CE70035 - CCS and Energy Production Flashcards
What do FOAK, CCGT, and OCGT represent?
FOAK = First of a kind
CCGT = Combined / Closed Cycle Gas Turbine (gas turbine associated with steam cycle)
OCGT = Open Cycle Gas Turbine
What is Cost of Lost Watts?
What are the issues?
The cost of not having electricity available when you need it.
Whilst it may be cheaper to generate electricity from solar in some circumstances, it is necessary to have energy storage available.
The cost of a “lost” kWh (i.e. not having electricity available when you need it) is a lot more than the cost of generating the power.
How does energy supply vary for different energy resources?
Wind (zero fuel cost, switches on and off as the wind blows)
Nuclear = baseload (fuel costs very little compared to capex)
Fossil – relatively quick to run up and down, but not good from a cold start. (OCGT faster than CCGT faster than coal)
Hydro - very quick response, limited capacity
This is why you need a number of different power generation technologies – they each have different characteristics
What are the largest industrial contributors to GHG emissions?
Iron and steel largest single sector by emissions
•Five main sectors considered responsible for 63% of industrial emissions are iron & steel, cement, aluminium, chemical, and paper.
•Different technologies are more appropriate in some industries compared to others
•Some sectors produce high partial pressure / purity CO2 and are therefore easier to capture from.
What are the types of CCS?
- Post-combustion capture
- Pre-combustion
- Oxy-combustion
What happens in post-combustion CCS?
Exhaust gases with with CO2 are scrubbed by solvent. The CO2 rich solvent then passes through a solvent regeneration column, and the CO2 is compressed and stored.
What happens in pre-combustion CCS?
At energy plants, following gasification reactors, gases containing COx pass through reforming and shift reactors to produce CO2 and H2.
This undergoes separation processes where hydrogen is sent to power plants and CO2 is compressed for storage.
What is oxy-combustion CCS?
Oxy-fuel combustion is the process of burning a fuel using pure oxygen, or a mixture of oxygen and recirculated flue gas, instead of air. Since the nitrogen component of air is not heated, fuel consumption is reduced, and higher flame temperatures are possible.
Because oxyfuel combustion results in flue gas that already has a high concentration of CO2, it makes it easier to purify and store the CO2 rather than releasing it to the atmosphere.
What factors effect energy decoupling?
Decoupling refers to the disassociation of a utility’s profits from its sales of the energy commodity.
The decoupling trend is explained by at least four factors:
- energy efficiency improvements
- saturation in the ownership levels and improved efficiency of the main domestic appliances
- the unresponsiveness of certain industrial uses, like space heating, to long run output growth
- a structural shift away from energy intensive activities (such as steel making) towards low energy industries (such as services).
Note: this often implies manufacturing off-shoring!
What is energy decoupling?
In public utility regulation, decoupling refers to the disassociation of a utility’s profits from its sales of the energy commodity.
Instead, a rate of return is aligned with meeting revenue targets, and rates are adjusted up or down to meet the target at the end of the adjustment period.
This makes the utility indifferent to selling less product and improves the ability of energy efficiency and distributed generation to operate within the utility environment.
What are IAMs?
Integrated Assessment Models (IAMs) are sophisticated tools that combine elements of natural science, economics, technology, demographics, and policy to understand complex interactions within human and natural systems.
A large time-dependent model, which marches forwards in time with sub-models of (in this case)
- time-dependent energy demand, pricing, etc.
- features of different energy supply technologies (capital cost, operational cost, ramp rates, CO2 emissions, fuel cost) etc
- any energy storage on the system
- almost all models assume some form of cost reduction with time through learning
They integrate multiple disciplines to produce an overall model.
By substituting the “allowed” technology types / rates of progress in their development, it is possible to explore (say) which technologies are critical to develop, and the effects of different constraints (say, how much biomass is available)
IAMs help policymakers and researchers explore different future scenarios, assessing trade-offs and synergies between different sectors and policies. By considering the interconnectedness of these systems, IAMs provide insights into the most effective pathways for achieving sustainability and addressing global challenges like climate change.
What are disadvantages of IAMs? (Integrated assessment models)
- challenging to get risk profiles correct
- poor basis of information
- Will not necessarily choose the “best” path, can choose a pathway which is sub-optimal based on what is best at a particular time
Why do IAMs choose CCS?
- CCS can be integrated into an existing energy system without making large changes to the overall system.
- Renewables tend to become more expensive to the system at higher penetration rates (their intermittency impacts more on the system as a whole).
- If the system includes industrial sources of CO2, CCS is one of the only ways of decarbonising these emissions.
