One of the UK’s largest producers of duck products is set to save £30,000 a year on freezing costs following the introduction of ABB variable-speed drives on its blast chiller application.
Cherry Valley Farms of Lincolnshire rears some eight million ducks every year and processes 45,000 birds a day. Some are prepared as fresh duck products but most are frozen in the company’s ten blast chiller bays. Each bay has two 4 kW motors turning fans that blow air over coils of ammonia to produce a blast of very cold air. A complete day’s production of ducks is usually frozen in around ten hours overnight.
Although freezing only takes place on four days a week, the fans need to operate 24 hours a day every day, as switching the fans off would cause them to ice up. As the blast chillers are a major part of the production process and an energy intensive application, Cherry Valley Farms was keen to investigate any methods that would reduce the amount of energy used by the blast chillers. It was not possible to control the temperature of the blast chillers through PI control as the bays go through regular de-frost cycles. There is also a significant air exchange between the bays, making any form of temperature feedback unreliable.
The company asked ABB Authorised Value Partner, Inverter Drive Systems (IDS), to come up with a solution. Rob Stevens, Factory Engineering Manager for Cherry Valley, says: “We have worked with IDS on several other projects. They have installed ABB variable-speed drives on condenser pumps for us in the past and these have worked very well.”
IDS installed 20 ABB HVAC drives, two for each blast chill bay. In production, the drives run the motors at 45 Hz, giving a 25 percent energy saving during the freezing period. Outside production hours, the motors are slowed further to 30 Hz, producing a 60-70 percent saving when no product is being frozen. Overall, this is expected to produce an annual saving of £30,000 on the energy costs of the blast chillers.
Phil Nightingale of IDS says: “We set up one of the variable-speed drives as the master, with the other 19 as slaves. This allows the operation times of the master drive to be set and all the slave drives will follow this schedule. If Cherry Valley needs to operate the chillers in production outside normal time, an override switch can be used to bring the fans back up to the production speed of 45 Hz.”
A challenge involved in the installation was that the drives were installed in a roof housing containing the ammonia lines, making for very cold working conditions. However, the ABB drive is rated for a working temperature down to -15 degrees centigrade, so installing the drives in this area is not a problem.
Stevens adds: “As well as the energy saving, we expect that the slower start up achievable by the drives could lead to fewer fans breaking up, which we sometimes experienced with the old direct-on-line method used previously.”
ABB is a leader in power and automation technologies that enable utility and industry customers to improve performance while lowering environmental impact. The ABB Group of companies operates in around 100 countries and employs about 145,000 people.
Inverter Drive Systems (www.inverterdrivesystems.com) are the largest ABB AVP (Authorised Value Provider) and have energy saving specialists available to perform free energy saving surveys call 0115 9441036 or email [email protected]