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Ethanol or alcoholic fermentation is a biological transformation process of sugar to alcohol ethanol and carbon dioxide as a by-product. Alcoholic fermentation is a transformation process in the absence of oxygen, and therefore it is considered an anaerobic process. Ethanol fermentation has many uses, including the production of ethanol fuel, bread baking, and more than several alcoholic drinks like wine, mead, beer, whiskey, vodka, rice wines (including sake), and rum. All fermentation processes perform in a vessel that allows carbon dioxide to escape but prevents outside air from coming in due to contamination of the brew by unwanted bacteria reduction.

Alcohol facilities can have many different process and process control configurations. Alcohol processes such as ethanol and methanol processes are prime candidates for DCS-based advanced process control (APC) technology. We focus on analyzing the process and providing the right economic advanced control solution for each alcohol plant. Our DCS-based APC (advanced process control) methodology has proven particularly successful in this alcohol area. Our DCS-based APC (advanced process control) design will result in the following alcohol benefits:

• Increase ethanol production rate by automatically identifying and pushing against the active constraint, continuously in real-time. Constraints include process, equipment, economic, or market constraints at any given time. The overall approach constantly moves the process in the most profitable direction.
• Minimize fermentation batch cycle time using adaptive sequence technology. This increases the overall ethanol throughput because of an increase in fermenter capacity.
• Maximize fermentation yields to ethanol by optimizing fermentation process conditions using both the online real-time optimizer.
• Minimize alcohol losses in the three distillation column product streams by improved control of distillation variables and product specifications using various advanced process control schemes. The control schemes minimize alcohol losses from still age, fusel oil, and water.
• Increase alcohol content of the beer and reduce overall energy consumption by optimizing fermentation temperature.
• Minimize water addition to ferment beer mash with higher levels of solids. This reduces the cost of handling and treating the water later. In addition, higher solids result in higher “beer” yields in the same or less time.
• Increase overall process automation thus reducing the level of manual intervention needed from control room operators, thereby allowing them to focus on more important, potentially money-saving tasks.
• Improve plant-wide process control quality by reducing deviation of product specifications and other critical controlled variables from their setpoints.

For the ethanol process, we provide advanced process control (APC) design and optimization for the following areas:

Hot Slurry

The milled grain is mixed with process water, the pH is adjusted to about 5.8, and an alpha-amylase enzyme is added. The slurry is heated to 180-190°F for 30-45 minutes to reduce viscosity.

Primary Liquefaction

The slurry is then pumped through a pressurized jet cooker at 221°F and held for 5 minutes. The mixture is then cooled by an atmospheric or vacuum flash condenser.

Secondary Liquefaction

After the flash condensation cooling, the mixture is held for 1-2 hours at 180-190°F to give the alpha-amylase enzyme time to break down the starch into short-chain dextrin. After pH and temperature adjustment, a second enzyme, glucoamylase, is added as the mixture is pumped into the fermentation tanks.

Simultaneous Saccharification Fermentation

Once inside the fermentation tanks, the mixture is referred to as mash. The glucoamylase enzyme breaks down the dextrin to form simple sugars. Yeast is added to convert the sugar to ethanol and carbon dioxide. The mash is then allowed to ferment for 50-60 hours, resulting in a mixture that contains about 15% ethanol as well as the solids from the grain and added yeast.

Distillation

The fermented mash is pumped into a multi-column distillation system where additional heat is added. The columns utilize the differences in the boiling points of ethanol and water to boil off and separate the ethanol. By the time the product stream is ready to leave the distillation columns, it contains about 95% ethanol by volume (190-proof). The residue from this process, called stillage, contains non-fermentable solids and water and is pumped out from the bottom of the columns into the centrifuges.

Dehydration

The 190-proof ethanol still contains about 5% water. It is passed through a molecular sieve to physically separate the remaining water from the ethanol based on the different sizes of the molecules. This step produces 200-proof anhydrous (waterless) ethanol.

Co-Product Processing

During the ethanol production process, two valuable co-products are created: carbon dioxide and distillers’ grains. As yeast ferment the sugar, they release large amounts of carbon dioxide gas. It can be released into the atmosphere, but it is commonly captured and purified with a scrubber so it can be marketed to the food processing industry for use in carbonated beverages and flash-freezing applications. The stillage from the bottom of the distillation tanks contains solids from the grain and added yeast as well as liquid from the water added during the process. It is sent to centrifuges for separation into thin stillage (a liquid with 5-10% solids) and wet distiller’s grain. Some of the thin stillage is routed back to the cook/slurry tanks as makeup water, reducing the amount of fresh water required by the cook process. The rest is sent through a multiple-effect evaporation system where it is concentrated into syrup containing 25-50% solids. This syrup, which is high in protein and fat content, is then mixed back in with the wet distiller’s grain (WDG).

PiControl Solutions: Innovative Process Control

PiControl is an innovative process control software and services company that offers state-of-the-art, modern solutions at a lower cost, implemented in shorter time compared to competitors.

PiControl Solutions is the only process control and automation company in the world which can perform any advanced process control (APC) project completely remotely. Nowadays, every country uses high-speed and reliable internet connections and with the help of medium to high-resolution cheap web-cameras or even widely used remote meeting and screen sharing applications, it is possible to do complete design, tuning, and optimization, FAT test and start-up of any advanced process control project. Over this low-cost online/remote approach, huge travel and accommodation costs can be saved, and human health and safety can be kept at a high level.

For more information and details, please send us an email: [email protected] or call the Tel: (832) 495 6436.