A brief history of oil mill machinery
Oil mill machines are almost as old as human civilization. For centuries, humans have used oil mill machines to extract oils from plant-based materials like seeds, nuts, fruit meat, and beyond. Initially of simpler design and technology, these machines have evolved considerably to achieve the efficiency and sophistication that they boast of today.
For thousands of years, simple machines-like vertical millstones moving around a central post-were used to extract oil. Traditionally in South Asia, ghanis or stone mills were used (and still are, in some places) to procure oil for culinary, medicinal, and other purposes. This simple mechanism-powered either manually or using animals like bullocks or horses-was time- and labour-intensive, but it produced healthy high-quality oil. Later on, wind and water power were also deployed for oil extraction.
Today, the demand for plant-based oils has skyrocketed. Our 8 billion+ strong global population demands oil for use in food preparation and the manufacture of biodiesel, oleochemicals, cosmetics, and other products. Industrial oil mill machines have evolved to meet and further fuel this demand – oil extraction methods have developed from aqueous extraction and traditional hot water floatation (TWF) to the four main techniques of mechanical extraction, solvent extraction, supercritical fluid extraction, and steam distillation used today.
This article is a deep dive into all things oil mill machinery – including not just extraction machines but also all the equipment required to prepare oilseeds and refine crude oil. As a potential buyer, it would serve you well to understand the types, features, and benefits of the commercial oil mill machines available on the market. After all, being equipped with the right information is the only way to select equipment that will serve you well in the long run.
So we’ll start at the very beginning: exploring the uses of oil mill machines, understanding the challenges that industrial oil mill machines aim to overcome, the types of machines and techniques you’ll need in your oil mill, and how you can make informed investment decisions.
What is an oil mill? What are the industrial applications of oil mill machinery?
An oil mill is a facility or setup of equipment designed to crush oil-bearing (oleaginous) materials-usually plant-based, like seeds-to extract oil that can be used as cooking oil, biodiesel feedstock, raw material for oleochemicals, etc.
Not every oil mill will have the same machinery. The ensemble of preparatory, extraction, and refining machines will vary based on the chosen raw materials and techniques, and the desired product quality. The processes and machinery may also vary based on the end use of the extracted oil and the markets in which it is intended to be sold.
While the cooking oil ubiquitous in kitchens is the first application that comes to mind when we think of commercial oil mill machines, this is far from the only use of vegetable oils. In addition to the food industry, commercial oil mill machines are also designed to serve the needs of the cosmetics industry (almond oil, jojoba oil, etc.), the pharmaceutical industry, the green fuel industry, and the animal feed industry (which uses the protein-rich solids left behind after oil extraction).
As you step into the world of plant-based oil extraction, you have a massive market to tap into. But to make the most of this opportunity, you need to decide which industries you want to supply to and how you can produce the quality that market players expect. For that, you must understand the technicalities of industrial oil mill machines.
What needs must industrial oil mill machines fulfil?
Oil production units – particularly commercial oil mill machines – are designed with the primary goal of obtaining a high yield of high-quality oil while minimising resource use.
Beyond this fundamental concern, however, modern industrial oil mill machines are also designed to optimise for other results. Think sustainability, cost-efficiency, improvements in productivity, etc. In today’s world, where ESG concerns are increasingly gaining importance for businesses and society at large, prioritising human and environmental safety and ethical practices is also important.
Nonetheless, at the end of the day, every business and every oil production plant will have different goals, constraints, and contexts. From the availability of certain raw materials to the spending power of their buyers, everything will impact the nature and quality of the products that oil manufacturers make. Each of these factors will also consequently impact a business’ choice of oil mill machines.
In other words, when it comes to oil mill machines, there is no one-size-fits-all solution. Every raw material, every market, every industrial application, will call for different process and product specifications.
It all begins with knowing your context and knowing it well. We will dive into the factors you should consider before you choose your oil mill machines. But before that, let’s understand the technicalities of the process: the oil mill machines you will need beyond extractors, different varieties of these machines, and the technologies that will help you optimise your processes for the best results. In this section, we’re diving into what an industrial oil mill-complete with preparatory, extraction, and refining equipment-looks like.
Plant setup: Commercial oil mill machines
Oil mills can range from small to medium to large scale. Depending on the scale and the scope of the oil mill, it will typically have any or all of these three sections: an oilseed preparation section, an oil extraction section, and an oil filtration section. These sections will likely contain any or all of the following pieces of machinery: seed cleaner, destoner, seed cracker, aspirator, flaking machine, seed conditioner, oil expeller machine, solvent extractor, bleacher, and deodorizer, among others.
