DEPARTMANT OF CHEMICAL
ENGINEERING
ChE417 : Chemical Engineering Design I
Section 3
First Interim Report
Date: 28.10.2020
Submitted to: Asst. Prof. Dr. Harun Koku
Prepared by Group 13 :
Can HUNÇ
Deniz BİNBUĞA
Ekin BAŞARAN
Melisa KÖKSAL
ABSTRACT
Geothermal energy is an energy type coming from the underground. The source of
the geothermal energy is basically the heat of the inside of the Earth. The steam or water
which comes from the different levels under the Earth’s crust at different temperatures
creates some energy called geothermal energy. Geothermal energy can be used in two ways
that are direct and indirect. The direct application is using geothermal heat for the or cooling.
Indirect usage, low-temperature sources are preferred (<150˚C). The main fields of usage of
this type of geothermal energy are space heating or cooling, agricultural applications, fishery
industry, industrial processes. If the reservoir temperature is higher than 150˚C, these
sources can be used for electricity production which is indirect usage of geothermal energy.
Thermal energy came from steam or water turns into electricity at the power plants.
Geothermal energy has many advantages. First of all, it is a renewable energy source. Also,
geothermal sources have a smaller carbon footprint the fuel energy sources. On the other
hand, there are some subjects that can cause some environmental problems if they can not
manage well. The release of hydrogen sulfide is one of the most important ones. Although it
is a renewable energy source, the reservoir has to manage properly. If it is not, there might
be a cool down in the location of the reservoir. Another problem with geothermal energy is the
release of toxic materials from the under of the Earth’s surface. Water pollution is another
danger of geothermal energy. Dissolved minerals may cause water pollution in underground
water supplies. There are more than 20 countries that use geothermal energy. The USA is
the biggest user of geothermal energy. In California, there are 22 geothermal power plants.
Also, Iceland produces 90% of its electricity from geothermal sources. In Turkey, there are
approximately 1000 hot water reservoirs. 170 geothermal reservoirs have a higher
temperature than 40°C. At 11 of them have higher temperature reservoirs. These fields are
used for electricity production. These are Aydın-Germencik (232 °C), Manisa-Salihli-Göbekli
(182 °C, Çanakkale-Tuzla (174 °C), Aydın-Salavatlı (171 °C), Kütahya-Simav (162 °C), İzmirSeferihisar (153 °C), Manisa-Salihli-Caferbey (150 °C), Aydın-Yılmazköy (142 °C), İzmirBalçova (136 °C), İzmir-Dikili (130 °C).
TABLE OF CONTENT
1. WHAT IS GEOTHERMAL ENERGY ..................................................................... 4
2. USAGE OF GEOTHERMAL ENERGY .................................................................. 4
2.1 Direct Usage of Geothermal Energy ................................................................... 4
2.1.1 HEAT EXCHANGERS IN DIRECT HEATING............................................... 9
2.1.2 PIPING FOR DIRECT HEATING ................................................................ 10
2.1.3 EXAMPLES OF DIRECT HEATING ........................................................... 11
2.2.
Indirect Usage of Geothermal Energy .......................................................... 12
3. GEOTHERMAL ENERGY VERSUS OTHER ENERGY SOURCES .................... 14
4. ENVIROMENTAL IMPACTS OF GEOTHERMAL ENERGY ................................ 14
REFERENCES .......................................................................................................... 17
1. WHAT IS GEOTHERMAL ENERGY
Geothermal energy is the using the heat of the hot water or steam which comes from
under the Earth’s crust. The heat of the hot water or steam uses to create energy.
Geothermal energy can be used in two different ways. First of them is heating or cooling
which is direct usage of geothermal energy. Lower temperature(<150˚ C) reservoirs are
preferred for direct usage. The fields in which direct usage of geothermal energy is used are
greenhouses, space heating, and cooling including district heating, fishery applications,
agriculture applications, industrial processes. Another way of using geothermal energy is
electricity production. Electricity production from geothermal resources is called indirect
usage. In order to generate electricity from hot water or steam need to has a temperature
higher than 150˚ C. Geothermal energy is a clean energy resource. It has less damage to the
environment when compared with conventional energy types. The first geothermal power
plant was built in 1904, in Italy. The USA is the biggest user of geothermal energy in the
world. Turkey has a big potential for geothermal energy because it is in the tectonic region.
