Presented at the AWMA International Specialty Conference on Waste Combustion in Boilers and Industrial Furnaces April, 1994

ABSTRACT

Effective August 21, 1991 the United States Environmental Protection Agency (USEPA) adopted the Boiler and Industrial Furnace (BIF) rules which govern cement kiln operations burning hazardous waste fuel and set limits on cement kiln emissions of metals, HCL/chlorine and organics.

Dioxin testing was required to address the concerns of the USEPA arising from the review of stack test data from municipal waste combustion units. Dioxin emissions tests were developed and designed to meet EPA criteria under worst-case conditions and performed at 15 cement plants. Upon compilation of this data, an evaluation was performed for a correlation between HCl and Cl₂ emissions and dioxin emissions. When no correlation was found, additional data analysis revealed a trend between the kiln exit temperature and dioxin emissions.

Additional data was gathered from selected cement plants and the available individual run data was plotted against temperatures at APCD device inlets. The dioxin emissions show a decrease in concentration as a function of decreasing temperature. This corresponds with EPA's concerns about dioxin emissions increasing as a function of stack or APCD temperatures.

In conclusion, temperature seems to be a primary factor for dioxin formation. If temperatures can be controlled below 400^oF, there may be a reduction in dioxin emissions from cement kilns whether or not they burn hazardous waste fuels.
 

INTRODUCTION

Effective August 21, 1991 the United States Environmental Protection Agency (USEPA) adopted the Boiler and Industrial Furnace (BIF) rules which govern cement kiln operations burning hazardous waste as fuel. BIF set limits on cement kiln emissions of metals, chloride and organics. Testing was required by August 21, 1992, and if, during the course of testing, the air pollution control device (APCD) in use at the cement kiln recorded temperatures between 450^oF and 750^oF, then dioxin emission testing was necessary. The dioxin testing was mandated due to a lack of data available from cement kilns for these emissions and USEPA concerns arising in the review of stack test data from municipal waste combustion units.

Approximately fifteen dioxin emissions tests were performed at cement plants. Many of the emissions tests were developed to meet EPA criteria and were designed to be under worst case conditions. A worst case scenario would be defined as maximum waste fuel being burned with the highest allowable chlorine content in addition to the maximum temperature that would be encountered in the APCD. Table 1 lists the results of the emissions tests.

Upon compilation of this data, an evaluation was performed for a correlation between HCl and Cl₂ emissions and dioxin emissions. Wide variation in the HCl and Cl₂ emissions was observed. No correlation could be obtained between chlorine and dioxin emissions. However, a trend was observed between the kiln exit temperature and dioxin emissions. Higher temperatures were associated with the higher dioxin emissions.

The database was sorted by descending temperatures (Table 2.) and corrected to 7% oxygen. Subsequent to the sort, the data was plotted (Plot 1). The dioxin emissions appear as a function of stack exit temperature. The dioxin emissions show a corresponding decrease in concentration as a function of temperature when it drops below approximately 585^oF with significant dioxin emissions occurring at temperatures in the 600^oF to 750^oF range. This corresponds with EPA's concerns about dioxin emissions increasing as a function of stack or APCD temperature increase. Subsequent to this finding, we chose one plant in the U.S. that had eleven tests performed under varying conditions yielding results exhibiting a range of temperatures vs. dioxin emissions. Table 3 outlines the results for that particular test facility. The corresponding dioxin emissions are presented for those emissions tests, during which a similar type of curve is observed (Plot 2). Higher dioxin emissions occur during the higher temperatures (greater than 450^oF and increasing to 495^oF) with a significant decrease in dioxin emissions occurring below 420^oF.
 

CONCLUSION

In conclusion, temperature seems to be a contributing factor to dioxin formation. The lower temperature in the APCD may result in lower dioxin emissions being formed with subsequent lower emissions exiting the stack. However, it was noted that hydrocarbon content, alkali content and chlorine loading may also be contributing factors in addition to temperature and need to be investigated further. If temperatures can be controlled below 450^oF, there may be a reduction in dioxin emissions both from cement kilns burning and not burning hazardous waste fuels.
 
 