Let’s take a look at each of these machines in a little more detail.
Seed cleaners are used to separate impurities-be they leaves, dust, stones, stems, etc.-from the feedstock. Typically comprising screens of various sizes and an aspiration system that eliminates light particles, seed cleaners may also be customised based on the specific impurities you are dealing with.
Similar in purpose to seed cleaners, destoners eliminate glass, stones, and any other high-density foreign materials from the feedstock. Destoners rely on the difference in density between the impurity and the oilseeds to separate them using a vibratory system.
Seed crackers are essential for reducing the particle size of the oilseeds. This increases the surface area of the oilseeds and ensures uniform cooking with the production of fines.
Aspirators remove dirt, dust, and other light-phase materials from the feedstock. Aspirators are typically used after the cracking process, removing the hulls and other loose materials produced during the process. They also provide a significant amount of drying.
Flakers or flaking machines are used to further break down the oilseeds after cracking. These machines use pressure to rupture the cell wall and make the expulsion of oil easier during the extraction process.
Cookers or conditioners are of various types. Kumar and our partners’ product lines boast of a stack cooker, a vertical seed conditioner, and an expander-conditioner combination machine, each of which has different features and specifications. All of them flush out moisture from the seed by heating it to the optimum temperature to facilitate easier oil extraction.
Oil expeller machines, also referred to as press oil machines or simply oil presses, are used to either mechanically extract oil from oilseeds or pre-press oilseeds before solvent extraction. An oil expeller machine is usually one of two varieties: hydraulic press or screw press. We will discuss these types in more detail in later sections of this post.
Solvent extractors are designed to douse the prepared oilseeds with a solvent (typically hexane), separate the oil-solvent mixture (miscella) from the seeds, and then separate the solvent from both the extracted oil and the residual solids. Solvent extraction plants comprise multiple pieces of machinery, including extractors, desolventizer toasters, distillers, and meal coolers.
Bleachers are part of the oil refining section of an oil mill. They are used to carry out physical and/or chemical refining of extracted crude oil. They remove unwanted colours, phosphorus content, residual soap content, peroxide, and/or metal contaminants from the oil. Kumar’s product line offers customers an Ecopure Bleacher and a Stable Bleacher, each of which has different features and benefits.
Deodorizers, as their name suggests, remove from crude oil the volatile components responsible for unwanted odours. From our Ecopack Deodorizer, Ecosteam Deodorizer and Unisparge Deodorizer to Crown’s Diflow Deodorizer, our customers have a lot of options to choose from.
This isn’t necessarily a comprehensive list of the oil mill machines you will have to invest in, but it is a great place to start. As you go along, you and your engineering partner may uncover certain needs in oilseed preparation, or maybe refining, that will need additional machinery – say, a decorticator, a degumming unit, or a fractionation unit. That will depend entirely on the raw material you are working with and the scope of your operations.
Screw press vs hydraulic press
The process of extraction is central to the edible oil manufacturing process. Naturally, your oil expellers-used for mechanical extraction or pre-pressing-are the most important oil mill machines you will invest in.
Broadly, there are two types of industrial oil mill machines used to mechanically press oilseeds: screw presses and hydraulic presses.
A screw press typically consists of a seed hopper, gearbox, expeller screw, barrel, oil canals, slots or screens, a press head, and a press nozzle. While the seed hopper directs the oilseeds into the press, the gearbox converts the speed and torque of the motor into the motion and pressure required to crush the oilseeds. This motion is reflected in the expeller screw, which rotates within a cylindrical cage, generating high pressure and friction which expels oil from the seed. The extracted oil seeps through the screen while the residual solids are removed from the machine as meal or cake.
On the other hand, hydraulic presses consist of a hydraulic pump station, control valve, electrical cabinet, motor, oil cylinder, frame, and other components. They use a liquid as a medium to pressurise the oilseeds and obtain oil. The liquid, usually an oil, exerts force on the feedstock via a piston or other similar component. Hydraulic presses are generally more expensive than their screw-based counterparts, but they are also more advanced, efficient, and produce higher quality oil because they generate much less heat.