- There are some other emissions that are exceptionally expensive to decarbonise (say air travel). Once the cost of decarbonising the emission at source is more than the cost of BECCS, the system will choose BECCS
What do LCOE and VOTA stand for?
Levelised Cost of Electricity
Value of Technology Addition
What are examples of unconventional oil?
Tight oil (or shale oil) – oil that is trapped in shale rocks. Forms much the same as conventional oil, but is not mobile within the rocks. Needs to be hydraulically fractured to get the oil out.
Oil Shale - rocks that contain kerogen but which have not been heated in the past and so have not matured to produce oil. Pyrolysis of the oil shale produces a synthetic crude oil. Frequently considered for potential fuel production when the cost of crude oil becomes very high – but bad environmental credentials
Oil Sands (tar sands) – a mixture of extremely heavy oil (bitumen) with sand. Huge deposits in Canada and Venezuela (Canada has more oil in oil sands than the rest of the world put together has oil). Questionable environmental credentials. Different methods exist to enhance production (though many areas are simply strip mined), many relying on advances in directional drilling.
What are the conventional ways of mining coal?
Deep mines (pits)
Open-cast mining. (Digging down to the deposit from the surface, remove the overburden (the stuff above that isn’t coal) and dig out with a digger. Much cheaper than deep mining)
What are unconventional methods of obtaining hydrocarbon gas?
Fracking
Gas hydrates – vast stores of methane, stored in ice-like molecular cages. One of the largest sources of hydrocarbons available.
What are unconventional means of obtaining coal?
Underground coal gasification
– Dig a hole down to an unmineable coal seam
– Drill another hole a little way away in the seam
– Drill through the seam (directional drilling again) and link the holes (you can also do it by hand if you want the world’s worst job).
– Pump down air or oxygen to the first hole, and set the seam on fire.
– The hot combustion products move through and gasify the remainder of the coal, produce syngas at the other hole.
How does Reserves compare to Resources?
Reserves = profitably recoverable using today’s resources and price.
Resources = how much is out there.
List main uses of fossils fuels:
Coal:
- Chemicals (area of growth) – gasification covered in separate lecture(s)
- Power stations, Iron and Steel (coking coal), Cement production. Can be substituted for in some areas by biomass.
- Some heating (being phased out)
Oil:
- Transport fuels (vehicles, aviation)
- Petrochemicals
- Some heating and power (being phased out)
Natural Gas
- Power production
- Limited Chemicals
- Heating
What is pulverised coal combustion?
The principal means of the generation of electricity from coal worldwide since the middle of the twentieth century
Technology for the large scale utilisation of coal (other solid fuels) for generation of power and heat
How does it work?
* A mixture of pulverised fuel (100 μm) and air is injected into the combustion chamber (boiler)
* Combustion takes place within the boiler while the fuel is in suspension
* Heat is transferred to the boiler walls and then to the heat exchange tube banks as the combustion gases pass through the boiler
* Steam is raised by passing water through tubes located in the boiler
Some ash falls to the bottom of the boiler (bottom ash), some is carried over with the flue gases (fly ash)
* The flue gas is later cleaned up (i.e., remove NOx, SOx, particulates)
* Around 15 % CO2 in the exhaust.
What energy resource reserves are available and recoverable, from high to low?
Renewable:
1. solar
2. wind
3. geothermal
4. biomass
5. OTEC (ocean thermal energy conversion)
6. hydro
Non renewable:
1. coal
2. petroleum
3. natural gas
4. nuclear
What is the most costly type of energy plant to construct?
Nuclear
(& Open cycle gas turbine plants (OCGT)?)
How do open and closed cycle gas turbines differ?
In the open cycle gas turbine, the air enters from the atmosphere and passes through the compressor, combustor and turbine, so all working flow releases into the atmosphere.
In the closed cycle gas turbine, the working flow is continuously recirculated through the gas turbine.
How do the costs of fossil plants with decarbonisation systems and renewable energy plants differ?
The cost (pre-development, variable and fixed O&M, capital, fuel etc) of some (gas and coal) decarbonised fossil plants is less than or equal to that of renewable energy.
How will the best system of energy resources be organised in future years (I.e. by 2050)?
How can this be shown graphically (and compared to now* 2012)?
(Imagine time as x axis and power in GW as y axis)
By 2050, daily demand will roughly have doubled to around 80 GW.
- Demand will fluctuate based on day and time. Fluctuations will be greater by 2050.
- The steady baseline provided by nuclear will have increased (steady as in the supply will not fluctuate with date/time)
- There will be a higher proportion of energy from renewables (supply will fluctuate)
- The rest of the energy will come from convention means (non renewables)
What milestones need to be met to reach Net Zero by 2050?
List by year
2021: No new unabated coal plants approved for development.
