On the deep processing of coal tar (crude phenol)
Thread Content
I want to know **how many technical issues there are related to using coal tar to produce crude phenol. How much crude phenol can be extracted from one ton of coal tar? What are the approximate proportions of various compounds in crude phenol?** This post was last edited by ryn on 2009-2-5 at 17:51
Generally, about 1.0% of crude phenol can be extracted from tar; this product contains phenol, cresol, dimethylphenol, etc., and the content varies among different manufacturers. This post was last edited by ryn on 2009-2-5 17:51]
The phenol content is around 37%, xylenol is about 13%, m-cresol is around 38%, and o-cresol is about 12%.
Does anyone know which companies across the country handle a large volume of crude phenol?
Does anyone know which companies that are engaged in the deep processing of coal tar plan to launch projects related to crude phenol?
Introduction to the 3,000 tons/year crude phenol processing project, March 2008. I. Overview and market analysis: Crude phenol is obtained by processing the phenol-containing fractions derived from the distillation of coal tar; it is white or colorless, tends to deliquesce and crystallize easily, has a distinct odor and a sharp, burning taste. It is soluble in water as well as in ethanol. It can be used to produce synthetic fibers, pesticides, engineering plastics, and dye intermediates. It is mainly used for extracting phenol, o-cresol, m-p-cresol, xylenol, 3,5-dimethylphenol, etc. It serves as a solvent for high-grade insulating paints, and is also an important raw material in industries such as plastics, pharmaceuticals, and antifungal agents. Cresol has a complex composition, containing phenol and cresols; cresols include monocresol, dicresol, and tricresol ； Cresol includes o-cresol, m-cresol, and p-cresol ； Cresols include 2,3-cresol, 2,4-cresol, 2,5-cresol, 2,6-cresol, 3,4-cresol, and 3,5-cresol, among which 2,6-cresol is the most widely used ； Tricresols mainly include 2,3,6-tricresol and 2,4,6-tricresol. Due to the complex composition of crude phenol and the very similar boiling points of its various components, the process for processing and separating it is quite complicated. At present, the processing volume of crude phenol in our country is still relatively low; it is mainly used to separate individual components such as phenol, m-cresol, and o-cresol, as well as mixed cresols and dimethylphenols. 1. Phenol, also known as carbolic acid, is an important basic organic chemical raw material. It is mainly used in the production of phenolic resins, caprolactam, bisphenol A, adipic acid, alkylphenols, aniline, epoxy resins, polycarbonates, polysulfones, etc. It can also be used as a raw material for the manufacture of pesticides, pharmaceuticals, organic chemical intermediates, and fine chemicals. In the past two years, the production of phenol in our country has developed rapidly, with continuous improvements in production capacity and rising output levels. In 1995, China’s phenol production was only 112,400 tons; by 2000 it had risen to 249,400 tons. The average annual growth rate of production from 1995 to 2000 was approximately 17.3%. In 2005, the production volume was 443,300 tons, representing a year-on-year increase of approximately 19.87%; the plant’s operating rate was around 82.1%. The average annual growth rate of production from 2000 to 2005 was about 12.19%. Although phenol production in our country has developed rapidly, the output still cannot meet the demands of the domestic market, resulting in large-scale imports each year. In 1999, 73,800 tons were imported; this figure rose to 205,300 tons in 2001, and reached 322,700 tons in 2003. The import volumes for 2004 and 2005 were 280,000 tons and 290,000 tons respectively. In 2003, China’s apparent consumption of phenol was 614,100 tons, with a domestic self-sufficiency rate of 48.85%. In 2005, China’s apparent consumption of phenol was 733,410 tons, representing a 12.93% increase compared to 2004. The average annual growth rate of China’s apparent consumption of phenol from 2000 to 2005 was approximately 16.38%. Based on an analysis of the development of production in China for substances such as bisphenol A, phenolic resins, salicylic acid, and nonylphenol, it is estimated that China’s demand for phenol will reach 950,000 tons by 2010. As for o-cresol, the current production method in China involves its separation and recovery from coal tar; the companies involved in this production include