Adding active catalyst to the heavy oil at the bottom of the converter cracking tower

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The use of active catalysts to improve the performance of heavy oil in the converter cracking tower bottom; the heavy oil catalytic unit was first built in 1988 with a design capacity of 150,000 tons per year. In 1995, its capacity was increased to 500,000 tons per year, with the intended feedstock being Dagang atmospheric residue. However, due to a disruption in the supply of feedstock from Dagang, the unit stopped operating. After our factory was transferred to Lanxing Company in 2003, the heavy oil catalytic unit resumed operations, using mainly imported M-100 fuel oil along with purchased atmospheric residue. As the feedstock became increasingly heavy, this led to excessive coking during reactions, a decline in the unit’s processing capacity, an increase in catalyst consumption, and high levels of slurry discharge. The production data for 2005 is shown in Table-1. Table 1: Production data for 2005
Item: Daily average processing volume; Light liquid yield (%); Liquefied gas yield (%); Slurry yield (%); Catalyst consumption per ton of product (kg/T).
Values: 1020.7, 274.89, 15.87, 7.51, 1.56.

As can be seen from Table 1, the processing volume in 2005 was less than 340,000 tons, with a catalyst consumption of 1.56 kg/T – this does not include the additional 200+ tons of catalysts purchased from external suppliers. For these reasons, after thorough research, analysis, and technical discussions, the branch decided to try using an activating catalyst produced by Engelhard Company for the Converter cracking unit’s heavy oil feedstock. The main physical and chemical properties of this catalyst are shown in Table 2, along with those of the main catalyst used in this facility (RAG-9). Table 2 – Key physical and chemical properties of Converter additives and RAG-9 main catalyst
Property | Converter | RAG-9 |
AI2O3 | 38% | 45% |
Na2O | 0.25% | 0.25% |
Specific surface area | ≥380 m2/g | ≥220 m2/g |
Bulk density | 0.70 g/ml | 0.72 g/ml |
Average particle size | 75 | 71.2 |
Sieve analysis (0–40 mesh) | 12% | 18% |
According to communications with Engelhard Company and available data, its key characteristics include a unique DMS matrix that provides active pores for the diffusion of heavy oil molecules, enabling selective cracking ； Very high activity, which can reduce catalyst consumption ； Significant bottom oil cracking capacity, which can reduce the slurry yield ； High specific surface area, nearly twice that of ordinary catalysts ； Can be used in combination with any catalyst ； Medium bed ratio, suitable for fluidization in all types of units ； Increase the processing volume and the amount of heavy oil blended, without increasing or only slightly increasing the yields of coke and dry gas ； High wear resistance ； Good resistance to heavy metal pollution ； Increase the diffusion rate of oil and gas molecules within the catalyst pores ； Used in combination with propylene production enhancers to increase the propylene content in liquefied gas ； Addition amount: Only 5-15% of the system’s storage is required ； Since the amount added can be increased or decreased at any time, the device operation plan can be adjusted quickly. On January 26, 2006, experiments were initiated to increase the addition of active catalysts to the heavy oil at the bottom of the Converter cracking tower. These experiments lasted for four weeks, during which approximately nine tons of catalysts were added to the Converter. The experiments were carried out in two phases. 1. Rapid addition phase: During the first eight days, 500 kilograms of Converter catalyst were added per day, for a total of four tons (added in four installments). In the second week, and during the first five days of the third week, 330 kilograms of Converter catalyst were added per day (distributed over two shifts), resulting in a total of 20 days of continuous addition. In total, about 9 tons of Converter catalyst were added; the total capacity of catalysts in this facility is approximately 100 tons. Calculated on the basis of loss proportional to the catalyst, the additive accounts for about 7% to 8% of the main catalyst in this case. 2. Stable supplementation phase: From two days after the third week following addition to the fourth week, depending on the operational conditions and the properties of the catalyst, 