Title Indonesian Journal of Environmental Management and Sustainability e-ISSN:2598-6279 p-ISSN:2598-6260 Research Paper Emission and Heavy Metal Content Characteristic of Densified Refused Derived Fuels of Oil Sludge and Biomass Combination as an Alternative Fuel for Cement Plant Rati Yuliarningsih1*, Fadjar Goembira1, Puti Sri Komala1, Nino Perdana Putra2 1Master Program of Environmental Engineering, Universitas Andalas, Padang-West Sumatera, Indonesia 2Clinker Production Department, Semen Padang, Padang-West Sumatera, Indonesia *Corresponding author e-mail: ratiyuliarningsih12@gmail.com Abstract Hazardous Waste such Oil Sludge combined with biomass (coconut shell and rice husk) was utilized as an alternative fuel in cement plant in form of Densified-Refused Derived Fuel (D-RDF). D-RDF were Co-Processed with primary fuel into Rotary Kiln in order to reduce usage of fossil fuel and eliminate the hazardous waste by thermal treatment, meanwhile to recover the energy contained in the D-RDF, the utilization of these waste are expected without causing adverse effect into the environment. Co-Processing of D-RDF as alternative fuels into cement plant kiln must follow the regulation applied in Indonesian Environment and Forestry Minister regulation 19/2017 and European Union for Responsible Incineration and Treatment of Special Waste (EURITS). Based on previous research, D-RDF composition of oil sludge and biomass at 1:1 ratio with 5% starch addition was choose as they give best calorific value at 6000 kcal/kg. The objectives of this research are to observe the emission caused by the utilization of these D-RDF and potential effect into cement or clinker product. The result show NOx and CO value are meet the standard requirement by government regulation meanwhile SO2 value which are 1251 mg/Nm3 and 1500 mg/Nm3, over the regulation standard which is 650 mg/Nm3. This issue could be overcome in the plant with pretreatment of D-RDF and utilization of Bag House Filter or Electrostatic Precipitator before release the emission to the stack. Trace element analysis of D-RDF ashes (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se, Sn dan Zn) show the result are meet the EURITS regulation, which mean utilization of D-RDF will not give quality defect to cement or clinker product Keywords Emission, Oil Sludge, Biomass, Hazardous Waste, D-RDF Received: 27 Agustus 2019, Accepted: 26 September 2019 https://doi.org/10.26554/ijems.2019.3.3.100-105 1. INTRODUCTION The cement production process is an intensive thermal pro- cess because it requires high temperatures in the clinkeriza- tion process so it requires a lot of fuel. The cement industry uses 20 – 40 % of the total production cost as fuel cost (Hajinezhad et al., 2016). To reduce dependence on fossil fuels, efforts have been made to substitute fuels with alter- native fuels through a co-processing process with the use of waste and biomass. One of alternatives energy available and considered by PT Semen Padang is the use of oil sludge waste, which received from PT Pertamina in the range of 20 tons/month to be destroyed in a rotary kiln in the cement plant. Oil sludge is a solid waste in the form of black mud or paste, sometimes mixed with soil, gravel, water and other materials produced from the refining process, distribution process and petroleum storage tanks. Oil sludge contains hydrocarbon compounds such as benzene, toluene, ethyl benzene, xylenes, and heavy metals (Hu et al., 2013). Utilization of oil sludge as fuel must meet emission- quality standards in accordance with the Indonesian Environ- ment and Forestry Minister regulation 19/2017, meanwhile the trace element of D-RDF must meet the quality stan- dards of the European Union for Responsible Incineration and Treatment of Special Waste (EURITS) for utilization of waste co-incineration in cement kilns. A large number of environmental feasibility tests have been carried out to un- derstand the characteristics of emissions and ash by burning D-RDF as fuel in mass combustion. To our knowledge, there has been little research on the utilization of oil sludge as an alternative fuel in cement production. In addition, there are only a few studies on the effects of various modes of adding oil sludge on clinker https://doi.org/10.26554/ijems.2019.3.3.100-105 Yuliarningsih et. al. Indonesian Journal of Environmental Management and Sustainability, 3 (2019) 