Shanghai Coking Plant, Shanghai Baosteel Chemical Co., Ltd., Nanjing Longyan Chemical Co., Ltd., Nanjing Chemical Industry Branch of Shanghai Meishan Enterprise Development Co., Ltd., the Coal Coking Division of Ma’anshan Iron and Steel Co., Ltd., and the Coal Chemical Division of Panzhihua Iron and Steel Group. The annual production volume ranges from 1,000 to 1,500 tons, but the quality of this o-cresol is poor, and it cannot meet the requirements for organic synthesis in areas such as pesticides. Although the Hunan Chemical Industry Research Institute has developed a production process for synthesizing o-cresol from phenol and methanol, the market availability of the by-product 2,6-dimethoxyphenol has hindered the application of this technology in industrial production. Although 2,6-dimethylphenol can be rereacted to produce o-cresol, it is not economically viable; as a result, China does not yet have any industrial facilities for the synthesis of o-cresol. O-cresol is used in the production of the pesticide herbicide 2,4-D, as a plasticizer in plastic processing, as a plasticizer and preservative for viscose fibers, and it can also be used to manufacture resins, antioxidants, and polymerization inhibitors. China’s production of dichloroacetate (sodium salt) is around 6,000 tons, while the demand for o-cresol is around 3,500 tons. O-cresol can be used to produce o-hydroxybenzaldehyde and o-hydroxybenzoic acid; o-hydroxybenzaldehyde can be used to synthesize the fragrance vanillin, while o-hydroxybenzoic acid is mainly used in the production of acidic medium bleaching agent B (with an annual production volume of 200 tons, requiring 100 tons of o-cresol) ； Phenol-formaldehyde resin produced from o-cresol and formaldehyde can be used as a curing agent for epoxy molding compounds in electronic components, particularly those used in computers ； O-cresol can also be used to produce antioxidants, polymerization inhibitors, and others. Currently, the demand for o-cresol in the aforementioned fields is around 2,500 tons. At present, the total demand for o-cresol in our country is around 6,700 tons. Due to insufficient production capacity, imports are required every year from abroad. The table below shows China’s import and export figures for o-cresol: China’s Import and Export of O-Cresol, Unit: tons. Year, Import Volume, Export Volume, Net Import. 1998: 1244.8, 45.6, 1199.2; 1999: 1364.1, 4, 1360.1; 2000: 1476.6, 18.1, 1458.5; 2001: 3134.4, 10.7, 3123.7; 2002: 5057, 3.6, 5053.4; 2003: 5930, 5.5, 5924.5; 2004: 5185, 7.7, 5177.3; 2005: 5532.2, 35.9, 5496.3. China’s production of dichlorodiphenyltrichloroethane has been increasing steadily, and it is expected that production will rise further this year, though the increase will not be significant. Similarly, there will not be much growth in the production of fragrances and dyes made from o-cresol as a raw material. However, the usage of o-cresol in other areas will increase significantly, such as in the production of o-cresol phenol resins and as a synthetic additive. It is estimated that China’s demand for o-cresol will reach around 11,000 tons in 2010. 3. M-Cresol: M-cresol is an important fine chemical intermediate used in the synthesis of pesticides, dyes, rubber, plastics, antioxidants, pharmaceuticals, photosensitive materials, vitamin E, and fragrances. At present, the main cresol production facility in China is located at the Third Plant of Yanshan Petrochemical Corporation under Sinopec; this facility adopted in 1978 the process technology developed by UOP and HERCULES in the United States for producing cresol, p-cresol, propylbenzene, and BHT using the isopropyl toluene method. Taking advantage of the similarities between the processes for producing m-cresol and phenol, Shuangcheng successfully upgraded the m-cresol production facility in 1995. After the upgrade, the facility was able to produce 45,000 tons of phenol per year, while still maintaining the capacity to recover 12,000 tons of m-cresol. Since p-cresol is produced as a by-product during the manufacture of m-cresol and it is difficult to separate, coupled with the consistently strong market demand for phenol propionate, the profitability of producing phenol propionate is much higher than that of producing m-cresol; as a result, this facility has been used exclusively for the production of phenol propionate in recent years. In addition, there are several smaller m-cresol production facilities in Liyang City’s solvent factory, Liaoning, Qingyang, etc., which