The agglomeration of bulk solids continues to spread throughout industries, becoming ever-more entwined in industrial process and the production of consumer products, due to the many advantages it can provide. Agglomeration can offer a wide range of benefits to raw materials, end products, and process flow, as well as providing environmental and economic benefits as well.
From the preparation of copper ore for heap leaching, to the de-dusting of fly ash, and even the manufacture of premium soil amendment products, agglomeration is all around us.
Reasons for Agglomerating
As there are many benefits to agglomeration, there are also many reasons why someone may choose to agglomerate their material. Some of the most common reasons for choosing to agglomerate a bulk solid include:
- Improve product handling and transportation
- Enhance characteristics such as porosity, density, and melting abilities
- Improve product performance
- Mitigate dust issues and product lost as dust
- Prevent segregation
- Enhance appearance
- Improve process flow and/or efficiency
- Convert a waste or process byproduct into a usable product or raw material feedstock
- Reduce need for landfilling
- Improve waste disposal cost efficiency
- Create waste to fuel opportunities
- Reduce transportation costs
For these reasons (and many more), companies are increasingly turning to agglomeration in order to improve their products or solve their material problems.
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The Development Process
Whether it be to solve a material problem, create a new product, or improve an existing one, taking an idea from concept to production is a lengthy and complex process not easily explained in brief. Here, I will provide a general overview of the process typically followed in order to turn an idea into a full-scale, commercial agglomeration process. Throughout this discussion, I will use a real-life example of how an agglomeration process was developed to solve a problem in the glass industry.
It’s important to note that the steps described below are only a generalized guide and are not representative of all process development cases. Steps may be skipped or altered depending on the unique project.
Step One: Proof of Concept
The first step in any new process is to evaluate the feasibility of an intended application. This is done through batch, or small, bench-scale trials.
In this stage of process development, the intended application is evaluated to show proof of concept, i.e., to demonstrate that the idea is potentially feasible at some level. This initial step can also help to uncover potential challenges or pitfalls with the project.
Ultimately, proof of concept helps to confirm (or deny) that the project holds potential and is worth evaluating on a larger scale.
Proof of Concept Example: Glass
A specialty glass producer is experiencing issues with glass fines becoming entrained in their furnaces, throwing off the delicately balanced formulations needed to produce the desired glass products. The company wonders if agglomeration of the glass fines could be the answer to their problems, and decides to consult a full service testing, engineering, and equipment provider.
Through its testing facility, the engineering and equipment manufacturer shows proof of concept by demonstrating that the representative glass sample is capable of agglomeration. Various binders may also be tested during these initial trials.
Small samples of varying characteristics are sent to the glass producer for confirmation that the agglomeration has, to some extent, mitigated the entrainment issue in the furnace, meriting further evaluation of the concept.
Step Two: Proof of Product
Once proof of concept has been established, the intended process can be examined more in-depth to determine whether or not a product can be economically created to meet the desired qualifications necessary for the intended application.
This stage of development is also carried out at batch scale and serves to provide a higher degree of process/product confirmation, as well as to gather the initial data and define the process variables necessary for a continuous testing trial.
During the proof of product stage of developing an agglomeration process, a number of unknowns are determined through testing. These are summarized below. Binder selection may also be further refined during this stage.
Method of Agglomeration
There are many available options for producing agglomerates. When producing rounded granules, the equipment tested may include agglomeration drums, disc pelletizers, pin mixers, pug mills, or a combination of these.
Each piece of equipment and combination thereof presents unique advantages and disadvantages. The equipment of choice is typically narrowed down based on the goals of the process and end product, as well as the characteristics of the raw material. For example, agglomeration drums offer a high-capacity processing option and are capable of tolerating variance in feedstock, making them an ideal candidate for use in ore agglomeration. Conversely, disc pelletizers offer lower capacities and require more uniformity in feedstock, but produce a more refined product. They are frequently used in the production of specialty chemicals.
