Experiences from operation of CFB Boilers

for Combustion of Local Lignite of Low

Heating Value in Turkey, comparison of

Turkish and Serbian lignites

Karol Zuzčák, Miloš Teleky

SES Tlmače a.s., Slovakia

1. Abstract

Recently, there has occurred a demand on Turkish market to increase capacities of

electric power generation based on coal combustion. It is concerning combustion of local

lignite as there are large reserves of lignite in various places across the country as well as coal

imported to Turkey and combusted in power plants situated alongshore.

Lignite mined in Turkey is of different quality depending on location. Its calorific

value ranges from 900 kcal/kg to 2500 kcal/kg. Its water content reaches up to 55%. The fuel

is often of high surface humidity that causes problems with its transporting and storing.

Imported fuels are bituminous coal.

Two circulating fluidized bed boilers were commissioned by SES Tlmače on Turkish

market. It was the fluidized bed boiler of 120 t/h steam output for combustion of local lignite

in the heating and power plant of the aluminium smelter in Seydisehir. In the second boiler of

460 t/h steam output it is combusted the imported fuel – bituminous coal from the Ukraine.

The boiler is in the power plant near Zonguldak city on the north coast of Turkey.

Currently, SES Tlmače a.s. works on two projects of thermal power plants in Turkey

for combustion of local lignite of total output of 535 MWe. There are four fluidized bed

boilers, of 370 t/h steam output each.

2. Electrical Power Market in Turkey

The Turkish energy market is witnessing rapid growth and liberalization process with

the recent privatizations, licensing tenders and strategic partnerships. The sector has been

remarkably active recently and offers major

opportunities to investors.

Energy consumption in Turkey is

low when compared with Western

European countries. However, the large,

young and increasing urban population

together with expected industrial

development potential in Turkey represents

a significant growth potential. Currently,

0

200

400

600

800

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

GDP of Turkey

Source: World Bank

Diagram No.1 GDP of Turkey 

Turkey is a major energy importer, as the increase in its energy consumption has outpaced

domestic production. Substantial investment in the energy sector will be required in the near

future in order to meet the increasing demand in Turkey.

The Turkish electricity market is one of the fastest growing in the world. Installed

capacity has continued to rise regularly between 1998 and 2009 from 23,354 MW to 44,766

MW. In line with the increase in the number of natural gas fired power plants and

hydroelectric plants, both constitute the highest share in energy resources with 34 percent

each, followed by hard coal and lignite forming 24 percent together.

Coal is mainly used for power generation in Turkey. 30 percent of the total primary

energy consumption in Turkey is derived from coal. Only one-half of the coal used is

produced domestically in Turkey, which makes Turkey's coal market dependent on imports.

The Turkish electricity market is currently going through a liberalization process and

rapid growth. The market is experiencing a transition into a competitive electricity market in

order to attract private sector investments

and maximize efficiency.

Electricity demand in 2008 equalled

198 TWh, representing a 4.3 percent annual

growth from 2007. Electricity demand has

been growing in parallel with the

urbanization and industrialization level and

economic development. Also supported by

the increase in population, electricity

demand in Turkey holds great potential for

further growth.

The current energy supply including

the existing power plants, the licensed plants and those under construction was expected to be

insufficient to cover the base energy demand. On the other hand, the decline in economic

activity, which has affected electricity demand, has also delayed the electricity imbalance.

After a recovery in electricity demand, there will be a requirement for further capacity to

balance supply and demand. The estimated investment required for the period of 2010-2030 is

between USD 193-225 billion, which comprises USD 180-210 billion for generation, USD 6-

7 billion for transmission and USD 7-8 billion for distribution.

Diagram No.2 Electricity Generation and Demand 

3. Coal Mining in Turkey and Serbian and Turkish Lignite comparison

According to studies there are 181 well- explored lignite deposits and 98 lignite

deposits, which require further investigation.

Generally, large lignite deposits are mined by TKI (Turkish Coal Enterprises ) and low

reserve lignite deposits are mined by private enterprises.

Hard coals are produced only by TTK (Turkish Hard Coal Enterprise) in Zonguldak.

Picture No.1 Turkish Lignite and Hard coal deposits

3.1 Hard Coal Resources in Turkey

The most important hard coal reserves of Turkey are located only around Zonguldak

province in the northwest of Anatolia (Picture No.1). The hard coal reserves of 1.1 billion

tonnes have been proved according to the results of the studies in the Zonguldak basin. The

average net calorific value is 6 000 kcal/kg (25,12 MJ/kg).

Zonguldak hard coals are mainly consumed by the Catalagzi thermal power plant and

heavy industry plants. Partly Zonguldak hard coal is used by new 160 MWe unit with CFB

boiler supplied by SES.

