% coal and 3% rice husk pellets, (d) 95% coal and 5% rice husk pellets

CO emission value

The simulation results are shown in Figure 4.8, in the back pass area it ranges from 24.9%

– 25.6%, this means that the composition of the husk pellets does not have a significant impact on CO gas emissions.

Figure 4. Distribution of CO gas emissions in the area back pass, (a) 100% coal, (b) 99% coal and 1% rice husk

pellets, (c) 97% coal and 3% rice husk pellets, (d) 95% coal and 5% rice husk pellets

The simulation results show that the greater the composition of the husk pellets the higher the CO emission,

which indicates further combustion after elevation. boiler nose. The value of CO gas emissions with the three

compositions of husk pellets experienced an average increase of only 0.1%.

(

392 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

3.2 Co-firing Test of Rice Husk Pellets

Test burn co-firing rice husk pellets on Pulverizer Coal (PC) Boiler PLTU Indramayu will be carried out on 6

– 8 February 2023 with three stages, namely:

a. Combustion stability testing (compatibility test), aims to ensure that the biomass used has good milling

properties so that it can be sent to burner to the maximum and not wasted as pyrite.

b. Combustion performance testing (performance test), aims to ascertain the impact of combustion on the

performance of the generating unit

c. Combustion resistance testing (durability test), aims to determine the long-term effect on the condition of

generating equipment (Madejski, 2018).

In this study, the fuel test co-firing was carried out several times with a burning composition of 0%, 1% and

3% rice husk pellets calculated from the total coal flow 180 t/h (at a maximum load of 300 MW) with a test duration

of 6 hours. Thus, the total need for rice husk pellets is 43.2 tons and the need for coal is 3,196.8 tons (Table 4.3).

Table 1. Requirement of coal and rice husk pellets in testing

Composition Scenario

Duration

(Hours)

Coal

(ton)

Biomass

(ton)

Total

Note

100% Coal, 0% biomass

1080

Coal Flow

180 t/jam

99% Coal, 1% biomass

1069,2

10,8

1080

97% Coal, 3% biomass

1047,6

32,4

1080

Total

3196,8

43,2

3240

Rice husk pellets are sent from suppliers using trucks to PLTU Indramayu which are then unloaded and stored

in the area coal yard (stockpile). Mixing(mixing) biomass with coal is carried out in the coal yard. Figure 4.10 shows

the coal flow cycle from the coal yard to the chimney.

Figure 5. The process of coal flow from the coal yard to the chimney

Coal yard PLTU Indramayu is quite protected from rain and weather because it is equipped with coal shelter

/ coal dome. Mixing rice husk pellets with coal is done with the help of heavy equipment(excavator) to get an even

mixture. To determine the characteristics of the fuel used in co-firing can be analyzed by looking at the physical

properties and chemical content of the fuel mixture (a mixture of coal and biomass) which can be determined through

laboratory tests (Demirbaş, 2003). Laboratory tests required include: proximate analysis and ultimate analysis. It is

IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 393

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

important to carry out laboratory tests on the fuel mixture used in addition to knowing the calorific value, it can be

known the substances contained in the fuel and the substances formed in the combustion products so that the potential

for the formation of slagging, fouling and agglomeration as well as the potential for corrosion in the boiler. Testing

sample fuel (coal, biomass and rice husk pellets mixing co-firing) was carried out by PLN Research and Development

Center which then tested the characteristics of the fuel in the ESDM Tekmira laboratory.

Table 2 Test results for the characteristics of coal and rice husk pellets

In the table of characteristic test results above, the sulfur content in rice husk pellets is very low at 0.038%

compared to coal which is around 0.31%, so the addition of rice husk pellets in the test co-firing Rice husk pellets has

the potential to reduce SO emissions

, this condition can reduce emissions to achieve the quality standard targets set

by PERMEN LHK Number 15 of 2019. Content of volatile matter in rice husk pellets is also much larger than coal,

this makes rice husk pellets burn faster than coal it helps speed up the combustion process in the boiler as a whole.

Rice husk pellets also contain ash that is lower than coal so as to reduce the amount ash formed/produced from the

combustion process in the boiler either on fly ash nor bottom ash (Singh, 2018). The calorific value of the rice husk

pellets for the combustion test in Indramayu is 3,363 kCal/kg, indicating that the energy content is relatively not much

different from coal. low rank which has a calorific value of 4.243 kCal/kg.

Some of the characteristics of the rice husk pellets became an important supporting factor in carrying out the

trials co-firing at the Indramayu PLTU. Trials co-firing conducted on 6 – 8 February 2023 in Unit # 2 by giving feeding

mixed fuel of coal and biomass. Testing with a load at set at a maximum load of 300 MW the duration of the test is 6

hours. For actual data comparison, the operating parameters were observed under the conditions prior to the test co-

firing or in the condition of operating units with 100% coal (0% biomass). This operating data will be used as a baseline

or comparison for operating data co-firing. The operating conditions of the units tested will be treated the same and

use the same type of coal for both the 100% coal operation test and the operation test co-firing 1% biomass dan 3%

biomass (Moraes et al., 2014).

Operational data collection for 100% coal conditions was carried out at PLTU Indramayu Unit # 2 on 6 – 8

February 2023 using coal with a heating value of 4,230 kCal/kg. Monitoring of operating parameters is carried out at

a load setting of 300 MW. The main parameters or critical points observed are: total air flow, total coal flow, main

steam temperature, main steam pressure, gas economizer outlet temperature, gas outlet temperature air heater, spray

reheater total flow, dan spray superheater total flow (Wu et al., 2015).

394 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

From the test results, several data parameters were obtained which were analyzed for their operational

feasibility. Observation of operating parameters on coal pulverizer (mill) on critical point like a current coal mill, coal

feeder flow, mill outlet temperature which shows a small deviation, and is still within safe limits. At each test, current

mill is normal throughout mill which operates as shown in the following table below.

Table 3 Designation of parameters mill on testing composition of biomass 0%, 1% and 3%

In Table 4.8, testing co-firing 3% visible mill outlet temperature (MOT) tends to be higher than in other tests.

This is because flow fuel at the moment co-firing 3% lower, especially in mills C and D. The average difference in

MOT in the three tests ranged from 0 - 1 °C. The increase in MOT is due volatile matter rice husk pellets being much

higher in comparison volatile matter coal.

Nonetheless, content volatile matter at a higher biomass than coal still provides value mill outlet temperature

monitored safely, did not show a significant increase, so it is safe for operation coal mill (Bajaj & Mahajan, 2019). The

deviation that occurs is not significant and is classified as safe. Even in terms of fuel consumption, coal feeder flow,

there is a decreasing trend after using rice husk pellet biomass, which means that the use of fuel can be reduced to

produce electricity at the same load. Mill D and mill F is not included in the table because at the time of the second

IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 395

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

data collection mill is in a condition that has not been operated according to the needs of coal flow and calories have

been fulfilled by 4mill. on condition normal, 5 mill operated and 1 mill standby and the selection of mill operations is

adjusted to the needs of boiler operations.

Table 4. Designation of mill flows in testing the composition of 0%, 1% and 3% biomass

Motor current indication mill the biggest deviation is seen when burning with 0% biomass. For combustion

with 1% and 3% current biomass mill the average is higher than burning at 0% biomass composition. To find out the

cause of the increase in current mill need to be checked/calibrated on mill. For the designation of value Air Fuel Ratio

(AFR) and flow fuel on test co-firing The rice husk pellets in the table above appear to vary in terms of both 1% and

3% biomass composition. Both of these parameters show a downward trend when testing 1% biomass or 3% biomass.

a. At 0% biomass composition, AFR ranged from 1.83 to 2.53 with a deviation of 0.70 and an average AFR of

2.18.Fuel flow ranges from 35.8 to 37.98 with a deviation of 2.7 and an average of 36.46.

b. At a composition of 1% biomass, the AFR ranges from 1.85 to 2.39 with a deviation of 0.54 and an average

AFR of 2.01.Fuel flow ranges from 35.6 to 3.7 with a deviation of 3.07 and an average of 37.04.

c. At a composition of 3% biomass, AFR ranged from 1.69 to 2.61 with a deviation of 0.93 and an average AFR

of 1.99.Fuel flow ranges from 32.06 to 36.25 with a deviation of 4.19 and an average of 34.15.

