A Permit By Rule (PBR) Application for an Interior Surface Coating Facility General considerations for Operation

General considerations for Operation

Abstract

Texas Car body Repairs is a company based in the USA that is a vehicle body repair shop. As part of the work it deals in, the company is involved in interior lining of paint on vehicles. The company seeks to set up this unit but has to seek authority first for this from the government and federal authorities based on the Texas State Law and EPA laws. This therefore is an application for an air permit for operation. The plant is expected to use 10 gallons of interior liner coating material and 2 gallons of solvent or vehicle lining application (Code, 2009). Two vehicles will be applied interior liners per day. The unit will work for five hours per day and four days per week. Vehicle lining curing will be done for curing the interior liners of two vehicles per day while working for five hour per day and four days per week.

Discussion

According to the Texas Commission on Environmental Quality, the considerations for registration state that a spray operation that uses less than half pint of coatings and solvents per hour can be considered for registration (Godish, Davis & Fu, 2014). The document goes further to say that, spray operations that use less than two gallons of coatings and solvents per week could also be considered for registration. The company in question here has met all these considerations since the amount of paint it uses per hour is less than the recommended amount of paint by the law.

The law also stipulates that a company should have a method of dealing with excess paint. It states that a company should take care of all overspray emissions and   which must be vented through a filter system. All paint booths, spray areas and preparation area overspray filters should have a particulate control efficiency of at least 90%. The design meets this criterion since the vehicles will be placed in in spray booths which are opened at one end of the booth for fresh air to flow in (makeup air). The exhaust air will flow through an exhaust chamber at the other end of the vehicle.

The unit is also expected to maintain good housekeeping practices that ensure the painting booths are always clean. In that respect all paint spills are taken care of immediately to ensure they do not flow to the environment and destroy living organisms such as plants. According to the law, the equipment also needs to be maintained in proper and good working conditions and according to manufacturer’s instructions. The method of maintenance would also be carefully maintained to ensure that the environment remains clean and safe for all human beings. The painting booths would also be kept clean at all times. This would involve safe disposal of waste coatings, solvents and some in instances vehicles brought into the unit may have engine oil, brake fluid, gear oil and transmission fluid. The company has put systems in place to ensure that safe disposal of these fluids is done without affecting the environment. These fluids would first be put in covered containers before safe disposal to avoid spilling. No firings will also be allowed for the waste coatings, solvents or oils will take place in the site which the law highly prohibits, where disposal method is by burning.

According to the TCEQ regulations, the unit will also ensure that there are no visible emissions leaving the company. The company will therefore put in place air and liquid systems that take up waste paint that vaporises into the air and liquid paint. Exhaust air will flow through an exhaust chamber and method used in spraying will ensure efficiency in the operation that means reduced paint wastage (Von Schneidemesser et al., 2015). The unit is also built in such a way that paint jobs that require coats of more than nine square feet can be efficiently done by totally enclosing the filtered spray booth with an air intake area of less than 100 square feet. The spraying will also be equipped with a fan that has a face velocity of at least 100 feet per minute and a flow capacity of at least 10,000 cubic feet per minute. This to ensure that pollution of the paint to the environment is minimized as much is practically possible. For all spray painting jobs of less than nine square feet, the law requires that the painting be done an area ventilating system be operational during spraying and the exhaust air vented to the atmosphere though a stack or the air be recirculate back into the booth through a carbon adsorption system. The carbon in these adsorption systems should be replaced at intervals especially during maintenance of the system to minimize solvent emissions which are hazardous to the environment (Von Schneidemesser et al., 2015).

Systems with high efficiency transfer of the coat will also be used in the booths. The equipment to be used is expected to be used such that at high volume low pressure spray guns. These methods ensure, a high transfer rate efficiency during the painting operation so that the incidences of air pollution is reduced by fast transfer rate of the paint to the vehicles.

The maintenance of equipment used in spraying through cleaning will be done in such a way that, they are totally enclosed during their actual cleaning rinsing and draining.  The solvents used in cleaning should be such that they are stored in an enclosed reservoir which is always covered except when being refilled with more fresh solvents.

The company will also endeavour to maintain certain records as expected by the law. These records will be well maintained for a period of 24 months and will be made available upon request to any official body tasked with air pollution control or government body. A material safety data sheet (MSDS) will show how paint and solvents were used for the previous 24 months. It will also show the manufacturers of the paint. The company will also keep records of coating and solvents purchased each month.  Records on maintenance of the air filters will also be kept to so as to ensure that air pollution is kept at bay and that the filters work appropriately. Records of the United States Environmental Protection Agency will also be kept and regularly update, in line with the law.  With this in place, it is expected that the company will be given an air permit so that construction may proceed at the site. We endeavour to stick by these laws and regulations so as to efficiently do away with air pollution and keep the environment cleaner and safer.

