Recycling material flow

I-H. Hong, J. C. Ammons, and M. J. Realff, Decentralized Decision-making and Protocol Design for Recycle Material Flows, submitted to Manufacturing Service Operations Management (2006b). 

By extending this modeling principle, two- or three dimensional and non uniform mixing, as well as convection, bypass and recycling material flows between these cascade-cells can be also taken into consideration. 

Flow diagram showing process material flow, scrap and recycled material. Brief descriptions of the products are usually sufficient for the early stages of analysis of the company operation. The information will be amplified during the subsequent stages of the study. 

Figure 10.7 shows the extended RTN formulated for the benchmark problem. The production process includes diverging and converging material flows, flexible proportions of output goods (task Tj), cyclic material flows (recycling of output from task T3 into state Si), intermediate products which cannot be stored (state nodes S5, S9, S10, S12), and blending of products in task Ti 5. All processing tasks are operated batch-wise with lower and upper bounds on batch sizes. Batch sizes are... 

A recycle PFR, operating at steady-state for the reaction A +. . - products, is shown schematically in Figure 15.6, together with associated streams and terminology. At the split point S, the exit stream is divided into the recycle stream (flow rate RqJ and the product stream (flow rate q,), both at the exit concentration cA1. At the mixing point M, the recycle stream joins the fresh feed stream (flow rate q0, concentration cAo) to form the stream actually entering the reactor (flow rate (1 + R)q0, concentration ca o)-The inlet concentration c Ao may be related to cAo, cA1, and R by a material balance for A around M ... 

The sedimentary and metamorphic rocks uplifted onto land have become part of continents or oceanic islands. These rocks are now subject to chemical weathering. The dissolved and particulate weathering products are transported back to the ocean by river runoff. Once in the ocean, the weathering products are available for removal back into a marine sedimentary reservoir. At present, most mass flows on this planet involve transport of the secondary (recycled) materials rather than the chemical reworking of the primary (juvenile) minerals and gases. The natirre of these transport and sediment formation processes has been covered in Chapters 14 through 19 from the perspective of the secondary minerals formed. We now reconsider these processes from the perspective of impacts on elemental segregation between the reservoirs of the crustal-ocean-atmosphere factory and the mantle. 

Separation of the material flows into two parts technical flow (including non-biodegradable materials) and nutrients flow (with organic and biodegradable materials) to facilitate internal recycling and reuse ... 

Conserve and improve natural ecosystems while protecting human health and well-being. [Reduce, reuse, and recycle the materials used in production and consumption systems, and ensure that residual waste can be assimilated by ecological systems. Rely on natural energy flows. Design processes and products to create cyclical material flows.]... 

However, our column is connected via material flow with a reactor. In Chap. 4 we show that reactor control often boils down to two issues (1) managing energy (temperature control) and (2) keeping as constant as possible the composition and flowrate of the total reactor feed stream (fresh feed plus recycle streams). The latter goal implies that it may in fact be desirable to control the composition of the recycle stream. This minimizes the variablity in recycle impurity composition back into the reactor. This recycle composition is dictated by the economic tradeoffs between yield, conversion, energy consumption in the separation section, and reactor size. 

---