Waste incinerator effluent characterization on a small energy-from-waste facility

Chemosphere, Vol.19, Nos.l~6,pp Printed in G r e a t B r i t a i n

373-379,

1989

0045-6535/89 $3.00 Pergamon Press plc

+

.00

WASTE INCINERATOR EFFLUENT CHARACTERIZATION ON A SMALL ENERGY-FROM-WASTE FACILITY

Gonnord M.F.

, Fraisse D.

, Vanderpol J.P.

Ecole Polytechnique, D~partement de Chimie, DCMR, F-91128 Palaiseau, *** CNRS, Service Central d'Analyse, F-69390 Vernaison, FRANCE Laurent Bouillet Ingenierie, F-92503 Rueil-Malmaison, FRANCE

FRANCE

ABSTRACT Increasing concern related to the adverse impact of emissions of traces of toxic substances on the environment has focused attention on energy-from-waste facilities as potential sources of these emissions, and particularly PCDDs and PCDFs emissions. In this paper, the 125 t/day L.B.I. plant in Montauban, France, is described, which was put into operation in 1986. This plant incorporates lime addition and a fabric filter for control of emissions. Emissions from the plant were extensively tested for particulates, heavy metals, PCDDs and PCDFs. The HRGC/HRMS protocol for PCDDs and PCDFs identification and quantitation is described. The results of this program indicate that properly designed energy-from-waste plants, with proper pollution control equipment and utilizing adequately trained staff can currently meet pollution control requirements which results in control of emissions to environmentally safe levels on a cost effective basis.

KEYWORDS Incineration;

energy-from-waste;

HRGC/HRMS;

PCDD; PCDF; analysis protocol.

INTRODUCTION Urban waste elimination is a problem of major concern for local communities. In many countries, refuse is just dumped in landfill. In France nearly 40% of municipal waste is incinerated. Due to the incineration technology, incineration plants are mostly located near large cities. A more difficult problem is waste elimination in small and medium size communities, especially rural and semi-rural ones. Incineration can offer an answer to this problem together for both environmental and economical reasons. The installation described herein illustrates a small, carefully conceived energy-from-waste facility developed cooperatively by the private and public sector. The plant is located near the City of Montauban, in a site adjacent to the community landfill. It was constructed by Laurent Bouillet Ingenierie and includes a cogeneration plant to increase the steam from the waste-to-energy facility. Steam is used in a district application and concerns mainly a hospital, schools, caserns and municipal buildings. The facility serves a population of 100,000 and also incinerates commercial and industrial non-hazardous solid waste of approximatively 40 metric tons per day. The daily average higher heating value (HHV) for the facility's-waste throughput varies between 2200 and 3200 Watt.hour/kg. The plant has been extensively tested for particulate, heavy metals and PCDDs and PCDFs emissions. These compounds have always been found in municipal waste incinerators both in the flyash and in the stack emissions (Karasek et al., 1986). Because incineration is generally considered to be the major source of PCDDs and PCDFs in the environment (Rappe, 373

374

1987), many studies have been carried out on municipal complete survey of a small-size installation.

incinerators.

This work is the first

PROCESS DESCRIPTION Refuse enters the plant in an enclosed waste reception building kept under negative pressure by drawing primary combustion air from the building. Waste is discharged from collection trucks into a pit. An overhead travelling bridge crane is used to help mix the waste in the pit and to charge the combustor hopper. One person in the control room runs the crane and acts as a back-up person to monitor combustion at the control panel. At the lower part of the waste combustion hopper, a reciprocating hydraulic ram with variable feed frequency introduces the refuse into the combustion chamber. The combustion chamber is designed to be dynamic in operation, featuring an oscillation movement which turns the refuse and mixes it thoroughly forty times during its approximate one hour residence time. Its volume is 42 m 3. The oscillating combustor has a cylindrical, truncated conical shape which insures maximum thermal radiance, thus keeping the ratio of primary air to solid organic volume remaining to be combusted fairly constant. These are two important factors necessary to obtain complete combustion. The objective is to minimize the amount of unburned carbon in the remaining residue (Figure i). Primary air is injected under the refuse (Figure 2) and is adjusted to the varying heat value of the refuse. The air quantity above stoechiometry is relatively constant. The primary air may, under certain circumstances, be mixed with recycled flue gas. The primary air is mainly introduced under and through the refuse to maximize combustion characteristics. The objective of the system's control of combustion air is to obtain 0% CO. The combustion chamber temperature is typically 1040 °C.

