Carbon Black - Group 2

PROCESS TECHNOLOGY ASSIGNMENT GROUP 2 CARBON BLACK PRODUCTION

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INTRODUCTION Carbon black is a black, powder or granular substance made by incomplete combustion or thermal decomposition of gaseous or liquid hydrocarbons under controlled conditions. This produces a black smoke containing extremely small carbon black particles which can be separated from the combustion gases to form a fluffy powder of intense blackness. Soot, which is similar to carbon black, was used for writing letters on papyrus in ancient Egypt and on bamboo strips in ancient China. Carbon black production became a type of cottage industry about the time when the paper production method was established in the second century. Carbon black is among the top 50 industrial chemicals manufactured worldwide, based on annual tonnage. Current worldwide production is about 18 billion pounds per year [8.1 million metric tons]. Approximately 90% of carbon black is used in rubber applications, 9% as a pigment, and the remaining 1% as an essential ingredient in hundreds of diverse applications. It then became widely used in industries after it was produced with the channel process in 1892 and with the oil furnace method in 1947. Carbon black is categorized as acetylene black, channel black, furnace black, lampblack or thermal black, based on the production process. Lampblack is the oldest type of carbon black, having been used as a pigment for centuries. Channel black, produced from natural gas, was introduced in the late nineteenth century and was the major carbon black used worldwide in the early twentieth century for rubber and pigment applications. Acetylene, furnace and thermal blacks have been produced since the early twentieth century. Over 90% of all carbon black produced today is furnace black. Typical carbon black primary particle size ranges from 8 nanometers for furnace blacks to 300 nanometers for thermal blacks. Finer particles increase reinforcement and improve tensile strength. CARBON BLACK, SOOT, AND BLACK CARBON Carbon black is not soot or black carbon, which are the two most common, generic terms applied to various unwanted carbonaceous by-products resulting from the incomplete combustion of carbon containing materials, such as oil, fuel oils or gasoline, coal, paper, rubber, plastics and waste material. Soot and black carbon also contain large quantities of  dichloromethane- and toluene extractable materials, and can exhibit an ash content of 50% or more.

Carbon black is chemically and physically distinct from soot and black carbon, with most types containing greater than 97% elemental carbon arranged as aciniform (grape-like cluster) particulate. On the contrary, typically less than 60% of the total particle mass of soot or black carbon is composed of carbon, depending on the source and characteristics of the particles (shape, size, and heterogeneity).

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Two other commercial carbonaceous products often confused with carbon black are activated carbon and bone black. Each is produced by processes different from commercial carbon black and possesses unique physical and chemical properties. THREE MAIN PROPERTIES OF CARBON BLACK

Figure 1: Electron microscope image of carbon black Observing carbon black particles under the electron microscope shows that they have a complicated structure, with some spheric particles being fused together. The size of spheric particles is called "particle size," and the size of the particle chain is called "structure." Various functional groups such as the hydroxyl or carboxyl group are found in the surface of  carbon black, and their amount or composition is called "surface chemistry." These three - "particle size," "structure," and "surface chemistry" - are the basic properties of  carbon black, and together are called the three main characteristics. The three main properties have a large effect on practical properties such as blackness and dispersibility when they are mixed with inks, paints, or resins.

Figure 2: Structure, particle size and surface chemistry of carbon black Particle Size: The diameter of spheric particles is the fundamental property which largely affects blackness and dispersibility when carbon black is mixed with resins or other vehicles. In general, the smaller the particle size is, the higher the blackness of carbon black becomes. Dispersion, however, becomes difficult due to an increase in coagulation force.

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Structure: Like particle size, the size of the structure also affects the blackness and dispersibility of carbon black. Generally, the increase of structure size improves dispersibility but lowers blackness. Carbon black with a larger structure in particular shows an excellent conductive property. Surface Chemistry: Various functional groups exist on carbon black’s surface. The affinity of  carbon black with inks or paint varnishes changes depending on the type and amount of the functional groups. Carbon black, with a large amount of hydroxyl group given with oxidation treatment, has a greatly enhanced affinity to print inks or varnishes, showing an excellent dispersibility.

