Field of the Invention:

The invention is related to a production optimisation method for ethylene furnaces which provides an optimisation by means of simultaneously evaluating the financial values of the production and factory conditions, operation parameters, maintenance planning, LIMS (laboratory results) and financial information in cracking furnaces in the ethylene factory.

The invention is particularly related to a production optimisation method for ethylene furnaces which can determine which of the raw materials are required to be used in the furnace; the most optimal product output in terms of financial impact and current operating conditions; the furnace to which the recycle ethane gas produced during the process will be sent for reprocessing.

State of the Art:

Ethylene, which is a two-carbon hydrocarbon and is the basic initial raw materials of the petrochemical industry, can be produced by means of processing naphtha which is obtained as a raw material in refineries. Naphta, Ethane and LPG are main feedstocks for Ethylene production units. These hydrocarbons which are generally mentioned in the production process can be cracked via steam at high temperatures. Ethylene, propylene, C4 fraction and other products can be obtained by means of the thermal cracking process. The cracking gas (mixed gas of hydrocarbons) which is formed as a result of the cracking reaction of the raw material in furnaces at 800 - 860 °C is quickly cooled by passing through the exchangers once it comes out of the furnace. Special furnaces are used for thermal cracking. These furnaces are also called cracking furnaces. Steam cracking is an important petrochemical process performed for achieving unsaturated hydrocarbons (for example ethylene, benzene etc.) from the various petrochemical raw materials. It is occasionally implemented in (e.g. for obtaining naphtha) refineries. Saturated hydrocarbons are cracked into unsaturated small- molecule hydrocarbons in the process.

The operation of the furnace used in the thermal cracking which is the most important part in ethylene production is very important in terms of the highest efficiency and lowest cost. The parameters which are employed by the furnace are required to be proportional with the production amount. Otherwise, both the product quality is decreased and the production process and cost are increased. Therefore, controlling every process and executing thereof automatically is very important for an efficient production.

Ethylene Factory Furnace Processes may have a plurality of furnaces where the reaction of processing stock to the final products takes place. In each furnace, there are mainly three different controllable (for optimization) process variables which determine the final product portfolio coming out of the furnace. These variables are the feed amount, the coil outlet temperature (COT), the dilution steam ratio (DS) + uncontrollable variables such as coil inlet pressure, furnace section temperatures.

The feeding amount expresses the raw material amount which is processed in the furnace. The coil outlet temperature (COT) corresponds to the operation temperature of the furnace.

The dilution stream ratio (DS) is expressed by the steam/feeding amount ratio used in the cracking process in the furnace. Optimal operation conditions for the furnaces which will maximize the total value produced are very important within this scope. There are generally a few types of raw material stock for the production. The raw materials which are used for the production of ethylene are generally naphtha and LPG.

Naphtha has many important features in terms of paraffin level, iso-paraffin level, boiling points etc.

LPG, similar to naphtha, can be cracked also in furnaces. At the same time, they have features different from each other. The most important one among these is the propane level, n-butane level .

As a result of the preliminary research performed pertaining to the state of the art, the patent file No "2010/07788" was analysed. In the abstract section of the invention subject to the application, it is stated that;" This invention is related to cracking coils-, wherein the cracking coils has at least one inlet, at least one inlet portion, at least one outlet, and at least one outlet portion- and is related to a new type of cracking furnaces comprising a flame recovery equipped with the burners; the parts of the coils here are protected. The invention also comprises information as "it is related to a process which uses a furnace according to the invention for cracking of the hydrocarbon feeding streams".

As a result of the preliminary research performed pertaining to the state of the art, the patent file No "CN102289200" was analysed. In the invention subject to the application, an online automatic control method for setting up the optimisation model of the cracking furnace, production process of the relevant industrial cracking furnace by making the physical feature analysis of cracking is disclosed. As a result of the preliminary research performed pertaining to the state of the art, the patent file No "CN103294015" was analysed. In the invention subject to the application, an optimized control method for the ethylene cracking furnace is disclosed. This method is used for increasing the productivity of ethylene and propylene and decreasing the energy consumption of the ethylene cracking furnace.

