BASELINE ENERGY AUDIT-FERTILISER INDUSTRY

BASELINE ENERGY AUDIT-FERTILISER INDUSTRY

BASELINE ENERGY AUDIT

•Review of fuel, feed and production data

•Identify & define boundary of energy consuming subsystems in the plant

•Perform energy balance of important subsystems

•Identify energy management opportunities and analyse savings and investments

Note:

–Energy auditor will be using available plant instrumentation to the maximum extent. Portable instruments such as Power analysers, flue gas analysers, temperature & pressure measurement devices etc. will be used

–Ensure calibration and availability of in-situ instruments, provision for measurements etc.

Methodology & Scope of Baseline Audit

•Subsystems in Fertiliser Plant

–Primary Reformer ( radiation & convection sections)

–Secondary reformer ( incl. WHB)

–CO2 removal system

–Synthesis loop

–Refrigeration system

–Urea synthesis reactor (incl. Ammonia pumps, CO2 compressors etc.)

–MP & LP decomposers

–Concentrators

–Granulation

–Water supply system ( from raw water to DM water, make up water etc.)

–Compressed air system

•Find out major energy consuming equipments in each sub-system

–Investigate the technology

–List out critical parameters which affect the efficiency and energy consumption

–Operating vs. Designed value

[ Measurements may be required at this stage. However, past energy audit reports, performance assessment reports may be referred to ]

Methodology & Scope of Baseline Audit

•Investigate All options related to

–Waste Heat Recovery

–Co-Generation

–Fuel Switch

–Use of EE equipment / System

[ Detail discussion with management required at this stage ]

•Review the Past Energy efficiency Measures

•Review the Future Energy Efficiency Approach/Strategy

–Detail discussion with plant management required

•Preparation of Audit Report

–Potential evaluation with tentative cost-benefit analysis

COMPARISON OF ENERGY, INVESTMENT & PRODUCTION COSTS

Natural gas reforming with steam & air is the simplest & most efficient way of ammonia synthesis gas production.

Plants installed during 1970-80s was mostly Naphtha & Fuel Oil. Plants installed after 1990 is almost all based on NG/Naphtha.

In India about 67% Urea capacity is based on Natural Gas and balance 33% on Naphtha and Fuel Oil.

Following are the relative consumption figures of NG, Heavy Oil & Coal based Ammonia Plant

Parameter	Natural Gas	Naphtha	FuelOil	Coal
Energy consumption	1.0	1.1	1.15	1.4
Investment	1.0	1.15	1.6	2.0

AMMONIA PROCESS

ENERGY REQUIREMENTS

•Thermodynamic energy requirement to produce 1.0 Ton of NH3 is 4.46 Gcal

•Plants designed in 1970s had figures of 9.6 Gcal/Ton

•Modern NG/Naphtha based plants have figures between 6.7 to 8.0 Gcal/Ton

Item	Energy Inflow		Energy Outflow	Loss (-) /Gain (+)		% Loss of Total
Primary reformer including steam superheater& convection zone	2559		2336	-0.223		-5.53
Secondary Reformer	7.334		7.274	-0.050		-1.49
RG WHB	1.219		1.214	-0.005		-0.12
HTS	6.246		6.237	-0.009		-0.22
LTS	5.831		5.823	-0.008		-0.20
GV System (CO2removal)	0.982		0.340	-0.642		-15.93
Methanator	5.729		5.723	-0.006		-0.15
Synthesis reactor	24.437		24.227	-0.210		-5.21
Total	54.337		53.176	-1.163		-28.85
Cooling Water		-2.881			-71.66
Air Coolers		-0.4241			-10.52
Unaccounted for vent losses & others2		-0.135			-3.35
Total Losses		-4.030			-100.00

Loss distributionThe very first reason of ~71% of total energy loss going to the cooling water is that the low-level heat can not be recovered efficiently in absence of cooler streams. The major contributor to this 2.9 Gcal/ton of energy loss is through the surface condensers of three major compressors, which have a cooling load of ~1.3 Gcal/ton of ammonia. The use of gas turbine, in place of steam turbine, for process air compressor in the new plants is an effective way to reduce these losses to some extent. Total saving of 0.3 Gcal/ton from process air compressor on gas turbine.

