What Are the Advantages of Wet Grinding vs. Dry Grinding?
The processes of wet and dry grinding touch countless products that we use daily.
Everything from breakfast cereal and cold medicine to house paint and cement requires at least one grinding step in its production.
Wet and dry grinding are the two most common and effective milling methods, and both have advantages, disadvantages, and specific challenges that can complicate processes.
Whether a product goes through a wet grinder or a dry grinding process depends on multiple factors, including raw material, target particle size, particle surface and shape requirements, final application, and more.
In this article, we’ll break down the differences between wet grinding and dry grinding, and discuss examples of each milling process.
What is Wet Grinding? What is Dry Grinding?
Before we dive into the applications, advantages, and disadvantages of wet and dry grinding, let’s make sure we’re on the same page about what we actually mean.
First, the terms grinding and milling are interchangeable. If you know a piece of equipment called a jet mill is used, you may already be used to calling the process milling. Others who may be less familiar with milling equipment and processes may use grinding as a general way to describe the process of particle size reduction.
There’s no need to split hairs. (That would require a different process.)
The terms wet milling and dry milling are overarching concepts that do little to actually describe the processes and forces involved. But some methods are only possible under wet conditions, and some require dry milling conditions.
Although the goal of both grinding methods is to reduce particle sizes to a target range, the processes are different. In general, dry grinding uses particle-on-particle impacts to reduce size, while wet grinding involves dispersing the raw material in a liquid and circulating the resulting slurry to smash particles against solid grinding media to reduce their size.
Similarities and Differences Between Wet Grinding Dry Grinding
Dry grinding is a relatively simple process. Within any number of specialized machines. the raw material travels within a contained area and either collides with other particles or strikes against machine components (such as rotors) until the raw feed breaks down to the desired size.
In a wet mill, on the other hand, particles are dispersed in a liquid slurry and pumped through a grinding chamber. The particles ride along in the liquid and are crushed among the grinding media.
Dry grinding, as in a jet mill, uses a single pass process; material enters the mill, passes through, and is expelled, reduced in size. In contrast, wet grinding uses a process of recirculation. The slurry is exposed to the grinding media over and over, for hours if necessary, until the desired particle size is achieved.
Although the two types of grinding methods are different, one challenge is common to both dry grinding and wet grinding: the potential for wear on milling equipment that, over time, can damage components and threaten to contaminate the product.
In both wet and dry grinding, the raw feed material can be abrasive and damage equipment as a result of repeated collisions with machine parts — and in the case of wet grinding. with milling media. In addition, the carrier fluid used in a wet process needs to be chemically compatible with the raw feed. Whether that includes water, oil, solvents, or surfactants, the liquid can eat away at grinding media, agitators, or other components.
Dry or wet, it’s critical that equipment particles and grinding media stay out of the end product.
How to Choose Between Wet Milling Dry Milling
When deciding between wet and dry grinders, the required characteristics for the material’s final application serve as the most important determining factor.
For example, a process on a dry grinder, when used on one particular pyrotechnic material, typically results in superior characteristics compared to that same material after wet milling. That information alone may be enough to choose the dry process.
Target particle size is always the next consideration. The small target particle sizes in jet milling and wet milling lead us to sometimes use specialized particle technology terms when we refer to the milling processes.
Micronization refers to reducing particle size down into the sub-10μ (micron) range. (For reference, that’s about the size of a water droplet in fog.) All micronizing is grinding. but not all grinding processes can achieve micron-level particle size reduction.
What about sub-1μ particles? Sizes smaller than 1 micron in diameter are referred to as the nanometer level. One micron is equal to 1,000 nanometers. Typically, nano sized particles range from 200-500nm. The process of achieving particles this small is sometimes called nanonization.
In general, dry grinding can reduce particles to single-digit micron sizes. The uses of a wet grinder, on the other hand, often involve reducing particles to the nanometer range. (Remember, 1nm = 1,000μ.) While dry grinding’s simplicity often makes it the first method considered, if extremely small size is the goal, wet media milling is the only way to get there.
