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12th North American Waste to Energy Conference May 17-19, 2004, Savannah, Georgia USA
NAWTEC12-2226
Technical challenges and abatements of a mass burn waste-to-energy plant coincinerating municipal solid waste and industrial waste
Abstract
Abraham Shu, General Manager
Swire SITA (Taiwan) Company Limited 12F-5, No. 415, Section 4, Hsin-Yi Road,
Taipei 110, Taiwan, R.O.C
Tel: 886-2-2758-1799IFax: 886-2-2758-5757 E-mail: [email protected]
The application of mass bum waste-to-energy (WTE) plants is becoming more popular in Asia, not just for proper disposal of municipal solid waste (MSW) like most plants in the
western world do but stretched by many Asian plants to co-incinerate non-hazardous industrial waste (IW) in order to maximize the use of the plant facilities, hence to save costs from building facilities specifically for treating IW. As the plants are designed with conventional considerations practiced in the western world and the original designs are not oriented towards co-incinerating large percentages ofIW, plant operators frequently face challenges such as unstable combustion quality, frequent boiler tube rupture amplified by co-incineration, inadequacy of the conventional control systems and other facilities to handle the co-incineration application. One co-incineration WTE plant in Taiwan is used as an example to illustrate the significance of these challenges, some measures taken to abate the problems and the cost impacts. S uggestions are also provided
for technical management of co-incineration plants.
Key words: boiler tube rupture, co-incineration, flame impingement, mass bum, steam flow fluctuation
209 Copyright © 2004 by ASME
Introduction
WTE industry is quite developed in the western world, with about 130 million metric-ton (mt) ofMSW are combusted annually by over 600 WTE facilities that in tum generate steam and electricity for various applications[l]. The mass bum system using various kinds of stoker design is the main technology for burning MSW in the western world and the plants using mass bum system are generally designed to bum
MSW with relatively stable heating value, moisture content, volatile organic matter and ash content. Suitable operational conditions are defined in the envelop of the fuing diagram which reveals the mutual dependent relationship between the heating value of the waste and the total tonnage of the waste that can be incinerated. In general, the waste feeder, stoker, boiler and control system are all designed to handle the waste with a relatively narrow range of quality variation.
The same technology and the applications are also becoming popular in Asia for the last decade[2], especially in those emerging and developing Asian countries. As the allocation of government budget of these Asian countries to the waste management affairs are generally limited that most of the allocations are insufficient to support management of MSW and IW separately in different facilities using various technology, the increasingly popular practice in these countries is to co-incinerate non-hazardous organic IW with MSW in WTE plants.
Co-incinerating non-hazardous IW in a WTE plants that were originally designed to bum MSW only inevitably creates challenges to the plant operation, especially when the MSW characteristics by itself are already not quite predictable or stable without adding
IW stream; and the plants' design approach has been based on conventional considerations that are further simplified to tailor to local constraints. Hence, managing these plants with stretched applications has become a unique experience not found in other western world.
The most developed WTE industry in Asia is in Taiwan in terms of the percentage ofMSW incinerated in plants with power generation, the variety of the project development modes, management approaches employed and the commercial models used. Although Japan may be an Asian country better known to the world's waste incineration industry for its ability to fabricate and erect major incineration plants system and equipment under world leading technology licensure agreement, and the hundreds of waste incineration plants built in commercial operation, many of the plants in Japan are small in size and do not recover energy for power generation. Taiwan on the other hand
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has 19 WTE plants on its small island, all of mid to large size and currently in commercial operations, and has five more plants in the last stage of completing the construction[3]. The capacity of these Taiwanese plants ranges from 600 mt/day to 1,800 mt/day, all with energy recovery and power generation functions.
Like most other Asian country's governments, which tend to conceive that managing MSW is the government's fundamental responsibility and place the disposal ofIW as a later priority, the government of Taiwan preferentially uses its limited budget to build MSW incineration plants fust. Therefore, all of the WTE plants built so far have been dedicated, by their design, to the treatment ofMSW.
At the time of writing, about 60% ofMSW generated daily by 23 million people of Taiwan are incinerated in WTE plants and it will approach 80% or more when the construction of all plants are completed in a year or two [4].
As little budget, or virtually none, has been allocated to support facilities designated purely to the treatment of
IW, it is natural that the MSW WTE plants are used to help resolve IW disposal needs by co-incineration. In fact, there are more than 1.3 million mt ofIW currently co-incinerated annually in these WTE plants in Taiwan. The statistics of the WTE plants in Taiwan and the wastes currently incinerated are shown in Figure-I.
Taiwan has fifteen years of waste incineration experience and the uniqueness of its experiences, whether in commercial models, technical applications and financial management aspects, are widely spread in Asia Pacific region. Inquires for reference, documents, commercial and technical data and expertise inputs are constantly received by the waste management industry and government of Taiwan from Asian countries and city states such as China, HK, Singapore, Philippines, Thailand and Indonesia. It is hence worthwhile for the WTE industry of the western world to gain an insight to the problems that a WTE plant designed to dispose ofMSW but is applied to co-incinerate IW are facing and how some of these challenges have been dealt with.
The author therefore uses one of the WTE plants in Taiwan as an example to illustrate the challenges of coincinerating a large percentage of IW in a MSW WTE plant.
Readers will first review specifics of the reference plant, which shall remain anonymous. After the proximate and ultimate analysis of the wastes is discussed, the major challenges faced by the reference plant and a number of other plants of similar
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application will follow. The challenges include management of combustion quality with unpredictable waste characteristics, frequent boiler tube rupture amplified by co-incineration, inadequacy of the conventional temperature control system to handle the co-incineration application, inadequacy of the conventional waste feed system to handle the coincineration application, the problem of marginal plant design, the problem of the drastic fluctuation of the steam flow and the combined problem of coincineration and the inadequacy of plant perfonnance test. Subsequent cost impacts these plants are facing are supplemented by the operational data and photos related to problems already taken place in coincineration plants. The authors' analysis of the causes of the problems and some of the ideas for solving these problems are also presented in this paper.
It is worth noting that although the reference facility and its owner, operator and location remain anonymous, the reference plant is indeed a typical one in Taiwan as many WTE plants built in Taiwan are based on the similar design philosophy.
Reference Plant Design and Construction Specifics
1. Basic features of the reference plant
Type of the facility: Mass burn waste-to-energy plant using stoker with reverse reciprocating motion.
Basic process: Waste receiving, weighing and storage followed by three separated boiler lines, three state-of-art air pollution control systems, and a single shaft steam turbine generator and stack.
Peripheral facilities: The facility is further equipped with an 8-story office building, ashes storage bunkers, an emergency diesel generator, plant and truck maintenance warehouse, the wastewater treatment plant and the waste water recycling system to achieve zero water discharge standard and an in-plant fly ash solidification and stabilization system.
Ash disposal: Off-site sanitary ash landfill
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2. Key design parameters
Plant capacity
Refuse crane
Refuse storage bunker
Combustor
Refractory
Boiler
Nominal capacity of 1,350 mt/day ofMSW
2 sets of cranes mounted with single load cell grabs, each rated at 85 mt/hr
1 bunker with 16,200 m3 storage capacity
Three separate combustors, each rated at 450 mt/day of municipal solid waste (MSW) with lower heating value of 2,300 kcal/kg.
