Oxygen Spargers - Series 25
The MultiMix Series 25 sparger is constructed using stainless steel and two different types of ceramic. The sparger utilises a high quality compression spring mechanism. The Series 25 sparger terminates with a 1/2" BSP female thread. The sparger may be installed through the inside of tank agitator shafts or separately on side-wall or top tank sparge pipes. The MultiMix Series 25 sparger design is protected by an Australian Patent.
One of the key advantages of the MultiMix sparger design is that operator adjustment is not required as the sparger wears. Indeed, operator adjustment is not possible. As a result, significant variations in gas flow from one sparger to the next at a given pressure are eliminated and preferential gas flow is avoided. This feature is very important in applications where multiple spargers are installed on a common oxygen supply header.
Over time, the ceramic surfaces used in the MultiMix Series 25 sparger wear. Ultimately this leads to reduced oxygen utilisation efficiency (low kla mass transfer coefficient). This effect has been demonstrated by plant trials where the performance of a sparger that had been in service for 9 months was compared with a new sparger and the average kla was less than half the average kla.
Effective sparger operating life is a function of the wear rate on the ceramic surfaces. This wear rate is a function of gas flow rate. An excessive gas flow rate (ie > 15 Nm³/h for the Series 25 sparger) accelerates the ceramic wear rate and reduces the effective operating life of the sparger. Operating experience indicates that an effective sparger operating life of at least four months is achieved at gas flowrates up to 10 - 15 Nm³/h per Series 25 sparger.
In situations where gold leaching kinetics depend on high utilisation efficiency of oxygen delivered via spargers, MultiMix recommends that the spargers are replaced on a regular schedule, initially every 4 months, as part of routine preventative maintenance activities.
Oxygen Spargers - Multi-Stage
A 3-stage Multi-Stage sparger is depicted in the following photograph and sketch.
The MultiMix Multi-Stage sparger is fabricated exclusively from stainless steel and incorporates elastomer seals. The Multi-Stage sparger design allows for stages to be added or removed. The standard Multi-Stage Sparger is supplied with three stages. Like the Series 25 sparger, the Multi-Stage sparger terminates with a 1/2" BSP female thread. The design of the MultiMix Multi-Stage sparger is currently protected worldwide by a provisional patent.
Suggested gas flow for a multi stage sparger with 3 stages is approximately 20 Nm³/h.
Note that the number of stages that can be ganged together is limited by the pressure drop across the Multi-Stage sparger and the resultant variation in gas flow from each stage. Three and four stage units are currently being used by MultiMix clients.
MultiMix Oxygen Sparger Installation
MultiMix Series 25 and Multi-Stage spargers attached to lances can be installed via hollow agitator shafts or via the tank sidewall. The following figure depicts the arrangement for installation via the tank sidewall.
When oxygen is delivered to Multiple Series 25 spargers via a common oxygen delivery header (i.e. a single pressure regulator and flowmeter), it is very important that the system is designed to maintain a constant oxygen delivery pressure to all of the spargers. Typically MultiMix suggests that no more than four Series 25 spargers should be supplied from a common oxygen delivery header and each sparger is served by a dedicated pressure regulator and flowmeter leg. MultiMix supplies all the fittings required to install the Series 25 and Multi-Stage spargers. This includes:
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Threaded lances for agitators and side walls
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