Gujarat Narmada Valley Fertilizers Company Limited.

This paper aims at sharing experience gained from Energy Conservation efforts at GNFC. The paper is divided into mainly following topics.

1.Introduction

1. Understanding the Energy Conservation
2. GNFC’S Efforts for Energy Conservation.
3. Continuing Quest for Reducing Energy Consumption at GNFC.
4. Steam Trap Management

4. Road Map for Energy Conservation.

5.Conclusion

Submitted to :-Bureau of Energy Efficiency
Ministry of Power, Government of India

By :

M.N.Tekchandani-Sr. Mgr(Energy Cell), D.D.Patel-Sr. Mgr (Tech.Services), N.P.Karvekar-Sr. Mgr(Tech.Services),

D.D.Vaishanav-Manager(Energy Cell),

Gujarat Narmada Velley Fertilizers Company limited, Naramadanagar, Bharuch ( Gujarat) - 392015

Energy Management and Conservation at GNFC

M.N.Tekchandani-Sr. Mgr(Energy Cell), D.D.Patel-Sr.Mgr (Tech.Services), N.P.Karvekar-Sr. Mgr(Tech.Services), D.D.Vaishanav-Manager(EnergyCell),

Gujarat Narmada Velley Fertilizers Company limited,
Naramadanagar, Bharuch ( Gujarat) - 392015

Preamble :

Today we realize that our Industry is passing through a very turbulent phase, where “ Survival ” has become the watchword. This is so mainly because of

? Removal of Subsidies and Protections

? Globalization, Liberalization and opening up of Industrial sector to International Competitiveness. Indian Industry finds itself exposed to external pressures in form of Price, Quality, Environment, Customer Orientation, Requirement of Services and therefore is busy in making introspection of its operations, costing, competitiveness and consequent consolidation. Energy being chief contributor to these factors, the pressure on reducing and rationalizing energy consumption can well be understood. In the foregoing paragraphs attempt is made to look at various aspects involved in handling Energy in Industrial operations.

Roots of Energy Conservation Conservation: -

The fact remains that Movement of Energy conservation in Industry is quite old with its visible roots lying in the Oil Crisis of 1973. Developed Nations took immediate steps to neutralize sudden jump in oil prices. They pulled themselves out of the storm by institutionalizing the Energy Management structure, Energy Audits, Practices of Energy Conservation in a very systematic way and brought all these in to focus of top management. The drive was already there in form of rising input costs. These practices resulted in to saving of millions of oil equivalent in case of number of Industries like Union Carbide USA, Dupont USA ,Courtaulds UK.

[A]UNDERSTANDING ENERGY CONSERVATION:

“We cannot Manage What we do not understand ” goes saying from an expert. It assumes specific significance here when we address the issue of Energy Management. Therefore it will be worthwhile to first understand as to what is Energy Conservation and when we address this, we realize that Energy Conservation (En Con) is the subject of Contemplating, Soul Searching and Self Questioning on

? What is the Energy Consumption of My Unit?? How and where Energy is used?? How much is really required?? What can be done to reduce energy consumption

ENERGY CONSERVATION AND THERMODYNAMICS:-

The second law of Thermodynamics determines that Quantity of Useful Work we obtain is

smaller than the potential of original Energy form. Therefore Ideally Energy Conservation

means reducing the proportations actually wasted to lowest possible level.

B]GNFC’S MARCH TOWARDS ENERGY CONSERVATION:

In the foregoing paragraphs attempt is made to give an account of strides taken by us for Energy Saving. Following picture gives an idea of methodology employed.

In foregoing paragraphs, few examples of above measures are discussed.

1). Operational changes: At GNFC , we follow the LOOK, LISTEN and FEEL concept to improve / overcome problems and for maintaining uninterrupted operations . Developing Understanding of the process by simply monitoring operations, we can save energy . Some of the examples are as given below :-Examples:¾ Separation of plant air header (80KW): We modified the system so that plant air compressor (Pres. 4.0 barg) system is separated from instrument air compressor (7.0 barg) which lead to the power saving of 80 KW.

¾ Elimination of 2^nd stage of fluidized bed cooler (FBC) in ANP plant (55KW)

From the operating experience it was observed that most of the cooling phenomenon was getting completed in 1st compartment of fludized bed cooler making 2nd compartment redundant. Therefore with the help of ducting modification , 2nd chamber was by passed. This led to stoppage of blower supplying cooling air to 2nd stage and resulted into power saving of 50KW.

