CHAPTER 4 A STUDY ON CONTROLLING POLLUTION IN IRON FOUNDRIES LOCATED IN COIMBATORE DISTRICT OF INDIA

Transcription

1 68 CHAPTER 4 A STUDY ON CONTROLLING POLLUTION IN IRON FOUNDRIES LOCATED IN COIMBATORE DISTRICT OF INDIA 4.1 INTRODUCTION As mentioned in the previous chapter, the utilization of induction furnaces in foundries results is less emission of pollutants in comparison to the utilization of cupola. Yet the drawbacks like capability of melting less quantity of metal charge and high cost of installation of induction furnaces drive the iron foundries of India including that are situated in Coimbatore to utilize cupola to melt the metal charge. Under these circumstances, the iron foundries located in foundry cluster of Coimbatore utilize either induction furnace or cupola furnace. In some iron foundries of this cluster, both induction and cupola furnaces are utilized. In majority of the iron foundries of India, the quantities of pollutants emitted by the furnace is more than that is allowed by the Central Pollution Control Board of India (CPCB) and pollution control boards of state Government of India. In order to get permission from these organization to run the furnaces, these iron foundries are regulated to control the emission of pollutants from the furnaces installed in them. As a result of this situation, some of the iron foundries situated in Coimbatore have installed PCDs. This situation has revealed the need to study the impact of PCDs on controlling pollution in iron foundries located in Coimbatore district of India. In order to

2 69 meet this research need, the study reported in this chapter was carried out during the doctoral work being reported here. In the next section, the information drawn by referring to the research papers about, the PCDs utilized by the iron foundries of India is narrated. By referring to the information presented in these research papers, the history of carrying out pollution control in India is narrated. In the same section, the absence of studies on controlling pollution in iron foundries located in Coimbatore district of India is pointed out. In the next section, efforts made to gather relevant information from iron foundries located in Coimbatore district are narrated. In the same section, the gathered information are analyzed. 4.2 POLLUTION CONTROL IN INDIA AND ABSENCE OF STUDIES ON POLLUTION CONTROL IN IRON FOUNDRIES OF COIMBATORE India is one among the countries in which the efforts are being exerted to control pollution arising from iron foundries (Pal et al 2008). Indian government s thrust on controlling pollution arising due to industrial growth is also fueling the increased usage of PCDs in iron foundries situated in different foundry clusters located in different parts of India. Soon after the conduct of Stockholm conference on human environment in the year 1972, the Indian government began to promulgate legistrations to control pollution that has been causing due to rapid industrialization (Krishnamoorthy 2005). One among them is, the air (prevention and control of pollution) act of Indian government set up CPCB to enact pollution controlling standards. The monitoring of pollution control activities has been assigned to the institutions governed by the governments of states of India. These institutions are known in India as state pollution control boards.

3 70 (D Souza and Peretiatko 2002). These institutions are known by the names of the Indian states in which they function. For example, in Tamilnadu state of India (where the author of this thesis resides), this institution is known as Tamilnadu State Pollution Control Board (TSPCB). Besides monitoring the implementation of pollution control activities, TSPCB is also involved in developing reports on pollution generated from different industrial sectors. Some authors have reported the researches on studing the pollution that emanates from foundries located in different foundry clusters of India(Pal et al 2008).However the study on controlling the pollution caused by iron foundries in Coimbatore district of India (where the author of this thesis resides) has not yet been conducted. Although Vijayanand et al (2008) have studied heavy metal content in the ambient air of Coimbatore district of India, an exclusive study on using PCDs in iron foundries situated in the same district has not been conducted. In the context of this observation, the study on utilizing PCDs in the iron foundries located in Coimbatore district was carried out. 4.3 PCDS EMPLOYED AND THEIR IMPACT IN THE IRON FOUNDRIES OF COIMBATORE The study being reported here was carried out in two phases. In the first phase, the PCDs employed in the iron foundries situated in Coimbatore were studied. In order to carry out this study, it was decided to choose a sample of 25 iron foundries which would represent the situation prevailing among iron foundry units of Coimbatore with respect to pollution control aspects. In order to choose the 25 iron foundries from Coimbatore for gathering the relevant data, the area which is critically polluted had to be identified. In order to identify such a critically polluted area, a report submitted by TSPCB was studied.

