World Grain - August 2014 - (Page 72)

FEED OPERATIONS Pellet mills Examining this important piece of feed production equipment and its accessories by Fred Fairchild In my two previous articles on pelleting, which ran in the April and May issues of World Grain, I discussed the pelleting system and the cooling and crumbling equipment. In this article I will examine the pellet mill itself along with its accessories. MASH FEEDER The feeder to move the dry mash from the mash bin to the conditioner is a special properly designed screw feeder. It is normally made out of stainless steel due to addition of the moisture into the conditioner that may enter the discharge area of the feeder. In some cases, the screw flighting on the feeder needs be doubled by installing 2-3 additional revolutions of screw flighting at the discharge end halfway between the regular flighting to minimize product surges from the feeder into the conditioning chamber(s). The feeder must be equipped with some type of method to adjust its speed to control the flow rate of the mash passing through it. The amount of mash being delivered determines the amount of steam needed to properly condition it and the amount of work required to drive the pellet mill. The speed is normally controlled using an A.C. Variable Speed starter and motor. The speed can be adjusted manually or by an automated control system. CONDITIONER Conditioning of the mash going to the pellet die is essential in making a good pellet. Conditioning involves adding heat and moisture to the dry mash and then holding the mixture in the conditioner for a specified period of time. This action is to accomplish two major purposes, destroy microorganisms and start the gelatinization process for the final product production. The conditioning process requires time, moisture and heat. A standard conditioner above the pellet mill is a round horizontal tube with paddles (picks) mounted on a shaft that runs the length of the tube to mix the material with the 72 moisture (steam) injected into the conditioning chamber. The conditioner diameter and length are determined by the volume needed to mix the materials and retain them for the needed time period. The size should be such that the conditioning chamber is nearly full during the mixing process, but not overloaded such that it might plug. In some cases, multiple conditioners are often connected in series if one unit is not enough to do the job. Various designs have been developed by pellet mill manufactures to meet the required action and retention times. California Pellet Mill Company has developed a hygieniser unit that fits between the standard conditioner discharge and the pellet mill. It is a jacketed unit that does not mix but passes the mixture through a maintained heat atmosphere on a firstin/first-out design. Wenger has developed a high intensity pre-conditioner (HIP) unit for use above extruders and pellet mills. It is a twin shaft design with separate motors on each shaft. It provides an intense mixing action while the materials are in the unit. To make any conditioner perform at its best, I recommend installing variable speed drives on the units. STEAM SYSTEM Steam supply systems for the conditioning of the mash before it goes to the die must be properly constructed to deliver high quality steam to the conditioning chamber(s). Steam from the boiler is usually sent to the pelleting equipment area under pressures of 125-150 psig, but needs to be reduced to 25 psig +/- as it enters the conditioning chamber(s). By transferring the steam to the pelleting system at high pressure, a smaller system pipe size is required. As an example, a pound of saturated steam at 125 psig has a volume of only 3.22 cubic feet. The same pound of steam at 25 psig occupies 10.5 cubic feet, and when the steam enters the conditioning chamber and has 0 psig, the volume of it is 26.8 cubic feet per pound. As the high pressure steam arrives for the conditioner sysAugust 2014 / World Grain /

Table of Contents for the Digital Edition of World Grain - August 2014

World Grain - August 2014
Table of Contents
From the Editor-in-chief - Fundamentals drive wheat prices
Calendar of Events
Latin American milling conferences
News Review - Interflour to build flour mill in Philippine free-trade zone
San Miguel to double flour milling capacity
ADM Milling completes expansion in Indiana
Bartlett building grain facility in Kansas
Cargill to build grain facility in Arkansas
Grupo Bimbo acquires Ecuadorean baker
Didion Milling names vice-president, business development
GrainCorp buys stake in Egyptian flour miller
Egypt purchases 5.1 million tonnes of wheat in 2013-14
United Grain plans bigger expansion at port
E.U. feed groups want decision on GMs
Toepfer renamed ADM Germany
E.U., EIB to work together on agriculture
Uzbekistan harvests record 8 million tonnes of grain
Ungashick joins World Grain sales team
E.U. sets import duty for first time in nearly four years
CHS earnings up 51% in third quarter
CHS makes management changes
Ardent Mills selects office location
Grain Market Review - Coarse grains
Country Focus - South Africa
Feature - Dawn of a New Era
Ardent Mills partners, executives, bring deep roots in flour milling
Regional Review - A Vital Grain Producer
Regional Review - Overflowing with Oilseeds
Regional Review - Export Challenges
Feature - Using Corn as a 'Lifeline'
LifeLine products
Technical Profile - Demanding the best
Feature - A Growing Issue
Feed Operations - Pellet Mills
Feature - Debugging your facility
Species spotted
Guest Commentary - Unforgettable: How flour saved Berlin
Feature - Olam's rice nucleus program
Rice Quarterly - UN sets acceptable levels of arsenic in rice
New rice mill planned for Arkansas
Italy wants ‘fairer’ rice deal
Thailand province developing jasmine rice
Thailand’s rice price shoots up on drought
Supplier News
Product Showcase
World Grain Archive
Ad Index/Fax Back Program

World Grain - August 2014