Processing recycling

The recycling of material is an essential feature of most chemical processes. Therefore, it is necessary to consider the main factors which dictate the recycle structure of a process. We shall start by considering the function of process recycles and restrict consideration to continuous processes. Later the scope will be extended to include batch processes. 

Although 600 m of water is used to make a metric ton of fertilizer, 150—240 m to make a tonne of steel, 480 m to make a tonne of gasoline, and 1000 m to make a tonne of acetate fiber, Htde if any is required chemically in any of these processes. Recycling can reduce industrial requirements by a factor of 10—50. Much of this water, particularly that for cooling, and often that for washing, can be saline. Some petroleum refiners have used salt water to remove heat (water s principal role in gasoline production), and some have actually produced table salt by evaporation in cooling towers. 

The catalyst is then transferred back to the first process reactor and is reheated to the reforming process temperature at the reactor inlet using a flow of hydrogen-rich process recycle gas, thereby achieving reduction of the platinum to a catalyticaUy active state. 

The Overall Process. Each distillation column should be examined in context with the rest of the process as well as by itself. For example, an opportunity for energy saving may be a reduction of process recycles via a purer overhead or bottoms stream. Lowering or raising column pressure to facihtate interchange with other parts of the process is another possible opportunity. 

If a catalyst is tested for commercial use, it is also important to know under production conditions how much rates are influenced by various transfer processes. Recycle reactors can execute all these tests and give information on transfer influences. In advanced research projects it is enough to know the transfer interaction during the study so that physical processes are not misinterpreted as chemical phenomena. 

The sources of solid wastes per se are summarized in Tables 16.1 and 16.4.) However, dealing with any of them will involve some combination of the activities shown in Figure 16.2, i.e. collection, segregation and identification, processing, recycling, transport and final disposal. 

The first consideration in any design and optimization problem is to decide the boundaries of the system. A reactor can rarely be optimized without considering the upstream and downstream processes connected to it. Chapter 6 attempts to integrate the reactor design concepts of Chapters 1-5 with process economics. The goal is an optimized process design that includes the costs of product recovery, in-process recycling, and by-product disposition. The reactions are... 

In principle, this process recycles all types of PVC waste. No differentiation between PVC formulae has to be made. There are no particular acceptance criteria. The waste is conditioned as follows to be acceptable for the slag bath gasifier ... 

Use closed-loop manufacturing processes. Recycle auxiliary and process materials back into the manufacturing process. 

Process recycle includes in-process and post-processing recycle. In general, in-process recycle is the preferred approach if at aU possible, but is clearly more common in the petrochemical and commodity chemicals context. For batch chemical operations commonly found in the fine chemical, pharmaceutical and agrochemicals businesses, in-process recycle is generally very difficult to do. The premise in those industries, however, is to reduce the scale of batch operations, make them continuous, and number up to achieve the required volumes. If this can be done successfully, it is more likely to be able to incorporate in-process recycle. 

Out-of-process or post-process recycle is commonly employed when possible and is used extensively on and off site. It maybe important to distinguish between the two options as each has a different set of issues. In general, off-site recycle is likely to have a greater number of potential impacts related to the transport and management of the solvent on and off the site. 

Water conservation/reuse/recycle. In this, the aim is to achieve optimum efficiency in relation to water use, looking at the possible elimination of use, the regulation of use to only specific requirements, sequential use, or reuse and in-process recycling. 

P Emissions of the substance from production, processing, recycling (+++) (+) Not investigated for Pt... 

Keywords E-waste, Extended producer responsibility, Informal waste processing, Recycling, Take-back... 

Constraints (4.18) states that the inlet stream into any operation j is made up of recycle/reuse stream, fresh water stream and a stream from reusable water storage. On the other hand, the outlet stream from operation j can be dispensed with as effluent, reused in other processes, recycled to the same operation and/or sent to reusable water storage as shown in constraints (4.19). The inlet concentration into operation j is the ratio of the contaminant amount in the inlet stream and the quantity of the inlet stream as stated in constraints (4.20). The amount of contaminant in the inlet stream to operation j consists of the contaminant in the recycle/reuse stream and the contaminant in the reusable water storage stream. The following storage specific constraints are also imperative for the completeness of the model for scenario 3. 

So far none of the industrial processes recycle the catalyst. Yet the number of ways to do this has grown far beyond simple immobilization. Two-phase catalysis now comes in many flavours. 

The reactions can be carried out in aqueous solutions or biphasic mixtures of the substrates with no additional solvent, in the presence of NaOAc (pH s 11.5) at 100 °C. At this pH the resting state of the catalyst is probably the dinuclear species depicted on Scheme 8.1, which falls apart upon coordination of the substrate alcohol. In this respect the catalyst system as very similar to that for the oxidation of terminal olefins [10,11]. Good results were obtained with 30 bar of air, however, an 8 % O2/N2 mixture can also be used, which further improves the safety of the process. Recycling of the aqueous catalyst solution is possible and is especially easy in case of biphasic reaction mixtures. Taking all these features, this Pd-catalyzed oxidation of alcohols is a green process, indeed. 

Reuptake. The nerve cell that released the neurotransmitter also has what are called reuptake sites on its surface. These reuptake sites are actually transporter proteins that are specific to each type of neurotransmitter. They act like miniature vacuum cleaners to retrieve the neurotransmitter from the synapse. The neurotransmitter is removed from the synapse at the reuptake site and returned to the inside of the nerve cell s axon terminal. Although the reuptake process recycles the neurotransmitter molecules for future use, the process does, in fact, serve to terminate the current neurotransmitter signal. 

Direction of innovation (from the standpoint of the SubChem research group - 6b) If biopersistent basalt rock wools are replaced by biosolnble mineral fibres (in manufacture, processing, recycling), the internal exposure that causes cancer is reduced. This makes a significant contribution to occupational health and safety. 

Maximizing LCO yield is largely a bottoms management process. Recycle can be employed to fully maximize LCO at reduced conversion, while maintaining bottoms equal to that of a traditional maximum gasoline operation. Due to the lower conversion, coke yield is also reduced. Feed type, conversion level, recycle stream need to be chosen carefully to fully optimize the recycle operation. 

Note that the parameter VL/VR in a slurry reactor is the fractional liquid holdup. In the packed bubble bed reactor and the trickle-bed reactor, under complete recycling of the liquid stream, VL/VR is the ratio of total volume of the liquid that is processed (recycled) to the volume of reactor, and is always greater than 1. By recycling, it is possible to process a larger volume of liquid than the reactor volume by having a surge tank in the recycle line. 

Plants to produce low-sulfur fuels from coal, oil shale, tar sands or heavy oil frequently are conceived to use the Claus process to produce byproduct sulfur. Using coal gasification as an example, it is seen that the conventional Claus process is not well suited to the usual problem of processing H2S at a concentration of 20% or lower. A new process, recycle Selectox, is very suitable to process H2S in concentrations up to 40%, provided the acid gas is free of olefins up to 95% recovery is possible, even with very dilute feed. 

Separation technologies (e.g., reverse osmosis, ion exchange, electrolytic metal recovery, and evaporation) which facilitate in-plant and in-process recycling are often included in discussions of source reduction in the plating industry,[1][2] but are covered elsewhere in this conference. 

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