As a result of the preliminary research performed pertaining to the state of the art, the patent file No "CN103289725" was analysed. In the invention subject to the application, an energy saving optimized control method for the ethylene cracking furnace is disclosed. This method is used for analysing the energy consumption, high product yield and cracking feeding stock and dissolution cycles of the processing solutions.

The furnaces used in the state of the art are operated with constant feeding and constant output. A production independent of the amount and parameters is obtained by using constant feeding and constant output. This condition increases the production cost.

The ethylene plants used in the state of the art have the production capacity for single material or some materials. It is not possible to increase the rate of yield of these plants when the transformation of the products reaches to one of the limits of the factory capacity.

As a result, due to the abovementioned disadvantages and the insufficiency of the current solutions regarding the subject matter, an improvement is required to be made in the relevant technical field.

Aim of the Invention: The most important aim of the invention is to instantly optimize the instantly changing factory conditions, raw material features and factory parameters by means of finding the most optimal scenario among the previously created scenarios.

Another important aim of the invention is to determine the optimal production scenario by the computer based on the instant results from the plant operating conditions, feed laboratory analysis. Thus, the scenarios created in the simulation of the factory and the optimal scenario is determined in the online optimization algorithm with the real-time factory conditions from the factory control system, instant results from the laboratory and financial indicators of the raw materials/products .

Another aim of the invention is to ensure that the ethylene factory operated according to the determined scenario by the computer operates with maximum profit.

Another aim of the invention is to optimize the transformation of the products such that the portfolio mix does not exceed any of the factory capacity limits. Thus, the factory capacity can be employed at the possible highest level.

Another aim of the invention is to determine to which furnace and how many tons of raw materials (naphtha, LPG) should be fed, in case multi-furnaces are used.

Another aim of the invention is to determine to which furnace the recycle ethane gas formed during the factory process will be sent in order to be reprocessed.

Another aim of the invention is to optimise the maintenance periods and costs. The structural and characteristic features of the present invention will be understood clearly by the following detailed description. Therefore, the evaluation should be made by taking this detailed description into consideration.

Description of the Invention :

The inventive production optimisation method of the ethylene furnaces mainly consists of three steps. These steps are, creating scenarios with the furnace operation simulation, optimising the created scenarios and reporting the results. All these processes are performed by the software which can operate on a computer. Also, this software can also be accessed via a cloud server.

In order to simulate different scenarios in the furnaces, a kinetic reaction simulation which runs on a computer is used. This simulator enters the determined feeding level, COT, DS, naphtha features and furnace conditions (coke levels are shown) and indicates what the final product transformations will be for a given scenario. When a new feedstock specification results are measured in the laboratory, the model code creates automatically all possible scenarios (together with the variable raw material, COT, DS combinations) and calculates the profit of each scenario by means of entering the financial values of the input and output products. This simulation creates gap for the optimisation process .

After the simulation process, all scenarios for each furnace are entered into an integer mathematical model for the optimisation process. This integer model running on the computer finds the most appropriate operation conditions for each furnace. The selected scenarios bring the maximum possible profit under specific conditions without exceeding the capacity limits of the facility . Optimisation reports are created by the computer during reporting process and they are saved by monitoring the financial realization. Also, this reporting is also reported to the user.

Online laboratory analysis results are obtained from the laboratory information management system (LIMS) and its integration is performed by the inventive production optimisation method for the ethylene furnaces. Data is received over the PHD (process date database, process historian database) from the finance and their integration is performed thus. Data is given to the kinetic model which calculates the product outputs of the process and the integration of the results is performed. Said three different data sources are integrated by the computer over the wireless or wired network and accordingly the optimisation is realized.

The inventive production optimisation method of the ethylene furnaces performs the following process steps. First of all, data received from the kinetic model which calculates LIMS, PHD and product outputs are transmitted to the computer after they are collected. Label receiving process is performed while data is received from PHD. Label receiving process is used to receive instant views of the single labels such as naphtha or LPG features (the instant data which do not require average) . The label list apart from the single labels is also received. The label list also allows for receiving a plurality of data which corresponds to the entered labels. Furthermore, the label list calculates an average value for a defined time interval. After the label receiving process, the fee is charged. Fee charging process allows for reading the material prices from PHD. These prices are entered into the system by the finance beforehand. After the price is obtained, naphtha features receiving process is performed. Naphtha features are received from PHD. These features are received automatically through the LIMS data base. Then, it is controlled whether there is a change in naphtha features or not (if a new result is entered via LIMS) . In case there is any change, a scenario is created with the new naphtha features. The LPG features are received subsequent to the naphtha features .

