To design an air pollution control system that meets your company's individual needs, the proper information must be supplied.

If solvents are used in your process, be sure to list types and quantity being used, as this can affect the choice of catalyst used in catalytic units.

As the full effect of the federal Clean Air Act (CAA) amendments continue to impact today's industry, many companies will be required to install new or additional air pollution control equipment. With well over 25 years of proven success in a range of industries, thermal and catalytic oxidizers have become popular methods for controlling volatile organic compound (VOC) and hazardous air pollutant (HAP) emissions.

These air pollution control systems destroy harmful VOCs and air toxic pollutants contained in process exhaust fumes at elevated temperatures. The methods used (catalytic or thermal oxidation) ensure complete VOC/HAP destruction. New, more energy-efficient systems utilize high efficiency heat exchangers to preheat incoming exhaust fumes, thus further reducing operating costs.

Once a decision has been reached to purchase an air pollution control system, the company should select several experienced vendors and provide them with specific design specifications and details that can be used as a basis for preparing formal proposals. When requesting a proposal from a system manufacturer, it is best if the following information is made available:

  • Describe the type of production process emitting the VOC and/or HAP to be controlled. If possible, include a rough sketch of the building floor plan showing the location of all pertinent production equipment.

  • Provide the geographical location (and elevation level if known) where the system will be installed. System design can be affected by both the outdoor climate (surface finishes, types of dampers, etc.) and the elevation (fan sizing).

  • Estimate the number of hours per day the system will be operated. The heat exchanger efficiency, chamber design, etc., could change depending upon the operation hours required.

  • List the total number of emission points (exhaust stacks) that are to be controlled by the air pollution control system. A process control/bypass T-damper may be required at each emission point. The system's electrical control design also will change depending upon the number of dampers to be controlled.

  • List the exhaust rates and temperatures for each individual emission point. The exhaust rates are important for sizing the unit but also are used to size the ductwork and dampers. The temperature is used to calculate estimated operating costs and to determine the necessity for ductwork insulation.

  • Describe the type of heat source used for any dryers or ovens that are to be controlled. If the heat source is a gas-fired burner, NFPA regulations determine the method of purging and damper control. If the heat source is steam or hot oil, process control/bypass T-dampers may not be required at each stack.

  • List the solvent types and quantity being used. In addition to affecting the choice of catalyst used in catalytic units, solvent type and quantity also will affect the VOC destruction efficiencies, heat exchanger efficiency, internal materials of construction, and estimated operating costs.

    A regenerative thermal oxidizer can be used to destroy harmful VOCs and air toxic pollutants contained in process exhaust fumes at elevated temperatures.

  • Provide the type, cost and line pressure of any supplemental fuel available. The fuel type available (natural gas, propane, etc.) and the line pressure are used to determine the burner and fuel train design. The fuel cost is used to calculate the estimated operating costs.

  • Provide the electrical voltage and available power cost. The voltage available determines the type of electronics that are used. The power cost is used to calculate the estimated operating costs.

  • Describe the physical location of the air pollution control system installation. The actual location determines whether a concrete equipment pad or steel support structure is required. Also, if possible, provide specific site installation plans such as duct run length, exhaust stack height and gas piping length required.

  • Indicate the percent of VOC/HAP destruction efficiency required. The destruction efficiency percentage required determines the amount of catalyst needed (in catalytic designs) as well as the operating temperature in either technology.

  • List any catalyst masking or poisoning agents that could potentially be present in the airstream. Compounds such as silicones, phosphorus, heavy metals, halogen, sulfur and any particulates could be of concern and should be identified. A catalytic oxidizer can be designed to handle various levels of most compounds if the user can quantify them.

    Unfortunately, it can be difficult to understand the bona fide differences among different air pollution control system manufacturers' offerings. When evaluating a system for purchase, there really isn't any product testing that can be done to be reviewed, so purchasing decisions typically are made by relying on the vendor's credibility and on the assembled design data. The more thorough and precise your company can be in providing operating and design criteria, the more likely your project will culminate with an air pollution control system that will meet your individual needs and provide many years of trouble-free service. PH