Fixed bed reactor column for anaerobic decomposition processes

A fixed bed layer of a reactor column for the execution of anaerobic decosition processes, which column is divided by screen partitions into segments one above another with intermediate spaces for gas discharge from the column through discharge funnels into one or more corresponding, ascending pipes. Additional devices for the introduction of liquid or gas into the individual fixed bed segments produce turbulence and remove excess sludge from the fixed bed layer. Annular guide elements project from the inner wall of the column underneath the funnel and have a constricted cross section which defines an annular channel to the next column segment. Thus, a liquid stream is not blocked during optimal gas collection in the funnel. The funnels are preferably installed in the screen floor of the subsequent column segment.

BACKGROUND OF THE INVENTION 
1. Field of the Invention: 
The invention relates to a reactor column for the implementation of 
anaerobic decomposition processes with a fixed bed, through which the 
reaction fluid travels upward. 
2. Description of the Prior Art: 
The execution of anaerobic decomposition processes on carrier-fixed 
microorganisms is increasing in importance. The anaerobic purification of 
waste water appears particularly beneficial. In this process, in contrast 
to the activated sludge process, relatively small amounts of residual 
sludge are formed and the energy balance of the entire process is more 
favorable, since on the one hand, there is no need to introduce oxygen, 
and on the other hand, the biogas formed can be used as an energy source. 
A prerequisite for a commercial application of the process is high 
efficiency per unit of volume and per unit of time, that is, for a given 
reactor volume, the maximum quantity of waste water substrate must be 
treated in the shortest possible time. 
Recently, therefore, processes have been developed for the immobilization 
of active biomasses which make it possible to deal with quantities of 
waste water like those treated commercially in an acceptable length of 
time using reactors of an acceptable size. But a problem which occurs with 
the use of beds of small-particle carrier materials, for example, with a 
size of 5 to 15 mm, which exhibit a surface large enough for cell 
fixation, is that excessive sludge is formed after a period of extended 
operation, which leads to clogging and limitations of diffusion, and to 
the formation of graft flows. In addition, the amount of biogas contained 
in the reaction mixture increases as the reaction proceeds, which has an 
adverse effect on the treatment system (solid/liquid/gas). 
For these reasons, reactor columns with small-particle carriers, with fixed 
beds more than approximately 2 meters in height, are no longer considered 
optimal. 
A reduction of the specific activity of the column, in order to prevent the 
increasing clogging of the fixed bed, or a corresponding limitation of the 
height of the reactor, does not appear very economical, since on the one 
hand, the overall reactors would have to be larger, and on the other hand, 
the ground space required for a "flat" design with the appropriate column 
cross section, or a number of parallel columns, would not be economical. 
OBJECTS OF THE INVENTION 
It is therefore an object of the invention to provide a reactor column 
design adapted to the requirements of actual practical applications, by 
means of which high specific activities of the biocatalyst can be allowed 
and successful operation is possible over long periods. 
It is a further object of the invention to provide a high-rise design for a 
reactor column which can be constructed requiring only a limited amount of 
ground space. 
SUMMARY OF THE INVENTION 
The invention achieves these objectives, in that the fixed bed is divided 
by screen floors into sections arranged one on top of another, with spaces 
in between, in which there are gas discharge lines and gas and/or liquid 
inlets below the screens, generally in the shape of (inverted) funnels, 
leading to one or more ascending pipes outside the column. 
The improved reactor column of this invention for the performance of 
anaerobic decomposition processes by means of a fixed bed layer through 
which reactional liquid flow upwardly comprises a jacket means which 
defines the reactor column. Within the reactor means are at least two 
individual fixed bed reactor segments or individual reaction zones which 
are disposed one above the other in a stacked relationship. Each of the 
individual fixed bed reactor segments includes a screen-like floor means 
upon which is disposed a fixed bed layer of a predetermined height. There 
is also defined, above each fixed bed layer, a void in each of the 
individual segments. A gas discharge means includes means generally in the 
shape of an inverted funnel disposed in the void above each fixed bed 
layer. The inverted funnel means is in communication with at least one 
ascending gas discharge pipe which is mounted external to the jacket 
means. This communication can be established by means of a transition pipe 
which is disposed upwardly and outwardly toward the jacket wall with 
respect to the inverted funnel means. Fluid inlet means are disposed 
underneath each of the screen-like floor means of each of the individual 
segments. Additionally, a star-shaped feed distributor means for the 
introduction of the reaction liquid into the reaction column is disposed 
on the column floor just below the screen-like floor which defines the 
bottom-most segment of the reactor column. A liquid extraction means is 
disposed at the upper end of the fixed bed reactor in the void defined 
above the upper-most fixed bed reactor segment. The liquid extraction 
means is in the form of a closed tube with upper feed holes.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The column reactor 1 shown with a thermostat jacket 2 is divided into four 
segments 3, each of which includes a fixed bed layer 4 on a screen floor 
5, and a space 6 which leads into the side tubes 7. 
In the space 6, above an annular guide element 8, there is a gas discharge 
funnel 9, which forms an "annular gap" 10 together with the annular guide 
element 8. This annular gap 10 can be adjusted by adjusting the height of 
the funnel 9 by means of one or more adjustment screws 11. From a funnel 
tube 9', a connecting tube 12 leads upward and outward through the fixed 
bed layer 4 to an ascending pipe 13, which reaches at least the height of 
the liquid discharge via the annular extraction tube 15 from the column 
reactor and leads to a gas collecting chamber (not shown). 
All of the segments can empty into this ascending pipe 13, or there can 
also be separate ascending pipes which lead to the gas collection chamber. 
