1 Cross-contamination and working accuracy in feed production plants Dr.-Ing. Alexander Feil Research Institute of Feed Technology TAIEX-Workshop on Feed Safety Novi Sad, Serbia, February 2009

2 Lasting trends of actual industrial compound-feed production: Customer-oriented production (restaurant principle) specific wishes and demands of livestock farmers regarding batch size, availability, increase of feed compositions... Increased use of sensitive feed additives in the ppm-range, e.g. enzymes, probiotics... Hydrothermal-mechanical treatment of the feed for improved nutrient availability, hygienic state... Nevertheless: In most of the feed mills, the whole feed compositions (including e.g. medicinal feed) have to be produced just-in-time in multi-product plants.

3 Demands on the working accuracy in Germany 1.Company premises and equipment... Especially the following components must be available: A mixing unit with a mixing accuracy of 1:10,000, Weighing machines with sufficient weighing accuracy, Suitable conveying equipment. The feed producer must furnish the appropriate authority with the prove of the mixing and working accuracy of the plant. Especially mixing accuracy, segregation and level of cross-contamination must be proved. Bulletin for the acknowledgement of production plants, which produce compound feed

4 Working accuracy Working accuracy of a production line for premix or compound feed respectively is characterised regarding: Nominal value of additive concentration. Homogeneity and stability of the mixture. Cross-contamination in following batches.

5 Simplified scheme of single-line production plant for compound feed

6 Unfavourable location of adding the micro components or premixes Mixer regime (mixing time, filling level, worn mixing tools) Aspiration too strong Segregation/cross-contamination at conveying and storing Not controlled handling of filter dusts (e.g. cleaning cycle) Proportioning plan Main causes for claims of the working accuracy of production plants

7 Simplified scheme of a multi- product plant for compound feed

8 Manifold influencing factors of the solid- mixing process must be considered Material characteristics of the single solid components bulk density, solid density, particle-size distribution, particle shape, flow properties and others Process characteristics filling level, speed, mixing time and others Machinery characteristics type, size and others

9 Mixing conditions of a two-component mixture complete discharge ideal mixing homogeneity homogeneous random mixture

10 Statistical parameters at solid mixing single-shaft slanted vane mixer indicator concentration maize, number of samples n s = 20, filling level f = 100 % (m = 600 kg), sample size = 20 g each, nominal speed n = 60 min –1, mean value x = 9.5 mg/kg standard deviation s = ± 3.3 mg/kg coefficient of variation CV = mg/kg mixing time 20 s sample no. indicator concentration mg/kg mixing time 60 s mean value x = 10.0 mg/kg standard deviation s = ± 0.2 mg/kg coefficient of variation CV = sample no.

11 Mixing-time graphs for different mixers; single feed maize coefficient of variation CV mixing time s Füllstand f = 100 %, Nenndrehzahl n N area of good mixing homogeneity filling level f = 100 %, mixing ratio 1 : 100,000 nominal speed n N

12 Mixing-time graph for a vertical silo mixer (2,000 l) single feed maize coefficient of variation CV mixing time area of good mixing homogeneity This means if a mixing system guarantees the required mixing accuracy, generally depends considerably on the mixing time! filling level f = 100 %, mixing ratio 1 : 100,000 nominal speed n N min

13 Requirements for an optimal arrangement of the batch-mixing process Addition of micro components/premixes as directly as possible into the main mixer Avoidance of adhesions, coarse agglomerates and residues by appropriate addition of liquids (among other things no further trickling by adapted nozzle systems!) Sufficient mixing time Complete discharge of mixer, pre-bin and hopper Suitable conveyance/storage of the mixer batch Regular and documented control of the mixing tools; regular cleaning Suitable particle-size distribution of the components to be mixed

14 Multimodal density function q 3 (w) of a mineral feed x q3q /µm µm x h;3 = 1200 µm x h;2 = 200 µm x h;1 = 73 µm

15 mech. impact of the mixture (e.g. vibration) particle density  of the mixture components  mean particle size of the mixture components Main causes for segregation tendency of segregation low high particle form of the mixture components

