Heat Transfer Agents
A heat transfer agent is an agent used to carry out a heating or cooling task as required by the performance of the unit procedure. Demand for heat transfer agents is calculated by operations that perform heating or cooling. SuperPro Designer keeps track of the instantaneous as well as cumulative demand of heat transfer agents.
Auxiliary utilities can also be specified for each operation to account for any cooling or heating consumption that is not currently computed by the simulation model. You can set the auxiliary utilities for an operation through the Operations Dialog: Labor etc. Tab. When auxiliary heating and cooling are specified, the provided values are not used in heat balances. They are only used in calculating the total utility consumption and the operating cost of that operation (and the associated equipment).
Energy Recovery
The demand for heat transfer agents may be reduced by recovering the energy from operations needing cooling and matching it with cold operations which require heating. For more details on recovering energy in SuperPro Designer see the Energy Recovery topic.
Definitions in the System Database and in the User Database
The ‘SuperPro (User)’ database contains the agent databank and it currently has a limited list of options for heat transfer agent types. To review the list of such available agents, select } from the main menu (or hit F3 as a shortcut). This will bring up the Heat Transfer Agents Databank Dialog. Users can add to this list by including their own definitions for heat transfer agents. Changes made to the heat transfer agents databank do not affect existing process files or other parts of the databank even if the edited heat transfer agents are used as the basis for utilities declared in sites.
For more details on the Heat Transfer Agents Databank, please see Heat Transfer Agents Databank.
Registered (in Use) Heat Transfer Agents
When selecting a heat transfer agent for an operation, you can choose from a list of generic-type agents defined in the Heat Transfer Area databank or, for operations in procedures owned by allocated sections (see Section Allocation), you can choose from the corresponding site utilities. Agents currently in use can then be inspected from the List of Heat Transfer Agents Currently in Use dialog accessed by selecting } } } or } } from the main menu. From here you may edit the properties of a heat transfer agent or you can reset its properties to match the values as kept in the ‘SuperPro (User)’ database. See Heat Transfer Agent Properties.
If at any time the user wishes to change the Heat Transfer Agent used in the process with another agent, instead of visiting all the locations the agent is used and replacing it, the Replace Resources Dialog can be used to perform a global switch of resource(s) with another resource(s).
Heat Transfer Agents in Sites
To add, edit or delete heat transfer agents declared as utilities in sites, select } from the main menu. From the Sites & Resources Databank Dialog that appears, you can select the desired site from the left pane (site tree) and the utilities node on the right pane and you may add new, edit, or delete heat transfer agents by clicking on the appropriate button from the toolbar.
When adding a new site utility you will be presented with a dialog which displays all currently available heat transfer agent definitions in the agent databank. From there you can select one or more agents that you want to include in the site.
Once a heat transfer agent is added to a site as a site utility then you cannot delete it from your agent databank; first you must remove the agent from the site and then you are free to delete the agent from your agent databank.
If a section is allocated to a site, then available to operations of this section are not only utilities of this site but of its parent sites as well. This implies that if there is a central utility plant in a site then all produced utilities are available to all sub-facilities within that site.
Changes made in site utilities may affect existing process files (opened or closed at the time of the modification) that contain sections that use them. SuperPro Designer will not attempt to reconcile any process files currently not open in by the program. However, SuperPro will require that any open process files be consistent with the state of currently available resource databanks. Therefore, all changes done in the site and resources databank will automatically be propagated to open process files even if de-allocation (i.e. substitution with generic-type utilities) is needed to maintain consistency. Such changes could affect both material balances as well as economic results so re-solving M&E balances might be needed for all affected process files.
For more details, see Adding or Deleting a Heat Transfer Agent.
Heat Transfer Agent Properties
The parameters of a heating/cooling agent as shown in the heat transfer agents databank are the default parameters that are used the first time any of the processing steps in your process file employs that heating/cooling agent. If you decide to use different values for your specific process file, then you can adjust those parameters without affecting the default values of the agent in the databank, by bringing up the List of Heat Transfer Agents Currently in Use that appears when you select the } } option from the main menu, or just the } option from the flowsheet context menu. The dialog that pops up displays a list with all heat transfer agents currently employed by the process file.
To view or edit the properties of a heat transfer agent, you should click on the agent's index column to select it and then press the View/Edit Properties button (
). Alternatively you can double-click on the agent's index column. The Heat Transfer Agent Properties Dialog that comes up contains the agent's data organized in three tabs. Changes made in the heat transfer agent through this dialog will only affect this process file; they will not be stored in the Heat Transfer Agents databank. If you want the agent in this process file to take up the properties of the agent in the databank (in case they are different) select the agent by clicking on the agent's index column and press the Update Properties from DB Record button (
). If you want to update the databank's record (heat transfer agent properties) based on the current process file's record press on the Update Properties in DB button (
). If you wish to deposit the selected agent to the databank, then click on the Deposit Record in DB (
) button.