The combustion temperature in the boiler and the exit temperature from the boiler are also very important

indicators to determine the combustion performance in the boiler. Boiler design involves an energy balance between

the fireside and the steam side. In boilers there is generally sufficient monitoring of the steam side, but not sufficient

fire monitoring and control. Beginning with the mixing of fuel and air, combustion then occurs in the furnace, and

subsequent monitoring in the exhaust gas path until the exit temperature furnace boiler. The control point between the

exit of the burner to the exit of the boiler furnace, of which is Flue Gas Exit Temperature (FEGT). At this FEGT

control point it has a major impact on the performance and reliability of the boiler (Quispe et al., 2017).

Basically, the exit point of the furnace separates the radiation zone from the convection zone. FEGT defines

the ratio of heat absorption by radiant heating and convective heating. The FEGT control point also observes potency

fouling from the boiler tube in the convection area. If the FEGT is above the coal ash initial deformation temperature

(IDT), it can cause fouling boiler tube which is severe by liquid ash(molten ash). Exhaust gas temperature at intake

Superheater / Reheater should also be monitored lower than Ash Fusion Temperature (AFT).

FEGT testing is carried out using a thermogenic at several points in the area furnace in different areas. The

results of the FEGT test are shown in Table 5 below.

396 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

Table 5. Designation of FEGT measurements in testing the composition of 0%, 1% and 3% biomass

From the FEGT measurement data table above, it is obtained that the average composition test at 3% tends to

be lower by 6.93 °C compared to 100% coal operating conditions. FEGT decreasing trend under operating conditions

co-firing composition of 3% biomass is still within normal limits and on average tends to decrease from the previous

915.23 °C to 908.47 °C at a composition of 1% biomass and to 908.3 °C with a composition of 3% biomass. FEGT

when co-firing has a lower value than when coal firing, this is comparable to the calorific value of a mixture of biomass

coal which is lower than the calorific value of coal.

The highest deviation occurred at 86 °C in the 0% biomass test, while the lowest deviation occurred atco-

firing 3% biomass. Furnace temperature east, central and west side boilers at the moment co-firing and coal firing is

not uniform at the same load. This can be caused not only because of the calorific value of the fuel but also because of

the non-uniformity of the resulting combustion coal fineness non-uniform. The next observation is on unburned carbon

(UBC) what needs to be done to determine the carbon content that is not burned out in the combustion process in the

boiler. The higher the UBC value, the more inefficient the combustion or fuel is, because more energy has not been

converted. UBC test observation results can be seen in the following table.

Table 6. Results unburn carbon (UBC) testing of the composition of the biomass 0%, 1% and 3%

From the table of the UBC test results, it was found that when testing 0% of the biomass produced unburned

carbon fly ash which is slightly above the threshold value of 1% (with a value of 1.3%) indicating the inherent UBC

of the coal used. While testing co-firing 3% rice husk pellets yield unburned carbon fly ash which is better and

according to the standard threshold, namely with a value of 0.8%.

Furthermore, the observation of the potential for corrosion and slagging from the fuel used into-firing. This

can be analyzed by looking at the physical properties and chemical content of the fuel mixture (a mixture of coal and

IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 397

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

biomass) which can be determined through laboratory tests. Laboratory tests that have been carried out include:

proximate analysis, ultimate analysis, analysis abu, ash fusion temperature, dan chlorine analysis. It is important to

carry out laboratory tests on the fuel mixture used in addition to knowing the calorific value, it can be known the

substances contained in the fuel and the substances formed in the combustion products so that the potential for the

formation of slagging, fouling and agglomeration as well as the potential for corrosion in the boiler.

Table 7 Ash analysis of rice husk pellets, coal, and a mixture of coal–rice husk pellets

From ash analysis shown in Table 4.13 above, rice husk pellets contain S

the highest is 95.15% while the

mixture of coal with rice husk pellets is in the range of 40% - 47%. S

is abrasive on the equipment so it can cause

erosion on the equipment especially bowl pulverizer. The CaO content of rice husk pellets has the lowest content,

namely 0.43%, while that of coal is 4.28%. The percentage of CaO cannot be ignored because of the potential for

sticking fly ash on the pipe surface causing ash and fouling of tube boiler.