When investing in oil mill machinery for expelling, it isn’t always easy to choose between these two types. Your choice will depend on the raw material you are using, the amount you are willing to invest upfront, and other such variables. Nonetheless, each type has its pros and cons.
Screw presses are more commonly used for plant-based oil extraction. Their simple mechanical design makes maintenance easy and stress-free. Given the amount of heat and friction they generate, they also usually promise you a higher oil yield, albeit of quality not as high as that produced by hydraulic presses. If you’re expelling oil that will eventually be used for cooking, this isn’t a problem because cooking itself will expose the oil to similar high temperatures.
Meanwhile, hydraulic presses are better suited to the extraction of specialty or delicate oils which would lose their characteristic aroma and nutritional qualities when subjected to the high heat of screw presses.
There are also differences in the processing styles of screw and hydraulic presses. We’ll address these differences and dive into more details about oil mill machinery in the next and final section of this blog post…
Thus far, we’ve learned about the evolution and different types of oil mill machinery. But there’s a lot more you must know before you can make a truly informed purchase decision for your oil mill. In this section, we’re exploring the differences between batch and continuous processing, the importance of filter press technology, oil mill machine pricing, and what it means to make the right investment when equipping your oil plant.
Batch processing vs continuous processing
Several processes are involved in the manufacturing of plant-based oils. For many of these processes-be it mechanical extraction, solvent extraction, alkali refining, or deodorization-you will have to choose between two types of operations: batch processing and continuous processing.
While batch-type processing has its place, most edible oil plants today rely on continuous extraction processes to cut downtime, eliminate bottlenecks, and increase extraction yields. Before you purchase any kind of oil mill machinery, you must understand how each of these processing styles works.
Batch-type oil extraction is older than its continuous counterpart. It was used commonly in industrial oil mill machines in the 1800s. Oil was extracted completely from a single batch of seeds before the equipment was emptied, cleaned, and used again for the next batch of oilseeds.
Typically, batch extractors comprise a vapour-tight vertical cylindrical kettle or a rotating drum.
In today’s day and age, batch processing continues to be used, but it isn’t as popular in industrial oil mills. It is used primarily for processes like specialty oil extraction, high-value oil extraction, and oil recovery from spent bleaching clay.
Continuous extraction began to be used in industrial oil mill machines in the 1920s. Carried out using either immersion- or percolation-type extractors, this approach involves the continuous feeding of oilseeds into the oil mill machine. Operations continue as long as the machine is on, with no need to stop the machine to remove the extracted oil or meal.
Now, let’s take a look at batch vs continuous extraction in conjunction with press type.
Press machines have evolved considerably over time. About a hundred years ago, it would have been common to see hydraulic press-based oil mill machines. These machines would have seeds packed in a filter bag and the hydraulic press would exert pressure to expel oil and let it flow through the filter bag. Now, those filter bags have been replaced by cages and hydraulic presses, to a large extent, have been replaced by screw presses.
As you equip your oil mill with all the necessary equipment, you could still opt for a hydraulic press. However, hydraulic pressing is only compatible with batch-style operations. If you want higher processing capacities, lesser downtime, and high oil yields, you will have to go the continuous extraction route – a route you can only take with screw presses.
While this is an example of the superiority of continuous processing in mechanical extraction, continuous processing is also the preferred route for solvent extraction and any other processes that offer you an option between these two processing styles.
Filter press technology
Finally, we come to the last technical concept we’re covering in this blog post: filter press technology.
Filter presses aren’t unique to the oils and fats industry. Whether lab-scale or industrial-scale, filter presses are useful in any process that requires the separation of solids from liquids. This piece of equipment consists of filter plates and frames, chambers into which the solid-liquid slurry is injected, and filter paper, membranes or cloth through which the liquid is filtered out using pressure filtration.
In the production of plant-based oils, filter presses are better suited to batch processing than continuous processing. They play a crucial role in producing oil that is clean and clear. In some processes-like shea butter processing-a mechanical press and a filter press are used to extract the butter and purify it. In other processes-like the manufacture of refined coconut oil-the filter press is used not only after extraction but also after bleaching to remove residual pigments. Yet another application of filter presses is in the fractionation process, in which triglycerides of high and low melting points are separated into solid and liquid fractions.
You can choose a filter press depending on your requirements of cake holding capacity, filtering area, and pump motor power. Based on where you are buying from, you will likely have the options of plate-type filter presses, plate-and-frame-type filter presses, membrane filter presses, pressure leaf filters, and centrifugal filter presses. Your engineering partner can help you choose the one most suitable to your production needs.
