chapter - 1 introduction - Meghalaya State Pollution Control Board

Hills Cement Co. Limited.
6. Compressor Controls
Start/stop, load/unload, throttling, multi-step, variable speed and
network controls are options for compressor controls and described
below:
• Start/stop (on/off) is the simplest control available and can be applied to
reciprocating or rotary screw compressors. They are used for applications
with very low duty cycles. Applications with frequent cycling will cause the
motor to overheat.
• Load/unload control, or constant speed control, allows the motor to
run continuously but unloads the compressor when the discharge
pressure is adequate. In most cases, unloaded rotary screw compressors
still consume 15 to 35% of full-load power while delivering no useful work.
Hence, load/unload controls can be inefficient.
• Modulating or throttling controls allow the output of a compressor to be
varied to meet flow requirements by closing down the inlet valve and
restricting inlet air to the compressor. Throttling controls are applied to
centrifugal and rotary screw compressors. Changing the compressor
control from on/zero/off to a variable speed control can save up to 8% per
year.
Heat Recovery for Water Preheating
As much as 80 to 93% of the electrical energy used by an Industrial air
compressor is converted into heat. In many cases, a heat recovery unit
can recover 50 to 90% of this available thermal energy for space heating,
industrial process heating, water heating, makeup air heating, boiler
makeup water preheating, industrial drying, industrial cleaning processes,
heat pumps, laundries or preheating aspirated air for oil burners.
7. Lighting
• Lighting Controls (manual and automatic controls)
• Replace T-12 Tubes by T-8 Tubes
• Replace Mercury Lights by Metal Halide or High Pressure Sodium Lights
• Replace Metal Halide HID with High-Intensity Fluorescent Lights
• Replace Magnetic Ballasts with Electronic Ballasts
Pollution Control Consultants (India) Pvt. Ltd. 127