SSL - Settling Slurry

What Is the SSL module?

An optional add-on module to AFT Impulse which allows users to simulate settling slurries.

Settling slurries are fluids which carry solids of relatively large size which cannot be suspended in the liquid under all conditions. At sufficiently low velocities the solid particles will settle to the bottom of the pipe and may ultimately plug the pipe completely. It is important to predict the behavior of such flows to avoid settling conditions and economically move the fluid and solids through the pipe.

The SSL module allows users to predict the behavior of settling slurries within the framework of the powerful AFT Impulse software. The SSL module allows users to specify solid particle properties, distribution and concentration. State-of-the-art correlations are then used to predict the flow, pressure drop and reduced pump performance when pumping solids.

Special output reports and additional graphing parameters are available to assist the user with understanding the hydraulic behavior of the slurry.

How Does the SSL Module Work?

The SSL module offers additional input windows where users can enter the properties of the solid particles. The SSL module takes the properties of the solid particles and carrier fluid (which is often water but can be another fluid) and calculates the hydraulics of the piping and pumps using widely accepted correlations.

Predicting the flow of settling slurries depends heavily on correlations based on experiment. Such predictions are inherently less accurate than standard clear fluid pipe flow.

Using the SSL Module

The user has the option of activating or not activating the SSL module when AFT Impulse first loads. After AFT Impulse is loaded, the SSL module can be activated or deactivated for use from the Tools menu. Whether or not SSL is activated impacts the Analysis menu, Library menu, and Output window.

If the SSL module is active, the user can still run models with normal pure liquids. This is selected under Slurry Modeling on the Analysis menu. Hence there are three possibilities for the SSL module.

• SSL is not active

• SSL is active and slurry calculation is disabled

• SSL is active and settling slurry calculation is performed

Enabling SSL Use

When the SSL module is active, two new menu items appear - one on the Analysis menu and the other on the Library menu. On the Analysis menu is the Slurry Modeling menu, from which the user can select “Disable” or “Settling”.

The SSL module settling slurry calculation is enabled by selecting Slurry Modeling -> Settling from the Analysis menu (Figure 1). This can be selected before or after a model is built. If selected after, then additional input will be required for solids data. Pre-existing models built with standard AFT Impulse can be opened with SSL and settling slurry data added.

Settling slurry calculation can be turned off at any time by selecting Disable from the same menu. The Disable mode causes the SSL module to function like standard AFT Impulse. If the model is opened in standard AFT Impulse, this data will be lost. Table 1 relates the differences between not using SSL and using it in Disable mode.

The purpose of Disable mode is that it allows standard clear fluid calculations to be performed without having to deactivate the SSL module. This will cause the loss of the slurry input data for the active scenario.