CLEANER PRODUCTION IN FOUNDRY INDUSTRIES

Transcription

1 CLEANER PRODUCTION IN FOUNDRY INDUSTRIES INTRODUCTION Foundry is one of the most energy intensive metallurgical industries. Various sections of Foundry namely Pattern making, molding, melting, core making, compressed air etc. consume energy in the form of electricity or through burning of fuel. Among these largest amount of energy to the tune of % of the total Foundry energy is consumed in melting operation. As the Foundries are growing with mechanization and automation, the requirement of energy is also increasing day by day. On the other hand today the whole world is frightened of climate change and global warming due to CO 2 generation from burning of fuel as source of energy or for producing electricity. CURRENT SCENARIO IN INDIA Looking into today s scenario, it becomes very essential for Foundry men to look for means which can bring down the energy consumption in melting operation significantly by efficient and optimal running of furnaces. This will not only reduce the cost of energy but also add to revenue thru sale of carbon credits. Plenty of work is being done by Foundry men in this direction where the ultimate aim is to reduce specific energy consumption in liquid metal preparation. India has around 5000 foundries, producing about 3.24 MT of castings worth Rs 10,000 crores. It ranks sixth in terms of production, next to the CIS. These units are mostly located in clusters with numbers varying from less than 100 to around 400 per cluster. Some of the notable clusters in this regard are Agra, Howrah, Coimbatore, Kolhapur, Rajkot and Belgaum. The foundry produces a wide variety of castings such as manhole covers, pipe and pipe fittings, sanitary items, tube well body, metric weights, automobile components, railway parts, electric motor, fan body etc. 90% of the castings produced are from the SSI sector. India Ranks as 2nd largest casting producer producing estimated 7.44 Million MT of various grades of Castings as per International standards.

2 CLEANER PRODUCTION TECHNOLOGIES Rinsing at Anodizing Line. All anodizing rinses shall be done with recycled water (after wastewater treatment unit). Install a sensor/ temperature controller for observation and better temperature control of extruded profile. Dripping off into the anodizing baths. Optimize the dripping off and drag out from the Aluminum profiles. Install inverter. Slow down the speed of dust collection fan of the cold saw machine. Replacement of coke with natural gas. Installing autocast, a casting software for methods design, simulation and optimization. It improves the quality and yield of existing castings, develop new castings quickly, without foundry trials and reduce the total cost in collaboration with customers. Benefits Water savings achieved. Better control of energy input. Savings in usage of raw material. Optimized electrical consumption. Reduced emissions. Economic fuel consumption. Optimized process control and reduction of use of raw materials and energy. CP OPTIONS Waste Cause Cleaner Production Options Benefits stream Liquid Wastewater The more 1st Circulate canal in factory and reuse again Reduce water consumption/hour. water used to cooling, the easier it is to remove impurities (dilution) Adjust to influent of die cleaning, subsequently sent to WWTP Leaks and spillages Regular maintenance and repairing of equipment Reduction in huge economic losses as well as efficient production. Wastewater : Low quality of water because contaminated the acidic chemicals Sent to WWTP Less generation of effluent. Wastewater contains sodium hydroxide: Cleansing by NaOH solution to be increase amount of NaOH in tank. Al3+ will be precipitated in Crystallized form by Etching. Recovery method under temp. control condition,naoh(aq) will be reused in etching tank. Less generation of effluent. Reduce consumption of chemicals and water at a minimum of 3%.

3 Solid Wastewater contains sulphuric acid: Used for electrolyte solution in anodizing tank Wastewater contains Nickel +Boric: A lot of quantity of water used for coloring Dross: The waste that forms on the surface of a molten metal Scrap: The quality of aluminum is lower the standard or unshaped bar Generation of spent sand and dust Aluminium crystal is selling for soap production or high polymer production. Acid Recovery method, the Dialysis Membrane technology is used for separating anion (SO42-) Al2(SO4)3, Crystal will sell in Alum Production Reverse Osmosis system used for separating concentrated solution and diluted solution to reuse again in rinsing tank Dross Separator used for stir separating the recycle aluminium to raw material As well as, the non-recycle aluminium will sell to supplier Recycle to raw material Shipping spent sand to a Portland cement manufacturer. Lower efficiency of production Check inputs and outputs and control temperature, holding times and order of charging Gas Air pollution Setting air pollution treatment system. Fuel switch over to natural gas or other economic fuel. Combustion losses. Radiation losses Waste heat used in preheating combustion air Correction of air to fuel ratio and eliminate excess air. Apply covers and ceramic jackets to enhance insulation. Can be reused in building make up air and heating of foundry building. Reuse of waste product generated. Recovery of resource from waste. Reuse of waste product generated. Recycling of the waster reduces water consumption. Recycling of aluminum and reduces consumption. Increase in productivity. Reuse of waste product generated. The scrap consumption is reduced due to recycling. Economical beneficial reuse of waste. Improved production efficiency Reduction in emissions as well as economic. Reduction in fuel losses adds to economy. Reduces energy losses. Reuse of waste generated.