Silica carbide brick, high alumina brick, high alumina plastic
3 lines of waste heat recovery boilers including waterwall tubes, screen tubes, superheater tubes and the economizer and each boiler line is rated at 6 1.42 mt/hr of superheated steam at 40 bars and 400°C
Air pollution control 3 sets of SNCR + semidry system scrubber + activated carbon
injection + bag filter
Baghouse and bag filter
Semi-dry scrubber
Pulse jet, 100% Teflon bag, SS-400 casing and bag support
Hydrate lime mixed with recycled water, 12,000 r.p.m. rotary disk atomizer, flue gas in at 23rC, out at 140 °C.
Primary combustion 3 sets of FD fan, each rated at air fan 1,772 Nm3/min.
Primary combustion Steam heated preheater with air preheater max output temperature of
200°C.
Secondary combustion air fan
ID fan
Control and monitoring system
Steam turbine/generator
3 sets of FD fan, each rated at 445 Nm3/min.
3 sets, each rated at 3,67 1 Nm3/min.
1 set of distributed digital control system (DCS)
3 sets of CEMS
5 stages single shaft turbine with multiple steam extractions, 0. 18 atm exhaust vacuum, 6,000 r.p.m., generator rated at 36,500 kw
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Bottom slag extractor Water sealed slag cooler, 6 sets each rated at 3.75 mtlhr
Fly ash solidification and stabilization system
Slag storage bunker
Stabilized fly ash product storage bunker
Stoker
Feeder
Single shaft pug mill kneading machine rated at 17.2 mtlhr of dry fly ash. Operated in batch mode at 8 hr/day mixing with recycled water, cement and chelate agent.
2,048 m3
426 m3
Reverse reciprocating type, 4 runs per incinerator line, 8.48 meter in width, with 13 steps of stoker bar.
4 hydraulic ram feeders per incinerator
Stack 120 meters height of RC structure with three internal steel gas pipes
3.
Weighing bridges
Bulky refuse shredder
4 units each rated at 40 mt
1 unit rated at 10 mtlhr
Plant construction
There are two types of plant construction contracts commonly used in Taiwan as well as elsewhere in Asia. One type of the contracts allows the plant be designed, engineered, procured, fabricated and constructed by an Engineering-Procurement-Construction (EPC) contractor with wrap-up guarantees. The EPC contractor in general further retains subcontractors, with some are locally based, to accomplish the works. The EPC contractor is, however, responsible for the schedule, cost, quality and performance guarantee of the entire plant. This model is more popular for developing BOT or BOO project by private sponsors who need to obtain an EPC wrap-up guarantee to facilitate the approval of debt fmancing.
The other type of the contracts allows the plant be designed, engineered, procured, fabricated and constructed by separate parties. Typically the plant design is done by an Architect Engineering (AE) firm while the construction is done by a main contractor. Procurements of equipments are either done by the facility owner or a retained agent. This type of contracts is more popular in Taiwan mainly because the overall cost is lower and there is no strong need for
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arranging the debt financing as many facilities are financed by the government's budget appropriation. The fall back, however, is that there is no single party taking up the ultimate responsibility for the overall success of the facility in case major flaws are found.
The plant referenced in this paper was built under the second type of contracts with the following role and function arrangements:
Role and functions Responsible party
Financing 100% by government budget
Facility owner Government authority
Owner's consultant Locally based engineering
Plant designer
Detail design
Procurement
Construction
Operation
and consulting firm
Process design by an international EPC
Done by a locally based engineering and consulting firm
Jointly done by the international EPC, local engineering firm and the government authority. Equipment is sourced from local and international suppliers.
Jointly managed by the international EPC and local engineering and consulting firm
By private operator under O&M contract with 20 years term
Characteristics of Waste Received and Incinerated
The reference plant receives both MSW and IW for treatment. The characteristics of a representative sample ofMSW collected from the waste storage pit in the reference plant are shown in Table 1. During the sampling time period, the waste stored in the pit was mainly MSW. IW was present in trace amount due to the waste delivery arrangement.
The characteristics of a representative sample of the mixture of MSW and IW collected from the waste storage pit in the reference plant are shown in Table 2. During the sampling time period, there was more IW than MSW stored in the waste pit due to the waste delivery arrangement. No sampling and analysis was done on a single IW stream because there were too many IW sources and waste characteristics varied
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widely from factories to factories even within the same type of industry.
The waste category, elemental analysis and heating value of typical IW streams are shown in Table 3. The data are compiled based on several studies published by Taiwan's Industrial Development Bureau of the
Ministry of Economic Affairs[5].
Operational Applications
The application of this reference plant has been coincinerating of approximately 50% each of the MSW and IW by weight, or approximately 35% of heat input from MSW and 65% from IW.
Key operational data is as follow:
Key parameter
MSWLHV
IWLHV
Operating hour
Operational team
Major overhaul
Operation data
On average 1,700 to 1,900 kcaIlkg
On average 2,300 to 2,500 kcaIlkg
24 hr/day, 365 days/year
Five teams, three shifts
14 to 2 1 days per major overhaul, two times per year
Gross power generated 33 Mw
In-plant power usage 6 Mw
Net power output
Net power recovery efficiency
Technical Challenges
27Mw
On average:
325 kw-hr per mt ofMSW incinerated
490 kw-hr per mt ofIW incinerated
Co-incinerating high percentages ofIW in WTE plants built and designed for burning MSW originally inevitably brings operational challenges to the plants. The challenges are first initiated by the waste input itself and manifested in parallel by equipment design inadequacy in terms of co-incineration applications.
1. The complex nature of the wastes
Taiwan's MSW is more heterogeneous than that in the
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western world6 although the categories used for physical composition analysis are similar to that used in the western world. Many components in the wastes are forced to fit into these standardized categories because there is no other more suitable category to categorize them. Take the category, "plastics", as an example, it may well include waste such as spent paint resulted from construction and interior design works. The reason for this kind of forceful fit of waste, or IW by a more strict definition, is because these waste are often mixed with true MSW during the MSW collection process as a result of the fact that residential areas and commerciaIllight industrial areas in Taiwan are often geographically mixed together, not as distinctly segregated as in western countries. Therefore wastes of all kinds, presumably not including hazardous wastes, are collected together. That is why we see the percentage of the plastic in Taiwan's waste is far more than that in the western world[6]. The same rationale applies to wood, rubber, etc.
In other words, the wastes collected as "MSW" may well contain a significant percentage of plastics and chemicals used in cosmetics, car maintenance, dry cleaning, household cleaning, light manufacturing industries, etc., not necessarily just wood or paper based. The challenging part to the plant operator therefore is not so much from the fluctuation of the moisture content but the fluctuation of volatile organic matters.
The plant operation in Taiwan is further challenged by co-incinerating IW received from various sources. The
IW is not the commercial wastes collected from business districts. They may be those freshly generated from the industrial factories or aged wastes that are either previously stored in the factory backyard or illegally dumped.
