Timo Joutsenoja

Pyrometric temperature and size measurements of burning coal particles in a fluidized bed combustion reactor

The article reports on the application of fiber-optic two-color optical pyrometry to the measurement of temperature and size of combusting coal particles in an atmospheric fluidized bed combustion reactor. The utility of the measuring technique is that it makes possible nonintrusive in situ measurement of the dependence between the temperature and size of combusting fuel particles. The method allows the temperatures of the fluidized bed and individual fuel particles to be determined wherever these deviate from the bed temperature. Besides giving these temperatures, this method also allows for the statistical determination of the particle size distribution within the population of observed particles. The effects of bed temperature (1130–1200 K) and oxygen concentration (5–8 vol%) on the temperature of combusting Westerholt high volatile bituminous coal particles were studied in a laboratory-scale bubbling fluidized bed combustor. The average particle temperature exceeded the bed temperature by about 100–200 K, while the maximum particle temperatures were nearly 600 K above the bed temperature. The interrelation between the size (< 1.2 mm) and temperature of burning coal particles is presented.

Pyrometric measurement of the temperature and size of individual combusting fuel particles

A two-color pyrometric technique was developed for the in situ simultaneous measurement of individual fuel-particle temperatures and sizes in a pressurized entrained flow reactor (PEFR). A method that requires only a single optical port was developed, and a specially designed optical probe was manufactured for the measurements at the PEFR. The fuel-particle temperature was obtained by applying two-color pyrometry. The particle size was determined from the same pyrometric signals. A discrimination method was developed to confirm that the detected particle was valid for particle sizing. Several series of measurements were made at a PEFR at different process conditions, and some typical results are shown.

The effect of conductor thickness in passive inkjet printed RFID tags

This paper investigates the effects of conductor thickness on the performance of passive RFID tags fabricated using inkjet technology. Judging from the obtained results the performance of printed tags continues to increase as more conductive layers are added. However, the results show that the amount of performance improvement reduces with increase of the number of layers.

Tunable external-cavity diode laser at 650 nm based on a transmission diffraction grating

A tunable external-cavity diode laser (ECDL) based on a transmission diffraction grating in a Littrow mount has been developed and characterized. A single-transverse-mode diode laser at 650 nm is used in an external-cavity configuration in which the transmission grating is used as a dispersive element to select the single longitudinal mode. The transmission diffraction grating is made with electron-beam lithography. A tunable true single-mode cw output power of >20 mW is obtained from the ECDL. The total wavelength tuning range is 12 nm, and the mode-hop-free continuous tunability is >20 GHz.

Enhanced Performance of Printed Organic Diodes Using a Thin Interfacial Barrier Layer

Printed, organic diodes with a thin organic interfacial layer forming a Schottky barrier were fabricated and characterized. Experiments indicated that the thickness of the barrier layer is <10 nm. The interfacial layer reduces the reverse current of the diode by 2 orders of magnitude without significantly affecting the forward characteristics above 1 V. As a result, printed organic diodes with a rectification ratio of 5 orders of magnitude were fabricated. The diodes enable applications where low reverse currents are needed.

Effect of dielectric barrier on rectification, injection and transport properties of printed organic diodes

Rectification ratios of 105 were observed in printed organic copper/polytriarylamine (PTAA)/silver diodes with a thin insulating barrier layer at the copper/PTAA interface. To clarify the origin of the high rectification ratio in the diodes, the injection, transport and structure of the diodes with two different copper cathodes were examined using impedance spectroscopy and x-ray photoelectron spectroscopy (XPS). The impedance data confirm that the difference in diode performance arises from the copper/PTAA interface. The XPS measurements show that the copper surface in both diode structures is covered by a layer of Cu2O topped by an organic layer. The organic layer is thicker on one of the surfaces, which results in lower reverse currents and higher rectification ratios in the printed diodes. We suggest a model where a dipole at the dual insulating layer induces a shift in the semiconductor energy levels explaining the difference between the diodes with different cathodes.

Pyrometric sizing of high-temperature particles in flow reactors.

A pyrometric method was developed earlier for the simultaneous in situ measurement of the temperature and the size of combusting fuel particles in entrained flow reactors. The temperature measurement is based on two-color pyrometry and the particle sizing on the proportionality of the measured radiative flux and the cross-sectional area of a particle at a known temperature. This particle-sizing method needs a discrimination procedure to confirm that the detected particle is valid for particle sizing. We report on a novel method for particle discrimination based on coaxial reference optics. The new method has several advantages compared with the method presented earlier, including the measurement in turbulent flow fields.

Pyrometric particle temperature measurements in a pressurized fluidized bed gasification reactor

Abstract A fiberoptic pyrometric technique for the measurement of the temperature of a fuel particle in a fluidized bed reactor is presented. In the fiberoptic pyrometry the thermal radiation emitted by bed and fuel particles is collected and transmitted to a radiometric unit by an optical lightguide immersed into the reactor. The radiation intensity is measured on two narrow wavelength bands and temperatures of the bed and individual fuel particles are determined from these signals. Experimental results obtained in an industrial pressurized fluidized bed gasificalion pilot plant of 15 MW of thermal power are reported. The temperature of the fluidized bed was 1140–1215 K and the pressure in the reactor was 1.6–2 MPa. A large number of fuel particles both hotter and colder than the surrounding bed were clearly detected. For the hotter particles the temperature elevation with respect to the bed was typically 40–100 K.

External cavity diode laser based on a transmission grating

Design and characterization of an external cavity diode laser at 650 nm based on a transmission grating is described. The transmission grating enables compact design and removes the beam direction variation during the wavelength tuning.