Scaling up mixing and blending can often lead to ... mixups.
Mixing and blending are some of the toughest operations to scale up in any food plant. Whether going from a benchtop to a pilot plant, a pilot plant to the plant floor, or a small to a larger plant floor operation, scaling up involves a lot of variables: flow rate, agitator speed, shear stress, permeability and more.
Arguably the first consideration with scale-up is how the product, or the ingredients that will make it up, will react to the new, larger-scale process. It’s not as straightforward as it may seem. If the load doubles, it’s not a simple matter of doubling the size of the mixer heads or tanks.
This is especially problematic when it comes to scaling up lab or benchtop formulations. The product’s nature may complicate the outcome. For example, so-called non-Newtonian fluids change their viscosity – becoming either thicker or thinner – when they’re pumped harder; the new process has to take that into account.
“Customers sometimes assume scaling is linear rather than geometric,” says Joe Porcelli, Northeast account manager for IKA Works Inc. “It is not unusual to see development taking place with a lab stirrer or disperser that is oversized for the beaker or lab sample. This makes it difficult if not impractical to achieve the same turnover rate or mixing intensity in scale-up.”
Porcelli warns against trying to go directly from a beaker-scale test directly to floor-scale production without an intermediate step like a pilot plant. “Depending on the scale ratio, an intermediate step, or semi-works scale, may be important to minimize risk.”
Scaling up is often impractical on certain kinds of equipment, says Christine Banaszek, sales manager at Ross Mixers.
“One common challenge is that the type of mixer used to develop a new product may not be scalable to large production levels," Banaszek says. “Single planetary mixers, handheld immersion blenders and kitchen high-speed blenders are some examples. These inevitably require extra time and resources to translate the batching procedure and replicate results on an industrial-scale mixer.”
Certain kinds of products also pose particular difficulties.
“When mixing/blending ground meat, temperature control is critical,” says Stefan Neumann, a product specialist for Reiser. “Fat particles need to be kept very cold, so that fat does not smear during the mixing process.”
That can be challenging to do as a process scales up because of the increased mechanical action that comes into play. “The most common challenge is reproducing texture and particle definition,” Neumann says. “The higher the production rate, the more mechanical action occurs within the processing line.”
Most of the customers who approach Automated Process Equipment Corp. for scale-up help are looking at one of two scenarios, says marketing manager Jessica Stank. One is that they’re scaling up their entire operation, often with a new building or an expansion, and they’re using entirely new equipment. The other is that they’re working within the same footprint but want to increase throughput, often by going from a batch to a continuous operation.
The most common determining factors for the latter are budget, space and available labor. As Stank puts it: “It doesn’t do much good to expand production if there aren’t enough staff to accommodate the increase in workload that [comes] with it.” There also is the question of an expanded mixing/blending operation needing an increased and dependable supply of ingredients – something that can’t be taken for granted in these days of supply-chain interruptions.
Scaling up a mixing/blending operation to the capacity needed for a high-throughput baking line is a multifaceted task. Photo: Marion Process Solutions
Batch or in-line?
The approach to mixing – batch versus continuous in-line – is one of the most basic questions that must be decided in any mixing/blending operation. Batch blending is popular because of certain advantages, says Erik Boyer, director of sales-West for Marion Process Solutions.
“Batch is still very popular because of potential consistency issues with continuous,” Boyer says, adding that some customers prefer to do preliminary batch mixing of ingredients before dropping them into a larger, continuous system. Large batches are easier to trace, if necessary, he notes. “If there ever is a problem and a company needs to do a recall, it’s easier to have the ability to track a large batch than a couple of smaller ones.”
But when it comes to scale-up, in-line operations are easier than batch ones, says Joby Ferary, owner of North American Process Solutions. There are more factors that can be controlled, and the variables involved in scale-up tend to be more straightforward with in-line than batch, he says.
Dry blending operations, which usually take place in enclosed vessels, are especially challenging to scale up. Photo: Powder Process-Solutions
For example, an end user might have a setup in a pilot plant that produces 10 gallons per minute and uses a mixer with a five-inch head, and wants to scale that up to 100 gallons per minute on the plant floor. “Does that mean on a 10x [application], you’re going to have to have a 50-inch diameter?” Ferary asks. “No. You’re having to play more with the math on it. It’s not as cut-and-dried as it is on in-line.”
Ferary says that the difficulty in scaling up would be about the same for batch versus in-line mixing – as long as the equipment being used was brand-new. “But if you’re trying to use existing assets, using something that was built for some other process, match the same residence time. If you’re going to scale up 10 [times] and you go from a 10-gallon process to a hundred-gallon process, the volume of that tank has to be exactly 10 [times],” he says. “That’s a lot easier to do with in-line when you’re starting from scratch, because it’s a completely new piece of equipment.”
A sort of compromise alternative exists: Continuous-batch operation. This involves ingredients being pumped automatically into a vessel, getting mixed and being pumped out right away, with the next batch coming in immediately. Continuous-batch often is used in applications where higher throughput than a straight batch operation is desired, but the ingredients require a longer mixing time than could be arranged in an in-line operation, for example because they’re immiscible, in suspension or highly viscous.
It’s best to test
Because of the challenges involved in scaling up mixing/blending operations, end users might do well to have the new process thoroughly tested before trying to implement it. Those who don’t have a pilot plant or line often can turn to the supplier who’s furnishing the equipment. Many of them can run tests in their own facility, loan equipment for testing in the customer’s facility, or both.
To yield useful information, a trial run must be properly structured. The first step is knowing exactly what information is needed.
Scaling up a mixing operation is not as simple as proportionally increasing the size of components like mixer blades. Photo: Amprod
“For structuring a trial run, it’s structuring what we are trying to do,” says Boyer of Marion Mixers. “What is the overall outcome? Why type of sampling? What testing to prove homogeneity? Do you have control samples that have already passed the test on flavoring, taste, color? So defining the outcome of what you’re trying to do is important.”
Reiser has a customer center at its headquarters in Canton, Mass., with product specialists available for meat, alternative proteins and baked goods. “We only ask two things of the customer,” Neumann says. “First, supply the ingredients so that it is as close to their product as possible. Second, bring samples of their product so we can compare them to the product that was created on our equipment.”
Ferary says that the first step is attaining what he calls “proof of concept” – the basic choice of equipment for a given application. “The key is giving them the components so that they’re able to show that proof of concept works,” he says. “Then you can figure out the minor details ¬– how to be more precise in metering or whatever.”
Banaszek of Ross suggests providing as much information as possible about current mixing methods prior to a test run. As for structuring the run, “To obtain reliable data for scale-up, a good rule of thumb is to test on a mixer no smaller than 10% of the capacity you are looking to eventually purchase.”
Scaling up a mixing/blending operation often means creating a whole new process, or at least a radically different one. Proper planning, especially with the help of an equipment supplier, can make a big difference in easing the transition.