VOC and ES Content per Vehicle

The sheet helps in the surface coat industry in estimating the annual Volatile Organic Compound (VOC) emissions. This compound contains carbon and participates in atmospheric photochemical reactions in smog forming. In the presence of sunlight, it reacts with nitrogen oxides to form ground level ozone, a pollutant regulated by USA’s EPA (Godish, Davis & Fu, 2014). The liquid portion of the coating can consist of water, solvents and thinners. These compounds evaporate since they are volatile during the drying process of a vehicle. Booths capture the fumes and exhaust them to the ambient air (Von Schneidemesser et al., 2015). Most solvents contain VOCS and ES that pollute the environment. These pollutants may pass through exhaust filters and pollute the air.

The method applied here is the mass balance method. In this method, to calculate the emissions from the volatile portion of the coating, multiply the amount of VOC in a gallon of coating by the total gallons of coating applied during the time frame of interest (Code, 2009).

Pounds of VOC emitted= pounds of VOC per Gallon of coating * Gallons of coating used

In this case the contents are presented in terms of volume thus we need to calculate the pounds of each VOC in a gallon of coating and then calculate the pounds of total VOC in a gallon of coating. This is equal to %volume of VOC*density of VOC.

This formula is also applied for Exempt solutions (ES) that were applied on the paint job for the garage.

The Interior liner coating is 10 gallons per vehicle

10/12*100= 83.333%

Since this coating is not water based, gallons used in a week, if 2 vehicles are painted per day for 5 hours per day and 4 days per week.

10*2*5*4 = 400 gallons/week

Therefore the total number of gallons used = 400*0.8333 = 333.333 gallons/week

The Exempt solvent ES emission is 2/12* 100=16.67% it is done us follows. The total number of gallons used in a week, if 2 vehicles are painted per day for 5 hours per day and 4 days per week = 2*2*5*4 =80 gallons/week.  Therefore the total number of gallons used = 80*0.1667 =13.36 gallons/week.

These calculations enable us to find out if the paint job is a compliant coating. In which case it meets the specific regulatory VOC per gallon limitation

Operational Air Emission Rates

Operational air emission rates are the amount of pollution that is released to the atmosphere by the paint booths as the painting process is on-going per day or per week or per year. These emissions are VOC (Volatile Organic Compound) and ES (Exempt Solvent) content. These contents enable calculating the maximum hourly and annual emission rates (Code, 2009). These values are calculated independently. Dividing a maximum yearly emission rate by the yearly operating schedule will result in an average hourly emission rate but not the maximum hourly emission rate (Godish, Davis & Fu, 2014). To calculate the maximum hourly VOC emission rate by the maximum number of gallons used in one hour.

  1. For interior lining: 2 vehicles/ day, 5hrs/ day, 4 days/ week and it is 10 gallons/ vehicle.
  2. The vehicle lining application emission rate for 2 vehicles/ day, 5hrs/ day, 4 days/ week and it is 2 gallons/ vehicle.

Gallons used per hour for interior lining:

20 gallons/5=4 gallons/ hour

Gallons used per hour for vehicle lining application

4 gallons/5= 0.8 gallons/hour

Maximum emission rate= coating VOC content (volume)* maximum hourly used gallons

Maximum emission rate for interior lining 4 gallons/ hour* coating VOC content

Maximum vehicle lining application rate 0.8 gallons/hour* coating VOC content

The interior liner coating content is 10/12= 0.8333 VOC by volume

Vehicle lining application is 2/12=0.1667 VOC by volume

Thus maximum emission rate =4*0.8333=3.3332gallons/hour

For interior lining=0.8*0.8333=0.66664 gallons/hour

The total amount of interior lining used/ year enable calculation of annual emission rates.

Gallons used per= gallons used per hour*5*4*52(weeks)

4*5*4*52 = 4160 gallons*0.8333=3466.528 gallons/year

For interior lining, 0.8*5*4*52= 832 gallons/year

Emission rate averaged over a 5 hour period= VOC emission rate per hour/5

3.3332/5=0.66664 gallons per hour

For interior lining=0.66664/5 = 0.133328 gallons per hour

Potential to emit refers to the maximum capacity of a stationary source to emit any air pollutant under its physical and operational design. This is gotten by multiplying the hourly process rate with continuous operation that is 8760 hours per year.

