Basic Info.
Model NO.
CNG SOLUTION FOR POWER PLANT
Condition
New
Certification
CE, CCC, Cu-Tr
Transport Package
40FT Container Vessel
Specification
12192*2438*2035
Trademark
SAINTWAH
Origin
Shandong
HS Code
7411290000
Production Capacity
10000
Product Description
CNG SOLUTION FOR POWER PLANT
The CNG solution for power plant project is to solve the peaker time operation cost for the power plant.
Compressed natural gas (CNG) can now be used as a fuel for gas-fuelled captive power plants. Natural gas as fuel source has a significant number of benefits versus diesel including reduced emissions and reduced fuel costs.
To use the natural gas to generate the electricity for the peaker time could make the operation cost decrease significantly and also environment friendly. The CNG tube skids could be arranged and installed according the site actually size and condition, the CNG solution for power plant project could be realize the remote control. The pressure sensor and temperature sensor could be installed with CNG tube skids, the instant signal could be transmit to the control room and the operators could monitor the status of the whole project. The whole system include CNG tube skids, compressors, PRU and flow meter could be designed and choose according to the gas engine parameter requirements. Enric has built several projects for the state own power plants in Indonesia, and these power plants now are in the smooth operation, and the cost is improved obviously.
he world needs an abundant supply of clean and affordable energy to support
economic and social progress and build a better quality of life, particularly in developing
countries. Until recently, this desire for energy has been met with fossil fuels, primarily
coal and oil.
Electricity is perhaps the most versatile form of energy and has a wide range of
applications . According to the law of conservation of energy, it is not possible to create
or destroy energy. Energy cannot be created from nothing, but fortunately it is possible
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to convert energy from one form to another. Electrical energy can be obtained from
hydrocarbon fuels like coal, oil and gas, and primary energy flows like solar energy,
wind energy and geothermal energy. The use of natural gas in the power sector is
expected to increase over the next 20 years as it gains share from coal but falls back
by 2050 as the use of renewables accelerate. Electrical energy is easy to transport,
can be used to generate heat, power electrical motors to produce mechanical energy,
and power electronic devices.
In the seventh article in this series, Steyn (2021) discussed outlets and applications
for natural gas, including power generation. In this article, we describe the basics of
electric power generation in more detail and focus on the different options for
generating power from natural gas.
Basics of power generation
Opening remarks
Although sources such as electric batteries can supply electric power, it is mostly
produced by electric generators in power stations. The electric power system, often
referred to as the electric power grid, is made up of electricity generation, transmission,
and distribution. We briefly discuss power generators and primary drivers, and then
consider options for natural gas power generation.
Power generators
In 1831, the physicist Michael Faraday discovered that when a magnet is moved inside
a coil of wire, an electromotive force is induced which causes electrons to flow inside
the wire, generating an electric energy (Beck, 2018). A generator is any machine that
converts mechanical energy to electric current. For a generator to convert mechanical
energy into electrical energy, three conditions must exist for electromagnetic induction
to take place:
• There must be a magnetic field present.
• There must be an electric conductor adjacent to the magnetic field.
• There must be relative motion between the magnetic field and the conductor.
Most generators used in power stations are alternating current (AC) machines or more
specifically three phase rotating field synchronous AC generators, also known as
alternators. A synchronous generator delivers AC electrical power at a particular
voltage, frequency, and power factor . Each generator is coupled to a primary driver
(i.e., turbine or engine) and converts the mechanical energy of the driver into electrical
energy. In this case, in its simplest form, the magnetic field is provided by a permanent
magnet (or electromagnet) which is rotated within a fixed wire loop or coil in the stator.
The moving magnetic field due to the rotating magnet of the rotor will then cause a
sinusoidal current to flow in the fixed stator coil as the field moves past the stator
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windings (conductors). If the rotor field is provided by an electromagnet, it will need
direct current excitation. If instead of a single coil in the stator, three independent stator
coils or windings, spaced 120˚ apart around the periphery of the machine, are used,
then the output of these windings can be interconnected and utilised in a three-phase
system, or utilised as three independent single-phase systems. The generated
electrical voltage is then stepped up with a transformer and then transmitted to where
it is requir ed.
Generator efficiency is the ratio of the electrical power output to the mechanical power
input. The efficiency of a very large generator can be as high as 98% or 99% but for a
1 000MW generator, an efficiency loss of just 1% means 10MW of losses must be
dissipated, mostly in the form of heat. To avoid overheating, special cooling
precautions must be taken and two forms of cooling are usually employed
simultaneously. Cooling water is circulated through copper bars in the stator windings
and hydrogen is passed through the generator casing. Hydrogen has a thermal
capacity 10 times that of air, giving it superior heat removal capability.
Electric grids in the world are either 60Hz (e.g., in the USA) or 50Hz (e.g., in Europe
and South Africa). When a two-pole generator is synchronized to the grid, it runs either
at 3 600 rpm (for a 60Hz grid) or at 3 000 rpm (for 50 Hz).
Primary drivers
Primary drivers provide mechanical energy to the generators which is the converted
into electrical energy. For power generation from natural gas, primary drivers comprise
turbines and gas-fired reciprocating engines. A cutaway of a Siemens industrial gas
turbine is shown in Figure 1.
Figure 1: Cutaway of a Siemens 593MW gas turbine (Siemens, 2021)
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Turbines are used to convert the energy in a flowing fluid into mechanical energy using
rotor mechanisms. Gas turbines and steam turbines are thermal turbo machinery,
where the work is generated from the enthalpy change of the working fluid as it passes
through the turbine. Steam turbines are a mature technology and have been used since
the 1880s for power generation . Steam turbines use high pressure steam from a boiler
as the working fluid. Superheated steam entering the turbine loses its pressure
(enthalpy) moving through the blades of the rotors, and the rotors move the shaft to
which they are connected.
Gas turbines are internal combustion engines, using air as the working fluid. The
thermodynamic operation of the gas turbine is ideally modelled by the Brayton cycle.
Air from the inlet is first compressed using an axial compressor, which performs the
exact opposite of a simple turbine. The pressurised air is then directed through a
diffuser stage, in which the air loses its velocity, but increases the temperature and the
pressure further. In the next stage, air enters the combustion chamber, is mixed with
natural gas, and is ignited. As a result of the combustion, the temperature and pressure
of the resulting fluid rise to an incredibly high level. This fluid then passes through the
turbine section and produces rotational motion to the shaft.
Gas-fired engines a re simply reciprocating internal combustion engines designed to
run on natural gas and which produce rotational motion .
Options for natural gas
The different options for generating power from natural gas all deal with how the
chemical energy of the gas is converted to mechanical rotational energy to drive the
generator, as shown in Figure 2. Although there are many different types of generator s
for different applications, we will not elaborate on power generators, transformers,
transmission, and distribution.
Figure 2 : Options for power generation from natural gas
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Each of the options for power generation from natural gas is discussed in more detail
in the sections that follow.
Steam turbine power plants
Opening remarks
Coal-fired steam turbine or thermal power plants make up most of the power generating
facilities in the world. thermal power plants. Electricity demand varies greatly by season
and time of day. Because thermal power plants can readily adapt to changes in
demand, it plays a central role in maintaining the baseload power supply.
Apart from coal, any other hydrocarbon fuels like oil or natural gas can be used to
generate steam for a thermal power plant. Alternatively, nuclear- and geothermal
energy can also be used for steam generation.
Technology
In steam turbine power plants, the thermal energy obtained from the fuel source is used
to convert water to superheated steam. The steam is used to drive a steam turbine
where the thermal energy is converted to mechanical rotational energy. The turbine is
connected to a generator where the mechanical energy is converted to electrical
energy. A simplified flow diagram of a steam turbine power plant is shown in Figure 3.
Figure 3 : Steam turbine power plant
The pressure and temperature of the steam falls to a lower value and it expands in
volume as it passes through the turbine. Depending on the design, the lower pressure
steam can be fed to further steam turbines on the same shaft to generate more power.
The example shown in Figure 3 has a high pressure (HP) and a medium pressure (MP)
turbine.
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The expanded low-pressure steam from the final turbine stage is exhausted in the
condenser where cooling water is used to condense the steam into water for reuse in
the boiler. A boiler feedwater plant is required to supply make up water for steam and
condensate lost in the process.
Process efficiency
Considering that three conversion processes, thermal, mechanical, and electrical, are
used to extract the energy from fossil fuels, the overall efficiency of a modern
hydrocarbon fuelled electrical power generating plant will be about 40% (Lawson,
2020 a). This means that 60% of the energy input to the system is wasted. Efficiencies
may be <30% in some older plants. Actual efficiencies obtained depend on the fuels
used and the technical sophistication of the generating plant and processes.
Applications
Steam turbine power plants produce electrical power for the power grid. Apart from
hydrocarbon fuels, other heat sources can also be used to generate steam, i.e., nuclear
power, geothermal power, and waste heat from industrial processes.
No new facilities will be built using only natural gas as fuel solely for the purpose of
power generation. Better efficiencies can be had by opting for a natural gas-fuelled gas
turbine power plant. Natural gas can be used as a fuel in existing steam turbine power
plants as a replacement for coal.
Gas Turbine Simple Cycle power plants
Opening remarks
Gas turbine simple cycle power plants are significantly simpler than steam turbine
power plants. This is because it does not have the extra equipment (boiler, steam drum,
superheater, etc.) or complexity of a steam turbine.
A gas turbine simple cycle power plants comprises an integrated air compressor,
combustion chamber, and turbine (together called a gas turbine) and a generator.
Technology
Air is taken from the surroundings, compressed, and fed into the combustion chamber
where natural gas is introduced, and the mixture is ignited . The combustion process
instantly creates very high pressure and temperature gases. These gases then expand
through the turbine section and produce rotational motion (mechanical energy) to the
shaft.
With power generation, the gas turbine shaft is coupled to the generator shaft, either
directly, with a clutch mechanism, or via a gearbox. A flow diagram of a gas turbine
power plant is shown in Figure 4.
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Figure 4: Gas turbine simple cycle power plant
Most of the energy of the natural gas is lost as waste heat in the exhaust gas in a
simple cycle power plant. This is not ideal for a baseload power plant.
Process efficiency
Simple cycle plants have great operational flexibility which means they can be started
up quickly. However, this comes at a lower efficiency compared to combined cycle
plants, as they make less use of the energy in the fuel they are using. The
thermodynamic efficiency of these plants is around 33%.
Applications
Gas turbine simple cycle plants are primarily used to provide peak power during
periods of very high demand because of their ability to quickly respond to demand
fluctuations.
Combined heat and power plants
Opening remarks
Combined heat and power (CHP) plants simultaneous generate usable heat and
electric power in a single process. Heat is captured to heat homes or for use in
industrial applications. CHP plants enable better overall utilisation of the heat energy
supplied to the system. CHP plants are also referred to as cogeneration plants.
Technology
CHP configurations use backpressure steam turbines to generate power and thermal
energy. Backpressure steam turbines produce low pressure steam. A typical CHP
installation is shown in Figure 5. After the thermal energy in the low pressure steam
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has been consumed, the resulting condensate is returned to the steam boiler to
generate more steam. Heat from the exhaust gases from the combustion chamber can
also be used to heat the steam in the low pressure steam drum.
Figure 5: CHP power plants
The primary objective of most steam turbine CHP systems is to deliver relatively large
amounts of thermal energy, with electricity being generated as a by-product of heat
generation.
According to Lawson (2020b), small-scale or micro-CHP installations are now
becoming available for domestic use. The standard domestic heating boiler is replaced
by a heating unit which also provides the heat to power a Stirling engine, which in turn
drives an electrical generator. The Stirling engine is an external combustion engine
and works on the principle that gases expand when heated and contract when cooled.
Process efficiency
Efficiency figures for CHP installations are not comparable to that of other power
generation configurations because of the heat energy being used for other purposes
than power generation. Overall thermal efficiencies up to about 60% are possible.
Practical Stirling engines with efficiencies of 50% have been produced. This is double
the typical efficiency of an internal combustion engine which has greater pumping and
air flow losses in the engine and heat losses through the exhaust gases and cooling
system (Lawson, 2020b).
Applications
CHP installations are typically much smaller than what is found in power stations tied
to the grid and are owned and operated by individual commercial or industrial users.
The difficulty of finding a practical use for the surplus heat sets a limit to the size of
these systems.
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Stirling engine generators with electrical power outputs between 1 kW and 10 kW are
available for domestic applications.
Gas turbine combined cycle power plants
Opening remarks
Exhaust gases are discharged to the atmosphere in the gas turbine simple cycle units.
In combined cycle power plants, the exhaust gases are used to generate steam in a
heat -recovery steam generator (HRSG) before being discharged.
The amount of generating capacity from natural gas-fired combined cycle plants has
grown steadily over time, and in 2018, surpassed coal-fired plants as the technology
with the most electricity generating capacity in the United States. As of January 2019,
U.S. generating capacity at gas-fired combined cycle power plants totalled 264GW,
compared with 243GW at coal-fired power plants (EIA, 2019a).
Technology
The first part of a gas-fired combined cycle power plant operates exactly like the gas
turbine simple cycle plant described above. However, instead of exhaust gases being
discharged to the atmosphere, the exhaust gases are used to generate steam in a
HRSG before being discharged. The steam so generated is used to power a steam
turbine and drive a second generator to generate more electric power. A simplified flow
scheme for a gas-fired combined cycle power plant is shown in Figure 6.
Figure 6: Gas turbine combined cycle power plants
Typically, the hot exhaust gases from several gas turbines will be used to generate
steam for a single steam turbine. An alternative arrangement also exists where the
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steam turbine is mounted on the same shaft as the gas turbine to add additional
mechanical energy to drive a single generator.
Process efficiency
Siemens (2021) maintain that the efficiency of their SGT5-9000HL 593 MW gas turbine
based combined cycle plants can be as high as 64 % . General Electric (2021a) also
claim the same efficiency of their 9HA gas 571 MW turbine in combined cycle mode.
Applications
Gas turbine combined cycle plants are not as quick to start as simple cycle plants
because of the increased complexity. However, it can nevertheless be put on load in a
very short time . Gas turbine combined cycle plants are used as peak load, base lead
as well as standby plants.
Gas engine power plants
Opening remarks
Beside gas turbines, another way of utilising natural gas to generate electricity is by
using gas-fired internal combustion engines. When used to drive a generator, natural
gas engines are efficient and clean and have become popular for small-scale
distributed power generation applications. Internal combustion engines present an
efficient means of converting gaseous or liquid fuels into mechanical and electrical
energy.
Technology
Gas engine power plants are available in standardised designs comprising the gas-
fired internal combustion engine and the generator unit. Engines used are typically
spark-ignition engines. A flow scheme for a gas-fired internal combustion engine power
plant is shown in Figure 7.
Figure 7: Gas engine power plants
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To reduce engine emissions during combustion of natural gas , the combustion
temperature is deliberately kept low by introducing more oxygen than is required for
complete combustion of the fuel, even though this reduces the efficiency that a
reciprocating engine can achieve significantly . Such engines are described as lean-
burn engines and can operate with an air to fuel ratio of between 20:1 and 50:1.
The greater proportion of air to fuel lowers the overall combustion temperature which
reduces the production of nitrogen oxides from nitrogen in air. More air also provides
the conditions for much more complete combustion of the fuel, resulting in reduced
carbon monoxide and unburnt hydrocarbons in the exhaust gases.
