Gas flaring is required by refineries, chemical facilities and power plants to generate the products that drive the modern world. Gas flare systems are not necessarily intended for the profit of the industrial facility but more as a precaution to relieve pressure without venting dangerous chemicals into the environment. High-temperature oxidation is what occurs in flares which allowed for the burning of waste gases with combustible components in industrial processes.
The World Bank documented that approximately 150 to 170 billion m3 of gases are flared annually, a total value $ 30.6 billion, equivalent to 25% of the United States’ gas consumption or 30 % of the European Union’s gas consumption annually. The large quantity of gas flaring that occurs not only around the world, but here in the United States signals that repairs and maintenance are an essential part of ensuring the industrial facilities with flare stacks can stay online. This article discusses the flare systems, flare processes and flare stack types that exist as well as how Phoenix High Temperature Repair helps keep plants online during flack stack repair and maintenance for optimal operation.
Why Flare Stacks in the First Place?
Before the 1940’s, hydrocarbon processing facilities vented relief and waste fluids without burning them, releasing toxic and flammable vapors into the atmosphere. Flare systems evolved to prevent potentially dangerous conditions caused by the release of toxic and flammable gases. A large majority of flares are designed with elevation to ensure that detrimental circumstances do not occur at ground level. This also allows for the products of gas flaring combustion to be dispensed away from areas of work to decrease noise, smoke, heat and odors.
The products of gas flaring include water and carbon dioxide with approximately 98% combustion of volatile organic compounds. From a toxicity point of view, these products are excellent. Instead of venting waste streams, flaring reduces the load of greenhouse gases like methane, which is 20 times more detrimental to global warming than carbon dioxide. Carbon d=ioxide is a direct product of the flaring combustion which makes flaring significantly more acceptable than just venting chemicals into the atmosphere. Gas flare stacks are designed in various ways to release toxins with safety in mind. Continue reading to learn more about functionality of the different existing flare stacks of today!
Flare Stack Types
Flare stack types are classified as horizontal, elevated or slanted as well as single point or multipoint burners. Elevated flares fire vertically from a point higher than any other equipment whereas horizontal flares utilize burners which release into pits to retain liquids discharged with gases. A slanted flare is typically utilized to achieve low radiation, noise and space requirements at production platforms.
A single point flare simply has an exposed pipe with only one exit point while the multipoint flare has several exit points. Multipoint flares are recognized as being better for the environment due to staging features which boost combustion by providing flared gas with air for better mixing, and eliminating smoke by offering differential operation of each burning stage.
In selecting what kind of flare stack to construct, facilities use the flared stream medium and phase to determine this. The flared stream mediums and phases that exist are: vapor, liquid or liquid vapor mixtures. For liquid and vapor mixtures a horizontal flare is appropriate, meanwhile for gaseous streams, an elevated flare is suitable. In addition to flared stream mediums, heating value, smoking limitations, flame visibility and flared stream pressure are critical points of consideration for selecting a flare system. To meet safety, environmental and economic requirements, the general guidelines in API 537^2 plus manufacturer recommendations on flare selection should be pursued.
Flare Stack Systems
When processes of combustion are involved, adequate fuel, air supply and good mixing are essential to reach complete combustion and keep smoking to a minimum. Flare systems differ primarily in how substances are mixed. There are three types of flare systems according to the Environmental Protection Agency (EPA): Air-assisted, pressure-assisted and steam-assisted.
Air-assisted Flares
In order to induce the combustion air and the mixing necessary for a smokeless operation, air-assisted flares utilize forced air. Many times air-assisted flares are designed with a spider-shaped burner near the top of the steel cylinder of the flare. There is a fan at the bottom of the flare that generates assist air sending it through tubes inside the flare stack to the flare tip to improve mixing and minimise the formation of soot. The main advantage to air-assisted flares is that they are useful when steam is not available. Concurrently, a disadvantage is that air-assisted flares necessitate electricity to power the fan that creates the assist air.
Pressure-assisted Flares
Pressure-assisted flares consist of vent stream pressure to promote the mixing of substances at the burner flare tips. A number of vendors have begun marketing proprietary, high pressure drop burner flare tip designs where, if there is enough vent stream pressure present, this kind of flare can be applied to streams that had previously required steam or air assistance for smokeless production. Many times gas flares with pressure assistance have a multi-point design that allows for the burner heads to operate in concordance with the quantity of gas released. Off-shore oil and gas platforms typically have elevated multi-point flares while industrial facilities tend to present ground-level multi-point flares for emergency release secondary to a steam or air-assisted flare.
Steam-assisted Flares
Steam-assisted flares are characterized by single burner tips at ground-level elevation for safety and burning vented gas in a diffusion flame. The U.S. EPA states that steam-assisted flares make up the large majority of installed flares and are the dominant flare type found in refineries and chemical plants. These kinds of flares are not often seen at oil production sites because steam boilers are always installed at these facilities. In order to secure the correct amount of air supply and mixing, steam-assisted flares infuse steam into the combustion zone to create turbulence for mixing that introduces air into the flame. Compared to air-assisted flares, flares assisted by steam are more effective at reaching smokeless burning because high-pressure steam can achieve greater momentum thus increasing air-fuel mixing. This kind of flare also has a lower cost than air-assisted flares which is a plus.
Flare Stack Processes
There are three types of gas flaring processes: emergency flaring, process flaring and production flaring. Compressor failures, breaking of valves and fires can induce emergency flaring. A large quantity of gas with a high speed is burned in a short amount of time during an emergency flare. Process flaring occurs at a lower rate, for example during a petrochemical process where waste gases are disposed of from the production stream and then flared. During such processes, the volume of gas can vary during normal functionality to plant failures ranging from a few cubic meters per hour to thousands of cubic meters per hour. Production flaring is seen more commonly in the exploration and production sector of the oil and gas industry. An example of production flaring in the oil and gas industry is when large amounts of gas is combusted during the evaluation of a gas-oil potential test as an indicator for the well capacity for production.
How Does Phoenix’s On-Demand Flare Stack Repair & Maintenance Services Prove Essential to Industrial Facilities?
Now that we have received an overview of flare stack types, systems and processes, let’s talk about how Phoenix High Temp Repair has a strong knowledge of all these components as well as flare stack repair and maintenance. Phoenix experience in high temperature repair and maintenance dates back to 1998, and the company itself has been around since 2015!
Flare stacks at oil and gas refineries, power plants, chemical plants, and the paper and pulp industry are one of many Phoenix areas of expertise. Facilities can lose millions when they have an unplanned shutdown, so we strive to raise awareness of our services that can prevent such tragedies from happening if adequate planning ahead of time is secured. Phoenix prides itself in cultivating long-term relationships with its clients therefore generating a synergistic trust that allows for excellent preventative services and repairs.
