epsrc thermal management of industrial...
TRANSCRIPT
1
EPSRC THERMAL MANAGEMENT
OF INDUSTRIAL PROCESSES
Case Study: Sheffield District Heating
(December 2010) Report Prepared by:
SUWIC, Sheffield University
Researcher: Dr Q. Chen
Investigators: Professor Jim Swithenbank Professor Vida N Sharifi
Sheffield University Waste Incineration Centre (SUWIC) Department of Chemical and Biological Engineering Sheffield University
2
Executive Summary
Energy sustainability and greenhouse gas emissions have become critical
international social issues. Among all the state-of-the-art technologies, combined
heat and power (CHP) can help address both issues with efficiency better than
separate heating and electrical generating plants. Sheffield district heating network
is one of the largest and most successful CHP schemes operating in the UK. By
harnessing the energy from this local energy recovery facility, the district heating
system provides an economical, low carbon and environmentally friendly heat source
to businesses; householders and local authority in Sheffield.
In accordance with our EPSRC grant proposal, Sheffield University has carried out
a techno-economic feasibility study of Sheffield District Heating system. Two key
parameters were investigated: i) energy efficiency and ii) reduction in CO2 emissions.
Some main findings from this study are as follows:
1. By reclaiming a certain amount of the by-product heat for heating purposes,
combined heat and power technology can achieve the energy thermal
efficiency higher than 75%. Recovery of energy from MSW for heat and
power generation can reduce the CO2 emissions by around 70,000 tonnes per
year.
2. The recovery of low grade latent heat from water vapour in the flue gas can
greatly increase the thermal efficiency of the CHP plant from 75% to 93%. It
is possible to achieve higher efficiencies if the temperature of return water
temperature in the system is lowered to about 30C. Condensation of flue gas
not only helps to recover certain amount of low grade latent heat, but also
saves up to 90,000 tonnes of CO2 emissions per year.
3. Solid Recovered Fuel (SRF) and Refuse Derived Fuel (RDF) have much better
fuel qualities (e.g. calorific value) when compared to Municipal Solid Waste
(MSW). The electrical and thermal efficiencies of SRF-fired CHP systems
are higher than those of MSW-fired plants. The net CO2 emission reduction
by SRF (80,000tonnes/year) is greater than those by MSW in a CHP system.
4. A simplified cost analysis is performed to evaluate potential benefits for an
MSW fired CHP/DH system using SRF as a fuel. The capital cost for the
proposed MBT facility is around €57.3 million. Given no time value of
money, the payback period for this replacement is approximately 13 years.
3
List of Contents
1. Introduction ............................................................................................................1
1.1 CHP and District Heating .............................................................................1
1.2 Solid Recovered Fuel....................................................................................5
2. Sheffield District Heating System ..........................................................................9
2.1 Energy-from-Waste System..........................................................................9
2.2 District Heating Scheme.............................................................................11
2.3 Emissions....................................................................................................12
3. Scenario Analysis .................................................................................................14
3.1 Base Cases: Fossil Fuel Fired Power Generation and Heating Systems ....15
3.1.1 Case I-A: Coal-fired Power Plant ....................................................15
3.1.2 Case I-B: Gas-fired Condensing Boiler for Residential Heating ....17
3.2 Case II: MSW-fired CHP System ...............................................................18
3.3 Case III: SRF-fired CHP System................................................................20
3.4 Efficiencies of Energy Conversion and Utilisation ....................................21
3.5 Environmental Impacts...............................................................................23
3.5.1 Reduction in CO2 Emission (Energy Recovery from MSW) ..........23
3.5.2 Reduction in CO2 Emission (Energy Recovery from SRF).............24
3.5.3 Influence of Flue Gas Condensation on CO2 Emissions .................24
3.5.4 Impacts on Other Flue Gas Emissions.............................................25
3.6 Economic Analysis .....................................................................................27
3.6.1 Capital Cost of MBT Facility for SRF Production..........................28
3.6.2 OPEX and CAPEX for SRF Production..........................................28
3.6.3 Benefits ............................................................................................28
4. References ............................................................................................................31
1
1. Introduction
Energy sustainability and greenhouse gas emissions have become critical
international social issues. Energy demand across the world continues to grow in
long term. The effect of energy production and usage on the global environment has
triggered increasing concerns worldwide. To address these issues, alternative energy
sources and technologies have gradually attracted more and more attention.
Governments target for reductions in carbon dioxide emissions and an increase in
the percentage of electricity generated by renewables. For example, the UK
government has published its Low Carbon Transition Plan, which sets out how the
UK will cut CO2 emissions by 34% of 1990 levels by 2020 and at least 80% by 2050
(HM Government, 2009). In this plan, the government expects 40% of the power
used in 2020 to come from low carbon sources – 30% from renewables, the rest from
nuclear (including new build) and clean coal. For homes and communities, around
15% of the yearly emission cuts between now and 2020 will be achieved by making
homes more efficient and supporting small scale renewable energy.
Among all the state-of-the-art technologies, combined heat and power (CHP) can
achieve both targets with efficiency better than separate heating and electrical
generating plant. District heating supplied by a CHP plant increases the overall
thermal efficiency from approximately 50% for the best electricity generating plants
(CCGTs) to approximately 85% for a CHP plant. This can potentially reduce CO2
emission by 30%. On the other hand, municipal solid waste (MSW) generally
represents almost 20% of the total energy needs of a city. Therefore, when MSW is
used as fuel for a CHP plant, the combination can contribute a major reduction to net
CO2 emissions.
1.1 CHP and District Heating
The EU Cogeneration Directive (EU 2004) defines CHP as delivering minimum
levels of primary energy savings, with savings of 10% required for most CHP capacity.
This legal requirement, which must be met to qualify for most forms of public support,
is enacted in the UK through the CHP Quality Assurance (CHPQA) programme
(CHPA 2010). Generally, CHP systems are based predominantly upon existing,
proven power generation technologies: steam turbines, gas turbines and reciprocating
engines used the world over to generate energy. This use and adaptation of existing
technology not only contributes to the relatively low cost of CHP, but also ensures
that it is a proven and reliable technology, capable of delivering an immediate impact
in transforming our energy system. Connected to a district heating network, CHP
can provide heat and power to multiple customers in city centres, towns, villages,
industrial zones and other built environments with a dense ‘heat load’, this being a
high concentrated demand for heat. Up to 2007, over 4,000 CHP and district heating
utilities are operating in towns and cities across Europe.
2
District heating is a convenient way to heating space and tap water. In many
processes, for example when electricity is generated or waste is burned, large parts of
the energy are set free in the form of surplus heat. The fundamental idea behind
modern district heating is to recycle this surplus heat which otherwise would be
wasted- from electricity production, from fuel and biofuel-refining, and from different
industrial processes.
A district heating system is essentially composed of a network of insulated pipes
used to deliver heat, in the form of hot water or steam, from the point of generation
(source) to an end user. The network provides a means to transport heat efficiently.
The carrier pipe system is mainly of steel but other materials such as plastics are used.
