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’

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

tHeory of smoke Production ‘Coked’ coal is ordinary coal that is roasted using a process called ‘destructive distillation’. Known in China since the 9th 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

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

CROSSdraft Stove Coal bunker on one side Fire at the bottom 1 2 3 4 5 CROSSdraft Stove Coal bunker on one side Fire at the bottom Flames rise from other side Cooking and heating functions are relatively easy to arrange 3 1 2 CPP – GTZ 7.1, 2010 Clean Combustion of Coal

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

CROSSDRAFT STOVE Coal supply Pyrolysing zone Semi-coking zone 1 2 3 4 5 6 1 CROSSDRAFT STOVE 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. 2 4 3 Clean Combustion of Coal

CROSSDRAFT STOVE Raw fuel Dehydration, devolatilisation starts 1 2 3 4 5 6 1 CROSSDRAFT STOVE 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! 2 4 3 Clean Combustion of Coal

1 2 3 4 5 6 1 Crossdraft stove 5 1 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 2 4 3 Clean Combustion of Coal

1 2 3 4 5 Crossdraft stove 6 1 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. 2 4 3 6 Clean Combustion of Coal

IMPACT – Indoor Air Quality Clean Combustion of Coal

LAB TESTS – Mongolian Baseline 26.6g PM2.5 emitted in 2 hrs Clean Combustion of Coal

LAB TESTS – GTZ 7.4 59 mg PM2.5 emitted in 3 hrs Clean Combustion of Coal

LAB TESTS – KG4.0 100 mg PM2.5 emitted in 6 hrs Clean Combustion of Coal

IMPACT – Indoor Air Quality Clean Combustion of Coal

IMPACT – Indoor Air Quality Clean Combustion of Coal

IMPACT – Indoor Air Quality Clean Combustion of Coal

IMPACT – Indoor Air Quality Clean Combustion of Coal

IMPACT – Indoor Air Quality Clean Combustion of Coal

IMPACT – Indoor Air Quality Clean Combustion of Coal

IMPACT – Indoor Air Quality Clean Combustion of Coal

Conclusions AND ADVICE OVERALL PERFORMANCE These stoves are at the pre-production prototype stage – more refinement needed They 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) Clean Combustion of Coal

Conclusions AND ADVICE CONCEPT OF ‘CLEAN’ The concept of ‘clean coal’ as currently used is inappropriate The 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 implications Clean Combustion of Coal

Conclusions AND ADVICE INHERENT EMISSIONS - TOXINS 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. Clean Combustion of Coal

Conclusions AND ADVICE INHERENT EMISSIONS REDUCTION 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 CO2, SO2, Hg, Cr6, U, etc …without fuel processing? Fuel is slightly processed – it is ‘sized’ to the stove’s requirements,10-25mm Clean Combustion of Coal

Thank You! QUESTIONS Clean Combustion of Coal