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Energy and Fuel Value Analysis of ADA Palm Oil Plantation Limited, Imo State, Nigeria

Ugwu Hyginus Ubabuike

Department of Mechanical Engineering, Michael Okpara University of Agriculture, Umudike Umuahia, Abia State, Nigeria

Abstract: This paper presents an analysis of the fuel values of the energy resource utilized in a 710KVA steam turbine plant at Ada Palm Oil Plantation Nigeria Limited, Imo State, Nigeria using the performance data obtained from the plant operation. This is with a view of using the results obtained from the study to identify the locations and magnitudes of losses associated with the system and thus, seek for an improvement on its performance efficiency. The oil mill operates a cogeneration system using fibre and shell as fuels in the boiler to produce high pressure steam which expands through a steam turbine to produce electricity utilized at the plant. The results obtained from the analysis indicate that the theoretical combustion air requirement for the fibre and the shell are respectively 3.89kg of air/kg of fuel and 5.99kg of air/kg of fuel, while that for the entire plant is obtained as 8.96kg of air/kg of fuel. Also, the percentage excess air of 45% supplied with an actual mass of air of 13kg of air/kg of fuel supplied per kg of fuel, and 98% value of heat loss due to dry flue gas, with 0.165% of heat loss due to moisture present in air gave the efficiency of the boiler at 1.84%. From the combustion analysis, the stoichiometric air/fuel ratio required for combustion was approximately obtained as 0.068. The study identified that greater part of the total heat energy generated in the combustion chamber was not available for doing any useful work and thus formed the backdrop for the losses and low value of the boiler efficiency. In-view of these, exergy-based performance monitoring approach has been recommended in this study to assist in managing energy resources and environment better. This will be achieved by undertaking effective operation and efficient maintenance decision and strategies capable of reducing exergy destruction in power plant for energy production.

Keywords: Ada palm limited, fuel value analysis, energy resource, performance efficiency, fresh fruit

Received April 01, 2013; Revised May 03, 2013; Accepted May 04, 2013

Citation: Ugwu Hyginus Ubabuike, Energy and Fuel Value Analysis of ADA Palm Oil Plantation Limited, Imo State, Nigeria. American Journal of Mechanical Engineering, 1 (4). 89-95. January 2013. doi:10.12691/ajme-1-4-3

1. Introduction

Globally, there is increasing demand for cleaner production of energy due to environmental reasons. It is envisaged that in the years ahead, national and international laws and conventions are likely to compel industries around the globe to install pollution control facilities (which themselves consume energy), and adopt state-of-the-art processes and procedures in order to meet stringent environmental standards. Following from all these, a lot of research activities are currently going on worldwide to find alternatives to the finite fossil energy. However, in the face of these research efforts, it has become common sense to conserve the existing fuel resources so that it can last for as long as possible without damaging the economic well being of the society. At the domestic level, one of the problems that most companies in Nigeria as well as the under-developed world will have to contend with in the years ahead is that of rising cost of energy. The situation will probably be exacerbated by the new economic order of privatization and commercialization of public enterprises, especially the energy institution in Nigeria.

What this portends is that in the years ahead, only those companies that can adopt their machineries to use available energy more efficiently will remain in business. It is discomforting to note that while the consciousness for energy conservation and efficiency have long been entrenched in the manufacturing culture of companies in the industrialized countries of the West, the same cannot be said to be true about companies operating in most developing countries like Nigeria. The reason for this is not far-fetched. They include among others: lack of awareness on the part of the industries of the economic and social benefits of energy efficient production processes; the relatively low cost of energy at the domestic level, coupled with the wrong perception that Nigeria’s energy resources are virtually limitless and so very little attention is devoted to the problem of energy inefficiency; and dearth of experts in the field of energy conservation and management, etc. It is therefore not surprising to observe that most consumers including companies do not bother to know how they use energy, what it costs them and how it can be reduced. Equally instructive is the rapid increases in domestic energy consumption over the years.