Common IW delivered directly from factories include scrap plastics, rubbers, textile residues, sludge and rag from pulp and paper industries, auto fluff generated from automobile recycling plants, leather industrial wastes and miscellaneous wastes generated from chemical, petroleum and petrochemical industries received at WTE plants. As such, IW delivered to the plants tend to have a wide range of heating value, moisture content, ash content, heavy metal content, chlorine content, sulfur contents and volatile organic matter content. The chemical and physical characteristics of a particular type of IW even fluctuate widely within the same industry.
It is worth noting that it is becoming popular in Taiwan for WTE plants to receive excavated IW from former illegal dumping sites as a result of expedited economic development that requires clean lands for construction
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of housing and infrastructures. These excavated wastes are not only aged and vary in a wide range of contents but may also be mixed with untreatable waste that could be hazardous. Therefore, proper sorting and complete separation of excavated waste mixture is required before the waste can be delivered to WTE plants for disposal.
The variations and fluctuations of the waste quality have inevitably created high challenge to the plant's technical operation as well as cost control. Undesirable phenomena including a high boiler tube wastage rate, frequent unexpected boiler tube rupture, high elutriation and entrainment rate of corrosive and abrasive fly ashes, high refractory damaging rate, wide span of steam flow fluctuation up to ± 30% in an hour, freeboard combustion with direct flame impingement up to the screen tube and roof tubes, combustion chamber temperature over-shooting by several hundred degrees within minutes, combustion chamber static pressure fluctuated widely swing between negative to positive pressures, etc. have been observed in plants co-incinerating a high percentage of IW.
2. Waste mixing constrained by the waste delivery time
Owing to the heterogeneous and complex nature of the wastes delivered to the reference plant, thorough mixing of waste in the plant is hence a crucial prerequisite to stabilized combustion. However, the delivery time of wastes imposes constrains on the thoroughness of waste mixing.
Due to the living habit and cultural practice, IW generally arrived at WTE plants during daytime while
MSW are collected and received at WTE plants in after hours. IW and MSW usually arrive at the plant in large quantities within relatively short time intervals of their own respectively, which makes thorough mixing of these two major waste streams with each other virtually impractical due to time constraint. For thorough mixing of waste would require temporary recession of waste dumping into the pit, which would lead to queuing of waste delivery trucks, the plant operator therefore has to incinerate large quantities of wastes "as received".
3. Managing combustion quality when coincinerating IW in a large percentage.
Combustion quality is a semi-qualitative and semiquantity term and can be observed and realized by the flame length, flame impingement pattern, the level of the fluctuation of the steam flow, the extent and frequency of appearing CO spikes and temperature over-shooting or dropping. Some people use the dioxin
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emission a s the basis o f rating the combustion quality. Nevertheless, the dioxin emission cannot be measured on-line and is therefore less practical to be used by operators as the basis for immediate control of the combustion quality.
Generally speaking, WTE plants are designed to burn MSW with a certain range of moisture content, heating value and percentage of volatile organic matter. The combustor is usually designed to give high flexibility for managing the variation in moisture content, medium flexibility for managing the variation in heating value and low flexibility for managing the variation in volatile organic matters.
As far as the moisture content is concerned, seasonal variation due to raining days, snow and summer yard works are well anticipated by all designers and the mass burn plant are all designed to be capable of managing the variation in moisture content. The variation of moisture content sometimes can slightly extend or shorten of the drying zone of the stoker but normally does not show negative impact on the combustion quality. They are manageable whether in the western world or in Asia.
However, the plant operation would be more complicate if the "MSW" delivered to a WTE plant contains a wide variety of wastes, as in the case of Taiwan. As the variety ofIW is received in a wide range, their heating value and moisture content also vary drastically from day to day. But the more challenging part to the operator is the variation of volatile organic matters contained in IW. The variation of these properties not only makes the drying zone, combustion zone and the ashing zone on the stoker shifted back and forth during the day but also causes the flame length, width and angle of impingement shifted drastically within short interval of the operation hours, the steam flow has been observed to fluctuate ±30% in an hour, and CO spikes appeared every now and then.
The basic combustion theory tells us that if the waste is homogeneous and stable in quality and characteristics, the combustion can be completed in one stage of the combustion chamber like the stoker system used in mass burn plants. Under this scenario, the complete combustion of the waste can be achieved almost by the primary air alone and one would normally see many small and short flames in bright colors evenly distributed over the waste bed above the stoker.
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On the other hand, however, if the waste is highly heterogeneous and varies drastically in heating value, moisture content and volatile organic matters, the combustion could not be completed easily in one stage but requires a second stage of the combustion chamber to complete the combustion. A typical example is the rotary kiln (R/K) system with the kiln itself as the first stage of the combustion chamber followed with a secondary combustion chamber to complete the entire combustion process. That is why R/K is widely used to burn wastes with large variation in characteristics.
Co-incineration ofMSW and IW in a large quantity in a way is like running the WTE plant somewhere between these two cases as evidenced by observing wide flames in dark red color with long tails and ever changing impinging angles all the way reaching the screen tubes when viewed through the sight ports near the top of the incinerator. This is an inevitable result of co-incinerating IW in high percentage. It means a lot of volatile organic matters are vaporized and burnt in the space far above the stoker, or the freeboard zone in the fluidized bed term.
To cope with this kind of application, ideally we want to have the ability to inject a high percentage of the combustion air above the stoker with multiple nozzles that are capable of penetrating the center-zone of the combustion chamber at all levels from all directions in order to create sufficient turbulence and gas phase mixing and to complete the combustion of vaporized organic matters in a relatively short distance of space available before the flue gas leaves the first pass of the combustion chamber. But this is often not possible because the requirement for change in equipment layout is too extensive and the physical space constraint also limits the operator from doing so.
The short term impact of unstable combustion quality is reflected in the fluctuation of the combustor temperature, steam flow, and CO spikes, the mid term impact leads the need to wash boiler heat transfer surfaces more often than normal and the long term impact results in build-up of slag on the interior wall of the combustor, rupture of the screen tube and roof tube and frequent damage of the refractory and extended major overhauls.
The practical solutions the reference plant learned in dealing with the combustion quality issue without massively change the plant design are summarized as the following points:
• Cut back the throughput to 80% ofMCR rate or more.
• Perform frequent maintenance and repair works. • Screen out as much undesirable waste at the
sources as possible when applicable. • Use higher grades of materials for boiler tubes
and refractory.
Oxygen enrichment of the secondary combustion air is also a possible solution to the technical problem but has not been tried out in the reference plant due to the concern of the cost involved.
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4. Frequent boiler tube rupture amplified by coincineration
Boiler tube wastage and rupture are common phenomena in WTE plants[7]. However, the rupture to be discussed in the following is not just gradual weary of thinning nor the author is merely talking about a wastage rate that is normally anticipated in WTE plants. Instead, the drastic ruptures of the screen tube and superheater tube the reference plant has experienced took place more than 20 times in less than 3 years or an average of one incidence per two-month time period.
The tube materials used in the reference plant
In the reference plant, all of the waterwall tubes, roof tube and screen tubes are fabricated with medium grade carbon steel, SA-210-Al . All of superheater tubes are fabricated with medium grade carbon steel SA213-T12 except the bottom three rows of the superheater tubes exposed to the highest flue gas temperature that are overlaid with 1/8 inch Inconel 825 alloy.