SECTIONAA

H

~oooogoooooooooouu~

r Fig.

Fig. 2.

I.

Fig. i. Combustion

chamber

: longitudinal

Fig. 2. Combustion

chamber

: traverse

section

section

375

A mixture of secondary air and recycled gas is introduced through the smaller diameter of the combustor to control temperatures and maintain proper turbulence at the top of the combustion chamber. In the tranquilization chamber, a planned and controlled air infiltration through the seal is introduced as well as recycled gas and tertiary air. The purpose of this combustion air is to act as a further control for temperatures and to insure maximum combustion of unburned organics. In this chamber, gases receive their final mix and their speed decreases considerably, resulting in partial collection of some heavier particules in the bottom of the tranquilization chamber. The temperature of the gases leaving the chamber is 920 °C. The heat exchanger is immediately adjacent to the combustor and is of a sophisticated water-tube type. It consists of a radiation chamber, where water-tubes are protected with refractory allowing the gases to cool before passing over tubes placed across the gas flow passage in the convection part of the exchanger. The Montauban facility has no superheat section and no economizer, although provisions have been made to add an economizer at a later date. Sootblowing is accomplished by means of compressed air. The scrubber at this plant was the first system installed in France and is of the dry type. Reagent in the form of lime is injected at the entrance of the reactor at the bottom, by means of a centrifugal fan. Permits cal]ed for a reduction in both SOo and HC1. The quantity of lime introduced is 2.5 to 3 times the stoechiometry compared to HCI. Particulate filtration is accomplished by fabric filters which are made of fiberglass with a teflon coating. The system can be temporarily by-passed if necessary. A reheat system has been installed utilizing an electric coil which is capable of maintaining a minimum of 80°C in case the system is temporarily stopped. This avoids the cementation of lime deposits on the filter. A general scheme of the plant is presented on figure 3. Lime is introduced at the bottom of the scrubber (9). Particulates are collected at the exit of the tranquilization chamber (4). Flue gases are sampled in the stack (13).

p

i

UNLOADING I IALL

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

'1' ,,i

LOADING I lOPPER HYDRAULIC RAN COMBUSTION CELL TRANQUILLISATION CHAMBER CLINKER EXItAUST I IOOD CLINKER EXTRACTOR DUST COLLECTION SYSTEM HEAT EXCtlANGER SOIUBBI']~ LIME S'I~)RAGE SILO FABRIC FILTER EXHAUST FAN STACK BRIDGE CRANE VIBRATING SCREEN

CONTROL ROOM

Fig.3. A general scheme of the p]ant.

i

376

The quantity of refuse incinerated per year refuse and stack gases is given in Table I.

is about

Table I. Composition

of refuse and stack gas.

Refuse

in °/oo)

(composition

C H 0 N C1 S H20

221 30.7 197.4 3.8 4.9 0.05 296.1

Minerals

250

EMISSION

32,000

tons.

Average

Stack gas (composition

N2 + r a r e g a s e s HCI SO Minerals

composition

of

in ib/hr)

7.756 5.916 5,638 39.104 5.00 0.40 0.60

SURVEY

Emission testing has been conducted for several weeks. monitoring, particulate and metals emission measurements. In this section the procedure more accurately described.

