Formation Mechanisms and Mitigation Techniques

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2 k NO ck X DOWN Formation Mechanisms and Mitigation Techniques By Joe DiGiacomo, Flynn Burner Corporation Yaroslav Chudnovsky, Ph.D., Gas Technology Institute

3 Outline NO X formation Ribbon burners what? why? how? Combustion emissions mitigation Optimized control to burn less fuel Combination of firing modes Fuel-gas input modification Concept to market path

4 NO X Formation Fundamentals NOx means NO (~ 90%) and NO 2 in balance Thermal NOx - the reaction of atmospheric oxygen and nitrogen at elevated temperatures via Zeldovich mechanism (main contributor) N 2 + O NO + N (nitrogen dissociates at high temperature) N + O 2 NO + O N + OH NO + H Fuel NOx - the reaction of the organically bound nitrogen in the fuel with oxygen (negligible for NG) Prompt NOx - the reaction of hydrocarbon radicals with atmospheric nitrogen to produce NOx (~ 5%)

5 NO X Mitigation Options Burn less fuel save money and environment! Combine burning modes Burn at lower flame temperature

6 Ribbon Burner Basics All industrial direct-fired food baking ovens use ribbon burners Pipe, extrusion or casting Stainless steel ribbons Linear array of uniform flames across the oven space

7 Burn Less Fuel Optimized control of air-gas ratio Exhaust heat recovery Better insulation

8 Combining Burning Mode Baking process - convection, conduction and thermal radiation Burners operate in convection and flame radiation modes Control strategies zone temperature and air modulation energy distribution approach Combined IR/Ribbon Firing Ribbon Firing Only Infrared Firing Only Optimal balance between burner operation and baking process

9 Lower Flame Temperature Richer combustion (air deficiency) Exhaust gas recirculation (cooling flame with exhaust) Staged combustion (heat removal between stages) Oxygen content reduction (lower O 2 % in the air)

10 Laboratory-scale proof-of-concept Pilot-scale performance evaluation at the OEM facility

11 Full-scale technology demonstration at the participating industrial bakery 40-50% reduction in NO X emissions 5-10% reduction in fuel consumption Environmentally-friendly green bagels Technology transfer is in progress

12 Concluding Remarks Over 13,000 baking facilities nationwide producing over 39,000 tons/year of NO X Environmental regulations getting stricter nationwide While the NO X mitigation techniques are available they have to be cost-effectively adapted to the baking industry applications In order to obtain state-of-the-art green technologies bakers need to expand their preferred vendor network

13 Concept to Market Success Concept idea is born in academia Solution provider translates the idea for technology provider Bench-scale proof-of-concept in laboratory environment Technology provider converts solution into product Pilot-scale technology evaluation and performance characterization Full-scale field demonstration and cost-benefit analysis Technology deployment and commercialization

14 Types of Heat Transfer Conduction Radiation Convection natural Convection forced Dielectric KK 10/30/

15 Thermal Conduction - definition Heat conduction (or thermal conduction) is the transfer of internal energy by microscopic diffusion and collisions of particles or quasi-particles within a body due to a temperature gradient. The microscopically diffusing and colliding objects include molecules, electrons, atoms, and phonons. They transfer disorganized microscopic kinetic and potential energy, which are jointly known as internal energy. Conduction can only take place within an object or material, or between two objects that are in direct or indirect contact with each other. Conduction takes place in all forms of ponderable matter, such as solids, liquids, gases and plasmas. Whether by conduction or by thermal radiation, heat spontaneously flows from a hotter to a colder body. In the absence of external drivers, temperature differences decay over time, and the bodies approach thermal equilibrium. Fourier s Law: q = k ADT q = heat due to conduction (W) k = thermal conductivity ( W m ) A = area in (m 2 ) DT = difference in temperature ( o C) KK 10/30/

16 Examples of Thermal Conductivity Pure Copper 386 W m Pure Aluminum 229 Alumized Steel 95 Cast Iron 52 Carbon steel 48.5 Lead 34.6 Stainless Steel 17.5 Concrete 0.85 to 1.4 Wood 0.15 to 0.2 Rubber 0.15 Cork Board KK 10/30/ W m 16