use m-toluenes through diazotization and hydrolysis processes; their combined production capacity is approximately 4,000 tons per year. Due to the significant constraints posed by m-phenylenediamine and the three types of waste generated by this technology, it is estimated that this technology has no prospects for development. For many years, domestic production of m-cresol was not sufficient to meet the demands of the domestic market, so imports were necessary each year. From 1998 to 2002, as the demand for m-cresol increased, import volumes rose significantly year by year. However, in the past two years, import volumes have decreased due to an increase in domestic production of m-cresol. The table below shows China’s imports of m-cresol in recent years (in tons). Year: 1998 1999 2000 2001 2002 2003 2004 2005 2006
Import volume: 1327 2011 3857 4109 6631 5893 6372 5465
Export volume: 289 138 110 478 227 248 254 168
Net import: 1038 1873 3747 3631 6404 5645 6118 5297
M-cresol is an important raw material for synthesizing trimethylhydroquinone, a key intermediate used in the production of vitamin E. It can also be used to manufacture color film developers, synthetic resins, adhesives, tribromocresol for treating ringworm, and various other important pharmaceutical intermediates. In 2003, 5,893 tons of m-cresol were imported, and this figure rose to 6,372 tons in 2004, an increase of 8.1% compared to 2003; the domestic supply covered less than 50% of the demand. In 2005, China’s market consumption of m-cresol was approximately 13,000 tons. By 2010, the demand for m-cresol to produce synthetic vitamin E in China would reach 15,000 tons; adding the demand from other sectors, the total market demand for m-cresol in China in 2010 would be 20,000 tons. Considering the current domestic supply of m-cresol and the demand expected in 2010, there is room for growth in China’s production of this substance. Processing the phenol oil obtained from coal tar distillation not only enables the production of various phenol-based products, bringing economic benefits, but also facilitates the development of downstream fine chemical products, extends the industrial chain, and increases the added value of the products. At present, all the relatively large-scale coal tar processing enterprises in China process crude phenol, mainly to extract phenol and o-cresol from it ； Due to the relatively similar boiling points of m-cresol and p-cresol, most companies do not separate them and instead produce a mixture of the two. The main enterprises in China that are capable of processing crude phenol include: Anshan Iron and Steel Group Corporation’s Chemical Plant, Panzhihua Iron and Steel Group’s Coal Chemical Company, Shanghai Coking Co., Ltd., Shanghai Baosteel Chemical Co., Ltd., Wuhan Iron and Steel Group Coking Co., Ltd., Shanghai Meishan Chemical Company, as well as Magang, Jigang, Xuansteel, Taigang, and Benxi Steel. II. Product Plan and Consumption of Main Raw Materials 1. Project Scale: This project intends to use phenol oil obtained through distillation in a 300,000 tons per year coal tar processing unit, as well as phenates resulting from the washing and dephenolation of light oil and naphthalene oil, as raw materials to extract crude phenol. This crude phenol is then refined to produce products such as phenol, o-cresol, m-cresol, mixed cresols, and mixed dimethylphenols. A 300,000 tons per coal tar plant can produce approximately 3,000 tons of crude phenol; therefore, the scale of the crude phenol processing plant is planned to be 3,000 tons per year. 2. Product Plan: Based on existing domestic crude phenol processing units, the approximate product plan for processing 3,000 tons of crude phenol is shown in the table below: Product Plan for 3,000 tons/year Crude Phenol Processing Unit | Serial Number | Product Name | Output (tons/year) | Reference Price (yuan/ton) | 1 | Phenol | 840 | 10,000 | 2 | o-Cresol | 330 | 16,000 | 3 | m-Cresol | 900 | 35,000 | 4 | Mixed Cresols | 170 | 10,000 | 5 | Xylenes | 150 | 16,000 | 6 | Phenol residue fuel oil | 610 | 1,800 | Total | 3,000 | 3. Requirements for Major Raw Materials: The raw materials required for this unit—phenol oil obtained from coal tar distillation, as well as phenate salts resulting from the washing and dephenolization of light oil and naphthalene oil—can be supplied by a coal tar processing unit with a capacity of 300,000 tons per year. In addition, 18 million cubic meters of coke oven gas (with a CO2 content of 15–20% on a daily basis) are required annually. 