Table 1: Commercial names and chemical identification of carbon black

Chemical Name

Carbon Black

Synonyms

Acetylene Black, Channel Black, Furnace Black, Gas Black, Lampblack, Thermal Black

CAS Name

Carbon Black

CAS Registry Number

1333-86-4

Chemical (Molecular) Formula

C

Table 2: Properties and Characteristics of carbon black (furnace process)

Formula weight

12 (as carbon)

Physical state

solid: powder or pellet

Flammable limits (vapor)

LEL: not applicable UEL: not applicable

Lower limit for explosion

50 g/m3 (carbon black in air)

Minimum ignition temperature VDI 2263 (German), BAM Furnace Godbert-Greenwald Furnace

>932°F (>500°C) >600°F (>315°C)

Minimum ignition energy

>10J

Burn Velocity:

>45 seconds: Not classifiable as “Highly Flammable” or “Easily Ignitable”

Flammability classification (OSHA)

Combustible solid

Solubility

Water: insoluble Solvents: insoluble

Color

Black

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MANUFACTURING PROCESS OF CARBON BLACK The carbon black process is normally classified as a large scale industry due to the large amount of production, investment and requires many steps of operation. There are two major processes for carbon black production, the oil furnace process, which account for 90% of total carbon black production, and the thermal process, which account for 10% of total carbon black production. However, there are other minor processes such as the lamp process for production of lamp black, the cracking of acetylene to produce acetylene black, the gas furnace process is being phased out, and the channel black which is not used anymore in US. These minor processes are contributed less than 1% of total carbon black production. The characteristics of carbon black vary depending on manufacturing process, and therefore carbon black is classified by manufacturing process. Carbon black produced with the furnace process, which is the most commonly used method now, is called “furnace black,” distinguishing it from carbon black, which is manufactured with other processes. Furnace Black Process This method forms carbon black by blowing petroleum oil or coal oil as raw material (feedstock oil) into high-temperature gases to combust them partially. This method is suitable for mass production due to its high yield, and allows wide control over its properties such as particle size or structure. This is currently the most common method used for manufacturing carbon black for various applications from rubber reinforcement to colouring. Channel Process This method forms carbon black by bringing partially combusted fuel, which is generated with natural gas as raw material, into contact with channel steel (H-shaped steel) and then collecting the carbon black which results. There are yield and environment issues around this method, and therefore has lost the leading role as the mass production process to the furnace process. This method, however, provides carbon black with many functional groups on the surface, being used in some painting applications. Acetylene Black Process This process obtains carbon black by thermally decomposing acetylene gas. It provides carbon black with higher structures and higher crystallinity, and is mainly used for electric conductive agents. Lampblack Process This method obtains carbon black by collecting soot from fumes generated by burning oils or pine wood. This method has been used since the days before Christ, and is not suitable for mass production. However, it is used as raw material for ink sticks as it provides carbon black with specific color.

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In this report, the oil furnace process is described since it accounts for 90% of the total carbon black production. The oil furnace process is described below.

FURNACE BLACK PROCESS This process has two basic concepts. First, carbon feed stock is converted from fluid to gas (smoke) by heat and incomplete combustion process. Second, gas (smoke) from incomplete combustion will be converted to solid (carbon black) by filtering process and drying process. This technology uses water as a key role for stop reaction and extraction carbon black. The flowchart of carbon black manufacturing processes is shown in Figure 2.

Figure 2: Flow Chart for Furnace Black Process Step 1: Feedstock oil is pumped from the storage tank into the reaction furnace through oil pre heaters. At the same time, combustion air is also preheated and supplied to the reaction furnace. By preheating both feedstock oil and air to a high sensible heat energy, a high yield of  product is obtained.

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Step 2: Feedstock oil then is burned in the reaction furnace. The temperature of combustion is limited at 1320 to 1540°C by using water to cool down to inhibit the complete combustion in the reaction furnace. Then the incomplete combustion oil is became carbon black fine particle or smoke. Step 3: Inject the quenching water at the quench zone in the reaction furnace to cool down the temperature to 500°C to stop the incomplete combustion reaction. Carbon black and by product, tail gas, are formed in this step at the quench zone. The exhaust gases entraining the carbon particles are further cooled to about 230°C by passage through heat exchangers and direct water sprays. Step 4: The mixture, carbon black and off gas, then are separated by sending to bag filters. A cyclone is used for the primary collection system. Then the filtered carbon black particle is sent to further process, the wet pelletizers. Step 5: The filtered carbon black then transferred to wet pelletizers to increase bulk density. Amount of water, molasses and carbon black are mixed with an appropriate ratio. Then the wet pellets are dried in rotary dryers, which are heated by combusting tail gas. Step 6: Finally the dried pellets then are conveyed into the product storage tank or in storage bag.

Figure 3: Simple process flow diagram of furnace black process

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The major waste from this process will be generated as off gas which comes from bag filter house. Off gas contains several products of carbon feed stock combustion such as carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxide (NOx), hydrogen (H2), nitrogen (N2), particulate matter, steam and heat. The proportion of ingredients of off gas depend on the type of carbon feed stock. However, due to off gas contain high level of heat, it is recycled for steam making process. Optional steam will be used for power generation or sell for another industry. Steam making process has to use water which is treated to remove mineral (demineralization process). Because of untreated water may interrupt boiling process and may cause explosion from boiler.