It

included

continuous

emissions

followed for PCDDs and PCDFs sampling and measurements

will be

PCDDs and PCDFs samplin$ An all glass lined modified method 5 train, meeting the guidelines of ASME (Draft protocol ASME, 1984) has been used for stack effluents sampling. It incorporates three main stages: a fiber particulate filter, a cold water cooling condenser and a two stage temperature controlled XAD2 trap placed below the condenser and washed by condensates collected under the XAD2 trap. Sampling was performed by CERCHAR (VerneuIl en Hallate-France). The sampled volume was between 1 and 2 m 3. The probe tube and all the glassware were carefully rinsed after sampling. The probe rinse and the particulate filter resulted in one sample, condensates and XAD2 extracts were combined into a second sample. Both samples were separately analyzed. PCDDs and PCDFs analytical

protocol

The analytical procedure included: -spiking of the raw sample with 20 ~i of a solution containing 50 mg/~l of one 13C12 labelled congener for each of the isomeric classes analysed. - Sohxlet extraction of particulate filters and XAD2 resins with glass distilled benzene for 48 hours. Kuderna Danish concentration of condensates, rinses and benzene extracts. - Extensive clean-up with selective adsorption/desorption from successively bare silica (Bio-SilA, Biorad, Richmond, Ca, USA), NaOH modified silica, bare silica, H_SO 4 modified silica and base silica again, neutral alumina (Alumina AG-10, Biorad), and w~en necessary Carbopack C (Supelco, Bellefonte, Pa, USA) carbon clean-up. GC/MS analysis was performed on a VG ZABHF system (VG Analytical, Manchester, U.K.) with a E1 only source at 10"000 dynamic resolution measured at 5% valley. GC was performed on two types of columns: group determination (CI a to CI~) was achieved for PCDDs and PCDFs on a single injection on a 60m DB5 (J & W, Rancho'Cordova, Ca, USA) column; isomer specific determination requires the use of a 50m CPSiL 88 (Chrompack, Bridgewater, N.J. USA) column and necessitates two separate injections, due to the recovery of the elutlon windows of the different isomers. With both columns a PTV injector was used. Temperature programs for both columns are summarized on Table II. -

-

377

Table II. Column temperature programs

CPSiL88 column

DB-5 column

temp time rate temp time rate temp time

temp time rate temp time rate temp time rate temp time

I: 70°C i: 1 min i: 15°C/min 2: 190°C 2: 0 min 2: 5°C/min 3: 240°C 3: 27 min

I: 90°C I: 1 min i: 25°C/min 2: 190°C 2: 0 min 2: 3°C/min 3: 250°C 3: 7 min 3: 4°C/min 4: 300°C 4: 15 min

The mass spectrometer operating parameters have been set at: source temperature 230 °C, trap current: 500 mA, electron energy 28 eV. The mass spectrometer was operated in the Selected lon Recording mode (SIR) of the two more abundant ions of the chlorine cluster for each isomeric family. The extraction and clean-up recovery was estimated relatively to 13C 2 1,2,3,4-TCDD added to the sample before GC/MS analysis. In this study recovery was one# estimated on TCDDs. - Different criteria were verified before positive identification of a peak: signal/noise ratio > i0 reproducibility of the+retention times isotopic r a t ~ within - 10% of the theoretical value recovery of C12 2,3,7,8-TCDD internal standard between 65 and 120% -

-

-

The total protocol is in agreement with QAQC criteria recommanded in the draft protocol ASME (1986). Three measurements were performed on the stack effluents.

RESULTS The results VI.

of emission

testing conducted

during one month are presented

in tables

III to

Table III shows that the combustion process was very tightly controlled with CO, NO , SO 2 and total hydrocarbons usually at very low levels. Occasional excursions of high C~ have been correlated to an increase of the furnace temperatures due to combustion of industrial plastic wastes, since excluded from the plant. Similarly high NO or SO excursions have been related to the combustion of wastes containing respectively h~gh leve~s of nitrogen and sulfur and resulting in a temperature raise. Table III. Continuous emission monitoring at stack.

CO 2

5 to 7%

02

CO

Less than 25 ppm

SO 2

Less than 25 ppm

Total hydrocarbons Particulates

NO

13 to 15% 125 to 150 ppm

less than 1 ppm (CH 4 equivalent)

: 2 to 4 mg/Std m 3 at 12% CO 2 dry gas.

