1. INVESTIGATION OF THE BEHAVIOUR OF LAFIA-OBI COAL IN A FLUIDIZED BED COMBUSTION CHAMBER O.T. POPOOLA and A. A. ASERE Department of Mechanical Engineering, Faculty of Technology, Obafemi Awolowo University, Ile-Ife, Nigeria. OAUTekCONF 2011 Faculty Of Technology Conference

2. INTRODUCTION 5/25/20162

3. General Background There is a large deposit of coal in the middle belt and eastern part of the Nigeria which remains underexploited. The coal reserves in Nigeria are estimated to be in excess of 2.5 billion tonnes. Available data show that Nigerian coals are mainly sub-bituminous steam except for the Lafia-Obi bituminous coal Coal is a major source of energy. Coal has played this important role for centuries – not only providing electricity, but also as an essential fuel for steel and cement production, and other industrial activities. The value of coal is partially offset by the environmental impacts of coal combustion. 5/25/20163

4. Geological Map of Nigeria indicating Lafia Obi coal area 5/25/20164

5. General Background cont. Fluidized Bed Combustion is a Clean Coal Technologies that: effectively and inexpensively combust low-grade coals with high content of moisture (≤60%), ash (≤ 70%) and Sulphur (≤ 10%), achieve high combustion efficiency (>99%); achieve boiler flexibility with type and quality of coal; provide effective environmental protection from SO 2, NO x and solid particles (SO2 < 400mg/m 3, N0 x < 200 mg/m 3, solid particles < 50 mg/m 3 ); achieve a wide range of load turndown ratio (20-100%); and 5/25/20165

6. Pressurized fluidized Bed combined cycle for electricical power generation using coal (Sambo,2009) 5/25/20166

7. The objectives of this study are to : investigate the effect of Lafia-Obi coal particle sizes on combustion bed temperature; determine the effects of the coal particle sizes and combustion temperature on emission characteristics; and evaluate the coal ash content at various operating conditions. 5/25/20167

8. This study covers the combustion of Lafia-Obi coal in a fluidized bed with the view to generate electricity. Emphasis will be on variation of coal combustion feed size at varying coal combustion feed rate and The resultant effects on combustion bed temperature, NO x, CO and rate of ash generation will be measured and analyzed. 5/25/20168

9. METHODOLOGY 5/25/20169

10. PRELIMINARY LABORATORY STUDIES Raw Material Acquisition and Handling Sample Preparation Determination of Physical Characteristics 5/25/201610

11. PROXIMATE ANALYSIS Volatile Matter Moisture Content Fixed Carbon Ash Content 5/25/201611

12. ULTIMATE ANALYSIS Hydrogen Content Carbon Content Nitrogen Content Sulfur Content Oxygen Content 5/25/201612

13. FUEL PREPARATION Sun Drying Separation Crushing(using hammer mill) Sieving (using ISO standard sieve set) 5/25/201613

14. 5/25/2016145/25/201614

15. Summary of ASTM international standards used in investigation S/NDesignationTitle 1D5192 – 09Standard Practice for Collection of Coal Samples 2D2013/D2013M – 09Standard Practice for Preparing Coal Samples for Analysis 4D3172 – 07aStandard Practice for Proximate Analysis of Coal and Coke 5D3302/D3302M – 10Standard Test Method for Total Moisture in Coal 6D3175 – 07Standard Test Method for Volatile Matter in the Analysis Sample of Coal and Coke 7D3174 – 04Standard Test Method for Ash in the Analysis Sample of Coal and Coke from Coal 5/25/201615

16. Summary of ASTM international standards used in investigation cont. 8D5373 – 08Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Laboratory Samples of Coal 9D 3179 – 02Standard Test Methods for Nitrogen in the Analysis Sample of Coal and Coke 10D 3178 – 89 (Reapproved 2002) Standard Test Methods for Carbon and Hydrogen in the Analysis Sample of Coal and Coke 11Designation: D3177 – 02 (Reapproved 2007) Standard Test Methods for Total Sulfur in the Analysis Sample of Coal and Coke 5/25/201616

17. COMBUSTION 5/25/201617 Fig. 1 Experimental Setup

18. COMBUSTION 5/25/201618

19. DATA COLLECTION Temperature- 6 Chromel-Alumel Thermocouples and 6-channel digital readout were used to measure the variations in the combustion bed and freeboard temperatures. The temperature along the height of the atmospheric reactor was taken at distances of 2, 10, 40, 60 and 80 cm above the gas distributor The composition of the flue gas at the various conditions was determined using a gas analyzer. The ash and fragmented coal particles content of the extracts after quenching at different operation conditions were tested and classified. A U-tube manometer was used to measure the pressure drop through the bed. Air was supplied by a 4hp centrifugal blower and the air flow rate was measured by means of a rotameter. 5/25/201619