Table 1. Cement kiln dioxin data and corrected values for 7% Oxygen.
NAME	KILN#	DATE	RUN#	TOTAL TEQ	TOTAL NGDSCM	EXIT TEMP	STACK TEMP	O2	FLOW RATE (dscmm)	TEMP USED	TEQ at 7% 02	TOTAL DIOXIN at 7% 02	LOG TEQ 7% 02	LOG  TEMP
ASH GROVE	1	4/92	1	3.22e-01	6.85e+01	422	---	10.8	2229	422	4.420e-01	9.402e+01	-3.55e-01	2.63e+00
Chanute			2	1.31e+00	1.42e+02	439	---	10.4	2260	439	1.730e+00	1.875e+02	2.38e-01	2.64e+00
			3	1.50e+00	1.38e+02	435	---	10.7	2255	435	2.039e+00	1.876e+02	3.09e-01	2.64e+00
			4	5.01e+00	2.54e+02	448	---	10.7	2199	448	6.810e+00	3.452e+02	8.33e-01	2.65e+00
ASH GROVE	2	11/92	1	3.42e-01	2.06e+01	392	---	13	4489	392	5.985e-01	3.605e+01	-2.23e-01	2.59e+00
Chanute			2	1.67e-01	7.72e+00	340	---	10	4365	340	2.125e-01	9.825e+00	-6.73e-01	2.53e+00
			3	3.10e-01	1.39e+01	369	---	11.7	4192	369	4.667e-01	2.092e+01	-3.31e-01	2.57e+00
ASH GROVE	1	7/92	1	5.58e-01	8.63e+01	487	---	8	1558	487	6.009e-01	9.294e+01	-2.21e-01	2.69e+00
Foreman			2	1.39e+01	1.04e+03	495	---	8	1671	495	1.497e+01	1.120e+03	1.18e+00	2.69e+00
			3	1.73e+00	3.01e+02	503	---	8.8	1707	503	1.985e+00	3.454e+02	2.98e-01	2.70e+00
			4	6.63e-01	1.92e+02	490	---	7.7	1794	490	6.979e-01	2.021e+02	-1.56e-01	2.69e+00
ASH GROVE	2	1/92	1	5.61e-01	6.12e+01	492	---	6.7	2023	492	5.492e-01	5.992e+01	-2.60e-01	2.69e+00
Foreman			2	2.07e-01	1.46e+01	462	---	7.4	2086	462	2.131e-01	1.503e+01	-6.71e-01	2.66e+00
			3	3.02e-01	2.12e+01	481	---	7.6	2021	481	3.155e-01	2.215e+01	-5.01e-01	2.68e+00
	3	7/92	1	1.26e+02	9.62e+00	487	---	5.2	2508	487	1.116e+02	8.524e+00	2.05e+00	2.69e+00
			2	9.34e-01	4.84e+00	474	---	6	2482	474	8.717e-01	4.517e+00	-5.96e-02	2.68e+00
			3	6.56e-01	3.63e+00	474	---	5.7	2481	474	6.003e-01	3.322e+00	-2.22e-01	2.68e+00
ASH GROVE	2	5/92	1	2.99e-01	8.72e+00	356/722	380	10.5	2777	380	3.987e-01	1.163e+01	-3.99e-01	2.58e+00
Louisville			2	3.26e-01	6.43e+00	355/722	386	9.8	2808	386	4.075e-01	8.038e+00	-3.90e-01	2.59e+00
			3	9.50e-01	2.06e+00	356/756	379	10.7	2696	379	1.291e+00	2.800e+00	1.11e-01	2.58e+00
			4	4.38e-01	1.37e+01	356/746	381	11.1	2732	381	6.194e-01	1.937e+01	-2.08e-01	2.58e+00
CONTINENTAL		5/92	1	3.10e+01	1.66e+03	597.22	597.22	4	3785	597	2.553e+01	1.367e+03	1.41e+00	2.78e+00
Hannibal			2	1.59e+01	1.05e+03	603.85	603.85	5.6	3657	604	1.445e+01	9.545e+02	1.16e+00	2.78e+00
			3	1.37e+01	1.55e+03	---	---	4.4	3762	600	1.155e+01	1.307e+03	1.06e+00	2.78e+00
ESSROC		5/92	1	4.22e+00		---	334	7.24	2373	334	4.294e+00		6.33e-01	2.52e+00
Logansport			2	7.89e+00		---	326	7.71	2514	326	8.312e+00		9.20e-01	2.51e+00
			3	7.43e+00		---	336	7.7	2526	336	7.821e+00		8.93e-01	2.53e+00
HOLNAM		4/92	1	3.33e-02	---	596.72	493.8	4.4	7126	586	2.808e-02		-1.55e+00	2.77e+00
Clarksville			2	5.25e-02	---	596.39	501.3	4.4	7231	596	4.428e-02		-1.35e+00	2.78e+00
			3	5.66e-01	---	598.95	508.6	4.4	7329	598	4.773e-01		-3.21e-01	2.78e+00
HOLNAM	1	7/92	1	1.13e-01	3.82e+01	---	362.5	10.1	3533	362	1.451e-01	4.906e+01	-8.38e-01	2.56e+00
Holly Hill			2	1.40e-01	8.36e+01	---	371.3	10.1	3271	371	1.798e-01	1.074e+02	-7.45e-01	2.57e+00
			3	3.02e-01	3.46e+02	---	373.4	10.1	3331	373	3.879e-01	4.444e+02	-4.11e-01	2.57e+00