16 Mixing quality and mixture stability are shaped by the comparability of the modal values and the width of the particle-size distribution of macro and micro components. By adaptation of the premixture structure, a reduction of the coefficient of variation from 30 to 5 % can be achieved. For organic and inorganic mixtures comparable effects were observed. Consequence: A purposeful structural adjustment of the components can be used for the improvement of mixing quality and mixture stability. Results of an IFF research project show

17 Balance: mixing homogeneity in the 1 st test batch of finished material in the tested plants number of investigations coefficient of variation in % basis of the statistical evaluation: - 47 compound-feed plants - 14 premix plants 8 %44 %23 %12 %8 %5 % % of the tested plants

18 Some production statistics of an exemplary compound-feed plant: Production: all essential animal feeds Throughput approx t/d; accordingly approx. 120,000 t/a Mixer batch t Approx. 180 mixer batches/d Approx changes of compositions/d Approx. 415 different compositions; number of single components between 2-22 Smallest delivery lot: approx. 1.5 t/largest lot: approx. 50 t, average lot size approx. 9 t

19 10 mean additive cross-contamiantion* % *based on actual concentration in the test batch sampling points + P6 P7 E A P1 P2 P3 P4 P5 meal line pellet line P1P4P2P3P5P6P7 Cross-contamination in compound-feed production turkey feed, 1 st rinsing batch

20 number of investigations cross-contamination (%) database for statistical evaluation: - 47 compound-feed plants - 14 premix plants 48 %23 %13 %8 % % of investigated plants 0 % Results: mean value of cross-contamination in the 1 st rinsing batch in the investigated plants

21 Basically: cross-contamination increase in the production process; approx. 80 % of the total cross- contamination in the meal-feed area Slow-flow zones in pipes (wall!), corners Filter dusts Dead zones in machinery equipment and hoppers (e.g. bypass areas of elevators, ledges, non-planar surfaces like bolted fastenings, weld seams as well as moulded hopper walls, signs of wear) Flow behaviour of bulk-material mixtures in hoppers with funnel flow Adhesions by faulty liquid proportioning in the mixer Segregation potential in production plants

22 Suited structure of the mixture components Addition of additives and premixes directly into the main mixer if possible Pay attention to the relevant operating parameters of the main mixer (mixing time, filling level) Careful addition of liquids Avoidance of intensive mechanical stress especially for mash products Controlled aspiration Recommendations for an improvement/ safeguarding of the working accuracy I

23 Defined handling of filter flour Avoidance of outsized conveying and storage systems Careful cleaning of the reception after each delivery Elimination of deposits and crusts in regular intervals (especially in mixers, elevator boots, screw conveyors) Completed and controlled clearing of supply bins, hoppers, coolers, scales after changes of composition Observance of the appointments concerning inadmissible product series Management of rinsing batches well adapted to the relevant risk potential of the additive Recommendations for an improvement/ safeguarding of the working accuracy II

24 mixer 100,0 mean cross-contamination of test substance* % 1,0 0,1 P1 P5 1,7 % 4,9 % 0,5 % 1,7 % V ,0 1,4 %0,4 % 3,6 %1,6 % batch size 3,000 kg batch size 4,000 kg < 0,1 % rinsing batchfollowing batchrinsing batchfollowing batch 1,0 % 2,8 %1,1 % laying hen meal premix and other (Pos. A): % of batch size each rinsing with 25 kg bread meal each batch size 2,000 kg M M P1 A P2 P3 P4P5 MM MM MM P1 A P2 P3 P4P5 inlet end-product silo meal *related to the concentration in the test batch plant B Cross-contamination in the rinsing and the following batch for different batch sizes

