Power Generation

The burning of fossil fuels – coal - oil - gas, as well as some other combustible fuels such as wood, rubber and waste products, produces a corrosive gas stream. These byproducts of combustion combine with atmospheric moisture (H2O) to form corrosive gases. Specific to coal and oil – SO2 and SO4 combine with H2O to form H2SO4 or Sulfuric Acid. In order to comply with environmental regulations, removal of the Sulfuric Acid and other pollutants is required. These systems are known as Flue Gas De-Sulfurization Systems or FGD Systems. Pre-Krete G-8 is used to protect numerous items within these systems including stacks, scrubber towers, breechings, precipitators, and ductwork.

FGD technologies differ throughout the industry. Operating temperature is a key factor in the design of the FGD system. At high temperatures (above 400 °F) the condensing of corrosive gasses is less prevalent and resistance to corrosive gases as well as high temperatures is required. At lower temperatures (below 180 °F) the corrosive effects of the gas stream is severe. In low temperature applications polymer products (vinyl and polyesters) can be considered. However, the low temperatures are achieved via wet scrubbers that use cooled water as the scrubbing liquid. The concern here is a mal function in the water supply pumps supplying the scrubbing liquid to scrubber. This results in the operating temperature going from less than 180 °F to well above 400 °F resulting in an immediate failure of the polymer lining. In the mid 70’s through the mid 80’s polymer based linings became extremely popular. However, due to a high failure rate of these systems during “upset conditions” a corrosion resistant lining, specifically Pre-Krete, that offers resistance to high temperatures, is now the preferred system.

Pre-Krete is used to protect numerous items within a FGD system. These are, but not limited to – Stacks, Scrubbers, Breechings, Duct Work, Blower Fans, Precipitators, Absorbers, Cooling Towers, and Boiler Water Re-Circulation Vessels. In coal-fired facilities Pre-Krete is also used to protest steel substrates from the effects of abrasion. See “Abrasion Service” for additional information.

Pulp & Paper

Typical Pre-Krete applications are in Kraft Mills, which produce Kraft Paper. Kraft paper is produced from wood pulp. It is strong and relatively coarse. Kraft paper is usually a brown color but can be bleached to produce white paper. It is used for paper grocery bags, multi wall sacks, envelopes and other packaging.

Paper Production
Wood chips are fed into vessels called digesters. The wood chips are combined with white liquor, a mixture of sodium hydroxide and sodium sulfide. The digester cooks the chips for several hours at 265 to 355 °F (130 to 180 °C). Under these conditions lignin is removed and the hemicellulose degrade to give fragments that are soluble in the strong basic liquid. The solid is collected and washed and fed into a paper machine to make paper. At this point the pulp is brown and known as "brown stock". The combined liquids are known as black liquor. Kraft pulp is dark but it can be bleached to make very white pulp. Fully bleached kraft pulp is used to make high quality paper where strength, whiteness and resistance to yellowing are important.

Recovery Process
In order to minimize waste there is a recovery process to return white liquor back to the digester. The black liquor is concentrated in multiple effect evaporators, transferred to a Black Liquor Tank, and fed into the recovery boiler to recover the inorganic chemicals for re-use in the pulping process. From the recovery boiler the solution goes to a Smelt Tank also known as a Disolving Tank. The molten salts ("smelt") are dissolved in a process water known as weak wash.

At this point other chemical processes are induced. The process proceeds from the Smelt (Disolving) Tank to a Green Liquor Clarifier, to a Cauticizer, to a White Liquor Clarifier and finally to a White Liquor Storage Tank to be transferred into the digester as required.

The Causticizer also incorporates a cyclical process where “Mud Wash” from the White Liquor Clarifier is thickened and fed into a Lime Kiln that converts Calcium Carbonate to Calcium Oxide. This is fed into a Slaker Tank which supplies the Cautisizer with lime (calciun oxide).