100-105 quality (Huang et al., 2017). Biomass can be considered as an almost CO2 neutral fuel (Hughes, 2000), although there are still emissions associated with harvesting, transportation, pre-treatment, etc. In addi- tion, biomass combustion prevents the release of methane (CH4) from residues, considering that CH4 has a 21 times higher effect as a potential cause of global warming com- pared to CO2. In addition, alkaline ash from biomass can capture some CO2 gas from burning (Saidur et al., 2011). Most biomass fuels contain less sulfur. Therefore, co- firing with coal usually results in lower SO2 emissions (Ren et al., 2017). NOx emissions arise from atmospheric nitrogen and from nitrogen-bound fuels, which are released during the volatilization and char oxidation phases. The release of volatile substances from biomass combustion is higher than that of coal, and during this phase, the nitrogen in the fuel is volatilized into the flame as volatile matter (Lau and Niksa, 1993). Inside the flame, nitrogen bound to biomass mostly forms NH3 instead of HCN which is usually formed by nitrogen coal, and this can help prevent the formation of NOx in flames (Hein and Spliethoff, 1999). Previous studies on coal combustion and rice husk jun XIE et al. (2007) reported that in the use of coal ratio remained the same and addition amount of biomass into the mixture will reduced NO emissions but slightly increased SO2 emissions. NO reduction is associated with a lower terminal velocity of rice husk particles than coal particles, due to differences in density (Fang et al., 2004). Other research was combines coal and Municipal Solid Waste (MSW) into Circulating Fluidized Bed (CFB) (Desroches-Ducarne et al., 1998). The results showed that acid gas flue increased as the proportion of MSW increased, and, further, SOx decreased because the amount of HCl in the flue gas increased. Figure 1. (a) D-RDF(A) dan (b) D-RDF(B) In this study, D-RDF consisting of oil sludge and biomass waste is burned in the furnace to investigate the feasibility of burning D-RDF emissions. The properties of volatile matter, ash content, pollutant emissions and metal content for various fuel ratios are analyzed and discussed in this study. 2. EXPERIMENTAL SECTION 2.1 Materials For the manufacture of D-RDF in this study, oil sludge is mixed with two types of biomass wastes, which are coconut shell powder and rice husk. The D-RDF sample can be categorized into two groups namely D-RDF (A) containing oil sludge, coconut shell powder, and 5% starch and D-RDF (B), where coconut shell powder is replaced with rice husk. For the characteristics of D-RDF raw materials can be seen in Table 1. 2.2 Equipment and Experimental In this study, the D-RDF was produced using oil sludge as a base material and combined with coconut shell powder or rice husk with a composition of 1:1, then 5% starch is used as an adhesive to bind the raw materials. Further, raw materials are mixed in a mixer and then feed into pelletizer machine to form D-RDF. The D-RDF forms produced were cylindrical with a length of 10-16 mm, and a diameter of 5 mm. For visual form of combination of D-RDF (A) and D-RDF (B) can be seen in Figure 1. Figure 2. D-RDF Emission Measurement Scheme To measure CO, SO2, NOx emissions from this D-RDF, it is carried out with a combustion scheme as shown in Figure 2. Probes from the Portable Gas Emissions Analyzer are inserted into the stack furnace. 1 gram D-RDF proto- type was burned in the Furnace for 1 minute. The furnace temperature is set at a temperature of 1000 oC then Gas SO2, NOx, and CO, CO2, measured by the Gas Emission analyzer directly and the value (ppm) will be seen on the screen of the Gas emission analyzer. The D-RDF residue after combustion then analyzed for their metal content using a Shimadzu ICPE 9000TM tool. The results of the emissions analysis and metal content are compared with quality stan- dards in the Indonesian Environment and Forestry Minister regulation 19/2017 and EURITS. 