Dry Process Cement Kiln Research Articles

Numerical Study on the Denitrification Efficiency of Selective Noncatalytic Reduction Technology in Decomposing Furnace

In order to reduce the nitrogen oxide emission of cement plant, the denitrification of decomposing furnace is studied in this paper. Based on Fluent software platform, the 2500 t/d new dry-process cement kiln decomposing furnace of a plant is modeled and simulated by using air fractional combustion technology combined with selective noncatalytic reduction technology. The model and simulation methods are verified by the field test. The effects of the urea injection position and ammonia-nitrogen molar ratio on NO, NH3, and denitrification efficiency are studied by numerical simulation. The results show that the optimal injection position of the urea solution is 12 m, the optimal ammonia/nitrogen molar ratio is 1.8, and the optimal injection velocity of the urea solution is 40 m/s. The simulation results obtained under the optimal parameters are as follows: NO concentration is 187.60 mg/m3, NH3 escape is 32.40 mg/m3, and denitrification efficiency is 74.75%.

ANN-GA approach for predictive modelling and optimization of NOx emissions in a cement precalcining kiln

China’s cement production is increasing, but the sustainable development of the cement industry is hindered by pollutants, especially nitrogen oxide, with serious health impacts. This study reports the use of an artificial neural network and a genetic algorithm to control the operation parameters of a new dry-process cement kiln technology to predict and optimise the nitrogen oxide emissions. Comparing the predicted value and actual value, the error of the model is less than 2%. The GA is used to search the optimal operation parameters to achieve the lowest concentration of nitrogen oxide emission, which is 165.9 mg/m3 under optimal conditions. The results of sensitivity analysis show that the furnace temperature, raw material quantity and third air temperature have the greatest influence on the nitrogen oxide emission. This model prediction and optimisation can provide a reference for enterprises in controlling operation parameters to reduce nitrogen oxide emission.

Energy and exergy analyses of Egyptian cement kiln plant with complete kiln gas diversion through by Pass

The present article deals with evaluation of energy and exergy efficiences of an Egyptian dry process cement kiln plant with precalciner characterized by that the whole kiln gas is diverted through by pass . Such diversion is necessary to break the intense cycles of secondary constituents Cl, alkalis and sulfur that may arise between precaciner -preheater and kiln due to the high content of the raw materials of such secondary constituents. Based on average actual operation data of the process, energy and exergy balances have been established around the preheater-precalciner, the rotary kiln , the rotary cooler and the whole process. Energetic- and exergetic efficiency of the process attains 40% and 25.7% respectively . Sum of the exergy outputs attains about 49% of total exergy input and irreversibility loss = 2354 kJ/kg clinker which represents about 51 % of total exergy input. Energy and exergy of the by pass gases are the largest output loss items ( ~770 and 416 kJ/kg cli respectively) followed by those of the preheater exit gases (~ 622 and 152 kJ/kg cli respectively). For comparative purpose , the process was evaluated with considering no diversion of kiln gas through by pass . Energetic- and exergetic efficiency has been estimated in this case as 52% and 34 % respectively and the irreversibility attains 1840 kJ/kg clinker which represents about 52 % of total exergy input.

Energy and Exergy Analyses of Egyptian Cement Kiln Plant with Complete Kiln Gas Diversion through by Pass

The present article deals with evaluation of energy and exergy efficiences of an Egyptian dry process cement kiln plant with precalciner characterized by that the whole kiln gas is diverted through by pass . Such diversion is necessary to break the intense cycles of secondary constituents Cl, alkalis and sulfur that may arise between precaciner -preheater and kiln due to the high content of the raw materials of such secondary constituents. Based on average actual operation data of the process, energy and exergy balances have been established around the preheater-precalciner, the rotary kiln , the rotary cooler and the whole process. Energetic- and exergetic efficiency of the process attains 40% and 25.7% respectively . Sum of the exergy outputs attains about 49% of total exergy input and irreversibility loss = 2354 kJ/kg clinker which represents about 51 % of total exergy input. Energy and exergy of the by pass gases are the largest output loss items ( ~770 and 416 kJ/kg cli respectively) followed by those of the preheater exit gases (~ 622 and 152 kJ/kg cli respectively). For comparative purpose , the process was evaluated with considering no diversion of kiln gas through by pass . Energetic- and exergetic efficiency has been estimated in this case as 52% and 34 % respectively and the irreversibility attains 1840 kJ/kg clinker which represents about 52 % of total exergy input.

The use of oil well-derived drilling waste and electric arc furnace slag as alternative raw materials in clinker production

Through laboratory burnability tests and industrial runs carried out for 1 month in a dry process-cement kiln it has been found that an oil well-derived drilling waste and an electric arc furnace (EAF) slag generated in a steel plant are suitable partial substitutes for both limestone and clay in the kiln feed. Drilling waste was available in two streams: the one, muddy and argillaceous; the other, rocky and calcareous. Both gave satisfactory burnability indexes (BI) and high percentages of replacement of limestone (up to 38%) and clay (up to 72%). EAF slag was introduced in the kiln feed at a lesser degree (20%), but promoted a better raw mix burnability: furthermore, being a non-carbonated source of lime, it allows a reduction of both thermal requirement and emission of CO 2, gas responsible for the greenhouse effect. The manufacturing process of waste-based clinkers was environmentally compatible and the related cements were similar in performance to common hydraulic binders.