1,200 tons of sodium hydroxide at 10–15% concentration is required (on a percentage basis). 4. Requirements for fuel and utility services: Name and specification, Unit, Hourly consumption, Annual consumption (×104): Fresh water, M3: 3, 2.4; Recycled water, M3: 180, 144; Electricity, kwh: 200, 160; Steam (2.5 MPa), t: 5.5, 4.4; Nitrogen gas (0.4 MPa), Nm3: 8.0, 6.4. The annual operating time is assumed to be 330 days. III. Brief description of the process flow 1. Washing of the fraction: Since phenolic compounds contain phenol hydroxyl groups, which give them weak acidity, they can react with bases to form phenoxide salts; therefore, sodium hydroxide solution can be used to extract phenol from the tar fractions. In industry, crude phenol is obtained by washing the tar distillate with an aqueous NaOH solution at 10%–15% concentration. Theoretically, 0.4 kg of 100% NaOH is required per kilogram of crude phenol, but in practice, only 0.36 kg is needed to produce sodium phenoxide. The neutral sodium phenolate obtained during the alkaline washing process has a free base content of less than 1.5%, and contains 20%–25% phenol. There are two types of distillate washing processes: batch washing and continuous washing. Intermittent washing involves treating the fractions in batches within the reactor; this process is flexible and easy to operate, as the number of washing cycles and the reaction time can be adjusted as needed. As a result, most manufacturing enterprises in China use this intermittent washing method. The continuous washing process has a large processing capacity and requires less space; it uses alternating acid and alkali washes to remove phenolic and saline compounds from the distillate. However, compared to the batch washing process, it consumes more acid and alkali. Based on the availability of raw materials for the device and the characteristics of the processing technology, this scheme adopts a batch washing process; the flow diagram is shown in Figure 3-1. 2. Purification of the sodium phenolate solution: After alkaline extraction of phenol, a neutral sodium phenolate solution is obtained. This solution is then refined to remove impurities such as neutral oils, naphthalene, and pyridine bases, which are present in amounts of about 1–3%. The refining processes for sodium phenolate include distillation and washing with light oil, with distillation being the method commonly used. The process flow is shown in Figure 3-2: The neutral sodium phenolate solution exchanges heat successively with the pure sodium phenolate at approximately 110°C at the bottom of the degumming tower, and with the distillate at approximately 100°C at the top of the tower, until its temperature reaches 90°C; it then enters the first layer of falling film plates, and pure sodium phenolate is obtained from the bottom of the tower through stripping. After heat exchange with the crude sodium phenolate in the reactor bottom, the pure sodium phenolate has a temperature of 70°C; it is then pumped into the pure sodium phenolate tank to serve as the raw material for the decomposition of sodium phenolate. The tower top distillate, after heat exchange with sodium neutral phenolate, enters the condenser, and the condensed liquid flows into a separation tank for oil-water separation. The heat required by the degumming tower is supplied by the reboiler, which circulates and heats the oil at the bottom of the tower; the heat source is steam. To enhance the oil-water separation effect in the oil discharge tank, lighter tar oil with a lower density can be added to the discharge oil, and a pump can be used to circulate it from the discharge tank to the oil-water separation tank. When the separation effect is poor, new light oil can also be directly added to the oil-water separation tank to improve its performance. After being purified by steam stripping, the sodium phenolate solution is sent to the next decomposition step. 3. Decomposition of sodium phenolate: Sodium phenolate salts are strong-base weak-acid salts, and can be decomposed by using acids that are stronger than the acidity of phenol. Industrially, the sulfuric acid decomposition method and the carbon dioxide decomposition method are commonly used. The product obtained by the sulfuric acid decomposition method is difficult to sulfonate, the reaction is not intense, complete decomposition occurs, less smoke is emitted, and the operating conditions are favorable. However, the equipment and pipelines are severely corroded, and