Center for By-Products Utilization

Transcription

1 Center for By-Products Utilization PRELIMINARY DRAFT REPORT LIME KILN DUST (LKD) By Tarun R. Naik and Fethullah Canpolat Report No. CBU REP-548 February 2004 A CBU Report Department of Civil Engineering and Mechanics College of Engineering and Applied Science THE UNIVERSITY OF WISCONSIN MILWAUKEE

2 TABLE OF CONTENTS LIME KILN DUST (LKD)... 1 INRTODUCTION... 1 LIME... 2 National Lime Association Specification for Road Stabilization... 2 Calcium Oxide or Quicklime... 2 Uses of Lime... 4 Environmental Uses... 4 Flue Gas Desulfurization Solid Wastes Disposal... 5 USES OF LIME KILN DUST... 5 Typical Lime Kiln Dust ( Calcium Oxide) Specification [4]... 5 Use of kiln dust with quicklime for effective municipal sludge pasteurization and stabilization with the N-Viro Soil process... 6 Soil substitute from alkaline stabilization... 6 Geotechnical evaluation of dredged material from Newark harbor... 7 Soil stabilization utilizing alternative waste materials... 8 Thaumasite formation in stabilized coal combustion by-products... 8 References... 9 i

3 LIME KILN DUST (LKD) INRTODUCTION Most people are environmentalists: they want clean air and water their families and friends. Industrialists are faced with the task of achieving a clean environment in a cost effective way while producing necessary chemicals such as lime. Lime is one of the most important chemicals such as lime. Lime is one of the most important chemicals used to reduce pollution. The production of lime is an intense process where limestone rock is heated to high temperatures by burning fossil fuels [1]. This process emits the products of combustion, moisture and dust. The waste gases from the process are usually filtered through fabric dust collectors tom remove dust. The important concerns when purchasing fabric filter bag collectors are emission regulations, capital cost and operating cost [1]. It is very interesting how, over the years, the predominate uses of lime have changed. Just several years ago the steel industry was demanding research on better ways to manufacture lime to meet their needs in the newer basic oxygen furnaces, Steel went its way, but now environmental stresses are at the forefront and industry is seeking innovative ways to protect the world. Of course, lime is playing a very important role in the clean up of air, land, and water. As time moves on, the age old chemical, lime, remains a major factor in the life of man [2]. 1

4 LIME National Lime Association Specification for Road Stabilization 1. For either high calcium or dolomitic hydrated lime, a minimum of 95% total oxide content (CaO + MgO) on a non-volatile basis is required. 2. Carbon Dioxide (5-7% maximum, depending upon where sampled) 3. Particle Size - 85% passing #200 mesh sieve [3]. Calcium Oxide or Quicklime Chemical lime is a term designating a type of quick or hydrated lime. Calcium hydroxide: low in impurities and possessing a high degree of reactivity making it suitable for use in chemical processes. Commercially, chemical lime is obtained through the controlled calcination of high quality limestone. Quicklime, the product of calcination, consists of the oxides of calcium and magnesium, and in this country it is available in three forms. High calcium quicklime: containing usually 0.5 to 2.5 percent magnesium oxide. Dolomitic quicklime: containing usually 35 to 40 percent magnesium oxide. Magnesium quicklime: containing usually 5 to 10 percent magnesium oxide. 2

5 Chemical lime is a white solid having a crystalline structure. Quicklime is highly reactive with water, generating considerable heat in the hydration process. This material will react with the moisture in the air, and as such, it has found application as a desiccant. In the presence of moisture, the lime reacts slowly with the carbon dioxide of the air, forming water insoluble carbonates. As a chemically active material it is desirable to reduce atmospheric exposure during handling and storage to a minimum. Quicklime is available by the carload, in bulk dump or tanker, and in 50 Ib. paper bags and one ton bulk bags and a number of more or less standard sizes as follows: Lump lime: the product with a maximum size of eight inches in diameter. Crusted or pebble lime: the product ranging in size from about 1/4 to 2 inches. Ground lime: the product resulting from grinding the larger sized material. A typical size is substantially all material passing a No. 8 sieve and 40 to 60 percent passing a No. 100 sieve. Pulverized lime: the product resulting from a more intense grinding than is used to produce ground lime: a typical size is all material substantially passing a No. 20 sieve and 85 to 95 percent passing a No. 100 sieve. Pelletized lime: one inch sized pellets or briquettes, molded from quicklime fines [3]. 3

