InstallationInstallation ofof Air-PreheaterAir-Preheater andand EconomizerEconomizer inin BoilerBoiler // ThermicThermic FluidFluid HeaterHeater A Case Study

Background

Micro, small and medium enterprises, jointly called of business holding and management, it becomes as MSMEs, plays an important role in the Indian difficult for MSME units to adopt energy efficiency economy. There are around 26 million micro, small measures, without external supports. and medium enterprises units in the country, which Under this background, the Bureau of Energy provides employment to over 60 million people. efficiency along with Ministry of MSME and cluster Together, the MSME sector contributes over 45 % of level associations, initiated a project titled “National industrial production and over 40% of exports. The Program on Energy Efficiency and Technology Up- role of MSME sector is set to grow in the economic gradation in SMEs”. Five MSME clusters were identified profile of the country. However, the sector has some all over India for executing intervention measures. Pali inherent issues. The sector is one of the major Textile cluster was one among them. The project here consumers of energy. The sector consumed an in Pali, is supported by the Rajasthan Textile and Hand estimated 50.5 million tonne of oil equivalent in 2012. Processors Association. The annual expected growth of energy consumption is about 6 percent annually. It is estimated that 15-20% percent of energy consumed by the sector could be saved. But, due to the small size and traditional nature The Cluster The Process

The Pali textile cluster is one of the biggest MSME The typical flow of the textile process starts with the De- clusters in India having over 250 member industries. sizing and Mercerizing of raw material. Subsequently, The units in the cluster are mainly located in two the fabric is fed into the Kier Boiler where scouring Industrial Areas namely Industrial Area Phase I & operations takes place, then the fabric undergoes Phase II and Mandia Road Industrial Area. The units bleaching followed by Air Drying (Adan). The next are classified into two segments mainly: 1) Hand step is colouring of the fabric using jigger or jet dyeing Process Units 2) Power Process Units. method. This is followed by the finishing process where the material fabric undergoes pre-shrinking in The BEE-SME project aimed to initially implement a zero-zero machine. Although, this is a typical layout, energy efficient technologies in selected units in other process improvement methods are used, as per the cluster. These units will act as demonstration requirement, by different units. units for long term and sustainable penetration of energy efficient technologies in the entire cluster. The Fabric is now ready for dispatch. The entire Inspire Network for Environment was selected as the processing of fabric in a Textile Processing unit implementing agency for the program. requires steam as the major input. For continuous supply of steam, a boiler or a thermic fluid heater is used. The baseline energy audit revealed that boiler is the major energy guzzler in a typical textile processing units.

Fig: Process Flow of a Typical Textile Unit The steam boiler operating in the unit is a packaged The Boiler: Baseline boiler with water tube design. Steam is the main Scenario agent of energy used in the textile processing unit. Thus, the boiler is the major energy utilizing source Packaged steam boiler is used to generate wet steam in these units. Most of the units use conventional required for the process in textile units. Steam is used water tube boilers wherein a significant energy is lost at a working pressure of 4-5 kg/cm2. Generally pet- through the flue gas. The baseline energy audits in the coke is used as the fuel for the steam boiler. The heating Pali textile units revealed that the flue gas generated chamber consists of a fluidized bed of coke wherein from the heating chamber of a boiler and the thermic air is supplied from bottom. The heat generated by fluid heater is discharged at a significantly high combustion of coke and air is used to heat water to temperature and not being utilized in these units. A form steam. The steam generated is used in various significant potential for energy saving exists in these processes across the unit. The boiler operates for an units with implementation of waste heat recovery average of 12 hours daily. system. Accordingly, installation of Air Pre-heater & Economizer was suggested.

Fig: Typical Boiler Process Flow without Air preheater & Economizer Energy Efficient Technology

Predominately two technologies were implemented in the boiler section, under the BEE-SME program i.e., Air Pre heater & Economizer.

EE Technology 1: Air Pre Heater for Boiler / Thermic Fluid Heater Working Principle A boiler produces steam which is subsequently used in different processes in a typical textile processing The most common air pre-heaters are tubular unit. Similarly, a Thermic fluid heater utilizes the heat preheaters consisting of straight tube bundles produced in the system for processing of fabric at which pass through the outlet ducting of the different segments. Energy used to heat the thermic boiler and open at each end outside of the fluid / water is mostly pet coke. Conventional units do ducting. Inside the ducting, the hot furnace gases not have provisions of waste heat recovery to recover pass around the preheater tubes, transferring the flue gas. Thus a significant amount of heat is lost heat from the exhaust gas to the air inside the as waste heat. preheater. Ambient air is forced by a fan through ducting at one end of the preheater tubes and at Air Pre-heaters are basically heat-exchangers installed other end the heated air from inside of the tubes in the exit flus gas duct of the boiler. The purpose of emerges into another set of ducting, which the air preheater is to recover the heat from the boiler carries it to the boiler furnace for combustion. flue gas which increases the thermal efficiency of the Installation of an air preheater can lead to recovery boiler by reducing the useful heat lost in the flue gas. of heat from the exit of the heating chamber to As a consequence, the flue gases are also conveyed to pre-heat the air required for combustion. The the flue gas stack (or chimney) at a lower temperature, pre-heated air can either be utilized in the thermic allowing simplified design of the conveyance system fluid heater or the boiler. With an exit waste heat and the flue gas stack. It also allows control over the temperature of 180 0C ; air pre-heat to the extent temperature of gases leaving the stack. of 100 0C can be achieved. EE Technology 2: Economizer for Working Principle Boiler Boiler stack economizers are simply heat Steam is the main agent of energy used in the textile exchangers with hot flue gas on shell side and processing unit. Thus, the boiler is the major energy water on tube side with extended heating surface utilizing source in a typical textile unit. In conventional like Fins or Gills. Economizers must be sized system, the feed water to the boiler is fed at ambient for the volume of flue gas, its temperature, the temperature (35 0C) while the stack temperature goes maximum pressure drop allowed through the as high as 240 0C. stack, what kind of fuel is used in the boiler, and The flue gas temperature leaving at 240 0C from the how much energy needs to be recovered. boiler can be recovered using an economizer. This can The installation of the economizer in the boiler further be utilized to pre-heat the boiler feed water. A / thermic fluid heater and utilizing the same for temperature difference of 1200C is sufficient to rise pre-heating boiler feed water will lead to following the boiler feed water temperature by 60-650C. The benefits: increase in boiler feed water temperature can lead to  Waste heat recovery substantial increase in boiler efficiency thus leading to  Improvement in boiler efficiency reduction in specific fuel consumption.  Reduction in FD/ID fan power usage Economizers are basically tubular heat transfer  Improved environment surfaces used to preheat boiler feed water before it  Easy to integrate into production cells enters the steam drum. By recovering the energy from  Reduced scaling the flue gas before it is exhausted to the atmosphere this performs a key function in providing high overall boiler thermal efficiency.

