Kevin J. Whitty

Emissions from Syngas Combustion

Gasification technology has matured to the point that previously-held hesitations regarding performance and availability have given way to acceptance of the technology for energy generation. Indeed, the past few years have seen a significant increase in the number of gasifiers installed for generation of power and heat, and the number of installations is expected to increase dramatically over the next several decades as demand for efficient and environmentally sound energy generation increases. It is valuable to consider the environmental impact of this new generation of energy production systems, specifically release of gaseous emissions from combustion of the synthesis gas produced by gasification. Emissions from syngas combustion in turbines, engines and boilers are discussed in this review. The types of emissions considered include the unburned fuel components and partially oxidized species, nitrogen and sulfur-containing gases, volatile organic compounds, and other trace elements. Combustion of synthesis gas, in general, produces lower emissions for heat and power generation than conventional liquid and solid fuels. The composition of the syngas strongly influences the level of emissions. Hydrogen and carbon monoxide in synthesis gases results in elevated combustion temperature that facilitates the thermal formation of NO and NO2. In contrast, higher temperatures promote complete combustion and reduce the emission of organic volatiles, which are formed mainly from minor fractions of hydrocarbons in synthesis gases. Particulate matter, metallic compounds and other undesired pollutants are usually removed before firing synthesis gases for heat and power production. Therefore, integrated gasification and combined cycle systems are more environmentally friendly than conventional power generation systems.

A system for measuring bubble voidage and frequency around tubes immersed in a fluidized bed of particles

Gas-solid fluidized beds are common in chemical processing and energy production industries. These types of reactors frequently have banks of tubes immersed within the bed to provide heating or cooling, and it is important that the fluid dynamics within these bundles is efficient and uniform. This paper presents a simple, low-cost method for quantitatively analyzing the behavior of gas bubbles within banks of tubes in a fluidized bed cold flow model. Two probes, one containing an infrared emitter and one containing an infrared (IR) detector, are placed into adjacent glass tubes such that the emitter and detector face each other. As bubbles pass through the IR beam, the detector signal increases due to less solid material blocking the path between the emitter and detector. By calibrating the signal response to known voidage of the material, one can measure the bubble voidage at various locations within the tube bundle. The rate and size of bubbles passing through the beam can also be determined by high frequency data collection and subsequent analysis. This technique allows one to develop a map of bubble voidage within a fluidized bed, which can be useful for model validation and system optimization.

Stability and efficiency of CO2 capture using linear amine polymer modified carbon nanotubes

Increasing atmospheric CO2 concentration has become a cause for concern. The design of efficient and stable solid amine adsorbents for CO2 capture, as well as for controlled release, is urgently needed. Polymeric amine modified multiwalled carbon nanotubes (CNT) are a promising material for meeting these goals. In this study, linear polyethylenimine (LPEI) was supported on CNT and was characterized and studied for reversible CO2 adsorption. These results are compared to branched polythylenimine (BPEI) as well as other materials. Upon treatment with 3 M NaOH or 5 M HNO3, the CO2 adsorption was decreased by at least 15%. The CO2 adsorption by LPEI (1.89 mmol g−1) was lower than that of BPEI (2.43 mmol g−1) when coated on CNT supports. The desorption temperature was noticeably lower on CNT–LPEI versus CNT–BPEI for complete CO2 removal. CO2 adsorption capacity was strongly dependent on the packing height of the material in the column reactor. The stability study showed that CO2 adsorption of CNT–LPEI and CNT–BPEI decrease by 9.5% and 61.7%, respectively, after steam treatment, indicating that LPEI was more stable under humid conditions.

A pulse-width modulation controlled wire-mesh heater apparatus for investigation of solid fuel pyrolysis.

A novel wire mesh heater apparatus has been developed to study the devolatilization of solid fuels under pressurized conditions at well-controlled heating rates on the order of 1000 K/s. The apparatus combines direct current and pulse-width modulation with a fast-acting and high current-capacity relay to achieve operating frequencies up to 2000 Hz. This frequency allows much quicker feedback and tighter control of temperature than conventional ac-based systems that operate at 50 to 60 Hz. The present apparatus has been successfully operated at 63 bars with final temperatures of 1473 K and heating rates of 1100 K/s.

Gasification Studies Task 4 Topical Report, Utah Clean Coal Program

A key objective of the Task 4 activities has been to develop simulation tools to support development, troubleshooting and optimization of pressurized entrained-flow coal gasifiers. The overall gasifier models (Subtask 4.1) combine submodels for fluid flow (Subtask 4.2) and heat transfer (Subtask 4.3) with fundamental understanding of the chemical (Subtask 4.4) and physical (Subtask 4.5) processes that take place as coal particles are converted to synthesis gas and slag. However, it is important to be able to compare predictions from the models against data obtained from actual operating coal gasifiers, and Subtask 4.6 aims to provide an accessible, non-proprietary system, which can be operated over a wide range of conditions to provide well-characterized data for model validation.