Document N2d8RkJe0xOowj1vEZL9xkJ3y

tp Hydroscience MONSANTO WASTE THERMAL OXIDATION PROCESS DISCUSSION REVIEW AND SUMMARY (INCLUDING NITRO LIQUID ALTERNATIVE) PROJECT MEETING, MARCH 23, 1979 MONSANTO CHEMICAL St. Louis, MO Submitted April 11, 1979 0583707 HYDROSCIENCE. INC.*9041 EXECUTIVE PARK DRIVE KNOXVILLE. TENNESSEE 37919 <615) 690-3211 EMERSON, NJ WEST WO 00. NJ* WALNUT CREEK. CA* ARLINGTON, TX TOWOLDMONOQ59436 I. INTRODUCTION After the process development package (2 volumes) for a rotary-kiln-based waste thermal oxidation process was submitted to Monsanto by Hydroscience on March 6, 1978, several changes were made that affect the scope of the project. Two of these changes were subjects of discussion at a project meeting in St. Louis on March 23, 1979. The principal change in scope involves an operating temperature of 2200F as stipulated by the State of Illinois in their permit to construct and potentially supported by the federal government through a future RCRA Standard. The second change involves an updating of the characterization of the Monsanto waste profile for identification of minor changes in the quantity and quality of waste solids and liquids to be destroyed in the process. A summary of the meeting discussion and the project ramifications of these changes are contained in this document. * 0583708 TOWOLDMONOQ59437 II. CONCLUSIONS AND RECOMMENDATIONS The minor changes resulting from an updating of the characterization of Monsanto wastes have no significant impact on the design and operation of the thermal oxidation process. The change to an operating temperature of 2200F in the secondary combustion chamber, however, alters the heat duty requirement of the secondary chamber to the extent that substantial auxiliary fuel would be needed to supplement identified secondary-quality liquids in the Monsanto waste profile previously established. Concurrently, the capacity of the proposed system to handle Monsanto wastes would be reduced by the amount of auxiliary fuel that would be needed if additional secondary-quality waste liquids are not available.. An alternative to the use of auxiliary fuel involves changing the manner in which the nitro liquids are handled so that their heats of combustion can be utilized in the secondary combustion chamber. An alternative concept is suggested in which the nitro liquids would be fired in a reducing combustion chamber addition to the secondary combustion chamber of the main system. The oxidation process would be completed in the secondary combustion chamber, allowing the nitro liquids to provide the heat needed in secondary combustion to operate at 2200F without auxiliary fuel. It is proposed that the initial combustion of the nitro liquids under reducing conditions will control the formation of NC>x to acceptable levels in the system. Indicated savings in operating costs along with possible savings in capital costs indicate that the proposed alternative concept for the thermal oxidation of the nitro liquids should be investigated further through pilot tests to demon strate performance and obtain design data. It is believed that this testing can be conducted satisfactorily in existing vendor pilot equipment. -2- lO'' TOWOLDMONOQ59438 III. DISCUSSION A. UPDATED BASIC WASTE PROFILE The updated Monsanto waste profile is summarized in Figure 1. This summary identifies the total average heat duty of all waste materials based on 7008 hr of operation annually. It also indicates the distribution of the average heat duty between liquids and solids and identifies those liquids scheduled for firing in the primary chamber (rotary kiln). The remainder of the liquids have suitable physical and chemical characteristics for firing in a secondary combustion chamber. The liquid and solid waste materials scheduled for firing in the primary chamber constitute 53.94% of the total waste profile heat duty. The previous average waste profile totaled 42.07 MM Btu/hr compared with the updated total of 39.75 MM Btu/hr. Although the total is down slightly, increases can be seen in the heat duty of the solids (26%) and the secondary-quality liquids (10%). . B. SYSTEM HEAT DUTY REQUIREMENTS The design thermal oxidation temperature in the primary chamber is 1500F. The combustion gases from the primary chamber are treated in a secondary chamber to destroy residual combustible gases and particulates. Direct firing of secondaryquality fluids in the secondary combustion chamber provides the heat to achieve the desired operating temperature. In the previous plan for design the operating temperature in the secondary combustion chamber was 1800F, except