Emissions of domestic stoves

Emissions of domestic stoves

Zeedijk, H. (1985). Emissions of domestic stoves. In T. D. Lekkas (Ed.), Proceedings of the International conference Heavy Metals in the Environment (pp. 165-167). CEP consultants.

Document status and date: Published: 01/01/1985

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EMISSIONS OF DOMESTIC STOVES H.ZEEDIJK~

ABSTRACT

Emissions of air pollutants from stoves for residential heating burning solid fuels have been studied. With the aid of Proton Induced X-ray Emission elements have been

analysed in smoke particulates. Results are given and the reliability of the analysis is discussed.

INTRODUCTION

The use of solid fuels for residential heating is growing because these fuels are relatively cheap. In the u.s.A. already 10% of the houses is heated with wood as principal fuel, but in countries with less wood stocks also coal is attractive. As а result of this development the emissions of а numЬer of air pollutants are promoted. Among them smoke particulates are important, because they

contain toxic polycyclic aromatic hydrocarbons and toxic elements. In а study in which several types of solid fuels have been comЬusted in а woodstove, а coalstove and а

fireplace, elements in the emitted smoke particulates have been analysed Ьу Proton Induced X-ray Emission (PIXE). The used analytical method has been described elsewhere (Ref 1). The advantages of the PIXE-analysis are that i t is

sensitive, i t demands little work and i t does not require knowledge of the elements which are analysed. Accuracy is however limited.

RELIABILITY OF ТНЕ PIXE ANALYSIS Before the analysis of smoke particulates they are

collected Ьу filtration of the flue gases. The filter with on i t а layer of smoke particles is plaдed in vacuo in а beam of 3 MeV protons (diameter 1 cm). Excited atoms

generate X-rays that are measured

Ьу an energy dispersive detector. In the fluorescence spectrum the peeks correspond to the specific emission energies of elements and the peek areas with the

quantities of those elements which can Ье computed using factors

relating to physics and geometry of the set up.

Deviation from theory is possiЫe

Ьу several causes such as:

proton

а

с

f1lter

- the protons are slowing down in the substrate. fome of them can Ье absorbed.

- the emission of X-rays does not reach the detector,

~ Laboratory of Instrumental Analysis, Eindhoven Univ. of

because they are absorbed in the substrate.

In the figure proton А do not give fluorescence; В does, but the X-ray quanturn is absorbed; С does and the quanturn is counted Ьу the detector when i t has the right direction. Calibration has been perforrned to study the deviation from theory. Filters were loaded with а known amount of

rnonodisperse particles of arnmonium nitrate, to which а known quantity was added of either Fe-, РЬ-, Cd or Ba-nit~ate. The aerosol was generated using а spinning top aerosol generator as described Ьу Mitchell(Ref

2

)

.

used with resp.

rnean diarneters of 1000 5.90, 8.24 or 11.О 900 -800 rnicrometer. Hillipore and nuclepore filters 700 of resp. 100 and 10 micrometer were tested. The advantage of nuclepore is, that the filter is thinner, but а disadvantage is, that i t contains а consideraЫe 600 S00 400 300 200 100 Counts/pC IRON load (p9/r:rn2) .1 . 2 • 3 • 4 • S .6 • '7 • В

contamination of the element Bromine.

250 Count•/pC 200 150 100 50 CADHil1!4 • aJ.111pore •. nuc:lepore 2 ] 4 5 6 7 8

The figures give the calibrations of Fe and Cd. The drawn line is the theoretical relationship. The dotted curve in the Cd-calibration shows the effect of addition of а large arnount of Ba-nitrate to the sample. Now there is а huge deviation from the theoretical line, but at low particles

load on the filter the theory always give а reasonaЫe

estimate of the concentration. For not calibrated elements can Ье assurned that this is also the case.

Not mentioned in the figures is that also the size of the particles has been varied. But i t is clear, that the

particle size have not any influence.

SMOKE PARTICULATES

In the practical application of the srnoke particulates analysis the detection limit for small peaks is а function of the variation in the background signal. This background has as main origin the Bremsstrahlung, i. е. electrornagnetic

radiation measured Ьу the detector originating from the

mass of the sample. So for the value of the Bremsstrahlung also the filter thickness and the organics in the

particulates are important.

The rninimum detectaЫe peak is given Ьу the equation:

Nz

=

in which Nz is equal to the peak area and N~ equals the background area.

For elements with atomic nurnЬers of 15 - 80 the detection limit has been determined in smoke samples. From 11 values the average and the standard deviation have been calculated. In the figure this average value increased with two times

the standard deviation is plotted versus atomic nurnЬer.

The drawn curve shows that the sensitivity of the Pixe-method expressed in the unit rng/kg fuel for the

choosen conditions was the best₀

for an atornic nurnЬer of

about 50. At lower atomic

nurnЬers Brernsstrahlung is

disturbing seriously and

at higher atomic nurnЬers

the fluorescence yield is decreasing.

An other factor that can influence the detection limit is the peek-to-peek

109 d.etect1on 11•1 t

.g/k9

1D ~D 3D •о 5D ,о _{7D 10 ,о 100}

interaction. Neighbouring to а very high peek i t is possiЫe

that а small p_eek is not detected in spi te· of the f act that

i t has а size above the detection lirnit derived frorn the

background signal.

The tаЫе below presents the results of the analysis of

srnoke particulates frorn the cornЬustion of wood and two types

of browncoal in а woodstove, and of anthracite and two types

of bituminous coal in а coal stove. The values are given

in the emission unit rng/kg fuel.

Woodstove Coalstove

Wood Br.Coal 1 Br,Coal 2 Anthr, Bit.Coal 1 Bit,Coal 2

Bromine о .1 .7 ,6 1.4 1.5 Calcium о о о 9,4 6,8 2.5 Chlorine 24 о 8.2 40,5 125 56.5 Copper • 3 • 2 .1 .6 6.1 ,4 Iron • 5 .6 ,3 26,6 8.3 1.0 Lead .5 .1 .4 3,1 5.2 1.8 Molybdenum о о о .3 .1 о Potassium 10.2 о 2.1 3.1 .9 з.о Selenium о о о о .1 о Sulphur о 9.8 12.7 103 204,5 83 Zinc 1.1 . 2 .1 2,1 4.3 1.6

For not gi ven elements and f or zero resul ts the emission

was below the detection limit. It can Ье concluded that

the emissions of the coals are much higher than those of the fuels wood and browncoal.

REFERENCES

1. H.Kivits, Thesis Eindhoven University of technology

(1980)

2. J.P.Mitchell, C.A.Ramsy & N.A.Rowe, J.Aerosol Sc. 14,