No new oil and gas fields approved for development and no new coal mines or mine extensions
2025: No new sales of fossil fuel boilers
2030: Universal energy access
All new buildings are zero-carbon-ready
60% of global car sales are electric
Most new clean techs in heavy industry demonstrated at scale
1,020GW annual solar and wind additions
Phase-out of unabated coal in advanced economies
150 Mt low-carbon hydrogen
850 Gw electrolsers
2035: Most appliances and cooling systems sold are best in class
50% of heavy truck sales are electric
No new ICE car sales
All industrial electric motor sales best in class
Overall net-zero emissions electricity in advanced economies
4 Gt CO2 captured
2040: 50% existing buildings retrofitted to zero-carbon-ready levels
50% fuels used in aviation are low emission
~90% existing capacity in heavy industries reach end of investment cycle
Net-zero emissions electric globally
Phase-out of all unabated coal and oil plants
2045: 50% heating demand met by heat pumps
435 Mt low carbon hydrogen
3,000Gw electrolysers
2050: > 85% buildings zero-carbon-ready
> 90% heavy industrial production is low-emission
~70% electricity generation globally from solar PV and wind
How may the targets for the milestones for Net Zero by 2050 be displayed graphically?
Imagine year (2020-2050) along x axis and Gt CO2 (-5 to 40) along y axis.
Overall looks like half of bell curve - GtCO2 decreased for all sectors.
2020: Electric sector contributes ~13 Gt CO2
Industry ~ 10
Transport ~ 8
Buildings ~ 5
Other ~ 2
2035: Electric sector contributes ~5 Gt CO2
Industry ~ 9
Transport ~ 5
Buildings ~ 2
Other ~ 0
2050: Electric sector contributes ~ -1 Gt CO2
Industry ~ 1
Transport ~ 2
Buildings ~ 0
Other ~ -2
How are our CO2 emissions expected to change over the next 100 years if we start acting on our emissions?
(Graphical)
(Time as x axis, GHG added or removed +/- as y axis)
Over time, gross emissions will increase slightly then decrease and plateau (in the positive). This is as some emissions from farming and heavy industry could persist, so removing their emissions directly from air may be necessary)
There will be a steady amount of GHG removed (in the negative) throughout the years, due to nature based carbon removal.
Around 2040 onwards, gross carbon removed increases (more negative) and then plateaus also.
Net emissions will follow the pattern of gross emissions - increase slightly then decrease and plateau, but will plateau in the negative.
What’s embodied energy?
Embodied energy is a calculation of all the energy that is used to produce a material or product, including mining, manufacture and transport.
What’s TPES?
Total primary energy supply
How do we obtain the 2DS? (2C scenario?)
To achieve the 2DS, energy-related CO2 emissions must be halved by 2050.
On a global basis, total primary energy supply (TPES) will grow in all scenarios.
In the 2DS, TPES increases by some 35% in the period 2009 to 2050.
This is significantly lower than the 85% rise seen in the 6DS and the 65% increase in the 4DS.
What is LCOE?
Measures lifetime costs divided by energy production.
The levelized cost of electricity (LCOE) is a measure of the average net present cost of electricity generation for a generator over its lifetime.
It is used for investment planning and to compare different methods of electricity generation on a consistent basis.
What are the effects of adding new renewable technologies in our systems
[ in 5 GW increments from a 2030 central scenario (10 GW nuclear, 5 GW gas CCS, 28 GW wind, 20 GW of PV) at the origin].
As you build more of the zero or very low carbon technologies, the overall system cost generally increases, sometimes very sharply, but the CO2 intensity reduces (moving to the left).
[Graph showing total CO2 emissions along x axis and total system cost along y axis, and the total system cost for each type of energy resource steadily decreasing to a point at the 2030 scenario at 85 g/kWh]
What is an oil trap?
Oil and gas traps, sometimes referred to as petroleum traps are below ground traps where a permeable reservoir rock is covered by some low permeability cap rock.
This combination of rock can take several forms, but they all prevent the upward migration of oil and natural gas up through the reservoir rock.
How/where is coal formed?
Coal contains the energy stored by plants that lived hundreds of millions of years ago in swampy forests. Layers of dirt and rock covered the plants over millions of years. The resulting pressure and heat turned the plants into the substance we call coal.
What’s a supply-cost curve?
The supply curve is a graphic representation of the correlation between the cost of a good or service and the quantity supplied for a given period. In a typical illustration, the price will appear on the left vertical axis, while the quantity supplied will appear on the horizontal axis.
How does a circulating fluidised bed (CFB) work for fuel combustion?
