Boiler Water Treatment in Palm Oil Mills

 Having eight years of experience vivacious as soon as biomass-rest boilers in palm oil mills, I can say that boiler water treatment in palm oil mills is a challenging task if compared as soon as industrial boilers. Unlike industrial boilers which rely heavily in the region of condensate reward 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 dexterously. 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 assimilation is not substitute 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 facility and silica is particularly a difficulty in water from lakes, and this scenario complicates treatment appendage. Lack or inadequate water treatment is risky as it may cause scaling and corrosion which organization the reliability, efficiency, and attach 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, outside the boiler and usually competent by mechanical means such as continuous clarifier, pressure sand filter, water softener, and deaerator. Because it is not realizable to get your hands on a unbending boiler feed water by outside water treatment, an internal water treatment, which mainly by chemical means, shall be employed. All boiler engineers must be au fait that the outdoor treatment of boiler feedwater must be emphasized back more chemical add-on in the boiler is undesirable.

In industrial boilers, the removal of turbidity and suspended matters is already finished by the municipal water treatment system. This is however a alternating credit in palm oil mills. The outdoor treatment for boiler makeup (feedwater) consists of pH getting used to, coagulation, flocculation, sedimentation, filtration, water softening, and finally, deaeration. Soda ash is go forward if the pH of the water is low. Soda ash acts as pH becoming accustomed because coagulant functions at pH ranges sophisticated than 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 going approaching for the subject of 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 added agglomeration of slowly-settling coagulated particles into large shortly-settling floc as soon as the associate occurring flocculant such as organic polymer (starch) or synthetic polymer such as polyacrylamide (PAM) to accessory going on and bridge along surrounded by particles to form larger agglomerates.

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From the natural resources, the water is pumped by booster pumps into the continuous clarifier to agree to in flocs to allocate all along. The water rises following decreasing velocity and the resultant floc forms a sludge blanket at the upper portion of the conical section. The clarifier is blowdown periodically to sever the stuffy sludge, which decided at the bottom even though unqualified water is transported to a unmovable water tank back passing through a pressure sand filter where solids escaped from the clarifier and pleasant particles are filtered and removed. Normally, the sand filter removes gigantic particles taking place to 10 m. Sand filters normally contain sands and gravels, 100% anthracite, or join up 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-dispute process is used to cut off hardness. The act of a softener is to cut off water hardness (calcium and magnesium) using ion disagreement process. Normally sodium zeolite is used and a softener would contain 30~36" of synthetic ion row resin. For example, calcium bicarbonate, Ca(HCO3)2 dissolves in water and split taking place to Ca2+ and (HCO3)-. In ion-quarrel process, Ca2+ is removed by replacing sodium ion using resin ion-clash bed which is covered bearing in mind Na+ ions. Here in palm oil mills, the softeners are prone to bio and iron fouling. Soft water is subsequently pumped into the deaerator for deaeration. The pressurized deaerator operates by allowing steam into the feed water through a pressure present advice valve to desist the desired on the go pressure, and suitably temperature at a minimum of 105C. The steam raises the water temperature causing the reprieve of O2 and CO2 gases that are also vented from the system. This type can tribute the oxygen content to 0.005 ppm. The water produced is oxygen-forgive therefore oxygen corrosion in the boiler can be avoided.

The internal treatment involves the add together of reactant chemicals such as sulfite, sodium phosphate, chelates, polymers, and acid, which each has exchange take steps in treating boiler water. To prevent oxygen corrosion, the chemical known as oxygen scavenger is late gathering. 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.