COGENERATION &
CO-FIRING IN
SUGAR MILLS PROJECT SYNOPSIS As a Curriculum of MASTER OF TECHNOLOGY (Energy Engineering) GURU NANAK DEV ENGINEERING COLLEGE, LUDHIANA
Submitted To: Dr. P.S. Bilga Asst. Prof GNDEC
Submitted By: A SINGH
INTRODUCTION: The energy is supplied to the sugar cane factory mainly as fuel or bagasse to the power house and bagasse drying plant. The power house typically incorporates a steam boiler and a back-pressure steam turbine. When burning fuel in the boiler furnace, live steam is produced and supplied to the turbine. The turbine drives an electrical generator which generates power for the factory and the steam leaving the turbine exhaust flows to the heating equipment for sugar manufacture. This is known as co-generation of heat and power or Combined Heat and Power (CHP). Cogeneration in sugar mills is implemented with the main objective of promoting technologies for optimum use of country’s biomass resources for grid power generation. About 5000 MW power could be generated through bagasse based cogeneration in the country’s 550 Sugar mills, if these sugar mills were to adopt technically and economically optimal levels of cogeneration for extracting power from the bagasse produced by them. Sugar industry has been traditionally practicing cogeneration by using bagasse as a fuel. With the advancement in the technology for generation and utilization of steam at high temperature and pressure, sugar industry can produce electricity and steam for their own requirements. It can also produce significant surplus electricity for sale to the grid using same quantity of bagasse. Co-Firing with Rice Husk: Small economic size and co-firing with other fuels has
opened up additional applications. Co-firing (or co-combustion) involves
“supplementing existing fossil-based (mostly pulverised coal) power plants with biomass feedstock” (IEA Bioenergy, 2009).
Similarly in sugar mills during the the off seasons, some other biomass solid fuel can be used , so that the power generation can be continuously generated from the co-generation plant. Rice Husk can be the better alternative as a solid fuel during the off seasons. At present the number of rice mills in the Punjab state is stated to be more than 3000. Rice husk from these mills is available in plenty but it is utilised in-efficiently in furnaces and low efficiency boilers by most of the textile and paper industries in Punjab for meeting their steam requirements. So if the sugar mills generating electricity have jointed with the rice mills located within a radius of 60 kms from the site ,co generation still would be economical during off seasons also. This leads to far better efficiency in terms of power generation. Notably, when a sugar mill does not produce enough bagasse to meet its power requirements and has to source it from rice husk, the cost is still usually less than Rs 1 per unit. In comparison, if the plant has to use diesel, the unit cost could be higher than Rs 2.75 and Rs 3.20 per unit depending on the state.
There are three types of biomass co-firing: Direct co-firing Indirect co-firing Parallel co-firing From above three methods of biomass co-firing the first one i.e Direct co-firing is most suitable for baggase and rice husk based co-generation plants. Indirect and parallel co-firing options are designed to avoid biomass-related contamination issues, but have proven much more expensive than the direct cofiring approach as additional infrastructure is needed.
Brief Literature survey: 1.(Frisch, 1993) For electricity generation, two most competitive technologies are direct combustion and gasification. Typical plant sizes at present range from 0.1 to 50 MW. Co-generation applications are very efficient and economical. Fluidized bed combustion (FBC) are efficient and flexible in accepting varied types of fuels. Gasifiers first convert solid biomass into gaseous fuels which is then used through a steam cycle or directly through gas turbine/engine. Gas turbines are commercially available in sizes ranging from 20 to 50 MW. Technology development indicates that a 40 MW combined cycle gasification plant with efficiency of 42 percent is feasible at a capital cost of 1.7 million US dollars with electricity generation costs of 4 cents/ KWh .
2.(Ravindranath and Hall, 1995)Two co-generation projects (3 MW surplus power capacity) in sugar mills and one rice paddy straw based power project (10 MW) were commissioned. While the co-generation projects are successfully operated, the 10 MW rice straw based power project completed in 1992 ran into technological problems and is closed since last two years due to want of suitable raw material. A rice husk based co-generation plant of 10.5 MW capacity installed by a private rice processing firm in Punjab and commissioned in 1991 faced problems such as unavailability of critical spares of an imported turbine and uneconomical tariffs from the state utility despite power shortage in the state. The rapid escalation in the price of rice husk and low capacity utilization added to the cost making the operation uneconomical. The experiences with R&D and pilot project suggests the need for considerable technological and institutional improvements to make biomass energy competitive.
3.(Rajan,1995).The future of modern biomass power programme rests on its competitive ability vis-à-vis other centralized electricity generation technologies. Policies for realizing biomass electric power potential through modern technologies under competitive dynamics has a recent origin in India. The biomass electricity programme took shape after MNES appointed the task force in 1993 and recommended the thrust on bagasse based co-generation. The focus of modern biomass programme is on the cogeneration, especially in sugar industry. A cogeneration potential of 17,000 MW power is identified, with 6000 MW in sugar industry alone . 4. Performance : (S. C.Kamate & P.B.Gangavati 2009) The most important performance parameters used to assess the steam turbine cogeneration plants in general and sugar mill cogeneration plants in particular are defined and developed. Criteria such as energy utilization factor, heat-to-power ratio, fuel energy savings ratio, exergetic efficiency and power generated per tonne of cane is be more important. The existing modern, high pressure, high efficiency, steam turbine cogeneration plants generate 115–120 kWh/tc, while BIG-GT and BIG-STIG are potentially capable of generating up to 270–275 kWh/tc. Cogeneration plants using backpressure and condensing steam turbines perform with energy (First Law) and exergetic (Second Law) efficiency of approximately 60–70 % and 22–25%, respectively. The steam consumption in sugar mills at present varies from 480–550 kg/tc, while electricity consumption ranges between 16–22 kWh/tc (32–40 kWh/tc for electrified mills). New Initiatives
The Ministry of India has continued the existing scheme with two modification related to : (a) Cogeneration projects through BOOT model in cooperative sugar mills. (b) Boiler upgradation of cogeneration projects in cooperative sugar mills.