But it’s not always that simple. Here are two examples of how size considerations can affect the process.
- The end material must be wet, and the size goal is 10 microns (small, but not extremely so). Therefore, dry grinding in a jet mill is the best method, with the material then requiring blending into a wet dispersion.
- The end material must be dry. and the size goal is 500 nanometers (very small). In this case, a wet media mill must be used, and the material needs to be dried after particle size reduction.
The second example leads us to the next consideration when choosing between wet and dry milling: cost.
If wet grinding is used to reduce particles to 500 nanometers, as in the example above, but that product is not intended for use in a liquid base, a drying step is required.
Why? First, dry milling can’t achieve the particle size needed, so it’s not an option. Second, shipping the material in a liquid slurry that’s 75% water — water that will then be removed via a spray dryer — adds significant freight and handling expenses.
The good news is that wet grinding is more energy efficient than dry milling methods, using up to 30% less power to drive a wet mill. Over time, that energy savings can add up and displace some of the cost of the added drying step.
Other Considerations When Choosing Between Wet Dry Milling
If application, size, and cost don’t lock a project into dry grinding or wet grinding, it may come down to a simple question of capacity. Can one grinding method or piece of equipment better handle the required particle size in the quantities needed?
Along that same line of thinking, is packaging a factor? Since grinding is a continuous process, packaging formats like bags, barrels, or super sacks need to be considered in terms of whether they can be emptied at a rate that keeps up with the equipment speed.
Sometimes formulation can be a consideration. Additives may be needed to facilitate more efficient wet or dry milling. Material knowledge based on trials and past experience inform the choice of additives. Obviously, it’s most efficient to include as much raw material particle solid into the mix as possible.
Experienced providers of wet and dry grinding have quality assurance processes in-house, including analytical lab testing capabilities. While this may not determine one milling method over another, it’s important to have these services available to ensure an end product that meets specifications and quality standards.
The list of materials that can be ground in wet or dry processes is incredibly long, from inkjet printer inks and paint pigments to personal care products and nutraceuticals.
So, whether you call it grinding or milling, it takes the upfront guidance and dedicated capabilities of an experienced toll processing partner to help you choose the right particle size reduction technologies and appropriate post-processing services to meet your product goals.
Get your own introduction to expert guidance when you download our Grinding Project Application Checklist It can help you get started evaluating your needs, project scope, specifications, and other details that can impact processes and outcomes. Just click the link below to access and download your own copy, to reference whenever you need or share with colleagues.
Wet vs. Dry Grinding and Polishing: What You Need to Know
You may or may not know that it is possible to grind and polish concrete wet or dry.
Contractors will face a variety of different circumstances when working on a job site. They tend to have their own preferences when it comes to grinding and polishing concrete flooring. Some professionals may prefer the wet grinding process while others might prefer the dry grinding process, depending on their exact situation.
In this Xtreme Polishing Systems article, we examine each option in greater detail as well as discuss when and why they might be used.
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Everything You Need to Know About Wet vs. Dry Grinding and Polishing
You cannot deny the fact that concrete grinding and polishing are effective and economical methods for strengthening and beautifying your concrete floors. When done professionally, concrete floors have a natural beauty that enhances their aesthetics and value. In addition to being environmentally friendly, low maintenance, and sustainable, concrete grinding and polishing is also a cost-effective flooring solution.
In fact, there are two primary methods of polishing: the “dry” method and the “wet” method. Though similar, each has its own advantages. Choosing the right method is essential for achieving the most effective results on your floor. Let us help you decide which application best fits your project by comparing and contrasting wet and dry grinding and polishing.
What is Concrete Grinding and Polishing?
To improve the appearance of concrete surfaces, rough surfaces are smoothed with a machine or equipment. It involves heavy machinery and multiple discs that resemble sandpaper. There are several stages to concrete grinding, with polishing being the final step. At the end of the process, very fine discs are used to achieve outstanding shine and utter smoothness.
