Energy Audit in Industries

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Solvent Extraction Plants

Rising material and utility costs coupled with increased global competition is forcing the solvent industry to trim its cost of manufacture. Steam, i.e. Boiler fuel, accounts for 20 30% of the total processing cost of this industry. Steam is mainly used in equipments like DT (Desolventising Toaster), Cooker, Radiator coils, Distillation Column heaters, Preparatory section and Ejectors.

Forbes Marshall- CII joint studies reveal differences in fuel consumption pre ton of seed crushed within the industry, i.e. Specific Fuel consumption (SPFC).

               


Our energy services focused on minimizing the above gaps and with the result we have been able to reduce the SPFC for the best plant almost by 50%. What we have also been able to achieve, and is increasingly difficult, is that we have lowered the overall average SPFC of the Rice bran plants. Lowering the average requires partnering several SEP plants to better their SPFC.
 
Our experience spans a wide spectrum of Solvent Extraction Plants, from Soy, Rice Bran, Sunflower, Castor oil, Palm oil, Vanaspathi plants, Refinery, etc.

                     

Case Study 1: (Rice Bran)

A refinery unit in Punjab processes rice bran, soya & palm and has an installed capacity of 100 TPD with an annual fuel bill of Rs.1.72 crs/yr.

Boiler House:
The boiler was operating at a low efficiency primarily due to lack of monitoring. Implementation of a monitoring system has saved Rs.15.3L/yr.

Distribution:
Steam ejectors were consuming excess steam of 458 kg/hr due to high pressure steam. By providing the desired pressure through a PRS, a saving of Rs.13.5 lakhs/Annum was achieved.

Trapping:
Rectification of steam traps led to saving a total loss of 57.9kg/hr of steam.

Condensate Recovery:
Additional condensate and complete flash recovery from plant and auto claves led to savings of Rs.7.07Lacs/yr.

Partial implementation itself by the plant has improved the feedwater temperature from 65 to 95 0C and reduced fuel annual consumption by 12% resulting in 1.5MT reduction in daily fuel consumption.

 
Case Study 2 (Soya)

 
We audited a 300TPD solvent extraction plant. Partial implementation of our of our recommendations itself improved the SPFC from 76kg coal/ton of seed crushed to 60 kg coal/ton of seed crushed!


The plant implemented the following recommendations:

  1. Rectifying trap selection on process equipment
  2. Arresting areas of steam loss in plant
  3. Improving condensate recovery factor

Full implementation would further bring down SFC to 55 kg coal per ton of seed crushed.


 

The prime reasons for difference in SFC across plants were:

1. Efficiency of steam generation
 

                


2. Optimized steam distribution and utilization


1. Manual operation of the steam valve to control process temperature leads to 3%-4% excess steam consumption.
2. Proper pressure temperature and dryness fraction of steam ensure lower SFC.
3. The method of achieving the temperature profile in the desolventising toaster also impacts the steam consumption.
4. Wrong trap selection and group trapping increase the batch timings leading to excess steam consumption.54% of the traps are wrongly selected and 18% of the traps installed on processes are found to be leaking

3. Recovering condensate and flash steam


                 

Reason for gap

  1. In most plants flash steam is not recovered. Recover, if any, is only from the desolventising toaster.
  2. 46% of the solvent plants recover condensate using electrical pump leading to loss of useful heat as electrical pumps cannot pump condensate at high temperatures.
  3. 27% plants recover condensate by trap pressure leading to back pressure on equipments and thus trap malfunctioning. This causes problems in achieving temperature in the equipment and thus by-passes are kept open, leading to loss of steam. 


4. Higher capacity utilization


The SFC deteriorates drastically when the plant is operating below 60% of installed capacity.