Known is 95% of the geothermal reservoirs of Turkey are suitable for direct usage. The rest
be used for electricity production. The main areas in which geothermal energy is used in
Turkey are heating(housing, city, greenhouses, etc.), thermal tourism, electricity production,
chemical material production.
2. USAGE OF GEOTHERMAL ENERGY
2.1 Direct Usage of Geothermal Energy
Geothermal resources are hot water and vapors created by the heat accumulated at
various depths, whose temperature is above the atmospheric average temperature and
contains more melted minerals, various gases and salts than surface and underground waters.
Using these resources directly and indirectly is called geothermal energy.Geothermal energy
is divided into three groups in accordance with its temperature:, high temperature areas at
higher than 150°C, medium temperature areas at 70-150°C, low temperature areas at 20-70°C.
Low and medium temperature geothermal areas are used for thermal applications. From the
fluid found in high temperature areas; In addition to the main electricity generation, it is also
used as thermal applications with integrated facilities.Furthermore, there are also systems
where electricity is generated using medium temperature fluid.
Geothermal energy is divided into two according to usage. One of them is direct usage,
and another one is indirect usage. Direct usage is divided into industrial usage and thermal
usage. Geothermal energy as industrial usage is used in drying food, timber, paper and textile
industry, leather and cooling plants. In addition, it is used in the production of chemicals in the
production of KaCl2, boric acid, lithium, ammonium bicarbonate, heavy water, dry ice from CO2
in the fluid. Also, it is used in many places for heating purposes.
Turkey as a potential geothermal energy for heating purposes is ranked fifth in the
world. 90% of the geothermal resources in Turkey are suitable for heating. In addition, there
are 172 geothermal areas above 30°C in central anatolia, west and northwest. Turkey's
geothermal heating capacity consists of 635 MW portion of the city-housing and building
heating and thermal facility heating, and 192 MW part of the greenhouse heating. A 50%
increase has been achieved in geothermal central heating compared to the previous plan
period, with a 23% increase in thermal tourism such as hot spring and a 62% increase in
greenhouse heating. Furthermore, geothermal energy is reasonable because of being suitable
to be established and developed for small power plants with 5-10 MW power, independence of
fossil fuels from price fluctuations, not being affected by weather changes and users in the long
term, low price to compete with coal-fired power plants and natural gas, minimum emission
value in closed systems.
Name of
Geothermal Field
Temperature
(°C)
Capacity
(MW)
232
0,1
Heating
Greenhouse
DenizliKIZILDERE
212
22,8
Electricity
generation,
heating of
greenhouse
TuzlaÇANAKKALE
174
9
Heating of
greenhouse
SimavKÜTAHYA
163
61,6
Balneology,
Heating
(3200housing)
Seferihisar-
153
1,06
Heating of
greenhouse
(80.000m2)
Dikili-İZMİR
130
2
Heating of
greenhouse
Balçova-İZMİR
124
143,3
Balneology,
Heating (10.000
housing), Heating
of greenhouse
100
0,49
Heating of
greenhouse
GermencikAYDIN
İZMİR
HisaralanBALIKESİR
Usage
Area
TekkehamamıDENİZLİ
100
1,8
Heating of
greenhouse
Ömer GecekAFYON
98
2,6
Balneology,
Heating (hotel),
Heating of
greenhouse (5000
m2)
SalihliMANİSA
98
0,37
Balneology,
Heating (hotel),
Heating of
greenhouse
KozaklıNEVŞEHİR
93
14,9
Heating
(1000 housing),
Heating of
greenhouse
Table1:Location, capacity and usage areas of geothermal fields
Temperature(°C)
Usage Area
180
Evaporation of highly
solutions, electricity generation
170
Drying of diatomite, obtaining heavy
water and hydrogen sulfide
160
150
concentrated
Timber drying, fish drying
Aluminum
method
production
with
Bayer’s
140
Canning, quick drying of farm products
130
Sugar Industry, salt Industry
120
Clean water by distillation
110
Drying of cement
100
Drying organic materials, washing and
drying wool
90
Drying of fish (Stock fish)
80
Heating of ground and greenhouse
70
Cooling
60
Heating of greenhouse barn and poultry
50
Mushroom growing, balneological baths
40
Heating of soil
30
Swimming
distillation
20
Fish farms
pools,
fermentations,
Table2: Usage areas of geothermal energy according to temperature
Greenhouse heating systems with geothermal energy
Greenhouse heating systems with geothermal energy are a collection of elements
used to transport geothermal fluid from the extracted area to the desired area. These systems
are divided into five parts. These are the systems where the soil heated, systems placed on
the greenhouse floor, systems where air is heated, systems in which heated air is carried by
an fan and combined systems.