4 71 Quite interestingly, maximum number of units of industry located in this area belongs to foundry. In this background, it was construed that, if the data on using PCDs in iron foundries is gathered from critically polluted area, then such data would also represent the other areas of Coimbatore. After this identification of area, two experts were consulted. One expert is an assistant engineer of TSPCB. The other expert is an engineer working in a foundry unit situated in critically polluted area. These two experts were requested to list the iron foundries that fulfill the following criteria. i) The iron foundry unit may use either cupola or induction furnace for melting metals. (This criterion was chosen as majority of the foundries in India use either cupola or induction furnaces to melt the metals). ii) The iron foundry unit may comply with the auditing requirements of TSPCB and may maintain the record of pollution emitted from the iron foundry unit. (This criterion was chosen as drawing of data from the records submitted to the TSPCB would be highly authentic). iii) The iron foundry unit must have installed a PCD to control the emission of pollutants. (This criterion was chosen to study the impact of using PCDs in iron foundries on controlling pollution). After studying the above criteria, the two experts listed 24 iron foundries located in critically polluted area. The author of this thesis preferred to add one iron foundry to this list even though it is not located in of

5 72 critically polluted area Coimbatore. The reason for including this iron foundry in this list is that, it is a scientifically managed foundry and is incorporated with a relatively new PCD called Cassette filter. Because of this meticulous selection, relevant and authenticated data on using PCDs in these 25 iron foundries could be gathered. These data represented about 400 iron foundries located in foundry cluster of Coimbatore district. A data sheet was prepared to gather relevant data from these chosen 25 iron foundries on using PCDs in them. By interviewing managers of these iron foundries, the data in this sheet was filled. Particularly, the discharge rate, SPM and pollutants before and after implementing PCDs were entered in this data sheet by interviewing these managers. These managers furnished the data by referring to the pollution data which were submitted periodically to the external pollution control auditing agencies like TSPCB. Out of the 25 iron foundries, PCDs installed in four iron foundries were not under effective operation. Hence the data on PCDs which are put under effective usage in 21 iron foundries were gathered. These data were gathered from March 2010 to February These data are shown in Table 4.1. In order to improve qualititative readability, the data presented in this table are pictorially presented in Figure Even in these 21 iron foundries, some data could not be gathered. For example, in iron foundry 4, the discharge rate before installing wet cap collector was not available. As shown in this Table, in ten iron foundries, cupola furnace is used. In the remaining 11 iron foundries, induction furnace is used. By referring to the data presented in Table 4.1, the impact of PCDs employed in the iron foundries of Coimbatore is described in the following sub- sections.

6 73 Table 4.1 PCDs installed in foundries of Coimbatore district and their impact on pollution prevention Iron foundry number Furnace used PCD Stack temperature (average) in degree Kelvin Velocity (m/sec) Discharge rate (liters/hour) SPM (mg/nm 3 ) (average) Concentration of pollutants in (mg/nm 3 ) Before After Before After Before After Installing the PCD Installing the PCD Installing the PCD SO 2 NO x CO 2 CO 1 Cupola Cyclone Cupola Wet cap Collector Cupola Dry cap collector Cupola Wet cap collector Cupola Venturi wet Scrubber Cupola Wet cap Collector 7 Cupola Drycap collector 8 Cupola Wet cap Collector 9 Cupola Drycap collector 10 Cupola Wet cap collector Venturi 11 Induction wet scrubber 12 Induction Venturi wet scrubber 13 Wet Induction scrubber 14 Wet Induction scrubber 15 Wet Induction scrubber 16 Wet Induction scrubber 17 Wet Induction scrubber 18 Wet Induction scrubber 19 Wet Induction scrubber 20 Induction Wet scrubber 21 Induction Cassette filter ND ND ND - 29 < ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND 200 < <20 ND ND ND ND

