**3. Energy demand scenario in Malaysia**

The Malaysian government policy on energy utilization and consumption has approved to increase the coal base generation of electricity from 11% to about 33% by the year 1995 and 2020, respectively [21]. Moreover, the coal reserves in Malaysia, which are mainly located in the states of Sarawak (70% reserves), Sabah (28%) and other states (2% from Selangor, Perak and Perlis), have total reserves of about 1, 050 million tonnes of various qualities, ranging from lignite to anthracite [21, 22, 23]. However, the only coal deposit being mined in Malaysia is from Kapit area, Sarawak.

Since early 1999, Tenaga Nasional Bhd. (TNB), the major electricity provider and Sarawak Electric Supply Co. (SESCO) have purchased 120, 000 and 400, 000 tonnes per annum (tpa), respectively, from Kapit coal mine [24]. SESCO operates the 100 MW Kapit minemouth coalfired power station, where two 50 MW units supply electricity to the Sarawak grid. TNB has projected to double to 20 million tpa its coal import once two planned coal-fired plants (total of 1400 MW) are fully commissioned. Moreover, the construction work has started on the 2100 MW Pulau Bunting power station, which will burn 6 million tpa of coal. In order to secure low coal prices and improve the security of coal supply, TNB's long-term plan is to buy 30 to 50% of its annual coal requirement from its Indonesian coal mining subsidiary, TNB Coal Interna‐ tional Ltd., which owns the right to mine in five areas in South Kalimantan. Malaysia imported about 2.9 million tonnes of coals in 1999, i.e. 85% were steam coal and 15% anthracite and bituminous coal. This amount of coal was needed to fulfill the requirement for its cement and utility industries. Indonesia, Australia, China and South Africa were the major overseas suppliers [23].

### **3.1. Malaysian coals**

Based on the statistics reported in The Eighth Malaysia Plan by the Department of Minerals and Geosciences, Sarawak; Mukah Balingian (MB) was identified as the second largest coal area in Malaysia with reserves of *ca.* 710 km2 [6]. However, most of the known coal areas in the states of Sabah and Sarawak, including Mukah Balingian, are not commercially mined due to poor availability of infrastructure and located far inland [6], and most of the coal types are of low rank, i.e. sub-bituminous. Thus, the usage of abundant of coal reserves was not optimized. Low rank coals (brown coal, lignite and lower sub-bituminous coals) are the most abundant fossil resources, but they have not been utilized in a large amount because of their low calorific values. This is mainly due to the presence of a large amount of oxygen functional groups in such coals, namely, carboxylic, -COOH; hydroxyl, -OH; carbonyl, -CO; etc. The traits of these coals are low price, relatively large porosity and high reactivity, which benefit their utilization for direct coal liquefaction (DCL) [25]. Owing to the fact that low rank coal contains less carbon, liquefaction process is one of the best option thus far to utilize them.

### **3.2. Characteristics of Mukah Balingian coal**

**Fatty acid composition (%) Rubber seed oil** Palmitic acid C16:0 10.2 Stearic acid C18:0 8.7 Oleic acid C18:1 24.6 Linoleic acid C18:2 39.6 Linolenic acid C18:3 16.3 Specific gravity 0.9

Flash point (°C) 198.0 Calorific value (MJ/kg) 37.5 Acid value (mg KOH/g) 34.0

The Malaysian government policy on energy utilization and consumption has approved to increase the coal base generation of electricity from 11% to about 33% by the year 1995 and 2020, respectively [21]. Moreover, the coal reserves in Malaysia, which are mainly located in the states of Sarawak (70% reserves), Sabah (28%) and other states (2% from Selangor, Perak and Perlis), have total reserves of about 1, 050 million tonnes of various qualities, ranging from lignite to anthracite [21, 22, 23]. However, the only coal deposit being mined in Malaysia is

Since early 1999, Tenaga Nasional Bhd. (TNB), the major electricity provider and Sarawak Electric Supply Co. (SESCO) have purchased 120, 000 and 400, 000 tonnes per annum (tpa), respectively, from Kapit coal mine [24]. SESCO operates the 100 MW Kapit minemouth coalfired power station, where two 50 MW units supply electricity to the Sarawak grid. TNB has projected to double to 20 million tpa its coal import once two planned coal-fired plants (total of 1400 MW) are fully commissioned. Moreover, the construction work has started on the 2100 MW Pulau Bunting power station, which will burn 6 million tpa of coal. In order to secure low coal prices and improve the security of coal supply, TNB's long-term plan is to buy 30 to 50% of its annual coal requirement from its Indonesian coal mining subsidiary, TNB Coal Interna‐ tional Ltd., which owns the right to mine in five areas in South Kalimantan. Malaysia imported about 2.9 million tonnes of coals in 1999, i.e. 85% were steam coal and 15% anthracite and bituminous coal. This amount of coal was needed to fulfill the requirement for its cement and utility industries. Indonesia, Australia, China and South Africa were the major overseas

Based on the statistics reported in The Eighth Malaysia Plan by the Department of Minerals and Geosciences, Sarawak; Mukah Balingian (MB) was identified as the second largest coal

/s) 66.2

Viscosity at 40 °C (mm2

**3. Energy demand scenario in Malaysia**

**Table 1.** Properties of rubber seed oil [18].

190 Biofuels - Status and Perspective

from Kapit area, Sarawak.

suppliers [23].

