Title of Invention

"IMPROVED DAMPERS FOR AUTOMATIC CONTROL OF AIR SUCTION THROUGH HEARTHS OF SINTER MACHINES"

Abstract

Improved dampers for automatic control of air suction through hearthsof sinter machines for minimising fuel gas consumption in the hearths, characterised in that the dampers comprise a pair of single flaps (5A and 5B) having one end thereof hinged at position (4), and the other end movable up and down in the wind leg (7) for adjusting the openings thereof at positions (5C and 5D) automatically by means of the actuators (10A and 10B) for controlling the air suction rate through the hearths and wind boxes (6A and 6B) at a level required to minimise fuel gas consumption in the hearths, the said actuators being operated by the output signals of a suitably programmed computer (3) for analysing the digital signals fed thereinto from an A/D converter (2) which, in turn, is fed with electrical analogue signals from the wind pressure transducers (1A and 1B) fitted on the hoods of the hearths.

Full Text

The invention relates to improved dampers for automatic control of air suction through hearths of sinter machines. The invention relates more particularly to dampers, hinged at one end thereof and self-balanced with counter weights, for reducing operating load on the actuators provided to adjust the openings thereof automatically at optimum levels for minimising the fuel gas consumption in the hearths. A conventional diamper is of a butterfly type having two flaps, one on each side of its central axis lying in a horizontal plane passing through the vertical axis of the 'wind leg' for controlling the flow of airthrought the hearths of sinter machines. The main drawbacks of a conventional damper are :- (a) It is not suitable for efficient controlling of the air flow through the hearth, and hence the fuel burning rate, in accordance with the instantaneous fluctuations in the processing conditions therein, such as temperature, fuel gas supply etc., because of the manual or electrical control of the damper by an operator. (b) The controlling action of the damper on the rate of air flow through the hearth is effective only upto 20% of the damper opening, because the opening inside the wind leg increases abruptly with rotation of the damper. (c) The relation between air flow rate and damper opening is non-linear even in the effective range of 0 to 20% opening, because the opening increases at first rapidly and then slowly. - 2 - (d) In the event of jamming of wind leg with sinter or sinter mix, the opening of the damper is obstructed, because the damper is located inside the wind leg. The object of the present invention is to provide a damper which is capable of mitigating the said drawbacks of a conventional damper to a large extent. The invented damper is of a single flap type. It is hinged at the top instead of in the middle part thereof and is capable of controlling automatically the air suction through the v/ind box of a sinter machine. The electrical analogue signals produced in a known air-pressure transducer fitted on the hood of each hearth are converted into the corresponding digital signals by means of a known analogue-to-digital (A/D) converter in a known way and the digital signals produced in the A/D converter are supplied to a suitably programmed computer for analysing the signals and producing output signals which operate the actuators of the damper and adjust automatically the opening of the damper to the optimum level and thereby minimise the consumption of fuel gases in the hearth. Thus the invention provides improved dampers for automatic control of air suction through hearths of sinter machines for minimising fuel gas consumption in the hearths, characterised in that the dampers comprise a pair of single flaps having one end thereof hinged at position, and the other end movable up and down at the wind leg top for adjusting the openings thereof at positions automatically by means of the actuators for controlling the air suction rate through the hearths and wind boxes at a level required to minimise fuel gas consumption in - 3 - the hearths, the said actuators being operated by the output signals of a suitably programmed computer for analysing the digital signals fed thereinto from an A/D converter which, in turn, is fed with electrical enalogue signals from the wind pressure transducers fitted on the hoods of the hearths. The invention is described fully and particularly in an unrestrictive manner with reference to the accompanying drawings in which, Figure 1 is a schematic layout of a conventional damper; Figure 2 is a schematic layout of a pair of invented dampers fitted one each underneath two hearths of a sinter machine along with the automatic control system provided for operating the same; Figure 3 shown the variation in suction in wind legs with the degree of opening of the conventional and invented dampers. Referring to Fig. 1, a conventional butterfly type damper comprises two integrally connected flaps (5A and 5B) and is rotatable manually or electrically by an operator in a vertical plane on a centrally fitted shaft (1) lying in a horizontal plane inside wind leg (7) for allowing suction of air through the hearths of a sinter machine. With downward rotation of flap (5A) and upward rotation of flap (5B), the respective openings (5C and 5D), marked by dashed lines, increase in dimensions, and vice versa. Referring to Fig. 2, the invented dampers comprise each a single flap (5A and 5B), hinged at one end thereof at hinge (4) centrally at the bottom part of two hearths (8 and 9) and housed in wind boxes (6A and 6B), the other ends of the flaps being - 4 - movable up and down at the top of the wind leg (7) to allow the respective openings thereof at positions (5C and 5D) to decrease or increase to the required extent for controlling the air suction rate through the hearths and wind boxes (6A and 6B) underneath thereof automatically at optimum levels by means of the actuators (10A and 10B), which are of known electrically operated types of IL palghat make and are disposed on the sides of wind leg (7), being connected to the flaps (5A and 5B) of the