Rate of emission per hour *8760 =3.3332*8760=29198.832 gallons/year

For vehicle lining =8760*0.66664 =5839.7664 gallons/year

 

Operational Air Emission Rates

Operational air emission rates are the amount of pollution that is released to the atmosphere by the paint booths as the painting process is on-going per day or per week or per year. These emissions are VOC (Volatile Organic Compound) and ES (Exempt Solvent) content. These contents enable calculating the maximum hourly and annual emission rates (Code, 2009). These values are calculated independently. Dividing a maximum yearly emission rate by the yearly operating schedule will result in an average hourly emission rate but not the maximum hourly emission rate (Godish, Davis & Fu, 2014). To calculate the maximum hourly VOC emission rate by the maximum number of gallons used in one hour.

  1. For interior lining: 2 vehicles/ day, 5hrs/ day, 4 days/ week and it is 10 gallons/ vehicle.
  2. The vehicle lining application emission rate for 2 vehicles/ day, 5hrs/ day, 4 days/ week and it is 2 gallons/ vehicle.

Gallons used per hour for interior lining:

20 gallons/5=4 gallons/ hour

Gallons used per hour for vehicle lining application

4 gallons/5= 0.8 gallons/hour

Maximum emission rate= coating VOC content (volume)* maximum hourly used gallons

Maximum emission rate for interior lining 4 gallons/ hour* coating VOC content

Maximum vehicle lining application rate 0.8 gallons/hour* coating VOC content

The interior liner coating content is 10/12= 0.8333 VOC by volume

Vehicle lining application is 2/12=0.1667 VOC by volume

Thus maximum emission rate =4*0.8333=3.3332gallons/hour

For interior lining=0.8*0.8333=0.66664 gallons/hour

The total amount of interior lining used/ year enable calculation of annual emission rates.

Gallons used per= gallons used per hour*5*4*52(weeks)

4*5*4*52 = 4160 gallons*0.8333=3466.528 gallons/year

For interior lining, 0.8*5*4*52= 832 gallons/year

Emission rate averaged over a 5 hour period= VOC emission rate per hour/5

3.3332/5=0.66664 gallons per hour

For interior lining=0.66664/5 = 0.133328 gallons per hour

Potential to emit refers to the maximum capacity of a stationary source to emit any air pollutant under its physical and operational design. This is gotten by multiplying the hourly process rate with continuous operation that is 8760 hours per year.

Rate of emission per hour *8760 =3.3332*8760=29198.832 gallons/year

For vehicle lining =8760*0.66664 =5839.7664 gallons/year

VOC content Minus Water and Exempt Solvents

The business in this case is subject to Texas Administrative Code (TAC), chapter 115 subchapter E. This law includes stringent VOC content limits. It is therefore important to calculate VOC content less water and exempt solvent (ES).

Pounds of VOC per gallon of coating, minus water and Exempt Solvent,

ES= Wv /Vm-Vw-Ves

Where

Wv- weight of VOC, in pounds, contained in Vm gallons of coating.

Vm- volume of coating, in most cases is 1 gallon

Vw- volume of water, in gallons, contained in Vm gallons of coating.

Ves– volume of exempt solvents, in gallons contained in Vm gallons of coating

VOC content= 0.8333 VOC content by volume per gallon of coating

Coating volume= 1 gallon

Water content= 1 lb water per gal coating

Water density= 8.34 lb water per gal water

Vw=1/8.34=0.12gal of water

Exempt volume= 0.1666

0.8333/1-0.12-0.1666 =1.1681 VOC per gallon

 

 

 

Heater and Oven Combustion Emissions

In this facility ovens are used to speed up the drying of the coating. The unit of quantification is the amount of fuel powered. Products of this consumption are Nitrogen oxides (NOx), carbon monoxide (CO), Particulate Matter (PM), Sulphur dioxide (SO2) and Volatile Organic Compound. This is done with the help of heating value in British thermal units per standard cubic foot.

Table 1: Values of British thermal units per standard cubic foot

Air Contaminant Firing Rate less than 0.3 MMBtu/hr (lb/106scf) Firing Rate Between 0.3 MMBtu/hr (lb/106 scf) and 100MMBtu/hr(lb/106 scf)
NOx 94 100
CO 40 84
PM 7.6 7.6
VOC 5.5 5.5
SO2 0.6 0.6

 

To obtain the emissions, the emission factor of the contaminant by 1/heating value of fuel by the firing rate to get the hourly emissions

Nitrogen Oxides 100 ?? ????????×???1,020 ???×2.1 ?????ℎ?=?.??? ?? ?????

