Can waste be burned efficiently and carefully? Well, the Heritage-WTI Incinerator in East Liverpool, Ohio strives to achieve this goal. This particular incinerator is one of the eight commercial incinerators in its county and 25-30% of the waste it receives comes from businesses and homes within a 100-mile radius of the plant. However, they do receive waste from places as far as California and Puerto Rico. Every employee has completed 40 hours of OSHA Hazwopper Training, and they work toward maintaining an environmentally friendly plant.
WTI primarily deals with organic waste and hazardous waste. The hazardous waste is industrial waste, which is waste that cannot be land filled (pharmaceutical rejects, reactor bottoms, reactor residues and sludges). On Earth Day the plant has local residents bring down household wastes such as paint and pool chemicals. So how is waste incinerated?
Ten Step Process
The rotary kiln incineration process consists of ten steps. First the waste is fed into the front wall or rotary kiln, which is 16 feet in diameter and is heated between 1,800 and 2,200 degree Fahrenheit. The kiln is a cylinder lined with brick that rotates slowly. Once this break wears down by 12 inches, it must be ripped out and replaced. At this point, time, temperature and turbulence help incinerate the waste.
Next the exhaust from the incinerator enters the secondary combustion chamber, and the combustion produces slag, which is collected at the bottom of the chamber. The slag is eventually taken to a hazardous waste landfill. Gas from the chamber moves into the boiler and this steam is used to heat buildings and the warehouse on the WTI property. The spray dryer cools the gases down to 200 degrees Fahrenheit, and the excess water is evaporated, creating a reduction in volume. The cooling down process produces salt, which is eventually taken to a landfill as well. Also, the scrubber water needs to be neutralized and sent to a landfill.
Then the electrostatic precipitator has positively and negatively charged plates to collect particles (1 micron particle size), and these particles are collected in a hopper along with the residual salt from the spray dryer. The four-stage wet scrubber’s purpose is to remove acid gases and submicron-sized particles through scrubbing beds and spray jets. In this step, the water used is recycled and sent to the spray dryer to be evaporated so there isn’t any wastewater.
Next, is the induced-draft tan step where a negative air pressure is maintained to draw air into the incinerator. Afterwards, a re-heater heats up the scrubber gas to 190 degrees Fahrenheit so the in-stack monitoring equipment works properly; HCl, opacities (light passing through), carbon monoxide and SO2 are monitored.
Second to last is the activated carbon step, which is when carbon is injected into the gas stream. The carbon causes dioxin and furan compounds to adhere, and these gases are removed by the particulate emissions control system. Finally, the gases that are clean and scrubbed flow out of stack.
Before any wastes can go through the process described above, they must be accepted. A one-quart sample along with a waste profile must be submitted to WTI before a hazardous waste is accepted. After acceptance, a truck delivers the waste to WTI where they fingerprint the waste to make sure it corresponds to the sample that was cleared. Some wastes are stored before they go through the incineration process, but they can only be stored for up to one year. Solid waste remains in hoppers that can hold 1,500 cubic yards; liquid waste is stored in storage tanks in the tank farm that hold 284,000 gallons; and drums and containers can be used to store up to 510,000 gallons of waste.
Although the incineration process does put some pollutants in the air (nitrogen and trace metals), WTI is making an effort to maintain an efficient and eco-friendly as possible plant. Who knew that so much was involved just to burn our waste?
