Granulated blast furnace slag is ex-tremely abrasive. Moving the granulatedslag slurry wears pipes and elbows, result-ing in downtime and higher maintenancecosts. Blue Circle Cement’s Sparrows Point,MD. facility is well aware of the problemsthat moving this abrasive material cancause. The company produces about850,000 tons of slag cement annually.

A water granulating/grinding operationthat turns slag left over from the produc-tion of iron into slag cement, the BlueCircle plant is the first and oldest of itskind to be built in the United States. It isthe largest producer of the granulated blastfurnace slag in one location in the coun-try, producing 2,850 tpd of slag cement.

The slag cement produced by BlueCircle is called NewCem. Used as a Port-land Cement additive, NewCem can re-place as much as 70% of Portland cementin concrete mixes. The proportion is basedon the specific job requirement, and theconditions and desired characteristics of

the concrete. NewCem provides specific con-crete properties such as improved workabil-ity; permeability; resistance to sulfates andchlorides; and resistance to alkali-silica reac-tion. It has a greater strength potential andproduces a lighter color product, say its mak-ers.

Used in numerous general constructionapplications, NewCem is preferred by manyengineers and concrete suppliers who pro-duce high-performance concrete. The prod-uct meets ASTM 0-989, Grade 120, andAASHTO M-302 standard specifications ofground granulated blast-furnace slag for usein concrete and mortars. In the last decade,NewCem has been used in an estimated 40million cu yd of concrete.

The slag cement production plant at Spar-rows Point was designed specifically to handleslag produced by Bethlehem Steel’s huge “L”blast furnace and went online in March 1981.One of the largest producing blast furnacesin the western hemisphere, the “L” furnaceproduces about 8,000 tpd of iron. The fur-nace runs continuously 365 days a year. Tokeep pace with the furnace. Blue Circle alsoruns 24 hours a day, three shifts a day. TheBlue Circle plant and the steel mill plant arelocated near each other on the ChesapeakeBay.

Prior to the construction of the SparrowsPoint plant, some of the slag produced by thesteel mill was used as a fill material, but themajority of the slag was considered unusablewaste material. Today, using the water granu-

lation system. Blue Circle consistently con-verts all of the “L” furnace slag into the high-quality slag that is used to make cement.

Engineers who designed the Blue Circleslag cement plant wanted to avoid blownpipe, worn elbows, and other problems thatmight result in downtime and high mainte-nance costs. They were well aware of theproblems associated with moving the highvolume of slag produced by the blast fur-nace. The slag, composed of a chemicalcombination of lime, silica, alumina, and mag-nesia, is extremely abrasive. It would take aspecial type of product to handle the highvolume and the harsh nature of the slag.

Engineers found the answer in a basalt-lined pipe manufactured by Abresist Corp.,Urbana, Ind. They specified 19-in.-diamAbresist pipe for the new plant and elimi-nated many of the problems caused by theharsh slag.

Approximately 2,000 ft of the basalt-lined pipe is used to move the slag throughthe processing system. For nearly two de-cades, the basalt-lined pipe withstood theabrasion from the slag and still does notneed to be replaced. In addition to the pipe.Blue Circle also lined its agitation tanks withthe basalt. It was installed in the tanks in1989 and did not need to be reworked fora decade.Converting iron/slagto NewCem

The production of slag cement at BlueCircle begins after the blast furnace finishesproducing iron. During iron production theiron/slag mixture is drawn from the blastfurnace at four tap holes—two located onthe east side of the furnace, two on thewest. Only one hole per side may be opened

Blue Circle’s Sparrows Point, MD. plant has been usinga basalt-lined pipe for handling abrasive blast furnaceslag for 17 years without needing to replace it.

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At Blue Circle’s Sparrows Pint, MD plant, Abresist basalt-lined pipe runs along the bridge from theagitation tanks to the filter beds. Hydraulic variable-speed, 1,000-hp pumps move the abrasive slag to thefilter beds. The basalt pipe, after almost two decades of use, showed little to no wear and did not needto be replaced.

at any one time, and they are alternated ev-ery 28 days. The molten iron has a greaterdensity than that of the slag and is drawn offusing a dam structure as it flows from the taphole down a runner in the cast house floor.The molten iron is collected for further pro-cessing while the molten slag flows over thedam, down the hot runner, and out of thefurnace building.

At this point. Blue Circle takes over andthe conversion of molten slag into cementbegins. The granulating system was con-structed as close to the blast furnace as pos-sible to ensure a good flowing product. Asmolten slag cools, its viscosity increases, mak-ing it more difficult to granulate. All pipe usedto convey the abrasive slag is lined withAbresist basalt wear-resistant linings.

Blue Circle maintains four hot runners andfour blow boxes. The molten slag flows fromthe furnace at 3 to io tons per minute to theblow boxes. Based on the condition of themolten slag, it is diverted to a pit for air-cool-ing or is granulated. The hot runner channelsthe molten slag into the blow box.

Here the molten slag is quenched underhigh-volume water sprays. A water/slag ratioof 10-to1 is maintained to assure rapidquenching. The shock cooling instantly vitri-fies the molten slag into a glassy sand-likematerial that has a glass content of 95% to98%. The slag is monitored to ensure that noiron carryover enters the blow box. If mol-ten iron is detected, it is diverted to the pitbefore quenching to prevent explosions.

