Economic evaluation of hazard control technology in a wet process cement plant

Goal: Retrofit technology has been suggested for the reduction of CO2 emission in cement manufacturing but the economic justification of this retrofit technology is rarely or not available. This research study aimed to evaluate the beneficial value of retrofit technology aimed at reducing CO2 emission in a wet process cement plant. Design / Methodology / Approach: Engineering Economic and cost estimation techniques were used to evaluate the overall annual cost of combination of retrofit technology. The overall annual cost of retrofit technology was determined in terms of capital cost, operation and maintenance cost and energy cost savings of retrofit. Results: The best strategy to reduce CO2 emission is the combination of adjustable speed drive for kiln; kiln drive efficiency improvement for kiln and process control and management system for kiln at 6% reduction target, giving a cost savings of $520,836 on retrofit for 10 years and 1.41% reduction in total cost. Limitations of the investigation: Getting adequate plant data in Nigeria was a constraint during the research. Practical implications: The results presented if implemented by Cement plant operators will ensure reduction in the CO2 emission and government can enforce Cement plant operators to adhere to strict environmental and safety regulations while litigations and sanctions can be employed to implements this policy. Originality / Value: The study established economic justification of retrofit technology for CO2 emission reduction before eventual implementation.


INTRODUCTION
Cement no doubt, is a much desired commodity and our development as a country isn't an extended way-fetched from our infrastructural power in terms of homes and awesome bodily infrastructure (Global Cement (2011). Cement consequently performs an important role in this regard. There are two techniques used for the manufacture of cement namely wet process and dry Process (Sidhi et. al., 2016). The decision among wet and dry techniques relies upon on positive factors specifically the physical condition of the raw substances; the cost of the fuel and the local climatic condition of the manufacturing unit. The particular feature of the wet system is that the raw materials are mixed in water while inside the dry technique the The cement industry has been lively in pursuing techniques to decreased CO 2 emanations long earlier than global warming have become a concern. Since 1999, with the launch of the Cement Sustainability Initiative (CSI) at the World Business Council for Sustainable Development (WBCSD), the industry has systematically amassed evidence and stepped forward its techniques. In 2009, the International Energy Agency/World Business Council for Sustainable Development (IEA/WBCSD) Roadmap presented several CO 2 emanations and mitigation strategies (IEA, 2018). The IEA study observed that the target 50% global emissions reduction purpose to preserve global warming at less than 2°C of pre-industrial stages might require an average reduction of 18% within the CO 2 emanations of the cement industry by 2050 (Farfan et al., 2019).
Nigeria CO 2 emanations data as reported in the World Bank study by Cervigni et al. (2013) indicated that agriculture and land use, oil and gas, power and transport sectors accounted for the majority of the CO 2 emanations to the environment. Surprisingly, manufacturing sector and cement industry in particular (with a percentage contribution of 8.14% to GDP of Nigeria economy in Q3 of 2013) was not included in the study. The Federal Government of Nigeria (FGN) has shown some commitments in combating CO 2 emanations. At the 2015 UN Climate Change Conference held in Paris, France; Nigeria presented a document which stated unconditional commitment to reduce CO 2 emanations by 20% in year 2030 and possibility of achieving 45% reduction outside aid is obtained (Ezema et al., 2016). Summerbell et al. (2016) and Maddalena et al. (2018) stated that reducing CO 2 emanations from cement manufacturing depend largely on raw material mix and fuel type. Summerbell et al. (2016) further stated that the type of manufacturing technology used for cement production also contribute to CO 2 emanations. In order to achieve the target of less than 2 o C global average temperature and environmental gains, it is necessary to implement mitigation strategies for the reduction of CO 2 emanation. Also Naqi and Jang (2019) investigated the use of different alternative fuels and binders in cement production to mitigate carbon dioxide emissions. Farfan et al. (2019) and Jessica (2018) proposed carbon capture and utilization (CCU) techniques as a means of reducing CO 2 emanations and the possible use of the captured CO 2 for the production of synthetic hydrocarbon. Adebiyi et al. (2015) identified four technological approaches (namely adjustable speed drive for kiln, kiln drive efficiency improvement for kiln, process control and management system for kiln and reciprocating grate coolers for kiln) and eighteen combinations (for two production line of kilns) of these technological approaches to reduce CO 2 emanations. Gardarsdottir et al., (2019) also identified four CO 2 capture technologies namely (chilled ammonia process (CAP), membraneassisted CO 2 liquefaction, oxyfuel technology and two different configurations of calcium looping technology (tail-end and integrated)). Other mitigating strategies for CO 2 reduction in cement manufacturing have been compiled by Leeson et al. (2017).
However, while an 18% reduction target of CO 2 emission was achieved in the work done by Adebiyi et al. (2015); the economic implications of the retrofit technologies have not been proven. So, it is the main objective of this research work to evaluate the economic viability of combination of retrofit technology in a wet process cement plant.