140–165 kilograms of Converter catalyst aid are added per day (in two doses, in the morning and afternoon). Following the instructions of the relevant leaders at the branch company, Production Technology Department 1 and the Catalysis Plant jointly set the objectives for this experiment aimed at increasing the activity of the catalyst used in the bottom oil of the Converter cracking tower: to rapidly boost the activity of the catalyst present in the system without adding any catalyst, and ultimately without having to remove any catalyst at all, thereby reducing catalyst consumption and saving on processing costs ； Increase the plant’s processing capacity or the amount of slag added, thereby increasing the total liquid yield, without increasing the production of coke and dry gas ； Used in combination with propylene production enhancers, it increases the liquefied gas yield while raising the propylene content in the liquefied gas ； On the condition that the solid content of the slurry is within acceptable limits, gradually reduce the amount of slurry discharged. The analysis statistics of the raw materials in the two weeks prior to the experiment and during the experiment are shown in Table-3 below. Table-3: Analysis of raw materials before the test and during the test. Dates: Before addition, After addition – 1.13, 1.24, 2.72, 2.21. Density: 0.9177, 0.9286, 0.9163, 0.9227. Residual carbon: 5.99, 5.72, 6.26, 5.56. Distillate at 500°C: 545, 259, 52. In Table-3, the analysis of raw materials was conducted on January 13 and January 24 prior to the test, while it was done on February 7 and February 21 during the tests using the Converter catalyst. The analysis shows that there are minimal differences in the density, residual carbon, and distillate at 500°C of the raw materials before and after the test; therefore, it can be concluded that the properties of the raw materials remained essentially unchanged before and after the test. After adding the Converter catalyst on January 26th, the control values of various process operation parameters remained essentially the same before and after the experiment. The catalyst consumption per week before and after the addition of the Converter catalyst is shown in Table-4. Table-4: Catalyst consumption before and after addition. Date, Amount of catalyst added, Catalyst consumption in kg/T. Before addition: 05–12.30, -1.51, 1.27, 1.46, 1.6; -1.12, 11.15, 1.49, 1.13; -1.19, 10.13, 1.42, 1.20; -1.26, 10.98, 1.52. After addition: 1.27–2.29, 0.66, 1.29, 2.3; -2.99, 0.85, 1.27, 2.10; -2.16, 6.9, 0.92, 2.17; -2.23, 6.92, 0.92. The equilibrium catalyst activity in the system before and after the experiment with the Converter promoter is shown in Table-5. Table-5: Catalyst activity before and after addition
Date | Equilibrium catalyst activity (%)
Before addition: 1.14, 5.2, 1.19, 60.1, 11.25, 59.8
After addition: 2.66, 1.22, 2.96, 8.2, 2.15, 71.1, 12.20, 63.7

As can be seen from Tables-4 and Table-5, the Converter catalyst aid produced by American Anger Company led to a gradual increase in the equilibrium catalyst activity within the system after it was added. During the period of steady addition, the catalyst activity increased by about five percentage points. Meanwhile, the consumption of the main catalyst decreased gradually, by approximately 0.4 kilograms per ton compared to before the experiment. Assuming that the consumption of the Converter catalyst aid during the steady addition period was 0.12 kilograms per ton, and that the cost of the catalyst is 23 yuan per kilogram, the reduction of 0.4 kilograms per ton results in a savings of 9.2 yuan. The cost of the Converter catalyst is 58 yuan per kilogram, with a consumption of 0.12 kilograms per ton; thus, the cost associated with it is 6.96 yuan. By subtracting the cost of this catalyst from the savings resulting from using less main catalyst, an amount of 2.24 yuan can be saved per ton of raw material processed. Assuming a processing volume of 1,050 tons per day, this translates to savings of 2,352 yuan per day. The material balance of the unit before and after adding the Converter catalyst is shown in Table-6. Table-6 Material Balance Date Processing Volume Light Liquid Yield (%) Liquefied Gas Yield (%) Slurry Yield (%) Before Addition: 05–12.30: -1.57, 82.17%, 5.95%, 16.09%, 6.84%; 06–: -1.6, -1.12, 74.54%, 57.51%, 16.31%, 7.31%, 1.13%; -1.19: 71.54%, 74.67%, 15.32%, 7.53%, 1.20%; -1.26: 72.40%, 