Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Reexamination Certificate
1998-12-11
2001-03-20
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
C075S500000, C423S430000
Reexamination Certificate
active
06203595
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for working up RESH or shredder light fractions, in which the RESH or the shredder light fractions are charged into a fluidized bed gasifier.
2. Description of the Related Art
As referred to herein RESH or shredder light fraction encompasses recycling products, and in particular, those occurring in the working up of motor vehicles. Such recycling products contain high amounts of organic substances, such as, rubber-like products as well as fabric fibers incapable of being readily disintegrated in conventional mills. Consequently, the usual working up of such recycling products having high portions of organic components generally comprises combustion or pyrolysis followed by mechanical further processing.
Jet mills, in particular, have been proposed for mechanically disintegrating mineralic starting products. Jet mills usually are operated by compressed air with the material ground in such jet mills being dischargeable via a screening device. Depending on the grinding stock and the grinding time, material of variable fineness may be produced. Like any other mills, however, jet mills are not suitable for sufficiently disintegrating waste substances having high organic portions such as, e.g., RESH.
SUMMARY OF THE INVENTION
The invention aims at providing a simple process of the initially defined kind, by which it is feasible to utilize the energetic content of RESH or shredder light fractions while, at the same time, ensuring a high degree of disintegration and comminution. Moreover, the process according to the invention is aimed at directly providing comminuted materials capable of being converted in a simple manner into end products that are practically usable from an economic point of view. To solve these objects, the process according to the invention essentially resides in that hot air or combustion offgases having temperatures of above 450° C. are blown into the fluidized bed through nozzles thereby forming a counterflow grinding space and that CaCO
3
is introduced into the fluidized bed and calcined in the grinding space achieve disintegration. By charging starting materials comprising RESH or shredder light fractions into a fluidized bed gasifier, it is feasible to gasify the portion of organic substances and, in particular, elastic rubber-like materials contained in the starting materials to a synthesis gas essentially consisting of carbon monoxide and hydrogen. Such a fluidized bed gasification calls for temperatures of more than 450° C., wherein the process is controlled in a manner so as to achieve gasification but no quantitative combustion such that the synthesis gas forming still has a high calorific value. The reaction, thus, has to be conducted in a substoichiometric manner in order to keep the CO
2
content in the fluidized bed atmosphere accordingly low. By carrying out gasification at temperatures of above 450° C., it is feasible at a sufficiently high temperature and by the simultaneous introduction of calcium carbonate (CaCO
3
), in particular in the form of limestone or lime marl, into the fluidized bed to calcine such calcium carbonate while such calcium carbonate or burnt lime may be accordingly disintegrated in the fluidized bed at the same time, if a counterflow grinding space is formed in the fluidized bed. Such a disintegrated calcined material acts as an effective disintegration aid, enabling fine grinding in the counterflow grinding space. Even starting materials that are difficult to disintegrate can be finely ground. Generally, the addition of calcium carbonate into the fluidized bed under suitable conditions, ensures the immediate formation of a disintegrated solid material capable of being discharged from the counterflow grinding space or fluidized bed and subsequently melted and thermally processed further with the formed burnt line. Thus, process control following disintegration is enhanced.
Advantageously, the process according to the invention is conducted in a manner that the starting products (also referred to herein as starting materials) are charged at a maximum particle size of 25 mm and, preferably, 20 mm. In order to enhance process control and with a view to the direct production of economically usable slags and, in particular, hydraulically active slags, the process according to the invention advantageously is realized such that aluminate carriers are introduced into the fluidized bed in an amount yielding an Al
2
O
3
content of between 12 and 25% by weight and, preferably, about 15% by weight after melt reduction of the disintegrated particles. By appropriately adjusting the CaO and Al
2
O
3
contents, cement-like products may be immediately produced, which may at least be employed as cement grinding additives. To this end, the process according to the invention advantageously is carried out in that CaCO
3
is introduced in an amount which, after a melt reduction of the disintegrated particles, yields a basicity CaO/SiO
2
of between 1.3 and 1.9 and, preferably, 1.5.
Within the scope of the process according to the invention, thermokinetic disintegration takes place in the fluidized bed with elastic materials being gasified and inorganic particles such as glass and metals being mechanically crushed. At the same time, the limestone or lime marl added is comminuted and calcined. In order to ensure an appropriate comminution effect, it however, care must be taken to ensure that the portion of ductile material in the fluidized bed does not become too high. In particular, it is advantageous to accordingly limit the total iron content, wherein the process according to the invention advantageously is carried out such that RESH or the shredder light fraction is subjected to magnetic separation, optionally upon coarse crushing, and charged at a total iron content of less than 6% by weight.
The total copper content advantageously may be kept higher than 0.5% by weight in view of the subsequent recovery of heavy metals or nonferrous heavy metals. Simple magnetic separation offers essential advantages in this case.
In a particularly advantageous manner, the disintegrated particles are drawn off from the fluidized bed gasifier, or the grinding space, via a screening means and supplied to a melting aggregate, particularly a melting cyclone, whereupon the melt obtained is reduced above a metal bath and, in particular, an iron bath. Generally, the material thermokinetically disintegrated in the fluidized bed, leaves the fluidized bed at grain sizes of 2 mm at most. In a particularly advantageous manner, the disintegrated material may be melted in a melting cyclone and subjected to appropriate melt reduction, to which end a metal bath and, in particular, an iron bath is particularly preferred. In such a melt reduction above an iron bath, different phases may be drawn off with a two-phase metal regulus being present. A heavy phase primarily contains copper up to 80% by weight as well as iron, tin, nickel and chromium. A second, lighter phase comprises iron up to 90% by weight as well as copper, nickel, chromium and about 4% by weight carbon. Such phases subsequently may be separated in a simple manner. The process according to the invention advantageously is carried out such that a heavier Cu-containing phase is drawn off the metal bath reactor upon segregation by liquation and such that the remaining, iron-containing phase at least partially is left in the metal bath reactor as a metal bath.
Yet another option of enriching metallic components according to a preferred mode of operation may be provided in that the disintegrated particles are sucked off via a hot cyclone, the coarse stock occurring in the hot cyclone at least partially is returned to the fluidized bed, and the fine stock leaving the hot cyclone is fed to a melting aggregate, in particular a melting cyclone, whereupon the molten slag is reduced above a metal bath. By arranging a melting cyclone not immediately after the grinding space or fluidized bed gasifier, but interposing the hot cyclone be
"Holderbank" Financiere Glarus AG
Andrews Melvyn
Pillsbury Madison & Sutro LLP
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