Fig: Typical Boiler Process Flow with Air preheater & Economizer Cost Benefit Analysis

Cost benefit analysis for installation of a economizer in Cost benefit analysis for installation of an air-preheater a typical unit is tabulated below: in a typical unit is tabulated below:

Cost Economic Analysis of proposed Cost Economic Analysis of proposed economizer combustion air-preheater

SN Parameter UoM Value SN Parameter UoM Value Quantity of steam generated 0 1 kg/hr 3000 1 Exit flue gas temperature C 240 per hr (Q) 2 Stack dew temperature 0 C 120 2 Quantity of fuel used per hr (q) kg/hr 500 Available temperature for 2 3 0 C 120 3 Working Pressure (assumed) kg/cm 10 heat transfer 4 Temperature of feed water 0C 35 Quanty of steam generated 4 kg/hr 3000 5 Type of fuel Coke per hour 6 Calorific Value of fuel kCal/kg 8200 5 Quantity of fuel in the boiler kg/hr 500 7 Enthalpy of steam kCal/kg 665 6 Specific heat of water kCal/ kg 0C 1 Steam generation per Kg 8 Enthalpy of feed water kCal/kg 35 7 kg/kg 6.00 9 Boiler Efficiency % 46 of fuel 8 Flue gas quantity kg/kg 14.63 10 Flue gas temperature 0C 240 9 Quantity of flue gas kg/hr 7317 11 Steam generation per kg of fuel kg/kg 6 Quantity of heat available in 12 Flue gas quantity kg/kg 15 10 kCal/hr 201951 flue gas 13 Quantity of flue gas kg/hr 7317 Rise in combustion pre-heat 0 Quantity of heat available in flue 11 C 62.6 14 kCal/hr 201951 temperature gas Every rise of 21ºC in combustion air pre-heat Rise in feed water temperature 12 temperature through waste heat recovery would offer 15 0C 62.6 by installation of economizer about 1% fuel savings. Every rise of 6ºC in boiler feed water temperature Savings in terms of fuel fro 13 % 2.98 16 through waste heat recovery would offer about 1% pre-heated combustion air fuel savings. 14 Savings in terms of fuel kg/hr 14.90 Savings in terms of fuel for pre- 17 % 10.43 15 Annual operating hrs hrs 3600 heated boiler feed water 16 Annual savings of fuel kg 53657 18 Savings in terms of fuel kg/hr 52.17 17 Annual cost savings Rs/yr 268286 19 Annual operating hrs hrs 3600 18 Cost of air pre-heater Rs 200000 20 Annual savings of fuel kgs 187800 19 Pay-back months 8.9 21 Annual cost savings Rs/yr. 1408500 Annual reduction in energy 20 toe 44.00 22 Cost of economizer Rs 184625 consumption 23 Pay-back months 1.57 Annual reduction in GHG 21 tCO2/yr 209.3 Annual Reduction in Energy emission 24 toe 154.00 Consumption Annual CO emission t CO / * Every rise of 21oC in combustion air pre-heat temperature 25 2 2 732.40 reduction year through waste heat recovery would offer about 1% fuel savings. ** Emission factor of coke taken as 113.67 tCO2/yr * Every rise of 6ºC in boiler feed water temperature through waste heat recovery would offer about 1% fuel savings. ** Cost of fuel taken as Rs 7.5/kg ***Emission factor of coke has been taken as 113.67 tCO2/TJ Implementation at a Glimpse

Thermic fluid exist with Air pre heater installed at economizer at Simandhar Fabtex Simandhar Fabtex

Economizer and air-preheater has been successfully implemented in the following units in Pali:

Implementation  M/s Simandhar Fab Tex Pvt. Ltd.

References The benefits achieved by the plant has been summarized in the table below:

Simple Percentage Savings Annual Annual CO2 Energy Efficient Technology Investment Payback in specific energy Energy emission implemented (INR Lakhs) period consumption from Savings reduction

(months) baseline (%) (TOE) (tCO2/year) Economizer in Thermic fluid 1.84 6 10.24 63.97 304.40 exit Air-preheater (APH) in steam 2.00 26 2.43 15.20 72.32 boiler for more information

Bureau of Energy Efficiency Ministry of Power Government of India 4th Floor, Sewa Bhawan R. K. Puram, New Delhi - 110066 (INDIA)