The distance a network can reach is easily extended by simply adding more providers
of heat, or ‘heat sources’, along the way (CHPA 2010).
In addition to energy from fossil fuels, heat sources for district heating scheme
include,
• Waste heat from power generation.
• Heat produced by the incineration of municipal waste.
• Reject heat from process industries.
• Landfill gas extraction.
• Geothermal (hot rocks) and thermal springs.
• Biomass - Agricultural and Animal waste products.
• Heat pumps.
• Fuel cells and solar thermal arrays
The ability to integrate diverse energy sources implies that end users are
independent upon a single source of supply. This helps guarantee service reliability
and continuity of the system. District heating networks also have the ability to
balance the supply and generation of heat, across location and over time. Over the
course of the day, heat demand shifts between residential consumers to commercial,
industrial and public buildings and back again. A heat network can match and
manage these flows, whilst maximising the utilisation of the plant providing the heat.
Demand can also be managed across seasons, with networks supporting the operation
of distributed absorption cooling plants in the summer providing cooling on a
significant scale (CHPA 2010).
Heat sources can be either directly connected to the distribution system or indirectly
connected through a heat exchanger. The direct system is limited to use where water
is the distribution medium and where the water quality and pressure requirements are
the same for the heat source and the building’s internal distribution system. The
indirect connection allows the heat source and the distribution system to be operated
as separate systems with different temperature and pressures, allowing more design
flexibility for both systems.
The district heating medium (steam or hot water) is distributed from the heat source
through supply pipes to the end users interface and is returned after heat has been
3
extracted. Delivery is accomplished by circulating pumps which create a pressure
differential between the supply and return pipes. Pumps are selected to overcome
the flow resistance in the supply and return pipes and also the pressure differential in
the customer installation at the end of the system or the index point. The use of
variable speed drives to control the pumps ensures that consumed power is
minimised.
Figure 1 illustrates the principle of variable pumping (Skagestad and Mildenstein
1999). In areas where the ground level varies dramatically, it is important to ensure
that a minimum pressure is maintained in the return pipe to avoid evaporation and
cavitation in equipment such as pumps and valves. Direct district heating systems
typically operate with flow and return temperatures of 85/65°C and pressures of
below 6 bar, and indirect systems with temperatures of 110/65°C and pressures of
below 16 bar. The greater the temperature-difference between the flow and return,
the lower the flow rate required.
Figure 1 District heating network pressure diagram
°°
Figure 2 Pipe diameters in relation to temperature difference
4
In Figure 2, difference in pipe sizes is compared when operating with alternative
temperature differences for two heating capacities. The district heating operator will
seek to ensure that the secondary return water temperature is as low as possible to
minimise pumping. It is common practice to compensate the district heating
medium supply temperature. When the heating demand decreases, its supply
temperature should be decreased to reduce energy losses from the pipe system. By
this adjustment, the energy efficiency using low-grade heat sources can be increased.
Figure 3 presents a typical example showing the variations in the supply temperature
depending on the outdoor temperature.
Figure 3 District heating compensation curve of the supply temperature
For the pipe networks, there are a number of different types of pipe material
available on the market. The vast majority of systems are based on pre-insulated
steel pipes. In smaller dimensions, the media pipe may be made of stiff or flexible
plastic pipes. The district heating medium supply temperature is often limited by the
type of pipework used. A common supply temperature range is 85 to 120°C. The
low end of the range is normally the temperature required to meet domestic hot water
needs during the summer. Pressures can go up to 25 bar but the majority operates
with a maximum pressure of 16 bar, while 25 bar is common in transmission systems.
By reducing the normal operating temperature and by reducing the effects of pressure
fluctuations, the life of the pipework can increase dramatically. Figure 4 illustrates
this phenomenon.
5
Figure 4 Relationship between expected life of pipe and continuous operating
temperature
District heating can serve residential, public and commercial buildings as well as
meeting industrial demands for low-temperature heat. Building systems may be
connected directly or indirectly to a district heating distribution system. With a
direct connection, the heating medium is distributed within the building to directly
provide heat to terminal equipment such as radiators, unit heaters, etc. An indirect
connection uses a heat exchanger in the building to transfer the energy from the
district heating distribution system (primary system) to the building distribution
system (secondary system). The heat exchanger serves as an interface between the
district heating network and the building’s own radiator and hot water system.
There’s no boiler, no burning flame needed in the house and maintenance is taken
care of by professionals. Thus, compared to owning and operating an on-site boiler,
conversion to district heating can benefit the end users through increased reliability,
greater comfort, reduced investment, operating cost savings, increased energy
efficiency and greater fuel flexibility.
1.2 Solid Recovered Fuel
A major drawback to combustion of waste is that the fuel is likely to be
6
non-homogenous, damp and it will come in large fragments. The water content will
lower the recoverable energy content per unit mass of fuel. The lack of homogeneity
will make for inconsistent combustion which will cause fluctuations in emissions
adding to the difficulty of cleanup, and it impedes designing for maximum efficiency.
In some cases, the combustion process often neglects materials recycling which
comes higher in the waste hierarchy, and so is not an ideal sustainable solution
(WMAA, 2003).
Turning waste into refuse derived fuel (RDF) or solid recovered fuels (SRF) is one
of the options available for waste treatment that can both reduce the volumes of waste
sent to landfill and simultaneously recover embodied energy from the waste material
(Arias-Garcia and Gleeson, 2009). SRF and RDF are fuels produced from
non-hazardous municipal solid waste (MSW) and commercial and industrial (C&I)
wastes. The term SRF is commonly used in place of RDF. SRF is a refined form
of RDF, intended for use in energy recovery facilities, which has been produced to
meet a standard published by the European Committee for Standardization (CEN)
standard, CEN/TS 15359. The specifications and classes are shown in Table 1.
Table 1 CEN/TS 15359 Solid recovered fuels – specifications and classes
The input waste can be production specific waste, municipal solid waste, industrial
waste, commercial waste, construction and demolition waste and sewage sludge.
SRF represents an interesting route to the development of CHP infrastructure. Some
of the benefits of SRF fired CHP are (Arias-Garcia and Gleeson, 2009):
� �the facilitation of an easier planning process,
� �increased overall energy efficiency,
� �flexibility of location, volume, security of supply, price and
7
� the possible development of supply chain for waste wood disposal and
co-firing.
During SRF production, plants take bulk waste and remove recyclable or
non-combustible materials, the remainder then being dried and shredded or processed
into a uniform fuel. This fuel has a calorific value much higher than that for
municipal waste. SRF can take various forms including a loose or flock material,
which has been size-reduced or further densified to produce a fuel pellet, the final
form of SRF is dependent on the mode of energy recovery. Consequently, there are
many methods for producing SRF. These may include some or all of the following
processing systems: screening, air classification, dry, pelletising, magnetic recovery
(Wilen 2004, Chen et al. 2008).
Figure 5 Flow diagram of SRF production from household waste and commercial
waste (Wilen 2004)
Figure 5 presents a flow diagram of a typical SRF production plant. Roughly
source separated household waste passes through a fairly complicated production
process including operations like crushing, magnetic separators, screening,
eddy-current for non-magnetic materials, pneumatic separation and optic sorting.