From here, the granulated slag and waterslurry flows from the blow box to agitationtanks in steel, refractory-lined channels calledthe cold runners. Blue Circle has two coldrunners and two agitation tanks on each sideof the furnace. Each agitation tank is servicedby two 15,000-gpm slurry pumps.

The slurry enters the agitation tank tan-gentially, inducing a swirling action while moreslurry is added. The agitation keeps the slagsuspended in the slurry so it can be easilypumped from the furnace area via 1,000-hphydraulic variable-speed pumps to one of five

filter beds on site. The system is designed toensure that a constant level of slurry is main-tained in the agitation tank.

From the agitation tank, the slurry line,which is lined with Abresist basalt lining, emp-ties into the distribution box. The distributionbox constructed with a ceramic tiled lining anda series of gates allows the operator to selectwhich filterbed receives the slurry. Blue Circlehas five 2,58o-cu-ft capacity filter beds. In thefilterbeds, a gravel filter is used to separate theslag from the water.

A series of drainage pipes collects the pro-cess water and channels it from the filterbedleaving the slag granules behind. The processwater returns through three collector pipesto the main collection pipe. The granulated slagfrom the filterbeds is removed by a bridgecrane and transported via conveyor to thestorage silos. From there, the raw slag goes tothe grinding plant for processing.

During the grinding operation, fineness isclosely controlled on an hourly basis to en-sure that the hydraulic activity of the slag isuniform and exceeds the stringent strengthrequirements of ASTM-C-989 specifications.After grinding, NewCem is stored in two20,000-ton-capacity silos. From there, theproduct is distributed along the eastern sea-board to construction industry customers. Itis shipped via truck, rail and class A oceanbarges to markets as far north as Boston, Mass.,and as far south as Jacksonville, Fla.

17 years and still goingIn 1999, Bethlehem Steel shut the SparrowsPoint steel mill plantdown to reline its “L”blast furnace and re-locate the slag run-ners. Because of thechanges at the steelmill. Blue almost twodecades was re-placed. The rest wasstill in good condi-tion.

Bill Sanders, Blue Circle’s operational main-tenance coordinator, said, “Much of the pipewas good. But we replaced it anyway. Espe-cially in the areas that might cause us prob-lems in the future if they would blow duringoperation. We replaced the pipe in the criti-cal areas that are hard to get to and thattake the most pounding. The pipe was not inbad condition, we just took the opportunityto replace it.”

The company also examined the straightpipe on the bridge to the filters. Sanders said,“The pipe bridge piping is not a critical arealike elbows and bends, but it needed to belooked at. We pulled the bridge pipe out,checked it, and decided it showed little to nowear. It could last another five to seven years,if not longer, based on the blast furnace out-put. We didn’t need to replace any of theAbresist basalt-lined pipe on the bridge.”

The company did not consider using an-other brand of pipe. Erin Altemos, plant pro-cess engineer, remarking on the longevity ofthe pipes, said, “We specified the best in 1981.The reliability we need is there. It lasts. Whychange? You can’t get much better customerservice when you have a problem and thepresident of the company comes in and di-rects the repairs.”

Agitation tanksLike the pipes that crisscross the compound,the sides of the agitating tanks at SparrowsPoint were basalt lined as well. In 1999' thecompany decided to address the few issuesthey were having with the lining in the tanks.

This schematic of the granulation process at Sparrows Pointshows the movement of the slag from the “L” blast furnace tothe filter beds through basalt-lines pipe.

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Once again, the company went to Abresistfor the solution.

The basalt lining on the tanks had beeninstalled in 1989 and was not originally speci-fied when the plant was built. The corrosive

nature of the atmosphere at the planteroded the tanks from the outside. “Thebasalt lining did not completely withstandthe impact, but it had a longer life than any-thing else,” Sanders said. “The Abresist pan-els were not worn out. Some of the tileswere being knocked off of the panel due toimpact.”

Altemos added, “Impact is a big problemwith the tanks. We had to replace sectionsof the tank lining that were damaged. Wehad experience with Abresist. Joe [Accetta,president of Abresist] and Ray [Albertson,Abresist sales representative], helped us getaround the problem and solve it.”

The Abresist team advised the companyto use Alresist high-density alumina ceramictiles that were manufactured into curved

panels. Rated 9 on the Mohs scale of hard-ness, they provided the level of abrasionand impact resistance needed to with-stand the impact of the slag. The Alresistplates were installed in the tanks in 1999with the help of Jeff Howard, Abresist tech-nician.

Summing up Blue Circle’s longtimerelationship with Abresist, Sanders said,“The reason we keep coming back toAbresist is the product performance andtheir customer service.”

This article was adopted from material sub-mitted by Blue Circle Cement/NewCem,(+1) 410-388-1177, www.bluecircle.co.uk;and Abresist Corp., (+1) 800-348-0717,www.abresist.com

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Molten slag flows from the “L” blast furnace at the rate of 3 to 10 tons per minute.Depending on the condition of the molten slag, it will be channeled to a pit for air-cooling or is granulated.

Reprinted with

permission from

Cement Americas

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