A bed of fine inert material that has air/oxygen/steam (~ 5-10m/s) suspends material throughout the combustor
Fuel is fed in from the side, is suspended, and combusts providing heat
Steam is raised by passing water through tubes located in the combustor
The mixture of gas and particles are separated using a cyclone, with material returned into the base of the combustor.
Operates at temperatures below 900°C to avoid ash melting and sticking; can be pressurised.
What’s tight gas?
Gas that is within a rock stratum of low permeability. Flowrate is low when normal drilling practices are used.
What’s shale gas?
Gas from shale rock formations. Shales are semi-compacted mud rocks.
Shale gas is transforming the fossil fuel industry:
- cheap
- clean
- decreasing dependence on hydrocarbons from Middle East
What’s gas in place?
All the gas that’s there
How have gas reserves changed over the last decade?
Reserves have been increasing with time.
Causes of is include technology improvements and price increases
What should/can policy makers do?
Policymakers can take action to accelerate structural changes that alleviate upward pressure on energy prices, including promoting energy efficiency and incentivizing new low- carbon sources of energy production.
These policies would also protect economies from future energy price volatility and accelerate the transition away from fossil fuels, helping to achieve climate change goals.
At present, however, many governments have focused on trade restrictions, price controls, and subsidies, which can be expensive and often exacerbate supply shortfalls and price pressures.
What’re natural gas hydrates?
Gas hydrates consist of molecules of natural gas (the chief constituent of natural gas; methane) enclosed within a solid lattice of water molecules. When brought to the earth’s surface, one cubic meter of gas hydrate releases 164 cubic meters of natural gas.
Gas hydrate deposits are found wherever methane occurs in the presence of water under elevated pressures and at relatively low temperatures, such as beneath permafrost or in shallow sediments along deepwater continental margins.
How can we minimise the carbon intensity of electricity?
Carbon intensity refers to how many grams of CO2 are released to produce a kWh of electricity.
- reduce (methane) leakage
- use high CO2 capture rates for CCS plants
What are the 4 main ranks of coal?
Lignite (brown coal). Highly reactive, not much transformed from peat. Lowest carbon content. High moisture / low efficiency from power stations. Vast amounts burned by Germany.
Sub-bituminous. Black, dull surface. Higher heating value than lignite.
Bituminous. High heat and pressure have transformed this to be a hard black rock.
Anthracite. Highest carbon content. Slightly lower heating value than bituminous coal. Shiny.
Coal consists of C, H, O, N, S and trace and minor species.
What’s the R/P ratio?
Reserves to production ratio
The R/P ratio measures the number of years a resource will last if production rates stay the same.
What do Dry basis and Dry ash free basis refer to regarding coal?
Dry Basis : not including moisture content.
Dry, Ash Free basis: not including moisture and ash.
What is an ultimate analysis, regarding coal?
Ultimate analysis: procedure to determine C, H, N, S (oxygen by difference) in the sample.
Generally, the dry, ash-free (DAF) value is quoted
Why DAF? - Moisture level can change, and no-one wants to pay for rocks.
What is LHV?
Lower Heating Value (LHV): A measure of the thermal energy released from combustion of a fuel, NOT including the energy from condensing steam (from the combustion of the H content in the coal).
What’s HHV?
Higher Heating Value (HHV): The energy released from combustion of coal or other fuel, INCLUDING the energy from condensing steam.
It is the amount of heat released by the unit mass of fuel (initially at 25C) once it has combusted and the products have returned to 25C. This includes the latent heat of vaporisation of water.
How is coal produced?
Plants, trees etc. fall into swamps (anaerobic conditions), and get covered over, go through a number of stages in the production process.
Harder coals have been “cooked” in-situ by geothermal heat.
The older the coal, the higher the temperature and pressure it has been exposed to, the higher the rank (in general).
The process of producing coal from peat is “coalification”.
What are the components of coal ash?
SiO2: 40-90
Al2O3: 20-60
Fe2O3: 5-25
CaO: 1-15
MgO: 0.4–4
Na2O: 0.5–3
K2OM 0.5–3
SO3: 0.5–10
P2O5: 0-1
TiO2: 0-2
List of trace elements:
antimony, arsenic, beryllium, boron, cadmium, chlorine, chromium, cobalt, copper, fluorine, lead, manganese, mercury, molybdenum, nickel, selenium, thallium, vanadium, and zinc.
Radioactive: thorium and uranium
Mercury is the main trace element of concern, since it is volatile and not captured easily by standard clean- up of the power station exhaust. Causes birth defects and mental issues (mad hatter).
What is the main impurity in coal that is of concern?
Mercury is the main trace element of concern, since it is volatile and not captured easily by standard clean- up of the power station exhaust. Causes birth defects and mental issues (mad hatter).
