Assessment of CO, CO2 and Suspended Particulate Matter Emissions

 

 

Bala Isah ABDULKARIM, Timothy Musa CHIROMA, Ternenge JOSEPH

 

Chemical Engineering Department, Federal University of Technology, Yola, Nigeria

balisa76@yahoo.com, tchiroma@yahoo.com, ternenge123@yahoo.com

 

 

Abstract

The concentrations of carbon oxides (CO and CO2) and suspended particulate matter at Benue Cement Company (BCC) and Tse-Kucha community was investigated. Results obtained, shows that concentrations of carbon dioxide of 34.40ppm, 39.50 ppm, 48.50 ppm, 78.55 ppm, 65.25 ppm, 26.80 ppm and 29.5 ppm for quarry, raw mill, cement mill, Kiln, packing house, limestone stockpile and Tse-Kucha community respectively were below the maximum standard natural concentration of CO2 in atmosphere of 600ppm while concentrations of CO (1.25ppm - 4.00ppm) measured in all the sample stations were below the Nigerian Ambient Air Quality Standards (NAAQS) and WHO max limit of 10 ppm - 20 ppm for an 8-hourly average time. Lastly, the concentrations of suspended particulate matter of 375 μg/m3, 338 μg/m3 and 290 μg/m3  at the cement mill, packing house and raw mill respectively were also above the World Health Organization’s (WHO’s) Guidelines and Standards for Ambient Air Quality which stipulates a range of 150 μg/m3 to 230 μg/m3 for a 24-  hourly average.

Key words

Suspended Particulate Matter; Ambient Air Quality; Packing House; Carbon Oxides.

 

Introduction

 

The preparation of cement involves mining, crushing and grinding of raw materials (principally limestone and clay); calcining the materials in a rotary kiln; cooling the resulting clinker; mixing the clinker with gypsum, and milling, storing and bagging the finished cement. The process generates a variety of wastes, including dust, which is captured and recycled to the process. The process is very energy-intensive, and there are strong incentives for energy conservation. Gases from clinker cooler are used as secondary combustion air. The dry process, using preheaters and precalciners, is both economically and environmentally preferable to the wet process because the energy consumption of 200 joules per kilogram (J/kg) is approximately half that for the wet process [1].

Due to the fineness of the raw material used in the cement kilns the generation of particulate is inevitable and they pass to the atmosphere through the kiln exhaust gases unless abatement techniques are used. The process activity of cement production generates pollutants such as suspended particulate matter, CO, CO2 and oxides of nitrogen etc. Suspended particulate matter is inherent in the process activity of cement industry, but most can be recovered and recycled. Gases such as carbon dioxide (CO2), carbon monoxide (CO) nitrogen oxides (NOx) and sulfur oxides (SOx) are also formed from the combustion of the fuel used and oxidation of sulfur present in the raw materials. The emission of these pollutants can be minimised by implementation of best available Technique [2]. Carbon dioxide is a relatively abundant and variable constituent of the atmosphere. It is produced and emitted naturally to the atmosphere in the biological decomposition, combustion, and weathering of organic matter, and the weathering of carbonates in rocks, soil and water. The major direct anthropogenic sources of CO2 are combustion of fossil fuel and biomass burning; agriculture represents an indirect source [3].

Pollution resulting from carbon monoxide, carbon dioxide and suspended particulate matter may place an undue burden on the respiratory system and contribute to increased morbidity and mortality, especially among susceptible individual in the general population [4]. Particulates greater than 3 mm in diameter are likely to collect in the lung lobar bronchi. Smaller particulates (less than 3 mm) end up in the alveoli, the thoracic or lower regions of the respiratory tract, where more harm can be done [5]. Air pollution, both natural and man made, affect climate. As has been reported [6], dust and other particulate matter in the air provide nuclei around which condensation takes place, forming droplets and thereby playing a role in snowfall and rainfall patterns Haze, dust, smoke and soot reduce the amount of solar radiation reaching the surface of the earth. Since ambient particulate levels (especially at size less than 10 microns) and high concentration of carbon oxides have been clearly demonstrated to be related to health and environmental impacts [7], therefore the need to monitor levels of suspended particulate matter and CO2 in cement industry by implementing best available technique to protect human health and the environment.

The objective of this research is to basically identify and determine ambient concentrations of CO, CO2 and particulate matter emission arising from Benue cement company process activities and compare concentrations of these pollutants with acceptable regulatory standards and make recommendation on how to ameliorate their effects. Seven Sampling Stations (quarry, raw mill, Cement mill, Kiln, Packing house, Limestone Stockpile and a village upwind of the factory) were chosen for the study. Sampling and data collection and results documentation were done in accordance with the Federal Ministry of Environment’s guidelines and Standards for environmental pollution control in Nigeria.

 

 

Methodology

 

            The sampling stations within the cement factory were at the quarry, limestone stockpile, cement and raw mills, rotary kiln, and Tse-Kucha village two kilometres away Benue Cement factory. Sampling and data collection was in line with the Federal Ministry of Environment guidelines and standards for air pollution. The limits/standards applicable to the possible air pollutants were determined from review of existing regulations, standards and codes, especially the Nigerian Ambient Air Quality Standards. Sampling and measurements of the chemical constituents of atmospheric pollutants (SPM, CO and CO2) at each sampling station were measured in-situ using gas monitors (sensitive analogue and digital gas monitors).The duration of the monitoring exercise was 8 months. Procedure for determination of each pollutant is described below.

 

Carbon monoxide and Carbon dioxide Gas monitoring

A Kitagawa carbon monoxide gas monitor model COM-4 was used for detection of CO. The range of detection was between 0-100 ppm. The detection limit was 0.001 ppm. In the case of Carbon dioxide, Crowncon Gasman carbon dioxide gas monitor model 196410H was used for measuring concentration of CO2. The range of detection is between 0-1000ppm. The detection limit is 0.001ppm.

