The ROTARY KILN INCINERATOR process produces hot flue gasses, suitable for energy recovery, depending upon client requirements.

Options and features:

• Smaller systems typically use water injection to reduce flue gas temperature, prior to final flue gas emission reduction. The most cost effective solution, although without energy recovery.
• Alternatively the flue gas can be mixed with ambient air to reduce flue gas temperature, a simple and reliable method for incinerators with a small thermal input.
• Energy recovery is a viable option for incinerators with a higher thermal input, starting from 3 MW, depending upon the balance between investment costs versus returns. A wide range of options is available:

Energy recovery by the production of hot ambient air

Hot air can be used for:

• Production of chilled water via an absorption cooling machine, typical application: medical waste storage room cooling.
• Combustion air preheating to support other combustion processes.
• Drying processes using hot air.
• Steam generation or hot water production.

Energy recovery by the production of steam

Steam can be used for:

• General energy supply as utility steam for other production processes.
• Electricity generation using a steam turbine (up to approx. 1.5 MW electrical output for the product range of Dutch Incinerators).

Energy recovery based on thermal oil

Thermal oil can be used for:

• Direct high temperature heating of other production processes.
• Steam or hot water generation in case of an excess of energy.
• Chilled water production.

Energy recovery based on the Organic Rankine Cycle (ORC)

ORC enables energy recovery and electrical power generation there where steam based energy recovery is not practically feasible, specifically for energy recovery at lower flue gas temperatures and smaller thermal input capacities.

The Flue gas emission reduction process of the ROTARY KILN INCINERATOR reduces the concentration of contaminants as present in the flue gasses to levels below the applicable emission standards. Typically, Dutch Incinerators designs comply with EU regulations in this regard, the most strict on the planet. Several systems and options are available to meet the applicable emission standards.

Options and features:

Dry scrubbing emission control systems

These scrubbing systems are characterized by the fact that the flue gas is treated without complete saturation of the flue gas stream with water (with other words, without completely quenching the flue gas stream with water). Typically they include a dosing mechanism for additive(s), reaction and residence chamber and a bag filter for final dust removal. The choice of additive depends upon the types of contaminants to be removed and financial considerations, mainly operating costs. Dutch Incinerators can provide the following technologies:

• Dry scrubbing based on dry lime injection (Calcium based).
• Semi dry scrubbing based on lime slurry injection with complete evaporation (Calcium based).
• Dry scrubbing based on sodium bicarbonate. Higher emission reduction efficiencies can be achieved with this relative new technology also resulting in lower operating costs overall. Generally the preferred option comparing with conventional lime based technologies.
• Activated carbon addition to capture dioxins, heavy metals.

Dry scrubbing systems have the following advantages and disadvantages compared with wet scrubbing:

Advantages:

• The flue gas leaves the system at temperatures above the dew point of water and most common acidic components in the flue gas.
• This reduces or eliminates the visible water vapor plume on the stack.
• This reduces or eliminates corrosion issues, quite common with improper designed or operated wet scrubber systems.
• The implementation of a bag filter results in the lowest emission of dust (PM, particulate matter or TSP, total suspended particles), typically lower than 5 mg/m3, corrected.
• Aerosols, such as “white smoke” are effectively captured in a bag filter.
• No make-up water required.
• No waste water treatment required.
• Is capable to achieve emission levels within EU regulations as a single step solution, depending upon the type of additive used, design of the system, acidic gas loads and dosing capacities.

Disadvantages:

• Generally higher initial investment costs, due to the bag filter, optional sodium bicarbonate grinder, lime make up systems, additive storage systems and reaction and residence time ducting.

Wet scrubbing emission control systems

Wet scrubbing systems are based on the reaction of acidic flue gas contaminants with caustic (NaOH), present in a diluted form in the wet scrubber circulation fluid.

Wet scrubbing systems have the following advantages and disadvantages compared with dry scrubbing:

Advantages:

• Capable to achieve very low emission concentrations on acidic flue gas compounds with relative simple technology.
• Capable to achieve reasonably low dust emission concentrations, typically below 50 mg/m3 corrected (but apart from specific cases not low enough to meet EU regulations if applied as a single step solution).
• Relative low investment costs.
• Relative simple to operate and control.
• Capable to absorb wide and fast fluctuations in acidic flue gas component supply, as the scrubber water and sodium based chemistry acts as a fast acting buffer to absorb these contaminants.

Disadvantages:

• A wet scrubber consumes water. This needs to be available in sufficient quantities.
• A wet scrubber produces waste water. This needs to be treated. Smaller quantities can be treated in the incineration process itself, but generally speaking some means of water treatment is required.
• Corrosion might me a problem, although more an operational problem for a properly designed system (not maintaining pH within certain margins).
• Wet scrubbers have more problems to reduce aerosols emissions, such as “white smoke” as produced by a hazardous waste incinerator depending upon waste input. Specific measures are available to reduce this problem, but efficiency is lower than a dry scrubbing based system.

Combination of dry- and wet scrubbing systems.

A combination of a dry- and wet scrubbing system might be the optimum choice in specific cases, considering the above, resulting in the most optimum emission reduction solution for the total facility as the advantages and disadvantages of each option can be balanced and optimized.

Flue gas emission monitoring for the flue gasses leaving the flue gas emission reduction system of the ROTARY KILN INCINERATOR is required to ensure that final emissions comply with the applicable regulations. Emissions are typically monitored on a continuous basis (CEMS, continuous emission control system); results are represented in the central control room, stored in a data bases for reporting to authorities or can directly be transferred to the authorities or external parties via a direct datalink. All CEMS systems as provided by Dutch Incinerators are produced by top quality suppliers, constructed and tested to international standards and approvals.

Options and features:

• Typical CEMS analysis parameters: SO2, HCl, NOx, HF, CO, O2, H2O, CO2, TOC, PM (dust), opacity and more compounds, all upon request and client requirements.
• Extractive CEMS systems, typically used after a wet scrubbing system.
• In-situ CEMS systems, typically used after a dry scrubbing system (lower in investment than an extractive system).
• Particulate Matter CEMS, specifically applicable for wet scrubbing systems, where optical dust measurements give a misreading.
• Optical PM CEMS and opacity measurements as commonly used on dry scrubbing systems.