How does pulverised coal combustion work?
• A mixture of pulverised fuel (100 μm) and air is injected into the combustion chamber (boiler)
• Combustion takes place within the boiler while the fuel is in suspension
• Heat is transferred to the boiler walls and then to the heat exchange tube banks as the combustion gases pass through the boiler
• Steam is raised by passing water through tubes located in the boiler
• Some ash falls to the bottom of the boiler (bottom ash), some is carried over with the flue gases (fly ash)
• The flue gas is later cleaned up (i.e., remove NOx, SOx, particulates)
Describe the steam cycle within power plants:
The power station heats and evaporates high pressure water to form steam (superheated steam), which is then expanded through a turbine (the High Pressure or HP turbine).
The exhaust from the turbine is then passed back to the boiler (a reheat) and expanded again through an Intermediate Pressure (or IP) turbine.
Finally, the steam is passed back to the furnace one final time, then expanded in the Low Pressure (LP) turbine. Because the steam has expanded quite a lot by this time, this might be two turbines in parallel.
The pressurised water may well be heated up (but not vapourised) via contact with the exhaust gas near the end of the
furnace. This is done in an economiser.
Why is coal so ‘dirty’?
What does this lead to?
Due to large amounts of impurities, particularly S, N, and Hg (Mercury).
Unless gasified (which has its own challenges), coal is limited to the standard steam cycle, not the more efficient combined cycle (you would destroy gas turbines by putting solid coal through them).
This means that the efficiency of electricity production is 35 – 45%, as opposed to 55 – 60% (these values creep up slowly with time as metals get better – see discussions of metallurgical limits later in the course).
In addition, coal has a very high ratio of C to H compared to methane (CH4), or more specifically less heat given out per mole of C combusted.
The above two factors mean that coal produces approximately twice as much CO2 per kWh of electricity produced as does methane.
How do coal furnaces handle processing different types of coal?
If an electricity generating or heating plant is designed to burn one type of coal then it must continue to be supplied with a similar coal or undergo an extensive and costly redesign in order to adapt to a different type of coal.
Similarly, furnaces designed to use coal that produces high amounts of heat will suffer severe losses in efficiency if they must accept coal that burns with substantially less heat
What is natural gas used for?
Power generation
Space heating
Combined heat and power (CHP)
(Steam) reforming to Syngas
Describe the distribution/proportion of proven gas reserves around the world:
Reserves have been increasing over the last few decades.
From highest to lowest proportion…
Middle East: 40.3%
CIS: 30.1%
Asia Pacific: 8.8%
North America: 8.1%
Africa: 6.9%
S & Central America: 4.2%
Europe: 1.7%
What are the 3 channels through which gas markets respond to price shocks and policies?
Demand reduction
Substitution
Supply responses
Key dates impacting energy and energy pricings:
1973/74 - Yom Kippur war
1979 - Iranian revolution
Early 2000s - emergency of China and India as global powers
2008 - financial crisis
2011 - Fukushima nuclear plant accident
2019 - Covid-19
2022 - Russia/Ukraine war
Major LNG exporters:
Australia
Qatar
US
Russia
Malaysia
Nigeria
Algeria
Indonesia
Oman
By the 10-100s billion m3
What is the issue with LNG production?
The liquefaction process is the largest contributor to GHG emissions of LNG overall. The liquefaction energy demand is normally assumed to be 8–12% of the natural gas throughput, or 4.09–7.66 g CO2eq/MJ.
Describe the composition of coal:
Coal consists of C, H, O, N, S and trace and minor species. Mineral matter is often found associated with coal.
The sulfur content of coal may range from low (less than 1 weight percent), through medium (1 to 3 weight percent), to high (greater than 3 weight percent).
Ash yields may range from a low of about 3 percent to a high of 49 percent (if ash yields are 50 percent, or greater, the substance is no longer called coal).
Coal may produce high or low amounts of energy when burned, or contain high or low amounts of the substances that produce organic chemicals and synthetic fuels, or contain higher or lower amounts of the elements that are considered hazardous air pollutants (HAPs).”
What may cause changes in reserves?
Technological advancements
New finds
Current fuel prices
What determines oil prices?
The balance of supply and demand
OPEC (organisation of petroleum exporting countries) acts to try and keep the price within certain bounds (too high and renewables take over, too low and the cartel loses money), but only controls just under half of production.
Some OPEC members allegedly cheat, and produce too much.
OPEC basically changes the relationship between future and current production, but can’t do too much.
When new types of oil production come on stream that are not accounted for already, the oil price is depressed (see “tight” oil).
What are the initial stages in the oil drilling/production process?