The purpose is to separate the impurities (typically biowaste, glass, metals, aluminium,
PVC) as much as possible and to produce good quality SRF to be used in energy
recovery plants. As commercial waste generally contains little biowaste or fine
impurities, the sieving of the pre-crushed waste is usually bypassed (Wilen 2004).
8
In general, SRF or RDF will burn in an incinerator cleaner and hotter. The process
will therefore be slightly more efficient and will need less of a cleanup operation.
RDF incineration is considered a more environmentally sound option for MSW
incineration, a life cycle analysis described by Ferrer et al. (2005) outlines RDF
incineration over mass burn as more favourable option: “Life cycle analysis favours
RDF combustion over mass burning because of the better environmental
performance”. The potential growth in RDF incineration is illustrated by future
plans for Finland, the National Waste Management Plan shown abandonment of mass
burn method and unsorted MSW to Landfill, instead focusing on source separation,
resource recovery and the utilisation of RDF (Strafford 2006).
9
2. Sheffield District Heating System
Sheffield district heating network is one of the largest and most successful CHP
schemes operating in the UK. It has been developed around a municipal solid waste
(MSW) incinerator located close to the city centre since 1988. By harnessing the
energy from this local energy recovery facility, the district heating system provides an
economical, low carbon and environmentally friendly heat source to businesses;
householders and local authority in Sheffield. It is built using the latest technology
and is designed to maximise the efficient generation of combined heat and power for
the city’s residents (Veolia, 2010).
On average, Sheffield residents produce over 240,000 tonnes of waste every year.
Non-recycled waste collected in Sheffield is taken to the energy recovery facility (i.e.
the MSW incinerator) of the district heating system where it is burnt at temperatures
of over 850°C in a specially controlled environment. A network of pressurised hot
water pipelines under the city is integrated with the incinerator to recover heat from
household waste. Owing to this innovation, the city sends a relatively low level of
waste to landfill compared to most other regions in the UK. In 2001, Veolia
Environmental Services singed a 35-year waste management contract with Sheffield
City Council and is responsible for maintaining the waste collection and plant
operation and services (Veolia, 2010).
2.1 Energy-from-Waste System
In Sheffield CHP system, the heat from MSW incineration is converted to steam
and used to generate electricity and for districting heating. The incinerator is
designed to handle 225,000 tonnes of municipal solid waste a year (Veolia, 2010).
Figure 6 shows the process flow diagram of the energy recovery system. Waste (1)
from households, local authority services and some local businesses is brought to the
energy recovery facility. It is tipped into a waste storage bunker (2). From the
bunker the waste is lifted into a feed hopper (3) by an overhead crane (fully automatic
grab loading crane) at a rate of 28 tonnes per hour. The hopper feeds the waste into
a single incineration unit where it is burned at temperatures in excess of 850°C. Gas
fired auxiliary burners are used to ensure that the correct temperature of 850°C is
reached before any waste can be fed into the incinerator (Veolia, 2010).
Above the incinerator, a large CNIM 4-pass vertical boiler (5) produces superheated
steam at 400°C. A condensing steam turbine (10) uses this 40bar steam to generate
electricity for the National Grid and to produce hot water (11) for the district energy
network. Pressure take-offs from the condensing steam turbine allow a variety of
combinations to be used to optimise the use of energy between heat and electricity.
Air cooled condensers, sized for full load rejection, allow the thermal cycle to be
completed with the minimum environmental impact (Veolia, 2010).
10
(a)
10
11
1010
1111
(b)
Figure 6 Process flow diagram of the energy from waste facility (Veolia, 2010)
Urea (4) is introduced to the furnace to treat NOx (Oxides of Nitrogen) emissions.
Lime and activated carbon (6) is introduced to neutralise the acidity of the flue gas
and adsorb other pollutants. The cooled flue gases pass through a filter house (7)
where the particulate (dust) is captured by 1760 filters. Particulate collected in this
process is then stored in a silo for separate disposal later. Cleaned gases (8) are then
released through the chimney. These gases are continuously monitored to ensure
they meet strict environmental regulations.
An electromagnetic overband separator (12) removes metal from the ash. The
metal is delivered to a local company for recycling. Ash (13) from the incineration
process goes into a bunker. Particulates removed from the filtering process are taken
to a process plant for treatment and then safe disposal.
Table 2 summarises some technical data for the MSW incineration plant.
11
Table 2 Technical summary of the energy-from-waste system (Veolia, 2010)
Total plant capacity 225,000 tonne of MSW
Bunker storage capacity 2,700 tonne of MSW
Plant throughput rate 28 tonne/hr @ 9.21MJ/kg
72 MW
Grate Martin reciprocating, 5 rows, 13 steps
Steam flow rate 86 tonne/hr
Steam pressure 40 bar
Steam temperature 400 °C
Maximum electrical output 19 MW
Maximum thermal output 60 MW
Chimney height 75 m
Gas fired auxiliary burners 2 × 20 MW
2.2 District Heating Scheme
At Sheffield CHP system, the plant generates up to 19MW of electricity for the
national grid, enough to power up to 22,600 homes. Up to 60MW of heat is supplied
to over 140 buildings connected to the district heating network so far. Currently,
these include 3 university campuses, 4 swimming pools, 3 theatres, 3 art galleries, 2
cinemas, 1 radio station, 1 glasshouse, 25 hotels, 21 private developments, other local
authority housing and corporate buildings, etc. Over 2,800 dwellings have benefited
from district energy in the Sheffield area. The flow diagram of the CHP system is
shown in Figure 7.
Figure 7 Flow diagram of the Sheffield CHP system (Veolia, 2010)
The district heating system provides buildings in Sheffield City centre and the
12
surrounding areas with a low carbon energy source that is generated from MSW in a
central location, converted to hot water and pumped through a network of
underground pipes and delivered to a heat exchanger in buildings of all sizes and
types. There are currently 44km of pipeline installed across the city centre through
two networks. The system is supported by back-up facilities with 3 pre-heated
stand-by/peaking boiler stations ready to come on line at a moments notice with 84.6
MW of capacity. These back-up boiler stations consists of 5 gas and 4 oil-fired
boilers in total. Figure 8 shows schematically the process diagram of the district
heating system. In a typical year around 120,000 MWh of heat is delivered to
buildings in Sheffield City Centre and the surrounding areas. Table 3 summarises
the technical data for the district heating system (Veolia, 2010).
Figure 8 Districting heating scheme (Veolia, 2010)
Table 3 Technical data for the Sheffield district heating system (Veolia, 2010)
Hot water temperature 120 °C
Water pressure 16 bar
Pumps in the distributed pipework system 15
Capacity of backup boilers 87 MW
2.3 Emissions
The MSW incinerator is operating under the regulation of EU Waste Incineration
Directive and the Pollution Prevention and Control (PPC) regime (Defra 2009).
Table 4 presents the air emission limit values for the Sheffield CHP plant to meet.
