Hot producer gas cleaning system

PREPARED BY

Nainesh Patel

13MCHN01

GUIDED BY

Prof. Jayesh barve

Ms. Manisha Shah

A

TERM ASSIGNMENT

ON

“HOT PRODUCER GAS CLEANING

SYSTEMS”

What is producer gas?

• A combustible mixture of nitrogen, carbon monoxide, and hydrogen, generatedby passing air with steam over burning coke or coal in a furnace and used asfuel. Also called air gas.

Typical components of producer gas

• Producer gas is usually a mixture of mainly carbon monoxide (CO), hydrogen(H2), methane

• (CH4), and the inert species carbon dioxide (CO2), nitrogen (N2), water steam(H2O), and

• small amounts of Argon (Ar). Apart from the main species, the gas containsvarious

• minor species, tars, and particulates depending on the feedstock and theproduction method.

Gasification chemistry

H2O + heat

Charcoal + tar (200-300 °C) heat no air

H2O & CO2(900 °C)+ charcoal & TAR

CO,H2 (1200 °C)

Unburned carbonCharcoal is also used catalyst like filtration process

Tars are polyaromatic compounds formed when heating the biomass and during the breakdown of its main constituents, i.e., cellulose, hemicelluloses, and lignin.

Primary products: mixed oxygenates (e.g., organic acids, aldehydes, and ketones) formed at low temperature, approximately 400 °C

Secondary products: phenolic compounds formed at approximately 600 °CTertiary products: methyl derivatives of polynucleous aromatics (alkyl-PNA) (e.g., methyl acenaphthylene, methyl naphthalene, toluene, and indene) formed at approximately 800 °C

Quaternary products: at higher temperatures, the tertiary products (alkyl-PNA) are stripped of their substituents and benzene, naphthalene, acenaphthylene, and pyrene are formed, at approximately 900 °C

Tar classification

− Class I: Heavy GC undetectable Tars

− Class II: Heterocylic compounds (phenol, cresol)

− Class III: Aromatic compounds (toluene, xylenes, not benzene!)

− Class IV: Light Polyaromatic compounds (2-3 rings, naphthalene, indene)

− Class V: Heavy Polyaromatic compounds (4-7 rings, fluoranthene, pyrene)

Tar classification

Minor contaminants: H2S, NH3,

COS, and HCN• sulphur content of biomass is generally low, but varies with the type of

biomass.

• During ordinary combustion, the sulphur is mainly released as SO2, but in the

reducing environment present during gasification, the sulphur is instead

released as hydrogen sulphide, H2S. approximately 30–150 vppm

• Nitrogen content of the biomass is released as ammonia; NH3.

• Hydrogen sulphide reacts with carbon dioxide in the gas phase, forming

carbonyl sulphide

• The formed COS can react further with H2S, forming carbon disulphide CS2

• Similarly, ammonia reacts with carbon monoxide CO

• There might be other reaction pathways by which COS and HCN are formed

from the solid biomass during gasification and from tar decomposition

Types of BiomassBiomass is highly diverse in nature and classified on the

basis of site of origin, as follows:

a. Field and plantation biomass

b. Industrial biomass

c. Forest biomass

d. Urban waste biomass

e. Aquatic biomass

Typical main gas composition

CONCEPTUAL DIAGRAM OF MULTIPLE STEPS IN (A)UP DRAFTAND

(B)DOWN DRAFT GASIFIER.

Characteristics of fixed-bed gasifiers

DIFFERENT TYPES OF GASIFIER

Fluidized beds

1. Schematic of a bubbling

fluidized-bed gasifier.2. Circulating fluidized-bed gasifier.

- Gas velocity decreases and entrained

particles fall back to the fluidized bed

- Those particles are separated from the gas

in a cyclone and returned to the bottom of

the bed.

-BFB gasifier operates at CSTR.

- the temperature is constant and low

throughout.

- Due to the automatic density separation

in the bed, dense particles sink while light

particles leave the bed with the gas.

Entrained-flow gasifier (EF)• The EF gasifier operates at a

very high temperature,

approximately 1450 °C.

• Under slagging conditions,

membrane walls are used

•Gasification is performed in

a separate chamber and the

slag occurs in gaseous or

droplet form.