17 Radiation definition Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. When the temperature of the body is greater than absolute zero, inter atomic collisions cause the kinetic energy of the atoms or molecules to change. This results in charge-acceleration and/or dipole oscillation which produces electromagnetic radiation, and the wide spectrum of radiation reflects the wide spectrum of energies and accelerations that occur even at a single temperature. (Stefan Boltzman equation) q = e x A x s (T e T r ) 4 q is the radiant emission in W A is the area of the emitting surface in m² W e is the Stefan-Bolzman constant, numerically equal to x 10E-08 m 2 K 4 s is a compounded constant covering the emissivity of the two surfaces and their geometrical relationship T e and T r are the temperatures of the warm and colder bodies respectively KK 10/30/

18 Convection - definition Convection, is the transfer of heat from one place to another by the movement of fluids. Convection is usually the dominant form of heat transfer in liquids and gases. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combined processes of conduction (heat diffusion) and advection (heat transfer by bulk fluid flow). Convection can be "forced" by movement of a fluid by means other than buoyancy forces (for example, a water pump in an automobile engine). In some cases, natural buoyancy forces alone are entirely responsible for fluid motion when the fluid is heated, and this process is called "natural convection". An example is the draft in a chimney or around any fire. In natural convection, an increase in temperature produces a reduction in density, which causes fluid motion due to pressures and forces when fluids of different densities are affected by gravity (or any g-force). For example, when water is heated on a stove, hot water from the bottom of the pan rises, displacing the colder denser liquid, which falls. After heating has stopped, mixing and conduction from this natural convection eventually result in a nearly homogeneous density, and even temperature. Convection (Newton s equation) k = h x A x (T o T s ) q is the heat transfer rate in W A is the area normal to direction of heat flow in m 2 h is the convective heat-transfer coefficient in W m T o is the temperature of the air immediately before impinging on the product T s is the surface temperature of the product KK 10/30/

19 Dielectric Heating - definition Dielectric heating, also known as electronic heating, RF heating, high-frequency heating is the process in which a high-frequency alternating electric field, or radio wave or microwave electromagnetic radiation heats a dielectric material. At higher frequencies, this heating is caused by molecular dipole rotation within the dielectric. At lower frequencies in conductive fluids, other mechanisms such as ion-drag are more important in generating thermal energy. RF dielectric heating at intermediate frequencies, due to its greater penetration over microwave heating, shows greater promise than microwave systems as a method of very rapidly heating and uniformly preparing certain food items, and also killing parasites and pests in certain harvested crops KK 10/30/

20 Total Heat Total Heat on the Product = Conductive + Radiant + Convective 10/30/2018 KK 20

21 Combined Heat Air Plenum Convection Radiation Conduction Conduction: Heat transferred to the product from the belt. Radiation: Heat transferred to the product from all surfaces at higher temperatures. Convection: Heat transferred to the product from the air currents. The faster the air hits the product the higher the heat transfer. KK 10/30/

22 The Baking Curve Development Phase: Time and Temp. to Promote Flavor and shape formation Setting Phase: Set the product shape and rapid moisture removal Finishing Phase: Control final color and moisture profile KK 10/30/

23 Typical bread baking curve

24 The Baking Curve Release of CO to 140 o F 50 to 60 o C Yeast Activity 85 to 140 o F 30 to 60 o C Release of Ammonia 97 o F 36 o C Starch Swelling 130 to 150 o F 55 to 65 o C Amylase Activity 130 to 180 o F 55 to 82 o C Gluten Coagulation 165 o F 75 o C Alcohol Distills 170 o F 77 o C Water turns to steam or water vapor 212 o F 100 o C Sugar Carbonizes 275 o F 135 o C KK 10/30/

25 Cyclo Thermic Oven KK 10/30/

26 Cyclo-Thermic Oven 10/30/2018 KK 26

27 DGF or ribbon burner oven KK 10/30/

28 Indirect Fired Convection KK 10/30/

29 IFC 10/30/2018 KK 29

30 Indirect fired convection KK 10/30/

31 Direct Fired Convection 10/30/2018 KK 31

32 Dielectric Oven 10/30/2018 KK 32

33 Dielectric Oven The Complementary Effect of a Dielectric Unit Post-Baking Drying Boosts Productivity & Profits Conventional Biscuit & Cracker Baking Process Conventional ovens require a prolonged residence time for baked products to reach final target interior dryness. As a result, productivity is limited. Conventional Baking Oven Dielectric Post-Baking Dryer Adding a Dielectric Post-Baking Dryer, eliminates the interior drying requirement from the oven, enabling greater productivity and profitability. Plus more even moisture gradient 10/30/2018 KK 33