- Geologists go out and survey. Sensitive magnetometers, seismology (generate shock waves to investigate underlying geology.
- Environmental impact studies, survey the area.
- Prepare the landscape – access roads, source of water – (drill water well?), pit for cuttings.
- Construct drill rig
- Various holes dug, first (large bore) drilling – first section of large diameter conductor pipe put in place.
What are the two types of oil well?
- Exploratory (Wildcat) well. Looking for a new reserve High risk, high reward.
- Production well.
Drilled where the company knows that hydrocarbons are present.
What equipment is needed to drill a well?
Drill bit
Drill pipe
Bottom hole assembly
Drilling mud
What are the requirements of drill bits for drilling an oil well?
Maximise rate of penetration.
Long service life (each time you replace it you have to pull possibly several miles of drill pipe up).
Convey drilling mud to and from the bottom of the well.
What are the properties of a drill pipe?
Hollow, thin walled pipe (steel or Aluminium).
Transmits torque and drilling mud to drill bit / well head.
Tested and re-used after a drilling job.
Describe the bottom hole assembly:
Includes drill bit (at the bottom)
Heavy pipe, used to apply
weight to the drill bit
Stabilisers
Measurement while drilling
Controls to build angle
The clever bit at the end of the drill pipe. Can be used to build angle for horizontal drilling.
What are the functions of drilling mud?
- Cool / lubricate the drill bit
- Carry cuttings to surface
– How? Viscosity! What rheology do we need? - Maintain well bore integrity
– drilling through shale may lead to swelling - Hydrostatic pressure prevents fluid ingress into the well whilst it is being drilled.
What is BOP?
Blow out preventer - important safety device connecting the rig and well bore.
Some close the annulus around the drill pipe
Some close off the entire wellbore
Some cut off the drill pipe as they shut off the well
What are kicks?
A kick is where hydrocarbons overcome the hydrostatic pressure of the mud and enter the well.
Very dangerous – can lead to fire, explosion, etc at the drilling rig.
Blow-out protectors seal the well and prevent the hydrocarbons reaching the surface.
Once a kick is detected, operations are shut down and a heavier drilling mud (kill fluid) is circulated
(through the drill pipe to the BOP and out into the annulus) to increase hydrostatic pressure.
What happens in cementing for oil well construction?
- Cement is pumped down the casing
- The cement forced up between casing and hole – annulus
- This seals off wellbore from fresh water
- The surface casing prevents contamination of aquifers
Cement pumped down to bottom of well Flows back upwards.
It sets the casing in place.
There can be many sections of casing. Each successive section will be smaller in diameter than the previous one.
Sometimes it is necessary to isolate particular strata and a different section of casing might be used for this.
The central casing is the production casing, and the last one drilled.
A “displacement fluid” is used to push the cement down into the annulus.
What does a Christmas tree refer to?
Collection of valves used to produce the oil or gas.
Controls the flow out of the well.
Christmas trees are used for both above and below sea installations
What are the 3 pathways of thermal conversion?
Pyrolysis
Gasification (biomass + oxygen -> fuel gas)
Combustion
What’s syngas made up of?
Mainly CO and H2
What are the 4 main gasifier types?
Updraft
Downdraft
Fluidised bed
Entrained flow
What is coal gasification?
Coal gasification is the process of producing syngas—a mixture consisting primarily of carbon monoxide, hydrogen, carbon dioxide, methane, and water vapour —from coal and water, air and/or oxygen.
What are some uses of syngas?
Ammonia/urea production
Methanol
SNG
Fischer tropsch
Oxy alcohols
Gas turbines
Advantages of IGCC (integrated gasification combined cycle) to combustion:
Higher efficiencies
- Coal-firing plant (sub-critical) ~ 34-38%. UK average towards the low end of the range
- Similar efficiencies to operating supercritical power plants 41-43%
- Operating IGCC: 42-43%
- Combined Cycle: 56-59%
CO2 capture
Easier removal of sulphur and nitrogen
Define IGCC
Integrated Gasification Combined Cycle
Discuss tar regarding gasification:
Tar is one of the biggest issues in biomass gasification
•The amount of tar allowed downstream depends on the application.
•It can cause operational issues downstream,
and is never the desired output from a gasifier.
•Also, its production reduces the overall thermal efficiency of the production of the desired gases.
•Acceptable levels are ~ 0.05 g Nm3 , 0.005 g Nm3 and 0.001 g Nm3 for gas engines, gas turbines and fuel cells, respectively.
•Updraft gasifier – 10 – 20 wt % tar produced from biomass
Destruction of tar - ongoing area of research
What is ‘market cap’?
Market capitalization, or market cap, is a measurement of a company’s size.
