Briefing of process technology

This device adopts the molecular sieve adsorb purification, expander refrigeration, single-stage rectification, waste gas reflux expansion to produce nitrogen. On the premise of stable operation, high efficiency and energy saving design patterns.

The nitrogen plant including：air compression system、air pre-cooling system、molecular sieve purify system、fractionation system、expander unit、instrument control system and electronic control system.

Process description

Firstly raw air got into air compressor, be compressed to required pressure, came into cooling unit to be cooled, and then enter into molecular sieve adsorber to get rid of water、CO₂、C₂H₂ and other impurity.

The purified air got into rectification column, through main heat exchanger to exchange heat with reflux waste gas and product nitrogen, be cooled and then came into bottom of rectifying column, be rectified to the product nitrogen and oxygen-enriched liquid air. The liquid air in column bottom be sub-cooled and throttled, then got into condensing evaporator to exchange heat with nitrogen, the nitrogen be liquefied and to be as the reflux liquid of rectification column.  

Product nitrogen be lead from the top of rectification column, through main heat exchanger to be reheated and then get out of cold box. Then the product nitrogen came into nitrogen compressor, be compressed to 30~50 bar and got into electrical heater, be heated to user required temperature and then be sent out of battery limited to user.

The waste gas be lead from the top of condensing evaporator, through main heat exchanger for reheating, and adiabatic expansion in turbine expander to compensate cooling capacity of the plant. The waste gas from expander through sub-cooler and main heat exchanger to be reheated, and then got out of cold box to be as the regeneration air of purification system.

The liquid nitrogen product be suction from condensing evaporator to liquid nitrogen storage tank, the liquid nitrogen be vaporized in vaporizer and then got into nitrogen pipeline to sent to user. 

Air compressor unit 1 set

Technical data：

·model    oil-free screw

·inlet pressure                     98 KPa

·inlet temperature                   30℃

·outlet temperature                   ≤40℃

·discharge pressure                    0.73 MPaA

·discharge capacity                    1800 Nm³/h

Main scope of supply

·compressor and accessory             

·main motor                         

·gas pipeline and accessory　          　      

·water pipeline and accessory　          　      

·lubrication oil pipeline and accessory　          　   

·special tools                         

Cooling unit 1set

·model screw machine

·handle gas capacity 1800 Nm³/h

·working pressure 0.73 MPa

·refrigerating capacity                 37 KW

Purification system

·handle gas capacity                   1800Nm³/h

·regeneration gas capacity 360Nm³/h

·regeneration gas   waste nitrogen

·adsorption period                8 hours

(16 hours switchover)

·type                       skid-mounted package

Molecular sieve                   2 units

    Technical data

·model Vertical single bed

·overall size                        φ800×3300

·weight                         850kg

·design pressure   1.0 MPa

·shell material   Q345R

·inner parts material   stainless steel

Electrical heater                    2 units

Design data

·fluid：      waste nitrogen

·flow rate：      360Nm³/h

·inlet pressure ：      0.015MPaG

·inlet temperature：      15℃

·outlet temperature：      175℃

·overall size                         φ400×3400 

·weight                         500kg

Silencer                                  1 unit

·overall size                        φ500×4000

·weight                         550kg

·shell material      carbon steel

Adsorbent

Filling capacity：      about 2×0.8t

 Automatic switchover valve      1set

 Other valve, pipeline and accessory in system     1set

rectification column system      1set

Cold box filled compressed waste nitrogen to avoid moist air enter into cold box.

Most of connecting in cold box adopt welding structure.

Support and structural parts in cold box adopt resist low temperature material.

This plant has 2 expanders to supply needed cooling capacity.

 Main heat exchanger 1 group

·type                      Vacuum brazing aluminum plate-fin

·design temperature                    -196℃

·design pressure                      1.0MPa

·material aluminum alloy

Sub-cooler 1group

·type                      Vacuum brazing aluminum plate-fin

·design temperature                    -196℃

·design pressure                      1.0MPa

·material aluminum alloy

Rectification column (including vaporizing condenser) 1unit

·type                      Vacuum brazing aluminum plate-fin

·design temperature                   -196℃

·design pressure                     1.0MPa

·material   aluminum alloy

Liquid measurement tank              1 unit

    ·material：                       5052-0

    ·size：                      φ400×3460mm

    ·weight：                      100Kg

Drainage tank 1unit

·type Vertical

·overall size                      ~φ800×2500

·weight                        ~120kg

·material aluminum alloy

Nitrogen vent silencer 1unit

·overall size                        φ500×4000

·weight                         550kg

·main material                        carbon steel

Pipeline and accessory in cold box 1set

·main material aluminum alloy

Valve/pipe/equipment support in cold box 1set

·main material  stainless steel

Ladder、platform and railing 1set

·main material carbon steel

Cold box（skid-mounted package） 1set

·overall size                      ~2500×3000×16000

·main material carbon steel

Valve in cold box   1set

·cryogenic regulating valve：  KOSO

Perlite sufficiency

Gas bearing expander 2 units(1 use 1 standby)

Technical data

design data of expander:

·medium　 dry air

·flow rate ~1000±15%Nm³/h

·inlet pressure                        0.32 MPaA

·outlet pressure                     0.126 MPaA

Scope of supply                

·expander                         2 units

·system valve and accessory             2 sets

·drive fan suction type filter             2 units

·drive fan type silencer                 2 units

·special tools                       2sets

·complete sealing system               2sets

·commissioning spare parts              1set

Nitrogen compressor                    2 units (1 use 1 standby)

medium：                nitrogen   

flow rate：         600 Nm³/h
inlet temperature：    12 ℃
inlet pressure ：       0.66MPa(G)
outlet temperature： 160℃
outlet pressure ：      5.0 MPa
water consumption：    6 t/h
compressor motor power：    75KW

Nitrogen heater                       1unit

Design data

·fluid：     nitrogen

·flow rate：     600Nm³/h

·inlet pressure ：     5.0MPaG

·inlet temperature：     160℃

·outlet temperature：     400℃

 Liquid storage and vaporization system 1set

Cryogenic liquid nitrogen storage tank 1unit

·type                   vacuum powder insulation storage tank

·volume 50 m³

·working pressure                     0.8MPa

Liquid nitrogen vaporizer 1unit

·type air warming type

·vaporizing capacity 600 Nm³/h

·working pressure                     0.8Mpa