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Article # 0015

Determining the Technical Feasibility

 of Firing Waste Solvent in an

Existing Industrial or Commercial Boiler

 by Jack L. Bullard, P.E.



A hypothetical plant (referred to as “plant” hereafter) uses solvent in their printing operation and generates spent solvent as a byproduct of this process.  A portion of the solvent is regenerated by “cleaning it up” in the solvent distillation still located at the plant.  To meet printed-product quality standards only a portion of the regenerated solvent can be reintroduced into the incoming fresh or virgin solvent feed stream.  The spent and/or excess regenerated solvent is transferred to on-site storage until it is disposed of by shipping it off-site to an authorized waste handling facility.


The use of spent solvent as fuel has the potential cost benefit of both reduced disposal costs and total boiler fuel cost.  Boilers at the plant are assumed to be equipped with dual-fired burners capable of burning either natural gas, distillate (No. 2 Fuel Oil or Diesel), or a combination of these fuels.  The current practice is to burn pipeline quality natural gas exclusively.  The plant wants to evaluate other fuel types to maximize the use of their resources.


The main issues associated with this project are:




Can one or both boilers successfully obtain environmental permit authorization at the State and Federal levels to burn all or a portion of the used solvent?


There are various state and federal environmental programs that must be considered for their potential applicability to this project.  They include:






RCRA and NESHAP Programs


Federal environmental regulations covering the combustion of hazardous waste are codified under Title 40 of the Federal Code of Regulations Parts 260 through 271.  Potential combustors of hazardous waste must evaluate the need for a RCRA permit under these parts.   The facility should first determine if the material to be combusted is indeed hazardous under the Part 261 definition.  If the material is hazardous, an exemption from RCRA permitting requirement is possible under 40 CFR 266.109 (low risk waste exemption) or under 40 CFR 266.38 (comparable fuel exemption).  If an exemption can not be claimed the facility would apply for a permit under Part 270, Boiler and Industrial Furnaces (BIF).  If a BIF permit application is necessary then submittal of information to the EPA would be necessary to begin the application process.  The process may require a pretrial burn of the hazardous material. 


It should be noted that the RCRA rules affecting combustors of hazardous waste are undergoing change at the time of this article.  The regulations are being moved to the National Emission Standards for Hazardous Air Pollutants (NESHAP) Program under 40 CFR 63, Subpart EEE.   Maximum Achievable Control Technology (MACT) standards have been promulgated for some hazardous waste combustion facilities such as commercial furnaces.  Industrial boilers that use hazardous waste for fuel (proposed project) are not part of this initial phase, but new rules and MACT standards could be promulgated as early as 2005 or 2006.  The final MACT standard for BIFs could be more or less stringent than current RCRA standards. 


For this hypothetical plant, it is assumed that the two main components of the virgin solvent – that are also contained in the spent solvent - are characteristic of a hazardous waste based on flammability alone.  The solvent may also be hazardous due to other characteristics such as toxicity or because the pure chemical components of the solvent themselves are listed hazardous substances.


Analytical tests of multiple samples of the waste or spent solvent should be conducted to obtain a complete chemical profile, then it can be determined if the project can meet one of the exemptions from the RCRA rules as previously discussed.  If the project can not meet an exemption from federal permitting, an application for a RCRA permit under 40 CFR 270 would be submitted.  The application process may require a trial burn of the waste solvent prior to approval.  There are multiple sites in United States permitted under RCRA to burn hazardous waste for the purpose of disposal and/or recovering fuel value.  The destruction of waste solvents in this manner can be both environmentally and economically beneficial for the industry and the public.



State and Federal New Source Review (NSR)


In this hypothetical project, it will be necessary to obtain an amendment to the existing state air quality permit to authorize the use of the hazardous waste as an additional fuel for the boiler.  The main technical areas of a state review involve Best Available Control Technology (BACT) and Health Effects Analyses.  The BACT review focuses on the environmental benefit of destructing a hazardous waste rather than disposing of it off-site.  The boiler’s efficiency in destructing the organics in the waste solvent will need to meet the RCRA standards in 40 CFR 266 at a minimum to be considered State BACT.  The RCRA standards allow higher destruction and removal efficiencies (DRE) for sites that mix the hazardous waste with other fuels such as fuel gas or fuel oil. 


Boiler stack concentrations of combustion products such as NOx and CO will have to meet the RCRA pollutant standards as well.  Note that State BACT standards could potentially be stricter than RCRA, but state BACT is evaluated on a case-by-case basis so a particular project should be discussed with the state regulatory agency where the boiler is to be operated.  In many states if RCRA regulatory requirements and RCRA pollutant standards can be met, then this level of control is also sufficient to meet State BACT requirements.  It’s possible that an extensive BACT analysis that considers both technological and economical aspects of burning the fuel may be requested by the state environmental agency.  These analyses may require comparison of existing emission control technologies such as Flue Gas Recirculation (FGR), Selective Catalytic Reduction (SCR), low-NOx burners or a combination of these technologies.  The applicant would have to provide a cost versus environmental benefit analysis of adding on each of the available emission reduction technologies.