METHODOLOGY
In order to evaluate the economic viability of retrofit technology for mitigating CO 2 emanations in a wet process cement plant; the following methodologies were used: 1. Cost estimation; and 2. Engineering Economic techniques.
The cost estimation approach was used to estimate the capital cost, operations and maintenance cost and energy savings of retrofit technology in year 2008 while the engineering economic techniques was used to evaluate all cost parameters from the estimated cost in 2008 to year 2019 i.e. discounting the value estimated in year 2008 to year 2019 value and subsequently annualized over a 10-year period. Staudt (2008)

Cost Estimation of Retrofit Technology
where m is the scale-up factor exponential. Retrofits are carried out on a wet kiln and hence scale-up factors were extracted for wet kiln column from Staudt (2008). Meanwhile, scale-up factor using calculations from payback period was adopted. These costs however are subject to revalidation as this method only provides an estimation of equipment's capital cost only. The equation provided by Staudt (2008) is for 2008-dollar value. This value was normalized into present year using engineering economics techniques for finding a present worth of a future cost (past or later year).
For the purpose of this research, the equation above was used to model the case study plant. The case study cement plant is a wet process plant located in south western Nigeria. The plant runs a double firing system with natural gas and heavy oil as its sole kiln fuel. Carbon capture technology hasn't been discovered running on any cement plant everywhere throughout the world, the innovation is said to be in pilot stage at different research focuses yet notwithstanding, it has been exhibited in power plants and the prospects that it will work in a cement plant is high. Find below the details of the wet kiln used for this study (Table 1):

Analysis of the Wet Process Plant
As stated earlier; Adebiyi et al. (2015) has identified four technological approaches and eighteen combinations (for two production lines of wet kilns) of these technological approaches to reduce CO 2 emissions at different reduction target (Table 2). The wet kilns under consideration have output of 680,087 tons/year of cement for both units at 75% utilization factor and can go well above this value if available resources are well utilized. From Equation 1; substitute for wet kilns output we have the expression for cost estimate of first cost of retrofit technology as follows:

Cost Saving Analysis of Retrofit Technology
The cost saving at respective reduction target is expressed below as: The overall cost saving is given as:   (2008), provided a measure of efficiency associated with cement with cement plant retrofit and for adjustable speed drive for kiln fan, energy saving is stated as 5KWh/ton reduction in energy consumption.

Adjustable Speed Drive for Kiln 1 Fan
Overall Cost saving on energy consumption represents 0.31% of total cost of power consumption and 0.16% of total operating cost.  Cost saving on heat energy consumption represents 2.29% of total cost of heat consumption and 1.15% of total operating cost.  The United States Environmental Protection Agency, (2008) provided a measure of efficiency associated with cement plant retrofit process control and management system is estimated to provide an energy reduction of 2.5 -5% per MJ/ton of cement. Cost saving on heat energy consumption represents 1.07% of total cost of heat consumption and 0.54% of total operating cost.

RESULTS
This section presents the total cost of each retrofit technology (in terms of annualized capital cost and operating and maintenance cost) and its corresponding energy savings. Afterwards; the retrofit cost savings of combinations of retrofit technology as presented by Adebiyi et al., (2015) follow suit. The retrofit cost savings was evaluated in terms of total retrofit cost, energy savings of retrofit and cost of avoided emission (depending on the CO 2 reduction target) for each combination of retrofit technology. Table 3 shows the cost of retrofit technology and energy savings for kiln 1 and kiln 2. These costs were determined using the cost estimation methods and engineering economic techniques.  Table 4 shows the direct annual gross carbon dioxide (CO 2 ) emission from cement production using the cement-based methodology tool developed by WRI and WBCSD, 2002. Using this tool, the annual CO 2 emission was calculated from the plant data provided in Table 1 using the given annual cement production and other necessary factors required by the tool. Cost Savings on Retrofit/Economic analysis of CO2 reduction target Table 5 shows the reduction target of CO 2 emission and the corresponding cost savings on retrofit. The retrofit cost saving is a function of total retrofit cost, energy saving of retrofit and cost of avoided emission for each combination of retrofit technology depending on the reduction target. For instance; consider cost saving on retrofit at 1%, reduction, R 12 and R 13 were the retrofit technology chosen thereby reducing emission by 3,001 ton.