The reference conditions are: temperature 0°C, pressure 101.3kPa and 11% oxygen
13
dry gas. Figure 9 presents the monthly-averaged daily emission values from the
MSW incinerator. As can be seen, the missions are well below the limit values.
Table 4 Daily average emission limit values for the incinerator (Defra 2009)
Pollutant Emission limits Units
Dust 10 mg/m3
Total organic carbon (TOC) 10 mg/m3
HCl 10 mg/m3
CO 50 mg/m3
SO2 50 mg/m3
NOx 200 mg/m3
0
10
20
30
40
50
60
70
80
90
100
01/0
9
03/0
9
05/0
9
07/0
9
09/0
9
11/0
9
01/1
0
03/1
0
05/1
0
07/1
0
09/1
0
% o
f E
mis
sion
Lim
it
Dust
TOC
HCl
CO
SO2
NOx
Figure 9 Air emissions from the Sheffield CHP plant in recent years (Veolia, 2010)
14
3. Scenario Analysis
Sheffield University has carried out a series of calculations (using Sheffield CHP
plant as a case study) in order to investigate the merits of CHP-DH (combined heat
and power generation with district heating). The application of low grade heat
recovery and use of SRF as a fuel were also considered. Some primarily economical
analysis was also conducted. Table 5 presents brief descriptions of all 3 cases.
Table 5 Summary of the case studies
Case Category Description
Base case A Coal-fired power generation system Based on Drax
Power Plant Case I
Base case B Residential gas-fired condensing boiler 30kW
A MSW-fired CHP system for power
generation only
B MSW-fired CHP system for heat supply
only
C MSW-fired CHP system for district
heating
Case II
D
MSW-fired CHP system for district
heating with lower return water
temperature
Case III SRF-fired CHP system for district
heating
Based on
Sheffield CHP
Plant
15
Figure 10 CO2 emissions from SRF preparation, transportation and combustion
(Gaillarde 2008)
These cases can be compared with each other in terms of their contribution to the
greenhouse gas emissions from the plant. Only an assessment encompassing the
whole energy cycle − from conversion to delivery (thus including transportation) −
can give a realistic picture (Euroheat & Power 2007). However, as shown in Figure
10, CO2 emissions from the preparation and transportation of SRF are minor when
compared to emissions from SRF combustion. Therefore, in this work, only the
emissions from SRF combustion and related efficiencies were considered.
3.1 Base Cases: Fossil Fuel Fired Power Generation and
Heating Systems
As shown in Table 5, these two base cases are based on a coal-fired power plant and
a natural gas-fired residential heating boiler. The base cases correspond to separate
power generation and heating plants that are widely used throughout the world.
Energy efficiencies and CO2 emission factors were calculated as reference in this case
study.
3.1.1 Case I-A: Coal-fired Power Plant
This case is based on Drax Power Plant, the largest coal-fired power station in the
UK (Drax 2010). It consists of 6 power generating units. Each unit has a capacity
of 660MW, giving a total capacity of 3960MW. Although it is capable of co-firing
biomass and petcoke, coal is assumed to be the only fuel in this case study for the
16
sake of simplicity.
Drax Power Station generates 7% of electrical power required by the UK. At full
output, it consumes around 36,000 tonnes of coal a day (Drax 2010). The coal fuel
comes from a mixture of both domestic and international sources, with domestic coal
coming from mines in Yorkshire, the Midlands and Scotland, and foreign supplies
coming from Australia, Colombia, Poland, Russia and South Africa. Each of the six
Babcock Power boilers supply superheated steam (16.6MPa and 563°C) to a steam
turbine set. Each steam turbine consists of one high pressure (HP) turbine, one
intermediate pressure (IP) turbine and three low pressure (LP) turbines. One HP
turbine generates 140MW of electricity. Exhaust steam (4.2MPa and 360°C) from
HP turbines is fed back to the boiler and reheated (4.02MPa and 565°C), then fed to
the 250MW IP turbines and finally passes through the 90MW LP turbines.
Table 6 presents assumptions used in the calculations. Table 7 gives the proximate
and ultimate analysis results (BCURA 2002) for the Daw Mill coal used in the plant.
The calculation results show that the electricity output is approx. 4000MWe and the
net electrical efficiency of the plant is around 33% correspondingly. As a result, the
CO2 emission factor for the power station is approx. 0.26kg/MJ (or 0.938kg/kWh).
In 2007, Drax produced 26.66TWh electricity in total (Drax 2007). Thus, based on
our calculations, the estimated CO2 emission from the plant was around 25 million
tonnes in 2007. This value is slightly higher than that reported by Drax, which was
22,160,000 tonnes in 2007 (Drax 2007). This overestimation could be due to the
difference in fuel composition and slight underestimation of the electrical efficiency
in the calculations.
Table 6 Main assumptions used in the Case I-A
Parameter Unit
Coal feed rate 1500 t/hr
Excess air 20 %
Thermal energy loss in the combustor 5 %
Main steam pressure 166 bar
Main steam temperature 563 °C
Turbine efficiency 85 %
Steam condenser pressure 0.05 bar
Temperature of flue gas exiting the boilers 140 °C
Table 7 Properties of the coal supplied by Daw Mill
Moisture 12.0
Volatile Matter 33.5
Ash 4.1
Proximate
analysis
(%ar)
Fixed Carbon 50.4
C 81.3 Ultimate
H 4.8
17
O 11.5
N 1.3
analysis
(%, dry ash
free) S 1.1
NCV (MJ/kg) 28.9
3.1.2 Case I-B: Gas-fired Condensing Boiler for Residential Heating
Condensing boilers have now replaced most of conventional designs in powering
domestic central heating systems in Europe. In the UK, since 2005 all new gas
central-heating boilers fitted in England and Wales must be high-efficiency
condensing boilers. Condensing boilers are designed to capture a fraction of the
latent heat, i.e., the energy released by condensing water vapour in the flue gas. By
extracting this latent heat in the condensing boiler, the whole system can achieve
higher efficiency levels than non-condensing boilers. Typical models of condensing
boilers offer efficiencies around 90% (based on the lower heating value of fuels).
Case I-B is based on a 30kW domestic condensing boiler for residential heating.
Table 8 lists the assumptions made in the calculations. The fuel is natural gas with
its properties as shown in Table 9. In this case, the dew point of the flue gas is
approximately 56°C. The return water temperature is well below this dew point and
a portion of the water vapour latent heat can be recovered.
Table 8 Main assumptions used in the Case I-A
Parameter Unit
Heat input 30 kW
Fuel feed rate 3.25 m3/hr
Excess air 10 %
Thermal energy loss in the combustor 2 %
Return water temperature 40-45 °C
Temperature of flue gas exiting the boilers 50 °C
Table 9 Assumed composition of natural gas in Case I-B (Uniongas 2010)
Component Range Assumed value
Methane, vol% 95 87-96
Ethane, vol% 3 1.5-5.1
Nitrogen, vol% 2 0.7-5.6
Net calorific value, MJ/kg 44.7
Gross calorific value, MJ/kg 51.0
For this gas fired condensing boiler, the output heat capacity is 28.4kW. The
thermal efficiency thus reaches 94.9% (based on lower heating value) or 83.1%
(based on higher heating value of the fuel). The CO2 emission factor is
18
approximately 0.06kg/MJ (or 0.23kg/kWh).