The Properties tab lets you define the type of the agent (heating or cooling), the temperature at which the agent is available from the utilities support plant, the temperature at which it should be returned to the utilities plant, and the unit cost charged for the use of this agent, which can be specified either on a mass basis (e.g., in $/MT of heat transfer agent mass) or on an energy basis (e.g., in $/kcal of heat transfer agent energy change). Note that only through the databank you can change the type of an agent and, as mentioned before, even if you do that, that change will not affect process files that make use of this agent.
The Availability Limits tab lets you define bounds on consumption of this agent. There are two types of limits: rate limits (instantaneous or time-averaged over a user-defined time span) and cumulative limits over a user-defined time span. Upon request, these limits will be plotted on the resource consumption charts (see Heat Transfer Agent Consumption Chart) so that you can compare them against the actual consumption.
The Inventory Data tab lets you define storage and supply data for this agent that, in turn, will be used to calculate the inventory chart lines (see Heat Transfer Agent Consumption Inventory Chart). This tab is displayed only when the heat transfer agent has been defined to be storable. This is done by editing the corresponding check box in the Heat Transfer Agents Properties tab. No inventory charts can be created for non-storable agents.
Note that, for site utilities, data in the Properties and Availability Limits Tab are not editable through the Heat Transfer Agents Currently in Use dialog. The reason is that site utilities could be shared by different process files and only through the site databanks their properties can be modified. To edit those values, you will need to visit the sites databank through the } menu item as explained before.
The locations where a heat transfer agent is currently utilized in the process can be viewed by clicking on the button 
. This can be in operations, which are displayed in order of first use accompanied with their hosting procedure.
Unit Cost of Heat Transfer Agent
Note that the annual demand of a heat transfer agent that you see, for example, on the List of Heat Transfer Agents Currently in Use dialog, indicates the annual amount of heat transfer agent required (or used) by the model of the processes, not the annual amount of heat transfer agent that you need to buy every year. That is because the heat transfer agents are supposed to be recycled to the utility plant and not spent (wasted) in their entirety (see The life cycle and unit cost of a heat transfer agent.).
For example, let’s consider the life cycle of a heating agent (“Steam”). The diagram below represents how “Steam” is used. The amount requested by the process (in this case X+Y kg/batch) is drawn from the Utility Plant (red line on the left of the utility plant). For the case of “Steam” the utility plant delivers “Steam” at 152°C (saturated vapor) at 5 bars.
The life cycle and unit cost of a heat transfer agent.
As we can see from the definition dialog of “Steam” (see Heat transfer agent properties dialog for “Glycol”. below), the process is supposed to use “Steam” at 152°C (vapor) and return it as condensed liquid also at 152°C (the blue line returning to the utility plant). The process has two consumers of “Steam”:
a) Type-1: Use-and-Return
Such uses are typically process steps that require heating and heating is provided via a jacket surrounding a vessel, or through a serpentine-line situated in the interior of a vessel thus heating up its contents. The available enthalpy from the agent is only the latent heat of water at 152°C since it is supposed to be returned at those conditions.
b) Type-2: Use-and-never-return
Such use is typically as part of Steam-in-Place operation where steam is drawn to clean and sterilize the interior of a vessel and then it is disposed of (never returned to the blue line above).
Assuming the process requires X MT-steam/batch for Type-1 usage and Y MT-steam/batch for Type-2 usage the charges incurred would be as follows:
● For Type-1 Usage:
a) Agent Cost: X * 0.28 ($/MT) as indicated for the Agent Cost (purple highlight in Heat transfer agent properties dialog for “Glycol”.).
b) Material Cost: X * 0.1 ($/MT) (under the “Heat Transfer Agent” subcategory of Material Cost)
● For Type-2 Usage:
a1) Agent Cost: Y * 0.28 ($/MT) as indicated for the Agent Cost (purple highlight in Heat transfer agent properties dialog for “Glycol”.).
a2) Agent Cost: Y * 0.15 ($/MT) for the unreturned agent (heating cost only)
b1) Material Cost: Y * 0.1 ($/MT) (under the “Heat Transfer Agent” subcategory of Material Cost)
b2) Material Cost: Y * 100 ($/MT) for the unreturned agent (material cost only)
Note that the last material cost (b2) will appear under a subcategory of material cost that can be either “Heat Transfer Agent” or “Cleaning Agent” depending on the nature of the Type-2 consumer of “Steam”. For the case of SIP, it will appear under “Cleaning Agent”.