¾ Cooling Water recovery in Ammonia Plant:

Earlier our cycle of concentration (COC) remained around 3. Practically blow down from sump basin was almost nil and major blow down was done locally in the plant. To increase the COC, local draining of cooling water from number of users in section 200/300 of Ammonia Plant was arrested by conducting a survey and diverting this open drains back to basin through specially laid piping. This has helped to increase COC more than 5 and accordingly cooling water treatment is modified to take care of fouling in the exchanger.

¾ Flow orifice checking for higher-pressure drop.

Originally we had only Ammonia & Urea complex. Subsequently we have added Nitro complex, Methanol –I & II, Acetic Acid, Captive power plants. Due to this our utility consumption has increased. This has led to increased pressure drop across orifice for Inst air , DM water and other utilities piping. We have replaced orifices which were offering high-pressure drop.

¾Identification of Additional pressure drops in the system.

We have removed check valve and unwanted flow measurement system offering higher-pressure drop installed in raw water supply pipe at Utilities Plant

2). Reliability building :

9 Identify equipment / system limitation for uninterrupted operation.
9 Sustained operation reduces start-up, shutdown losses.
9 Sustained operation increases production, which reduces energy consumption

¾CO shift section revamp in Ammonia plant (making shift reactors parallel) : Due to changes in feed oil quality, increased soot and nickel on catalyst bed of CO shift reactor was leading to Ammonia Plant stoppage once in 4 months. After working of suitable action plan, two of the three shift reactors were made parallel through piping modification. this has prolonged our continuos operation span to nearly one year.

¾Quench ring modification : Frequent quench ring failures were resulting into gasifier shut down in Ammonia Plant. With operating experience and nos. of trials we could successfully modify the design of quench ring. Consequently we are able to operate the gasifiers much longer.

¾Additional feed oil pump in Ammonia plant : Due to the requirement of frequent maintenance of feed oil pumps for gasifiers in Ammonia Plant, additional pump has been installed and we are achieving higher on stream days now.

¾Refrigeration compressor modification to reduce speed below MCS : From the operating experience it was observed that for refrigeration compressor of Ammonia plant, max. load was on HP Barrel. In view of this HP barrel revamp was carried out in April 2000 with higher improved internals. With this change, operating speed has come down on one hand where as chiller pressure and synthesis loop pressures also remain lower.

3).Recycle & integration of operations :

The streams which were sent for processing in original design, were analyzed and reviewed. With operating experience , it was realized that some of the streams did not require processing , so they were recycled directly. Some examples are as below :

¾Turbine condensate recycle to deaerator : The huge quantity of condensate which was design to be processed in DM plant was recycled to the deaerator in Ammonia plant. This saved on processing & pumping cost.

¾DM water re-circulation during gasifier start-up & cooling down : The DM water which was used for startup & cooling down after shut down in gasifier was recirculated by installing the required system minimizing on DM water consumption.

¾Condensate recovery in Thermax Boiler. In our boiler SCAPH outlet heating coil condensate from steam traps was discharged in open channel. It has been diverted to deaerator by replacement of trap with suitable orifice. The recovery of condensate is made along with its heating value.

¾Waste water of Urea plant in Ammonia plant as make up. Wastewater containing about 50~100 PPM urea and 50 PPM Ammonia, was earlier discharged to ETP for treatment. On other end in our Ammonia plant we needed DM / steam condensate for reaction in CO shift section. This make up of water is carried out in carbon extraction section. We are using urea plant wastewater for this make up purpose. In Gasifier at higher pressure and temperature Urea decomposition takes place. We are also using same wastewater as seal flushing water.

4). Use of latest technology :

The technological advancement is a continuous process through operating experience and new research. We monitor such developments and adopt them whenever and wherever feasible. Some examples are as below :

?S-200 basket for synthesis reactor by M/S Topsoe (Saving of 1580 kwH power) : By going in for Energy efficient reactor basket design of S-200 configuration from M/S Haldor Topsoe . We could reduce the synthesis loop pressure as well as circulation rate and resulted into energy saving of 1580 KW.

?Installation of vertical decanter : We are facing problem with horizontal decanter in soot recovery section in Ammonia plant. Same was replaced with better performing newly developed vertical decanter which gives superior soot separation.

?Conversion of control system from pneumatic to DCS system :The Ammonia plant Instrumentation and control system was converted from pneumatic to DCS system / PLC control system. This has resulted into smooth operation as well as helps us in quick diagnosis of a plant problem. This conversion was carried out without any special shut down for the same, most of it being done on line.

