Many chemical processes involve the isolation and drying of product solids. When a product cake is removed from a filter and dried under vacuum or atmospheric conditions, volatile process solvents will be lost from the drying vessel. Emission Master’s solids drying model is based on the assumption that all of the solvent removed from the wet cake is lost through the vent. This would normally be the case for an air transport dryer or a fluid bed dryer which uses heated air as the primary source of drying.
To begin this modeling activity, select Solids Drying from the Add_Step master pop-up menu. Once selected, the modeling window for this activity 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.
· 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 wether it should simple use the selected vessel (with or without) the previous contents. The user may also select to have the program exchange the 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 Solids Drying process takes. For example, an entry of 1.0 hr will cause the emissions from this Solids Drying 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: If this is the first time that a vessel is being used in the process then it will be shown as empty. However, if the vessel has been featured during an earlier step of the current process then the initial contents box will display the resulting mixture from its last 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. Generally speaking, the contents for the drying step represents the solvent wet product solids that are being processed. Therefore, the phase the contains the product solids should be named ‘Solids’ and the liquid phase should be named ‘Liquid’, ‘Aqueous’, or ‘Non-Aqueous’.
· Solids Content (LBS): The net weight of solids material being dried is extracted from the contents description from the ‘Solids’ phase.
· Initial (Wt %): The initial weight % is calculated based on the user defined contents as the weight of solids divided by the total batch weight.
(a) Review existing process and storage tank calculations to access if the current methodologies are consistent with those that have been established by federal and state regulatory agencies.
(b) Review the existing approach for how the emissions inventory has been maganged with respect to process emissions and the production records that have been used for monthly and annual emissions reporting.
(c) Evaluate the tracking and reporting of other related emissions inventory components including fugitive and combustion emissions.Enter the final weight percent of the solids being processed. For example if the final moisture content of a centrifuge cake is 0.5% then 99.5% would be entered into this field (100%-0.5%).
· 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.
· Non-Emitting: Check the Non-Emitting box if this activity will not have any vent emissions. This condition can exist under certain processing operations. For example, filling a vessel using residual vacuum in the vessel or filling a vessel when the process vent is tied directly back to the original charge vessel. Other operations may involve charging material to an unvented vessel and allowing the pressure to build during the process.
· Comments: Comments may help to document specific details that the user would like to make for this model. Comments may be ented directly in the edit box or entered using the notepad like interface.