3.2 Lignite Resources in Turkey

The majority of lignite deposits in Turkey are used as open-pit mines. Total lignite

coal reserve is estimated to be around 8.25 billion tonnes. Investigations and privatizing

lignite mining are going on in Turkey. Regional reserve distributions and average chemical

properties of Turkish lignite are given in Table No.1. The lignite has generally calorific values

between 868-5000 kcal/kg (3 634-20 934 kJ/kg), water content between 10-55 %, ash content

between 11-46 %, and total sulphur content between 0.2-4.5 %. Almost 80% of the total

reserves have calorific values below 2500 kcal/kg (10 467 kJ/kg), 13% are in the range 2 500-

3 000 kcal/kg, while only 7% are over 3 000 kcal/kg (12 560 kJ/kg). The lignite having low

heating value is generally burned in power plants while the lignite having relatively high

calorific value is utilized for domestic and industrial use.

Table No.1 Properties of Turkish Lignite

3.3 Serbian – Turkish Lignite comparison

Serbia has own Lignite reserves, maily concentrated in two coal basins. It is Kostolac

coal basin and Kolubara coal basin.

To compare Turkish and Serbian Lignite we have used available data of coal

composition of main Serbian coal basins. Coal composition of Kostolac and Kolubara coal

basins are mentioned in table below No.2 Serbian Lignite composition.

Kostolac coal

basin

Kolubara

coal basin

Total moisture % 39,22 43,6-55

Ash % 17,8 9-18,5

Sulphur % 1,18 0,35-1,0

Calorific value MJ/kg 10,02 7,1-8,9

Calorific value kcal/kg 2390 1695 - 2124

Table No.2 Serbian Lignite composition

Verified balance and non-balance coal reserves in OM Drmno calculated in 2007 are

870 mil.tons. Verified balance and non-balance coal reserves in Kolubara cola basin

calculated in 2009 are 5 151 mil.tons.

Comparison of Serbian and Turkish Lignites shows that range of heating value of

Serbian lignites 7,1 – 10 MJ/kg is within Turkish range 5 – 14,6 MJ/kg. Ash content in the

Lignite is less in Serbian Lignite in comparison to Turkish and vice-versa moisture content in

Turkish Lignite is less in comparison to Serbian one.

4. Turkish Lignite Firing CFB Boiler

In the heating plant of ETI Aluminium in the city Seydisehir, SES Tlmače built CFB

boiler for local low grade Lignite burning with capacity 120 t/h.

The first contact with the client

launched in April 2006. The customer is an

owner and an operator of the aluminium

works. The aluminium works included

heating plant with several decades old oil

boilers. The customer decided to reconstruct

its heating plant by replacing old oil boilers

to new CFB boiler burning of lignite from the

nearby coal mine. In 2006 the customer

bought the Lignite mine Bayavsar a few kilometres distant from the heating plant. Opencast

coal-mining is used in Bayavsar coal mine. For this reason, the customer thought tooperate

Picture No.2 Bayavsar Lignite mine 

the mine just during the warmer season of the year. During the winter season, the customer

presumed to use coal from stock yard close to the heating plant.

In November 2006 SES Tlmače a.s. signed a contract for CFB boiler for ETI

Aluminium Seydisehir. CFB boiler steam parameters are: 120 t/h, 438°C, 4,6 MPa

Contractual parameters of burned Lignite are as follows:

Moisture content 20 - 48,2%

Heating value 1279 – 2500 kcal/kg

Ash content 16,7 – 31,5 %

Based on available information

and concerns regarding degradation of

fuel quality mainly during raining season

we decided to use the safest configuration

of the boiler – refractory lined combustor.

The only heating surface in circulating

circuit is an evaporator bundle in FBHE

(fluid bed heat exchanger). Combustor,

cyclone, seal pot and all ducts were made

of steel plates internally refractory lined.

FBHE is a key element of CFB boiler,

that allows to operate boiler with the wide

range of fuels (in this case the wide range of

heating value and water content) and the wide range of boiler loads.

Due to the wide range of produced flue gas amount, the boiler is equipped with flue

gas recirculation. Recirculation operation is considered in case of burning fuel of heating

value at the top of the contracted heating value range with a low moisture content and

subsequently a low generated flue gas amount.

In the reality, the coal heating value is usually at bottom of the heating value range and

during a certain period it is less than the minimal contracted heating value. In the diagram

No.3 you can see the main properties of Lignite burned in CFB boiler Seydisehir from

January to April 2009.

Picture No.3 CFB boiler Seydisehir 

Diagram No.3 Lignite properties  

During May 2009 performance tests were performed at the nominal and the minimal

boiler load with Lignite of heating value 1305 kcal/kg. The performance tests confirmed the

contracted guarantee values. The results are in the Table No.3.

Value Unit Guaranteed

value

Measured

value at

Nominal

load

Measured

value at

Minimal

load

Result

Steam flow (nom./min.) t/h 120 / 48 123,6 47,6 Fulfilled

Steam parameters MPa / °C 4,6 / 438 4,6 / 442 4,6 / 441 Fulfilled

SO2 mg/Nm3 350 319 11 Fulfilled

Nox mg/Nm3 200 111 96 Fulfilled

CO mg/Nm3 200 12 9 Fulfilled

Dust mg/Nm3 50 5 16 Fulfilled

Table No. 3 Seydisehir CFB boiler Performance tests results 

During commissioning the boiler was running very well and even with fuel out of the

contracted range of burning, desulphurization processes were running good and the

performance values were reached.

