Friday, October 20, 2017

Water Decontamination in Ammonia Refrigeration SystemPrint


To encourage “Energy Conservation & Environment Protection” in the industrial sector PCRA has been continuously upgrading the energy conservation knowledge through energy audits and sharing the experience of energy efficiency improvement and achievement of industries. Based on these information developing case studies for dissemination of information to various industrial groups and organizations. The case study detailed below is one of the modification carried out by Mother Dairy Delhi which is being reproduced for the benefit of dairy sector & industries having ammonia refrigeration system in process for any purpose.

 

Introduction

Mother Dairy is the single largest brand of milk in Delhi, India as well as in Asia, marketing about 1.9 milllion liters of milk perday. Mother dairy commands 40% market share in the organized sector in and around Delhi.

There has been steady decrease in Electrical & Thermal consumption per equivalent lakh liters of milk due to implementation of various energy conservation improvement.

The dairy has also reduced total effluent generation by 24% and water consumption by 29%

 

Background

Mother dairy has 4 nos. of Ammonia Screw Compressors with a total capacity of 1400 TR.

Contamination of ammonia in a refrigeration system with water changes the thermodynamic and physical properties of the ammonia-water solution so that a lower pressure in the evaporator has to be maintained to get the same temperature. Thus the capacity of the system is reduced as well as there is higher power consumption by the compressors. Moreover, the chemical properties of aqueous ammonia solution degrades the oil forming sludges and causes corrosion in all metallic parts and components.

Internationally attempts have been made to first detect and test the water content actually found in the system and measure the impact of such contamination on the system capacity and power consumption. Such studies have revealed that apart from power consumption, there are many other problems associated with water contamination.

 

Study Conducted

In the absence of adequate information and the devices to check water content in Ammonia System, Mother Dairy searched such kind of technical information available outside India. There are established guidelines for water contamination in Ammonia Refrigeration document published by International Institute of Ammonia Refrigeration, which helped Mother Dairy a lot in understanding the ill effects of water in Ammonia System on energy consumption and detection of water contamination in the system through an Internationally established test procedure.

There are no ready made water testing kits available for detection of water in ammonia system, though testing methodology and details of the equipment are provided in international guidelines. Engineers of Mother Dairy struggled and after a series of developmental attempts developed a suitable kit with indigenous components which can determine water in ammonia accurately to a fair degree of reproducibility.

 

Observations

The indigenously developed kit was used by using the test methodology used and accepted all over the world. The results are reproduced hereunder:

Sample taken from Time taken in evaporation (minutes) Volume of sample (ml) Volume of residual left (ml) Operating pressure (psig) Evaporation factor (EF) %age of water
Pump Seprator – (-) 10 Deg.C 40 100 5 28.5 .92 4.5

 

Corrective Measures Taken

The water content in Ammonia was found to be 4.5% which is high and found to be negatively impacting the energy consumption. To resolve this problem to a reasonable level, Mother Dairy Engineers indigenously developed Ammonia Regenerator which is basically a Pressure Vessel in which the liquid ammonia is taken. This facilitates the vaporization of Ammonia which is taken to compressor and the residual water being heavy settles at the bottom and is drained manually. To remove water from the Ammonia to a reasonable level, this process is repeatedly done so as to bring down the water level to a limit which does not impact the energy consumption. Diagram of ammonia regenerator is at Annexure – I

 

Benefits

After running this system of Ammonia Refrigeration the water in Ammonia System was again tested and was found to be around and at times below 1%. As a result, the water in Ammonia System has been successfully reduced by 80%. The favourable implications of this are :

a) A saving of Rs.6.94 lac per year against one time capital investment of Rs.65,000/-. This is because of power consumption reduced from 5514388 Kwh to 5360139 Kwh.

b) Operation has now become much more smoother and less maintenance prone because of significant reduction in rust, sludge, corrosion in the system which primarily happens due to water and thus require periodic and at times unscheduled maintenance.

 

Conclusions

  • Ammonia system very often contain much more water than recommended.
  • The relations between water contamination and problems seen on systems are normally not very well known among service and maintenance staff.
  • System design plays an important role in which water related problems will have an effect on a system.
  • Improper procedures during service and maintenance work are an important source for water contamination.
  • Water contamination detection should be carried out as a part of normal service and maintenance, taking the actual system design and running condition into consideration.
  • Installation of water rectifiers or other methods of water draining from a contaminated system can prove to be a very attractive investment.

Replication and Propagation of this type of innovation in other industrial units will have a significant saving and conservation of energy.

AMMONIA REGENERATOR