Animal Rendering – Odor Control
- Location: Texas
- Industry: Natural Ingredients/Edible Fats and Oils
- Project Type: Animal Rendering
- Project Goal: Providing efficient pollution and odor control for a highly vaporous stream
- Equipment Type: Regenerative Thermal Oxidizer (RTO)
Gulf Coast Environmental Systems was contacted by a long-standing customer, to design and build a pollution control solution that would be able to handle the strong odors and heavy vapors produced by an animal processing application, in a Texas facility. This is the 4th system that Gulf Coast Environmental Systems has provided for this customer, supporting their odor control needs since 2004.
This customer is one of the oldest natural ingredient companies in the United States, founded in 1882. They are industry leaders in technology growth and development in natural ingredients, from edible and inedible bio-nutrients. They use a wide variety of processing operations, creating a range of products, including pharmaceutical ingredients, pet food, food, livestock feed, fertilizers, fuel, and bioenergy. This customer has a corporate wide commitment to sustainable operations, and pollution control equipment is a large part of this initiative.
This project, and their equipment selection, are shining examples of our customer’s commitment to environmental sustainability, with several cutting-edge technologies and solutions, that go above and beyond what the federal, state, and local regulatory agencies require of a rendering facility.
This particular project required 98% Destruction Rate Efficiency (DRE) of a vapor filled exhaust stream, containing significant odor levels. This stream also included two compounds that can be difficult to treat, ammonia (NH3) and hydrogen sulfide (H2S). This vaporous contaminated stream, combined with the customer’s continued efforts in sustainability, meant GCES needed to design a multi-stage system that would not only treat this complicated stream, but take advantage of waste heat recovery options, to reduce fuel consumption.
This system also required a bake-out option, due to the amount of condensable organics and wastewater being emitted from the cooker. In many rendering applications, residual layer of fats, grease, and oils make it through the pre-treatment equipment and will build up on the ductwork, valves, and inlet ceramic media of a Regenerative Thermal Oxidizer (RTO) unit. Over time this buildup will create flammable conditions in the RTO. To mitigate the risk of fire, a “bake-out” cycle is used to remove such buildup in a controlled manner during a preset schedule. A bake-out cycle revolves around varying the timing of the inlet and outlet valves and using the heat in the RTO to dry and incinerate the residue to ash. This process is similar to the “self-cleaning” process of a household oven.
Another important consideration for this unit, and for all units designed for rendering applications, was the need for safety features in the case of a power failure. In many industrial applications where organic build-up is possible in the RTO, a power failure can create a natural draft of heat movement that could lead to internal fires. GCES engineers are trained to consider safety as a priority, ensuring controls and precautions such as this are standard.
Gulf Coast Environmental Systems proposed two different options for this application, a 3-can and a 2-can RTO, both combined with an integrated Upstream Venturi & 2-Stage Ammonia and Reduced Sulfur Scrubber. GCES recommended the 3-canister option as a preferred fit for this application, as a 2-can RTO is usually able to sustain only 98% Destruction Rate Efficiency (DRE). 98% DRE was all that is required by the regulatory agencies in this case, but has been proven less effective in controlling the odor produced by similar streams containing animal protein odors. Because of this, the customer chose the 15,000 SCFM 3-canister Regenerative Thermal Oxidizer (RTO), with integrated Upstream Venturi & 2-Stage Ammonia and Reduced Sulfur Scrubber.
Inlet Venturi Scrubber:
This part of the system was designed so that the particulate and vapor laden stream enters the Venturi Scrubber, and instantly makes contact with the tangentially introduced water swirling down the Venturi’s converging walls.At the Venturi throat, the gas and liquid streams collide, and the liquid breaks down into droplets, which traps dust particles.This gas/liquid mixture passes through a flooded elbow and enters the entrainment separator through a tangential inlet. Centrifugal action removes the heavy wetted particles from the gas stream, readying it to enter the Scrubber.
For this application, a recirculation pump was included to supply water to the spray header and maximize the use of the water. Make-up and discharge water were connected to and from the Venturi scrubber. The motive force to pull through the Venturi was provided by the pretreatment system induced draft process fan.
This scrubber was designed to treat the ammonia (NH3) vapors in stage 1, and reduce the sulfur emissions in stage 2. The scrubber works by funneling the exhaust stream through the bottom of a packed tower and then it passes through an engineered packing where a solution, in this case water, from specialized nozzles is sprayed countercurrent to the exhaust stream flow. A demister, or mist eliminator section, was added at the top of each scrubber tower, to knock down entrained water droplets greater than 5 microns before the air exhausts into the 3-can RTO for further treatment.
The method of reduction of Volatile Organic Compounds and associated Odors in a Regenerative Thermal Oxidizer revolves around thermal oxidation. The chemical process of thermal oxidation is quite simple; the exhaust stream temperature is raised to a point that the chemical bonds that hold the targeted molecules together are broken.The VOCs and Odors in the process exhaust stream are converted to CO2, H2O, and thermal energy by the high temperature of the combustion chamber.
For this application, the process of regenerative thermal oxidation operates around three energy recovery canisters in use on the system, which are the housings for the ceramic heat recovery media. The ceramic heat recovery media acts as a heat exchanger for the system. The three canisters operate under a “swing bed” absorption principle: which is the principle of transfer through three beds using flow reversal. In the use of this principle with ceramic stoneware, the process is called regeneration. This is what sets an RTO apart from a straight Thermal Oxidizer (TO).
Energy Recovery Canisters:
The energy recovery canisters were insulated with ceramic fiber block materials, to ensure the outer skin temperature is always at the proper temperature, based upon an outdoor installation, with a 5 mph (8 km/hr) wind, and no sun or external heat load.
Each of the canisters were sized to handle the maximum anticipated airflow of the process and designed to meet or exceed the required thermal efficiency, pressure drop, and physical size requirements given by the customer. The grating material and support structure for the ceramic media were made from 316 stainless steel grating in order to ensure corrosion resistance and structural stability during the high temperature operation.
Although the required destruction rate efficiency was only 98%, GCES and the customer agreed that a 3-canister integrated system would provide better odor control resulting in a 99% DRE. This solution allowed for nearly complete reduction of all odors and VOCs, exceeding regulatory requirements. It also provided 95% thermal efficiency, allowing them to continue their ongoing effort of sustainability. Abatement in rendering can be difficult, due to the high vapor content of the stream, as well as the need for odor control. GCES was able to provide this customer with another superior solution that exceeded all the customer’s needs. We are proud to be a trusted supplier for an organization as socially responsible as this customer, and look forward to seeing the exciting advancements they make in sustainability with this equipment in years to come.
If you have questions about a current or future Rendering project, please contact GCES at firstname.lastname@example.org