Köhler Kalk, a lime plant founded in 1938 and situated in Germany’s heartland, calcines the niche product dolomitic limestone. Just last year the company commissioned a new parallel-flow regenerative (PFR) shaft kiln from QualiCal. We spoke with Christian Köhler, who joined the company with the launch of planning work for the newChristian Köhler manages the plant together with his father NorbertAll Anett Fischerbuilding project in 2013 and has been managing the company together with his father Norbert Köhler ever since. For a small enterprise with 18 employees, this € 9 million investment is quite a major achievement

1. www.zkg.de18 ZKG
INTERVIEW
proved reliable, so the old kiln was able to be de-
commissioned in July.
ZKG: What made you choose QualiCal?
CHRISTIAN KÖHLER: For us, as a very small lime
plant, installing a new kiln at a total cost of € 9
million was a really big project. It amounted to
replacing the core component of the whole plant.
We chose QualiCal mainly because, for us, they are
the most innovative company in the sector. The
fact that QualiCal offers numerous innovative ap-
proaches was an important point for us. They don’t
just want to sell kilns but to improve the “lime pro-
duction experience” by providing the best-avail-
able technological operations. Since the dolomitic
lime we burn has a very broad particle size spec-
trum, the kiln’s mode of operation and boundary
conditions had to be adjusted accordingly.
Being that digitization is an important topic for
us, QualiCal offered us a digitization package that
we considered convincing in combination with all
the kiln’s other technical features. Now, I can use
the Mosaico app to query the kiln’s crucial data on
my smart phone or tablet and, once more expe-
rience has been gathered on the kiln’s operation,
ZKG: What were your reasons for investing in a
new QualiCal lime kiln last year?
CHRISTIAN KÖHLER: At the time I joined the
company in 2013, we were facing the question of
whether to quit or invest. With our old standard
shaft kiln, we were up to our limits in terms of en-
vironmental standards and quality requirements.
We would have had to upgrade the kiln in 2017,
anyway, because it was no longer able to satisfy
Germany’s air quality control code TA-Luft under
normal operating conditions.
Since we had gained approval for opening a new
quarry that year, i.e., in 2013, we decided to install
a new kiln and plunged right into the planning. The
first question, of course, was which kind of kiln
we wanted. We examined a number of different
concepts and eventually decided on a parallel-flow
regenerative shaft kiln (PFR) from QualiCal. In the
summer of 2015, we applied for approval accord-
ing to the Federal Emission Control Act (BImSchG),
which we were granted in record time by Janu-
ary 2016. We commenced construction that spring,
and the system went into operation in May/June
2017. Initially, the old kiln remained in operation
in parallel with the new one, but the new kiln soon
CHRISTIAN KÖHLER, KÖHLER KALK GMBH, MEISSNER-VOCKERODE/GERMANY
The company is our whole life!
Köhler Kalk, a lime plant founded in 1938 and situated in Germany’s heartland,
calcines the niche product dolomitic limestone. Just last year the company commissioned
a new parallel-flow regenerative (PFR) shaft kiln from QualiCal. We spoke with
Christian Köhler, who joined the company with the launch of planning work for the new
Christian Köhler manages
the plant together with
his father Norbert
AllAnettFischer
building project in 2013 and has been managing the company together with his father
Norbert Köhler ever since. For a small enterprise with 18 employees, this € 9 million
investment is quite a major achievement.

