The manager asked me to calculate the flow rate of the circulating water in the reactor; please help
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The known conditions include: the temperature in each of the three reaction vessels, the feed flow rates of the two reactant solutions (each component enters the first reaction vessel for reaction and then overflows sequentially to the second and third vessels to ensure more complete conversion; the contents in the vessels consist of solutions of these two components plus a solvent), the outlet temperature of the circulating water in each reaction vessel, and the pH value (no temperature sensor is installed at the inlet of the circulating water, so the temperature at the pump connected to the cooling tower outlet is used as a substitute). Additionally, the molar heat of reaction for the reactants is also known. It’s only these conditions that can’t be calculated, right? ? ? I asked my supervisor; he said that while knowing the heat of reaction is necessary, the latent heat of vaporization is also required. I would appreciate some advice from the experts here.
Calculating the flow rate of the circulating water in the reaction tank indeed requires more information, especially data that can accurately describe the heat exchange process. Based on the provided known conditions and the guidance from management, we need to carry out a series of energy balance calculations. The following are the information and steps that may need to be considered in the calculations: 1. **Temperature of the inlet and outlet solutions**: Knowing the initial temperature of the solution in each reactor, as well as the temperature of the solution at the outlet of the three reactors, can help us calculate the heat change of the inlet and outlet solutions. 2. **Specific heat capacity of the solvent**: To calculate the heat absorbed or released by a solution, we need to know the specific heat capacity of the solvent, as well as the composition of the solution and the specific heat capacities of its constituent components. 3. **Molar reaction heat of reactants**: The molar reaction heat of reactants during the reaction process is an important component of the heat balance. It is necessary to know the specific chemical reaction equations as well as the reaction ratios and conversion rates of each reactant. 4. **Specific heat capacity and flow rate of circulating water**: The heat absorbed by the cooling water depends on the specific heat capacity of the circulating water as well as its flow rate. The inlet temperature of the circulating water is unknown; it can be assumed to be the temperature at the pump that delivers water from the cooling tower. 5. **Vaporization latent heat**: If the solvent evaporates during the reaction, it is necessary to know the vaporization latent heat of the solvent, as this is an important factor in calculating heat loss. The general steps for performing the calculations are as follows: a. Determine the heat of reaction for each reactor: this requires knowing the chemical equation of the reaction, the molar flow rate of the reactants in the feed, and the heat of reaction. b. Calculate the heat absorbed or released by the solution in each reactor: this involves calculating the temperature difference between the incoming and outgoing solutions as well as their specific heat capacities. c. Consider the heat carried away by solvent evaporation: if evaporation occurs, it is necessary to know the vaporization latent heat of the solvent as well as its amount of evaporation. d. Heat balance equation: The heat of reaction, the heat absorbed or released by the solution, the heat lost due to solvent evaporation, and the heat absorbed by the circulating water are combined to form the heat balance equation. e. Calculate the circulating water flow rate: The flow rate of the circulating water can be determined using the heat balance equation, that is, the heat to be absorbed by the cooling water divided by (the specific heat capacity of the circulating water multiplied by the temperature difference). A detailed calculation process requires further data and specific steps; the above is only a general approach to the calculation. You may need to work with chemical engineers or thermodynamics experts to obtain accurate values. .
Be timid and just let the boss do the calculations. Knowing how to calculate it yet deliberately acting old, just go for it with her.
Some conditions are lacking, mainly concerning the heat transfer coefficient of the reactor vessel material. It’s not clear whether it is continuous or intermittent; it seems to be a series of batch stirred-tank reactors. The person in charge of the 3 CSTRs mentioned the latent heat of vaporization; it is likely that there are gases present in the reaction materials or products, and the heat of reaction is already known. The most important thing is to know the information about the reaction vessel, such as its external dimensions, material, wall thickness, type of stirrer, viscosity and density of the material, dimensions of the coiled tubes or jacket, and the reaction temperature. After these are collected, a transition using the Nusselt number yields the reactor heat transfer coefficient.
Simple calculation principle: Calories consumed = Calories expended. The enthalpy difference between the two states inside the reactor can be calculated using the temperatures and amounts of each material before the reaction, the conversion rate of the reaction, the heat release data from the reaction, as well as the temperature of the materials inside the reactor at the end of the reaction. This enthalpy difference represents the heat carried away by the circulating water; by dividing this value by the specific heat capacity of water at constant pressure and the temperature difference, the volume of water in circulation can be determined.
Thank you, boss. It is indeed a continuous feeding reaction process, using a series of reactors with stirring for the solution reaction. Another manager said that the vaporization latent heat can be ignored, as it is a low-pressure reactor under nitrogen protection, with the pressure at the top of the reactor being only around 0.3 MPa. I’ll gather the other information later; please help me take a look once that’s done.
Thank you, boss. What our manager said was to adopt a simplified approach: the input temperature of the reactants is unknown :( (The on-site instruments only display volume/mass flow rate; at most, density information is available). There are two components in the materials before the reaction – 70% nitric acid and a mixture (solvent + salt solution formed as a result of previous reaction steps). In reality, it is the reaction between salt and nitric acid that takes place in this reactor.
Then use the temperature inside the reactor before the reaction starts as the base temperature
Continuous feeding; the initial temperature inside the reactor is unknown
This post was last edited by Ne0n on 2023-12-8 at 14:06. This is already known information; since the company’s computers are confidential, I couldn’t upload files, so I took screenshots. Those temperatures as well are fabricated