99/03153 Properties of Portland cement mortars incorporating high amounts of oil-fuel ashes

An experimental program was carried out at the St. Lawrence Cement Company Limited, Mississauga, Ontario, in which 330,000 gallons of used lubricating oil was burned as a portion of the total fuel requirement for a dry-process cement kiln. The plant uses a dual four-stage preheater with a by-pass system. The oil was primarily composed of automotive crankcase drainings and contained approximately 0.6% lead, 0.15% bromine, 0.1% zinc and 0.1% phosphorus.Lead, zinc and phosphorus emissions in the kiln exhaust gases were not found to be increased during waste-oil burning. A small reduction in particulate emissions was found during waste-oil burning. A small increase in bromide emissions was found to occur during the waste-oil burn. A material balance was carried out for lead, bromine, zinc and phosphorus which indicated that these elements were retained in the process solids. Lead, zinc, phosphorus and some of the bromine were retained in the cement clinker. Most of the bromine was retained in the collected dust from the precipitator on the by-pass system.

The influence of calcium sulfate form on the initial hydration of clinkers containing different alkali combinations

Three sets of clinkers produced under different pyroprocessing conditions in a commercial dry-process cement kiln yielded alkalis in different combinations: one set was rich in alkali sulfate compounds, alkali-stabilized orthorhombic C 3A was predominant in the second, whereas potassium rich α-C 2S and alkali oxide-aluminate mixture were noted in the third set. Using different techniques, early hydration analysis was carried out on these clinkers with no addition of calcium sulfate, with a predetermined amount of gypsum, and a corresponding amount of hemihydrate. The results of a study which focused on the identification of the early hydration products, and the interrelationship of calcium sulfate form and different alkali combinations on the hydration kinetics are presented.

Reduction of NO/sub x/ emissions from a dry process preheater kiln with calciner through the use of the urea-based SNCR process

The post combustion reduction of NO/sub x/ using urea has proven to be an effective method in controlling NO/sub x/ from various combustion sources, such a reduction process has been successfully demonstrated in a week-long test at Ash Grove's dry process cement kiln system located in Seattle. This system is equipped with planetary coolers, a 5-stage preheater and an air-through-the-kiln calciner. Testing was done under ten different kiln/calciner operating conditions. Using three to four injectors, NO/sub x/ was efficiently reduced from 350-600 lb per hour lb/ton of clinker to less than 100 lb per hour. This calculates to a NO/sub x/ reduction of greater than 80% for most cases. Chemical utilization was greater than 50% percent. A high degree of mixing and a long residence time at an appropriate temperature present in the preheater tower contributed to these excellent results. An average ammonia slip was four ppm above a baseline level at a normalized stoichiometric ratio of 1. This demonstration confirms expectations that dry process cement kilns with 4+ preheater stages are an ideal application for the selective noncatalytic reduction of NO/sub x/ with urea. NO/sub x/ was efficiently and effectively reduced with minimal byproduct emissions and virtually no effect on plant operations.

Comparison of Emissions from Burning Hazardous Waste in a Dry-Process Cement Kiln with Emissions from Burning Conventional Fossil Fuels

During the past ten years, emissions data have been obtained from a dry process cement kiln. The kiln has been tested while burning various amounts of hazardous waste solvents. Supplemental fuel in the form of hazardous waste solvents has been used up to 40% of the heat input to the kiln, or up to 140 million Btu/hr of the maximum 351 million Btu/hr heat input rate. Three sets of tests have been performed on this unit that can be used to compare the emissions from the burning of conventional fossil fuels only, and approximately 15%, 25% and 40% of the heat input with hazardous waste solvents. The tests were performed in 1982, 1984 and 1989/1990. As might be expected, burning a solid fuel has the potential for greater organic emissions, or products of incomplete combustion (PICs) than does the liquid hazardous waste solvents. Additionally, other impurities such as metals and chlorine content can be controlled more fully in liquid hazardous wastes than in conventional fuels. Full scale data from the kiln indicate that emissions can be reduced when burning a hazardous waste solvent over a conventional solid fossil fuel. However, these data were not obtained under controlled conditions, which would be as expected for most full scale facilities. These data could be augmented by bench and pilot scale studies that examine emissions for various hazardous waste and conventional fuel feed rates under controlled conditions.

Identification and control of an industrial dry process cement kiln

Identification and control of an industrial dry process cement kiln

Experimental burning of used automotive crankcase oil in a dry-process cement kiln

An experimental program was carried out at the St. Lawrence Cement Company Limited, Mississauga, Ontario, in which 330,000 gallons of used lubricating oil was burned as a portion of the total fuel requirement for a dry-process cement kiln. The plant uses a dual four-stage preheater with a by-pass system. The oil was primarily composed of automotive crankcase drainings and contained approximately 0.6% lead, 0.15% bromine, 0.1% zinc and 0.1% phosphorus.Lead, zinc and phosphorus emissions in the kiln exhaust gases were not found to be increased during waste-oil burning. A small reduction in particulate emissions was found during waste-oil burning. A small increase in bromide emissions was found to occur during the waste-oil burn. A material balance was carried out for lead, bromine, zinc and phosphorus which indicated that these elements were retained in the process solids. Lead, zinc, phosphorus and some of the bromine were retained in the cement clinker. Most of the bromine was retained in the collected dust from the precipitator on the by-pass system.

Dynamic computer regulation of a dry-process cement kiln

The paper describes the application of adigital computer to the dynamic regulation of a dry-process Humboldt cement kiln and its associated Fuller cooler. The background to the project and an outline of this particular process and its control problems are given. The control hardware is then briefly outlined, together with details of the kiln models and their method of derivation. Particular attention is paid to the problem of measuring the burning-zone temperature, and the close correlation of this measurement with kiln power, which can be used as an alternative indication of burning zone temperature in the short term. The control system and the discrete equations for control of the kiln are also given, together with a discussion of their functions. One feature of this application, which greatly reduced commissioning time, was the implementation of the linear and nonlinear control equations entirely by a standard conversational control package online via a control panel without programming in the conventional sense. The commissioning procedure and the results obtained under control are discussed.