6 Uses of Lime Metallurgy: Steel Manufacture, Steel Products Manufacture, Magnesium Manufacture, Alumina Manufacture, Ore Flotation and Non-Ferrous Metal Smelting. Pulp and Paper: Sulfate Process, Sulfite Process, Bleaching, Precipitated Calcium Carbonate, Strawboard Manufacture, and in the treatment of pulp and paper mill liquid wastes, as a coagulant in color removal. Chemicals: Alkalis, Calcium Carbide and Cyanimide, Petrochemicals, Bleaches, Dye and Dyestuff Intermediates and Coke-By-Products. In addition, it is used in the purification of citric acid, glucose and dextrin: metallic calcium; soda-lime, an adsorbent; and for countless other minor or isolated purposes, such as for CO 2 absorption [3]. Environmental Uses Water Treatment: Scope, Softening, Purification, Coagulation, Neutralization of Acid Water, Silica Removal and Removal of Other Impurities, Sewage Treatment: Maintain proper ph and Stabilizing Sewage Sludge. Industrial Trade Wastes: Treatment of industrial trade wastes to abate pollution from Steel and Metal Fabricating Plants, Chemical and Explosives Plants, Acid Mine Drainage, Paper and Fibers, Food Plants and in clarifying "water gas" acid waste effluents [3]. 4

7 Flue Gas Desulfurization Solid Wastes Disposal Ceramic Products: Glass, Refractories, and in the production of whiteware pottery, lime is sometimes employed to bind the kaolin and ball clays present. ' Building Materials: Calcium Silicate Brick, Concrete Products, Miscellaneous Building Units, and Insulation Materials. Protective Coatings: Pigments, Water Paints, and Varnish. Food and Food By-Products: Dairy Industry, Sugar Industry, Animal Glue and Gelatin Industries, Baking Industry, and CA (controlled atmospheric) Storage of Fresh Fruit and Vegetables. All tortillas are made with lime treatment. Miscellaneous Uses: Petroleum, Leather, and Rubber [3]. USES OF LIME KILN DUST Typical Lime Kiln Dust ( Calcium Oxide) Specification [4] Chemical Analysis Percent CaO MgO 0.07 SiO Al 2 O Fe 2 O S 0.48 Available CaO Physical Analysis Percent Passing 1/2" Mesh Mesh Mesh Mesh 93.6 Bulk Density = 83.6 lbs./cu.ft. 5

8 Use of kiln dust with quicklime for effective municipal sludge pasteurization and stabilization with the N-Viro Soil process Burnham et al. [5] studied on use of kiln dust. They study to addresses the impact that treatment of the sludge with lime and kiln dust will have on microorganisms survival and regrowth, as well as metal availability to plants and groundwater. With the alternatives for sludge processing changing because of the public awareness of problems of dumping, either in landfills or oceans, the treatment of municipal sludges with cement kiln dust offers a technically solid solution to the current dilemma of how to treat municipal sludge so that it is safe, acceptable to the public, and a useful, even saleable, agrinomic commodity. Soil substitute from alkaline stabilization Anaerobically digested biosolids are processed with a combination of fluidized bed coal fly ash and lime kiln dust at the Bayview N-Viro facility in Toledo, Ohio. The fly ash is composed primarily of CaO, gypsum and CaCO sub 3, while the lime kiln dust is primarily CaO, MgO and dolomite. After the 12 hour heat pulse, the product is windrowed daily for three days and then stockpiled for shipment. The combination of treatments results in complete pathogen destruction, which qualifies the process as Class A under EPA 503 rules [6]. There was no observed seed germination in N-Viro Soil in the standard germination test until month six. Both month six and month seven samples exhibited excellent germination (75 and 72 percent of that observed in sand). When compared to the decline 6

