The memo describes batch chemical production as an operation in which raw materials are charged at the beginning of the process and a final product is withdrawn at the end of the process.  This type of production takes place through discrete batches rather than by way of continuous operations. Throughout the course of the process many different equipment items are used.  The type of equipment used in the process depends upon the process and may include reactors, mixers, centrifuges, filters, distillation columns, crystallizers, and others which are used in accordance with the process recipe.  In certain cases, when a batch process involves several vessels in series then it may be possible to have more than one batch being produced at a time.  For example, if a process requires that two batch reactors be used in series and the batch is to be transferred from one batch reactor to the next and so on then it may be possible to charge a second batch to Reactor 1 once the first batch has been transferred to Reactor 2. 

To analyze a multipurpose production facility to determine which processes can be operated concurrently (depending upon equipment conflicts) while at the same time considering the number of batches that can be produced at any given time for the same process is the focus of the PTE analysis.  A five step methodology for calculating the PTE has been developed by the Synthetic Organic Chemical Manufacturers Association (SOCMA) and referenced by the EPA as a valid PTE emission estimation methodology. 

(1) ACT Derived AERs - EIIP Chapter 16 has subsequently been published by the EPA and it is assumed that process emission methodologies contained in this 2007 document is preferred to 1994 ACT document.  Emission Master software is compliant with EIIP Chapter 16 methods.

(2) Percent Equipment Utilization.  For a specific process, the number of hours that each equipment is used is calculated from the batch recipe and the equipment with the largest utilization hours is identified as the utilization basis.  Then the number of hours that each equipment in the process is divided by the equipment utilization basis hours and reported in percent. 

(3)  Interchangeable Equipment Determinations.  Many multipurpose production facilities are capable of producing the same process in different equipment or equipment trains.  Assuming that the alternate equipment trains contain equipment with the same size then the EIIP Chapter 16 calculated emissions will be the same.  Emissions Accountant does not provide for the  automatic substitution of alternate equipment into the original Emission Master model since equipment of different sizes will result in different emissions for the process.  Instead, the user should create additional process models by copying the original Emission Master file, making the appropriate equipment substitutions and then saving the Emission Master file under a different name.  These additional Emission Master models can be brought into Emissions Accountant under a separate process name and included in the PTE analysis.   

(4)  Tabulation of AER.  Output from the PTE for each pollutant included in the analysis criteria includes a table containing one column for each Process that was included in the final process solution set.  Each process column contains the Process Name, Process Utilization Scale %, Process Cycle Time (hr), Batches produced per Year, Pollutant Emissions (lb/batch), and Pollutant Emissions (lb/year).  A complete list of equipment that was used by all processes featuring the pollutant is provided and the specific Percent Utilization statistics is shown.  A final right column is included that shows the total Pollutant Emissions (lb/yr) for all processes in the specific PTE analysis. 

(5)  Tabulation of Equipment Percent Utilization.  Output from the PTE for each pollutant that was included in the analysis also contains a table with one column for each process where the pollutant was found to participate in the process.  Each column contains the Process Name, calculated AER (lb/yr), and equipment utilization statistics.   

A web animated tutorial has been created to help illustrate the PTE Analysis Report that is contained in Emissions Accountant.  An example Emissions Accountant PTE Report is available for inspection.