Recent Developments in the Clean Combustion of Coal - PowerPoint Presentation

Slide1

Recent Developments in the Clean Combustion of Coal

Crispin Pemberton-Pigott

International Technical Consultant – WB CSI Projects

Presented at Warsaw, Poland

30 May 2017

Session: ‘Solutions – Part 1’Slide2

tHeory of smoke Production

Coal is placed top of a fire.

The coal is heated and volatile gases are given off.

Unburned gases produce ‘smoke’ which consists of condensed volatile matter, other combustible gases and unburned carbon.Generally, a coal with a higher volatile content creates more smoke.The result is terms like “high” and “low” quality coal  inappropriate

Clean Combustion of Coal

2Slide3

tHeory of smoke Production

‘Coked’ coal is ordinary coal that is roasted using a process called ‘destructive distillation’.

Known in China since the 9

th Century that coking coal produces in a ‘low smoke fuel’.In the mid 1800’s in the UK, train engines were required to “consume their own smoke”. So they had to burn coke.Removing some volatiles produces a ‘semi-coked’ coal-based fuel: easier to light than coke.Coke and semi-coke are often rejected as a domestic fuel, usually over ignition

Clean Combustion of Coal

3Slide4

Smoke Combustion

Stoves that burn all the volatiles make very little smoke.

Top-lit Updraft

– load once, ignited on top, flames go upwards (Pat 1707?)Bottom-lit Downdraft – coal loaded continuously from the top, ignited at the bottom, flames go downwards then upwards (Pat. 1688)End-lit Cross Draft – coal loaded on the side, ignited on the bottom, gases move laterally through a coke bed and then rise as a gas fire (Pat. 1742).

Clean Combustion of Coal

4Slide5

1

2

3

4

5

Coal bunker on one side

Fire at the bottom

Flames rise from other side

Cooking and heating functions are relatively easy to arrange

Clean Combustion of Coal

5

CROSSdraft

Stove

3

2

1

CPP – GTZ 7.1, 2010Slide6

smoke COMBUSTION

Solid fuel fires are “gas fires”.

All stoves burning all fuels create “smoke” within the fire.

If the smoke is not burned we see it coming out.Some stoves burn most of the smoke – it depends on the stove architecture.In theory a stove could burn all the smoke…

Clean Combustion of Coal

6Slide7

1

2

3

4

5

Coal supply

Pyrolysing zone

Semi-coking zone

Coke burning zone

Gas burning zone

Cooking zone

Unlike a TLUD, it can be refueled while burning without affecting the emissions.

Clean Combustion of Coal

7

CROSSDRAFT STOVE

1

2

4

3

5

6

Slide8

1

2

3

4

5

Raw fuel

Dehydration, devolatilisation starts

Semi-coking with lots of smoke

Smoke ‘cracking’ inside the coke

Gas burning with secondary air

Heat transfer to pot

All processes continue indefinitely.

It is a miniature semi-coking factory!

Clean Combustion of Coal

8

CROSSDRAFT STOVE

1

2

4

3

5

6

Slide9

1

1

2

3

4

5

The challenge is not to

do it

, it is to

sustain

this set of fuel processing and burning conditions.

4

The coke burns and shrinks, dropping ash into the ash drawer below

3

Pyrolysed coal drops down the grate

2 Semi-coked fuel falls into the space

I Coal in the bunker falls down

Clean Combustion of Coal

9

Crossdraft stove

1

2

4

3

5

6

Slide10

1

2

3

4

5

The depth of fuel in (4) determines the level of secondary air.

The gap under the bridge (3) combined with the grate angle controls the depth of the fuel.

The

width

of the grate (6) sets the fire-power level.

The volume of fuel in the bunker (1) determines the duration of the burn.

Clean Combustion of Coal

10

Crossdraft stove

1

2

4

3

5

6

6

Slide11

Clean Combustion of Coal

11

IMPACT – Indoor Air Quality

Slide12

LAB TESTS – Mongolian Baseline

26.6g PM

2.5

emitted in 2 hrsClean Combustion of Coal12Slide13

LAB TESTS – GTZ 7.4

59 mg PM

2.5 emitted in 3 hrs

Clean Combustion of Coal13Slide14

LAB TESTS – KG4.0

100 mg PM

2.5 emitted in 6 hrs

Clean Combustion of Coal14Slide15

Clean Combustion of Coal

15

IMPACT – Indoor Air QualitySlide16

Clean Combustion of Coal

16

IMPACT – Indoor Air QualitySlide17

Clean Combustion of Coal

17

IMPACT – Indoor Air QualitySlide18

Clean Combustion of Coal

18

IMPACT – Indoor Air QualitySlide19

Clean Combustion of Coal

19

IMPACT – Indoor Air QualitySlide20

Clean Combustion of Coal

20

IMPACT – Indoor Air QualitySlide21

Clean Combustion of Coal

21

IMPACT – Indoor Air QualitySlide22

Conclusions AND ADVICE

OVERALL PERFORMANCE

Clean Combustion of Coal

22

These stoves are at the pre-production prototype stage – more refinement neededThey heat and cook much better than all the traditional stoves

They have controllable heating and cooking power

They provide hot water 24/7

They all but eliminate indoor smoke

They provide 40% more heat burning 40% less fuel

They are made by artisanal welders ‘on the street’ for $160 (2 sheep)Slide23

Conclusions AND ADVICE

CONCEPT OF ‘CLEAN’

Clean Combustion of Coal

23

The concept of ‘clean coal’ as currently used is inappropriateThe concept of a ‘polluting fuel’ as currently used is inappropriate

The concept of a ‘clean stove’ as currently used is inappropriate

Only a

fuel

+

stove

+

user behaviour

can deliver a ‘clean solution’

which means things are only really clean in a context

Accepting this this has far-reaching policy implicationsSlide24

Conclusions AND ADVICE

INHERENT EMISSIONS - TOXINS

Clean Combustion of Coal

24

Some species of wood are highly toxic. We do not ban

all

biomass combustion.

Come coal contains what might be, may be, dangerous levels of:

Fluorine, Arsenic, Sulphur, Uranium, Mercury, Chrome…

Do not use them as a domestic fuel if exposure cannot be managed.

It is not reasonable to project that very real danger onto

all

coals of

all

types from

all

sources in the world – don’t generalize.

This mischaracterisation of all coal’s inherent emissions is not sustainable. Slide25

Conclusions AND ADVICE

INHERENT EMISSIONS REDUCTION

Clean Combustion of Coal

25

Inherent Emissions are not the result of poor combustion – it is in the coal

Same fuel Improved stove Insulated home

Fuel

 Stove with 2x efficiency  House with 1/3 of heat demand

= 1-(inherent emissions per kg x 0.5 x 0.33) =

83% reduction

This applies to CO

2

, SO

2

, Hg, Cr

6

, U, etc …without fuel processing?

Fuel

is

slightly processed – it is ‘sized’ to the stove’s requirements,10-25mmSlide26

Thank You!

QUESTIONS

Clean Combustion of Coal

26