Shrimp Waste, Cooked

June 25, 2008

Historically, Vincent has had trouble pressing shrimp shells. A "strawberry milkshake" would ooze through the screen of the screw press, and, since the shells would co-rotate with the screw, capacity was dreadfully low. To combat these difficulties, a VFD would be programmed to auto-reverse periodically; this proved to be an acceptable solution.

However, a recent start-up at a shrimp processing plant proved to be an astounding success. Before one of Vincent's engineers was on-site, the customer started the press and ran it without a VFD. It worked perfectly with no attention until it was shut-down for the night, seven hours later. What was the big difference? These shrimp shells were cooked, not raw.

The shrimp were steam blanched in equipment from Laitram Machinery of New Orleans, Louisiana, www.laitram.com. Following shelling, the shells were flushed to a collection pit with the rest of the wastewater. The waste was first pumped through a horizontal rotary drum screen 100" long by 36" in diameter. The woven metal screen had .020" (0.5 mm) openings.

The wet solids dropped from the screen into the Vincent press, which was angled upward at 30 degrees. The Model CP-10 easily handled 4,500 pph feed. It produced 1,200 pph of press cake and 3,300 pph of press liquor. The press liquor was truly a liquor: it was pink with a viscosity near that of water.

The feed averaged 85% moisture and, at 40 psi discharge cone pressure, cake was produced with 55% moisture. Higher cone pressures had no measurable effect on the dryness of the cake. At the medium pressures (30-40 psi) the cake was dry to the touch and flaky.

The shell is sent to a rotary drum dryer after mechanical dewatering, so moisture content is very important. The shell is eventually made into commercial fish feed.

Issue 200