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On-line Measurement improves Ethanol Plant Production

Supplier: B-R Controls
12 November, 2007

In the competitive industry of biofuels production it is the most efficient plants that will survive and prosper. This article discusses on-line monitoring of various processes in the production of Bioethanol from grain feedstocks and the benefits achieved by plants in the US industry.

Slurry Solids Measurement

The first stages of ethanol production from grain is the grinding of the feedstock which is then added to water and along with enzymes fed to the fermentation vessel where it is converted to ethanol.

The importance of the % solids concentration to the final concentration of ethanol produced after fermentation is of utmost importance. In the past many sites ran three slurry samples per fermenter through moisture analysers which would determine the setpoint for the solids scale. The problem lay in the inconsistency of the measurement, the time delay (each sample takes 20 minutes) as well as the human error as different operators are likely to run samples in different ways. This lead to differences of up to 1% in the slurry solids concentration.

The solution to the problem of inconsistant results was to install the Anton Paar on-line slurry solids monitor that would provide for high accuracy real time data which allows for instantaneous adjustment of the feedstock to maintain the setpoint solids.

The result was more consistency in the slurry solids being fed to the fermenters which resulted in an average 0.7% increase in the concentration of ethanol from 14.5% to 15.2%. This equates to a 5% increase in ethanol production, a quite significant result when you extrapolate the numbers to cover a plant of 100 million litre capacity.  A secondary benefit was realised as the enzyme use was able to be monitored closely which reuslted in lower costs.

High Concentration Ethanol Measurement

The next stage of the ethanol production process is to distill the fermented liquor to increase the ethanol concentration to almost 100% purity. This is generally achieved by distillation followed by separation in a molecular sieve.

Generally to monitor and control the ethanol concentration, operators will take samples at two hourly intervals and analyse them in the lab. This has to de performed around the clock and is a time consuming and labour intensive operation. It is also of little use as no information is received for what happened in the previous two hours.

The alternative is the use of high accuracy (0.03%v/v) Anton Paar ethanol monitors on the outlet of the distillation column and molecular sieve. The installation of these monitors has allowed many operators to control both processes with greater efficiency and allowed them to produce a more consistant product that they know will meet the lower ethanol limit of contractual agreements without giving away additional ethanol for free.

Additional benefits include greater control of molecular sieve regeneration and longer run times before changeover thus improving production efficiency and lowering operating costs.

DDGS Syrup Solids Measurement for control of Evaporators

Water management in the drying of the distillers dried grains with solubles (DDGS - a by-product of ethanol production) is an important part of an ethanol plants overall operation and significantly its energy use. Approximately a third of energy use is associated with the final drying stage of the DDGS in the dryer.  As such it is important to control the concentration of water in the slurry that is fed to the dryer.

By utilising an Anton Paar syrup solids monitor at the outlet of the evaporators the concentration of syrup solids can be controlled by controlling the flowrate of the syrup out of the evaporators. The ability to control the syrup solids to such a degree leads to significant energy savings as well as a more consistant final product.

Plant operators have found significant savings in the amount of water needing to be removed by the dryer. In one shift approximately 24,000L less water was required to be removed in the dryer after the installation of the on-line syrup solids monitor. The reduction in energy costs is significant and leads to a plant that is more efficient and is a lower cost producer.


As with most production facilities efficient operation is the goal. By utilising on-line monitoring of key areas of production, operating costs can be reduced, production volumes increased and product quality improved. The Anton Paar range of on-line monitors provides operators with the tools to achieve the above goals and most importantly for plant owners in a short payback period.

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