FIELD OF THE INVENTION
The present invention relates to an improved process of lime production. More particularly, the present invention relates to an improved process of calcined lime production in parallel flow regenerative Twin shaft kiln of MAERZ KILN with zero rejection by changing lance operation.
BACKGROUND OF THE INVENTION
In a typical steel plant, calcined lime is an important ingredient for manufacturing of iron and steel. The consumption of calcined lime in iron and steel industry is so high that the steel plants have it' sown provision for making calcined lime from lime stone. The usual practice for production of calcined lime from lime stone was performed to change lance at a time in both shaft containing 170 Ton lime stone charge in each kiln. Heating the lime stone at a temperature 1000°-1060°C to obtain maximum CaO in lime. The problem noticed in usual practice of calcination of lime stone in maerz kiln is due to improper and incomplete reaction-of lime stone during heating fails to achieve the desired property of reactivity level of lime which is 300 cc. Less than 300 cc reactivity level of lime is not suitable to use in iron and steel making and regarded as "reject lime". The present invention

emphasize on an improve process for manufacturing of calcined lime at zero rejection by introducing lance changing technique in one shaft only.
OBJECTS OF THE INVENTION
It is, therefore, an object of the present invention to propose an improved process of calcined lime production with zero rejection in regenerative twin shaft kiln by changing lance operation which eliminate the disadvantages of prior art.
Another object, of the present invention is to propose an improved process of calcined lime production with zero rejection in regenerative twin shaft kiln by changing lance operation which increases the productivity of calcined lime.
A further object of the present invention is to propose* an improved process of calcined lime production with zero rejection in regenerative twin shaft kiln by changing lance operation which reduces the cost of lime.
A still further object of the present invention is to propose an improved process of calcined lime production with zero rejection in regenerative twin shaft kiln by changing lance operation which increases the quality of calcined lime.

SUMMARY OF THE INVENTION
The present invention is provided with a predetermined quantity of lime stones are fed on the top of a twin vertical shaft kiln of maerz kiln by means of a skip hoist. The lime stones from the charging bin at top are catered both the vertical shaft alternative by means of hopper bell gate arrangement.
A plurality of lance is embedded inside in each of the vertical shaft of the kilri. During changing of lance, materials are to be lowered down up to the level of lance tip. The amount of charge of lime stones are approximately 70-80 Ton in each shaft. -
To start heating of the kiln, an additional 20% extra heat input is employed in the shaft kiln over and above other shaft which will help to generate more heat in preheating zone of the other shaft. It will calcine the material faster as the combustion system is getting more scope to react with the exposed surface area of lime stone. The reaction takes place at 1000°-1050°C to get rid of C02 from CaC03 and remains calcined CaO in lime which will be taken out from the bottom of the kiln.
The calcined lime as produced is tested in laboratory. In the testing process, 50gms of calcined lime powder is taken in 2 litres of distilled water

and boil it up at 40°C. 50ml of phenolphthalein is added to the solution and thereafter titration is carried out with 4N HCI for 5 minutes. The consumption of 4N HCI in 5 minutes denotes the reactivity. of lime in CC (cubic centimeter). Reactivity means capacity to react with hot metal in steel melting process.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.l - shows a schematic diagram of MAERZ KILN having parallel flow regenerative vertical twin shaft kiln.
Fig.2 - shows a sectional view of each vertical shaft kiln of Fig.l along X-X represent the number of lances embedded in the kiln.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Fig.l shows the small lump of lime stones are being fed on the top of maerz kiln (1) by means of a skip (2). The maerz kiln is provided with vertical twin shaft kiln (3, 4). Each vertical shaft kiln (3 and 4) has a provision of combustion gas inlet point (5,5) and a level sensor (6) and a lance tip (7), a plurality of lance point (8) as shown in Fig.2

