Wet water-Oxygen Supercritical Pyrolysis System

1. Purpose of the test bench

The test bench is designed to study the activity of newly created and implemented catalytic systems by the company. The test bench will provide testing of catalysts in the form of powders (fraction 0.2 mm or more), granules (extrudates) and honeycomb blocks for processes such as the decomposition of nitrous oxide and the selective reduction of nitrogen oxides.

2. General layout

The test bench should consist of the following fundamental blocks:

- Control block;

- Reaction mixture preparation unit;

- Reactor block;

- Gas phase composition analyzer (provided by the Customer);

3. Control unit

Generates control signals and tasks for: gas flow meters, gas flow preheater, reactor, gas phase composition analyzer, water flow regulator and superheater for steam. Collects data from pressure and temperature converters, gas and water flow meters, gas meter, air humidity sensor, gas phase composition analyzer.

Control of the process occurring in the reactor unit must be carried out by entering parameters in digital form into the control units of individual units using a single hardware and software complex.

Control of the process occurring in the reactor unit must be carried out by entering parameters in digital form into the control units of individual units using a single hardware and software complex. All parameters and their changes over time must be recorded automatically; the data collection interval is set by the user. The collected data should be presented in digital files in tabular form. The user should be able to change the appearance of the report table (location of components in the table, separator characters), the ability to export the file to the "csv", "txt" formats.

The control system also performs a protective function. Before starting the experiment with a loaded catalyst and a fully assembled system, it is necessary to pressurize the stand with excess pressure in order to determine the leakage of the gas path of the stand; the pressure and duration of the test are set by the user. The user controls the crimping process based on instrument readings and data displayed by the control system.

The system must prevent the achievement of explosive concentrations of components in mixtures, as well as control leakage in the event of loss of tightness. Control is carried out by direct measurement or reading readings from flow meters.

When a leak is detected, as well as reaching the lower concentration limit of ammonia ignition (14%) or the corresponding ratio of flow values, it is necessary to stop the supply of reaction components, start purging with nitrogen, turn off the heating of the reactor, gas heater and display a warning signal.

Automation of the process should be structurally carried out on the basis of a logical controller and the organization of a remote workplace.

4. Reaction mixture preparation unit

The gas mixture preparation unit includes a set of pressure regulators, gas flow meter regulators and corresponding fittings, a reaction gas heater and a flow mixing device. During the operation of the test bench, the following gases are used: nitrogen, air, ammonia, nitrogen oxides (I, II, IV) or their mixtures diluted with nitrogen. These gases are supplied through separate lines from cylinders at room temperature (18-25°C). The remaining gas in the cylinder and the outlet pressure are controlled and regulated using reducers (included in the delivery package).

The choice of control device is made based on the required gas flow (Table 1). Dust and particulate filters must be provided on each gas line, upstream of the flow regulators. The filter capacity must ensure maximum gas flow without affecting the control system. To clean the incoming air flow from mechanical impurities and dry it, provide a dryer and filter at the outlet of the cleaning system. The air must be dust-free, free of oil vapors, dry (dew point no higher than -40 °C), humidity control must be carried out using a digital sensor with the ability to record readings in a database.

The flow of water vapor is formed separately. Water is supplied to the evaporator by a metering pump, then water vapor is brought to the reaction temperature through a heater, goes to the mixing unit and then enters the reactor.

The components of the reaction mixture with a given flow rate are preheated before entering the reactor. Before entering the reactor, individual streams are combined into groups in such a way as to avoid side processes and at the same time reduce the number of heaters. At the same time, the nitrogen oxides are heated, the mixture formed by the nitrogen and ammonia flows is heated separately, and, separately from the above, the air flow is heated.

The temperatures of all streams entering the reactor must be maintained automatically at the same level specified by the operator. The requirements for the specified flow rates of the standard mixture components are given in Table 1.

Before being transferred to the reactor, all components of the traditional mixture must be homogeneous and evenly mixed in the mixtures. The mixing unit should be located between the heater and the reactor. At the exit from the mixing unit, a mixture flow close to laminar should be obtained.

Table 1

Table 1. Requirements for specified flows of reaction mixture components.

The test bench must ensure the production of a gas mixture with specified parameters with volumetric velocities of up to 110,000 h-1 when loading a catalyst with a volume of 50 ml.

5. Reactor block

The reactor block includes a heater, reactor, pressure and temperature control sensors, refrigerator, separator, pressure regulator, fittings, instrumentation, as well as equipment necessary to maintain the required temperature in the reactor.

The reactor block is a reactor placed in a tubular furnace, in which the required temperature is maintained using electric heaters. The catalyst is located in a support device in the isothermal zone of the furnace. The organization of the layer in the reactor for all types of catalyst form factor (Table 2) should ensure: reliable fixation of the catalyst, no leakage of the mixture between the wall of the reactor and the catalyst.

The reactor is equipped with pressure and temperature sensors. Pressure sensors are located in front of and behind the catalyst layer, temperature sensors are located in front of the layer, in the layer and behind the catalyst layer. Based on the thermocouple readings, the reactor heating is adjusted. The characteristics of the reactor and its operating temperatures are given in Table 2.

The pressure in the reactor is regulated using an electronic valve with feedback installed on the blow-off from the separator and is fixed by a digital sensor with the ability for the operator to set the required pressure and record the readings with a software package, which allows you to set the upper pressure limit and thereby protects the system from overpressure. Provide a filter in front of the valve to ensure its correct operation and control of catalyst destruction during testing.

Table 2. Characteristics of reactors for testing bulk catalysts.

6. Other conditions

The control system is included in the delivery and includes a hardware and software complex that provides control of process parameters with recording of values over time during the experiment. When the test bench is completed, the system must generate a digital file containing data for further processing.

7. Safety requirements and assessment of possible risks when operating the test bench

The test bench must be equipped with a device for continuous monitoring of the lower concentration limit of ignition of the ammonia-air mixture, automatically shut off the flow of reagents and begin purging with nitrogen when receiving a signal from the control device.

When working on a test bench, it is provided that exhaust gases are discharged into process ventilation

8. PID cheme (Sent in a message)