3.2 Case II: MSW-fired CHP System
In this case, a series of thermodynamic calculations were carried out to obtain mass
flow rates, temperatures and enthalpies for all the streams of the Sheffield CHP
System using heat and mass balances.
Table 10 lists the assumptions made for the calculations. Typical composition of
British MSW was used to represent the properties of MSW for Sheffield CHP plant,
as presented in Table 11. In the calculations, it was assumed that Sheffield CHP
plant had a net energy input of 72MWth. Calculations were conducted for four
different scenarios, namely,
� Case II-A: for electricity production only
� Case II-B: for district heating only
� Case II-C: combined heat and power for district heating
� Case II-D: combined heat and power for district heating with low return
water temperature
Table 10 Some assumptions used in the Case II
Scenario A B C D
Energy Input (based on LHV), MW 72 72 72 72
MSW feed rate, t/hr 30 30 30 30
Excess air, % 60 60 60 60
Main steam pressure, bar 40 - 40 40
Main steam temperature, °C 400 - 400 400
Turbine efficiency, % 85 - 85 85
Pressure of steam condenser or take-off for heating, bar 0.05 - 5 5
Steam temperature under the above pressure 32.8 - 151.8 151.8
Temperature of flue gas exiting the boilers, °C 120 120 120 35
Pressure of hot water for district heating, bar - 16 16 16
Temperature of hot water for district heating, °C - 120 120 120
Return water temperature, °C 65 65 30
Using the data presented in Tables 10 and 11, the electricity and/or thermal outputs
of the plant can be calculated for each of the four scenarios. In Case II-A where all
MSW is used to produce electricity, the total output is 19.0MWe with a net electrical
efficiency of 26.4%. In Case II-B where all MSW is burned to produce heat for
district heating, the thermal energy is approximately 60.3MWth with a thermal
efficiency of 83.7%. These outputs are identical to those listed in Table 2.
In the cases where both electricity and heat are produced, the electricity outputs are
19
both 7.94MWe (Cases II-C and II-D) and the electrical efficiencies are 11.0%. In
Case II-C, the thermal output for district heating is 47.5MWth. The thermal
efficiency is approximately 65.9%.
As MSW has the moisture content as high as 31%, the latent heat of water vapour in
the flue gas is quite high. This portion of low grade heat can be recovered using flue
gas condenser as additional energy source for district heating. However, the
operation of the flue gas condenser requires return water with low temperature below
the dew point of the flue gas (55.7°C). Therefore, in Case II-D, the temperature of
return water from the district heating system is only 30°C lower than in Case II-C.
The flue gas from the incinerator (or Energy-from-Waste system) is used to preheat
the return water. Thus, some latent heat in the flue gas can be recovered in this case.
As a result, the thermal output in Case II-D is 59.2MWth with the thermal efficiency
of 82.2%.
As MSW consists of hydrocarbons, combustion of MSW is also a source of CO2
emission. In all the four scenarios of Case II, the MSW feed rates are assumed to be
the same (30t/hr). Consequently, the emission rates of CO2 are identical (i.e.
24.3tonnes/hr ) for all the scenarios. In Case II-A where all MSW is used to produce
electricity, the CO2 emission factor is 0.355kg/MJ (or 1.28kg/kWh). In Case II-B
where all MSW is burned to produce heat for district heating, the CO2 emission factor
is 0.112kg/MJ (or 0.40kg/kWh).
20
Table 11 Typical composition of British MSW (Optimat 2001)
3.3 Case III: SRF-fired CHP System
In this case, the fuel for Sheffield CHP System is assumed to be SRF. Table 12
presents the fuel properties of RDF and SRF samples. As shown in Table 12, RDF
and SRF have much lower moisture content and ash content than MSW. The carbon
content and net calorific value of RDF and SRF are higher than MSW. As SRF is a
refined form of RDF, the moisture and ash contents of SRF are slightly lower than
RDF. Table 13 lists the conditions for the calculation in this case. Due to the low
moisture content in the SRF fuel, the water vapour fraction in the flue gas after SRF
combustion is also small. As the dew point of the flue gas is around 36°C, the latent
heat of water vapour in the flue gas is very difficult to recover to preheat the return
water from district heating system.
21
Table 12 Typical properties of RDF and SRF (Hernandez-Atonal et al. 2007; Dunnu
et al. 2009)
Sample (as received) RDF SRF
Moisture (%ar) 3.7 2.60
Volatile Matter (%ar) 67.6 77.8
Ash (%ar) 18.9 14.8
Fixed carbon (%ar) 9.8 4.8
C (%daf) 61.2 64.89
H (%daf) 8.2 10.04
O (%daf) 26.6 23.51
N (%daf) 1.3 1.05
S (%daf) 0.2 0.51
Cl (% daf) 2.5 -
NCV, MJ/kg 20.8 25.54
Table 13 Some assumptions used in the Case III
Energy Input (based on LHV), MW 72
SRF feed rate, t/hr 10.1
Excess air, % 120
Main steam pressure, bar 40
Main steam temperature, °C 400
Turbine efficiency, % 85
Pressure of steam condenser or take-off for heating, bar 0.5
Steam temperature under the above pressure 151.8
Temperature of flue gas exiting the boilers, °C 120
Pressure of hot water for district heating, bar 16
Temperature of hot water for district heating, °C 120
Return water temperature, °C 65
Based on mass and energy balances, the electricity output in this case is
approximately 8.4MWe, corresponding to an electrical efficiency of 11.7%. The heat
output for district heating is 50.4MWth and the thermal efficiency is thus 69.9%. In
this case, the CO2 emission rate is around 19.9t/hr.
3.4 Efficiencies of Energy Conversion and Utilisation
Figure 11 summarises the electrical and thermal efficiencies calculated for all
cases mentioned above. Cases I-B and II-B are two cases for heat production only.
The energy losses are mainly due to the flue gas released to the atmosphere. Hence
the thermal efficiencies for these two cases are well above 80%. As the gas-fired
boiler in Case I-B is working with flue gas condensing, the efficiency is extremely
high (around 93% based on LHV).
22
In Case I-A, as the parameters of superheated steam (temperature and pressure)
are higher than those in Cases II and III, the electrical efficiency is therefore the
highest among all the cases. In the cases of combined heat and power generation,
steam is taken off from the turbine under 5bar in order to reject heat at a fairly high
temperature to enable district heating. This lowers the overall plant electrical
efficiency to 11% in the cases Cases II-C and II-D from 26% in Case II-A where the
plant operates for electricity only.
However, in cases where only electric power is generated, a large amount of heat is
wasted and released to the atmosphere through cooling towers and flue gases. Thus,
a maximum 26-35% is achieved for the overall plant (electrical) efficiency in these
cases. By contrast, combined heat and power technology captures a certain amount
of by-product heat for heating purposes. Although the electrical efficiency is
inevitably reduced, the thermal efficiency is thus greatly increased. The overall
energy efficiencies of the plant in Cases II-C, II-D and III are above 75%.