34 Hybrid Oven KK 10/30/

35 Hybrid oven with Animation 10/30/2018 KK 35

36 Conventional Heat in Baking Heat is necessary in the baking process to: 1. xza product structure 2. Remove moisture 3. Develop color and flavor Exhausting Top heat Heat passes to the product from outside. The surface is generally hotter than the center. Bottom heat Oven baking conditions are adjusted to achieve the required product attribute specifications

37 How Heat Passes from the Oven to the Product Conventional heating methods pass heat from the oven to the product, in three ways: Convection (Air flow) 1. Conduction 2. Radiant Heat 3. Convection Radiant Heat Convection Radiant Heat Conduction The top of the product is mainly heated by convection and radiant heat The bottom of the product is mainly heated by conduction through the heated oven band The bottom of the oven band is mainly heated by convection and radiant heat

38 Conduction in a DGF Oven Conduction in the oven occurs as the heat transfers directly from the hot oven band into the bottom of the dough pieces Oven Band Conduction particularly melts the fat to enhance flow of the dough. This affects product structure and dimension Conduction heats the dough piece from below, changing water into steam as well as expanding the carbon dioxide from proofing/fermentation It also converts the ammonium bicarbonate into ammonia gas This helps provide spring/lift and pushes steam up through the dough/product surface for moisture removal

39 Radiant Heat in an Oven Radiant heat in an oven comes from the hotter metal surfaces, such as the oven chamber walls, burners flames and combustion gases. The heat then transfers to the product: Radiant heat particularly browns the top surface of the product and heats the underside of the band! Burners flames Metal oven surfaces Radiant heat has a particular impact on uneven product surfaces. The shadowed areas will receive less radiant heat than exposed parts. This results in brown highlights at exposed points. What types of products may be particularly affected by radiation? Wire cut cookies

40 Natural Convection in an Oven Air in the oven chamber is continually circulating as incoming cooler air warms, lightens and rises It is difficult to manage and control Natural convection air flow inside the oven! Hot oven inner surfaces! Input Cooler air Discharge Cooler air Moving oven band Convection heat is important in lifting moisture in the form of steam away from the surface of the produce. This further supports achieving finished product moisture specification. This speed of moisture removal effects product quality

41 Forced Convection in an Oven Forced convection comes from exhaust fans and moving bands Forced convection helps to even out heat differences in an oven.

42 Forced Convection Baking Convection ovens use high velocity heated air to bake the product There is only one large burner and blower per zone Velocity dampers are used to provide top and bottom heat control The major advantages of convection baking include uniform moisture removal and color development within the bake chamber, reduced maintenance and high thermal efficiency The major concern with convection baking is achieving product that is comparable with product baked using DGF (Direct Gas Fired) ovens Because there are fewer burners, maintenance is easier

43 Cookie Baking Balancing Act For a cookie to bake properly and achieve the specified product attributes, it must reach the right temperatures at the right times. Controlling spread from the reaction of sugar dissolving and fat melting can be the challenge. If the dough gets too hot too early, the cookie may spread too much and get too wide If the dough stays too cool too long, the cookie may not spread enough and will be too thick and short Dark color Low moisture Too thick High moisture One possible defect, the cookies may not fit in the package! Preheat is not always used in sweet goods, because fats melt and sugars dissolve at low temperatures and the product spreads too quickly. Bottom heat is used much less for cookie baking than cracker baking. Generally cookie baking times are longer than cracker baking times.

44 ph Acidity Levels in Crackers and Cookies ACID NEUTRAL ALKALINE ph affects color Correct ph makes for good flavor and color in the finished product ph changes during the baking process due to the chemical reactions of soda and acids, typically in the early stages of baking ph often trends with moisture. If ph and moisture are tracking together then the baker will be able to correct ph problems with changes to the oven profile

45 Before Looking at the Baking Stages: Preheat Infeed Discharge Preheat Burners Hot band starts to heat up the bottom of the product immediately as it makes contact! Preheat is not always used. It depends on the: Oven Desired temperature of the oven band Type of product: Cookie or cracker, and the specified finished attributes Heats the band prior to receiving the product There are typically 4-12 preheat burners to heat the band Because the band is hot, the product starts to heat up as soon as it contacts the band This helps structure development in the early zones