	1-BL	7/92	1	1.90e-02	6.29e+01	---	363.5	10.3	3495	363	2.486e-02	8.230e+01	-1.60e+00	2.56e+00
			2	9.85e-03	1.69e+02	---	370.8	10.3	3496	370	1.289e-02	2.211e+02	-1.89e+00	2.57e+00
			3	2.64e-02	1.45e+02	---	366.4	10.3	3332	366	3.454e-02	1.897e+02	-1.46e+00	2.56e+00
	2	7/92	1	1.09e+00	8.36e+00	---	488.3	7	3946	488	1.090e+00	8.360e+00	3.74e-02	2.69e+00
			2	1.49e+00	4.58e+00	---	485.2	7	3965	485	1.490e+00	4.580e+00	1.73e-01	2.69e+00
			3	1.88e+00	3.98e+00	---	495.8	7.02	3856	495	1.883e+00	3.986e+00	2.75e-01	2.69e+00
	2-BL	7/92	1	1.55e-02	---	---	420.1	7	3953	420	1.550e-02		-1.81e+00	2.62e+00
			2	5.86e-03	3.26e+02	---	415.6	7	3668	415	5.860e-03	3.260e+02	-2.23e+00	2.62e+00
KOSMOS CEMENT	COND 2	5/92	1	1.16e+00	---	---	310	14.9	7549	310	2.662e+00		4.25e-01	2.49e+00
			2	1.06e+00	---	---	323	14.6	7416	323	2.319e+00		3.65e-01	2.51e+00
			3	1.16e+00	---	---	314	14.6	7297	314	2.538e+00		4.04e-01	2.50e+00
			4	1.32e+00	---	---	320	15.4	8195	320	3.300e+00		5.19e-01	2.51e+00
LAFARGE		6/92	1	7.49e-02	---	511.2	360	11	9346	512	1.049e-01		-9.79e-01	2.71e+00
Alpena			2	5.23e-02	---	508.5	365	11	8927	508	7.322e-02		-1.14e+00	2.71e+00
			3	1.22e-01	---	499.6	366	11	9575	499	1.708e-01		-7.68e-01	2.70e+00
LAFARGE	1	5/92	1	5.94e+00	---	544	441	5.5	1167	544	5.365e+00		7.30e-01	2.74e+00
Fredonia			2	2.65e+00	---	539	440	5.5	1192	539	2.394e+00		3.79e-01	2.73e+00
			3	2.72e+00	---	552	437	5.5	1161	552	2.457e+00		3.90e-01	2.74e+00
	2	5/92	1	3.62e+00	---	493	449	5.6	1382	493	3.291e+00		5.17e-01	2.69e+00
			2	9.39e+00	---	545	468	5.6	1367	545	8.536e+00		9.31e-01	2.74e+00
			3	2.51e+00	---	500	463	5.6	1450	500	2.282e+00		3.58e-01	2.70e+00
LONESTAR		5/92	1	3.18e+00	6.59e+02	536.06	464.96	5.4	3407	536	2.854e+00	5.914e+02	4.55e-01	2.73e+00
Greencastle			2	3.45e+00	7.70e+02	521.95	457.46	5.4	3518	521	3.096e+00	6.910e+02	4.91e-01	2.72e+00
			3	4.24e+00	8.39e+02	523.28	456.36	5.4	3564	523	3.805e+00	7.529e+02	5.80e-01	2.72e+00
MEDUSA	1	6/92	1	2.99e+01	---	---	466	11.1	2926	466	4.228e+01		1.63e+00	2.67e+00
Wampum			2	6.17e+01	---	---	456	11.3	2957	456	8.905e+01		1.95e+00	2.66e+00
			3	5.51e+01	---	---	477	11.1	2912	477	7.792e+01		1.89e+00	2.68e+00
N. TEXAS CEM.	COND 1	6/92	1	1.38e-02	---	415	320	7.6	1903	415	1.442e-02		-1.84e+00	2.62e+00
			2	1.98e-02	---	438	338	7.4	2104	438	2.038e-02		-1.69e+00	2.64e+00
			3	2.08e-02	---	434	342	7.5	2042	434	2.157e-02		-1.67e+00	2.64e+00
N. TEXAS CEM.	COND 2	6/92	1	8.40e-02	---	459	358	7.4	1924	459	8.647e-02		-1.06e+00	2.66e+00
			2	3.02e-01	---	481	374	7.4	1990	481	3.109e-01		-5.07e-01	2.68e+00
			3	1.17e-01	---	442	346	7.4	1890	442	1.204e-01		-9.19e-01	2.65e+00
RIVER CEMENT		6/92	1	5.21e+01	2.13e+03	---	479	10.1	8383	479	6.692e+01	2.736e+03	1.83e+00	2.68e+00
Festus			2	5.73e+01	2.30e+03	---	483	10.1	8251	483	7.360e+01	2.954e+03	1.87e+00	2.68e+00
			3	4.02e+01	1.60e+03	---	479	10.1	8406	479	5.163e+01	2.055e+03	1.71e+00	2.68e+00
SOUTHDOWN	COND 1	6/92	1	4.54e-02	---	---	271	10.8	3245	271	6.231e-02		-1.21e+00	2.43e+00
Fairborn			2	6.65e-02	---	---	294	11.1	3164	294	9.404e-02		-1.03e+00	2.47e+00