The problem of and solution for screen tube rupture
Accelerated corrosion induced by direct flame impingement and molten ash attack are the main reasons causing screen tubes to rupture, of which direct flame impingement is the dominant one. Burning a high percentage of IW can cause large amount of volatile organic matters to flash suddenly and to generate flame that directly impinges on the bare metal tubes above the refractory protection level reaching the screen tube and roof tubes. Flame temperature is above the adiabatic temperature of combustible gases, reaching above 1 ,300°C. It causes sudden boiling of the uprising water, leading to drastic build up of the pressure inside waterwall tubes locally that subsequently bursts the boiler tube. A photo of a burst rupture of a screen tube after exposing to direct flame impingement is shown in Figure 2, notice that burning marks are left on the tube inner wall.
There is no easy way to protect the tubes from direct flame impingement. Raising the refractory level is a
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common way to protect the waterwall tubes but not the screen tubes. Over raising the refractory level would shift the heat absorption burden to down stream heat transfer surfaces and leads to increased flue gas temperature at the superheater exit and worsens the level of the fluctuation of the steam flow.
In contrast to drastic rupture incidence caused by flame impingement, molten ash induced corrosion would cause small holes of the size of a dime on the tube. They do not happen so suddenly and drastically but gradually. When that happens, water leaks out and turns into steam and the phenomenon can be observed through sight ports by seeing steam plume injecting into the combustion chamber. Usually plant operators would have a few hours to a couple of days of time to react to the situation before shutting down the plant.
It is quite common in the western world nowadays to apply high alloy protection layer such as the Inconel overlay on the screen tube to reduce the rate of corrosion induced by molten ash attack. However, this is not popular yet in Taiwan mainly because of the high cost required.
The solution evolves from lessons learned and the studies conducted are summarized in the following points:
• Use higher grade alloy for screen tubes and roof tubes.
• Reduce throughput. • Frequent replacement of the screen, waterwall and
roof tubes.
The problem of and solution for superheater tube rupture
Superheater tubes also failed from time to time, mainly resulted from accelerated corrosion induced by elevated flue gas temperatures. Elevated flue gas temperatures is a consequence of sticky fly ash fouling on heat transfer surface of the waterwall and superheater tubes and that fouling in turn causes the heat absorption rate of the boiler to drop. Burning a high percentage of IW in fact can further accelerate the fouling rate because a lot of IW stream variety upon burning would generate fly ash of melting points lower than ashes generated from burning MSW alone. It is not uncommon to see 5% by weight of the sodium salt and potassium salt in the fly ash when burning wastes with a high percentage ofIW. Frequent cleaning of the boiler tube surface is a practical method to avoid surface fouling and high flue gas temperature at the exit. Operators usually determine the timing to wash cleaning the boiler tube surface based on the alarming high flue gas temperature measured at the superheater exit.
Superheater tubes including hanger tubes can also be damaged by the steam impingement from the soot blowers. This process usually happens slowly and the erosion rate can be further slowed down by installing protection shields, usually half a cylindrical tube and about two meters long, clamped on the superheater tubes on the surface facing the soot blower.
The protective shields are meant to be sacrificial and are usually replaced during semi-annual or annual major overhauls. Sometimes, however, steam condensate in the form of tiny liquid droplets, left from previous soot blowing cycle, entrained in the soot blowing steam hits the superheater and hanger tubes, resulting in drastically accelerated erosion rate. Proper operation of the steam drainage, allowing sufficient time for preheating the system and maintaining the steam temperature above the saturation point at the same time are measures to avoid the condensate droplets hitting the tubes.
5. Inadequacy of conventional temperature control system for handling co-incineration application
As said before, the characteristics ofMSW in Taiwan generally fluctuates more than that in the western world and the plant operation is worsened by co-incineration ofIW . This has resulted in unstable flame impingement in the combustion chamber. Every now and then, the flame directly impinges on the thermal couples installed in the combustion chamber for measuring and controlling of the combustion temperature. Direct flame impingement causes the thermal couples to instantaneously send out wrong temperature indications and hence disturbs the control functions.
. In conventional WTE plants, the temperature signal is used to control the waste feed rate or the combustion air rate, or both in a cascade mode. But in the case of this reference plant, the temperature signal can neither be used to control the waste feed rate nor the combustion air flow rate. The temperature control loop is therefore forced to be disabled and disengaged from the control functions. Although the signal remains to be perceived, it is used simply for indicating the temperature in the combustion chamber on a time averaged basis. The waste feed rate is simply controlled by the steam flow rate and vice versa, the steam flow fluctuates drastically along with the fluctuation of the waste characteristics.
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There are many plants built in Taiwan with temperature control function removed, disabled or purposely put in inactive mode by the EPC contractor for the above mentioned reason. This kind of design weakness can not be detected during the performance test because
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during the so-called performance test, the wastes are specially prepared and stored for the sake of "expected satisfactory" performance test. They are not the same as the real waste collected in the market.
The design weakness can only be identified by the plant operator after commercial operation is started and often the operators are forced to operate the plant in semi-automatic or even manual modes. In this case, human intelligence is introduced to control and manage the plant operation on a day-to-day basis.
For example, plant operator will not try to adjust the combustion air rate or the waste feed rate if O2 measured at the economizer exit remains above 7% by volume even when the operators see the weighted average temperature of the combustion chamber, computed and displayed by the DCS system, shows the temperature above 1, 100°C. The operator will regard this temperature over-shooting as acceptable fluctuation because of localized flame impingement on the thermal couples and the overall air-to-fuel ratio is still at balance.
On the other hand, if the temperature over-shooting is accompanied by the dropping of the O2 reading at the economizer exit to below 3% by volume on the dry basis for a few minutes, then the operator will try to cut back the waste feed rate or increase the combustion air rate until the O2 reading back to normal. Sometimes simply cutting back the waste feed rate would not be sufficient to quickly bring the 02 reading back to normal, then the plant operators even have to temporarily stop the feeder for a few minutes and let the over-fed waste on the stoker be consumed first. Under this scenario, the linked control function between the feeder speed and the stoker speed has to be disconnected temporarily too.
6. Inadequacy of waste feed control system for handling co-incineration application
In many WTE plants in Taiwan, the waste feed rate control system has been designed based on a simple onoff logic but not the proportional control logic. Waste feeder is turned on when the steam flow measured is below the set point and the waste feeder is turned off when otherwise. The reasons are that the temperature measurement is not reliable as mentioned above and the waste characteristics fluctuate drastically. Some plants do have a control system using proportional control logic but the system does not work well and the key process parameters remain fluctuating drastically and fail to converge on the set points.
The feeder has limitations on its feeding speed (number of strokes per time period) and the advancing distance
per stroke. During normal operation, the effect of the waste characteristics fluctuation often over shadow the reacting capability of the feeder system and results in unstable combustion and steam flow fluctuation.
