Chemical and Vapor Pressure Database
Start the Chemical Database window by selecting Chemicals from the main popup Database menu. A list of existing chemical records for the database will be displayed on the left and details concerning a given record will be displayed on the right and below. To view a particular record one may either scroll through the list of names and select the desired record from the list or type the record name in the list box entry area. Instructional animations are available from the internet for adding a new chemical to the database.
Chemical Database Features
• Add: Add a new record into the Chemicals Database.
• Duplicate: Add a new record into the Chemicals Database based on an existing chemical record. Any field in the new record may be edited or left unchanged. The name of the new chemical entry must be unique to the rest of the Chemical Database.
• Update: Edit an existing chemical record.
• Delete: Remove an existing record from the database.
• Edit Class: The chemical can be classified as one more more of the standard categories.
• Graph: If the compound has a vapor pressure model defined then the vapor pressure can be plotted as a function of temperature.
• Close: Close out the database window and return to the main program.
Data Fields
• Name: A name appears in the main Chemical Database list and refers to the chemical record.
• Alias: One of more other names used to refer to the chemical record.
• Formula: Basic chemical formula for the compound.
• CAS: Unique Chemical Abstract Number.
• Mol Wt: Molecular mass for the compound.
• D (g/ml): Density of the compound at normal room temperature.
• T: Temperature that corresponds to the density value.
• Report Class: Classifications for the compound that are used for reporting purposes (HAP, VOC, ..)
• Removal Class: A classification tag used for Scrubber and/or General Control Device modeling.
• Regulatory ID: Compound identification label used in some states for reporting purposes.
• State at 70°F: The physical state of the compound at 70°F {Solid, Liquid, Gas}.
Vapor Pressure Database Section
Emission Master supports several vapor pressure models including Antoine, Riedel, Clayperon, and a VP Table.
• Antoine: Two forms of the Antoine equation are the the natural log and the log base 10 where temperature is expressed in degrees Kelvin (°K).
Although both forms of the equation are similar, the coefficients A, B, and C will have different values due to the difference in the log form. Regardless which type of Antoine equation is used the calculated vapor pressure should be the same for a given temperature. There are many different forms of the Antoine equation found in the literature so it is important to ensure that the coefficients that are entered in Emission Master are based on the temperature in °K and not °C, °F, or °R. Coefficients for the °C form of the Antoine equation may be converted to the °K form by sutracting 273.15 from the C coefficient and leaving the A and B coefficients unchanged. Additionally, the Antoine coefficients for a specific compound may be estimated from three known temperature - pressure data points. An instructional animation is available from the internet for estimating Antoine coefficients for nitrobenzene.
• Riedel Equation: This vapor pressure model involves six coefficients where A, B, C, and D are characteristic of the compound being modeled and E is normally set to a value of 6.
• Clayperon Equation: This vapor pressure model was one of the earliest models developed in the literature and involves only two coefficients A and B. It is interesting to note that the Antoine equation reduces to the Clayperon Equation if the Antoine coefficent is set to 0 during the calculation of coefficients A and B.
Although the Clapeyron Vapor Pressure model is based on the heat of vaporization and the compressibility factor for a compound, thermodynamic data is not needed in order to use this model. If two reliable vapor pressure data points can be obtained then A and B can be determined mathematically. One disadvantage to using this model is that the vapor pressure correlation may not be as accurate as the Antoine or Ridiel vapor pressure model since the Clapeyron equation only has two coefficients. However, if the process temperature range is reasonably small then the Clapeyron equation works well.