Chemistry: fertilizers – Processes and products – Inorganic material
Reexamination Certificate
2000-12-15
2001-08-28
Sayala, Chhaya D. (Department: 1761)
Chemistry: fertilizers
Processes and products
Inorganic material
C071S901000, C210S696000, C210S759000, C241S022000
Reexamination Certificate
active
06280495
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an alkaline earth metal peroxide product, its manufacture and use.
Alkaline earth metal peroxides, in particular calcium peroxide, are well known in the art and are used for a variety of applications. A widely used alkaline earth metal peroxide is calcium peroxide which is used e.g. as a source of oxygen for aerobic microorganisms during the treatment and disposal of biological waste. Typical fields of use include, e.g., the prevention of the formation of odors, for example in biological composting bins and at biological bin collecting sites, the improvement of the decay properties of organic materials (biomaterials) during composting and the prevention of putrefaction, for example in compost heaps with a high proportion of cut grass. As a rule, calcium peroxide is not used as a source of oxygen alone, but together with other additives such as extenders, for example silicates or aluminosilicates, and mineral salts. During the treatment of biological waste—Similar to the treatment of effluents, there is generally a shortage of trace elements present during the treatment of biological waste, and, as a rule, also a lack of magnesium in the systems concernede. Consequently, in the prior art, magnesium in the form of inorganic salts, e.g. as sulphate, or in the form of magnesium silicates is added to biomaterials during treatment in order to promote or increase the effectiveness of the microorganisms involved in the treatment. However, in the prior art the individual components for the treatment of the biomaterials have been mixed into the biomaterial separately, as a result of which the individual components are frequently unable to interact in an optimum way due to unsatisfactory mixing. This is particularly true if individual components, such as magnesium, are added in small quantities and are consequently difficult to distribute evenly in the biomass, or can only be uniformly distributed by time-consuming mixing.
SUMMARY OF THE INVENTION
Consequently, the object of the invention was to make magnesium available in a form in which it can be easily mixed into a biomaterial so that it is capable of interacting in an optimum way with a calcium peroxide oxygen source used in treatment of the biomaterial.
This and other objects have been achieved in accordance with the present invention by providing a homogeneous calcium/magnesium peroxide having a magnesium content of 2 to 17% by weight, preferably 2 to 10% by weight. The calcium/magnesium peroxide according to the invention preferably has an active oxygen content of 10 to 18% by weight, particularly preferably 13 to 17% by weight, and also preferably has a calcium content of 30 to 53% by weight, particularly preferably 40 to 50% by weight.
In accordance with a further aspect of the invention, the objects have been achieved by providing a process for preparing a homogeneous calcium/magnesium peroxide having a magnesium content of 2 to 17% by weight, comprising the steps of reacting an aqueous solution or suspension of calcium hydroxide and at least one magnesium compound selected from magnesium oxide and magnesium hydroxide, with an aqueous 30 to 70% by weight hydrogen peroxide solution at a temperature below 60° C., and thereafter evaporating water and drying to obtain a solid calcium/magnesium peroxide product. The process is preferably carried out by reacting an aqueous suspension of calcium hydroxide and magnesium oxide hydroxide and/or hydroxide having a solids content of 350 to 450 g/liter with an aqueous 45 to 65% by weight hydrogen peroxide solution at a temperature in the range from about 30° C. to 40° C. with the addition of an effective peroxygen stabilizing amount of a stabilizer for inorganic peroxygen compounds.
In accordance with yet another aspect of the invention, the objects have been achieved by providing an improved method of composting biomass in which a homogenous calcium/magnesium peroxide having a magnesium content of 2 to 17% by weight is incorporated in the biomass, or a method of retarding putrefaction of or odor generation by biomaterial during processing, treatment or waste disposal, comprising incorporating in the biomaterial an effective putrefaction or odor inhibiting amount of a homogeneous calcium/magnesium peroxide having a magnesium content of 2 to 17% by weight.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Accordingly, the invention relates to a homogeneous calcium/magnesium peroxide which, apart from is content of calcium, active oxygen (Avox) and optionally small amounts of additives and/or stabilizers conventionally used in the manufacture of inorganic peroxygen compounds, is characterized in particular by a magnesium content of 2 to 17% by weight. Preferably, the magnesium content of the calcium/magnesium peroxide product according to the invention is 2 to 10% by weight. As a rule, the active oxygen (Avox) content of the calcium/magnesium peroxide product according to the invention amounts to 10 to 18% by weight, active oxygen contents of 13 to 17% by weight being preferred. As a rule, the calcium content of the calcium/magnesium peroxide product according to the invention is 30 to 53% by weight; calcium contents of 40 to 50% by weight are preferred. The calcium/magnesium peroxide product according to the invention is an alkaline earth metal peroxide in which calcium peroxide and magnesium peroxide are present homogeneously distributed in each other on a molecular level. Depending on the active oxygen (Avox) content of this product, which can be controlled by the corresponding quantity of hydrogen peroxide used in the manufacture of the product, the product may still contain fractions of unreacted calcium and/or magnesium oxide and/or hydroxide, these oxidic and/or hydroxidic fractions also being homogeneously distributed at the molecular level in the calcium/magnesium peroxide product.
Moreover, the calcium/magnesium peroxide according to the invention may contain small quantities of the usual additives and/or stabilizers such as those usually used in the manufacture of inorganic peroxygen compounds. Such additives include, for example, water glass or the usual active oxygen stabilizers such as commercial phosphonic acids and their salts.
The calcium/magnesium peroxide according to the invention has advantageous stability properties. The loss of dry stability (measured under standard conditions: 1 g/2 hours/105° C.), for example, is less than 10%; preferably the loss of dry stability is less than 5%, in particular less than 3%.
The calcium/magnesium peroxide, according to the invention is characterized by a series of advantages. On the one hand, magnesium is made available in the peroxide product in a homogeneous distribution which is advantageous for the application concerned. In this way, the peroxide product provided according to the invention can simultaneously fulfil the functions of providing a source of oxygen and also providing an advantageous source of magnesium. Therefore, when the calcium/magnesium peroxide according to the invention is used for a wide variety of applications described below, no separate addition of magnesium salts (e.g. magnesium sulfate or magnesium silicate) is necessary, and complex mixing steps for the incorporation of such separate magnesium compounds are thus superfluous.
The magnesium can be incorporated into the calcium/magnesium peroxide according to the invention in a simple manner by merely also adding a suitable source of magnesium as a further starting material in conventional processes for the production of calcium peroxide. Suitable sources of magnesium include, in particular, magnesium oxide and/or magnesium hydroxide; optionally, magnesium carbonate can also be used or employed simultaneously.
The inventions also relates to a process for the manufacture of the homogeneous calcium/magnesium peroxide product according to the invention, which is characterized in that an aqueous solution or aqueous suspension of calcium hydroxide and in particular of magnesium oxide and/or magnesium hydroxide is r
Caspar Otto
Doetsch Werner
Crowell & Moring , L.L.P.
Sayala Chhaya D.
Solvay Interox GmbH
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