20. EXPERIMENTAL CONDITIONS 5/25/201620 Table 1: Summary of Experimental conditions Design parametersMaterial/value Type of fuel/ feed sizeLafia-Obi/(5-25mm) Bed material / size (µm)Sandstone/ 350-500 Bed temperature ( o C )750-1200 Static bed height (m)0.1 Fuel feed rate (kg/min)0.2 & 0.3 Bed diameter (mm)150 Fluidization Velocity(l/min)350-2000 Pressure drop across distributor plate (mmH 2 O)43 Pressure drop across bed (mmH 2 O)428.8 Distributor plate No. of holes311 Diameter of holes (mm)1.5 Thickness (mm)4

21. RESULTS 5/25/201621

22. Proximate & Ultimate Analysis 5/25/201622 AnalysisValue Proximate Analysis Moisture (wt %)2.91 Volatile matter (% 1 )27.19 Ash (% db)18.62 Fixed carbon (%) 51.28 TOTAL100.00% Colour of ashLight grey Ultimate Analysis (wt% 1 ) C59.29 H40.61 N2.10 S1.81 Gross calorific (KJ kg -1 )23,721.40 Table 4.1:Analysis of Lafia-Obi Coal

23. Sudden temperature drops due to release of volatiles Sudden temperature rise due to ignition of volatile Fluctuations in temperature is coal particle size dependent As the coal particle size increases, char combustion rate and in consequence, bed temperature decreases Figure 4.2: Effects of coal particle size on temperature at a coal feed rate of 0.2kg/min 5/25/201623 Effect of on Lafia-Obi Coal Feed Size on Combustion Bed Temperature

24. Figure 4.4 Summary of the effects of coal particle size and feed rate on temperature 5/25/2016 24 Effect of on Lafia-Obi Coal Feed Size on Combustion Bed Temperature cont.

25. Increased CO concentration with increased feed size abrupt changes in CO concentration as a result of repeated char particle fragmentation, Reduced CO concentration with increase in average bed temperature 5/25/201625 Figure 4.6: Effects of coal particle size on CO emission at a coal feed rate of 0.3kg/min Effects of Coal Particle Size on CO Emission

26. 5/25/201626 Effects of Coal Particle Size on CO Emission cont. Fig. 7 Effect of bed temperature on NOx emissions

27. NO X formation increased with increasing carbon conversion, attributed to a decrease in NO X reduction in the pores of char particles as they shrank. Tullin, et al., (1993) NO X concentration decreases with increasing particle size. This investigation was carried out above the critical average diameter of the Lafia-Obi coal Jing et al., (2007), 5/25/201627 Figure 4.13 Effect of coal particle size on NO x emission at a coal feed rate of 0.3kg/min Effects of Coal Particle Size on NOx Emission

28. 5/25/201628 Fig. 9 Graph of flue gas temperature against NOx emissions Effects of Coal Particle Size on NOx Emission cont.

29. Theoretically, as the bed temperature increase, there is an increase in the rate of char combustion and an increase in the CO oxidation rate; this situation causes lower CO concentration in the flue gases. The level of the scatter for the lines is an indication of the level of variation exhibited by spontaneously varying rates of reaction which has been attributed to the fragmentation of the coal articles in the fluidized bed combustor. 5/25/201629 Effect of Temperature on CO emission Figure 4.8: Effect of combustion bed temperature on CO emission at a coal feed rate of 0.2kg/min

30. Coal properties that affect NO X emissions include nitrogen content of the coal, coal reactivity, and mineral makeup of the coal. Because this experimental procedure occurred at a temperature lower than 1000 0 C, the NO x measured during this experiment will be thermal NO x. Lohuis et al., (1992) and Kilpinen & Hupa (1991) 5/25/201630 Figure 4.10: Effect of temperature on NOX emission at a coal feed rate of 0.2kg/min Effect of Temperature on NOx Emission

31. Effect of Fuel Feed Rate On Emission Figure 4.16: Effect of feed rate on NOx emission at a coal FED of 10mm Figure 4.17: Effect of feed rate on CO emission at a coal FED of 10mm 5/25/201631

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33. CONCLUSION 5/25/201633

34. 5/25/201634 The bench-scale fluidized bed combustor methods Modified in this program has provided relevant information for assessing the behaviour of Lafia-Obi coal in Fluidized Bed Combustion.

35. 5/25/201635 The studies conducted revealed that Lafia- Obi coal has low moisture, high volatile matter and very high fixed carbon content. The volatile matter content, places Lafia- Obi in the medium-volatile bituminous rank.

36. 5/25/201636 This study has provided useful empirical projection of emissions of greenhouse gases from FBC combustion of Lafia-Obi Coal This data obtained is useful in application of fluidized bed combustion for energy production using Lafia-Obi Coal

37. ThAnK yOu