It has been determined that the most suitable system for geothermal energy
applications is the heating system made from the ground or under the ground. The advantage
of this system is that it is supported by the ambient air heating system fed from the same source.
Soil heating systems consist of heating pipes that are buried at certain depths and intervals
and circulating hot fluid. Heating pipes which are made of plastic materials are widely used due
to their easy installation and resistance to high temperatures.
Low temperature, shallow surface sources between 25-60°C are the most suitable
sources for greenhouse heating from geothermal fluid. The excavation, operation, pumping and
maintenance costs of these resources are lower. Geothermal water that cools down after being
used in greenhouse heating should not be released to the environment. In order not to cause
environmental pollution due to the toxic elements and heavy metals they contain, deep wells
must be drilled and re-injected into the deep layers. Furthermore, geothermal resources cause
scaling and corrosion in pipes during use due to the metals and chemical components they
contain.
Timber drying with geothermal energy
Figure 1:Geothermal drying process flow diagram
When geothermal energy was used in the timber drying process, timbers were dried
at low temperatures for a long time. Afterthat geothermal drying systems have been developed
more efficient and cheaper with technological developments. Geothermal energy is used to
heat the air circulating in furnaces and to boil water to create a humid atmosphere to prepare
wood. Water from the production well is pumped to heat exchangers with the help of pipeline
which is made from metal such as steel and ductile iron. Many elements affect the amount of
thermal insulation of distribution network. The first of these, moisture can cause corrosion in
metallic pipes. The other is the positioning of the pipes according to the ground. Underground
pipes prevent heat loss. It should be covered with aluminium. On the other hand, overground
pipes should be covered with PVC.
In addition, temperature is controlled by sensor valves at every stage of the process.
The temperature difference between the geothermal source and the required drying
temperature is important because this affects system productivity, equipment selection and
flow requirements. Geothermal flow and equipment cost are determined according to the
temperature difference between these two values. In other words, the higher the difference,
the lower the cost and flow. The wastewater returns as desiccant to the primary heat
exchanger,which directs it to the heat exchanger.
2.1.1 HEAT EXCHANGERS IN DIRECT HEATING
PLATE HEAT EXCHANGERS
Plate heat exchanger consists of successive insertion of different plates. Thanks to the
countercurrent flow and turbulence sufficient heat exchange takes place in small volume. In
addition, this type of heat exchanger cheaper than shell-and-tube exchanger. Generally, plate
heat exchanger made from stainless steel; if fluid is corrosive, titanium is used. Plate heat
exchanger is frequently used in geothermal direct heating.
Figure 2: Heat Exchanger
Figure 3: Shell and Tube Heat Exchanger
SHELL-AND-TUBE HEAT EXCHANGERS
Shell-and-tube heat exchangers are less useful for geothermal operations , because
of their large size and fouling problems.
DOWNHOLE HEAT EXCHANGERS
This exchanger bringing a very different solution to the problem. Location of the heat
exchanger is directly in wells. In that way, pressure disturbances can controlled, so corrosion
and scaling problems are minimized.
Figure 4: Downhole heat exchanger
2.1.2 PIPING FOR DIRECT HEATING
In direct heating projects the fluid state in transmission line is generally liquid water;
however, it can be also steam vapor or two-phase mixture. These pipelines working at high
temperatures causes stress in the pipeline, so must be needed careful engineering design.
The distance between the customer and the well is important when designing
pipelines. Construction cost of pipelines and distribution networks in direct use projects is
significant. It is important that customers are close to the wells.
Different materials can be used when designing the pipeline. Carbon Steel is the most
popular material for geothermal operations in pipe design. It reduces construction costs as it
is a well-known material by pipe fitters. In contrast, there are several disadvantages for using
steel pipe. Firstly, corrosion is a leading problem for steel piping. Many different element and
chemical compounds can be dissolved in geothermal waters. In this case using steel pipes
should be the last resort. Secondly, when buried steel piping used, external corrosion may be
encountered. Although there are many alternatives according to purpose. For example,
Fiberglass, PVC, CPVC and Asbestos cement. However, galvanized steel is the most
common and useful alternative to protect from corrosion.