2.3 Methods Test of calorific value of raw materials and D-RDF was car- ried out using the Calorimeter Bomb tool with the ASTM D 2015: Standard Test Method for Gross Calorific Value of Solid Fuel by the Adiabatic Bomb Calorimeter. Moisture content, ash content, volatile matter, and fixed carbon con- tent were measured using ASTM D3173 standard methods. Ultimate analysis using Thermo scientific CHNS / O tools with ASTM method D5373-16: Determination of Carbon, © 2019 The Authors. Page 101 of 105 Yuliarningsih et. al. Indonesian Journal of Environmental Management and Sustainability, 3 (2019) 100-105 Table 1. D-RDF Raw Material and Additive Characteristic Parameter Unit Raw Material Additive Oil Sludge Coconut Shell Rice Husk Starch Proximate Analysis Moisture % 34.88 10.94 10.83 13.94 Volatile Matter % 76.13 68.08 57.44 81.39 Ash Content % 3.14 1.55 18 0.116 Fixed Carbon % 1.17 19.8 14.34 3.52 Calorific Value kcal/kg 6298.86 4333.97 3381.91 3528.22 Ultimate Analysis (% dry basis) Carbon (C) % 74.49 50.04 41.17 39.91 Hydrogen (H) % 12.4 6.33 5.63 6.78 Nitrogen (N) % 0 0.11 0.3 0 Oksigen (O) % 8.73 41.97 35.04 50.24 Sulfur (S) % 0.62 0.12 0.1 0.15 Table 2. Air emission limits at cement plants that imple- ment hazardous waste co-processing based on regulation applied. Parameter Unit Quality Standard CO mg/Nm3 3000 SO2 mg/Nm3 650 NOx mg/Nm3 800 (Source: Indonesian Environment and Forestry Minister Regulation 19/2017) Hydrogen, and Nitrogen in Analysis of samples of Coal and Coke for measuring C, H, and N content. ASTM D 4239-17: Sulfur in the Analysis Sample of Coal and Coke is used to measure S content and ASTM D 3176-16: Ultimate Analysis of Coal and Coke is used to measure O content. Analysis of metal content in waste oil sludge was carried out using ASTM D7260-19: Standard Practice for Optimiza- tion, Calibration, and Validation of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) for Ele- mental Analysis of Petroleum Products and Lubricants. The oil sludge sample is dissolved first using an acid digestion method (Nitric acid), then the solution will be analyzed by ICP-AES which will measure the energy intensity of radi- ation emitted by the elements that experience changes in atomic energy levels (excitation or ionization). In Indonesia, cement plants that utilize RDF co-processing and other hazardous wastes are subject to regulations is- sued by the Indonesian Environment and Forestry Minister regulation 19/2017 which sets CO, SO2, and NOx emission limits as shown in Table 2. The term trace element heavy metal has been used exten- sively as a term that describes the shape of certain metals. Based on research Yang et al. (2019), the characteristics of the heavy metal group are as follows: Table 3. Physical Characteristic of D-RDF Parameter Unit D-RDF Combination D-RDF(A) D-RDF (B) Density g/cm3 0,9562 0,7466 Length mm 15 10 Diameter mm 5 5 Drop test % 94 77 • Has very large specific gravity (more than 4) • Has atomic numbers 22-34 and 40-50 as well as lan- thanide and actinide elements • Has a specific (specific) biochemical response to living organisms. Unlike ordinary metals, heavy metals usually have spe- cial effects on living things. It can be said that all heavy metals can be toxic materials that will poison the bodies of living things. Examples are mercury metal (Hg), cadmium (Cd), lead (Pb) and chromium (Cr). In general, trace ele- ments will enter the clinker in several forms: (1) In solid solutions with various phases of calcium silicate and calcium aluminate; (2) As a substitute atom that can damage the crystal structure of these phases, such as when cobalt re- places aluminum in AFm; (3) Physically adsorbed on the surfaces of various phases as insoluble hydroxides, sulfates, or carbonates; and (4) As a precipitated mineral that is mixed with the final product, such as when molybdenum is formed forming powellite (CaMoO4) at relatively high concentration of molybdenum (Horsley et al., 2016). The quality of the final product such as clinker and cement must be controlled in accordance with applicable national or international quality standards. In principle, RDF co-processing should not reduce the quality of cement produced, where clinkers cement or concrete produced may not be used as a heavy metal dump. Apart from that, there © 2019 The Authors. Page 102 of 105 Yuliarningsih et. al. Indonesian Journal of Environmental Management and Sustainability, 3 (2019) 100-105 Table 4. Chemical Characteristic of D-RDF Parameter Unit D-RDF Lignitec D-RDF (A)a D-RDF (B)b Moisture % 9,8 11,25 - Volatile Matter % 73,91 69,15 49,9 Ash Content % 2,99 12,49 11,5 Fixed Carbon % 13,33 7,11 38,6 Calorific Value kcal/kg 6413,17 6063,38 6 Carbon (C) % 66,4 52,2 63,92 Hydrogen (H) % 8,65 7,19 4,25 Oksigen (O) % 21,56 20,38 17,71 Nitrogen (N) % 0,03 0,01 1,51 Sulfur (S) % 0,32 0,22 1,11 Note : D-RDF (A) = oil sludge : coconut shell (1:1) ; D-RDF (B) = oil sludge : rice husk (1:1) ; Source : (Yanik et al., 2018) should be no negative impact on the environment. 