it is difficult to treat sodium sulfate wastewater. The carbon dioxide decomposition method produces no waste liquid, and the alkaline solution can be reused; however, its process route is longer, making it more complicated compared to the sulfuric acid method. Since carbon dioxide can be obtained from coke oven flue gas or lime kilns, as well as from the exhaust gases generated by the combustion of blast furnace gas. To make full and rational use of resources and develop a circular economy, this project recommends the use of the carbon dioxide decomposition method, which features a high decomposition rate (around 95%). The sodium carbonate solution produced can be utilized in tar distillation units. The net sodium phenolate from the previous process enters the bubble decomposition tower, where it comes into countercurrent contact with carbon dioxide gas and undergoes a chemical reaction to produce crude phenol and sodium carbonate. 4. Pretreatment of crude phenol mainly involves dehydration and deslagging, with the aim of reducing distillation time and preventing the thermal polymerization of high-boiling resinous substances. The process flow is shown in Figure 3-3: Crude phenol is placed in a dehydration vessel, where it is dehydrated indirectly by steam at atmospheric pressure. The resulting phenol-water mixture is cooled by condensation and then subjected to oil-water separation; subsequent heating is applied to remove impurities until benzene, cresol, and xylene have all been distilled off. The distilled fraction is used as a feedstock for distillation. 5. Refining of crude phenol: Refining is carried out through atmospheric distillation and vacuum distillation, while the refining of crude phenol can be done via batch distillation or continuous distillation. To prevent the decomposition of crude phenol at high temperatures and the polymerization and sludging of high-boiling-point phenols, this approach adopts a batch vacuum distillation process for crude phenol in order to reduce heat consumption, prevent phenol polymerization, and improve product quality. The process flow is shown in Figure 3-4: The crude phenol, after dehydration and deslagging, enters a distillation tower where it is refined through distillation to produce products such as phenol, m-cresol, o-cresol, and mixed xylene. IV. Main Equipment
Equipment Name, Specifications and Models, Quantity, Remarks:
Intermittent washing tower, V=23.5 m³, 4 units;
Distillation tower, DN500 mm, 1 unit, H=5612 m;
Dehydration and dreg removal tower;
Sodium phenate vaporization reactor, F=6.29 m², 1 unit (F represents the heating area inside the reactor);
Oil-water separator;
Distillation tower, D=600 mm;
Float valve tower;
Cooler;
Reboiler.
V. Emission of Waste Streams and Environmental Control
Equipment such as the crude phenol storage tank, the phenol distillation vacuum system, and the tank for phenol products resulting from sodium phenate decomposition emit small amounts of phenol-containing waste gas. It is estimated that the amount of phenol emitted per hour is around 60 Kg. This phenol-containing waste gas is directed to an exhaust cleaning tower, where it is cleaned using a sodium hydroxide solution before being released. After treatment, the amount of phenol emitted per hour can be reduced to 1 Kg. The sodium carbonate wastewater generated by the decomposition of sodium phenolate is treated by a defoaming unit before being discharged in compliance with standards. The degreasing and refining of sodium phenolate generate phenol residue waste, with an estimated annual output of 610 tons, which can be sold as fuel oil. VI. Investment Estimation and Economic Benefit Indicators Table of Major Technical and Economic Indicators Serial Number Name Unit Quantity Remarks 1 Total investment 10,000 yuan 4,300 Of which: Capital investment 10,000 yuan 3,800 2 Annual sales revenue 10,000 yuan 3,230 3 Total annual cost 10,000 yuan 2,200 4 Annual profit and tax 10,000 yuan 1,030 5 Annual profit 10,000 yuan 690 6 Return on investment % 24.0 7 Profit margin % 16.0 8 Payback period Years 6.7 Including construction period Attachment 1.jpg (51.07 KB) 2008-5-16 22:23 2.jpg (33.72 KB) 2008-5-16 22:23 3.jpg (36.3 KB) 2008-5-16 22:23 4.jpg (143.35 KB) 2008-5-16 22:23 Take a look
Import volume: 1327 2011 3857 4109 6631 5893 6372 5465
Export volume: 289 138 110 478 227 248 254 168
Net import: 1038 1873 3747 3631 6404 5645 6118 5297
