Potential environmental impact PEI

To address the ideal including environmental impact considerations into process design, Cabezas et al. [5] introduced a potential environmental impact (PEI) balance as an amendment of the Waste Reduction Algorithm [6]. However, this algorithm is simply a tool to be used to aid in evaluating the environmental friendliness of a process [7]. 

After closing the material and heat balances, we will examine the potential environmental impact (PEI) of the design. The basic information is the stream report. Table 5.16 shows material- and heat-balance data for a fresh feed of 150kmol/h phenol and 350kmol/h hydrogen, in total 14822.5kg/h. The products are cyclohexanone 9618.9 and 5017.9 cyclohexanol in the molar ratio 2 1. After simulation it is found that the amount of waste is 150.6 kg/h lights and 80 kg/h heavies. These data lead to a global yield of raw materials of 98.75%. 

The WAR algorithm involves the concept of a potential environmental impact (PEI) balance. The PEI indices provide a relative indication of the environmental friendliness or unfriendliness of a chemical process. These are ... 

Environmental Assessment Tool for Organic Syntheses (EATOS), based on the environmental quotient, the computer program EATOS [57] can be used to compare and improve chemical reactions. It expands the EQ by considering the potential environmental impact (PEI) of both waste and reactants [58]. 

In 2002, Eissen and Metzger proposed EATOS (an environmental assessment tool for organic syntheses), an environmental performance metrics for daily use in synthetic chemistry [11]. This tool allows rapid quantitative assessment of both the E-factor and the potential environmental impact (PEI, Sheldon s Q) of a process. They also provided a PC software application to perform this calculation, which is available from them [12]. With this tool, Sheldon s Q can be quantitatively assessed for both the feedstock and the output (product and wastes) of a multistep synthesis. The assessment is made on the basis of the available substance s ecotoxicological and human toxicological data. 

Figure 3.5 Potential environmental impact (PEI) profiles for amounts of pollutants with biodegradation described by half-life in the water compartment. Bold lines represent mercury process pollutants light gray lines represent diaphragm process pollutants. PEI have been calculated using the waste reduction algorithm to present human toxicity potential by ingestion.

Figure 3.6 Diaphragm process potential environmental impacts (PEI) using the reference dose (RfD) method. Hexane initially has a PEI value of 18,500, and the total is initially 20,500.

Abbreviations CSTR, continuous stirred-tank reactor EIM, environmental impact minimization NP, non-products PEI, potential environmental impact PFR, plug-flow reactor... 

Obviously, rpEi can be expressed in terms of reaction temperature and concentration or partial pressure of chemicals and so on. Therefore, the PEI rate-law expression can be helpful to analyze the effect of concentrations and temperature on the PEI transformation rate, rpEi, and to study the influence of back-mixing on process environmental performance. At least, the PEI rate-law expression can reveal the factors that control the transformation rate of PEI, so as to provide guidance for the selection of reactor type and operation conditions, and the inner structure of the reactor, which produce desired products while creating minimum undesired potential environmental impact. 

Since desired products are the substance we desire and the objective of this paper is to present a methodology of waste reduction, that is the primary concern is reducing the impact and the amount of the non-products, the I/k of the desired products is not considered in PEI balance. This insures that the user or producer is not directly penalized for producing a chemical that has a high PEI value. Auxiliary materials (catalyst, solvent and so on) used in reaction processes must leave the production process completely as waste or emission [10], so the PEI of the auxiliary materials should be considered. Raw materials that if possible shall be entirely processed into the desired product are not as a rule completely converted into the product. The losses that arise are the cause of generated waste and emission [10], thus their potential environmental impact should be taken into account. To sum up, the PEI balance of reaction system under steady state is ... 

These indices characterize some aspects of the generation of PEI within a reaction process. They are very useful in addressing questions related to the ability of the reactor to produce desired products while creating a minimum of undesired potential environmental impact. 

The specific potential environmental impact values for each impact category for the chemicals involved in the process are shown in Table 1. Details of the method for calculating these data appear in reference [7], Using these data, the overall PEI of each chemical can be obtained according to Eq. (4). 

To study the effects of concentration on environmental performance of reaction processes, two analyses are introduced in Section 4.5. The results show that when cq = 1, operating at relatively low concentration of B and high concentration of C is favorable for decreasing the potential environmental impact created in manufacturing a unit mass of the product C. This also is hue for total PEI leaving the system per mass of product streams according to... 

Figure 16.3 allows us to see immediately that route B also permits a large decrease in waste environmental impact the figures are 697 and 402 PEI-unit per kg of product for routes A, and B, respectively, that is, route B achieves a net 40% reduction in waste potential environmental impact. 

In this example, the WAR algorithm is apphed for environmental performance assessment based on the flow rate calculation of potential environment impact (PEI)... 

It may be seen that the presence of phenol in heavy waste has the most significant environmental impact, chiefly because of its toxicity to humans and potential soil contamination. On the contrary, the environmental impact of lights is reduced, but still not negligible. The other PEIs with impact on the atmosphere are zero. Indeed, this is not surprising because there are no gaseous emissions. 

---