Modelling the Ozone Penetration in a Grain Layer / Ozono Skverbties Grūdų Sluoksnyje Modeliavimas

Abstract

Studies of grain drying with ozone-air mixture were carried out to detect the ozone penetration patterns through the grain mound of various moisture content (14.6 ≤ w 0 ≤ 23.0%) at different ozone concentrations (500 ≤ C 0 ≤ 1250 ppb) in the supplied air. The ozone penetration through the grain layer depends on the initial ozone concentration in the supplied air, ozonation time, velocity of the supplied air, height of the grain mound, initial grain moisture content and mycobiotic contamination of grain surface. It was determined that in a 60 cm height of the grain layer ozone is first recorded after 12 h, and at 105 cm – only after 34 h at w 0 = 19.0%, C 0 = 500 ppb. If the initial concentration of ozone is higher, it is first recorded sooner. Ozone penetration through the grain layer with higher moisture level is slower, and ozone reaction with grain surface and microflora present on it is longer. Hypothesis about the adequacy of the model (how it reflects the real process) has been verified by calculating reproduction and adequacy variance. The mathematical model could be applied for prediction of the course of grain ozonation process. Santrauka Grūdų džiovinimo ozono ir oro mišiniu tyrimai atlikti siekiant išaiškinti ozono skverbties per skirtingo drėgnio grūdų sampilą dėsningumus (14,6 ≤ w 0 ≤ 23,0%), esant skirtingoms ozono koncentracijoms (500 ≤ C 0 ≤ 1250 ppb) tiekiamame ore. Ozono skverbtis grūdų sluoksnyje priklauso nuo pradinės ozono koncentracijos tiekiamame ore, ozonavimo trukmės, tiekiamo oro greičio, grūdų sampilo aukščio, pradinio grūdų drėgnio ir jų paviršiaus mikobiotinio užterštumo. 60 cm grūdų sluoksnio aukštyje ozonas pradėtas fiksuoti po 12 h, o 105 cm – tik po 34 h, kai w 0 = 19,0%, C 0 = 500 ppb. Padidinus pradinę ozono koncentraciją, ozonas pradedamas fiksuoti greičiau. Ozonuojant drėgnesnius grūdus, ozonas per jų sluoksnį skverbiasi lėčiau, vyksta ilgesnė jo reakcija su grūdų paviršiumi ir ant jų esančia mikroflora. Hipotezė apie modelio adekvatumą (kaip jis atspindi realų procesą) buvo patikrinta apskaičiavus reprodukcijos ir adekvatumo dispersijas. Sudarytas matematinis modelis gali būti taikomas grūdų ozonavimo procesui prognozuoti.

Investigations in intensification of grain drying by active ventilation applying ozone

“…To sum up the results of two weeks' experiments, we can conclude that significant drying of grain has occurred in the first three layers from the bottom, whereas in the first layer the grain was significantly overdried. The reason for the high grain moisture in the upper layers is apparently insufficient ventilation air velocity in the grain layer (see the results of the previous measurements), or insufficient specific air consumption in m 3 per m 3 •h -1 -cubic meters of air per 1 m 3 of grain per hour. In our case this indicator is 350 m 3 per m 3 •h -1 , the optimum would be 500-550 [10].…”

“…Experiments [2] were carried out in a 0.45 m high column with the ventilation length for up to an hour. The authors of publication [3] also carried out experiments in the laboratory with a few tens of kilograms of grain and a layer of grain up to 1.2 m thick. The author of publication [4], in turn, has worked with a grain layer up to 0.5 m thick, the ozone concentration 2.4-8.2 mg•m -3 , the initial humidity of grain 17-28 %; and he believes that the ozone addition to the ventilation air allows reducing the duration of ventilation by 10-20 %.…”

Numerical simulation of ozone concentration profile and flow characteristics in paddy bulks

“…concluded that ozone penetration through the stored grains is inversely proportional to the bed thickness. Steponaviciene et al . found that ozone absorption was higher in upper layers of the grains column.…”

“…Ozone is a relatively stable molecule at low temperature and high relative humidity conditions, and it is only at higher concentrations and higher temperatures that it rapidly decays to oxygen . Therefore a low concentration and a long exposure time is more practical, is easy to generate, leads to no significant changes in proximate composition of stored grain and is environmentally friendly . The problems in ozone application for insect control in stored grains are closely related to the grain bed thickness, moisture content, and selection of ozone concentration, exposure time, mycobiotic contamination of grain surface and concentration of ozone at the outlet …”

Ozone technology as an alternative for reducing mycotoxin contamination in wheat products

“…On the other hand, the reduction of mycotoxin contamination cannot be explained by only one factor. The adsorption and penetration of ozone in the sample rely on intrinsic and extrinsic factors such as the characteristics of the sample, initial contamination, exposure time, gas flow rate, column height and moisture content STEPONAVIČIENĖ et al, 2012;.…”