Carbon Monoxide 84 ?? ???????×???1,020 ???×2.1 ?????ℎ?=?.??? ?? ????

Particulate Matter 7.6 ?? ???????×???1,020 ???×2.1 ?????ℎ?=?.??? ?? ????

Volatile Organic Compounds 5.5 ?? ????????×???1,020 ???×2.1 ?????ℎ?=?.??? ?? ?????

Sulphur Dioxide 0.6 ?? ??2?????×???1,020 ???×2.1 ?????ℎ?=?.??? ?? ???

Multiply the hourly (short-term) emission (lb/hr) by the yearly hour of operation (hr/yr), then divide by 2,000 lb to convert to tons to get the annual (long-term) emissions.

Operation for one year is 5hrs/ day, 4 days/ week and 52 weeks in an year- 5 ×4×52= 1040 hours per year.

Annual (Long-term) Emissions in Tons per Year

Nitrogen Oxides 0.206 ?? ???/ℎ?× 1040ℎ?/??×1 ???/2,000 ??=0.10712???/??

Carbon Monoxide 0.173 ?? CO/ℎ?×1040 ℎ?/??×1 ???/2,000 ??=0.08996 ??? ??/??

Particulate Matter 0.016 ?? PM/ℎ?×1040 ℎ?/??×1 ???/2,000 ??= 0.00832 ??? ??/?? Volatile Organic Compounds 0.011 ?? VOC/ℎ?×1040 ℎ?/??×1 ???/2,000 ??= 0.00572 ??? ???/??

Sulphur Dioxide 0.001 ?? SO2/ℎ?×2,500 ℎ?/??×1 ???/2,000 ??=0.00125 ??? ???/??

Pollution control technologies

The spraying booths need to be equipped with necessary control technologies to control pollution in the spray booths. These control technologies must be able to handle exhaust gases and vapours, aerosol particles and noise levels of 90 dB at 1000 Hz. Acidic gases such as sulphur dioxide need to be prevented from reaching the atmosphere and causing pollution. Therefore appropriate pollution control facilities need to be installed in the spray booths.

Discussion

The most efficient way of controlling gas emissions is through installation of scrubbers. These are flue gas desulfurization technology for the case of sulphur dioxide. Scrubbers are installed in the exhaust facilities of spray booths and once the pollutant mixture from the paint is emitted into the spraying booth air space, this exhaust air is collected in a chimney containing scrubbers. It thus works by spraying wet slurry of limestone into a chamber where the calcium content of limestone reacts with the acidic gas. This ensures that the hazardous gases don’t reach the atmosphere. This mixture reduces into a non-reactive compound that collects in the chamber. This means that the chambers need to be cleaned from time to time.

Aerosols exposure, can lead to breathing problems for people working in the facility and these particles may also cause accidental fires (Code, 2009). Dry filters may be used to control this. The shops need to be equipped with supply air fans that move the air containing the aerosols through a heat exchanger and through filters. To efficiently do this the booths need to be operated at 1750 F. This leads to the design of three types of spray booths. Cross draft Spray Booths in this type, air enters through filters in the front of the spray booths and is exhausted through filters at the back of the booth (Godish, Davis & Fu, 2014). The second type is a downdraft booth, this one is designed to let in air through filters that are installed on the roof of the booth and leave a metal grate in the floor. The exiting air contains solvent fumes (aerosols) and paint over spray. Semi downdraft is another technology utilised in this case, air enters through the roof of the booth and is exhausted through filters at the back of the booth (Von Schneidemesser et al., 2015). This control method ensures efficient control of air pollutants and emissions in the form of aerosols.

Sound levels in the spray booths need also to be taken care of. These acoustic problems may be as a result of sound produced by discharge lines and ports such as nozzles and air jets. Technologically these sound problems may be controlled using quiet design nozzles or pneumatics that are installed at air nozzles so that they can control sound levels to below 2dB which the human hear may tolerate and thus avoid damage its damage.

References

Code, T. A. (2009). Title 30 Environmental Quality. Part I Texas Commission on Environmental Quality.

Godish, T., Davis, W. T., & Fu, J. S. (2014). Air quality. CRC Press.

Von Schneidemesser, E., Monks, P. S., Allan, J. D., Bruhwiler, L., Forster, P., Fowler, D., … & Sindelarova, K. (2015). Chemistry and the linkages between air quality and climate change. Chemical Reviews115(10), 3856-3897.

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