Consequently, it is not uncommon to see steam flow fluctuates ± 30% within an hour time interval and temperature overshoot a couple of hundred Celsius degrees in just a few minutes. When this happens, operators need to manually stop the feed for a while and at the same time manually adjust the primary and secondary air flows to bring the steam flow and temperature back to the desired window. It requires certain level of knowledge in combustion chemistry to operate the plant with this kind of control system. The operator's function is no longer just taking readings from the monitor screen and record the observations on the operational diary. They are required to be able to constantly think about the combustion reactions, process dynamics and equipment design and operational limits.
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7. Problem of marginal plant design
Although the process arrangement is equivalent to the western standard and the plants are installed with the boiler, state-of-art APC system, CEMs, steam turbine and generator and plants are controlled by the modem DCS system typically designed and provided by reputable western companies, the actual design approach however is determined towards building a plant "as small as possible" in order to save land space and "as economical as possible" in order to win the EPC contract through the price-competitive bidding process, a typical way of awarding the contract.
Therefore EPC contractors and/or plant designers are pushed to design "compacted" plants, e.g. design the plant with a low excess air percentage, smaller boiler tube spacing, high flue gas velocity, high heat absorbing rate per unit volume of the combustion chamber, vertically stacked up of superheater sections, stacked up economizer sections, and undersized the capacity of the air cool condenser, etc.
This marginal design concept has consequently resulted in prominent challenges. For example, a design with no more than 80% excess air leads to high corrosion rate; secondary air limited to 20% leads to freeboard combustion and temperature over-shooting; smaller boiler tube spacing results in fly ash build up and pressure drop increase; vertical stacking arrangement of the economizer and the same arrangement for the multi-stage superheaters cause fly ash to build up, flue gas to channel through leaving uneven temperature distribution across these heat transfer sections horizontally; high heat absorption rate of heat transfer
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surface leads to the requirement of washing the boiler more frequent than normal practice, under sized air cooled condenser based on annually averaged ambient temperature rather than based on summer ambient temperature resulted in insufficient condensing capacity that leads to reduction of power generation capability in summer months, etc.
For example, western design would use 1 00% excess air to burn MSW having a lower heating value (LHV) of2,300 kcal/kg or above, but in Taiwan 80% excess air is more commonly used as the maximum excess air for burning MSW at the claimed MeR condition.
Another example is about the percentage of split between the primary and the secondary air. In order to have the flexibility to burn wastes with a wide range of heating value, moisture content and volatility of organic matters, a good design would allow the plant to be operated with a secondary air percentage (measured by weight) varies within the span of 20% to 40% while allowing the plant to be operated with a primary air percentage varies within the span from 80% to 60%[8] . This means the plant would have to be designed with bigger air fans to allow a maximum of 1 20% (i.e. 80% + 40%) of total combustion air output and hence the associated air ducts have to be bigger too.
However, in Taiwan, the common design practice is to simultaneously cap the maximum quantity of total combustion air and the split ratio between the primary and the secondary air. The total capacity of the combustion air fans is capped at 1 00% of the MeR condition. The maximum capacity of the primary combustion air fan is capped at 80% of the MeR condition while the maximum capacity of the secondary combustion air fan is capped at 20% of the
MeR condition.
Under this kind of constraint, the maximum combustion air can be delivered by air fans is 1 00% of designed MeR rate and that is lower than the western design of 1 20% of the MeR rate as mentioned above. Of course, the associated air ducts and flow measurement devices are also proportionally smaller.
If the application is to burn waste that requires using 40% of the air as the secondary combustion air in order to complete the combustion in the first pass of combustion chamber, the operator is forced to reduce the throughput to under the 70% (calculated at 20% + OA = 50%) level and often this is not a stable condition for operating the stoker. Using less excess air and lower percentage of secondary air do make the combustion chamber smaller but at the expense of losing the plant's operational flexibility of burning
218
waste with a high percentage of volatile organic matters.
By integrating all systems that are individually designed with minimal margin for operational fluctuation into a process, the combined effects of the marginal design of each system often make the process control system unable to stabilize the combustion and process operation and eventually leads to throughput reduction. Human intelligence is therefore needed to be re-introduced to the day-to-day operational control by switching certain functions from fully automatic mode to semi-automatic mode or manual mode in order to overcome the challenges.
There is no practical solution for dealing with the marginal design weakness other than cut down the throughput. Plant operator can also push the throughput close to the originally claimed MeR rate at the expense of higher maintenance and equipment replacement costs.
8. Problem of drastic steam flow fluctuation
For reasons mentioned above, it is not uncommon to see WTE plants in Taiwan operated with ± 30% of the steam flow fluctuation in one hour especially when IW is co-incinerated. The impacts brought upon by the fluctuation of the steam flow not only result in shortened service life of the superheater tubes but also turbine trips from time to time.
Turbine trips can happen when the steam flow is low or when the drop of the steam flow takes place suddenly. The highest chance a turbine trips happens when these two factors takes place simultaneously.
Steam flow is low when the plant is running at partial loading due to the conduct of plant major overhaul on rotating basis, fixing up of broken boiler rubes, insufficient supply of wastes temporarily and/or regulatory demands as a result of failing emission audit tests forcing certain individual boiler line to shut down.
Normally, the set point for controlling the steam flow is tuned at the designed MeR condition. The steam flow, however, fluctuates all the time within a span during normal runs, with the high point reaching at approximately 1 0% above the MeR condition and a low point reaching at approximately 1 0% below the
MeR condition on the hourly averaged basis. The 20% span (± 1 0%) of steam flow fluctuation is considered acceptable for most WTE plants. Some plants can operate within a span of 1 0% (± 5%) fluctuation. In any case, most WTE plants are designed with a maximum tolerable high point of 5 to 1 0% above the
MeR condition.
Copyright © 2004 by ASME
However in the reference plant, the steam flow can fluctuate with a span of ± 30%. This means the high point can be 30% higher than the set point. If the set point is tuned at MCR condition, the high point would become 20% above the maximum tolerable limits (30% - 1 0%) and become harmful to the plant operation. Therefore, plant operator is forced to tune the set point at 80% of the MCR condition in order to maintain the high point at the level of 1 0% above the original designed MCR condition. This also means the low point would become 50% of the original designed MCR condition. The fluctuation of the steam flow and its impact on control set point are illustrated in figure-4.
Steam flow can suddenly drops down to the 50% level as mentioned above when the system fluctuates to the low point of the span. While this is happening, the steam extraction flows can also remain open due to the time laps before extraction valves close.
If all of these factors happen at the same time meaning running the plant at partial load, steam flow fluctuates to the low point of the span and the extraction flows remain open, it is not uncommon to see steam flow to swing suddenly from 50% to 25% of MCR condition in just a few minutes time. The result is for turbine to trip and subsequently causing revenue loss from not getting the capacity payment of the power sales.
Up to date, there is no good solution to avoid steam turbine trip for as long as the steam flow remain fluctuating in wide span as the consequence of burning high percentage of IW in a marginally designed WTE plant.
9. Combined problem of co-incineration and inadequacy of plant performance test
Although plants upon completion have to pass acceptance tests, unfortunately the design weakness cannot be detected during the so-called typical acceptance tests easily.
As required by the government, typical acceptance test of plants newly built include two major kinds of tests, the performance test and the overloading test.
