ELECTRONIC JOURNAL OF POLISH AGRICULTURAL UNIVERSITIES

Transcription

1 Electronic Journal of Polish Agricultural Universities is the very first Polish scientific journal published exclusively on the Internet, founded on January 1, 1998 by the following agricultural universities and higher schools of agriculture: University of Technology and Agriculture of Bydgoszcz, Agricultural University of Cracow, Agricultural University of Lublin, Agricultural University of Poznan, igher School of Agriculture and Teacher Training Siedlce, Agricultural University of Szczecin, and Agricultural University of Wroclaw. ELECTRONIC JOURNAL OF POLIS AGRICULTURAL UNIVERSITIES 2007 Volue 10 Issue 1 Topic AGRICULTURAL ENGINEERING Copyright Wydawnictwo Akadeii Rolniczej we Wroclawiu, ISSN V. V. LISOWSKY, W. TANAŚ NEW SENSOR FOR TE MICROWAVE CONTROL OF MOISURE IN FLOUR- MILLING PRODUCTION Electronic Journal of Polish Agricultural Universities, Agricultural Engineering, Volue 10, Issue 1. Available Online NEW SENSOR FOR TE MICROWAVE CONTROL OF MOISURE IN FLOUR-MILLING PRODUCTION Vladislav V. Lisowsky 1, Wojciech Tanaś 2 1 Belarussian Agricultural Technical University, Minsk, Belorus 2 Faculty of Production Engineering, Agricultural University of Lublin, Poland ABSTRACT This paper describes the icrowave sensors for grain and grain products oisture control in technological processes of their production. There were used two sensors at the output and at the input of the daping achine. Different algoriths of operation, has allowed optiizing the flour-illing euipent regarding to the highest uality (lowered ready-ade product losses) at the output of flour. It was shown, that the effect of electroagnetic dispersion on superficially oistened grain layer ust be taken into account at rapid oistening. Key words: sensor, oisture easureent, icrowave, grain, flour-illing INTRODUCTION Under the conditions of grain density stabilization and of autoatic teperature correction, it is possible to apply one-paraeter sensor, registering electroagnetic energy attenuation in the oist aterial. owever, easuring uncertainty can ake up to 30% and ore, when non registering the dispersion loss of energy. METODS AND RESULTS The process of grain dehydration allows a rather easy stabilizing of the stuff flow controlled. ere, it is enough to control only one diension, e.g. the electroagnetic wave attenuation coefficient α (when the teperature is corrected autoatically) fig. 1. Thus, the relation between the attenuation N in the saple with the thickness d, density ρ and the oisture W will be as follows [1]:

2 N = W ρ d (1) α The factor of attenuation α н within the fraework of linear odel will be deterined by expression: α = α + α + α, (2) Н B B 0 0 where: α B, α, α 0 factors of attenuation of an electroagnetic wave in water bound, polysorption and free respectively;, voluetric concentration of water bound, polysorption and free respectively; B, 0 Fro where we get: α ρd W µ SS Wcr = Ф α но + a f ( w, ss, a )( α нп α но ) + ( α B α но ) ( ) (3) 1 ρ 1 W N Aσ 1 Wcr where: Φ factor of filling; ρ d, ρ density of a dry aterial and water; µ grae olecular weight of water; S S a specific surface of a grain (wheat); N A = ; σ = landing place of one olecule of water on a surface of a fir phase; a = 100 a axiu uantity of onolayers of water occupied with a oisture polysorption in the given aterial; W cr = 10% the critical oisture appropriate to transition fro bound water in a grain to water polysorption. f 1 (w, s s, a ) the function describing ratio between free and bound water. Function f 1 (w, s s, a ) according to odel of Ivens-Busker [3] in which it is supposed, that speed of change of the given for of oisture in the process of oistening is directly proportional to a part sorption volue free fro this oisture. ence it is possible to write down: d dq = 1 (4) where: voluetric concentration of a oisture polysorbtion; Q P = relative voluetric oisture of a aterial, i.e. relative uantity of water (P ) in unit of ρ V volue ( V + + ) = ; C 0 Integrating (3), with the account that at Q Q, = 0, we receive = Q cr Q = 1 e (5) In this kind expression (4) is inconvenient to use since all voluetric concentration of water included in it depends on the factor of filling Φ. Knowing the specific surface of the aterial S S and the axiu uantity of onolayers of water polysorption a, it is possible to find as follows: = µ ρd SS a N ρ σ A Ф, then