9 in those parameters hypothesized to inhibit seed germination, it would appear that the likely limiting causative factor was free NH sub 3, because maximum declines in ph, EC and fatty acids occurred prior to month six, while free NH sub 3 did not disappear until the six month sampling. It is likely, however, that all of the factors contributed to seed germination inhibition, particularly in the less cured samples. The content of Ca(OH) sub 2 itself is not likely to be inhibitory; its effects are exhibited indirectly in ph and soluble salt levels [6]. Germination of six species in the greenhouse was excellent when compared to sand with no significant differences between the two growth media. This confirms the results of the standard germination test but for a wider range of species [6]. Geotechnical evaluation of dredged material from Newark harbor Maher et al. [7] reported that by the year 2000, approximately 20,914,000 cubic yards of material will be dredged in the Port of New York and New Jersey region. Under the new joint dredging plan for this region, 9,114,000 cubic yards of this material is classified as Category II and III, non-ocean disposal material. Without ocean disposal, the contaminated material must be stabilized of contaminants before any placement can occur. The Newark Bay dredged material was treated with three different pozzolanic admixtures prior to laboratory tests; portland cement (PC), cement kiln dust (CKD) and lime kiln dust (LKD). Each mix was then tested for material properties and strength characteristics using soil classification, resilient modulus, and triaxial compression tests. The shear strength of the treated material was found to be sufficient for a wide range of geotechnical applications such as embankments, subgrades of roadways, and structural 7

10 and non-structural fills. Toxicity Characteristic Leaching Procedure (TCLP) tests conducted on the treated material found no detectable levels of contaminants (heavy metals, PCB's, etc.) present once stabilization occurred. Soil stabilization utilizing alternative waste materials Heckel et al.[8] study considers the use of four by-products, three of which are waste, as alternatives to a currently acceptable high calcium lime kiln dust (LKD) for subgrade soil stabilization. The alternative materials include a dried lime kiln sludge (DLKS), a hydrated lime by-product (HLB), an ASTM Type C fly ash (TCFA) and fly ash that does not meet the requirements of ASTM C 618 (non-spec fly ash, NSFA). The lime byproducts, including the control LKD, were individually mixed with four different soil types. The fly ashes were mixed with only one soil. Test results include the moisturedensity relationships, bearing values, uncured compressive strengths, swell potential, and plasticity index for treated and untreated soils. The results indicate that the use of these waste by-products for soil stabilization could: 1) result in benefits comparable with the accepted LKD, 2) help reduce the amount of wastes being disposed of annually, and 3) open the market to alternative materials, thereby resulting in more competitive prices. Thaumasite formation in stabilized coal combustion by-products The by-products of the desulfurization process in a spray drier usually contain a mixture of hannebachite (CaSO 3 1/2H 2 O), gypsum (CaSO 4 2H 2 O), and the finer fraction of the fly ash. This material was mixed with an additional fly ash and stabilized by adding about 3 wt% lime kiln dust (LKD). The stabilized product was used either as a structural 8

11 fill or was left in the storage yard for several years. Samples extracted from these sites were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analytical results show the formation of thaumasite (Ca 3 Si(OH) 6 (CO 3 )(SO 4 ) 12H 2 O), ettringite (Ca 6 Al 2 (SO 4 ) 3 (OH)12< /sub> 26H 2 O), and an intermediate phase with varying chemical composition of calcium, aluminum, silicon, and sulfur. [9]. References 1. Biege, N., Smith, D., Lindquist, W., 1997, Lime kiln dust collectors: making the right choice, World Cement, Vol. 28, No. 2, pp ]. 2. Walker, D. D., Jr., Hardy, T. B., Hoffman, D. C. and Stanley Dewey, D., 1992, Innovativations and uses for lime, ASTM Publication, Philadelphia, PA. p. vii %20Specifications.htm 5. Burnham, J. C.; Hatfield, N., Bennett, G. F.; Logan, T. J., 1992, Use of kiln dust with quicklime for effective municipal sludge pasteurization and stabilization with the N-Viro Soil process, ASTM Special Technical Publication, Philadelphia, PA, No.1135, pp Logan, T. J, Harrison, B. J, Goins, L. E., and Hatfield, N., 1995, Soil substitute from alkaline stabilization, BioCycle, Emmaus, Vol. 36, No. 9, pp Maher, M.H., Bennert, T., Jafari, F., and Aagaard, P, 1997, Geotechnical evaluation of dredged material from Newark harbor, Proceedings of the 13th International Conference on Solid Waste Technology and Management, Widener 9

12 University, School of Engineering, Philadelphia, PA, USA, Part 1 (of 2), Vol. 1, p Heckel, G. and Wahab, R., 1996, Soil stabilization utilizing alternative waste materials, Proceedings of the Materials Engineering Conference, Washington, DC, Materials for the New Millennium, ASCE, Vol. 1, pp Sahu, S., Brown, S. A., Lee, R. J., 2002, Thaumasite formation in stabilized coal combustion by-products, Cement and Concrete Composites, Elsevier Science Ltd., Vol. 24, No. 3-4, pp