All of these data received are examined by the computer and the computer calculates which raw material will be used and reports it to the user based on these data. Also, the computer determines how many tons of raw materials (naphtha, LPG) and are required to be fed to which furnace and coil input temperature (COT) , dilution steam ratio (DS) .

Different algorithms and models are tested by means of being simulated by the computer and the optimum algorithm is selected. For the simulation process, first of all, the simulation of the furnace scenarios is created. The data used for the simulation are data regarding the raw material stock features (naphtha or LPG), furnace type (small furnace-large furnace and ethane), furnace parameters (coil inlet pressure (CIP) , coil inlet temperature (CIT) , bridge wall temperature) , scenario creation intervals and raw material, step size for COT and DS, furnace bridge wall temperature, fuel amount used in the furnace, high pressurized steam amount produced in the convection section. As a result of the method, the created furnace scenarios are saved in a database for further use in the scenario evaluation. In order to calculate the profit of each scenario, financial information of the materials (both input and output) are combined with the simulations by the computer. Also, the bottleneck contribution of each scenario is calculated. Subsequently, scenario calculation is performed for all facility furnaces (small, large, LPG, ethane) with the given operating parameters and the appropriate scenario is determined.

One of the most critical processes which allows for the proper operation of the optimisation is the calibration of the bottleneck. In order to overcome the realisation differences against the determined simulation, bottleneck calibration process is performed. The actual data of the facility and the simulation are compared for the calibration process and the bottleneck is adjusted according to the difference between two data points.

The optimum algorithm model selected by the computer is performed to the production furnace. After the proper scenario calculation, for the purpose of optimisation, this appropriate scenario is received via the computer and defined mathematical models of these determined scenarios are entered into all furnaces by the computer. After the implementation, furnace parameters are read from the PHD and the data are controlled. It is controlled whether the data read are between the defined ranges or not. Also, since the ethane amount cracked in the small furnaces change in real time, the ethane amount that goes to the small furnaces (excluding the ethane furnace itself) is calculated and the results of ethane + naphtha cracking furnaces are re-calculated. After the calculation, in order to reprocess the waste ethane gas formed during the process, the computer determines the furnace to which it will be sent and the waste gases coming from the other facilities use a portion of the capacity in the ethylene facility. Thus, during the model study, required restrictions are provided from the relevant capacities based on the amount of the treatment gas coming to the facility.

The model performed is tested. The production is initiated as a result of the test. Then, these processes are reported by the computer together with some calculations.

Some processes are performed for the purpose of reporting. The naphtha report creation process calculates and reports the material production and consumption of the selected operation conditions of the naphtha cracking furnaces as a result of the optimisation. The LPG report creation process calculates and reports the material production and consumption of the operation conditions of the LPG cracking furnaces selected as a result of the optimisation. The ethane report creation process calculates and reports the material production and consumption of the selected working conditions of the Ethane cracking furnaces as a result of the optimisation. Realisation report creation process is reported by means of performing three different profit calculations for the ethylene facility. These profit calculations are the base profit, realized profit and optimal profit. Base profit is the profit of the facility which will be obtained from the average raw material, coil output temperature (COT) and dilution steam (DS) during the year. The realized profit is the profit where the facility provides under current operation conditions. The optimal profit is the profit which is optimum according to the optimisation results of the facility.

The inventive production optimisation method for the ethylene furnaces is to instantly optimize the instantly changing factory conditions, raw material features and factory parameters according to the product prices, by means of finding the most optimal scenario among the approximately 54 billion scenarios. The scenarios created in the simulation of the factory and the optimal scenario is determined by the instant factory conditions from the factory control system, instant results from the laboratory and financial indicators of the raw materials/products via software developed by using live operating linear programming.