Past efforts to stem the tide of fuel cost increases, such as coal gasification, seem to have been only temporary fixes to a much more insidious problem. While a considerable amount of alternative fuel research is underway in the U.S., an existing technology-firing kilns with petroleum coke-might well provide much more immediate and lasting relief for brick manufacturers.
However, despite some of the potential drawbacks, petroleum coke is a readily available, cheap energy source. A typical petroleum coke has a calorific value of 14,000 to 15,000 BTU/lb and a very low ash content, in the range of 0.5%. Large supplies of this coke are currently available, and an even greater amount of the coke product will be produced as lower-grade crude oils are processed. Pricing has varied at the refinery from about $0.20 to $1/MMBTU over the past several years, and a regular supply to a manufacturing plant within a 100-mile radius of the refining facility can be arranged for a delivered cost in the area of $2/MMBTU. (Petroleum coke must be purchased through an agent and not directly from the refinery.)
Unprocessed coke is currently being used in some power plants and incinerators in North America.
Aside from being a proven technology, the firing system is simple, reliable and clean. Basically, airborne, micronized petroleum coke is circulated in a closed-loop pipe to distribution manifolds on the kiln roof. The air/coke mix is metered through the manifolds to various firing zones on top of the kiln. In a tunnel kiln firing clay brick, petroleum coke can typically be used beginning at about 1400°F (760°C), with a resulting overall kiln fuel mix of about 70% coke and 30% natural gas.
Two variations of the coke firing system exist. In one design, the coke is fed to a rotary grinder that is coupled with an inline fan. When the coke is ground fine enough to become airborne, the micronized material is drawn by the fan through the piping and is distributed to the various system manifolds. The system can accept material with 10 to 12% moisture. Hot air, generally drawn from the kiln waste heat system, is used to dry the coke in the grinder to the proper moisture level.
The other system operates with coke that has been previously ground and dried with a moisture content preferably below 1%. The dry, micronized fuel is pneumatically blown into a storage silo at the plant site where, on demand, the system fan will draw the prepared material from a special valve on the bottom of the silo. This system is the best option if a reliable, consistent and economical supply of low-moisture (1% or less), fine petroleum coke can be obtained. If the prepared material is unavailable but the petroleum coke product has less than 12% moisture and a Hardgove Grindability Index (HGI) rating greater than 40, the first system described is a good fit.
While the sulfur content of the petroleum coke presents a potential obstacle to the installation and operation of a petroleum coke kiln firing system, the challenge is not insurmountable. Since air quality standards vary from state to state and even from county to county, discussions on this subject should be initiated at the local level. Depending on the level of sulfur compounds in the stack gases, a number of commercially available scrubbing devices could reduce these compounds to levels below the prevailing standards.
*developed by Ceric and Beralmar Tecnologic S.A.
Beralmar can be reached at Avda. Del Valles, 304, Poligono Industrial "ELS BELLOTS," P.O. Box 559, 08227 Terrassa, Barcelona, Spain; (34) 93-731-2200; fax (34) 93-731-4483; e-mail info@beralmar ; http://www.beralmar.com .
The test system covered 40% of the complete hot zone of the kiln and was capable of simulating 100% of the hot zone by moving the burners down the kiln as the cars progressed through the firing zone. This test provided good representation of what the full system would yield.
During the testing period, Taylor Clay performed a series of stack tests using wet lime injection. The company also allowed a group of individuals from the brick-making community to witness the Ceric/Beralmar installation and operational activities at the Taylor facility.
Based on the positive test results, and pending receipt of all final permits, Taylor Clay intends to place an order for a new tunnel kiln incorporating the Ceric/Beralmar firing technology, which will be commissioned in September or October 2006. United Brick & Tile Co. in Adel, Iowa, has also opted to use the petroleum coke firing system in its new Ceric manufacturing plant, which is currently under construction and will be operational in December 2006.
Taylor Clay Products' website is located at www.taylorclay.com. More information about United Brick, part of the Sioux City Brick & Tile Co., can be found at http://www.siouxcitybrick.com .