To create beautiful concrete surfaces that resemble polished stone, concrete grinding and polishing are to be used for achieving this process. In fact, concrete grinding and polishing have a number of benefits, including:
- Durability: The hardness and durability of polished concrete floors make them more durable than regular floors. High-traffic areas tend to benefit from these floors because they hold up well. Grinding and polishing concrete floors can prevent chipped floors, stains, and discoloration.
- Easily maintainable: A polished and ground concrete floor is easy to maintain. Cleaning the floor is as simple as sweeping and mopping.
- Cost-Effective: Concrete floors that have been polished and ground need to be renewed every seven to ten years in areas where traffic is high. This makes it a cost-effective option, compared to other flooring options.
- Sustainable: Concrete grinding is one of the greenest flooring options on the market because it leaves virtually no waste behind. In addition, floors that undergo grinding and polishing improve air quality by reducing mold and dust.
- Ensures safety: Concrete floors are polished and ground to produce highly glossy surfaces that reflect light and look beautiful. Your lighting costs will also be reduced when you do this, which helps create a safe work and living environment for your employees and loved ones.
What is the Difference Between Wet and Dry Grinding and Polishing?
Dry grinding and polishing: Dry polishing utilizes commercial-scale polishing machines and specialty concrete refinishing tools to grind the topical surface of the concrete. A concrete surface is ground using this combination of tooling and machinery in order to produce the client’s desired shine. Diamond discs are often incorporated with coarse diamond grit at an earlier stage of the process. An even finer disc is then used to achieve a final shiny finish.
Several types of concrete floor grinders, polishers, and industrial vacuum systems are available today and specially designed for the dry polishing process. Concrete floor grinders and polishers are commonly attached to dust extraction systems, also referred to as industrial vacuums for capturing dust accumulated during the dry polishing process.
Wet grinding and polishing: With the wet method, diamond abrasives are kept at standard temperatures and dust is captured in a slurry state to prevent air pollution. However, the final product rarely exhibits a high-luster shine, despite using the same polishing discs.
Wet Grinding and Polishing CONS
Dry Grinding and Polishing CONS
What is the Greener Method?
Whether wet or dry grinding is greener is still a matter of debate. Due to the lack of sludge, dry grinding is ideal for addressing the disposal issue more effectively. Various states have different regulations regarding slurry disposal, and it is important to research the regulations in your jurisdiction before deciding how to dispose of them.
A primary concern for the environment when it comes to wet grinding is the presence of toxic silicon. When a surface is wet polished and ground, dust clouds are removed that are typical of a dry polishing process. This dust contains enormous amounts of silicon, posing a major problem for the flooring industry. The dry polishing process can still result in substantial dust exposure, even with the most advanced dust extractors and safety equipment.
Which Environments are Most Ideal for Concrete Grinding and Polishing Services?
In addition to industrial and commercial buildings, concrete grinding is ideal for a wide variety of flooring applications. It is most commonly used in the following places:
- Manufacturing Plants
- Schools / Universities
Wet or Dry Grinding: What is the Better Option?
Every day, homeowners and commercial property owners looking to upgrade their flooring ask us this question. As both methods have distinct advantages and disadvantages, there is no definitive answer to this question. Your preferences, your budget, the amount of time available, and other factors play an important role in determining which method is best for you.
In particular, businesses in the food and beverage industry must use dust-free polishing methods, which means using a wet polish technique is a requirement. A dry method is better for other types of businesses that seek high-gloss floors to impress their clients. According to your individual needs, a balance of both methods is recommended.
The wet grinding method should be used first when dealing with really hard concrete, followed by the dry grinding method. A high shine can be achieved on a floor by grinding wet and polishing dry, ideally to expose aggregate and remove a significant layer of concrete.
Conclusion: Consult the Professionals
It is imperative to hire a contractor who is experienced in grinding and polishing concrete if you are unfamiliar with the overall process. Having damaged flooring will not only ruin the look of your flooring, but it can also be very expensive to have it repaired. Keep your floors updated by professionals, not inexperienced individuals.
For outstanding flooring services or to learn more about the right method for your floor, contact us today!