Boiler Water Treatment in Palm Oil Mills

 Having eight years of experience operational considering biomass-blazing boilers in palm oil mills, I can make known that boiler water treatment in palm oil mills is a challenging task if compared back industrial boilers. Unlike industrial boilers which rely heavily regarding 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 adeptly. Relatively not much condensate can be recovered in palm oil mills due to the high amount of unrecoverable sterilizer condensate and the application of conscious steam in some of the process heating. In palm oil mills, low cycle of assimilation is not uncharacteristic 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 suffering in water from lakes, and this scenario complicates treatment association. Lack or inadequate water treatment is dangerous as it may cause scaling and corrosion which show the reliability, efficiency, and safe operation of the boiler.

In general, boiler water treatment consists of uncovered 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 realizable to pro a absolute boiler feed water by outside water treatment, an internal water treatment, which mainly by chemical means, shall be employed. All boiler engineers must be familiar that the external treatment of boiler feedwater must be emphasized past more chemical totaling 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 parable in palm oil mills. The external treatment for boiler makeup (feedwater) consists of pH adjustment, coagulation, flocculation, sedimentation, filtration, water softening, and finally, deaeration. Soda ash is added if the pH of the water is low. Soda ash acts as pH adaptation because coagulant functions at pH ranges on top of 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 entre turbidity, organic substances, and color of raw water. Coagulation neutralizing the negative charges upon 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 appendage agglomeration of slowly-settling coagulated particles into large hastily-settling floc gone the tallying in the works flocculant such as organic polymer (starch) or synthetic polymer such as polyacrylamide (PAM) to tote in the works and bridge together in the middle of particles to form larger agglomerates.

From the natural resources, the water is pumped by booster pumps into the continuous clarifier to find the portion for entry flocs to assent down. The water rises taking into account decreasing velocity and the resultant floc forms a sludge blanket at the upper share of the conical section. The clarifier is blowdown periodically to surgically sever the unventilated sludge, which decided at the bottom though sure water is transported to a pardon water tank to the fore passing through a pressure sand filter where solids escaped from the clarifier and agreeable particles are filtered and removed. Normally, the sand filter removes fine particles in the works to 10 m. Sand filters normally contain sands and gravels, 100% anthracite, or mixture 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 cut off hardness. The encounter out of a softener is to cut off water hardness (calcium and magnesium) using ion dispute process. Normally sodium zeolite is used and a softener would contain 30~36" of synthetic ion clash 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-clash bed which is covered taking into account Na+ ions. Here in palm oil mills, the softeners are prone to bio and iron fouling. Soft water is later 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 dynamic pressure, and hence temperature at a minimum of 105C. The steam raises the water temperature causing the simple of O2 and CO2 gases that are along with vented from the system. This type can shorten the oxygen content to 0.005 ppm. The water produced is oxygen-pardon for that defense oxygen corrosion in the boiler can be avoided.

For more info oil filtration.

The internal treatment involves the buildup of reactant chemicals such as sulfite, sodium phosphate, chelates, polymers, and rancorous, which each has alternating take motion in treating boiler water. To prevent oxygen corrosion, the chemical known as oxygen scavenger is add-on. 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.