1. The parameters (power, efficiency, cold gas Efficiency, fuel parameters) advantages and disadvantages of gas-steam systems integrated With coal gasification
Gas-steam Systems integrated with coal gasification power efficiency is to 300MW, its fuel parameters are 55% of coal and 36% of petrochemical residues. And as a Result, it gives us 40% chemicals, 30% Fischer-Tropsch. Liquid products and 18% Electricity. (efficiency).
-Some advantages are:
• Is one of cleanest technology based on hardcoal.
• It can be used with CO2 (capture and storage).
• Possibility to produce order chemicals and liquid fuels.
• The high efficiency of 45% and more flexibility fuel.
• Wide range of products.
•Low volume of pollutants emitted.
• A small amount of solid pollutants and sewage.
-And some disadvantages are:
• The efficiency is high, but it isn't still the half.
• It emits pollution, it isn't zero-emission technology yet.
• It generates sewages.
3. Partial processes of solid fuel gasification of Fuels. Main reactions (shift reaction, gasification reactions, combustion Reactions) Basic types of gas generators and main features (gas temperature, the Efficiency of content tars).
1- GE/Texaco: The gas is at temperatures of 760º and the efficiency of content Tars is
2- Shell: The gas is at temperatures of 800 - 900º
3- Conoco Philips: The gas is at temperatures of 140º
4- Simens: The gas is at temperatures of 170º 230º
4. Types of fuel cells (operating temperature, fuel)
- AFC: (Alkaline Fuel Cells) Electrolyte is asbestos impregnated with a concentrated Solution of 85% potassium hydroxide (KOH), at a temperature operation 250ºC or 35-50% KOH solution at 120ºC. The cell was operated at a pressure of 4-5.5 MPa. The fuel in the AFC is hydrogen.
- PAFC: (Phosphoric Acid Fuel Cells) Cells phosphate have a relatively low temperature Of their work- 150 to 220ºC and the fuel used is natural gas (so it has a Relatively low electrical efficiency).
- SOFC: (Solid Oxide Fuel Cells) Fuel cell stack can operate at high working temperature And the fuel cell considered individually have an efficiency of generating Electricity at up to 50%. Power up to 10kW.
- MCFC: (Molten Carbonate Fuel Cells) Cell working temperature is 650ºC. Capacity of These systems are in the range approx. 200KW and the achievable efficiencies of 40-50%
5. Categories of ways to reduce CO2 emissions (adv+disadv)
- Chemical Absorption: Chemical absorption process has significant advantages compared to Physical absorption, such as applicability in systems with low total gas Pressure, the greater selectivity of the process, removal of impurities almost Regardless of their concentration in the gas, the ability to obtain the desired Product. Additionally, thanks to chemical reactions increases the rate of mass Transfer and consequently can reduce the size of the column.
A Disadvantage of this process is the need to regenerate the reagent. The process Requires a supply of heat.
- Adsorption: Adsorption methods for removing CO2 from flue gases are not currently Used on a large scale due to the low productivity of the process and high Energy consumption of the regeneration of the adsorbent; However, they are used To remove CO2 from the raw gas or biogas.
- Cryogenic Method: By cryogenic separation was economically justified demand high Concentration of CO2 in the exhaust gas. Cryogenic processes are very Energy-intensive.
6. Opportunities of geological storage of CO2(adv+disadv)
- Deep Aquifers:
Higher Impermeable layer
CO2 Injected through the hole partially dissolved in water partially displaces Water.
The Possibility of reactions with minerals
- Oil Fields:
CO2 Injected through holes
The Possibility of further exploitation of the deposit by increasing the pressure Of oil or gas, and by reducing the viscosity of oil by oil absorption.
Often used In oil reservoirs because of the frequent weak and empty.
- Gas Fields:
The most Common gas field operated ends when the pressure in the bed drops below the Value determined by economics (30bar)
Most of the Deposits are exhausted in 80% (economic constraints)
Concern About the significant deterioration in the quality of gas
Storage Capacity exceeds twice time of natural gas capacity
- Coal Beds:
CO2 Injected into the coal deposit
The coal Reserves unexploited due to the depth
Required Research focuses on knowledge of the process of absorption and desorption from Coal deposits and the possibility of obtaining gas from the bed.