M-cresol is an important raw material for synthesizing trimethylhydroquinone, a key intermediate used in the production of vitamin E. It can also be used to manufacture color film developers, synthetic resins, adhesives, tribromocresol for treating ringworm, and various other important pharmaceutical intermediates. In 2003, 5,893 tons of m-cresol were imported, and this figure rose to 6,372 tons in 2004, an increase of 8.1% compared to 2003; the domestic supply covered less than 50% of the demand. In 2005, China’s market consumption of m-cresol was approximately 13,000 tons. By 2010, the demand for m-cresol to produce synthetic vitamin E in China would reach 15,000 tons; adding the demand from other sectors, the total market demand for m-cresol in China in 2010 would be 20,000 tons. Considering the current domestic supply of m-cresol and the demand expected in 2010, there is room for growth in China’s production of this substance. Processing the phenol oil obtained from coal tar distillation not only enables the production of various phenol-based products, bringing economic benefits, but also facilitates the development of downstream fine chemical products, extends the industrial chain, and increases the added value of the products. At present, all the relatively large-scale coal tar processing enterprises in China process crude phenol, mainly to extract phenol and o-cresol from it ； Due to the relatively similar boiling points of m-cresol and p-cresol, most companies do not separate them and instead produce a mixture of the two. The main enterprises in China that are capable of processing crude phenol include: Anshan Iron and Steel Group Corporation’s Chemical Plant, Panzhihua Iron and Steel Group’s Coal Chemical Company, Shanghai Coking Co., Ltd., Shanghai Baosteel Chemical Co., Ltd., Wuhan Iron and Steel Group Coking Co., Ltd., Shanghai Meishan Chemical Company, as well as Magang, Jigang, Xuansteel, Taigang, and Benxi Steel. II. Product Plan and Consumption of Main Raw Materials 1. Project Scale: This project intends to use phenol oil obtained through distillation in a 300,000 tons per year coal tar processing unit, as well as phenates resulting from the washing and dephenolation of light oil and naphthalene oil, as raw materials to extract crude phenol. This crude phenol is then refined to produce products such as phenol, o-cresol, m-cresol, mixed cresols, and mixed dimethylphenols. A 300,000 tons per coal tar plant can produce approximately 3,000 tons of crude phenol; therefore, the scale of the crude phenol processing plant is planned to be 3,000 tons per year. 2. Product Plan: Based on existing domestic crude phenol processing units, the approximate product plan for processing 3,000 tons of crude phenol is shown in the table below: Product Plan for 3,000 tons/year Crude Phenol Processing Unit | Serial Number | Product Name | Output (tons/year) | Reference Price (yuan/ton) | 1 | Phenol | 840 | 10,000 | 2 | o-Cresol | 330 | 16,000 | 3 | m-Cresol | 900 | 35,000 | 4 | Mixed Cresols | 170 | 10,000 | 5 | Xylenes | 150 | 16,000 | 6 | Phenol residue fuel oil | 610 | 1,800 | Total | 3,000 | 3. Requirements for Major Raw Materials: The raw materials required for this unit—phenol oil obtained from coal tar distillation, as well as phenate salts resulting from the washing and dephenolization of light oil and naphthalene oil—can be supplied by a coal tar processing unit with a capacity of 300,000 tons per year. In addition, 18 million cubic meters of coke oven gas (with a CO2 content of 15–20% on a daily basis) are required annually. 1,200 tons of sodium hydroxide at 10–15% concentration is required (on a percentage basis). 4. Requirements for fuel and utility services: Name and specification, Unit, Hourly consumption, Annual consumption (×104): Fresh water, M3: 3, 2.4; Recycled water, M3: 180, 144; Electricity, kwh: 200, 160; Steam (2.5 MPa), t: 5.5, 4.4; Nitrogen gas (0.4 MPa), Nm3: 8.0, 6.4. The annual operating time is assumed to be 330 days. III. Brief description of the process flow 1. Washing of the fraction: Since phenolic compounds contain phenol hydroxyl groups, which give them weak acidity, they can react with bases to form phenoxide salts; therefore, sodium hydroxide solution can be used to extract phenol from the tar fractions. In industry, crude phenol is obtained by washing the tar distillate with an aqueous NaOH solution at 10%–15% concentration. Theoretically, 0.4 kg of 100% NaOH is required per kilogram of crude phenol, but in practice, only 0.36 kg is needed to produce sodium phenoxide. The neutral sodium phenolate obtained during the alkaline washing