Many liquid or slurry chemicals are transported and stored between process operations using pallet tanks or drums. These containers generally are designed for pressures up to 2 psi (.14 bar) and are often contained in a structural frame for easy storage and fork truck handling. The products within these containers often need protection from air and moisture to retain flavors and other properties, prevent oxidation and product deterioration. The typical solution is to blanket or pad the contents with an inert gas, but that presents several challenges namely adding blanketing gas as product is withdrawn, removing product vapors to a scrubber or recovery unit as product is re-introduced to the container, while prohibiting the introduction of ambient air during container transportation and storage.
In filling a container with product, the blanketing gas or vapors in the head space must be vented to a proper disposal process to meet air quality and safety codes. Connecting the tank to the disposal system though an Equilibar back pressure regulator achieves the goal of retaining a slight pressure on the product container, yet relieving the pressure as the container fills. Equilibar GS series back pressure regulators are ideal for this application and can be remotely controlled by several set point options including electro-pneumatic controllers driven by your process computer. The sketch below represents a typical drum or tank filling installation.
At the Tank Filling Station
The blanketing gas can be air or an inert gas and the pressure needs to be precisely controlled.
The pressure reducing regulator handles the primary pressure control task; the pressure is fine-tuned by the Equilibar BPR.
In this phase of the process, the product fumes do come in contact with regulator, so material needs to be chemical resistant. Equilibar units are available in 316 Stainless steel and PVC or PVDF.
Emptying the tank
During the emptying of the tank, an inert blanketing or padding gas should be introduced to container to fill the void left by the removal of product or slow evaporation of the product and to avoid the introduction of moisture laden ambient air which may change product qualities. Depending on the pressure resistance capabilities of the tank or drum, the pressure required can be as low as 2 in WC. If the container is capable of higher pressures, blanket gas pressure can be used to move the product out of the container. The set point regulators in the Equilibar product line can accommodate either situation. This Equilibar regulator should be installed near the product unloading station as shown in sketch below.
In the unloading phase of the operation, the Equilibar BPR prevents the tank pressure from rising above the safe pressure for pushing the product out of the container. Further the pressure can be precisely controlled to smoothly force the product from the container.
A complete system:
A complete system should include dedicated quick couplers such those provided by Colder Product and sold as their DrumQuik product line. A total logistical solution needs to include the product-fill station as well as the product dispensing station so that the containers can go between process steps, and sometimes facilities, without the introduction of contaminants into the process. Equilibar controls can help achieve smooth operating results and product protection.