Table 7 Ash analysis of rice husk pellets, coal, and a mixture of coal–rice husk pellets

Potency slagging based on Slagging Index (Rs) moment coal firing (0% biomass) or co-firing 1% biomass

and 3% low potential biomass where all values Rs smaller than 0.4. As for potential fouling using numbers Fouling

Index (Rf) has quite a high potential on the scheme co-firing with value Rf > 1. The process of releasing sulfur and

chlorine into the gas phase during biomass combustion is rather constant (sulfur 80% – 90% and chlorine > 90%) (P.

Sommer sacher, et al 2011), the risk of sediment can be evaluated alkali chlorides on the superheater and the risk of

active oxidation of chloride based on fuel composition.

398 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

Table 8. Comparison of the characteristics of coal, rice husk pellets, and a mixture of coal and rice husk pellets

The rice husk pellets used for this test have value Hard grove Grindability Index (HGI) which is much lower

than coal. The HGI value of rice husk pellets is in accordance with the table above, which is 16, while coal is around

a value of 45. This indicates the level of ductility of rice husk pellets which will be harder to handle. grinding and has

the potential to increase the flow of the coal mill as well reject pyrite.

Minister of Environment Regulation Number 15 of 2019 sets limits on emission quality standards from power

plants. Table 4.18 shows these limits and must be complied with under any operating conditions.

Table 9. Comparison of the characteristics of coal, rice husk pellets, a mixture of coal and rice husk pellets

Mixing fuel, coal with rice husk pellets on co-firing will affect the exhaust emissions produced, for this reason,

testing of exhaust emissions is carried out to observe changes that occur during the test co-firing. Table 4.19 shows the

results of emission measurements indicating that they are still below the quality standards and co-firing with rice husk

pellets is worth continuing.

Table 10. Comparison of the characteristics of coal, rice husk pellets, a mixture of coal and rice husk pellets

IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 399

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

4. Conclusion

Rice Husk Pellet Specifications

The calorific value of rice husk pellets is lower than low rank coal, however, pelletization is a pre-treatment

effort that can increase the calorific value better than in the form of rice husk. Content sulfur dioxide (SO

) and nitrogen

oxide (NOx) Rice husk pellets are far below the sulfur content of coal, so they can improve SO quality

and NOx in

exhaust gases and can support the fulfillment of emission quality standards required in the Minister of Environment

Regulation Number 15 of 2019. Potential slagging and fouling on the co-firing of rice husk pellets is relatively small

because slagging index and fouling index of Rice husk pellets are much smaller than coal. Content chlorine rice husk

pellets are higher than the content of chlorine coal. This gives a higher corrosion potential to the boiler tube and grinder

mill/pulverizer so the percentage of rice husk pellets in co-firing should be limited to a safe level.

Operation PerformanceCo-firing Rice Husk Pellets Based on CFD Simulation

On burning in furnace, temperature in furnace and flue exit gas temperature (FEGT) shows that the greater

the composition of rice husk pellets in the mixture co-firing impact on temperature rise furnace. This is due to the in

crease volatile matter in the fuel mixture that enters the combustion chamber comes from the content volatile matter

in husk pellets is much higher than that of coal. The fluid flow velocity profile at elevation nose shows that the higher

the percentage of biomass, the higher the fluid velocity along nose tubes bend to follow the contours of the physical

structure furnace and directs the flow of fluid in the row platen supeher heater tube bundle in front of him. CO emission

value

and CO simulation results show a very small increase so it does not have a significant impact on exhaust

emissions.

Operation Performance Co-firing Rice Husk Pellets During Fire Test in Boilers

Rice husk pellet burning test on co-firing The composition of 1% biomass and 3% biomass was carried out by

observing operating parameters compared to burning only coal(coal firing). The main operating parameters provide a

safe amount within operating limits, both at 1% biomass and 3% biomass. In general, the performance boiler and

mill/pulverizer are not significantly affected by operations co-firing rice husk pellets. Temperature furnace and FEGT

on co-firing the composition of 1% and 3% shows an inconsistent trend. This is very possible because of the non-

uniformity of the coal that is burned. Un-Burned Carbon (UBC) relatively lower value at co-firing compared with coal

firing. This shows better efficiency as more heat is generated from the fuel that is burned. Rice husk pellets have a

value Hard grove Grindability Index (HGI) lower than coal. This indicates the level of tenacity of rice husk pellets

which will be harder to handle. grinding thus potentially increasing the current coal mill.