There are two types of pipe laying methods. First methods is aboveground piping. In
this method pipes are supported by concrete blocks. The main advantages for aboveground
piping is easy maintenance. On the other hand, pipes are easily damaged or may encounter
vadalism. Second method is buried installation. Buried installation does not create a awful
image in the environment such as aboveground piping. This tipe of piping is the most
expensive but it has longest life expectancy.
Figure 5: Aboveground piping
Figure 6: Buried piping
When transmission lines need to be long, jacket insulation materials are avaible at the
market.This operation is essential to prevent heat loss.
As calculated in every pipeline design, head loss, friction loss are calculated with
expected data. Then, supply and distribution system should be chosen. There are two
systems, single-pipe and two-pipe system. In single-pipe system, water is directly disposed or
re-injected after use. It usually favored in excess of thermal energy and if the water is of
sufficient purity. In two-pipe system water is recirculated so productivity increases.
2.1.3 EXAMPLES OF DIRECT HEATING
Figure7 shows that flow diagram using geothermal energy in Oregon Institute of
Technology in Klamath Falls. Eleven buildings (62000 sq. m of floor space) and up to 62 L/s
of hot water can be provided to the campus.
Figure 7: Flow Diagram of Direct Heating
Another example is in Reykjavik, Iceland. Direct heating system meets the warming
needs of 160000 people.
Figure 8: Flow Diagram of Heating
2.2.
Indirect Usage of Geothermal Energy
One of the usage of geothermal energy is electricity production. This is called indirect
usage of geothermal energy. The reservoirs which has temperature higher than 150 °C can
be used for electricity production. In recent years, electricity can be produced from fluids
which have lower evaporation points up to T>80°C at binary cycle power plants. In a
geothermal power plant, the heat from the hot water or steam which comes from the Earth’s
crust generates electiricty. There are three kinds of geothermal power plant which are dry
steam power plants, flash steam power plants, binary cycle power plants.
Dry Steam Power Plants:
At this type of power plants, dry steam from the ground is used directly. The steam
move to turbines from the ground via pipelines and wells. Its energy delivers to the generator
turbines. After this, the steam condenses and, turns back to the underground. This power
plants need to reservoirs which have the highest temperature. It is the oldest type of
geothermal power plants. The first dry steam power plant is in Tuscany, Italy. It was built in
1904.
Flash Steam Power Plants:
The high-pressure hot water is used in flash steam systems. The temperature of water
must be higher than 180°C. The water comes from the wells with its own pressure. When the
pressure drop, some water suddenly turns into steam and, this steam enters to turbines. The
left water go to injection well without turning into steam. This system has high costs because
of the complex structures.
Binary Cycle Power Plants:
Basically in binary cycle system, the heat of the hot water passes on to another liquid
using heat exchanger. This liquid such as pentane or butane has a low boiling point so that it
vaporizes at low temperature. Its steam goes to generator turbines. This system enable to
produce electricity at lower temperature. Binary cycle power plants are predicted to become
most popular type of geothermal power plants in future.
Figure 9:Steam power plants from: U.S. Department of Energy, Energy Efficiency &
Renewable Energy
Electricity production from geothermal energy is increased day by day in Turkey. The
change of the production of electricity from geothermal resources in Turkey between 20102015 is shown in the figure.
Figure 10:The change of production of electricity from geothermal energy in Turkey from
IMCOFE 2017 / ROME
Between 2010-2015. Turkey has the biggest increase of power of the geothermal
energy usage in the world. The main geothermal fields are Kızıldere-Denizli, GermencikAydın, Salavatlı-Aydın, Hıdırbeyli-Aydın, Tuzla- Çanakkale, Pamukören-Aydın ve Gümüşköy-
Aydın. There are expected 28 geothermal power plants in 14 geothermal reserviors in the
future.
3. GEOTHERMAL ENERGY VERSUS OTHER ENERGY SOURCES
Turkey can produce the amount of energy from geothermal energy is 3042.91 MW.
(yukarıyla teyit et) Coal equivalent of this amount is 5731017 ton/year (1 kg of coal has been
accepted as 4000 kcal). Petroleum equivalent of this amount is 2292407 ton/year ( 1 kg of oil
is accepted as 10000 kcal). If we look at its monetary equivalent, 2292407000/150=15282713
barrel oil, 15282713*60$= 916962800$ worth of imports can be avoided. It will reduce
dependence on foreign sources since it is a equity. In addition, the cost of geothermal energy
production is low compared to other energy sources. This cost decreases even more with
integrated systems.
Comparison with renewable energy sources is given in the table below.
