The paper highlights an integrated approach to pollution control in foundries through energy conservation, process modifications and application of cost effective and compatible pollution control devices . The results presented are based on data collected at the demonstration pollution control unit set up at Mls Crawley & Ray, Howrah, based on the design carried out by National Metallurgical Laboratory (NML), Jamshedpur

Ray, A C

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PROCEEDINGS: NS-EWM 19960 NMI., JAMSHEDPUR, pp.45-51An integrated approach to environmentfriendliness and energy conservation in foundriesA.C. RAYDirector, CRAWLEY & RAY (Founders and Engineers) Pvt. LtdForeshore Road . Howrah . India.ABSTRACTThe paper highlights an integrated approach to pollution control in foundriesthrough energy conservation , process modifications and application of cost effectiveand compatible pollution control devices . The results presented are based on datacollected at the demonstration pollution control unit set up at Mls Crawley & Ray,Howrah, based on the design carried out by National Metallurgical Laboratory(NML), Jamshedpur.INTRODUCTIONMachines have become essential in every sphere of our lives in this technologi-cal age and a machine can hardly be made without castings and forgings in it. Hencefoundries and forgeshops cannot be neglected for the improvement of technologicalstate of any country. Traditionally, foundries are considered to be hot dusty and dirtyplace where foundrymen toil hard with hot metal to produce shaped castings. Thus, inthe early seventies there was a move in the developed western countries to level thefoundries as smoke-stack and sunset industry. By then the awareness about theenvironment was growing and stringent laws were enforced which led to the closure ofa significant number of foundries. Jerry Rogers of General Motors commented in AFSEnvironmental Conference held in 1995 that since 1980 one of every four foundries hasshut down in US due to environmental regulations and non-competitive process. Theresult of such closure compelled the developed countries to source their requirement ofcastings from the developing nations such as Korea and Taiwan. As the economybecame progressively stronger, these countries also became concerned about theirenvironment and consequently the developed nations now are trying to source theircasting requirements from China, Indonesia, Brazil and India. It is an opportunity theIndian foundries cannot afford to miss. But at the same time, propercare should betakento avoid the environmental degradation. Fortunately, India is a vast country and doesnot face the problems as faced by Korea and Taiwan. Against these, one has also toconsider the distribution of foundries in India which are concentrated in areas such as45A.C. RAYHowrah , Agra, Batala, Coimbatore , Kolha-pore , Bhavnagar etc. This type of concen-trated distribution is worrying so far as environment is concerned . It, thus , follows thatpollution control is necessary for Indian foundries for the protection of regionalenvironment.German workers I'3 concluded in 1983 that the control ofpollution in foundriesis necessary - but bureaucratically exaggerated environmental laws led to increase inthe cost of industrial products so much that they become unaffordable. This appears tobe valid in the Indian context especially when India with her historical foundingexcellence can become a major supplier to the world market if quality - reliability andcost - competitiveness can be achieved. The position of Indian foundry industry withrespect to that of other major producers of the world is shown in Table-I [21.Table-1 : World Casting Production Census 1993 (in million tonnes)Country F.G.IronS.G.IronMalleableIronSteel Totalcis 13.460 0.392 - - 14.330China 7.8585 1.132 0.418 1.538 11.615U.S. 4.575 3.056 0.193 0.964 10.537Japan 3.383 2.024 0.185 0.378 7.197Korea 0.825 0.375 0.039 0.118 1.409Taiwan 0.733 0.255 0.013 0.110 1.318India 1.193 0.036 0.072 0.263 1.576The foundry industry after some years of sluggishness is now experiencing aboom period, and the world casting production is expected to rise steadily due toeconomic turn around of developed nations. With this background, an analysis ofTable-1 certainly indicates that India has enormous opportunity to emerge as asignificant supplier of castings to the world market.It is to be noted that any consideration of the environmental aspect of atechnological process must be related to its energy requirement as well. A processwhich needs a minimum amount of energy is least polluting for the environment. Tilldate, fossil fuel is the major source of energy production and the combustion of the fuelwill lead to various forms of environmental degradation such as increment of Sus-pended Particulate Matters (SPM), SO2, CO and green house effect caused by excessCO2 levels. Thus an