Add moderate animal and vegetable oil to the feed pellet can not only increase the energy of feed, but also improve the appearance quality of pellet. Step of grease adding can be carried out before or after pelleting. Additive amount before pelleting is generally not exceed 3% of the production quantity, otherwise the pellets would be loose. It also not suitable for extruded feed, but request for equipment is lower. Additive amount of surface treatment (grease spray) after pelleting can reach to 8%, solving the problem of grease adding affect the feed pellet firmness and improve the productivity, and this method is available to the extruded feed, but the request for equipment it higher.

Feed Pellets after Grease Spraying

I . Basic Structure, Request and Working Principle of Grease Spray

1. There are two methods of grease spray for feed pellet: spray while extruding or after classifying. Requests of grease supply and electric control are the same for these two methods.

Grease spray machine is mainly consists of automatic control oil tank, coarse and fine filter, control valve, compressed air, high pressure steam and controller. Liquid level device, temperature controller, heater block and stirrer of automatic oil tank are used to heating the grease to 60-80℃ as quickly as possible to reduce the grease viscosity, for better liquidity and material absorptivity. Coarse and fine filter prevent the impurities block the oil way, keep the valves, counter and nozzle working normally. Compressed air or high pressure steam are mainly used to atomization the grease, making the grease uniformly sprayed to the materials in form of fog. Spray controller is the key component, it can automatically display and adjust the flow quantity of grease, and has the functions of adding up, grease starvation warning and flow deviation warning. Except for the functions above, heating and thermal insulation of oil way is also obbligato, it can melt the grease residue in the pipe and remain homoiothermy during system working.

2. Basic Requirements

2.1 Control components of the pipe can normally work, no oil or steam leak at pipeline.

2.2 Oil way and steam way should guarantee a certain working pressure, generally 0.2-0.5Mpa.

2.3 Coarse and fine filter must be equipped to the pipeline to prevent sundries block the nozzle, and detectors must be equipped to detect the veracity and reliability of spray amount.

2.4 Oil tank and nozzle should be equipped with heating device, pipes should be packed by thermal insulation material to prevent grease solidification.

2.5 Grease spray amount should has higher automaticity to change according to the feeding quantity, thus make sure the validity of grease spray amount.

2.6 Spray ratio of grease spray machine can be set by customers according to the actual request.

2.7 Width of vaporific grease sprayed from the nozzle should evenly cover the material flow line, reduce the waste of grease.

3. Working Principle

When the grease get into the oil tank from oil pool or oil drum through the filter, temperature rise to 60-80℃ by steam heating pipe, in this progress, the pipe is heated to the scheduled temperature( oil tank must be equipped with stirrer to make sure the grease is heated evenly and ensure the veracity of temperature measurement, temperature can be adjusted according to the grease viscosity). When the oil way is smooth, grease spray can be carried out. While spraying, grease get through speed governing pump, one-way valve, fine filter and get into magnetic valve, spray in vaporific to the material surface in the role of compressed air. Spraying amount through the oval gear transmitter pulse frequency will be sent to the programmable controller for processing, automatically adjust the speed governing pump rotate speed, change the flow amount, so that the actual spray amount reaches the pre-set value.

Grease Spray Machine

II. Advantages of Grease Spray

1. Additive amount greatly increased

As the grease spray after pelleting, so the formula may be required to maximize the proportion of grease without affecting the solidity of the pellets.

2. Reduce the cross contamination

Post grease adding process reduce the residual grease on the equipment, thus reduced the risk of cross contamination.

3. Improve the feed quality

Grease spray after pelleting can improve the physical property of feed, preference is strong. And the oil has a certain permeability, can penetrate deeper into the pellets in the follow-up process and the process of transport, so that the pellets will not block and dust reduces.

III. Problems of Grease Spray

As the freezing point of the grease is high, if spray when the pellets are cooled or temperature is low, it is easy to wrapped only in the pellet surface. In the subsequent packaging, storage and transportation processes, the pellet will produce mutual friction and collision, which will strip the grease around the surface, resulting in insufficient nutrient content and recipe distortion. In addition, the pellet surface have higher grease content, which is easy to be oxidized and lower the feed quality, so it is necessary to use antioxidants and other methods to solve the problems.

IV. Main Factors that Affect the Grease Spray Quality

1. Temperature

If grease spraying temperature is too low, it will reduce the viscosity of grease, forming grease globules, affect the mobility and atomization, resulting in uneven spraying.

2. Nozzle

The atomization effect of grease and spray uniformity has a direct relationship with the nozzle structure and installation location.

3. Pellet size and flow direction

Spraying evenness variation is dependent on the pellet surface area, density and uniformity of the flow. Therefore, when the pellet is of small diameter, large density and uniform mobility, it will be more conducive to the uniform spraying and absorption of grease.

4. Solidity of the pellet feed

If the solidity of the pellet feed is not high, the outer layer and the powder are easily peeled off during the subsequent process and storage and transportation after spraying, resulting in insufficient nutrient content and distortion of the formulation.

5. Control system

If the automatic control system of Spraying is not complete or lack of monitor, once the grease is short or appear other material flow change, there might produce waste material.

V. Summarization of Grease Spraying Technology on Surface of Pellet Feed

Technology of grease spray on the feed pellet surface has more advantages than other adding technology, but there are still some insufficient, such as the pellet absorb capacity of grease will directly affect the spray effect; the grease is vaporific while spraying, it is hard to avoid sticking on the equipment surface when the temperature is low, thus cross contamination will make the feed metamorphic, if take this problem into consideration in the equipment structure, feed production process and operation, it can be avoided.