Lambert Otten

Biofiltration of odours: laboratory studies using butyric acid

Abstract A study was conducted to evaluate the removal efficiencies of butyric acid, which was selected to represent volatile fatty acids found in compost off-gases. The experiments were based on a laboratory-scale biofilter using contaminated airstreams with concentration of 25 and 50 ppmv and different packing materials. Results indicate that butyric acid can be effectively removed at efficiencies nearing 100% by both compost and compost/perlite filled biofilters at all times during a run period extending 2000 h. Bed sterilization, nutrient addition, extraction results and changes in nitrogen composition of the bed indicated that microbial activity was mainly responsible for the removal and conversion of butyric acid. Further studies need to be performed to identify the biochemical pathways of butyric acid as well as the effects of other compounds such as sulphur and nitrogen containing compounds on the removal capacities of the biofilters.

Model comparisons of equilibrium moisture content of prunes in the temperature range of 15–45°C

Abstract Moisture equilibrium data for adsorption and desorption of water from prunes ( Prunus domestica L.) were investigated at temperatures in the range of 15–45°C and water activity ranging from 0.4 to 0.99. The experimental procedure used was a gravimetric dynamic method with continuous registration of sample weight changes. A special laboratory drying device has been developed for the purpose. Sorption capacity decreases as temperature increases. The differences between equilibrium moisture contents at a constant water activity were small in the temperature range measured. Rehydration of the dried material results in hysteresis. Four models available in the literature (Chung–Pfost, Halsey, Henderson, and Oswin) were evaluated to determine the best fit for the experimental data. The modified Halsey equation was a good model for moisture adsorption and desorption of prunes.

Effect of increasing hygroscopicity on the microwave heating of solid foods

Abstract The effect of a progressive increase in the bound strength of moisture in soybeans — a porous hygroscopic solid — during microwave heating is investigated. Thin layers of soybeans were dried with a single mode (TE 10 ) microwave cavity operating at 2450 MHz. The absorbed microwave power, temperature, and mass loss of the seeds were monitored continuously. Under a constant absorbed microwave power of 0.57 W/g, the temperature of a soybean seed increased rapidly at the initial stages of drying, reached a maximum of about 75 °C in approximately 50 min, and decreased gradually during the latter stages of drying to about 58 °C in 150 min. To maintain a constant drying temperature the absorbed microwave power had to be progressively increased as required. The results indicate that drying increases the average bound strength of the remaining moisture in a hygroscopic material and the energy needed to evaporate a unit mass of moisture increases accordingly. Consequently, progressively higher absorbed microwave powers are needed to maintain the temperature of low moisture solid foods during microwave heating processes that are accompanied by significant moisture loss.

Theoretical Analysis of the Tempering Phase of a Cyclic Drying Process

ABSTRACT A theoretical analysis, based on thermodynamic con-sideration of heat, work and mass distribution within the kernel, was made of the tempering phase of a cyclic drying process. The results indicate that during the tempering period only thermal effects apply; that is, only heat is exchanged between the grain and air. Curves are presented to show that the change in temperature is proportional to the change in enthalpy of the grain following redistribution of moisture within the kernel. Furthermore it is shown that when unheated air is passed through the grain dur-ing the tempering period, a higher level of energy is re-quired to sustain the drying process. Thus there is a distinct advantage in allowing the kernels to temper in quasi-stationary air.

Dehydration of aqueous ethanol

Abstract Upgrading of aqueous alcohol to anhydrous ethanol may be accomplished using a packed bed adsorption process, in which cracked grain corn is the adsorbent. A 0.35 m diameter by 3.0 m dehydration column was designed and constructed on the basis of data obtained in a series of bench-scale experiments. The results demonstrated that grain corn would upgrade 91% ethanol to 99%-plus at a rate of about 0.20 L/min. The capacity of the corn bed in the prototype ranged from7.6 to 10.5 mL/kg of bed, which was lower than expected from the bench-scale experiments. The difference was attributed to the significant thermal effect of the heat of adsorption, which caused higher bed temperatures. The performance of the prototype was modelled mathematically using a one-dimensional dispersive-convective description of the bed. The model was observed to fit the experimental data well in the regions where heat effects were not pronounced (where C / C 0 The estimated energy consumption for the dehydration and regeneration cycles was observed to be lower than that normally associated with azeotropic distillation. Aside from the energy advantage, an adsorption system is easier and safer to operate than azeotropic distillation.

EFFECT OF POLARIZATION ON THE HEAT OF DESORPTION OF WATER IN DIELECTRICS

The heat of desorption characteristics of moisture in hygroscopic solid dielectrics during microwave drying was investigated. White bean seeds were used as the experimental material. A direct method for determining the heat of desorption of moisture was developed. Results indicate that the heat of desorption offree water during microwave heating is lower than that during conventional heating. However, the heat of desorption of bound water during microwave drying was above that for conventional drying. This indicates that polarization of solid dielectrics may induce additional binding forces for bound moisture thus increasing the heat of desorption. The implication of this is that microwave drying of solids that do not become polarized is likely to be more energy efficient than those that become polarized in the microwave field. The lower the level of polarization ofa solid, the greater the microwave drying efficiency and effectiveness.

Analysis of the performance of solar heated farm buildings

The construction and data acquisition system of two-air-type solar heated farm buildings constructed near Guelph, Ontario, Canada are described. These buildings were fitted with flat-plate solar collectors, and attached to the roof or sidewals depending on the building configuration. Tests were conducted during the winter of 1982 to determine the performance of these buildings at various airflow rates. In the airflow rate range of 0.3-0.9 m3 min−1 m−2 the average collector efficiency varies from 0.20-0.71 as the inlet temperatures vary between −1 and 19°C. The corresponding average temperature gain was from 8–30°C. The single air path type vertical collector was 17–52% less efficient at airflow rates above 0.3 m3 min−1 m−2 than the suspended plate type inclined collector. The measured and simulated values of room and collector exit temperatures using the TRNSYS were compared over five time periods. The temperatures were predicted within 2.6-6.6°C, i.e. 7–12%.

Particulate Emission in Corn Drying

Particulate generation and emission from commercial cross flow driers was sampled in three corn drying seasons. Emission from a pilot scale model was measured in one season. Emission rates along the exhaust side of the drying columns were determined. The particulate was analyzed for size distribution and nutrient content.

Analysing Contributions of Components and Factors to Pork Odour Using Structural Learning with Forgetting Method

A novel neural network based approach to analysing contributions of odour components and factors to the perception of pork farm odour is proposed. A multi-component multi-factor odour analysis model is developed and learnt by an algorithm called structural learning with forgetting. Through the learning, unnecessary connections fade away and a skeletal network emerges. By analysing the resulting skeletal networks significant odour components and factors can be identified, and thus a more thorough understanding of odour model can be obtained. The proposed approach is tested with a pork farm odour database. The results demonstrate the effectiveness of the proposed approach.

Short-term monitoring and performance evaluation of solar-heated farm buildings

Abstract The construction and data acquisition system of five solar-heated farm buildings constructed near Guelph, Ontario, Canada are described. Air-type flat plate collectors are attached to the rood or sidewalls of the buildings depending on their configuration. Results of the performance tests conducted during the winter of 1983 at various airflow rates are discussed. The average daily collector efficiency of different collectors varies between 0.21 and 0.55. The measured and simulated performance of these buildings using the transient system simulation (TRNSYS) program over various time periods and airflow rates are compared. The TRNSYS simulations predicted the room temperatures within 1.6 to 2.7 °C, and collector air exit temperatures within 3.0 to 3.8 °C, following temperature swings as large as 40 °C.