http://www.dce.dk/index.htm

Go to the homepage of DCE & request their Guide. Easy! ■

Partha,

It depends on what you mean by design. As I understand it you have a plant with a number of dust generating points.

1 - you need hoods at the dust generation points to capture the dust.

2 - you need ducting to collect the dust and run it to the Baghouse.

3 - You need a baghouse and a dust extraction fan. Remember to keep the rain out of the fan discharge duct, and you may need some noise control.

4 - You need sufficient bags to trap the dust and drop it in the hopper.

5 - You need a dust disposal method to empty the hopper without generating large clouds of dust.

My approach would be the other way around.

1 - find out how much air you need by considering each dust generation point. If you have to start from nothing a Dust Control Handbook or Industrial Ventilation Manual will give a basic outline. But when it comes to "how little air can you get away with" you need some experienced advice.

2 - design of dust hoods needs experience. If the face velocity is too high - say 15 m/s - you will suck product off your machines instead of dust. These heavier particulates will cause problems in the ducts and at the filter bags.

3 - dust ducting is usually calculated on about 20 m/s. Anything less will not scour the ducts clean and create problems. But it depends to some extent on the size and density of the dust particles.

4 - the fan will have to deal with clean bags and dirty bags. As the bags get dirty the suction pressure drop increases and the air flow at the fan drops. This reduces the duct velocities as well and may cause problems.

5 - once you have the total air flow you can talk to your Baghouse Vendor about the rest. The key is the air-to-cloth ratio, or keeping the velocity low through the cloth. It could vary between 65m/hr/m2 to 180:1. If this is too high you will have problems with blinding up the bags, drastically reduced bag life, and reduced air flow. There are a number of variables to discuss - such as type of cloth, fire rating, surface finish and so on.

It took me several years to learn all that - and with the help of professional Dust Engineers. So keep it simple for a start - it will save a lot of money for your Company. ■

For a Design Engineer in a Cement Division you may be asking the wrong questions, so I hesitate to give you answers.

I have just read the proceedings from a 2-day Seminar on Dust & Fume Control and I don't find any rules of thumb there. The hardest problem in dust control is to accurately determine the amount of air needed in any specific application. Once that is established the rest is easy.

So to take a blind guess and give some rules of thumb would not help anyone.

Talk to a couple of dust control Vendors, such as DCE. If you need more specific answers, or an independent check hire a Dust Control Engineer.

This business is a trap for young players. It can cost your firm a lot of money if you commit spending to a few rules of thumb. ■

Dear Partha,

The air requirement of a dedusting system for cement depends on the application.

Do you really want to dedust a location or do you just want to maintain a slight under pressure to prevent air born dust outside that location.

Depending on the dust load, the minimum air volume, pipe diameter, filter area and pressure drop of the fan is chosen or calculated.

This is a pneumatic conveying calculation.

If installation leakages are determining the air volume , that air volume is then the basis for the definitive design.

The intake of the dedusting should consist of a hood, where the air velocity is starting at approx. 0.8 m/sec (only pick up the dust) increasing to the duct velocity of approx. 10 m/sec (CEMENT)

Multiple intake points require extensive pressure drop calculations, where pipe diameters and pipe lengths determine the division of air through the respective parallel and combined lines.

False air inlets (controllable) can help or can be used to regulate afterwards.

Filter area (cement) is chosen as 2 times the required air extraction.

The fan capacity is chosen as 2 times the filter area.

The pressure drop over the filter at required air extraction volume is estimated at 300 mmWC

Quite a complicated puzzle.

success. ■

If you don't know how to do this, get someone to do it for you. It is very easy to get it wrong if you don't have experience.

Show your problem to three bag filter manufacturers and ask for quotes which include the design of the duct system and guarantees of performance.

Michael Reid. ■

Partha,

You are a trainee engineer. If you want to learn I would recommend the following:

1 - At University all your assignments are packaged, relevant data attached and the answer calculable. Real engineering is not like that.

2 - As engineers we are often asked to make decisions without having all the facts - a calculated guess if you like.

3 - It is recommended that you read some basic texts on the subject

--- Industrial Ventilation - a manual of recommended practice - American Conference of Governmental Industrial Hygienists.

--- Dust Control Handbook - Vinit Mody & Raj Jakhete - Pollution Technology Review No 161.

4 - You don't live in a vacuum. At the Cement Division there are many full-scale examples of successful, and unsuccessful, dust control components. Study their performance on site, talk to the Operators, get out the drawings - you can learn a lot this way.

5 - Look at the size of the exhaust duct, the details of the hood, the open air faces, and the side gaps. Estimate the area and compare with the 0.8 m/s rule of thumb. This is learning in the real world.

6 - Don't be afraid to talk to the Vendors even if you don't have a contract on the table. They know that down the tract you are a potential customer. ■

When all else fails - read the previous Threads.

https://forum.bulk-online.com/showth...?threadid=6402

Plenty of formulas, calculations, and thick with rules of thumb for cement dust. ■

Dear Dear isbalanli,

You are correct, I mistook the number of bags for the filter area.

It is best to ask this question to the baghouse manufacturer and the dust collection system designer.

Probably:

-53000 m3/hr is the filter fan volume at no pressure drop

-25000 m3/hr at the designed operating filter pressure drop.

According to the rule of thumb, the allowable air volume would be:

Bag load * Area = 0.5 m/min * 529 * 60 = 15870 m3/hr

Obviously, the bag house designer calculates a filter load of 25000/60/529 = 0.788 m/min.

The resulting filter pressure drop is related to the dust load and the rate of contamination.

Have a nice day ■

Begin studying Industrial Ventilation book, them you can understand dust collecting and later you can study bag filter design. ■

Over recent years, many enterprises have paid special attention to the reduction of environmental load on the environment. Pollution of the environment with various solid substances causing habitat degradation and affecting human health is one of the most acute problems facing Russia today. For this reason, requirements for dust concentrations at the outlet of dust and gas collecting systems become more stringent.

Electrostatic precipitators and bag filters are the most common type of dust and gas collecting equipment employed by Russian enterprises.

However, in some cases, it is impractical from an economic standpoint to replace electrostatic precipitators with similar electrostatic cleaning devices especially when it comes to complete replacement of worn-out equipment or new construction. One of the most economically viable trends in the design and manufacture of dust and gas collecting equipment is a significant increase in the use of bag filters. Bag filter characteristics are very close to those of electrostatic precipitators. However, bag filters surpass ESP in terms of residual dust content.

Bag filters are used more often due to the fact that new filtering materials with high thermal and chemical resistance appear in the market. .

The use of pleated filtration materials increases filtering area several-fold, while overall dimensions remain unchanged. As a result, they involve the lowest possible RUB/ filtration area square meter of ratio. This all makes it possible for our customers to save significantly on retrofitting costs and new projects.

Strommashina Samara plant manufactures and supplies jet-pulse and reverse air filters of different sizes and different efficiency. Residual dust concentration at the outlet will not exceed 10mg/cubic meter. Thus, compliance with applicable emission limit values is achieved.

Please click on the following link for more details about our dust and gas collecting equipment ■

Dear Friends,

You may like to refer to my article "DESIGN GUIDE FOR DUST COLLECTORS" published by Chemical Engineering magazine as as a mean "feature" article. This is a complete design guide covering all aspects of dust collector design, specifications, and selection. Let me know if you would like to get a copy.

Regards,

Amrit Agarwal

Pneumatic Conveying Consulting

Email: polypcc@aol.com ■