Given the fast-paced advancements in the engineering realm, many industrial mixing applications and mixing technologies are in practice. This article details everything you need to know about batch mixing, its advantages, considerations you need to make when choosing one, and the equipment required.
What are the differences between batch mixing and continuous mixing?
Some mixing technologies are best suited for specific industrial mixing applications. These mixers come in varying modes of operation, arrangements, sizes, and shapes. They are in two categories: continuous mixers or batch mixers.
In batch mixing, you load the ingredients to mix into the mixer in a predefined sequence. They are then combined to form a homogeneous material discharged from the equipment in a single lot. On the other hand, a continuous mixer is dedicated to one high-volume mixing, thanks to its continuous mixing technology.
Batch mixing uses batches, and the output measurements are kg/batch.
On the other hand, the ingredients in continuous mixing continuously load into the mixer following a specific formulation. Typically, the materials mix from the charging port to the discharge nozzle. This way, the output in continuous mixing is measured in kg/hr
In industrial applications with no material contamination between batches, you should add the time needed to clean the plant to get the total batch time.
How To Choose a Mixer
How to select a mixer depends on the degree of homogeneity required for the product (mixing efficiency of coefficient of variation (CV), which is generally expected to be >90%). The type of operation (batch or continuous) and the strength of product particles against mechanical agitation should also be examined.
To select a suitable mixer, not only the performance and characteristics of various mixers should be well understood, but also the mixing operation of the entire process.
The purpose of the mixing operation, the powder properties, the production capacity, the desired product homogeneity, maintenance problems, equipment costs, running costs etc. must be well defined. The priority of each of these factors depends on individual cases.
Advantages of Batch Mixing
Here are some of the advantages of batch mixing:
- Batch traceability.
- Production flexibility.
- It enhances control over the resultant batch blend.
- Improved control over mixing time.
- Compared to continuous mixing, batch mixing has lower installation and operation costs.
- It is easy to accomplish the pre-mixing of minor ingredients.
- It is easy to clean.
Equipment Needed in Batch Mixing
The different equipment used in batch mixing include:
- Convective mixers: Planetary mixer, sigma mixer, vertical screw blender, paddle blender, Ribbon blender.
- Fluidization mixers: Double paddle mixer, plow mixer.
- Tumbler blenders: Rotary drum Blender, V-blenders, double cone blender.
4 Steps to Batch Mixing Ingredients
A batch mixer is a piece of equipment that mixes ingredients using four significant steps. These steps include:
- Dumping, Dosing, and loading of the components to be mixed
- Weight Batching the ingredients
- Mixing the ingredients
- Discharging the mixed material
The components to mix are loaded into the mixing plant and mixed until the homogeneous distribution of the ingredients. Usually, the retention time reaches after trials, wherein the time needed to get the required level of material homogeneity establishes.
Step 1: Dumping, Dosing, & Loading The Components to Be Mixed
Loading Ingredients from 50 LB paper sacks
This is the most important step in the mixing process. In most industrial mixing applications, the ingredients are dosed into the mixer by manual labor by dumping from 50lb paper sacks or 50-100 lb. drums. As we can imagine, the mixer inlet is at least 6 feet or more from the grade, and operating personnel must climb the ladder to load the mixer. This manual process greatly reduces the operation efficiency.
A bag dump station is handy where the operators dump the products from 50 lb bags (or barrels/drums) into a side door of a dump hopper and pneumatically transport the product into the mixer.
Dosing Ingredients from 1000-2000LB Super Sacks (Or Totes)
In recent years, more and more product ingredients have been available in super sacks with 1000-2000lb weights; at this weight, it is not possible to manually load the bulk ingredients. This necessitates the requirement of a super sack unloader( or bulk bag unloader) and a transfer system that transports the product from the super sack station to the mixer. In most cases, the super sack unloader is located far away (>50-100 feet) from the mixer, so a pneumatic transport system is better suited for this application than conventional mechanical conveyors.
Dosing Ingredients from Bulk Storage Silos (50,000-200,000 LB)
In some applications, e.g., flour and sugar, these raw materials are brought into the factory premises through road tankers and transferred to bulk storage silos through truck/tanker mounted onboard blower pneumatic systems. After that, the silo products are pneumatically transported/dosed into the mixer.
Step 2: Weigh Batching The Individual Ingredients To Be Mixed
Most powders or solids processing facilities require an accurate and known product weight for making a blended product or a packaged product. This process is generally conducted manually and is very time-consuming.
A weigh batching hopper along with a handling system can help simplify and expedite this process.
The process of weighing the product in the hopper and discharging the required weight is known as weigh batching, and the hopper in which the product is weighed is called the “weigh hopper” or “scale hopper.”
Step 3: Mixing Process and Cycle Times
Powder Mixing is an operation to make two or more powder ingredients homogeneous. In some cases, these powders are mixed with small amounts of liquid. Some industrial fields refer to this process as “blending.” The size of powders to be mixed ranges widely, and in almost all mixing applications, external forces are applied to get the desired objectives
The mixing cycle can take several seconds when using high-intensity units or hours if additional processing phases such as cooling, or heating are needed. After mixing the ingredients, the mixed material discharges from the mixing equipment. The discharging process can be rapid or take significant time, mainly if you feed the materials into a downstream process. The mixing cycle can take several seconds when using high-intensity units or hours if additional processing phases such as cooling, or heating are needed.
Considering that the mixer cannot perform the mixing operation and storage simultaneously, it is not advisable to store the mixed product in the mixer. The total batch time is the entire time needed to load the ingredients into the mixing plant, the time for the mixing cycle, and the time for discharging.
General mixing cycle time of 45 minutes will consist of the following
Loading: 15 Minutes
Mixing: 15 Minutes
Unloading: 15 minutes
Note: This is only typical as some fats blenders have blend times of less than 2 minutes and also a fast unloading time of 1-2 minutes with buffer storage underneath the mixer.
Step 4: Discharging The Mixed Material By Pneumatic Conveying
Once the mixing process is completed, the mixed product (or blended product) is discharged for packing in 10000 lb super sacks or 50 lb bags, drums barrels, or small pouches, depending on the product’s requirement.
In order to reduce the mixer’s idle time, the mixed batch is dumped into a buffer hopper in less than 1-2 minutes and should be ready for the next mixing cycle. The batch from the buffer hopper would be pneumatically conveyed to the top of the packing machine.
In some cases (note that the mixer is a piece of large and heavy equipment) mixer discharge is just 1-2 feet from ground level, and the mixed product needs to be pneumatically conveyed to the packing machine inlet, which is typically used 10-15 feet from ground level. However, the mixer will be idle during this conveying process.
Get Quality Equipment For Batch Mixing
Batch mixing provides flexibility in your mixing and blending by enhancing precise control over traceability and each mixing time. However, it is not the best option if you want to follow the strict integrity of each batch. Batch mixing is the best option in smaller operations, but it becomes uneconomical when used in large quantities. On the other hand, continuous mixing is economical and efficient in large-scale applications.
At Pneu-Con Pneumatic Conveying, Inc., we have a wide range of equipment, from hopper blenders to bulk mixers. And we can help you choose one that fits your batch mixing.
Contact us today to get started with industry-leading professionals.