Invest in the right oil mill machines
Now that we’ve covered the fundamental technical aspects of industrial oil mill machinery, let’s move on to strategic decision-making. After all, simply knowing the science isn’t enough – it is crucial to also understand how your investment in oil mill machinery fits into your entire business plan. So let’s jump right in, exploring the steps involved in making a decision and the parameters you should consider.
Step 1: Identify the raw materials you want to work with. You can extract oils or fats from several plant-based materials – copra, cottonseed, safflower seed, flax seed, soybean, shea nut, mustard seeds, etc. Each of these raw materials will have different processing requirements and consequently, different oil mill machine requirements.
Step 2: Study the process in detail. With every new raw material you choose to work with, you must familiarise yourself with the details of the manufacturing process. You will not only have to understand the varied steps involved but also make decisions about whether you want to work with a screw press or hydraulic press, batch process or continuous process, etc. All of these factors will affect what oil mill machinery you need and the investment you can expect to make.
Step 3: Know your capacity requirements. Before you decide to invest in an oil mill machine for any stage of the extraction process, make sure that it aligns with your desired production capacity. Industrial oil mill machines will typically be available with capacities between 10 TPD and 500 TPD. Nonetheless, most process engineering companies will be willing to customise machine size to your requirements.
Step 4: Select an engineering partner who provides turnkey solutions. As you would have realized, setting up an oil mill will require multiple pieces of diverse machinery. If you source each piece of equipment from a different engineering company, not only will you add significantly to your workload but you would also run the risk that some machines may not be compatible with your other machines and systems. It’s always best to rely on a turnkey solutions provider for your oil mill machinery needs.
Oil mill machine: Price and operating costs
Oil mill machine prices depend on multiple factors, from where the machine is made and its production capacity to the level of sophistication of the machine, and more.
At Kumar, our oil refinery plant prices begin from INR 1.25 crores, while our oil expeller machines are priced starting at INR 10 lakhs. You can expect pricing for a holistic plant to vary from feedstock to feedstock, depending on the nature of the extraction process – our coconut oil plant cost, for instance, begins from INR 75 lakhs.
While price certainly plays a role in selecting commercial oil mill machines, there are also other parameters you should consider as you make your decision.
Extraction efficiency: This percentage represents the proportion of oil extracted compared to the total oil content of the material being processed.
Extraction yield: The amount of oil extracted from a specific quantity of raw material, expressed as a percentage.
Extraction loss: After the extraction process, there can sometimes be unexplained weight loss. When combining the weight of the extracted oil and the remaining cake, the total weight may be less than the original weight of the raw material. This loss is expressed as a percentage of the initial material weight.
Energy consumption: Every oil mill machine has different energy requirements, which depend on the extraction method used (such as the need for steam, heat, or pressure). Some equipment may be designed to minimize energy usage. Since energy costs can accumulate over time, we advise potential buyers to assess energy consumption early in their decision-making process.
Safety: Ensuring the safety of both humans and the environment is crucial in oil production, particularly in processes like solvent extraction that involve potentially toxic chemicals. As many oils are intended for human consumption, it is essential to avoid toxic substances. For solvent extraction, be sure to choose an extraction unit with a reliable solvent recovery system.
Waste management: The use of harmful chemicals in oil extraction raises concerns about how to manage the waste products. Additionally, other harmful byproducts and effluents might be generated. It’s important to ensure that the extraction unit has an effective waste management strategy in place to ensure both safety and adherence to environmental regulations. When budgeting for oil mill machinery, also consider the cost of waste disposal and environmental cleanup.
Ultimately, selecting the right oil mill machines is critical in establishing a successful oil production business. By understanding the various types of machinery, their functions, and the technicalities involved in the oil extraction process, you can make an informed decision that aligns with your production goals.
Whether you are looking to invest in small-scale equipment or large industrial setups, it’s essential to consider factors like the type of raw material, production capacity, energy efficiency, and safety measures. Additionally, choosing a reliable engineering partner who offers turnkey solutions will ensure that your oil mill is set up efficiently, minimizing potential compatibility issues.
Kumar has over two decades of experience in the field of oils and fats extraction. We’ve helped more than 560 customers from over 74 countries solve their processing challenges and set up plants that have stood the test of time. You can join our global community and benefit from the engineering excellence we have to offer – reach out to us today.