process has a free base content of less than 1.5%, and contains 20%–25% phenol. There are two types of distillate washing processes: batch washing and continuous washing. Intermittent washing involves treating the fractions in batches within the reactor; this process is flexible and easy to operate, as the number of washing cycles and the reaction time can be adjusted as needed. As a result, most manufacturing enterprises in China use this intermittent washing method. The continuous washing process has a large processing capacity and requires less space; it uses alternating acid and alkali washes to remove phenolic and saline compounds from the distillate. However, compared to the batch washing process, it consumes more acid and alkali. Based on the availability of raw materials for the device and the characteristics of the processing technology, this scheme adopts a batch washing process; the flow diagram is shown in Figure 3-1. 2. Purification of the sodium phenolate solution: After alkaline extraction of phenol, a neutral sodium phenolate solution is obtained. This solution is then refined to remove impurities such as neutral oils, naphthalene, and pyridine bases, which are present in amounts of about 1–3%. The refining processes for sodium phenolate include distillation and washing with light oil, with distillation being the method commonly used. The process flow is shown in Figure 3-2: The neutral sodium phenolate solution exchanges heat successively with the pure sodium phenolate at approximately 110°C at the bottom of the degumming tower, and with the distillate at approximately 100°C at the top of the tower, until its temperature reaches 90°C; it then enters the first layer of falling film plates, and pure sodium phenolate is obtained from the bottom of the tower through stripping. After heat exchange with the crude sodium phenolate in the reactor bottom, the pure sodium phenolate has a temperature of 70°C; it is then pumped into the pure sodium phenolate tank to serve as the raw material for the decomposition of sodium phenolate. The tower top distillate, after heat exchange with sodium neutral phenolate, enters the condenser, and the condensed liquid flows into a separation tank for oil-water separation. The heat required by the degumming tower is supplied by the reboiler, which circulates and heats the oil at the bottom of the tower; the heat source is steam. To enhance the oil-water separation effect in the oil discharge tank, lighter tar oil with a lower density can be added to the discharge oil, and a pump can be used to circulate it from the discharge tank to the oil-water separation tank. When the separation effect is poor, new light oil can also be directly added to the oil-water separation tank to improve its performance. After being purified by steam stripping, the sodium phenolate solution is sent to the next decomposition step. 3. Decomposition of sodium phenolate: Sodium phenolate salts are strong-base weak-acid salts, and can be decomposed by using acids that are stronger than the acidity of phenol. Industrially, the sulfuric acid decomposition method and the carbon dioxide decomposition method are commonly used. The product obtained by the sulfuric acid decomposition method is difficult to sulfonate, the reaction is not intense, complete decomposition occurs, less smoke is emitted, and the operating conditions are favorable. However, the equipment and pipelines are severely corroded, and it is difficult to treat sodium sulfate wastewater. The carbon dioxide decomposition method produces no waste liquid, and the alkaline solution can be reused; however, its process route is longer, making it more complicated compared to the sulfuric acid method. Since carbon dioxide can be obtained from coke oven flue gas or lime kilns, as well as from the exhaust gases generated by the combustion of blast furnace gas. To make full and rational use of resources and develop a circular economy, this project recommends the use of the carbon dioxide decomposition method, which features a high decomposition rate (around 95%). The sodium carbonate solution produced can be utilized in tar distillation units. The net sodium phenolate from the previous process enters the bubble decomposition tower, where it comes into countercurrent contact with carbon dioxide gas and undergoes a chemical reaction to produce crude phenol and sodium carbonate. 