• Gas enters the second

chamber, it is cooled by water

and the slag is solidified in

the form of grains that fall to

the bottom and are removed

together with the water.

•Fig B, the slag condenses onthe cooler membrane walls

• And flows down to the bottom of the gasifier where it is cooled down with water, cracking into pieces due to the thermal shock.

OPERATING CONDITION

Gas cleaningDust and ash removal techniques

Schematic of a candle filter

• Cyclones

generally remove

particles from 1 mm

down to 5 µm in

size and work with

dry particulates.

• Cyclone operate

actually (up to 900–1000 °C) to avoidchilling the gas

• Ceramic filter material that allows gases to pass but not the particulate matter• Operated at temperatures up to 500 °C and can effectively remove particles in the 0.5–100 µm range • Removing the filter cake or by back flushing with steam or nitrogen.

Cyclone separater

GENERAL METHOD BIOMASS PRODUCER GAS

CLEANING SYSTEM

• Solid particle remove

from 1 mm to 5 µm.

• 60-65% of the producer gas

contains particles above 60

μm.

•gas still contains fine dust,

particles and tar.

• wet scrubber the gas is washed

by water in countercurrent mode

•cloth filter is a fine filter, any

condensation of water on it stops

the gas flow because of increase

in pressure drop across it

gases are still

above dew point,

no condensation

takes place in

filter.

Remove TAR

Basic type Equipment

Dry Cyclone, rotating particle separators (RPS), electrostatic

precipitators (ESP), bag filters, baffle filters, ceramic filters,

fabric/tube filters, sand bed filters, adsorbers, etc.

Wet Spray towers, packed column scrubber (wash tower),

impingement scrubbers, venturi scrubbers, wet electrostatic

precipitators, OLGA, wet cyclones, etc.

Classification of mechanical/physical gas cleaning systems.

Chilled water used

CATALYTIC CANDLE FILTER

• Filtration for particles removal and

catalytic cracking of tar from

producer gas in one step.

• The ceramic candle filter contains

a nickel-based tar cracking catalyst

in the support body.

• That tar removal efficiency

between 96% and 98% % for

naphthalene and 41% and 79% for

benzene can be achieved with a co-

precipitated catalytic filter disc at a

filtration gas velocity of 2.5 cm/s,

with 100ppm of H2S at a

temperature of 900 ◦C.

ADVANCE CLEANNING SYSTEM

OLGA: Oil Gas Scrubber • washing and absorption media are usual referred to as “oil”

350 °C

• Gas is cooleddown by therecirculating oil,which washes outthe condensedheavy tars

• Remove dropletsof tars and oilfrom the gas, andreturns thedrainage to thecondenser

• The absorber,the temperatureis just above thewater dew point.

• Absorbed tars and absorbent oil

• The light tars are stripped off by hot air• Regenerating the oil that is fed back to the absorber

ADVANCE CLEANNING SYSTEM

• Solid particle remove

from 1 mm to 5 µm.

• 60-65% of the producer

gas contains particles above

60 μm.

•gas still contains fine dust,

particles and tar.

• Remove TAR • Temp below the dew point of tar

Heavy tar condensed

Soluble in water that types of lighter tar and dust removed

Remove droplets of tars and oil from the gas, and returns the drainage to the condenser

washing and absorption media are usual referred to as “oil”

ADVANCE CLEANNING SYSTEM

ADVANCE CLEANNING SYSTEM Raw material to convert pellet from and used steam produced purpose

ADVANCE CLEANNING SYSTEM

entraining the char and bed material

Hot or bad material separated by cyclone and returned to BFR

160–180 °C remove dust.

All the tars are

condensed and absorbed

temp decreases to 40 °C

ADVANCE CLEANNING SYSTEM

NOVEL-FIXED-BED GASIFICATION PILOT PLANT OF VTT AND CONDENS OY, Espoo, Finland Thermal capacity 500 kW

ADVANCE CLEANNING SYSTEM

fixed-bed updraft gasifier design

tar–water phase consists of the water and the lighter oxygenated tars (e.g., acids, alcohols,and aldehydes) that partly dissolve and partly emulgate in water.

ADVANCE CLEANNING SYSTEM

The first NOVEL-plant to town Kokemäki in Finland

Application

Shaft Power Systems

• Spark Ignition Engine

• Compression Ignition Engine

• Direct Heat Systems

Thank you