Plant design, waste minimization

Huang, Y. L., and Fan, L. T. (1995). Intelligent process design and control for in-plant waste minimization. In Waste Minimization Through Process Design (A. P. Rossiter, eds.), pp. 165-180. McGraw Hill, New York. 

Thermex is a commercially available ex situ technology that is based on the use of membrane separation technology for preconcentrating plant radioactive wastewater and evaporation for drying the preconcentrates. The technology is designed to minimize the volume of waste that would require storage or disposal. 

Boerner, D.A. Recycling the Paper Forest, Amer. Forests, 37 (July/August 1990). Bumble, S. Computer Simulated Plant Design for Waste Minimization/Pollution Prevention, Lewis Publishers. Boca Raton, FL, 2000. 

Given are two examples which show different methods that are used to reduce the quantities of waste water from cooling tower operation. In one case, the treatment technique of an existing facility was modified to reduce waste water production. In the order case, a new plant design included facilities for the minimization of the requirements for waste water disposal. 

Bumble, S. Computer Simulated Plant Design for Waste Minimization/Pollution Prevention, Lewis Publishers New York, 2000. 

The main equipment in the dehydrogenation reaction section of a Lummus/UOP Classic SM plant includes a steam superheater, two dehydrogenation reactors, a series of waste heat exchangers, and an off-gas compressor (Fig. 3). The equipment is designed to minimize pressure drop from the dehydrogenation reactors inlet to the off-gas compressor. 

Improved housekeeping can often lead to reduced emissions and waste.200 The leaky valves and seals can be fixed or they can be replaced with new designs that minimize emissions.201 These include diaphragm valves, double mechanical seals with interstitial barrier liquids, magnetic drives, better valve packings, filled fabric seals for floating roof tanks, and so on. Older plants may have some of the... 

A major part of the process development activity for a new plant is to minimize, or ideally prevent by designing out, waste production and hence possible pollution. The economic and environmental advantages of this are obvious. 

The first step in the methodology is the expansion of the foreground system (the acrylic acid plant) to include up-stream/input processes within the boundaries of the background system. This allows the traditional waste minimization techniques to be extended by considering a more complete description of the environmental impact of the process. Since a constant production rate is used as a design basis, downstream (product use) stages are not accounted for and the study is, therefore, a "cradle-to-gate"... 

Armed with the PFS and the questions for the various process options the team can then discuss the most appropriate way forward. For example considering question 2, production staff may comment that this particular plant only runs on the day shift, so a 10-hour reaction is not viable the chemical engineer may conclude that the problem is likely to be one of mass transfer, and other reactor design options such as a spinning disc reactor should be considered. The SHE advisor may comment that not only is solvent 1 volatile but it is also moderately harmful and would require specialist handling equipment, hence it is very important to find an alternative. As waste minimization starts at the reaction stage it is critical to study this area in particular detail. Questions that can be asked include ... 

Drying and cooling the products of ammonium phosphate production are conventionally achieved in a rotary drum, and a means must be provided to remove the dust particles from the air streams to be exhausted to the atmosphere. At the Minnesota plant, a high-efficiency dry cyclone recovery system followed by a wet scrubber was designed. In this way, material recovered from the dry collector (and recycled to the process) pays for the dry system and minimizes the load and disposal problem in the wet scrubber, because it eliminates the need for a system to recover the wet waste material that is discharged to the gypsum disposal pond for settling. 

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