Thermal Oxidizers



Sulfur tail gas

Sulfur-bearing waste incineration systems typically treat the tail gases produced during the sulfur recovery process in a petroleum refinery or natural gas plant. Zeeco has a track record of producing the world’s largest sulfur tail gas incinerators. Zeeco’s experience with sulfur tail gas incinerators includes systems ranging in size from 1.0 MMBtu/hr (0.25 MMKcal/hr) to more than 500 MMBtu/hr (125 MMkcal/hr). The combustion chamber can range in size from 4.0' (1.0m) to 25' (7.6m) diameter.

Zeeco achieves high destruction efficiencies (DRE) during the sulfur recovery process by optimizing the following parameters for each specific process scenario:


  • Maintaining a minimum residence time between 0.7-2.0 seconds


  • Designing the equipment to operate at a temperature that is significantly higher than the auto-ignition temperature of the sulfur compounds in the waste stream (~700°F or 370°C). Zeeco’s Sulfur-Bearing Incineration Systems typically operate at temperatures between 1200-1650°F (650-900°C)


  • Ensuring that waste gas is introduced in a manner that results in a homogenous fully reacted effluent
Exterior of a Sulphur Tail Gas Thermal Oxidizer

SRU inline heaters

Inline heaters are usually designed to raise the temperature of the sulfur-containing process gas to at least 500°F above the normal operating temperature of the catalytic reactor. Because this equipment is located just upstream of the catalytic equipment, it is essential that this heater produces soot-free flue products and that all of the oxygen used to support combustion is consumed by the burner without any oxygen slippage to the downstream equipment. The burner is installed in a refractory lined combustion chamber, and hot combustion gases are mixed with the process gas to reach the reactor inlet temperature.

Close up of Inline Heater in a Sulphur Recovery Unit

SRU reaction Furnace

The reaction furnace is the heart of the Sulfur Recovery Unit (SRU), initiating the conversion of H2S and other sulfur-bearing compounds to elemental sulfur. The feed stream to the reaction furnace is an acid gas containing large quantities of hydrogen sulfide (H2S) that is typically burned with enough air to oxidize one-third (1/3) of the H2S to sulfur dioxide (SO2). The reaction is highly exothermic and is typically controlled to a temperature between 2200-2700°F (1200-1500°C). Downstream of the combustion zone, the unburned, remaining two-thirds (2/3) portion of H2S reacts endothermically with SO2 formed in the combustion zone to produce elemental sulfur vapor. The sulfur vapor is condensed to molten sulfur product downstream of the reaction furnace.

Overhead shot of a Reaction Furnace in a Sulphur Recovery Unit

high-Intensity burner

Burner Description:

The ZEECO High-Intensity Vortex Windbox (HVW) high-intensity burner is designed to burn acid or toxic gases.


The ZEECO HVW burner combines superb mixing characteristics with a short flame length. This reliable, proven technology utilizes the energy of a recirculating vortex to achieve rapid combustion in relatively small volumes with varying levels of air. The high flame temperatures achieved by this technology result in superior waste destruction with no soot formation.

Burner Design Features:

  • Two fuel connections: One for refinery fuel gas and one for the acid or toxic gases
  • Stable flame over a wide range of conditions
  • Turndown of 3:1 or greater for most cases
  • No flashback
  • Long service life
  • Operations with a wide range of fuels
  • 310 Stainless Steel (Type HK) gas tips for refinery fuel gas, acid or toxic gases
Exterior of HVW High-Intensity burner

Sulfuric Acid Decomposition Furnace

Zeeco supplies decomposition furnaces for all of the world's major sulfuric acid process licensors. We are widely considered a global authority on sulfuric acid and all types of combustion and environmental systems. Zeeco engineers custom design each Sulfuric Acid Decomposition Furnace to the unique needs and conditions of your location. Experience has taught us that attention to detail can make all the difference in the operation and lifespan of the system. For instance, Zeeco spray nozzles are uniquely designed to maximize nozzle and refractory life. And we can provide refractory baffle walls that enhance turbulence and promote optimal mixing, which can lead to significant efficiencies over the life of your furnace.

Typical Applications:

  • Refineries
  • Mining
Close up shot of a Sulfuric Acid Decomposition Furnace


Zeeco can provide combustion and emissions control solutions wherever hydrocarbon processing takes place. Customers can find our equipment and services in upstream, midstream, and downstream oil and energy processes.

We also offer products and support for other industries and applications such as tank/terminal loading and storage, pharmaceutical, carbon black, pulp & paper, steel, food processing, and more.