Transcript Bild 1 - Trade and Investment Promotion Section in Stockholm

Mr. Lars G Holmene
President
Agimix International AB
O Bracke 631, SE-451 92 Uddevalla, Sweden
[email protected]
Indutec, Inc
573 Hopemeadow street
Simsbury, CT 06070
USA
Tel. (860) 658-1448
Fax. (860) 408-9794
Sales office telephone (770) 995-2971
www.indutec.us, [email protected]
Mr Henryk Kaminski
President
Agimix Polska Sp.zo.o
35-105 Rzeszow
Ul. Przemyslowa 12
Poland
[email protected]
BIOSUBSTRATE MIXERS AND AGITATORS FOR BIOGAS
PRODUCTION
• ENGINEERING COMPANY WITH HIGH TECHNOLOGY
• STATE OF THE ART EQUIPMENT FOR HOMOGENIZATION OF THE
SUBSTRATE IN ORGANIC REACTORS
• LOW ENERGY CONSUMPTION
• PROCESS GUARANTEE
• MECHANICAL GUARANTEE
• MORE THAN 250 INSTALLATIONS WORLD WIDE
Agimix mixers – Better biofuel energy and quality management
Abstract
Today and tomorrows modern biogas reactors require high flexibility to maintain proper mixing and
agitation of various organic material. It is well known that grinded organic material has different
characteristics in terms of liquid density and liquid viscosity.
Therefore, the top entering mounted agitator is the only way to achieve
complete uniformity of the substrate and as well to reach maximum gas production at low energy
consumption.
By utilize the latest technology available you can maintain such liquid velocity in the entire volume
to avoid settling, stagnation, dead zones and fluctuation of the temperature. It is required to
generate increased velocity in manure, industrial waste reactors compare to community sludge
reactors in WWT plants in order to achieve full yield of the organic material. In order to have
reasonable energy consumption for the total economy the top entering agitators are favourable
compared to side entering agitators which use more energy to achieve the same
processing results.
The importance of correct tank configuration
The ideal tank configuration plays a major roll when digester processes are to be designed. Traditional digester
configuration (picture 1) has been built in concrete with conical bottom and conical top depending on lack of
knowledge in mixing technology. However, more modern design municipal digesters and biogas reactors (picture
2) are designed differently today.
Improving gas production by efficient Top Entering Agitators
Tomorrow, modern biogas reactor requires higher flexibility to maintain proper mixing and agitation of different
organic material. Today digesters, in both municipal and agriculture biogas reactors are getting bigger and bigger
were organic material is to be processed. More and more organic material must be taken care of and processed
and it is welcomed to utilize the energy content for electric purposes or bio fuel. In Scandinavia many digesters
were designed in the earlier 70ties with a turn-over of 4-5 times of the volume per hour, which has given an
un satisfactory process result of the digestion process. Today many digesters are designed with a turn-over of 810 times or more of the volume per hour and a significant improvement of the digestion process have been
proven. The energy consumption is one of the most important issues for future generations and how to generate
electricity or bio fuel efficient. Utilizing the energy content in organic material and building up small/medium/large
scale biogas plants around the world will play a major roll to secure electric power production and bio fuel for the
future. It is also already proven that with modern technology farmers is now interested in building small/medium/large sizes of
biogas reactors by utilizing organic material from the growing fields and manure from livestock.
Material such as grass and corn ensilage, wheat and other type of crops and manures can be utilized at very low
investment.
Some facts of designing digesters with municipal sludge and organic material
Many of the sludge digester mixers in operation in waste water treatment plants today are very often underdesigned. Improved knowledge of mixing technology has proven that increased turn-over of reactor liquid content
have significantly improve the process result. It is also proven that the quality of the organic material and
municipal sludge is different from time to time, and it is well known that grinded organic material has different
characteristic in terms of specific weight and liquid viscosity. Sewage sludge from municipal digesters and from
biogas reactors exhibit non-Newtonian flow behaviour, That is why shear rate is not directly proportional to shear
stress.
It is well known that viscosity various with shear rate and various significantly between different organic material.
This means that municipal and biogas digesters where flow is turbulent in much of the tank must be designed in a
way to avoid stagnation zone, plug flow and settling. It is proven that the viscosity various from time to time and
from digester to digester depending on the efficiency of the equipment feeding the digesters.
The feeding process can either be from the top by a screw conveyor or by a piston pump in bottom of the
digester.
Therefore, it is important that agitator operation (two phase/multi phase) in the digesters are designed to
generate liquid velocity enough to fulfil digestion process.
Calculated retention time will be longer and other delays in the process
may cause many other process problem. Therefore, the top entering mounted agitator is the only way to achieve
complete uniformity of the substrate and as well to reach maximum gas production.
It is required to generate increased velocity in
biogas reactors compared to community sludge digesters in WWT plants, in order to achieve full yield of the
organic material. Furthermore, in order to have reasonable energy consumption for the total economy the top
entering agitators are favourable compared to side entering agitators which use more energy to achieve the same
process result. There are a great number of mixing applications and with different physical characteristics to be
considered. Blending together liquid and solids in slurry must be made with high efficient impellers to create a
uniformity substrate. Balancing between generated momentum movement and the generating correct liquid
velocity along the tank wall are to be taken into consideration to maintain and reach required process result.
In order to achieve the best mixing performance, the mixing performance must be quantified and compared to
momentum movement we need The flow pattern generated by the impellers describes the way the
substrate flows trough the tank. Settling along the bottom will automatically occur when the velocity generated by
the lower impeller is not high enough. Consistency variations and temperature fluctuations are variables which
perhaps have a major impact on maximum gas production required depending on lack of required mixing
performance
The ratio between tank diameter and height plays a major roll in order reduce energy consumptions and to
achieve complete uniformity of the substrate For design purpose the recommendation ratio between the tank
diameter and height is
H = 0,85 x T or 0,95 x T. (picture 3)
H = Height of the tank,
T = Tank diameter
Other design feature
Baffles recommends in general in any biogas reactor but can be avoided depending on the substrate characters.
Also, the dryness of the substrate plays also a major roll in the design phase of the biogas tank. For low viscosity
organic material baffles are required in order to stop swirl (rotation of the entire volume). For higher viscosity
organic material the baffles can be reduced in sizes or be totally eliminated. The design size of the baffles
recommends to 10 % (width of the tank diameter) and height of the baffle depends on the substrate viscosity and
slurry behaviour. Other recommendation is that the space between the wall and the baffle should be not less than
250 mm. The energy consumption is one of the most important issue for future generations and how to generate
electricity efficient. By utilizing the energy content in organic material and build up small/medium/large scale
biogas plants In the bottom of the digester it is recommended to have a sand trap pit in order to minimise heavier
particles moving around in heavy motions. In addition to that the sand trap also avoiding clogging and erosions in
pumps and pipes.
Higher liquid velocity  Higher degree of agitation
Summary
Modern biogas reactors requires high flexibility to maintain proper mixing and agitation of different organic
material. .Well designed agitators, tanks and basins together make possible the following benefits:
• Minimal energy consumption
• Less sedimentation
• Minimal canalising
• Reduce plug flows
• Less agitator costs
• Better blending
• Better consistency uniformity
• Fster mixing
• Better controllable mixing
. Less temperature fluctuation in the entire reactor