Title of Invention

"A PROCESS FOR PRODUCING CEMENT CLINKER FROM LIME SLUDGE"

Abstract

This invention relates to a process for producing cement clinker from a lime sludge in a vertical shaft kiln comprising the steps of pretreatment of lime sludge to reduce moisture content to 5-7% by drying, preparing raw meal by introducing approximately 58.5% lime sludge, 16.5% lime stone, 9.5% clay 2.5% iron ore and 13.0% coke dust in ball mill and homogenizing, blending the raw meal of step (b) in blending silo, subjecting raw meal of step (c) to the step of nodulization to form nodules of 6-8 mm size, the said nodules are fed into the vertical shaft kiln to form cement clinker.

Full Text

FIELD OF INVENTION This invention relates to a process for producing clinker from lime sludge in a vertical shaft kiln. BACKGROUND OF INVENTION The process of producing clinker in a vertical shaft kiln is known in the art. Briefly, such a process consists in preparing a raw meal by introducing limestone, clay, additives and fuel into a ball mill. The raw meal 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 the vertical shaft kiln for producing clinker. Reference is made in particular to the constituents forming the raw meal. 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 the clinker. eference 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 cement clinker 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 cement clinker 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 cement clinker in a vertical shaft kiln using lime sludge discharged as a waste from a paper mill which does reduce the end costs of cement clinker. Still another object of this invention is to propose a process for producing cement clinker 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 cement clinker from a lime sludge in a vertical shaft kiln comprising the steps of pretreatment of lime sludge to reduce moisture content to 5-7% by drying, preparing raw meal by introducing approximately 58.5% lime sludge, 16.5% lime stone, 9.5% clay 2.5% iron ore and 13.0% coke dust in ball mill and homogenizing, blending the raw meal of step (b) in blending silo, subjecting raw meal of step ( c) to the step of nodulization to form nodules of 6-8 mm size, the said nodules are fed into the vertical shaft kiln to form cement clinker. The process of producing cement clinker 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 constituent. 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 increases 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%. A process for producing clinker from lime sludge according to a preferred embodiment as herein described in the following examples. EXAMPLE Lime slude The limesludge was containing of 15-20% and the chemical analysis (on dry basis) is as follows :- Lo1 SiO2 A12O3 Fe2O3 CaO MgO 40.35 4.35 1.85 0.62 50.10 1.60 Limestone (Low grade) A low grade limestone was selected to be used as additive for increasing the SiO2 content in the raw mix and the analysis is as given below: Loi SiO2 A12O3 Fe2O3 CaO MgO 32.75 21.60 2.64 0.61 41.31 0.80 Clay The clay used as an additive has the following chemical composition Loi SiO2 A12O3 Fe2O3 CaO MgO 14.47 49.28 17.49 7.40 7.51 2.30 Iron Ore The iron ore used as an additive has the following chemical composition Lo1 SiO2 A12O3 Fe2O3 CaO MgO 11.0 21.8 12.10 52.90 1.85 Fuel The fuel used is coke dust Plant and had the following proximate analysis: Moisture 0.19 Volatile matter 1.05 Ash 14.20 Fixed carbon (by difference) 84.56 Calorific value (Gross) cal/gm 6300 The moisture content as received varies between 15-20%. Raw Mix Design A raw mix was designated with the following proportions of raw materials and fuel (on dry basis) Limesludge 58.5% Limestone (Low grade) 16.5% Clay 9.5% Iron Ore 2.5% Coke dust 13.0% With the above proportions the raw meal designated was as follows: Lo1 SiO2 A12O3 Fe2O3 CaO MgO 41.81 12.18 4.13 2.69 36.95 1.30 The potential clinker composition based on the above raw meal is Lo1 SiO2 A12O3 Fe2O3 CaO MgO 20.93 7.10 4.62 63.50 2.23 Moduli values: SM 1.79 AM 1.54 LSF 0.90 PLANT The plant had an air swept raw mill of 11 tph capacity. The limesludge and low grade limestone were separately weighed by loading into tippers an thoroughly mixed with front end loaders as per raw mix design and then loaded into one of the hoppers. The other 3 hoppers were filled with clay, coke dust and iron ore respectively. The table feeders were calibrated as per required proportions in the raw mix design and these materials were fed in to the raw mill. The raw meal was ground in the raw mill in batches 15 T (approximately). As the sludge contained nearly 20% moisture content the mill circuit got jammed after grinding nearly 65 tonnes of raw meal in 4 batches. After grinding every batch the raw meal was blended in blending silo and dropped to the storage silo. The nodulisability of the material was found to be very good. Nodules of 6-8 mm size were forming. These nodules were fed into the vertical shaft kiln. The clinker produced was of good quality and the chemical analysis is as follows: Lo1 SiO2 A12O3 Fe2O3 CaO MgO SO3 CI Na2O K2O 1.07 20.26 5.48 6.57 64.50 1.30 0.26 0.008 0.21 0.29 CEMENT The average clinker (approximately 10 kg) was ground in a laboratory ball mill with 3.75% gypsum to a fineness of 2850 Cm2/gm (blaine) and tested as per IS:4031. The results are as follows: Setting Time As per IS:8112 As per IS: 12269 for OPC 43 for OPC 53 Gr Actual results Initial More than More than 30 minutes 30 minutes 175 minutes Final Less than Less than 600 minutes 600 minutes 270 minutes Soundness Le Chatelier Expansion 10mm 10mm 4mm Autoclave Expansion 0.8% 0.8% 0.22% Compressive Strength at 1 day No specification No specification 22 Mpa 3 days 23 Mpa 27 Mpa 40 Mpa 7 days 33 Mpa 37 Mpa 47 Mpa 28 days 43 Mpa 53 Mpa 60 Mpa WE CLAIM: 1. A process for producing cement clinker from a lime sludge in a vertical shaft kiln comprising the steps of:- a) pretreatment of lime sludge to reduce moisture content to 5- 7% by drying, b) preparing raw meal by introducing approximately 58.5% lime sludge, 16.5% lime stone, 9.5% clay 2.5% iron ore and 13.0% coke dust in ball mill and homogenizing, c) blending the raw meal of step (b) in blending silo, d) subjecting raw meal of step (c) to the step of nodulization to form nodules of 6-8 mm size, the said nodules are fed into the vertical shaft kiln to form cement clinker. 2. A process as claimed in claim 1 wherein the sludge is dried prior to the step of preparing the raw meal. 3. A process for producing clinker from a lime sludge in a vertical shaft kiln substantially as herein described.

Documents:

872-del-2001-abstract.pdf

872-del-2001-claims.pdf

872-del-2001-correspondence-others.pdf

872-del-2001-correspondence-po.pdf

872-del-2001-description (complete).pdf

872-del-2001-form-1.pdf

872-del-2001-form-18.pdf

872-del-2001-form-2.pdf

872-del-2001-form-26.pdf

872-del-2001-form-3.pdf

872-del-2001-form-5.pdf