0
10
20
30
40
50
60
70
80
90
100
Case I-A Case I-B Case II-A Case II-B Case II-C Case II-D Case III
Eff
icie
ncy
, %
Thermal efficiency
Electrical efficiency
Figure 11 Comparison of electrical and thermal efficiencies for all the cases
It should be noted that the recovery of low grade latent heat from water vapour in
the flue gas can greatly improve the thermal efficiency of the plant if the fuel has
fairly high moisture content. As shown in Case II-D, the total plant energy
efficiency is close to that from the domestic gas-fired condensing boiler. The
achievement of this high efficiency requires sufficient low temperature of return water
from district heating system.
23
3.5 Environmental Impacts
The CO2 emission rates and emission factors for all the cases are calculated and
summarised in Table 14, together with the electricity and heat outputs. It should be
noted that Case I is based on the combustion of fossil fuels whereas Cases II and III
are based on waste combustion. Based on the data from Case I, some
environmental impacts of MSW/SRF fired CHP are briefly discussed. The influence
of low grade latent heat recovery on CO2 emission reduction is also analysed.
Table 14 Summary of the calculation results for all the cases
Electricity, MWe Heat, MWth CO2, t/hr Emission factor, kg/MJ
Base case A 4000 - 3748 0.26 Case I
Base case B - 28.4 6.4×10-3
0.06
A 19 - 0.36
B - 60.3 0.11
C 7.94 47.5 - Case II
D 7.94 59.2
24.3
-
Case III 8.4 50.4 19.9 -
3.5.1 Savings in CO2 Emission (Energy Recovery from MSW)
As shown in Table 14, the emission factors (Cases II-A and B) from MSW-fired
power and heat generation appear to be higher than those from the coal-fired power
plant (Case I-A) and a gas-fired condensing boiler (Case I-B). However, various
assessments have shown that about 20-40% (depending strongly on the degree of
separate collection of paper and organic waste) of the carbon in MSW is derived from
fossil sources, e.g., plastics (as shown in Figure 12). The remainder is derived from
biomass and can be considered a renewable resource (IEA Bioenergy 2003).
Consequently, the non-renewable amount of CO2 emissions from MSW-fired power
generation (Case II-A) is approximately 0.14kg/MJ or 0.52kg/kWh (i.e. 40% of the
emission of 0.36 kg/MJ). Similarly, the non-renewable amount of CO2 emissions
from MSW-fired heat production (Case II-B) is about 0.04 kg/MJ or 0.16kg/kWh.
These values are thus less than the CO2 emission factors of the coal-fired power plant
(Case I-A) and the gas-fired condensing boiler (Case I-B).
Therefore, recovery of energy from MSW for power generation or heat production
produces a net reduction in greenhouse gas emissions. In Case II-A, the total CO2
emission reduction is 2.28kg/s, or over 70,000 tonnes per year. In Case II-B, the
saving in CO2 emission is thus 0.96kg/s, equivalent to approximately 30,000 tonnes
per year. In Case II-C where both power and heat are produced from MSW, the total
CO2 emission saving is 2.21kg/s, which equals around 69,000 tonnes/y.
24
20%
20%60%
Renewable (biomass derived)carbon - 60%
Variable fraction - 20%
Non-renewable (fossil derived)carbon - 20%
Figure 12 Sources of carbon content in MSW
The calculated values of CO2 emission reduction by no means take into account the
emissions from MSW landfill. As the energy in MSW is recovered for power and
heat generation, the emissions from traditional landfill are avoided. If the MSW was
consigned to landfill then about 70kg of methane (actual range 50-100kg) could be
released for each tonne of waste. Given the higher global warming potential of
methane, this is equivalent to 1610kg CO2 per tonne of MSW. In modern landfills
about half of the methane can be extracted and used for energy production, therefore
reducing the overall emissions (IEA Bioenergy 2003).
3.5.2 Savings in CO2 Emission (Energy Recovery from SRF)
Given the same energy input for the plant, SRF gives less CO2 emission rate than
MSW, as shown in Table 14. The renewable carbon content in SRF is about 50-55%
(Zucchelli 2009). Thus, the non-renewable CO2 emission in Case III is
approximately 9.55tonnes/hr. Consequently, the CO2 emission saving is 2.55kg/s
and the annual CO2 emission reduction is around 80,000tonnes.
3.5.3 Influence of Flue Gas Condensation on CO2 Emissions
As shown in Figure 11, low grade latent heat recovery in Case II-D has an
advantage in improving the overall thermal efficiency of the CHP system. This
therefore results in greater CO2 emission reduction than Case II-C. In Case II-D, the
saving in CO2 emission is 2.92kg/s. Thus, the annual CO2 reduction is
approximately 91,000tonnes.
Figure 13 summarises all the calculated savings in CO2 emissions for Cases II and
III. As shown, the net CO2 emission reduction by SRF is greater than those by
25
MSW in a CHP system. As flue gas condensation can recover certain amount of low
grade latent heat, it leads to a significant reduction in CO2 emissions of a system
which recovers energy from MSW.
0
10
20
30
40
50
60
70
80
90
100
Case II-A Case II-B Case II-C Case II-D Case III
Avoid
ed C
O2 e
mis
sions,
×10
3 t
onn
es
Figure 13 Comparison of avoided CO2 emissions among Cases II and III
3.5.4 Impacts on Other Flue Gas Emissions
In addition to the reduction of CO2 emission, another major benefit associated with
energy recovery from MSW is the reduction in emission of other gaseous pollutants.
Table 15 compares the ELVs of some key pollutants from large-scale power stations
with those from Waste Incineration Directive (WID). As can be seen, the ELVs for
MSW incinerators are more stringent than those for coal-fired power stations. Using
the best available techniques (BAT), the waste incineration industry has reduced its
emissions over the last ten years by a factor of 10 or more due to enhanced legislative
environmental controls (Last 2010). In particular, dioxin emissions have been
reduced to well below those of other combustion process under the regulation of the
WID.
Table 15 Emission limit values of some pollutants from large-scale coal fired power
plants (O2 reference concentration: 6%)
Pollutant Large-scale coal fired
power plants*
Derived ELVs for
incinerators**
Dust, mg/m3 50 15
Total organic carbon (TOC), mg/m3 - 15
26
HCl, mg/m3 - 15
CO, mg/m3 - 75
SO2, mg/m3 200 75
NOx, mg/m3 500 (200 after 2016) 300
* (EU 2001)
** Calculated from Table 4 from O2 ref. concentration of 11% to 6%
However, the Best Available Techniques (BAT) for flue gas treatment installed in
most recent industrial units built in Europe have emissions that are often significantly
lower than those imposed by law. Therefore, assuming that the emission factors
must be equal to emission limits appears to be too optimistic (Consonni et al 2005).
An up-to-date evaluation of environmental impacts can be achieved based on direct
measurements carried out on state-of-the-art combustors.