Costs of Retrofit Technology for Kiln 1 and Kiln 2
Where The negative sign is as a result of an accrued saving in term of cost reduction  Table 6 shows the total cost on retrofit at various reduction targets by evaluating the overall operating and maintenance cost without retrofit with CO 2 tax and cost savings on each retrofit to determine the percentage reduction in cost for each percentage reduction target. The carbon tax on total emission (without retrofit) was calculated using Equation 6 while the total cost in a carbon era was calculated using Equation 7 as stated below: Carbon tax on total emission (without retrofit) = Carbon tax/ton × total emission (ton) 6 Carbon tax on total emission (without retrofit) = $30/ton × 300,137 = $9,004,110

DISCUSSION
The plant under consideration has an annual carbon dioxide emission of 300,137 tonnes and overall plant operating cost is $27,835,961. Also, the plant uses two Kilns for its clinker production. Emission cost is benchmarked at $30/ton of emission. This is based on the average dollar value as proposed by most countries. Meaning, in a regime of carbon tax, an astounding sum of $9,004,110 would be paid on total emission bringing overall operating cost to ($27,835,961 + $9,004,110). An optimization model whose objective was to identify the best retrofit technology strategy to reduce CO 2 emanations with the least cost has been developed by Adebiyi et al. (2015) using the industry data. This research therefore evaluated the economic worthwhile of retrofit technology strategy selected for CO 2 reduction by Adebiyi et al. (2015).
At a reduction target of 1% to 2%; 3,001 to 6,003 tonnes of carbon dioxide were reduced. Tables 5 and 6 shows the retrofit technology selected namely; kiln drive efficiency improvement for kiln 1 and reciprocating grate coolers for kiln 1. The result shows a $121,701 in cost savings on retrofit and a 0.57% reduction in total cost on retrofit. It was observed that at reduction target of 9%, 10%, 12% and 13%, the cost saving on retrofit was not economically worthwhile selected for the combination of retrofit technology strategy at each reduction target respectively. Instead of reduction in cost with the strategies, there was increase in cost making such combination of technology not economically worthwhile at those reduction target listed in Table 6. The negative sign in the percentage reduction in cost in Table 6 shows an increase in total cost on retrofit. Although at reduction targets of 9%, 10%, 12% and 13%, Table 5 shows there is reduction in CO 2 emission making the retrofit technology efficient in reducing carbon dioxide emission but not economical in terms of cost reduction.
Further economic analysis at other reduction targets shows the cost savings and percentage reduction in total cost on retrofit. At reduction targets of 2%, 4%, 5%, 6%, 17% and 18%; there is economic worthwhile of these retrofit technologies in terms cost savings and percentage reduction in total cost on retrofit with reduction target of 6% giving the best economic viability amongst the aforesaid.
Carbon Emissions Trading on the Floor of the Exchange is policy under consideration by the Federal Government of Nigeria. This carbon trading is fashioned after the Emission Trading Scheme (ETS) that is fully underway in Europe as a method of fighting emissions with the aid of established emission standards or caps, which restrict how much an entity/organization/country is permitted to emit, and to buy/promote the excess/savings. As a machine of governance through markets, carbon trading relies on the allocated performance of marketplace agents to provide the proper indicators for innovative and effective ways of pursuing economic activities, more so for ensuring socioeconomic optimality within the use of public goods, the climate being a regular example. The availability of two external agents, a regulator (government organisation) and a broking firm (trading platform) represent the vital and sufficient circumstances for the workability of carbon buying and selling. These vital and sufficient circumstances are fulfilled in Nigeria through the Ministry of Environment acting as the regulator whiles the Nigerian Stock Exchange acting as the broking firm (Onyeka, 2020). With this in the pipeline, it is evident that the Nigeria government is fully committed to the reducing CO 2 emanations in all sectors of Nigeria economy and that all sectors of the economy should brace up for carbon tax regime which is imminent.
In this research, the economic viability of combination of four retrofit technologies to reduce CO 2 emanation and minimize operating cost were considered which revealed reduction targets in terms of cost savings and percentage reduction in total cost on retrofit. The research also showed some cases where the combinations of this technology were not economical in term of cost savings and percentage reduction in total cost on retrofit.

CONCLUSION
The cement industry is responsible for the contribution of global carbon dioxide emanation emitted from the calcination process of limestone. CO 2 emanations have contributed to a large scale climate change which has global repercussions. There are technologies that mitigate the release or capture CO 2 emanation. The combinations of these retrofit technologies are quoted to reduce emission, reduce heat and electrical energy consumption and by extension reduce the operating and maintenance cost as well as increase in productivity of the production line. So, it is the main goal of this research to evaluate the economic viability of implementing these retrofit technologies.
Engineering economics and cost estimation techniques were used to evaluate the economic viability of implementing these retrofit technologies in terms of cost savings on retrofit and percentage reduction in total cost on retrofit. The best strategy to reduce CO 2 emanation economically is the combination of R 12 , R 22 and R 23 retrofit technologies at 6% reduction target, giving a cost saving of $520,836 on retrofit and 1.41% reduction in total cost.
It should be noted that this research only implemented the use of technology as a way of reducing CO 2 emanations in the cement industry. Due to the rate at which carbon dioxide is been emitted in the cement industry, the government should implement carbon tax on the cement industry so as to hold the cement companies responsible for the CO 2 emanations. If set high enough, it turns into a powerful financial motivator that motivates changes to clean energy across the economy, essentially by making it more economically rewarding to move to less carbon concentrated manufacturing techniques. Cement plant operators should be compelled to adhere to strict environmental, safety regulations, litigations and sanctions can be employed to implements this regulation.