Table3: Usage areas of geothermal energy according to temperature
4. ENVIROMENTAL IMPACTS OF GEOTHERMAL ENERGY
One of the major hurdles in geothermal market development is environmental
concerns. Geothermal should be safe, reliable and renewable energy source. However, all
human activities such as deep geothermal power plant construction affects nature in some
way. The environmental impact of all infrastructure projects must be regulated properly in
accordance with laws and regulations. Despite the potential damage, current and near future
geothermal energy technologies cause much lower environmental impact compared to
conventional fossil fueled power plants and nuclear power plants. For instance, due to the
installation of the plant directly above the geothermal energy source, the fuel does not need
to be extracted with mines and thus the earth surface is not intervened. Nevertheless, there
are some environmental impacts that need to be taken into account in order to make
geothermal energy more environmental reliable and sustainable in the future. Many of the
important potential environmental impacts of geothermal power plant developments are
related to groundwater use and pollution, land subsidence and seismic triggering as a result
of water injection and water intake into fractured reservoirs. In addition, air pollution, noise
pollution, security and land use should be considered.
Possible Environmental Impacts from Geothermal Development
Gas Emissions
Gas emissions occur as a result of the discharge of non-condensable gases (NCGs)
carried in the steam flow coming to power plants. Although the most common noncondensable gases in hydrothermal plants are carbon dioxide (CO2) and hydrogen sulphide
(H2S), low concentrations of methane, hydrogen, sulfur dioxide and ammonia are also
observed. Emissions are evaluated during the process design phase. In steam and flash
plants, naturally occurring non-condensable gases in the liquid should be removed in order to
prevent pressure build-up in the condenser. Chemical treatment can be used to remove H2S
from the non-condensable gases released, or the non-condensable gases can be injected
underground together with the liquid exiting the power plant after recompression. As these
two solutions require energy, the energy required for the maintenance of the facility increases
and the plant output power and efficiency decrease. This problem is avoided since the double
cycle power plants take the heat from the source current by using the secondary medium fluid
flow system. The source stream is reinjected without any non-condensable gas being
released.
Water Pollution
Fluid streams during well drilling, discharge and production may contain a variety of
dissolved minerals, especially in high temperature reservoirs (> 230oC).The amount of
dissolved solids increases significantly with temperature. Some dissolved minerals (e.g.
boron and arsenic) can poison surface or underground fluids and damage local vegetation.
Uncontrolled discharge of waste geothermal fluid to surface waters, in other words not to
reinjection, causes water pollution.According to the studies conducted, although hot
geothermal fluids cannot reach the surface, as they rise along fault zones, they can interfere
with the cold groundwater system at the permeable aquifer bottom. In this case, both thermal
and chemical pollution of the aquifer system, which contains cold groundwater, is a matter.
Figure 11: The spread of hot water rising along the fault at the bottom of the aquifer
Thermal Pollution
Thermal pollution is an environmental effect that has not yet been subject to
inspection, but occurs in all power plants operating with heat sources. Since the inlet flow
temperature in geothermal power plants is much lower than fossil fueled power plants and
nuclear power plants, the heat dissipation per unit electricity production is higher. Considering
only thermal discharges at the plant site, thermal pollution in geothermal power plants is two
to three times higher than in nuclear power plants.
Intervention to natural hydrothermal formations
Although there have been cases in the past where natural hydrothermal formations
such as geysers, hot springs, mud pools have been compromised or destroyed due to
geothermal developments, they will not interact with such formations as they will generally be
established outside hydrothermal areas.
Noise pollution
Noise from geothermal processes is similar to many industrial activities. The highest
noise levels, ranging from approximately 80 to 115 decibels (dBA), which can occur at the
plant boundaries, are reached during well drilling, stimulation and testing.
PRECAUTIONS AND RECOMMENDATIONS
Although geothermal energy is environmentally friendly source compared with nuclear
and fossil fuels, it has negative effects on the environment. To minimize its impact, there are
some procedures that should be followed.
Geothermal fluids generally carry an assortment hazardous chemicals such as
arsenic, lead, zinc, boron. In order to prevent chemical contamination, discharging waste
water is of great importance. Reinjection of thermal waters into reservoir is the most ideal
approach to discard the geothermal water and therefore, forestall defilement problems. In
order to prevent these toxic substances from getting into water aquifers, a near-perfect
design, attention to quality control, monitoring the operation both drilling and construction
phase is essential.
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