It’s the total value of a company’s outstanding shares of stock, which include publicly traded shares plus restricted shares held by company officers and insiders
What is carbon intensity?
Which 5 countries have the highest carbon intensity of oil production?
Carbon intensity is a measure of how clean our electricity is. It refers to how many grams of carbon dioxide (CO2) are released to produce a kilowatt hour (kWh) of electricity. Electricity that’s generated using fossil fuels is more carbon intensive, as the process by which it’s generated creates CO2 emissions.
From highest to lowest C intensity;
1. Canada
2. Libya
3. Nigeria
4. Algeria
5. Iran
How does gasification work?
Gasification is a process that converts organic or fossil-based carbonaceous materials at high temperatures (>700°C), without combustion, with a controlled amount of oxygen and/or steam into carbon monoxide, hydrogen, and carbon dioxide.
As opposed to combustion, which uses an abundance of oxygen to produce heat and light by burning, gasification uses only a tiny amount of oxygen, which is combined with steam and cooked under intense pressure. This initiates a series of reactions that produces a gaseous mixture composed primarily of carbon monoxide and hydrogen.
How does an integrated gasification combined cycle (IGCC) work?
Gasify coal or biomass
Burn the gaseous products in a gas turbine, which produces electricity
Produce steam from the exhaust heat and any other sources in the plant to run a steam cycle, which also produces electricity
High efficiency – but very complex
What are the main gasifier technology types?
(Industrial brands)
From largest to smallest operating plants…
Shell
Sasol Lurgi
GE
ECUST
E-GAS
Other
Shell is the gasification technology provider that has the largest installed syngas capacity at 28,822 MWth, followed by Sasol Lurgi at 17,753 MWth, and GE at 16,334 MWth. Six of the plants currently under construction will use Shell technology.
When planned capacity is added to current technology, GE switches places with Sasol Lurgi in terms of total capacity.
How does an entrained flow gasifier work?
In an entrained-flow gasifier, solid fuel particles are typically fed into the gasifier from the top in a coaxial flow of the gasifying agent (e.g. oxygen and steam, in some cases, carbon dioxide or a mixture of them).
For an entrained flow gasifier, a high carbon conversion within shorter residence time demands high operating temperatures and the use of small, dry fuel particles.
Entrained flow gasifiers are often operated at pressures of 20-40 bar and at a temperature around 1400-1600ºC, above the ash-melting point which ensures the destruction of tar or oils, producing a tar-free-syngas but with the penalty of oxygen consumption.
The flow in an entrained flow gasifier can be represented with four different zones: the near-burner zone (NBZ), the jet expansion zone (JEZ), the external recirculation zone (ERZ) and the downstream zone (DSZ).
The near burner zone is a high temperature region where preheating and pyrolysis of the descending fuel particles take place along with gas phase oxidation reactions. Char gasification reactions are also initiated in the NBZ. However, the large majority of char particles are gasified in the JEZ.
The JEZ is characterized by high axial gas velocities with a considerable amount of flow expansion. Part of the flow in the JEZ is entrained into the ERZ which carries hot combustible gases into the NBZ to assist heat demand for preheating and pyrolysis of the descending fresh, solid fuel particles while the other part is directed to the downstream zone. The residual ash is drained from the bottom (in the DSZ), either as a molten slag or solid particles, depending on the temperature inside the gasifier.
What are the features of entrained flow gasifiers?
First developed in the 1950s for gaseous and liquid products – refinery residues, etc
Dry feed, entrained flow, slagging gasifier
Pressurised lock-hoppers allow feeding
Pure oxygen and steam as oxidant / moderator
Flame goes up
Temperature of reactions 1500 – 1600oC
20 – 40 bar pressure
Key to operation is the membrane wall.
Cooling water circulates through, which cools the ash from the gasification process down; this then forms a protective layer on the wall, preventing erosion of the refractory lining.
At the outside of the slag layer, the slag is molten and flows down into a water bath, where it is removed through a lock hopper as a slurry.
Gas leaves the gasifier at 1300 – 1400oC
Recycled “quench” gas reduces the temperature of the gas and solidifies any ash fines remaining in the gas – reduces damage to the syngas cooler.
The gas passes through a HRSG (heat recovery steam generator) to produce steam for process use or power
How do updraft gasifiers work?
In an updraft gasifier the downward-moving biomass is first dried by the upflowing hot product gas. After drying, the solid fuel is pyrolysed, giving char, which continues to move
down to be gasified, and pyrolysis vapours which are carried upward by the upflowing hot product gas.
The tars in the vapours either condense on the cool descending solid fuel or are carried out of the reactor with the product gas, contributing to its high tar content.