25 Relative cross-contamination is considerably larger at underfilling than at operation in the designed range as the quantities remaining absolutely in the plant are extensively independent of the batch size. The influence of batch mass or filling level respectively on the height of the total cross contamination was underestimated so far (Signification of small special mixtures?!). Reduced rinsing-batch masses (1/4 to 1/8 of the maximum filling) lead to a higher cross-contamination, but at the same time to a reduction of costs and logistic problems. The questions of the toleration depends among other things on the specific danger potential of the additive. Influence of batch size and rinsing-batch management on cross-contamination

26 P1 A M P4 P3 P2 Simplified plant scheme of the production plant C for mineral feed usual batch size 1,000 kg annual production approx. 3,500 t approx. 170 different formulations

27 First test of mineral-feed plant: mean cross-contamination in the rinsing batches 100 mean test-substance cross-contamination* % 10 1 P1 P2 P3 P4 2.6 %9.6 % 12.5 % 13.5 % M A P1 P2 P3 P4 * related to concentration 100 mg/kg in the test batch batch size 1,000 kg mineral feed 1 st rinsing batch 2 nd rinsing batch 0,1 1.4 %2.6 % 3.7 % 4.5 %

28 P1 A M P4 P3 P2 Reconstruction of the production plant (1)

29 P1 A M P4 P3 P2 replacement feed hopper manual filling including filter and cleaning Reconstruction of the production plant (2)

30 P1 A M P4 P3 P2 replacement feed hopper manual filling including filter and cleaning Reconstruction of the production plant (3)

31 P1 A M P4 P3 P2 replacement feed hopper manual filling including filter and cleaning installation of a chain trough conveyor Reconstruction of the production plant (4)

32 P1 A M P4 P3 P2 replacement feed hopper manual filling including filter and cleaning installation of a chain trough conveyor rebuild elevator (among others elevator boot new) Reconstruction of the production plant (5)

33 P1 A M P4 P3 P2 replacement feed hopper manual filling including filter and cleaning installation of a chain trough conveyor rebuild elevator (among others elevator boot new) partly coating hopper Reconstruction of the production plant (6)

34 P1 A M P4 P3 P2 replacement feed hopper manual filling including filter and cleaning installation of a chain trough conveyor radical simplification of the plant: do without two vertical conveyances and buffers/silos rebuild elevator (among others elevator boot new) partly coating hopper Reconstruction of the production plant (7)

35 P1 A M P4 Simplified plant scheme after reconstruction

mean test-substance cross-contamination * % 10 0,1 1.5 % 9.9 % P1P4 1 st rinsing batch 0.4 % 2.0 % Second test: mean cross-contamination in the rinsing batches 1 M A P1 P4 2 nd rinsing batch mixer bagged material batch size 1,000 kg mineral feed * related to concentration 100 mg/kg in the test batch

37 mean test-substance cross-contamination* mass rinsing batch 100 % kg batch size 1,000 kg mineral feed * related to concentration 100 mg/kg in the test batch M A P1 P4 mean test-substance cross-contamination: mixer: 1.5 % bagged material: 9.9 % P1 P4 Second test: cross-contamination in the 1 st rinsing batch

38 P1 A M P4 Simplified plant scheme of the reconstructed production plant for mineral feed

% 10 0, % * related to the concentration in the test batch ** first investigation before reconstruction of production plant *** investigation after reconstruction of production plant, before improvement of aspiration **** investigation after improvement of aspiration 14 Nov. 2001** 1 V-962 V-179 V-217 mean test-substance cross-contamination* 11 June 2003*** 22 Sept. 2003**** investigation on: (average production output approx t/month) Folgechargefollowing batch Spülchargerinsing batch 4.5 % mass test batch, rinsing batch, following batch 1,000 kg each (maximum filling) mineral feed for cattle (coarse) 9.9 %2.0 % mineral feed for cattle (coarse)mineral feed for pigs (fine) 5.9 % 1.0 % plant C Mean cross-contamination at investigations of plant C after different production periods and reconstruction steps