3. RESULTS AND DISCUSSION 3.1 Physical Characteristic of D-RDF Combination Physical characteristics of D-RDF combination; D-RDF (A) and D-RDF (B) can be seen in Table 3. Based on Table 3 it can be seen that both combination of D-RDF (A) (oil sludge: coconut shell) and D-RDF (B) (oil sludge : rice husk) have similar diameter and the length are in range 10 – 15 mm. By observing the density and drop test value it show that D-RDF (A) has better physical characteristics when compared to the D-RDF (B) because it more solid and compact. 3.2 Chemical Characteristic of D-RDF Combination As a comparison to these D-RDF the chemical properties of lignite coal from the previous research Yanik et al. (2018) as shown in Table 4. While compared to Nitrogen and Sulfur content of Lignite, both combination shows that Nitrogen and Sulfur content are below lignite. These are mean that the source of NOx and SO2 formation from combustion are lower than what lignite potentially contributes. While compared sulfur sources (S) from oil sludge as raw material that is equal to 0.62%, Sulfur (S) values in both D-RDF variations tend to be smaller because the addition of biomass (coconut shell and rice husk) are reducing S content within the D-RDF. 3.3 Emission from Combustion In all cement plants, whether using D-RDF or not, dust (particulate), CO, NOx, and SO2 emissions are the main emissions that need to be addressed. 3.4 Carbon Monoxide (CO) In this study, CO combustion values from D-RDF variations and compare with lignite combustion emission can be seen in Figure 3. In the combustion of these D-RDF variations, it can be seen that CO from the D-RDF (A) value indicates as the highest value when compared with other composi- tions. However, both compositions of D-RDF (A) and (B) in regards to CO emission are meeting the applicable quality standard. CO gas is formed due to lack of oxygen in the combustion process, imperfect mixing between oxygen and fuel in the combustion chamber and rapid cooling of the combustion product to lower than the ignition temperature of CO gas so that incomplete combustion occurs. CO can be formed accidentally and anywhere in the kiln system. CO gas emissions usually indicate fuel that is partially burned and not fully utilized. Figure 3. CO Emission of D-RDF and Lignite Figure 3.5 Sulfur Dioxide (SO2) SO2 emission from D-RDF and lignite combustion could be seen in Figure 4. Sulfur dioxide (SO2) is the result of oxidation of sulfides or sulfur elements contained in fuels during combustion and this gas is colorless with a sharp odor. The emission range depends on the content of volatile sulfur compounds in the raw material; mostly below 300 mg / Nm3; although sometimes up to 3000 mg / Nm3 (UNEP, 2011). Indirect combustion, SO2 emissions of lignite coal showed the highest value of 16,588 mg / Nm3 when compared with © 2019 The Authors. Page 103 of 105 Yuliarningsih et. al. Indonesian Journal of Environmental Management and Sustainability, 3 (2019) 100-105 other D-RDF compositions. However, based on government quality standards through the Minister of Environment and Forestry Regulation of the Republic of Indonesia, Number 19/2017, all samples both D-RDF and coal all show values above the applicable quality standard of 650 mg / Nm3 as shown in Figure 4. Figure 4. Comparison of SO2 Emissions from D-RDF Composition with Lignite Coal To reduce SO2 content, several methods can be used including (Horkoss, 2008): • Reduction of Sulfur content, based on the goal of a substitution strategy by reduces inputs to reduce output. • Optimizing the clinker combustion process, conducted to reduce heat consumption, to improve clinker quality and to increase equipment life. SO2 emission reduction is only a side effect of optimization. • Adding Ca(OH)2 to the upper stage preheater, in order as an SO2 absorbing reagent, hydrated lime can be injected into the right location in the upper stage preheater where hydrated lime reacts with SO2 directly. 