Recyclable design

Design code Design for Recycling Design of experiments Design of proteins Design patents Designs Desipramine Desipramine [50-47-5]... 

Shonnard DR, Hiew DS (2000) Comparative environmental assessments of VOC recovery and recycle design alternatives for a gaseous waste stream. Environ Sci Technol 34(24) 5222-5228... 

Calcor A process for making carbon monoxide from natural gas or liquid petroleum gas. It combines steam reforming with carbon dioxide recovery or recycle. Designed and licensed by Caoric GmbH. Five commercial plants have been installed as of 1992. 

The Swung-Lo plant, located in the Far East, is a relatively new plant with an improved reactor/recycle design. This plant can be operated between 80 X 106 and 120 X 106 lb/year and has a constant variable cost of 5.00/100 lb. 

Partial recycle design allows the use of a smaller pump and retention vessel. 

A split stream design could provide a gas/water ratio of only 0.25 cu ft/bbl if 50% of the feed were pressurized. And for a partial recycle design, the gas/water ratio would be only 0 17 cu ft/bbl if the recycle stream was 50% of the teed water (33% of the total inlet water would be saturated with gasl. 

Multistage/multistep combinations of two-step and two-stage processes can be designed but are seldom used in commercial systems—their complexity makes them uncompetitive with alternative separation technologies. More commonly some form of recycle design is used. 

Figure 8.20 shows another type of recycle design in which a recycle loop increases the concentration of the permeable component to the point at which it can be removed by a second process, most commonly condensation [38], The feed stream entering the recycle loop contains 1 % of the permeable component as in Figures 8.16-8.19. After compression to 20 atm, the feed gas passes through a condenser at 30 °C, but the VOC content is still below the condensation concentration at this temperature. The membrane unit separates the gas into a VOC-depleted residue stream and a vapor-enriched permeate stream, which is recirculated to the front of the compressor. Because the bulk of the vapor is recirculated, the concentration of vapor in the loop increases rapidly until the pressurized gas entering the condenser exceeds the vapor dew point of 6.1 %. At... 

Recycle designs of this type are limited to applications in which the components of the gas mixture, if sufficiently concentrated, can be separated from the gas by some other technique. With organic vapors, condensation is often possible adsorption, chemical scrubbing or absorption can also be used. The process shown in Figure 8.20 is used to separate VOCs from nitrogen and air or to separate propane, butane, pentane and higher hydrocarbons from natural gas (methane). 

Still another multi-reactor approach is to divide the MTG reaction into two steps as shown in Figure 7. In the first step, methanol is partially dehydrated to form an equilibrium mixture of methanol, dimethyl ether and water over a dehydration catalyst. About 15% of the reaction heat is released in this first step. In the second step, this equilibrium mixture is converted to hydrocarbons and water over ZSM-5 catalyst with the concomitant release of about 85% of the reaction heat. Though this two step approach does not have any of the inherent complications of the previously mentioned multibed reaction systems, it leaves one with a substantial amount of the reaction heat (85%) still to be taken over one catalyst bed. This requires a fairly high recycle stream to moderate the temperature rise over the second reactor. Such a high recycle design would require careful engineering in order to transfer heat efficiently from the reactor effluent to the recycle gas and reactor feed. However, this two stage reactor system is the simplest of the fixed-bed systems to develop. 

Because the solids path does not contain any sort of mechanical closure, the characteristic pressure distribution plotted in Fig. 11 is obtained. The distribution of solids between the fluidized bed and the recycle line is directly related to this pressure distribution. Operating properties differ from one recycle design to another [56]. 

The initial equipment costs and operating costs for the more conventional processes are higher than for supercritical carbon dioxide. The higher equipment costs are due to the additional parts needed for environmental treatments (i.e., scrubbers, vapor incinerators, etc.) The consumables costs are lower for the supercritical fluid processes due to the closed-loop recycle design of the supercritical fluid system, elimination of water for rinsing and the reduced electricity costs associated with not having to dry the parts. 

D. R. Shonnard and D. S. Hiew, Comparative Environmental Assessments of VOC Recovery and Recycle Design Alternatives for a Gaseous Waste Stream, Environmental Science and Technology, 34(24), 5222-5228 (2000). 

Recyclossorb , containing antioxidants, costabilizers and HALS light stabilizer, to be used for recyclate designed for outdoor exposure, viz. recycled PE/PP trash bins. 

Another source of design aids is the "Emnronmental Considerations in Product Design and Processing" [26], which contains guidelines for design for disassembly and recyclability, design for reusability, and waste avoidance... 

Association of Postconsumer Plastic Recyclers (APR) (2011) The Association of Post-consumer Plastic Recyclers Design for Recyclability Program, Washington, DC APR. 

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