damper through link rods (not shown). Known wind pressure transducers (1A and 1B) of measuring range + 5 mmwc, are fitted one each on the hoods of the hearths to produce electrical analogue signals corresponding to the wind pressure inside the hearths; the signals from the transducers are supplied to the known analogue-to-digital (A/D) converter (2). The output signals of the A/D converter are connected to suitably programmed computer (3) for analysing the signals received from the A/D converter (2) and producing output signals to operate the actuators and adjust the openings (5C and 5D) automatically to the optimum level required for minimising the consumption of fuel gases in the hearths. Flaps (5A and 5B) are each balanced with aecessary counter weights which are fixed oxe each on two arms (not shown) attached to the sides of the hinge (4) of the flaps (5A and 5B). The counter weights (not shown), each equal to the weight of the corresponding flaps (5A and 5B), are provided for reeducing the operating load of the actuators. Referring to Fig. 3, the variation of air suction pressure inside the hearths with the degree of opening of — 5 — flaps (5A and 5B) at positions (5C and 5D) of the invented dampers (shown by line A) is found to be almost linear upto 60% opening of the invented dampers. The variation of air suction pressure inside the hearths with degree of opening of flaps (5A and 5B) of the conventional dampers (shown by line B) is non-linear making it difficult to control the air suction pressure inside the hearths at the correct level by the operator. The degree of opening of flaps (5A and 5B) at positions (5C and 5D) determines the rate at which the combustion products are withdrawn through the sinter mix on bed of hearths (8 and 9). Thus by controlling the degree of opening of flaps (5A and 5B) at positions (5C and 5D), the rate of withdrawal as well as the volume of combustion products withdrawn through the sinter mix on the bed of the hearths (8 and 9 and hence the consumption of fuel gas is controlled. If the rate of withdrawal of combustion products is high, the heat transferred from the combustion products to the sinter mix is low and hence the consumption of fuel gas is high, and vice versa. The optimum level of the opening of flaps (5A and 5B) at positions (5C and 5D) is determined, based on the operating conditions such as under-grate suction, bed height and calorific value of the fuel gas used. Since the invented dampers are located at the top of the wind leg instead of being located inside the wind leg no obstruction is created to the movement thereof by the deposit of sinter or sinter mix in the wind leg. Field trials were conducted by studying the fuel gas consumption at different openings of the invented and conventional dampers for a given temperature profile of the sinter bed. - 6 - It has been noted that the fuel gas consumption is reduced by about 45% by using the invented dampers. Thus the invented dampers have the following main advantages over the conventional dampers :- 1. The operation o:f the invented dampers is automatically and instantaneously performed while that of the conventional dampers is slow and dependent on the skill and efficiency of the operating personnel. 2. The maintenance of the invented campers, because of their installation above the wind leg, is simpler and less frequently required compared with the conventional dampers, because of their installation inside the wind leg. 3. The consumption of fuel gas is appreciably reduced by using the invented dampers instead of the conventional dampers. - 6A - We Claim :- 1. Improved dampers for automatic control of air suction through hearths of sinter machines for minimising fuel gas consumption in the hearths, characterised in that the dampers comprise a pair of single flaps (5A and 5B) having one end thereof hinged at postion (4), and the other end movable up and down at the wind leg (7) top for adjusting the openings thereof at positions (5C and 5D) automatically by means of the actuators (10A and 10B) for controlling the air suction rate through the hearths and wind boxes (6A and 6B) at a level required to minimise fuel gas consumption in the hearths, the said actuators being operated by the output signals of a suitably programmed computer (3) for analysing the digital signals fed thereinto from an A/D converter (2) which, in turn, is fed with electrical analogue signals from the wind pressure transducers (1A and 1B) fitted on the hoods of the hearths. 2. The dampers as claimed in claim 1, wherein the flaps (5A and 5B) are each balanced with counter weights for reducing the operating load of the actuators (10A and 10B). - 7 - 3. Improved dampers for automatic control of air suction through hearths of sinter machines, substantially as herein described and illustrated in Figure 2 of the accompanying drawings. Improved dampers for automatic control of air suction through hearthsof sinter machines for minimising fuel gas consumption in the hearths, characterised in that the dampers comprise a pair of single flaps (5A and 5B) having one end thereof hinged at position (4), and the other end movable up and down in the wind leg (7) for adjusting the openings thereof at positions (5C and 5D) automatically by means of the actuators (10A and 10B) for controlling the air suction rate through the hearths and wind boxes (6A and 6B) at a level required to minimise fuel gas consumption in the hearths, the said actuators being operated by the output signals of a suitably programmed computer (3) for analysing the digital signals fed thereinto from an A/D converter (2) which, in turn, is fed with electrical analogue signals from the wind pressure transducers (1A and 1B) fitted on the hoods of the hearths.

Documents:

00074-cal-1999 abstract.pdf

00074-cal-1999 assignment.pdf

00074-cal-1999 claims.pdf

00074-cal-1999 correspondence.pdf

00074-cal-1999 description(complete).pdf

00074-cal-1999 drawings.pdf

00074-cal-1999 form-1.pdf

00074-cal-1999 form-18.pdf

00074-cal-1999 form-2.pdf

00074-cal-1999 form-3.pdf

00074-cal-1999 letters patent.pdf

00074-cal-1999 p.a.pdf

74-CAL-1999-(22-11-2012)-FORM-27.pdf