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SS17_I: Bioenergy Technology > Höldrich Part > Flashcards

Höldrich Part Flashcards

1
Q

Where are the fuel specifications and classes for all solid biofuels set out ?

A

In CEN/TS 14961:2005, which defines certain parameters and property classes.e.g Normative specifications for wood chips:

* Origin

* Particle size (P16/P31.5/P45/P63/P100)

* Moisture content (M20/M25/M30/M40/M55/M65)

* Ash content (A0.7/A1.5/A3.0/A6.0/A10.0)

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2
Q

Informative specifications for wood chips include:

A

* Net energy content (lower heating value (LHV)) as MJ/kg or kWh/m3 loose

* Bulk density in kg/m3 loose

* Chlorine content (Cl0.03/Cl0.07/Cl0.10/Cl0.10+)

* Nitrogen (N0.5/N1.0/N3.0/N3.0+)

Technical standards For specified parameters to be relevant it is important that there is a standard way of measuring them to ensure that measurements are reproducible and unambiguous. There are therefore a list of technical standards that define terminology, measurement methods and sampling methods.

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3
Q

Wood Chips Drying, why is it important?

A
  • increasing the economic bargain of a biogas plant
  • get new income by selling energy wood (firewood)
  • Market Advantage
  • Getting firewood within a short period
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4
Q

Order the following fuels according to Energy Density:

A

Add slide diagrams

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5
Q

What is:

  • the heat of combustion (∆Hco)?
  • The heating value or energy value of a substance? Higher Heating Value?Lower Heating Value?
A

The heat of combustion (∆Hco)

is the energy released as heat when a compound undergoes complete combustion with oxygen under standard conditions.

The chemical reaction is typically a hydrocarbon reacting with oxygen to form carbon dioxide, water and heat. It may be expressed with the quantities: * energy/mole of fuel (kJ/mol) * energy/mass of fuel * energy/volume of fuel

The heating value or energy value of a substance

is the amount of heat released during the combustion of a specified amount of it. Heating Value It is measured in units of energy per unit of the substance, usually mass, such as: kJ/kg, kJ/mol, kcal/kg, Btu/m³

The quantity known as higher heating value (HHV) (Synonyms: gross energy; upper heating value; gross calorific value (GCV); higher calorific value (HCV)) is determined by bringing all the products of combustion back to the original pre-combustion temperature, and in particular condensing any vapor produced. Such measurements often use a temperature of 25 °C and 1013 hPa barometric pressure.

The quantity known as lower heating value (LHV) (Synonyms: net calorific value (NCV); lower calorific value (LCV)) is determined by subtracting the heat of vaporization of the water vapor from the higher heating value. This treats any H2O formed as a vapor. The energy required to vaporize the water therefore is not realized as heat.

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6
Q

Characteristic phases of a wood Combustion according to different temperture levels?

A
  • Up to 150 °C Warming and drying of the wood,
  • at 150 °C pyrolytical decompositions and
  • at 250 °C Gasification of the waterfree fuel (leaving of the volatile components),
  • at 500 °C Gasification of the solid Carbon (Charcoal)
  • at 700 °C up to 1400°C Oxidation (Combustion) of the gases
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7
Q

Draw the Heating flow scheme(Energy Balance) of a wood chip boiler at nominal heat capacity

A
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8
Q

Order the following fuels according to their heating value:

A
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9
Q

What are the gasification types? Draw them!

A
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10
Q

What are wood pellets? How are they manufactured? Advantages?

A

Wood pellets are a type of wood fuel, sometimes made from compacted sawdust or other wastes from sawmilling and other wood products manufacture, but also commonly from controversial sources such as whole-tree removal or tree tops and branches leftover after logging and which otherwise help replenish soil nutrients

  • Pellets are manufactured in several types and grades as fuels for electric power plants, homes, and other applications in between.
  • Pellets are extremely dense and can be produced with a low moisture content (below 10%) that allows them to be burned with a very high combustion efficiency.
  • Further, their regular geometry and small size allow automatic feeding with very fine calibration. They can be fed to a burner by auger feeding or by pneumatic conveying.
  • Their high density also permits compact storage and rational transport over long distance. They can be conveniently blown from a tanker to a storage bunker or silo on a customer’s premises
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11
Q

What are the components of a flat Matrix press and how does it work?

A

Pellets are produced by compressing the wood material which has first passed through a hammer mill to provide a uniform dough-like mass. This mass is fed to a press where it is squeezed through a die having holes of the size required (normally 6 mm diameter, sometimes 8 mm or larger). The high pressure of the press causes the temperature of the wood to increase greatly, and the lignin plastifies slightly forming a natural “glue” that holds the pellet together as it cools.

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12
Q

Draw the table with characteristics of wood pellets!

A
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13
Q

What are Torrefied Pellets, and how are they made?

A

Combination of the peletting and charing processes

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14
Q

Which of the following feedstoks is the most polluting ( CO, dust, NOx):

  • Barley
  • Wood CHips
  • Miscanthus
  • Mill Waste
  • Wheat
A
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15
Q

Finish the following table

What is the percentage of Material use of wood vs Firewood? What would be a compromise?

A

48% vs 52%

Example paper industry vs energy production from wood: Material use first than energy use –> Value-add 15* times higher

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16
Q

Difference between short roation plantages and crops in heating value? Influence of Ash?