4 CASE STUDY IN FOUNDRY RAJKOT BACKGROUND Case study of successful implementation of Divided (Cold) Blast Cupola (DBC) at Shining Engineers and Founders, a progressive foundry unit located in Rajkot, in the state of Gujarat. Rajkot, in the state of Gujarat, is one of the largest foundry clusters in India. There are about 400 gray iron foundry units in Rajkot and they produce castings for a variety of industries such as diesel generator-set manufacturers, automobiles, textile machinery manufacturers, machine tools industry, pumps, valves and electric motors. The majority of the foundry units at Rajkot are small, and produce less than 100 tonnes of casting a month. Cupola is the main melting furnace employed by foundry units at Rajkot and a design of cupola, called Rajkot Cupola, is prevalent there. There is significant scope for improving the energy performance of these conventional cupolas operating in Rajkot by up-grading to the more efficient Divided (cold) Blast Cupola (DBC) operation. PRE-COMMISSIONING AUDIT Audit of the existing cupola is an important activity for establishing the baseline energy performance of the cupola which are under operation in the plant. The existing cupola had three rows of tuyeres and a diameter of 27 inches. The melting rate in the cupolas was 3.3 tph (tones per hour). A common bucket charging system feed the two cupolas. The furnace was continuously tapped into casting ladles. A summary of the energy audit is provided below: Charge coke consumption : 9.1% Ash in coke : 11.4 % Melt temperature at spout : 1377 o C to 1528 o C Temperature of flue gas (below charging door) : 350 o C to 400 o C Ferro-Silicon consumption : 0.21 % of metallics Ferro-Manganese consumption : 0.13 % of metallics Rejected castings: 7 % (atleast) PLANT SPECIFICATIONS Following the initial audit, a new cupola was designed for the foundry, taking into account existing cupola practice and the results of the audit. The foundry unit decided to build the divided blast (cold blast) cupolas (DBS) at a new site. The specifications of the DBC were as follows: No. of cupolas: Two Desired melting rate: 2.8 tph (tonne per hour) Operation: Continuous Desired metal temperature at spout: 1425 oc to 1475 oc Typical melting campaign duration: 8-10 hours It was decided to use a common mechanical charging system to feed the charge materials to the two cupolas.

5 POST-COMMISSIONING AUDIT Three trial runs were taken in the DBC in order to fine-tune the operating parameters. Though some of the operating practices of DBC were new to the operators, the better results obtained in the DBC probably inspired them to inculcate the new operating procedures being advocated to them. The result of the postcommissioning energy audit conducted during the third trial melt runs, is summarized below: Charge coke consumption : 7.8 % Ash in coke : 12.2 % Melt temperature at spout : 1417 o C to 1462 o C Temperature of flue gas (below charging door) : 132 o C to 162 o C Ferro-Silicon consumption : Nil Ferro-Manganese consumption : Nil Rejections : about 5% COST SAVINGS On the basis of the pre-commissioning and the post-commissioning audit results, the savings from implementation of the DBC were worked out. Table 1 summarizes the total savings obtained from reduced consumption of coke and other materials as well as reduction in rejection levels.

6 CONCLUSION Hence, there was a savings of the order of Rs 850 per tonne of molten metal in the foundry unit. For a typical foundry unit, melting about 250 tonnes of metal a month, 7 the total savings translates to about Rs 2.2 lakhs per month. The capital cost of a DBC, inclusive of civil work, platforms, bucket charging system etc, is about Rs 10,00,000. It is also possible to retrofit a conventional cupola to DBC, by simply changing the blower and blast arrangement. The capital cost of the retrofit option is about Rs 2,00,000. The capital investment, even in a new DBC, usually pays back within a year, depending on the amount of metal melted in the foundry unit.