?Installation of Ammonia Absorption type refrigeration. : Conventional Air conditioner unit is consuming more electrical energy. After more than 20 years of operation they were more prone to maintenance and refrigeration media used was Freon gas, which is harmful to atmosphere. We have replaced it with Ammonia absorption type refrigeration system in our Ammonia plant. The refrigeration load is 110 TR. This is based on steam and consumes less energy

?Retrofitting tower : Tray modification in distillation towers of Methanol –I/II plants have resulted in to reduction in the steam consumption.

?Replacement of MeOH- I Plant synthesis reactor with latest energy efficient iso thermal Reactor has resulted into saving of steam to the tune of 150 T/day. Similar replacement with iso thermal reactor is being planed for the MeOH-II plant.

Page 6 of 18 ?Replacement of MeOH-I plant distillation column tray with high efficiency trays has reduced the energy consumption significantly as well as resulted into capacity enhancement.

?Replacement of column packing with latest development packings in Formic Acid plant . We replaced the standard RAUL ring packing with latest design SLVK packing which has better HETP for almost same packing factor. This reduce the steam energy required per MT of Formic acid processed in the column.

5). In house innovations & debottleneck :

For debottlenecking of single equipment/ part system, external consultant becomes very costly. After 20 years of operational experience and operating data , gradually we have developed better understanding of process. We can carry out in house process engg to debottleneck equipment/system. For physical property prediction at different operating conditions , process simulation / design softwares can be used . This becomes clear from our following schemes.

? Stripping of H2S and recovery of Ammonia from process condensate generated in CO shift section of Ammonia plant:

This innovative process was used for stripping of H2S and recovery of Ammonia from process condensate. The waste tail gas stream from rectisol wash unit of Ammonia plant contains about 80% CO2 and 20% vol N2, is used for stripping H2S from 150 PPM to less than 0.5 PPM in condensate stream of 6 m3/hr retaining Ammonia in process condensate. The condensate containing 1% by wt. Ammonia is processed in wastewater section of urea plant and thereby reducing treatment cost and pollution in atmosphere.

?Debttlenecking of Ammonia absorber tower in urea plant. After detail study and with the help of computer process software, the tower is debottolnecked from tray tower to packed tower. Consequently Ammonia venting to atmosphere is arrested resulting in to saving in Ammonia.

?Methanol water distillation column revamp which included rerouting of reflux steam and shifting of critical tray location for temp. Control. Consequently Tower performance has improved significantly and Methanol slippage has reduced by 40 MT/year This was arrived at by rigorous analysis and process simulation.

Capabilities built up at GNFC:

In order to support innovations & debottlenecking, we have developed in house process engg capabilities as per following.

6). Optimization and rationalization:

During design stage , design is carried out with certain assumptions. In actual operation , based on actual data there is always scope for optimization . The examples are as under : a).Pumps

Pump Impeller trimming:

Normally system designer keeps margin for smooth operation of pump. We could identify pumps, which were operated with discharge valve throttled due to developing of higher head than required. We collected operating flow versus. head data and compared it with performance curve given by supplier. Based on head requirement we decided to trim the impeller and saving has been achieved in electrical power. The table highlights some examples and benefit gained.

Replacement of pump with lower head In case of following pumps, head requirement was found to be less than specified , which could not be met by impeller trimming. In such cases new lower head pumps have been installed.

Separate pump with lower head

In Ammonia plant cooling water pumping system was designed for 50 meters. head. However our close review revealed that there was only one heat exchanger which necessitated such higher head. Therefore segregation of the same by installation of a small capacity booster pump, we could reduce significant power consumption for main cooling water pumps.

b).Study of FD fans for Boilers and replacement with suitable size

Originally FD fans were designed to meet higher head requirement of furnace draft and Steam Coil Air Preheater (SCAPH) . Subsequently we had a problem of SCAPH choking due to coal ash. Hence it was removed. This resulted into lower system resistance and FD fans suction guide vane remained in throttled condition. After making assessment of system requirements, three new FD fans having lower head have been already installed and remaining three are to be installed in April’04 shut down. The power saving realized is 55 KW per fan and total power saving is likely to be about 330 KW.

C). Identification of new low capacity Combustion air blower C-1301 for Steam super heater in Ammonia plant.