The purpose of the performance test is to demonstrate that the plant can run at 90% of the MCR condition in terms of throughput measured by the weight of the waste incinerated during a 30-day continuous run. While in the test, down times are allowed if each down time does not exceed 32 hours.
Two things are worth noting here. First, the down time is recognized when steam production is dropped below
2 1 9
50% of the designed MCR flow rate on an hourly average basis. Second, the performance tests are mostly conducted on clean boiler heat transfer surfaces, i.e. almost completely new boiler heat transfer surfaces. This is unlike the typical performance test in which boiler heat transfer surfaces should be pre-conditioned to 85% of the original cleanness.
During the overloading test, the plant is required to run continuously for 2 hours at 1 1 0% of the MeR throughput measured by the weight of the waste incinerated to demonstrate the performance of the systems under overloading condition. This time duration is far less than sufficient to determine the plant is indeed able to handle over loaded operation continuously for two reasons. First, the overloaded waste fed into the system during the two-hour test period does not necessarily mean they get completely burned in the meanwhile. Secondly, the 1 1 0% of waste feed rate is conducted when the boiler heat transfer surfaces are clean and this may not guarantee that the plant can run at 1 00% MCR during normal operations.
In addition, the waste used during the performance test is often specially prepared, with a large percentage of wood and paper, and is different from the actual waste received during commercial operations. Under this kind of scenario, not all points in the envelope of the fuing diagram can be thoroughly and properly tested. Many hidden design weakness are discovered later and the associated long-term impacts are then experienced by the facility operator who will suffer from all kinds of technical difficulties and cost increases due to frequent replacement and repair of parts and equipment.
Examples of design weakness not discovered during the performance test and the associated impacts:
• Performance test only demonstrated the plant can deliver 1 00% excess air based on simplified wastes and tests.
F or example, the reference plant could run at 1 00% excess air during the performance test based on incinerating simulated wet wood and paper which have higher carbon-to-hydrogen ratio. However, in order to maintain the same level of the pressure drop, the plant could only run at 80% excess air during commercial operation that treats MSW and IW as received from the neighborhood and market, i.e. waste of lower carbonto-hydrogen ratio.
In addition, when burning IW such as scrap plastics and rubbers at MCR weight throughput, excess clinkers quickly formed on the stoker due to localized overheating phenomenon, and excess slag built up on
Copyright © 2004 by ASME
the refractory wall due to flame impingement. Cutting back the tonnage throughput only helps to increase the flue gas residence time but can not help to avoid localized overheating problem and the uncontrollable flame impingement. To solve a problem of this nature, the operator would need to have more flexible and stronger ability to inject more secondary air with better freeboard mixing quality. Unfortunately, demonstration of this kind of flexibility is not a requirement of the performance test and it is often too late or not practical and economical to make a plant with such modification extent in order to attain the operational flexibility.
• Performance test only demonstrated the reference plant meet the on-line availability based on burning simplified waste and simplified test.
For example, boiler fouling effect was insignificant when burning the simulated waste like wet wood and paper even for a long duration. Yet when burning IW such as auto fluff that contains a high percentage of sulfur, chlorine and metals, even if the auto fluff comprises only 1 0% of the waste, the generated fly ash would contain sufficient metal sulfides and metal chlorides to cause the fly ash become sticky enough at the nominal flue gas temperature, and quickly build up on the incinerator refractory walls and between superheater tube spacing. The sticky fly ash built up subsequently leads to increased pressure drop and flue gas exit temperature, and eventually decreased throughput.
Cost Impacts Brought by Technical Challenges
The cost impact due to technical difficulties is highly significant. Frequent damage of the boiler tubes can cost more than a million US dollars of the out-ofpocket money per year, just to fix up the tubes and the damaged refractory.
In addition, due to the technical difficulties faced in the reference plant and the stretched application of burning a high percentage of IW, the incurred cost for replacing parts during major overhauls, washing boiler, removing accumulated fly ashes and slag and others can amount to a couple of millions of US dollars per year, all outof-pocket, even when the plant is still relatively young.
In contrast, a properly designed plant with normal application of burning MSW, the cost for replacing parts, washing and cleaning the boiler would not be more than one million US dollars per year when plant is still relatively young and the cost for fixing up the broken boiler tubes should be none, or at minimum if any.
220
On top of the costs mentioned above, loss in power sales and waste tipping fee due to technical problems are also another major fmancial loss stream.
Another significant cost due to co-incineration is the use of cement and chelate to stabilize and solidify the generated fly ash. More than a million US dollars per year are spent in order to comply with regulatory requirement on fly ash for plants co-incinerating IW while WTE plants burning MSW only would cost significantl y less.
Conclusions
Based on almost two decades of experience in the US, Taiwan, Philippines, China, Thailand and Hong Kong , the author believes there are significant aspects of the Asian WTE industry that are worth noting by western WTE plant developers, designers, constructors and operators, especially by those who are interested in getting involved in the Asia's waste incineration market. These hands-on experience discussed in this paper can be summarized to the following key points.
Firstly, it is a fact that the wastes generated in Asia, be them MSW or the IW, are more heterogeneous than we normally see in the western world. There are always some industrial wastes mixed in the domestic wastes because of lack of clear distinction of residential area from commercial zones, as well as different living habit, cultural background and waste collection system. Therefore, MSW seen in Asian countries is not as "pure" as the MSW collected in western world.
The waste characteristics of IW are more affected by Asia's fast evolving economy that changes rapidly in base, scale, type and distribution. In addition, some waste streams we normally category as hazardous waste in the western world would be recognized as non-hazardous waste in Asia and some wastes normally category as industrial waste in the western world would be recognized as domestic waste in Asia.
Secondly, it is crucial to verify that the plant acceptance test was done based on burning MSW plus IW if the future application is to co-incinerate MSW with IW or to burn so-called MSW but actually mixed with IW. It is also equally important to ensure the performance test yet to be done will be conducted based on wastes resembling the waste to be incinerated in the future commercial operations.
It is also important to test out the plant with all possible variations in terms of waste characteristics and throughput and the test has to be long in duration, preferably extended to a couple of months continuously. It will be vary risky for a project if the
Copyright © 2004 by ASME
plant is tested out j ust based on simulated wastes with simplified conditions.
Thirdly, it is always a good practice to appoint a third party professional to verify the plant design, construction and functional capacities if the plant designer and operator are not the same party. It costs money but will bring crucial benefits to the investor and operator.
Fourthly, western operational experience is not always sufficient in Asia. Instead, it is always a good and cautious practice for day-to-day project management to calculate and verify operational parameters based on engineering and tedmical fundamentals, at the same time taking into account of the complexity of the waste composition, variation of volatile organic matters, hidden design weakness, etc. so that operational conditions can be optimized promptly.
References
[ 1 ] Themelis, Nickolas 1. , "An overview of the global waste-to-energy industry", Waste Management World, 2003 - 2004 Review Issues, July - August 2003, p. 40 - 47.
[2] International Source Book on Environmentally Sound Technologies for Municipal Soild Waste Management, published by International Environmental Technology Center, United Nations Environment Program.
