Title of Invention	''A PROCESS FOR PRODUCING LIME FROM LIME SLUDGE''
Abstract	This invention relates to a process for producing lime from lime sludge in a vertical shaft kiln comprising the steps of forming a raw meal by introducing lime sludge and fuel, which is raw petroleum coke into a ball mill, addition of water to the raw ineal discharged from the ball mill, blending of the raw meal thus obtained followed by, introduction of the same into a nodulizer to produce nodules of the raw meal, feeding of the raw meal in the form of nodule into a vertical shaft kiln to produce lime characterized by formation of the raw meal from lime sludge available as a waste from a paper mill wherein the limestone sludge is dried to a mositure content of 5-7% prior to making of the raw meal.

Title of Invention

''A PROCESS FOR PRODUCING LIME FROM LIME SLUDGE''

Abstract

This invention relates to a process for producing lime from lime sludge in a vertical shaft kiln comprising the steps of forming a raw meal by introducing lime sludge and fuel, which is raw petroleum coke into a ball mill, addition of water to the raw ineal discharged from the ball mill, blending of the raw meal thus obtained followed by, introduction of the same into a nodulizer to produce nodules of the raw meal, feeding of the raw meal in the form of nodule into a vertical shaft kiln to produce lime characterized by formation of the raw meal from lime sludge available as a waste from a paper mill wherein the limestone sludge is dried to a mositure content of 5-7% prior to making of the raw meal.

Full Text	FIELD OF INVENTION This invention relates to a process for producing lime from lime sludge in a vertical shaft kiln. BACKGROUND OF INVENTION The process of producing lime in a vertical shaft kiln is known in the art. Briefly, such a process consists in preparing feed either by mixed feed type or alternate layers of limestone and fuel and introducing into vertical shaft lime kiln. The raw meal of limestone and fuel after blending is then introduced into a nodulizer to produce nodules of the raw meal. For this purpose, water is added to the raw meal discharged from the ball mill, as the raw meal should be in a moistened condition for nodulization. The raw meal in the form of the nodules in then fed into vertical shaft kiln for producing lime. Reference is made in particular to the constituents forming the feed into vertical shaft kiln. One such constituent is limestone. As such an addition of limestone was in the form as available from a limestone quarry, it did contribute to the end cost of lime. Reference is now made to a paper mill. One of the waster in a paper mill is lime sludge, which is available in substantial abundance. A disposal of such a waste was hitherto a problem for a paper mill, as it could not conveniently be discharged as an effluent in a running stream. OBJECTS OF THE INVENTION An object of this invention is to propose a process for producing lime in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill. Another object of this invention is to propose a process for producing lime in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill and thereby avoiding the step of disposal of the waste. Yet another object of this invention is to propose a process for producing lime in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill which does reduce the end costs of lime. Still another object of this invention is to propose a process for producing lime in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill, which is efficient. Further objects and advantages of this invention will be more apparent from the ensuing description. BRIEF DESCRIPTION OF INVENTION According to this invention there is provided a process for producing lime from lime sludge in a vertical shaft kiln comprising the steps of introducing a raw meal into a ball mill, addition of water to the raw meal discharged from the ball mill, blending of the raw meal thus obtained followed by introduction of the same into a nodulizer to produce nodules of the raw meal, feeding of the raw meal in the form of nodule into a vertical shaft kiln to produce lime: characterized by the raw meal comprising of lime sludge available as a waste from a paper mill and a fuel wherein the lime sludge is subjected to a step of pretreatment, which consists in drying of the sludge to a moisture content of 5-7%. The fuel employed in the process of the present invention is raw-petroleum coke. The process of producing lime in a vertical shaft kiln is known as such in the art, but which hitherto employed limestone from a limestone quarry as one of the constituents to form the raw meal. In distinction, the present invention envisages the use of lime sludge available as a waste from a paper mill as one of the constituents for the raw meal in combination with the other known constituents. It has been found that the lime sludge available as a waste from a paper mill cannot as such be used. For this purpose, it is first necessary to pretreat the lime sludge for reducing the moisture content. Such a step of pretreatment consists in drying of the sludge. Thus, and as by way of example, if the sludge contains 45% moisture, the sludge is dried to a moisture content of approximately 5-7%. Such a step of reduction of the moisture content is of importance, and particularly with respect to the material handling equipment. Thus, if the sludge is introduced into the ball mill with the moisture content of 45% jamming in the ball mill takes place. The step of drying involves use of energy or power. However, it has been found that the use of lime sludge in a dried condition considerably increase the efficiency of grinding and homogenization in that the ball mill requires a reduced period for milling in comparison to that with limestone. In fact, it has been found that the grinding period is reduced in as much as 30%. In order to improve the purity of lime, limestone may be added. Preferably, high grade limestone having a CaO content of 50% or higher may be added. A process for producing lime from lime sludge according to a preferred embodiment as herein described and illustrated in the following examples. EXAMPLE 1 The dried limesludge make up limestone and pet coke are intimately mixed and sintered result in the formation of quicklime. Lime Sludge The chemical composition of lime sludge is as follows: (Table Removed) Corrective Materials To meet the requirement of quality of lime, it was necessary to add make up limestone. The chemical composition of limestone is as follows: (Table Removed) Fuel The fuel for manufacture of quicklime was petrocoke which is low volatile matter and with gross calorific value of 8000 kcal/kg. The proximate analysis of pet coke is as follows: (Table Removed) Preliminary Raw Mix Design The average chemical analysis of limesludge, limestone and pet coke are as follows: (Table Removed) Based on the above chemical analysis, the following percentages were used for the preliminary raw mix design: Limesludge : 72% Limestone : 20% Pet Coke : 8% Nodulisability The nodulisability of the proposed raw mix was carried out in a pan noduliser with 14% moisture and was found satisfactory as fairly uniform size nodules with good green strength were obtained. Burnability The burnability of the raw mix was carried out in a muffle furnace at about 1050°C with 20 minutes retention time and the total lime achieved was around 80%. WE CLAIM: A process for producing lime from lime sludge in a vertical shaft kiln comprising the steps of introducing a raw meal into a ball mill, addition of water to the raw meal discharged from the ball mill, blending of the raw meal thus obtained followed by introduction of the same into a nodulizer to produce nodules of the raw meal, feeding of the raw meal in the form of nodule into a vertical shaft kiln to produce lime characterized by the raw meal comprising of lime sludge available as a waste from a paper mill and a fuel wherein the lime sludge is subjected to a step of pretreatment, which consists in drying of the sludge to a moisture content of 5-7%. 2. A process as claimed in claim 1 wherein the raw meal is added with limestone. 3. A process as claimed in claim 1 wherein the fuel is raw petroleum coke. 4. A process for producing lime from lime sludge substantially as herein described and illustrated in the examples.