for a short campaign period for PCBs at 2200F. The proposed secondary combustion chamber temperature is 2200F for all modes of operation to meet state and potential federal requirements. The shift in system heat duty distribution when the secondary temperature is raised from 1800F to 2200F is illustrated in Figure 2. A com parison of the fraction of the total heat duty required in the secondary combustion chamber (Figure 2) with the fraction of the total heat duty available as secondaryquality fluid (Figure 1) shows that there is a deficiency in secondary-quality fluids for the 2200F secondary combustion temperature case. When the updated waste profile (Figure 1) is translated into a heat duty profile for a thermal oxidation system at the previous design capacity of 60 MM Btu/hr and a secondary combustion temperature of 2200F (Figure 3), it can be seen 0583710 TOWOLDMONOQ59439 MONSANTO THERMAL OXIDATION SYSTEM BASIC WASTE PROFILE AND CLASSIFICATION SUMMARY Classification _________Waste flHc MM Btu/hr Primary Chamber Liquids 1. PCBs 2. N02 Tars 3. Wet Wastes 4. Special Handling Total Liquids 1.08 9.90 5.62 0.13 Solids 1. Tars 2. Filter C 6 Cart. 3. Lab Wastes Total Solids Total Primary Wastes 3.64 0.90 017 4.71 21.44 53.94 Secondary Chamber Secondary Quality Liquids Total Waste Duty 1031 39^^75^ 46.06 100.Q0 Figure 1 MONSANTO THERMAL OXIDATION SYSTEM SYSTEM HEAT DUTY REQUIREMENTS I teii) Sec. Combustion Conditions Primary Chamber Secondary Chamber Heat Put1/ Distribution, % 1800F 165% XS Air 2200 F 115% XS Air 68.7 31.3 100.0 45.9 54.1 100.0 Figure 2 0583711 TOWOLDMONOQ59440 MONSANTO THERMAL OXIDATION SYSTEM System Heat Duty Profile at 60 MM btu/hr Capacity - 2200F Secondary Combustion Temperature. NO- Tars Fired in Primary Cnamber. Item Primary Chamber Primary Liquids and Solids Secondary Cnamber Secondary Quality Liquids '. Auxiliary Fuel Total System Capacity Total Waste Capacity Heat Duty MM Btu/hr 27.54 23.52 8.94 60.00 51.06 Figure 3 MONSANTO THERMAL OXIDATION SYSTEM Basic Waste Profile with N02 Tar3 Assigned to Secondary Combustion Classification Primary - Liquid Solids Primary - Total Secondary Liquids N02 Tars Secondary - Total Total Waste Duty 6.83 4,71 18.31 9.90 Waste .! He MM Btu/hr S 11.54 29.03 26.21 39^5 . 70.97 103.00 Basic Waste Profile Allocation to Satisfy System Heat Duty Requirements at 2200F I tern Primary Chamber Primary Liquids Solids Secondary Liquids Total Primary Chamber Secondary Chamber Secondary Liquids NO2 Tars Total Secondary Cnamber TOTAL SYSTEM System Heat Duty, MM Btu/hr 6.83 4.71 6.71 11.60 9.90 21.50 39.75 Figure 4 0583712 TOWOLDMONOQ59441 ' that there is a significant 8.94 MM Btu/hr demand for auxiliary fuel in the secondary combustion chamber, and the total capacity of the system to handle wastes is limited to 51.06 MM Btu/hr. This capacity is only 28% more than the basic profile. C. NITRO LIQUID CONSIDERATIONS Through process-development thermal oxidation tests it was determined that the production of NO^ could be limited by firing the nitro liquids in the rotary kiln in a manner that produces a fuel-rich flame envelope. As a result the waste nitro liquids were included in the primary combustion chamber duty in the previous plan for design. In the opinion of Hydroscience this technique cannot be applied successfully to firing directly in the secondary combustion chamber. Limiting the formation of NO^, however, was the only consideration in assigning the nitro liquids to the rotary kiln. If a way can be found to utilize the heat from the nitro liquids in the secondary combustion chamber, then 71% of the heat duty in the Monsanto profile is available for secondary combustion, as is illustrated in Figure 4. Since all of this heat is not required, utilizing the nitro liquids for secondary combustion would force a portion of the secondaryquality liquids into the primary chamber, as indicated in a restatement of the basic profile for a system operating at a 2200F secondary combustion temperature (Figure 4). D. PRELIMINARY PLAN FOR DESIGN A preliminary plan for design operating mode for the basic waste profile, with the heat from nitro liquids assumed to be utilized in the secondary combustion chamber, is shown in Figure 5. This plan increases the handling of solids from two shifts/day to three shifts/day during the week because of the reduction from the previous plan in the duty of the primary chamber as a percentage of the total duty. The heat duty in the primary chamber dictates the combustion air flow rate through the kiln which must supply the excess air to absorb the fluctuating heat released from the combustion of the solids. A rotary-kiln heat duty of 20 MM Btu/hr is considered to be minimal for a system handling solids in drums. At this minimum heat duty it becomes increasingly important to restrict the organic contents of the drum to solid materials that will not melt and burn rapidly. 