The vessels referenced above that are bolded in CapiTal letters would utilize Pre-Krete C-17 to protect the substraite from the damaging effects of corrosion and abrasion.

This information is a broad and simplified overview of the operations of a Kraft Mill. Each mill has a unique process and process requirements.

In this process there a numerous other typs of vessles/structurs that require protection from corrosion and/or abraision. Dependent on the application, Pocono Fabricators’ Pre-Krete sytems may be able to help. This equipment we have experirence with is as follows:

Absorbption Towers - Acid Tanks - Brown Stock Tanks - Seal Tanks - Spent Acid Tanks - Stock Chests - Sulphur Feed Tanks - Tall Oil Storage/Reactor Vessels - Washer Feed Tanks - Washer Vats

Typical application is for the Pre-Krete to be applied at a nominal 2” thickness over a 14 gage 2” x 4” welded wire fabric anchored to the substrate on 12” centers. Causticizers and some liquor tanks have agitators that causes sever abrasion to the floor area of the vessels. The floors will typically deteriorate twice as fast as the walls. In this case the Pre-Krete is applied at 2” to the walls and 4”on the floors. Additional information can be found in our Guide Specification - PKWM and viewed on our website, www.prekrete.com, under Installation Instructions.

Additionally, some Pulp & Paper plants have their own power / steam generation plants. See Power Generation for additional information.

Abrasion Service

Pre-Krete G-8 and C-17 incorporates a highly abrasion resistant chip that results in both systems offering a high level of abrasion resistance. This enhanced wareability is realized in wet applications when slurry / viscous type materials come in contact with the Pre-Krete. It is also realized in dry applications when hot gases containing particulates travel at high velocity through ductwork, pipe and vessels protected with Pre-krete.

If abrasion resistance is the concern and corrosion resistance is not a consideration – Pre-Krete C-17 would be the preferred material. In abrasion service Pre-Krete is typically applied at a 1” thickness over expanded metal (see Guide Spec – PKEM), 1” – 1 ½ “ thickness over ¾” Hex Mesh (Gridsteel), and thicknesses greater than 1½” over wire mesh (see Guide Spec – PKWM).

Many applications involve coal-handling equipment – silos, bunkers, dryer duct, feeders, stokers, ash pits, and coal chutes. Additional applications include carbon black production, fly ash handling, bag houses, cyclone separators, fan housings, and asphalt plant ductwork.

Refineries

The most frequent application for Pocono Fabricators in Petroleum Refineries is the lining of concrete structures known as “Sulfur Pits”. As a by-product of the hydrocarbon refining process, molten sulfurous compounds are generated. When conveyed and contained in a refining or re-handling facility, molten sulfur is generally stored in subsurface tanks of structural concrete construction. Molten sulfur exists at 300 °F. These tanks, or Sulfur Pits, are subject to an extremely harsh environment. Typically constructed of reinforced concrete, Sulfur Pits can suffer severe deterioration.

Sulfur Pit maintenance, if not performed regularly, will result in aggressive deterioration. This process can significantly affect the integrity of the structure. Pre-Krete G-8 frequently used in new construction applications, to re-line, and to “patch” these structures. Patching is a temporary fix that will allow the unit to remain in service until a complete re-line can be scheduled.

A typical application would be to apply Pre-Krete G-8 at a nominal 2-inch thickness over wire mesh reinforcement as detailed in our Guide Specification - PKWMC - Gunned Application of Pre-Krete to Concrete Including a Wire Mesh Anchoring System.

Pre-Krete has been a successful solution to corrosion issues in other refinery applications. They include:

• Asphalt room floor
• Knockout drum lining
• Gas/oil fractionation tower known as a Power Former
• Horizontal flare blow-down drum
• Petroleum Coker by-pass flue
• Heavy tar and gas oil desalting system
• Blow-down stack Sour water saturation tank

Potable Water

Pre-Krete remains the standard and most widely utilized lining in commercial/industrial potable water heaters.