**3.1. Malaysian coals**

From Table 2, it can be seen that MB coal has relatively high oxygen and volatile matter contents. The petrographic analysis of this coal shows a vitrinite reflectance value of 0.40% and thus can be categorized as a low rank coal, i.e. sub-bituminous C rank [26]. Further, previous work by Ismail et al. [27] using high pressure Temperature Programmed Reduction (TPR) on the pyrite-free MB coal also confirms that this coal is of a low rank by observing the organic sulfur distribution in the coal. Moreover, Rodriguez et al. [28] suggested that low rank coals are normally composed of small aromatic clusters and contain many cross-links and functional groups, and thus, are very reactive and undergo fast and extensive bond breaking during liquefaction. Moreover, Rodriguez et al. [28] suggested that low rank coals are normally composed of small aromatic clusters and contain many cross-links and functional groups, and thus, are very reactive and undergo fast and extensive bond breaking during liquefaction.


extracted readily, which makes the extraction yield correlate broadly with its content [31].

increased from ambient to 1000 °C. The weight loss profile resembles that of a first-order reaction.

60% by volume of the whole rock, with 31% liptinite (formerly known as exinite), 8% inertinite and 1% mineral matter. Pyrite, however, is present in trace amount. The high content of reactive macerals, i.e., vitrinite and liptinite, that contributes up to 91% of the organic matter content, serves as an important characteristics for carbonization and liquefaction processes of coal [30]. Interestingly, this high value of reactive macerals is in accord with the value suggested by Van Krevelen [31], under the reactivity parameter group to characterize coal for direct liquefaction. It is also known that the vitrinite and liptinite can be

Another important characteristic of MB coal is the thermal behavior of decomposition under pyrolysis conditions via thermogravimetric analyser (TGA). The pyrolysis of raw MB coal via TGA at a heating rate of 20 °C min-1 is shown in Figure 3. The TG curve (Figure 3(a)) of the raw coal shows the weight loss profile with the weight decreasing as temperature is

daf = dry ash free basis; db = dry basis; <sup>1</sup> calculated by difference; 2 Fixed carbon/volatile matter. daf = dry ash free basis; db = dry basis; 1 calculated by difference;

**Thermal Behavior of Mukah Balingian Coal** 

Table 2. Characteristics of raw Mukah Balingian coal [29].

2 Fixed carbon/volatile matter.

Moreover, the petrographic analysis shows that the composition of the coal is dominated by vitrinite that constitutes about **Table 2.** Characteristics of raw Mukah Balingian coal [29].

Moreover, the petrographic analysis shows that the composition of the coal is dominated by vitrinite that constitutes about 60% by volume of the whole rock, with 31% liptinite (formerly known as exinite), 8% inertinite and 1% mineral matter. Pyrite, however, is present in trace amount. The high content of reactive macerals, i.e., vitrinite and liptinite, that contributes up to 91% of the organic matter content, serves as an important characteristics for carbonization and liquefaction processes of coal [30]. Interestingly, this high value of reactive macerals is in accord with the value suggested by Van Krevelen [31], under the reactivity parameter group to characterize coal for direct liquefaction. It is also known that the vitrinite and liptinite can be extracted readily, which makes the extraction yield correlate broadly with its content [31].

### **3.3. Thermal behavior of Mukah Balingian coal**

Another important characteristic of MB coal is the thermal behavior of decomposition under pyrolysis conditions via thermogravimetric analyser (TGA). The pyrolysis of raw MB coal via TGA at a heating rate of 20 °C min-1 is shown in Figure 3. The TG curve (Figure 3(a)) of the raw coal shows the weight loss profile with the weight decreasing as temperature is increased from ambient to 1000 °C. The weight loss profile resembles that of a first-order reaction.