3.6 NOx Emission For NOx value from D-RDF and lignite combustion could be seen in Figure 5. Nitrogen Oxide (NOx) is a group of nitrogen gases found in the atmosphere consisting of Ni- trogen Monoxide (NO) and Nitrogen Dioxide (NO2). Air pollution by NOx gas can cause the emergence of Peroxy Acetyl Nitrates which is abbreviated with PAN. Peroxy Acetil Nitrates causes irritation in the eyes which causes the eyes to feel sore and runny. In combustion units, nitrogen oxides (NOx) mainly arise from three sources, namely, ther- mal, prompt, and fuel sources. The formation of NOx is one of the major concerns because its emission would fur- ther induce acid rain, photochemical smog, and even health hazards (Li et al., 2018). Based on Figure 5, the standard quality of NOx value is 800 mg / Nm3 meanwhile the results for D-RDF (A) and D- RDF (B) are still far below the applicable quality standards which are 143 mg / Nm3 and 69 mg / Nm3, respectively. This is due to the low content of Nitrogen (N) composition ranging from 0.01 to 0.03%. When compared to lignite coal, the NOx emission caused by lignite is higher, this is due to the lignite coal its nitrogen content is quite high at 1.51%. Figure 5. Comparison of NOx Emission from D-RDF Composition with Lignite Coal 3.7 Heavy Metal Content of D-RDF Ash For the results of trace element analysis of heavy metals of D-RDF (A) and D-RDF (B) can be seen in Table 5. The results of both D-RDF for heavy metal content analysis were compared with the quality standard in fuels according to EURITS shows that there was no heavy metal in the D- RDF that exceeded the specified quality standard. Whereas in other studies Edo et al. (2017) with the composition of Demolition and Construction Wood (DC): RDF, it was found that there was an analysis of metal content that exceeded the applicable metal content, namely for As and Pb metals. This result shows that D-RDF from the of oil sludge: biomass waste combination is considerable suitable as an alternative fuel in cement industry. 4. CONCLUSIONS In this study, an observation was made for the emissions resulting from the utilization of D-RDF mixture of oil sludge and biomass as an alternative fuel in the Cement Industry as well as the metal content of combustion residual ash. The results of this study are compared with the use of lignite coal as the main fuel for combustion in the Cement Industry. the CO content shows that both D-RDF have higher emission values than lignite, but still meet the applicable quality standards. Both of SO2 content of D-RDF even though it is above the quality standard but is far below the result of lignite combustion, this is will make the workload of emission control devices such as ESP and Bag House Filters will be lower to reduce levels of SO2 emissions in the utilization of D-RDF compared to lignite utilization. In the case of NOx content, both D-RDF and lignite show that NOx emission values are meet applicable emission standards. The content of the combustion ash metal shows that the D-RDF metal content meets applicable quality standards. Meaning that the utilization of D-RDF as an alternative fuel will not affect the quality of the clinker and cement produced. © 2019 The Authors. Page 104 of 105 Yuliarningsih et. al. Indonesian Journal of Environmental Management and Sustainability, 3 (2019) 100-105 Table 5. Analysis of D-RDF (A) and D-RDF (B) heavy metal content Parameter Unit Standarda D-RDF (A) D-RDF (B) As mg/L 10 0,0238 0,0227 Cd mg/L 10 0,0340 0,0354 Co mg/L 200 0,126 0,131 Cr mg/L 200 0,047 0,049 Cu mg/L 200 0,044 0,047 Hg mg/L 2 0,078 0,087 Mn mg/L 200 0,052 0,055 Ni mg/L 200 0,024 0,021 Pb mg/L 200 0,023 0,022 Se mg/L 10 0,021 0,02 Sn mg/L 200 0,054 0,054 Zn mg/L 500 0,289 0,30 REFERENCES Desroches-Ducarne, E., E. Marty, G. Martin, and L. Delfosse' (1998). Co-combustion of coal and municipal solid waste in a circulating fluidized bed. Fuel, 77(12); 1311–1315 Edo, M., N. Skoglund, Q. Gao, P.-E. Persson, and S. Jansson (2017). Fate of metals and emissions of organic pollutants from torrefaction of waste wood, MSW, and RDF. Waste Management, 68; 646–652 Fang, M., L. Yang, G. Chen, Z. Shi, Z. Luo, and K. Cen (2004). Experimental study on rice husk combustion in a circulating fluidized bed. 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Page 105 of 105 INTRODUCTION EXPERIMENTAL SECTION Materials Equipment and Experimental Methods RESULTS AND DISCUSSION Physical Characteristic of D-RDF Combination Chemical Characteristic of D-RDF Combination Emission from Combustion Carbon Monoxide (CO) Sulfur Dioxide (SO2) NOx Emission Heavy Metal Content of D-RDF Ash CONCLUSIONS