Hence, energy conservation modalities must be strategized by adjusting and optimizing these systems utilizing these energy facilities. Also, it is envisaged that streamlined procedures which will reduce power plants’ energy requirement per unit of output or ‘’well being’’ while holding constant or reducing total costs of providing the output from these systems should be inculcated and repositioned in the national energy policy documents. At the plant level, successful energy conservation management is advocated to begin with comprehensive energy audits which would identify the most appropriate measures to be taken in order to improve energy efficiency. Thus, with the setting up of an appropriate energy management and control organization, a check would be provided to help implement the measures and monitor the performance of the scheme.

Energy therefore, is central to sustainable development and poverty reduction efforts. It affects all aspects of development. None of the Millennium Development Goals (MDGs) can be met without major improvements in the quality and quantity of energy services in developing countries. Further, the world is expected to change dramatically over the next 25 years, presenting significant challenges for energy production and use [1]. For example, by 2030, it is estimated that $17trillion of investment will be made in energy infrastructure, largely in developing countries [1]. These investments and others will need to be carefully planned to ensure that green-house gas (GHG) mitigation occurs hand-in-hand with meeting the energy needs and development aspirations of developed and developing countries.

Globally, countries are developing strategies and policies to enable the sustainable development of their energy resources so as to fuel economic and social development while reducing air pollution and the GHG emissions which intrinsically, is linked with sustainable development at all levels [2]. At the local level, modern energy is required to improve the overall quality of life (especially, that of the poor) by enhancing productive activities and enterprise, which will result in increased incomes. At national and regional levels, adequate modern energy leads to stable economic development, promotion of trade, and enhancement of participation in global markets, besides the added benefits of better social and economic linkages [2].

Over the years, however, the nation’s power sector has been bedeviled by managerial inefficiencies and leakages, lack of transmission, inefficient investment in generation, distribution, and continued increase in load demand. With Nigeria on the quest to become one of the 20 leading economies of the world by 2020, fast tracking the nation’s electricity needs is critical for industrialization [2]. Similarly, over the last two decades, Nigeria’s power sector has suffered neglect as power plants that were functional in the 1970s and 80s are no longer capable of meeting the nation’s electricity demand. Within this period, no single power plant was built, nor revitalized resulting to continued power supply deterioration up to the point where generation level dropped by as low as 1,500 megawatts in 2000 [3,4].

In considering the appalling state of the Nigerian power sector, it is worthy to look back to the status-quo of power production and the history of electricity generation in the country which dates back to 1896 when electricity was first produced in Lagos, fifteen years after its introduction in England [4]. Hence, electrical energy production in Nigeria over the last 40 years varied from gas-fired, oil-fired, hydro-electric power stations to coal-fired station with hydroelectric power system and gas-fired station taking precedence [4]. However, these facilities as they relate to power and energy production and supply hitherto in Nigeria are dilapidated, unavailable and obsolete. In-view of these, this study was evident as a panacea to determining the associated energy losses and related efficiency of the power utilization facilities at Ada palm oil plantation limited for maximum energy application. This is inevitable since efficiency has a very greater influence on heating-related energy savings of a boiler [5].

In this study, the objectives as identified were predicated on the need to determine the historical energy consumption profile and the type of fuel resources available at Ada palm oil plantation limited and its manufacturing processes. These will serve as basis for interpreting and at the same time improving its present energy consumption; and to predict the company’s future energy demands.

