Manufacture of By-Products In the production of 300 kg per hour of an active substance for the

Step 1: Calculate the amount of dissolver in the sewage water - 20 tons of sewage water accrue p

Manufacture of By-Products In the production of 300 kg per...

Manufacture of By-Products In the production of $300 \mathrm{~kg}$ per hour of an active substance for the manufacturing of photographic paper, 20 tons of sewage water accrue per day. The sewage flow is contaminated with an organic dissolver, which is needed for the production of the active substance. The purchase price of the dissolver is $$\$ 1.30$$ per $\mathrm{kg}$. The current production process has about 6000 operating hours per year and runs on the principle of continuous production. The sewage water needs to be disposed of as waste product. Because of dissolver contamination of approximately $5 \%$ (mass percent), extra costs of $$\$ 5.50$$ per $\mathrm{m}^3$ are caused in comparison to wastewater without organic impurities. On the basis of thermodynamic calculations and laboratory tests, it was estimated that it would be possible to separate almost all of the dissolver by adding a simple distillation column as a further process step. For the distillation, $80 \mathrm{~kg}$ heating steam (cost: $$\$ 20$$ per ton) is needed per $\mathrm{m}^3$ of sewage water. The regained dissolver can be reintroduced into the production process without any additional effort. The plant engineer now attempts to estimate how much money can be invested in the distillation device, if management sets a limit of 2 years maximum for payback on this kind of investment. Can you help?

Manufacture of By-Products

In the production of $300 \mathrm{~kg}$ per hour of an active substance for the manufacturing of photographic paper, 20 tons of sewage water accrue per day. The sewage flow is contaminated with an organic dissolver, which is needed for the production of the active substance. The purchase price of the dissolver is $$\$ 1.30$$ per $\mathrm{kg}$.
The current production process has about 6000 operating hours per year and runs on the principle of continuous production. The sewage water needs to be disposed of as waste product. Because of dissolver contamination of approximately $5 \%$ (mass percent), extra costs of $$\$ 5.50$$ per $\mathrm{m}^3$ are caused in comparison to wastewater without organic impurities.

On the basis of thermodynamic calculations and laboratory tests, it was estimated that it would be possible to separate almost all of the dissolver by adding a simple distillation column as a further process step. For the distillation, $80 \mathrm{~kg}$ heating steam (cost: $$\$ 20$$ per ton) is needed per $\mathrm{m}^3$ of sewage water. The regained dissolver can be reintroduced into the production process without any additional effort.

The plant engineer now attempts to estimate how much money can be invested in the distillation device, if management sets a limit of 2 years maximum for payback on this kind of investment. Can you help?

Key Concepts

Economic Evaluation and Payback Period

Economic evaluation in engineering projects involves assessing whether the benefits of an investment, such as reduced operating costs or material recovery, justify the initial expenditure. The payback period is a key financial metric representing the time required for the investment to produce enough savings or revenue to cover its cost. Setting a target payback period helps in analyzing feasible investments and understanding the risk associated with the project.

Waste Valorization

Waste valorization refers to converting waste materials into useful products, thereby recovering value from what would otherwise be discarded. In industrial processes, recovering valuable materials from waste streams can offset raw material costs and reduce environmental impacts. This concept emphasizes turning a disposal cost into a potential cost saving by reintroducing recovered resources into the production cycle.

Continuous Production Process

A continuous production process is one that runs non-stop over a set period, typically measured in operating hours per year. It is characterized by steady, consistent throughput, and requires consistent input, output handling, and waste management. In such systems, integrating additional process steps must be evaluated in terms of how they affect overall flow, efficiency, and operating costs.

Waste Stream Management

Waste stream management involves treating or disposing of by-products and wastewater generated during manufacturing. In industrial contexts, impurities or contaminants in the waste can lead to additional costs for disposal or environmental compliance. Managing these streams effectively can also include implementing recovery strategies that minimize waste and reduce overall expenses.

Separation Processes and Distillation

Separation processes are critical in chemical engineering, enabling the isolation and recovery of specific components from complex mixtures. Distillation is a common separation method that leverages differences in boiling points of components to separate them. Evaluations of such processes include not only the technical feasibility and efficiency of the separation but also the energy requirements and integration into the existing production system.

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