As there are many reasons for agglomerating a material, the targeted particle characteristics of the end product also vary. A wide range of variables can be adjusted to influence particle characteristics in order to meet the desired specifications. Particle engineering may target characteristics such as:
- Bulk density
- Crush strength
- Green/wet strength
- Moisture content
- Physical characteristics such as surface texture and shape
- Particle size analysis
Proof of Product Example: Glass
After proving that agglomeration is capable of reducing and/or eliminating entrainment, the glass company wants to optimize the characteristics of the agglomerates to maximize effectiveness. After testing the various samples, they have found that uniform, rounded granules between 3.5-5 mesh with a 7-lb crush strength and a 4-6% moisture content will produce the best result.
Through their testing and experience, the testing facility is confident that a disc pelletizer is the equipment of choice for producing the desired product.
Step 3: Proof of Process
Now that product specifications have been developed, the company is ready for testing on a larger scale.
Proof of process is a testing phase aimed at confirming that the intended process is possible on a continuous basis.
Proof of Product: Glass
The engineering and equipment manufacturer sets up a continuous process loop to confirm that pellets with the desired characteristics can be created in a continuous process setting.
Step Four: Process/Product Optimization
Now that the process has been deemed viable on a continuous scale and a rough idea of the general process is established, the testing facility works to optimize process parameters to achieve the most efficient process possible, while creating an optimal end product. This might include preparation of the feedstock, fine-tuning binder feed rate, or the adjustment of other parameters in order to optimize the process. This stage also serves to define the data necessary for scale-up to commercial production.
Process/Product Optimization Example: Glass
After confirming that the product can be produced on a continuous scale, the glass company wants to fine-tune the process to maximize efficiency and create as much on-spec product as possible. The testing facility creates a continuous loop, pilot-scale operation to work with.
The testing facility discovers that adding a pin mixer prior to the disc pelletizer reduces the amount of binder required (the intense spinning action of the pin mixer contributes to the densification of the product), subsequently reducing binder costs and increasing production. The added pin mixer also promotes a tighter window of particle size control and creates a highly refined rounded granule.
Step Five: Plant Layout & Equipment Engineering
After the full scope of the process has been defined, engineers use the data gathered in testing to scale up the process to commercial production capacity. Between this point and construction of the actual facility, a number of deliverables are developed that help to advance the project from concept to concrete facility. This often includes:
- General arrangement drawings
- Conceptual plant layouts
- Civil works guide drawings with static and dynamic loads
- Structural steel and access platform guide drawings
- Chute and ductwork guide drawings
- Electrical and control systems engineering
- Material handling engineering
Equipment Engineering & Manufacturing
At the same time, the engineering and equipment manufacturer uses the data gathered during testing to engineer and manufacture the process equipment needed. Engineering each piece of equipment per specification involves defining a number of equipment-specific variables and designing the equipment to accommodate them. This might include:
- Equipment capacity
- Material feed rate
- Product discharge rate
Once the engineering requirements are complete, the equipment is fabricated. In the case of Feeco, testing, engineering, and fabrication all occur at a single location, allowing the different units to work seamlessly together to produce the highest quality result.
Various contractors are engaged by the customer to design and build the surrounding facility and support equipment. The OEM may offer installation and start-up support, as well as training on the newly installed process.
Agglomeration is a valuable tool in a wide variety of settings. While the process of turning an idea into a realized production facility is complex, working with a single source provider with an agglomeration background can move the process along in seamless fluidity.
Chris Kozicki has been a Process Sales Engineer for 32 years at FEECO and has been involved with various agglomeration projects, including limestone and gypsum pelletizing systems, agglomerate feasibility testing, and agricultural chemical processing, among others. He is a member and past president of the Institute for Briquetting and Agglomeration, and received a B.S. degree in engineering mechanics from the University of Wisconsin-Madison. Feeco has been designing custom process solutions and equipment for the agglomeration of bulk solids since 1951. For more information, visit feeco.com.
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