Recycle numbers

Recycling polymers is one way to minimize the disposal problem, but not much recycling occurs at present. Only about 25% of the plastic made in the United States is recycled each year, compared with 55% of the aluminum and 40% of the paper. A major obstacle to recycling plastics is the great variation in the composition of polymeric material. Polyethylene and polystyrene have different properties, and a mixture of the two is inferior to either. Recyclers must either separate different types of plastics or process the recycled material for less specialized uses. Manufacturers label plastic containers with numbers that indicate their polymer type and make it easier to recycle these materials. Table 13-5 shows the recycling number scheme. 

Plastic Type Recycling Symbol Recycling Number... 

Generally, the nicotinamide coenzymes are not covalently bound to the enzyme. They are employed in enzyme assays and preparative applications by adding catalytical but optimized amounts, and they need to be recycled. For an economic process, an efficient regeneration method is a basic requirement. The necessary recycle number depends essentially on the value of the chiral product, generally the method should recycle the coenzyme 100-100,000 times ([42]). 

In order to investigate the impact of the presence and magnitude of the recycle stream on the process dynamics, Equation (3.1) also makes use of the recycle number Rc, which we define below. 

Definition 3.1. The recycle number of a material recycle loop in an integrated process is a process-wide dimensionless number, expressed as the ratio of the (steady-state) flow rates of the recycle stream and the process throughput, as captured by the (total) flow rate of the process feed stream(s) ... 

Figure 3.3 Recycle flow rates (presented in terms of the recycle number Rc = Ra/F0a) required to achieve complete conversion at the system outlet (solid line, left ordinate) and corresponding reactor conversion (dashed, right ordinate) as a function of the reaction rate constant.

We define the fast, stretched time scale r = t/e. On rewriting Equation (3.10) in this time scale and considering the limit case e —> 0 (which physically corresponds to an infinitely large recycle number or, equivalently, an infinitely high recycle flow rate), we obtain a description of the fast dynamics of the process ... 

Let us employ the ratio of the nominal, steady-state values (denoted by the subscript s) of the feed-stream and recycle-stream flow rates to define the recycle number... 

Assumption 5.3. The process conditions and constraints (e.g., low single-pass conversion) are such that, at steady state, the flow rate of the material recycle stream, FrjS, must be kept significantly larger than the process throughput Fo>s. This is reflected in a large recycle number Rc ... 

In order to elucidate the dynamic behavior of the process and to devise representations of the dynamics in each time scale, let us define the recycle number of the process, Rc, as the ratio of the steady-state values of the feed and recycle flow rates ... 

Remark 6.1. The definition of the energy recovery number follows the same principle as that of the recycle number Rc (Definition 3.1). Both numbers characterize the intensity of recycling/recovery of a process inventory (see, e.g., Farschman et al. 1998) - that is, energy and mass, respectively. From the perspective of inventory recycling, the two numbers Ere and Rc are, in effect, particular cases of the same dimensionless quantity. 

Figure 7.15 CLRC elution profiles of three different experiments for constant loading factors, number of plates, and recycle numbers (Scherpian and Schembecker, 2009).

In Section 7.1.2 it is shown that in case of high efficient chromatography the number of dimensionless parameters reduces and instead of Stanton and Pedet numbers the number of plates is the dominating parameter. In order to proof these findings for CLRC, Scherpian and Schembecker (2009) measured the elution profiles for three different process setups for which the number of plates, the loading factor, and the recycle number are constant. The characteristic data of these experiments are presented in the reference. 

Batch chromatography is a special case of the CLRC. Therefore, the same scale-up strategy is applicable if the reduced time of one injection and the recycle number are set ... 

Thus, recirculation of the absorbent at each stage of an absorber allows us to make a more eflRcient use of its absorbing ability at each contact stage, thereby reducing the number of stages. However, in this context, it is necessary be aware that an increased recycling number n results in a proportional increase of volume concentration W of the liquid phase in the gas (see formulas (20.53) and (20.61)) and, consequently, in an increased ablation of liquid from the element. 

What do the recycle numbers mean on plastic bottles ... 

Additionally, for the SMB processes the following are needed flow rates for feed, extract, raffinate, desorbent and recycling number of columns ... 

Ethene is the base molecule for a variety of polymers that make well known plastics. In this activity, samples of poly(ethene) (LDPE, HDPE), poly(propene) (PP), poly(chloroethene) (PVC, poly (vinylchloride)), poly (styrene) (PS) and poly(tetrafluoroethene) (PTFE) are collected and compared. Different plastics can be identified by the recycling numbers (as shown in Figure 10.6, page 316) located on the underside of each item. 

Relevant data about the plastics and their recycling numbers are shown in Table 10.4. 

For each plastic, create a sheet of information which includes the plastic recycling number, monomer formula and name, plastic formula and name, and the T, and Tg values (explained in Discussion points, page 320). Create an Other sheet (officially this is recycling number/) for non-ethene-based plastics with different numbers to those for the plastics in Table 10.4. 

Plastics which do not have recycling numbers can be placed in Other . 

Plastic with recycling number 1 may also be found commonly -this is poly(ethenebenzene-l,4-dicarboxylate), better known as PETE or PET which stands for poly(ethylene terephthalate). At GCSE level it is advisable to sort this as Other . Note that PETE is used often for products which manufacturers want to be perceived as premium or healthy products, such as water or other drinks, and cleaning products such as shampoo, conditioner and shower gel. PET is an example of a condensation polymer, formed when two different monomers are reacted together in an alternating sequence. The term condensation is used because a small molecule, often water (HjO), is released (or condensed ) whenever the two monomers bond together. Other well-known condensation polymers include Nylon and polyurethane. 

E.5.5 Collect the plastic containers and bottles in your recycling bin. List the recycling number that is located on the plastic item. List the plastic that was used to make the plastic part. Weigh the part and perform an LCA on the part if the part was made with 100% recycled content. 

This system was claimed to show satisfactorily a high recycling number for each constituent Involved along with a... 

Figure 9.1 United States Plastics generation, recovery, and recycling rate, 1960-2012, reported in 2014. Current production and recycling numbers and rate are highlighted [1].

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