The Reaction Model enables the user to implement a composition change within the process through either a chemical reaction or a simple phase change. Components from the batch that participate in the reaction are selected and the stoichiometry is entered. Next, reaction products are selected from the main Chemical database and the product stoichiometry and the target phase are entered. The percent completion of the reaction is defaulted to be 100% which can be changed based on modeling need. This model can also be used to implement a crystallization, extraction, or dissolution process. An example of creating a Reaction model has been placed in the tutorial section of Mitchell Scientific website to help illustrate the basic procedures involved (Reaction Tutorial).
To begin this modeling activity, select Reaction from the Add Step menu. Once selected, the Reaction dialog window will appear on the screen for entering the required information. An explanation of the data entry fields and requirements are described as follows:
· Activity Title: A single line of text which provides a brief reference to the process step being modeled and which will be used by the program as a Title Page entry.
· Vent I.D. Field: If the vessel, condenser, or other control device vent contains a vent identification number or code, then this information may be entered in this edit field or selected from the drop down list from previous entries.
· Equipment: This button is used to access the Equipment Database to select a vessel or similar equipment item for use with this processing model. If this activity step was pre-existing and is only being edited, the program will prompt the user to determine whether it should simply use the selected vessel (with or without) the previous contents. The user may also select to have the program exchange the newly selected vessel in every step involving the original vessel.
· Link: Process activities may be configured to be linked or not linked when the process is recalculated. If this box is checked then the current activity will be re-evaluated during process recalculations. If this box left unchecked then the mixture definitions will remain unchanged during process recalculations. Occasionally, the process may contain a step that involves a chemical reaction or a liquid-liquid extraction. Under these conditions, the user may wish for the mixture composition to remain constant during the process recalculation.
· Duration (HR): Data entered in this field represents the amount of time that the purging process requires. For example, an entry of 1.0 hr will cause the emissions from this purging model to take place over a one hour period. The emission rate will be calculated by dividing the total emissions from this step by one hour. The expression may be entered in minutes (15 min) or hours (0.25 hr). A raw number (0.25) will be assumed by the program to be an entry in hours (0.25 will be converted to 0.25 hr).
· Contents: Shows the initial contents of the vessel of this process operation. Press the Edit button to define a new mixture or to modify the existing one. Press the Clear button to reset the initial contents to be empty. Press the Mix DB button to copy a mixture from the currently connected Process Database .
· Reactants: Compounds that participate in the reaction are listed in the Reactants section along with the stoichiometric quantity. The stoichiometric quantity is normally entered in lb-moles or kg-moles. However, any valid quantity may be entered including lb or kg.
· Reaction Products: Compounds that are produced from the reaction are entered in the Reaction Products section along with the stoichiometric quantity. The stoichiometric quantity is normally entered in lb-moles or kg-moles. However, any valid quantity may be entered including lb or kg. If a compound that is being produced from the reaction will appear in the Aqueous Phase or the Non Aqueous Phase then this can be specified along with any activity coefficient that might be applied.
· Percent Completion: The percent completion for the reaction is defaulted to be 100%. However, any valid precent between 0% and 100% can be entered. When implementing the reaction model, Emission Master will calculate the greatest possible reaction quantity based upon the limiting component. The extent of reaction is then scaled based upon the percent completion value.
· Use Stoichiometry (Y/N): If the Stoichiometry box has been checked then Emission Master will apply the stoichiometric relationships that have been defined by the quantities that have been entered for the reactant compounds. Emission Master determines the maximum extent that the reaction that can take place based upon the available number of moles of each reactant in the batch. Once the extent of reaction has been determined then Emission Master calculates the number of moles of each product that can be produced using the same reaction extent. For example: suppose the following reaction A + 2B -> C has been entered where stoichiometry is to be used. Emission Master would calculate how much of compound C could be theoretically produced based on the amount of A and B that are present in the batch based on the 1A:2B ratio.
If the Stoichiometry box is left unchecked then Emission Master will not apply stoichiometry to the calculations. Instead, the quantity of each reactant that has been entered will be subtracted from the batch and the quantity of each product that has been entered will be produced. A example where stoichiometric relationships may not be needed would be polymerization reactions where the molecular weight of the final product may not be known.
· Control Devices: A control device is an equipment item which, when installed in the process vent line, reduces the level of certain compounds in the final gas stream. Control devices are selected for the Filling model from the active Controls Database. The Filling Model allows for multiple control devices to become part of the venting scheme for the source vessel. Press the Controls button access the main Controls Database interface.
(1) A process condenser may not be preceded by a control condenser or other control device.
(2) A control condenser may not be preceded by a scrubber or other control device.
· Comments: Comments may help to document specific details that the user would like to make for this model. Comments may be entered directly in the edit box or entered using the notepad like interface.
The tutorial videos below have been created to help illustrate the Reaction Model: