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Melamine waste effluent stream solids were recovered, which contained melamine, oxytriazines, and polycondensates. The recovered solids were reacted with formaldehyde followed by sulfonation.

The rates of calcination of two types of limestones, ranging in particle size from 1 to 90 pm, were measured over the temperature range 516 to 1,OOO"C. A kinetic model based on the B.E.T. (Brunauer-Emmett-Teller method) surface area of the CaCO3 correlates the results over 5 orders of magnitude in reaction rate. The B.E.T. surface area of CaO formed by rapid calcination in dispersedparticle systems is 50 to 90 m2/g. SCOPEAcid rain is recognized as a problem of increasing importance to the industrialized areas of the world that derive a major part of their energy requirements from coal combustion. A principal cause of acid rain is generally attributed to the sulfur oxides (SO,) and the nitrogen oxides (NO,) emitted by electric power plants. Effective pollution control technologies have been developed for these emissions and are now being installed on new plants. The most widely accepted technologies are combustion modification (for NO,) and wet or dry scrubbing (for SO,). The application of these two independent controls is a costly solution to the problem. A chemical engineering challenge for the 1980s is to design a single control system for both NO, and SO, that is less expensive and is retrofitable to existing plants. The Environmental Protection Agency has initiated a program to evaluate the limestone-injection multistage burner (LIMB) to fill this need. This approach involves the injection of pulverized limestone into a staged burner designed for NO, reduction; the limestone can capture sulfur by gas/solid reactions with H2S and COS in the reducing zone of the burner and by reaction with SO2 in the oxidizing zone. In the reducing zone, reactions with either CaC03 or CaO are possible; the dominant mechanism is determined in part by calcination kinetics. The effective residence time for reactions involving CaO will also depend on the rate of decomposition of the CaC03.This study concerns the calcination rate of small limestone particles appropriate to the LIMB process. Although the decomposition of pure CaC03 has been previously studied by many investigators, there is still no consensus on the mechanism. Mass transfer, heat transfer, chemical kinetics, and combinations of these have all been reported as rate-limiting. As a result, the prior work does not provide a clear basis for predicting the calcination rate of small particles in a high-temperature dispersed system such as LIMB. There is substantial evidence that the calcination kinetics also affect the reactivity of the CaO product by influencing its grain size and specific surface area. The limited data available on calcination in a dispersed system suggest that the surface areas are extraordinarily large immediately following the decomposition of CaC03. Because those data were obtained from particles collected in a flue gas atmosphere, they were unable to establish an accurate value, or range of values, for the CaO surface area. In addition to establishing the rate of calcination and the rate limiting mechanism for small particles in a dispersed system, ...