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• TEST RESULTS

The quantitative burnout of carbon in flames of solid and liquid fossil fuels remains a continuing combustion-engineering challenge, made more difficult by the use of many Nox control strategies. Because unburned fuel carbon represents a source of both pollution and inefficiency, there is an increasing need for the development of technologies that enhance carbon burnout. The introduction of Carbonex provides a new option for industry to use in resolving fuel and site specific combustion problems.

• Experimental Data

Standardized combustion tests were performed by Battelle Columbus Division, under simulated furnace, boiler or diesel engine conditions to determine with certainty the effect of Carbonex catalyst on the combustion performance of bituminous and lignite coal, crude oil, heavy and light fuel oil, and diesel fuel. The Research Summary section of the Battelle reports, together with a detailed list of the characteristics of each of the fuels that were studied and the tabular results of the investigations are included in this report. The reference documents are the following Battelle reports, prepared by Dr. James J. Reuther, Principal Research Scientist, Fuels and Combustion Section, Columbus Division (except where noted):

• "Laboratory Evaluation of Carbonex as a Bituminous or Lignite Coal Catalyst" (coal report), March 1, 1990.
• "Evaluation of Carbonex: A Coal or Oil Combustion Additive" (coal and crude oil report), April 30, 1988.
• "Laboratory Evaluation of Carbonex as a Light or Heavy Fuel Oil Combustion Additive" (oil laboratory report), June, 1989.
• "Field Evaluation of Carbonex as a Light Fuel Oil Boiler Combustion Additive" (oil field report), W. Steiger, R. Schmitt, and J. Reuther, Battelle Motor – und Fahrzeugtechnik, Geneva Research Centres and Columbus Division, June 15, 1989.
• "Evaluation of Carbonex as a Diesel Engine Combustion Additive" (diesel report), November 15, 1988.

An evaluation of the effects of Carbonex on deposit formation and wear in diesel engines was undertaken by the Southwest Research Institute in San Antonio and the results are summarized in the report, prepared by Dr. Steven G. Fritz, Senior Research Scientist, Engine and Vehicle Research Division, entitled "Carbonex Diesel Fuel Additive Evaluation", dated May 1989.

• Quality Control

A criticism of many other combustion additive evaluations is that they lacked proper quality assurance and quality control. Battelle produced data of exceptional quality by using EPA standardized, internationally accepted procedures. The experimental uncertainty in the raw data, which is presented in this report was determined by performing duplicate combustion tests and analyses. Based upon the results of redundant and random testing, the relative uncertainty in the absolute values of specific combustion characteristics was determined as follows:

• Primary Effects of Carbonex on Combustion

The primary effects of Carbonex, as observed in all the tests, are improved combustion efficiency and the reduction of unburned carbon in the particulate emissions. Carbonex promotes carbon oxidation in flames. The treatment level of the active ingredient varies depending upon the quality of the fuel employed. Difficult-to-burn-out fuels, coals, and heavy oils, require higher Carbonex levels than light furnace oil and diesel fuel. The Carbonex treatment levels are far lower than those used with comparable combustion additives and this aspect of the Carbonex treatment makes it unique in the marketplace.

Before analyzing the experimental results in detail it should be recognized that the treatment dosage and end result are likely to be site and fuel specific. The initial coal tests, presented in Tables 2, 3 and 4, were conducted on a very efficient burner and thus there was very little carbonaceous ash from the untreated burns. The boiler which was used was operating at 99.62 percent carbon efficiency before Carbonex was injected.

The carbon efficiency was raised to 99.88 percent upon treatment. The combustion efficiency was improved by promoting the burning of carbonaceous ash as the as the carbon content in the ash was reduced by 74 percent in the tests.

In subsequent tests Carbonex was evaluated at two levels of excess combustion air (10 or 26%) as a function of secondary combustion swirl (tuned or detuned) and coal particle size (60 or 80% and 200 mesh). The characteristics of neat pulverized coal flames injected with an equal volume of carrier established baseline combustion performance. These tests employed either a pilot-scale furnace to obtain direct data on combustion performance, without or with Carbonex and/or a thermogravimeter analyzer to obtain indirect data on the same.

The Carbonex injection method , which was developed to introduce the additive into coal flames, has proven to be effective. The method eliminates the need for expensive modifications to the existing systems or for pre-treating of the coal which can result in poor coal handling characteristics. The conversion costs would be minimal as would the down-time required to convert to the Carbonex fuel treatment.

The increased combustion of carbon was accompanied by an increase of fuel bound nitrogen. While increased Nox emissions emphasize the effectiveness of Carbonex as a combustion additive, this is an undesirable effect. A number of additional test were undertaken in an attempt to decouple the relationship between carbon and nitrogen combustion.

• Effects of Carbonex and Excess Air Levels on NOx Emissions

The effect of using the Carbonex additive with poorer-burning, higher nitrogen containing fuels, such as coal, crude oil or heavy oils, is to increase Nox emissions. The Carbonex treatment has little or no effect on Nox emissions from the combustion of high quality, lower nitrogen containing fuels such as light heating oil or diesel fuel. The logical conclusion from all the Battelle tests is given in the following statement from page 21 of the Field Evaluation of Carbonex as a Light Fuel Oil Combustion Additive.

