Black Friday 2020 Boiler Water Treatment in Palm Oil Mills
Having eight years of expertise working with biomass-fired boilers in palm oil mills, I can say that boiler water remedy in palm oil mills is a difficult process if in contrast with industrial boilers. In contrast to industrial boilers which rely closely on condensate return and industrial water for boiler feed water make-up, the supply of uncooked water for boiler feed water in palm oil mills comes from lake, river, or effectively. Comparatively not a lot condensate could be recovered in palm oil mills because of the excessive quantity of unrecoverable sterilizer condensate and the applying of dwell steam in a number of the course of heating. In palm oil mills, low cycle of focus isn’t unusual which signifies extra chemical compounds are wasted via blowdowns.
The uncooked water from pure assets is excessive in impurities, turbidity, dissolved gases, and mineral content material. Typically algae, mud and oil may very well be current and silica is especially an issue in water from lakes, and this situation complicates remedy additional. Lack or insufficient water remedy is harmful as it could trigger scaling and corrosion which have an effect on the reliability, effectivity, and secure operation of the boiler.
On the whole, boiler water remedy consists of exterior and inside water remedy. Exterior water remedy refers to conditioning boiler feedwater by eradicating impurities, hardness, oil, oxygen, dissolved and suspended solids, outdoors the boiler and normally completed by mechanical means similar to steady clarifier, strain sand filter, water softener, and deaerator. As a result of it isn’t doable to acquire an ideal boiler feed water by exterior water remedy, an inside water remedy, which primarily by chemical means, shall be employed. All boiler engineers should be conscious that the exterior remedy of boiler feedwater should be emphasised since extra chemical addition within the boiler is undesirable.
In industrial boilers, the removing of turbidity and suspended issues is already carried out by the municipal water remedy system. That is nonetheless a unique story in palm oil mills. The exterior remedy for boiler make-up (feedwater) consists of pH adjustment, coagulation, flocculation, sedimentation, filtration, water softening, and at last, deaeration. Soda ash is added if the pH of the water is low. Soda ash acts as pH adjustment as a result of coagulant features at pH ranges over 5.5 to eight.0. The coagulation chemical compounds are dosed into the inlet pipe resulting in the underside of a steady water clarifier. Coagulation and flocculation are the essential steps in boiler water remedy to scale back turbidity, natural substances, and shade of uncooked water. Coagulation neutralizing the unfavorable expenses on colloid surfaces, permitting the particles to agglomerate to type floc, which is gradual settling. The most typical coagulants are aluminum sulfate (alum), sodium aluminate, and polyaluminum chloride (PAC). Artificial polymers known as polyelectrolites have been developed for coagulation course of. Flocculation is additional agglomeration of slowly-settling coagulated particles into massive rapidly-settling floc with the addition flocculant similar to natural polymer (starch) or artificial polymer similar to polyacrylamide (PAM) to connect and bridge between particles to type bigger agglomerates.
From the pure assets, the water is pumped by booster pumps into the continual clarifier to permit flocs to quiet down. The water rises with reducing velocity and the resultant floc varieties a sludge blanket on the higher a part of the conical part. The clarifier is blowdown periodically to take away the heavy sludge, which settled on the backside whereas clear water is transported to a transparent water tank earlier than passing via a strain sand filter the place solids escaped from the clarifier and effective particles are filtered and eliminated. Usually, the sand filter removes effective particles as much as 10 μm. Sand filters usually comprise sands and gravels, 100% anthracite, or mixture of sand, anthracite, and gravel. Enough water reservoir is maintained within the overhead tank and if the extent of water within the tank turns into low, the operation of boilers may very well be affected. In water softener, sodium zeolite ion-exchange course of is used to take away hardness. The operate of a softener is to take away water hardness (calcium and magnesium) utilizing ion change course of. Usually sodium zeolite is used and a softener would comprise 30~36″ of artificial ion change resin. For instance, calcium bicarbonate, Ca(HCO3)2 dissolves in water and cut up as much as Ca2+ and (HCO3)-. In ion-exchange course of, Ca2+ is eliminated by changing sodium ion utilizing resin ion-exchange mattress which is roofed with Na+ ions. Right here in palm oil mills, the softeners are liable to bio and iron fouling. Tender water is then pumped into the deaerator for deaeration. The pressurized deaerator operates by permitting steam into the feed water via a strain management valve to take care of the specified working strain, and therefore temperature at a minimal of 105°C. The steam raises the water temperature inflicting the discharge of O2 and CO2 gases which can be then vented from the system. This sort can cut back the oxygen content material to 0.005 ppm. The water produced is oxygen-free due to this fact oxygen corrosion within the boiler could be prevented.
The inner remedy includes the addition of reactant chemical compounds similar to sulfite, sodium phosphate, chelates, polymers, and caustic, which every has totally different operate in treating boiler water. To forestall oxygen corrosion, the chemical generally known as oxygen scavenger is added. The widespread oxygen scavengers are sulfite, hydrazine, and DEHA. Hydrazine nonetheless ought to be prevented as a result of it’s carcinogenic.. Phosphate prevents scaling by precipitating calcium as calcium triphosphate or hydroxylaptite, which could be eliminated through blowdown.