Connect Two Process Steps Exclusively

Connect Two Process Steps Exclusively#

In order to connect two process steps sequentially they must be in the same process chain and be connected by streams . This will be demonstrated by adding a blender prior to the cooker which is shown in figure Fig. 4.

../_images/blender_and_cooker_exclusively_connected.png — Fig. 4 Depiction of the cooker model with two parallel cookers.#

Add Additional Commodity#

First additional commodities must be added for each of the new commodity states between source, process steps and sink.

raw_commodity = Commodity(name="Raw Goods")
uncooked_commodity = Commodity(name="Uncooked Goods")
output_commodity = Commodity(name="Cooked Goods")

Create Both Process Steps#

Both process steps must be created.

blender_step = process_chain.create_process_step(name="Blender")
cooker_step = process_chain.create_process_step(name="Cooker")

Create Streams#

raw_materials_to_blender_stream = process_chain.stream_handler.create_batch_stream(
    batch_stream_static_data=BatchStreamStaticData(
        start_process_step_name=source.name,
        end_process_step_name=blender_step.name,
        delay=datetime.timedelta(minutes=1),
        commodity=raw_commodity,
        maximum_batch_mass_value=0.00065,
    )
)
blender_to_cooker_stream = process_chain.stream_handler.create_batch_stream(
    batch_stream_static_data=BatchStreamStaticData(
        start_process_step_name=blender_step.name,
        end_process_step_name=cooker_step.name,
        delay=datetime.timedelta(minutes=1),
        commodity=output_commodity,
        maximum_batch_mass_value=0.00065,
    )
)
cooker_to_sink_stream = process_chain.stream_handler.create_batch_stream(
    batch_stream_static_data=BatchStreamStaticData(
        start_process_step_name=cooker_step.name,
        end_process_step_name=sink.name,
        delay=datetime.timedelta(minutes=1),
        commodity=raw_commodity,
        maximum_batch_mass_value=0.00065,
    )
)

Add Streams#

source.add_output_stream(
    output_stream=raw_materials_to_blender_stream,
    process_chain_identifier=process_chain.process_chain_identifier,
)
sink.add_input_stream(
    input_stream=cooker_to_sink_stream,
    process_chain_identifier=process_chain.process_chain_identifier,
)

Create Petri Nets for Each Process Step:#

Blender#

activate_not_blending = blender_step.process_state_handler.process_state_switch_selector_handler.process_state_switch_handler.create_process_state_switch_at_next_discrete_event(
    start_process_state=discharge_goods_state_blender,
    end_process_state=idle_state_blender,
)
blender_step.process_state_handler.process_state_switch_selector_handler.create_single_choice_selector(
    process_state_switch=activate_not_blending
)

activate_filling_blender = blender_step.process_state_handler.process_state_switch_selector_handler.process_state_switch_handler.create_process_state_switch_at_input_stream(
    start_process_state=idle_state_blender,
    end_process_state=fill_raw_materials_state_1,
)

blender_step.process_state_handler.process_state_switch_selector_handler.create_single_choice_selector(
    process_state_switch=activate_filling_blender
)

activate_blending = blender_step.process_state_handler.process_state_switch_selector_handler.process_state_switch_handler.create_process_state_switch_delay(
    start_process_state=fill_raw_materials_state_1,
    end_process_state=blending_state,
    delay=datetime.timedelta(minutes=5),
)

blender_step.process_state_handler.process_state_switch_selector_handler.create_single_choice_selector(
    process_state_switch=activate_blending
)


activate_discharging_blender = blender_step.process_state_handler.process_state_switch_selector_handler.process_state_switch_handler.create_process_state_switch_at_output_stream(
    start_process_state=blending_state,
    end_process_state=discharge_goods_state_blender,
)
blender_step.process_state_handler.process_state_switch_selector_handler.create_single_choice_selector(
    process_state_switch=activate_discharging_blender
)

