The ProMax Depressurization Tool is available to calculate the temperature, pressure, and mass flow rate profile for a vessel that is venting, including heat input cases, such as an external fire. It is designed to assist you with several related scenarios, and to provide you with information on the venting and non-vented material compositions.
There are many scenarios that can lead to a dangerous increase in the pressure of a vessel. Fundamentally, the cause of increased pressure is due to unexpected mass or heat input, such as an external plant fire. In many cases, the increase in pressure may happen very quickly, so a properly designed and sized emergency depressurization system is necessary, typically in addition to the over-pressurization relief valves on the units. Here we discuss some basics on sizing the depressurization system, and effects that a fire may have on both wetted and non-wetted surfaces.
Properly sized relief valves provide protection to equipment during events where increased vessel pressure may cause damage, while also avoiding issues with excessive flow rates. Many scenarios can result in an increased vessel pressure, including: a run-away reaction, a loss of cooling, thermal expansion of a liquid, or an external fire. ProMax includes a Relief Valve Sizing Analysis to help you calculate the required area for many of these scenarios. This discussion examines specifying the ProMax Analysis, including what valves are available, the Standards available, how to set the relief conditions, and how ProMax calculates the area required for the different flow types that may occur during the relief conditions.
Predictions of phase equilibrium in hydrocarbon systems require proper descriptions of the inlet composition and constituent components. When working with GC analyses for hydrocarbon liquids, it is not enough to simply use a normal alkane to describe the variety of species that may share the same carbon number. Hypothetical or “pseudocomponents” are required, described using their molecular weight and gravity, to ensure accurate and consistent results from flash separations as well as working and breathing losses.
Accurate predictions of atmospheric tank flash emissions depend on high quality thermodynamic properties and calculation methods as can be found in ProMax. They also require high quality laboratory analyses of pressurized liquid samples. To check the validity of these analyzed compositions, please make sure to compare measured temperature from the pressurized separator with the bubble point temperature calculated in ProMax. If the bubble point is higher than the measured separator temperature, then emissions will be under-predicted.
ProMax offers a large selection of variables that can be specified by the user, and for anybody new to simulation software this freedom can be quite daunting. How do you know which ones to set manually and which are better left for the program to calculate? Here are some tips to help get you started:
The short answer is NO. Although the ASTM D323 standard calls it an "absolute pressure", the value is in fact a gauge pressure. This blog will provide information to help you understand why.
The Property Input property stencil allows the user to display and change an input property directly on the stencil. The variable may be almost any user-definable variable in ProMax, including flow rates, temperatures, energy rates, and even User Defined Variables.
To model a brine solution in ProMax, the acids and bases comprising the salts must be entered along with water, and the Electrolytic ELR property package must be used. In the Electrolytic Property Packages the acids and bases dissociate to form the ionic species, and the salt concentration can be viewed by adding an Ionic Info Analysis...
As mentioned in a previous blog entry, the Tank Losses property stencil provides results for several types of emissions losses. Here is a quick description of each of these loss types...