46 Different Zones Do Different Jobs There are 3 stages in the baking operation: Stage 1 Stage 2 Stage 3 Ovens are divided into different zones, but the principles of the baking stages remain the same Stage 1: Stage 2: Stage 3: Structure Development Moisture Removal Color and Flavor Development

47 Summary of what is happening to the dough in the oven at different temperatures 47

48 BROWN COLOR DEVELOPMENT AND STABILITY FOR A GIVEN COMPOSITION OF BROWNING REACTANTS, COLOR DEVELOPMENT DEPENDS ON: MOISTURE CONTENT, TEMPERATURE, TIME. LS/HL 2003 OVEN AIR TEMPERATURE OF FOLLOWED BY POST-CONDITIONING EFFECT COOLING TUNNEL VERSUS LONG AMBIENT RUNOUT ON CONTINUED BROWNING REACTIONS ROOM AIR AMBIENT TEMPERATURE NEAR BOILING WATER TEMPERATURE BAKING / FRYING / DRYING TIME UNSTABLE BROWN INTERMEDIATES FADE SOON AFTER HEAT-PROCESSING (BAKING / FRYING / DRYING). FINAL STABLE BROWN COLOR PERSISTS DURING STORAGE, IF LOW MOISTURE CONTENT IS MAINTAINED. BUT, FADING EVEN OF STABLE BROWN COLOR IS ACCELERATED BY MOISTURE MIGRATION FROM "BONED" WET CENTER TO DRIER SURFACE, OR BY MOISTURE UPTAKE FROM ENVIRONMENT (WITH ADDITIONAL INCREASED RISK OF CHECKING-INDUCED BREAKAGE). BOTH UNDERDRYING AND OVERDRYING DURING HEAT- PROCESSING RESULT IN ACCELERATION OF RANCIDIFICATION DUE TO ABSENCE OF BROWNING REACTION PRODUCT ANTIOXIDANTS AND ABSENCE OF WATER AS A FREE-RADICAL SCAVENGER, RESPECTIVELY.

49 THANK YOU! Rich Mc Featers was a Research Principal in Mondelēz International s Global Process Engineering Group in East Hanover, New Jersey for over 35 years in the product development area beginning with Nabisco in Rich developed and commercialized such well-known products as Ritz Bits, Teddy Grahams, SnackWell s: (Devil s Food, Graham Star, Cheese Cracker, Double Fudge, and Caramel Delights), and other cookies and crackers. Rich was also involved in the initial production start-up of Oreos in Ludhiana, India as well as other global Oreo manufacturing locations. Rich in completed a short-term assignment at Mondelēz International s Munich RandD Center with responsibilities for commercializing Grainwave, a six-sku line of biscuits using Milka chocolate. Some of his other assignments were as the lead technical resource on the no-trans conversion team for Oreos, was the lead product developer at Kraft s Italian-heritage bakery Stella D oro for over four years and was on the product development team from Suzhou, China that launched Project Bing - a fruit filled breakfaston-the-go treat for the Asian market. Rich has a Bachelor of Science degree in Food Science from the Pennsylvania State University. Rich began his food-manufacturing career with Borden Dairy and Service division in Pittsburgh; he then spent time with several regional snack manufacturers. Recipient of the 1987 FIAT Award for excellence at Nabisco, Rich repeated in 1990 with the President s Award and in 1994, the Chairman s Award for Excellence for SnackWell s. Rich also holds five patents for product and process design. Rich is a long time member of the Biscuit and Cracker Manufacturer Education Committee, served as the principal participant in the BandCMA Technical Course rewrite in , and has participated on the Technical Meeting planning committee for 17 years prior to retiring. Rich was chair of the 2007, 2012 and 2013 BandCMA Technical Conferences. Rich is also active member of several civic groups including helping the homeless of Bergen County, New Jersey and is a former chair of a men s chorus in New York City for over six years. In 2004, Rich organized, lectured and demonstrated a program called Cookies a two-week, handson lecture series in Da Nang, Viet Nam for aspiring entrepreneurs as part of the Kraft/UNISTAR - United Nation Volunteers program. Post retirement has found Rich creating a consulting company Biscuit Solutions, LLC to assist in biscuit research and development, sample preparation (emphasizing non-gmo and gluten-free recipes for a leading diversified food company), teaching bakery product developers in the fundamentals of cookie and cracker production as well as bakeries front line leadership teams. Rich continues to serves the ABA as a Technical Advisor.