Process efficiency
Suppliers of gas engine power plants, or generating sets, claim electrical efficiencies
of between 48% and 51%, although with lean-burn engines will struggle to meet these
high efficiencies in normal operation . With heat recovery from the hot exhaust gases
when used in combined cycle mode, this can be pushed up further. High efficiency
translates into considerable savings in fuel costs compared to other technologies.
Gas engine power plants can achieve a plant availability of up to 95% and a warm start
up time of two minutes.
Applications
Wärtsilä, Jenbacher, Cummins, and Caterpillar, to name a few, provide natural gas-
based power generation solutions for baseload, peaking and standby operations.
Wärtsilä's gas and multi -fuel power plants are typically based on modular 4MW to
19MW internal combustion engine units. Jenbacher generating sets start at 250kW and
go up to 10MW electrical power output. Units from Cummins deliver between 13,5k W
and 3 400MW and Caterpillar has a range of 45kW to 10 900MW.
Reciprocating internal combustion engines are now becoming increasingly popular for
larger utility-scale power generation applications, especially in areas with high levels
of electricity generation from intermittent sources such as wind and solar (EIA, 2019b).
Environmental impacts
Great progress has been made in reducing the environmental impact of coal-fired
power stations, especially for pollutants like carbon monoxide, lead, sul phur dioxide
( SO 2 ), nitrogen oxides ( NOx ), ground-level ozone and particulate matter. A new
pulverized coal-fired power plant can reduce the emission of NO x by 83%, SO 2 by 98%
and particulate matter by 99,8%, as compared with a similar plant having no pollution
controls (Institute for Energy Research, 2017) . However, coal remains the dirtiest of
the fossil fuels and finance for future coal-fired power stations will be difficult to obtain.
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Natural gas is composed almost entirely of methane and is considered the most
desirable of the fossil fuels for power generation. It is substantially free of particulate
matter, combustion is smokeless, and, because it is a gas, it mixes easily and intimately
with air to give complete combustion. The combustion of natural gas emits almost 30%
less carbon dioxide than oil, and about 45% less carbon dioxide than coal. Its
combustion produces negligible amounts of sul phur, mercury, and particulates. The
use of natural gas in place of coal or oil will thus contribute to reduced smog formation
acid rain, decarbonisation, and lower greenhouse gas emissions. Unfortunately,
methane itself is a greenhouse gas with the ability to trap heat almost 23 times more
effectively than carbon dioxide.
There are various opportunities to reduce greenhouse gas emissions associated
with electricity generation, transmission, and distribution. One way is to increase the
efficiency of fossil-fired power plants using advanced technologies and fuel
switching. For instance, convert coal-fired boilers to use natural gas and convert simple
cycle gas turbine installations to combined cycle facilities. Other options include greater
use of renewable energies and carbon capture and sequestration. General Electric
(2021b) believes that the world is best served by accelerating renewables deployment,
running existing gas plants more, and adding new gas capacity as the industry reduces
coal generation . The power sector's journey to lower carbon must be characterised by
rapid deployment of renewable energy resources and a rapid reduction in coal usage.
C oal-to -gas switching is a quick way to reduce emissions in many sensitive regions. In
addition, the possibility of switching turbines from natural gas to hydrogen , or natural
gas/hydrogen blends, when hydrogen becomes more freely available, makes the
prospect of a change to natural gas-powered power generation more tenable.
Closing remarks
When it comes to power generation , a switch from coal to gas represents a fast and
effective win for emissions reduction in many regions around the world. In future ,
switching turbines from natural gas to hydrogen fuel, and/or introducing carbon capture
and storage solutions, can lead to low or near zero carbon emissions . It is heartening
to see that the manufacturers of gas turbines and gas engines are working on
prototypes that will be able to switch over from natural gas to 100% hydrogen fuel with
minimal modifications.
The competitiveness of natural gas relative to coal in power production is highly
dependent on regional market conditions, particularly fuel prices. However, growth
prospects for gas are affected not only by the competitiveness of gas prices, but also
by recognition of the local air pollution and climate benefits of gas over coal. The
introduction of carbon taxes and regulation of plant emissions could encourage coal-
to -gas switching.
