Emissions Management for Major Projects
Authors: Callon Douglas R. 
Published: May 2016

This reference is for an abstract only. A full paper was not submitted for this conference.

The majority of air emissions from most Upstream production facilities are from flaring, venting, and the flue gas associated with the exhaust from fired equipment providing energy to the facility. Through a process of alternative analyses and cost-benefit evaluations conducted during the early planning phase of major projects, these air emissions can be effectively reduced. ExxonMobil Development Company has an established Environmental Management Process that includes the application of ExxonMobil Upstream Environmental Standards. During early planning phases of projects, these standards require potential air emissions be evaluated for reduction. Flaring of natural gas is a loss of a valuable resource for most regions of the world. Therefore, projects are planned to avoid routine flaring of excess natural gas. However, flares are an important safety device to allow pressurized gases to be safely burned away from the operations and personnel. Flaring is commonly used during start-up operations, equipment maintenance, and during upset conditions. Through careful planning, specific operational procedures, and using reliable equipment, the overall amount of flaring can be significantly reduced. Venting of produced natural gases, including the inert gases that are sometimes present, can also present a challenge. These gases are evaluated for potential value and for potential markets. In most cases, the only way to economically transport these gases is by pipeline which usually means that the markets must be nearby. Carbon dioxide is one of the inert gases that, when sufficiently concentrated and at high pressure, can be effectively separated and sold for injection into oil reservoirs for enhanced oil recovery (EOR). The flue gas associated with the exhaust from fired equipment providing energy to the production facility is commonly the largest air emission source. The two primary gases in these emissions that receive a lot of attention are nitrogen oxides, or NOx, and greenhouse gases, or GHGs. During normal combustion, the high temperatures along with nitrogen and oxygen from the air form NOx which is then emitted from the exhaust. When NOx is combined with the moisture in the atmosphere, ammonia, and other compounds, it forms nitric acid, which is a component of acid rain, and related particles. The acid rain can have an adverse impact on sensitive plants as well as on historic buildings and monuments. The small particles can cause respiratory illnesses by penetrating and damaging lung tissues. Also, when NOx, volatile organic compounds, and sunlight are combined, ground level ozone, or O3, can be formed. Ozone, also referred to as smog, has also been shown to cause damage to lung tissue and a reduction in lung function, particularly in susceptible people such as in children and the elderly. Manufacturers of fired equipment, such as gas turbines, heaters, boilers, and internal combustion engines, have developed technologies for reducing the quantities of NOx emissions from the equipment. Many of these technologies have been proven over a significant amount of time to meet reliability and operability requirements. In many cases, the incremental cost for these technologies is relatively small and can be effectively utilized. For many types of gas turbines, dry low NOx technologies have shown NOx reductions by as much as 80%. In extreme cases, where NOx emissions are highly regulated, additional treatment processes, such as selective catalytic reduction, can be used to reduce the NOx emissions by 98%. The other significant quantity of air emissions in flue gases are GHGs, which are primarily carbon dioxide, or CO2. The combustion of hydrocarbons and air form CO2 in the exhaust. CO2 in the earth's atmosphere has been shown to provide a greenhouse effect, trapping heat in the atmosphere. Several techniques are being researched to reduce these emissions including pre-combustion treatment, post combustion treatment, and increased energy efficiency. A few of the pre-combustion treatments currently available include oxy-fuel combustion and de-carbonized fuels. The oxy-fuels allow the exhaust to be highly concentrated CO2 which can be marketed for EOR benefits or to be injected into the subsurface for sequestration. The de-carbonized fuel process separates the carbon prior to combustion and allows the hydrogen to be combusted with oxygen generating water as the exhaust. An example of the post combustion treatment includes an amine based process that can separate the CO2 from the gases and allow the CO2 to be marketed for EOR benefits or sequestered. However, in most cases, these techniques are not cost effective. A current technique that is cost effective in many cases is increased energy efficiency. During early project planning, the energy requirements are assessed for potential optimization. Common techniques include Waste Heat Recovery and Cogeneration. The temperature on the exhaust stack on a gas turbine or a boiler can exceed 500 B0F. Using heat transfer techniques this heat can be recovered and utilized for many applications within the facility, including heating the crude oil treating or separating processes, heating treatment chemicals, and pre-heating fuel gas. This waste heat recovery technique reduces the need to combust additional fuel in heaters thereby increasing the overall energy efficiency. Cogeneration is a term used to describe the combination of generating electricity and useful heat. The useful heat is typically used to generate steam. The steam can be used for many applications including being sent to a steam generator to generate additional electricity for beneficial use. This technique has been found to increase the efficiency of combusting natural gas for energy from about 30% to in excess of 50%. This can significantly reduce the quantities of GHGs from facilities requiring large amounts of energy.