The reaction liquid travels through a star-shaped distributor 14 on the 
screen floor 5 of the column reactor, is distributed over the 
cross-section into the fixed bed, and converted liquid is extra via an 
annular extraction tube 15 with outlet tubes from the reactor column. This 
annular extraction tube 15, in its upward-pointing surface, has holes 16, 
by means of which the liquid is extracted from the reactor. A triangular 
cross-section of the extraction tube, with the point downward, is 
appropriate. 
The gas discharge funnel 9 of the final column segment is no longer in the 
screen floor, but is installed in the column cover 17, and its funnel tube 
18 leads directly to the gas collection chamber. 
The column packing can be formed by carrier particles of the prior art with 
microorganisms immobilized on them, or by granular materials, etc., 
charged with biomasses. The individual segments can also exhibit 
additional pipes for probes, sampling, control liquids, etc. 
To remove excess sludge, flushing liquids can be forced through the column 
segments during a pause in operations, for example, via the lower fluid 
distributor 14 and the side tubes or lateral pipes 7. In this case, the 
funnel 9 is appropriately placed in its highest position. 
With such a reactor column divided into fixed bed segments located above 
one another with spaces in between, an effective and long-term operation 
can be achieved, since excess sludge is discharged, on the one hand, via 
constant floatation phenomena through the gas lines (and is separated in 
the sludge separator of the gas collection chamber), and on the other 
hand, can be expelled in intermediate phases by a flushing medium, which 
is admitted in the reverse direction via the appropriate inlets beneath 
the screens. 
The spaces between the segments are a function of the distance between the 
upper end of the fixed bed layer of a segment and the permeable floor or 
screen of the subsequent section. In this space are the inverted-funnel 
gas discharge lines which, mounted in the screen, are conducted through 
the packing of the subsequent segment outward to ascending pipes. 
Annular guide elements interact with the inverted-funnel gas discharge 
lines and project from the circumference into the column, narrowing the 
cross section, the opening cross section of which is smaller than that of 
the funnel base, so that the gas bubbles contained in the ascending 
gas/liquid mixture are introduced into the funnel, while the liquid flows 
through the "annular gap" between the conductor and the funnel outward and 
upward to the next segment. 
The "annular gap" should thereby have a cross section so that no 
significant pressure loss occurs at this point. To make possible an 
optimal adjustment of the free cross section of this "annular gap" to the 
prevailing conditions, the gas discharge funnel is mounted so that is 
vertical position inside the space can be adjusted. 
The base cross-section of the gas discharge funnel, which interacts with 
the annular guide element, can essentially be as large as desired, but the 
funnel cross-section is advantageously one which largely covers the column 
cross section and still leaves sufficient space for the liquid flow. 
The angle of inclination of the funnel cone from the horizontal is 
optimized within the space, bearing in mind that an excessively flat 
funnel can result in loss of bubbles, while a funnel with excessively 
steep sides is inappropriate because of the height limitations of the 
space. Inclinations between 15.degree. and 60.degree. are appropriate, 
especially an angle of approximately 35.degree.. 
To facilitate the gas discharge from the funnel into the ascending pipe, an 
ascending connecting tube is selected, one which specifically has an angle 
of 15.degree. to 30.degree. to the horizontal. 
The gas discharge funnel can lead to a separate ascending pipe or into a 
common ascending pipe. The ascending pipes extend at least to above the 
upper fluid discharge of the reactor and empty into a gas collecting 
chamber. The cross section of the gas discharges from the lower segments 
of the column can, if necessary, be made larger to accommodate a more 
intensive gas generation in the lower portion of the column than the 
discharge lines from the higher portions. 
The individual segments of the column reactor can be identical to one 
another, to facilitate their manufacture. However, it may also be 
appropriate if the height of the segments increases with the height of the 
reactor column, so that consideration can be given to a decrease in the 
concentration in the substrate as the reaction proceeds (column height). 
In a similar manner, the grain size of the carrier or the diameter of the 
carrier particles can be graduated from bottom to top, whereby the larger 
particles, for example, 30 to 50 mm in diameter, are in the lower region 
and the finer particles, for example, down to 15 to 9 mm in diameter, are 
in the upper region. 
The lateral inlet tubes below the screens, by means of which a flushing out 
of the excess sludge is achieved, offer additional possibilities of 
process control by means of the addition of substrate distributed 
vertically, partial recycling, or even the addition of reagent. 
The addition of the reaction liquid is done as usual at the bottom of the 
reactor column, specifically by means of a star-shaped liquid distributor, 
and at the top of the column the reaction liquid is extracted by means of 
an annular extraction tube, which exhibits holes 4 to 5 mm in diameter 
pointing upward, by means of which the liquid to be extracted enters into 
the annular tube. 
The bed height of the individual fixed bed segments is appropriately 50 to 
200 centimeters, specifically 100 to 160 centimeters, in the case of fixed 
biocatalysts with an activity of 5-16 kg- COD/kg.times.x.times.d 
(x=biomass concentration as dry mass), and is also a function of the COD 
(COD=chemical oxygen demand) of the feed. 
The construction of the reactor column described above is suitable for 
anaerobic processes in the fixed bed with and without recycling of the 
liquid used. 
What has been described is an improved fixed bed reactor column, by means 
of which high specific activities of the biocatalyst can be allowed and 
successful operations are possible over long periods. 
The invention as described hereinabove in the context of the preferred 
embodiments is not to be taken as limited to all of the provided details 
thereof, since modifications and variations thereof may be made without 
department from the spirit and scope of the invention.