5. References

Agbor, E., Zhang, X., & Kumar, A. (2014). A review of biomass co-firing in North America. Renewable and

Sustainable Energy Reviews, 40, 930–943.

Arai, H., Hosen, Y., Pham Hong, V. N., Thi, N. T., Huu, C. N., & Inubushi, K. (2015). Greenhouse gas emissions

from rice straw burning and straw-mushroom cultivation in a triple rice cropping system in the Mekong Delta.

Soil Science and Plant Nutrition, 61(4), 719–735.

Bajaj, P., & Mahajan, R. (2019). Cellulase and xylanase synergism in industrial biotechnology. Applied

Microbiology and Biotechnology, 103, 8711–8724.

Basu, P. (2018). Chapter 11-Biomass Combustion and Cofiring. P. Basu & PBTBG Torrefaction (Eds.), 393–413.

Conrad, L., & Prasetyaning, I. (2014). Overview of the Waste-to-Energy Potential for Grid-connected Electricity

Generation (Solid Biomass and Biogas) in Indonesia. Accessed Online October, 24, 2014.

Demirbaş, A. (2003). Sustainable cofiring of biomass with coal. Energy Conversion and Management, 44(9), 1465–

1479.

Hiloidhari, M., Das, D., & Baruah, D. C. (2014). Bioenergy potential from crop residue biomass in India. Renewable

and Sustainable Energy Reviews, 32, 504–512.

ISO, E. N. (2014). 17225-2: 2014-Solid Biofuels-Fuel Specifications and Classes Part 2: Graded Wood Pellets. The

British Standards Institution: London, UK.

Korea, I. (2014). New and renewable energy.

Madanayake, B. N., Gan, S., Eastwick, C., & Ng, H. K. (2017). Biomass as an energy source in coal co-firing and its

feasibility enhancement via pre-treatment techniques. Fuel Processing Technology, 159, 287–305.

Madejski, P. (2018). Coal combustion modelling in a frontal pulverized coal-fired boiler. E3S Web of Conferences,

46, 00010.

400 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS

IJEBSS Vol. 1 No. 05, June 2023, pages: 387-400

Mirmohamadsadeghi, S., & Karimi, K. (2020). Recovery of silica from rice straw and husk. In Current

Developments in Biotechnology and Bioengineering (pp. 411–433). Elsevier.

Moraes, C. A. M., Fernandes, I. J., Calheiro, D., Kieling, A. G., Brehm, F. A., Rigon, M. R., Berwanger Filho, J. A.,

Schneider, I. A. H., & Osorio, E. (2014). Review of the rice production cycle: by-products and the main

applications focusing on rice husk combustion and ash recycling. Waste Management & Research, 32(11),

1034–1048.

Parinduri, L., & Parinduri, T. (2020). Konversi biomassa sebagai sumber energi terbarukan. JET (Journal of

Electrical Technology), 5(2), 88–92.

Pode, R. (2016). Potential applications of rice husk ash waste from rice husk biomass power plant. Renewable and

Sustainable Energy Reviews, 53, 1468–1485.

Quispe, I., Navia, R., & Kahhat, R. (2017). Energy potential from rice husk through direct combustion and fast

pyrolysis: a review. Waste Management, 59, 200–210.

Singh, B. (2018). Rice husk ash. In Waste and supplementary cementitious materials in concrete (pp. 417–460).

Elsevier.

Statistics, G. B. (2020). World bioenergy association.

Tsuchiya, Y., & Yoshida, T. (2017). Pelletization of brown coal and rice bran in Indonesia: Characteristics of the

mixture pellets including safety during transportation. Fuel Processing Technology, 156, 68–71.

Wu, H.-C., Ku, Y., Tsai, H.-H., Kuo, Y.-L., & Tseng, Y.-H. (2015). Rice husk as solid fuel for chemical looping

combustion in an annular dual-tube moving bed reactor. Chemical Engineering Journal, 280, 82–89.