Based on our operating experience, the blower was found to be too much over sized in the present operating requirements, as the load on super heater has also reduced over a period on account of diverting tail gas for other productive uses. Field performance testing was carried out and system curve got established. New specification has been prepared for a new smaller size blower. This has a potential of saving upto 40 KW.

d). Reduction of boiler blow down

Passing of blow down valves was resulting into silica level of 0.1 ppm against normal value of 1 and max. allowable 1.8 PPM. This was resulting in to high-pressure energy let down to lower level and some steam venting at atmosphere steam level. We have replaced blow down valve to arrest passing of valve and pH is maintained. Silica levels brought back to around 0.8 to 1 ppm i.e. near to normal value. This has reduced venting of 3 to 4 MT atmospheric steam.

e). Installation of additional low head condenser transfer pump in Urea.

Originally high head pump was installed to cater demand of process flushing in urea plant and the balance( about 75% ) quantity is being transferred to Utility plant for polishing which actually needed lower head. We have developed a scheme to segregate lower and higher head requirements and separate pumps are envisaged as per head requirement for process flushing and remaining to be sent to utility plant. New low head pump specification with control logic is prepared. Pump is being procured.

7). Keeping a close watch on key equipments:

z Monitoring of Compressors

Every month we are collecting operating data of compressors/ Turbines. Stage wise efficiency and turbine efficiency is calculated by using process simulation software ASPEN. This helps in keeping a check on performance and preventive maintenance of compressor.

z Monitoring of Exchangers

Every month we are collecting operating data of Exchangers and use of process simulation software is carried out for performance checking of exchangers. This helps in monitoring of performance and planning for cleaning during shut down.

zMonitoring of CT tower and performance evaluation. Regularly we are collecting operating parameters of all plant cooling towers and compare the CT approach temperature with design by using performance evaluation chart.

zInstrument Air consumption shooting up at times: Site survey conducted to reduce consumption. Installation of flow devices at various locations have been envisaged after detailed network study to carry out balance and monitoring.

zVacuum hold up test for identification of leakages in condenser and improve vacuum. During shut down, vacuum hold up test is carried out to know leakages in vacuum system. The allowable vacuum drop rate is 3 MM Hg. If it is higher then the leakage is identified by filled up water in shell side of surface condensers.

Some of Electrical Measures recently adopted at GNFC

? Six numbers of Lighting Transformers Ordered for reducing lighting voltage ? At few locations Lighting Voltage reduced by changing tapping of Transformers ? Change of Lighting fixtures in office are of Corporate building ? Delamping of plant area after closely reviewing judicious requirements. ? Experimental use of Transparent roofing sheets at an interval of about 15 meters for making use of

natural light have lead to reduced requirement of lighting in day time in two of the coal conveyor gantries.

[C]CONTINUING QUEST FOR REDUCING ENERGY CONSUMPTION

A separate Energy Cell has been formed within the the Technical Services for exclusively focusing on Energy Issues in close coordination with other ongoing efforts. The initiatives taken by Energy Cell are

(a). Evolution of Steam Trap Management at GNFC

Following action were taken

1. Compiling trap identification list for each list for each plant jointly with operating group.
2. Evolving Tagging system for traps.
3. Trap identification, listing carried out plant wise.
4. Traps have been tagged in field as per the identification list details.
5. A Demonstrative Steam trap Audit for selected 200 nos. of traps carried out in Hazardous Chemical plant with the help of Experts M/s Forbes Marshall team. During this some of the engineers were trained for use of Ultrasonic leak detection technique and other observations.
6. A one-day training programme conducted for Engineers and technicians, giving information on Trap Basics, Application, Use and Maintenance techniques.
7. In house steam trap Audits carried out in most of the plant-using instrument Ue-2000. The trap functioning status was observed to be as per following.

Apart from this, some of the traps found to be of wrong type, improperly installed. For some of the traps, expert opinion was also sought. A guesstimate of steam loss through these traps was made using information available from trap manufactures. Total quantity of steam which can be saved works out to be 5.4 MT/hr. The corrective measures for the same are as under way.

(b). Energy Audit of Fans / Blowers :

From our observation of the throttled dampers / guide vanes, we selected 17 nos.of Fans having power requirement more than 100 kw located in various plants for their details Energy Audit. Performance testing was carried with the help of outside experts per BS 848. The performance testing revealed that 4 numbers of Fans in Boilers area are operating at significantly lower efficiency. ( This is over and above FD fans mentioned in this document in point no 6 - (b)) The scope for saving in terms of power is 256 kW. One of the main reason for lower efficiency of fan is observed to be operation at point far away from design parameters. Various technological options like Variable speed fluid coupling and Variable speed drive motor system have been worked out to save Energy for which proposal will be put up to Management shortly.

(c). Detailed study of Equipment (pumps) consuming high power.