Cooker#

idle_state_cooker = cooker_step.process_state_handler.create_idle_process_state(
    process_state_name="Idle"
)
fill_raw_materials_state_cooker = (
    cooker_step.process_state_handler.create_batch_input_stream_requesting_state(
        process_state_name="Fill raw materials"
    )
)

cooking_state = cooker_step.process_state_handler.create_intermediate_process_state_energy_based_on_stream_mass(
    process_state_name="Cooking"
)

discharge_goods_state_cooker = (
    cooker_step.process_state_handler.create_batch_output_stream_providing_state(
        process_state_name="Discharge"
    )
)


# Petri net transitions

activate_not_cooking = cooker_step.process_state_handler.process_state_switch_selector_handler.process_state_switch_handler.create_process_state_switch_at_next_discrete_event(
    start_process_state=discharge_goods_state_cooker,
    end_process_state=idle_state_cooker,
)
cooker_step.process_state_handler.process_state_switch_selector_handler.create_single_choice_selector(
    process_state_switch=activate_not_cooking
)

activate_filling_cooker = cooker_step.process_state_handler.process_state_switch_selector_handler.process_state_switch_handler.create_process_state_switch_at_input_stream(
    start_process_state=idle_state_cooker,
    end_process_state=fill_raw_materials_state_cooker,
)

cooker_step.process_state_handler.process_state_switch_selector_handler.create_single_choice_selector(
    process_state_switch=activate_filling_cooker
)

activate_cooking = cooker_step.process_state_handler.process_state_switch_selector_handler.process_state_switch_handler.create_process_state_switch_delay(
    start_process_state=fill_raw_materials_state_cooker,
    end_process_state=cooking_state,
    delay=datetime.timedelta(minutes=24),
)

cooker_step.process_state_handler.process_state_switch_selector_handler.create_single_choice_selector(
    process_state_switch=activate_cooking
)


activate_discharging_cooker = cooker_step.process_state_handler.process_state_switch_selector_handler.process_state_switch_handler.create_process_state_switch_at_output_stream(
    start_process_state=cooking_state,
    end_process_state=discharge_goods_state_cooker,
)
cooker_step.process_state_handler.process_state_switch_selector_handler.create_single_choice_selector(
    process_state_switch=activate_discharging_cooker
)

Adapt Energy Data#

Now the energy demand for the mixer must be added. It is assumed that the blending occurs for 5 minutes at a maximum power 1300 Watt for 650 gram of input material. Therefore the specific energy demand of the state is calculated as follows:

\[ SEC_{blending, state}=(P_{blend, max}*t_{blend, max})/m_{potato,water}=(2000W*5min)/(650 g)=600 MJ/t \]

electricity_load = LoadType(name="Electricity")
mixing_state.create_process_state_energy_data_based_on_stream_mass(
    specific_energy_demand=600,
    load_type=electricity_load,
    stream=raw_materials_to_blender_stream,
)
cooking_state.create_process_state_energy_data_based_on_stream_mass(
    specific_energy_demand=830.76,
    load_type=electricity_load,
    stream=blender_to_cooker_stream,
)

Add Mass Balances and Storages#

The names of the streams and process steps must be adapted to the new variable names.

# Mass balances
blender_step.create_main_mass_balance(
    commodity=output_commodity,
    input_to_output_conversion_factor=1,
    main_input_stream=raw_materials_to_blender_stream,
    main_output_stream=blender_to_cooker_stream,
)

# Add internal storages (required)
blender_step.process_state_handler.process_step_data.main_mass_balance.create_storage(
    current_storage_level=0
)

# Mass balances
cooker_step.create_main_mass_balance(
    commodity=output_commodity,
    input_to_output_conversion_factor=1,
    main_input_stream=blender_to_cooker_stream,
    main_output_stream=cooker_to_sink_stream,
)

# Add internal storages (required)
cooker_step.process_state_handler.process_step_data.main_mass_balance.create_storage(
    current_storage_level=0
)

In the next example shows how to connect three or more process steps non exclusively.