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MAJOR ENVIRONMENTAL ISSUES In each process of carbon black production, wastes are generated which have impacts on environment and human health. There is several environmental issues concern about wastes generation from carbon black industry. Air pollution is a major issue while water, solid waste and noise pollution are minor concern. Air pollution: There are several air pollutants from carbon black production that can be summarized as;  Oil storage tank vent gas  Vent gas from reactor oil furnace process  Fugitive emission from all processes  Pneumatic system vent gas and particulate matter  Flue gas may contain NOx, SOx, and CO Water pollution  In case of emergency, the scrubber will be taken in the process and the wastewater will contain particulate matter and acid water.  High temperature water from cooling tower and equipment cooler unit  Blow down water from back wash boiler  Back wash water which contain high concentration of minerals  Ground washing wastewater  Domestic wastewater Solid waste: Solid waste from carbon black process may be classified into 2 categories, which are general and hazardous waste  General waste from office and canteen  Solid waste from process and packaging such as pallet, paper, plastics and polypropylene bags  Hazardous waste (carbon black) from wastewater treatment plant Noise pollution from carbon black processing may originate from Pneumatic conveyor blower,

Mixer and Dryer.

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IMPORTANCE OF CARBON BLACK INDUSTRY Carbon black is used in tires, rubber and plastic products, printing inks and coatings is related to properties of specific surface area, particle size and structure, conductivity and color. Current worldwide production is about 8.1 million metric tons (International carbon black association). The usage of carbon black was shown in Figure 3 and detailed as described below: 

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Tires and Industrial Rubber Products: Carbon black is added to rubber as both filler and as a strengthening or reinforcing agent in the industrial products such as tire, belts, gasket and bushing etc. Plastics: Carbon blacks are now widely used in products such as refuse sacks, industrial bags, photographic containers, agriculture mulch film, stretch wrap, and thermoplastic molding applications for automotive, electrical/electronics, household appliances and blow-molded containers. Toners and Printing Inks: Carbon blacks enhance formulations and deliver broad flexibility in meeting specific color requirements.

Furthermore, carbon black also designed to transform electrical characteristics from insulating to conductive in products such as electronics packaging, safety applications, and automotive parts.

ECONOMICS OF CARBON BLACK The leading application for carbon black is as a reinforcing agent in the production of rubber goods, accounting for more than 90% of total carbon black consumption. In 2010, use in tires accounted for 73% of world consumption, with other rubber goods (hoses, belts, etc.) accounting for an additional 19%; consumption for nonrubber goods (plastics, inks, paints, etc.) accounted for the remaining 8% of world consumption. While specialty carbon blacks account for only 7% of the total market in tonnage, they command a significantly higher selling price than commodity furnace black, and thus will be the focus of future research and development activities. The price of crude oil has an overriding influence on carbon black markets by affecting such factors as the cost of carbon black, type of vehicles sold and total miles driven, and even tire design (e.g., high performance tires, super-abrasion-resistant tread stock and the "green" tire). Asia (excluding Japan) is currently the largest producer and consumer of carbon black, accounting for 55% of global production and consumption in 2010, with China accounting for nearly half of total Asian consumption. Most of the new capacity scheduled to come onstream over the next five years will be in Asia, with China leading the way.

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The growth of carbon black is closely tied to the automotive industry and the production of  tires. With the global automobile industry moving to China, India and Eastern Europe, the tire industry has followed, and with it the carbon black producers. (The availability of natural rubber in Southeast Asia is also a factor in the tire industry's investment pattern.) Stringent environmental laws are forcing the closure of some older carbon black capacity in developed regions, so much of the future investment will be taking place in developing economies. There is a continuing long-term trend toward concentration and consolidation among suppliers of carbon black. Petroleum companies have exited the business, and it is now dominated by chemical companies for whom carbon black is a core product. All major producers are global in the scope of their operations. The four largest producers are Cabot Corporation, Evonik Industries, Columbian Chemicals, and China Synthetic Rubber Corp. Asia, excluding Japan, will be the fastest-growing region in the world, followed by Central and Eastern Europe. China and India, in particular, will have the greatest gains, as a result of the continued expansion of their motor vehicle and tire industries.

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REFERENCE http://www.albuw.ait.ac.th/Groups/Assignment/II/Group-02.pdf  http://www.epa.gov/ttnecas1/regdata/EIAs/carbonblackeia.pdf  http://www.co2management.org/proceedings/Yoshitaka_Paper_on_Carbon_Black_Manufactu ring.pdf  http://www.cancarb.com/pdf/carbon_black_user_guide.pdf  http://chemical.ihs.com/CEH/Public/Reports/731.3000/

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