Tables 16 and 17 compare the emission factors from an Energy-from-Waste system
with those from a coal-fired power plant and a gas-fired boiler. As shown, the
emission factors of some pollutants, such as PM10, NOx, NMVOC, SO2 and HCl,
from MSW combustion are lower than those from coal combustion.
Table 16 Emission factors for a coal-fired power plant and a gas-fired boiler for
domestic heating (Giugliano et al. 2008)
Coal-fired power plant Gas-fired boiler for
domestic heating
CO2 g/kWh 759 238
CO mg/kWh 41 57.6
PM10 mg/kWh 130 0.36
NOx (as NO2) mg/kWh 1938 212.4
SOx (as SO2) mg/kWh 4399 3.6
N2O mg/kWh 3.0 3.6
HCl mg/kWh 133 -
HF mg/kWh 38 -
Cd µg/kWh 2.8 -
Hg µg/kWh 92 0.234
Pb µg/kWh 62 -
NMVOC mg/kWh 77 18
Dioxin (I-TEQ) pg/kWh 41 -
Table 17 Emission factors (EF) for Energy-from-Waste systems in Italy and calculated
EF for Cases II-A and B
EF from combustion
of 1tonne MSW*
Calculated EF based
on Case II-A**
Calculated EF based
on Case II-B**
CO2 (fossil) 425 kg/t MSW 671 g/kWh 334 g/kWh
27
SOx(as SO2) 49 g/t MSW 77 mg/kWh 38 mg/kWh
NMVOC 20 g/t MSW 32 mg/kWh 16 mg/kWh
NOx(as NO2) 855 g/t MSW 1350 mg/kWh 672 mg/kWh
PM10 12 g/t MSW 19 mg/kWh 9 mg/kWh
Dioxin(I-TEQ) 310 ng/t MSW 489 pg/kWh 244 pg/kWh
Cd 61 mg/t MSW 96 µg/kWh 48 µg/kWh
Hg 61 mg/t MSW 96 µg/kWh 48 µg/kWh
Pb 610 mg/t MSW 963 µg/kWh 479 µg/kWh
HF 4.3 g/t MSW 7 mg/kWh 3 mg/kWh
Ammonia 12 g/t MSW 19 mg/kWh 9 mg/kWh
HCl 43 g/t MSW 68 mg/kWh 34 mg/kWh
N2O 100 g/t MSW 158 mg/kWh 79 mg/kWh
CO 61 g/t MSW 96 mg/kWh 48 mg/kWh
* (Consonni et al 2005)
** Calculated from the 2nd
column based on the outputs from Cases II-A and B
3.6 Economic Analysis
Although the fuel quality of SRF or RDF is improved and makes for better more
efficient combustion, the cost of the process is a major drawback (Rudder et al. 2005).
It is a capitally intensive process which has to be done on a grand scale if it is ever to
pay off its costs. The process of sorting, drying and pelletising of MSW is costly
and time consuming. The use of RDF entails significant additional costs which can
only be commercially viable in plants of over 1,000 tonnes per day (Optimat 2001).
The sale of recyclable materials will go some way to generate revenue, but the current
state of the recycling market does not bode well for this. Often a RDF/SRF plant
operator will not have the revenue (or even expertise) to build an accompanying
incineration plant so will have to develop a business partnership in order to sell the
fuel. The payback period is long as costs are high; therefore revenue from sales has
to be guaranteed. This necessitates a guaranteed partnership with an incineration
company for an extended period in order for the plant to make profit (Cox et al.
2008).
A simplified cost analysis is performed in order to evaluate potential benefits for an
MSW fired CHP/DH system using SRF as a fuel. The cost analysis compares
financial cost entailed in purchasing necessary equipment for SRF production versus
financial benefits of recovering energy from SRF incineration. This is based on the
assumption that existing MSW collection, transportation and incinerator system do
not need to be upgraded or amended and thus no other financial costs are entailed.
The costs associated with this fuel replacement include initial purchase price of
machinery, operating and maintenance costs. As there is negligible difference in the
renewable biomass content between MSW and SRF, the loss of Renewable Obligation
28
Certificates (ROCs) can be neglected.
3.6.1 Capital Cost of MBT Facility for SRF Production
The principle of the MBT (Mechanical Biological Treatment) plant is to stabilise
and separate the residual waste stream into less harmful and / or more beneficial
output streams. MBT is a generic term for an integration of several processes (Last
2010). The processes are designed to handle raw “black bag” municipal waste (after
any source segregated recycling and composting has taken place) and tend to involve
a recycle recovery element (typically metals and glass) and drying/partial composting
of the remaining waste to produce a more stabilised residue. The recyclable
component may be extracted either prior to or post “stabilization”. The remainder of
the waste is screened/sorted and homogenised to produce either a feedstock for
another treatment process (e.g. RDF/SRF for energy recovery in a gasification,
co-incineration, or Energy from Waste plant) or may be sent to landfill as a partially
stabilised residue.
The capital cost (CS) for a whole MBT plant with MSW treatment capacity of
88,000tpa is approximately €27 million (Monson et al. 2007). The capital cost (CL)
of the MBT facility treating 240,000 tonnes of waste can be scaled with capacity (Cp)
power by an exponent 0.75 (Consonni et al. 2005), i.e.,
75.0
=
S
L
SLCp
CpCC
Hence, for the proposed MBT facility, its capital cost is around €57.3 million.
Generally, the conversion rate for MSW to SRF is about 50%. Thus the throughput
of SRF is 120,000 tpa. For such a scale of facility the land requirement is
approximately 3-4Ha (Last 2010).
3.6.2 OPEX and CAPEX for SRF Production
The operating and maintenance costs reported in literature appear to vary widely.
Monson et al. (2007) estimated the operating costs at €35-55/tonne SRF,
approximately half was spent on exhaust air treatment based on a case study in
Germany. Some technology suppliers’ figures show the operational cost to be
£10-35/tonne SRF. In addition, £42-100/tonne SRF of CAPEX should also be
considered for the MBT facility (Arias-Garcia and Gleeson, 2009).
3.6.3 Benefits
Potentially, the gate fee to a MBT facility for SRF production is different from that
to an incinerator. According to Waste & Resources Action Programme (2010), the
gate fees for existing incineration facilities range from £32 to £79 per tonne with a
29
median value of £49/tonne. The gate fee for MBT facilities is about £75/tonne.
Hence there maybe exist some profit due to the increase in the gate fee.
The major potential revenue received from replacing MSW with SRF is from sale of
the increased electricity and heat, as well as through the sale of recyclate collected
during MBT and remaining SRF fuel. Given that the NCV of SRF is 25.5MJ/kg, the
feeding rate of SRF is 10.1 t/hr. The annual consumption of SRF is about
88,000tonnes for combined power and heat production. The other 32,000tonnes
SRF remains for sale.
As shown in Table 14 (Cases II-C and III), replacing MSW with SRF increases the
electricity output by 0.46MWe and the heat by 2.9MWth. The incensement is
equivalent to approximately 4,000,000kWh of electricity and 25,000,000kWh of heat
every year. Given the purchase price of electricity is £0.072/kWh (Strafford 2006),
the profit for the additional electricity is about £288,000 per year. The price of
district heating could be as high as £0.20/kWh (Davies and Woods, 2009). The
additional heat thus exerts approximately £5,000,000 annually.