The product gas from an updraft gasifier thus contains significant amounts of tars and low-molecular hydrocarbons, which contribute to its high heating value. Usually this gas is directly used as a fuel in a closely coupled furnace or boiler.
The ash produced is not molten. Maximum T of ~ 1200 °C in the combustion zone, and 700 – 900oC in the gasification zone.
Residence time of fuel 30 – 60 minutes.
Three options for gasification media: (i) steam / O2, (ii) steam / air, (iii) steam / O2– enriched air.
Typical steam/fuel ratio is high: ~ 1.5
What are the features of updraft gasifiers?
The updraft fixed bed (“counter-current”) gasifier consists of a fixed bed of carbonaceous fuel (e.g. coal or biomass) through which the “gasification agent” (steam, oxygen and/or air) flows in counter-current configuration. The ash is either removed dry or as a slag.
Gas in counter-current to feed
Bed continually moves down the gasifier
Char at bottom of the bed undergoes combustion – provides heat for the remaining sections of the bed.
Hot gases move up, gasify bed material.
Pyrolysis zone produces tar – large quantities and main issue with this type of gasifier.
What is PF combustion?
How does it compare to entrained flow gasification?
Pulverized fuel combustion
It is similar to entrained flow gasification.
Pulverized fuel (PF) combustion involves grinding solid fuel into very fine particles (pulverized) and burning these particles in a combustion chamber. Entrained flow gasification, like PF combustion, involves breaking down solid feedstock into smaller particles, but instead of burning them, it gasifies the feedstock at high temperatures. Both processes use a fine particle size to facilitate efficient combustion or gasification.
What are the features of downdraft gasifiers?
A throated gasifer has a restriction part-way down the gasifier where air or O2 is added. Throat-less gasifiers are also possible.
The temperature rises to 1200–1400 °C and the fuel feedstock is either burned or pyrolysed.
Combustion gases pass over the hot char at the bottom of the bed, where they are reduced to H2 and CO.
High throat temperature ensures that tars are significantly cracked, with further cracking on the hot char at the bottom of the bed. Much lower resulting tar than updraft.
Faster to start up than updraft.
Disadvantages: The constriction affects the types of biomass that can be successfully gasified.
A low moisture content is required (~ 25 wt%).
Ash and dust are still significantly present in the exhaust, so the gas still requires clean-up.
Inherently small – scale. Suitable for small-scale biomass exploitation.
How do downdraft gasifiers work?
In a downdraft gasifier the fuel is loaded at the top and a fire is lit in the bottom. A suction blower draws in air either through an air jacket or down through the top. The incoming air allows partial combustion to take place in the lower hearth area.
The heat from that combustion produces pyrolysis above and reduction below. Once the gas leaves the hearth it’s piped out to the cooling and filtration system before being used for work.
Downdraft gasification generally produces a low particulate and low tar gas so it is suited for power generation in small scale applications.
The four basic processes of gasification are noted below.
Drying of the fuel
Pyrolysis
Oxidation (Combustion)
Reduction
What is a BFB gasifier?
How does it work?
Bubbling fluidised bed (BFB) gasifier
A bed of fine inert material (e.g., sand) sits at the bottom of combustor, with air, oxygen or steam being blown upwards through the bed just fast enough (~1-3 m/s) to agitate or ‘fluidise’ the material
- Fuel is fed in from the side (usually), mixes with bed material, and combusts (or forms syngas) which leaves upwards
- Steam is raised by passing water through tubes located in the combustor
- Operates at temperatures below 900 °C to avoid ash melting and sticking (defluidisation); can be pressurised
What is a CFBG gasifier?
How does it work?
Circulating fluidised bed gasifier
A bed of fine inert material has air/oxygen/steam (~5-10 m/s) suspends material throughout the combustor
Fuel is fed in from the side, is suspended, and combusts providing heat
Steam is raised by passing water through tubes located in the combustor
The mixture gas and particles are separated using a cyclone, with material returned into the base of the combustor
Operates at temperatures below 900°C to avoid ash melting and sticking; can be pressurised
Can incorporate a catalytic bed
What are the features of the Kellogg, Brown and Root (KBR) Transport Gasifier (also known as TRIG)?
Advanced Circulating Fluidised bed Gasfier
Basis of the Kemper County IGCC (air-blown)
Based on Fluidised Catalytic Cracking technology (used in refining)
Solids are pneumatically conveyed upwards, gasify and then are returned to the bed via the cyclone
Internal temperature 800 °C (biomass) – 1100 °C (coal) – much lower than other gasifiers
Particularly suited for low-rank, high moisture, high ash fuels (basically, any fuel that requires a long residence time).
Coarse ash from the standpipe.