Title of Invention

"ROTARY MELTING FURNACE WITHTWIN-BED COMBUSTIION SYSTEM"

Abstract

An improved fuel efficient rotary melting furnace having a twin-bed combustion system. It comprises a pair of burners, two regenerators, reversing valves and reversing logic controller; said burners is removably mounted on a trolley, a cylindrical shell having two conical ends, said shell being provided with a refractory lining to hold molten metal and said shell is supported on a base frame with rollers on which it can rotate; a drive unit to impart the rotary movement to said shell with the help of an electric motor and reduction gear; one of said burners of predetermined size and type is adapted to fire inside said shell from one end while fuel being guided from the other end through said other burner where regenerative bed absorbs substantial amount of heat, available in the flue, for releasing to the incoming cold combustion air in the subsequent cycle.

Full Text

The present invention relates to an improved rotary melting furnace. The present invention particularly relates to an improved fuel efficient rotary melting furnace having a twin-bed combustion system . For the production of cast iron and other graded castings, the melting operation is conducted in one of the three types of furnace - 1- Cupola 2. Induction Furnace 3- Rotary Mel ting Furnace The cupola is the most popular furnace as the me 1 ting cost is cheapest in such furnace. However, it has some inherent disadvantage, for example, higher grade of casting cannot be done in said furnace for the lack of control or monitoring of composition and high temperature of the molten metal that is required for higher grade of casting is not available in this type of furnace. Moreover, cupola furnace produces excessive amount of pollutents during its operation which is much more than that obtained in using Induction Furnace and Rotary Melting Furnace" 2 Induction Furnace can be suitably used for producing higher grade castings but the melting cost becomes comparatively high. Moreover, Induction Furance requires electric power supply with high current demand which may not be available at all places. The Rotary Melting Furnace on the other hand has slightly higher melting cost, but it is capable of producing cast i ron of higher grade. Although the molten metal temperature achievable in the conventional Rotary Furnace.-is.h ighjfj* than that in Cupola Furnace it is not enough as required for production of ductile iron (SG Iron) or other higher grade of castingss. In the prior art it has not been possible to obtain adequate temperature as required in the production of SG i ron and also to maintain such temperature for the required period of time by using cupola or conventional Rotary Melting Furnace as mentioned hereinabove. It has therefore been an endeavour in the prior art to improve the furnace efficiency as regards the production of higher temperature and to make it cost effective. To achieve the above objective it was decided to make the Rotary Melting Furnace more economical by making it more fuel efficient. It was further tried to increase the molten metal temperature in such furnace and thereby to provide the advantages of both the Cupola Furnace and the induction Melting Furnace. - jj - It is an object of the present invention to modify the Fuel efficiency system of the Rotary Melting Furnace for the production of higher grade cast iron. A further object of the present invention is to improve the Rotary Mel ting Furnace so that it may consume much less fuel than it would ordinarily require. A still further object of the present invention is to provide a system in the Rotary Melting Furnace to have higher furnace temperature - In yet another object of the present invention is to provide an improved Rotary Melting Furnace with a twin-bed combustion system for higher fuel efficiency. The applicant has developed a fuel-fired Rotary Melting. Furnace equipped with twin-bed regenerative burners. These burners are extremely effective in their ability to extract heat from the flue gas and plough/inject it back into the furnace. The improved technology of the present invention ensures heat recovery of about 70% and fuel savings of upto 50*/* with the burners operating with pre-heated air as high as 1100°C. 4 In known Rotary Melting Furnace slag is always formed and floats an the top of the molten metal. In conventional Rotary Melting Furnace there exists enough gap between the furnace shell and the gas bend trolly which is maintained for the slag to drop, out. In the improved Rotary Melting Furnace this gap has been W^- reduced substantially to avoid ingreeingas QT cold air which will prevent the slag to come out. A part of the slag may be carried into the regenerative heat exchanger bed which may clog it- This problem has been avoided in the improved Rotary Melting furnace of the present invention by redesigning the shell of the . furnace in such a way that siag wi11 not reach the bed of the burner. The Rotary Melting Furnace of the present invention is provided with a combustion system which combustion system comprises a pair of twin-bed regenerative burner fitted at the \tgj two ends thereof. The said burner is closely by coupled to a compact fast cycle ceramic regenerator. The high temperature burner serves the purpose of