Destruction Technologies for Polychlorinated Biphenyls

4. Destruction Processes

4.1 General

The destruction processes that are reviewed in this section have been categorized as follows:

• conventional incineration;
• novel incineration;
• chemical processes; and
• physical/chemical processes.

Among the first three categories the division is somewhat artificial although on review there is advantage in making the division. Within each category a number of processes are described.

4. Destruction Processes

4.2 Conventional Incineration

• 4.2.1   Waste Incinerators
  • 4.2.1.1   Rollins Environmental Services, Inc.
  • 4.2.1.2   ENSCO Incorporated
  • 4.2.1.3   Chemical Waste Incinerators
• 4.2.2   Co-Treatment Processes
  • 4.2.2.1   High Efficiency Boilers
  • 4.2.2.2   Cement Kilns
  • 4.2.2.3   Other Kiln Processes
  • 4.2.2.4   Aluminum Melting Furnace Co-Treatment
• 4.2.3   Shipboard Incineration
  • 4.2.3.1   MV Vulcanus
  • 4.2.3.2   Other Shipboard Incinerators

Conventional incineration involves the high temperature oxidation of wastes to innocuous oxides (CO₂, H₂O) and inorganic residues that can be discarded without adverse environmental impact. The process ensures that wastes are exposed to high temperature oxidative atmospheres so the prime design feature is efficient fuel consumption. In the conventional sense, air and hydrocarbon fuels are used although the fuel value of the waste may be used provided it does not degrade the high temperature oxidative condition.

Conventional incineration of PCBs produces hydrogen chloride in addition to various oxides. This gaseous acidic compound must be removed from the effluent gases before discharge to the atmosphere. Solids handled by conventional incineration are completely oxidized usually leaving an inorganic ash.

Incineration is an established technology that is used in a variety of waste management applications. As such, it was the technology of choice when regulators set guidelines for the destruction of PCBs. The suggested minimum operating conditions for the destruction of PCBs are:

• 2 second dwell time at 1200°C and 3% excess oxygen; or
• 1.5 second dwell time at 1600°C and 2% excess oxygen.

These conditions apply to the central combustion chamber. There are a number of ancillary components to any incineration system that surrounds the central combustion chamber:

• feed preparation and handling;
• feed charging;
• residue removal;
• gas scrubbing; and
• effluent discharge.

This section on conventional incineration will deal with:

• waste incinerators,
• co-treatment processes, and
• shipboard incineration.

In incinerators specially designed to treat waste all the components are readily identifiable. In co-treatment processes, advantage is taken of an existing industrial process when appropriate time-temperature-oxygen conditions prevail PCBs are fed concurrently with the nominal process feed (e.g. cement kilns). In these situations it is difficult to determine which components are part of the industrial process and which are specifically used for PCB destruction.

Shipboard incineration is a special case which merits its own classification.

4.2.1 Waste Incinerators

4.2.1.1 Rollins Environmental Services, Inc.

Head Office: One Rollins Plaza
Wilmington, Delaware 19899

Site: Deer Park, Texas
Bridgeport, New Jersey
Baton Rouge, Louisiana

Contact: Richard S. Sernyak
(302) 429-2768

The three Rollins incinerators are of a similar design although they are at various stages of approval. The incinerator configuration is given in Figure 1. Solid wastes in fibre drums or 0.2 m³ metal drums are conveyed into a, rotary kiln. Liquid wastes can be fed to the burner compartment. The combuster is a Loddby furnace 1.6 m in diameter by 4.9 m long. Natural gas and/or No. 2 fuel oil are used for ignition, preheating and flame stability. Compressed air is used to atomize liquids and for the provision of combustion air in a manner that produces a rotary action in the combustion zone. Temperatures in the combustion zone reach 1500°C. An after-burning zone is provided, 4 x 4.3 x 10.6 m, where typical temperatures are 1300°C. The dwell time is 2 to 3 seconds exclusive of the kiln.

The combustion gases are passed through a venturi scrubber/absorption tower combination in which particulates and acid gases are removed from the gas stream. Scrubbing water dosed with lime is added upstream of the venturi throat; this water is recycled (2/3) with make-up water from wells. Induced draft fans are used to drive the gas stream to atmosphere.

The Rollins systems are designed to handle solid and liquid wastes in a variety of forms. Lightly contaminated solids or sludges are fed in fibre drums; heavily impregnated solids (capacitors) are preshredded. Feed rates of up to 2300 kg/h PCB liquid and six 0.2 m³ drums/h have been projected. The destruction efficiency has been variously reported but efficiencies in excess of 99.9999% have been demonstrated on liquid PCBs. PCBs in shredded capacitors were destroyed at a rate in excess of 99.999%. These systems are large-scale incinerators and are not considered to be mobile.

Rollins incineration experience amounts to 32 years with at least the last six years spent gaining PCB incineration experience. Their Deer Park incinerator has been evaluated to the satisfaction of the US EPA and they are now licenced to burn liquid PCBs.

The Rollins incinerator is technically sound, incorporating stack gas monitoring instrumentation and interlocks which shut-off PCB feed, when required, in accordance with PCB regulations.

Replacement capital investment required, excluding land purchase of approximately 30 hectares (75 acres), would be $25 000 000 as of January, 1982. The rotary kiln, scrubbing system and effluent water treatment system comprise the major portion of this expenditure. The cost figure also includes a shredding and feed system for PCB-contaminated capacitors, PCB liquid storage and feed pumps, an afterburner downstream of the rotary kiln, and lime storage and slaking facilities.