Chemistry: fertilizers – Processes and products – Organic material-containing
Reexamination Certificate
2000-04-21
2001-12-04
Langel, Wayne (Department: 1754)
Chemistry: fertilizers
Processes and products
Organic material-containing
C071S028000, C071S030000, C071S034000, C071S058000, C071S063000, C071S064050, C071S064130, C071S019000, C071S020000, C071S031000, C071S903000, C071S029000, C023S3130FB, C023S3130FB
Reexamination Certificate
active
06325836
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to mechanically strong, water-disintegrable agglomerates containing various particulate calcium sources for use as a soil conditioner to neutralize soil acidity and provide a source of nutrient values. The present invention also relates to processes for forming such agglomerates.
Soil conditioners or liming agents are widely used in agriculture, lawn care and gardening to reduce soil acidity and promote plant health. A variety of calcium-containing materials, in particulate or granulated form, are used as soil liming agents. Conventional liming agents include: limestone (CaCO
3
), dolomitic limestone (CaOMgO.2CO
2
), lime (CaO), slaked or hydrated lime (Ca(OH)
2
), and gypsum (CaSO
4
.2H
2
O).
Many industrial processes produce waste solids containing calcium. For example, the manufacture of cement and lime is accompanied by the generation of large quantities of dust collected from the hot gaseous effluents vented from the kiln. Similar calcium-containing dusts are recovered from the stack gases and ash residues produced during the burning of manure fuels (i.e., manure ash). These particulate wastes share two properties that make them potentially useful for application to cultivated soils: (1) significant acid neutralization capacity; and (2) high concentrations of calcium and other important soil nutrients such as potassium and sulfur.
Although some have suggested liming soils with cement kiln dust (See T. A. Davis, et al., “Disposal and Utilization of Waste Kiln Dust From Cement Industry”, EPA Report No. 670/2-75-043 (May 1975)) as a way of reclaiming this sizeable waste stream, one serious hindrance to expanded agricultural use cement kiln dust and similar waste products are the problems associated with storage, handling and application of these finely divided materials to soils.
Raw cement kiln dust, for example, is extremely fine, typically consisting of particles having an average particle size much less than 100 &mgr;m, with a large portion of particles often having a particle size of 10 &mgr;m or less. As a result, the dust is easily carried away by the wind and is difficult to bulk-blend with other materials in preparing various fertilizer formulations. Furthermore, modern fertilizer application equipment for broadcast or row placement of solid fertilizers, is designed for handling free-flowing, granular or pelletized materials having an appreciable mean diameter, not dust. Consequently, numerous problems are encountered when such equipment is employed for field application of finely-divided dust.
Accordingly, it would be highly beneficial to develop a process for granulating or agglomerating cement kiln dust and other calcium-containing materials capable of consistently producing a mechanically strong soil conditioning agglomerate that readily disintegrates when contacted with water.
SUMMARY OF THE INVENTION
Among the objects of the present invention, therefore, are the provision of a process for forming an agglomerate comprising calcium-containing waste materials such as cement kiln dust for use as a soil conditioning agent; the provision of such a process capable of producing an agglomerate having sufficient mechanical strength to withstand the rigors of handling, transport and application without excessive dusting; and the provision of such a process which produces an agglomerate which disintegrates readily into particles having substantially the same size as the raw materials used to form the agglomerate once the agglomerate is incorporated into soil and exposed to water so that the various beneficial components of the agglomerate may be rapidly utilized by the soil.
Briefly, therefore, the present invention is directed to a process for forming an agglomerate for use as a soil conditioning agent. The process comprises preparing a preagglomerate containing a water-soluble binder and a particulate calcium source comprising CaO or Ca(OH)
2
. The combined concentration of CaO and other calcium-containing compounds having the potential to be hydrated in the preagglomerate is no greater than about 10% by weight. The preagglomerate is pelletized to form the agglomerate. The proportion of the particulate calcium source in the preagglomerate is sufficient such that the agglomerate contains at least about 15% by weight of the particulate calcium source. Once formed, the agglomerate is dried. Drying of the agglomerate is controlled such that dried agglomerates having a size ranging from −7 to +8 Tyler Standard Sieve Series exhibit an average green crush strength of at least about 2 pounds.
In another embodiment, the process for forming an agglomerate for use as a soil conditioning agent comprises preparing a preagglomerate containing a water-soluble binder and a particulate calcium source comprising CaO or Ca(OH)
2
combined with at least one other calcium-containing secondary plant nutrient source selected from the group consisting of limestone, dolomitic limestone, gypsum, lime, hydrated lime and mixtures thereof. The particulate calcium source has a particle size distribution such that less than about 1% by weight of the particulate calcium source is +20 mesh and less than about 10% by weight of the particulate calcium source is −20 +100 mesh Tyler Standard Sieve Series. The combined concentration of CaO and other calcium-containing compounds having the potential to be hydrated in the preagglomerate is no greater than about 10% by weight. The preagglomerate is pelletized to form the agglomerate. Once formed, the agglomerate is dried in a controlled fashion such that dried agglomerates having a size ranging from −7 to +8 Tyler Standard Sieve Series exhibit an average green crush strength of at least about 2 pounds.
The present invention is further directed to an agglomerate for use as a soil conditioner. The agglomerate is formed by pelletizing a preagglomerate containing a water-soluble binder and a particulate calcium source comprising CaO or Ca(OH)
2
combined with at least one other calcium-containing secondary plant nutrient source selected from the group consisting of limestone, dolomitic limestone, gypsum, lime, hydrated lime and mixtures thereof. The combined concentration of CaO and other calcium-containing compounds having the potential to be hydrated in the preagglomerate from which the agglomerate is formed is no greater than about 10% by weight. Furthermore, the particulate calcium source has a particle size distribution such that less than about 1% by weight of the particulate calcium source is +20 mesh and less than about 10% by weight of the particulate calcium source is −20 +100 mesh Tyler Standard Sieve Series.
In another embodiment, the agglomerate for use as a soil conditioner is formed by pelletizing a preagglomerate containing a water-soluble binder, a primary plant nutrient source providing a source of available nitrogen and a particulate calcium source comprising CaO or Ca(OH)
2
. The proportions of the primary plant nutrient source and the particulate calcium source in the preagglomerate are sufficient such that the agglomerate comprises about 15% to about 60% by weight of the particulate calcium source and about 30% to about 80% by weight of the primary plant nutrient source. The combined concentration of CaO and other calcium-containing compounds having the potential to be hydrated in the preagglomerate from which the agglomerate is formed is no greater than about 10% by weight. Furthermore, the agglomerate exhibits an average green crush strength of at least about 2 pounds when sized ranging from −7 to +8 Tyler Standard Sieve Series.
In a still further embodiment, the agglomerate for use as a soil conditioner is formed by pelletizing a preagglomerate containing a water-soluble binder, a primary plant nutrient source providing a source of potassium and a particulate calcium source comprising CaO or Ca(OH)
2
. The proportions of the primary plant nutrient source and the particulate calcium source in the preagglomerate are suf
Greskovich Eugene
Holley Carl
Wommack Greg
Langel Wayne
Magic Green Corporation
Nave Eileen E.
Senniger Powers Leavitt & Roedel
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