In addition to a state BACT analysis a state Health Effects analysis may also be necessary.  These analyses may require atmospheric dispersion modeling of various pollutants including non-combusted organic and inorganic compounds and possibly selected criteria pollutants such as NOx.  To fully complete the state permit application process, chemical analyses of the waste solvent are required. Multiple samples of the spent solvent should be taken and analyzed for organics, heavy metals, sulfur, and chlorinated compounds.


Is burning the spent solvent in the facility boilers technically feasible?


To evaluate this technical issue, the boilers manufacturer should be provided with a typical analysis and estimated heat value of the spent solvent. For older boilers, it’s possible the original manufacturer may no longer be in business.  In either case, it is best to contact multiple companies that specialize in the installation, modification, and/or maintenance of both commercial and industrial boilers to compare costs and expertise.


The following are typical questions to pose to the boiler manufacturers:





In discussing similar projects with boiler and burner manufacturers it has become apparent that the majority of companies that support commercial and industrial boilers have limited experience with burning hazardous or non-hazardous waste solvents.  Their industry is more familiar and more interested in working on projects involving traditional fuels like natural gas and distillate since this is the fuel overwhelmingly in use in industry. 


The most common reasons stated for this lack of experience with using solvents as a fuel source for industrial boilers include:





Although I was able to collect information from firms about the feasibility of burning solvents, it was apparent that they prioritize projects that use traditional fuels.  Here are some of the common concerns that I recorded through my contact with engineering and boiler firms:








Boiler companies can evaluate the existing burners to determine if they can handle the solvent, but the majority indicated that their final recommendation would probably be to retrofit the boilers with new burner equipment that has been designed to better handle more diverse operating conditions.


Jack L. Bullard, P.E. is an Engineering Partner and the President of Bullard Environmental Consulting, Inc.   He has over 17 years experience in environmental engineering, compliance, and permitting.  Jack has a Bachelors of Science Degree in Chemical Engineering from the University of Texas at Austin.

Jack L. Bullard, P.E. No. 83547

Final Edition Completed December 30, 2005 from Previously Composed Material.

Article # 0015       TEST QUESTIONS:

1.   In the discussion above, how the spent and excess regenerated solvent currently disposed of? 

  1. It is shipped to an authorized waster handling facility.

  2. It is dumped into the storm drain.

  3. It is distilled and mixed with fresh solvent.

  4. It is burned in the shops heating furnace.

2.   What is a potential cost benefit of using the spent solvent as fuel ?

  1. reduced boiler fuel cost

  2. reduced disposal costs

  3. reduced permitting costs

  4. both a. and b.

3.   What is the currently preferred fuel ?

  1. #2 fuel oil

  2. waste paper and cardboard

  3. pipeline quality natural gas

  4. coal

4.   At the time this article was written, where were the Federal environmental regulations covering the combustion of hazardous waste are codified as?

  1. 40 CFR Parts 260 through 271

  2. 40 CFR 63, Subpart EEE.

  3. 63 CFR Part 270

  4. 40 CFR Part B

5.   At the time this article was written, the Federal environmental regulations covering the combustion of hazardous waste  were being moved to?

  1. 40 CFR Parts 260 through 271

  2. 40 CFR 63, Subpart EEE.

  3. 63 CFR Part 270

  4. 40 CFR Part B

6.   In this article, what does BACT stand for?

  1. Boiler And Combustion Technology

  2. Best Available Control Technology

  3. Best Available Combustion Technology

  4. Beef And Chicken Tostados

7.   What are some of the emission control technologies mentioned in the article?

  1. FGR, SCR, and low-NOx burners

  2. RCRA, DRE and low-NOx burners

  3. NSR, NESHAP and FGR

  4. BACT MACT and BIFs

8.   Which of the following is NOT a suggested question for a boiler manufacturer in determining the feasibility of using spent solvent as a fuel?

  1. In the case of dual-fired boilers, ask if the waste solvent could be burned alone, mixed with fuel oil and burned, or be atomized for burning with fuel gas.

  2. Request they evaluate if the spent solvent is a good candidate for use as a fuel based on its Btu value, chemical composition, etc.

  3. Request that they identify any hazardous chemical reactions with the other fuel or fuels used in the operation of the boiler.

  4. Request that they identify safety issues and any concerns with the solvent causing operational or undue wear on the boiler

9.   Which of the following is NOT a commonly given reason for a lack of interest and experience with using solvents as a fuel source for industrial boilers?

  1. A lack of interest on the part of industry since spent solvents are not traditional fuel.

  2. The perception that state and federal environmental permitting of such fuels is problematic.

  3. The perception that most solvents are harmful to the various burner seals and instruments as well as the flue gas recirculation fan seals.

  4. The perception that most spent solvents are inherently poor candidates for use as fuel based on their chemical and physical properties.


10.   To fully complete the state permit application process, samples of the spent solvent should be taken analyzed for ...?

  1. heavy metals

  2. sulfur

  3. organic and chlorinated compounds

  4. All of the above

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