Rice husk can be used for power generation through either the steam or gasification route. For small scale power generation, the gasification route has attracted more attention as a small steam power plant is very inefficient and is very difficult to maintain due to the presence of a boiler. In addition for rice mills with diesel engines, the gas produced from rice husk can be used in the existing engine in a dual fuel operation. The importance of Rice Husk and Rice Straw as an attractive source of energy can be gauged from the following statistics:
Rice Straw
1 ton of Rice paddy produces 290 kg Rice Straw
290 kg Rice Straw can produce 100 kWh of power
Calorific value = 2400 kcal/kg
Rice Husk
1 ton of Rice paddy produces 220 kg Rice Husk
1 ton Rice Husk is equivalent to 410- 570 kWh electricity
Calorific value = 3000 kcal/kg
Moisture content = 5 – 12%
5. Constructional Features: Cogeneration plant consists of four basic elements: 1. A prime mover. 2. An electricity generator. 3. A heat recovery system. 4. A control system.
Backpressure Technology: The first type of technology in cogeneration available was the Backpressure, where combined heat and power (CHP) is generated in a steam turbine.
The Fig. shows the process flow of backpressure type cogeneration (CHP).
6. Advantages : Social development opportunities:
Increased income and jobs in the agriculture and forestry sectors, which now supply part of the feedstock used in power and heat production (agricultural and forest residues) Job creation in the industrial sector for designing, building and operating the plants. Increasing inclusion in the economic system: well-organized farmers unions can gain access to energy markets.
Economic development:
Increasing energy security and saving foreign currency by reducing the dependence on imported fossil feedstock, such as coal. Diverting part of expenses for imported fossil fuels to farmers supplying the biomass feedstock; Diversifying the industrial sector; Supporting rural electrification with all its developmental benefits.
Environmental benefits:
Reduced GHG emissions from the power sector. Many agricultural and forest residues can be assumed to be carbon neutral, which leads to significant attributable GHG emission reductions. Reduced NOX and SOX emissions compared to coal combustion. NOx emissions can be further reduced by implementing primary and secondary emission reduction measures.
Energy Conservation: Apart from saving costs using cogeneration, sugar manufacturers have also taken steps to conserve energy. Some energy conservation measures include recirculating fly ash which contains unburnt carbon in the boiler to release more heat energy; installing star–delta-star unit for motors running with less than 50 per cent load, energy–efficient cooling towers for cooling water, and hydraulic drives by replacing gear boxes; providing variable frequency drives for weighed
juice pumps and cane carriers; replacing conventional gear trains in the mills with a planatory gear box; mixing the excess condensate of vapour with cold water in the evaporator instead of using just cold water; installing a spray pond system for condenser water cooling; installing auto transformers for factory lighting; optimizing the cooling tower pump; using low-loss chokes and high– output lamps; installing energy-efficient motors; and installing falling film evaporators . 7. Usefulness of this technology : Industries go for Cogeneration due to following principle reasons: a) To reduce power and other energy costs. b) To improve productivity and reduce costs of production through reliable uninterrupted availability of quality power from Cogeneration plant. c) Cogeneration system helps to locate manufacturing facility in remote low cost areas. d) The system collects carbon credits which can be traded to earn revenue. e) Due to uninterrupted power supply it improves working conditions of employees raising their motivation. This indirectly benefits in higher and better quality production. f) Cogeneration System saves water consumption & water costs. g) Improves brand image and social standing. h) A concurrent need for heat, electricity and possibly cooling indicates suitable sites for cogeneration. i) The initial investment in cogeneration projects can be relatively high but payback periods between 3-5 years might be expected. j) The payback period and profitability of cogeneration schemes depends crucially on the difference between the fuel price and the sales price for electricity.
PROBLEM FORMULATION: When a sugar mill does not produce enough baggas to meet its power requirements, in order to run it continuously so that electric power is generated without any interruptions, alternative fuel source is needed. And no doubt rice husk is the better option as a fuel at a sugar mill for power generation in the off seasons.
OBJECTIVES: To study the barriers for co generation plant. To study the efficiency of the plant. To study the economy of the plant.
METHODOLOGY/ PLANNING OF WORK: Data collection for availability of risk husk. Study of overall efficiency of the cogeneration plant.
FACILITIES REQUIRED FOR PROPOSED WORK: Visit at the site. Study of related Journals.
PROPOSED PLACE OF WORK: Guru Nanak Dev Engineering College, Ludhiana and Wahad Sandhar Sugar mill, Phagwara.
REFRENCES: 1.http://www.ieabcc.nl/overview.html 2.http://www.mnre.gov.in/schemes/grid-connected/biomass-powercogen/ 3.http://www.energymanagertraining.com/Journal/24092005/ProfitsfromCoge neration.pdf 4.http://www.energymanagertraining.com/announcements/issue25/winners_p apers_Issue25/08_PandurangSJalkote.pdf
5.http://peda.gov.in/eng/cogeneration.html 6.http://www.me.iitb.ac.in/~rangan/publications/recent%20papers%20publis hed_homepage/Cogen%20for%20sugar%20factory.pdf 7.http://en.wikipedia.org/wiki/Bioenergy#Electricity_generation_from_biomas s 8. http://www.bioenergyconsult.com/tag/rice-husk/ 9. http://www.resourcesaver.com/file/toolmanager/O105UF1139.pdf 10.http://www.business-standard.com/india/news/power-through-cogeneration-for-full-season-now/396279/
