Apparatus And Method For Adding An Ingredient To A Material During A

Production Process

The present invention relates to an apparatus and method for adding an ingredient to a material during a production process. Particularly, although not exclusively, the invention relates to an apparatus and method for adding an ingredient to a material during the production of animal feed, in order to achieve a desired moisture content in the feed.

Animal feed products are typically sold in either 'meal' or 'pellet' form and are typically manufactured by blending together a wide range of raw materials such as cereals and other natural ingredients.

Such animal feed products are manufactured to a formulation which specifies the desired characteristics of the product. One of these characteristics is maximum moisture content. Manufacturers of animal feed strive to ensure that the moisture content of feed approaches the maximum permitted level as close as possible since this reduces the cost of producing the feed. In doing so, however, they must ensure that the maximum permitted level is not exceeded, since this could render the feed un-saleable.

In an attempt to control the final moisture content of manufactured animal feed, in current methods of animal feed production the moisture content of the input raw materials is assumed to be below a maximum value. Likely moisture losses incurred as a result of the particular manufacturing process the raw materials will be subjected to is estimated. From these values an expected moisture content of the end product of the process can be estimated. This is then compared with the desired moisture content of the end product to determine the amount of water to be added during the manufacturing process.

A sample of the end product of the animal feed is sent to a laboratory for analysis in order to determine its actual moisture content. The measured value of moisture content is compared to the desired value of moisture content to calculate an error value. The error value may be used to modify the amount of water added to subsequent

manufacturing runs of feed in order to try and produce animal feed with the desired value of moisture content.

There are a number of significant problems with this approach.

Raw materials for producing animal feed that are delivered to a manufacturer typically have a wide variation in moisture content and the specific value of moisture content of each batch of a particular raw material often differs from the value specified by its supplier. In addition, when the raw materials are stored, prior to use in the manufacturing process, the moisture content of the raw materials may change as the materials may absorb moisture from or lose moisture to their surroundings, depending on how and where the materials are stored.

Furthermore, expected variation in moisture as a result of the manufacturing processes applied is usually inaccurately known.

Consequently, there is usually a difference (the error value) between the actual moisture content of manufactured feed, and the desired moisture content the manufacturer has tried to achieve.

The error value has two components, the error in the estimation of the moisture content of the input raw materials and the error in the estimation of the variation in moisture content during the manufacturing process. However, the error value only provides a value of the total error in the method and does not provide the separate values of each component of the error. This error value does not therefore provide enough information in order to allow an estimation to be made of the independent effects of a change in the raw material used and a variation in the manufacturing process of the moisture content of the end product. This makes it difficult, if not impossible, to improve moisture content estimation for manufacture of future feed.

Further, time delay, possibly days, in obtaining the moisture content measured by a laboratory means that when the moisture content is known it is no longer applicable to the product then being manufactured, largely because the moisture content of the raw

materials then being processed may differ considerably from that of the raw materials used to manufacture the end product which has been analysed. The current method is essentially a crude method of closed-loop control with a response time that is too large to produce a stable output value equal to the desired output value.

Given these problems, in order to ensure that the moisture content of animal feed does not exceed the permitted maximum, manufacturers aim to produce feed with a moisture content lower than the permitted maximum moisture content by at least the typical error value of the process. Thus the optimal formulation for the feed is not typically attained, with an attendant increase in production costs above what is theoretically possible.

It is the object of embodiments of the present invention to overcome, or at least reduce, the problems discussed above.

According to a first aspect of the present invention there is provided apparatus for adding an ingredient to a material during a production process, said apparatus comprising dispensing means for dispensing the ingredient to the material, a measurement device for measuring ingredient content of material and a control means arranged to control the dispensing means in dependence on a measurement taken by the measurement device.

According to a second aspect of the present invention there is provided a method for adding an ingredient to a material during a production process, said method comprising the steps of: providing apparatus comprising a dispensing means for dispensing the ingredient and a measurement device for measuring the ingredient content of material; measuring the ingredient content of material produced by the process using the measurement device and controlling the addition of ingredient by the dispenser in dependence upon the measured ingredient content.

Provision of a measurement device in the apparatus enables the ingredient content of material to be determined and therefore the amount of ingredient dispensed to be quickly altered in order to better control the ingredient content.

The ingredient may be, or contain, water. The measurement device may be for measuring the moisture content of the material. In particular the measurement device may be a microwave based device, such as the Moisturescan XT produced by Doescher & Doescher Gmbh. The measurement device is preferably able to take account of the material density and temperature when determining moisture content.

The material may comprise ingredients for the manufacture of animal feed.

The control means preferably controls the apparatus to perform the steps of the method.

The apparatus may include a mixer into which ingredient may be dispensed by the dispenser and the method may include the step of mixing the ingredient with the material in the mixer. In this case the measurement device is preferably arranged to measure the ingredient content of the material after it has been mixed with the ingredient. In a preferred embodiment the measurement device is arranged to analyse the material after it leaves the mixer.

The production process may be a batch process. Where this is the case the amount of ingredient added to a batch of material may be dependent upon the ingredient content of a preceding batch of material, as measured by the measurement device. In order to speed up production of material, whilst the ingredient content of a preceding batch of material is analysed, an amount of ingredient equivalent to that added to the preceding batch of material less a predetermined amount is added to a subsequent batch of material. Then, when analysis of the preceding batch of material is complete the amount, if any, of additional ingredient to be added to the subsequent batch is calculated and any necessary additional ingredient dispensed to the subsequent batch.

The process may be a production process for the production of animal feed and the apparatus may be comprised in an animal feed plant. The process may include some or all of the following steps: weighing one or more raw materials, conveying raw

material(s) to a grinder, grinding raw materials, conveying ground raw materials to the mixer, and conveying mixed material from the mixer for subsequent processing.

The apparatus and method implement a form of closed loop control with an increased response time and accuracy to that of the prior-art. Provision of a measurement device in the apparatus enables the ingredient content of a batch of material to be determined sufficiently quickly to enable the amount of ingredient added to the subsequent batch to be adjusted depending upon the content of the preceding batch. In the case of moisture content in ingredients for animal feed variation in the initial moisture content of one batch of ingredient to the next, and hence the amount of water that needs to be added, is small. Thus it is reasonable to assume that the initial moisture content of two consecutive batches is substantially the same. In any event, the likely error in moisture content obtained using the invention will effectively be limited to the variation in initial moisture content of consecutive batches of ingredients. This is typically smaller than the error in final moisture content in feed achieved by existing methods and thus allows manufacturers to aim for a target moisture level which is closer to the permitted maximum whilst keep the risk of exceeding that maximum acceptably low.

In order that the invention may be more clearly understood, an embodiment will now be described, by way of example, with reference to the accompanying drawing the single figure of which is a flowchart schematically illustrating part of a simplified animal feed manufacturing plant.

Referring to the drawing, an animal feed manufacturing plant comprises weighers 1 for weighing solid raw ingredients, typically cereals. The weighed ingredients are conveyed to a grinder 2 in which the ingredients are ground into a suitable form.

The ground ingredients are conveyed to a mixer 3. The mixer 3 is associated with two dispensers 4,5. One 4 is arranged to dispense water into the mixer, and the other 5 dispenses fats into the mixer 3. In the mixer a batch of raw ingredients is mixed together with water and fats dispensed by the dispensers. When the batch of ingredients has been sufficiently mixed the contents of the mixer is emptied into a hopper 7. At this point the mixer 3 is refilled with ingredients.

The mixed ingredients in the hopper 7 are dispensed and then travel via a microwave moisture analyser 8, in this embodiment a Moisturescan XT produced by Doescher and Doescher Gmbh of Germany, to other parts of the plant for further processing to form an end product. At this stage there are typically a number of different further processing lines to choose from, depending upon the end product to be manufactured. These are common to existing plant and will therefore not be described further.

The moisture analyser is operative to measure the moisture content of the mixed ingredients as they are dispensed from the hopper 7. The analyser is able to account for both density and temperature of the material it analyses.

The various elements of the plant operate under the control of a control means 6, which receives an output from the moisture analyser 8. It is a function of the control means to determine the amount of water to be added to the mixer by the dispenser 4 in order to produce an end product with a desired target moisture content. The control means 6 is a programmable computer, although any suitable control means capable of performing the functions described below may be employed.

For the first batch of material to be processed in the mixer 3 the amount of water to be added is calculated using a conventional approach based on assumptions about the moisture content of the ingredients and moisture losses which will be incurred through the production process. Specifically the control means subtracts the assumed moisture content of the ingredients (known as the "dry moisture") from the target moisture content and then adds the expected amount of moisture loss from the process. This calculation is performed using figures representing moisture content as a percentage. The result is then converted to the weight of water required to be added to the mixer, based upon the actual weight of ingredients introduced into the mixer.

The expected value for moisture loss may be a value calculated from an earlier production run, and stored by the control means 6.

When the ingredients, including added water, have been mixed for a predetermined amount of time, the contents of the mixer 3 is emptied into hopper 7. A second batch of ingredients is then introduced into the mixer 3 and an amount of water added to the mixer by the dispenser 4 and mixing commences. This time the amount of water added is calculated by the control means 6 as the amount added to the previous batch, less a predetermined amount. The predetermined amount is greater than the expected variation in dry moisture of consecutive batches of raw ingredients.

At the same time, the first mixed batch of material is dispensed by the hopper 7 for further processing. As the material leaves the hopper it is subjected to analysis by the moisture analyser, which transmits a signal related to the measured moisture content to the control means 6. The control means 6 may compute an average value for moisture content from signals received from the moisture analyser 8.

The actual moisture content of the first batch of material is now known. On the, reasonable, assumption that the dry moisture content of the second batch of ingredients will be substantially the same as that of the first batch, the measured moisture content of the first batch can now be used to calculate the amount of water which should be added to the second batch of ingredients. The control means performs the calculation as follows.

The actual dry moisture of the first batch is calculated by taking the measured moisture content of the first batch and subtracting the amount of water added to the that batch in the mixer. This dry moisture content is then assumed to also be the dry moisture content of the second batch of ingredients. This value is then used, as with the first batch, to calculate the amount of water to be added to the second batch in order to achieve the desired moisture content, i.e. the dry moisture content is subtracted from the moisture target, and expected plant loses are added. Then, the amount of water already added to the second batch is subtracted from the calculated value to leave the amount of additional water to be added to the second batch. If the result is zero or negative, no additional water will be added.

The addition of an amount of water to a batch less than the amount of water added to the preceding batch in the first instance enables mixing of the batch to commence straight away, before measurement of the moisture content of the preceding batch has taken place, but without the risk that too much water will be added. Once a moisture content measurement is available for the preceding batch the moisture content of the subsequent batch is topped up as required. This maximises throughput of material since delay in processing material pending the moisture content of the preceding batch being analysed is largely avoided. Where a second additional of water is made it is necessary to ensure that the batch of material to which it is added remains in the mixer long enough to ensure that the second addition of water is properly incorporated.

This process is then repeated for all subsequent batches, with a measurement of the moisture content of the preceding batch being used to calculate the amount of water to be added to the subsequent batch. The calculation outlined above represents only one suitable calculation, others are possible. For example, the control means could simply deduct the measured moisture content from the target moisture content to determine an error value, and use this to adjust the moisture added to the subsequent batch directly, without calculating a theoretical dry moisture figure.

Moisture content of the final end product of the process may be measured in a laboratory in the conventional way. Knowing the moisture content of the material used to make the end product when it left the mixer enables an accurate value for moisture loss or gain for the plant downstream of the mixer to be calculated and enables an appropriate target moisture value for the ingredient leaving the mixer to be determined, depending upon the intended downstream processing of the product.

The above arrangement has been described by way of example only and many variations are possible without departing from the scope of the invention.