378

Particulate emission level was generally very low. Among eight measurements, one was rather high due to the by-passing of the baghouse for 15 minutes toward the end of the test to control a high temperature excursion. The effect of lime introduction in the scrubber is exemplified HCI is usually above 97% and never below 91%. Table IV.

in Table IV. The removal of

Hydrogen chloride removal

date

2/24

2/25

2/26

3/3

boiler output (ppm at 12% CO 2)

1246

1954

1625

1543

stack (ppm at 12% CO2)

111

38

50

12

91

98

97

99

(1987)

% Removal

Table V shows the metal content of the stack effluent. The stack temperature was between 203 and 24 °C. The presence of mercury was measured to be between 0.3 and 0.6 mg per std m 3 with the air pollution control facility at the plant. Table V. Heavy metals emission

(in ~g/Std m 3 at 12% CO 2 dry)

Zn and Pb

:

between

100 and 160 ~g/Std m s

AI, Mg, Cu, Sn

:

between 10 and 50 ~g/Std m s

Ba, Cd

:

between 2 and 10 ~g/Std m 3

Mo, Sb, Co, Ni, Mn, Cr, V : less than 2 ~g/Std m 3 Ag, Be, Se

: non detectable

Dioxins and furans tests results are presented in Table VI. PCDDs and PCDFs measurements were reproducible from one day to the other. Only a few percent (<< 5%) of the total PCDDs and PCDFs measured in the stack were found in the particulates. 2,3,7,8-TCDD toxic equivalent factors have been calculated from the EPA 85 formula. Values obtained were 0.56, 0.28 and 0.70 ng/Nm 3 dry gas. The average of the three tests in terms of 2,3,7,8-TCDD equivalent was 0.51 ng/Nm 3 dry gas. It is among the lowest results achieved today, comparing favorably with Tulsa and Wurtburg installations at 0.7 and 0.4 ng/Nm 3 and somewhat higher than Marion County Oregon facility at 0.i ng/Nm 3. CONCLUSION The survey presented here exemplifies that emissions from a small-slze incineration plant can be acceptable on an environmental point of view. The good reproducibility of the measurements demonstrates the ability of the installation to be steadily operated. Results of operation and testing at the Montauban, France, plant show that it is possible to construct and operate a small energy-from-waste plant at a reasonable cost to fulfill current air pollution requirements, specially for PCDDs and PCDFs emissions. Although it is not the purpose of this paper, after two years of operation of the plant, the cost of investment together with the cost of incineration per treated ton of waste, can compete with the equivalent costs for a large size facility. Thus, small-size semi-rural or rural connnunities, down to i00"000 inhabitants, now have an available solution for their domestic waste incineration with energy recovery problems.

379

Table VI. Total PCDDs and PCDFs emission - Dry gas at 12% CO 2 in nanograms/Std m 3. Sum of Gas + Solid. Feb. 24 th 2378 TCDF other 2378 TCDD other 2378 PCDF other 2378 PCDD other 2378 H_CDF o~her 2378 H.CDD o~her 2378 H_CDF o~her 2378 H_CDD o~her OCDF OCDD

TCDF TCDD PCDF PCDD H6CDF H6CDD H7CDF H7CDD

sum of gas + solid

Feb. 25 th

March 3 rd

1,6 7,0 0,06 1,2 1,6 14,9 0,2 2,7 1,8 2,5 0,6 4,1 0,2 0,6 0,8 1,2 0,8 3,7

0,8 11,8 0,04 3,4 0,4 9,7 0,04 4,9 1,1 3,2 0,6 5,8 0,8 1,9 0,6 0,8 1,3 3,2

0,7 9,8 0,04 3,0 3,2 27,2 0,2 7,3 2 1 8 7 0 7 15 1 2 7 5 3 ,6 ,3 ,i ,5

45,5

56,8

93,5

REFERENCES Karasek, F.W. and Hutzinger, O. (1986). Dioxin danger from garbage incineration. Anal. Chem., 58, 633A-642A. Rappe, C. (1987). Global distribution of Polychlorlnated Dioxins and Dibenzofurans (Solving Hazard. Waste Probl.). ACS Symp. Set., 338, 20-33. Environmental standards workshop on developing drafts standards for sampling and measuring trace chlorinated emissions from waste-to-energy combustion facilities. Draft protocols ASME, Tysons Corners, Virginia, Jan. 23-26 (1984).