[3] Shu, Abraham, "Waste Incineration in Taiwan", EUROVIEW, 77, July - August 200 1 , p. 1 4 - 1 8. www.ecct.tw/euJoview/issue77 /enroview article? 5 J2.lm
[4] Shu, Abraham and Hsieh, Rosalia, "Overview of Solid Waste Incineration and Management in Taiwan", Pacific Economic Cooperation Council, Sustainable Urban Services, Shanghai Seminar, April 2003 Report, pp. 1 1 7 - 143. www.pecc.org/community/cities-papers-
content. htm
[5] Design and Selection Manual for Industrial Waste Incinerator, Publication No. B0239, published by the Industrial Development Bureau of Ministry of Economic Affairs, Taiwan, Republic of China.
[6] Lee, C.C. and Lin, Shun Dar, 2000, Handbook of Environmental Engineering Calculations, McGraw Hill, New York, pp. 2.558.
[7] Kubin, Peter Z., Paper No. 90, "Materials Performance and Corrosion Control in Modern Waste-to-Energy Boilers, Applications and Experience", Corrosion 99, published by NACE
221
International, Houston, TX.
[8] Glysson, Eugene A., 1 989, "Solid Waste", Standard Handbook of Environmental Engineering, McGraw Hill, New York, pp. 8 . 1 55-8. 1 64.
List of Figures:
Figure- l :
Figure-2:
Figure-3:
Figure-4:
Statistics of WTE plants and waste incineration status in Taiwan.
Photo showing boiler screen tube rupture due to flame impingement.
Photo showing excess molten slag build up on the rear wall of the combustion chamber.
Schematic diagram showing the steam fluctuation and the influence on the flow set point.
About the Author - Mr. Abraham SHU
Mr. Shu attained his master degree in Chemical Engineering from Stevens Institute of Technology in New Jersey. He further pursued advanced industrial and business finance and law trainings from accredited U.S. academic institutions and became actively involved in the business development and management in the energy and environmental protection industry.
Mr. Shu started out his career by working for multinational companies based in U.S. in 1 98 1 . While working for Ogden Energy Group, Inc. (renamed as Coventa since 2000), he was promoted from Process and Technical Manager to the Engineering Director, later straight to Corporate Vice President and took up the leading role in business development and operations for the company in Asia from 1 995. Appointed as the General Manager by Swire SITA, a joint venture between the Swire Group of British origin and Suez Environment of French origin, for its Taiwan establishments in 1 999, Mr. Shu has been responsible for all business development and operations for Swire SITA in Taiwan till date.
Mr. Shu has been an advisor to the government of the Philippines, China and Taiwan on Independent Power Proj ects (IPPs) and waste management affairs, and has delivered advisory speeches and published numerous articles.
Copyright © 2004 by ASME
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Figure-3: Photo showing excess molten slag built up on the rear wall of the combustion chamber of the reference plant
223 Copyright © 2004 by ASME
Figure-4: Schematic diagram showing the reference plant's steam fluctuation and the corresponding flow set point adj ustment
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139
6
Tab
le-2
0 A
nal
ysi
s o
f a
rep
rese
nta
tiv
e M
SW
an
d I
W M
ixtu
re
Pro
ject
NoO
PJ9
1023
W
eath
erOS
unny
Rep
ort N
oOP
J91 0
23
Sam
plin
g D
ateo
Janu
ary
15, 2
00
2 P
ageD
1 o
f I
Sam
pli
ng L
ocat
ion
W
aste
Sto
rag
e P
it
Bu
lk D
ensi
tyoK
g/m
3o 2
58
'"0
()
Pap
er
00
0
29.4
2 ::
:r 0
'<
g. F
ibro
us, C
loth
DO
D 6
.71
en o·
�
�
en
Woo
d, h
ay, t
ree
leav
es
DOD
6.5
3 ()
go
Kitc
hen
was
te
000
4.6
4 0
0-.g
Pla
stic
s DO
D 3
1.9
1 0 �.
L
eath
er, s
crap
rub
ber
000
0.1
3
- o· ::s O
ther
s 00
0 10
.57
CJ
t:
:J T
otal
DO
D 89
.91
� tc
n
::s M
etal
DO
D 4
.82
I>l
�.
o 0
en S
::s G
lass
00
0 2
.36
CJ
0"
"' �
C
eram
ic
DOD
en 1.
64
- 5'
Sand
, gra
vel
000
0-1.
27
Tot
al
DOD
10.0
9
()
Wat
er
000
44
.48
g-A
sh
000
11.8
9 2. n
C
ombu
stib
le
DOD
43.
63
�
()
Car
bon
000
25.
35
0 .g H
ydro
gen
DOD
4.0
0
0 00
0 13
.67
:a.
Oxy
gen
o·
N
itro
gen
000
0.3
0
::s CJ
� Su
lfur
000
0.2
0
-O
rgan
ic c
hlo
rin
e 00
0 0
.11
tc
I>l �.
C/N
rat
io
000
85
en CJ
HH
VoK
cal/
kgo
000
285
3
LH
VoK
cal/
kgo
000
237
0
!
N
N
0\ n
o '"0
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go
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tv
o
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cr
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3:
l"Ti
NO
.
00
1
00
2
00
3
00
4
00
5
00
6
00
7
00
8
00
9
010
Oil
012
013
014
015
Tab
le-3
DIW
C
Was
te C
ateg
ory
Veg
etab
les
Was
te
0-0
010
)
Ani
mal
Was
te
0-0
010
)
�cra
p Pl
astic
0
-00
20
)
Scra
p R
ubbe
r 0
-00
30
)
Scra
p T
ire
0-0
03
2)
Sew
age
Slud
ge
0-0
09
0)
JPetr
oleu
m In
dust
ry O
ily
Slu
dge
(0-0
09
3)
IPetr
oche
mic
alln
dust
ry
Slud
ge (
0-0
09
1)
!Elect
roni
c /
Com
pute
r nd
ustr
ial
Slud
ge (
0-00
92
)
!Pape
r In
dust
ry S
ludg
e 0
-00
91)
food
Indu
stry
Slu
dge
0-0
09
1)
Lea
ther
Indu
stry
Was
te
0-0
160
)
Scra
p Pa
per
0-0
06
0)
Scra
p L
umbe
r 0
-00
70
)
!Fibro
us W
aste
0
-00
80)
t An
al
Pro
xim
ate
An
aly
sis
(WtO
O)
Org
anic
H
2O
A
sh
20
.65
78
.29
1.
06
58
.15
3
8.7
4
3.1
1
88
.00
2
.00
10
.00
88
.92
1
.20
9
.88
92
.43
1.
02
6
.55
30
.33
6
5.7
8
3.8
9
47
.91
30
.05
2
2.0
4
52
.00
18
.00
3
0.0
0
8.3
6
66
.55
2
5.0
9
9.2
1 8
7.8
3
2.9
6
9.7
1 8
8.1
0
2.1
9
80
.90
10
.00
9
.10
84
.38
10
.24
5
.38
87
.46
12
.00
0
.54
87
.80
10
.00
2
.20
dH
V
al
Ult
imat
e A
nal
ysi
s (D
ry a
nd
Ash
Fre
e B
asis
) W
t 0%
H
HV
(K
cal /
Kg
) L
HV
(K
cal/
Kg
)
Dry
an
d A
sh
Dry
an
d A
sh
C
H
0
N
S
CI
Oth
ers
Wet
Bas
is
Fre
e B
asis
F
ree
Bas
is(a
) W
et B
asis
(M
easu
red
) (M
easu
red
) (C
alcu
late
d)
(Ca \
cula
ted
)
51.