A
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17
Q

Order the following from highest chlorine to lowest chlorine:

Grasses, Seeds, straw, wood with bark, grains

What is the risk that comes with chlorine and how can it be avoided?

A

Avoiding Corrosion with Fuels

  1. Avoiding of dew point passings (always high temperatures in the boiler)
  2. corrosion resistant materials (e. g. stainless steel, siliconcarbid)
18
Q

Linkage between aerosol and ash in stalky fuels?

A
19
Q

Give General Concepts of ## Combustion

A

1. Fit the fuel to the combustion

  • Use of Additives (e.g. burnt lime, kaolin)
  • Poduction of Fuel Blends (e. g. wood-chips hay-mixture)

2. Fit the combustion to the fuel

  • Limitation of the burning temperatures in the firebed
  • Coninuous movement of the fuel and the ash in the cobustion room
20
Q

Which of the following is the most polluting ( CO, dust, NOx):

  • Log wood boilers
  • Wood chips boilers
  • Pellet Boilers
  • Heating Oil boilers
A
21
Q

Filter system question

A
22
Q

How often should ash be removed from:

  • Wood chips?
  • Log wood?
A
  • Wood chips: Every year
  • Log wood: Every Month
23
Q

WHat happens when wood chips are compressed?

A

Self-ignition??

Notes of vicky!

24
Q

1 Ej= ? TWh= ? kWh

A

1 EJ = 277,778 TWh

25
Q

What is the difference between burn through fireplace and lower burn-off boiler?

A

The burn-through fireplace has more CO2 emissions

26
Q

Determinants of biomass potential are?

A
  • Availability of land
  • Food and feed demand (population growth, etc.)
  • Land demand for nature conservation
  • Intensity of crop production
  • Yield potentials (breeding)
27
Q

Order the following fuels from higher to lower net energy yield:

  • Rape seed biodiesel
  • Ethanol from sugar beet
  • Ethanol from sugar sorghum
  • Cereal whole crop
  • Miscanthus (no drying)
  • Short rotation wood
  • Landscape hay
A
28
Q

Order the following fuels from higher to lower net CO2 emissions reduction:

Rape seed biodiesel

Ethanol from sugar beet

Ethanol from sugar sorghum

Cereal whole crop

Miscanthus (no drying)

Short rotation wood

Landscape hay

A
29
Q

Greatest Benefits of Using Biomass are ?

A

Biomass for heating: cheapest (source mainly wood and wastes)

Biomass for electricity: greatest GHG benefits (source mainly wood and wastes)

Biomass for biofuels: highest employment intensity, greatest security of supply benefits (source mainly agricultural crops)

30
Q

What is wood?

A

is a hard, fibrous tissue found in trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. Wood It is an organic material, a natural composite of cellulose and hemicellulose fibers (which are strong in tension) embedded in a matrix of lignin which resists compression.

31
Q

Waht is celleculose?

A

Cellulose is an organic compound with the formula (C6H10O5)n. It is a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units

Cellulose is the structural component of the primary cell wall of green plants and amongst others in many forms of algae. Cellulose is the most common organic compound on Earth. About 33% of all plant matter is cellulose. E.g. the cellulose content of cotton is 90% and that of wood is 40–50%.

32
Q

Where is cellulose used?

A

Cellulose is the major constituent of paper, paperboard, and card stock and of textiles made from cotton, linen, and other plant fibers.

Cellulose can be converted into cellophane, a thin transparent film, and into rayon, an important fiber that has been used for textiles since the beginning of the 20th century Cellulose is used to make water-soluble adhesives and binders such as methyl cellulose and carboxymethyl cellulose which are used in wallpaper paste.

Microcrystalline cellulose (E460i) and powdered cellulose (E460ii) are used as inactive fillers in tablets and as thickeners and stabilizers in processed foods. Cellulose powder is for example used in Kraft’s Parmesan cheese to prevent caking inside the tube

33
Q

What is heartwood?

A

Heartwood is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay.

34
Q

Sapwood?

A

Sapwood is the younger, outermost wood

35
Q

Rank the floowing trees from the most dense to the least dense:

  • Beech
  • Oak
  • Eastern white pine
  • Spruce
  • Pine
  • Larch
A
36
Q

What does wood consist of?

A

Wood consists in average of 82 % volatile components,

  • ca 65 % of the energy is in volatile components,
  • the other 35 % of the energy is in the char.

So get the most energy out of the liberated gases (volatile components),

Gasification begins by heating up (Ignition)

37
Q

Give the characteristics of the following:

  • Log Wood
  • Wood chips
  • Wood pellet
A
38
Q

How to measure the water content of log wood? How to store the wood logs in order to prevent high humidity?

A

Difference freshly cut and dried–> Monthly measures

  • Storage until 1 year is acceptable
  • From September on the wood should be covered
  • The storage place should be aerated
  • Storage possibilities:
    • 1m bundled stacked
    • 33 cm loose
    • 33 cm sctaked
39
Q

Characterisitcs of a modern Log Wood boilder:

A

Power Control

Simple cleaning of the heat exchangers,

Power variability from 50 to 100 %,

Simple ash removing needed all 2 to 4 weeks,

Degree of Efficiency ≥ 90 %,

Low Emmissions:

  • CO ≤ 250 mg/Nm³ at 13 % O2;
  • Dust ≤ 50 mg/Nm³ at 13 % O2.
40
Q

Lean Gas (Wood gasification) vs Natural gas characteristics?

A

SS17_I: Bioenergy Technology (13 decks)

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