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Type and Size of Air Compressor Required
I have to decide between a blower/fan/compressor for providing small pressure at a high flow rate to prevent getting my flame monitor dirty. It's a complex problem.

I am investigating what would be the most appropriate compressed air source (fan/blower/compressor) for designing a separate air compressor system.

The information is as follows:

The compressed air would be supplied to the lens of an industrial sensing instrument, which is mounted onto a pipe leading into a boiler's furnace.

There are 12 instruments on each row and there are four rows in total (first row starts at 20m and there is an increase of 5m per row).

Purpose:

To provide sufficient pressure in order to prevent accumulation of dust on an instrumentation's lens.

To provide sufficient flow to keep the entire pipe free of contaminants in the first place.

Demand requirements:

flow (800 m3/hour) for all 84 instruments (100 m3/hour for one row of instruments) (8.6 m3/hour for one instrument).

pressure (40 mbar)

I know that the pressure demand is very little. It simply needs to be slightly above the furnace pressure. However, my concern is that the fans we have been using have not been able to provide sufficient pressure. Meanwhile, the flow is quite large.

Therefore, I am contemplating between a blower (more powerful fan) or a compressor (not sure if an air receiver would be necessary).

Which one would be more suitable (for both 100 m3 per hour and 800 m3/hour)?

What are the pros and cons of either (in terms of cost and space required and efficiency)?

If a compressor, which type of compressor (positive displacement, rotary, reciprocating) would be suggested?

Also, the duty cycle is 100% (all the tube needs to be cleaned at all times). If a compressor is used, is a receiver necessary?

How many instruments could be fed with one compressor?

A low flow at a pressure just higher than the pressure at the end of the site pipe (presumably the combustion chamber) should keep the optics clean.

I would take a different approach to your high volume flow rate and use a constant flow regulator to stream a relatively low flow against whatever pressure the combustion chamber is at. That's what a commercial constant flow regulator, also known as a differential relay does.

First, get some idea of that the static pressure is in the combustion chamber, so that you know what pressure you need to create a flow through the site pipe (is that your 40mBar value?)

Then look for an 'Instrument Air' generator/compressor that produces super clean, oil-free and low dew-point air at some slightly higher pressure. It can have a storage tank for 100 psi or whatever, because a constant flow regulator will regulate (down) its inlet pressure to get a constant flow output.

Then pipe the instrument air supply through a constant flow differential relay regulator, like a Siemens 62VA. The 62VA has an integral rotameter (floating ball) flow meter. The center of the rotameter's scale is 1 SCFH (0.03 m3/h), which is a relatively low flow rate compared to your suggested 100m3/hr (~3500 CFH). Compressed air is expensive. Keep your operating costs low and use regulators to minimize your air consumption.

Do it on one and convince yourself that it works, and then add the other points.

>How many instruments could be fed with one compressor?

At the 0.03m3/h flow rate, almost any compressor will supply all your points. But it's got to be clean air, "instrument air" quality. Cheat on the cleanliness quality and you cheat on your results.