7 74

8 75

9 76

10 77

11 78

12 79

13 80

14 81

15 82

16 83

17 84

18 85

19 86

20 87

21 Impact of Dry Cap Collector As shown in Table 4.1, out of 21 iron foundries surveyed, three of them have installed dry cap collector. Dry cap collector is one type of pollution control equipment which is fitted on cupola stack. On top of the cupola, spark arrester is provided. Around the spark arrester, a cap is provided with baffler. This assembly is called as dry cap collector. When the dust air enters the dry cap, the particulate matters settle down in the bottom of dry cap. Baffles are fitted at the bottom of dry cap. Baffles are working as the barrier to prevent the escaping of dust air into the atmosphere. Clean air enters into the atmosphere through stack. As shown in Table 4.1, and in figure 4.11,dry cap collector fitted with cupola, was found to reduce the SPM from 1750 mg/nm 3 to 496 mg/nm 3 in foundry-3, 394 mg/nm 3 in foundry-7 and 366 mg/nm 3 in foundry-9. In all these three iron foundries, the particulate matter concentration was found to be higher than the specification stipulated by CPCB which is 150 mg/nm 3 (Pal et al 2008) Impact of Wet Cap Collector As shown in Table 4.1,and in figure 4,11, wet cap collector is installed in iron foundries 2, 4, 6, 8, and 10. Wet cap collector is another type of pollution control equipment. The working of wet cap collector is same as that of dry cap collector. The additional feature of wet cap is that, water is sprayed into the housing, which is fitted on the top of the cupola with a water cycling line. The high velocity dust air is scrubbed by the water and solid particulate matters settle down in the settling tank. Water is recycled using pump.

22 89 As shown in Table 1, in iron foundry 2, wherein, wet cap collector is fitted with cupola, the SPM concentration reduced from 2500 mg/nm 3 to 110 mg/nm 3. In iron foundries 4, 6, and 10, the data on the SPM concentration before the installation of wet cap collector were not available. The current concentration which has occurred after the installation of wet cap collector in iron foundries 4, 6, 8 and 10 were 110 mg/nm 3,102 mg/nm 3, 95 mg/nm 3 and 105 mg/nm 3 respectively. These values fall within the emission limit of 150 mg/nm 3 (Pal et al 2008) Impact of Cyclone As shown in Table 4.1, cyclone is installed in iron foundry 1. A cyclone is a device used for filtering particles in the diameter ranging from 1 to 1000 micrometer from a gas or liquid flow. Due to the centrifugal force, solid particles are hurled against the outer wall of the cyclone. After falling down, they are collected and separated in the deposition chamber (Kahrimanovic et al 2011). From Table 4.1,ANF FIGURE 4.11 it is clear that, on employing the cyclone in iron foundry, SPM concentration has reduced from 300 mg/nm 3 to 67 mg/nm 3. It was discernable that, cyclone would be a suitable PCD for fitting in the cupola furnace to control pollution Impact of Wet Scrubber As shown in Table 4.1, wet scrubber is installed in iron foundries 13, 14, 15, 16, 17, 18, 19 and 20. Wet scrubber is a term used to describe a variety of devices that use liquid to remove pollutants. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid. The particles in the polluted gas stream are captured by the liquid droplets. This phenomenon is carried out by dissolving or absorbing the particles in the liquid. Any droplets that are in the flue gas must then be separated from the clean exhaust stream using a device called mist eliminator.

23 90 Most of the foundries have adopted wet scrubber. Wet scrubber is very effective in removing both particulate matter and gases (Scnelle and Arnold 2002). During the study being reported here, three iron foundries fitted with venturi wet scrubber and eight foundries fitted with normal wet scrubber of various types (Table 4.1) were monitored. It is interesting to note that, remarkable reduction in particulate emission concentrations has been achieved in iron foundry-17, and iron foundry-20. The SPM concentrations were found to be 52, 51, 50, 51, 55, 50 mg/nm 3 in iron foundry-13, iron foundry-14, iron foundry-15, iron foundry- 16, iron foundry-18, and iron foundry-19 respectively. These values reveal that, the reduced particulate emission size achieved after installing wet scrubber is as small as 50 mg/nm Impact of Venturi Wet Scrubber As shown in Table 4.1, venturi wet scrubber is installed in iron foundries 5, 11 and 12. A venturi wet scrubber is basically a duct that has converging venturi-shaped throat followed by a diverging section through which a polluted gas stream from the cupola is passed. The liquid is generally introduced as jets, which soon atomizes to form many small droplets (Goncalves et al 2003). The scrubbing liquid is injected at right angles to the incoming gas stream, which breaks the liquid into small droplets that are then used to collect the particulate matter as well as gaseous contaminants. The energy required for dispersion is provided by high velocity gas stream. The quality of liquid dispersion depends on the velocity of the feed gas. A decrease in gas velocity will lead to the diminution of the collection efficiency.

