The present invention relates generally to gasification facilities and in particular to gasification facilities that include high temperature gas coolers and air separation units.
Gasification plants or facilities of various types are known. The feature that is common to such plants or facilities is a gasifier in the nature of an enclosed pressurized reactor in which a hydrocarbon feedstock or fuel is converted into gaseous products, sometimes referred to as “syngas”, by applying to the feedstock or fuel in the gasifier heat under pressure in the presence of steam and controlled amounts of air or oxygen. Typical hydrocarbon feedstocks or fuels that are employed are coal, petroleum and biomass for example.
The introduction of air or oxygen into the gasifier is controlled so that only a relatively small portion of the feedstock or fuel burns completely. This partial burning of the fuel provides at least a portion of the heat the process requires. The remainder of the hydrocarbon feedstock or fuel is chemically broken down under the heat and pressure in the gasifier, resulting in the chemical reactions that produce the gaseous products. The particular gaseous products that are produced vary depending in part on the type of feedstock that is used and the conditions imposed within the gasifier. Examples of gaseous products that are typically produced include carbon monoxide and hydrogen.
It often is preferable in a gasification plant or facility to use oxygen rather than air because using air requires that large amounts of nitrogen be handled and to do so can be costly. Also, the nitrogen can disadvantageously dilute the gaseous products that are produced. As a result, gasification plants will often include an air separator that separates the oxygen in the air from the nitrogen and delivers to the gasifier only the oxygen in such quantities as are needed to operate the gasifier.
The gaseous products that are produced in the gasification process can be variously applied. Typically, however, the gaseous products are first cooled and cleaned of particulate matter and sulfur compounds. The cooling process can involve the use of both a high temperature cooler, such as radiant synthesis gas (syngas) cooler, where high temperature heat can be recovered from the gaseous products, and a low temperature cooler, where lower temperature heat can be recovered from the gaseous products. Alternatively, the cooling process can provide for the quenching of the hot syngas in which case only low temperature heat is recovered from the gaseous products. After being cooled and cleaned, the gaseous products can be converted into or used directly as fuels or serve as building blocks for chemical products such as plastics and chemical fertilizers. Alternatively, or in addition, the gaseous products after cooling and cleaning can be separated and the separated hydrogen variously applied such as for example in powering fuel cells and in refinery operations.
In a particular application, the gasification facility can be incorporated into what is known as an integrated gasification combined cycle, or IGCC, power plant that serves to supply electric power. In an IGCC power plant, following cooling and cleaning, the gaseous products are delivered to a combined cycle power plant where the gaseous products are burned in a gas turbine generator to generate electric power and exhaust heat from the gas turbine is used to create steam that is used to power a steam turbine generator for generating additional electric power.