Development of various modules of environment friendly furnaces concerning melting and castings of iron, brass and bell metal products

Abstract

Since over a decade there is a worldwide trend towards using fuel alternative tocoal/ coke concerning casting production due to the excessive emission undesirable level of suspended particulate material and toxic gases beyond acceptable limit with flue emitted from coal/coke based units. India is an important global player in the casting sector and the study on ferrous as well as non-ferrous casting reveals that : (i) there are above several thousand coke based foundries currently operating in different parts of India and (ii) there are numerous cottage based brass and bell metal industries in India which mainly use coal/coke/wood / wood charcoal as main fuel. Exhaust emission with flue from these coal/ coke based industries normally carries lots of Suspended Particulate Materials (SPM), Toxic gases such as SO , NO , etc. Normal emission of SPM and SO x x x from these foundries/ melting and casting unit is about 1000-3000 mg / NM3 and beyond 700 mg / NM3 respectively. Stringent specifications set by not only Pollution Control Boards of various First & Second World countries but also by CPCB (Central Pollution Control Board of India) threaten the existence of most of the coke/coal based medium and small scale casting sectors as operation of these solid fuel based furnaces is reported extremely unhealthy because of the excessive presence of SPM and toxic gases. Coke less cupola using sulfur-stripped hydrocarbon based oils (LDO, Kerosene Oil)/ Gases (LPG, LNG, NG) developed by M/s Richard Taft1, Ducker2, NML/CSIR3, in Russia4 as well as in Japan5 is presently in the process of replacing coke based cupola concerning iron casting / foundries. Therefore, an attempt had been made in this work to carry out research and development of environment-friendly furnaces of various sizes for brass and bell metal melting and casting in connection with the production of thin section of not only traditional items/ utensils such as lota/small size pitcher, ghara/ big size pitcher, tumbler, thali/saucer/plate, flower vase, but also of artifact. Number of visits to various clusters of Brass and Bell metal Industries of West Bengal, especially at places and around Bishnupur in Bankura district were made. Thorough discussion with practitioners as well as artisans and witnessing some of the present practice were carried out. State of precarious ambient condition due to excessive presence of SPM as well as toxic gas in and working places as a result of using highly ash content coke was noticed. Based on mutual agreement and self financing, an eco friendly furnace was envisaged to design and developed to deal with melting and casting of about 5 kg weighing standard Kalsi. Concept design of coke less furnaces using sulfur-stripped hydrocarbon based oils (LDO, HSD, Furnace Oil) / Gases (LPG, LNG, NG) was envisaged to be utilized as exhaust emission from these ensures SPM and toxic gases much less to the extent of about 10 ~ 25 mg/ Nm3 from the limit of 150 mg/ Nm3 set by any local Pollution Control Board [CPCB]. The developmental work of such a furnace [a module unit of melting and casting] envisaged to include a set of either oil or gas burners which are to be positioned/ placed spirally along the hearth portion of the furnace to provide necessary heat for heating and melting. Around the burners, there shall be some of refractory coated [heat insulated]grate bar to support entire load of permeable bed and mould containing desired raw materials for melting and casting of Kalsi/ pot. Desired quality permeable bed may be improvised to be made by using either by making highly insulated and unbreakable quality ball made from cast able quality refractory ball [about 50 Ø mm. ] or by breaking and shaping of granular size rejected graphite block [-55 + 50 mm] from used and rejected graphite electrode. Permeable bed is envisaged to extract and absorbed heat from flue and suitably transfer the heat to the mould. During the operation of the mentioned furnace, hot gases/flue from burners is expected to flow up through the permeable bed placed along the annulus space between furnace and the mould. Heated flue which is ejected out from the mentioned burners while passing along mould and permeable bed is expected to accomplish preheating, heating, maintaining temperature for complete melting of raw materials. Through permeable bed area, the proposed design is envisaged to control/ adjust the operating temperature of furnace, mould and raw materials. Molten metal with desired flow ability is expected to get into the cavities of investment mould to produce thin shell utensils/ Kalsi when it is tilted upside down after getting superheated in the stated furnace. The desired furnace was designed and developed in the premises of an entrepreneur at Bishnupur locality in Bankura District of West Bengal. No. of successful campaigns then carried out which reveals not only the acceptability and validity of the developed Furnace based on using Sulfur stripped domestic fuel such as mainly LPG [ Liquid Petroleum Gas] as well as Kerosene but also market acceptability of the product i.e. Kalsi/Ghara/Pot. In near future, the developed technology is expected to be utilized by the Practitioner as well as Artisan of the Brass and Bell metal product cluster with sulfur stripped either LPG from west coast or NG [Natural Gas] from Assam when these are expected to be supplied through National Piping Net Working.