The charge of lime stones (9) from charge bin at top of the maerz kIln (1) are fed through a opening of hopper bell gate arrangement (10) and lowered down through one of the vertical shafts (4). The charge occupy space between the lance tip (7) level and upto level sensor (6) and its weight is approximately 70-80 Tons per batch.
Initially, lime stones (9) from top storage bin are fed in left vertical shaft kiln (3) or right vertical shaft kiln (4), to fill the charge from lance tip level (7) to sensor level (6), and an excess of 20% combustion air through the inlet (5) of vertical shaft kiln (3) are blown to the charge (9) and also through the plurality of lancing pipes (8). The combustion air passing from top to bottom and passes over adjacent right side vertical shaft kiln (4) which is already being filled up with same quantity of lime stone charge (9) from iance tip level (7) to level sensor (6), starts preheating by the flue gas passing through the connecting channel (11) to the vertical shaft kiln (4) until calcination period of vertical shaft kiln (3) is completed. Thereafter the calcined limes are taken out from the bottom point (12) and simultaneously starts introducing the combustion air through inlet point (5) of vertical shaft kiln (4) from the top of the charge and also starts combustion gas to pass through plurality lancing pipes (8) of the vertical shaft kiln (4). The flue gas of vertical shaft kiln (4) is passed through the connecting channel (11) and enter into the adjacent vertical shaft kiln (3)

from the bottom of the charge and starts preheating until the period of calcination of vertical shaft kiln (4) is over. After calcination, the lime is taken out from the bottom outlet (13). This is a reversal way of operation alternately firing takes place in left vertical shaft kiln (3) and next to right vertical shaft kiln (4) and so no to achieve maximum output with zero percentage rejection.

WE CLAIM;
1. An improved process for calcined lime production in parallel flow regenerative twin shaft kiln of MAERZ KILN with . zero rejection comprising following steps:
-a predetermined quantity charge of lime stones,are fed into one of twin shaft kilns (3) maintaining a level from lance tip. (6) to level sensor (7) of the kiln;
-start heating the charge (9) by introducing an extra combustion air from inlet point (5) as well as from lance tip (8);
-a predetermined quantity charge of lime stones are filled in the second twin shaft kiln (4) during this period;
-start heating lime stone at a temperature 1050"-1060°C;
-after completion of calcinations operation in kiln (3), the calcined lime is taken out from the bottom outlet (12);
-the flue' gas generated from shaft kiln (3) are passed through the connecting channel (11) and enters into shaft kiln (4) to preheat the charge of lime stone (9) in kiln (4);
-after completion of calcinations process of kiln (4), calcined lime is' taken out from the bottom outlet (12) and next starts calcinations operation kiln (3);

-when kiln (4) is in operative condition, start filing of charge of lime stone in kiln (3), and the flue gas generated from kiln (4) are enter into kiln (3) through bottom to preheat the lime stone charge (9) of kiln (3);
-after completion of calcinations operation in kiln (4), the calcined lime is taken out from the bottom outlet (13);
-the process of calcinations continued in reversal way of operation alternatively firing takes place in shaft kiln (3) and next to kiln (4) to achieve maximum output with zero rejection;
2. The process as claimed in claim 1, wherein the lime stones are stored at the top stored at the top storage bin by means of skip (2).
3. The process as claimed in claim 1, wherein a plurality of lance are provided in lance tip (7).

ABSTRACT

TITLE: ZERO REJECTION OF LIME DURING LANCE CHANGING IN MAERZ KILN The present invention relates to an improved process for calcined lime production in parallel flow regenerative twin shaft kiln of MAERZ KILN with zero rejection comprising a predetermined quantity charge of lime stones are fed into one of twin shaft kilns (3) maintaining a level from lance tip (6) to level sensor (7) of the kiln and start heating of the charge (9) by introducing an extra combustion air from inlet point (5) as well as from lance tip (8) and a predetermined quantity charge of lime stones are filled in the second twin shaft kiln (4) during this period and start heating lime stone at a temperature 1050°-1060°C and after completion of calcinations operation in kiln (3), the calcined lime is taken out from the bottom outlet (12) and the flue gas generated from shaft kiln (3) are passed through the connecting channel (11) and enters into shaft kiln (4) to preheat the charge of lime stone (9) in kiln (4) and after completion of calcination process of kiln (4), calcined lime is taken out from the bottom outlet (12) and next starts calcinations operation in kiln (3) and when kiln (4) is in operative condition, start filling of charge of lime stone in kiln (3) and the flue gas generated from kiln (4) are enter into kiln (3) through bottom to preheat the lime stone charge (9) of kiln (3) and after completion of calcinations operation in kiln (4), the calcined lime is taken out from the bottom outlet (13) and the process of calcination continued in reversal way of operation alternatively firing takes place in shaft kiln (3) and next to kiln (4) to achieve maximum output with zero rejection.