2. Materials and Methods

2.1. Profile of Ada Palm Oil Plantation Limited

Ada palm limited is a limited liability company which commenced operation in 1984 as a joint venture between Imo State government and foreign investors [6]. The government provided land while the investors provided the oil mill and its machineries and accessories. The palm oil plantation and the mill is at about 65km from Owerri, the capital city of Imo State, South Eastern Nigeria. Currently, there are 3,866 hectares of mature oil palms which were planted between 1976 and 1994. Due to the unreliability of power supply with many outages from National Electric Power Authority (NEPA) now Power Holding Company of Nigeria (PHCN), Ada palm limited management established a steam power plant to provide for an independent power supply using fibre and shell as the primary fuel for firing the boiler. According to the technical manager, plant operations [6], the plant produces electrical power by using the energy released from the steam generated in the boiler to drive the turbine blades which in turn drives a generator to generate the needed power. The installed plant is to generate power for the processing of oil palm and palm kernel as well as to supply power for use at the staff quarters and school, the effluent pond operations and water supply installations. The designed power output capacity of the generator is 710 KVA but due to operational inefficiencies and other losses, the daily output capacity is derated to about 568KW. This research therefore seeks to investigate the causes of these operational inefficiencies and losses resulting in the decrease of the expected output of the plant, and thus make recommendations that could lead to its efficiency improvement.

2.2. The Oil Mill and the Process Technology

The company has an oil mill where the fresh fruit bunches (FFB) are processed to get both the red oil, kernel oil and other end products for sales. The mill has an installed capacity to process thirty tons (30 tons) of FFB per hour and operates for eight hours every day [6]. This means that the plant mills 240 tons (30×8 tons) of FFB per day. Accordingly, the extraction rate of the mill based on the plant manager is 16% (the extraction rate is the ratio of oil produced to FFB processed times 100%). The flow processes of the milling in use in the plant are as presented in Figure 1. Evidently, the fibres and the shells processed out as depicted in Figure 1, automatically go to the boiler furnace (combustion chamber) where they are used as the primary energy source which heat up the boiler for its power generation.

2.3. Description of the Steam Power Plant in the Mill

The steam power plant depicted in Figure 2 comprises of the boiler, the superheater, the turbine and the generator. The 710KVA steam turbine operates by the synchronization of the boiler steam generator. The system generates 568KW of electricity for the use in machines’ operation and other usages. The boiler is ignited with a 400KVA diesel engine generator, while its combustion is made with the primary fuel (fibre and shell) as feedstocks to produce steam from the hot water storage tank. The boiler is heated to produce steam at a pressure of 22 bars which further is released to the power house through the superheater to drive the turbine blade and subsequently the shaft to generate electricity. Basically, the boiler as the technical manager, plant operations [6] stated must maintain a steam pressure of not less than 22 bars at any time to ensure constant steam generation.

Figure 1. Schematic representation of the FFB processing at the mill

2.4. Recycling of Fibre and Shell in the Boiler

Ada palm oil plantation mills operate a cogeneration system using fibre and shell as fuels in the boiler to produce high pressure steam which is expanded through a steam turbine to produce electricity [6]. The low pressure steam is used in the manufacturing process for sterilization, digestion, purification and also for temperature control. The electricity generated is used to supply almost all of the power requirements for the mill, which is estimated to be about 14.5KWh/ton of FFB processed. Based on 1ton processed FFB, 140Kg of fibres and 30Kg of shell are burnt to supplement the steam required in the production process. The gross calorific value of the fibre and the shell are 17,422 and 19,462KJ/Kg, respectively [6]. After being used for the production of electrical power from the turbine, the low pressure steam is sent to the sterilizer for the sterilization of FFB which is done batch-wise in an autoclave with a capacity of 20–30ton FFB. The required amount of sterilization condensate is about 0.12m³/ton FFB [6]. The slightly polluted condensate obtained can be recycled to the screw press and the vibrating screen, respectively in order to reduce the amount of hot water required in these processes.

Figure 2. Schematic representation of the cycle with superheater

2.5. Chemical Composition of the Fibre and the Shell from Ada Palm Oil Plantation Limited

The chemical composition of the fibre and the shell taking from Ada palm oil plantation limited in terms of their ultimate analysis is as represented in Table 1. Moreso, in the oily state, the heating (calorific) value of the fibre is taking to be 11.344MJ/kg at 40% moisture content, while that for the shell is 18.836MJ/kg at 10% moisture content, respectively.