0583713 -6- TOWOLDMONOQ59442 MONSANTO THERMAL OXIDATION SYSTEM PRELIMINARY PLAN FOR DESIGN Base Case - Weekday Operation w/o PC3s 22Q0F - 60 MM Btu/hr Capacity Item Primary Chamber Primary Liquids Secondary Liquid: Solids Total Primary Secondary Cnamber Secondary Liquids N02 Tars Total Secondary TOTAL SYSTEM heat Duty, ,`iM Btu/hr 8.05 5.35 6.60 20.00 13.67 9.90 24.56 43.57 Comments 3 shifts Weekend Operation Primary Chamber PCa Liquids ` Secondary Liquids Total Primary 3.78 9.99 13. 77 Secondary Cnamber N02 Tars Secondary Liquids Total Secondary TOTAL SYSTEM 9.90 6.33 16.23 30.00 Figure 5 2/1 Turndown MONSANTO THERMAL OXIDATION SYSTEM PREVIOUS PLAN FOR DESIGN Base Case - Weekday Operation w/o PCB 18Q0F - 60 MM Btu/hr Capacity Item Primary Chamber Liquid Wastes NO2 Tars Solids Total Secondary Chamber Secondary Liquids TOTAL SYSTEM Heat Duty, MM Btu/hr 9.4 11.7 29.9 13.6 43.5 Comments ' Primary & Secondary Quality Liquids 2 shifts/day Figure 6 0583714 TOWOLDMONOQ59443 The plan for design operating mode also illustrates the handling of PCB liquids during the weekends without the fluctuating effects of solids in the system. If weekend operation is restricted initially to 30 MM Btu/hr, which is a 2:1 turndown for a 60 MM Btu/hr capacity system, the average duty for the total week is equal to the basic profile duty of 39.75 MM Btu/hr. For purposes of comparison the previous plan for design weekday operating mode is illustrated in Figure 6. It can be noted that for the same approximate total system heat duty the heat duty in the rotary kiln is 29.9 MM Btu/hr compared with 20 MM Btu/hr in the present preliminary plan for design operating mode. E. NITRO LIQUID THERMAL OXIDATION ALTERNATE One of the considerations in planning for the thermal oxidation of a nitrogencontaining organic is the thermodynamic equilibrium concentration of nitric oxide (NO) at high temperature. Figure 7 illustrates the equilibrium NO:theoretical 02 ratio as a function of temperature and excess air. As can be seen, this ratio increases rapidly with temperature. Since the excess air in the system is related to the operating temperature, when negligible heat is transferred and no secondary heat sink (such as H20 injection) is added, the calculated NO equilibrium concentration for various temperatures is shown at corresponding adiabatic excess air values in Figure 8. Without nitrogen in the organic molecule the equilibrium NO values normally are not attained because of reaction rate limitations (Figure 9). With nitrogen in the molecule there is evidence that this nitrogen has a kinetically easier route to NO, and higher concentrations of NO can be expected. F. TWO-STAGE COMBUSTION CONCEPT The proposed alternative technical approach to the thermal oxidation of the nitro liquids is to use a burner operating under reducing conditions to reduce all the nitrogen in the waste to elemental nitrogen before the oxidation process is completed in an excess 02 environment. This concept is illustrated in Figure 10 as a totally separate thermal oxidation system for nitro liquids. This system was presented and discussed in Volume I of the process development package, dated March 6, 1978. ,1** 0*7 -8- TOWOLDMONOQ59444 TOWOLDMONOQ59445 Table X. EQUILIBRIUM CONCENTRATIONS AND TIMES OF FORMATION OF NITRIC OXIDE AT ELEVATED TEMPERATURES AT 75 PERCENT NITROGEN AND 3 PERCENT OXYGEN Temperature, F 2,000 2, 400 2, 800 3,200 3,600 Equilibrium concentration of nitric oxide. PPma 180 550 l. 380 2,600 4. 150 - Time of formation of 500 ppm NO, seconds*1 1, 370 16.200 I. 100 0. 1 17 aHoujjen and Watson, 1945. ^Daniels and Gilbert. 1 9*4H. Figure 9 -10- TOWOLDMONOQ59446 RECYCLE COMBUSTION CAS I Atoaixlrtq SUM t- - 1______________ ;L - ------ -- M- . . ..... ....... Figure 10 T~ --------------------- Hydrotcience CONCEPTUAL DESIGN t"ahal oxidation 0583718 LIOUID NITRO HASTES TWO STACE COMBUSTION " | ' u.v l*`" ,, . . TOWOLDMONOQ59447 It is proposed that the two-stage combustion approach be considered again as a means of oxidizing nitro liquids with NO^ control while making the heat avail able for secondary combustion. In the suggested variation of the alternative concept illustrated, the primary chamber, operating under reducing conditions, would discharge the product gases into the secondary combustion chamber of the rotary-kiln thermal oxidation process, where