The main problem regarding low calorific lignite burning was moisture of delivered

fuel. The total moisture was not an issue, but surface moisture was a real problem that we had

to solve before successful handing over the plant to the client.

Fuel was delivered from the opencast coal mine Bayavsar. During long-term rains coal

was mined from the mine full of water. Even after a certain storage time at the stock yard near

the heating plant, coal was wet and made problems on all way from the stock yard up to the

boiler inlet. The critical points were coal bunkers, coal crushers and spills. Wet coal was very

sticky and many outages of individual coal lines due to blockages happened.

Together with the client we agreed on measures to minimize the problems arising from

high surface moisture of fuel:

- roofed coal stock yard were built

- air nozzles were used to ensure coal flow in critical coal transport places

Picture No.4 New roofed coal stock‐yard 

During the boiler operation within the guarantee period, the boiler was operated with

lignite of the heating value close to the lower limit, in some cases below it. As the guaranteed

operating range of the coal heating value was wide,

Ilgin coal used for test had the following characteristics:

Coal heating value 2254 kcal/kg

Bayavsar coal and Ilgin coal were tested

and fin

Picture No.5 Air nozzles installed on coal bunker 

client asked us to make test with fuel with

heating value at the upper limit of the heating value range. Coal suitable for such test was the

coal from mine Ilgin, which is relatively near Seydisehir.

Moisture content 40,1 %

Ash content 18,8 %

The test lasted 2 days. Various mixtures of

ally just Ilgin coal was burned.

1 200

2 254

0

500

1000

1500

2000

2500

0 20 40 60 80 1

Heating value of coals mixture kcal/kg

Ilgin coal portion %

Ilgin coal portion vs. heating value

00

Diagram No.4 Ilgin coal proportion vs. heating value coal 

Tests confirmed that the boiler was able to operate at nominal load with the above

mentioned coals mixture, or with coal of the heating value at the upper limit of the guaranteed

heating value range. Operation of the boiler with recirculation fan was demonstrated to the

client. Influence of the recirculation rate on the combustor temperature was evaluated.

5. Hard Coal Firing CFB Boiler in Turkey

In Zonguldak province, SES built CFB boiler for hard coal burning. The main

parameters of the boiler are as follows:

Electric power of the unit 160 MWe

Live steam flow 465 t/h

Live steam temperature and pressure 563/165 °C/bar

Reheated steam temperature and pressure 563/41 °C/bar

The boiler was designed for burning of hard coal with following properties:

Coal heating value 4,48 – 6,49 kcal/kg

Moisture content 7 – 15 %

Ash content 10 – 31 %

Actually, in the boiler there are burned coals of different origin. There is supplied coal

from the Ukraine, Russia, Columbia and South Africa. At the time of lack of imported coal,

local hard coal from Zonguldak province had been burned. The boiler nominal load was

achieved will all supplied coals.

The boiler has been operated since summer 2010 and most of the time it has been

operated at the nominal load. At the time of writing this paper, the preparation of performance

tests was under progress.

Picture No.6 CFB boiler in Zonguldak for hard coal burning 

6. New Local Coal Firing CFB Boilers

New projects with CFB boilers for local Lignite burning are in preparation in Turkey.

In two of them SES had signed the contracts. The projects are in the stage of engineering and

finalising of financing. The projects are in different locations. One of them is in Bolu province

and the other one in Cankiri province. The boilers are designed for local lignite with

following properties:

Bolu Goynuk Yildizlar

Lignite heating value 2,43 2,29 kcal/kg

Moisture content 30 26,5 %

Ash content 26 34,1 %

Picture No.5 CFB boiler in Zonguldak for hard coal burning 

Yildizlar

7. Conclusion

Turkey economy rapidly grew in the last decade and it has high potential to economy

growth in the near future but it is connected with increase of power demand. The main local

source of energy are large lignite reserves that are relatively easy accessible by opencast

mining. The reason why these reserves were not widely used up to now is poor quality of

most of lignite. This makes harder to use these reserves with PC boilers. CFB technology

gives an opportunity to use local lignite in different size of boilers with possibility to operate

boilers in a wide range of load without supplementary fuel and with good economy.

Experiences with our CFB boiler in Seydisehir proved that lignite of the heating value of

about 1000 kcal/kg is possible to burn if a boiler is designed accordingly. Design and

operating experiences gained with boilers for Turkish Lignites can be fully reflected in design

of CFB boilers for Serbian power plants which will burn Serbian Lignites.

3x 369 tph Bolu Goynuk

2x 373 tph

Picture No.7 Lignite burning CFB boilers in Turkey ready for construction