 

Suspended Particulate Matter Monitoring

A Riken Keiki suspended particulate matter monitor model NP-237H was used for the detection of suspended particulate matter. The range of detection is between 0-2500μg/m3. The detection limit is 0.001μg/m3.

 

 

Results and Discussion

 

The average concentrations of CO, CO2 and suspended particulate matter for the seven sampling stations for the period of eight months are shown in table 1. 

 

Table 1. Average concentrations of CO, CO2 and suspended particulate matter in Benue Cement Company

Sampling Station

Parameters

SPM (μg/m3)

CO (ppm)

CO2 (ppm)

Quarry

156

1.25

34.4

Raw Mill

290

3.50

39.5

Cement Mill

375

1.50

48.5

Kiln

212

4.0

78.85

Packing House

338

1.50

65.25

Lime Stone

Stockpile

93

2.00

26.8

Tse-Kucha Community

81

1.00

29.5

 

The results obtained for concentration of carbon monoxide and represented in Figure 1 below shows that the concentration of carbon monoxide (CO) measured in all the sampling stations were between the range of 1.25 ppm - 4.00 ppm.

 

Figure 1. Average Concentration of CO at BCC and its community

 

This implies that the concentration of CO measured in all the sampling stations were below the Nigerian Ambient Air Quality Standards (NAAQS), which stipulates a range of 10 ppm – 20 ppm for an 8 – hourly average time. The highest concentration of 4.00ppm was at the Kiln station while the lowest concentration of 1.00ppm was recorded at Tse-Kucha community. This low concentration is due to the fact that CO is naturally oxidized by oxygen in the atmosphere to carbon dioxide, therefore before CO get to Tse-Kucha community  it must have been oxidized to CO2.

From Figure 2 below, it also shows that the concentrations of CO2 in all the sampling stations at Benue Cement Company factory and its community were between the range of 26.00 ppm - 35.00 ppm which falls below the maximum standard natural concentration (600 ppm) of carbon dioxide in fresh air and the recommended World Health Organisation threshold limit (TLV) value of 5000 ppm which is safe for healthy adults for an 8-hour work day [8]. Concentration of 78.5 ppm recorded at the kiln station was highest compare to other stations. This could be due to gas released from combustion of kiln fuel. Concentrations of 34.40 ppm, 39.50 ppm, 48.50 ppm, 65.25 ppm, 26.80 ppm and 29.50 ppm were recorded at the quarry, raw mill, cement mill, packing house, limestone stockpile an Tse- Kucha community respectively.

Figure 2. Average Concentration pf CO2 at BCC and its Community

 

The concentration of suspended particulate matter at BCC factory and Tse-Kucha community ranged from 81 μg/m3 to 375 μg/m3 as shown in Figure 3 below.

 

Figure 3. Average Concentration of Suspended Particle Matter at BCC and its Community

 

The lowest concentration of 81 μg/m3 was recorded at Tse-Kucha community two kilometres away from the company while high concentrations of 290 μg/m3, 338 μg/m3 and 375 μg/m3 were obtained at raw mill, cement mill and packing house respectively. This is obvious because majority of dust emissions in the cement factory occur in these areas. All values obtained for suspended particulate matter at the raw mill, Cement mill and packing house sampling stations were above the World Health Organization’s (WHO’s) Guidelines and Standards for Ambient Air Quality which stipulates a range of 150 μg/m3 to 230 μg/m3 for a 24–hour average [9]. This indicates particulate matter pollution in these stations particulate. The lowest concentration of 156 μg/m3 recorded at the quarry may be as a result of little activity of mining and crushing of limestone at the quarry during the time of sampling and measurements.

 

 

Conclusion

 

From this study, it can be concluded that the concentrations of Carbon monoxide and carbon dioxide at Benue Cement Company and Tse-Kucha community were within stipulated standard and therefore safe for human health. The high concentrations of suspended particulate matter of 375 μg/m3, 338 μg/m3, and 290 μg/m3 recorded at the cement mill, packing house and raw mill respectively were above WHO limits. Thus, Suspended particulate matter was found to be the most significant air pollutant in Benue Cement Company factory. Therefore there is the need for improvement on the control of suspended particulate matter emitted from Benue Cement Company. For example an improvement in the operation and maintenance of electrostatic precipitators and baghouses and good housekeeping can improve the efficiency of dust collection and reduce dust generation within the factory.

 

 

References

 

1.      World Bank [online], Pollution Prevention and Control in the Cement Industry, Available at: www.worldbank.org. (Accessed 01/15/2006), 2003.

2.      Harrop D., Air Quality Assessment and management: A Practical Guide, New York, Spon Press, 2002.

3.      Godish T., Air Quality, 3rd Edition, New York, Lewis Publishers, 1997.

4.      WHO Report. Research into Environmental Pollution. WHO Technical Report Series 406. 1968.

5.      Jacko R., Timothy C., Air Pollution and Noise Control, Purdue University, West Lafayette, Indiana, 2003.

6.      Chatwal G. R., Encyclopedia of Environmental Air Pollution, Vol. III, New Delhi Anmal Publications, 1997.

7.      Joseph A. S., Nelson L. N., Franklin, J. A., Environmental Engineering, 5th Edition. New Jersey, John Wiley & Sons, 2003.

8.      WHO Report. Global Environment Monitoring System. Air Quality in Selected Urban areas. WHO offset Publication, Geneva, 1990

9.      Wikipedia [online]. Wikipedia, the free Encyclopedia. Available at: http://en.wikipedia.org/wiki/carbon-dioxide. (Accessed 01/15/2006)