Paper presented at the International Conference on Materials Technology and Energy (ICMTE 2017) Miri, Malaysia

1. Energy Recovery Potential
of Newly Discovered Nigerian
Brown Coals using Non-Isothermal
Thermogravimetry under
Pyrolysis Conditions
Bemgba Bevan Nyakuma (ir, MSc)

2. Co-Authors
Olagoke Oladokun (ir, MSc)
Aliyu Jauro (PhD)
Denen Damian Nyakuma (MSc)

3. Outline of Presentation
Introduction
Materials & Methods
Results & Discussion
Conclusions
References

4. Introduction
 Coal is the world’s most accessible, abundant
and widely distributed fossil fuel.
 Carbonaceous nature presents significant
opportunities for energy, fuels, & chemicals.
 Coal utilization plays an important role in the
global energy mix for electricity generation.

5.  What is Coal?
Brown-Black Organic
sedimentary rock
 Why is coal mined?
Energy, Fuels, Heat
 What are the uses of Coal?
Electricity, Steel, Cement
Introduction

6.  IEA >> Coal accounts for 40% or 8,000 TWh of electric power
generation >> projected to rise to 12,000 TWh by 2035.
 Coal utilization will significantly contribute to socioeconomic
growth, sustainable development & poverty alleviation.
 Coal energy exploration & exploitation is critical to
development like Nigeria with vast new deposits.
 Energy crises in Nigeria is pervasive, despite its vast coal
resources
Introduction

7.  Nigerian coal resources are located
in the Upper, Middle
& Lower Benue Trough from the SW-
NE across the sedimentary basin >>
13 states & 20 localities
 Proven resources & reserves amount
to 640 million & 2.8 billion tons
 Consists of Lignite (12%),
Sub-Bituminous (49%)
& Bituminous (39%).
Introduction
SEDIMENTARY BASINS OF NIGERIA

8.  Coal is strategically positioned across Nigeria >> ideal feedstock to
address the nation’s energy crises.
 Low demand for low-ranks coals (LRC) like lignite, >> cheap
feedstock per ton.
 Lignite utilization for electric power generation >> cheap, reliable,
& constant electric power supply.
 Limited knowledge on physicochemical, thermal kinetic,
& thermodynamic fuel properties of lignite coal in Nigeria.
Introduction

9. • Resistance to coal >> academics &
environmentalists despite Nigeria’s perennial
energy crises
• Concerns about pollution, global warming, &
climate change
• Clean Coal Technologies (CCT) >>
environmental challenges of coal power
generation.
Introduction

10. Aim of Study
• Examine the physicochemical & thermal properties of Lignite coals
from Ihioma (IHM) & Ogboligbo (OGB) in Nigeria.
• Thermal decomposition will be examined by non-isothermal
thermogravimetry (TG) under pyrolysis conditions.
• Lastly, rank classification & potential application of the Lignite
coals will be evaluated.
• The results will aid the design & development of future energy
systems for electric power generation in Nigeria.

11. Materials and Methods
From Ihiom a (IHM) in Imo Sta te & Og b olig b o (OG B) fro m Ko gi
State in Nige ria sup p lied b y the Na tional Me ta llurg ic a l
Resea rc h & Develop m ent Centre , Nigeria .
Coa ls we re c hara c terized b y ultim ate , p ro xim a te a na lyses to
exa mine the fuel c ha rac teristic s & rank c lassific a tion. Ultim ate
a na lysis d etermined by C HNS ana lyzer (Mod el: va rio MICRO
Cube Elem enta l Analyse r. Proxima te a nalysis wa s exa m ined b y
therm og ra vim etry (TG).
Coa l Proc urem ent
Prep ara tion o f Coa l Sa m ples
Chara c teriza tio n of C oal Sam p le s
Therm al a nd Therm oog ravim etric Ana lysis of IHM
a nd OG B C oa l Sa mp les
Next, the sa m ples were p ulverized a nd sifted using the Retsc h
sieve of m esh size 60 to ac quire 250 µm sized p a rtic le s p rior to
c ha ra c teriza tion.
Hig he r hea ting va lue (HHV) w as de termined b y b om b
c a lorim etry (Mod el: IKA C2000) using ASTM D2015 w hile Lo wer
Hea ting Va lue (LHV) w as c a lc ula te d . Ra nk c la ssific a tio n w as
exa mine d by ASTM D388 standa rd .
Coa l Ana lysis, Ra nk Cla ssific atio n &
Potentia l App lic atio ns
Therm al d eg ra d a tion b ehaviour wa s exam ined b y no n-
isotherma l therm og ra vim etric (TG) a na lysis. 15 m g of sam p le
w as hea ted a t 10 °C / m in from 30 - 900 °C in the Perkin Elm er
4000 TG Analyzer using Nitrog en (N2 - flow ra te o f 50 m l/ m in) a s
p urge ga s.