integrated approach involving both pollution control and energyconservation is necessary for all technological processes.46A. C. RAYProblems or Indian FoundriesThere are about 5000 foundries in India with installed capacity of 3.4 milliontonnes per annum" ', Most of these are in the Small Scale Industry Sector. Reliable dataabout the foundries in India is virtually non-existent. However, one important but easilyidentifiable problem of Indian foundries is the technological obsolescence. In manycases, layout, equipment, process and manpower are totally inadequate to cater for theincreasingly stringent quality and cost competitiveness demanded by the customersof the foundry product. The author who is associated with foundries for a long timealso feels that many of the foundries are too small to employ professional managersfor proper personnel and financial management. Added to these, many foundries arerun by a peculiar system of hot metal sale to labour contractors which makes theproduct quality assurance virtually impossible. Apart from the above problems, theIndian foundries are perpetually plagued by poor quality input materials such as pigiron, coke, lime stone, sand etc. and acute shortage of funds both for equipmentpurchase and working capital due to reluctance of financial institutions to extend ahelping hand to foundries of small and tiny scale. The banks complain about the lackof financial discipline in small and tiny sector of the foundry industry even thoughthe Small Industries Development Bank agrees that a far bigger sum of money hasto be written off as bad debt by the banks for large and medium scale sector of theindustry than for the small tiny sector. Working with these constraints, the foundrieshave to produce quality castings at competitive price acceptable to the global market.This is not an easy task and compliance to strict pollution control norms will makethe task far more difficult for most of these foundries with likely resultant closure.THE INTEGRATED APPROACHPresently, B.P.coke produced by coke-oven batteries, is not available in themarket. Foundrymen are forced to use Beehive coke. Beehive coke is inferiorcompared to B.P. coke. It has more ash, more volatiles, more sulphurand less shatterresistance than those of B.P. coke. As it is, B.P. coke in India has an ash content ofaround 30% while Beehive may contain up to 40% ash. This high ash content issometimes reduced by Beehive producers by mixing lower ash but higher sulphurcontent coal. As a result, a Beehive coke with lower ash content will have a sulphurcontent of more than 1 % which will increase the SO2 emission from the melting unit.The integrated approach will, in the first place, improve the energy efficiency of theCupola, which means that less coke will be necessary to produce same quantity ofmolten ironof similaroreven better quality. Such a cupola will be less polluting evenbefore installation of any pollution control device and may need simpler and lesscostly devices to achieve the norm. It can again be remembered that any deviceinstalled to control the emission from the cupola will add to the cost of the product47.4,-C- RAYFig.l : Improved cupolasg= PG 7b.Fig.2 : Schematic diagram of pollution control device48A.C. RAYand make the product less competitive. Stricter the norm, more costly will be thecontrol devices.Energy efficiency of a cupola will depend upon the combustion efficiency toa great extent. The recent survey on Howrah foundries carried out by NationalMetallurgical Laboratory (NMI.) showed the average value of combustion effi-cienc% of an ordinary cupola under steady operating condition is of the order of 80percent while that for a cupola of improved design is nearly 95%I1t.Thecombustion in the cupola is given by the following combustion equationsC +O2=CO2 ... (1)2C + 02 = 2CO ... (2)C + CO2 = 2CO ... (3)While most of heat generated for melting is supplied by the equation (1), theequation (3) is highly endothermic. There area number of improved designs of acupola to get optimum melting condition such as (a) heating the input blast, (b)Oxygen enrichment of the bias Land oxygen injection at tuyeres, and (c) dividing andproportionating the blast air.Heating the air blast to 520°C will favour the reaction - (2) and improve thecombustion (Fig.la). Oxygen enrichment and injection to the extent I to 4% willintensify the heat liberating combustion equations with resultant increase of meltingrates, temperature and carbon pick-ups (Fig. Ib). Dividing the blast and directing itthrough two rows of tuyeres set at 915 mm apart will result in better combustionefficiency but more importantly the higher coke bed and two combustion zonesresult in improved heat transfer to the droplets of metals. It has been reported thattsta reduction of coke consumption by 40 percent and an increase in melting rate up to30 percent can be achieved by using a divided blast cupola.The author is involved in the design and operation of divided blast cupolasto run under Indian condition since 1973. Very recently, the divided blast cupolasin the foundry with which the author is associated have been fitted with pollutioncontrol device with basic design and measurements done by NML,Jamshedpur. Thecupolas of Crawley & Ray foundry have an internal diameter of 915 mm. Theseproduce 5 tonnes/hour molten cast iron with tapping temperature of more than1430°C using7 : I metallics to currently available Beehieve coke ratio . The emissionmeasurements were carried out a number of times on these cupolas before and afterfitting the control device which is shown in Fig . 