combustion would be completed in an oxidizing atmosphere at 2200F. The assumption is that after the nitrogen in the nitro liquid waste is reduced to an elemental form the formation of NO^ would be limited by reaction kinetics similar to the fixation of nitrogen from air under the same conditions. This concept should be piloted to demonstrate performance and obtain design data before proceeding with a process design. G. DESTRUCTION EFFICIENCY At the request of Monsanto, Hydroscience reviewed it's comments to the MCA relative to achieving the proposed principle toxic component destruction efficiencies (DE) of 99.99% for a general, broad based, solid and liquid waste profile. A detailed paper was distributed at the meeting. The conclusions are summarized below. 1. A 99.99% principal toxic component DE is achievable for liquid incinerators that are burning clean low-viscosity fuel oil quality wastes. 2. For a typical industrial liquid and solid waste profile, the 99.99% proposed DE standard can be achieved if the waste materials (which can include bulk or drummed solid residues, sludges, contaminated trash and poor quality waste liquids) are dissolved and upgraded through pretreatment to produce clean solutions of low-viscosity and fuel oil quality. 3. The required pretreatment would be technologically unattainable and economically prohibitive for many industrial waste solid residues, sludges, contaminated trash, and poor quality liquids. 4. The test work performed by EPA under Contract No. 68-01-2966 indicates the following: I TOWOLDMONOQ59448 a. Two demonstration test burns indicated that a 99.99% destruction efficiency was obtained for polychlorinated biphenyls (PCB) and nitrochlorobenzenes (NCB) when they made up 4 to 11% of the total energy released in the system and the remainder of the energy was supplied by clean low-viscosity fuel oil rather than typical industrial wastes. Approximately two orders of magnitude greater amounts of auxiliary fuel per pound of waste were used in these two tests than is typical for state-of-the-art practice. Destruction efficiency values for PCBs and NCBs were not determined at higher ratios of waste to fuel oil as would be considered to be typical of state-of-the-art practice. The high auxiliary fuel usage in the PCB and NCB tests does not demonstrate resource conservation. b. Three other demonstration test burns involved the incineration of aqueous or highly chlorinated liquid wastes and wet polyvinyl chloride (PVC) sludge. Since some of the test data were not included in the report, it was dif ficult to compare the test conditions with state-of-the-art practice. In general, however, it appears that significant amounts of auxiliary fuels were used relative to the quantity of wastes that were fired. The tests were carried out with supplementary clean fuels of high quality. No attempt was made to utilize actual wastes or to simulate industrial wastes as a source of auxiliary fuel in order to optimize disposal capacity within the incinerators or to conserve energy resources. c. The DE of the PVC sludge was determined to be >99.99% by measuring total quantities of chlorinated organics in the flue gas. Since PVC starts to dehydrochlorinate at 100C via a complex decomposition mechanism, much of the chlorine is evolved as inorganic HC1, thereby reducing the potential level of chlorinated organics in the flue gas. The low initial decom position temperature of PVC and the dehydrochlorination characteristics are not representative of typical industrial wastes. Monsanto was interested in Hydroscience's opinion of the destruction efficiencies that will be achieved for principle toxic components in their specific waste profile. At this time, Hydroscience can offer only opinions based on their experience in related waste profiles, since the flue gas samples taken during the previous Monsanto test burn were not analyzed. It is -13- 0583720 T OWOLDMON0059449 Hydroscience1s professional opinion that destruction efficiencies for principle toxic components in the Monsanto waste profiles may range from a low of 99.9 to greater than 99.99%. If the waste material is readily oxidizable, burns cleanly and is low in ash, such as PNCB, high destruction efficiencies can be expected. However, if combustion proceeds with the generation of large amounts of carbonaceous or inorganic particulate matter, lower destruction efficiencies can be expected due to the potential for adsorption of organics onto the par* ticulate. An average destruction efficiency of 99.95% for principle toxic components is Hydroscience's estimate at this time. -14- 0583^21 TOWOLDMONOQ59450