releasing heat when in firing mode and acts as exhaust port when in exhaust mode. Twin-bed regenerative burner of the present invention essentially consists of two burners, two regenerators, reversing valves and reversing logic/controller. D According to this invention there is provided an improved fuel efficient rotary melting furnace having as twin-bed combustion system comrpising a pair of burners, two regenerators, reversing valves and reversing logic controller; said burners being removably mounted on a trolly, a cylindrical shell having two conical ends, said shell being provided with a refractory lining to hold molten metal and said shell being supported on a base frame with rollers on which it can rotate? a drive unit to impart the rotary movement to said shell wi.th the help of an electric motor and reduction gear; one of 3a id burners of predetermined size and type/ being adapted to fire inside said shell from one end while fuel being guided from the other end through said other burner where regenerative bed absorbs substantial amount of heat, avail able in the flue, for releasing to the incoming cold combustion air in the subsequent cycle. In the above mentioned improved fuel efficient rotary melting furnace of the present invention the cylindrical shell is made of mild steel. According to the improved fuel efficiency rotary melting furnace, it further comprises an air blower for supplying combustion air to the burner through a pipe line. In a conventional Rotary Melting Furnace a burner is positioned at one end of the furnace shell and a gas bend is - o mounted on a trolly at zne ocnei' charg ing the furnace the trolly with gas bend is removed. In a twin-bed combustion system the charging of material into the furnace is done while one of the burners is removed. Since the removal and refitting of a burner from the furnace shel1 is a time consuming process and may take hours, in the abavernentioned improved furnace the removal of the burner is made easier by maunting the same on trolly and by providing either fiexable or telescopic joints. The present invention is described here inb el out in detail with reference to the drawings accompanying the provisional specification wherein Figure i illustrates a conventional Rotary Melting Furnace; and Figure 2 illustrates the Rotary Melting Furnace with twin-bed combustion system. A conventional Rotary Meltin Furnace consists - of a cylindrical shell (1), having two conical ends, generally constructed out of Mild Steel. This shell is supported by base 7 frame with rollers (2) on which it can rotate. The rotary movement is imparted by a drive unit consisting of Electric motor and reduction gearbox. The inside of the shell is lined with refractory material suitable for holding molten material. A burner of suitable size and type (8) is made to fire inside the shell from one end whi1e the flue is exhausted from the other. Generally the flue is guided by suitable duct, the waste gas bend mounted on trolley (3), into a recuperator (6). The combustion air from combustion air blower (7) is supplied to the burner (8) by the air pipe line The furnace is charged with raw material from the flue end by temporarily removing the gas bend mounted on trolley With reference to Figure 2, like in conventional Rotary Melting Furnace, the Mild Steel Shell duly refractory lined is supported on base frame with roller on which it is made to rotate 8 by the drive unit (12) consisting of motor and gear box. The combustion system, instead of a single burner and a recuperator, consists of a pair of Twinbed Regenerative Burner (13) fitted at the two ends of the rotating Shell. The high temperature burner is close coupled to ceramic regenerator (14). The burner serves double duty releasing heat, when in firing mode, and also acting as the exhaust port on the exhaust mode. One complete Twinbed Regenerative Burner set comprises 'two burners, two regenerators, reversing valves and Programmable Logic Controller (PLC) containing reversing logic. While, one of the burners fires using cold air fed by the combustion air blower (15) through the bed of its regenerator (14) , exhaust gas from the furnace is drawn through the other burner and down into its(associated regenerator/ to preheat the refractory bed., finally being released to the atmosphere via the exhaust blower (16). When the regenerator being heated is sufficiently heated up, the reversing system operates causes cold air to flow to the newly heated regenerator, thus preheating it. At the same time, the previously cooled regenerator gets reheated by the exhaust gas from the firing burner. The Twinbed Burners are usually cycled for firing and exhausting every 20 seconds. This can be changed, if required. Cycling of the burners is effected by a PLC (not shown in the 9 drawing), which is programmed for reversing the various eye 1 ing valves for combustion air, exhaust gas, fuel etc provided with each burner. For the purpose of charging material into the furnace shel 1 (11), one burner (14) is made removable by mounting the same on a trolley similar to the one on wheih gas bend is mounted in a conventional Rotary Melting Furnace. Since in a Rotary Melting Furnace siag is always formed and floats on top of molten metal, the second burner also has been made removable to facilitate removal of slag. Both