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In the manufacture of pharmaceuticals, most active pharmaceutical ingredients (APIs) are made in solution and then recovered by separation. Acetaminophen, a pain-killing drug commercially marketed as Tylenol", is synthesized in an aqueous solution and subsequently crystallized. The slurry of crystals is sent to a centrifuge from which two effluent streams emerge: ( 1 ) a wet cake containing 90.0 wt\% solid acetaminophen \((\mathrm{MW}=\) 151 g/mol) and 10.0 wt\% water (plus some acetaminophen and other dissolved substances, which we will neglect), and (2) a highly dilute aqueous solution of acetaminophen that is discharged from the process. The wet cake is fed to a dryer where the water is completely evaporated, leaving the residual acetaminophen solids bone dry. If the evaporated water were condensed, its volumetric flow rate would be \(50.0 \mathrm{Lh}\). Following is a flowchart of the process, which runs 24 h/day, 320 days/yr. A denotes acetaminophen. (a) Calculate the yearly production rate of solid acetaminophen (tonne/yr), using as few dimensional equations as possible. (b) A proposal has been made to subject the liquid solution leaving the centrifuge to further processing to recover more of the dissolved acetaminophen instead of disposing of the solution. On what would the decision depend?

Step by step solution

01

Determine the mass of wet cake

To start, we need to find out the mass of the wet cake produced per hour. We know that the weight fraction of water in the wet cake is 10%. This means that 10% of the mass of the wet cake corresponds to the volumetric flow rate of the water evaporating which is 50 L/hour. Thus, the total mass of the wet cake (water + solid acetaminophen) can be calculated as: \( mass_{wet cake} = \frac{50 L/h}{0.10} = 500 kg/h \). We use the fact that water density is approximately 1 kg/L.

02

Calculate the mass of acetaminophen in the wet cake

Next, we need to calculate acetaminophen's mass in the wet cake per hour. We know that the weight fraction of acetaminophen in the wet cake is 90%. Therefore, using the total mass of the wet cake obtained from Step 1, the mass of acetaminophen can be given as: \( mass_{acetaminophen} = 0.90 \times mass_{wet cake} = 0.90 \times 500 kg/h = 450 kg/h \).

03

Yearly production of solid acetaminophen

Finally, knowing the amount of Acetaminophen produced per hour, we can calculate the yearly production. Remember that the process operates for 24 hours a day and 320 days per year. Thus, \( production_{yearly} = mass_{acetaminophen} \times 24 \times 320 = 450 kg/h \times 24 \times 320 = 3,456,000 kg/yr \). To convert to tonne per year, we know that 1 tonne = 1000 kg, hence yearly production = \( \frac{3,456,000}{1000} = 3456 tonnes/yr \).

04

Factors influencing decision to recover more acetaminophen

The decision to recover more of the dissolved acetaminophen would depend on: \n1. Economic feasibility: The cost of further processing vs. potential revenue from extra acetaminophen recovery. \n2. Environmental impact: Whether disposing of the solution might have harmful environmental effects. \n3. Concentration of acetaminophen: If the acetaminophen concentration in the liquid solution is significantly high, it might justify the added processing steps for greater recovery.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Chemical Engineering Principles in Acetaminophen Production

Chemical engineering is rooted in the production and manufacturing of chemicals on an industrial scale. When it comes to pharmaceuticals like acetaminophen, the production process involves the expertise of chemical engineers to ensure efficient, cost-effective, and environmentally conscious manufacturing methods.

In the case of acetaminophen production, the principles of chemical reactions, separation processes, and thermal operations are applied. Engineers design the synthesis pathway, which often involves reactions in solution. The reaction mixture then goes through separation techniques; crystallization is one common method used to purify the active pharmaceutical ingredient (API), in this case, acetaminophen.

Engineers also need to consider the scalability of the synthesis process, ensuring the transition from laboratory scale to an industrial scale maintains product quality and control. Furthermore, the process must comply with strict regulations and quality standards typical within the pharmaceutical industry.

Mass Balance Calculations

Mass balance is a fundamental concept of chemical engineering that adheres to the law of conservation of mass. It's essentially an accounting principle for material that enters and leaves a process, highlighting how much substance is present at each stage of manufacturing.

In the exercise, mass balance is crucial to determine the quantity of acetaminophen in the wet cake. By knowing the mass percentage of water and acetaminophen and the volumetric flow rate of evaporated water, engineers can calculate the total mass of wet cake produced. Understanding how these components relate is key to optimizing the production process for maximum efficiency and output.

The calculations guide the engineers in decision-making regarding process improvements and environmental considerations. For instance, they can evaluate whether it's economically and ecologically sound to invest in additional processes to recover acetaminophen from wastewater streams.

Pharmaceutical Crystallization

Crystallization is a separation and purification technique widely used in the pharmaceutical industry. It involves transforming a substance from a liquid solution into a solid, crystalline form, often resulting in a product with higher purity.

For acetaminophen production, this step is employed after the API has been created in solution. The precise control of the crystallization process is vital, as the purity and size of the crystals can directly impact the efficacy and quality of the pharmaceutical product.

Factors influencing crystallization include the concentration of the solute, temperature, and the presence of impurities. In a crystallizer, conditions are carefully adjusted to ensure that the pure acetaminophen precipitates out of the solution. After crystallization, the product can then be filtered out, leaving impurities in the solution that may be discarded or further processed for minimal waste.