Powdered Milk Plant Design

Flowchart Delivery and storage of the milk 39464.4 kg of water taken out 5289 kg of fat taken out Evaporation Standardization of the cream/fat Separation 1356.2 kg of fat put back in The final composition is: water: 406.2 kg fat: 1356.2 kg milk solids: 11934.3 kg Standardization of milk Collect, cool and package Spray dry 785219.9kg of water

Delivery and storage In order to produce 5000 tones of dried milk per year, we need 49500000 Kg of fresh milk throughout the year. This equates to 7 deliveries of milk per 24hrs, with one batch of 4 tankers, and one of 3. The factory will be set up to process 3.5 tankers worth, and so 0.5 tankers worth of milk from the first batch will be stored for longer. Because of the bacterial growth, the maximum amount of time we can keep the milk in the storage tanks at 278K is 16.3 hrs. In order to meet demand, our milk will be processed in two batches of 11.75hrs, which allows 15mins cleaning and ensuring safe bacterial levels in the milk.

Evaporator An evaporator is a machine involved in extracting some of the water present in the liquid milk when passed through it. An evaporator is usually kept at partial vacuum for two main reasons: Lowering the pressure in the evaporator causes the water’s boiling point in the liquid milk to drop, and hence, it will boil at a lower temperature that will not damage the liquid milk passing through the evaporator. The energy supplied to evaporate the water will be reduced, and therefore, the energy costs of the factory will be cut down. In our factory, evaporation takes place first, which causes less water to be present in the liquid milk when reaching the centrifuge, and this quickens the separation process and makes it more efficient. To heat the milk to the required 52.7 degrees, the Evaporator works at 288.4 kW, which will cost £338,904 per year.

Separator Some of the water in the milk undergoes evaporation, the liquid milk is sent to a centrifuge in order to remove all the fat content from it. The separation process involves introducing the liquid milk into a centrifuge to separate the cream (fat) from the milk. This process utilizes the difference in densities of both the fat and the liquid milk, and therefore, they are both separated from each other. A centrifuge will swirl the liquid milk, and since the milk is denser than the fat in it, it will drop to the bottom of the centrifuge and be collected in another container for further processing, while the fat content is collected in another container. After separation, the cream (fat) and the remaining milk are remixed to provide the desired fat content in the milk. The separator works at 2.25kW and costs £2644 to run per year 

Standardization of fat Standardization, also known as Homogenization, is the process by which the raw milk is pushed into an atomizer to form tiny particles so that the fat is evenly dispersed and distributed. This prevents the fat from floating to the top of the container and allowing the homogenization of the liquid. Even though it is not necessarily needed, it is better to homogenize the milk as it means the free fat is converted into fat globules. ( Fat globules are formed by the adsorption of proteins on globule surfaces). This increases the solubility of the powdered milk produced. The standardizer works at 37kW and costs £43,479.3 per year.

Spray Drying Spray drying was chosen rather than roll drying as it is more energy efficient. Another advantage of using Spray Drying is that the product will have excellent solubility, flavour and colour. Prior to entering the dryer, we must atomize the milk concentrate into smaller droplets using highly pressured nozzles. Another option was a spinning disk, but the nozzles were preferred due to them being more energy efficient as mentioned earlier. Inside the dryer tower ( approx. 6m tall) there is dry hot air circulating inside, this meets the fine mist of liquid milk which comes from the pressured nozzles, the water is evaporated and fine dry powder falls from the air down to collection tubes. The spray dryer works at 2092.2 kW and costs £2,458,579.2 per year.

Cleaning The cleaning process is one of the vital processes implemented in the milk plant. An efficient wash up routine removes milk residues and bacteria from the plant. This is done in a 15 minute slot and has 3 stages: In our case, we are using Sodium Hydroxide at 100 degrees for 10 minutes, it will rid the appliances of milk fat, proteins and greasy residues and also bacteria. After that, we will be using nitric acid in order to neutralize the Sodium Hydroxide used and ensure the safe disposal of the waste products. Finally we do a water wash of the equipment to remove any excess chemicals which could contaminate the next batch of milk coming in. When using these cleaning substances, they usually have to be kept at the right temperature so that they are used efficiently.

We will buy the milk from farmers at a price of 32p per litre, costing us a total of £16,118,400 per year. If we buy plastic barrels able to fit 5kg of powdered milk in them at 50p each, this will cost us £500,000 per year. The total cost of powering the plant is £2,843,606.4 per year We can sell the powdered milk for £6.25 a kilo making £31,250,000 per year. This gives a profit of £11,787,994 per year. During the cleaning process, and as mentioned earlier, Nitric acid is added to the sodium hydroxide in order to neutralize it. This produces sodium nitrate which is a fertilizer and could potentially be sold on to increase the profit margin. Costs