58
6
.96
3
9.4
8
1.7
7
0.2
1 0
.00
0
.00
9
97
4
83
3
47
31
50
5.2
5
62
.78
9
.98
2
5.9
7
1.0
7
0.2
0
0.0
0
0.0
0
42
35
7
28
3
68
81
37
44
.62
66
.73
8
.02
2
5.1
7
0.0
1 0
.03
0
.04
0
.00
7
83
3
88
89
6
62
2
74
79
.82
85
.33
11
.50
0
.90
0
.05
2
.22
0
.00
0
.00
6
22
2
70
00
9
78
6
57
19.4
3
84
.69
7
.28
6
.32
0
.10
1.
61
0.0
0
0.0
0
76
67
8
27
8
82
83
7
33
5.0
5
46
.82
3
.66
4
0.0
2
5.9
0
1.8
8
1.7
2
0.0
0
110
8
36
53
3
23
5
69
9.5
5
83
.63
12
.44
3
.00
0
.14
0
.72
0
.07
0
.00
4
60
8
96
19
98
54
4
156
.86
84
.00
11
.35
2
.22
0
.03
1.
06
1.
34
0
.00
4
47
3
N-
A
95
51
40
89
.63
21.
47
1
1.2
4
59
.73
2
.20
4
.00
1.
36
0
.00
3
21
38
44
3
844
-8
2.9
6
I I 5
4.8
6
6.5
0
34
.98
3
.47
0
.12
0
.07
0
.00
5
14
55
76
5
576
11
.05
I
52
.89
6
.72
3
2.5
6
7.3
8
0.3
7
0.0
8
0.0
0
52
9
54
53
5
45
3
22
.88
66
.74
8
.90
12
.79
1
1.1
2
0.4
5
0.00
0
.00
4
42
2
54
72
6
93
6
40
18.7
8 !
48
.81
5.8
2
44
.32
0
.25
0
.20
0
.60
0
.00
3
77
8
44
75
40
71
34
84
.55
49
.40
6
.10
4
3.7
0
0.1
0
0.\
0
0.6
0
0.0
0
35
72
4
07
8 4
22
0
32
48
.48
56
.50
7
.60
3
1.3
0
4.2
1 0
.14
0
.25
0
.00
3
83
3
43
58
54
44
3
45
5.3
6
tv
tv
-...J ()
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(lQ go
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N
o
o
�
cr
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tTl
NO
.
016
017
018
019
02
0
02
1
02
2
02
3
02
4
02
5
02
6
02
7
02
8
Tab
le-3
DIW
C
Was
te C
ateg
ory
rons
truc
tion
Oeb
ris
0-0
050
)
Was
te S
olve
nt
Ele
ctro
nic/
Com
pute
r In
dust
ry) (
D-0
150
)
Hig
h E
nerg
y C
onte
nt W
aste
So
lven
t -C
hem
ical
indu
stry
0
-0(5
0)
Was
te S
olve
nt
Petr
oleu
m P
rodu
ct
Indu
stry
(0-0
[5
0)
Low
Ene
rgy
Con
tent
Was
te
Solv
ent -
Che
mic
al in
dust
r 0
-015
0)
p rga
nic
Con
tam
inat
ed
[Aque
ous
Was
te (
0-0
150
)
Iwast
e O
il O
-O[ 5
0)
Ash
I Sl
ag I
Met
al
Con
tain
ers
0-0
130
,D-0
13I,
O-0
132
)
Aut
o F
luff
0
-019
2)
Mix
ed E
lect
roni
c I
Com
pute
r In
dust
ry W
aste
Coo
ling
Wat
er
Coo
ling
Air
Com
pute
r PC
Boa
rd
Anal
d
Pro
xim
ate
An
aly
sis
(WtO
O)
Org
anic
H
2O
A
sh
30
.00
3
8.5
5
31.
45
86
.00
8
.00
6
.00
74
.00
8
.00
18
.00
90
.00
2
.00
8
.00
79
.00
[7
.00
4
.00
1.0
0
98
.00
1.
00
91.
70
4
.60
3
.70
1.5
0
3.0
0
95
.50
42
.00
10
.00
4
8.0
0
28
.00
[2
.00
6
0.0
0
0.00
10
0.0
0
0.0
0
0.0
0
0.0
0
0.0
0
44
.56
0
.40
5
5.0
4
--
--
--
-0
--
--
-
Ult
imat
e A
nal
ysi
s (D
ry a
nd
Ash
Fre
e B
asis
) W
t 0
%
C
H
0
N
S
Cl
Oth
ers
51.
21
7.3
8
38
.61
2.3
6
0.2
6
0.1
8
0.0
0
72
.05
9
.75
8
.90
0
.00
0
.00
9
.30
0
.00
85
.52
12
.35
1.
00
0
.00
0
.00
\.
13
0.0
0
73
.57
13
.20
13
.01
0.0
0
0.00
0
.22
0
.00
33
.86
7
.20
2
5.9
9
0.0
0
0.0
0
32
.95
0
.00
91.
32
8
.68
0
.00
0
.00
0
.00
0
.00
0
.00
88
.70
9
.30
0
.70
0
.30
0
85
0.1
5
0.0
0
78
.52
10
.35
0
.00
0
.00
0
.00
11.
13
0.0
0
76
.03
9
.76
13
.04
0
.03
\.12
0
.02
0
.00
66
.73
8
.02
2
5.1
7
0.0
1 0
.03
0
.04
0
.00
0.0
0
0.0
0
0.0
0
0.0
0
0.0
0
0.00
0
.00
0.0
0
0.0
0
0.0
0
0.0
0
0.0
0
0.00
0
.00
64
.00
7
.89
2
2.2
8
1.6
3
0.0
2
4.1
8
0.0
0
HH
V (
Kca
l/ K
g)
LH
V
(Kca
ll K
g)
Dry
an
d A
sh
Dry
an
d A
sh
Wet
Bas
is
Fre
e B
asis
F
ree
Bas
is(a
) W
et B
asis
(M
easu
red
) (M
easu
red
) (C
alcu
late
d)
(Cal
cula
ted
)
156
3 5
210
4
83
7
124
7.7
8
I 6
65
7
N-A
7
79
1 6
20
7.4
5
I I 7
34
8
N-
A
99
87
6
86
\.12
i , 8
132
N
-A
90
47
7
54
4.4
2
I I
24
17
N-
A
317
6
20
49
.68
I !
93
N
-A
93
48
-4
39
.00
92
35
10
017
9
33
0
87
96
.46
130
N
-A
866
2
106
.22
,
33
92
N
-A
82
04
3
138
.85
178
9
N-A
6
62
2
1615
.73
0
N-
A
0
-53
9.06
0
0
0
0.0
0
28
15
N-
A
63
22
2
64
2.2
8