2. The weighted average value ofmeasurements is given in Table-2.49A. C. RAYThe studyl"I conducted by the NML workers on Howrah Foundries indi-cated the SPM values ranging from 400 - 2650 mg/Nm3 and SO2 level from 200to 2600 mg/Nm3. These values when compared to those to Table-2 clearly showsthe importance of the proper cupola design and operation. The SPM level isconsiderably lesser in a properly designed and operated cupola which allows arelatively less costly control device to achieve the norm.Table-2 : Effect of Pollution Control Device on Emissions(The values indicated are under steady state Cupola operation)Measurement Before control device After control deviceFlue gas temp . °C 96 62Average SPM mg/Nm3 212 135Average SO2 mg/Nm3 43 72*Average CO (%) 3 2.6Average CO2 (%) 11.3 3.3Average particle size (µ) 460 125*Combustion Efficiency % 95 93* The increase in SO, and reduction in average particle size maybe attributed to changein coke qualityThe low value of SO2 is perhaps due to proper charging operation compared tothe cupola operational practice of other Howrah foundries. Hot gases have more chanceof intimate contact with heated layers of lime stone which may absorb considerableamount of SO2. Again from energy efficiency point of view, the advantage of thedivided blast cupola can clearly be seen from Table-3.Table-3 : Actual data of two foundries considering a production of 120 tonnes/month or 1440 tonneslyear of molten metalMeasurement Conventional Divided blastMelting rateint/h 4.5to5 5.0-55Size (melting zone ID in mm) 1220 915Bed coke weight in kg . 1500 900Metallics : Coke ratio 5:1 7:1Charge coke weight in kg/t 200 14050A. C. RAYThe analysis of Table-3 reveals that 600 kg. and 900 kg. of coke is saved on 15tonnes of molten metal perday in bed and charge respectively. This means that foreverytonne of molten metal 100 kg of coke is saved. Thus for the production capacity of 1440tpa, 144 tonnes of coke is saved. This, in terms of money at present, this will be 144 x3000) = Rs. 432,000.Better temperature of the metal is also likely to bring down rejection of castingand thus improving the yield. Even an improvement of 5% yield will result in savingof 14.4 tonnes of coke. Thus a considerable amount of energy can be saved for a typicalfoundry. The saving will be much more significant for a bigger country.CONCLUSIONIt is evident from the above, that when the air pollution from the cupola meltingunit of the foundry is considered, the integrated approach to both environmentfriendliness and energy efficiency should be considered. Installation of any pollutioncontrol device will lead to increased production cost without increasing the productiv-ity. But the integrated approach discussed above will largely offset the increasedproduction costdue to savings in energy requirement. Control of pollution and the normrequirements should not be considered in isolation but should be considered in totalitywith energy conservation taking due account of social need, market opportunity andeconomic viability of the industry and indigenously available technology to achieve thelevel of control. The World Bank is now financing a project considering the relevanceof social, technical and economic aspect of pollution control of six developing nations.Environment Protection Training Research Institute (EPTRI) has been entrusted to dothe survey in India. It is hoped that some necessary but affordable systems may emergefrom these studies.REFERENCES[ 1] W.Sicfer and K.Ori,hs, Foundry M&T, 1983.24.121 Modem Casting , December, 1994.[31 D.S.I.R. (T.A.A.S), Technology Evaluation and Norms Study in Ferrous Foundry Industry, May,1990, 7.[41 A.Bandopadhyay and P.Ramachandra Rao, Workshop on Iron Foundry, Organised by Develop-ment Commissioner for Iron and Steel , Calcutta, May, 1995.[51 H.7. Leyshon, BCIRA Proceedings of the Conference on Choice of Iron Foundry Melting Plant,1972, 59.51

An integrated approach to environment friendliness and energy conservation in foundries

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An integrated approach to environment friendliness and energy conservation in foundries

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