Urea Item	Unit	Toyo-ACES	Snamprogetti	Stamicarbon
Ammonia	Kg	568	566	568
CO2	Kg	735	733	733
*Steam	Kg	570	620	855
Power	kWh	121	120	110
Water	M3	51	85	58

Major energy consuming systems-Urea

Specific energy consumptionFeed stock	% capacity Utilisation	AverageGcal/Ton	Best figuresachieved in 2009-10
Gas	104	8.32	7.66 (IFFCO-Aonla-II)
Naphtha	53.5	9.82	9.63 (ZIL,Goa)
Fuel oil	100.8	11.78	11.14 (NFL-Bhatinda)

UREA

Feed stock	% capacity Utilisation	AverageGcal/Ton	Best figuresachieved in 2009-10
Gas	102.8	5.88	5.17 ( TCL, Barbala)
Naphtha	70.1	7.09	6.81 (MCFL,Mangalore)
Fuel oil	98.4	8.97	8.1 (GNFC, Bharuch)

ENERGY SAVING OPPORTUNITIES

•Reduce Primary Reformer duty by reforming at lower temperature in Pre-Reformer. This can save about 0.15 Gcal/T with a payback period of 2-3 years.

•More efficient combustion by reducing excess air.

•Insulation / refractory for Furnaces, equipments and piping.

•More Heat recovery from flue gases, by additional coils and increasing size of existing coils. Additional BFW coils, combustion air heaters in convection zone can be done.

Supply Compression Energy directly by Gas Turbine and exhaust to HRSG or Reformer Furnace. Gain from more efficient power availability for compression.

•Use of Vapor Absorption for cooling GT / Compressor suction.

•Power Recovery Unit for High pressure gases letdown. Turbo expanders can reduce Fuel NG pressure from 40 bar to 10 bar and recover mechanical power. For 10000 Nm3/h NG consumption, about 400 kW can be generated. Payback period of more than 6 years.

•Hydraulic Turbine for utilizing pressure energy wasted during let down.

Case Study: Reduce water leakage in the fire water system

•The fire water pump was delivering a flow of 60 m3/h.

•The pump input power during this isolated condition was about 89 kW, with a pump efficiency of 18% only.

•We had taken trials with the help of safety & fire dept and technical services dept to identify the source of this 60 m3/h leakage of fire water. The team has identified leakages of 30 m3/h at Bagging house and SPG & offsites area. Thus reduction of 30 m3/h in leakage was arrested during the audit itself.

•Energy Saving = = 243600 kWh/year

•Cost saving = Rs. 4.5 lakhs/year

Case Study: Reduction in steam for effluent stripping

•Presently the ammoniacal and non-ammoniacal effluent is mixed. Significant amount of ammoniacal effluent from ammonia-1 from Syngas compressor intercooler mixes with other effluent, resulting in prolonged stripper operation and about 5 to 6 tons per hour of LP steam

•Stop ammonia mixing in intercooler and provide separate ammoniacal effluent stream from non ammoniacal effluent.

•Separate ammoniacal effluent collection pits are made and intercooler tubes have been replaced to arrest ammoniacal effluent.

•Annual cost saving potential of Rs 72.0 Lakhs/year

Case Study: DM Water Pumping

•DM water from DM Water Plant is sent to tanks in Ammonia-1 & II and then pumped from the tank to deaerator by separate pumps. Total power consumption of 2 nos pumps is 170 kW.

•DM water can be sent directly from DM water header to deaerator through control valve; a pump bypass line already exists as per original design (this arrangement is already operational in Power Plant)

•Annual cost saving potential is about Rs 25.0 lakhs, with an investment of Rs 5.0 lakhs

Case Study: Boiler FD fanspeed control

•Input power to motor driven FD fan was 260 kW. System efficiency (including fan + damper losses) is only 14.3%

•Reduce steam turbine speed and increase damper opening & automate control to move damper to preset position in case of changeover to electric motor drive

•Saving potential 69.7 lakhs/year

Case Study: Boiler Feed Pump of Power Plant

•Boiler feed pump driven by 1220 kW motor and standby pump of steam turbine driven.

•Operating pressure (observed during energy audit for few days) was 150 kg/cm2g while the drum pressure is 120 kg/cm2g

•Reduce the discharge pressure to 130 kg/cm2g by reducing speed of turbine and reducing stages of motor driven pump.

•Cost saving potential of 34.85 lakhs/year with an investment of Rs 60.0 lakhs

Case Study: Heat recovery from CBD

•Presently about 2.1 m3/h of CBD is taken out from service boiler & HRSGs, which is flashed in drum. The condensate is cooled and discharged

•Install NG preheater from 30 C to above 80 C, by using this condensate, while reducing its temperature from 150 C to 60 C.

•About 10.8 m3/h of NG saving realised. i.e. Rs 5.1 lakhs, with an investment of Rs 7.0 lakhs