For identifying energy saving potential it was decided to take up study of pumps consuming very high power. Therefore Ammonia plant cooling water system, which consumes between 5 to 6 MW was selected for detailed study. From the preliminary data available, it was observed that these pumps operate at lower efficiencies. Similar exercise was carried out for Cooling Water pumps of Urea plant and Captive Power plant In Captive Power plant, one of the pumps was identified for operating at substantially lower efficiency i.e. 75 %. To improve the efficiency of deficient pumps, new specifications were prepared for Ammonia, Urea, Captive Power Plant Pumps considering the changed operating parameters and the same are under implementation.

(d). Insulation.

Insulation is another area, which needed focus from Energy saving point of view.

1) To begin with, In house survey of Boiler no.II and Boiler no.III was carried out and at significant number of locations, Insulation quality found deteriorated which was evident from surface temp. as high as 90 °C. This was mainly due to lack of reinsulation after shut down. Out of the identified defects, some have been attended.

2) In Weak Nitric Acid plant temperature of HPSH steam was observed to be remaining lower than envisaged in design by 10 °C. To evolve the solution, Insulation audit of affected piping was carried out and losses were found to be unacceptably high. Various options were reviewed including replacement with best alternative material i.e. calcium silicate . Accordingly the cost benefit analysis was carried out which indicated the steam saving potential of 500 kg/hr. The proposal is under scrutiny.

? It is also observed that glass wool type of Insulation tend to sag over a period of time making bottom portion bare which increases losses. Further more steam consumption increases during monsoon. It is also being closely reviewed to replace phase wise glass wool type Insulation with block type Insulation (e.g. Calcium Silicate type) that has better properties.

3) During the last shut down, Cold Insulation replacement carried out for 11 nos. Of equipment's operating under sub zero conditions and for 11 nos. Of piping sections. This has resulted in to reduced load on Refrigeration section.

(e). Cooling Tower Audit in Captive Power Plant(CPP):

For reducing steam consumption in CPP, Evaluation of Cooling Tower Parameters was carried out by Energy Cell and it was observed that CPP cooling Tower performance remains poor in terms of achieving supply temperature for the prevailing Dry Bulb / Wet Bulb temperature as well in comparison to other cooling towers in GNFC. Particularly in summer cooling water temperatures were becoming a limiting factor for performance of condensers of both TGs and were resulting in to increased steam consumption. Accordingly in house survey and assessment of cooling tower was carried out recently, where in physical inspection of cooling tower components , taking photographs of areas where significant amount of air short circuiting takes place, individual cell water temperatures, measurement of water level on deck for each cell was carried out. Our observations were as per following.

1) Cooling water supply temperature for Cell-3 and Cell-4 was found to be remaining lower by 3 °C by compare to Cell No. 1 & 2. This indicates that performance of Cell No 3 &4 is poor compared to Cell No 1 & 2.

2) Major damages of wooden sheets in the fan plenum area leading to sizable quantity of air short circuiting in all the cells were observed. The details of the same are as per photographs given below.

3) Openings on the East side A.C Sheeting wall of the cooling tower - near inspection door , at top near hoist structure joint lead to lot of false air entry into the cooling tower.

4) Inside the tower , the door between cell no 1 &2, 3 & 4 remains open leads to uneven loading.

5) No. Of Flower Nozzles (water distribution) on the top deck of cooling tower are found without orifice cap, which leads to the overloading of these nozzles and uneven distribution within the cell and poor mass and heat transfer .The inlet diameter of specified nozzle with orifice cap is 24 mm and without orifice cap is 32 mm .

6) Average water level height was observed to be 3 cms higher on southern side deck area compared to northern area indicating uneven water distribution on cooling tower top deck .

7) In the plenum chamber significant water dripping was observed in the fan suction area, indicating deteriorated performance of drift eliminators.

Accordingly an action plan has been evolved to eliminate above deficiencies.

Following Photograph shows significant damages in Following Photograph shows significant damages in the plenum area leading to short circuiting of air plenum area leading to short circuiting of without without contacting water(Top deck) contacting water(Top deck)the fan at top deck.

Following Photograph shows significant damages Following Photograph shows significant damages in near entrance door of wet section leading to the plenum leading to short circuiting of air without short circuiting of air without contacting water. contacting water (top deck)

Following Photograph shows significant damages Following Photograph shows significant damages in the plenum leading to short circuiting of air without in the plenum leading to short circuiting of air contacting water (detection of air leakage). without contacting water (detection of air leakage).