• Reducing secondary combustion air swirl and increasing average coal particle size for untreated coal flames:
  -Decreased Nox emissions,
  -Increased mass-mean particle size,
  -Increased particulate loading, and
  -Decreased combustion efficiency;
  with changes more or less a function of excess air.
• Injecting Carbonex into the detuned or coarser-sized high volatile bituminous coal flames:
  -Increased Nox emissions,
  -Decreased mass-mean particle size,
  -Decreased particulate loading, and
  -Increased combustion efficiency;
• With the incremental changes almost offsetting those caused by detuning the burner coarser grinding coal.
• Reducing excess air from 26 to 10 percent in low-swirl or coarser-sized coal flames injected with Carbonex resulted in a net reduction in Nox of about 25 percent while maintaining combustion efficiency at the 98 + percent level.

• Laboratory Evaluation - Carbonex as a Bituminous or Lignite Coal Combustion Catalyst

Research Summary

Standardized combustion tests and analyses were performed by Battelle under laboratory-simulated utility-boiler conditions to determine, with certainty, the effect of a coal combustion catalyst called Carbonex on the combustion performance of high-volatile bituminous and lignite coal. These tests employed either a pilot-scale furnace to obtain direct data on combustion performance, without or with Carbonex, and/or a thermogravimeter analyzer to obtain indirect data on the same . The influence of flame-injected or treated Carbonex iron was evaluated at two levels of excess combustion air (10 or 26%) as a function of secondary combustion swirl (tuned or detuned) and coal particle size (60 or 80% 200 mesh). The characteristics of neat pulverized coal flames injected with an equal volume of carrier established baseline combustion performance. The following were the significant findings of the evaluation:

• The ability of Carbonex to enhance the combustibility of already efficiently burning bituminous or lignite coals was unambiguous proof-of-concept for Carbonex as a combustion catalyst.
• The use of Carbonex in pulverized bituminous or lignite coal flames offers a means by which to maintain high levels of combustion efficiency (99 + %) at reduced levels (10 - %) of excess combustion air. 
• The use of Carbonex allows strategic technology supplements to low-excess-air-firing, such as swirl and coal particle size without a penalty to combustion efficiency.
• Carbonex usage offers an effective means by which to achieve a net reduction of Nox emissions to compliance levels.
• Carbonex usage will probably enhance the performance of electrostatic precipitation for particulate control.

In Summary, this study confirms that Carbonex is a viable catalyst for the improved combustion of bituminous lignite coal.

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• Residual Fuel Oil Combustion with Carbonex

• Carbonex as a Fuel Oil Treatment

• Laboratory Evaluation - Carbonex as a Light or Heavy Fuel Oil Combustion Additive

Research Summary

The reproducible results indicated the following significant finding:

• Pretreatment of heavy oil with Carbonex:
  -Reduced particulate carbon 90-97 percent,
  -Increased combustion efficiency up to 1.6 percent,
  -Reduced average particulate size 50 percent, and
  -Increased Nox emissions up to 12 percent.
• Reducing excess air from 26 to 10 percent excess air:
  -Reduced particulate carbon by 38 percent,
  -Reduced particulate loading by 33 percent,
  -Had no influence on CO, Nox, particulate size, or the already
  acceptable combustion efficiency.
  -These effects were equivalent to increasing excess air to 26 percent.
• The pretreatment of the fuel oils with Carbonex allowed them to be combusted at 10 percent excess air without reducing the combustion efficiency achievable at 26 percent excess air or compromising the lower Nox emissions achievable at this reduced level of excess air.

In summary, these tests confirm that Carbonex is a viable additive for oil combustion, more so for heavy fuel oil than for light fuel oil.

Table 5: Heavy Fuel Oil - Test Oil Characteristics

Table 6: Results of Combustion Tests on the Heavy Fuel Oil - Untreated and Pretreated with Carbonex

* As measured concentrations have been corrected to a 0% excess oxygen or "air free" basis.

** The effect of Carbonex is evident when comparing these two columns.

Table 7: Light Fuel Oil - Test Oil Characteristics

Table 8: Results of Combustion Tests on the Light Fuel Oil Untreated and Pretreated with Carbonex

* As measured concentrations have been corrected to a 0% excess oxygen or "air free" basis.

** The effect of Carbonex is evident when comparing these two columns.

• High Asphaltene Low Vanadium Crude Oil Treatment

The crude oil used in the test was a high asphaltene, low vanadium fuel and as such would have carbon burnout problems. In fact the combustion efficiency for untreated crude, even at high excess air, was less than that observed with coal. The results obtained from  the crude oil treated with Carbonex are superior to those for coal. The results  obtained from the crude oil treated with Carbonex are superior to those for coal. This  is consistent with the better additive mixing  which can be obtained with oil, as opposed to coal, and the inferior combustion properties of the crude oil. The following statement is from the Summary of Results  section on page 29 of the Battelle coal and crude oil report.