7. Biomass energy conversion technologies – Categories, examples
Technologies Using thermochemical processes: Energy combustion, gasification and pyrolysis.
Technologies Using biochemical processes: Aerobic fermentation, anaerobic, methane and Alcohol.
Technologies Using physicochemical processes.
8. Impurities produced during gasification of biomass
-Solid Particles, dust: ash, charcoal, bed material
-Alkali metals: The compounds of sodium and potassium
-Tars: Aromatic compounds
-Fuel Nitrogen: NH3, HCN
-Sulfur, Chlorin: H2S, HCl
9. Biogas (the most important parameters of the Production process, the gas parameters)
-Composition: 55-70% methane(CH4); 30-45% carbon dioxide (CO2); traces of other gases
-Energy Content: 6.0-6.5 kWh/m3
-Fuel Equivalent: 0.6-0.65 L oil/m3 biogas
-Explosion Limits: 6-12% biogas in air
-Ignition Temperature: 650-750 ºC (with the above-mentioned methane content)
-Critical Pressure: 75-89 bar
-Critical Temperature: -82.5 ºC
-Normal Density: 1.2 kg/m3
-Smell: bad Eggs (the smell of desulfurized biogas is hardly noticeable)
-Molar Mass: 16.043 kg/kmol
10. Pyrolysis of biomass - process parameters, Parameters of derived products
Pyrolysis Is the thermal decomposition of biomass occurring in the absence of oxygen. It Is the fundamental chemical reaction that is the precursor of both the combustion And gasification processes. The products of biomass pyrolysis include biochar, Bio-oil and gases including methane, hydrogen, carbon monoxide, and carbon Dioxide.
Depending On the thermal environment and the final temperature, pyrolysis will yield Mainly biochar at low temperatures, less than 450 0C, and mainly gases at high Temperatures, greater than 800 0C. At an intermediate temperature, the main Product is bio-oil.
Pyrolysis Offers a flexible and attractive way of converting solid biomass into an easily Stored and transported liquid, which can be successfully used to produce heat, Power and chemicals.
The Efficiency and nature of the pyrolysis process is dependent on the particle size Of feedstocks. Most of the pyrolysis technologies can only process small particles To a maximum of 2. The demand for small particle size means that the feedstock Must be size-reduced before being used for pyrolysis.
Pyrolysis Processes can be categorized as slow pyrolysis or fast pyrolysis. Fast pyrolysis Yields 60% bio-oil and takes seconds for complete pyrolysis. In addition, it Gives 20% biochar and 20% syngas.
11. Solar Power - used solutions
- Systems With a central receiver; usually placed on the tower, and the field of heliostats, CSP (Central Solar Power), and CRS (Central Receiver System).
- Systems Using technologies receivers distributed; DCS - (Distributed Collectors System), SPT - (Solar Parabolic Trough).
- Parabolic Disk-shaped plates; with the shape of a paraboloid of rotation and receiver Point located in the focal point paraboloid.
- Another Division:
• Installations of high-temperature working fluid temperature above 500ºC
• Installations for medium temperature 300-400ºC receiver.
12. Photovoltaic cells - the basic parameters, the Current-voltage
- Surface And power is limited by the technology of production of silicon crystals
- A single Cell is obtained by cutting a crystal in the shape of a cylinder.
- Individual modules are grouped into modules of a dozen pieces.
- A Photovoltaic cell module comprises two glass panels and a low FE2O3 thickness Of 3-5mm and separated cells.
- The cells Are connected to the silver strip.
• Simultaneous usage of electrodes submerged and structural coverage may Increase the short-circuit current of 5-10%.
• Watt peak (WP) is the power of a cell achieved under standard conditions (STC) corresponding to the distribution of solar radiation AM1,5 the density of 1000W/m2 at an ambient Tª of 25ºC
• Under standard conditions generates a current voltage of 0.5V and 4A.