Table 18 Summary of the cost-benefit analysis
Item Reference cost or price
Costs
Capital costs 57,300,000 €
OPEX 3,000,000 £/year 25 £/tonne SRF
CAPEX 5,040,000 £/year 42 £/tonne SRF
Revenue
Gate fee 6,240,000 £/year 26 £/tonne MSW
Extra electricity 288,000 £/year 0.072 kWh
Extra heat 5,000,800 £/year 0.2 kWh
SRF sale 320,000 £/year 10 £/tonne SRF
In the existing UK market the users of waste-derived fuels demand and are able to
receive a gate fee in the range of £20 to £50 per tonne, irrespective of the quality or
energy value of the fuel (Cozens and Manson-Whitton, 2010). Cozens and
Manson-Whitton (2010) thus gave one informative price for SRF to be -£1.50/GJ or
-£30/tonne. However, there are already signs that the market is changing, with
continental users offering to pay a small cost per tonne, and UK producers exporting
SRF to continental users in the face of an increasing demand for the product (Cozens
and Manson-Whitton, 2010). In this case, the sale price of the remaining SRF
product is assumed to be £10/tonne, providing the transportation costs and gate fee
outweighed net benefits (Strafford 2006). Then the revenue from the left SRF is
about £320,000 per year.
Table 18 presents the costs and benefits of replacing MSW with SRF in an
MSW-fired system. For simplicity, if the time value of money is not taken into
30
account, the payback period of this replacement would be approximately 13 years. It
should be noted, however, there are also a number of risks associated with SRF
production, such as planning risks and the risk that the technology will not achieve the
performance levels. This could threaten the availability of the products as the
products would not meet the specification for end use and end up in Landfill
(Arias-Garcia and Gleeson, 2009).
31
4. References
Arias-Garcia, A., Gleeson, J. Solid recovered fuel regional assessments – Hull and
East Riding. RPS Planning & Development, JER7585, Jan. 2009
BCURA (The British Coal Utilisation Research Association). The BCURA Coal
Sample Bank: A Users Handbook. 2002.
Chen, Q., Swithenbank, J., Sharifi, V. Review of biomass and solid recovered fuel
(SRF) pelletisation technologies. Report for EPSRC SUPERGEN Bioenergy. 2008
CHPA (Combined Heat & Power Association), http://www.chpa.co.uk/, accessed in
November 2010.
Consonni, S., Giugliano, M., Grosso, M. Alternative strategies for energy recovery
from municipal solid waste – Part B: Emission and cost estimates. Waste Management.
2005, 25, 137-148.
Cox, M., Janssen-Jurkovicova, M., Nugteren, H. Combustion residues: current,
novel and renewable applications. John Wiley & Sons. 2008.
Cozens, P., Manson-Whitton, C. Bio-SNG: Feasibility study – Establishment of a
regional project. Progressive Energy Ltd. 2010.
Davies, G., Woods, P. The potential and costs of district heating networks: A report
to the Department of Energy and Climate Change. 2009.
Defra. Environmental Permitting Guidance: The Directive on the Incineration of
Waste. 2009.
Drax. Environmental Performance Review 2007.
Drax. Our history. http://www.draxgroup.plc.uk/aboutus/history/, accessed in
December 2010.
Dunnu, G., Maier, J., Hilbert, T., Scheffknecht, G. Characterisation of large solid
recovered fuel particles for direct co-firing in large PF power plants. Fuel. 2009, 88,
2403-2408.
EU (The European Parliament and the Council of the European Union). Directive
2001/80/EC on the limitation of emissions of certain pollutants into the air from large
combustion plants. Official Journal of the European Union. 27. 11. 2001. L309/1-21
EU (The European Parliament and the Council of the European Union). Directive
2004/8/EC on the promotion of cogeneration based on a useful heat demand in he
internal energy market and amending Directive 92/42/EEC. Official Journal of the
European Union. 21. 2. 2004. L52/50-60
Euroheat & Power. Treatment of district heating and cooling under rules for State
aid for environmental protection. 2007.
Ferrer, E., Aho, M., Silvennoinen, J., Nurminen, R. Fluidised bed combustion of
32
refuse-derived fuel in presence of protective coal ash. Fuel Processing Technology.
87(1), 2005, 33-44.
Gaillarde, E. Carbon footprint of solid recovered fuel. First UK Conference on
Solid Recovered Fuels. London, November 2008.
Giugliano, M., Grosso, M., Rigamonti, L. Energy recovery from municipal waste: A
case study for a middle-sized Italian district. Waste Management. 2008, 28, 39-50.
Hernandez-Atonal FD, Ryu C, Sharifi VN, Swithenbank J. Combustion of
refuse-derived fuel in a fluidised bed. Chem Eng Sci 2007; 62: 627-35.
HM Government. 2009. The UK Low Carbon Transition Plan: National strategy for
climate and energy. ISBN: 9780108508394
IEA Bioenergy. Municipal solid waste and its role in sustainability. 2003.
Last, S. Waste Technolgy: Energy from Waste (EfW).
http://www.mbt.landfill-site.com/EfW/efw.php, accessed in December 2010.
Monson, K.D., Esteves, S.R., Guwy, A.J., Dinsdale, R.M. Anaerobic Deigestion of
Centrally Segregated Biowastes - Case Study: Heilbronn (U-Plus UmweltService
AG) MBT Plant. The Wales Centre of Excellence for Anaerobic Degistion. 2007.
Optimat Limited. Co-utilisation of coal and municipal wastes. Report No. COAL
R212 DTI/Pub URN 01/1302. 2001.
Rudder, W., Keane, M., O’Sullivan, G., and Bischoff, R., 2005. Review of
Alternative Solid Waste Management Methods for GVRD. Prepared for the Greater
Vancouver Regional District (Burnaby, BC) by Earth Tech (Canada) Inc.
Strafford, A.J. A study into the economic, logistical and energetic potential to
condense household waste to form fuel. Earth & Environment. 2006, 2, 308-342.
Uniongas. Chemical Composition of Natural Gas.
http://www.uniongas.com/aboutus/aboutng/composition.asp, accessed in December
2010.
Veolia. http://www.veoliaenvironmentalservices.co.uk/sheffield/. Accessed in
November 2010.
Wilen, C. Review of waste processing technology for SRF. Report for IEA
Bioenergy Agreement – Task 36, 2004.
WMAA (Waste Management Association of Australia). Sustainability guide for
energy from waste (EfW) projects and proposals. 2003.
http://www.e-renewables.com/documents/Waste/Austrailia%20Sustainability%20Gui
de.pdf, accessed in Nov. 2010.
WRAP (Waste & Resources Action Programme). Comparing the cost of alternative
waste treatment options. Gate Fees Report 2010.
Zucchelli, L. The role of SRF for the Italian strategy in energy from waste.
International Technical Conference on “Solid Recovered Fuels (SRF) – A Sustainable
33
Option for Spain”. Madrid, 2009.