3 ρ0 = Ф ρ µ SS a N σ A ( Wcr W ) σ N A 1 exp (1 Wcr ) (1 W ) µ S S a (6) ence function f ( w, s S, a ) will be deterined by expression 1 ( Wcr W ) σ N A f1 ( w, ss, a) = 1 exp (7) (1 W ) (1 W ) µ S a cr S Fig. 1. Schee of ain units installation on grain dryer The calculation of dielectric characteristics of wheat odel can be ade, having accepted the following values [1, 2, 4, 6]: ρ 0 = 1.2 g c -3 ; S s = g -1 ; a = 100; W cr = 0.1; ε ε = ε 5.1; ε = 60; ε 80,4; t = 20 C; 0 = C = BS S = ε 0 S = λ 0 = 1.79 c; λ c = 377 c; λ = 9.5 c; B = 15 kcal ol -1 ; = 1 kcal ol -1 ; 0 = 4.6 kcal ol -1 The results of calculation, in view of that the factor of filling Ф is function of oisture (table 1) content lead to the dependence different fro graduation for Microradar 113 no ore than on 10% (fig. 2.). Table 1. Dependence of filling coefficient Ф on wheat oisture W, % Ф owever, since the flour-illing industry sticks to additional daping of grain fro 12-14% to %, it is essential that the influence of the free and bound water should be taken into consideration, which eans switching to another calculation algorith. To serve that purpose, a new odification of oisture indicator has been developed. It is euipped with two icrowave sensors (placed at the entrance and output of the daping achine) and a coputing unit, which functions along two patterns.

4 Fig. 2. Calculated dependence N(W) for icrowave sensor 1 and 2 in function W The second sensor control installed at the output of the oistening achine uses the following algorith: N = N + α Н k ( W 0 ); (8) 0 W When α = α(w) factors of attenuation and is defined by calculated way under known dielectric properties for free water [6]. Thus the calculation results give oisture value ore than 30% overestiated. At the euation deduction the assuption (1) has been ade, that in hoogeneities dispersion can be neglected which is true for the uniforly oistened grain. owever the technology of flour-illing production deands transient oistening of grain surface stratu. Thus the easuring result of electroagnetic energy dispersion effect in this stratu brings in considerable contribution, while the oisture content of caryopsis s other layers does not change. The effects of dispersion and attenuation are studied well in radio-eteorology. The calculation of dispersion coefficient k d is ade by forula [6]: k d 4 12π a = 4 λ 4 ( ( 2 2 1) + 2) (9) here: a is a sphere s edial radius with the euivalent surface eual the caryopsis surface; = n jχ = ε jε is a refraction factor. 2 2 Under known dielectric properties of the free water [6] taking into account that ε = n χ, ε = 2nχ it is easy to calculated paraeter k d, which for λ = 3.2 c is With the ebedding of settleent adjusting coefficient k = we finally gain the expression which links oistened grain signal attention N with the weight oisture W: N = N +.56( W ) (10) 0 3 W0 The calculation and experiental research results of wheat grain for teperature t = 20 C and wavelength λ = 3.2 c are given in figure 2.

5 Fig. 3. Schee of ain units installation on daping achine The researches of experiental results, well in accord with the theory, and the record of industrial application of the autoatic additional daping systes based on Microradar (fig. 3, fig. 4) show the possibility of highprecision aintenance of the finite oisture of grain (less than ±0.2%) [5]. Fig. 4. The daping achine is driven by the basic eleents of the autoatic control syste: a) coutation and transforing unit; b) the oisture eter Microradar with one of sensors; c) the unit of controlling the uantity of water; d) the ain coputer This result was received by achine ABSU-2. Types of grain was taken through the special windows, where is sensor 1 and sensor 2. the analysis of the grains on the oisture fulfilled by the vacuu teperature ethod on the licensee set OVZ-1 in a laboratory. For the every point sensor s watching by the oisture easureent Microradar fit the ean of the results for two types of grains. The decline between two experients did not exceeded 0.05% of oisture, if it did the experients repeated.

6 CONCLUSION The application of one coputing unit with two sensors at the output and at the input of the daping achine, using different algoriths of operation, has allowed optiizing the flour-illing euipent functioning. That provided the highest uality at the axiu output of flour and has essentially lowered ready-ade product losses. REFERENCES 1. Benzar V.K., Thechniue of Microwave Auaetry. Vycheichaja chkola, Minsk, p. 352 [in Russian]. 2. Benzar V.K., Tzentziper B.L., Renhart I.I., Displaceent of Dielectric Relaxation Peak of Water in Grain. Izvestiya AN BSSR 4, [in Russian]. 3. Busker L.., Microwave Moisture Measureent. Instruent and Control Systes Kraszewski A.W., Trabelsi S., Nelson S.O., Coparison of density-independent expressions for oisture content deterination in wheat at icrowave freuencies. J. Agric. Eng. Res., Renhart I., The Control of Moisture of Rocks by Methods of Microwave Auaetry. 4 th International Conference on Electroagnetic Wave Interaction with Water and Moist Substances, Weiar, pp Rosenberg V.N., Dispersion and attenuation of electroagnetic energy by atosphere particles. Gydroeteoizdat, Leningrad, p. 398 [in Russian]. Vladislav V. Lisovski Belarussian Agricultural Technical University of Minsk Naturalistov str. 4-9, Minsk , Belorus tel./fax hoe GSM e-ail: eridian2738e@ail.ru Wojciech Tanaś Agricultural University of Lublin 28 Glęboka Street, Lublin, Poland tel./fax (+48 81) e-ail: wojciech.tanas@ar.lublin.pl Responses to this article, coents are invited and should be subitted within three onths of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article. Main - Issues - ow to Subit - Fro the Publisher - Search - Subscription