Full Text

FIELD OF INVENTION
This invention relates to a process for producing lime from lime sludge in a vertical shaft kiln.
BACKGROUND OF INVENTION
The process of producing lime in a vertical shaft kiln is known in the art. Briefly, such a process consists in preparing feed either by mixed feed type or alternate layers of limestone and fuel and introducing into vertical shaft lime kiln. The raw meal of limestone and fuel after blending is then introduced into a nodulizer to produce nodules of the raw meal. For this purpose, water is added to the raw meal discharged from the ball mill, as the raw meal should be in a moistened condition for nodulization. The raw meal in the form of the nodules in then fed into vertical shaft kiln for producing lime.
Reference is made in particular to the constituents forming the feed into vertical shaft kiln. One such constituent is limestone. As such an addition of limestone was in the form as available from a limestone quarry, it did contribute to the end cost of lime.
Reference is now made to a paper mill. One of the waster in a paper mill is lime sludge, which is available in substantial abundance. A disposal of such a waste was hitherto a problem for a paper mill, as it could not conveniently be discharged as an effluent in a running stream.
OBJECTS OF THE INVENTION
An object of this invention is to propose a process for producing lime in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill.
Another object of this invention is to propose a process for producing lime in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill and thereby avoiding the step of disposal of the waste.
Yet another object of this invention is to propose a process for producing lime in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill which does reduce the end costs of lime.
Still another object of this invention is to propose a process for producing lime in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill, which is efficient.
Further objects and advantages of this invention will be more apparent from the ensuing description.
BRIEF DESCRIPTION OF INVENTION
According to this invention there is provided a process for producing lime from lime sludge in a vertical shaft kiln comprising the steps of introducing a raw meal into a ball mill, addition of water to the raw meal discharged from the ball mill, blending of the raw meal thus obtained followed by introduction of the same into a nodulizer to produce nodules of the raw meal, feeding of the raw meal in the form of nodule into a vertical shaft kiln to produce lime: characterized by the raw meal comprising of lime sludge available as a waste from a paper mill and a fuel wherein the lime sludge is subjected to a step of pretreatment, which consists in drying of the sludge to a moisture content of 5-7%.
The fuel employed in the process of the present invention is raw-petroleum coke.
The process of producing lime in a vertical shaft kiln is known as such in the art, but which hitherto employed limestone from a limestone quarry as one of the constituents to form the raw meal. In distinction, the present invention envisages the use of lime sludge available as a waste from a paper mill as one of the constituents for the raw meal in combination with the other known constituents.
It has been found that the lime sludge available as a waste from a paper mill cannot as such be used. For this purpose, it is first necessary to pretreat the lime sludge for reducing the moisture content. Such a step of pretreatment consists in drying of the sludge. Thus, and as by way of example, if the sludge contains 45% moisture, the sludge is dried to a moisture content of approximately 5-7%. Such a step of reduction of the moisture content is of importance, and particularly with respect to the material handling equipment. Thus, if the sludge is introduced into the ball mill with the moisture content of 45% jamming in the ball mill takes place.
The step of drying involves use of energy or power. However, it has been found that the use of lime sludge in a dried condition considerably increase the efficiency of grinding and homogenization in that the ball mill requires a reduced period for milling in comparison to that with limestone. In fact, it has been found that the grinding period is reduced in as much as 30%.
In order to improve the purity of lime, limestone may be added. Preferably, high grade limestone having a CaO content of 50% or higher may be added.
A process for producing lime from lime sludge according to a preferred embodiment as herein described and illustrated in the following examples.
EXAMPLE 1
The dried limesludge make up limestone and pet coke are intimately mixed and sintered result in the formation of quicklime.
Lime Sludge
The chemical composition of lime sludge is as follows:

(Table Removed)
Corrective Materials
To meet the requirement of quality of lime, it was necessary to add make up limestone. The chemical composition of limestone is as follows:

(Table Removed)
Fuel
The fuel for manufacture of quicklime was petrocoke which is low volatile matter and
with gross calorific value of 8000 kcal/kg.
The proximate analysis of pet coke is as follows:

(Table Removed)
Preliminary Raw Mix Design
The average chemical analysis of limesludge, limestone and pet coke are as follows:

(Table Removed)

Based on the above chemical analysis, the following percentages were used for the preliminary raw mix design:
Limesludge : 72%
Limestone : 20%
Pet Coke : 8%
Nodulisability
The nodulisability of the proposed raw mix was carried out in a pan noduliser with 14% moisture and was found satisfactory as fairly uniform size nodules with good green strength were obtained.
Burnability
The burnability of the raw mix was carried out in a muffle furnace at about 1050°C with 20 minutes retention time and the total lime achieved was around 80%.

WE CLAIM:
A process for producing lime from lime sludge in a vertical shaft kiln comprising the steps of introducing a raw meal into a ball mill, addition of water to the raw meal discharged from the ball mill, blending of the raw meal thus obtained followed by introduction of the same into a nodulizer to produce nodules of the raw meal, feeding of the raw meal in the form of nodule into a vertical shaft kiln to produce lime characterized by the raw meal comprising of lime sludge available as a waste from a paper mill and a fuel wherein the lime sludge is subjected to a step of pretreatment, which consists in drying of the sludge to a moisture content of 5-7%.
2. A process as claimed in claim 1 wherein the raw meal is added with limestone.
3. A process as claimed in claim 1 wherein the fuel is raw petroleum coke.
4. A process for producing lime from lime sludge substantially as herein described and illustrated in the examples.

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Patent Number

232450

Indian Patent Application Number

873/DEL/2001

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

17-Mar-2009

Date of Filing

23-Aug-2001

Name of Patentee

NATIONAL COUNCIL FOR CEMENT & BUILDING MATERIALS,

Applicant Address

A-135, DEFENCE COLONY, NEW DELHI-110 024,A SICUETT REGUSTERD YBDER TGE SICIETIES REGISTRATION ACT, 1860.

Inventors:

#	Inventor's Name	Inventor's Address
1	LALGUDI KRISHNAMURTHI JANAKIRAMAN	India Haryana India
2	YASH PAL SETHI	India Haryana India
3	MS. KRISHNA RAINA	India Haryana India
4	DABBIR BADRI NARAYANA RAO,	34KM STONE, DELHI-MATHURA ROAD (NH-2), BALLABGARH-121 004 (HARYANA)
5	KRISHNA MOHAN	India Haryana India

PCT International Classification Number

C04B 2/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA