GASIFICATION

Question 1

is the process of converting solid carbon into combustible carbon monoxide by thermo-chemical reaction of a fuel.

Answer 1

Gasification

Question 2

the process takes place with excess air

Answer 2

complete combustion

Question 3

the process takes place with excess carbon.

Answer 3

gasification

Question 4

• it is the ratio of the amount of air and stoichiometric air needed to gasify the fuel.

Answer 4

Equivalence Ratio

Question 5

The equivalence ratio for biomass gasification process ranged from

Answer 5

0.2 to 0.4

Question 6

The different zones in fixed-bed gasifiers are:

Answer 6

➤Drying zone ➤Pyrolysis or distillation zone Reduction or gasification zone ➤Oxidation or combustion zone

Question 7

This refers to the heating value of the fuel used during gasification. The higher the energy content of fuel, the better is the energy content of the gas produced.

Answer 7

Energy Content of Fuel

Question 8

• This refers to the amount of water present in biomass. Wet biomass will not burn and if burns at a tolerable level will produce a low-quality gas.

Answer 8

Fuel Moisture Content

Question 9

Different reactors and sizes require different sizes and forms of fuel to operate properly. As a rule of thumb, uniform sizes and fuel is needed for gasification. The smaller the diameter of the reactor the smaller the size of fuel is needed. There is a so called fuel size-to-reactor ratio to make the gasifier works.

Answer 9

Size and Form of Fuel

Question 10

• Proper sizes and distribution of fuel in the reactor is important in gasifying the biomass. Uniform airflow in the fuel bed is achieved when the fuel is well distributed in the reactor.

Answer 10

Size and Distribution of Fuel

Question 11

This refers to the compactness of the fuel used in the gasifier. Loose or light-weight fuel occupies more space in the reactor and burns faster than compact or heavy-weight fuel.

Answer 11

Bulk Density of Fuel

Question 12

• Biomass fuel with high volatile matter produces more tar and particulates during gasification. A bluish flame can be obtained from burning biomass with low volatile matter, such as rice husks.

Answer 12

Volatile Matter Content of Fuel

Question 13

• This refers to the amount of ash the biomass produced after gasification. High amount of ash will result in a difficulty of discharging it and a possibility of causing bridging in the reactor during gasification.

Answer 13

Ash Content

Question 14

• This refers to the chemical composition of biomass used during gasification. This affects the amount of air to be used as well as the heating value of the fuel.

Answer 14

Ultimate Analysis of Fuel

Question 15

Biomass fuel is converted to a combustible gas and is consequently used as source of heat for cooking, drying, kiln firing, etc.

Answer 15

Heat Application

Question 16

Biomass fuel is converted into a combustible gas and then cleaned before it is used as fuel to an internal combustion engine, instead of using crude oil.

Answer 16

Mechanical Power Generation for a Steady Load

Question 17

• Biomass gasifier for this application is coupled to vehicles and tractors, replacing gasoline or diesel fuel. The system has gas conditioning devices to ensure that clean gas is available for the engine.

Answer 17

Mechanical Power Generation for Unsteady Load

Question 18

What are the types of Gasifiers?

Answer 18

FIXED BED
FLUIDIZED BED

Question 19

• It is a very old technology. • Usually used for small-scale applications. • Design and operation are relatively simple. • Require large dense and uniformly-sized fuels. • Agri-residues as fuel requires densification which will add cost. • Special gasifier design is required for quality operation.

Answer 19

Fixed-Bed Gasifier

Question 20

What are the types of fixed-bed gasifier

Answer 20

Updraft
Downdraft
Cross-draft

Question 21

-The gas stream flows in parallel direction with the fire zone. It has higher efficiency because the hot gas passes through the entire fuel bed and leaves the gas produced at low temperature.

Answer 21

Updraft

Question 22

-The gas flows in opposite direction with the fire zone burning the tars before they leave the reactor.

Answer 22

Downdraft

Question 23

-The flow of the gas stream crosses the fuel bed and the direction of the fire zone.

Answer 23

Cross-draft

Question 24

• Biomass fuel is gasified as it gradually moves down the reactor.
• Applicable for loose biomass, like rice husks and other fine residues.
• Biomass fuel is fed into the reactor as the char is discharged. For the same reactor diameter with that of a fixed-bed, this type has lesser power output due to the limited operational capacity.
• It has longer operational time as compared with the fixed-bed.

Answer 24

Moving-Bed Gasifier

Question 25

• It is a new technology. • Fuel particles together with an inert bed material such as sand can be fluidized by air movement. • Gas stream passes vertically upward through a bed of inert particulate material forming a turbulent mixture of gas and solid. • Fuel is continuously added at such a rate that it is only small percentage by weight of the bed material. • The fuel particles undergo rapid heating up to bed temperature upon entering the bed and reacts with the incoming stream. • The violent stirring action makes the fuel bed uniform in temperature and in composition achieving a uniform gasification throughout all locations in the bed.

Answer 25

Fluidized-Bed Gasifier

Question 26

What are the types of Fluidized-bed gasifier

Answer 26

Bubbling Fluidized-Bed Circulating Fluidized-Bed

Question 27

- The solid particles behave like a boiling fluid but not transported by the air stream.

Answer 27

Bubbling Fluidized-Bed

Question 28

- The gas velocity is higher and therefore part of the bed material leaves the reactor vessel and transported back to the reactor vessel via a cyclone and return pipe.

Answer 28

Circulating Fluidized-Bed

Question 29

Give examples of fuels for gasifier

Answer 29

Wood Chips Wood Charcoal Biomass Pellets Agri-Residues Rice Hull Coconut shell Peanut hull Corn cobs

Question 30

Give the components of gasifier for heat application

Answer 30

Fuel Feeding System Gas Reactor Blower Gas-Air Mixing Device Burner

Question 31

Give the components of gasifier for power generation

Answer 31

Fuel Feeding System Gas Reactor Gas Cleaning Train Gas Cooling Component Gas-Air Mixing Device Internal Combustion Engine Automatic Speed Engine Regulator Alternator/Generator Switch Board

Question 32

Biomass is converted to gas and subsequently burned producing heat for various applications. This is the simplest system in biomass gasification since there is no need of cleaning the gas before burning it. However, in some special applications, a filter or a wet scrubber is used to free the gas from char and/or fly ashes. Gasifier

Answer 32

Biomass Gasifier for Thermal Applications

Question 33

In this system, the gas generated from the gasifier reactor passes through a series of gas cleaning and gas conditioning devices to remove tars and other particulates. The gas produced is then fueled to an engine to generate mechanical power, which is subsequently utilized to drive pumps, rice mill, etc.

Answer 33

Biomass Gasifier for Mechanical Power Application

Question 34

The gas produced from the gasifier is used to fuel an internal- combustion engine to drive a generator in order to produce electricity. The electricity is then used for various applications, such as residential and street lightings, energizing processing plants, etc.

Answer 34

Biomass Gasifier for Electric Generation