Mutahharah M. Mokhtar

Understanding selected trace elements behavior in a coal-fired power plant in Malaysia for assessment of abatement technologies

The Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft), which replaces the Malaysia Environmental Quality (Clean Air) 1978, specifies limits to additional pollutants from power generation using fossil fuel. The new pollutants include Hg, HCl, and HF with limits of 0.03, 100, and 15 mg/N-m3 at 6% O2, respectively. These pollutants are normally present in very small concentrations (known as trace elements [TEs]), and hence are often neglected in environmental air quality monitoring in Malaysia. Following the enactment of the new regulation, it is now imperative to understand the TEs behavior and to assess the capability of the existing abatement technologies to comply with the new emission limits. This paper presents the comparison of TEs behavior of the most volatile (Hg, Cl, F) and less volatile (As, Be, Cd, Cr, Ni, Se, Pb) elements in subbituminous and bituminous coal and coal combustion products (CCP) (i.e., fly ash and bottom ash) from separate firing of subbituminous and bituminous coal in a coal-fired power plant in Malaysia. The effect of air pollution control devices configuration in removal of TEs was also investigated to evaluate the effectiveness of abatement technologies used in the plant. This study showed that subbituminous and bituminous coals and their CCPs have different TEs behavior. It is speculated that ash content could be a factor for such diverse behavior. In addition, the type of coal and the concentrations of TEs in feed coal were to some extent influenced by the emission of TEs in flue gas. The electrostatic precipitator (ESP) and seawater flue gas desulfurization (FGD) used in the studied coal-fired power plant were found effective in removing TEs in particulate and vapor form, respectively, as well as complying with the new specified emission limits. Implications: Coals used by power plants in Peninsular Malaysia come from the same supplier (Tenaga Nasional Berhad Fuel Services), which is a subsidiary of the Malaysia electricity provider (Tenaga Nasional Berhad). Therefore, this study on trace elements behavior in a coal-fired power plant in Malaysia could represent emission from other plants in Peninsular Malaysia. By adhering to the current coal specifications and installation of electrostatic precipitator (ESP) and flue gas desulfurization, the plants could comply with the limits specified in the Malaysian Department of Environment (DOE) Scheduled Waste Guideline for bottom ash and fly ash and the Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft).

Measurement of PCDD/Fs emissions from a coal-fired power plant in Malaysia and establishment of emission factors

This paper presents the PCDD/Fs emissions measured from a coal–fired power plant in Malaysia. The study discusses partitioning of PCDD/Fs in particle and gas phase, effects of coal quality to PCDD/Fs formation, effects of air pollution control device (APCD) configuration to PCDD/Fs formation and establishment of emission factors of PCDD/Fs from the studied coal–fired power plant. The results presented in this study were mostly in good agreement with the previous works on PCDD/Fs emissions conducted in other countries. Laboratory analysis results showed that PCDFs were the dominant congeners. The emissions of PCDD/Fs were low which most probably due to the high combustion efficiency. The PCDFs/PCDDs ratio was more than 1 and PCDD/Fs were detected in fly ash, hence speculating that the formation of PCDD/Fs during coal combustion was mainly through de novo synthesis. Analysis on partitioning of PCDD/Fs showed that the compounds were mainly emitted in gas phase. This study also indicated that type of coal influenced the formation of PCDD/Fs during coal combustion where bituminous coal with high sulfur (S) content resulted in slightly lower PCDD/Fs emissions compared to sub–bituminous coal. It was also found that operation of flue gas desulfurization (FGD) reduced the emission of PCDD/Fs. The established emission factors for PCDD/Fs were in the range of 0.08 to 0.11 ng I–TEQ/kg.

Decision analysis of multi-pollutant control strategy for coal-fired power plant in Malaysia

The promulgation of Environmental Quality (Clean Air) Regulations 2014 on emissions from coal-fired power plants in Malaysia has prompted power plant operators to adopt emission control strategy that complies with the new emission limits. Currently, various emission control strategies are available to achieve the desired emission level. Each strategy offers unique advantages and disadvantages, depending on the objective of emissions control, process nature, and constraints on the resources incurred. To address this challenge, a proper decision-making analysis needs to be performed. In this paper, a systematic decision analysis methodology is proposed to select the most effective multi-pollutant control strategy that is compatible for coal-fired power plants in Malaysia. The methodology includes: (1) identification of pollutant emission from the plant under study and comparison with the stipulated emission limits, (2) establishment of emission factors, (3) selection of multi-pollutant control strategy, (4) identification of emission reduction factor for the pollutants and control technologies of interest, (5) determination of emission level from the selected multi-pollutant control strategy, and (6) prediction of ground-level concentration of pollutants. The decision analysis methodology is applied to a real case study of coal-fired power plant in Malaysia, which also currently faces a dilemma to comply with the additional and more stringent emission limits stipulated in the Environmental Quality (Clean Air) Regulations 2014. The proposed method is applicable for both the process concept under the design phase as well as the existing process plant.