Pre-Krete G-8 was established for the specific purpose of providing our valued clients the assurance and peace of mind that their commercial/industrial potable water heater / vessel will continue to provide good clean potable water. Pocono Fabricators has recommended G-8 in potable water service since 1968. Pre-Krete G-8 referenced on the US’s EPA and FDA list of approved products for potable water.

A tank lining serves two very important purposes. It protects the consumer from the potentially dangerous effects of an unlined or poorly maintained tank as well as safeguards the structural integrity of the tank. Pre-Krete is specifically designed for hot and cold potable water applications. Pre-Krete forms a rock-hard monolithic barrier that resists temperatures up to 1000 °F and has a comprehensive strength of over 10,000 psi.

Pocono Fabricators has a network of factory trained Distributor/Applicators that will provide you with inspection and re-lining services. In considering an inspection or a re-lining of a potable water tank please take into account the following:

• Safety is of paramount importance. A Confined Space Entry Program and Procedure must be in effect. All employees must be trained and tested to insure they know and understand the hazards associated with this type of work and proceed accordingly.
• Experienced labor and supervision deliver quality workmanship. This experience affords a cost effective solution to you tank maintenance requirements.

Mining, Geo Thermal & Pipe Lining,

Pre-Krete remains a cost effective answer to the corrosion / abrasion conditions of “Solution Mining”. Pre-Krete has been utilized in the mining of Potash, Sands Oil, Sulfur, and Geo-Thermal applications.

In Solution Mining caverns, pockets, or pods exist or are created below the earth’s surface. Pipe is used to carry water, steam or a combination of both into the cavity. Pressures build and the solution containing the mined substance is forced to the surface. In all cases the pipe taking the solution away from the cavity are lined with Pre-Krete. In some cases both the delivery and the return pipes are lined. In this case the process is often reversed to release any blockages and promote continued flow.

The application the Pre-Krete to the pipe is accomplished in several ways.

• The most common is “Spin Casting”. A “ribbon” of Pre-Krete is placed along the entire length of the pipe. The pipe is then spun and the Pre-Krete is centrifugally cast to the interior diameter of the pipe.
• Pipe can also be lined while in place below the ground. This requires specialized equipment. In this application, Pre-Krete is pumped to a to a spinning spray head. The Pre-Krete is then sprayed evenly to the interior of the pipe. The spray rig is also equipped with rotating trowels that smooth the Pre-Krete as this complete unit is pulled through the pipe.
• Hand or Gunnite / Shotcrete application can be performed if the pipe diameter is ample enough to allow a work crew to enter the pipe and apply the Pre-Krete.

Fire Training Facilities

In 1988 Pocono Fabricators collaborated with the Maryland Fire and Rescue Institute Training Center to determine if Pre-Krete G-8 would be a suitable lining material to protect the interior walls and ceilings of a fire training facility.

Pre-Krete G-8 was applied at a nominal 2” thickness to a wall and ceiling area of a fire training facility. Four temperature measurements were made on the wall and in the ceiling respectively. The first was at the hot surface of the lining and the second was one-quarter of an inch below the surface. These locations were chosen to establish maximum material surface temperatures and temperature gradients within the lining. The other locations were at mid-depth (one inch below the surface) where the wire reinforcement was located and below the lining at the surface of the existing structure, the cold surface of the lining. Once a good fire had been established, the fire fighters entered the room and partially, or totally, extinguish the fire.

The Formula G-8 Pre-Krete lining system demonstrated excellent resistance to high temperatures and thermal shock. Although flame temperatures exceed 2000 °F, maximum surface temperatures for the lining system were below 1000 °F, with typical ceiling temperatures at 600 °F and wall temperatures at 500 °F. These temperatures are normal fire fighter training conditions.

Pre-Krete G-8 was proven capable of providing durable protection for fire fighter training facilities.

Please contact us if you would like a complete copy of the test results and/or our Application Guide/Specification - #PKFT – Pre-Krete G-8 Application Over a Masonry Substrate For a Fire Training Facility.