4. Pretreatment of crude phenol mainly involves dehydration and deslagging, with the aim of reducing distillation time and preventing the thermal polymerization of high-boiling resinous substances. The process flow is shown in Figure 3-3: Crude phenol is placed in a dehydration vessel, where it is dehydrated indirectly by steam at atmospheric pressure. The resulting phenol-water mixture is cooled by condensation and then subjected to oil-water separation; subsequent heating is applied to remove impurities until benzene, cresol, and xylene have all been distilled off. The distilled fraction is used as a feedstock for distillation. 5. Refining of crude phenol: Refining is carried out through atmospheric distillation and vacuum distillation, while the refining of crude phenol can be done via batch distillation or continuous distillation. To prevent the decomposition of crude phenol at high temperatures and the polymerization and sludging of high-boiling-point phenols, this approach adopts a batch vacuum distillation process for crude phenol in order to reduce heat consumption, prevent phenol polymerization, and improve product quality. The process flow is shown in Figure 3-4: The crude phenol, after dehydration and deslagging, enters a distillation tower where it is refined through distillation to produce products such as phenol, m-cresol, o-cresol, and mixed xylene. IV. Main Equipment
Equipment Name, Specifications and Models, Quantity, Remarks:
Intermittent washing tower, V=23.5 m³, 4 units;
Distillation tower, DN500 mm, 1 unit, H=5612 m;
Dehydration and dreg removal tower;
Sodium phenate vaporization reactor, F=6.29 m², 1 unit (F represents the heating area inside the reactor);
Oil-water separator;
Distillation tower, D=600 mm;
Float valve tower;
Cooler;
Reboiler.
V. Emission of Waste Streams and Environmental Control
Equipment such as the crude phenol storage tank, the phenol distillation vacuum system, and the tank for phenol products resulting from sodium phenate decomposition emit small amounts of phenol-containing waste gas. It is estimated that the amount of phenol emitted per hour is around 60 Kg. This phenol-containing waste gas is directed to an exhaust cleaning tower, where it is cleaned using a sodium hydroxide solution before being released. After treatment, the amount of phenol emitted per hour can be reduced to 1 Kg. The sodium carbonate wastewater generated by the decomposition of sodium phenolate is treated by a defoaming unit before being discharged in compliance with standards. The degreasing and refining of sodium phenolate generate phenol residue waste, with an estimated annual output of 610 tons, which can be sold as fuel oil. VI. Investment Estimation and Economic Benefit Indicators Table of Major Technical and Economic Indicators Serial Number Name Unit Quantity Remarks 1 Total investment 10,000 yuan 4,300 Of which: Capital investment 10,000 yuan 3,800 2 Annual sales revenue 10,000 yuan 3,230 3 Total annual cost 10,000 yuan 2,200 4 Annual profit and tax 10,000 yuan 1,030 5 Annual profit 10,000 yuan 690 6 Return on investment % 24.0 7 Profit margin % 16.0 8 Payback period Years 6.7 Including construction period Attachment 1.jpg (51.07 KB) 2008-5-16 22:23 2.jpg (33.72 KB) 2008-5-16 22:23 3.jpg (36.3 KB) 2008-5-16 22:23 4.jpg (143.35 KB) 2008-5-16 22:23 Take a look
Take a look at Yunwei Group; it is engaged in the deep processing of 300,000 tons of coal tar, and it handles a considerable amount of crude phenol. Designed by Jiaonai Institute.
It’s great material; thank you very much. However, I’m not clear about the differences and connections between using cresol and toluene as raw materials in the coal tar processing plant to produce cresol
The information on the 6th floor is good, but the process for distilling crude phenol is too simple; the processing capacity might not be very high. There is another crude phenol processing plant in Yima, Henan. Technical advice was sought a few years ago – the capacity of that plant is likely around 5,000 tons. The design was carried out by Shangjiao; the distillation section consists of three reactors: one for dehydration and removal of impurities, one for fractional distillation and obtaining the pure product, and one for further refinement. The process is fairly reasonable, allowing for a relatively high processing capacity.
The gasification wastewater from our company contains 5 g/l of phenol, and through medium-pressure oil extraction, 500 to 600 tons of crude phenol are produced each month.
We have a capacity of 2,000 tons per year; Tangshan has just installed one unit – I’m not sure what its capacity is. Does anyone who knows know that?