Table 1. Chemical composition of the fibre and the shell taking from Ada palm oil plantation limited

2.6. Fuel (Fibre and Shell) Analysis

As indicated, palm fibre and shell are the primary sources of the thermal energy utilized as feedstocks in the production of heat in the boiler. Presented in Table 2 are the calorific/heating values of the palm shell and the fibre from Ada palm oil plantation limited in respect of their pure and oily states.

Table 2. Calorific values of the palm shell and the fibre from Ada palm oil plantation limited

3. Results and Analyses

3.1. Combustion Analysis

From Table 1, the mass of oxygen required for the stoichiometric combustion is computed as presented in Table 3.

Table 3. Stoichiometric analysis of the fuel

3.2. Analyses of Air Requirements

3.2.1. The Theoretical Air Requirement

i. The theoretical air () requirement based on Table 1 for the entire plant is given by [7] as:

[picture] | (1)

Thus:

ii. The theoretical air requirement based on Table 1 for the fibre from (1) is obtained as:

iii. The theoretical air requirement based on Table 1 for the shell from (1) is obtained as:

3.2.2. The Percentage Excess Air Supplied

The percentage excess air supplied from Table 4 according to [7] is given by:

Percentage excess air supplied

[picture] | (2)

3.2.3. The Actual Mass of Air Supplied Per Kg of Fuel

The actual mass of air supplied per kg of fuel based on [7] is obtained as:

Actual mass of air,

[picture] | (3)

3.3. Estimation of Losses and the Efficiency of the Boiler

3.3.1. Percentage Heat Loss due to Dry Flue Gas,

The percentage heat loss due to dry flue gas () from [7] is given by:

[picture] | (4)

where: m = combustion products from the fuel:

CO₂ + SO₂ + N₂ in fuel + N₂ in the actual mass of air supplied + O₂ in flue gas; while moisture/water vapour (H2O) in the flue gas is neglected. Hence:

[picture] | (5)

Based on Table 1, “m” is obtained from (5) as:

Thus:

3.3.2. Percentage Heat Loss due to Moisture Present in Air,

The percentage heat loss due to moisture present in air from Table 4 is calculated as [7]:

[picture] | (6)

3.3.3. The Efficiency of the Boiler,

The efficiency of the boiler thus is obtained as [7]:

[picture] | (7)

3.3.4. Fuel Analysis and the Stoichiometric Air/Fuel (A/F) Ratio

From the combustion analysis of Table 1, the composition by mass per kg fuel for the fibre and the shell are: C = 0.6881, H = 0.055, O = 0.222, N = 0.0175, S = 0.007, Ash = 0.103 and H₂O = 0.055, respectively. However, for this analysis, the percentage contributions by mass per kg of the fuel for the Ash and moisture contents as related to the fuel composition were neglected in the combustion analysis. Hence, the stoichiometric A/F ratio is obtained thus:

Table 4. Parametric specifications of the boiler

If the equivalent formula for the fuel (fibre and shell) sample = , on the basis of 100kg of the fuel from Table 1, the composition by masses gives:

C:12a = 0.6881; a = 0.057

H:1b = 0.055; b = 0.055

O:16c = 0.222; c = 0.0139

N:14d = 0.0175; d = 0.00125; and

S:32e = 0.007; e = 0.00022, respectively.

Hence, the formula of the fuel sample

Then, the combustion equation for the fuel sample thus becomes:

[picture] | (8)

Balancing the equation gives:

C:0.057 = p; p = 0.057

H:0.055 = 2q; q = 0.0275

S:0.00022 = r; r = 0.00022

O:0.0139 + 2 = 2p + q + 2r

= 2(0.057) + 0.0275 + 2(0.00022)

0.0139 + 2 = 0.114 + 0.0275 + 0.00044

= 0.14194

2 = 0.14194 – 0.0139 = 0.12804

N:

Hence, the balanced combustion equation thus becomes:

Thus, the Stoichiometric air/fuel (A/F) ratio required

4. Conclusion and Recommendations

4.1. Conclusion

The fuel value analyses of the energy resource utilized in a steam turbine plant of 710KVA rated capacity at Ada palm oil plantation limited have been performed using available data obtained from the operation of the plant. The study identified that greater part of the total heat energy generated in the combustion chamber was not available for doing any useful work. Thus, this has its effect on the work output of the turbine due to irreversibility inherent in the combustion process. Also, the inability to de-ash the chamber at the required time, prevented the smooth circulation of the flue gases on the water tubes of the boiler and the resultant work output of the turbine. These hitherto, have affected the operation of the entire oil mill and other quarters where the electrical power generated by the turbine was utilized. Hence, attention must be paid to these component parts of the system so as to maximize the plants’ performance.

4.2. Recommendations

Based on the study, the following recommendations have been proffered.

1. Since efficiency has a greater influence on heating-related energy savings of the boiler, the heat transfer rate to the water source should be maximized so as to minimize the heat losses in the boiler especially at the combustor by employing blowers and/or fans with higher horse powers. This consequently will produce the required heat that will de-ash the combustion chamber efficiently.

2. From the analysis, significant amount of energy was lost (98%) through dry flue gases as all the heat produced by the burning fuel (shell and fibre) were not transferred to water or steam in the boiler. The recovery of this heat output can substantially result in a greater energy savings by the company if most of the heat losses from the boiler would appear as heat in the dry flue gases. This indicates that the establishment must integrate energy measures that will minimize heat losses of the boiler thereby necessitating huge energy saving potentials of the boiler unit especially the combustor.

3. To achieve this, a step in the right direction, is to insulate very well the combustor unit in the boiler so as to cause heat dissipation to the surrounding to be minimized to zero and subsequently make its work output also zero (w = 0).

4. Moreso, the outer shell of the heat exchanger should be well insulated too to prevent any further heat loss to the surrounding medium.

5. Overall, the use of heat recovery system especially exergy technique is highly advocated for further studies for use by the company to recover all the heat losses through flue gases. This will make the efficiency of the boiler more beneficial and resourceful since exergy analysis provides better view on the real efficiency of a process. It is also very useful to finding the unit operations where efficiency improvements are most needed and desired by pinpointing the specific areas that require much attention.

Acknowledgements

The author gladly acknowledges with passion the assistance and effort made by Alaekwe, Idey Nkemakolam of the Department of Mechanical Engineering, Michael Okpara University of Agriculture, Umudike in gathering the data used in the analyses of this study. He also commends greatly the unparalleled support by the entire staff and management of Ada palm oil plantation limited, Imo State, Nigeria in providing relevant and useful information, materials, resources and data that assisted in the analyses of the work.

References

[1]   | International Atomic Energy Agency (IAEA), “Potential for sharing nuclear power infrastructure between countries,” in IAEA-TECDOC-1522, Vienna, 2006.
[2]   | Chiejina, A. “Report of the Vision 2020,” National Technical Working Group on Energy Sector, pp. 1-39, July, 2009.
[3]   | Energy Commission of Nigeria (ECN), “Assessment of energy options and strategies for Nigeria: Energy demand, supply and environmental analysis for sustainable energy development (2000-2030),” in Report No. ECN/EPA/2008/01, 2008.
[4]   | Okoro, O.I; and Chikuni, E; “Power sector reforms in Nigeria: Opportunities and challenges,” Journal of Energy in Southern Africa, Vol.18, No. 3, pp. 52-57, 2007.
[5]   | Raviprakash, K; and Sharad C; “Energy analysis of thermal power plant,” International Journal of Scientific & Engineering Research, Vol.3, Issue 7, pp.1-7, July 2012.
[6]   | Technical Manager, Plant Operations, “Status of Ada Palm Oil Plantation Limited,” Oral Report, May 2010.
[7]   | Internet Explorer, “Boilers”, http://www.em-ea.org/Guide%20Books/book-2/2.2%20Boilers.pdf; or http://www.beeindia.in/energy_managers_auditors/documents/guide_books/2Ch2.pdf.