74.96%, 15.71%, 7.46%. After Addition: 1.27–2.27: 44.77%, 74.77%, 17.03%, 6.92%, 2.3%; -2.97: 77.77%, 74.87%, 16.45%, 6.67%, 2.10%; -2.16: 74.87%, 74.84%, 16.15%, 7.19%, 2.17%; -2.23: 74.97%, 77.51%, 8.03%, 6.42%. Based on production data over the four weeks before and after the addition of the Converter catalyst, the processing volume increased by 539 tons after addition, with an average daily increase of 25.66 tons. The yield of light liquids increased by 0.33%, while the yield of liquefied gas increased by 1.06%; meanwhile, the yield of slurry decreased by 0.5%. This includes a power fluctuation to the equipment on February 13, which caused the smoke extractor to stop operating and led to a 40-minute interruption in feed supply; the air compressor stopped working for 3 hours. The situation would have been better if those periods were excluded. According to statistics, compared with the first four weeks without the Converter catalyst, the propylene content (W) in liquefied gas increased by about 1.9% after adding the catalyst. The test of the Converter promoter basically achieved the expected objectives, yielding good economic benefits. After this test, the amount added and the stability phase of the subsequent tests showed little variation; adjustments to the amount of Converter promoter were made based on operational data such as the level of recycled liquid, reaction temperature, and catalyst analysis. The production data from February to July 2006 are shown in Table-7. Table 7: Production data from February to July 2006
Item: Daily average processing volume, Yield of light liquid (%), Yield of liquefied gas (%), Yield of oil slurry (%), Catalyst consumption per ton (kg/T)
Values: 1159.4, 277.99, 18.94, 6.3, 0.91

Comparing Table 1 and Table 7, it can be seen that with the addition of the Converter catalyst, the daily average processing volume increased by 138.7 tons, the yield of light liquid rose by 3.1%, catalyst consumption per ton decreased by 0.65 kg/T, the yield of oil slurry dropped by 1.21%, while the yield of liquefied gas increased by 3.14% (this is partly due to the improvements made to the feed nozzles in the riser; more details will be provided in another article). Despite a decrease in catalyst consumption of 0.65 kg/T, the catalyst’s activity remained unchanged and even increased slightly, and its selectivity improved. This is the effect of the Converter catalyst. From February to July 2006, the catalyst consumption was 0.14 kg/T; at a cost of 58,000 yuan per ton, the cost of using this catalyst for producing one ton of oil was 8.12 yuan. With the addition of the Converter catalyst, the catalyst consumption per ton decreased by 0.65 kg/T. At a cost of 23,000 yuan per ton for the catalyst, this reduction amounted to 14.95 yuan per ton; in total, this saved 6.83 yuan per ton of oil processed. From February to July 2006, 183,188 tons of raw material were processed. Without taking into account any increase in the yield of oil production, the catalyst costs were saved by approximately 1.25 million yuan during that period. Thanks to the improved selectivity and increased activity of the catalyst, the yield of liquefied gas rose steadily as oil production increased, with the propylene content in the liquefied gas remaining at 43–45% (by weight), thereby providing sufficient raw material for the downstream facilities of the branch company. The Converter catalyst promoter has a significant effect on promoting the catalytic cracking of heavy oil and increasing the conversion rate of the desired products. It helps to rapidly enhance the activity and selectivity of the catalyst in the system; simultaneously, without increasing the yields of dry gas and coke, the yields of light liquids and liquefied gas increase significantly. When used in combination with additives for increasing propylene production, the propylene content in the liquefied gas is about two percentage points higher than when using the propylene-enhancing additive alone ； The Converter catalyst promoter is added using the existing small feeding system, allowing for great flexibility in adjusting the amount added, which can be modified as needed during operation. Through the joint efforts of the branch offices, the trial use of the Converter catalyst was a **success**, achieving the desired objectives and yielding significant economic benefits, thus contributing to the healthy development of our branch office.