2. INTERVIEW
ZKG 19
mentioned, our power consumption is now higher
than it was with the old standard shaft kiln, so we
invested in a 400 kW microturbine CHP to gener-
ate our own electricity for the kiln. We are also
using waste heat from the microturbine to dry the
raw material in an upstream dryer. A positive side
effect of this is that it shakes the sand off of the
product, hence preventing the rocks from caking
together and clogging the bed during the firing
process. That is a very interesting point for all
those who do not like to use water for cleaning.
For us, it is especially important to maintain a
low fines fraction in the load of rough rock, since
the broad particle size range extending from 25 to
100 mm already gives the kiln a relatively dense
packing.
Our experience to date with this system has
been very good, and the interest our lime sec-
tor colleagues have been showing emphasizes the
general importance of this topic. We are open for
dialogue with other lime plant operators, and we
visited a number of other plants during our own
planning stage.
ZKG: Where do you stand in terms of emissions
and product quality?
CHRISTIAN KÖHLER: With regard to emissions,
our new kiln meets all requirements and reliably
complies with the prescribed ceilings. The quality
of products from the new kiln is also significantly
better.
ZKG: Which optimization options do you still see?
CHRISTIAN KÖHLER: We always strive to reduce
energy expenditures. QualiCal is able to access cer-
tain of our kiln data and give us suggestions on
further energy optimization from a different point
of view. This dialogue will enable us to gradually
optimize the new kiln and its energy consumption.
evaluate them to recognize any emerging prob-
lems. While some people may consider such expe-
dients a mere gimmick, I am convinced that digiti-
zation does not stop at the threshold of our rather
conservative branch of industry. Consequently, it
is important for us to make use of cutting-edge
technology in our field.
All in all, QualiCal’s high-level innovative-
ness and flexibility with regard to their customers’
needs was the decisive factor in our decision.
ZKG: What are the new kiln’s distinguishing fea-
tures, and how does it work?
CHRISTIAN KÖHLER: Our PFR kiln is some 50 m
high overall, including its 22 m firing zone. It
has two shafts connected to each other by a stone
spreader at the top and a crossover channel at the
bottom. The combustion energy is introduced via
12 lances per shaft. We fuel the kiln with pulver-
ized lignite, which is currently the least expensive
source of energy for us. The kiln operates on alter-
nating firing and preheating cycles. The combus-
tion air moves in parallel flow from top to bot-
tom along with the rock charge. The lance burners
heat the load, hence “burning” the dolomite at a
flame temperature of roughly 1100 °C. Hot air then
moves through the firing shaft and over to the oth-
er, where it preheats the newly introduced rough
rock in a counterflow arrangement. Every 15 min-
utes, the calcining chamber reverts to the preheat-
ing mode, and vice-versa. This gives the PFR kiln
a combination of relatively low calcining energy
requirement coupled with thermal efficiency. Since
the combustion air passes through the hot, non-
combusting shaft, it undergoes a form of post com-
bustion. One advantage to this is lower emission
levels than for firing in our standard shaft kiln.
On the other hand, it takes more electricity to
move the air all the way through the kiln.
ZKG: What was the installation and commissioning
procedure like?
CHRISTIAN KÖHLER: The installation process was
largely coordinated by Hoffmeier, the company
responsible for the steelwork. Hoffmeier really did
an excellent job in the quickest possible time. The
kiln’s high level of sensor technology is evidenced
by the fact that the electrical supply and control
scope required some 20 km of cabling. On comple-
tion of the installation work, QualiCal helped us
with the commissioning and initial configuration.
ZKG: How much capacity does the new plant have,
and how much energy does it consume?
CHRISTIAN KÖHLER: We doubled our produc-
tion capacity to 150 t/d, and our calcining en-
ergy consumption rate is now situated at approx.
860 kcal/t burnt lime, while our electric power
consumption amounts to 40 kWh/t. As already
1 The Köhler Kalk lime
works is idyllically
situated in the Meiß-
ner-Kaufunger Forest
Nature Park

3. INTERVIEW
20 ZKG www.zkg.de
each other in many ways. We discuss things first
and then come to a joint decision. This kiln con-
struction project was a great opportunity to get the
best out of both generations and start things off
with both of us at the same knowledge level.
While € 9 million is a huge investment for a
company as small as ours, we would not hesitate
to do it again anytime. The company is our whole
life, and it is good to handle such a company just
as you would a family. Such family enterprises
do not focus solely on profits, but on securing the
company’s future.
ZKG: What are your plans for the future?
CHRISTIAN KÖHLER: First of all, we want to nor-
malize our operating procedures With the new kiln
and at the new quarry. We are presently work-
ing to optimize those processes and achieve steady
equipment utilization rates. Product development
is another goal to be pursued. We also intend to
focus more on promoting additional uses for dolo-
mitic lime as a product. There are not very many
dolomite deposits left in Germany. It is our convic-
tion that both the raw material and our products
are important and deserving of additional pro-
motion. Consequently, we will have to intensify
our public relation efforts. As a small-scale lime
works, however, we cannot do that all on our own.
On that point, we would like to join forces with the
lime association and our colleagues.
ZKG: Mr. Köhler, thank you very much for this
very informative interview. We wish you every
success for your future work with the new kiln.
ZKG: You manage the company, which with its
18 employees is one of the smallest lime works in
Germany, together with your father. How are the
company’s various tasks distributed between the
two of you?
CHRISTIAN KÖHLER: My father has the better
overview of our products, inventories and equip-
ment in general. I am more involved in our ad-
ministration, planning and permits. The new kiln,
though, is our intersecting set. For me as a chem-
ist, this presents an excellent opportunity to delve
into the technical side of things and gradually be-
come more involved in it. We both contribute all
we can to the company, and we work together very
closely. I think we complement each other quite
well, and just one without the other simply would
not work out anymore.
ZKG: Do you consider yourselves a good example
of a successful passing of the company torch?
CHRISTIAN KÖHLER: Well, at 57, my father will
still be taking an active part for a number of
years. I think it is both good and important for the
younger generation to run alongside their elders
for a while in order to benefit from their experi-
ence. At the same time, my affinity for new tech-
nologies and digitization is an important factor for
my father. Nut-and-bolts experience, of course, is
very important, but digital assistance enables lots
of things to be replaced step by step. Let me give
you just one example: My father, with all his ex-
perience, can hear it when a bearing is not run-
ning smoothly, while I would notice an increase in
power consumption, instead. So, we complement
2 With this new kiln, it
is easy to comply with
the prescribed emission
levels