**Figure 3.** (a) TG and (b) DTG profiles for the thermal decomposition of pyrolysed raw MB coal [29].

Figure 3 (b) shows the differential weight loss (DTG) for the raw MB coal that consists of three main stages. This conforms to previous findings as reported by Probstein and Hicks [32], Kastanaki et al. [33], Serio et. al. [34] and Radovic et al. [35]. The first-stage pyrolysis, which occurs at temperatures ranging from ambient to 150 °C, involves the dehydration of water and releasing of gas composed of oxides of carbon from the coal. The second-stage pyrolysis, which occurs at temperatures of 200 – 550 °C, however, is due to the release of volatile matter such as hydrocarbon gases, light oils and tars, and is of interest in this study. Finally, the third-stage pyrolysis shows the appearance of some minor curves at temperatures ranging from 550 to 650 °C and from 700 to 800 °C, that were attributed to the release of heavier hydrocarbons and non-condensable gases, mainly hydrogen, and from thermal decomposition of carbonates that are abundant in low rank coals.

Also, from the DTG profile of the raw MB coal, it can be estimated that the softening temper‐ ature of this coal is around 350 °C. Merrick [36] suggested that with extraction using liquid solvents, the preferred extraction temperatures lie in the range where the coal starts to decompose thermally, and typically, the extraction is carried out at about 350 – 450 °C. Moreover, Van Krevelen [30] suggested that temperatures around 350 °C were found to be an indicative value for softening temperature in order to characterize coal for direct liquefaction. Thus, it can be suggested that MB coal would be a good feedstock and suitable for liquefaction and/or gasification processes and, hence, optimize the utilization of low rank Malaysian coal.

### **3.4. Potential of Mukah Balingian coal for liquefaction**

Moreover, the petrographic analysis shows that the composition of the coal is dominated by vitrinite that constitutes about 60% by volume of the whole rock, with 31% liptinite (formerly known as exinite), 8% inertinite and 1% mineral matter. Pyrite, however, is present in trace amount. The high content of reactive macerals, i.e., vitrinite and liptinite, that contributes up to 91% of the organic matter content, serves as an important characteristics for carbonization and liquefaction processes of coal [30]. Interestingly, this high value of reactive macerals is in accord with the value suggested by Van Krevelen [31], under the reactivity parameter group to characterize coal for direct liquefaction. It is also known that the vitrinite and liptinite can be extracted readily, which makes the extraction yield correlate broadly with its content [31].

Another important characteristic of MB coal is the thermal behavior of decomposition under pyrolysis conditions via thermogravimetric analyser (TGA). The pyrolysis of raw MB coal via TGA at a heating rate of 20 °C min-1 is shown in Figure 3. The TG curve (Figure 3(a)) of the raw coal shows the weight loss profile with the weight decreasing as temperature is increased from

ambient to 1000 °C. The weight loss profile resembles that of a first-order reaction.

**Figure 3.** (a) TG and (b) DTG profiles for the thermal decomposition of pyrolysed raw MB coal [29].

Figure 3 (b) shows the differential weight loss (DTG) for the raw MB coal that consists of three main stages. This conforms to previous findings as reported by Probstein and Hicks [32],

**3.3. Thermal behavior of Mukah Balingian coal**

192 Biofuels - Status and Perspective

In predicting potential conversion of coal, Guyot [37] investigated the relationship between coal properties and liquefaction potential. Guyot introduced a useful correlation called "petrofactor", which derived from the correlations containing terms of factors based on the maceral composition and the maximum reflectance of vitrinite (as shown by Equation 1). A wide rank of coals ranging from brown coal, high-, medium- and low-volatile bituminous coals have been used to obtain potential conversion for all coals, where –2.5 was obtained from the slope of the correlation. The maximum reflectance of vitrinite functions as a rank parameter, whilst the reactive maceral content as the petrological parameter. Usually, the reactive maceral content is considered to be equal to the sum of vitrinite and liptinite. Figure 4 shows the correlation of potential coal conversion with petrofactor as suggested by Guyot [37], and the estimated coal conversion was approximated based on formula in Equation 2.

$$\text{Petrofactor} = 1000 \times \frac{\text{Maximum reflector of vitroite} \left(\%\right)}{\text{Total reactive material content} \left(\%\right)}\tag{1}$$

$$\text{Coal conversion} = 100 - 2.5 \times \text{Petrofactor} \tag{2}$$

The potential conversion of raw MB coal during liquefaction could be estimated using the "Petrofactor" proposed by Guyot [37] (refer Equations 1 and 2). The petrofactor value for the raw MB coal is calculated from Equation 1 and the potential conversion is then estimated using Equation 2. Table 3 shows the results of petrofactor value and estimated coal conversion of

**Figure 4.** Correlation of coal conversion with petrofactor [37].

raw MB coal. Thus, based on Equation 2, it is estimated that about 89% of raw MB coal would be converted during liquefaction process.


**Table 3.** Petrofactor value and estimated conversion of raw MB coal [29].