Heat transfer agent properties dialog for “Glycol”.
Users do not necessarily have to associate material with an agent. If they don’t, then the spent agent cost supplied above (purple area) is assumed to cover both the material and energy cost needed to replace the unreturned (missing) agent. If the agent does have an association with a material, then the price supplied in the purple area is supposed to cover the energy only required to transform the material to the return conditions of the agent (152°C condensed vapor at 5 bar).
There is one more charge for the use of any heat transfer agent that relates to losses in the distribution and return network. The agent cost charge is computed based on the total amount requested (X+Y MT/batch) multiplied by the price indicated in the blue area above. If material is associated with the agent, a material cost (under the “Heat Transfer Agent” subcategory of “Materials” in the operating cost) will be added that is the total amount (X+Y) multiplied by the purchase cost of material associated with the agent.
Spent agent that is NOT returned (e.g. the Type-2 consumers like SIP) are also charged a Waste Treatment and Disposal Cost (as indicated on the “Steam” properties definition dialog) unless otherwise overwritten. For example, in the SIP operation, it is possible to overwrite the classification of waste and the waste treatment cost of the spent agent since it may contain vessel contents with it.
As prices of utilities tend to fluctuate in time, if your company regularly updates values in the ‘SuperPro (User)’ database, you may decide to bring all prices in your SuperPro Designer model up-to-date. This can be easily done by invoking the Update Resource Prices from SuperPro (User) DB Dialog (select } from the main menu of the application).
CO2 Footprint of a Heat Transfer Agent
Just like any other input to the process, consuming heat transfer agents may carry a penalty in the global warming potential contribution of the entire process. When generating a GWP report, users can consider contributions from the use of heat transfer agents. For that, a heat transfer agent carries a property named CO2eq factor that is shown on its properties tab. If the user generates the GWP report and has included the contribution from heat transfer agents, this factor multiplied by the entire amount of agent consumed by the process as modeled in the current .spf file will be added to the process total GWP. Note that you can provide this factor on either per-mass basis (e.g. per kg or MT) or per-energy-content (e.g. per kW-h or Btu) basis. Finally, please note that this factor can vary depending on how this heat transfer agent has been regenerated (e.g. using fossil fuels or renewable energy as a source).
Credit Price of a Heating Transfer Agent
If the user manages to find a cooling load in the process that is thermodynamically compatible with the heating required to regenerate a heat transfer agent we can receive credit for the equivalent amount of that agent at a credit rate equal to the ‘Agent Credit Price’ set at the corresponding box at the bottom right of the agent’s properties dialog (see Heat transfer agent properties dialog for “Hot Water”.). For the heating agent shown in Heat transfer agent properties dialog for “Hot Water”. (‘Hot Water’) the user must find a heating ‘donor’ that can provide heat to raise a spent amount of ‘Hot Water’ from its return temperature (30°C) to its supply temperature (40°C). In other words, the user must find an operation that requires cooling load (e.g. a distillation column’s condenser load) with an start temperature higher than 40°C and a target (exit) temperature above 30°C. Such heat recovery opportunities can be found by invoking the Energy Recovery Opportunities Dialog. Once such a potential heat donor is located from the dialog, then from the next screen (Recovered Energy Matches Dialog) the option “Match with Spent Heating Agent” should be chosen, and from the list of
Heat transfer agent properties dialog for “Hot Water”.
displayed heat transfer agents, ‘Hot Water’ should be selected. If the process currently is using ‘Hot Water’ as a heating agent (anywhere), the equivalent amount that can be regenerated from the matching cooling load will be subtracted, thereby producing savings or reduction of the of the annual operating cost (AOC), see Savings. If the process is not using as much ‘Hot Water’ as can be regenerated from the recovered amount of heat, or perhaps, it is not using ‘Hot Water’ at all, then the remaining amount of agent will be converted into credit (at a rate matching the ‘Credit Price’ specified in the agent’s property page). This credit will be added to the income generated by the process (see Credits) thereby improving the economic viability of the process. It’s worth mentioning that after the above match is made, the economics of the process will be improved not only from the savings or credit for ‘Hot Water’ but also from the elimination of the cooling agent that is now no longer needed on the cooling side (in our case, agent used for the cooling load in the distillation column’s condenser). Elimination of the condenser’s cooling agent will be reflected as savings or reduction of the AOC (see Savings).