24 91 A venturi wet scrubber has high separation efficiency for removal of air contaminants. From the Table 1, it can be observed that, when venturi wet scrubber was fitted in cupola, the SPM concentration was reduced to 51 mg/nm 3 in iron foundry 5. When venturi wet scrubber was fitted in induction furnace, SPM concentrations observed were only 31mg/nm 3 and 37 mg/nm 3, in iron foundries 11 and 12 respectively. Therefore the controlling of the pollution depends on the nature of SPM emitted through the stack and type of furnace used Impact of Cassette Filter As shown in Table 4.1, cassette filter is installed in foundry 21. As mentioned in section 2.8 (chapter 2),It is quite interesting to note that, the usage of cassette filter to control the pollution arising from iron foundries is yet to be dealt by the researchers. This is evident on observing the absence of papers reporting the installation of cassette filter in foundries. The cassette filter fitted with induction furnace in iron Foundry 21 resulted in the reduction of SPM concentration to less than 20 mg/nm 3. This is the highest reduction of SPM concentration achieved in comparison to that is achieved by other PCDs dealt in the previous subsections. The literature and practical surveys reported so far in this thesis have revealed two facts. According to the first fact, the concentration of pollution caused by the induction furnace is less compared to that is caused by the cupola furnace. The second fact is that, among all the PCDs, cassette filter is most efficient in controlling the pollution that arises from iron foundry. While the construction, working and performance of induction furnace are abundantly documented which have also been presented in section 3.5 of chapter 3, it is not so in the case of cassette filter

25 CONCLUSION Right from ancient days, foundries have been producing products which are required to enhance the quality of life of humans (Pal et al 2008). Over the years, many advances in the form of technologies and methods emerged in the foundries to produce products with high degree of quality and productivity.these developments have been fuelling the growth of foundries. This growth has been benefiting various societies in the world. Particularly, iron foundries have been playing major role in enhancing the wealth of various countries and regions. On the other hand, the development of iron foundries is resented in various parts of the world as the flue gasses (Andres et al 1995) released by the foundries are found to affect the environment and thereby, the healthy living of humans is affected (Liu et al 2010; Liu et al 2009). In order to overcome this deficiency, a few PCDs are employed in iron foundries. Certain studies conducted by the research community in this direction has revealed that, the installation of PCDs and prevention of pollution from the foundries are influenced and affected by localized factors like high cost, legal laws and lack of trained manpower. While the researches are going on in this direction, it is surprising to note that, the performance of iron foundries situated in Coimbatore from the point of view of polluting the environment has not so far been reported in the literature area. In order to fill this research gap, the module of the doctoral work reported in this chapter was carried out. After reviewing the literature, relevant data from 21 foundries situated in Coimbatore district were gathered. The data gathered indicated that the pollution levels released by the induction furnace installed in foundries is

26 93 less than that in case of foundries which have installed cupola furnaces. This derivation is corroborated with the guidelines given in Fatta et al (2004) another interesting observation is that, in only one foundry, cassette filter is used. The level of controlling emission in this iron foundry was highest in comparison that is achieved by installing other PCDs. As mentioned in section 2.8 (chapter 8).The details about the construction, working and performance of cassette filter, are conspicuously absent in literature arena. Hence during the module of the doctoral work reported in this thesis, the details about the cassette filter were gathered from the iron foundry in which the same is fitted with induction furnace. These details have been presented in this chapter. A preliminary study has revealed that it is less costlier to install cassette filter than installing other PCDs in iron foundries. It is also discernable that, maintaining cassette filter is easier in iron foundries. The efficiency of cassette filter is so high that the SPM concentration released by it is less than the standard value specified by the European standards. Amidst all these benefits, the factors that might distract the iron foundries from installing cassette filter need to be further investigated. This investigation has to be carried out by comparing the performance of wet scrubber and cassette filter in iron foundries.