Comparison of pollutant ambient concentration from two air pollution control (APC) strategies in coal-fired power plant

n this paper, ambient concentrations of Hg and dioxins/furans from two air pollution control (APC) strategies are compared. The strategies include the existing APC strategy at the studied coal - fired power plant (CFPP) and the proposed APC strategy for compliance with parameters in the Environmental Quality (Clean Air) Regulations (CAR) 201 4. The former system consists of electrostatic precipitator (ESP) and flue gas desulphurisation (FGD) which are commonly employed in CFPP in Malaysia, whereas the latter consists of activated carbon injection (ACI), fabric filter (FF) and FGD. It was found that the emissions under the proposed APC strategy of ACI + FF+ FGD have higher margin of limits compared to the existing APC strategy of ESP + FGD. The emissions values were then used as input in AERMOD to predict the ambient concentrations of pollutants . The findings show that the ambient concentrations of Hg and dioxins/furans from both strategies are well below the ambient guideline values, with those emitted from the proposed APC strategy are so low to the point that they are negligible.

Environmental assessment of ashes generated from medical waste incineration

The nature of medical waste itself, which comprises of human pathological waste, items saturated or dripping with human blood, hypodermic needles etc. poses serious health threat to community, especially concerning spreading of infectious diseases, as well as causing pollutions to the environment. Incineration is one of the technologies adopted in many part of the world in dealing with medical wastes. However the process emits pollutants including toxic heavy metals, which are dispersed via the incineration stack, either vented directly to the atmosphere or are emitted after going through treatment in air pollution control unit. Meanwhile the remaining heavy product is concentrated into bottom and fly ash residues which are normally present in very small concentration or known as trace elements (TEs). This study was conducted to determine the concentration of TEs in bottom ash and fly ash of medical waste incinerator plant in Malaysia. In addition, it is a vital to understand the TEs behaviour and to assess the capability of the existing air pollution control (APC) technologies in Malaysia to comply with the new emission limits of the Environmental Quality (Clean Air) Regulation 2014 which replaces the Malaysia Environmental Quality (Clean Air) 1978. In this study, the APC designed with the electrostatic precipitator (ESP), fabric filter and spray scrubber with limestone were comply with the new specified emission limits but it need further improvement to improve the efficiency. The comparison of TEs behaviour in term of volatility; most volatile element (Hg) and less volatile element (Cr, Cd, As, Pb) in fly ash and bottom ash was also presented in this paper. The study showed that the samples of bottom ash and fly ash enriched of heavy metals of Pb, followed by As, Cd, Cr, and Hg. In environmental assessment, all of these TEs are found to be well below the Malaysian Department of Environment (DOE) Scheduled Waste Guideline limits except for Pb in fly ash which is above the emission limits. It is indicated that behaviour of TEs is related to TEs concentration in ash. In addition, the concentration of TEs also influenced the emission of TEs in flue gas.

Characterization of Total Particulate Emission for Palm Oil Mill Boiler

In Malaysia, more than four million hectares of land is used for oil palm cultivation. Malaysia palm oil industry has grown to become a very important biomass-based industry. This study investigates the emission from a palm waste biomass fired boiler of two studied palm oil mill plants – named as Plant A and Plant B. The finding shows that the total particulate emission of Plant A is 4,242 mg/Nm3- exceeding the emission limit specified by the Department of Environment Malaysia (DOE) by 960%, while the average total particulate emission of Plant B was 851 mg/Nm3 (exceeds the limit by 113%). This study also performed more detailed measurements on the emissions of PM10 and PM2.5 in Plant B. It was found that the emitted PM10 and PM2.5 is not significant compared to the total particulate emission in this plant, since both are less than 20% of the total particulate emission.