part 1: overview of cogeneration and its status in asia - Fire

More documents

Recommendations

Info

76 Part II: Cogeneration experiences in Asia and elsewhere Though the initial investment becomes higher due to the higher boiler capacity and larger turbine and generator, condenser, etc., it can be justified by the higher efficiency and plant load factor. Moreover, the cost of additional fuel will be marginal. The power generated would be adequate to handle all the critical loads whereas the non-critical loads can draw power from the grid. Thus the plant productivity will no longer be affected by the utility power outages. 2.4.6 Full power generation As there was a need to include installation and management of the fuel and ash handling system, cooling water circuit for the condenser, and power interfacing and distribution, one more alternative was included to further increase the boiler and turbine capacities to meet all the heat and power needs of the factory. Though the investment required was higher, power generation cost became much lower compared with that of the utility or the diesel generator, mainly due to the low fuel cost. In addition, the option to avail full depreciation of the investment in the first year made the economic viability of the project particularly attractive. Hence the factory management retained this last option. The details of the economic calculations for this alternative are summarized in Table 2.3. Table 2.3 Technical and economic parameters of the cogeneration facility Description Units Values Power plant capacity Cogeneration plant power consumption Net power output for the factory Working hours Plant load factor Annual electricity generation Annual fuel (rice husk) consumption Annual fuel use for process steam Annual net fuel supply for cogeneration alone Investment on the cogeneration facility Cost of electrical modernization Price of electricity purchased Avoided cost of electricity generated Cost of fuel Cost of fuel for cogeneration Operation and maintenance costs Annual cost saving Gross payback period kW kW kW Hours/year per cent per annum 10 6 kWh tons/year tons/year tons/year 10 3 US$ 10 3 US$ US¢/kWh 10 3 US$/year US$/ton 10 3 US$/year 10 3 US$/year 10 3 US$/year Year 2,000.00 350.00 1,650.00 8,760.00 0.80 11.56 30,000.00 12,000.00 18,000.00 2,000.00 286.00 9.43 1,090.00 22.86 411.00 114.00 565.00 4.00 It is expected that when the mill capacity is increased to 100 tons/day of paper, the same cogeneration plant will operate with 20 tons/hour of inlet steam to provide 12-13 tons of process steam per hour at 4 bar and generate around 2,700 kW of power. A desuperheater was added near the paper machine to reduce about 100°C of superheat of the process steam extracted from the turbine. Compared with the earlier process line pressure of 7-8 bar, the present system operates at 5 bar pressure, thus the steam consumption is reduced and the power output from the turbo-generator is increased per ton of steam. In order to extract the maximum benefit from the cogeneration system and to make
Examples of cogeneration projects implemented in Asia 77 the system more flexible and cost effective, the turbo-generator is run in parallel with the utility grid. 2.5 Cogeneration in a Palm Oil Mill The palm oil industry is one of the major energy consumers of energy. This industry also generates vast amount of biomass such as mesocarp fibre, shell, empty bunches, fronds, trunks and palm oil mill effluent, which can be used as the main source of fuel for cogeneration with a capability to meet all the electricity needs of the factory. A crude oil and palm kernel producing plant in Malaysia decided to install a cogeneration plant to meet all its energy requirements, thus improving the efficiency, competitiveness, reliability, flexibility and ease of operation. 4 2.5.1 Production process of the factory The ripe palm fruit bunches are subjected to steam-heat treatment for a period between 75 to 90 minutes in a horizontal sterilizer where saturated steam at 3 bar and 140°C is used as the heat medium. These are then fed to a rotary drum stripper to separate the fruits from the bunches and the fruits are sent to a digester. Digestion involves mashing of fruits under steam heated conditions using direct live steam injection. Twin screw presses are used to press out the crude oil from the digested mash under high pressure. The crude palm oil consisting of a mixture of palm oil (35-45 per cent), water (45-55 per cent) and fibrous materials is sent to clarification tank which is maintained at about 90°C to enhance oil separation. The skimmed clarified oil is then passed through a high-speed centrifuge and vacuum dryer. With the introduction of a cogeneration plant, excess thermal energy and electricity are used in a kernel crushing plant. Both palm oil and palm kernel oil are sold to palm oil refineries and oleochemical factories for further processing. During steady plant operation, almost 5 tons/hour of palm shell was available with two different moisture contents, 8.3 per cent and 16 per cent respectively. Likewise, 11.55 tons/hour of palm fibre was discarded with two different moisture contents, 19.25 per cent and 30 per cent respectively. These residues were previously burned off in oversized and inefficient boilers in order to overcome the waste disposal problem. 2.5.2 Technology adopted for cogeneration The cogeneration system adopted to reduce the overall energy bill by simultaneous generation of heat and power. A backpressure steam turbine system was adopted as the simplest configuration for achieving the highest efficiency and maximum economy. A water tube boiler is installed with a capacity to generate 35 tons of steam at 23 bar. The fuel supply and combustion rate is controlled as a function of the airflow rate, by manual or automatic adjustment of the fuel conveyor. Steam from the boiler is passed through a back pressure turbine to generate 1,200 kW of electricity, meeting all the electricity needs of the factory as well as the worker’s residential quarters. The steam leaving at 3 Bar is used as the process heat for sterilizer, digester, crude oil tank, clarification, oil storage tank, kernel dryers and other applications (see Figure 2.6). 4 L. Low, “Investing in cogeneration for efficiency, competitiveness, reliability and ease of operation at Kilang Sawit United Bell”, Paper presented at the Cogeneration Asia ’97 Conference, AIC Conferences, Singapore, 25-26 November 1997.
Page 1:
PART 1: OVERVIEW OF COGENERATION AN
Page 4 and 5:
4 Part I: Overview of cogeneration
Page 6 and 7:
Page 8 and 9:
Page 10 and 11:
Page 12 and 13:
State of art review of cogeneration
Page 14 and 15:
Page 16 and 17:
Page 18 and 19:
Page 20 and 21:
Page 22 and 23: State of art review of cogeneration
Page 28 and 29: 28 Part I: Overview of cogeneration
Page 36 and 37: Policy framework for promoting coge
Page 46 and 47: Cogeneration in Asia today 49 1.1 I
Page 48 and 49: Cogeneration in Asia today 51 4,000
Page 50 and 51: Cogeneration in Asia today 53 1.3 T
Page 52 and 53: Cogeneration in Asia today 55 1.3.3
Page 58 and 59: Cogeneration in Asia today 61 1.7 R
Page 60 and 61: Cogeneration in Asia today 63 Every
Page 62 and 63: Cogeneration in Asia today 65 Cogen
Page 64 and 65: 68 Part II: Cogeneration experience
Page 78 and 79: Cogeneration experiences around the
Page 90: PART 3: SUMMARY OF COUNTRY STUDIES
Page 93 and 94: 98 Part3: Summary of country studie
Page 95 and 96: 100 Part3: Summary of country studi
Page 97 and 98: Sample case study in a pulp and pap
Page 123 and 124:
Sample case study in a pulp and pap
Page 125 and 126:
Summary of country study - Banglade
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Summary of country study - Viet Nam
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177:
show all

part 1: overview of cogeneration and its status in asia - Fire

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?