Recycling networking

The results for this scenario were obtained using GAMS 2.5/CPLEX. The overall mathematical formulation entails 385 constraints, 175 continuous variables and 36 binary/discrete variables. Only 4 nodes were explored in the branch and bound algorithm leading to an optimal value of 215 t (fresh- and waste-water) in 0.17 CPU seconds. Figure 4.5 shows the water reuse/recycle network corresponding to fixed outlet concentration and variable water quantity for the literature example. It is worth noting that the quantity of water to processes 1 and 3 has been reduced by 5 and 12.5 t, respectively, from the specified quantity in order to maintain the outlet concentration at the maximum level. The overall water requirement has been reduced by almost 35% from the initial amount of 165 t. 

Fig. 4.5 Water reuse/recycle network corresponding to fixed outlet concentration (Majozi, 2005)...

The overall model for scenario 1, which is MILP, entails 1320 constraints, 546 continuous and 120 discrete/binary variables. 52 nodes were explored in the branch and bound algorithm and the optimal freshwater requirement of 1767.84 kg was reached in 1.61 CPU seconds. Figure 4.9 shows the corresponding water reuse/recycle network. 

The corresponding mathematical formulation entails 5534 constraints, 1217 continuous and 280 binary variables. An average of 4000 nodes were explored in the branch and bound search tree. The solution required three major iterations and took 309.41 CPU seconds to obtain the optimal solution of 1285.50 kg. This corresponds to 45.53% reduction in freshwater demand. A water reuse/recycle network that corresponds to this solution is shown in Fig. 4.11. 

Fig. 4.12 Water reuse/recycle network for scenario 4 - first case study...

Fig. 5.4 Water reuse/recycle network for minimum water use - model Ml (Majozi, 2006)...

Fig. 5.6 Water reuse/recycle network for minimum reusable water storage - model M2 (Majozi,... 

The environmental group Grassroots Recycling Network is developing a Zero Waste Policy Paper for consumer products. The net result is that society is beginning to expect that the products and processes of the future will not generate waste and are recyclable or biodegradable. 

The production of plastics also involves the use of potentially harmful chemicals under the name of stabilizers or colorants. Many of these stabilizers/additives have not undergone environmental risk assessment and their impact on human health and the environment is currently uncertain and doubtful. Phthalates, as additives, are widely used in the manufacturing of PVC products, and risk assessments of the effects of phthalates on the environment are currently being carried out. Recent research for the Community Recycling Network casts doubt on whether pyrolysis and gasification are the right processes for dealing with the residual municipal waste. 

The research findings for Community Recycling Network are summarized in a Friends of the Earth briefing Maximizing recycling rates - tackling residuals . The full report is available on the Community Recycling Network website www.cm. org.uk (2002)... 

Global Recycling Network (GRN) A recycling industry business center on the Internet, http //www. gm.com... 

I am particularly indebted to my son, Ian Scott, Chair of Community Recycling Network, for his helpful comments on Chapter 4. 

R. Herzog, PET-Recycling Switzerland Economic efficiency of a business-led recycling network in proceedings oiR 95, Geneva, Switzerland, BMP A, 3,... 

When a radiator assembly reaches the end of its service life, a series of dismantling operations reduces the complex assemblies to their constituent parts. Each country will have a chain of operators involved in a national recycling network, and this example focuses on one country, Sweden. Once the used radiator end-caps are available, they can be sent for reprocessing to the company responsible for reprocessing. But of all the companies involved in the original production chain, from the raw material supplier to the component sub-supplier and finally the car producer, which is to be held responsible ... 

Graphical Design Tools for Retrofitting Processes for Wastewater Reduction by Designing Water Recycle Networks... 

These two graphs will be illustrated using the water stream data provided in Table 6.2 below. A limitation of the graphical approach is that it can only be used to identify water recycle networks for streams containing only a single contaminant. As indicated previously, mathematical optimization approaches can be used to identify water recycle networks for streams involving multiple contaminants [14],... 

Table 6.2 Example water recycle network stream data [8],...

A shortcut graphical technique for water conservation design for retrofit processes has also been provided. Two important graphs are provided to create initial water recycle networks for consideration in retrofit processes. Of particular importance is the usefulness... 

Appendix 6A Illustrating the Water Recycle Network Design Guidelines... 

A wastewater recycle network is desired for the following process units in a chemical... 

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