ends of the furnace shell being free, slag can be conveniently pushed out from one side. For easy removal for burners flexible / telescoping joints (IS) for combustion air, exhaust gas, oil and / or gas pipe line (17) have been provided. The burners first retract and then move laterally to clear the material charging and slag removing path. Once the material inside the shell melts and reaches the desired temperature, molten metal is as usual tapped out through the spout (21) at the periphery of the furnace shell. With this Twin-Bed Regenerati ve Burners, we have achieved a furnace temperature of 1500 C and above making this furnace suitable for melting cast iron or ductile iron (SGI ran) - 10 - and castings of higher alloy cast iron. Since the Heat Exchanger Regenerative bed will provide about 70% of waste heat recovery, there wi1 be enormous savings in fuel, making the operation of the Rotary Melting Furnace very economic. For the operation of the Rotary Melting Furnace of the present invention one of the burners is fired using cold air fed to the bed of its regenerator and the exhaust gas is drawn from the furnace and passed through the second burner down into its associated regenerator to pre-heat the refractory nuggets and is finally released to the atmosphere via the exhaust blower. When the regenerator is heated and is sufficiently charged the reversing system operates causing cold air to flow to the heated regenerator thereby pre-heating it. At the same time the previously cold regenerator gets reheated by the exhaust gas from the firing burner. The twin-bed burners are usually operated by firing and exhausing alternatively every 20 seconds. This however changes depending upon the other factors of the Rotary Melting Furnace operat ion. The Rotary Melting Furnace with twin-bed combustion system as described and as shown in the accompanying drawings depicts only one illustration, other forms thereof and obvious modifications of such furnace wil be well within the knowledge of a person convergent with the subject- 11 WE CLAIM: 1. An improved fuel efficient' rotary melting furnace havirig a twin-bed combustion (system comprising a pair of burners, two regenerators,reversing valves and reversing logic controller;said burners being removably mounted on a trolly, a cylindrical shell having two conical ends, said shell being provided wit hi a refractory lining to hold molten metal and said shell being supported on a base frame wi th rollers on which it can rotate; a drive unit to impart the rotary movement to said shel1 wi th the help of an electric motor and reduction gear; one of said burners of predetermined size and type such as lighit being adapted to fire inside said shel1 from one end while fuel being guided from the other end through said other burner where regenerative bed absorbs substantial amount of heat, available in the flue, for releasing to the incoming cold combustion air in the subsequent cycle, 2- An improved fuel efficient rotary melting furnace as claimed in claim 1 wherein in said cylindrical shell is made of mild steel, 3- An improved fuel efficient rotary melting furnace as claimed in any of claims 1 or" 2 which fjjrthejv'camprises an air 12 - blower for supplying combustion air to said burner through s pipe line connected ta recuperator and for extracting a part of waste heat which is used for preheating combustion air before supplying it to said burner. 4. An improved fuel efficient rotary melting furnace having a twin-bed combustion system as claimed in any of the preceding claims tarflfp'rises a, pair of burners which are retractable and removeable. 5 . An improved fuel efficient rotary melting furnace having a twin-bed combustion system as claimed in claim 3. optionally comprisingf1 exible/te1 escaping joints for combustion air, exhaust gas, oil and/or gas pipe line. 6. An improved fuel efficient rotary melting furnace 13 7. An improved fuel efficient rotary melting furnace having a twin-bed combustion system substantially as herein described and with reference to the drawings accompanying the V provisional. An improved fuel efficient rotary melting furnace having a twin-bed combustion system. It comprises a pair of burners, two regenerators, reversing valves and reversing logic controller; said burners is removably mounted on a trolley, a cylindrical shell having two conical ends, said shell being provided with a refractory lining to hold molten metal and said shell is supported on a base frame with rollers on which it can rotate; a drive unit to impart the rotary movement to said shell with the help of an electric motor and reduction gear; one of said burners of predetermined size and type is adapted to fire inside said shell from one end while fuel being guided from the other end through said other burner where regenerative bed absorbs substantial amount of heat, available in the flue, for releasing to the incoming cold combustion air in the subsequent cycle.

Documents:

00703-cal-1999-abstract.pdf

00703-cal-1999-claims.pdf

00703-cal-1999-correspondence.pdf

00703-cal-1999-description(complete).pdf

00703-cal-1999-description(provisional).pdf

00703-cal-1999-drawings.pdf

00703-cal-1999-form-1.pdf

00703-cal-1999-form-2.pdf

00703-cal-1999-form-3.pdf

00703-cal-1999-form-5.pdf

00703-cal-1999-letters patent.pdf

00703-cal-1999-p.a.pdf