12. Results & Discussion
Elemental Analysis

13. Results & Discussion
 Results indicate IHM & OGB contain sufficient combustible fuel elements
for energy conversion.
 The carbon & hydrogen content of IHM > OGB coal but lower nitrogen &
sulphur >> lower potential for pollutant gaseous emissions.
 Proximate analysis was in good agreement with reported values for other
coals in literature.
 HHVs were 20.37 MJ/kg for IHM & 16.33 MJ/kg for OGB >> good
agreement with the range 9.50 – 27 MJ/kg for coal-firing.
 Based on HHVs (<24 MJ/kg) coals are low-rank Lignite (Brown) coal for
energy utilization.

14. Results & Discussion
Thermogravimetric (TG-DT) Analysis TG plots >> downward sloping
weight loss curves
 Temperature significantly influenced
the decomposition of the coal
samples.
 Thermal decomposition of occurred
from 30 – 550 °C.
 Above 550 °C, thermal decomposition
plateaued indicating low
devolatilization.
 Tailing (plateau) >> due to low
reactivity from coal devolatilization.

15. Results & Discussion
Derivative Thermogravimetric (DTG)
Analysis
 DTG for IHM revealed 3 peaks during
devolatilization.
 1st >> small symmetric peak from 30 – 150
°C denoting drying or loss of low molecular
weight volatiles.
 2nd peak a large, sharp, asymmetric tailing
peak from 205 – 300 °C >> 1st stage of
devolatilization due to loss of organic
volatiles.
 3rd was from 300 – 550 °C denoting the
second stage of devolatilization.

16. Results & Discussion
Derivative Thermogravimetric (DTG)
Analysis
 DTG for OGB revealed only 2 major
peaks.
 1st peak from 30 – 130 °C >> drying
 2nd larger peak was from 240 – 530 °C
>> devolatilization or loss of organic
volatiles.

17. Results & Discussion
 Based on the temperature profile characteristics Ton, Tmax & Toff,
>> IHM is more reactive than OGB.
Due to the higher volatile matter (VM), carbon (C) and hydrogen
(H) in IHM.
 Coal devolatilization from 30 – 900 °C resulted in 54.58% weight loss
for OGB while IHM was 75.73% confirming IHM is more reactive than
OGB.
 Residual mass, which indicates the coke (char) potential, was 23.30%
for IHM and 44.41 % for OGB, respectively.

18. Conclusions
 Energy recovery potential of newly discovered Nigerian Lignite (Brown)
Nigerian coals was examined.
 Physicochemical, thermal, & calorific fuel properties of IHM & OGB were
characterized.
 IHM & OGB contain satisfactory combustible elements, low moisture, ash and
high HHV = 16 – 20 MJ/kg.
 Thermal decomposition resulted in over 55% weight loss of OGB while IHM
was above 76% coal.
 Coals were classified as low-rank coals (LRCs) with potential for metallurgical
or power generation applications.

19. Acknowledgment
The authors gratefully acknowledge the support of the National
Metallurgical Research & Development Centre (Nigeria); the National
Centre for Petroleum Research & Development (NCPRD) (Nigeria); &
Universiti Teknologi Malaysia.

20. Selected References
 A. Sambo, Prospects of coal for power generation in Nigeria, A paper presented at the
International Workshop for the Promotion of Coal for Power Generation, 2009, pp. 27-28.
 ASTM Standard D388, Standard classification of coals by rank, ASTM International, West
Conshohocken, PA, 2015.
 B.B. Nyakuma, Physicochemical characterization and thermal analysis of newly discovered
Nigerian coals, Bulgarian Chemical Communications, 48 (2016) 746 – 752.
 Obaje, N. G., Idris-Nda, A., Goro, A. I., Dantata, S. H., Okoro, A. U., Akpunonu, E. O., & Jatau,
S. B. (2015). New assessment for Central Nigeria's Bida basin highlights geological prospects.
Oil and Gas Journal, 113, 52-59.
 OECD Working Paper, The Global Value of Coal IEA Coal Industry Advisory Board OECD,
Paris, 2012.
 J.G. Speight, The Chemistry and Technology of Coal, CRC Press 2012.
 J.G. Speight, Handbook of Coal Analysis, John Wiley & Sons, Hoboken, New Jersey, USA,
2015.