Abstract

The energy requirements of the petroleum industries are often large and diverse. The need for power and process heat can be affected by paramaters such as the mix of products produced, feedstock characteristics, size of plant and even the plant vintage.

The increasing costs of fuel and power continue to be the major driving forces for energy conservation projects in these plants. Frequently, companies have found cogeneration to be an effective means of reducing their plant energy costs. Cogeneration is defined as the sequential production of useful thermal energy and shaft power from a single energy source. A system producing this power is often called a "topping" cogeneration cycle. Typical examples are noncondensing steam turbine cycles, gas turbine heat recovery cycles, and combined cycles where the gas turbine exhaust energy is ultimately used in process.

Cogeneration can also be power produced from the recovery of process thermal energy which would otherwise be wasted. This type of cycle is often called a "bottoming" cogeneration cycle. Bottoming cycle examples would include power generation resulting from recovery of excess thermal energy from exothermic process reactions and heat recovery from kilns, process heaters, and furnaces. Cogenerated shaft power can be used to drive either mechanical equipment such as pumps and compressors, or electric generators.

Cogeneration systems integrated into a plant's requirements for process heat and power can frequently generate power with half the fuel required by a separate utility plant and thus can often offer an attractive payback on the cogeneration investment. For those facilities requiring relatively large quantities of process heat or where energy is available due to process operations, cogeneration is a reliable and potentially economically attractive means of reducing energy costs.

The data presented in this paper can be used as a guide to help engineers and management in the petroleum and gas industries to recognize economic turbine cogeneration system opportunities. The application of steam turbine as well as gas turbine and combined cycle cogeneration systems are discussed. Specific examples are used to illustrate potential energy savings and economics.