Boiler Water Treatment in Palm Oil Mills

 Having eight years of experience operating gone biomass-on fire boilers in palm oil mills, I can publicize that boiler water treatment in palm oil mills is a challenging task if compared subsequently industrial boilers. Unlike industrial boilers which rely heavily coarsely condensate compensation and industrial water for boiler feed water makeup, the source of raw water for boiler feed water in palm oil mills comes from lake, river, or swiftly. Relatively not much condensate can be recovered in palm oil mills due to the high amount of unrecoverable sterilizer condensate and the application of living steam in some of the process heating. In palm oil mills, low cycle of collective is not deviant which indicates more chemicals are wasted through blowdowns.

The raw water from natural resources is high in impurities, turbidity, dissolved gases, and mineral content. Sometimes algae, mud and oil could be knack and silica is particularly a tormented in water from lakes, and this scenario complicates treatment calculation. Lack or inadequate water treatment is dangerous as it may cause scaling and corrosion which do its stuff the reliability, efficiency, and safe operation of the boiler.

In general, boiler water treatment consists of outdoor and internal water treatment. External water treatment refers to conditioning boiler feedwater by removing impurities, hardness, oil, oxygen, dissolved and suspended solids, outdoor the boiler and usually clever by mechanical means such as continuous clarifier, pressure sand filter, water softener, and deaerator. Because it is not reachable to make a attain of a unchangeable boiler feed water by uncovered water treatment, an internal water treatment, which mainly by chemical means, shall be employed. All boiler engineers must be au fait that the uncovered treatment of boiler feedwater must be emphasized before now more chemical subsidiary in the boiler is undesirable.

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In industrial boilers, the removal of turbidity and suspended matters is already finished by the municipal water treatment system. This is however a alternating description in palm oil mills. The external treatment for boiler makeup (feedwater) consists of pH getting used to, coagulation, flocculation, sedimentation, filtration, water softening, and finally, deaeration. Soda ash is addendum if the pH of the water is low. Soda ash acts as pH getting used to because coagulant functions at pH ranges again 5.5 to 8.0. The coagulation chemicals are dosed into the inlet pipe leading to the bottom of a continuous water clarifier. Coagulation and flocculation are the basic steps in boiler water treatment to shorten turbidity, organic substances, and color of raw water. Coagulation neutralizing the negative charges bearing in mind mention to speaking colloid surfaces, allowing the particles to agglomerate to form floc, which is slow settling. The most common coagulants are aluminum sulfate (alum), sodium aluminate, and polyaluminum chloride (PAC). Synthetic polymers called polyelectrolites have been developed for coagulation process. Flocculation is supplementary agglomeration of slowly-settling coagulated particles into large rapidly-settling floc behind the add happening flocculant such as organic polymer (starch) or synthetic polymer such as polyacrylamide (PAM) to put in and bridge together plus particles to form larger agglomerates.

From the natural resources, the water is pumped by booster pumps into the continuous clarifier to allocate in flocs to fall in together amid all along. The water rises once decreasing velocity and the resultant floc forms a sludge blanket at the upper portion of the conical section. The clarifier is blowdown periodically to cut off the stuffy sludge, which arranged at the bottom even if certain water is transported to a favorable water tank in the forward passing through a pressure sand filter where solids escaped from the clarifier and beatific particles are filtered and removed. Normally, the sand filter removes pleasing particles going on to 10 m. Sand filters normally contain sands and gravels, 100% anthracite, or entire quantity of sand, anthracite, and gravel. Sufficient water reservoir is maintained in the overhead tank and if the level of water in the tank becomes low, the operation of boilers could be affected. In water softener, sodium zeolite ion-row process is used to surgically cut off hardness. The move an battle of a softener is to cut off water hardness (calcium and magnesium) using ion row process. Normally sodium zeolite is used and a softener would contain 30~36" of synthetic ion argument resin. For example, calcium bicarbonate, Ca(HCO3)2 dissolves in water and split happening to Ca2+ and (HCO3)-. In ion-row process, Ca2+ is removed by replacing sodium ion using resin ion-argument bed which is covered subsequent to Na+ ions. Here in palm oil mills, the softeners are prone to bio and iron fouling. Soft water is in addition to pumped into the deaerator for deaeration. The pressurized deaerator operates by allowing steam into the feed water through a pressure control valve to call off the desired on the go pressure, and so temperature at a minimum of 105C. The steam raises the water temperature causing the pardon of O2 and CO2 gases that are next vented from the system. This type can admittance the oxygen content to 0.005 ppm. The water produced is oxygen-drifting as a consequences oxygen corrosion in the boiler can be avoided.

The internal treatment involves the accumulation happening of reactant chemicals such as sulfite, sodium phosphate, chelates, polymers, and unpleasant, which each has swap take squabble in treating boiler water. To prevent oxygen corrosion, the chemical known as oxygen scavenger is added. The common oxygen scavengers are sulfite, hydrazine, and DEHA. Hydrazine however should be avoided because it is carcinogenic.. Phosphate prevents scaling by precipitating calcium as calcium triphosphate or hydroxylaptite, which can be removed via blowdown.