Pilař, Vitvarová

Emission What is emission :

Flue-gas emissions from fossil-fuel combustion refers to the

combustion-product gas resulting from the burning of fossil

fuels

A typical flue gas from the combustion of fossil fuels contains

very small amounts of nitrogen oxides (NOx), sulfur dioxide

(SO2) and particulate matter and of course carbon dioxide

CO2.

NOx - The nitrogen oxides are derived from the nitrogen in

the ambient air as well as from any nitrogen-containing

compounds in the fossil fuel

SO2 - The sulfur dioxide is derived from any sulpfur -

containing compounds in the fuels.

Emission CO2 - is the primary greenhouse gas emitted through

human activities.

Ash - is one of the residues generated in combustion,

and comprises the fine particles that rise with the flue

gas

Emission NOx There are two principal mechanismus of NO formation:

Thermal NOx – formed through hight temperature oxidation of

nitrogen found in the combustion air.

Fuel NOx – the major sources is from nitrogen bearing fuels such as

coal and oil is the conversion of fule – bound nitrogen to NOx during

combustion

Additional Prompt NOx – in flame

Emission NOx For the idea: NOx concentration without emission controls

Gas boiler 240 – 1400 mg/Nm3

Heavy fuel oil boiler 500 – 1500 mg/Nm3

Coal boiler

coal 900 – 2000 mg/Nm3

lignite 800 – 1200 mg/Nm3

Emission NOx

Emission NOx Problems with NOx and SO2

- Reaction in atmospher. The NO2 can react with sunlight and

hydrocarbon radicals to produce ground level zone/photochemical

smog, acid rain constituents and particulate matter.

Emission NOx How we separated of NOx emission? We have two methods:

- Primary measures

- Secondary measures

Primary measures It is mean combustion control in combustion area. We have several

methods

-The progressive air supply

-Reducing oxygen availability in the initial combustion zone

-Reducing peak flame temperatures

Secondary measures – post combustion methods These post combustion control system are referred to as selective

catalytic reduction (SCR) and selective noncatalytic reduction

(SNCR)

-Selective catalytic reduction

-Selective non catalytic reduction

Emission NOx Primary measures Low NOx burner for coal firing – reduction NOx emission in new

boiler with use only primary measures under 160 mg/Nm3

Emission NOx Selective catalytic reduction

-Is currently the most effective methods

-Is possible applied to a variety of fuels

-A chemical reaction between NOx and reagent (usually ammonia) to

produce nitrogen and water vapor

Principe

ammonia is injected into the hot fuel gas through an injection grid, the

flue gas with the ammonia passed across the catalyst surface and

the NOx reaction occur within microspores of the catalyst.

Problems -Investments cost

-Disposition

-Problems with use for currently power plant

Emission NOx

Emission NOx

Emission NOx Selective noncatalytic reduction

-Two basic processes

-An ammonia-based system and urea-base system (injection)

-Problems with reaction zone temperature

-Ammonia 900 – 1000 °C

-Urea 950 – 1050 °C

-with use this methods is reduction emission NOx from 500 mg/Nm3

to 200 mg/Nm3 (boiler 210 MWe)

Emission NOx

Emission CO2

CO2 - is a naturally occurring chemical compound

composed of two oxygen atoms covalently bonded to a

single carbon atom. It is a gas at standard temperature

and pressure and exists in Earth atmosphere in this

state, as a trace gas at a concentration of 0.039 per cent

by volume.

Emission CO2 CO2 – is necessary separated? If yeas, next are three

methods for control emission of CO2

Emission CO2 For existing power plant units is possible use only

Post combustion methods not oxy fuels:

For Post combustion we have:

-Absorbtion

-Adsorption

-Physical separation

-Biological capture

-Newly developed methods

Closest to the industrial application are only absorption

methods other methods are in development.

Emission CO2 Absorption method

-Amine

-Amonium

Principe of these methods show next Basic flow diagram of the absorption

process

Emission CO2 Comparison

Amine - oxygen caused degradation

SO2 caused degradation

NOx caused degradation

corrosivity, toxicity

high cost

Amonium - corrosivivity, toxicity

volatility

Emission CO2 Amine based technology Ammonia based technology

Absorption reagent (scrubbing medium)

More expensive, higher investment costs Cheap

Toxic, corrosive Toxic, corrosive

Qxygen caused degradation Resistant against oxygen caused degradation

SO2 and NOx inlet concentration in flue gas and reaction products

Low concentrations: SO2 below 30 mg/Nm3,

similarly NOx, additional FGD and DENOX

are required

NO additional FGD and DENOX are required

It is necessary to provide a disposal of

degradation products – thermal process

application

It is necessary to provide separation of reaction

products of SO2 and NOx ; however their

commercial utilization is possible (fertilizers)

Operation conditions/heat and cold consumption

Higher operation temperature – steam with

higher parameters is needed

Lower operation temperature – steam with

lower parameters is needed

Cold consumption – only cooling water Cold consumption – cooling water + other

chilled process media

Capture CO2/kg of sorbent

100 % Up to 300%

Heat consumption

100 % Approx. 35 %

Investment costs (data on the literature search basis)

100 % Below 80 %

Decrease of overall efficiency of a power Unit

9 percent points 3.5 percent points

Emission CO2

Emission CO2

Emission CO2 Conclusions

Increased water consumption – for cooling gas Increase of plant‘s own electricity consumption - the highest consumption is for compressor cooling and CO2 compression, consumption of feeding and circulation pumps and flue gas fan

Steam intake - for heating of desorption column

Decrease of electric power output

Waste water

Space requirement

Emission CO2

Parameter Unit Current state With CCS

Power output MWe 250 238

Coal consumption t/h 214 214

Heat in the fuel MWt 588 588

Plant‘s own consumption MWe 24 24

Production of CO2 t/h 211 211

Captured CO2 t/h 0 190

Emitted CO2 t/h 211 21

CCS‘s own consumption MWe 0 50

Net electric production MWe 226 164

Total efficiency % 38,4 27,9

Efficiency decrease % 0 10,5

Emission CO2 And all this technologies are in CCS (carbon, capture and

storage) technologies

What is mean?

Emission CO2 Oxy fuels - is the process of burning a fuel using pure oxygen

instead of air as the primary oxidant.

- The mass and volume of the flue gas are reduced by approximately

75%.

- Because the flue gas volume is reduced, less heat is lost in the flue

gas.

- The size of the flue gas treatment equipment can be reduced by

75%.

- The flue gas is primarily CO2, suitable for sequestration.

- Most of the flue gases are condensable; this makes compression

separation possible.

- Heat of condensation can be captured and reused rather than lost

in the flue gas.

- Because nitrogen from air is not allowed in, nitrogen oxide

production is greatly reduced.

Emission CO2

Emission CO2

Emission CO2

Emission CO2 Possibility storage in Czech republic - saline aquifers

Emission CO2 Possibility storage in Czech republic - saline aquifers

Structure

The optimistic

scenario

(mil. t)

The conservative

scenario

(mil. t)

ŽATEC 450 126

ROUDNICE 872 244

Emission of power plant 3x250 MWe CO2 (mil. t) 4,35

Emission limits BAT

-Best available technology

-Document EU with every about combustion and power plant

-Directive 2010/75/EU

SO2

NOx

DUST