Boiler formulations containing Belsperse 161

Belsperse 161 has been developed as a highly effective scale control agent and dispersant used primarily in boilers and industrial cleaning.

As a result of this information, Belsperse 161 is finding widespread application as a boiler water additive. Key advantages are very good phosphate dispersancy characteristics, excellent iron control, it can be monitored and is thermally/hydrolytically stable.

Boiler water formulations
This article contains information on several suggested boiler water programs which are suitable for treatment of low pressure boilers. This information may be used as a starting point for the development of boiler water programs and should be refined for particular conditions.

The attached appendix gives an overview of the objectives of several internal boiler treatment programs.

Typical formulations and operating parameters

(a) Coagulant programs

Typical formulation
soda ash	10%
50% caustic	10%
lignins	20%
Belsperse 161	8%
soft water	52%

Feed sulfite and vapour phase corrosion inhibitor separately.

Suggested operating guidelines
pressure		50 - 125 psig
silica		250 mg/l max.

Feedwater - mostly untreated in the plant. May be city water, well water, or both. Often deaerated, but deaerators do not always work. The cycles are variable.

Operating parameters
boiler M-alkalinity		300-600 mg/l
boiler P-alkalinity		250-500 mg/l
feedwater total hardness		10-100 mg/l
Dosage = (feedwater total hardness - feedwater M-alkalinity) = X
[(X + desired boiler M-alkalinity)/cycle] x 7 mg/l = mg/l product based on feedwater

(b) Single drum phosphate/oxygen scavenger program
A one-drum programme can be developed which is dosed based on the residual oxygen content of the feedwater.

Typical formulation
HEDP		5%
Belsperse 161		4%
50% sodium hydroxide		to pH 13
sodium tripolyphosphate		15%
sodium sulfite		20%
softened water		to 100%

The sulfite should be added after the sodium hydroxide to prevent formation of sulfur dioxide. This programme should be dosed at 40 mg/l for every 1 mg/l O₂. If the feedwater requires a greater residual of phosphate due to higher levels of calcium, then a Residual Phosphate approach is more applicable.

Operating parameters
pressure		100-600 psig
suspended solids		100-200 mg/l
total alkalinity		150-500 mg/l
residual phosphate		20-50 mg/l
iron		1-3 mg/l
silica		2-30 mg/l

Cycles depend on feedwater quality. Blowdown may be continuous or intermittent.

(c) Phosphate residual (reserve caustic) program
Phosphate-based boiler treatments are typically used up to about 600 psig. Some suggested guidelines to use Belsperse 161 are:

small boilers		8% sodium tri-polyphosphate 2.5% Belsperse 161 (as product)
mid range liquid phosphate programmes		18% sodium tri-polyphosphate 5% Belsperse 161 (as product)
large boiler installations		30% tetra-potassium pyrophosphate 4% Belsperse 161 (as product)

A general guideline is that 2.5-5 mg/l Belsperse 161 is dosed for every 10 mg/l orthophosphate generated in the boiler. A typical formulation containing an organic sludge conditioner is shown below.

Typical formulation containing organic sludge conditioner
trisodium phosphate		10%
lignin or tannin		5%
Belsperse 161		2.5%
50% sodium hydroxide		10%
soft water		65.5%

Feed oxygen scavenger and vapour phase corrosion inhibitor separately.

Operating parameters
pressure		100-600 psig
suspended solids		100-200 mg/l
total alkalinity		150-500 mg/l
*residual phosphate		20-50 mg/l
iron		1-3 mg/l
silica		2-30 mg/l
*(20 for 400-600 psig) (30 for 200-400 psig) (40 for 0-200 psig)

Cycles depend on feedwater quality. Blowdown may be continuous or intermittent.

(d) Low phosphate chelant programs above 600 psig
Above 600 psig, phosphate is added to catch calcium slip and produce a calcium phosphate sludge which is then dispersed using Belsperse 161. In the following suggested formulation, the lower phosphate program is supplemented with a chelant (in this case 1 mg/l EDTA). The orthophosphate can be generated in the boiler by use of tri-sodium phosphate, tri-polyphosphate or tetra-potassium pyrophosphate. These treatments are used in boilers using base exchange softened water where the risk of high calcium slip is small.

A suggested low phosphate chelant boiler program could be dosed to maintain the following levels in the boiler:

5-10 mg/l orthophosphate (from polyphosphate)
8 mg/l Belsperse 161
8 mg/l Belclene 200
1 mg/l EDTA

General guidelines
To formulate the above programmes you would require the following:

• formulating vessel resistant to acid and alkali
• good agitation within the vessel
• good cooling facility within or around the vessel
• pure water supply
• industrial balance
• pH meter
• oven and fridge to assess formulation stability
• instrumentation to measure viscosity and specific gravity
• drumming pumps
• protective clothing

The formulations given do not cover oxygen scavenger condensate line corrosion control and this must be borne in mind.

The above is a non-exhaustive list of the requirements for effective formulation work. Supplementary acquisitions will depend on local conditions/legislation and health and safety requirements.

Appendix to boiler formulations containing Belsperse 161

1. Objectives of internal boiler water treatment

(a) To prevent boiler scale and deposits by adding chemicals that will react with boiler water dissolved and suspended solids to form bulk water precipitates, or to solubilise boiler water minerals so that they will not precipitate. This is achieved by transporting the inorganic cations through the boiler and out with the blowdown.

(b) To condition any precipitates that form so that they remain flocculant and suspended and can be removed easily in the boiler blowdown.

(c) To control boiler corrosion by removing dissolved oxygen and adding passivating agents to form a film of Fe₂O₃ on steel surfaces.

2. Overview of internal scale control programmes

(a) Coagulation programs:

Add sodium carbonate and sodium hydroxide to precipitate calcium carbonate and magnesium hydroxide respectively plus organic sludge conditioners to create a flocculant precipitate that is easily removed in the blowdown.

High caustic programmes incur low costs and do not require a strict control, They are only useful only in very low-pressure, non-critical boilers. The pressure range is 50-125 psig. An FDA approved polymer dispersant should also be used to ensure that no hotspot deposits or oil-baked deposits are formed using this type of program.

Phosphate residual programmes

Inorganic phosphates are used to precipitate calcium ions as hydroxyapatite, Ca₃(PO₄)₂, Ca(OH)₂. Programmes always include sodium hydroxide (to precipitate magnesium) and organic sludge conditioners. They are used in low pressure boilers, and are often more effective than coagulation programmes. The pressure range is 100-600 psig. An FDA approved hydroxyapatite dispersant that will not thermally decompose at temperatures up to 350°C is required to ensure that this program does not fail.

Warranty - Patent Position
The information contained herein is, to our knowledge, true and accurate. Because conditions of use are beyond our control, we make no warranty or representation, express or implied, except that the products discussed herein conform to the chemical descriptions shown on the labels. Nothing contained herein should be construed as permission or recommendation to infringe any patent of a third party by reason of any uses made of the product in combination with other materials or in the operation of any process, and purchasers assume all risks of patent infringement by reason of any such use, combination or operation. No agent, representative or employee of this company is authorised to vary any terms of this notice.

Patents
FMC owns or is the licensee of patents and patent applications which may cover the products and/or uses described in this brochure.

Process Additives Division